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Research ArticleStudy of Molecular and Ionic Vapor Composition over CeI3 byKnudsen Effusion Mass Spectrometry

A M Dunaev1 V B Motalov1 L S Kudin1 M F Butman1 and K W Kraumlmer2

1Research Institute of Thermodynamics and Kinetics Ivanovo State University of Chemistry and TechnologyIvanovo 153000 Russia2Department of Chemistry and Biochemistry University of Bern 3012 Bern Switzerland

Correspondence should be addressed to V B Motalov vmotalovgmailcom

Received 7 August 2016 Accepted 17 October 2016

Academic Editor Alessandro Longo

Copyright copy 2016 A M Dunaev et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

The molecular and ionic composition of vapor over cerium triiodide was studied by Knudsen effusion mass spectrometry In thesaturated vapor over CeI3 the monomer dimer and trimer molecules and the negative ions Iminus CeI4

minus and Ce2I7minus were identified

in the temperature range of 753ndash994K The partial pressures of CeI3 Ce2I6 and Ce3I9 were determined and the enthalpies ofsublimation Δ s119867∘(29815 K) in kJsdotmolminus1 in the form of monomers (298 plusmn 9) dimers (415 plusmn 30) and trimers (423 plusmn 50) wereobtained by the second and third laws of thermodynamics The enthalpy of formation Δ f119867∘(29815 K) in kJsdotmolminus1 of the CeI3(minus371 plusmn 9) Ce2I6 (minus924 plusmn 30) and Ce3I9 (minus1585 plusmn 50) molecules and the CeI4

minus (minus857 plusmn 19) and Ce2I7minus (minus1451 plusmn 50) ions were

calculated The electron work function 120593e = 33 plusmn 03 eV for the CeI3 crystal was evaluated

1 Introduction

Vaporization thermodynamics of cerium triiodide is thefocus of researcherrsquos attention so far The first measurementsof vapor pressure over CeI3 were carried out byKnudsen effu-sion mass spectrometry (KEMS) [1] and Knudsen effusionCahn microbalance [2] techniques Further KEMS studieswere performed by Chantry [3 4] Struck and Feuersanger[5] and Ohnesorge [6] In addition the vapor pressure ofCeI3 was determined by the torsion method [7] by opticalabsorption spectra [8] and recently byX-ray induced fluores-cence [9] In spite of the numerous experimental results [1ndash9] data on the vapor composition over CeI3 are very scantyMoreover information on the ionic species in saturated vaporover CeI3 is absent so far

The present work continues our systematic investigationsof the molecular and ionic sublimation of lanthanide halidesby KEMS see for example [10ndash14] The composition of thesaturated vapor of CeI3 was determined and the thermo-chemical data of the vapor constituents were refined on thebasis of the latest sets of molecular parameters

2 Experimental

A single-focusing magnetic sector type mass spectrometerMI1201 modified for high-temperature studies was usedThe combined ion source allowed carrying out successivemeasurements in two modes see Figure 1 (taken from [15])In addition to a standard mode of electron ionization (EI) foranalysis of neutral vapor species a thermal ion emission (TE)mode was introduced for the analysis of charged vapor con-stituents formed inside an effusion cell as a result of thermalionization In the latter case the ions are drawn out from thecell by aweak electric field (104ndash105 Vm) applied between thecell and the collimator (1) The sample (2) was placed into amolybdenum cell (3) under dry conditions in a glove box andthen transferred into the vaporization chamber of the massspectrometer and evacuatedThe lid of the cell had the cylin-drical effusion orifice (Oslash 03 times 08mm)The vaporization-to-effusion area ratio was about 400 A resistance furnace wasused for the heating of the cell Its temperature was measuredby a tungsten-rhenium thermocouple calibrated with silverto a plusmn5K accuracy in the separate experiment

Hindawi Publishing CorporationJournal of SpectroscopyVolume 2016 Article ID 2368131 9 pageshttpdxdoiorg10115520162368131

2 Journal of Spectroscopy

1

2

4

5

31067

8

9 11I

II

Udr

Figure 1 Scheme of the mass spectrometer (taken from [15]) ImdashEImode IImdashTE mode The details are given in text

The vapor species effusing from the cell form amolecularbeam which reaches the ionization chamber (4) and inter-sects with an electron beam of specified energy The ioniza-tion voltage 119880e is set by a computer using a programmablepower supply AKIP-1125 in the range of 0ndash150V with 10mVresolution The tungsten ribbon-type cathode (5) is directlyheated by an controllable DC source The current of thecathode was adjusted to provide a constant emission currentof 025A

The ions formed by the collision of molecular specieswith electrons are extracted from the ionization chamberfocused and accelerated by a system of electrostatic lenses(6) The electrostatic capacitor mounted after the exit slit ofthe ion source allows us to study the distribution of ionsby the vertical velocity component The accelerating voltage(3 kV) is applied to the ionization chamber (IE mode) orto the effusion cell (TE mode) The polarity of the highvoltage can be reversed with respect to the ground potentialThus both positive and negative ions can be analyzed Theions are separated according to their mass-to-charge ratioin the magnetic field of an electromagnet (7) (90∘ 200mmcurvature radius) The magnetic field strength is measuredby a Hall probe The ion current registration system (8 9)includes a secondary electron multiplier Hamamatsu R595(8) and a Picoammeter Keithley 6485 with 10 fA resolutionand 20 fA typical noise It allows measuring ion currentsdown to 10minus18 AThemovable shutter (10) operated by a com-puter (11) allows distinguishing signals caused by the effusingspecies from those of the background The special softwareldquoHTMSLabrdquo was used to control experimental parameterscollect and process the data and export the results into thedatabase Further details on the apparatus and experimentalprocedure can be found elsewhere [16ndash18]

The cerium triiodide sample was synthesized fromcerium metal (999 Metall Rare Earth Ltd) and iodine(pa sublimed Merck) The elements were sealed in anevacuated silica ampoule and slowly heated to 750∘C untilthe reaction was completed Afterwards the product wassublimed for purification in a sealed silica ampoule undervacuum at 750∘C that is slightly below the melting point ofCeI3 at 766

∘C The bright yellow CeI3 is very hygroscopicIts synthesis was performed under strictly oxygen-free andanhydrous conditions

820 840 860 880 900 920 940 960 980 1000800

T (K)

10minus3

10minus2

10minus1

100

101

102

I iI

(CeI

2+

) (

)

Ce+

CeI+CeI2

+

CeI3+

Ce2I5+

Ce3I8+

Figure 2 Temperature dependence of the mass spectra of CeI3Heating and cooling runs are marked by solid and open symbolsrespectively

3 Results and Discussion

31 Neutral Vapor Species In the IE mass spectra ofthe saturated vapor over cerium triiodide the Ce+(23)CeI+(16) CeI2+(100) CeI3+(31) Ce2I3+(002) Ce2I4+(001)Ce2I5+(22) I+(22) and Ce3I8

+(002) ions as well as thedoubly charged Ce++(05) CeI++(7) and CeI2

++ (3) ionswere registered in the temperature range of 753ndash994KThe relative ion currents are given in parentheses for thetemperature of 990K and the energy of ionizing electrons of40 eV The mass spectra were found to be constant over thewhole evaporation time see Figure 2

To determine the molecular precursors of the ions theionization efficiency curves (IEC) (Figure 3) and the temper-ature dependencies of ion currents (Figure 4) were analyzedThe ionizing electron energy in Figure 3 was corrected by thebackground signal of HI+ (119860119864 = 1038 eV [19]) Appearanceenergies (119860119864) were determined by vanishing current (VC)and linear extrapolation (LE) methods average values aregiven in Table 1 The linear part for the LE method wasdetermined as the segment between two points of inflectionon the first-order derivative of the IEC inverse function [20]The following conclusions were drawn the ions containingone atom of cerium are formed as a result of direct (CeI3

+)and dissociative (Ce+ CeI+ and CeI2

+) ionization of themonomer CeI3molecules with negligibly small contributionsfrom the fragmentation of more complex molecules theCe2I3+ Ce2I4

+ and Ce2I5+ ions were produced by the

dissociative ionization of the dimer Ce2I6 molecules and theCe3I8+ ion originated from the trimer molecule Ce3I9

Along with the abovementioned ions I+ was alsoobservedThe determined119860119864 equal to 107 plusmn 05 eV (Table 1)points out its origination from atomic iodine (ionizationenergy 119868119864(I) = 104 eV [21]) which can be attributed to thepartial decomposition of the sample with the formation of

Journal of Spectroscopy 3

Table 1 Ion appearance energies (eV)

Reaction Ion 119860119864This work [1] [3] [5] [30]

CeI3 + e = Ce+ + 3I + 2e Ce+ 172 plusmn 05 177 plusmn 05 1675 plusmn 015CeI3 + e = CeI+ + 2I + 2e CeI+ 131 plusmn 05 136 plusmn 05 1315 plusmn 015CeI3 + e = CeI2

+ + I + 2e CeI2+ 98 plusmn 05 97 plusmn 05 955 plusmn 01 112

CeI3 + e = CeI3+ + 2e CeI3

+ 91 plusmn 05 96 plusmn 05 905 plusmn 01 108 971Ce2I6 + e = Ce2I5

+ + I + 2e Ce2I5+ 93 plusmn 05

Ce3I9 + e = Ce3I8+ + I + 2e Ce3I8

+ 91 plusmn 05I + e = I+ + 2e I+ 107 plusmn 05 sim135 105

I i(a

rb u

nits)

915K957K

Ce+CeI+CeI2+

CeI3+

9 11 13 15 17 19 21 23 257

Energy of ionizing electrons (eV)

0

20

40

60

80

100

0

20

40

60

80

100

(a)

I i(a

rb u

nits)

Ce2I5+

Ce3I8+

HI+

242220181614121080

20

40

60

80

100

2614 2218 2016 241210


0

20

40

60

80

100

915K957K

957K

(b)

Figure 3 Ionization efficiency curves

CeI2 Nevertheless the reproducibility of the mass spectrain heating and cooling cycles (Figure 2) the shapes of IECsshowing no brakes and the determined 119860119864 values (Table 1)indicate unambiguously the absence of CeI2 in the vaporThisfact agrees with the expected much lower volatility of CeI2

ln(I

jmiddotT

)

minus8

minus10

minus12

minus14

minus16

minus18

minus20

minus22

Ce+

CeI+CeI2

+

CeI3+

Ce2I5+

Ce3I8+

105 110 115 120 125100 130

1000T (Kminus1)

Figure 4 Temperature dependence of ion currents in the EI regime

compared to that of CeI3 in the studied temperature rangeTherefore it is assumed that the activity of CeI3 in the solidstate was unity

The partial pressures of molecules (119901j) (see Table 2) werecalculated according to the conventional KEMS procedureusing the equation

119901119895 = 119896 sdot 119868 sdot 119879120590119895 (1)

where 119896 is the sensitivity constant of mass spectrometer(determined in a separate experiment with Ag the vaporpressure of silver was taken from [22]) 120590j is the ionizationcross section of the jth molecule at the working energy ofthe ionizing electrons (calculated from the experimentallydetermined atomic cross sections120590at [23 24] by the equation120590119895 = 075Σ120590at [25]) 119868119895 = sum119894(119868119894119895(119886119894 sdot120574119894)) is the total ion currentof the 119894th ion species formed from the jth molecule 119886119894 is thenatural abundance of themeasured isotope of the 119894th ion 120574i isthe ion-electron conversion coefficient of secondary electronmultiplier for the 119894th ion (120574119894 sim 119872minus12 [26] where 119872 is themass of ion) and 119879 is the temperature of the cell


Table 2 Partial pressures (Pa) of the molecules

CeI3 Ce2I6 Ce3I9T K 119901119895 sdot 103 T K 119901119895 sdot 104 T K 119901119895 sdot 105885 545 878 359 916 085872 478 915 268 957 745877 554 957 182 932 183877 547 933 570 907 041914 235 906 143 905 065957 1080 866 162 921 084934 445 829 015 945 429906 150 857 127 952 524868 298 882 580 962 125828 432 906 170 978 299786 052 920 398 992 581805 123 946 134 907 051753 0081 853 076 923 108872 435 952 170 943 274957 1210 963 323 969 153857 203 978 566 994 542882 595 992 1010906 145 907 239919 274 923 288942 575 883 419854 158 857 090951 786 829 020963 1280 811 0035979 1970 828 0081990 3020 857 064908 150 884 377923 244 917 240883 401 943 105856 155 969 343829 406 994 999811 148826 324856 137883 488918 189944 551969 1250994 2880

The temperature dependence of the saturated vaporpressures of the monomer and oligomer molecules wasapproximated by the equation

ln119901119894 = minus119860 times 103119879 + 119861 (2)

The coefficients of equation (2) are given in Table 3The partial pressures of the molecules of cerium triiodide

from different references are compared in Figure 5 Asone can see all experimental vapor pressure values arescattered within about one order of magnitude Temperature

Table 3 Coefficients of (2)

Species T K A BCeI3 753ndash994 3335 plusmn 036 3484 plusmn 041Ce2I6 811ndash994 4493 plusmn 062 4310 plusmn 069Ce3I9 905ndash994 4962 plusmn 143 4243 plusmn 152The standard deviation is given with a ldquoplusmnrdquo sign

1

2

34

5

1998400

29984002998400998400 5998400

08 09 10 11 12 1307

1000T (Kminus1)

10minus7

10minus6

10minus5

10minus4

10minus3

10minus2

10minus1

100

101

102

103

pj

(Pa)

Tm = 1033K

Figure 5 Temperature dependencies of the saturated vapor pres-sure (1) p(CeI3) from [9] (2) our data (3) [2] (4) [7] and (5) [6](11015840) p(Ce2I6) from [9] (21015840) our data and (51015840) [6] (210158401015840) p(Ce3I9) ourdata

dependencies from the work of Hirayama et al [2] Villaniet al [7] and Ohnesorge [6] lie below those obtained inthis work The fraction of the dimer molecules measured inthis work and in [6] is about the same whereas the absolutepressures differ considerably The vapor pressure of trimermolecules was determined in this study for the first time

The enthalpies and entropies of sublimation of ceriumtriiodide in the form of monomer and oligomer moleculeswere determined from the temperature dependencies of thepartial pressures of the saturated vapor species using theprocedure for experimental data processing according tothe second and third laws of thermodynamics see Table 4The thermodynamic functions required for calculations weretaken from [22] for CeI3cr and evaluated in this work for themonomer and oligomer molecules in the state of an ideal gas(see Appendix)

As it is seen from Table 4 the values of Δ s119867∘(29815)and Δ s119878∘(T) obtained in this work by the second and thirdlaws are in a fair agreement for both monomer and oligomermolecules The same can be said about the results for themonomer molecules from [2 7] The data of the work [9]are in notably worse agreement whereas those of [6 8] donot agree within the given uncertainties At the same timethe third law values for all the data are in a good consentwith each otherThe temperature trend of the third law valuesΔ s119867∘(29815) is given in Figure 6 fromwhich one can see thatthe data of this work and [2 9] do not show a pronouncedtemperature dependence as compared to those of [6 7]Taking into account this analysis the recommended values


Table 4 Enthalpies Δ s119867∘ (kJsdotmolminus1) and entropies Δ s119878∘ (Jsdotmolminus1sdotKminus1) of sublimation of cerium triiodide

ΔT K T K N1 II law2 III law3 RefΔ sv119867∘(T) Δ sv119878∘(T) Δ s119867∘(298) Δ s119867∘(298) Δ sv119878∘(T)CeI3crl = CeI3g

753ndash994 893 38 277 plusmn 3 194 plusmn 3 292 plusmn 4 294 plusmn 10 191 plusmn 10 This work 933 292 plusmn 21 307 plusmn 21 [1]870ndash1015 945 32 284 plusmn 4 197 plusmn 4 301 plusmn 4 298 plusmn 10 189 plusmn 10 [2]810ndash953 877 50 274 plusmn 2 288 plusmn 2 [5]854ndash1017 936 29 284 plusmn 1 164 plusmn 1 278 plusmn 1 307 plusmn 10 189 plusmn 10 [6]910ndash1031 970 81 284 plusmn 3 192 plusmn 6 301 plusmn 3 303 plusmn 10 189 plusmn 10 [7]

1000 1 291 plusmn 10 187 plusmn 10 [8]1072ndash1136 1094 5 201 plusmn 11 119 plusmn 10 272 plusmn 11 296 plusmn 10 155 plusmn 10 [8]1080ndash1400 1250 299 plusmn 1 119 plusmn 1 290 plusmn 1 301 plusmn 10 123 plusmn 10 [9]

297 [22]322 [27]280 [28]

300 plusmn 5 [29]Δ s119867∘(29815 K) = 298 plusmn 94

2CeI3crl = Ce2I6g811ndash994 893 30 374 plusmn 6 262 plusmn 6 395 plusmn 25 409 plusmn 30 278 plusmn 30 This work825ndash953 898 50 377 plusmn 5 400 plusmn 15 [5]854ndash1017 936 17 354 plusmn 1 219 plusmn 1 379 plusmn 25 428 plusmn 30 276 plusmn 30 [6]1080ndash1400 1250 251 plusmn 1 138 plusmn 1 413 plusmn 1 421 plusmn 30 148 plusmn 30 [9]

Δ s119867∘(29815 K) = 415 plusmn 303CeI3cr = Ce3I9g

907ndash994 949 16 413 plusmn 12 257 plusmn 13 443 plusmn 40 423 plusmn 50 236 plusmn 50 This workΔ s119867∘(29815 K) = 423 plusmn 50

1

Number of measurements2The original errors are given for the literature data the standard deviations for this work3The uncertainties are mainly determined by those in thermodynamic functions4The uncertainty of the recommended values was calculated by Studentrsquos method (monomer) and accepted as the third law ones (others)

ΔsH

∘ (29

815

K)

900 1000 1100 1200 1300 1400800

T (K)

1998400

2998400

5998400 2998400998400

54

3

2

1

Tm = 1033K

430

420

410

305

300

295

290

Figure 6 Temperature dependencies of the third lawΔ s119867∘(29815 K) values (1) monomer from [9] (2) our data(3) [2] (4) [7] and (5) [6] (11015840) dimer from [9] (21015840) our data and(51015840) [6] (210158401015840) trimer our data

were selected and emphasized in bold in Table 4 The earlyestimates [27 28] made for monomers differ considerablyfrom the recommended value while the assessments givenin [22 29] agree with the experimental data

The standard formation enthalpies Δ f119867∘(29815 K) areequal to minus371 plusmn 9 kJsdotmolminus1 (CeI3) minus924 plusmn 30 kJsdotmolminus1(Ce2I6) and minus1585plusmn50 kJsdotmolminus1 (Ce3I9) and were calculatedfrom the recommended Δ sH∘(29815 K) values The forma-tion enthalpy of crystalline cerium triiodide Δ f119867∘(CeI3cr29815 K) = minus669 kJsdotmolminus1 [22] was used

32 Charged Vapor Species In the TE mass spectra in thetemperature range of 747ndash960K the Iminus(044) CeI3

minus(018)CeI4minus(100) and Ce2I7

minus(008) ions were identified with therelative ion currents given in parentheses for T = 846K

Additional experiments with the CeI3-PrI3 binary systemwere performed to determine the enthalpy of formation ofCeI4minus ions The enthalpy of exchange ion-molecular reaction

(5) was found to be 1 plusmn 5 kJsdotmolminus1 The enthalpy of formationof PrI4

minus Δ f119867∘(29815 K) = minus860 plusmn 23 kJsdotmolminus1 was used asreference value It was obtained by recalculation of the data(minus865 plusmn 25 kJsdotmolminus1) [13] with the thermodynamic functionused in this workThe experimental equilibrium constants ofreaction (3) and reaction (4) investigated over pure CeI3 arelisted in Table 5

CeI3g + PrI4minusg = CeI4

minusg + PrI3g (3)

Ce2I7minusg = CeI4

minusg + CeI3crl (4)


Table 5 Experimental data for reactions (3) and (4)

Reaction (3) Reaction (4)T (K) ln119870∘119875 T (K) ln119870∘119875889 035 868 639865 039 862 661835 030 898 592846 049 932 543907 041 960 494934 039 924 549966 038 892 594956 037 846 667929 034906 022856 034806 038854 030884 038902 030950 040976 030

The reaction enthalpies were calculated by the second andthird laws of thermodynamics see Table 6 The evaluation ofthe thermodynamic functions of the CeI4

minus and Ce2I7minus ions is

described in AppendixOne can see that the agreement for the enthalpy of

reaction (3) obtained by the second and third laws is goodΔ f119867∘(CeI4minus 29815 K) = minus857 plusmn 19 kJsdotmolminus1 was recom-mended This value is in agreement with those minus850 plusmn33 kJsdotmolminus1 obtained by Chantry from the enthalpy of thereaction CeI4

minusg = Iminusg + CeI3g and recalculated with our

sublimation enthalpy and thermodynamic functions Theselected formation enthalpy of the Ce2I7

minus ion is minus1451 plusmn50 kJsdotmolminus1 (third law) and was obtained for the first time

33 Thermodynamic Properties Derived from IECs Theenthalpies of ion-molecular reactions were calculated fromthe differences of the measured 119860119864 values given in Table 1see Table 7 On their basis the standard formation enthalpiesof the ions were determined see Table 8 The accurate valuesofΔ f119867∘(Ce+ 29815 K) = 957plusmn01 kJsdotmolminus1 [22] andΔ f119867∘(I29815 K) = 10676 plusmn 004 kJsdotmolminus1 [22] and the formationenthalpies of the CeI3 Ce2I6 and Ce3I9 molecules obtainedin this work (see above) were used as referencesThe compar-ison of our results with the data obtained by photoelectronspectroscopy [30] computation [31] and assessment [32]shows that all data are in agreement within the given errorssee Table 8

Analysis of the ion-molecular reaction enthalpies con-firmed the weakness of the first cerium iodine bond incomparison with the other two Probably it explains thelower enthalpy of the formation of CeI2

+ (467 plusmn 10 kJsdotmolminus1)compared to CeI3

+ (497 plusmn 10 kJsdotmolminus1)

The formation enthalpy of gaseous CeI3 (minus371 plusmn9 kJsdotmolminus1) obtained from the vapor pressure measurementis in a good agreement with those calculated from theappearance energies (minus376 plusmn 50 kJsdotmolminus1) and with the value(minus381 kJsdotmolminus1) assessed by Sapegin et al [33] (Table 9)The coincidence of the formation enthalpy values of CeI3gas determined from the thermodynamic and thresholdapproaches points out a negligible contribution from theexcitation and kinetic energy of the fragments The atom-ization energy derived from Δ f119867∘(CeI3 29815 K) = minus371 plusmn9 kJsdotmolminus1 was found to be 1109 plusmn 10 kJsdotmolminus1 It yields theaverage bond strength equal to 370 plusmn 10 kJsdotmolminus1

34 Electron Work Function The mass spectrometricapproach for the work function determination is basedon the use of thermochemical cycles including desorptionenthalpies of ions and sublimation enthalpies of moleculesas described elsewhere [34] The desorption enthalpy of theCeI4minus ions Δ des119867∘(851 K) = 350 plusmn 8 kJsdotmolminus1 and the Ce2I7

minus

ions Δ des119867∘(902K) = 430 plusmn 18 kJsdotmolminus1 were obtainedfrom the temperature dependence of their ion currentssee Figure 7 The electron work function was calculated inaccordance with the following expressions

120593e = minus14119863 (CeI3) +54 sdot Δ s119867∘ (CeI3) + EA (I)

+ Δ diss119867∘ (CeI4minus) + Δ des119867∘ (CeI4minus) (5)


+ Δ diss119867∘ (Ce2I7minus) + Δ des119867∘ (Ce2I7minus) (6)

where EA(I) is the electron affinity of iodine [22]D(CeI3) is the dissociation enthalpy of the CeI3 moleculeΔ dissH∘(CeI4minus) is the enthalpy of the CeI4

minus = Iminus + CeI3reaction (Table 6) and Δ dissH∘(Ce2I7minus) is the enthalpy of theCe2I7minus = Iminus + 2CeI3 reaction

The 120593e values equal to 33 plusmn 03 eV and 35 plusmn 05 eV wereobtained from (5) and (6) respectivelyThey turned out to beclose to 120593e(LaI3) = 35 plusmn 03 eV [14]

4 Conclusions

New experimental data on the saturated vapor compositionof CeI3 have been obtained by a Knudsen effusion massspectrometer The monomer CeI3 dimer Ce2I6 and trimerCe3I9 molecules as well as the [I(CeI3)n]

minus ions (119899 =0ndash2)have been observed in the temperature range of 747ndash994KThe Ce3I9 molecules and the Ce2I7

minus ions were detected forthe first timeThe sublimation enthalpies of themonomer andoligomer molecules were calculated by the second and thirdlaws of thermodynamics Critical analysis of all available dataallowed us to recommend the following enthalpies of sub-limation Δ s119867∘(29815 K) in kJsdotmolminus1 298 plusmn 9 (monomer)415 plusmn 30 (dimer) and 423 plusmn 50 (trimer) and to calculate theformation enthalpies Δ f119867∘(29815 K) in kJsdotmolminus1 minus371 plusmn 9(CeI3) minus924 plusmn 25 (Ce2I6) minus1585 plusmn 50 (Ce3I9) minus857 plusmn 19


Table 6 Enthalpies (kJsdotmolminus1) of reactions (3) and (4)

ΔT K T K N1 II law2 III law3 RefΔ r119867∘(T) Δ r119867∘(29815 K) Δ r119867∘(29815 K)CeI3g + PrI4

minusg = CeI4

minusg + PrI3g

806ndash976 897 17 0 plusmn 3 1 plusmn 3 1 plusmn 5 This workCe2I7

minusg = CeI4

minusg + CeI3crl

842ndash960 896 12 minus99 plusmn 5 minus113 plusmn 6 minus75 plusmn 40 This work1

Number of measurements2The original errors are given for the literature data the standard deviations for this work3The uncertainties are mainly determined by those in thermodynamic functions

Table 7 Ion-molecular reactions (kJsdotmolminus1)

Reaction This work [1] [3] [5] [30] [31]CeI+g = Ce+g + Ig 391 plusmn 10 396 plusmn 50 347 plusmn 50 393CeI2+g = CeI+g + Ig 323 plusmn 10 376 plusmn 50 347 plusmn 50

CeI3+g = CeI2

+g + Ig 66 plusmn 10 10 plusmn 50 48 plusmn 50 39 62 plusmn 50

CeI3g + Ce2I5+g = Ce+g + 2Ig + Ce2I6g 750 plusmn 10


Table 8 Ion formation enthalpies (kJsdotmolminus1)

Ion This work [1] [3] [32] [31]CeI+ 673 plusmn 10 669 plusmn 50 717 760 671CeI2+ 467 plusmn 10 399 plusmn 50 476

CeI3+ 497 plusmn 10 496 plusmn 50 535

Ce2I5+ minus131 plusmn 10


Table 9 Formation enthalpies of CeI3g(kJsdotmolminus1)

This workfrom IEC

This workfrom Δ s119867∘ [1] [9] [33]

gtminus376 plusmn 50 minus371 plusmn 9 minus436 plusmn 50 minus349 minus381

(CeI4minus) and minus1451plusmn50 (Ce2I7minus)The electron work function

for cerium triiodide (33 plusmn 03 eV) has also been evaluated

Appendix

A Description of the Used ThermodynamicFunctions of Molecules and Ions

A1 1198621198901198683 119888119903119897 The thermodynamic functions of CeI3 in thesolid and liquid state were taken from [22]

A2 1198621198901198683 119892 For the first time the thermodynamic functionsof monomer molecules CeI3 in the state of an ideal gaswere evaluated by Myers and Graves [35] in the rigidrotator-harmonic oscillator (RRHO) approximation thesewere included in the handbooks by Pankratz [36] and Barin[37] Later the assessment of the functions was made byOsina et al [38] they can be found in the IVTANTHERMOdatabase [22] Recently Solomonik et al [39] performed

ln(I

jmiddotT

05)

CeI4minus

Ce2I7minus

130 135115 120 125105 110100

1000T (Kminus1)

minus24

minus22

minus20

minus18

minus16

minus14

minus12

minus10

Figure 7 Temperature dependencies of CeI4minus and Ce2I7

minus ioncurrents

quantum-chemical calculations for CeI3g at a multireferenceconfiguration interaction MRCISD+Q level of theory takinginto account relativistic effects a significant spin-orbit cou-pling effect on the molecular properties was revealed

The data used in this work are based on those from [22]taking into account the low lying electronic states computedin [39]

A3 11986211989021198686119892 The thermodynamic functions of dimer mole-cules were calculated in the RRHO approximation usingthe molecular constants (symmetry 1198632h) from [40] Theelectronic contribution was taken as doubled compared withthe monomers in accordance with [41]


Table 10 Coefficients of polynomial (A4)

119879K minus119886 10minus1 119887 102 ndashc 119889 10minus3 minus119890 10minus3 119891 10minus4

CeI3crl0ndash1033 4708 2326 3838 2391 8699 1760

1033ndash1500 1069 2603 1690 1830 3165 0289CeI3 0ndash1500 1100 1489 4011 3480 1277 2158CeI4minus 0ndash1500 1229 1780 4748 4156 1536 2604

Ce2I6 0ndash1500 1779 2760 7349 6477 2388 4043Ce2I7

minus 0ndash1500 2752 1659 2047 4390 9010 0966Ce3I9 800ndash1500 9921 4418 1946 2251 1601 1060Theerrors in the functions ofGibbs energy estimated in thiswork are assumed to be equal toplusmn5 (CeI3)plusmn25 (Ce2I6)plusmn40 (Ce2I7minus) andplusmn50 (Ce3I9) Jmolminus1 Kminus1

A4 11986211989031198689 119892 The thermodynamic functions of trimers wereassessed by the additive approach with an empiric correctionbased on the functions of the monomer and oligomermolecules of LuCl3 [42] using the following expressions

TDFLa3I9 = 120573119879 sdot (TDFLaI3 + TDFLa2I6)

120573119879 =TDFLu3Cl9

TDFLuCl3 + TDFLu2Cl6

(A1)

where TDF means the thermodynamic functions B∘(T) orH∘(T) minus H∘(0)

A5 1198621198901198684minus119892 The thermodynamic functions of the CeI4minus

ions were computed in the RRHO approximation assuminga coincidence of the functions for CeI4

minus and CeI4 based onthe molecular constants taken from [43] and the electronicstates from [39]

A6 11986211989021198687minus119892 The thermodynamic functions of Ce2I7minus ions

were evaluated by a comparativemethod on the basis of thosefor LnI3 LnI4

minus (Ln = La Ce) [22 44] Ce2I6 [40] and La2I7minus

[14] using the following relation

TDF (Ce2I7minus) = 1205731015840119879 sdot TDF (Ce2I6) (A2)

where

1205731015840119879 =TDF (CeI4minus) TDF (CeI3)TDF (LaI4minus) TDF (LaI3) sdot

TDF (La2I7minus)TDF (La2I6)

(A3)

The thermodynamic functions used in this work wereapproximated by the polynomial

B∘ (T) = 119886 ln119909 + 119887119909minus2 + 119888119909minus1 + 119889119909 + 1198901199092 + 1198911199093

(119909 = 1198791000)

(A4)

The coefficients of (A4) are listed in Table 10

Competing Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work was supported by the Ministry of Education andScience of the Russian Federation (Project no 413852014K)

References

[1] C Hirayama and P M Castle ldquoMass spectra of rare earthtriiodidesrdquo Journal of Physical Chemistry vol 77 no 26 pp3110ndash3114 1973

[2] C Hirayama J F Rome and F E Camp ldquoVapor pressures andthermodynamic properties of lanthanide triiodidesrdquo Journal ofChemical amp Engineering Data vol 20 no 1 pp 1ndash6 1975

[3] P J Chantry ldquoPositive ion appearance potentials measured inCeI3rdquoThe Journal of Chemical Physics vol 65 no 11 pp 4421ndash4425 1976

[4] P J Chantry ldquoNegative ion formation in cerium triiodiderdquoTheJournal of Chemical Physics vol 65 no 11 pp 4412ndash4420 1976

[5] C W Struck and A E Feuersanger ldquoKnudsen cell mea-surements of CeI3(s) sublimation enthalpyrdquo High TemperatureScience vol 31 pp 127ndash145 1991

[6] M Ohnesorge Untersuchungen zur HochtemperaturchemiequecksilberfreierMetallhalogenid-Entladungslampenmit keram-ischem Brenner [PhD thesis] Forschungszentrum JulichJulich Germany 2005

[7] A R Villani B Brunetti and V Piacente ldquoVapor pressure andenthalpies of vaporization of cerium trichloride tribromideand triiodiderdquo Journal of Chemical and Engineering Data vol45 no 5 pp 823ndash828 2000

[8] C S Liu and R J Zoilweg ldquoComplex molecules in cesium-rareearth iodide vaporsrdquo The Journal of Chemical Physics vol 60pp 2400ndash2413 1970

[9] J J Curry E G EstupinanW P Lapatovich et al ldquoStudy of CeI3evaporation in the presence of group 13 metal-iodidesrdquo Journalof Applied Physics vol 115 no 3 Article ID 034509 2014

[10] D N Sergeev M F Butman V B Motalov L S Kudinand K W Kramer ldquoKnudsen effusion mass spectrometricdetermination of the complex vapor composition of samariumeuropium and ytterbium bromidesrdquo Rapid Communications inMass Spectrometry vol 27 no 15 pp 1715ndash1722 2013

[11] D N Sergeev A M Dunaev M F Butman D A Ivanov L SKudin and K W Kramer ldquoEnergy characteristics of moleculesand ions of ytterbium iodidesrdquo International Journal of MassSpectrometry vol 374 pp 1ndash3 2014

[12] L S Kudin D E Vorobrsquoev and A E Grishin ldquoThe thermo-chemical characteristics of the LnClminus4 and Ln2Cl

minus7 negative ionsrdquo

Russian Journal of Physical Chemistry A vol 81 no 2 pp 147ndash158 2007


[13] V B Motalov D E Vorobiev L S Kudin and TMarkus ldquoMassspectrometric investigation of neutral and charged constituentsin saturated vapor over PrI3rdquo Journal of Alloys and Compoundsvol 473 no 1-2 pp 36ndash42 2009

[14] A M Dunaev L S Kudin V B Motalov D A Ivanov MF Butman and K W Kramer ldquoMass spectrometric studyof molecular and ionic sublimation of lanthanum triiodiderdquoThermochimica Acta vol 622 pp 82ndash87 2015

[15] D N Sergeev Energy characteristics of molecules and ions oflanthanide bromide (Sm Eu Yb) studied by high temperaturemass spectrometry [PhD thesis] 2011

[16] A M Dunaev A S Kryuchkov L S Kudin and M F ButmanldquoAutomatic complex for high temperature investigation on basisof mass spectrometer MI1201rdquo Izvestiya Vysshikh UchebnykhZavedeniy Seriya ldquoKhimiya I Khimicheskaya Tekhnologiyardquo vol54 pp 73ndash77 2011 (Russian)

[17] D N Sergeev A M Dunaev D A Ivanov Y A Golovkinaand G I Gusev ldquoAutomatization of mass spectrometer for theobtaining of ionization efficiency functionsrdquo Pribory i TekhnikaEksperimenta vol 1 pp 139ndash140 2014 (Russian)

[18] A M Dunaev V B Motalov and L S Kudin ldquoHigh tempera-ture mass spectrometric method for the determination of workfunction of the ionic crystals triiodide of lanthanum ceriumand praseodymiumrdquo Russian Chemical Journal vol 59 pp 85ndash92 2015

[19] K Kimura S Katsumata Y Achiba T Yamazaki and SIwata ldquoIonization energies Ab initio assignments and valenceelectronic structure for 200 moleculesrdquo in Handbook of HeIPhotoelectron Spectra of Fundamental Organic Compounds p268 Japan Scientific Societies Press Tokyo Japan 1981

[20] D N Sergeev M F Butman V B Motalov L S Kudinand K W Kramer ldquoExtrapolated difference technique for thedetermination of atomization energies of Sm Eu and Ybbromidesrdquo International Journal of Mass Spectrometry vol 348pp 23ndash28 2013

[21] D R Lide Ed CRC Handbook of Chemistry and Physics CRCPress Boca Raton Fla USA 90th edition 2009

[22] L V Gurvich V S Iorish I V Veitz et al Eds A Thermody-namicDatabase of Individual Substances and Software System forthe Personal Computer IVTANTERMO forWindows GlushkoThermocenter of RAS Version 30 2000

[23] S Yagi and T Nagata ldquoAbsolute total and partial cross sectionsfor ionization of free lanthanide atoms by electron impactrdquoJournal of the Physical Society of Japan vol 70 no 9 pp 2559ndash2567 2001

[24] T R Hayes R C Wetzel and R S Freund ldquoAbsolute electron-impact-ionization cross-section measurements of the halogenatomsrdquo Physical Review A vol 35 no 2 pp 578ndash584 1987

[25] K Hilpert ldquoHigh temperature mass spectrometry in materialsresearchrdquo Rapid Communications in Mass Spectrometry vol 5no 4 pp 175ndash187 1991

[26] J Drowart C Chatillon J Hastie and D Bonnell ldquoHigh-temperature mass spectrometry instrumental techniques ion-ization cross-sections pressure measurements and thermo-dynamic data (IUPAC Technical Report)rdquo Pure and AppliedChemistry vol 77 no 4 pp 683ndash737 2005

[27] R C FeberHeats of Dissociation of Gaseous Halides TID-4500Los Alamos Scientific Laboratory 40th edition 1965

[28] C W Struck and J A Baglio ldquoEstimates for the enthalpiesof formation of rare-earth solid and gaseous trihalidesrdquo HighTemperature Science vol 31 pp 209ndash237 1992

[29] R J M Konings and A Kovacs ldquoThermodynamic propertiesof the lanthanide (III) halidesrdquo in Handbook on the Physics andChemistry of Rare Earths K Gschneidner Jr J-C G BunzliandV Pecharsky Eds vol 33 pp 147ndash247 Elsevier Science BV2003

[30] B Ruscic G L Goodman and J Berkowitz ldquoPhotoelectronspectra of the lanthanide trihalides and their interpretationrdquoThe Journal of Chemical Physics vol 78 no 9 pp 5443ndash54671983

[31] L A Kaledin M C Heaven and RW Field ldquoThermochemicalproperties (D∘0 and IP) of the lanthanide monohalidesrdquo Journalof Molecular Spectroscopy vol 193 no 2 pp 285ndash292 1999

[32] SAMucklejohn ldquoMolecular constants and standard enthalpiesof formation for the lanthanide monohalide gaseous cationsLnX+ X = F Cl Br Irdquo Journal of Light and Visual Environmentvol 37 no 2-3 pp 78ndash88 2013

[33] A M Sapegin A V Baluev and O P Charkin ldquoFormationenthalpies and atomization energies of gaseous lanthanidehalidesrdquoRussian Journal of Inorganic Chemistry vol 32 pp 318ndash321 1987 (Russian)

[34] L S Kudin M F Butman D N Sergeev V B Motalov and KW Kramer ldquoDetermination of the work function for europiumdibromide by knudsen effusion mass spectrometryrdquo Journal ofChemical amp Engineering Data vol 57 no 2 pp 436ndash438 2012

[35] C E Myers and D T Graves ldquoThermodynamic propertiesof lanthanide trihalide moleculesrdquo Journal of Chemical andEngineering Data vol 22 no 4 pp 436ndash439 1977

[36] L B Pankratz ldquoThermodynamic properties of halidesrdquo UnitedStates Bureau of Mines Bulletin 674 1984

[37] I Barin Thermochemical Data of Pure Substances John Wileyamp Sons 3rd edition 1995ndash1999

[38] E L Osina V S Yungman and L N Gorokhov ldquoThermody-namic properties of lanthanide triiodidemoleculesrdquo Issledovanov Rossii vol 1ndash4 pp 124ndash132 2000 (Russian)

[39] V G Solomonik A N Smirnov O A Vasiliev E V Starostinand I S Navarkin ldquoNonemprirical study on the electronicstructure of cerium praseodymium and ytterbium trihalidemoleculesrdquo Izvestiya Vysshikh Uchebnykh Zavedeniy SeriyaldquoKhimiya IKhimicheskayaTekhnologiyardquo vol 57 pp 26ndash27 2014(Russian)

[40] A Kovacs ldquoMolecular vibrations of rare earth trihalide dimersM2X6 (M=CeDy X=Br I)rdquo Journal ofMolecular Structure vol482-483 pp 403ndash407 1999

[41] L N Gorokhov G A Bergman E L Osina and V S Yung-man ldquoHigh temperature materials chemistryrdquo in Proceedingsof the 10th International IUPAC Conference K Hilpert F WFroben and L Singheiser Eds pp 103ndash106 Forschungszen-trum Juelich Germany April 2000

[42] A M Pogrebnoi L S Kudin A Yu Kuznetsov and MF Butman ldquoMolecular and ionic clusters in saturated vaporover lutetium trichloriderdquo Rapid Communications in MassSpectrometry vol 11 no 14 pp 1536ndash1546 1997

[43] V G Solomonik A Y Yachmenev and A N Smirnov ldquoStruc-ture force fields and vibrational spectra of cerium tetrahalidesrdquoJournal of Structural Chemistry vol 49 no 4 pp 613ndash620 2008

[44] V G Solomonik A N Smirnov andM A Mileyev ldquoStructurevibrational spectra and energetic stability of LnXminus4 ions (Ln=LaLu X=F Cl Br I)rdquo Russian Journal of Coordination Chemistryvol 31 no 3 pp 203ndash212 2005

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy


Carbohydrate Chemistry

International Journal of


Journal of

Chemistry


Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of


Chromatography Research International


Applied ChemistryJournal of



Theoretical ChemistryJournal of


Journal of

Spectroscopy

Analytical ChemistryInternational Journal of


Journal of


Quantum Chemistry


Organic Chemistry International

ElectrochemistryInternational Journal of



CatalystsJournal of


1

2

4

5

31067

8

9 11I

II

Udr

Figure 1 Scheme of the mass spectrometer (taken from [15]) ImdashEImode IImdashTE mode The details are given in text

The vapor species effusing from the cell form amolecularbeam which reaches the ionization chamber (4) and inter-sects with an electron beam of specified energy The ioniza-tion voltage 119880e is set by a computer using a programmablepower supply AKIP-1125 in the range of 0ndash150V with 10mVresolution The tungsten ribbon-type cathode (5) is directlyheated by an controllable DC source The current of thecathode was adjusted to provide a constant emission currentof 025A

The ions formed by the collision of molecular specieswith electrons are extracted from the ionization chamberfocused and accelerated by a system of electrostatic lenses(6) The electrostatic capacitor mounted after the exit slit ofthe ion source allows us to study the distribution of ionsby the vertical velocity component The accelerating voltage(3 kV) is applied to the ionization chamber (IE mode) orto the effusion cell (TE mode) The polarity of the highvoltage can be reversed with respect to the ground potentialThus both positive and negative ions can be analyzed Theions are separated according to their mass-to-charge ratioin the magnetic field of an electromagnet (7) (90∘ 200mmcurvature radius) The magnetic field strength is measuredby a Hall probe The ion current registration system (8 9)includes a secondary electron multiplier Hamamatsu R595(8) and a Picoammeter Keithley 6485 with 10 fA resolutionand 20 fA typical noise It allows measuring ion currentsdown to 10minus18 AThemovable shutter (10) operated by a com-puter (11) allows distinguishing signals caused by the effusingspecies from those of the background The special softwareldquoHTMSLabrdquo was used to control experimental parameterscollect and process the data and export the results into thedatabase Further details on the apparatus and experimentalprocedure can be found elsewhere [16ndash18]

The cerium triiodide sample was synthesized fromcerium metal (999 Metall Rare Earth Ltd) and iodine(pa sublimed Merck) The elements were sealed in anevacuated silica ampoule and slowly heated to 750∘C untilthe reaction was completed Afterwards the product wassublimed for purification in a sealed silica ampoule undervacuum at 750∘C that is slightly below the melting point ofCeI3 at 766

∘C The bright yellow CeI3 is very hygroscopicIts synthesis was performed under strictly oxygen-free andanhydrous conditions

820 840 860 880 900 920 940 960 980 1000800

T (K)

10minus3

10minus2

10minus1

100

101

102

I iI

(CeI

2+

) (

)

Ce+

CeI+CeI2

+

CeI3+

Ce2I5+

Ce3I8+

Figure 2 Temperature dependence of the mass spectra of CeI3Heating and cooling runs are marked by solid and open symbolsrespectively

3 Results and Discussion

31 Neutral Vapor Species In the IE mass spectra ofthe saturated vapor over cerium triiodide the Ce+(23)CeI+(16) CeI2+(100) CeI3+(31) Ce2I3+(002) Ce2I4+(001)Ce2I5+(22) I+(22) and Ce3I8

+(002) ions as well as thedoubly charged Ce++(05) CeI++(7) and CeI2

++ (3) ionswere registered in the temperature range of 753ndash994KThe relative ion currents are given in parentheses for thetemperature of 990K and the energy of ionizing electrons of40 eV The mass spectra were found to be constant over thewhole evaporation time see Figure 2

To determine the molecular precursors of the ions theionization efficiency curves (IEC) (Figure 3) and the temper-ature dependencies of ion currents (Figure 4) were analyzedThe ionizing electron energy in Figure 3 was corrected by thebackground signal of HI+ (119860119864 = 1038 eV [19]) Appearanceenergies (119860119864) were determined by vanishing current (VC)and linear extrapolation (LE) methods average values aregiven in Table 1 The linear part for the LE method wasdetermined as the segment between two points of inflectionon the first-order derivative of the IEC inverse function [20]The following conclusions were drawn the ions containingone atom of cerium are formed as a result of direct (CeI3

+)and dissociative (Ce+ CeI+ and CeI2

+) ionization of themonomer CeI3molecules with negligibly small contributionsfrom the fragmentation of more complex molecules theCe2I3+ Ce2I4

+ and Ce2I5+ ions were produced by the

dissociative ionization of the dimer Ce2I6 molecules and theCe3I8+ ion originated from the trimer molecule Ce3I9

Along with the abovementioned ions I+ was alsoobservedThe determined119860119864 equal to 107 plusmn 05 eV (Table 1)points out its origination from atomic iodine (ionizationenergy 119868119864(I) = 104 eV [21]) which can be attributed to thepartial decomposition of the sample with the formation of








+ + I + 2e Ce2I5+ 93 plusmn 05

Ce3I9 + e = Ce3I8+ + I + 2e Ce3I8


I i(a

rb u

nits)

915K957K

Ce+CeI+CeI2+

CeI3+

9 11 13 15 17 19 21 23 257


0

20

40

60

80

100

0

20

40

60

80

100

(a)

I i(a

rb u

nits)

Ce2I5+

Ce3I8+

HI+

242220181614121080

20

40

60

80

100

2614 2218 2016 241210


0

20

40

60

80

100

915K957K

957K

(b)



ln(I

jmiddotT

)

minus8

minus10

minus12

minus14

minus16

minus18

minus20

minus22

Ce+

CeI+CeI2

+

CeI3+

Ce2I5+

Ce3I8+

105 110 115 120 125100 130

1000T (Kminus1)




119901119895 = 119896 sdot 119868 sdot 119879120590119895 (1)






ln119901119894 = minus119860 times 103119879 + 119861 (2)





1

2

34

5

1998400

29984002998400998400 5998400

08 09 10 11 12 1307

1000T (Kminus1)

10minus7

10minus6

10minus5

10minus4

10minus3

10minus2

10minus1

100

101

102

103

pj

(Pa)

Tm = 1033K










297 [22]322 [27]280 [28]





1


ΔsH

∘ (29

815

K)

900 1000 1100 1200 1300 1400800

T (K)

1998400

2998400

5998400 2998400998400

54

3

2

1

Tm = 1033K

430

420

410

305

300

295

290











minusg + PrI3g (3)

Ce2I7minusg = CeI4


















minus









4 Conclusions







minusg = CeI4

minusg + PrI3g


minusg = CeI4

minusg + CeI3crl





CeI3+g = CeI2










This workfrom IEC

This workfrom Δ s119867∘ [1] [9] [33]




Appendix




ln(I

jmiddotT

05)

CeI4minus

Ce2I7minus

130 135115 120 125105 110100

1000T (Kminus1)

minus24

minus22

minus20

minus18

minus16

minus14

minus12

minus10


minus ioncurrents







CeI3crl0ndash1033 4708 2326 3838 2391 8699 1760


Ce2I6 0ndash1500 1779 2760 7349 6477 2388 4043Ce2I7




120573119879 =TDFLu3Cl9


(A1)










where



(A3)


B∘ (T) = 119886 ln119909 + 119887119909minus2 + 119888119909minus1 + 119889119909 + 1198901199092 + 1198911199093

(119909 = 1198791000)

(A4)


Competing Interests


Acknowledgments


References

























































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of








+ + I + 2e Ce2I5+ 93 plusmn 05

Ce3I9 + e = Ce3I8+ + I + 2e Ce3I8


I i(a

rb u

nits)

915K957K

Ce+CeI+CeI2+

CeI3+

9 11 13 15 17 19 21 23 257


0

20

40

60

80

100

0

20

40

60

80

100

(a)

I i(a

rb u

nits)

Ce2I5+

Ce3I8+

HI+

242220181614121080

20

40

60

80

100

2614 2218 2016 241210


0

20

40

60

80

100

915K957K

957K

(b)



ln(I

jmiddotT

)

minus8

minus10

minus12

minus14

minus16

minus18

minus20

minus22

Ce+

CeI+CeI2

+

CeI3+

Ce2I5+

Ce3I8+

105 110 115 120 125100 130

1000T (Kminus1)




119901119895 = 119896 sdot 119868 sdot 119879120590119895 (1)






ln119901119894 = minus119860 times 103119879 + 119861 (2)





1

2

34

5

1998400

29984002998400998400 5998400

08 09 10 11 12 1307

1000T (Kminus1)

10minus7

10minus6

10minus5

10minus4

10minus3

10minus2

10minus1

100

101

102

103

pj

(Pa)

Tm = 1033K










297 [22]322 [27]280 [28]





1


ΔsH

∘ (29

815

K)

900 1000 1100 1200 1300 1400800

T (K)

1998400

2998400

5998400 2998400998400

54

3

2

1

Tm = 1033K

430

420

410

305

300

295

290











minusg + PrI3g (3)

Ce2I7minusg = CeI4


















minus









4 Conclusions







minusg = CeI4

minusg + PrI3g


minusg = CeI4

minusg + CeI3crl





CeI3+g = CeI2










This workfrom IEC

This workfrom Δ s119867∘ [1] [9] [33]




Appendix




ln(I

jmiddotT

05)

CeI4minus

Ce2I7minus

130 135115 120 125105 110100

1000T (Kminus1)

minus24

minus22

minus20

minus18

minus16

minus14

minus12

minus10


minus ioncurrents







CeI3crl0ndash1033 4708 2326 3838 2391 8699 1760


Ce2I6 0ndash1500 1779 2760 7349 6477 2388 4043Ce2I7




120573119879 =TDFLu3Cl9


(A1)










where



(A3)


B∘ (T) = 119886 ln119909 + 119887119909minus2 + 119888119909minus1 + 119889119909 + 1198901199092 + 1198911199093

(119909 = 1198791000)

(A4)


Competing Interests


Acknowledgments


References

























































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of





ln119901119894 = minus119860 times 103119879 + 119861 (2)





1

2

34

5

1998400

29984002998400998400 5998400

08 09 10 11 12 1307

1000T (Kminus1)

10minus7

10minus6

10minus5

10minus4

10minus3

10minus2

10minus1

100

101

102

103

pj

(Pa)

Tm = 1033K










297 [22]322 [27]280 [28]





1


ΔsH

∘ (29

815

K)

900 1000 1100 1200 1300 1400800

T (K)

1998400

2998400

5998400 2998400998400

54

3

2

1

Tm = 1033K

430

420

410

305

300

295

290











minusg + PrI3g (3)

Ce2I7minusg = CeI4


















minus









4 Conclusions







minusg = CeI4

minusg + PrI3g


minusg = CeI4

minusg + CeI3crl





CeI3+g = CeI2










This workfrom IEC

This workfrom Δ s119867∘ [1] [9] [33]




Appendix




ln(I

jmiddotT

05)

CeI4minus

Ce2I7minus

130 135115 120 125105 110100

1000T (Kminus1)

minus24

minus22

minus20

minus18

minus16

minus14

minus12

minus10


minus ioncurrents







CeI3crl0ndash1033 4708 2326 3838 2391 8699 1760


Ce2I6 0ndash1500 1779 2760 7349 6477 2388 4043Ce2I7




120573119879 =TDFLu3Cl9


(A1)










where



(A3)


B∘ (T) = 119886 ln119909 + 119887119909minus2 + 119888119909minus1 + 119889119909 + 1198901199092 + 1198911199093

(119909 = 1198791000)

(A4)


Competing Interests


Acknowledgments


References

























































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of






297 [22]322 [27]280 [28]





1


ΔsH

∘ (29

815

K)

900 1000 1100 1200 1300 1400800

T (K)

1998400

2998400

5998400 2998400998400

54

3

2

1

Tm = 1033K

430

420

410

305

300

295

290











minusg + PrI3g (3)

Ce2I7minusg = CeI4


















minus









4 Conclusions







minusg = CeI4

minusg + PrI3g


minusg = CeI4

minusg + CeI3crl





CeI3+g = CeI2










This workfrom IEC

This workfrom Δ s119867∘ [1] [9] [33]




Appendix




ln(I

jmiddotT

05)

CeI4minus

Ce2I7minus

130 135115 120 125105 110100

1000T (Kminus1)

minus24

minus22

minus20

minus18

minus16

minus14

minus12

minus10


minus ioncurrents







CeI3crl0ndash1033 4708 2326 3838 2391 8699 1760


Ce2I6 0ndash1500 1779 2760 7349 6477 2388 4043Ce2I7




120573119879 =TDFLu3Cl9


(A1)










where



(A3)


B∘ (T) = 119886 ln119909 + 119887119909minus2 + 119888119909minus1 + 119889119909 + 1198901199092 + 1198911199093

(119909 = 1198791000)

(A4)


Competing Interests


Acknowledgments


References

























































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of

















minus









4 Conclusions







minusg = CeI4

minusg + PrI3g


minusg = CeI4

minusg + CeI3crl





CeI3+g = CeI2










This workfrom IEC

This workfrom Δ s119867∘ [1] [9] [33]




Appendix




ln(I

jmiddotT

05)

CeI4minus

Ce2I7minus

130 135115 120 125105 110100

1000T (Kminus1)

minus24

minus22

minus20

minus18

minus16

minus14

minus12

minus10


minus ioncurrents







CeI3crl0ndash1033 4708 2326 3838 2391 8699 1760


Ce2I6 0ndash1500 1779 2760 7349 6477 2388 4043Ce2I7




120573119879 =TDFLu3Cl9


(A1)










where



(A3)


B∘ (T) = 119886 ln119909 + 119887119909minus2 + 119888119909minus1 + 119889119909 + 1198901199092 + 1198911199093

(119909 = 1198791000)

(A4)


Competing Interests


Acknowledgments


References

























































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of




minusg = CeI4

minusg + PrI3g


minusg = CeI4

minusg + CeI3crl





CeI3+g = CeI2










This workfrom IEC

This workfrom Δ s119867∘ [1] [9] [33]




Appendix




ln(I

jmiddotT

05)

CeI4minus

Ce2I7minus

130 135115 120 125105 110100

1000T (Kminus1)

minus24

minus22

minus20

minus18

minus16

minus14

minus12

minus10


minus ioncurrents







CeI3crl0ndash1033 4708 2326 3838 2391 8699 1760


Ce2I6 0ndash1500 1779 2760 7349 6477 2388 4043Ce2I7




120573119879 =TDFLu3Cl9


(A1)










where



(A3)


B∘ (T) = 119886 ln119909 + 119887119909minus2 + 119888119909minus1 + 119889119909 + 1198901199092 + 1198911199093

(119909 = 1198791000)

(A4)


Competing Interests


Acknowledgments


References

























































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of




CeI3crl0ndash1033 4708 2326 3838 2391 8699 1760


Ce2I6 0ndash1500 1779 2760 7349 6477 2388 4043Ce2I7




120573119879 =TDFLu3Cl9


(A1)










where



(A3)


B∘ (T) = 119886 ln119909 + 119887119909minus2 + 119888119909minus1 + 119889119909 + 1198901199092 + 1198911199093

(119909 = 1198791000)

(A4)


Competing Interests


Acknowledgments


References

























































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of











































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of










Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of

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Research Article Study of Molecular and Ionic Vapor Composition …downloads.hindawi.com/journals/jspec/2016/2368131.pdf · Study of Molecular and Ionic Vapor Composition over CeI