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ROTATIONAL SPECTROSCOPY OF CO SOLVATED ROTATIONAL SPECTROSCOPY OF CO SOLVATED WITH WITH PARAPARA-H-H22 MOLECULES MOLECULES
Paul Raston and Wolfgang JägerDepartment of Chemistry, University of Alberta, Edmonton, AB Canada
OSU 2009
S. Baroni and S. Moroni, ChemPhysChem 6, 1884 (2005)
parapara-H-H22 clusters clusters
*P. Sindzingre, D. M. Ceperley, M. L. Klein, Phys. Rev. Lett. 67, 1871 (1991)
Low temperature (<2 K) para-H2 clusters are liquid like
Small pH2 clusters predicted to be superfluid below ~2 K.*
Rotational temperature of seeded clusters <1 K
In this study NpH2<8
Sample & conditionsSample & conditions
Typically used 0.05-1% CO + 1-10% pH2 in Helium up to 150 bar
Nozzle cooled down to -40°C
Normal H2 (75% ortho- + 25% para-) converted to >97% pH2 in catalytic converter held at <20K for several hours
I. F. Silvera, Rev. Mod. Phys. 52, 393 (1980)
FTMWFTMW spectrometerspectrometer
Pulsed molecular beam polarized with MW’s: Coherent emission is recorded
Good up to ~27 GHz, below which 6 (pH2)N-CO end-over-end transitions should lie
paraparaHH22-CO dimer-CO dimer
A.V. Potapov, L.A. Surin, V.A. Panfilov, B.S. Dumesh, T.F. Giesen, S. Schlemmer, P.L. Raston and W. Jäger, in preparation.
We know 101-000 transition frequency for N=1 to within ±50 kHz
0
5
10
15
20
25
C O H para 2
J j l, , C O
00 010 1
20 2
30 3
50 5
60 6
40 4
11 0211
31 2
41 3
51 4
61 5
111
21 2
31 3
41 4
51 5
011
11 2
21 3
31 4
41 5
6 61
K e=0( )
K e=1( )
K= (f)1
K e=0( ), =1b ,C O
c
a
b
O
C
H 2
N0 1 2 3 4 5 6 7 8 9
Fre
quen
cy /
MH
z
0
10000
20000
30000
40000
50000
TheoryIRMW
ppHH22-CO-CO
Previous IR studyPrevious IR study
S. Moroni, M. Botti, S. De Palo, A. R. W. McKellar, J. Chem. Phys. 122, 094314 (2005)
R1(0) line observed for NpH2<18
Not able to fully separate rotational and vibrational contributions to line position
N
0 1 2 3 4 5 6 7 8 9
Wav
enum
ber
/ cm
-1
2142.4
2142.6
2142.8
2143.0
2143.2
2143.4
2143.6
2143.8
2144.0
2144.2
2144.4
N0 1 2 3 4 5 6 7 8 9
Fre
quen
cy /
MH
z
0
10000
20000
30000
40000
50000
TheoryIRMW
MW predictions from:MW predictions from:
Assumption that the vibrational shift scales linearly with N
S. Moroni, M. Botti, S. De Palo, A. R. W. McKellar, J. Chem. Phys. 122, 094314 (2005)
MW predictions from:MW predictions from:
Assumption that the vibrational shift scales linearly with N
Reptation Monte Carlo simulations
S. Moroni, M. Botti, S. De Palo, A. R. W. McKellar, J. Chem. Phys. 122, 094314 (2005)
N0 1 2 3 4 5 6 7 8 9
Fre
quen
cy /
MH
z
0
10000
20000
30000
40000
50000
TheoryIRMWCol 1 vs Col 6
N0 1 2 3 4 5 6 7 8 9
Fre
quen
cy /
MH
z
0
10000
20000
30000
40000
50000
TheoryIRMWCol 1 vs Col 6
MW linesMW lines
N=2 found close to IR predicted value
N0 1 2 3 4 5 6 7 8 9
Fre
quen
cy /
MH
z
0
10000
20000
30000
40000
50000
TheoryIRMW
MW linesMW lines
N=3-6 increasingly further from IR predicted values
N0 1 2 3 4 5 6 7 8 9
Fre
quen
cy /
MH
z
0
10000
20000
30000
40000
50000
TheoryIRMWCol 1 vs Col 6
MW linesMW lines
Turnaround of rotational frequency in going from N=6 to 7
N
Wav
enum
ber
/ cm
-1
2141.8
2142.0
2142.2
2142.4
2142.6
2142.8
2143.0
2143.2
2143.4
ActualAssumed (linear shift with N)
N
0 1 2 3 4 5 6 7 8
Fre
quen
cy /
MH
z
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
Difference
Vibrational shiftVibrational shift
N
Wav
enum
ber
/ cm
-1
2141.8
2142.0
2142.2
2142.4
2142.6
2142.8
2143.0
2143.2
2143.4
ActualAssumed (linear shift with N)
N
0 1 2 3 4 5 6 7 8
Fre
quen
cy /
MH
z
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
Difference
Vibrational shiftVibrational shift
Switched IR assignment for N=6 & 7
N0 1 2 3 4 5 6 7 8 9
Fre
quen
cy /
MH
z
12000
14000
16000
18000
20000
22000
24000
12161316
((ppHH22))NN--1313CC1616O MW linesO MW lines
((ppHH22))NN--1313CO MW linesCO MW lines
N0 1 2 3 4 5 6 7 8 9
Fre
quen
cy /
MH
z
12000
14000
16000
18000
20000
22000
24000
12161316
((ppHH22))NN--1313CO MW linesCO MW lines
Number of pH2 molecules
1 2 3 4 5 6 7 8
1216
/131
6
1.00
1.01
1.02
1.03
1.04
1.05"free" CO
solid pH2
SummarySummary
1216 1316 Assignment
22200.54 22054.30 (pH2)2-CO
16455.81 16326.93 (pH2)3-CO
15107.44 14959.44 (pH2)4-CO
14633.25 14473.32 (pH2)5-CO
13243.82 13096.04 (pH2)6-CO
17723.12 17403.17 (pH2)7-CO
15834.58 15727.36 pH2-He-CO
*Tentative
OutlookOutlook
MW transitions of (pH2)N=2-7-CO (1216 and 1316) measured and assigned
Turnaround in rotational frequency observed in going from N=6 to 7
Extend frequency range of spectrometer and search for N=8 at 30-40+ GHz….
Find 1218 and 1318 lines
AcknowledgementsAcknowledgements
Jäger group
Xu group
A.R.W. McKellar
Funding: University of Alberta Natural Science and Engineering Research Council of Canada Canada Foundation for Innovation Alberta Science and Research Investments Program
PESPES
• Reptation Monte Carlo algorithm used to simulate rotational dynamics for NpH2<18
• N=incremental density distribution
C O
AssignmentAssignment
Ratio of line intensities for 2 different gas mixtures differing only in the [pH2]; The 2nd mixture contained 0.125x the [pH2] in the 1st
N
1 2 3 4 5 6 7 8
Inte
nsit
y ra
tio
e0
e1
e2
e3
e4
e5
e6
e7
Assignments mostly from concentration dependence of line intensities
Comparison with HD solvated HCNComparison with HD solvated HCN
D. T. Moore, R. E. Miller, J. Chem. Phys. 119, 4713 (2003)
/ MHz
17722.8 17723.0 17723.2 17723.4 17723.6
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