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How to Get the Binding Energy by Mass Spectrometry. Speaker: Tianyu Sun Advisor: Prof. Wu Dr. Zhang. P reface. Empedocles ( 490–430 BC, Greek) said: “ Love will bring about the element hate will separate the element ”. love. hate. P reface. Binding energy. - PowerPoint PPT Presentation
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深圳研究生院SHENZHEN GRADUATE SCHOOL
How to Get the Binding Energy by Mass Spectrometry
Speaker: Tianyu Sun
Advisor: Prof. Wu Dr. Zhang
2
Empedocles (490–430 BC, Greek) said:“ Love will bring about the element hate will separate the element”
Preface
love
hate
3
Preface
Binding energy
我做了这么久计算和有机机理,对化学理解就是“能量和电子的分配”
4
Preface
O
HO
OHOPd
O
O
NO
OHOPd
O
O
NO
AcOH substrate OHOPd
O
O
NO
substrate
in organometallic reactions, the key reactive intermediates are coordinatively unsaturated transition metal–ligand complexes that have an open site by loss of one or more ligands.
These unsaturated intermediates are good catalysts because they are reactive
But transient and difficult to study
such information would enable predictions of the feasibility of desired reaction
5
PrefaceThe methods to get the binding energy:
photoelectron spectroscopy
Time resolved infrared spectroscopy
ion beam studies of endothermic reactions
flowing afterglow
kinetic energy release distributions
Energy resolved collision induced dissociation
1aser-powered homogeneous pyrolysis
guided ion beam mass spectrometry
Quantum chemistry……
6
Outline Kinetic theory of gases
maxwell speed distributionClassic Collision Theory
cross section Determination of cross section by MS
threshold energy (阈能 ) Determination of Binding Energy
Doppler broadeningthe relative velocity distributionthe models of cross section
Equipmention beam energyguided ion beampressure
Future work summary
7
kinetic theory of gasesIdeal gas
maxwell velocity distribution
vdekTmnvdvf
NdN kT
mv 3223
32
)2()(
v
v+dv
Often we more care about speed, no velocity!
maxwell speed distribution
dvekTmnv
dvvfvdvvFNdN
kTmv22
32
2
2
)2(4
)(4)(
vdvf 3)( the number of particles with velocity between and + in per unit volumev v vd
8
maxwell speed distribution
dvekTmnvdvvF
NdN kT
mv22
32
2
)2(4)(
kinetic theory of gases
9
Classic Collision Theory
b
θ
A
B
ur
dAB
ur is the relative speed between particle A and particle B
dAB=rA+rB
2
21
rr u μ is the reduced mass ba
ba
mmmm
cAB
rrrr dbuu )1()sin1(2
1)cos(21
2
2222
εc is the threshold energy, if ε’r > εc, the reaction can happen!
10
Classic Collision Theory
)1(22
r
cABr db
cAB
rr d
b )1( 2
2
b
θ
A
B
ur
dAB
cAB
rr db )1( 2
2
br :reaction radius
)1(22
r
cABrr db
define σr the reaction cross section
quantum states
11
Determination of cross section by MSUsing mass spectrometer can get the Ion intensities for reaction
+++++I0
+ + + + Massspectrometer
Ip(ArH+)
+ + +IR(Ar+)
gas cell
At a low pressureJust single collison
P. B. Armentrout ,J. Chern. Phys., 83, 166 (1985)
12
Determination of cross section by MSat low pressure, just single collison
first order reaction
)exp()(
ln)(
)(
)(
)()(
1
1
0 10
1
1
1
tkaxa
tkxa
a
dtkxa
dx
dtkxa
dx
xakdtdx
xakdt
xad
tx
)exp()( nlIII totPRR
l is the effective path lengthn is the density
nl tσtot k1
13
Taylor expansion
IR≈(IR+ΣIP)(1- σtotnl)
Determination of cross section by MS
)exp()( nlIII totPRR
At low pressure
PR III 0
)/( pPtotp II
Individual product cross sections σp
nlII pp 0/ σp→ threshold energy
14
Determination of Binding Energy
++++ ++++
gas cell gas cell
target molecule: stationary target molecule: Doppler broadening
high ion beam energy low ion beam energy
high low
the σ is a function of Elab
the relative velocity is important
Elab»kT Elab<kT
15
Determination of Binding Energy
center of mass(cm)
V0
mmonoenergetic ion beam
M
v
target molecule
Vcm
m
M
V
V0(cm)
v(cm)
VmM
mcmv
VmM
McmV
VcmvcmV
)(
)(
)()(
0
0
2
)(2 VMmMmE
if v=0
labEMm
MmVMm
ME )(21
)(200
E0 is nominal center of mass energy
how to get the relative velocity?
16
Determination of Binding Energythe thermal distribution of v gives rise to a distribution of V
V0
vV
V0-V
V0+V
dV0
dv
velocity space ρ: the volume of the red area to the volume of the whole shell of radius v
θ
vVVdV
dvvVdVdvVv
02
0 24)sin(sin2
G. J. SCHULZT, PHYS.REV., 32, 110 (1954).
17
Determination of Binding Energy
the ratio of particles with relative velocity between V and V+dV
VV
VVdvvF
NdN 0
0)(
vVVdV
02
dvekTmnvdvvF kT
mv22
32
2
)2(4)(
VV
VVkTmv
dvekTmnv
vVVdV
NdN 0
0
2
223
2
0)2(42
18
Determination of Binding Energy
VV
VVkTmv
dvekTmnv
vVVdV
NdN 0
0
2
223
2
0)2(42
integration gives:
dVVVkTMVV
kTM
VV
kTM
NdN )])(2exp())(2[exp()2(
20
20
0
21
dEEEfNdN ),( 0
It is convenient to introduce the parameters
mMm
kTE
kTE
00
dNdN )])(exp())([exp()4
1( 221
021
221
021
21
0
19
Determination of Binding Energy
dEEEEfEEEapp )(),()/()( 0
21
0 00
σapp(E0) is the apperent reaction cross section
dEEEfNdN ),( 0
convolution of σ(E)
The (E/Eo)1/2 factor accounts for the difference in the residence times of ions in the interaction region at different ion energies.
++++
target molecule: Doppler broadening
lowElab<kT
gas cell
low ion beam energy
P. B. Armentrout ,J. Chern. Phys., 83, 166 (1985)
relative kinetic energy disturbution
20
Determination of Binding Energy
σ(E) is a function of threshold energy
)1(22
r
cABrr db
classic quantum
Step-Function Cross Section
Linear Cross Section
Inclined Step-Function Cross Section
Exponential Cross Section
the models of σ(E):
21
Determination of Binding Energy
Peter Chen, J. Phys. Chem. A, Vol. 111, No. 30, 2007
dEEEEfEEEapp )(),()/()( 0
21
0 00
labEMm
MmVMm
ME )(21
)(200
E0 is nominal center of mass energy
σ0 is a scaling factorE the relative kinetic energyn an adjustable parameterquantum states(vibrational, rotational, and electronic)with energies Ei and populations gi
The σ0, n, and E0 parameters are fitted by least squares analysis
CRUNCH L-CID
22
Determination of Binding Energy
dEEEEfEEEapp )(),()/()( 0
21
0 00
threshold energy
there are three types of reaction used to determine the binding energy of M+–L
23
Equipment
The energy spread of Elab need to be very narrowBecause the cross section is a funtion of energy
++++
gas cell
Elab
The narrower , the better
dEEEEfEEEapp )(),()/()( 0
21
0 00
momentum analyzer serves to narrow the energy spread
P. B. Armentrout ,J. Chern. Phys., 83, 166 (1985)
V0
monoenergetic ion beam
24
Equipment
So we need to trap the ionic products regardless of scattering angle.
+
+
detector
The scattering can reduce the signal
+
+
detector+
+
25
EquipmentUsing octopole to trap the ion
Travelling wave (T-wave) ion guide
adjacent rings have opposite phases of radio frequence voltage
the effective potential
26
EquipmentAt a low pressure, Just single collison
Pressures 6.5e-6 Pa can be used for cross section measurements.
2.25e-2 Pa
++++
gas cell
27
Future research
Yu, J.-Q. Angew. Chem. Int. Ed. 2008, 47, 4882.)
COOH
NHBoc
COOH
NHBoc
COOH
NHBoc
COOH
NHBoc
COOH
NHBoc
COOH
NHBoc
ClCOOH
NHBoc
COOH
NHBoc
OCOOH
NHBoc
H
COOH
NHMe
COOH
NH2
CO2Me
NHBoc
COOH
N(Boc)2
COOH
BocN
COOH
NHPiv
COOH
NHFormyl
COOH
NHAc
COOH
HN
OMe
O
COOH
HN
O
O
CCl3
COOH
HN
O-(+)-Menthyl
O
COOH
HN
O-(-)-Menthyl
O
Ligand Yield[%] ee[%]Entry Ligand Yield[%] ee[%]Entry
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
63
60
69
85
60
66
83
47
65
n.r
n.r
90
52
70
72
80
81
83
85
88
---
---
86 0
74 7
63 6
58 7
53 6
74 80
88 79
89 85
87 85
91 87
N AA ligand
Pd(OAc)2 PdO
N
O
PGH
i-BuH
N
H Ph
Alkylation
RB(OH)2
NR
R
Pd II-Catalyzed Enantioselective Activation of C(sp2)-H and C(sp3)-H Bonds Using Monoprotected Amino Acids as Chiral Ligands
28
Summary
dEEEEfEEEapp )(),()/()( 0
21
0 00
threshold energy
Determination of Binding Energy
Equipment
29
Thanks for your attention