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Štefan Matejčík Comenius University Bratislava, Slovakia. Electron Impact Ionization of selected hydrocarbon molecules. Stephan Denifl Fabio Zappa Univ. Innsbruck. Coworkers. Dušan Kubala Jaroslav Kočíšek Peter Papp Pavel Mach Jan Urban. Electron impact ionisation - EII. - PowerPoint PPT Presentation
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Electron Impact Ionization of selected hydrocarbon molecules
Štefan Matejčík
Comenius UniversityBratislava,Slovakia
Coworkers
Dušan Kubala Jaroslav Kočíšek Peter Papp Pavel Mach Jan Urban
Stephan Denifl Fabio Zappa
Univ. Innsbruck
Electron impact ionisation - EII e + M → M+ + 2e
e + M → X+ + (M-X) + 2e
Appearance energies
Partial cross sections for EII
Crossed beams apparatus
low Tg
high Tg
E
σ
Electron impact ionization
Molecules studied in 2007 and 2008 Experiment
C2D6
CH3D
CD4
C3H8
C3H6D2
Theory BenHm
0 10 20 30 40 50 60 70 80 90 100 110 120 130 1400
1
2
3
10.09.2007
C
ross
se
ctio
n (
10-1
6 cm
2 )
Electron energy (eV)
Ar+ [10-16 cm2] Ne+ [10-16 cm2] Argon (nomalized) Ne (normalized)
Ar and Ne cross sections
R. Rejoub, B.G. Lindsay, R.F. Stebbings, Phys. Rev. A, 65 (2002) 042713.
Cross section EII C2D6 low temperature
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140
0
1
2
3
4
5
6
T = 100°C
C2D
4
+ (m/z=32)
C2D
6
+ (m/z=36)
C2D
3
+ (m/z=30)
C2D
5
+ (m/z=34)
C2D
2
+ (m/z=28)
C
ross
-sec
tion
[10-1
6 cm2 ]
Electron energy [eV]
Cross section EII C2D6 high temperature
0 20 40 60 80 100 120 140
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
7.0
C2D
4
+ (m/z=32)
C2D
6
+ (m/z=36)
C2D
3
+ (m/z=30)
C2D
5
+ (m/z=34)
C2D
2
+ (m/z=28)
Cro
ss-s
ect
ion
[10
-16cm
2]
Electron energy [eV]
T = 410°C
Comparison total cs C2D6
0 20 40 60 80 100 120 140
0
2
4
6
8
10
12
C
ross
se
ctio
n [1
0-16cm
2]
Electron energy [eV]
TOTALat100 TOTALat410
Comparison partial cs C2D6
0 20 40 60 80 100 120 140
0.0
0.5
1.0
1.5
2.0
cro
ss s
ect
ion
[10
-16cm
2]
Electron energy [eV]
C2D6at100 C2D6at410
(C2D
6)+/C
2D
6
Comparison partial cs C2D6
0 20 40 60 80 100 120 140
0.0
0.2
0.4
0.6
0.8
1.0
1.2
C
ross
se
ctio
n [1
0-16cm
2]
Electron energy [eV]
C2D5at100 C2D5at410
(C2D
5)+/C
2D
6
Comparison partial cs C2D6
0 20 40 60 80 100 120 140
0
1
2
3
4
5
6
7
C
ross
se
ctio
n [1
0-16cm
2]
Electron energy [eV]
C2D4at100 C2D4at410
(C2D
4)+/C
2D
6
Comparison partial cs C2D6
0 20 40 60 80 100 120 140
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
C
ross
se
ctio
n [1
0-1
6cm
2]
Electron energy [eV]
C2D3at100 C2D3at410
(C2D
3)+/C
2D
6
Comparison partial cs C2D6
0 20 40 60 80 100 120 140
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
C
ross
se
ctio
n [1
0-1
6cm
2]
Electron energy [eV]
C2D2at100 C2D2at410
(C2D
2)+/C
2D
6
Threshold cross sections C2D6
10 11 12 13 14 15 16 17 18 191E-5
1E-4
1E-3
0.01
0.1
1
C
ross
se
ctio
n [1
0-1
6cm
2]
Electron energy [eV]
IE = 11.72 eV
(C2D
6)+/C
2D
6
Threshold cross sections C2D6
10 11 12 13 14 15 16 17 18 191E-5
1E-4
1E-3
0.01
0.1
C
ross
se
ctio
n [1
0-1
6cm
2]
Electron energy [eV]
AE = 12.64 eV
(C2D
5)+/C
2D
6
Ion Mass (amu) AE (100°C) AE (420°C)
C2D6+ 36 11.72 11.48
C2D5+ 34 12.64 12.33
C2D4+ 32 12.00 11.54
C2D3+ 30 14.92 14.94
C2D2+ 28 14.95 14.42
CD+ 16 22.25 22.17
C2D5++ 17 35.71 34.12
CD2+ 18 15.69 15.66
C2+ 24 23.54
28.5423.1728.11
C2D+ 26 25.22 24.84
e + C2H6 Experiment Theory
AE [eV]293 K
Thermochemistry[eV]
G3B3AIE [eV]
C2H6+ 11.46±0.04 11.55
C2H5+ + H-
C2H5+ + H
12.06±0.0612.7±0.1
11.7212.47±0.03
12.0312.79
C2H4+ + H2 11.90±0.04 11.92±0.0006 11.93
C2H3+ + H + H2 15.02±0.1 14.47±0.46 14.83
C2H2++2H2 15.02±0.1 14.61±0.01 14.61
C2H++2H2+H
C2H++H2+3H 25.7±0.3
20.5±0.1525.1±0.15
21.6526.12
C2+ + 3H2 22.6±0.3 20.95±0.3 21.73
EII to CD4 cross sections
0 20 40 60 80 100 120 1401E-21
1E-20
1E-19
1E-18
1E-17
1E-16
Cro
ss s
ect
ion
(cm
2 )
Electron energy (eV)
Tarnovsky et al.
CD4
+
CD3
+
CD2
+
CD+
26°C
e + CD4 -->
CD4
+
CD3
+
CD2
+
CD+
C+
Tarnovsky et al. J. Phys. B: At. Mol. Opt. Phys. 29 (1996) 139
0 20 40 60 80 100 120 140
0.0
5.0x10-17
1.0x10-16
1.5x10-16
2.0x10-16
Cro
ss s
ect
ion
(cm
2)
Electron energy (eV)
CD4
+/CD4
303 K 683 K Tarnovsky et al.
CD4+/CD4
CD4+/CD4
6 8 10 12 14 16 18 20
0.0
5.0x10-18
1.0x10-17
1.5x10-17
2.0x10-17
Cro
ss s
ect
ion
(cm
2)
Electron energy (eV)
CD4
+/CD4
303 K 683 K Tarnovsky et al.
CD3+/CD4
0 20 40 60 80 100 120 140 160 180 200 220
0.0
5.0x10-17
1.0x10-16
1.5x10-16
Cro
ss s
ect
ion
(cm
2 )
CD3
+/CD4
303 K 683 K Tarnovsky et al.
Electron energy (eV)
CD2+/CD4
0 20 40 60 80 100 120 140 160 180 200 220
0.0
5.0x10-18
1.0x10-17
1.5x10-17
2.0x10-17
2.5x10-17
3.0x10-17
3.5x10-17
CD2
+/CD4
303 K 683 K Tarnovsky et al.
Cro
ss s
ect
ion
(cm
2)
Electron energy (eV)
CD+/CD4
0 20 40 60 80 100 120 140
0.0
2.0x10-18
4.0x10-18
6.0x10-18
8.0x10-18
1.0x10-17
1.2x10-17
1.4x10-17
Cro
ss s
ect
ion
(cm
2 )
CD+/CD4
303 K 683 K Tarnovsky et al.
Electron energy (eV)
Tarnovsky et al. J. Phys. B: At. Mol. Opt. Phys. 29 (1996) 139
EII to CH3D cs
0 20 40 60 80 100 120 140
10-20
10-19
10-18
10-17
10-16
Cro
ss s
ectio
n (
cm2)
E (eV)
CH3D300 CH2D300 CHDCH3m300 CDCH2 C CH3Dm683 CH2Dm683 CHDCH3m683 CDCH2m683 Cm683
EII to C3H8
0 20 40 60 80 100 120 1401E-3
0.01
0.1
1
100°C
e + C3H8 C
ross
Sec
tion
(in 1
0-16 cm
2 )
Electron energy (eV)
C2H
5
+
C2H
4
+
C3H
8
+
C2H
3
+
C2H
2
+
C3H
7
+
C3H
3
+
C3H
2
+
C3H
5
+
EII to C3H8
0 20 40 60 80 100 120 1401E-3
0.01
0.1
1
Cro
ss S
ectio
n (in
10-1
6 cm2 )
Electron Energy (in eV)
C3H
8
+
C3H
7
+
C3H
5
+
C3H
3
+
C2H
5
+
C2H
4
+
C2H
3
+
C3H
3
+
C2H
2
+
e + C3H
8
410°C
EII to C3H6D2
10.2 10.4 10.6 10.8 11.0 11.2 11.4 11.6
0
100
200
300
400 Fit amu46
Ion
yie
ld (
arb
. un
its)
Electron energy eV
10.8eV11.1eV
En
erg
y
Q
M+
M
VIE
En
erg
y
Q
M+
M
VIE
EII to C3H6D2
e + M → C3H8
AE (eV)290 K
C3H6D2
AE (eV)
(C3H8)+
v(C3H6D2)+
10.51 ± 0.0510.96 ± 0.05
10.81 ± 0.0511.13 ± 0.05
Kim-s BEB (binary encounter Bethe) theory [W. Hwang, Y.-K. Kim, M. E. Rudd, J. Chem. Phys. 104, 2956 (1996)],
HF/6-31++G(2df,2pd) orbital kinetic energies OVGF/6-31++G(2df,2pd) ionization potentials
for ionization from valence orbitals For core orbitals IP the HF values were used
(their contribution to total cross section in studied region is very small).
Ionization cross sections calculations
Ionization potential of Be5Hn clusters as a function of “n”.
5.5
6.5
7.5
8.5
9.5
10.5
11.5
12.5
Be
5H
10
B5
H8
Be
5H
6
Be
5H
4
Be
5H
3
Be
5H
2
Be
5H
1
IP [
eV]
Most stable cluster of given stechiometry.
Method:
MP4(SDTQ)/6-31++G(2df,2pd)
Geometry:
MP2/6-31++G(2df,2pd)
Total ionization cross sections for Be5Hn clusters
10 100 10000
2
4
6
8
10
12
14
16
18cr
oss
se
ctio
n [A
2]
Energy [eV]
Be5H
10
Be5H
4
Be5H
Increasing hydrogen content in mixed clusters increases IP and decrease cross section for ionization
Conclusions Measured partial cs for EII to
CH3D CD4
C2D6
C3H8
Appearance energy – C3H6D2
Calculated ionization energies Be5Hn
EII total cross sections Be5Hn
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