EII of plasma edge constituents, properties of BexHy molecules

S. Matejcik, P. Mach, J. Urban

Comenius UniversityBratislavaSlovakia

Bratislava

Overview

- Appearance energies of C2D6

- Cross section for EII to propane

- BeH and BeH2 – structure and energies

- Structure and energetics of BemHn clusters

Electron impact ionization

cross sections (total, partial) ionization energies appearance energies kinetic energy release gas temperature dependencies products of the reactions

Experimental setup

Cross section measurements

Absolute measurement of the pressure

Relative flow technique

Ar as a calibration gas

Atoms:

Wannier theory:

w(E,AE,A,d) = 0 E<AE A(E-IE)d E>AEd=1.127

Threshold behaviour of the cross sections

dEUEfAdAEEAdAEEI w ),(),,,(),,,(0

f(E,U) - EEDF

Fitting function:

23,5 24,0 24,5 25,0 25,5

0

100

200

300

400

500

He+/He

Ion

yiel

d (a

rb.

units

)

E (eV)

d=1.127±0.01

Threshold behaviour of the cross sections

CH3D

AE (eV)293 K

CD4

AE (eV)293 K

CH4

AE (eV)293 K

CH3D+ 12.75 ± 0.03 12.89 ± 0.03 12.65 ± 0.04 CH4

+

CH2D+ + H–

CH2D+ + H

13.66 ± 0.07 14.42 ± 0.05

- 14.54 ± 0.05

13.58 ± 0.1 14.34 ± 0.1

CH3+ + H–

CH3+ + H

Isotopic effect on AE

Denifl et al. IJMS 248 (2005) 29

PresentmeV

a)meV

b)meV

(CH3D)+/CH3D 100 50

(CH2D)+/CH3D 80

(CH3)+/CH3D 200

(CHD)+/CH3D 110

(CD4)+/CD4 190 170 160

(CD3)+/CD4 200 130

(CD2)+/CD4 310 90

a) F. P. Lossing, A. W. Tickner, W. A. Bryce, J. Chem. Phys. 19, 1254 (1951).b) V. H. Dibeler, M. Krauss, R. M. Reese, F. N. Harlee J. Chem. Phys. 42, 3791 (1965).

Isotopic shift

Denifl et al. IJMS 248 (2005) 29

EII of C2D6

e + C2D6 → C2D6+ + 2e

→ C2D5+ + D– + 2e

→ C2D2+ + 2D2 + e

EII to C2D6

11,0 11,5 12,0 12,5 13,0 13,5-1000

0

1000

2000

3000

4000

5000

6000

7000

8000Io

n S

igna

l (ar

b. u

nits

)

Electron energy (eV)

C2D

6

+ / C2D

6

11.46 eV

Izotopic effects in C2D6

aE. Vaseková, M. Stano, S. Matejcik, , J.D. Skalný, P. Mach, T.D. Märk, J. UrbanInt. J. of Mass Spect., 235 (2004) 155-162

e + C2D6 → AE (in eV)

Present Ethana

( C2D6 )+ 11.80 ± 0.05 11.46 ± 0.06

( C2D5 )+ 11.78 ± 0.07 ? 12.06± 0.03

( C2D4)+ 12.09 ± 0.08 11.9± 0.04

( C2D2)+ 15.06± 0.2 15.02± 0.2

Grill et al. ZPhysD 25 (1993) 217

EII to C3H8

10 11 12 13

0

2x10-19

4x10-19

6x10-19

8x10-19

Ion

yie

ld (

arb

. Un

its)

E (eV)

C2H

+ 5/C

3H

8

C3H

+ 8/C

3H

8

C2H

+ 4/C3H

8

C3H

+ 7/C

3H

8

Appearance energies C3H8

Denifl CPL 402 (2005) 80

EII to C3H8 cross sections

Exp: N. Duric, I. Čadež, M. Kurepa, Int. J. Mass Spectrom. & Ion Processes, 108 (1991) R1-R10.

9,5 10,0 10,5 11,0 11,5 12,0 12,5 13,0 13,5 14,0

0,0

2,0x10-17

4,0x10-17

6,0x10-17

C2H

+

5/C

3H

8

C3H+

7/C

3H

8

C2H+

4/C

3H

8

C3H

+

8/C

3H

8

Cro

ss S

ect

ion

[cm

2 ]

Electron Energy [eV]

Total cross sections

σBEB(12 eV) σPresent(12 eV) σExp(12 eV)

[10-16 cm2]

0.119 0.21 0.35

Exp: N. Duric, I. Čadež, M. Kurepa, Int. J. Mass Spectrom. & Ion Processes, 108 (1991) R1-R10.

BEB: W. Hwang, Y.-K. Kim and M.E. Rudd, J. Chem. Phys., 104 (1996) 2956

Cross sections at 700 K

Not finnished yet Problems with contamination

EII to BexHy

Experimental problems

Vaporisation only at T>1000°C

Toxicity of Be

BeH dissoc. energy

Roo

sAT

Z

Best Theor.

1.9

2.0

2.1

2.2

2.3

2.4

2.5

2.6D

e [e

V]

MP2(FC) MP2(Full)

CCSD(t,FC) CCSD(t,Full)

cc-pvXZ aug-cc-pvXZ cc-pCvXZ aug-cc-pCvXZ

CCSDT-R12

1exc. energy 2Σ – 2Π, experiment 17086 cm-1 , theory – 17116 cm-1

BeH bond lenght

X=3

X=2

X=3

X=4

X=5

Roo

sAT

Z

X=5X=4

X=3

X=2

X=2

X=5

X=4

X=5

X=4

X=3

X=2

R12-CCSD(T)

1.310

1.315

1.320

1.325

1.330

1.335

1.340

1.345

1.350

1.355

1.360

Be-

H [

A]

MP2(FC)

MP2(Full)

CCSD(t,FC)CCSD(t,Full)

aug-cc-pCvXZcc-pCvXZaug-cc-pvXZcc-pvXZ

BeH2

basis BeH2

Be-H [A]

TAEa)

[eV]DEBe+H2 [eV]

CCSD(T)-R12

Be:19s14p8d6f4gH: 9s,6p,4d,3f

1.3260 6.418 1.671

CCSD(T) Full

aug-cc-pCvDZ 1.3366 6.108 1.585

aug-cc-pCvTZ 1.3298 6.321 1.614

aug-cc-pCvQZ 1.3267 6.391 1.657

aug-cc-pCv5Z 1.3263 6.406 1.664

B3LYP6-311++G(3d,3p) 1.3248 6.741 1.965

aug-cc-pCv5Z 1.3239 6.748 1.964

BeH2 bond lenght

R12-CCSD(T)

1.315

1.320

1.325

1.330

1.335

1.340

1.345

Be-

H [

A]

MP2(FC)

MP2(Full)

CCSD(t,FC)

CCSD(t,Full)

aug-cc-pvXZ aug-cc-pCvXZcc-pvXZ cc-pCvXZ

BenH clusters – MP2

BenH1

0

2

4

6

8

10

12

1 2 3 4 5

Number of Beryllium Atoms

En

erg

y [e

V]

Energy Difference

Atomization Energy

Be3Hn

Be4Hn

Be4Hn

0

5

10

15

20

25

30

35

0 1 2 3 4 5 6 7 8 9

Number of Hydrogen Atoms

En

erg

y D

iffe

ren

ce

[e

V]

Energy Difference

Atomization Energy

Futher plans

Propane cross section at high T C2D6 – high T, cross sections Ionization energies of the Be compounds Appearance energies of the fragments Simulation of the Be surface Chemistry on the Be surface

Thank you for your attention