1. Department of Experimental Physics, Comenius University Bratislava, Slovakia Formation of positive ions by electron impact: Temperature effects Š. Matejčík

3. Department of Experimental Physics Division of plasma physics low temperature plasma low temperature plasma technological plasmas, glow discharges... high pressure discharges high pressure discharges corona discharge, barrier discharge... reactions in the plasma reactions in the plasma electron impact ionization, electron attachment to the molecules...

4. Electron interactions Electron interactions Photon induced reactions Photon induced reactions Ion – molecule reactions Ion – molecule reactions Neutral reaction Neutral reaction Reactions on the surfaces Reactions on the surfaces Reactions in plasma

5. Electron impact ionization Electron impact ionization Electron attachment Electron attachment Excitation Excitation Dissociation Dissociation Electron reaction on the surfaces Electron reaction on the surfaces Electron interactions in plasma

6. Comenius university Electron attachment Electron attachment Electron impact ionization Electron impact ionization Electron induced reactions on surfaces Electron induced reactions on surfaces Preparation Electron impact excitation Electron impact excitation

7. Electron impact ionization: e + AB → AB + + 2e Dissociative electron impact ionization: e + AB → A + + B + 2e Ion pair formation: e + AB → A + + B- + e Fusion related research Molecules: CH 4, CH 3 D, CD 4, C 2 H 6, C 3 H 8

8. We have studied - appearance energies (AE) of the positive ions - gas temperature effects on the AE - isotopic effects on AE Theory: Ionization energies (OVGF, CCSD(T)) Appearance energies (G3, G3B3 and CBS-APNO, CBS-Q)

9. Experimental setup: E = 0 – 150 eV FWHM ~50-140 meV Ie~20-100nA T = 293K 693K 693K

10. low T g high T g Electron impact ionization E σ

11. low T g Rate coefficient E σ f(E,T e ) high T g

12. A A+A+ IE VIE AIE AE

13. AE 1 AE 2 E f ΔAE = AE 2 -AE 1 = = E i (T 2 )-E i (T 1 ) E i (T)=E v (T)+E r (T)

14. σ E Sensitivity in present experiment: σ ~10 -26 - 10 -25 m 2

15. Problem of threshold energy estimation

16. Atoms: Wannier theory:  w (E,AE,A,d) = 0 E<AE A(E-IE) d E>AE d=1.127 Threshold behaviour of the cross sections for EII f(E,U) - EEDF Fitting function:  w (E,AE,A,d)

17. d=1.127±0.01 Threshold behaviour of the cross sections

18. Molecules - empirical formula:  w (E,AE 1,AE 2,d1,d2A) = 0E<AE 1 A(E-AE 1 ) d1 E>AE 1 Threshold behaviour of the cross sections for EII A(E-AE 2 ) d2 + A(E-AE 1 ) d1 E>AE 2...

19. Temperature effects on Appearance energies of the ions P. Plessis et al., Can. J. Chem. 65 (1987) 1424, J. Phys. B, 16 (1983) 1770 H. M. Rosenstock, Int. J. Mass Spectr. Ion Phys., 20 (1976)139 Predicted by: Rosenstock – review article Plessis & Marmet – in CH 4 and C 2 H 6 papers

20. CH 4 e + CH 4 → CH 4 + + 2e CH 3 + + H + 2e CH 3 + + H + 2e CH 3 + + H - + 2e CH 3 + + H - + 2e CH 2 + + H 2 + 2e CH 2 + + H 2 + 2e CH + + H 2 + H + 2e CH + + H 2 + H + 2e C + + 2H 2 + 2e C + + 2H 2 + 2e...

21. 293K CH 4 + /CH 4 693K

22. ExperimentAE (eV) T=293 K AE (eV) T=693 K ΔAE (eV) Plessis et al. AE(eV) T=293 K CH 4 + /CH 4 12.65  0.0412.51  0.04 0.14 12.62  0.02 CH 3 + /CH 4 13.58  0.1 14.34  0.1 13.45  0.1 14.20  0.1 0.14 - - - 14.01  0.08 E i (T) - rotational and vibrational energy of the molecule at T  E i =E i (693) – E i (293 K) ~ 0.12 eV Stano et al., J. Phys. B: At. Mol. Opt. Phys., 36 (2003) 261

23. CH 3 + /CH 4 693K 293K

24. CH 3 D + /CH 3 D AE 1 =12.75 eV AE 1 =12.62 eV 293K 693K

25. e+CH 3 D→AE(293K)AE(693K)D(AE(693K)- AE(293K)) (CH 3 D) + 12.75 ± 0.0312.58 ± 0.050.17 ± 0.07 (CH 2 D) + + H – (CH 2 D) + + H 13.66 ± 0.07 14.42 ± 0.05 13.49 ± 0.07 14.25 ± 0.05 0.17 ± 0.1 0.17 ± 0.06

26. C 2 H 6 + /C 2 H 6 693K 293K

27. e + C 2 H 6 ExperimentTheory AE [eV] 293 K Thermochemistry [eV] G3B3 AIE [eV] C2H6+C2H6+ 11.46±0.0411.55 C 2 H 5 + + H - C 2 H 5 + + H 12.06±0.06 12.7±0.1 11.72 12.47±0.03 12.03 12.79 C 2 H 4 + + H 2 11.90±0.0411.92±0.000611.93 C 2 H 3 + + H + H 2 15.02±0.114.47±0.4614.83 C 2 H 2 + +2H 2 15.02±0.114.61±0.0114.61 C 2 H + +2H 2 +H C 2 H + +H 2 +3H25.7±0.3 20.5±0.15 25.1±0.15 21.65 26.12 C 2 + + 3H 2 22.6±0.320.95±0.321.73 C2H6C2H6C2H6C2H6

28. C 3 H 8 + /C 3 H 8 693K 293K

29. MoleculeΔAE (eV) Exp. ΔAE (eV) Theory CH 4 0.12-0.140.12 CH 3 D0.12-0.170.13 CD 4 0.16-0.200.15 C2H6C2H6 0.19-0.30.31 C3H8C3H8 0.21-0.420.46 Summary Temperatures 293 and 693 K

30. Isotopic effect on AE Changes in vibrational energies in isotopomers Heavy isotopomer – lower zero point energy => larger AE Comparison: CH 4, CD 4, CH 3 D

31. CH 3 D AE (eV) 293 K CD 4 AE (eV) 293 K CH 4 AE (eV) 293 K CH 3 D + 12.75 ± 0.0312.89 ± 0.0312.65 ± 0.04CH 4 + CH 2 D + + H – CH 2 D + + H 13.66 ± 0.07 14.42 ± 0.05 - 14.54 ± 0.05 13.58 ± 0.1 14.34 ± 0.1 CH 3 + + H – CH 3 + + H Isotopic effect on AE

32. Present meV a) meV b) meV (CH 3 D) + /CH 3 D10050 (CH 2 D) + /CH 3 D80 (CH 3 ) + /CH 3 D200 (CHD) + /CH 3 D110 (CD 4 ) + /CD 4 190170160 (CD 3 ) + /CD 4 200130 (CD 2 ) + /CD 4 31090 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

33. Conclusions experimentally observed dependence of AE´s on the temperature magnitude of the shift ~ vibrational and rotational excitation of the molecule confirmed isotopic shift in the appearance energies of the molecules

34. Contribution to new CRP Experiment: The temperature effects: -estimation of the partial cross sections in C 3 H 8 for particular fragment ions - evaluation of the rate coefficients Theory - QM: - Be n H m - electronic structure, binding energies, volatility, ionization potentials and electron affinities - H 2 reactions with Be n

35. Coworkers Comenius University Bratislava M. Stano, E. Vašeková, J.D. Skalný, D. Kubala, J. Kočíšek Theorists: I. Hubac, J. Urban, P. Mach S. Denifl, T.D. Märk University Innsbruck Support VW Stiftung, EU (Euroatom-FUSION), IAEA, APVT