G.P. Karwasz, K. Fedus Nicolaus Copernicus University, Toruń, Poland

1. Electron scattering on molecules - Partial (and Total) Cross Sections:Search of Uncertainties and Errors in Experimental Procedures G.P. Karwasz, K. Fedus Nicolaus Copernicus University, Toruń, Poland IAEA Meeting, Wien, 19.12.2016

2. Data needed: 2. Partial cross sections: 1. Total cross section elastic scattering e+A →e+A rotational excitation e+CH4 (J=0) → e+CH4 (J=2) vibrational excitation e+AB(v=0) → e+AB(v>0) electron attachment (dissociative) e+AB → A- + B electronic excitation e+A →e+A* emission lines: A* → A + hv neutral dissociation e+AB → A + B + e emisison from dissociation e + AB → A* + B + e + hv ionization e+A →A++2e dissociative ionization e+AB → A + B+ + 2° ionization into excited states e + A → (A+)* + 2e

3. Data needed in: • Plasma modelling (electrical discharges, „economic” ligth sources); • (plasma temperature in Ar discharges, 0.3 eV is determined by minimum in MT cross section ) • 2. Plasma etching and deposition • (energy of etching radicals, ionization level) • 3. Chemical reactions in plasmas (ionization, dissociation) • 4. Radiation damage in materials and biological tissues • 5. Thermonuclear fusion reactors

4. Plasma temperature ← integral cross sections Ramsauer minimum (zero in s-wave) V. Godyak, Sendai 2006

5. Radiation damage in biological tissues M. C. Fuss, ... G. Garcia Chem. Phys. Lett. 486 (2010) 110

6. ¿ITER: electron T and power irradiated Electron temperature (and density) during three points of density ramp Power irradiated (0.5-1.5 MW) simulation: JET-C <10% JET-ILW factor 3! Guillemaut et al. Nucl.Fusion (2014)

7. Experimental methods: total attenuation method I = I0 exp(-σnL) precision <5% H. Nishimura et al., J.Phys. Soc. Japan 72 (2003) 1080

8. Experimental methods: total attenuation method I = I0 exp(-σnL) precision <5% Agreement generally within ±5% Apart from high E Mi-Young Song, Jung-Sik Yoon, Hyuck Cho, Yukikazu Itikawa, Grzegorz P. Karwasz · Viatcheslav Kokoouline, Yoshiharu Nakamura, Jonathan Tennyson, J. Phys. Chem. Ref. Data, 44 (2015) 023101

9. Total @ high energies: Born-Bethe fit σ(E) = A + B lnE C2H2 CH4 „In the high energy limit present (GK, Zecca) measurements are affected by angular resolution error. In order to evaluate it, differential cross sections at low angles would be needed. A rough evaluation from Born approximation for the elastic channel gives an error of a few percent. Note that the error in TCS can be higher, as Trento apparatus does not perform discrimination against inelastically forward-scattered electrons. Fig.4.Born-Bethe fit (σ/ao2) (E/R) = A + B ln (E/R) to TCS from Ariysainghe: A=52.31±17.3, B=232.2±8.6 where Rydberg constant is R=13.6 eV and the cross sections is expressed in atomic units a02=0.28x10-20m2

10. Total: experiment & theory (NF3) NF3 B. Goswami et al. PRA 88 (2013) 032707 (NF3)

11. Experimental methods: elastic I. Linert, B. Mielewska, G. King, and M. Zubek, PRA (2006)

12. Experimental methods: excitation (electronic, vibrational) e- + O2 (v=0) – e- + O2 (v=0, 1, 2, etc.) Experiments by: I. Linert, M. Zubek (Gdansk) J. Phys. B 39 (2006) M. Khakoo et al. (Fullerton California) M. Allan (Freiburg University)

13. Experimental methods: ionization WF6→ WF5+ > WF2+> WF3+ ≈ WF4+ Accuracy: ±15% R. Basner, M. Schmidt, K. Becker, Int. J. Mass Spectr. 233 (2004) 25

14. Diffusion coefficients → electronic distribution function ne(r, v, t)

15. Example: oxygen O2 • Rotational and vibrational

16. Oxygen – total cross section

17. Example: oxygen O2 • Electronic – not justified (a1Δ is resonant) • Zecca, G. Karwasz, R. S. Brusa, • Riv. Nuovo Cimento Vol. 19, No. 3 (1996)

18. Electronic excitation – dipole allowed and forbidden in H2

19. Hydrogen – a complete set

20. Hydrogen – a complete set

21. Hydrogen – a complete set Mark C. Zammit, Jeremy S. Savage, Dmitry V. Fursa, and Igor Bray Phys. Rev. Lett. 116, 233201 http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.233201

22. Hydrogen – a complete set Jung-Sik Yoona), Mi-Young Song, Jeong-Min Han, Sung Ha Hwang, Won-Seok Chang, and BongJu Lee Journal of Physical and Chemical Reference Data > Volume 37, Issue 2 > 10.1063/1.2838023

23. Electronic excitation – dipole allowed and forbidden in H2 Zecca, Karwasz, Brusa, Nuovo Cimento 1996

24. Hydrogen – electronic excitation (modelling)

25. Hydrogen – electronic excitation (2010)

26. Resonances: „Huston...” (N2O) Sarpal et al. 1996

27. Resonances: ¿elastic/ vibrational (N2O) Morgan et al. 1997

28. Dissociation into neutrals (H2O) Laser-induced fluorescence Herb and McConkey

29. Dissociation into neutrals (N2O) XeO* excimer decay N2O → O(1S0) LeClair and McConkey JCP 99 (1993) 4566

30. Dissociation into neutrals (CF4) Two electron beams: dissociation & ionization Nakano and Sugai, Jpn. J. Appl. Phys. 31 (1992) 2919

31. Dissociation into neutrals (CF4, CH3F…) „Volatile organotellurides” Motlagh and Moore JCP 109 (1988) 432

32. Dissociation into neutrals (CF3COOH) Thermal desorption Reactions in nanofilms of trifluoroacetic acid (CF3COOH) driven by low energy electrons, M. Orzol, T. Sedlacko, R. Balog, J. Langer, G. P. Karwasz, E. Illenberger, A. Lafosse, M. Bertin, A. Domaracka, R. Azria, Int. J. Mass Spectr. 254 (2006) 63

33. Polar molecules (HCN) A. G. Sanz, Applied Radiation and Isotopes 83 (2014) 57–67

34. Polar molecules (HCN) A. G. Sanz, Applied Radiation and Isotopes 83 (2014) 57–67

35. Polar molecules (e+/e- + HCOH) Independent atom model-screened additivity rule / Schwinger multichannel A Zecca, E Trainotti, L Chiari, G García, F Blanco, M H F Bettega, M T do N Varella, M A P Lima and M J Brunger Journal of Physics B: Atomic, Molecular and Optical Physics, Volume 44, Number 19

36. Polar molecules (e+/e- + HCOH) „in good qualitative agreement with our measured data” Experimental (¿possible?) errors: - Declared energy resolution 260 meV ↔ Theory: Independent atom model-screened additivity rule / Schwinger multichannel Experiment: weakly (9G) magnetically guided positron beam/ W monocrystal moderator A Zecca, E Trainotti, L Chiari, G García, F Blanco, M H F Bettega, M T do N Varella, M A P Lima and M J Brunger Journal of Physics B: Atomic, Molecular and Optical Physics, Volume 44, Number 19

37. Polar molecules (e++ H2O) NJP 11 (2009)

38. Polar molecules: e- + H2O

39. Check of congruence: CF4

40. Check of congruence: NH3 Really poor agreement...

41. Check of congruence: CHF3

42. Ionization

43. Conclusions • Quite few laboratories continue to produce partial cross sections • Some new labs yield very competitive (and promising) measurements • Electronic excitation is the main chalenge, both to experiment and theory • Extension of BEB ionization to partial ionizations would be „breaking” – correlation measurements seem to allow it but direct and secondary ionization (i.e. energy spectra) would be important • Vibrational excitation is poorly understood – both at thresholds (peaks or not?) and at resonances: agreement with swarms is only apparent • Rotational excitation, even if (maybe) not important for plasma temperature, can be decisive in electron slowing down, and (in biological tissues), in „brougthing” them to energies matching zero-energy alactron attachment resonances. • Comparative works are important, as this is the way to identify reasons for serious disagreements in some tagets (including positron scattering)