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Recent Experiments in Low-Energy Electron-Molecule Collisions

Recent Experiments in Low-Energy Electron-Molecule Collisions. Threshold phenomena. - valence s * shape resonances - diffuse dipole- (& polarizability-) bound resonances - vibrational Feshbach resonances - doorway states - molecules - with dipole moment: HF, HCl, HBr

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Recent Experiments in Low-Energy Electron-Molecule Collisions

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  1. Recent Experiments in Low-Energy Electron-Molecule Collisions Threshold phenomena - valence s* shape resonances - diffuse dipole- (& polarizability-) bound resonances - vibrational Feshbach resonances - doorway states - molecules - with dipole moment: HF, HCl, HBr - without dipole moment: CO2, N2O, CH4 - large molecules: - nitromethane - chlorobenzene - pyrrole - ethylene carbonate Electron collisions with a radical: NO·

  2. Sample Elastic Cross Sections

  3. Sample Elastic Cross Sections

  4. Differential cross sections in N2O Marinković B, Szmytkowski C, Pejčev V, Filipović D and Vuškoviš L, J. Phys. B 19 2365 (1986) Johnstone W M and Newell W R, J. Phys. B 26 129 (1993) Kitajima M, Sakamoto Y, Gulley R J, Hoshino M, Gibson J C, Tanaka H and Buckman S J, J. Phys. B 33 1687 (2000)

  5. Vibrational excitation in hydrogen fluoride: experiment and theory m=1.83D Martin Čížek, Jiří Horáček, Michael Allan and Wolfgang Domcke 2003

  6. HF: Spectra and Potential Curves

  7. HCl

  8. HBr and DBr red: experiment m=0.82D blue: nonlocal resonance model Čížek Horáček Sergenton Popović Allan Domcke Leininger Gadea, Phys. Rev. A 2000

  9. Generic potential curves

  10. CO2 m=0.0D bending

  11. N2O - Elastic & Vibrational Excitation m=0.16D elastic and fundamental vibrations overtone vibrations

  12. N2O - Dissociative Attachment Bound anion calculation: Kryachko et al., J. Chem. Phys. 2001

  13. m=5.3D Ethylene Carbonate Dissociative Electron Attachment in Cyclopentanone, g-Butyrolactone, Ethylene Carbonate and Ethylene Carbonate-d4: Role of Dipole-Bound Resonances M. Stepanović, Y. Pariat and M. Allan J. Chem. Phys.110 (1999) 11376

  14. Nitromethane CH3NO2 m=3.46D

  15. Nitromethane: Elastic DCS

  16. Selectivity of vibrational excitation in chlorobenzene m=1.54D

  17. Pyrrole m=1.77D

  18. Methane: Energy-Loss Spectrum

  19. Methane: DCS overview W. Sohn, K.-H. Kochem, K.-M. Scheuerlein, K. Jung, H. Ehrhardt J. Phys. B 19 (1986) 3625 B. H. Lengsfield III, T. N. Rescigno, C. W. McCurdy, Phys. Rev. A 44 (1991) 4296

  20. Methane: detail

  21. Conclusions I Threshold phenomena - often interaction diffuse state ↔ valence state - diabatic vs adiabatic potential surfaces - vibrational Feshbach resonances (VFR) - outer well resonances - (s*) shape resonances - doorway states

  22. Diffuse and Valence States of Anions

  23. NO: Potential Curves initial NO NO– resonance final NO

  24. NO: transitions between electronic fine structure states

  25. NO: transitions between electronic fine structure states

  26. NO: vibrational transitions

  27. Comparison of NO and O2 NO O2

  28. NO: angular dependence elastic Vibrational excitation

  29. Conclusions II NO·: transitions between electronic fine structure states - gigantic resonant cross section, » elastic - resonance parentage - elastic cross sections not equal?

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