1. Gas phase spectroscopy at the CLS http://www.lightsource.ca

2. VLS-PGM Beamline Y Hu et al, Rev. Sci. Instrum. 78 (2007) p083109

3. VLS-PGM Beamline

5. Instruments for gas-phase science at the VLS-PGM beamline Dual toroidal electrostatic analyser Wiley-McLaren time-of-flight mass spectrometer

6. Dual toroidal analyser T J Reddish et al (1997) Rev. Sci. Instrum. 68 2685 A E Slattery et al (2000) J. Phys. B. 33 4383 Toroidal analysers can energy select the charged particles (ions/ electrons) while preserving the initial angle of emission. Both analysers are independent and each can be switched to detect electrons or ions. Both can operate in threshold (TPES) mode Detectors can operate in coincidence mode

7. Dual toroidal analyser

10. Since the toroidal analyser preserves the azimuthal angle of emission of the photoelectron we can find the photoelectron asymmetry parameter across a photoelectron spectrum. That is we can record “beta paramer” spectra. The spectra here are beta parameter spectra for H 2 and will be the subject of the 2 nd half of this talk. Finally we remember that the detectors can be configured for electrons or ions.

11. Time of Flight Electron Start – Ion Stop, with multi-hit electronics No energy discrimination on the electron Allows ToF mass spectra and PePIPICO 2D maps

12. Time of Flight Parent “C 4 ” “C 3 ” “C 2 ” Water “C 1 ”

13. ToF PePIPICO para-nitroaniline

14. Time of Flight

15. http://www.lightsource.ca If any of this would be of interest to you please talk to me at this symposium. Michael MacDonald Canadian Light Source Inc. 44 Innovation Boulevard Saskatoon, SK, S7N 2V3 306 657 3812

16. Hydrogen

18. Direct mechanisms (a) and (b) produce only a limited range of electron energies due to Franck-Condon Factor restrictions Indirect mechanisms (c) and (d) produce a wide range of electron kinetic energies. Further mechanism (d) can decay to either the bound σ g or dissociative σ u state of the ion. Remember in quantum mechanics indistinguishable paths to the same destination interfere.

19. Hydrogen

20. Red – experimental results Black – full QM closed coupling calculations

21. Hydrogen

24. Results and the simplified model

25. Summary of H 2 results Unusual properties of observed interference Interference shows in direction of photoelectrons not intensity Direction of photoelectrons are dictated by nuclear motion (Ultimately it all comes back to symmetry !) Interference is from different autoionisation paths from a coherent superposition of electronic states. (Not direct ionisation and autoionisation from a single excited state) This is not a coincidence experiment, and, indeed, the oscillations would disappear in a coincidence experiment.

27. Acknowledgements Dr. Tim Reddish Dr. Arathi Padmanabhan Dr. Smialek-Telega Prof. Nigel Mason Dr. Lucia Zuin Ru Igarishi Antonio C.O. Guerra and Cássia C. Turci Instituto de Química, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ 21941-909, Brazil Dr. J. Fernández Dr. A. Palacios Prof. F. Martín