1. High Resolution Photoelectron Imaging Iker León Department of Chemistry, Brown University 68th International Symposium on Molecular Spectroscopy OHIO June 2013

2. - Experimental set up Imaging - Results Au 4 - Au 2 - - Conclusions Outline - Introduction More Au 2 - !!!

3. Introduction PES of anions: - EA - Density of states - Electronic excitation energies Electronic fingerprint limited by the resolution of the electron energy analyzer ZEKE (anions): - Resolution bellow cm -1 Difficult Wigner threshold law -> limited to electrons leaving as s-wave SEVI : - High detection efficiency - Resolution of few cm -1 - PAD D. M. Neumark, J. Phys. Chem. A 112, 13287 (2008). combines the advantage of both S. J. Cavanagh, S. T. Gibson, M. N. Gale, C. J. Dedman, E. H. Roberts, and B. R. Lewis Phys. Rev. A 76, 052708 (2007).

4. 3D presentation Apparatus A. T. J. B. Eppink and D. H. Parker, Rev. Sci. Instrum. 68, 3477 (1997). D. Townsend, M. P. Minitti, and A. G. Suits, Rev. Sci. Instrum. 74, 2530 (2003).

5. Au - Apparatus

6. * Bordas, C.; Paulig, F.; Helm, H.; Huestis, D. L. Rev. Sci. Instrum. 67, 2257 (1996) Apparatus Anions are photodetached in a dc electric field which will project the photoelectron velocity distribution onto a detector

7. Au - Apparatus Initial velocity vector  mapped on the same point on the detector

8. Abel inversion methods: the full three-dimensional (3D) information can be reconstructed What do we obtain? How? Apparatus Extract kinetic energy and angular distributions from the spatial appearance of the two-dimensional (2D) image

9. Apparatus

10. Results: Au 2 -

11. Results: Au 2 - * Leon, I.; Yang, Z.; Wang, L. S. J. Chem. Phys. 138, 184304 (2013)

12. Results: Au 2 - * Leon, I.; Yang, Z.; Wang, L. S. J. Chem. Phys. 138, 184304 (2013)

13. Results: Au 2 - * Leon, I.; Yang, Z.; Wang, L. S. J. Chem. Phys. 138, 184304 (2013)

14. Results: Au 4 -

15. Y-Shaped Vs. Diamond Results: Au 4 -

16. More Au 2 - …

18. G. F. Gantefor, D. M. Cox, and A. Kaldor, J. Chem. Phys. 2, 854-858 (1991)

21. Conclusions

22.  Good resolution: - low kinetic energy: 1.5 cm -1 - high kinetic energy: < 1% ∆E/E  Au 2 - : - success! - good resolution at low and high kinetic energies - accurate EA determination - high detection efficiency  Au 4 - : - low frequency mode resolved - accurate EA determination - anion and neutral vibrational information  high resolution PE imaging: electronic and vibrational information for size-selected clusters: cluster structure determination  Complementary to IR spectroscopy.

23. Thank you!