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Core spectroscopy of molecules and clusters

Core spectroscopy of molecules and clusters. Svante Svensson Department of Physics Uppsala University. Outline. RAS-PES-XPS Resonant and non-resonant processes Born-Oppenheimer approximation Interference quenching Clusters . N2. A. X. B. Resonant photoexcitation.

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Core spectroscopy of molecules and clusters

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  1. Core spectroscopy of molecules and clusters Svante Svensson Department of Physics Uppsala University

  2. Outline • RAS-PES-XPS • Resonant and non-resonant processes • Born-Oppenheimer approximation • Interference quenching • Clusters

  3. N2 A X B

  4. Resonant photoexcitation • Resonant excitation of electronic states • state selective • element selective • vibrational level selective • control of time scale • time information (fs)

  5. Bound and dissociative electronic states for di-atomic molecules - Non resonant excitation

  6. Vibrational mapping Excite to a discrete vibrational level Vibrational wave packet propagates, 5 fs period Decay to final ionic state maps wave packet Time information mirrored in PES

  7. Born Oppenheimer approximation The wavefunction develops on ONE potential curve

  8. Valence band electron spectroscopy on HCL

  9. 40 35 Avoided crossing 2 + 4 S 30 Potential energy (eV) 1h 2h1p 25 2 + 3 S F-C Region 20 1 R 2 3 4 5 6 0 Distance H-Cl(Å) Expected Franck-Condon projection (Adiabatic approximation) Potential curves in literature (f2) Binding Energy (eV) (4s)-1 (5s)-2(6s)1 (f1) M.Hiyama, S.Iwata, Chem. Phys. Lett.210,187(1993)

  10. Direct photoionization using hn=64eV BL I411 at MAX-lab PES of “4s” for HCl+ and DCl+

  11. Theory Born-Oppenheimer approx. no longer valid. SE equation must take two potential curves into account

  12. Franck-Condon projection

  13. Theory: Infinite resolution

  14. DCl latest results BESSY Spring 2002 lower photon energy available at Bl U125/2 Less Doppler broadening Ca 10 meV resolution

  15. Ordinary collapse and interference quenching

  16. Cluster source Can be rotated around SR beam

  17. Homogenous and mixed clusters

  18. Mixed clusters (13% Xe in Ar)

  19. Depth profiling of Ar clusters using variation of excitation energy

  20. Xe clusters at magic angle

  21. Xe-Ar mixed clusters Atom, surface, bulk components

  22. surface atomic bulk Xe-Ar mixed clusters Xe XPS Ar XPS Ar %

  23. Cluster device

  24. MAX II beam-line I411

  25. Scattering amplitude

  26. Resonant Photoemission cross section

  27. ”One phonon approximation Rc=1.1511 for -500 meV detuning

  28. Scattering amplitude

  29. Soft X-ray electron spectro-scopy

  30. Surface&Bulk

  31. The detuning leads to a non- monotonous behaviour

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