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An STM Measures I(r)

A Laser STM for Molecules Tunneling has transformed surface science. Tunneling is one of the simplest quantum mechanical process. Scanning the field around the molecule is like scanning the tip across a surface -- a molecular STM. An STM Measures I(r).

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An STM Measures I(r)

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  1. A Laser STM for Molecules Tunneling has transformed surface science. Tunneling is one of the simplest quantum mechanical process Scanning the field around the molecule is like scanning the tip across a surface -- a molecular STM An STM Measures I(r)

  2. H2 ionization in circularly polarized light e p • The electron direction determines the field direction at the moment of ionization • The bond softened ion determines the molecule’s direction at the moment of ionization

  3. COLTRIMS – measuring the 3d-momenta of correlated particles

  4. The angle-dependent ionization probability PRL 102, 033004 (2009)

  5. Implications of high tunneling rates: “DC” tunneling – The exponent is ~ 30-40. A small change in Ei is highly leveraged by the large Ea/E(t). Laser tunneling: -- The exponent is ~ 8. The leverage is weakened. Lower orbitals will contribute.

  6. Measuring excited states PRL 94, 033003 (2005)

  7. The laser STM senses the structure of orbitals: SU1 – direct tunneling SU2 – excitation by bound state interaction with the departing electron IP~4 eV

  8. Applying the “laser STM” to HCl

  9. Deeper orbitals tunnel ionize (directly)

  10. Two or more orbitals can ionize HCl

  11. Transient alignment of molecules time Phys. Rev. A. 68, 023406 (2003)

  12. A molecular STM has much more information

  13. Normalized Differences Notice: 1 Low lateral momentum structures – tunneling and 2 High lateral momentum structures – elastic scattering Science 3201478 (2008)

  14. q laser pmolecule pnormal • The Model: • Assume • Propagate swarm of electron trajectories classically • Including electron-ion interaction • Include alignment distribution

  15. Low Lateral momentum electrons Science 3201478 (2008)

  16. The angle dependent probability N2 CO2 O2 PRL 98, 243001 (2007)

  17. c b a a-SiO2 Al2O3 LiF Transparent Solids: DE = O(10eV) crystal structure

  18. 1.2 1.1 1 0.9 Normalized Transmission 0.8 0.7 0.6 0.5 0.4 0 50 100 150 200 250 300 Input Pulse Energy (nJ) Extending to Solids? The Lawn Mower Model • Self-controlled energy deposition. • electron and energy density is predicted. Opt. Express 13, 3208 (2005).

  19. Transmission as a function of angle

  20. (l/2) Angle dependent changes in the reduced-mass change the ionization rate. ~ m3 resolution

  21. Only the focal region is measured amorphous crystal 0 crystalline fused Phys. Rev. Lett. 101, 243001 (2008)

  22. The laser STM • Atoms:The filter function • using circular polarization. • Molecules:The orbital • Filtered image of the orbital • Quantify the contribution of lower orbitals. • Solids:The reduced tunneling mass • Measuring crystal symmerty • Link to HHG– correlated measurements

  23. A mixture of optical and collision science • Coherence can be transferred several times between electrons and photons • The mixture offers new opportunities for each • To optics -- Angstrom spatial imaging. • To collision physics-- Time resolution. Bertrand P1, Wörner P3, Meckel

  24. Three new forms of nonlinear spectroscopy • Tunneling (to characterize orbitals) • Elastic scattering or Laser Induced Electron Diffraction (to determine nuclear positions) – see Meckel et al. • Interferometry (to image orbitals --photoelectron spectroscopy in reverse) – see poster by Bertrand P1 and Wörner P3

  25. The tunneling electron wave packet of O2

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