Iodine Molecular Interferometer and Inversion Symmetry Mat Leonard

Molecular Structure o Properties of electronic wave functions describe molecular structure o symmetry o spatial extent o localization o energy eigenvalues o Traditional photoelectron spectroscopy focused on energy levels o Time-resolved photoelectron imaging allows insight into other properties of electron wave functions

Davis I 2 - Experiment o Time-resolved photoelectron spectrum of I 2 - experiment (Davis, et al J. Chem. Phys. 118, 999 (2003)) o Ti:Sapphire laser, 90 fs pulses o Pump with IR, probe with 3hν o Velocity Map Imaging

Photoelectron Energy Spectrum o From energy conservation, photoelectron energy spectrum reveals information about molecular states Probe only

Time-Resolved Photoelectron Energy Spectrum Probe onlyPump + Probe

Photoelectron Angular Distribution Interesting information lies in the photoelectron angular distribution (PAD) The PAD can be represented by: where, θ is the angle between the electron velocity and laser polarization vectors, β 2n is the anisotropy parameter associated with P 2n, the nth Legendre polynomial

PAD Anisotropy o β 2 varies in time, even after dissociation is complete (~300 fs) o Increase in β 2 after 350 fs is attributed to a shallow well in the long range potential o Decrease suggested to be related to localization of electron o |β 4 |<0.1, negligibly small and no time dependence is observed

Electron Localization o Localization occurs due to mixing of g and u states (gerade and ungerade refer to states being even or odd under inversion, respectively) o In the absence of an external field, the overall electron wave function is of the the form (I A - I B + I A I B - ) o The wave functions for localization on a particular I atom, i.e. I A - I B or I A I B -, are obtained from linear combinations of g ± u states o External extraction field of 500 V/cm can induce the g/u mixing

Sanov I 2 - Experiment o Time-resolved photoelectron spectrum of I 2 - experiment (Sanov, et al J. Chem. Phys. 123, (2005)) o Ti:Sapphire laser, 100 fs pulses o Pump with IR, probe with 2hν o Extraction field ~40-80 V/cm

PAD Anisotropy Complete oscillation of the anisotropy parameter in ~2.5 ps, R≈35 Å Again, fitting the measured PADs to we see β 2 change long after the dissociation is complete (~500 fs)

I 2 - Molecular Interferometer o Photoelectron with KE=0.12 eV has de Broglie wavelength λ=35.4 Å o Effective state mixing occurs when the field induced perturbation H´=eER is comparable to the energy separation of the two unperturbed potential-energy curves o Electron localization estimated at R≈35.6 Å, corresponding to ~2.5 ps delay o β 2 varies as R(t)/λ, as expected for double source interference