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R-Dependent Strong Field Ionization from a Neutral Ground State Diatomic Molecule

This presentation discusses the R-dependent ionization behavior of diatomic molecules in strong fields, with a focus on the implications of Lochfrass and the branching ratio between different ionization channels. The results shed light on the complex dynamics of ionization from mixed states in diatomic molecules.

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R-Dependent Strong Field Ionization from a Neutral Ground State Diatomic Molecule

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  1. R-dependent strong field ionization from a neutral ground state diatomic moleculeG. N. Gibson, H. Chen*, V. Tagliamonti*University of Connecticut*Also giving talks in this session DAMOP 2012 Anaheim, CA June 6, 2012 Funding from the National Science Foundation

  2. R-dependent ionization • Important test of any strong-field theory of ionization • Simple tunneling models do not agree with experiments on Iodine • Rcritical in even charged molecules? • Lochfrass – implies very strong dependence of ionization rate on R near Re: Γ(R) • » Want to measure Γ(R) directly from the ground state over a large range in R – should see a huge effect • Chen: ionization from the B-state vs. R • Tagliamonti: 1ω2ω ionization from the B-state vs. R DAMOP 2012

  3. Pump-dump-probe DAMOP 2012

  4. DAMOP 2012

  5. Depletion at 45 fs DAMOP 2012

  6. Wavepacket monitored in (2,0) channel (20% excitation)*(75% de-excitation) = 15% in high-v X-state DAMOP 2012

  7. Fourier Transform Spectroscopy DAMOP 2012

  8. What about I2+ signal? DAMOP 2012

  9. What happened to expected modulation? • NO modulation at 5 THz in the I2+ signal • However, we do see strong 6.3 THz modulation – this is due to Lochfrass in the ground state near Re • We know that Γ(R) must be a strongly increasing function of R, because of Lochfrass, which should lead to a huge modulation of the ionization rate, because the range of R is much bigger. • However, Lochfrass does not give the final state, only the rate out of the ground stateΓtotal(R) = Γ→X-state(R) + Γ→(1,0)(R)since (1,0) is the only other 1-e ionization signal. DAMOP 2012

  10. Γ(R) has strong dependence, just not to I2+ • (1,0) represents ionization from an inner-orbital or into strongly mixed states. • HOMO is antibonding - ionization won’t lead to (1,0). • Inner orbitals are bonding – ionization will weaken bond. DAMOP 2012

  11. Branching ratio between I2+ and (1,0) channels • Even single pulse branching ratio to (1,0) is very large ~67%. • Branching ratio increases with R, as measured from the B state. DAMOP 2012

  12. Orbital structure DAMOP 2012

  13. Conclusions • Ionization projects ion into mixed states • Asymmetric work of Tagliamonti • Branching ratio to (1,0) • At large R, molecule falls apart • Hard to claim we are cleanly removing an electron from one orbital of another – everything gets highly mixed by the field DAMOP 2012

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