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R-dependent strong field ionization from a neutral ground state diatomic molecule G. N. Gibson, H. Chen*, V. Tagliamonti* University of Connecticut *Also.

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Presentation on theme: "R-dependent strong field ionization from a neutral ground state diatomic molecule G. N. Gibson, H. Chen*, V. Tagliamonti* University of Connecticut *Also."— Presentation transcript:

1 R-dependent strong field ionization from a neutral ground state diatomic molecule G. 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 R critical in even charged molecules? Lochfrass – implies very strong dependence of ionization rate on R near R e : 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 20122

3 Pump-dump-probe 3

4 4

5 Depletion at 45 fs DAMOP 20125

6 Wavepacket monitored in (2,0) channel (20% excitation)*(75% de-excitation) = 15% in high-v X-state DAMOP 20126

7 Fourier Transform Spectroscopy DAMOP 20127

8 What about I 2 + signal? DAMOP 20128

9 What happened to expected modulation? NO modulation at 5 THz in the I 2 + signal However, we do see strong 6.3 THz modulation – this is due to Lochfrass in the ground state near R e 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 state Γ total (R) = Γ →X-state (R) + Γ →(1,0) (R) since (1,0) is the only other 1-e ionization signal. DAMOP 20129

10 Γ(R) has strong dependence, just not to I 2 + (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

11 Branching ratio between I 2 + 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

12 Orbital structure DAMOP

13 Conclusions Ionization projects ion into mixed states o Asymmetric work of Tagliamonti o Branching ratio to (1,0) o 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


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