Abstract
Anisotropy parameters and cross section ratios of two-color two-photon above threshold ionization sidebands from argon are measured using photoelectron velocity map imaging with the selected 13th or 15th high-order harmonics in a perturbative 800 nm dressing field. A new data analysis technique determines accurate anisotropy parameters of the photoelectron angular distributions for each sideband by subtracting a sequence of percentages of the single-photon ionization background from the above threshold ionization signal to correct for the angular averaging of overlapping photoelectron energies. The results provide a fundamental test of theoretical predictions based on second-order perturbation theory with a one-electron model and the soft-photon approximation and show agreement with theory for the cross section ratios. However, discrepancies between the theoretically predicted and experimentally determined photoelectron angular distributions demonstrate the need for a more comprehensive theoretical description of two-color two-photon above threshold ionization.
| Original language | English |
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| Pages (from-to) | 13152-13158 |
| Number of pages | 7 |
| Journal | Journal of Physical Chemistry A |
| Volume | 113 |
| Issue number | 47 |
| DOIs | |
| State | Published - 2009 |
| Externally published | Yes |