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High Harmonic Generation in SF$_{6}$: Raman-excited Vibrational Quantum Beats

Zachary B. Walters·Stefano Tonzani·Chris H. Greene
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Abstract

In a recent experiment (N. Wagner et al., PNAS v103, p13279) on SF$_{6}$, a high-harmonic generating laser pulse is preceded by a pump pulse which stimulates Raman-active modes in the molecule. Varying the time delay between the two pulses modulates high harmonic intensity, with frequencies equal to the vibration frequencies of the Raman-active modes. We propose an explanation of this modulation as a quantum interference between competing pathways that occur via adjacent vibrational states of the molecule. The Raman and high harmonic processes act as beamsplitters, producing vibrational quantum beats among the Raman-active vibrational modes that are excited by the first pulse. We introduce a rigorous treatment of the electron-ion recombination process and the effect of the ionic Coulomb field in the electron propagation outside the molecule, improving over the widely-used three-step model.

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Zachary B. Walters, Stefano Tonzani, Chris H. Greene. 2007-01-09. High Harmonic Generation in SF$_{6}$: Raman-excited Vibrational Quantum Beats. https://doi.org/10.1088/0953-4075/40/18/f01

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