Anomalous high harmonic generation cutoff of O₂ molecule

Bing Shan, X. M. Tong, Z. X. Zhao, C. D. Lin, Zenghu Chang
James R. Macdonald Laboratory, Kansas State University

The high harmonic generation (HHG) from O₂ molecule and Xe atom is compared experimentally. Even though they have almost identical ionization potential (12.06 eV for O₂ and 12.13 eV for Xe), the HHG cutoff order of O₂ (43th) was found to be almost twice higher than Xe(25th). The experiments were carried out with a 20fs kHz laser, the Kansas Light Source. We believe that this higher HHG cutoff for O₂ is related to the well-known ionization suppression of O₂ as compared to Xe. While the mechanism of ionization suppression for some molecules is still under debate, the extension of HHG cutoff in O₂ can be explained by the nonadiabatic ionization potential model of Guo [1] where the effective ionization potential of O₂ was estimated to be at 16.9 eV. Further simulations and theoretical calculations to test this model are underway.

References:

[1] C. Guo, Phys. Rev. Lett. 85, 2276 (2000).

This work was supported by the Chemical Sciences, Geosciences and Biosciences Division,
Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy.

Submitted to DAMOP 2002, May 2002 in Williamsburg, VA.

 

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