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Strong-Field Excitation of Liquid and Solid Xe Using Intense Femtosecond Pulses M. Pettersson, R. Zadoyan, J. Eloranta, N. Schwentner,| and V. A. Apkarian*
 

Summary: Strong-Field Excitation of Liquid and Solid Xe Using Intense Femtosecond Pulses
M. Pettersson, R. Zadoyan, J. Eloranta, N. Schwentner,| and V. A. Apkarian*
Department of Chemistry, UniVersity of California, IrVine, California 92612-2025
ReceiVed: December 20, 2001; In Final Form: February 22, 2002
Strong-field excitation of condensed xenon, both solid and liquid, are investigated using focused 60 fs pulses
at 400 and 800 nm. Both wavelengths lead to efficient generation of excitons, which are monitored through
their VUV emissions. The self-trapped Xe2* excitons are observed in both solid and liquid Xe; and although
weaker, emission from the free Xe* excitons is also detected in the crystalline samples. The photoionization
mechanism, which ultimately leads to the creation of excitons through electron-hole recombination, is
investigated through power dependence measurements of fluorescence and transmission. At 400 nm, the
ionization proceeds through the multiphoton mechanism, while at 800 nm, field-induced tunneling ionization
prevails. It is observed that the ionization process is self-limited, preempting the possibility of dielectric
breakdown. The failure of an electron avalanche process to develop is understood to arise from the small
scattering cross-section of electrons in condensed Xe whereby the field-driven electron energy distribution
localizes at the deep scattering minimum, near 0.7 eV. Additionally, the achievable field intensities are limited
by beam divergence, due to the negative refraction in the generated electron plasma. This is established in
the liquid-phase samples by transmission measurements through a limiting aperture. In the solid state, damage
triggered by defects limit the achievable irradiation intensities. It is estimated that exciton densities of 1018
cm-3
are reached (at pump intensities of 1012

  

Source: Apkarian, V. Ara - Department of Chemistry, University of California, Irvine

 

Collections: Chemistry