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Photodynamics in superfluid helium: Femtosecond laser-induced ionization, charge recombination, and preparation of molecular
 

Summary: Photodynamics in superfluid helium: Femtosecond laser-induced
ionization, charge recombination, and preparation of molecular
Rydberg states
A. V. Benderskii, R. Zadoyan, N. Schwentner,a)
and V. A. Apkarianb)
Department of Chemistry, University of California, Irvine, California 92697
Received 6 August 1998; accepted 9 October 1998
Femtosecond pulses 790 nm are used for nonresonant laser excitation of superfluid liquid helium
to prepare ionic and neutral excited states at energies above 18 eV. Measurements of laser-induced
fluorescence and photocurrent enable a detailed description of the primary photoprocesses. A
controllable excitation regime unique to femtosecond pulses is realized at laser intensities below the
dielectric breakdown threshold, I 5 1013
W/cm2
. A steady state of the long-lived triplet excimers
He2*(3
a) lowest Rydberg state is established; the concentration decays between laser pulses
through diffusion-controlled bimolecular annihilation to 1012
cm 3
at a laser repetition rate of 500
Hz. The triplet population is amplified with each pulse in a sequence that involves: 1 ionization of

  

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

 

Collections: Chemistry