International Workshop on Atomic Interactions in Laser Fields - Abstracts
G. Peach1 and F. Schuller2
1Department of Physics and
Astronomy, University College London, Gower Street, London WC1E
6BT, UK
2Laboratoire des Interactions Moleculaires et des
Hautes Pressions, C.N.R.S. 93430 Villetaneuse, France
The study of the response of an atom to an intense narrow-band
radiation field has become important ever since the advent of
laser sources. When atoms that are surrounded by a buffer gas are
absorbing or emitting radiation, the spectral line profile is
both broadened and shifted, and if the radiation field is
intense, additional effects are expected to occur. A general
theory has been developed [1], to describe the combined effects
of collisional and radiative perturbations on absorption and
fluorescence profiles, but this theory has not been applied in
practice. In [2], a scalarly-additive unified
theory of pressure broadening has been developed for
atom-perturber interactions of the form 1/Rp,
which reproduces the well-known results of the impact and static
approximations in the low-density/high-temperature and
high-density/low-temperature limits, and also predicts the shapes
of profiles in the crucial intermediate region. The theories
given in [1] and [2] have been combined, and the results obtained
for the case of Van der Waals interactions (p = 6) show that the
effect of an intense radiation field is to produce significant
extra broadening and shift of the profile. If the perturber
density is decreased while the temperature is held constant, the
width of the line decreases monotonically if there is no
radiation field, but if there is a radiation field present, the
line width at first decreases but eventually reaches a minimum
and then starts to increase again. Illustrative profiles and
simple criteria for assessing the relative importance of the
strength of the radiation field will be presented.