A simple completely analytical method for the calculation of the plasm
a radiation continuum in the visible and neighbouring regions is deriv
ed. It is based on the semi-classical quantum defect theory. In spite
of the simplicity the accuracy of the method is found to be comparable
with those of Schluter and Hofsaess calculations, but its main advant
age is the reasonable description of the plasma density (weak coupling
) effects in the near-threshold region. Thus, our calculation does not
show the sharp threshold of the photoionization continuum and a corre
ct comparison with experiment in the whole wavelength range under cons
ideration can be made. A good agreement with experimental data on the
continuous radiation of neon, argon, krypton and xenon plasmas is foun
d. The calculation scheme presented may be useful for moderately dense
plasma diagnostics and looks as reasonable basis for incorporation of
strong-coupling effects. (C) 1998 Elsevier Science Ltd. All rights re
served.