In this paper we review prior measurements and report new measurements
of elastic differential cross sections (DCSs) obtained in our laborat
ory for positron scattering by the inert gas atoms He, Ne, Ar, Kr, and
Xe. The gases (Ne, Ar, Kr, and Xe) for which low-energy measurements
have been made below and above the positronium (Ps)-formation threshol
ds show evidence that the Ps-formation channel is having an observable
''absorption'' effect on the elastic scattering channel when compared
with calculations that only consider the elastic channel. At low ener
gies where only the elastic channel is open, good agreement is found w
ith available calculations. DCS measurements made at high energies (gr
eater than or equal to 200 eV) for He, Ne, and Ar are also found to be
consistent with theoretical calculations. At intermediate energies (a
bove the Ps-formation thresholds and below a few hundred eV) theory ha
s not yet been able to match the relative DCSs obtained experimentally
owing to the difficulty of including the effects of the most importan
t inelastic channels (i.e., Ps formation and direct ionization). Some
initial attempts by our group to obtain absolute elastic DCSs at fixed
scattering angles versus positron energy revealed unexpected structur
e between 55-60 eV for Ar and at 25 and 200 eV for Kr. Our most recent
measurements reported here do not confirm the prior observations of t
hese structural features.