  We investigate the effect of electron beam irradiation on the dielectric
properties of As2S3 Chalcogenide glass. By means of low-loss Electron Energy
Loss Spectroscopy, we derive the permittivity function, its dispersive
relation, and calculate the refractive index and absorption coefficients under
the constant permeability approximation. The measured and calculated results
show, to the best of our knowledge, a heretofore unseen phenomenon: the
reduction in the permittivity of <40%, and consequently a modification of the
refractive index follows, reducing it by 20%, hence suggesting a significant
change on the optical properties of the material. The plausible physical
phenomena leading to these observations are discussed in terms of the homopolar
and heteropolar bond dynamics under high energy absorption.
