V. S. Naumov
Obninsk Branch of the Federal State Unitary Enterprise (FGUP) “Karpov Research Institute of Physical Chemistry,”
Kievskoe shosse 109 km, Obninsk, Kaluzhskaya oblast, 249020 Russia
e-mail: naumov@karpovipc.ru
Received July 1, 2010
Abstract—The long-wavelength tails of the fundamental electronic absorption spectra of alkali metal halide
melts have been investigated. The obtained values of the absorption characteristics of the alkali metal halide
melts have confirmed the assumption that, over a wide temperature range (600–900C), the exponential tail of
the absorption coefficient of these disordered systems is associated with the presence of the spectrum of fluc-
tuating electronic levels extended to the band gap in the melts under investigation. The fulfillment of the Urbach
rule is the limiting case of the general exponential dependence of the optical absorption coefficient in the ultra-
violet region of the fundamental absorption edge. In the studied series of melts of alkali metal halide salts, the
absorption coefficient in the region of tails of the spectral curves of the halide systems decreases from LiCl to
CsCl and from LiCl to LiI. An analysis of the results obtained from the investigation of alkali metal halides has
revealed an interrelation between the main parameters of the Urbach rule and between these parameters and the
temperature coefficient of the band gap.
Keywords: alkali metal halide melts, electronic absorption spectra, Urbach rule
DOI: 10.1134/S1087659611030096
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