Infrared absorption by localized polarons in the silver halides
Brandt, Richard Charles
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https://hdl.handle.net/2142/25716
Description
Title
Infrared absorption by localized polarons in the silver halides
Author(s)
Brandt, Richard Charles
Issue Date
1967
Doctoral Committee Chair(s)
Brown, Frederick C.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
infrared absorption
localized polarons
silver halides
silver halide crystals
Language
en
Abstract
The infrared absorption of silver halide crystals, induced
by simultaneous illumination of the crystals with light whose energy
exceeded the indirect band gap, was measured from 33 to 2000 cm-1 at
temperatures from. 90 K to 40 0 K.
The induced far infrared absorption was shown to be in
agreement with the predictions of an extension of the theory of
Buimistrov and Pekar for po1arons bound to a positive charge center.
In AgBr at 9.30 K, the induced absorption at 168 cm-1 was identified
as the 1s to 2p transition, and the absorpti.on at 192 ± 2 cm -1 as the
ls to continuum transition. In AgC1 at 9.30 K, the corresponding
transitions were at 272 cm and at 292 ± 3 cm
The induced infrared absorption at higher frequencies was
shown to be phonon side bands of the far infrared. absorption.
In the process of calculating the above transitions, the
Buimistrov-Pekar expression for the polaron self energy was evaluated
in a new manner. The results showed that for coupling constants O!
less than 6, the Buimistrov-Pekar formulation gives a lower value of
self energy than other polaron theories.
The longitudinal optical frequencies in AgBr and AgCl were
measured directly for the first time at low temperatures using a
variation of the technique of Berreman. At 7oK, the longitudinal
optical frequency was 140 ± 1 cm- l in AgBr, and 197 ±l cm-1 in AgCl.
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