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Abstract:
Raman spectra of cleaved, millimeter-sized single crystals of
mineral galena (PbS) have been measured between 100 and 1200
cm(-1) over the temperature range 80 to 373 K. Three low wave
number bands are observed which can be reconciled with the
results of earlier reports. However, changes in the peak wave
numbers and in the relative intensities of these bands in
response to changes in temperature do not conform with previous
assignments for the observed bands. Detailed assignments are
proposed which are based on resonance Raman processes. The
observed bands are assigned to forbidden longitudinal optical
excitations, which are allowed under resonance conditions by a
Frohlich interaction mechanism, and two-phonon excitations. (C)
2002 American Institute of Physics.