First- and second-order Raman spectra of galena (PbS)

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 Fröhlich interaction mechanism, and two-phonon excitations.

Temperature‐dependent Raman scattering of natural and isotopically substituted PbS

“…the usual behavior for the shifts of phonons with temperature) and a few other weak bands already reported in Refs. [8,11,12]. Fig.…”

“…Going farther into the visible (in the green, for example, at 514 nm, see + -ion laser) results in very weak intrinsic second-order spectra. Laser excitation around 647 nm seemed to be a good compromise between low background and reasonable signal-to-noise level (possibly aided by a weak resonance effect in the red [11]). Another important experimental detail is the power level of the laser.…”

“…The analysis presented here is based on the observation of two main structures in the Raman spectra: (i) one structure at high wavenumbers, around ∼ 430 cm −1 , which is a doublet and has already been related to the generation of two optical (actually LO) phonons [8,11] and, (ii) a second structure at ∼ 210 cm −1 , which is possibly also a doublet but cannot be well resolved in most of the measured spectra and must be related to either two acoustic phonons (2LA) or two optic ones (2T O) as will be discussed later. Our experimental approach is to characterize the behavior of these spectral features as a function of temperature and to ascertain how they differ between natural and isotopically substituted samples.…”

PbS nanopowder – synthesis, characterization and antimicrobial activity

“…From the inset, it is observed that the spectrum shows emission peaks at 173 cm −1 , 265 cm −1 and 481 cm −1 . The band centered at 173 cm −1 might have originated from the combination of longitudinal and transverse acoustic phonon modes associated with PbS crystal [19]. The peak at 265 cm −1 may be related to PbO formation due to photodegradation of PbS [20].…”

Pressure-Induced Phase Transition in Pb1-xSnxSe Studied by Raman Spectra

“…However, at the NaCl phases of all PbX, the forbidden first-order spectra preceding surface oxidation were still established under the variation of the laser line or the increase in laser power. [9][10][11][12][13][14][15][16][17][18][19] In the present work, we investigated the above phase transition in Pb 1-x Sn x Se (x=0.125) by Raman spectroscopy under a pressure of up to 6 GPa. Sn dopant was reported to decrease the transition pressure from 4.5 to 3 GPa.…”