Showing papers by "Ranjan K. Singh published in 1994"

Deconvolution of lorentzian Raman Linewidth: Techniques of polynomial fitting and extrapolation

Abstract: A simple, convenient and precise technique for deconvolving the Lorentzian (true) Raman linewidth, ΓL, from the observed Raman linewidth, (Δ1/2)R [the FWHM (full width at half-maximum) of the Raman line in question], through polynomial fitting, was developed. The precision of this technique is a consequence of the fact that the values of ΓL/(Δ1/2)R (= Y), obtained by exact numerical evaluation of the Voigt profiles for the Raman bands, were flitted to third- and fourth-degree polynomials in S/(Δ1/2)R (= X), S being the spectral slit width measured as the linewidth (FWHM) of a narrow spectral line recorded at the same slit settings as the Raman line. The procedure of obtaining ΓL, from the knowledge of S,(Δν1/2)R and X, which yields better results, is discussed. Another technique of deconvolution is described and discussed, involving the measurement of Raman linewidths of a particular Raman line for about five or six different slit widths. The measured linewidths (Δ1/2)R, when extrapolated to S 0, give the value of ΓL directly. A careful comparison with the other deconvolution techniques reveals that the method of polynomial fitting is relatively more precise than other semi-analytical deconvolution techniques, and the extrapolation technique also gives reasonably good results. The applicability of both methods was tested by taking some selected Raman lines.