Raman spectrum of diamond under high resolution

Abstract

Using the 2536.5 radiation of the mercury arc as the exciter and a Hilger Intermediate quartz spectrograph, the faint second-order Raman spectrum of diamond was first successfully recorded by me. Later investigations with somewhat larger diamonds and with a more powerful instrument, namely, a Hilger medium quartz spectrograph, resulted in a notable improvement in the clarity of the recorded spectra. I have now succeeded in obtaining a satisfactorily exposed picture with a large Hilger quartz spectrograph. The expectation that the greater dispersion and resolution given by this instrument would enable the true nature of the spectrum to be exhibited unambiguously has been fulfilled. Three prints of varying depth enlarged from the original spectrogram are reproduced herewith. The principal feature noticeable in the spectra is the appearance of a whole series of sharply defined Ram ail lines clearly resolved from each other. Twelve of the most prominent of these lines have been marked with their respective . frequency shifts in wave-numbers from the exciting radiation. The width of the individual Raman lines, as is evident from a comparison with the lines of the mercury arc, is no greater than that arising from the instrumental and photographic factors. Besides those marked, there are other fainter lines just discernible in the spectrogram against a fainter unresolved background of apparently continuous spectrum.