Some new features in the raman spectra of carbon and silicon tetrachlorides

Abstract

The Raman spectra of CCl4 and SiCl4 have been examined under low and high dispersion. In both cases a faint line has been observed close to the line corresponding to the total symmetric vibration. This faint line has a frequency shift of 434 cm.-1 in the case of CCl4 and is interpreted as the octave of the fundamental frequency 217·9 cm.-1 The corresponding line in the case of SiCl4 shows a frequency shift of 440·5 cm.-1 and is interpreted as the octave of the fundamental frequency 221 cm.-1 It is pointed out that the appearance of the octave in these cases might probably be due to its proximity to the total-symmetric vibration frequency which is respectively 459 cm.-1 and 423 cm.-1 in the case of CCl4 and SiCl4. An additional faint line with a frequency shift of 145 cm.-1 has been observed in the Raman spectrum of CC14 which is interpreted as a differential tone arising from the fundamental frequencies 459 cm.-1 and 314 cm.-1, the summational of which causes the splitting of the fourth frequency, and the octave of whose summational appears as a faint broad line at 1538 cm.-1 The broadening of the fourth frequency in the case of SiCl4 might be due to a cause similar to that which causes the splitting of the fourth frequency in the case of CCl4. The total symmetric vibration in the case of CCl4 shows a well-defined wing to its red side, sharply separated from the principal line.