Conseil national de recherches du Canada. Institut Steacie des sciences moléculaires du CNRC
Raman and IR spectra of neat n-pentadecane were measured as a function of increasing hydrostatic pressure up to 56 and 54 kbar, respectively. The application of high pressure leads to drastic changes in the frequencies, intensities and band shapes of the CH stretching and CH bending modes. The pressure-induced changes in the vibrational spectra of n-pentadecane are discussed in terms of phase transitions, molecular orientation, interchain interactions, frequency dispersions, and Fermi resonance interactions. The results are compared with the effect of pressure on the Raman and IR spectra of n-hexadecane. It is shown that the different pressure effect on these two n-alkanes results from differences in the effect of pressure on the frequency dispersion of the 2δCH₂ states in n-pentadecane and n-hexadecane.