Raman Spectra of Saturated Fat Acids

Raman spectra of saturated fat acids C_nH_2nO₂ (n = 4, 5,8,10,11,13, 15,18) have been investigated in the frequency range 0-3000 cm^-1. Longitudinal acoustical modes, Raman frequency of which decreases with the increase of the molecule length, have been discovered in the low frequency region. In the frequency region of the zigzagging carbon skeleton frame (skeleton oscillations) the modes of B_1g and A_1g type have appeared, Raman frequencies of which systematically changed with the change of the molecule length as well. Observed frequency shifts for acoustical and optical modes have been explained on the basis of the dynamic theory of diatomic crystalline finite-length chain vibrations. Obtained results open the way to the composition analysis of fat products and determination of the fat acid molecule type on the Raman spectra basis.