Abstract
This paper presents results of a theoretical study on nu(O-H(D)) band shapes in the polarized infrared spectra of 2-naphthylacetic acid (2-NA) crystals measured at the temperature of liquid nitrogen. The line shapes were studied within the frameworks of strong anharmonic coupling, Davydov coupling, Fermi resonance coupling, direct and indirect damping, and a selection rule breaking mechanism for forbidden transitions in IR. The present approach correctly fits the experimental line shape of the hydrogenated compound and predicts satisfactorily the evolution in the line shapes with isotopic substitution. Numerical calculations show that mixing of all these effects allows one to reproduce satisfactorily the main features of the experimental IR line shapes of hydrogenated and deuterated 2-NA crystals and is expected to confirm the importance of the Fermi resonances in reproducing the experimental spectra.