A theoretical study of C3 molecule trapped in rare gas matrices: Influence of bent or linear configuration on the infrared spectra Original Research Article

In the infrared spectra of C3 trapped in rare gas matrices at low temperatures T≌10 K, two bands in the v3 asymmetric stretching region have been observed, one intense at higher frequency (HF) and the other, weaker at lower frequency (LF). These bands have been attributed to two different trapping sites in the matrix. In this paper semi-empirical atom-atom potential energy calculations, based on pairwise additive interactions, have been performed in order to understand the nature of these trapping sites and the influence of the matrix on the C3 molecular geometry. The vibrational frequency shifts due to the matrix surroundings are calculated for bent and linear molecular configurations in several different trapping sites. In the calculated infrared spectra, no significant absorption occurs in the v1 symmetric stretching region, while the v2 bending and v3 asymmetric stretching modes exhibit weak and strong bands, respectively. Finally, from a comparison of the calculated and experimental spectra in the v3 region, it is predicted that C3 should be in the bent configuration when trapped in a matrix, as observed.