Linear four-atomic molecules in the vibron model

Abstract

We present a general scheme for calculating spectra of linear four-atomic molecules and apply it to the study of acetylene, C2H2, and its isotopic variations, C2D2 and C2HD. Particular emphasis is given to the phenomenon of l-splitting, which plays an important role in four-atomic molecules. We are able to describe all known experimental levels, including stretching and bending, with an average rms of 10 cm−1.