Theoretical study of the U.V. spectrum of acetylene

Potential curves for trans- and cis-bending and C-C and C-H stretching vibrations in ground and singlet excited states of acetylene of both valence and Rydberg character are calculated using a large-scale MRD-CI approach. The energy surfaces obtained will be used for an interpretation of the U.V. spectrum of acetylene. The computed vertical energies for the lowest two transitions Ã-[Xtilde] and [Btilde]-[Xtilde] are found to agree within 0·2 eV of the corresponding values reported experimentally.