Ab initioinvestigation of the vibronic structure of the C2H spectrum

Abstract
Potential surfaces for the three lowest-lying electronic states of C2H (1 2A′, 2 2A′ and 1 2A″) calculated by means of the ab initio MRD-CI method are transformed into their adiabatic counterparts. Three simple approaches for determination of diabatic transformation are investigated. Diabatic potentials and electronic transition moments obtained as functions of the C-C bond length and the bond angle represent a suitable basis for the calculation of vibronic energy levels and probabilities for transitions between them.
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