The a″ vibrations of singlet propynal

Abstract

The a″ vibrational frequencies of all possible H and D isotopomers of propynal (HCCCHO) are shown to allow two solutions for the a″ harmonic potential constants. Equations relating the solutions are given. In the [Formula: see text] ground electronic state one solution can be rejected as chemically unrealistic, but in the [Formula: see text] excited electronic state the choice is more difficult. It is shown that a choice can be made on the basis of the observed cross-sequence intensities in the [Formula: see text] band system.