l-Type Doubling in Three π—π Bands of HCN

Abstract
l‐type doubling constants have been determined for the 0112–0110, 0113–0110, and 0311–0110 bands of HCN. The results, in units of 10—3 cm—1, are: 011201130311q7.717.5415.4q′′7.517.267.21 The accuracy of the constants is ±5% for the 0113 and 0311 bands, and ±1% for the 0112 band. The q′—q″ values obtained for the 0113 and 0112 bands agree within experimental error with the prediction of our empirical equation which relates q to the vibrational quantum numbers.