Slightly asymmetric double minimum potentials

Abstract

Although the introduction of a small amount of asymmetry into a symmetric double minimum potential soon switches the infrared selection rule from even ↔ odd to well ↔ well, it is shown that the sum of the intensities of the transitions starting from the pair of lowest levels is insensitive to the anharmonicity. Hence if these transitions are not separately resolved, the vibrational spectrum will evolve smoothly from the symmetric to the asymmetric case. The data relating to a series of hydrogen bonded cations (B 1HB 2) + are used as an example.