New Observations of the Optical Spectrum of SiO + and the Prediction of Its Rotational Spectrum

Abstract

The (0, 0) and (1, 0) bands of the B<SUP>2</SUP>Σ<SUP>+</SUP>-Χ<SUP>2</SUP>Σ<SUP>+</SUP> system of <SUP>28</SUP>Si<SUP>16</SUP>O<SUP>+</SUP> have been observed with very high resolution using the technique of laser-induced fluorescence from a mass-selected fast ion beam. The data yield values of the υ" = 0 rotational and fine-structure constants with an improvement in precision by about an order of magnitude over earlier work. This makes it possible to predict the frequencies of pure rotational transitions within this vibrational level at a level of precision that allows unambiguous comparison with molecular lines observed in interstellar clouds. In particular, the transition (J = 5/2, N = 2) → (J = 3/2, N = 1), which has been considered as the source of the observed U86.2 line at 86,243.45(40) MHz, is predicted to occur at 86,037(6) MHz.