Analysis of some combination-overtone infrared bands of 32S 16O 3

Abstract

Several new infrared absorption bands for 32S 16O 3 have been measured and analyzed. The principal bands observed were ν 1+ ν 2 (at 1561 cm −1), ν 1+ ν 4 (at 1594 cm −1), ν 3+ ν 4 (at 1918 cm −1), and 3 ν 3 (at 4136 cm −1). Except for 3 ν 3, these bands are very complicated because of (a) the Coriolis coupling between ν 2 and ν 4, (b) the Fermi resonance between ν 1 and 2 ν 4, (c) the Fermi resonance between ν 1 and 2 ν 2, (d) ordinary l-type resonance that couples levels that differ by 2 in both the k and l quantum numbers, and (e) the vibrational l-type resonance between the A 1 ′ and A 2 ′ levels of ν 3+ ν 4. The unraveling of the complex pattern of these bands was facilitated by a systematic approach to the understanding of the various interactions. Fortunately, previous work on the fundamentals permitted good estimates of many constants necessary to begin the assignments and the fit of the measurements. In addition, the use of hot band transitions accompanying the ν 3 band was an essential aid in fitting the ν 3+ ν 4 transitions since these could be directly observed for only one of four interacting states. From the hot band analysis we find that the A 1 ′ vibrational level is 3.50 cm −1 above the A 2 ′ level, i.e., r 34=1.75236(7) cm −1. In the case of the 3 ν 3 band, the spectral analysis is straightforward and a weak Δ k=±2, Δ l 3=±2 interaction between the l 3=1 and l 3=3 substates locates the latter A 1 ′ and A 2 ′ “ghost” states 22.55(4) cm −1 higher than the infrared accessible l 3=1 E ′ state.