Analysis of ν 2, ν 4 Infrared Hot Bands of 32S 16O 3: Resolution of the Puzzle of the ν 1 CARS Spectrum

Further analysis of the high-resolution (0.0015 cm −1) infrared spectrum of 32S 16O 3 has led to the assignment of more than 3100 hot band transitions from the ν 2 and ν 4 levels to the states 2ν 2 ( l=0), ν 2+ν 4 ( l=±1), and 2ν 4 ( l=0,±2). These levels are strongly coupled via Fermi resonance and indirect Coriolis interactions to the ν 1 levels, which are IR-inaccessible from the ground state. The unraveling of these interactions has allowed the solution of the unusual and complicated structure of the ν 1 CARS spectrum. This has been accomplished by locating over 400 hot-band transitions to levels that contain at least 10% ν 1 character. The complex CARS spectrum results from a large number of avoided energy-level crossings between these states. Accurate rovibrational constants are deduced for all the mixed states for the first time, leading to deperturbed values of 1064.924(11), 0.000 840 93(64), and 0.000 418 19(58) cm −1 for ν 1, α 1 B , and α 1 C , respectively. The uncertainties in the last digits are shown in parentheses and represent two standard deviations. In addition, new values for some of the anharmonicity constants have been obtained. Highly accurate values for the equilibrium rotational constants B e and C e are deduced, yielding independent, nearly identical values for the SO r e bond length of 141.734 03(13) and 141.732 54(18) pm, respectively.