Analysis of high-resolution infrared and CARS spectra of 32S 18O 3

Abstract

As part of a series of investigations of isotopic forms of sulfur trioxide, high-resolution infrared and coherent anti-Stokes Raman spectroscopies were used to study the fundamental modes and several hot bands of 32S 18O 3. Upper levels of hot bands originating from the ν 2 and ν 4 bending mode states have been found to couple strongly to the upper levels of the IR-inactive ν 1 symmetric stretch through indirect Coriolis interactions and Fermi resonances. Coriolis coupling effects are particularly noticeable in 32S 18O 3 due to the close proximity of the ν 2 and ν 4 fundamental vibrations, whose deperturbed wavenumber values are 486.48813(4) and 504.28477(4) cm −1. The uncertainties in the last digits are shown in parentheses and are two standard deviations. From the infrared transitions, accurate rovibrational constants are deduced for all of the mixed states, leading to deperturbed values for ν 1, α 1 B , and α 1 C of 1004.68(2), 0.000713(2), and 0.000348(2) cm −1, respectively. The B e value is found to be 0.310820(2) cm −1, yielding an equilibrium bond length r e of 141.7333(4) pm that is, within experimental uncertainty, identical to the value of 141.7339(3) pm reported previously for 34S 18O 3. With this work, precise and accurate spectroscopic constants have now been determined in a systematic and consistent manner for all the fundamental vibrational modes of the sulfur trioxide D 3 h isotopomeric forms 32S 16O 3, 34S 16O 3, 32S 18O 3, and 34S 18O 3.