High-resolution infrared spectra of the ν2, ν3, ν4, and 2ν3 bands of 32S16O3

New measurements are reported for the infrared spectrum of sulfur trioxide, (SO3)-S-32-O-16, with resolutions ranging from 0.0015 cm(-1) to 0.0025 cm(-1). Rovibrational constants have been measured for the fundamentals nu(2), nu(3), and nu(4) and the overtone band 2nu(3). Comparisons are made with the earlier high-resolution measurements on SO3, and the high correlation among some of the constants related to the Coriolis coupling of the nu(2) and nu(4) levels is discussed in order to understand the areas of disagreement with the earlier work, Splittings of some of the levels are observed and the splitting constant for K = 3 of the ground state is determined for the first time. Other observed splittings include the K = 1 levels of 2nu(3) (l = 2), the K = 2 levels of nu(3) and nu(4), and the K = 3 levels of nu(2). The analysis shows that there are level crossings between the l = 0 and l = 2 states of 2nu(3) that allow one to determine the separation of the subband centers for these two states even though access to the l = 0 state from the ground state is electric-dipole forbidden. This is a generalized phenomenon that should be found for many other molecules with the same symmetry. The l-type resonance constant, q(3), that causes the splitting of the l(3) = +/-1, k = +/-1 levels of nu(3) also couples the l(3) = 0 and 2 states of 2nu(3). (C) 2001 Elsevier Science.