Predissociation Of The B-3 Sigma(-)(U) State Of S-2: A Coupled-Channel Model

Acoupled-channel Schrodinger equation model of predissociation in the B-3 Sigma(-)(u) state of S-2 is developed and optimized by comparison with recent photoabsorption spectra of the B-3 Sigma(-)(u) X-3 Sigma(-)(g) (v, 0) bands for 11 <= v <= 27, covering the energy range 35 800-41 500 cm(-1). All bands in this range exhibit varying degrees of diffuseness, with corresponding predissociation linewidths Gamma approximate to 4-60 cm(-1) full-width at half-maximum. Model comparisons with both low-temperature (T = 370 K) and high-temperature (T = 823 K) spectra indicate, for many bands, significant dependence of the linewidth on both the rotational quantum number J and the fine-structure component F-i. Just as in the analogous case of O-2, the B(v)-state predissociation in S-2 is caused principally by spin-orbit interaction with (3)Pi(u), (1)Pi(u), (5)Pi(u), and (3)Sigma(+)(u) states. The inner-limb crossing with B ''(3)Pi(u) is responsible for the predissociation of B(v = 11) and provides a significant slowly varying contribution for B(v >= 12). The outer crossings with the (1)Pi(u), (5)Pi(u), and 2 (3)Sigma(+)(u) states are responsible for oscillatory contributions to the predissociation widths, with first peaks at v = 13, 20, and 24, respectively, and the (5)Pi(u) contribution dominant. Prior to the photodissociation imaging study of Frederix et al. [J. Phys. Chem. A 113, 14995 (2009)], which redefined the dissociation energy of S-2, the prevailing paradigm was that only the (1)Pi(u) interaction was responsible for the B(v = 11-16) predissociation: this view is not supported by our model. Published by AIP Publishing.