Collision-Free Lifetimes of SO(B3Σ-, v ‘ = 0, 1, and 2) and Vibrational Level Dependence of Deactivation by He

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Vol. 107; no. 14; pp. 2442 - 2447
• Main Authors: Yamasaki, Katsuyoshi, Taketani, Fumikazu, Tomita, Sachie, Sugiura, Kazuyuki, Tokue, Ikuo
• Format: Journal Article
• Language: English
• Published: American Chemical Society 10.04.2003
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp027129a

Collision-free lifetimes and deactivation rate constants of SO(B3Σ-, v ‘ = 0, 1, and 2) by collisions with He have been determined. SO(X3Σ-) was generated in the photolysis of SO2 at 193 nm (ArF laser) and excited to a single rovibrational level of B3Σ- with a pulsed ultraviolet laser. We recorded dispersed fluorescence spectra, and found that 0−12 (350.8 nm), 1−14 (368.5 nm), and 2−17 (401.2 nm) bands are suitable for detecting fluorescence from single vibrational level of interest. Time profiles of wavelength-resolved fluorescence were recorded at various buffer gas pressures (5−165 Torr of He). Deconvolution by the integrated phase plane method derives apparent fluorescence lifetime at a given pressure. Total pressure dependence of fluorescence decay rates leads to collision-free lifetimes and rate constants for deactivation of SO(B3Σ-, v ‘ = 0, 1, and 2) by collisions with He. Lifetimes of SO(B3Σ-) have been determined to be (28 ± 2) ns (v ‘ = 0), (30 ± 3) ns (v ‘ = 1), and (27 ± 4) ns (v ‘ = 2). Rate coefficients for deactivation of SO(B3Σ-) by He have been obtained to be (6.3 ± 0.3) × 10-12, (3.9 ± 0.2) × 10-11, and (1.3 ± 0.2) × 10-10 in units of cm3 molecule-1 s-1 for v ‘ = 0, 1, and 2, respectively. To the best of our knowledge, deactivation rate constants for v ‘ = 0 and 1 of SO(B3Σ-) are measured for the first time in the present study. The large rate coefficient of deactivation by He and vibrational level dependence is explained by predissociation via the C3Π state.