Fluorescence and Phosphorescence of SO2 Vapor

Abstract

Stern–Volmer constants for SO2fluorescence [Ã( 1 B 1 )→X̃ 1 A 1 ] for six optically exciting wavelengths (3130, 3020, 2960, 2850, 2750, and 2650 Å) show a regular decrease in going to shorter exciting wavelengths in the pressure range 1–1000 μ Hg. Due to earlier work by Douglas, it is inferred that the principal change is occurring in the fluorescence lifetime, which decreases accordingly. If electronic quenching takes place at every gas–kinetic collision, then any amount of vibrational relaxation which occurs prior to emission has a larger‐than‐gas–kinetic cross section. The fluorescence yields (Q f )λ go to unity at zero pressure, within liberal error limits, for all exciting wavelengths. The phosphorescence [ã( 3 B 1 )→X̃ 1 A 1 ] essentially disappears at pressures below 10 μ and does not originate from vibrationally excited triplet levels even at low pressures. The phosphorescence yields (Q p )λ pass through a minimum at an exciting wavelength of 2850 Å, and the corresponding values at the exciting wavelength extreme are about the same.