Study of excitation transfer in a flowing helium afterglow pumped with a tuneable dye laser. III. Transfer and quenching reactions of the He2(3p 3Π) molecule

Abstract

The collisional transfer of excitation from the He₂(3p ³Π_g) state to other electronically excited states energetically lying within a few KT is examined by optically pumping a flowing helium afterglow with a tuneable dye laser. Rate coefficients for the transfer of excitation to states conserving spin, particularly 3d ³Π_u and 3d ³Δ_u, are found to be greater than 10⁻¹⁰ cm³/sec, resulting in a rapid thermalization of electronic and rotational energy. Relative probabilities of spontaneous radiation for transitions in the visible wavelength range from the product states are found to be 1 and 1/3 for the 3Π_u and 3Δ_u states, respectively, relative to that from the initial ³Π_g state. The absence of significant fluorescence from singlet states tends to confirm the conservation of spin during such reactions.