Radiative lifetimes and two-body deactivation rate constants for Ar(3p5, 4p) and Ar(3p5,4p′) states

Abstract

The radiative lifetimes and two‐body deactivation rate constants of the Ar(3p⁵4p and 4p′) levels have been measured by a time‐resolved laser‐induced fluorescence technique in a flowing afterglow apparatus. The flowing afterglow produced the Ar(3p⁵4s,³P₂) metastable atoms, which subsequently were pumped by the pulsed dye laser. The measured radiative lifetimes are in excellent agreement with the calculated transition probabilities based upon intermediate‐coupling theory. Radiative branching ratios of these states also were measured in order to assign the transition probabilities and the absorption oscillator strengths of the transitions between the 4s and 4p levels. The two‐body deactivation rate constants range from 1×10⁻¹⁰ to 2×10⁻¹¹ cm³ atom⁻¹ sec⁻¹. Specific product states from the two‐body collisions between Ar(4p and 4p′) atoms and Ar were identified from the laser‐induced emission spectra and rate constants for individual product states were assigned for each level. Our results show that two‐body collisions do not necessarily result in cascade down the p and p′ manifold, and for the Ar(4p and 4p′) levels more than 50% of the atoms are directly converted to the Ar(4s and 4s′) manifold.