A Pulsed Source for Kr(5s[3/2]1) Resonance State Atoms Using Two-Photon-Driven Amplified Spontaneous Emission: Measurement of Quenching Rate Constants

Abstract

Krypton resonance state atoms, Kr(5s[3/2]1), were generated in a static cell by two-photon laser excitation of the Kr(5p[5/2]2) state with amplified spontaneous emission (ASE) at 877.7 and 810.4 nm in a few Torr of Kr gas. The 877.7 nm transition, which terminates on the resonance state, constitutes ≥90% of the ASE intensity. The vacuum ultraviolet emission at 123.6 nm was used to monitor the Kr(5s[3/2]1) concentration, which decayed with an effective lifetime of 2 μs in the absence of added reagents. Total quenching rate constants at 300 K for the resonance state atoms were measured for 30 molecules by observing the decay rates of the Kr(5s[3/2]1) atoms as a function of added reagent gas. The rate constants (cm3 molecule-1 s-1) range from 1.4 × 10-11 for N2 and 0.60 × 10-11 for CF4 to (80−90) × 10-11 for hydrocarbons. Rate constants for most polyatomic molecules exceed 30 × 10-11 cm3 molecule-1 s-1. Comparison to the quenching rate constants of the Kr(5s[3/2]2) metastable atoms shows that the rate constants of the resonance states are ∼35% larger for reagents with quenching cross sections larger than 20 Å2. For a set of 11 reagents, comparison also is made with the rate constants for the (6s) and (6s‘) resonance states and the (6p) states of Xe; the latter have nearly the same energy as the Kr(5s) resonance state.