Collisional quenching of Cl[3p5(2P½)] by noble gases

Abstract

A kinetic study of the collisional quenching of Cl[3p⁵(²P_½)](²P_–½= 881 cm^–1) by the noble gases is presented. Cl(3²P_½) was generated by the repetitive pulsed irradiation of CCl₄ and monitored photoelectrically in absorption in the vacuum ultraviolet at λ= 136.34 nm [3p⁴4s(²P)â†� 3p⁵(²P⁰_½)] by time-resolved attenuation of atomic resonance radiation, coupled with signal averaging. The decay of the electronically excited atom was monitored in the presence of the noble gases He, Ne, Ar, Kr and Xe, yielding the following absolute second-order rate constants (k_Q/cm³ molecule^–1 s^–1 at 300 K): k_He= 3.8 ± 0.6 × 10^–15, k_Ne= 4.0 ± 0.5 × 10^–14, k_Ar= 1.1 ± 0.3 × 10^–12, k_Kr= 1.4 ± 0.2 × 10^–12 and k_Xe= 1.8 ± 0.2 × 10^–11. These data are considered within the context of non-adiabatic transitions based on a curve-crossing mechanism, spectroscopic data on noble gas–Cl diatomic molecules and a simplified Landau–Zener formalism.