Quenching rate constants for reactions of Ar(4p′[1/2]0, 4p[1/2]0, 4p[3/2]2, and 4p[5/2]2) atoms with 22 reagent gases

The total quenching rate constants of argon atoms in the 4p(')[1/2](0), 4p[1/2](0), 4p[3/2](2), and 4p[5/2](2) states (2p(1), 2p(5), 2p(6), and 2p(8), respectively, in the Paschen numbering system) by rare gases, H-2, D-2, N-2, CO, NO, O-2, F-2, Cl-2, CO2, NO2, CH4, C2H2, C2H4, C2H6, CF4, CHF3, and SF6 have been determined at room temperature. These four excited states of argon (energy 13.09-13.48 eV) were selectively prepared by two-photon excitation from the ground state using VUV (184-190 nm range) laser pulses. The total quenching rates were deduced from the pressure dependence of the decay times of the excited-state atoms, measured by observing their fluorescence emission intensities in the presence of added reagents. The quenching constants increase from values of congruent to0.01x10(-10) cm(3) atom(-1) s(-1) for Ne, to congruent to0.1x10(-10) cm(3) atom(-1) s(-1) for He and Ar, and to very large values, (5-15)x10(-10) cm(3) atom(-1) s(-1), for most polyatomic molecules, F-2, Cl-2, and O-2. The quenching mechanisms of the Ar(4p,4p(')) atoms are briefly discussed and compared to the reactions of the Ar(4s,4s(')) metastable and resonance state atoms, 11.55-11.83 eV, which can serve as a reference. (C) 2001 American Institute of Physics.