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The two-photon, laser-assisted reaction between Xe and Cl 2 has been used to generate XeCI(B,C) molecules for subsequent kinetic studies at 300 K. Two-body quenching rate constants for the collisionally coupled XeCl(B,C) molecules were determined from the pressure dependence of their decay rates on added molecular gases. The quenching constants for XeCl(B,C) by most molecules are large, even though acceptor electronic states are not available for quenching by an excitation-transfer mechanism. At higher pressure ( > 100 Torr) ofXe, Xe 2 CI(4 2n molecules were formed via three-body quenching ofXeCI(B,C), and the quenching rate constants for Xe 2 CI( 4 zn by added gases were determined and compared with those for XeCI(B,C). In all cases, the quenching rate constants for XeCl(B,C) are larger. The two-body quenching mechanisms for XeCl(B,C) and Xe z Cl( 4 2n, which are ionic molecules, are discussed. Three-body quenching of XeCl(B,C) with formation of Xe 2 CI( 4 2n was observed for Xe + N 2 , Xe + CF 4 , and Xe + SF 6 • J.

The two-photon, laser-assisted reaction between Xe and Cl 2 has been used to prepare XeCI (B,C) molecules in Xe and in Xe mixtures with lighter rare gases for kinetic studies of the coupled XeCI (B,C) states. The XeCI (B-X) spectra were used to assign the conditions for which the vibrational temperature was nearly 300 K. Relative intensity and coupled radiative lifetime measurements provide independent data which support an energy separation between the XeCI(B) and XeCl( C) states of -100 cm -I . The two-body quenching rate constant in Xe for XeCl (B,C) was measured as 5 ~ ~ X 10 -12 cm 3 s -I , and a three-body quenching rate constant of 13 ± 4x 10-31 cm 6 s -I is indicated. Experiments also were done with added Kr, Ar, Ne, and He to establish two-body and mixed (e.g., Xe + Ar) three-body quenching rate constants. The three-body quenching rate constants are nearly equal to the Xe 2 CI· formation rate constants and three-body dark quenching of XeCl(B,C) is negligible.

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The rate constants for XeF(B,C), XeCl(B,C), and XeI(B,C) formation from reactions of Xe(3P1) and Xe(3P2) with NF3, N2F4, NF2, CCl4, and CF3I have been measured relative to XeCl(B,C) formation from the reactions with Cl2. The XeCl(B,C) formation rate constants from Cl2 are assumed to equal the total Xe(3P2) and Xe(3P1) quenching rate constants. The dependence of the XeX* formation rate constants upon reagent for Xe(3P1) and Xe(3P2) are similar with the polyatomic reagents having considerably smaller XeX* product formation rate constants than does Cl2. The previous claim from this laboratory that the XeF(B,C) formation rate constant from NF3 was approximately equal to the total quenching rate constant is revised downward in this work.