Measurements of effects of pressure and temperature on the decay constants of excited Ar atoms (3p54s1) have been made in electron beam pulse irradiated Ar gas (100–700 Torr) by means of fast absorption spectrophotometry. Interpretation of the pressure and temperature dependence of the decay constants leads to the conclusion that the resonance state Ar (1s) species decay via formation of electronically excited molecular intermediates in this pressure range. The resonance state atoms are shown to decay in a manner consistent with a sequence of elementary steps involving collisional stabilization and radiative decay of excited molecules. Observed small positive temperature coefficients of all Ar (1s) species are attributed to effects of temperature on collision frequencies with virtually zero energies of activation at 153 to 300 K.

No abstract

No abstract

Fine structure of the metastable a 3Σ u + state of the helium molecule. Further results J. Chem. Phys. 69, 98 (1978); 10.1063/1.436350 Near infrared absorptions of neon, argon, krypton, and xenon excited diatomic molecules J. Chem. Phys. 68, 4595 (1978); 10.1063/1.435565Absorption spectra of matrixisolated alkaline earth metal diatomic moleculesThe transient absorption spectra of electron-irradiated 12-atm helium have been measured in the wavelength region 3000-11 000 A. The observed molecular absorptions correspond to the c 3I/ +--Q 3I/, e 3ll g +--Q 3I/, and i 3ll g +--Q 3I/ transitions, short-lived atomic absorptions arising from He·(2 3 S) being observed at several wavelengths. The rotational temperature of He· 2 (a 3It, v" = 0) produced initially is estimated to be room temperature from the intensity distribution of the P branch.The vibrational deactivation rate of He· z(a 3 I/, v" = I) depends linearly on helium pressure, the rate constant being 1.0X 10-14 cm 3 sec-I. The rate constants of the quenching reactions of He" 2 (a 3 I.+, v' = 0) by Ne, Ar, Kr, Xe, Hz, N 2 , O 2 , CO, NO, NzO, and CO 2 have been determined from time-dependent measurements of the absorption decay. The rate constants range from 0.4X 10-10 cm 3 sec-1 for Ne to I.OX 10-9 cm 3 sec-1 for CO 2 . An intense emission and absorption were observed at 7772 A in the quenching processes of He·2(a 3 I/, v" = 0) by oxygen-containing compounds.

No abstract