Collisional deactivation of two-photon-excited Ar (4p; J = 0, 2) states byH-2 and several hydrocarbon and fluorine containing molecules

The quenching rate constants of argon atoms in the 4p'[1/2](0)-(2p(1)), 4p[ 1/2](0)-(2p(5)), 4p[3/2](2)-(2p(6)) and 4p[5/2](2)-(2p(8)) states, the uppe r levels of the 750.4, 751.5, 763.5 and 801.5 nm lines respectively, by H-2 , CH4, C2H2, C2H4, C2H6, CF4, CHF3 and SF6 have been determined. Argon atom s at room temperature are two-photon excited in the 184-190 nm range, and t he decay time of the fluorescence emission is measured in the presence of v arious reagents. With H-2, the collisional quenching rate coefficients of A r(2p(1)), Ar(2p(5)), Ar(2p(6)) and Ar(2p(8)) are 0.27, 4.1, 6.8 and 5.4 x 1 0(-10) cm(3)s-(1), respectively. Therefore, in hydrogen rich plasmas, the 7 50.4 nm line of argon is the best suited for actinometry measurements. For the other studied molecules, the quenching rates range between 1.6 and 11 x 10(-10) cm(3)s(-1). For a correct estimation of the relative density of tr ansient species in plasma by the actinometry technique, it is recommended t o consider the collisional quenching of the upper states of the optical emi ssion lines used.