The quenching rate constants of argon atoms in the
4p′[1/2]0−(2p1), 4p[1/2]0−(2p5),
4p[3/2]2−(2p6) and
4p[5/2]2 − (2p8) states, the upper levels of the
750.4, 751.5, 763.5 and 801.5 nm lines respectively, by
H2, CH4, C2H2, C2H4, C2H6, CF4, CHF3
and SF6 have been
determined. Argon atoms at room
temperature are two-photon excited in the 184–190 nm
range, and the decay time of the fluorescence
emission is measured in the presence of various
reagents. With H2, the collisional quenching
rate coefficients of Ar(2p1), Ar(2p5), Ar(2p6) and
Ar(2p8) are 0.27, 4.1, 6.8 and 5.4 × 10−10 cm3s−1,
respectively. Therefore, in hydrogen rich
plasmas, the 750.4 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 × 10−10 cm3s−1. For a
correct estimation of the relative density of transient species
in plasma by the actinometry
technique, it is recommended to consider
the collisional quenching of the upper states of the
optical emission lines used.