Quenching of excited Ar I and H by H2in a gas discharge

The cross sections for quenching by H 2 of the 4p´[1/2] 1 and 4p´[1/2] 0 states of Ar I, corresponding to emission lines at 696.5 and 750.4 nm, are obtained in a gas discharge using emission spectroscopy in conjunction with a laser-induced fluorescence measurement of the atomic hydrogen density, and found to be (1.3±0.3) × 10 -19 and (1.5±0.3) × 10 -19 m 2 , respectively. The cross sections for the quenching of H( n = 4) and H( n = 5) by H 2 are obtained using emission spectroscopy and the known quenching cross section for H( n = 3) and are found to be 3.1(±0.1)(-0.9) × 10 -19 and 8.3(±0.7)(-2.5) × 10 -19 m 2 , respectively, where the first uncertainty is the random error and the second uncertainty is a possible systematic error.