Quenching of excited Ar I and H by H2 in a gas discharge

The cross sections for quenching by H2 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)x10-19 and (1.5±0.3)x10-19 m2, respectively. The cross sections for the quenching of H(n=4) and H(n=5) by H2 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)x10-19 and 8.3(±0.7)(-2.5)x10-19 m2, respectively, where the first uncertainty is the random error and the second uncertainty is a possible systematic error. (author)