The photochemical iron + molecular hydrogen reaction in argon and krypton matrixes by irradiation in the visible region

Abstract

The rate of the (first-order) photochemical reaction between Fe atoms and H/sub 2/ molecules at dilute concentrations in Ar and Kr matrices has been measured at a number of irradiation frequencies between 16,000 and 18,600 cm/sup -1/, which covers excited states of the Fe atom with both 3d/sup 6/4s/sup 2/ and 3d/sup 7/4s/sup 1/ configurations. The results show that excitation of the atom, either directly or indirectly, into the a/sup 5/P/sub 3/ (d/sup 7/s/sup 1/) state leads to reaction but that the higher energy a/sup 3/P/sub 2/ (d/sup 6/s/sup 2/) state is unreactive. In Ar matrices, the rate of formation of FeH/sub 2/ can be related to the lifetime of the /sup 5/P/sub 3/ state. Use of H/sub 2/, D/sub 2/, and HD shows the different isotopic effect on the formation rate in the two matrices as well as the lesser isotope effect on the photodecomposition of FeH/sub 2/. Vibrational intensities in the infrared spectra suggest a lower limit of about 170/sup 0/ for the valence angle in the HFeH molecule. 12 references, 9 figures, 3 tables.