Photochemical Fe + H2 reaction in Ar and Kr matrices by irradiation in the visible region

The rate of the (first-order) photochemical reaction between Fe atoms and H2 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-1, which covers excited states of the Fe atom with both 3d64s2 and 3d74s1 configurations. The results show that excitation of the atom, either directly or indirectly, into the a5P3 (d7s1) state leads to reaction but that the higher energy a3P2 (d6s2) state is unreactive. In Ar matrices, the rate of formation of FeH2 can be related to the lifetime of the 5P3 state. Use of H2, D2, 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 FeH2. Vibrational intensities in the infrared spectra suggest a lower limit of about 1700 for the valence angle in the HFeH molecule. 12 references, 9 figures, 3 tables