Cross-sections for de-activation of Fe(a5D)

Abstract

Atomic iron was produced in a number of excited states by the isothermal flash-photolysis of Fe(CO)₅. Relaxation rates between the spin-orbit multiplets of the a⁵D states were measured in various gases by kinetic spectroscopy and plate photometry. The populations in the J= 0, 1, 2 and 3 states rapidly acquire a Boltzmann distribution, and subsequently undergo a comparatively slow relaxation to the ground a⁵D state. The overall relaxation appears to be dominated by the rule ΔJ=±1. The rate coefficients for the J= 3→4 transition were recorded for relaxation by Ar, He, H₂, D₂, N₂ and CO; except for relaxation by Ar which is abnormally slow, the coefficients are of similar magnitude to those for deactivation of Se(4³P₀). Excited atomic iron and possibly Fe⁺(a⁶D) reacted with O₂ and CO₂ to produce FeO, which was detected by the band at 2410 Å.