The atomic line contribution to the radiation absorption coefficient of air

Abstract An IBM 7094 computer program has been devised to compute the atomic line contribution to the spectral absorption coefficient of air. The input to this program consists of a list of the possible atomic states present in the gas, and for each of these, its spectroscopic description, energy, and occupation number or concentration (obtained from a previous calculation). The program compares all pairs of levels, applies selection rules as appropriate and thereby picks out the allowed transitions. The contribution to the absorption coefficient due to each transition is then computed, using Hartree-Fock-Slater radial dipole integrals and Baranger-Stewart electron collision broadening in a Voigt profile. A progressive lumping of the atomic levels is employed. For principal quantum numbers n = 2 and 3 most multiplets are treated distinctly, for n = 4 to 8 and l ⩽ 3 transition arrays are computed, and for larger l and n ⩾ 9 hydrogenic approximations are made. Line series are terminated by a temperature-density dependent cut-off consistent with our photoelectric calculation. Representative results are presented and comparisons are made with other calculations. A discussion is presented of upper bounds on Rosseland and Planck mean absorption coefficients, including the derivation of a new bound for the Planck mean.