Free-Free Continuum of Oxygen*

Abstract

Oxygen is treated in an example calculation of the free-free absorption cross section. Wave functions for the free electron in the field of an oxygen atom under the assumption of no electron exchange or core polarization are calculated on the IBM 704. These wave functions are applied to the calculation of the free-free absorption corresponding to a particular continuum frequency and initial state energy. In this calculation the dipole acceleration form of the matrix element is computed. The matrix element calculation is carried out on the LGP-30. These partial cross sections are smeared over a Maxwell-Boltzmann distribution of initial electronic energies in order to obtain the free-free cross section. The results are in approximate agreement with the familiar classical Kramers result for an effective Z of 0.35, although the frequency dependence is noticeably different. We carry out the calculation for the temperatures 8000, 6000, and 4000°K and find there to be no temperature dependence in the cross section, at least in this range. The calculation is also carried out under the assumption of a mean electron velocity at 8000°K. The magnitude does not differ much although the wavelength dependence is somewhat less.