Absorption coefficients of the negative helium ion

Abstract

Free-free absorption coefficients of the negative helium ion are calculated by a phase-shift approximation, using continuum data that accurately account for electron-atom correlation and polarization. The approximation is considered to yield results within a few per cent of numerical values for wavelengths greater than 1μm, over the temperature range 1400–10080 K. These coefficients are expected to give the best current estimates of He– continuous absorption.