Role of temperature inhomogeneity in experiments measuring M-shell or L-shell spectral opacity

Abstract

As the value of the Rosseland mean of solar mixtures and β-Cepheid envelops around the “opacity bump” has been questioned, experiments measuring spectral transmission (directly related to opacity) of transition metals (Iron, Nickel, etc.) are ongoing with laser or ion beams created plasmas. Some authors have claimed that the observed discrepancy between experimental spectra and theoretical spectra may be partially understood as the effect of temperature inhomogeneity. We demonstrate that the transmission of a L- or M-shell weakly inhomogeneous plasma is identical to the transmission of a one-temperature plasma, and then that the experimental transmission in such a spectral range is not sensitive to the existence of a gradient. Origin of discrepancy must be searched elsewhere.