A note on the contribution of multi-photon processes to radiative opacity

TL;DR

This paper examines the potential impact of multi-photon processes on radiative opacity measurements, suggesting they are significant mainly for highly excited states under intense radiation conditions.

Contribution

It provides a simple estimate indicating that multi-photon processes are likely important only for highly excited states in high-radiation environments.

Findings

Multi-photon processes are significant for highly excited states.

Hydrogenic formulas suggest limited impact on lower states.

Implications for modeling stellar interior opacities.

Abstract

Recently, Bailey et al. performed iron opacity measurements on the Z machine at Sandia National Laboratory in conditions close to the ones of the base of the convective zone of the Sun. Such experiments have raised questions about the physical models commonly used in opacity codes. To understand the discrepancy between experiment and theory, More et al. investigated the role of two-photon processes. In the present work we show, by a simple estimate and using hydrogenic formulas, that due to the intensity of the backlight radiation seen by the sample, such processes are likely to play an important role only for highly excited states.