Effect of thermal collective modes on the Stark broadening of hydrogen spectral lines in strongly coupled plasmas

Abstract

The paper is motivated by the recent (2014) benchmark measurements of the full width at half maximum (FWHM) of the Hα line by Kielkopf and Allard (KA), which reached the electron densities Ne by two orders of magnitude greater than the corresponding previous benchmark experiments, namely up to Ne = 1.4 × 1020 cm−3. At this range of Ne, no theoretical calculations of the FWHM of the Hα line existed, except calculations by KA; however, the latter is inconsistent because of the neglect of the contribution by plasma electrons. In the present paper we develop a consistent analytical theory that is relevant to the range of the electron densities reached in KA experiment. At this range of Ne, a new factor becomes significant—the factor never taken into account in any previous simulations or analytical theories of the Stark broadening of hydrogen spectral lines: a rising contribution of the electrostatic plasma turbulence (EPT) at the thermal level of its energy density. We show that this contribution becomes comparable to the corresponding contribution by electron and ion microfields at this range of Ne. As a result, our theoretical FWHM of the Hα line becomes in a very good agreement with the experimental FWHM of the Hα line by KA in the entire range of their electron densities. The present theory can be also used for calculating Stark profiles and the FWHM of other hydrogen spectral lines.