A universal approach to Rydberg spectral line shapes in plasmas

Abstract

A universal approach for the calculation of Rydberg atom line shapes in plasmas is developed. This approach goes far beyond the calculation capabilities of the standard models. It is based on analytical formulae for the intensity distribution in radiation transitions n − n′ between highly excited atomic states with large values of principal quantum numbers n, n′ ≫ 1, with Δn = n − n′ ≪ n, and on the frequency fluctuation model to account for ion thermal motion effects. The theory allows us to describe a transition from the static to the impact broadening domains for every hydrogen spectral line. The specific cases of broadening of Hn−α(Δn = 1) and Hn−β(Δn = 2) lines are considered in detail for various values of plasma parameters. The line shapes are presented in a universal manner as functions of the relative frequency splitting and of the fluctuation rate ν of the ion plasma microfield, using dimensionless variables. For small values of ν, the static line shapes which generalize the well-known Underhill–Waddell data for the Rydberg state case are presented. For large values of ν, the transition to impact ion broadening is observed, resulting in a narrowing effect. A comparison with the hydrogen Hα line shape calculations shows a good agreement between the universal approach for Rydberg lines and traditional spectral line shapes.

Stark effect of high-nhydrogen-like transitions: quasi-contiguous approximation

“…where R 0 is a constant of the order of unity to be determined below. The full Stark width is then w = f w qs (26) (compare, e.g., with similar considerations in [13]). The meaning of the so-defined R 0 is now evident: it is a threshold determining the transition to the quasistatic limit.…”

The Coulomb Symmetry and a Universal Representation of Rydberg Spectral Line Shapes in magnetized Plasmas

“…Finally, we can obtain the formula for the intensity of radiation as the function of the energy shift(frequency). It is the convolution of the expressions (13) and (20).…”

“…The similar calculation, using the FFM, but without taking into account the influence of the magnetic field on the shape of spectral lines, is given in [20]. Moreover, this work contains the detailed analysis of the influence of the thermal ion velocity on the plasma line shapes.…”

Thomson Scattering in Iter Divertor

“…Для оценки влияния такого излучения в диверторе ИТЭР на точность томсоновских измерений была проведена оценка ширины спектральной линии Р7 (переход n = 7 → n = 3) [5]. При расчёте ширины линии были использованы упрощённые модели [6,7] расчёта статической зееман-штарковской структуры спектральных линий, а динамически уширенные контуры линии были получены на основе новой кинетической теории уширения [8]. На рис.…”