Semiclassical convergent calculations for the electron-impact broadening and shift of some lines of neutral helium in a hot plasma

Neutral helium spectral lines in dense plasmas

“…We find that the shift of this line is more sensitive to plasma screening, as the virtual transitions to neighboured states do not contribute to the line profile if the energy difference is comparable to the plasma frequency [66,78]. The discrepancy between our results and the available data is more Table I and II given by Bassalo et al [76].…”

“…Concerning the high densities, the data by Gigosos et al [75] already indicate the importance of strong coupling effects. Regarding the data point reported by Bassalo et al [76], the discrepancy might be due to neglect of the shift and width in the lower energy states. Bassalo et al [76] use the Debye radius for the maximum impact parameter and take the reduced matrix elements from the oscillator strength of the transition.…”

“…13, additional data for a larger range of densities are shown: i) values obtained by Pérez et al [3] for densities from (2.0 − 6.46) × 10 22 m −3 and temperatures between (1.9 − 4.3) × 10 4 K, ii) experimental values by Mijatović et al [27] and Kelleher [30], iii) measurement by Milosavljević and Djenize [31] was performed at electron densities between (0.3 − 8.2) × 10 22 m −3 and electron temperatures of (8−3.3)×10 4 K in five different plasma discharge conditions using a linear, low-pressure, pulsed arc as an optically thin plasma source, operated in a helium-nitrogen-oxygen gas mixture. Comparison with the theoretical results by Bassalo et al [76] are given as well. Furthermore, the results by Gigosos et al [23,75] in the density range (0.25 − 50.0) × 10 22 m −3 and temperature range (1.9 − 4.2) × 10 4 K are included.…”

“…7 and 8, respectively. Comparisons are made with: i) a number of measured [30,32,77] and theoretical data [76], ii) observation in a repetitively pulsed low-pressure arc hydrogen-helium plasma measured by Mijatović et al [27] with an electron density range (0.25 − 0.50) × 10 22 m −3 , electron temperatures of (1.93 − 2.36) × 10 4 K and gas temperatures of (0.5 − 1.2) × 10 4 K , the latter are measured from the Doppler broadening of He I line profiles, iii) theoretical results by Gigosos et al [23,75], covering a density range of (0.25 − 249) × 10 22 m −3 and a temperature range of (1.93 − 6.34) × 10 4 K, iv) the measured values of Pérez et al [5] in the plasma density range of (1 − 6) × 10 22 m −3 and temperature interval of (0.8 − 3) × 10 4 K with mean value 2 × 10 4 K, v) theoretical values from Griem's approach [52], reported by Pérez et al [5]. Good agreement between our results and other investigations is found.…”

“…We compare our results with the visible spectrum emitted by a helium plasma generated in a wall-stabilized arc, which is reported by Kelleher [30], the determined electron density was 1.03 × 10 22 m −3 at electron and gas temperatures of 2.09 × 10 4 K and 1.58 × 10 4 K, respectively. The semi-classical approach of Bassalo et al [76] assumed for Debye screening by introducing the Debye cut-off parameter. The broadening and shift due to electron collisions with and without Debye screening effect were estimated.…”