Место издания:Université Claude Bernard Lyon 1 Lyon
Первая страница:P12
Последняя страница:P12
Аннотация:Parameters of Stark broadening are of interest for plasma diagnostics since they can be fruitful for non-LTE plasmas. Not surprisingly, it is widely used to characterize the glow discharge, the discharge in a hollow cathode, high-density star plasma and other plasma objects. Unfortunately, there is a lack of the theoretical data on Stark broadening for transitions from high energy states such as singlet f-states of neutral calcium. Moreover, the spectral profiles of these lines are usually affected by strong ion broadening and distorted by it. On the other hand, experimental determination of the Stark parameters is seriously hampered by heterogeneity of plasma sources and self-absorption of lines which causes
apparent asymmetry of lines under investigation. The aim of the work is to study the asymmetric profiles of Ca I lines belonging to the transitions n(1)F°(3) →3(1)D(2).
In present work, a long plasma was produced on a piece of marble by a cylindrical lens in order to enhance collection of plasma radiation. Then it was projected on a slit of 0.32 m Czerny-Turner spectrograph. Such an arrangement allowed the estimation of spatial heterogeneity of long plasma across the plasma axis. Three lines of transition array n(1)F°(3) →3(1)D(2) were monitored: 487.81 nm (4f), 435.51 nm (5f), and 410.85 nm (6f). The line 410.85 nm was not observed. The resulting spectra were fitted to the theoretical line profile shifted and disturbed by H(β) function, which is Holtsmark distribution of plasma microfield, yielding the width w, shift d and the ion broadening parameter A. The latter for both lines is a linear function of temperature. Both lines have red Stark shift. As one can expect for high levels, all parameters obtained for line at 435.51 nm are larger than those obtained for line at 487.81 nm.