Stark broadening of Sr I spectral lines
Astron. Astrophys. Suppl. Ser.
Stark broadening of Sr I spectral lines?
M.S. Dimitrijevic 1
S. Sahal-Brechot 0
0 Laboratoire \Astrophysique, Atomes et Molecules", Departement Atomes et Molecules en Astrophysique, Unite associee au C.N.R.S. No. 812, Observatoire de Paris-Meudon , 92190 Meudon , France
1 Astronomical Observatory , Volgina 7, 11050 Belgrade , Yugoslavia
| Using a semiclassical approach, we have calculated electron−, proton−, and ionized helium−impact line widths and shifts for 33 Sr I multiplets for perturber densities 1013 cm−3 (for stellar plasma research) and 10151018 cm−3 (for laboratory plasma research) and temperatures T = 2 500 − 50 000 K.
lines; pro le-atomic data
1. Introduction
Strontium lines are present in solar and stellar spectra.
E.g.
Komarov & Basak (1993)
have found neutral
strontium lines in the spectra of Sun and two Praesepe's stars.
They are also of interest since Sr is one of thermonuclear
s - processes product in stars and its overabundance is
observed in CH and metal de cient barium stars
(Sleivyte
& Bartkevicius 1995)
. Neutral strontium lines are also of
interest for the investigation of laboratory plasmas.
Consequently,
Kato et al. (1984)
investigated wavelength shifts
of Sr I lines emitted by an inductively coupled plasma and
Karabut et al. (1980)
dynamics of strontium line shapes
during a pulsed discharge. Such lines have been
considered theoretically as well by
Davis (1972)
, for research
of a laser - generated barium plasma. In order to
continue our research of Stark broadening parameters needed
for the investigation of astrophysical and laboratory
plasmas and to provide the needed Stark broadening data, we
have calculated within the semiclassical-perturbation
formalism
(Sahal−Brechot 1969a,b)
electron-, proton-, and
ionized helium-impact line widths and shifts for 33 Sr
I multiplets. A summary of the formalism is given in
Dimitrijevic & Sahal-Brechot (1984).
2. Results and discussion
Energy levels for Sr I lines have been taken from
Moore
(1971)
. Oscillator strengths have been calculated by using
Send o print requests to: M.S. Dimitrijevic
?Table 1 is only available in electronic form: The material
published electronically can be accessed: by ftp at
cdsarc.ustrasbg.fr or 130.79.128.5 or on WWW at:
http//cdsweb.ustrasbg.fr/abstract.html
the method of
Bates & Damgaard (1949)
and the tables
of
Oertel & Shomo (1968)
. For higher levels, the method
described by
Van Regemorter et al. (1979
) has been used.
We note that
Gruzdev (1967)
has found that the
semiempirical and Hartree - Fock calculations of Sr I oscillator
strengths agree fairly well with the f values calculated by
the method of Coulomb approximation.
In addition to electron-impact full halfwidths and
shifts, Stark-broadening parameters due to proton-, and
He II- impacts have been calculated. Our results for 33
Sr I multiplets are shown in Table 1 (accesible only in
electronic form), for perturber densities 1013 cm−3 (for
stellar plasma research) and 1015− 1018 cm−3 (for
laboratory plasma research) and temperatures T = 2 500 −
50 000 K. We also specify a parameter c
(Dimitrijevic
& Sahal−Brechot 1984)
, which gives an estimate for the
maximum perturber density for which the line may be
treated as isolated when it is divided by the
corresponding full width at half maximum. For each value given in
Table 1, the collision volume (V ) multiplied by the
perturber density (N ) is much less than one and the impact
approximation is valid
(Sahal−Brechot 1969a,b)
. Values
for N V > 0.5 are not given and values for 0.1 < N V 0.5
are denoted by an asterisk. When the impact
approximation is not valid, the ion broadening contribution may be
estimated by using quasistatic approach
(Sahal−Brechot
1991; Griem 1974)
. In the region between where neither
of these two approximations is valid, a uni ed type theory
should be used. For example in
Barnard et al. (1974)
, a
simple analytical formulas for such a case are given. The
accuracy of the results obtained decreases when
broadening by ion interactions becomes important.
M.S. Dimitrijevic and S. Sahal-Brechot: Stark broadening of Sr I spectral lines
Acknowledgements. This work is a part of the project \Physics
and dynamics of celestial bodies", supported by Ministry of
Science and Technology of Serbia.
Barnard A.J. , Cooper J. , Smith E.W. , 1974 , JQSRT 14 , 1025
Bates D.R. , Damgaard A. , 1949 , Trans. Roy. Soc. London Ser. A 242 , 101
Davis J. , 1972 , JQSRT 12 , 1351
Dimitrijevic M.S. , Sahal−Brechot S. , 1984 , JQSRT 31 , 301
Griem H.R. , 1974 , Spectral Line Broadening by Plasmas. Academic Press, New York
Gruzdev P.F. , 1967 , Opt. Spektrosk. 22 , 169
Karabut E.K. , Kravchenko V.F. , Mikhalevskii V.S. , 1980 , Opt. Spectrosc. 48 , 386
Kato K. , Fukushima H. , Nakajima T. , 1984 , Spectrochim. Acta B 39 , 979
Komarov N.S. , Basak N. Yu ., 1993 , Astron. Zh. 70 , 111
Moore C.E. , 1971 , Atomic Energy Levels II , NSRDS-NBS 35, Washin (...truncated)