HAL Id: jpa-00219465
https://hal.archives-ouvertes.fr/jpa-00219465
Submitted on 1 Jan 1979
HAL
is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.
L’archive ouverte pluridisciplinaire
HAL, estdestinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
A MODIFIED ADIABATIC THEORY CALCULATION FOR THE STARK BROADENING OF He I (31P0-21S)
M. Dimitrijević, P. Grujić
To cite this version:
M. Dimitrijević, P. Grujić. A MODIFIED ADIABATIC THEORY CALCULATION FOR THE
STARK BROADENING OF He I (31P0-21S). Journal de Physique Colloques, 1979, 40 (C7), pp.C7-
119-C7-120. �10.1051/jphyscol:1979759�. �jpa-00219465�
JOURNAL DE PHYSIQUE CoZZoque C7, suppZ6ment au n07, Tome 40, JuiZZet 1979, naae C7- 119
l o 1 A MODIFIED ADIABATIC THEORY CALCULATION FOR THE STARK BROADENING OF He I (3 P -2 S)
M.S. ~irnitrijevig
',
P. ~ruji6".% 3 n s t i t u t e o f Applied Physics, P.O. Box 24, 11001 BeZgrade, YugosZavia.
I n s t i t u t e o f Physics, P. 0. Box 57, 11001 Be Zgrade, Yugos Zavia.
Curvilinear trajectory adiabatic In our particular case we retain only the approximation for calculatinq Stark broa- polarization potential
denin? parameters for neutral lines from 4 1 0
V = -C,/r, C,(3 P ) = -5.275 lo4 au plasr.as, as proposed by authors, l' has P
been applied. to H ~ I ( ~ ~ P O - ~ ~ S ) line, at T = in which case one obtains for the phase 5000. K and ~ ~ = 1 0 ~ ~ c m ' ~ . This line has be- shift 2
en chosen for two reasons: (1) The quad- 4
n(p) = F ( D ) .n(O)
,
P=(P/P,),
pC=(-4C4/E) 1 / 4 rupole perturber-enitter interaction po-v:here the universal function ~ ( 6 ) is given tential is much smaller than correspondinq
dipole polarization interaction, so that by
2 2
sinple analytical calculations can be car- 5 = ? 6 f i {F(Y) - ~ K ( Y ) ), B =1+1/6
,
Y = ( 8 - 1 ) / Z C ried out; (2) Stark constant C 4 of the up-per level of the transition is neqative and large, so that so called defocusing effect can be distinctly demonstrated.
V1ithin the semiclassical adiabatic theory3 half-halfwidth and shift of a line can be calculated by (we use atomic units)
where N is the electron density, e
;
is the mean electron velocity, ni(nf) is the phase shift for the elasticscatter in^
on the i- nitial (final) state of target atom and P is an impact paraneter of the perturber.Phase shift n(p) is evaluated along a cor- responding curvilinear path,2 as detemi- ned by motion of the impact electron in the long-range potential of the emitter.
E being (average) electron energy and K(y)
E ( y ) are the elliptic inteqrals of first and second kind, respectively. 0 (O) is the usual "strai~ht-line trajectory rhase shift". 3
In Figure 1 we have plotted n(O) and n for the upper level of the transi- tion. Since the lower level Stark constant C4(21~)=400.97 au is much smaller than the absolute value of the same constant of the upper level, we neglect nf(p) in the exp- ressions for tr and d. As can be seen from Figure 1, defocusing effect of the strong- ly repulsive potential V gives rise to
P
drastic change of behaviour of n ( p ) at small and medium values of the impact pa- rameter.
Evaluation of w and d has been carried out numerically, and results are
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1979759
7 10 100 Impact parameter fa,)
Figure 1. Semiclassical phase shifts for e
-
He 1(3lp) scattering, at Ee= 0.431 eV.presented in Table 1, together with cor- responding data from Griem (1974) .4 Since in low-density plasmas Stark parameters depend practically linearly on N, it is evident from Table 1 that the defocusing effect reduces w by 12%, whereas the shift has been increased by approximatelly 30%.
Table 1. Half-halfwidth and shift of He I (3lp-21s) line, X = 5017
2,
multiplet 4.Present 1015
calc. 5000 0.0321 -0.0361 Griem 1016 5000 0.3667 -0.250
spent inside the sphere with radius R = 1 . 1 2 3 . ~ ~ ~ one has as an estimate for p=O:
1 1
T ; 4 .lo4 au, whereas w-l(3 P-3 D)
-
2.1 .lo3 au. The same holds for other impact parameters not too close to R. 2
At higher temperatures inelastic collisions can not be ignored and the ef- fect of back reaction is less prominent, 5 as oposite to the low-temperature limit, where this effect may become dominant. 1
We conclude that, whenever there is a very close perturbing level below the upper level of the transition, defocusing effect may be noticeable at low temperatu- res and should be taken into account.
We are grateful to RZN of SR Ser- bia for the financial support.
R e f e r e n c e s 1. M.S.Dimitrijevi6 and P.V.Gruji6,
ESCAMPIG 1978, Essen, p. C44.
2. fl.S.Dimitrijevi6 and P.V.Gruji6, to be published.
3. H.van Regemorter, 1972, in Atoms and Molecules in Astrophysics, Academic Press
4. H.R.Griem, 1974, Spectral Line Broade- ning by Plasmas, Academic Press, New York
5. M.S.Dimitrijevi6 and P.Gruji6, 1978, J.Q.S.R.T.,
19,
407As is well knownI3 the very usage of the adiabatic approximation is justifi- ed if w-' < < T, where j corresponds to any
i j
perturbing level and T is the collision time. If we define the latter as time
