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LE JOURNAL DE

PHYSIQUE

STARK BROADENING OF NEUTRAL AND SINGLY IONIZED GALLIUM AND INDIUM LINES

M. N'DOLLO and M. FABRY

Laboratoire de

Physique

des Milieux Ionisés (C.N.R.S., U.A. 835),

Faculté des Sciences de

Nancy,

B.P. 239,
54506

Vandoeuvre-lès-Nancy Cedex,

France

(Regu le

18 novembre

1986, accepte Ie

19 fivrier 1987)

Résumé : Les

élargissements

Stark de raies du

gallium et de l'indium neutre (Ga I, In I) et une fois ionisé (Ga II, In II) sont calculés à partir d'une méthode semiclassique et mesurés. Les déterminations expérimentales sont déduites de l'observation spectroscopique d'un arc à cathode liquide utilisant un mélange sodium-indium ou potassium-gallium, la densité electronique pouvant varier de 1014 à 2 1015 cm-3 et la temperature électronique

étant voisine de 3300K.

Abstract : Stark widths for lines of neutral and

singly ionized gallium and indium are both calcu- lated and measured. Calculations are based on a semiclassical method. Measurements are carried out by observing the emission of a low-pressure sodium-indium or potassium-gallium mixture in a liquid cathode arc. The electron density ranged from 1014 to 2 x 1015 cm-3 and the electron temperature was close to 3300K. J.

Physique

48
(1987)

703-707 MAI

1987,

Classification

Physics

Abstracts

32.70J - 52.70K

1. Introduction.

Stark broadening parameters of spectral lines will be useful in the characterization of plasmas. Nu- merous measured and calculated Stark widths have been reported for neutral and singly ionized elements but no data are available for gallium and indium.

In this

paper we report calculated and measured

Stark widths for some lines of neutral or

singly ion- ized gallium and indium. Measurements consist in the spectroscopic observation of a potassium-gallium or a sodium-indium arc. In the plasma, electron den- sity ranges from 1014 - 2 x 1015cm-3 for an electron temperature of about 3300K. G.B.K.O. theory [1] is used for the calculations which was proved successful in predicting the widths of isolated lines for neutral atoms [2 - 3].

We used

semi-empirical relations [4] for ions ; indeed, experimental works show that the

G.B.K.O. widths are often too small

by a factor 2 to

10 for ion lines

[5 - 71. 2.

Theory.

The broadening of emission lines is treated by using the substantial difference in equilibrium veloc- ities for electrons and ions. For the slow moving ions, the quasistatic theory can be used : ions are as- sumed to be motionless while the perturbation acts, which significantly alters the atomic Hamiltonian. It results in a shift of the levels by the Stark effect.

The electron

impact theory requires that strong col- lisions are well separated in time while overlapping collisions are weak and can be treated by means of the second order perturbation approximation. The effect can be reduced to calculation of the scatteringArticle published online by 704
matrix for a single collision.

Averaging

over the pos- sible electron configurations is required.

Electrons

are assumed to have a Ma,xwellian velocity distribu- tion, to be randomly distributed in space and to have straight trajectories. The broadening calculations are greatly simpli- fied when only isolated lines are considered. This means that neighbouring energy levels do not over- lap.

The electron

impact width we and shift d of an isolated line with upper state i and lower state f can be obtained from G.B.K.O. theory by [1] : in terms of the S-matrix for collision of a single elec- tron with an atom. The curly brackets , indicate an angular average, the thermal average being com- pleted by integration over velocities v. The minimum impact parameter pmin is obtained by : and the cut-off in the integration over the parameter , P atquotesdbs_dbs32.pdfusesText_38

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