Convergent calculations for electron impact broadening and shift of neutral helium lines

Convergent calculations for electron impact broadening and shift of neutral helium lines

Z Quant. Spectrosc. Radiat. Transfer Vol. 28, No. 2, pp. 75-80, 1982 Printed in Great Britain. CONVERGENT BROADENING 0022--40731821080075-06503.0010...

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Z Quant. Spectrosc. Radiat. Transfer Vol. 28, No. 2, pp. 75-80, 1982 Printed in Great Britain.

CONVERGENT BROADENING

0022--40731821080075-06503.0010 © 1982Pergamon Press Ltd.

CALCULATIONS FOR ELECTRON IMPACT AND SHIFT OF NEUTRAL HELIUM LINES J. M. BASSALO

Departamento de Ffsica, Universidade Federal do Par:i, ParL Brazil

and M . CATI'ANI

and V. S.

WALDER

Instituto de Fisica, Universidade de Silo Paulo, Caixa Postal 20516, Silo Paulo, Brazil

(Received 22 September 1981) Abstract--Using the convergent semiclassical method, we have calculated the electronic widths and shifts of 42 neutral He lines for an electronic density of 10~6/cm3 and T = 5000, 10,000, 20,000, and 40,000 K. To account of ions effects, we have calculated the Stark parameter A and parameter R.

1. INTRODUCTION

The broadening and shift of spectral lines produced by electronic collisions can be estimated by using a semiclassical formalism with convenient approximations to determine the effects of strong collisions, 1'2 for which perturbation theory breaks down. There are two slightly different semiclassical impact theories I to evaluate the effects of electronic collisions in plasmas: an impact-parameter cutoff theory and a convergent theory. The cutoff theory has been adopted by , many authors 1 and has been used extensively by Griem and collaborators t'3'4 and by SahalBrechot 5-7 to study the line shapes of neutral atoms and ions. The convergent theory, developed by Vainshtein and Sobel'mana in a two-level approximation, was applied with some modifications by Dyne and O'Mara9 to calculate the widths and shifts of neutral He lines. For He(I) lines, it is necessary, in principle, to use a many-levelt'x5 instead of a two-level approximation, as is done in Ref. 2. We have verified2 that the cutoff and convergent methods are about equally successful in describing the experimental results. Within the experimental errors, the agreement between theoretical and experimental results is good for the widths and reasonably good for the shifts./° The calculations have been performed with and without Debye shielding and it has been verified, according to Griem, ! that somewhat better agreement with the experimental results is found if the Debye screening effects are neglected. In our preceding paper, 2 we have not analysed the validity of the straight-path approximation for the electron trajectory to evaluate the widths and shifts of He lines. We verified that, within the framework of the convergent approach used in the cutoff formalism,l'u it is a very good approximation since deviations of the straight-line trajectory are of minor importance and can be neglected. We have now calculated, with the convergent method, the electronic widths toe and de of 42 neutral He lines, for an electron density of N = 10~6/cm3 at temperatures T = 5000, 10,000, 20,000, and 40,000 K. For these conditions, we have also calculated the Stark parameter A and the parameter R defined by Griem) Our results for toe, de, A, and R are listed in the next section. 2. CALCULATION OF

fJ0e

AND d, FOR He(I) LINES

According to the convergent method in a many-level approximation,2 the half half-width ~, and the shift de caused by electron collisions for an isolated Lorentzian line (measured in Hertz) are given by

toe = N fo dr vF(v)

db b{1 - cos[~b1~(b, v)] × exp[- Flu(b, v)/21} 75

(1)

76

J. M, BASSAL~)et

al.

and

de = - N

dv vF(v)

Jo

db b sin[~t~(b, v)] x exp[-FiF(b, v)/2],

(2)

where the indices I and F refer to the initial and final states of the line, respectively, N is the density of the perturbing electrons, v the electron velocity, F(v) the Maxwell-Boltzmann velocity distribution, b the impact parameter, FIF(b, v)= Ft(b, v)+ Fv(b, v), and ~n:(b, v)= ~f(b, v) - ~bF(b, v). The functions Fr(b, v) and ~br(b, v), with K = I or F, have been calculated by assuming that the electron describes a straight path with constant velocity during the collision and that its interaction with this atom is dipolar; these are shown in our preceding paper. 2 As is easily verified, the contributions of the quadrupole interaction to the broadening and shift of He(I) lines are negligible. The He(I) states are indicated by InK'~lKmr), where a = 1 for para-helium and a = 3 for ortho-helium; the final state F has been chosen as the lowest energy level. In all cases, we have taken into account the contributions of both initial and final states to the widths and shifts. In some cases, since the lowest energy levels are much less polarizable than the initial states, their contributions to the widths and shifts could be neglected compared with those of the initial states. The reduced dipole matrix elements for n _<-4 have been calculated by using the oscillator strength of Wiese et al. j2 For n _->5, we have used hydrogen-like wavefunctions with principal quantum numbers adjusted to give the measured bound states energies. The energy differences htonol,nol between the states Inal) and [n~l') are given by Moore. 13 Using Eqs. (1)-(4), we have calculated the electronic half half-widths toe and shifts de. We have also calculated the Stark parameter A and the parameter R defined by 1 A

=

(47r/3)(C4/toe)3/4N I/4

and R = 61/3"n"I/6(e2/KT)I/2N

I/6.

These parameters have been introduced by Griem et al. 1"3to obtain the contributions of the ions to the widths and shifts of the lines. The total half half-widths to and shift d, due to electrons and ions, are given by to = toe[1 + 1.75A(1 - 0.75R)] and d = de -+2.0A(1 - 0.75R)toe. Our results for toe and de (measured in/~) and A are shown in Table 1. The R values for N = 10~6/cm3 and T = 5000, 10,000, 20,000, and 40,000 K are 0.5893, 0.4167, 0.2946, and 0.2083, respectively. The electron impact widths and shifts are linear in N, A scales as N TM, and R as N 1/6. The dependence of toe and de and, consequently, of A on temperature is not straightforward and an interpolation is necessary to obtain values for temperatures between 5000 and 40,000 K, which are not listed in Table 1. Comparing our electronic widths and shifts (see Table 1) with the corresponding values of Griem, 1 we see that our widths are smaller. These characteristics can be understood in view of Fig. 3 of Dyne and O'Mara, 9 who show the differences between the cutoff and convergent methods in calculating the widths and shifts of the lines.

Convergent calculations for electron impact broadening

77

Table 1. Electron impact widths (toe), shifts (de), and the Stark parameter A for He(I) for N = 1016/cm3 and T = 5000 10,000, 20,000, and 40,000 K.

L(.~) 584

11s ÷ 21p

537

11s ÷

31p

522

11s + 41p

20581

r (z)

21s ~ 31p 3965

21s + 41p 7281

21p ÷ 31s 5048

-0.1371E-03

0.1290E-03

-0.1328E-03

0.0112

20000

0.1472E-03

-0.1202E~03

0.0102

40000

0.1709E-03

-0.1019E-03

0.0091

5000

0.4066E-02

-0.2887E-02

0.1604

10000

0.3863E-02

-0.2383E-02

0.1667

20000

-0.1904E-02

0.1777

40000

0.3548E-02 0.3169E-02

-0.1474E-02

0.1934

5000

0.1624E-01

-0.1089E-01

0.2965

10000

0.1519E-01

-0.8826E-02

0.3118

20000

0.1373E-01

-0.6924E-02

0.3363

40000

0.1205E-01

-0.5269E-02

0.3710

5000

0.3066E+00 0.3724E+00 0.4524E+00 0.5427E+00

-0.4131E+00

0.0428

40000

21p -* 51s 6678

21p ÷ 31d 4922

21p ÷ 41d 4388

21p ÷ 51d

-0.4121E+00

0.0370

-0.3812E+00

0.0320

-0.3258E+00

0.0279

5000

0.3562E+00

-0.2587E+00

0.1610

10000

0.3394E+00

-0.2168E+00

0.1670

20000

0.3138E+00

-0.1770E+00

0.1771

40000

0.2832E+00

-0.1406E+00

0.1913

5000

0.9373E+00

-0.6303E+00

0.2958

10000

0.8769E+00

-0.5122E+00

0.3110

20000

0.7932E+00

-0.4035E+00

0.3353

40000

0.6968E+00

-0.3090E+00

0.3695

5000

0.2754E+00

0.3595E+00

0.0905

10000

0.3178E+00

0.3546E+00

0.0813

20000

0.3519E+00

0.3278E+00

0.0753

40000

0.3698E+00

0.2838E+00

0.0725

5000

0.5347E+00 0.6064E+00

0.6515E+00

0.1517

0.6235E+00

0.1380

0.5578E+00

0.1306

40000

0.6528E+00 0.6622E+00

0.4684E+00

0.1292

20000

4438

0.0126

0.1108E-03

10000

21p + 4 1 s

A

5000

20000

5016

d e (~)

10000

10000 21s + 21p

toe ( ~ )

5000

0.1265E+01

0.1460E+01

0.2171

10000

0.1406E+01

0.1371E+01

0.1995

20000

0.1488E+01

0.1203E+01

0.1912

40000

0.1481E+01

0.9927E+00

0.1918

5000

0.3954E+00

O.2332E+00

0.1539

10000

0.3576E+00

0.1801E+00

0.1659

20000

0.3128E+00

0.1362E+00

0.1835

40000

0.2683E+00

0.1014E+00

0.2059

5000

0.2254E+01

0.8776E+00

0.6947

10000

0.1923E+01

0.6398E+00

0.7827

20000

0.1598E+01

0.4526E+00

0.8991

40000

0.1300E+01

0.3120E+00

1.0497 1.2667

5000

0.5443E+01

0.1915E+01

10000

0.4620E+01

0.1350E+01

1.4325

20000

0.3810E+01

0.9213E+00

1.6552

40000

0.3069E+01

0.6133E+00

1.9468

J . M . BASSALO et aL

78

Table 1 (Contd) L([~) 15084

31s + 41p 11013

31s + 51p 9603

31s + 61p 19089

31p ÷ 41d 12968

31p ~ 51d 11045

31p ~ 61d 18697

31d + 41f 10830

23s ~ 23p 3889

23s + 33p 3188

23s + 43p 2945

23s + 53p 2829

23s ÷ 63p 7065

23p ~ 33s

T (K)

I

~e ( ~ )

d e (~)

5000

0.1375E+02

-0.9741E+01

0.2973

10000

0.1300E+02

-O.8162E+01

0.3~O1

20000

0.1196E+02

-0.6658E+01

0,3301

40000

0.IO73E+O2

-0.5272E+01

0,3581

5000

O.2121E+02

-0.134OE+02

O.4571

10000

0.197OE+O2

-0.1091E+02

0.4830

20000

0.1773E+O2

-0,8620E+01

0.5227

40000

0.1552E+O2

-0,6613E+01

0.5775

-O.2138E+02

0.6497

5000

0.3777E+02

10000

0.3471E+02

-0,1707E+02

{).6922

20000

0.3086E+02

-O.1321E+O2

O. 7560

40000

0.2666E+O2

-O,9903E+01

0.8436

0.6707

5000

0.3630E+O2

O.1588E+02

10000

O.3156E+02

O.12OOE+02

O.7449

20000

O.2675E+O2

O.8817E+01

0.8434

40000

0.2217E+02

O.6311E+01

~.9709 1,2556

5000

0.4826E+02

0.1774E+02

I0000

0.4122E+O2

O.1273E+02

1,4132

20000

0.3423E+02

0.8873E+01

1.6240

40000

0.2777E+02

0.6044E+01

1,9006

5000

0.8128E+02

O.2582E÷02

,.9498

10000

0.6844E+02

O.1763E+02

*.2182 2 .5744

20000

O.5611E+02

0.1178E+02

40000

O.4502E+02

O.7753E+01

3 .0369

5000

0.1873E+02

-O.5803E+O1

0.7524

10000

O.1555E+02

-0,4125E+01

O.8651

20000

0.1266E+O2

-0.2834E÷01

~.O094

40000

0,IO13E+02

-0.1882E+01

!.1928 O.0321

5000

0.4046E-01

-0.5627E-01

10000

O.5128E-01

-0,5718E-01

0.0269

20000

0.6718E-01

-0.5449E-O1

6,O219

40000

O.8896E-01

-O.4849E-01

O.0178

0.0848

5000

0.8537E-01

0.5968E-O1

10000

0.9425E-01

0.4610E-01

0,0788

20000

0.9863E-01

0,3230E-O1

0,O76~

40000

0.9836E-01

0.2075E-O!

0.0763

5000

0.2672E+00

0.1983E+00

0,1511

10000

0.2891E+OO

0.1620E+00

O~!424

20000

0.2959E+00

O.1261E+00

0,!400

40000

0.2871E+00

0.9512E-01

O.1431

5000

0.6823E+00

O.4261E+00

10000

(].7357E÷00

0.3268E+0(]

20000

0.7458E+00

(I.2355E+OO

40000

0.7139E+00

0.163OE+00

I

5000

0.1563E+01

0.9212E+00

10000

O.1649E+O1

O.6955E+O0

20000

0.1639E+01

0.4868E+00

0.

40000

O.1542E+01

O.3433E+0!)

0.3188

,

(). 3032 3046

5000

0,1532E+00

0.2 I7OE+OO

0 . 0758

10000

0.1798E+00

{I. 2 2 2 2

; , 0B ] ?

20000

0.2055E+OO

O ,2144E+I)i

40000

0.2253E+00

i). 1935E+00

E ÷ (}(I

i,05~7

79

Convergent calculations for electron impact broadening Table i (Contd) L(~)

4713

23p .

43s

4121

23p + 53s

5876

T (K)

4472

23p ÷ 43d 4026

23p ÷ 53d 12528

33S ÷ 43p 9464

33s ~ 53p

5000

0.2923E+00

0.3904E+00

0.1284

0.3391E+00

0.3888E+00

0.1149

20000

0.3780E+00

0.3630E+00

0.1059

40000

0.3989E+O0

0.3170E+00

0.1017

5000 10000 20000

0.7728E+00

0.9994E+00

0.1726

0.8905E+00

0.9817E+00

0.9807E+00

0.9020E+00

40000

0.I018E+01

0.7755E+00

0.1552 0.1444 0.1404

5000

0.1343E+00

-0.1157E+00

0.0722

10000

-0.9678E-01

0.0709

-0.7615Er01 -0.5715E-01

0.0725

40000

0.1377E+00 0.1338E+00 0.1253E+00

5000

0.1360E+01

0.7900E-01 0.6972E-02 -0.2754E-O1 -0.4055E-01

0.6144 0.6802 0.7653 0.8746

0.2518E÷00 0.4626E-01 -0.6152E-01 -0.1074E+00

1.0564

10000

0.1188E+0t

20000

0.1015E+01

40000

0.8495E÷OO

5000

0.3605E+01

10000

0.3129E+01

20000

0.2649E+01

40000

0.2187E+01

5000

o.411oz+oi

10000

0.4495E÷01

20000

0.4657E+O1

40000

o.4585z+oi

0.7501E+01

5000

0.8007E+01 0.6021E+01

0.3026

0.4266E+01

0.3038

0.2904E+01

0.3177

0.6114E+01

0.1009

0.6236E+01 0.6011E+01 0.5416E+01

0.0774

0.6076E+01 0.7482E+01 0.8654E+01 0.9331E+01

33p + 53d

0.2199 0.3151

0.0864 0.0732

5000

0.7423E+01

0.9304E+01

0.1682

0.8674E+01 0.9679E+01 0.1016E+02

0.9117E+01

0.1496

O.8383E+01

0.1378

0.7229E+01

0.1329

0.1528E+02

20000

0.1243E+02 0.1422E+02 0.1549E+02

40000

0.1587E+02

0.1665E+02

0.2454 0.2217 0.2080 0.2042

40000

5000 10000

11969

0.2153 0.2132

10000 20000

33p * 43d

0.2274

0.1337 0.1353

40000

5000 10000 20000 40000

17002

0.4400E+01 0.3319E+01 0.2324E+01 0.1539E+01

0.1373

0.7818E÷01

21120

33p + 63s

0.]468

20000

40000

10668

0.2645E÷01 0.1980E÷01 0.1333E+01 0.8161E+00

0.7716E+01

20000

33p * 53s

1.5370

0.7176E÷01

33s * 63p

12846

1.1749 1.3312

5000

10000

33p + 43s

0.0761

10000

0.1365E+02 0.1441E+02 0.1433E+02 0.1350E+02

8362

o de(A)

10000

20000

23p ~ 33d

~e(~)

0.1472E+02 0.1325E+02

5000

0.2007E+02

0.4487E+00

0.6020

10000

0.1778E+02

-0.5750E+00

0.6593

20000

0.1548E+02

-0.9799E+00

0.7313

40000

0.1323E+02

-0.I040E+01

0.8228

0.1987E+01 0.1455E+00

1.0529

-0.7953E+00 -0.1160E+01

1.3191

5000

0.3195E+02

10000

0.2781E+02

20000

0.2366E+02

40000

0.1965E+02

1.1683 1.5161

80

J, M. BASSAU) et aL

Table 1 (Contd)

L(~) 19543

33d ~ 43p

12985

33d + 53p

10997

33d -~ 63p 18686

33d + 43f

T (K)

We ( ,~ )

de(X)

5000

0.I034E+02

0.7777E+01

0.1546

10000

0.1126E+02

0.63,17E+01

0.1451

20000

0.1157E+02

0.4818E+01

0.1422

40000

0.1123E+02

0.3518E+01

0.1454

5000

0.1357E+02

0.8659E+01

0.2295

I0000

0.1460E+02

0.6698E+O1

0.2172

20000

0.1480E+02

0.4883E+O1

0.2151

40000

0.1418E+02

0.3430E+01

0.2221

0.3162

5000

0.2363E+02

0.1403E+02

10000

0.2496E+02

O.I064E+02

0.3035

20000

0.2483E+02

O.7652E+01

0.3046

40000

0.2340E+02

0.5329E+01

0.3186

5000

0.1102E+02

-0.1924E+01

0.8650

10000

0.9227E+01

-0.1120E+01

0.9884

20000

0.7622E+01

-0.609OE+00

1.1408

40000

0.6219E+01

-0.2951E+00

1.3289

REFERENCES H. R. Griem, Plasma Spectroscopy. Academic Press, New York (1974). J. M. Bassalo, M. Cattani, and V. S. Walder, Phys. Rev. A 22, 1194 (1980). H. R. Griem, M. Baranger, A. C. Kolb, and G. Oertel, Phys. Rev. 1.7,5, 117 (1%2). H. R. Griem, Phys. Rev. 128, 515 (1%2). S. Sahal-Brechot, Astron. Astrophys. I, 91 (1969). S. Sahal-Brechot, Astron. Astrophys. 2, 322 (1%9). C. Fleurier, S. Sahal-Brechot, and J. Chapelle, JQSRT 17, 595 (1977). L. A. Vainshtein and 1. I. Sobel'man, Opt. Spectrosc. 5, 279 (1959). R. J. Dyne and B. J. O'Mara, Astron. Astrophys. 18, 363 (1972). H. R. Griem and C. S. Shen, Phys. Rev. 145, 1% (1%2). M. S. Dimitrijevic and P. Grujic, JQSRT 19, 407 (1978). W. L Wiese, M. W. Smith, and B. M. Glennon, "Atomic Transition Probabilities", U.S. National Bureau of Standards, National Standard Reference Data Series-4. U.S. GPO, Washington D.C. (1966). 13. C. E. Moore, "Atomic Energy Levels". U.S. National Bureau of Standards Circ. Vol. I. No. 467. U.S. GPO, Washington D.C. (1949). 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.