! INIS DOCUMENT

ANALYSIS OF X-RAY SPECTRA EMITTED FROM HIGHLY IONIZED

ATOMS IN THE VACUUM SPARK AND LASER-PRODUCED*

HIGH-POWER PLASMA SOURCES.INIS-mf—11587

THESIS SUBMITTED FOR THE DEGREE

"DOCTOR OF PHILOSOPHY"

by

Plnchas Mandelbaum

Submitted to the Senate of the Hebrew University, May 1987

fNJS

ANALYSIS OF X-RAY SPECTRA EMITTED FROM HIGHLY IONIZED

ATOMS IN THE VACUUM SPARK AND LASER-PRODUCED

HIGH-POWER PLASMA SOURCES.

THESIS SUBMITTED FOR THE DEGREE

"DOCTOR OF PHILOSOPHY"

by

Pinchas Mandelbaum

Submitted to the Senate of the Hebrew University, May 19 87

This work was carried out

under the supervision of

Prof. J.L. Schwob and

Prof. B.S. Fraenkel.

CONTENTS.

page

INTRODUCTION 1

CHAPTER ONE : EXPERIMENTAL 5

1 . i Background 5

1.2 Plasma sources 5

1.2.1 The low inductance,high power vacuum spark 5

1.2.2 The laser-produced plasma facility at Soreq a

i. 3 The spectrometers a

1.3.1 The grazing incidence far UV spectrometer s

1.3.2 The crystal X-ray spectrometer 13

CHAPTER TWO: THEORY FOR ATOMIC COMPUTATIONS 15

2 .1 Background 15

2 . 2 The RELAC code 15

2.2.1 The relatlvistic central potential method 15

2.2.2 The parametric potential method 17

2.2.3 First order perturbation calculation ie

2.2.4 Transition probabilities and gf values is

2.2.5 Input of the code 19

2 . 3 The ANGLAR code 20

2.4 The WIDTH code . 22

2.4.1 Background 22

2.4.2 Input of the code 22

2 . 5 The COLRAD code 24

CHAPTER THREE: ANALYSIS OF THE SPECTRA OF THE FIFTH ROW ELEMENTS

EMITTED FROM THE LOW INDUCTANCE VACUUM SPARK 2 6

3 . i Background 2 6

3.2 The Nil isoelectronic sequence 2 6

3.2.1 Introduction 26

3.2.2 Results of computations in the Nil sequence 29

3.2.3 Discution of the energies 30

3.2.4 Discution of the gf-values 31

3.2.5 Conclusions 32

3.3 Measurements in the Molybdenum spectrum 32

3.4 The 3d-4p transitions in the Cul-like ions .33

3.s Conclusions 35

CHAPTER FOUR: ANALYSIS OF THE SIXTH ROW HIGH-Z ELEMENTS SPECTRA

EMITTED IN THE X-RAY RANGE FROM LASER-PRODUCED

PLASMA

1.i Introduction 3 6

4.2 Experimental 39

4.3 The 3d-4p transition in the sixth row elements spectra . . . .39

4.3.1 Background 39

4.3.2 The Col-like 3d9-3d84p transition 42

4.3.3 The Nil-like 3d10-3d94p transition 43

4.3.4 The Cul-like 3d104l-3d94p4l transitions 4 3

4.3.4.1 A Colllsional Radiative Model 43

4.3.4.2 The 3d 4s-3d94S4p transition 44

4.3.4.3 The 3d104p-3d94p2 transition 45

4.3.5 The Znl-llke 3d1°4l4l'-3d94p4l4l' transitions 46

4.3.5.1 The 3d1 °4s2-3d94s24p transition 46

4.3.5.2 The 3d104S4p-3d94S4p2 transition 4 8

4.4 The 3p-4s and 3p-4d transitions in the sixth row

elements spectra 4 8

4.4.1 Background 46

4.4.2 The Cul-like 3p-4s transitions so

4.4.2.1 The 3p63d1O4s-3p53d1 °4s2 transition 5 0

4.4.2.2 The 3p63d1O4p-3p53d1°4s4p transition 5i

4.4.3 The Cul-like 3p-4d transitions 5 2

4.5 The 3d-4f pseudo-continuum spectra in the sixth row

elements spectra 5 2

4.5.1 Background 52

4.5.2 The Col-like 3d'-3d84f transition 53

4.5.3 Analysis of the pseudo-continuum 54

4.5.3.1 The S.0.S.A m o d e l . . . . . 54

4.5.3.2 Correction for the departure from pure j j. . .56

4.5.3.3 Results of S.O.S.A computations 57

4.5.3.4 Comparison with experiment 58

4.6 The A n=2,3 transitions in the sixth row elements spectra . .59

4.6.1 Background 59

4.6.2 Theory 6 0

4.6.3 Results 60

4 . 7 Conclusions 6 i

CHAPTER FIVE: ANALYSIS OF THE RARE-EARTH SPECTRAA

5. i Experimental 6 2

5.2 Description of the spectra in the EUV range 6 2

5.3 The quasi continuum band in the rare -earth spectra 6 4

5.3.1 Introduction 6 4

5.3.2 Ab-initio calculation in the Pdl seguence 6 5

s.3.3 The Configuration Average Model 6 7

5.3.4 The UTA Model 68

5.3.5 Effects of configuration mixing 70

5.3.5.1 Individual line computations 7 0

5.3.5.2 Shift and narrowing of the bands 72

5.3.6 Comparison with experiment 74

5.3.7 Conclusion 7 5

5.4 Wavelength list for resolved lines .76

CONCLUSION 77

Bibliography 7 8

ABSTRACT I

- 1 -

ABSTRACT

The interest for atomic spectroscopy has greatly been reinforced in

the last ten years . This gain of interest is directly related to the

developments in different fields of research where hot plasmas are

created. These fields include , in particular controlled thermonuclear

fusion research by means of inertlal or magnetic confinement

approaches and also the most recent efforts to achieve lasers in the

XUV region . Indeed ,in many cases , the atomic spectroscopy is one of

the most usefull tools to get information on these hot plasmas i.e.

ionization states of the atoms , temperature and density of the

different species ,equilibrium and transport properties.Furthermore,in

such hot plasmas , the spectra emitted by the highly ionized atoms are

primarily in the far UV and X-ray region . This corresponds indeed to

the high energies of the free electrons in the plasma.These electrons

are responsible for the excitation processes leading to the emission

of the spectral lines.

The present work is based on the specific contribution of the

atomic spectroscopy group at the Hebrew University . The recent

development of both theoretical and experimental tools allowed us to

progress in the understanding of th& highly ionized states of heavy

elements. In this work , the low-inductance vacuum-spark developed at

the Hebrew University was used as the hot plasma source . The spectra

were recorded in the 7-300 A range by means of a high - resolution

exLreme - grazing - incidence spectrometer developed at the Racah

- 2 -

Institute by Profs. J.L. Schwob and B.S. Fraenkel . To extend the

spectroscopic studies to higher-Z atoms , we used the laser-produced

plasma facility at Soreq Nuclear Center . In this work , the spectra

of the 6 row elements were recorded in the X - rays by means

of a crystal spectrometer . All these experimental systems are

briefly described in chapter One.

Chapter Two deals with the theoretical methods used in the present

work for the atomic calculations . Atomic level and transition

probabilities have been computed using the RELAC code,wich is based on

the Parametric Potential Method developed by Prof. Klapisch (Klapisch

et al.,197 1).The advantage of this method consists in the fact that by

means of a single central potential one can , with a good accuracy ,

quickly compute energy levels and transition probabilities . The RELAC

code has been improved by Bar-Shalom (Ph.D. Thesis,1984} :the input of

the program has been reduced ,and new Breit and Lamb shift subroutines

have been added . This allowed us to perform accurate calculations for

more complex cases .Angular coefficients used in RELAC are provided by

the ANGLAR program,an improved version of the original Grant's program

(Grant et al.,i9 8o) .In our work ,we had generally to deal with highly

ionlzed heavy atoms with more than a few electrons in open shells ,

giving rise to complex configurations . In that case ,the numerous

spectral lines of the transition arrays may be blended in partially

unresolved broad emission bands . For this particular situation ,

C.Bauche-Arnoult,J.Bauche and M.Klapisch ( C.Bauche-Arnoult ,J.Bauche,

and H.Klapisch , 1979 , 1982 ,i98s ) developed the UTA ( Unresolved

Transition Array ) theory which gives the mean wavenumber and the

spectral width of these transition arrays. The WIDTH code , based on

this theory , has been extensively used for the interpretation of the

spectra all along this work . Finally , using a collisional-radiative

model (Bates et al. , 196 2 ) , we computed the contributions of the

different transition in the Cul-like ion line intensities.

Chapter Three deals with the spectra of elements of the fifth row

emitted from the vacuum-spark in the 30-15oA range .These spectra have

been studied by Schweitzer ( Ph.D. Thesis , 197 8 } and we used these

experimental data in order to test our ab-initio computations along

the Nil sequence 3d-nl transitions. This sequence is one of the long-

guest sequence known today which extends from Nil to Pt L. Using the

Z - expansion model we analyse the discrepancy between experiment and

theory;the importance of the relativistic effects and the relevance of

jj coupling in a wide range of ionization states are pointed out. The

measurement of the Molybdenum spectrum in the 5 0-isoA range ,which was

missing in Schweitzer's work was also done . On the basis of these

experimental data , the classification of 3d-3p transitions in CoI-,FeI

and Mnl-like ions has been performed . Eight new lines belonging to

3d104s-3d94S4p and 3d1°4p-3d9ip2 transitions of the Cul-like ions Y XI

tc Ag XIX have also been identified by means of ab-initio

calculations . These identifications were later confirmed by Wyart et

al. (1984) through a generalized least square fit method.

At the beginning of our work , the spectra emitted by the elements

of the sixth row from laser-produced plasma were mostly unknown . This

- 4 -

kind of spectra have been obtained by Zigler et al. ( 1980 ) at the

Soreq Nuclear Center.The analysis of these spectra was undertaken here

on the basis of the RELAC code wich is especially adapted to take into

account the important relativistic effects . The results of this work

are presented in chapter four.We started with the 3d-4p transitions ine

the 6-9 A range.Beside the prominent lines of the Nil-like ions ,lines

belonging to Col- (3d9-3d84p),CuI- (3d104s-3d94S4p,3d1°4p-3d94p2),and

Znl-like ions ( 3d104S2-3d94S24p, 3d1 °4S4p-3d94S4p2 ) have be identified.

A collisional-radiative model of the Cul-like ions in the plasma was

used and permitted us to show that the contribution of the

3d1°4d-3d94p4d and 3d1°4f-3d94p4f transition arrays to the observed

3d-4p spectrum is rather small . The importance of configuration

interactions has been pointed out.Using the same methode,based on

ab-initio calculations and isoelectronic sequence analysis,we were

able to Identify the satellite structures of the 3p-4s and 3p-4d

Nil-like transitions which arise from the 3p63d104s - 3p53d104s2 ,

3p63d104S4p - 3p53d1O4s24p and 3p63d1O4s - 3p53d104S4d transitions in

the Cul-like ions . The broad characteristic , quasicontinua

appearing in these spectra in the 5-8 A region were interpreted as

superpositions of Spin Orbit Split Arrays ( S.O.S.A ) , a particular

case of Unresolved Transition Arrays .It is shown that these

features pertain to ad-4f transitions in atoms isoelsctrcnic to

CuIrZnI,GaI and Gel . Some individual lines belonging to 3d~4f

transitions in Col-like ions were also Identified. The effect of

departure from pure jj coupling on the S.O.S.A. calculations are

- 5 -

discussed. Reabsorption effect on line intensities is also considered.

The pattern which appears at shorter wavelengths in these spectra

(3-4 A) has been identified as 3d-5f and 3d-6f S.O.S.A. transitions in

the same lonization stages ; this allowed us to correct the misidenti-

ficatlon of this type of pattern in Gold spectra previously made by

Kiyokawa et al. (i9 8 5 ) .

Chapter five is devoted to the measurement and analysis of spectra

emitted from the vacuum- spark by rare-earth elements . These spectra

show a feature common to the spectra emitted from very different

sources such as laser-produced plasmas ( Caroll and 0'Sullivan,1982 ),

and Tokamak plasmas ( Finkenthal et al.,i9 86):a narrow quasi-continuum

band (less than 5A width ) is emitted between 70A and IOOX and its

center shifts towards shorter wavelengths as the atomic number Z

increases . Since these bands are much brighter than individual lines

but still relatively narrow, they could represent excellent soft X-ray

sources for absorption spectroscopy , optical pumping for XUV laser

research or for photolithography .In order to evaluate these potential

applications , it is necessary to understand the basic mechanisms

underlying the emission , namely which are the ionization states

responsible for the emission,and the transitions involved.

Our work presents an explanation of the observed bands emitted by

these very different sources.lt addresses the following questions* :why

are the bands still narrow , even when as many as ten different

ionization states are involved , as in the case cf tokamak p?°ctra ?

Also, which are the transitions responsible for the large number of

- 6 -

unresolved intense lines which might produce these continuum features

regardless of the spectrometer resolution ? Although in the present

work, vacuum-spark spectra of several rare-earth elements have been

recorded in the range considered , the emphasis is on a general

explanation of these spectra as well as those obtained from higher

temperature sources such as tokamaks and high-power laser-produced

plasmas.We have shown ,by performing ab-lnitio level structure

computations, that the effect of configuration interaction between

the excited 4p54d 1 and 4p64d -14f configurations in various

lonization states ,leads to a strong narrowing of the emission array

originating from transitions between these levels and the ground

6 N

4p 4d .As a result,the above mentioned quasi-contlnuum , produced by

a very large number of lines ( thousands for each ionization stage

for N=3 to 7 ) , emitted within a spectral interval of 2 to 4 A , is

predicted to be created. Moreover , for a given element , with the

changing of the ionization state, the band is only slightly shifted,

in contrast with previous computations without configuration mixing .

Thus,even if as many as ten ions of a given element are emitting

lines belonging to these transitions , the entire emission remains

centered in a narrow band . These results predicted theoretically by

the present work , are in good agreement with the experimental

measurements on spark emission and with previously published

laser-produced plasma and tokamak spectra .

We end this last chapter with the list of the resolved lines which

were measured in the spectra of the rare-earths. A special effort was

- 7 -

made to get good calibration wavelengths in the 5 0-isoX range,in order

to achieve an accuracy of about 0.005A . Most of these five hundred

lines are still not yet classified.

5 o A - i 2 o A wtwm L a "PIU " ? J H • • z m N m r o n . 5 . 4 . 1

2LtAI

64.716

64.830

64.925

65 .002

67.689

6B . 01 4

68.054

68.059

86.400

88.564

88 . 692

88 . 746

SB . 829

91.164

91 .330

91 .404

91 .445

91.872

91.965

92.064

92.211

92 . 280

92.337

92.404

92.519

Int.

2

4

6

6

10

4

6

6

2

2

4

1

3

1 0

2

1 5

9

15

15

15

10

15

1 2

10

12

'hi

92 .

92.

93.

93.

93.

9*.

91.

9S.

94.

94.

94.

95.

95.

95.

95.

95 .

95 .

95 .

95 .

96.

96.

96.

96.

97 .

99.

0

Ai

627

993

068

123

193

201

«9«

• 97

222

75S

927

0*1

225

261

347

445

720

891

923

067

1 85

543

587

815

042

Int.

10

5

5

A10

20

1*

17

5

20

5

S

2

5

8

5

5

4

4

5

4

10

1 5

3

>(A)

99.200

99.727

99.923

99.9«i

10«.«*3

1««.9M

191.919

191.971

1I1.1M

191.211

191.194

101.497

101.119

101.792

101.964

102.136

102 . 297

102.535

102.630

102 .753

102.830

103.183

103. 331

103.405

103.552

Int.

2

5

6

3

2

19

14

•

•

•

«

15

7

7

10

1 5

2

2

10

15

2

1

10

2

n) 5oA-i2oA mnna La "JDJ *?jn ^ I I N nirun . 5 . 4 . 1

I n t . X(A) I n t . X(A) I n t .

103.701 10 114.307 6 118.048 10

103.917 8 114.640 5 118.223 5

105.513 1 114.865 8 118.356 6

107.858 20 114.906 5 118.412 7

110.138 2 115.297 2 118.558 3

1

1

1

1

1

1

1

1

1

1

10.518

10.999

11.793

11.903

12.030

12.110

12. 580

12.727

12.810

13.139

30

3

1

2

2

10

2

5

2

10

1

1

1

1

1

1

1

1

1

1

16.4-12

16.462

16.580

16.683

16.784

16.982

17.104

17. 149

17.451

17.583

4

10

10

5

10

3

1

1

0

5

1

1

1

1

1

19.299

19.471

19.546

19.603

20.006

3

10

10

5

2

50A-135A m m o . c e *?(u *?jn ^ " I I N Tinman . 5 . 4 . 2

I n t . AfA) I n t . A(A) I n t .

88.056

88.126

88.208

88.290

88.409

88.492

*8.568

88.693

88.830

68.925

89.012

89. 185

89.238

89.372

89.579

89.756

89.846

90.070

90.259

90.410

90.506

90.615

90.993

91.103

91 .232

Int.

35

30

35

50

30

30

40

45

50

35

10

40

50

20

35

30

25

20

10

20

20

20

10

20

8

59.774 7

61.116 5

61 . 668 6

62.234 10

79.661 1

80.060 2

80.279 5

83.201 2

83 . 387 3

83.724 5

83.937 1

84.560 1

85.655 18

85.879 10

86.512 8

86.564 20 89.756 30 101.643 5

86.615 10 89.846 25 101.889 8

86.835 13 90.070 20 102.460 6

87.041 15 90.259 10 102.595 2

87.141 7 90.410 20 103.575 10

87.173 7 90.506 20 103.655 5

87.508 30 90.615 20 103.719 13

87.695 40 90.993 10 103.799 3

87.828 35 91.103 20 103.961 5

87.987 40 91.232 8 104.214 2

91.34091.543

91.788

92.150

92.526

92.611

92.906

93.145

95.494

95.678

95.862

96.090

98.533

99.932

100.650

5

20

18

15

10

15

10

10

5

10

10

25

40

20

15

ce niron .5.4.2

A(A)

104.359

104.419

104.843

104.937

1 0 4 . * 7 3

Int.

8

7

6

8

9

A(A)

105.861

105.930

106.004

106.162

106.288

Int.

2

8

2

3

2

Alii

106.986

107.682

108.420

109.929

124.725

IE

10

7

10

16

10

105.041 5

105.116 12

105.177 8

105.220 6

105. 584 10

106.367 2

106. 538 3

106.694 2

106.782 10

106.956 10

132.280 10

132.748 20

133.237 25

135.174 7

5oX-i5oA m m u Pr *?ID n i r a n . 5 . 4 . 3

int. Int.

54

54

55

55

55

55

56

57

57

69

69

72

74

74

76

76

76

76

76

76

77

77

77

77

77

.891

.972

.202

. 383

.446

.515

.979

. 328

. 590

. 170

.628

.824

.090

. 285

. 022

.278

.404

.550

.689

.952

.033

.238

.426

.613

.736

5

5

20

15

5

1 5

20

20

20

10

10

10

20

20

L

5

8

5

10

12

8

15

13

L

30

77.

77.

77 .

1 -J a

77.

78.

78.

78.

78.

78.

78.

79.

79.

79.

79.

79.

60.

81 .

81 .

81 .

82 .

82.

82.

82 .

82.

788

868

028

981

026

1 19

189

400

592

832

204

360

416

582

844

756

466

594

703

1 10

204

324

483

579

25

20

22

15

A

10

6

A

10

L

5

25L

15

10

20

VL

10

5

10

10

20

20

8

4

82

82

83

83

83

83

83

83

83

83

83

83

84

84

84

84

84

84

84

84

84

84

84

86

87

.803

.913

.317

.399

.472

.585

.642

.704

.796

.856

.899

.978

.067

.171

.213

.330

.399

.494

.608

.706

.822

.864

.990

.269

.426

2

10

2

8

10

12

7

10

10

6

10

20

12

5

8

6

8

30

10

9

6

8

6

40

20

. Cliunn) 50X-150A IIITTJU Pr t?m "?jn mron .5.4.3

i n t . A(A) In t .

87.629

87.787

87.864

8 8.296

88.380

88.510

88.763

8 9.770

90.041

90.228

90.332

90.477

91.341

91.605

92.367

92.753

92.868

92.962

93.292

93.364

93.559

93.915

93.956

94.107

94.167

40

40

5

5

20

10

20

5

20

5

10

20

30

5

20

30

10

10

5

1 5

10

15

10

12

94.234

94.309

94.513

94.775

94.865

94.933

94.966

95.048

95.154

95.273

95.528

95 .665

95.734

95.959

96.213

96.378

96.507

96.554

96.703

96. 863

97 .027

97.601

103 . 346

104.247

104.627

8

10

IS

8

10

15

20

14

5

20

30

10

10

10

5

4

8

10

10

10

8

10

5

30

10

107.643

109.795

109.864

109.935

110.247

109.873

1 12.675

113.189

113.409

113.826

114.367

115.714

1 15.853

117.610

1 17.837

117.956

117.996

118.106

118.371

118.522

118.657

118.827

118.996

119.083

120.439

20

10

10

12

VL

10

2

10

50

60

10

5

3

15

8

10

10

12

3

5

4

5L

40

25

5

s o i - i s o A m n m Pr ^tn *?jn I D I I N m i 1 on . 5 . 4 . 3

*(A) Int. Int.

1

1

1

1

1

20.

20.

20.

21 .

21 .

844

889

982

1 30

722

10

9

10

10

30

122.091

122 .535

122.971

127.140

127 .420

15

30

10

30

25

128.112

128.253

128.384

128.515

131.032

12

15

5

20

20

12 1.827 10 127.994 1 5 150.097 30

50&-120A" U1TTIU Nd *2U) JIB*1 OH . 5 . 4 . 4 H1?JO

Int. MA) Int. >(A) Int.

53.090

64.013

64.204

68. 130

68 . 303

68.386

68.510

68.669

68.875

68.936

69.265

69.483

69.923

70.623

70.721

70.813

70.939

71 .448

71.679

71 .840

72.151

73 .286

7 3.588

73.744

73.881

1

1

4

2

3

5

2

5

8

3

2

L3

2

3

2

3

1

0

3

1

L4

1

1

74.239 8

74.578 5

74.663 4

74.733 2

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75.356 10

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75.861 3

76.040 2

76.274 1

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77.415 1

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79.019 1

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79.470 2

79.535 3

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