! 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
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! 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