X-RAY EMISSION SPECTRA FROM LASER-PRODUCED COBALT PLASMA

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X-RAY EMISSION SPECTRA FROM LASER-PRODUCED COBALT PLASMA

Q. Dong, J.-M. Li, Z.-Q. Zhang

To cite this version:

Q. Dong, J.-M. Li, Z.-Q. Zhang. X-RAY EMISSION SPECTRA FROM LASER-PRODUCED COBALT PLASMA. Journal de Physique Colloques, 1987, 48 (C9), pp.C9-371-C9-374.

�10.1051/jphyscol:1987965�. �jpa-00227383�

X-RAY EMISSION SPECTRA FROM LASER-PRODUCED COBALT PLASMA

Q. DONG*, J.-M. L I * , * * and 2.-Q. ZHANG*""

" ~ n s t i t u t e o f P h y s i c s , A c a d e m i a S i n i c a , B e i j i n g , C h i n a

t *

C e n t e r of T h e o r e t i c a l P h y s i c s , CCAST ( W o r l d L a b . ) , B e i j i n g , C h i n a

* * *

S h a n g h a i I n s t i t u t e o f O p t i c s and F i n e Mechanics, A c a d e m i a S i n i c a , S h a n g h a i , C h i n a

Based on theoretical calculations by our non-relativistic configuration interaction computer bode, we have success- fully identified the x-ray spectra from the cobalt plasma produced by high-power laser. Here we focus on the s ectra consigting of x-ray line emission from the. N-like. ans C- llke xons. Many new x-ray llnes have been identified.

Based on theoretical calculations by our non-relativistic configuration.interaction computer code, we have success- fully identified the x-ray spectra from the cobalt plasma produced by high-power laser. Here we focus on the s ectra consisting of x-rav line emission from the N-like ans C-

been identified.

In the controlled nuclear fusion research, the electromagnetic radiation from high Z (atomic number) atomic ions has important effects on formation of high-temperature plasmas. The photon-emission from high Z atomic ions in x-ray regions can also be utilized to diagnose the high-temperature plasmas. Another important research focuses on the x-ray stimulated emission where highly ionized atoms are as laser active media [ I ] . For these reasons, it is interesting to study various spectra emitted from high Z ions in x-ray regions. We have established the Non-Relativistic and Relativistic atomic Configuration Interaction methods (NRCI and RCI) to calculate excitation energies as well as radiative transition probabilities for optical allowed and forbidden transitions [ 2 ] . Now our NRCI computer code has been improved. It can be conveniently and efficiently applied to perform theoretical calculations for any neutral or ionized atoms.

Here we present our results for the N-like and C-like cobalt ions.

Our experiments were performed in Shanghai Institute of Optics and Fine Mechanics. The high temperature cobalt plasma was produced by a Nd glass laser with power intensity about 5x1013 W/cm2. The x-ray spectra from 4.5 to 15.0Awere measured by a.TALP crystal spectrometer and recorded on a 5F medical x-ray film [ 3 1 .

The exact Hamiltonian of an isolated multi-electron atom or ion can be separated into two parts: H = H o

+

^{H'. H o} is the atomic Hamiltonian under the non-relativistic self consistent field approximation [4,51. Based on H o , we can obtain the one-electron orbital wave functions and then construct the multi-electron configuration wave functions li>. All of the configuration wave functions {li>) span a complete Hilbert space for multi-electron atomic systems. An exact atomic wave function l o > can be expanded as:

> i CI , where Ci are expansion coefficients. When the total wave functions are orthogonormalized, it can recasted into an eigenvalue problem: Zj(HiJ-E)Cj=O, Here Hi j is the H matrix element.

After the H matrix is diagonalized, the eigen values E" and the corresponding expansion coefficients ( CP can be obtained.

Consequently, the transition energies can be easily calculated as the differences between the eigenvalues. With the calculated total wave functions, the radiative transition rates (i.e. oscillator strengths) can be calculated[21.

Since N-like and C-like cobalt ions are highly ionized atoms,

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1987965

C9-372 JOURNAL DE PHYSIQUE

their energy structures resemble the features of H-like ions 161.

The sub-orbitals with the same principle quantum number will be quasi-degenerate. Then the configurations with the 2s orbital occupied and unoccupied should be taken into account. The excited orbitals with the principle quantum number (n< 6 ) and angular momentum (&<2) are considered. More specifically, the following configurations are taken into account in our calculations: (1) lsz2s"pm, ls22sz2pm-lnp, 1s~2s2pmnsJ ls22s2pmndJ ls22pm+z, lsz2p=+lnp and (2) ls22s22pn-Ins, ls22s22p~-1ndJ 1s22sZpmtl, ls22s2p"npJ ls22pm+lns, lsz2pa+lnd where m=3 for the N-like ion, and m=2 for the C-like ion. The N-like ion has 12 LS terms: ZS, ZP, 2D, 4S, 4P, 4D, 2SoJ ZPo, 2D0, 4S0, 4P0, 4DO. The C-like ion has 12 LS terms: IS, 'P, ID, 3S, 3P, 3D, lSo, lPo, %DO

,

3S0, 3P0, 3DO. Our theoretical calculated x-ray transition energies agree with the identified experimental line positions [3,7] within a few thousandths. The calculated oscillator strengths are anticipated to be accurate within a few percent. Here, we calculated all of the possible spin allowed transition arrays to obtain their x-ray transition energies and their oscillator strengths. Many new x-ray spectral lines have been identified for the first time. Table I lists some of our calculated results for the spin allowed transitions from the N-like and C-like cobalt ions compared with theoretical measurements.

Fig.1 shows the experimental spectra (11.2A(i912.4A) [31. The

Figure I

upper two rows of short lines show the positions of the calculated wavelengths for C-like and N-like ions respectively. The spectral lines from the N-like ion gather around 12.OA. They are included the experimental strong lines: 12.081, 12.040, 12.001, 11.975, 11.949, 11.922A and so on. While the spectra around 11.5A are mainly from the C-like ion, e.g. 11.680, 11.640, 11.606, 11.556, 11.515, 11.477, 11.444, 11.391A etc. The two groups of transition lines are mixed

near about 11.77 A- The calculated wavelengths can be divided into three categories: (1) the configurations involving 2s orbital fully occupied (e.g. Is22s22pm); (2) involving 2s orbital one electron occupied (e.g. Is22s2pm+1); (3> involving without 2s orbital (e.g.

ls22pm+2). Here we rather emphasize the transitions in the third category; some x-ray transitions have quite big oscillator strengths.

Table I .

CONFIG.

2 8 2 p4 *S - 2 a 2 pa(aP ) 3 d *P0

2 s 2 p4 »P - 2 s 2 pa( * 0 ) 3 d »P0

2 s 2 p4 *P - 2a2p3(*D)3d "S0

2Po apo _ 2p4(1D)3d «P 2pB 2po _ gp4 ( 10)3 () 2Q 2 s 2 p4 *P - 2 a 2 pa(30 ) 3 d *S9

2 822 p3 *£)«» - 2a*2p* (3p) 3d »D 2 8 2 p4 *P - 2 8 2 pa(a0 ) 3 d 40°

2 s 2 p4 3P - 2s2pa(*P)3d 20°

2882pasp«> - 2as2p'(*D)3d*P gsiapaapo - 2a>2p>(iO)3d?D 2 8 2 p4 <9 - 2 s 2 pata0 ) 3 d *P°

2 8 2 p4 »8 - 2 e 2 palaP ) 3 d apo 2p6 2po _ 2p4(1S ) 3 d 80 2 8 2 p4 *9 - 2 a 2 pa(3P ) 3 d *&

2 p4 *S - 2pa(«P)3d JP°

2 8a2 pa aP" - 2 8 2 pa(a0 ) 3 p*D 2 8 2 pa *D« - 282pataD)3d *D 2 8 2 pa *P0 - 282ps(ap)3d *P 2 s a 2 pa *Sf - 28a2p8 (3p) 3d 4p 2 p4 ap - 2 p9( a o ) 3 d *P"

2p4 3p _ 2p 3(20) 3d %»

288gp2 lS - 2»»2p3d *P°

2a22p3 *5P - 2a2pa(»S)3p *9

2 p4 1Q _ sp3(8p)3d loo 2 8 2 pa *P° - 282pa(ap)3d *D 2 a 2 pa *P» - 2B2p2(*D)3d 8s 2p4 3p - 2 pa( a p ) 3 d 8QO 2sa2pa sp - 28a2p3d »p"

2 s 2 pa *D° - 282pa(aD)3d *0 Za*Zp* 8p - 2sa2p3d ap0

(1) N N N N N N N N N N N N N N N C N C C N

C C C N C C C C C C C

Wave Length (A) c a l axo 1 2 . 2 5 2

1 2 . 1 8 4 12.134 1 2 . 1 3 1 12.0BB 12.027 12.001

1 2 . 0 0 1 1 1 . 9 7 3 11.965 11.996 1 1 . 8 5 6 1 1 . 9 1 6 11.870 1 1 . 8 2 9 11.810 1 1 . 8 0 1 11.799 11.748 1 1 . 7 3 3 1 1 . 7 3 3 11.680 11.640 1 1 . 6 2 2 1 1 . 6 0 6 11.509 1 1 . 5 1 9 11.479 1 1 . 4 9 2 1 1 . 4 4 3 11.391

1 2 . 2 5 2 1 2 . 1 6 9 1 2 . 1 2 8 12.0B1 1 2 . 0 4 0 1 2 . 0 0 1

1 2 . 0 0 1 1 1 . 9 7 9 1 1 . 9 6 2 1 1 . 9 4 9 1 1 . 9 2 2 1 1 . 8 6 1 1 1 . 8 2 3 1 1 . 8 0 1 1 1 . 8 0 1 1 1 . 8 0 1 1 1 . 7 3 3 1 1 . 7 3 3 1 1 . 6 8 0 1 1 . 6 4 0 1 1 . 6 1 9 1 1 . 8 0 6 1 1 . 9 9 6 1 1 . 4 7 7 1 1 . 4 4 4 1 1 . 3 9 1

0SC COMMENT (2) 4.073E-01 4.902E-01 4.908E-01 7 . 9 7 7 E - 0 1 1.197E+00 9.892E-01 3.009E-01 N

3 . 0 3 8 E - 0 1 6.826E-01 3.344E-01 9.889E-01 0 . 6 6 3 E - 0 1 3 . 3 9 3 E - 0 1 3.197E-01 3 . 6 6 3 E - 0 1 2.193E+00 5.804E-01 K

3.119E-01 4.097E-01 1.796E+00 tt

4.998E-01 6.407E-01 1.377E+00 3.740E-01 4.B96E-01 6.670E-01 3.083E-01 7.301E-01

3.057E-01 Z 3.054E-01

9.494E-01 » (1) N : N-lllce cobalt Ion, C : C - l l k e cobalt Ion;

(2) K : Kelly 171. Z : Zhang I 3 j . * : d i f f e r e n t from Zhang'8 I d e n t i f i c a t i o n [3]

C9-374 JOURNAL DE PHYSIQUE

For example, N-like x-ray lines: 12.131A (with the oscillator strength f=0.7977), 12.088A (1.197), 11.870A (0.3197) etc.,C-like x-ray lines 11.810A(2.193), 11.733A(0.4998), 11.680A (0.6407), 11.606A (0.4696), 11.479A(0.7301) etc. They correspond to some very strong experimental spectral lines.

The laser-produced high temperature cobalt plasma is generally not in the Local Thermodynamical Equilibrium (LTE). Nevertheless, we estimate relative level populations by corresponding Boltzmann factors for N-like and C-like ions respectively. More precise simulations require 'rate-equationJ calculations. The calculated radiative transition rates multiplied by the Boltzmann factors with the plasma temperature T=272 eV are shown proportionally as the vertical lines in Fig.1. The calculated lines are generally matched with the experimental spectral pattern. It implies that the high temperature cobalt plasma is not far from the LTE.

Our NRCI computer code should be a very useful tool to analyze the x-ray spectra. Furthermore, the calculated oscillator strengths are very helpful to identify the unknown x-ray spectra. For the N-like and C-like ions, the calculated x-ray transition energies agree with the experimental line positions within a few thousandths. Many new x-ray lines have been successfully identified; the above mentioned transition lines involving levels without 2s orbital are found to be important. On the red side of the experimental spectra, some transitions between 12.1 and 12.4A are possibly from the F-like or 0-like cobalt ions as shown in Fig.1. On the blue side, several strong lines are not known yet which may be from the B-like or Be-like ions as indicated in Fig.1. Additionally, a few x-ray lines (such as 11.672, 11.576, 11.492, 11.367A, etc) may be due to the spin forbidden transitions or the fine structure splitting of the x-ray transitions.

This work was partially supported by the Chinese National Science Foundation and the President Science Foundation. Academia Sinica.

REFERENCE

[I] D. L. Matthews, et al., Phys. Rev. Lett.,

54,

(1985), 110;

[2] Zhong-Xin Zhao, Jia-Ming Li, Acta. Physica Sinica

34,

(1985), 1469;

[3] Chengchuan Chang, Pinzhong Fan, et al., Physica Scripta, 35, (1987), 798;

[4] Herman and S. Skillman, Atomic Structure Calculations (Prentice-Hall Inc. Englewood Cliffs. N. J. 1963);

[5] Jia-Ming Li, Zhong-Xin Zhao, Acta. Physica Sinica

30,

(1981), 105;

[6] Qi Dong, Jia-Ming Li, Acta. Physica Sinica

35,

(1986), 1634;

[ 7 ] R . L. Kelly and L. J. Palumbo, " Atomic and Ionic Emission

lines Below 2000A

" ,

NRL Report 7599, 1973;