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The KLL and KLX auger electrons of arsenic from the 75Se decay
Journal of Electron Spectroscopy and Related Phenomena, 43 (1987) 225-232 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands
THE KLL AND KLX AUGER “Se DECAY
A. KOVALfK,
M. RYSAVY,
V. BRABEC
Nuclear Physics Institute, Czechoslovak (Czechoslovakia) A. INOYATOV, Laboratory (Received
ELECTRONS
A.F. NOVGORODOV,
OF ARSENIC
225
FROM THE
and 0. DRAGOUN
Academy of Sciences, 250 68 Rei near Prague
T.S. VYLOV
and A. MINKOVA
of Nuclear Problems, JINR, Dubna (U.S.S.R.) 28 April 1987)
ABSTRACT The KLL and KLX spectra for Auger electrons of arsenic (2 = 33) emitted during “Se decay were recorded, with an instrumental resolution of lleV, using a combined electrostatic spectrometer. The relative energies and intensities of nine KLL and ten KLX transitions were determined by computer analysis of the spectra. The margins of error were estimated to be 14 eV for energies and 2-50% for intensities. Except for the KL, L, (‘5) transition, the measured relative intensities of the KLL transitions were found to agree, within 3 standard deviations (u), with those calculated relativistically using the intermediate coupling approximation with configuration interaction. The discrepancy for the KL, L, (‘5) transition amounted to 6 o. The KL, M,,,/KL, Mzs transition intensity ratio agreed with the prediction based upon the intermediate coupling scheme but deviated by 7 u from the value predicted by the jj coupling approximation.
INTRODUCTION
The two relativistic calculations of the KLL transition probabilities, one by Asaad and Petrini [l] and one by Chen et al. [2], are both based upon the intermediate coupling scheme and both take into consideration the interaction of the (2~)~ and (2~)~’ final atomic configurations. The results of the calculations are consistent with each other and, in general, are in better agreement with experimental data than are other existing calculations. However, some discrepancies between the predicted [l, 21 and measured transition intensities are observed, especially at low 2 (see e.g. ref. 3). To highlight the cause of these discrepancies it is necessary to increase the accuracy of the experimentally determined data, as well as to carry out measurements in the rarely studied region of Z 6 35. The relative KLM Auger transition rates measured for iron (2 = 26) [3] and for gallium (2 = 31) [4] indicate that the jj coupling approximation is not suitable for calculations over the entire range of 2. It turns out that the non-relativistic calculations of Babenkov et al. [5], based on the intermediate
03682048/87/$03.50
@$ 1987 Elsevier Science Publishers
B.V.
226
coupling scheme, describe the experimental KLM transition intensities for 2 5 40 more accurately than the relativistic calculations of Chen et al. [6] (calculated in the framework of the jj coupling approximation). Additional, more exact, measurements of the KLM Auger spectra of low and medium Z elements are inevitably required in order to draw a definite conclusion about ,the nature of the coupling. To date, there have been only three such measurements for 18 < 2 < 46, these being for, iron [3], gallium [4] and bromine (2 = 35) [7]. In this paper, we present results of the experimental study of KLL and KLX Auger electrons emitted during the electron capture decay of ESe (T,,, = 12Od) into $As. In a previous study, Johnston et al. [8] examined individual transitions of the KLL group but made no attempt to separate individual KLM lines. EXPERIMENTAL
The 75Se activity was induced by long-term irradiation of enriched 74Seusing reactor neutrons. The irradiated target was heated in a stream of air at 2OO’C in a quartz thermo-chromatographic column. The volatilized selenium thus produced was caught on the inner wall of an annealed quartz capillary which was subsequently mechanically crushed. The capillary fragments with their adsorbed selenium, served as original material for production of the 75Se sources. Vacuum evaporation from a crucible placed in a tantal heater was the method of production used, with both the crucible and the heater being annealed in vacua at 800 and 1000°C, respectively, for several minutes before use. Prior to selenium evaporation, the crucible and selected capillary fragments were heated in vacua to 200°C for about 10 min in order to catch possible impurities on a baffle. After this the baffle was removed and the selenium deposited on a backing through a slit (diameter 7 mm) in a titanium mask. This deposition took- 90 s at 35O’C in vacuum of 10e6 torr. To ensure a more homogeneous distribution of the active selenium, the backing, together with the mask, were rotated around an axis at a rate of 2000 turns min-‘. We prepared a total of ten 75Se sources under various conditions on Cu and Ni mirror-like semispherical backings, which had previously been etched by argon ions. However, only two of the selenium deposits on the Cu backing were not visible. Since Johnston et al. [8] observed sublimation into the spectrometer vacuum system of selenium evaporated on to an aluminium backing, we stored the selenium sources in special packings for several days under a vacuum of 10e5 torr before we took any measurements. In fact, we noticed considerable desorption of the selenium from the nickel backing even at room temperature and this is why we excluded these sources from the measurements in the spectrometer. The quality of each source on the copper backing was then tested by measuring the form of the KLL Auger spectrum of arsenic. As expected, the best spectra were obtained with the “invisible” sources which were then chosen for further measurements. It should be noted that the sources, even the “invisible” ones, became dark on exposure to air.
8.9
9.0 ELECTRON
9.1 ENERGY
9.2 (keV)
Fig. 1. Example of the measured KU Auger spectrum of arsenic. Results of the spectrum decomposition (full lines) made by the computer code ERIKA [lo] together with residuals are shown. The analysis yielded x2 per one degree of freedom, xf = 1.25.
The electron spectra in the energy range of 8.5-10.5 keV were recorded using the combined electrostatic spectrometer [9] at the JINR in Dubna, U.S.S.R. To compensate for the low electron intensity of the selected 75Se sources, we employed the electron pass energy through the cylindrical mirror analyser, 150 eV, which yielded the instrumental resolution of 11eV. Three runs of the KLL spectrum were taken using one of the aforementioned sources and two runs of the KLX spectrum using the other. In all cases, the energy step width was 2 eV and the exposure time was 600 s per point. Examples of the measured spectra are shown in Figs. 1 and 2. ANALYSIS
OF SPECTRA
To decompose the measured spectra into components, we applied the computer code ERIKA [lo]. The single line shape was described by an asymmetrical Gaussian-like function. The position, height and FWHM of each line in the spectrum were fitted independently while the remaining five line shape parameters, which were also varied during the least-squares procedure, were considered to be the same for all components. The background of the KLL group, as well as of the KLX, was assumed to be a constant, the value of which was also fitted. Altogether, three Auger electron spectra of the KLL and two of the KLX groups were evaluated. The weighted averages of our experimental results, together with our estimates of the standard deviations, are given in Tables l-3.
I
10.1
I
I
I
10.2
10.3
L
I
10.4
10.5
ELECTRON
ENERGY
10.6 (keV)
Fig. 2. The KLX Auger spectrum of arsenic. The spectrum analysis by the computer code ERIKA [lo] gave d = 1.30 (see caption to Fig. 1).
Examples of the decomposed spectra are shown in Figs. 1 and 2. According to the intermediate coupling theory of Asaad and Burhop [ll], the KLL Auger spectrum consists of nine lines, and these were in fact resolved during our measurements (see Fig. l)..Thus, arsenic is now the lightest element for which the full structure of the KLL spectrum can be observed (up until now it was bromine). TABLE
1
Relative intensities Transition
and eneraies of the KLL Auaer transitions
Intensities
(%)
Energies (eV)
Experiment
Theory (ref.
This work
KL,L,(‘W KL,Wp,) f=,Wp,) GM5) KL1LXpZ) KL&,(‘&) K-Wd4)
KL&d3pO) KL,.Mp,)
6.5(3)d 14.3(5) 2.2(7) 5.8(7) 3.0(5) 4.0(9) 49.9(14) 3.1(7) 11.3(6)
in arsenic
Ref. [81b
This work
5.8(5) > 16.9(28) 7.0(10) 8.9(16) 51 (10) 10.7(16)
“Normalized to ZKLL. bRenormalixed energies. d6.5(3) means 6.5 f 0.3.
Experiment
7.3 17.3 1.5 4.9 3.3 4.0 49.1 2.5 9.9
to ZKLL.
Theory (ref. [12])
121)
-
“Values
365(2) 204(2) 174(3) 155(2) 137(3) - 41(3) 0 + 26(2) + 45(l) obtained
Ref. [S] - 363(14) 1
-
203(14) 147(14) - 31(14) 0 + 34(13)
from the absolute
-
359.7 200.9 169.1 150.8 133.6 - 38.8 0.0 + 28.4 + 43.4
transition
229 TABLE 2 Relative intensities Configuration
Gw
of the KLL transition Transition
group
KL, L,
(2$‘(2$’
K-G-%,,
cw2
KJW,,,
groups Experiment
Theory (ref. [2])
This work
Ref. [8]
1.00(5) 3.89(26) 10.6(6)
1.00 4.15(43) 12.2(16)
1.0 3.7 9.0
TABLE 3 Relative intensities Transition
and energies of the KLX transitions Intensities” Experiment (this work)
KL, W KL, M2.s K&M, + K&M,,, KL, M, KL2M2,3 + KL,N KL, Mz.3 KL, Ma.6 K-G M4.5 KL,N KL,N
in arsenic
1.00(5) 1.62(6) 0.55(12) 0.86(16) 3.20(22) 3.80(14) 0.37(10) 0.49(9) 0*2(l) 0.34(8)
Energies (eV) Theory Ref. [S]
Ref. [5]
1.0 1.5 0.56 0.81 2.P 4.0 0.24 0.44 0.048’ 0.0848
1.0 1.7 0.54” 0.94 3.6’ 4.3 -
Experiment (this work)
Theoryb (ref. [12])
- 269(3)
- 264.2 - 202.5 - 93.0 - 58.3 - 30.3 0 + 72.5 + 109.8 -
- 204(3) - 95(4) - 57(4) -31(l) 0 + 70(3) + 105(3) + 124(4) + 154(4)
“Normalized to the KL,M, transition intensity. ’ Energy differences between the KL, M, f P,) transition and the most intense transition(according to the calculations of Asaad and Burhop [ll]) of the given multiplet. ‘The KL, MI transition intensity only. d Only the KL, NI transition intensity included. e The KL, Mza3transition intensity only. ‘Only the KL, NI transition intensity included. gOnly the KL,N, transition intensity included.
This same theory predicts 36 lines in the KLM group, contrary to the 15 predicted by the jj coupling approximation. To date, no measurements on the KLM Auger spectra have confirmed the predictions of the intermediate coupling theory. The main reason for this is a very low energy separation of the individual lines [12] and also their large natural widths. In our KLM spectra of arsenic, only the structure predicted by the jj coupling theory was observed. RESULTS
AND DISCUSSION
The theoretical Auger transition probabilities for 2 = 33 (presented in Tables l-3) were obtained by graphical interpolation from existing tables [2,5, 61. This method was chosen due to the non-monotonous Z-dependence of these quantities.
230
KLL Auger spectrum In the work of Johnston et al. [8], the KLL Auger spectrum of arsenic was recorded with approximately four times worse absolute instrumental resolution than were our measurements and, consequently, only five lines were disclosed. Nevertheless, the authors managed to deduce absolute energies and relative intensities of the six KLL transitions predicted by the jj coupling theory. As the lines were not well resolved, main emphasis was placed on the intensity determination of groups of the lines, namely KL,L,, KL,L,, and KL,&,,, . In Table 1, experimental relative intensities and energies of the KLL transitions in arsenic are compared with the results of calculations carried out by Chen et al. [2] (transition intensities) and by Larkins [12] (transition energies). As can be seen, relative transition intensities found here agree with those of the previous work [8] to within three quoted standard deviations. The worst agreement is that concerning the KL, L, (lS’,,)transition, this not being resolved in the measurement of Johnston et al. [8]. Except for the KL,L, (‘PI) transition, the predictions of Chen et al. [2] are in satisfactory accordance with the transition intensities found here. A similar discrepancy was observed for iron [3] as well, indicating yet again a role of correlation effects other than that of the interaction between the (2s))’ and (2~))’ configurations at low 2 [13]. The experimental intensities of the transitions to the (ZS))~, (2~))~ (2~))~ and (2~))~ final atomic configurations (the line PUPS KG L,, KG L2,, and KL,,, L,,, , respectively) are in accordance with each other as well as with the theory [2], but our values are closer to the theoretical ones (see Table 2). The theoretical transition energies presented in Table 1 were obtained from the extensive semi-empirical calculations carried out by Larkins [12]. The results of these calculations are in very good agreement with the experimental data over a wide range of atomic number. The values found here for arsenic agree with those obtained from the work of Larkins [12] within three quoted standard deviations, but they are systematically larger. KLX Auger spectrum As can be seen from Table 3, where a comparison is given, one cannot simply decide between the calculations of Babenkov et al. [5] and Chen et al. [6] as to which is the more accurate; they treat the relativistic effects and the coupling schemes differently. However, the authors [5] have proved that the intensity distribution among the transitions to the (2~))’ (3~))’ final atomic configuration is substantially changed when going from the jj coupling scheme to the intermediate one. In particular, the calculations presented by these two [5,6] predict the KL, M2,3/KL2M2,3intensity ratio for arsenic to be 1.2 and 1.8, respectively. Thus our experimental result for this ratio, 1.2 + 0.1, agrees only with the non-relativistic calculation [5] of the intermediate coupling scheme (see
231
0
20
40
60
ATOMIC
80
NUMBER
Fig. 3. Some experimental ([3], [4], [15]) and theoretical values of the KL,M,,/KL,M,,, transition intensity ratio as a function of Z: full curve, results of the relativistic calculations of Chen et al. 161in the jj coupling scheme; dashed and dot-dashed curves, results of the non-relativistic calculations performed in the intermediate coupling approximation by Babenkov et al. [5] and by Asaad and Burhop [ll], respectively. Our value is denoted by an open circle.
also Fig. 3). Since the relativistic effects were found not to play an important role for the KL,,,M2,3 transitions in arsenic (e.g. ref. 14), we conclude that the jj coupling scheme is not applicable for calculation of the KLM transition rates for 2 = 33. In our previous work [3] we came to the same conclusion for Z = 26. In the last column of Table 3, the theoretical relative KLM transition energies for arsenic are listed. The presented values were obtained from ref. 12 as the energy difference between the most intensive term in a given multiplet and the energy of the KL,M, (“P2) transition. Despite the apparent simplicity of this presentation the calculated transition energies are in good accord with the measured ones. REFERENCES 1 2 3 4 5 6 7 8
W.N. Asaad and D. Petrini, Proc. Roy. Sot. London, Ser. A, 350 (1976) 381. M.H. Chen, B. Crasemann and H. Mark, Phys. Rev. A, 21 (1980) 442. A. Kovalik, A. Inoyatov, A.F. Novgorodov, V. Brabec, M. Rysavy, Ts. Vylov, 0. Dragoun and A. Minkova, J. Phys. B, in press. M.I. Babenkov, V.S. Zhdanov and S.A. Starodubov, Proc. 36th Conf. on Nuclear Spectroscopy and Nuclear Structure, Nauka, Leningrad, 1986, p. 267 (in Russian). M.I. Babenkov, VS. Zhdanov and S.A. Starodubov, Proc. 36th Conf. on Nuclear Spectroscopy and Nuclear Structure, Nauka, Leningrad, 1986, p. 268 (in Russian). M.H. Chen, B. Crasemann and H. Mark, At. Data Nucl. Data Tables, 24 (1979) 13. P. Erman, I. Bergstrom, Y.Y. Chu and G.T. Emery, Nucl. Phys., 62 (1965) 401. R.E. Johnston, J.H. Douglas and R.G. Albridge, Nucl. Phys. A, 91 (1967) 505.
232 9 10 11 12 13 14 15
Ch. Briancon, B. Legrand, R.J. Walen, Ts. Vylov, A. Minkova and A. Inoyatov, Nucl. Instrum. Methods, 221 (1964) 547. M. RyHavy and M. FiEier, Comput. Phys. Commun., 29 (1983) 171. W.N. Asaad and E.H.S. Burhop, Proc. Phys. Sot., London, 71 (1958) 369. F.P. Larkins, At. Data Nucl. Data Tables, 20 (1977) 311. H.P. Kelly, Phys. Rev. A, 11 (1975) 556. M.I. Babenkov and V.K. Petukhov, J. Phys. B, 10 (1977) L 85. M.I. Babenkov, B.V. Bobykin, V.S. Zhd anov and V.K. Petukhov, Izv. Akad. Nauk SSSR, 40 (1976) 2065 (in Russian).
THE KLL AND KLX AUGER “Se DECAY
A. KOVALfK,
M. RYSAVY,
V. BRABEC
Nuclear Physics Institute, Czechoslovak (Czechoslovakia) A. INOYATOV, Laboratory (Received
ELECTRONS
A.F. NOVGORODOV,
OF ARSENIC
225
FROM THE
and 0. DRAGOUN
Academy of Sciences, 250 68 Rei near Prague
T.S. VYLOV
and A. MINKOVA
of Nuclear Problems, JINR, Dubna (U.S.S.R.) 28 April 1987)
ABSTRACT The KLL and KLX spectra for Auger electrons of arsenic (2 = 33) emitted during “Se decay were recorded, with an instrumental resolution of lleV, using a combined electrostatic spectrometer. The relative energies and intensities of nine KLL and ten KLX transitions were determined by computer analysis of the spectra. The margins of error were estimated to be 14 eV for energies and 2-50% for intensities. Except for the KL, L, (‘5) transition, the measured relative intensities of the KLL transitions were found to agree, within 3 standard deviations (u), with those calculated relativistically using the intermediate coupling approximation with configuration interaction. The discrepancy for the KL, L, (‘5) transition amounted to 6 o. The KL, M,,,/KL, Mzs transition intensity ratio agreed with the prediction based upon the intermediate coupling scheme but deviated by 7 u from the value predicted by the jj coupling approximation.
INTRODUCTION
The two relativistic calculations of the KLL transition probabilities, one by Asaad and Petrini [l] and one by Chen et al. [2], are both based upon the intermediate coupling scheme and both take into consideration the interaction of the (2~)~ and (2~)~’ final atomic configurations. The results of the calculations are consistent with each other and, in general, are in better agreement with experimental data than are other existing calculations. However, some discrepancies between the predicted [l, 21 and measured transition intensities are observed, especially at low 2 (see e.g. ref. 3). To highlight the cause of these discrepancies it is necessary to increase the accuracy of the experimentally determined data, as well as to carry out measurements in the rarely studied region of Z 6 35. The relative KLM Auger transition rates measured for iron (2 = 26) [3] and for gallium (2 = 31) [4] indicate that the jj coupling approximation is not suitable for calculations over the entire range of 2. It turns out that the non-relativistic calculations of Babenkov et al. [5], based on the intermediate
03682048/87/$03.50
@$ 1987 Elsevier Science Publishers
B.V.
226
coupling scheme, describe the experimental KLM transition intensities for 2 5 40 more accurately than the relativistic calculations of Chen et al. [6] (calculated in the framework of the jj coupling approximation). Additional, more exact, measurements of the KLM Auger spectra of low and medium Z elements are inevitably required in order to draw a definite conclusion about ,the nature of the coupling. To date, there have been only three such measurements for 18 < 2 < 46, these being for, iron [3], gallium [4] and bromine (2 = 35) [7]. In this paper, we present results of the experimental study of KLL and KLX Auger electrons emitted during the electron capture decay of ESe (T,,, = 12Od) into $As. In a previous study, Johnston et al. [8] examined individual transitions of the KLL group but made no attempt to separate individual KLM lines. EXPERIMENTAL
The 75Se activity was induced by long-term irradiation of enriched 74Seusing reactor neutrons. The irradiated target was heated in a stream of air at 2OO’C in a quartz thermo-chromatographic column. The volatilized selenium thus produced was caught on the inner wall of an annealed quartz capillary which was subsequently mechanically crushed. The capillary fragments with their adsorbed selenium, served as original material for production of the 75Se sources. Vacuum evaporation from a crucible placed in a tantal heater was the method of production used, with both the crucible and the heater being annealed in vacua at 800 and 1000°C, respectively, for several minutes before use. Prior to selenium evaporation, the crucible and selected capillary fragments were heated in vacua to 200°C for about 10 min in order to catch possible impurities on a baffle. After this the baffle was removed and the selenium deposited on a backing through a slit (diameter 7 mm) in a titanium mask. This deposition took- 90 s at 35O’C in vacuum of 10e6 torr. To ensure a more homogeneous distribution of the active selenium, the backing, together with the mask, were rotated around an axis at a rate of 2000 turns min-‘. We prepared a total of ten 75Se sources under various conditions on Cu and Ni mirror-like semispherical backings, which had previously been etched by argon ions. However, only two of the selenium deposits on the Cu backing were not visible. Since Johnston et al. [8] observed sublimation into the spectrometer vacuum system of selenium evaporated on to an aluminium backing, we stored the selenium sources in special packings for several days under a vacuum of 10e5 torr before we took any measurements. In fact, we noticed considerable desorption of the selenium from the nickel backing even at room temperature and this is why we excluded these sources from the measurements in the spectrometer. The quality of each source on the copper backing was then tested by measuring the form of the KLL Auger spectrum of arsenic. As expected, the best spectra were obtained with the “invisible” sources which were then chosen for further measurements. It should be noted that the sources, even the “invisible” ones, became dark on exposure to air.
8.9
9.0 ELECTRON
9.1 ENERGY
9.2 (keV)
Fig. 1. Example of the measured KU Auger spectrum of arsenic. Results of the spectrum decomposition (full lines) made by the computer code ERIKA [lo] together with residuals are shown. The analysis yielded x2 per one degree of freedom, xf = 1.25.
The electron spectra in the energy range of 8.5-10.5 keV were recorded using the combined electrostatic spectrometer [9] at the JINR in Dubna, U.S.S.R. To compensate for the low electron intensity of the selected 75Se sources, we employed the electron pass energy through the cylindrical mirror analyser, 150 eV, which yielded the instrumental resolution of 11eV. Three runs of the KLL spectrum were taken using one of the aforementioned sources and two runs of the KLX spectrum using the other. In all cases, the energy step width was 2 eV and the exposure time was 600 s per point. Examples of the measured spectra are shown in Figs. 1 and 2. ANALYSIS
OF SPECTRA
To decompose the measured spectra into components, we applied the computer code ERIKA [lo]. The single line shape was described by an asymmetrical Gaussian-like function. The position, height and FWHM of each line in the spectrum were fitted independently while the remaining five line shape parameters, which were also varied during the least-squares procedure, were considered to be the same for all components. The background of the KLL group, as well as of the KLX, was assumed to be a constant, the value of which was also fitted. Altogether, three Auger electron spectra of the KLL and two of the KLX groups were evaluated. The weighted averages of our experimental results, together with our estimates of the standard deviations, are given in Tables l-3.
I
10.1
I
I
I
10.2
10.3
L
I
10.4
10.5
ELECTRON
ENERGY
10.6 (keV)
Fig. 2. The KLX Auger spectrum of arsenic. The spectrum analysis by the computer code ERIKA [lo] gave d = 1.30 (see caption to Fig. 1).
Examples of the decomposed spectra are shown in Figs. 1 and 2. According to the intermediate coupling theory of Asaad and Burhop [ll], the KLL Auger spectrum consists of nine lines, and these were in fact resolved during our measurements (see Fig. l)..Thus, arsenic is now the lightest element for which the full structure of the KLL spectrum can be observed (up until now it was bromine). TABLE
1
Relative intensities Transition
and eneraies of the KLL Auaer transitions
Intensities
(%)
Energies (eV)
Experiment
Theory (ref.
This work
KL,L,(‘W KL,Wp,) f=,Wp,) GM5) KL1LXpZ) KL&,(‘&) K-Wd4)
KL&d3pO) KL,.Mp,)
6.5(3)d 14.3(5) 2.2(7) 5.8(7) 3.0(5) 4.0(9) 49.9(14) 3.1(7) 11.3(6)
in arsenic
Ref. [81b
This work
5.8(5) > 16.9(28) 7.0(10) 8.9(16) 51 (10) 10.7(16)
“Normalized to ZKLL. bRenormalixed energies. d6.5(3) means 6.5 f 0.3.
Experiment
7.3 17.3 1.5 4.9 3.3 4.0 49.1 2.5 9.9
to ZKLL.
Theory (ref. [12])
121)
-
“Values
365(2) 204(2) 174(3) 155(2) 137(3) - 41(3) 0 + 26(2) + 45(l) obtained
Ref. [S] - 363(14) 1
-
203(14) 147(14) - 31(14) 0 + 34(13)
from the absolute
-
359.7 200.9 169.1 150.8 133.6 - 38.8 0.0 + 28.4 + 43.4
transition
229 TABLE 2 Relative intensities Configuration
Gw
of the KLL transition Transition
group
KL, L,
(2$‘(2$’
K-G-%,,
cw2
KJW,,,
groups Experiment
Theory (ref. [2])
This work
Ref. [8]
1.00(5) 3.89(26) 10.6(6)
1.00 4.15(43) 12.2(16)
1.0 3.7 9.0
TABLE 3 Relative intensities Transition
and energies of the KLX transitions Intensities” Experiment (this work)
KL, W KL, M2.s K&M, + K&M,,, KL, M, KL2M2,3 + KL,N KL, Mz.3 KL, Ma.6 K-G M4.5 KL,N KL,N
in arsenic
1.00(5) 1.62(6) 0.55(12) 0.86(16) 3.20(22) 3.80(14) 0.37(10) 0.49(9) 0*2(l) 0.34(8)
Energies (eV) Theory Ref. [S]
Ref. [5]
1.0 1.5 0.56 0.81 2.P 4.0 0.24 0.44 0.048’ 0.0848
1.0 1.7 0.54” 0.94 3.6’ 4.3 -
Experiment (this work)
Theoryb (ref. [12])
- 269(3)
- 264.2 - 202.5 - 93.0 - 58.3 - 30.3 0 + 72.5 + 109.8 -
- 204(3) - 95(4) - 57(4) -31(l) 0 + 70(3) + 105(3) + 124(4) + 154(4)
“Normalized to the KL,M, transition intensity. ’ Energy differences between the KL, M, f P,) transition and the most intense transition(according to the calculations of Asaad and Burhop [ll]) of the given multiplet. ‘The KL, MI transition intensity only. d Only the KL, NI transition intensity included. e The KL, Mza3transition intensity only. ‘Only the KL, NI transition intensity included. gOnly the KL,N, transition intensity included.
This same theory predicts 36 lines in the KLM group, contrary to the 15 predicted by the jj coupling approximation. To date, no measurements on the KLM Auger spectra have confirmed the predictions of the intermediate coupling theory. The main reason for this is a very low energy separation of the individual lines [12] and also their large natural widths. In our KLM spectra of arsenic, only the structure predicted by the jj coupling theory was observed. RESULTS
AND DISCUSSION
The theoretical Auger transition probabilities for 2 = 33 (presented in Tables l-3) were obtained by graphical interpolation from existing tables [2,5, 61. This method was chosen due to the non-monotonous Z-dependence of these quantities.
230
KLL Auger spectrum In the work of Johnston et al. [8], the KLL Auger spectrum of arsenic was recorded with approximately four times worse absolute instrumental resolution than were our measurements and, consequently, only five lines were disclosed. Nevertheless, the authors managed to deduce absolute energies and relative intensities of the six KLL transitions predicted by the jj coupling theory. As the lines were not well resolved, main emphasis was placed on the intensity determination of groups of the lines, namely KL,L,, KL,L,, and KL,&,,, . In Table 1, experimental relative intensities and energies of the KLL transitions in arsenic are compared with the results of calculations carried out by Chen et al. [2] (transition intensities) and by Larkins [12] (transition energies). As can be seen, relative transition intensities found here agree with those of the previous work [8] to within three quoted standard deviations. The worst agreement is that concerning the KL, L, (lS’,,)transition, this not being resolved in the measurement of Johnston et al. [8]. Except for the KL,L, (‘PI) transition, the predictions of Chen et al. [2] are in satisfactory accordance with the transition intensities found here. A similar discrepancy was observed for iron [3] as well, indicating yet again a role of correlation effects other than that of the interaction between the (2s))’ and (2~))’ configurations at low 2 [13]. The experimental intensities of the transitions to the (ZS))~, (2~))~ (2~))~ and (2~))~ final atomic configurations (the line PUPS KG L,, KG L2,, and KL,,, L,,, , respectively) are in accordance with each other as well as with the theory [2], but our values are closer to the theoretical ones (see Table 2). The theoretical transition energies presented in Table 1 were obtained from the extensive semi-empirical calculations carried out by Larkins [12]. The results of these calculations are in very good agreement with the experimental data over a wide range of atomic number. The values found here for arsenic agree with those obtained from the work of Larkins [12] within three quoted standard deviations, but they are systematically larger. KLX Auger spectrum As can be seen from Table 3, where a comparison is given, one cannot simply decide between the calculations of Babenkov et al. [5] and Chen et al. [6] as to which is the more accurate; they treat the relativistic effects and the coupling schemes differently. However, the authors [5] have proved that the intensity distribution among the transitions to the (2~))’ (3~))’ final atomic configuration is substantially changed when going from the jj coupling scheme to the intermediate one. In particular, the calculations presented by these two [5,6] predict the KL, M2,3/KL2M2,3intensity ratio for arsenic to be 1.2 and 1.8, respectively. Thus our experimental result for this ratio, 1.2 + 0.1, agrees only with the non-relativistic calculation [5] of the intermediate coupling scheme (see
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0
20
40
60
ATOMIC
80
NUMBER
Fig. 3. Some experimental ([3], [4], [15]) and theoretical values of the KL,M,,/KL,M,,, transition intensity ratio as a function of Z: full curve, results of the relativistic calculations of Chen et al. 161in the jj coupling scheme; dashed and dot-dashed curves, results of the non-relativistic calculations performed in the intermediate coupling approximation by Babenkov et al. [5] and by Asaad and Burhop [ll], respectively. Our value is denoted by an open circle.
also Fig. 3). Since the relativistic effects were found not to play an important role for the KL,,,M2,3 transitions in arsenic (e.g. ref. 14), we conclude that the jj coupling scheme is not applicable for calculation of the KLM transition rates for 2 = 33. In our previous work [3] we came to the same conclusion for Z = 26. In the last column of Table 3, the theoretical relative KLM transition energies for arsenic are listed. The presented values were obtained from ref. 12 as the energy difference between the most intensive term in a given multiplet and the energy of the KL,M, (“P2) transition. Despite the apparent simplicity of this presentation the calculated transition energies are in good accord with the measured ones. REFERENCES 1 2 3 4 5 6 7 8
W.N. Asaad and D. Petrini, Proc. Roy. Sot. London, Ser. A, 350 (1976) 381. M.H. Chen, B. Crasemann and H. Mark, Phys. Rev. A, 21 (1980) 442. A. Kovalik, A. Inoyatov, A.F. Novgorodov, V. Brabec, M. Rysavy, Ts. Vylov, 0. Dragoun and A. Minkova, J. Phys. B, in press. M.I. Babenkov, V.S. Zhdanov and S.A. Starodubov, Proc. 36th Conf. on Nuclear Spectroscopy and Nuclear Structure, Nauka, Leningrad, 1986, p. 267 (in Russian). M.I. Babenkov, VS. Zhdanov and S.A. Starodubov, Proc. 36th Conf. on Nuclear Spectroscopy and Nuclear Structure, Nauka, Leningrad, 1986, p. 268 (in Russian). M.H. Chen, B. Crasemann and H. Mark, At. Data Nucl. Data Tables, 24 (1979) 13. P. Erman, I. Bergstrom, Y.Y. Chu and G.T. Emery, Nucl. Phys., 62 (1965) 401. R.E. Johnston, J.H. Douglas and R.G. Albridge, Nucl. Phys. A, 91 (1967) 505.
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Ch. Briancon, B. Legrand, R.J. Walen, Ts. Vylov, A. Minkova and A. Inoyatov, Nucl. Instrum. Methods, 221 (1964) 547. M. RyHavy and M. FiEier, Comput. Phys. Commun., 29 (1983) 171. W.N. Asaad and E.H.S. Burhop, Proc. Phys. Sot., London, 71 (1958) 369. F.P. Larkins, At. Data Nucl. Data Tables, 20 (1977) 311. H.P. Kelly, Phys. Rev. A, 11 (1975) 556. M.I. Babenkov and V.K. Petukhov, J. Phys. B, 10 (1977) L 85. M.I. Babenkov, B.V. Bobykin, V.S. Zhd anov and V.K. Petukhov, Izv. Akad. Nauk SSSR, 40 (1976) 2065 (in Russian).