Journal of Electron Spectroscopy and Related Phenomena 171 (2009) 53–56
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Journal of Electron Spectroscopy and
Related Phenomena
journal homepage: www.elsevier.com/locate/elspec
The KLL Auger spectrum of 65 Cu measured from the EC decay of 65 Zn
A.Kh. Inoyatov ∗,1 , L.L. Perevoshchikov, A. Kovalik 2 , D.V. Filosofov, V.M. Gorozhankin
Laboratory of Nuclear Problems, JINR, Joliot-Curie 6, 141980 Dubna, Moscow Region, Russian Federation
a r t i c l e
i n f o
Article history:
Received 16 October 2008
Received in revised form 18 February 2009
Accepted 19 February 2009
Available online 3 March 2009
Keywords:
Electron spectroscopy
Auger effect
KLL transitions
65
Cu
65
Zn
a b s t r a c t
The KLL Auger electron spectrum of 65 Cu following the EC decay of 65 Zn has been analyzed at the instrumental resolution of 4.5 and 7 eV using a combined electrostatic spectrometer. Energies and relative
intensities of the all nine spectrum components were determined and compared with data obtained from
X-ray induced spectra for metallic copper and with results of theories as well. Our value of 7041.8(1.3) eV
measured for the absolute energy of the dominant KL2 L3 (1 D2 ) spectrum line was found to be higher by
4 eV than those ones obtained in experiments with the use of X-ray photon excitation and by 11 eV (8)
than a prediction of the semi-empirical calculations by Larkins. This discrepancy indicates an influence
of the “atomic structure effect” on absolute energies of the KLL Auger transitions in 65 Cu. Its value was
estimated to be from 8 to 15 eV. Good agreement of the measured value of 0.08(2) and that one of 0.066
predicted by relativistic calculation for the KL1 L2 (3 P0 /1 P1 ) transition intensity ratio indicates appreciable
influence of the relativistic effects on the KLL Auger spectrum even for copper (Z = 29).
© 2008 Elsevier B.V. All rights reserved.
1. Introduction
2. Experimental
Theoretical and experimental investigations of the K Auger
spectrum were mainly concentrated on the KLL group which is
the simplest and the most intense K Auger group. Nevertheless,
there remained some discrepancies between theoretical results and
experiment data like those for intensity distribution between the
1 P and 3 P components of the KL L doublet [1] and for absolute
1
0
1 2
energies of transitions initiated by EC decay and by internal conversion (or “external” excitation). The low and high atomic number
regions are experimentally less investigated due to experimental
difficulties and, moreover, measured data from these regions are
usually less precise than those from the middle atomic number
region. Thus a systematic experimental investigation of the KLL
Auger electron group is still actual.
In this paper we present results on the first measurement of
the KLL Auger spectrum of 65 Cu generated in the EC decay of 65 Zn.
The spectrum was already measured using both external excitation
by X-rays [2–5] and EC decay [6]. In the works [3,4] energies and
relative intensities of the KL2,3 L2,3 transitions and their shake-up
satellites were only determined.
2.1. Source preparation
∗ Corresponding author. Tel.: +7 4962163956; fax: +7 49612165853.
E-mail address: [email protected] (A.Kh. Inoyatov).
1
On leave from the Institute of Applied Physics, National University, 700174
Taskent, Republic of Uzbekistan.
2
On leave from the Nuclear Physics Institute of the Academy of Science of the
Czech Republic, 25068 Řež near Prague, Czech Republic.
0368-2048/$ – see front matter © 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.elspec.2009.02.010
Radioactive isotope 65 Zn was produced in the reaction
by irradiation of natural copper by 65 MeV protons
at the phasotron particle accelerator of the JINR, Dubna, Russia.
The irradiated target was dissolved in nitric acid and the solution
obtained was then desiccated.
The chemical separation of 65 Zn from target material and other
radionuclides was performed by anion-exchange chromatography
in HCl media. The 65 Zn solution was desiccated on a teflon surface
to a dry residue. Afterwards the residue was dissolved in nitric acid
media and desiccated again to dryness. A 65 Zn nitrate obtained was
dissolved in bi-distilled water, transferred to a Ta evaporation boat
and dried up to dryness. Radioactive sources of 65 Zn for electron
spectroscopy were prepared by thermic evaporation in vacuum on
copper and gold backings at 900 ◦ C. Prior to use, surfaces of the
source backings were mechanically cleaned. During the evaporation, the source backing was rotated around its axis at a speed of
3000 turns/s at a distance of 10 mm from the Ta evaporation boat.
Efficiency of the source preparation method was about 20%. The
activity of the each 65 Zn source prepared was about 2 MBq. The
most probable chemical form of Zn in prepared sources was ZnO.
65 Cu(p,n)65 Zn
2.2. Spectrum measurement and evaluation
Electron spectra were measured in sweeps with the instrumental resolution of 4.5 and 7 eV and the 1 and 2 eV step, respectively
using a combined electrostatic spectrometer [7] consisting of a
54
A.Kh. Inoyatov et al. / Journal of Electron Spectroscopy and Related Phenomena 171 (2009) 53–56
Fig. 1. The KLL Auger spectrum of 65 Cu measured with the 4.5 eV instrumental resolution and the 1 eV step. Results of the spectrum decomposition are shown by
continuous lines. In the insert, the KL1 L2,3 line group of the spectrum is shown in a
different scale.
retarding sphere followed by a double-pass cylindrical mirror
energy analyzer. An example of the full KLL Auger spectrum of
65 Cu and the KL L
1 2,3 line group measured with the 4.5 eV instrumental resolution is shown in Fig. 1. The energy calibration of the
spectrometer was accomplished employing suitable low energy
conversion electron lines of nuclear transitions in 169 Tm with energies E␥ = 8.41008(21) [8], 20.74378(10) [9], and 63.12081(5) keV [10]
and those of the 14.41300(15) keV [10] nuclear transition in 57 Fe as
well. Energies of the calibration lines were evaluated (as E␥ − Eb,i ;
i is the atomic subshell index) with use of experimental electron
binding energies Eb,i [11].
A special computer code [12] was used to resolve the measured
spectrum into components. The individual spectrum line shape was
expressed by a convolution of a Gaussian (spectrometer response
function) and a “model” function. The latter one described the
natural distribution of the KLL Auger electrons originating in Cu
atoms (Lorentzian) and its deformation due to inelastic scattering
of the electrons in the source material. Because it is very difficult
to calculate electron energy loss spectrum with needed precision
(insufficient information on the 65 Cu source used including thickness, composition, homogeneity, structure, etc. and energy losses of
the KLL electrons in the source) we applied the Monte-Carlo method
in the evaluation. The experimental spectra were fitted with all reasonable shapes of low energy tails of the KLL Auger lines randomly
filling the specified tail area. The fitted parameters were positions
and heights of each line, constant background and the width of the
spectrometer response function. We took into account only the line
shapes giving statistically reliable 2 . From obtained values of fitted parameters and their errors we determined the final values of
spectrum line parameters and their standard deviations. Natural
widths of the individual KLL Auger lines needed for the evaluation
were derived using Cu atomic level widths [13] (“recommended values”). Results of evaluation of a measured KLL Auger spectrum are
shown in Fig. 1 (continuous lines) and in Tables 1 and 2. The quoted
uncertainties in the tables are our estimates of standard deviations
().
3. Results and discussion
3.1. Energies
It is seen from Table 1 that the measured absolute energy of the
KL2 L3 (1 D2 ) transition in 65 Cu generated in the EC decay of 65 Zn is
higher by about 4 eV (i.e., 3) than the latest values obtained from
X-ray induced spectra [3,4] of pure Cu metal. To our opinion, this
deviation cannot be explained by physico-chemical effects in our
65 Zn source because they increase electron binding energies and,
in consequence, decrease Auger transition energies. The most probable reason of the discrepancy observed seems to be the “atomic
structure effect” [14,15] which increases Auger transition energies
due to the additional screening of the nucleus by the “superfluous”
atomic electron of the mother isotope. In our case it is 4s electron. As
it was mentioned in section 2.1, the most probable chemical form of
Zn in our source was ZnO. A chemical shift of 1.13 eV was obtained
in Ref. [16] for the 2p3/2 electron binding energies in Cu between the
elemental Cu and CuO. In the work [17], a chemical shift of −5 eV
per oxidation degree was determined for the Mn KLL Auger transition energies. Taking into account these experimental data and
the above mentioned absolute energy discrepancies found for the
KL2 L3 (1 D2 ) transition in Cu from EC decay of 65 Zn and from the Xray induced spectra, the “atomic structure effect” in our case can
contribute to the absolute energies of the KLL transitions in 65 Cu
from 8 to 15 eV.
All experimental absolute energies are, however, higher by more
than 3 than the theoretical results [18–20]. The prediction of the
relativistic semi-empirical calculations by Larkins [18] based on the
intermediate coupling scheme and experimental electron binding
energies is the closest to the experimental data. Nevertheless, it is
lower by 12 eV (i.e., 8) than our value. A reason of this systematic shift of the theoretical results is not evident. In the case of the
semi-empirical calculations [18], the discrepancy found can also
indicate that experimental Cu electron binding energies used in the
calculations were measured not for metallic copper but for some its
compounds.
General view on relative energies of the KLL Auger transitions
in Cu indicates that theoretical spectra are “compressed”, i.e., they
occupy shorter energy interval than the experimental ones. Again
the best fit of our data give the semi-empirical calculations [18] by
Larkins with the exception of the KL1 L2 (1 P1 ) and KL3 L3 (3 P2 ) transitions where discrepancies reach 5 and 6, respectively. We have
no explanation for that. It should be, however, noted that similar
discrepancies were observed for some other elements.
3.1.1. Relative intensities
In Table 2, intensities of the KLL transitions in 65 Cu normalized to
the sum intensity of both the KLL Auger group and the KL2,3 L2,3 line
group (normalization used in the measurements [3,4]) are compared with data obtained from X-ray induced spectra [2–4] and
with results of the calculations [19,21,22].
In the case of normalization to the full intensity of the KLL
Auger group, rather poor agreement is seen between our values and
those of the work [2]. Discrepancies are higher than 4. Relativistic
calculations in intermediate coupling [21] correspond to our data
best. Deviations reaching 3 were found only for the KL1 L2 (1 P1 ),
KL2 L2 (1 S0 ), and KL3 L3 (3 P0 ) transitions. The lower measured intensity of the KL1 L2 (1 P1 ) transition may indicate [23] a presence of
the weak tenth line (KL2 L3 (3 P1 )) in the KLL Auger spectrum which
gains its intensity from the KL1 L2 (1 P1 ) one. Higher experimental
intensity of the KL2 L3 (1 D2 ) line supports this supposition as the
KL2 L3 (3 P0 ) line clings tightly to the dominant KL2 L3 (1 D2 ) line. It
should be, however, noted that the KL2 L3 (3 P0 ) Auger transition is
forbidden by the parity conservation law. Higher observed intensity
of the KL2 L2 (1 S0 ) line can be caused by its superposition on the first
discrete energy loss peak of the KL2 L3 (1 D2 ) line and resulting difficulties in the spectrum evaluation. According to the calculations
[21], intensity distribution between the 1 P1 and 3 P0 components
of the KL1 L2 transitions strongly depends on the relativistic effects.
Due to the contribution from the retarded current-current interaction, the intensity of the KL1 L2 (3 P0 ) transition drastically increases
with increasing of atomic number Z and becomes as large as that
A.Kh. Inoyatov et al. / Journal of Electron Spectroscopy and Related Phenomena 171 (2009) 53–56
55
Table 1
Energies (eV) of the KLL Auger transitions in 65 Cu from the EC decay of 65 Zn.
Transition
1
KL1 L1 ( S0 )
KL1 L2 (1 P1 )
KL1 L2 (3 P0 )
KL1 L3 (3 P1 )
KL1 L3 (3 P2 )
KL2 L2 (1 S0 )
KL2 L3 (1 D2 )
KL3 L3 (3 P0 )
KL3 L3 (3 P2 )
a
b
c
d
Experiment
Theory
a
This work, EC
Ref. [2] EE
−299.9(6)
−165.9(2)
−137.7(17)
−127.3(7)
−116.0(7)
−25.3(4)
7041.8(13)d
16.5(3)
28.7(2)
−296
−168
–
−126
–
−28.5
7034.5(10)d
28.5
–
c
a
Ref. [3] EE
Ref. [4] EE
Ref. [18] SE ICCIb
Ref. [19] SE ICCIb
Ref. [20] T
–
–
–
–
–
(26(1)
7038.2(5)d
15.9(10)
28.7(5)
–
–
–
–
–
−25.8(5)
7037.8d
17(1)
28.5(5)
−300.4
−166.8
−135.2
−126.2
−115.3
−24.2
7031.1d
16.3
27.6
−299.1
−166.4
−134.4
−125.9
−115.3
−23.6
7026.7d
15.7
26.9
−296
−167
−136
−127
−116
−28
7030d
15
28
a
X-ray photon excitation.
Semi-empirical calculations in intermediate coupling with configuration interaction.
299.9(6) means 299.9 ± 0.6.
Absolute energy related to the Fermi level.
of the KL1 L2 (1 P1 ) partner for heavy elements (see Fig. 2). As can
be seen from the Table 2 (bottom row), the influence of the relativistic effects on the KLL Auger spectrum is appreciable even for
copper (Z = 29). The measured KL1 L2 (3 P0 /1 P1 ) transition intensity
ratio agree within 1 with the prediction of the relativistic calculations [21] and differ from the non-relativistic calculations [19]
almost by 3. It should be noted that special attention was devoted
to determination of the KL1 L2 (3 P0 /1 P1 ) transition intensity ratio
from our spectra.
It is known that normalization of KLL spectrum line intensities
to intensity of one line or a group of lines is less correct than normalization to the total intensity of the KLL group for comparison
of experiment with theory for many reasons. Our values of the
KL2,3 L2,3 line intensities presented in the Table 2 were obtained
from a special evaluation of the KL2,3 L2,3 line group not from a
renormalization of data resulting from the evaluation of the full
KLL Auger spectrum. It is seen from the table that our values agree
within 1 with those of the previous measurement [2] with the use
of the X-ray photon excitation and within 2 with the experiment
[3]. Results of the latest measurement [4] substantially deviate from
the other experimental works. Discrepancies between our results
and those of the measurement [4] are from 5 to 21. The best fit
of our data was found for results of the relativistic calculation in
intermediate coupling [21].
Fig. 2. The KL1 L2 (3 P0 /1 P1 ) Auger transition intensity ratio, as a function of the atomic
number Z. results of both the relativistic [21] and non-relativistic [19] calculations
in intermediate coupling (IC) with configuration interaction (CI) are compared with
experimental data ([24] and references therein). Experimental values obtained from
fully or partly resolved KL1 L2 doublets are denoted as “more reliable” and those from
the unresolved KL1 L2 line as “less reliable”. Our value is shown by the full circle.
Table 2
Relative intensities (%) of the KLL Auger transitions in 65 Cu from the EC decay of 65 Zn normalized to the sum intensity of both the KLL Auger group and the KL2,3 L2,3 line group
as well (the latter normalization was applied in experiments with X-ray photon excitation).
Transition
KLi Lj /KLL (%)
KLi Lj /KL2,3 L2,3 (%)
Experiment
1
KL1 L1 ( S0 )
KL1 L2 (1 P1 )
KL1 L2 (3 P0 )
KL1 L3 (3 P1 )
KL1 L3 (3 P2 )
KL2 L2 (1 S0 )
KL2 L3 (1 D2 )
KL3 L3 (3 P0 )
KL3 L3 (3 P2 )
KL1 L2 (3 P0 )/(1 P1 )
a
b
c
d
e
Theory
Experiment
Theory
This work EC
[2] EEa
[21] RICCIb
[19] NRICCIc
[22] Rjjd
This work EC
[2] EEa
[3] EEa
[4] EEa
[21] RICCIb
[19] NRICCIc
[22] Rjjd
6.4(4)
16.3(7)
1.4(5)
4.1(5)
3.1(6)
6.1(5)
53.6(8)
1.8(2)
6.9(2)
0.08(2)e
4.3
13.4
–
5.5
–
7.9
61
7.9
–
–
6.9
18.5
1.2
3.7
3.2
4.6
52.2
1.9
7.5
0.066
5.7
19.2
0.5
2.7
2.7
4.6
54.1
2
8.4
0.028
9
9.7
–
17.2
–
1.7
40
22.2
–
–
–
–
–
–
–
8.7(15)
78.4(58)
2.2(3)
10.7(8)
–
–
–
–
–
–
10.3
79.4
10.3
–
–
–
–
–
12.5(13)
74.5(11)
3.7(8)
10.3(12)
–
–
–
–
–
–
25.8
61.4
5.5
7.4
–
–
–
–
–
–
7.1
78.6
2.9
11.4
–
–
–
–
–
–
6.7
78.3
2.9
12.2
–
–
–
–
–
–
2.7
62.6
34.7
–
–
X-ray photon excitation.
Relativistic calculations in intermediate coupling with configuration interaction.
Non-relativistic calculations in intermediate coupling with configuration interaction.
Relativistic calculations in jj-coupling.
The value obtained from a special evaluation of the KL1 L2,3 line group only.
–
56
A.Kh. Inoyatov et al. / Journal of Electron Spectroscopy and Related Phenomena 171 (2009) 53–56
4. Conclusion
Using high-resolution electron spectroscopy with radioactive
sources, we performed the first experimental investigation of the
KLL Auger spectrum of copper from the EC decay of 65 Zn. Results
obtained showed appreciable influence of the “atomic structure
effect” on absolute energies of the KLL transitions in 65 Cu and
revealed the predicted influence of the relativistic effects on the
KL1 L2 (3 P0 ) transition rate even at Z = 29.
Acknowledgments
The authors are very indebted to Prof. A.F. Novgorodov for his
invaluable support and discussions.
References
[1] P. Weightman, Rep. Prog. Phys. 45 (1982) 753.
[2] E. Sokolowski, C. Nordling, Arkiv för Fysik 14 (1958) 557.
[3] L. Kover, I. Cserny, J. Toth, D. Varga, T. Mukoyama, J. Electron Spectrosc. Relat.
Phenom. 114–116 (2001) 55.
[4] M.R. Went, M. Vos, J. Electron Spectrosc. Relat. Phenom. 148 (2005) 104.
[5] L. Kövér, W. Drube, Z. Berényi, I. Cserny, V.R.R. Medicherla, T. Ishii, H. Ikeno, H.
Adachi, Surf. Sci. 601 (2007) 1085.
[6] J.B. Bellicard, A. Moussa, S.K. Haynes, Nucl. Phys. 3 (1957) 307.
[7] Ch. Briançon, B. Legrand, R.J. Walen, Ts. Vylov, A. Minkova, A. Inoyatov, Nucl.
Instrum. Methods 221 (1984) 547.
[8] G.L. Borchert, W. Scheck, K.P. Wieder, Z. Naturf. A 30 (1975) 274.
[9] C.M. Lederer, V.S. Shirley, Tables of Isotopes, 7th ed., Wiley, New York, 1978
(Appendix 3).
[10] R.B. Fierstone, V.S. Shirley, Tables of Isotopes, 8th ed., Wiley, New York, 1996
(Appendix C-3).
[11] K.D. Sevier, Atom. Data Nucl. Data Tables 24 (1979) 323.
[12] A. Inoyatov, D.V. Filosofov, V.M. Gorozhankin, A. Kovalík, L.L. Perevoshchikov,
Ts. Vylov, J. Electron Spectrosc. Relat. Phenom. 160 (2007) 54.
[13] J.L. Campbell, T. Papp, Atom. Data Nucl. Data Tables 77 (2001) 1.
[14] P.G. Hansen, B. Johnson, G.L. Borchert, O.N.B. Schult, in: B. Crasemann (Ed.),
Atomic Inner-Shell Physics, Plenum Press, New York, 1985, p. 237.
[15] E.Yu. Remeta, A.I. Lendel, Izv. Akad. Nauk Rossii, ser. Fiz. 58 (1994) 143.
[16] C.D. Wagner, in: M.P. Seah, D. Briggs (Eds.), Practical Surface Analysis by Auger
and X-Ray Photoelectron Spectroscopy, 2nd ed., Wiley & Sons, 1990, p. 608.
[17] A.Kh. Inoyatov, D.V. Filosofov, L.L. Perevoshchikov, A. Kovalík, V.M. Gorozhankin,
Ts. Vylov, J. Electron Spectrosc. Relat. Phenom. 168 (2008) 20.
[18] F.P. Larkins, At. Data Nucl. Data Tables 20 (1977) 311.
[19] W.N. Asaad, Proceedings of the International Conference on Inner Shell Ionization and Future Applications, Atlanta, 1972–1973, p. 455, 1.
[20] D.A. Shirley, Phys. Rev. A7 (1973) 1520.
[21] M. Chen, B. Crasemenn, H. Mark, Phys. Rev. A 21 (1980) 442.
[22] C.P. Bhalla, D.R. Ramsdale, Zeitschrift für Physik 239 (1970) 95.
[23] A.V. Lubashevsky, A. Kovalik, D.V. Filosofov, E.A. Yakushev, V.M. Gorozhankin,
V.S. Zhdanov, Proceedings of the 52nd International Conference on Nuclear
Spectroscopy and Nuclear Structure “Nucleus-2002”, Moscow, Russia, June
18–22, 2002, p. 111.
[24] A. Kovalík, A.V. Lubashevsky, A. Inoyatov, et al., J. Electron. Spectrosc. Relat.
Phenom 134 (2004) 67.