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The KLL Auger spectrum of manganese
J
3*c
I
Nuclear
Physics
A92 (1967)
Not to be reproduced
by photoprint
THE KLL AUGER
of Physics
Received
E
RADIOACTIVITY
or microfilm
and
and Astronomy,
Abstract: The KLL Auger spectrum decay of 55Fe. The measured The relative intensities of the with the theoretical values of line intensities the agreement
@ North-Holland without
SPECTRUM
Y. Y. LUI Department
139-144;
written
Publishing
Co., Amsterdam
permission
from the publisher
OF MANGANESE
R. G. ALBRIDGE Vanderbilt 26 August
University,
Nashville,
Tennessee
f
1966
of manganese (Z = 25) was measured from the electron capture energies do not agree with values calculated semi-theoretically. groups of lines KL,L,, 3 and KL,, 3Lz, a agree within error limits Asaad and of Mehlhorn and Asaad; however for the individual is not good.
55Fe [from 54Fe(n, ATOMIC PHYSICS
y)l; measured Mn measured
I K-A”~~~. Enriched EK.A”~~~, IK_A”~~~.
EK-A~~~~,
target.
1. Introduction In previous publications ‘*‘) f rom this laboratory we have reported on the K-Auger spectra of elements in the region of Z = 26 to Z = 33 in order to help define clearly the differences which exist between experimental and theoretical energies and intensities. The present study of the K-Auger spectrum of manganese (Z = 25) is a continuation of this work. For a recent summary of experimental and theoretical K-Auger studies see ref. 2). 2. Experimental
procedures
The Vanderbilt iron-free, double-focussing spectrometer was used. The spectrometer was originally described by Baird et al. 3), and its application to low-energy Auger studies has been discussed in refs. ‘g2). In the present work, as in the previous low-energy studies, batteries provided the spectrometer current. The Geiger counter with post-acceleration, originally described by Mehlhorn and Albridge 4), has also been discussed in refs. ’ 22). In the work reported here accelerating potentials of z 5 keV were used in conjunction with zapon counter windows of z 50 of z 98 “/d Pgicm’ (cut-off energy of % 3 keV) to obtain window transmissions throughout the K-Auger spectrum. The spectrometer source material was radioactive 55Fe which produces manganese K vacancies by electron capture. The activity was electroplated onto 25 pm thick platinum foils from z 1 ml of a solution made by mixing 33 ml of a saturated (NH,), C20, with 0.4 ml of 3 M H,SO,. The plating solution has been described earlier by Maletskos and Irvine 5). t Work supported
by a grant
from
the National 139
Science
Foundation.
140
Y.
A small amount
of radioactive
Y.
LUI
“Co
AND
R.
G.
ALBRIDGE
was mixed with the 55Fe so that the 7.3 keV
conversion line in the 57Co decay could be used to determine the approximate shape of the low-energy lines. This procedure, which is reported in our previous papers refered to above, is necessary because the instrumental resolution is not sufficient to separate essential
the Auger lines and a graphical separation must be accomplished. It is to determine the shape of the Auger lines before the analysis is undertaken
and the 7.3 keV conversion line provides an initial approximation of this shape. Since the line shapes are affected by source mass, it is best if the 55Fe and 57Co activities are electrodeposited simultaneously so that the source is homogeneous. Unmixed sources of 58Co, 6oCo (they are cheaper than 57Co) and 55Fe were plated at different pH values to determine the optimum pH for the mixed-source deposition. A pH of 5 was chosen, but during the plating the pH was varied back and forth on both sides of this value so that the deposition of the cobalt and iron were alternately favoured. Thus, if the sources were not uniform, they at least would probably have alternate layers of cobalt and iron activity. Several sources were produced and studied and the data presented here are those obtained from one of the best sources. This source was heated in a Bunsen flame to a faint red to remove extraneous mass. Attempts to produce sources by vacuum vaporization from an electrically heated tungsten boat were unsuccessful. 3. Results and discussion The manganese K-Auger spectrum is shown in fig. 1. The background, consisting of natural background plus the low-energy tail of the iron K-Auger spectrum which lies at slightly higher energy, has been subtracted. The shape of the tail from the iron spectrum was determined by analysing the iron spectrum in the same manner as was the manganese spectrum (described below). We estimate that the uncertainty introduced by the background could cause an error as large as 25 % in the measured intensities of the weakest manganese Auger lines. The dotted lines in fig. 1 are the results of the graphical analysis. The basic line shape used for this analysis was that of the 7.3 keV conversion line in the 57Co decay but this shape was altered, in a manner described previously ‘), to account for the differences in electron scattering and instrumental line width at different electron energies. The contribution from natural line widths is negligible compared to that from scattering and instrumental effects. Many different attempts to resolve the spectrum were made before the results shown in fig. 1 were obtained. These results are consistent in that the sum of the individual lines is the same as the experimental spectrum except in the region of the tail of the KL,L, line. To illustrate this one discrepancy we show as a dotted line in fig. 1 the standard line in the position of the KL,L, Auger line. It is seen that the tail of the experimental line is too small. This discrepancy could be eliminated by altering slightly the background and/or tails of the higher-energy lines. Although such a change would increase by a large fraction the area of the KL,L, line, it would have
KIJ.
AUGER
SPECTRUM
141
Y.
142
Y.
L”I
AND
R.
G.
ALBRIDGE
negligible effect on the areas of the other lines. Furthermore, since the line shapes are the same, their areas are proportional to their heights. Thus, rather than attempting to obtain a proper fit for the tail of the KL,L, line, we have chosen to take peak heights rather than areas as a measure of the transition intensities. We estimate that the uncertainties in the intensities of the individual lines obtained % for the KL,L,, KLL,L,, and KL,L, lines and in this way could be as large as “zi _ from + 25 % to f 50 % for the others. However, since one of the largest contributions to these uncertainties is introduced when the close-lying lines are graphically resolved, the relative intensities of the line groups KL,L,,3 and KL.,,,L,, 3 are measured to a higher precision (standard deviation of about & 25 %). The spectrometer was energy-calibrated by means of the 7.3 keV conversion line in the decay of 57Co. The energy of this line was measured ‘) to be 7.278kO.006 keV but was later 2, revised to a value of 7.300f0.006 keV. The standard deviations of the measured energies of the present work are z +0.2 %. The energies are given relative to the Fermi level since the work function of the aluminium spectrometer tank (assumed to be 4 eV) has been added to the measured kinetic energies. TABLE
Experimental
and theoretical
Transition
Energy exp.
KLL
energies
and relative
Relative cal. “) 4948 5050 5088
8.6 17 13
KL,L, KL,L, KL,L,
5191&g 5205k6 5225h8
5164 5186 5206
11 82 7.4
have been normalized
KLL Auger
8.6
1 3o 100
to 100 for the KL,,,L,,,
transitions
intensities
theor.
exp.
4958*8 5065&7 5102&7
intensities
of the manganese
(eV)
KL,L, KL,L,
The relative
1
intensities
6.9 28 9 1 8.6 79 I 12
theor.
“) 6.9
“)
8.2
37
37
100
100
group.
“) Semi-theoretical values of Axelson et al. IS) b) Deduced by linear interpolation of the values in ref. s). “) Deduced by linear interpolation of the values in ref. “).
The results are presented in table 1. Also shown for comparison are calculated energies and theoretical intensities. The calculated energies were obtained by the Uppsala group using the semi-theoretical method of Hiirnfeldt, Fahlman and Nordling 6, but using new binding energies ‘). The agreement between the calculated and experimental energies is not good +. The relative intensities have been normalized to a value of 100 for the KL,, 3 L,, 3 group. The theoretical values were deduced by linear interpolation of the values of Asaad ‘) and of Mehlhorn and Asaad ‘). Only the values calculated by these authors with the use of the transition amplitudes of Rubenstein and Snyder lo) are shown t See note added
in proof
KLL AUGER SPECTRUM
here because
those calculated
with other transition
143
amplitudes
either
do not span
the region of Z = 25 or differ so markedly from the experimental values that a comparison is meaningless. The theoretical intensities published by Asaad and Burhop ’ ‘) also differ greatly from the experimental values presented here. To obtain the theoretical values shown in table 1 it was necessary
to interpolate
between
values at Z = 18 and
Z = 36. We estimate that this interpolation could introduce uncertainties of the order of 15 ‘A. The agreement between the experimental and theoretical values is well within the limits of errors for the groups of lines in one configuration. When the intensities of the individual lines are compared the agreement is not as good, in some case being outside the limits of error. Mehlhorn and Asaad 9, did not publish individual line intensities, thus only their group intensities can be compared.
TABLE 2 Comparison
of relative
intensities
Transition
of iron KLL Experimental this work
KL,L, KL,L, KL,L, KLJ-2 KL,L, KLJ+
The
earlier
work
was performed
1.9 19 11 i 11 II I 12
at higher
lines to those relative
‘)
work
I)
6.4 6.4 23 8.9 I 32 8.4 83 1 100 8.4
3o 100
resolution
work
intensities
previous
1.9
of previous
and
is considered
to be more
accurate.
As mentioned above, the KLL Auger spectrum of iron was also analysed in this work. A comparison of the intensity results of this analysis with the previous results of Mehlhorn and Albridge ‘) obtained at higher resolution and, hence, higher accuracy is shown in table 2. The agreement is good for the three main groupings and is within + 25 % for the individual lines except for the weak KL,L2 and KL,L, transitions. This agreement is evidence that the error limits assigned to the manganese Auger intensity data in table 1 are reliable. The work here points up the need for more detailed theoretical and experimental intensity data in this region of Z. Note added in proof Working in cooperation with K. Siegbahn et al. we have used the Uppsala 30 cm iron-free spectrometer to remeasure the KL,Lr, KL,L,, KL2L3, and KL,L, energies and obtain values of 4961, 5068, 5204 and 5227 eV with error limits of about + 2 eV. A work function correction of 4 eV has been added. Chemical shift effects of several eV were observed.
144
Y.
Y.
LUI
AND
R.
G.
ALBRIDGE
References I) W. Mehlhorn
and R. G. Albridge, Z. Phys. 175 (1963) 506 R. E. Johnston, J. H. Douglas and R. G. Albridge, Nuclear Physics A91 (1967) Baird, Nall, Haynes and Hamilton, Nucl. Instr. 16 (1962) 275 W. Mehlhorn and R. G. Albridge, Nucl. Instr. 26 (1964) 37 C. J. Maletskos and J. W. Irvine, Jr., Nucleonics 14 (1956) 84 0. Hornfeldt, A. Fahlman and C. Nordling, Ark. Fys. 23 (1962) 155 K. Siegbahn et al., Nova Acta Regiae Sot. Sci. Upsaliensis, to be published W. N. Asaad, Nuclear Physics 66 (1965) 494 W. Mehlhorn and W. N. Asaad, Z. Phys. 191 (1966) 231 R. A. Rubenstein and J. N. Snyder, Phys. Rev. 97 (1953) 1653; R. A. Rubenstein, Ph. D. thesis, University of Illinois (1955) 11) W. N. Asaad and E. H. S. Burhop, Proc. Phys. Sot. 71 (1958) 369 12) Axelson ei al., private communication to R. G. Albridge (July 1966) 2) 3) 4) 5) 6) 7) 8) 9) 10)
505
3*c
I
Nuclear
Physics
A92 (1967)
Not to be reproduced
by photoprint
THE KLL AUGER
of Physics
Received
E
RADIOACTIVITY
or microfilm
and
and Astronomy,
Abstract: The KLL Auger spectrum decay of 55Fe. The measured The relative intensities of the with the theoretical values of line intensities the agreement
@ North-Holland without
SPECTRUM
Y. Y. LUI Department
139-144;
written
Publishing
Co., Amsterdam
permission
from the publisher
OF MANGANESE
R. G. ALBRIDGE Vanderbilt 26 August
University,
Nashville,
Tennessee
f
1966
of manganese (Z = 25) was measured from the electron capture energies do not agree with values calculated semi-theoretically. groups of lines KL,L,, 3 and KL,, 3Lz, a agree within error limits Asaad and of Mehlhorn and Asaad; however for the individual is not good.
55Fe [from 54Fe(n, ATOMIC PHYSICS
y)l; measured Mn measured
I K-A”~~~. Enriched EK.A”~~~, IK_A”~~~.
EK-A~~~~,
target.
1. Introduction In previous publications ‘*‘) f rom this laboratory we have reported on the K-Auger spectra of elements in the region of Z = 26 to Z = 33 in order to help define clearly the differences which exist between experimental and theoretical energies and intensities. The present study of the K-Auger spectrum of manganese (Z = 25) is a continuation of this work. For a recent summary of experimental and theoretical K-Auger studies see ref. 2). 2. Experimental
procedures
The Vanderbilt iron-free, double-focussing spectrometer was used. The spectrometer was originally described by Baird et al. 3), and its application to low-energy Auger studies has been discussed in refs. ‘g2). In the present work, as in the previous low-energy studies, batteries provided the spectrometer current. The Geiger counter with post-acceleration, originally described by Mehlhorn and Albridge 4), has also been discussed in refs. ’ 22). In the work reported here accelerating potentials of z 5 keV were used in conjunction with zapon counter windows of z 50 of z 98 “/d Pgicm’ (cut-off energy of % 3 keV) to obtain window transmissions throughout the K-Auger spectrum. The spectrometer source material was radioactive 55Fe which produces manganese K vacancies by electron capture. The activity was electroplated onto 25 pm thick platinum foils from z 1 ml of a solution made by mixing 33 ml of a saturated (NH,), C20, with 0.4 ml of 3 M H,SO,. The plating solution has been described earlier by Maletskos and Irvine 5). t Work supported
by a grant
from
the National 139
Science
Foundation.
140
Y.
A small amount
of radioactive
Y.
LUI
“Co
AND
R.
G.
ALBRIDGE
was mixed with the 55Fe so that the 7.3 keV
conversion line in the 57Co decay could be used to determine the approximate shape of the low-energy lines. This procedure, which is reported in our previous papers refered to above, is necessary because the instrumental resolution is not sufficient to separate essential
the Auger lines and a graphical separation must be accomplished. It is to determine the shape of the Auger lines before the analysis is undertaken
and the 7.3 keV conversion line provides an initial approximation of this shape. Since the line shapes are affected by source mass, it is best if the 55Fe and 57Co activities are electrodeposited simultaneously so that the source is homogeneous. Unmixed sources of 58Co, 6oCo (they are cheaper than 57Co) and 55Fe were plated at different pH values to determine the optimum pH for the mixed-source deposition. A pH of 5 was chosen, but during the plating the pH was varied back and forth on both sides of this value so that the deposition of the cobalt and iron were alternately favoured. Thus, if the sources were not uniform, they at least would probably have alternate layers of cobalt and iron activity. Several sources were produced and studied and the data presented here are those obtained from one of the best sources. This source was heated in a Bunsen flame to a faint red to remove extraneous mass. Attempts to produce sources by vacuum vaporization from an electrically heated tungsten boat were unsuccessful. 3. Results and discussion The manganese K-Auger spectrum is shown in fig. 1. The background, consisting of natural background plus the low-energy tail of the iron K-Auger spectrum which lies at slightly higher energy, has been subtracted. The shape of the tail from the iron spectrum was determined by analysing the iron spectrum in the same manner as was the manganese spectrum (described below). We estimate that the uncertainty introduced by the background could cause an error as large as 25 % in the measured intensities of the weakest manganese Auger lines. The dotted lines in fig. 1 are the results of the graphical analysis. The basic line shape used for this analysis was that of the 7.3 keV conversion line in the 57Co decay but this shape was altered, in a manner described previously ‘), to account for the differences in electron scattering and instrumental line width at different electron energies. The contribution from natural line widths is negligible compared to that from scattering and instrumental effects. Many different attempts to resolve the spectrum were made before the results shown in fig. 1 were obtained. These results are consistent in that the sum of the individual lines is the same as the experimental spectrum except in the region of the tail of the KL,L, line. To illustrate this one discrepancy we show as a dotted line in fig. 1 the standard line in the position of the KL,L, Auger line. It is seen that the tail of the experimental line is too small. This discrepancy could be eliminated by altering slightly the background and/or tails of the higher-energy lines. Although such a change would increase by a large fraction the area of the KL,L, line, it would have
KIJ.
AUGER
SPECTRUM
141
Y.
142
Y.
L”I
AND
R.
G.
ALBRIDGE
negligible effect on the areas of the other lines. Furthermore, since the line shapes are the same, their areas are proportional to their heights. Thus, rather than attempting to obtain a proper fit for the tail of the KL,L, line, we have chosen to take peak heights rather than areas as a measure of the transition intensities. We estimate that the uncertainties in the intensities of the individual lines obtained % for the KL,L,, KLL,L,, and KL,L, lines and in this way could be as large as “zi _ from + 25 % to f 50 % for the others. However, since one of the largest contributions to these uncertainties is introduced when the close-lying lines are graphically resolved, the relative intensities of the line groups KL,L,,3 and KL.,,,L,, 3 are measured to a higher precision (standard deviation of about & 25 %). The spectrometer was energy-calibrated by means of the 7.3 keV conversion line in the decay of 57Co. The energy of this line was measured ‘) to be 7.278kO.006 keV but was later 2, revised to a value of 7.300f0.006 keV. The standard deviations of the measured energies of the present work are z +0.2 %. The energies are given relative to the Fermi level since the work function of the aluminium spectrometer tank (assumed to be 4 eV) has been added to the measured kinetic energies. TABLE
Experimental
and theoretical
Transition
Energy exp.
KLL
energies
and relative
Relative cal. “) 4948 5050 5088
8.6 17 13
KL,L, KL,L, KL,L,
5191&g 5205k6 5225h8
5164 5186 5206
11 82 7.4
have been normalized
KLL Auger
8.6
1 3o 100
to 100 for the KL,,,L,,,
transitions
intensities
theor.
exp.
4958*8 5065&7 5102&7
intensities
of the manganese
(eV)
KL,L, KL,L,
The relative
1
intensities
6.9 28 9 1 8.6 79 I 12
theor.
“) 6.9
“)
8.2
37
37
100
100
group.
“) Semi-theoretical values of Axelson et al. IS) b) Deduced by linear interpolation of the values in ref. s). “) Deduced by linear interpolation of the values in ref. “).
The results are presented in table 1. Also shown for comparison are calculated energies and theoretical intensities. The calculated energies were obtained by the Uppsala group using the semi-theoretical method of Hiirnfeldt, Fahlman and Nordling 6, but using new binding energies ‘). The agreement between the calculated and experimental energies is not good +. The relative intensities have been normalized to a value of 100 for the KL,, 3 L,, 3 group. The theoretical values were deduced by linear interpolation of the values of Asaad ‘) and of Mehlhorn and Asaad ‘). Only the values calculated by these authors with the use of the transition amplitudes of Rubenstein and Snyder lo) are shown t See note added
in proof
KLL AUGER SPECTRUM
here because
those calculated
with other transition
143
amplitudes
either
do not span
the region of Z = 25 or differ so markedly from the experimental values that a comparison is meaningless. The theoretical intensities published by Asaad and Burhop ’ ‘) also differ greatly from the experimental values presented here. To obtain the theoretical values shown in table 1 it was necessary
to interpolate
between
values at Z = 18 and
Z = 36. We estimate that this interpolation could introduce uncertainties of the order of 15 ‘A. The agreement between the experimental and theoretical values is well within the limits of errors for the groups of lines in one configuration. When the intensities of the individual lines are compared the agreement is not as good, in some case being outside the limits of error. Mehlhorn and Asaad 9, did not publish individual line intensities, thus only their group intensities can be compared.
TABLE 2 Comparison
of relative
intensities
Transition
of iron KLL Experimental this work
KL,L, KL,L, KL,L, KLJ-2 KL,L, KLJ+
The
earlier
work
was performed
1.9 19 11 i 11 II I 12
at higher
lines to those relative
‘)
work
I)
6.4 6.4 23 8.9 I 32 8.4 83 1 100 8.4
3o 100
resolution
work
intensities
previous
1.9
of previous
and
is considered
to be more
accurate.
As mentioned above, the KLL Auger spectrum of iron was also analysed in this work. A comparison of the intensity results of this analysis with the previous results of Mehlhorn and Albridge ‘) obtained at higher resolution and, hence, higher accuracy is shown in table 2. The agreement is good for the three main groupings and is within + 25 % for the individual lines except for the weak KL,L2 and KL,L, transitions. This agreement is evidence that the error limits assigned to the manganese Auger intensity data in table 1 are reliable. The work here points up the need for more detailed theoretical and experimental intensity data in this region of Z. Note added in proof Working in cooperation with K. Siegbahn et al. we have used the Uppsala 30 cm iron-free spectrometer to remeasure the KL,Lr, KL,L,, KL2L3, and KL,L, energies and obtain values of 4961, 5068, 5204 and 5227 eV with error limits of about + 2 eV. A work function correction of 4 eV has been added. Chemical shift effects of several eV were observed.
144
Y.
Y.
LUI
AND
R.
G.
ALBRIDGE
References I) W. Mehlhorn
and R. G. Albridge, Z. Phys. 175 (1963) 506 R. E. Johnston, J. H. Douglas and R. G. Albridge, Nuclear Physics A91 (1967) Baird, Nall, Haynes and Hamilton, Nucl. Instr. 16 (1962) 275 W. Mehlhorn and R. G. Albridge, Nucl. Instr. 26 (1964) 37 C. J. Maletskos and J. W. Irvine, Jr., Nucleonics 14 (1956) 84 0. Hornfeldt, A. Fahlman and C. Nordling, Ark. Fys. 23 (1962) 155 K. Siegbahn et al., Nova Acta Regiae Sot. Sci. Upsaliensis, to be published W. N. Asaad, Nuclear Physics 66 (1965) 494 W. Mehlhorn and W. N. Asaad, Z. Phys. 191 (1966) 231 R. A. Rubenstein and J. N. Snyder, Phys. Rev. 97 (1953) 1653; R. A. Rubenstein, Ph. D. thesis, University of Illinois (1955) 11) W. N. Asaad and E. H. S. Burhop, Proc. Phys. Sot. 71 (1958) 369 12) Axelson ei al., private communication to R. G. Albridge (July 1966) 2) 3) 4) 5) 6) 7) 8) 9) 10)
505