Precise measurement of Ag KLL Auger-spectrum

Volume 121, number 8,9

PHYSICS LETTERS A

18 May 1987

PRECISE MEASUREMENT OF Ag KLL AUGER-SPECTRUM H. KAWAKAMI, K. NISIMURA, T. OHSHIMA, S. SHIBATA, Y. SHOJI T. YASUDA2

l,

~•

SUGAI, K. UKAI,

Institutefor Nuclear Study, University of Tokyo, Tanashi, Tokyo 188, Japan

N. MORIKAWA, N. NOGAWA Radioisotope Centre, University of Tokyo, Bunkyo-ku, Tokyo 113, Japan

T. NAGAFUCHI, F. NAITO, T. SUZUKI, H. TAKETANI Department ofApplied Physics, Tokyo Institute of Technology, Meguro-ku, Tokyo 152, Japan

M. IWAHASHI Department of Chemistry, Faculty of Hygienic Sciences, Kitasato University, Sagamihara 228, Japan

K. HISATAKE Faculty of GeneralEducation, Jissen Women’s University, Hino, Tokyo 191, Japan

M. FUJIOKA Cyclotron and Radioisotope Center, Tohoku University, Sendai 980, Japan

Y. FUKUSHIMA, T. MATSUDA and T. TANIGUCHI National Laboratoryfor High Energy Physics, KEK, Oho-machi, Tsukuba-gun, Ibaragi 305, Japan Received 14 January 1987; revised manuscript received 24 March 1987; accepted for publication 24 March 1987

The Ag KLLAuger spectrum has been measured with an energy resolution of 8 eV. The energies and the intensities of all nine lines are precisely determined with 1—2 orders of magnitude better accuracies than those in the previous experiment. The data obtained are found to be in good agreementwith the theoretical calculations.

From extensive studies of KLL Auger spectra for many different atoms it is found that the line intensities can be well explained by the relativistic calculations in intermediate coupling with configuration interaction performed by Asaad and Petrini [1] and by Chen et al. [2], and that the energies can be fairly well reproduced by a semi-empirical calculation by Larkins [31. Precise experimental information,

2

Present address: National Laboratory for High Energy Physics, KEK, Oho-machi, Tsukuba-gun, Ibaragi 305, Japan. Present address: Northeastern University, Boston, MA 02115, USA.

414

however, is further necessary to have an unambiguous insight on the mechanism of the KLL Auger transition. Especially, the experimental data on lowintensity lines, such as KL 3P 3P~), 1 L2 ( scarce 0), KL1L3 KL 1So) and KL 3P~),are and ( have 2L2uncertainties ( 3L3to ( poor energy resolution of large due the spectrometer system. This paper reports a measurement of the KLL Auger spectrum in ‘°9Agwith an energy resolution of 8 eV; all the nine lines were clearly identified so that their intensities and energies were obtained precisely and reliably. The measurement was performed with the double 0375-96011871$ 03.50 © Elsevier Science Publishers B.V. (North-Holland Physics Publishing Division)

Volume 121, number 8,9

PHYSICS LETTERS A

focusing iron-free fl-ray spectrometer at the Institute for Nuclear Study (NS), University Tokyo. As 9Cdwasofprepared in a source of Auger electrons, ‘° form of arachidic (C 20H4002) Cd-salt with a thickness of two molecular layers (.-~50 A) by means of 69Yb source, the Langmuir—Blodgett method [4]. A’ evaporation which was prepared by a vacuum method [5], was used to calibratethe absolute energy of the spectrometer using the M conversion lines of the 20.744 keV transition in ‘69Tm. The ‘°9Cdand I69yi~ sources had activities 120 and 40 j.tCi, respeclively, on the2. conductive These two sources plates with werethe set size in the of 25 x 100 of mm position the Spectrometer interchangeably. The firays analyzed by the spectrometer were detected by a 40-cell proportional counter placed on the focal plane. A focusing electric potential was applied over the source plate, and the spectrum was scanned electrostatically by changing the acceleration voltage (Vacc)field also strength applied constant. on the source, keepingofthe netic The details themagsetup were reported elsewhere [6]. The instrumental energy resolution in this experiment was 8 eV in the energy region of the Auger lines. Auger spectra were measured by a scanning step of 2.4 eV with 18 steps in total. Fig. 1 shows an examplc of the observed Auger spectra. The energy dispersion of an individual detector cell was measured by shifting the Auger spectrum with Vacc. The M-conversion lines of ‘69Tm were measured in the same way as the Ag KLL Auger lines and is shown in fig. 2. The conversion spectrum as well as the Auger spectrum was fitted to evaluate their intensities and energies with a standard function having four free parameters (an amplitude normalization constant, a peak position and two horizontal scaling factors for the function at higher and lower energies than the peak) and a flat background cornponent. The form of the standard function was constructed to reproduce the M 1 spectrum by using several gaussian, lorentzian and Landau functions. Solid and dashed curves in fig. 1 are the result of the fit. The energies of the Auger lines relative to that ofthe KL2L3 line and the relative line intensities are listed in table the 1 measured energy dispersion of this To examine

spectrometer, the energy differences among the M1, M2 and M3 lines were compared;

M2

18 May 1987

M, = 217.1 ±0.5 eV, M3 M, = 423.0 ±1.6 eV and M3 = 205.9 1.7 this measurement agree wellM2 with 217.0± ± 1.0eV eV,in422.3 ±1.3 eV and —

—

—

205.3 ±1.3 eV, respectively, from ref. [7]. To check thethe systematic uncertainty due toand a possible drift of system, the ‘°9AgAuger the ‘69Tm M lines were measured simultaneously by setting both sources in the source position of the spectrometer. No appreciable difference from the result reported above was observed. The energy difference between the KL 2L3 and M, lines±0.3 74.7 was±1.0obtained eV, whereasthe first E(KL2L3) error was —E(M1) the sta= tistical one and the second error was the systematical one arosen from an ambiguity in the relative alingment ofthe two source positions. The absolute energy of the Auger lines was obtained as listed in table 1 by the use of this energy difference together with E(M 1) = 18437.0 ±0.7 used eVtI. in this experiment, the 9Cdsource In the ‘° is covalently bonded with the oxygen ‘°9Cdatom atoms of the arachidic acid so that the influence of this chemical state of the atom on the Auger transition has to be considered in principle. However, since the K and L atomic electrons are deeply screened by many outer shell electrons, we believe that the energy shift due to the chemical effect on the Auger lines is at most a few eV. Moreover, it is expected that the chemical effect might be nearly the same for all the KLL Augerlines. Therefore its effect on the relative energies and on the relative intensities should be very small and hence was not taken into account in the present analysis. The energies of the Auger lines calculated semiempirically by Larkins [3] are in good agreement with the present measurement, except that an average difference of 3 eV is observed. This difference of 3 eV may be attributed to the chemical effect as mentioned above. It is then better to compare the relative energies as listed also in table 1. A better agreement can be seen except 3P that there are large discrepancies on the KL1L2( 0) and K.L2L2 ( ‘St,) lines by 5.2 and 5.6 eV, respectively. Similar discrepan69Ybby Kçssler et al. [8], E(M) 18437.0 togetherwith theM±0.7 eV is obtained from the precise measurement of the y.ray energies from ‘ 1 binding energy of2306.8 ±0.7 eV [7].New data of the y.ray energies from I69’~j1~by Adam et al. [9] are in very good agreement with thoseof Kessler et al.

415

Volume 121, number 8,9

PHYSICS LETTERS A

18 May 1987 3002

~,L~P 1)~

0

11950

18000

~

18060

~

~

~

19100

10150

0 ~ 18160

10250

10300

‘~‘

0 ~ 1857018850

18380

61CTR~4EJ.ERGY Coy)

D..ECTRC4’4 Et’ERGY (eV)

~

10170

18100

ELEOTRCt’l Er’BRGY Coy)

10000

1 P2> 8000

Kl_2l_3(

_J

I~

z <

6000

~4000

8

17438

17600

17800

18000

18200

18400

18600

18800

19000

ELECTRON ENERGY (eV) Fig. 1. KLL Auger spectrum in ‘°9Agfrom the decay of °9Cd The experimental data measured in steps of2.4 eV are shown by dots. The dashed curves show the contributions of individual lines and ofthe background and the solid one isthe total spectrum fitted. Upperthree figures from the left to the right are the spectra of KL 1L2, KL~L3and KL2L2 and KL3L3 lines, enlarged to show the details of their structures, where the fine solid curve represents the tail components of higher KLL Auger lines.

416

Volume 121, number 8,9

PHYSICS LETTERS A

18 May 1987

4000

M

1 (18437 eV)

3000 -J LU

z z ~

2000

uJ~

9

0~ Cr) I—

~.

z

‘S

> ID

O

01000 5:,

==

0 17438

=

\~~___

,_~

—-

17600

17800

18000

18400

18200

—

,-

18600

18800

19000

ENERGY 69Tmfrom the decay ofELECTRON ‘69Yb The experimental data(eV) measured in steps of 2.4 eV are shown by dots. Fig. dashed The 2. M conversion curves show spectrum the contributions in ‘ of individual lines and ofthe background, and the solid one is the total spectrum fitted.

Table I Energy and intensity of KLLAuger lines in Ag. The values within parentheses are errors to the final decimal position. The error of the absolute energy is the square root ofthe quadratic sum ofthe statistical and the systematic errors; see text. Line

Relative energy (eV)

Absolute energy (eV)

this work

ref.

this work

ref. [11]

[3] ~

Relative intensity KLLJ~KLL b)

ref. [3]

a)

this work

ref. [11 J’~

ref. [2]

KL,L,

‘S~

—717.8(6)

—718.1

17793.9(14)

17.70(6)

17789.6

0.103(3)

1.0(2)

0.094

KLL

‘P 3P 3P,10

—437.2 —409.9(10) —273.5 (8) (4)

—436.5 —404.7 —273.1

18074.5(15) 18101.8 18238.2 (16) (13)

1798 66 18

18071.2 18103.0 18234.6

0.114(3) 0.027(1) 0.102 (3)

13 1 3 22

0.125 0.029 0.105

—234.1 (6)

—232.1

18277.6 (14)

.14(

18275.6

0.036(1)

—180.8 (2)

—175.2

18330.9(13)

18.25(6)

18332.5

0.028(1)

0.5(2)

0.028

18511.7(13)

18.42(6)

18507.7

0.413(7)

3.2(4)

0.412

18665.5 (15) 18696.5 (13)

18.61 (6)

18662.4 18689.5

0.035 (2) 0.143 (4)

1.8 (2)

0.031 0.140

2

KL L

~P 2

KL,L2

‘S0

KL2L3

‘D, 3P 3P 0 2

KL L

0.0 153.8 (8) 184.8 (4)

0.0 154.7 181.8

0.037

Values calculated with configuration interaction. Energy in keV. ~ Intensity relative to that ofKL,L,. a)

b)

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Volume 121, number 8,9

PHYSICS LETTERS A

cies were observed by Babenkov et al. [10] for the 3P KLIL, ( ‘Se) and KLLLI ( 0) lines in palladium. They may be attributed to an inaccuracy of the electron binding energies for the L subshells used by Larkins as was pointed out by Babenkov et al. The intensities of the Auger lines obtained in this experiment are also compared in table 1 with the result calculated by Chen et al. [2]. A very good agreement is observed except for the KL,L1 (‘S0) and KL1 L2(’ P,) lines. The data on the individual intensities in the doublet KL,L2 line are scarce, and indicate a large disagreement with the calculation, especially at 3Phigh Z [2]. The obtained intensity ratio of KL,L2( 0)/KL,L2(’Pl) of the Ag KLL Auger lines, however, is in a remarkable agreement with the calculated value of Chen et al. perIn conclusion an accurate measurement9Cd of was the KLL Auger spectrum of Ag in the decay of ‘° formed by the use of a high-resolution, high-efficiency iron-free fl-ray spectrometer system; all the nine Auger lines were clearly resolved. The resultant accuracy for the energies and intensities improved those of the previous data [11] by 1—2 orders of magnitude. The result indicates a good agreement with the calculations by Larkins and by Chen et al. But some discrepancies for low-intensity lines suggest a necessity of finer theoretical investigation on the mechanism of the KLL Auger transition. We would like to acknowledge Professors S. Kato, T. Nomura, H. Okuno, S. Ozaki and H. Sugawara for their support and useful advices for this experiment.

418

18 May 1987

We would like to thank the staffs of Machine Shop, Radiation Control Center and Computer Center at INS for their kind hospitalities, and also express our special thanks to Radioisotope Centre at the University ofTokyo for their kind support for the source preparation. This experiment is supported in part by a Grant-in-Aid for Scientific Research of the Japanese Ministry of Education, Science and Culture, Yamada Science Foundation, National Laboratory for High Energy Physics (KEK) and INS.

References [1] W.N. Assadand D. Petrini, Proc. R. Soc. A 350 (1976) 381. [2] [4] [3]

M.H. Chen, B. Craseman and H. Mark, Phys. Rev. A 21 (1980) 442. J. Am. Chem. Soc. 56 (1935) 1007; K.B. Blodgett, F.P. Larkins, At. Data Nucl. Data Tables 20 (1977) 311. K.B. Blodgett and I. Langmuir, Phys. Rev. 51 (1939) 964. [5] H. Kawakami et al., submitted to Nucl. Instrum. Methods. [6] 0. Facker and J. Tran Thanh Van, eds., Proc. VIth Moriond Workshop, ‘86 Massive neutrinos in astrophysics and in particle physics, Jan. 25—Feb. 1, 1986, Tignes, France (Editions Frontieres, Dreux). [7] J.A. Bearden and A.F. Burr, CRC Handbook of chemistry and physics, 66th Ed., ed. R.C. Weast (CRC Press, Boca Raton, 1985). [8] E.G. Kessleret al., Nucl. Instrum. Methods 160 (1979) 435. [9] J. Adam et al., Preprint JINR, USSR, P6-86-315. [10]M.I. Babenkovetal.,J. Phys. B 15 (1982) 35. [11] F.A. Johnson and J.S. Foster, Can. J. Phys. 31(1953) 469.