Journal of Radioanalytical and Nuclear Chemistry, Articles, VoL 147, No. 2 {1991) 371-375

DETERMINATION OF PERTURBED ANGULAR CORRELATION PARAMETERS IN SOME COMPOUNDS

OF l 3 3 Ba USING THE SUM PEAK METHOD

KULWANT SINGH, K. SINGH

Department of Physics, Garu Nanak Dev University, Amritsar-143005 (India)

(Received April 23, 1990)

The sum peak intensity relative to its single peak was determined in various compounds of ~ 33 Ba by the technique of gamma-ramma-ray sum peaks observed in a single HPGe detector. The change in intensity ratio was used to determine the time integral perturbed angular c6rrelation coefficients for BaC12, Ba(NO3)2, BaSO4, Ba-EDTA, Ba-MES and Ba-BSA compounds.

Introduction

The after-effects of electron capture decay of 1 a 3 Ba and the effect of the long

half-life of the 81 keV level, on the directional correlation parameter of the cascade,

involving this level as an intermediate level, are still controversial. SHARMA et al. 1

studied the perturbat ion of 356 -81 keV directional correlation, in 133Cs ' using

various compounds of barium. No attehuation was found for the Ba(NO3)2 com-

pound. SINGH et al. 2 studied the same cascade to see the at tenuation effect of

81 keV level by changing the concentration of ethylenediaminetetraacetic acid

(EDTA). The attenuation in Akk coefficients was found and interpretat ion was

given as an after-effect in the electron capture decay of 133 Ba. But no effort was

made to understand the nature of interactions. SIDHU and SAHOTA 3 performed the

276-161 keV cascade in BaCt2 and BaSO4 in order to see the contribution to

at tenuation coefficient (G22) by the after effects of preceding K-capture and K-con-

version. Since the 161 keV level is short-lived, any correlation of the at tenuation

function would only be due to the after-effects. But no effect was observed by

them. IWASHITA 4 studied the perturbat ion of 4 8 6 - 1 3 3 keV cascade from 131Ba

in Ba(NO3)2 and thus the higher interaction frequency was at tr ibuted to the after-

effects which is in contradiction with the findings of SHARMA et al. 1 All these

measurements were performed using conventional coincidence technique.

In the present work, the sum peak method proposed by KUDO et al. s has been

applied for the determination of perturbed angular correlation parameters G22-

Elsevier Sequoia S. A., Lausanne Akad~miai Kiad6, Budapest

KULWANT SINGH, K. SINGH: DETERMINATION OF PERTURBED ANGULAR

This method has good applicability to the sources with fInite dimensions. Moreover,

it is relatively simple and requires only a small quantity of radionuclides.

The change in sum peak intensity due to chemical environment was first studied

by DE BRUIN et al.,6 who detected only a very small effect in the case of i s 1 Hf. YOSHIHARA et al.7,s studied this effect in more detail using 11 1 In, is 2.1 s 4Eu and

6 o Tb radionuclides.

Experimental

The radioactive isotope 13 s Ba was obtained from Bhabha Atomic Research Centre

(B. A. R. C.), Bombay, India, in the form of BaC12. Compounds of barium, viz. BaSO4,

Ba(NO3)2, Ba-MES, Ba-TES and Ba-BSA were prepared by chemical processing of

BaC12. Radioactive BaC12 was added in a sufficient quantity so as to give a count rate

of the order of 1000 counts/s. The source strength was kept low to avoid pile-up effects.

Thereafter, the number of sum spectra, with each sample, were taken by keeping the

cylindrical vial, containing the sample, at the face of the HPGe detector. Special atten-

tion was paid to keep the source-detector geometry and resolution time of the detector

fixed. The relevant port ion of a typical sum spectrum taken with high resolution HPGe

detector (10 mm 2 • 10 mm) is shown in Fig. I .

t in 107

e- ~e"

0

u -̂ Iu ~ . ..

;'.':. "

a l0 s r / - . . ~ "" .x --.~ t l ~ I , ~ �9 o . j ~ . ** : �9 ~. o

10' ~ ' " " " : ' ' 2 " "" ~ E ~176

. . ; ~

�9 �9 . . ~ lO* §

�9 o �9 l l

:4 . i

10 I t I~ t I = I 1 I 1 " ~ t - 4 0 120 200 10/13 1120 1200 1320

C h a n n e l n u m b e r

Fig. 1. Relevant portion of sum spectrum of ~ 3 ~ Ba taken with a high resolution HPGe detector

372

KULWANT SINGH K. SINGH: DETERMINATION OF PERTURBED ANGULAR

Results and discussion

The decay scheme of Z aaBa is shown in Fig. 2. The 356-81 keV cascade is well

populated and has an anisotropy of about 3%. The small anisotropy is compensated

by long half-life of the intermediate level enabling the isotope suitable for PAC studies.

1/2" 10.7y / ' EC

/ o. -x ~.

5/2* 5/2* 7/2*

i ~r

437.0 383.8

160.6 81.0 0

E, key

Fig. 2. Decay scheme of 133 Ba

It is an established fact that a sum peak appears when two gamma-rays, emitted

from the cascade decay of a radioactive nucleus, enter the detector simultaneously.

This peak corresponds to the sum of energies of both gamma-rays in the energy scale.

The ratio of the sum peak intensity to that of the single peak has been measured

for various compounds of barium. The results are shown in Table 1.

YEH et al. 10 proposed that sum peak intensity change has an intense interrelation

to perturbed angular correlation (PAC) in various chemical systems.

Table 1 Sum peak in tensity ratios in different surroundings of 1 ~3 Ba

Material Isum/13 s 6 Isum/151

BaCI 2 (solution 0.004146 + 0.000263 0.000348 + 0.000022 BaCI~ (solid) 0.005818 + 0.000144 0.000459 + 0.000012 BaSO s 0.006799 + 0.000142 0.000529 + 0.000011 Ba(NOa) z 0.003527 + 0.000126 0.000302 + 0.000011 Ba-EDTA 0.003536 + 0.000231 0.000291 + 0.000019 Ba-MES 0.005616 + 0.000178 0.000442 + 0.000014 Ba- BSA 0.003373 + 0.000303 0.000285 + 0.000026

373

KULWANT SINGH, K. SINGH: DETERMINATION OF PERTURBED ANGULAR

The possibility of applying the sum peak method to determine the time integral

at tenuation facto~ (G22) was discussed by KUDO et al.s The relationship between

Isum/I ~ and G22 proposed by them is given by

Isu m/13,1 = r2 X/Z 1 + r2 Y/Z 1 (A2 2 G2 2 ) (1)

where

X ~ f f dxdye l (x , y) e2(x, y)

Y - f f dxdyel (x, y ) e2 (x, y) Fgeo (x, y)

Zl =- f f el(X, y) dxdy

In these expressions Isu m and I.rl are the intensities of (356 + 81) keV sum peak

and 356 keV transition, respectively, el and e2 are the detect ion probabilities, of

photons 1 and 2, respectively, whereas r2 is the emission probabil i ty of photon 2.

Once the constants r2X/Z1 and r2 Y/ZX1 are determined experimentally the G22

value for any compound can be evaluated.

To determine these unknown constants, sum peak measurements on two specimens,

namely, BaC12 and BaSO4, whose A22 Gz 2 values are known, were performed. The

Az2 G22 values for these two specimens were taken from the l i te ra ture)1 There-

after, by taking sum peak intensity ratios for different 133 Ba labelled samples

together with the calculated values of unknown constants, A22 G2 2 values for other

compounds were determined and are shown in Table 2. The last column of Table 2

shows the weighted average values of A22 G2 z as determined from Isum/Is 1. Using

Table 2 A22 G22 values for different compounds

Material A22G22 A2~G22 A22G~2, from Isum/I3s e from lsum/l~l wt. av.

BaCI 2 (solution) 0.0360 + 0.0017 0.0360 + 0.0014 0.0360 + 0.0011 BaC12 (solid) 0.0267 + 0.0010 0.0272 + 0.0008 0.0270 + 0.0006 BaSO4 0.0220 + 0.0008 0.0220 + 0.0008 0.0220 + 0;0006 Ba(NOa)2 0.0395 + 0.0008 0.0393 + 0.0007 0.0394 + 0.0005 Ba-EDTA 0.0404 + 0.0018 0.0392 + 0.0012 0.0396 + 0.0009 Ba-MES 0.0287 + 0.0011 0.0283 + 0.0009 0.0284 + 0.0007 Ba-BSA 0.0408 + 0.0019 0.0401 + 0.0016 0.0404 + 0.0012

374

KULWANT SINGH, K. SINGH: DETERMINATION OF PERTURBED ANGULAR

A2 2 = 0 .042 + 0 .005 as m e a s u r e d b y A R Y A , 12 Gz z for var ious c o ~ p o u n d s o f

b a r i u m have b e e n d e t e r m i n e d and are s h o w n in Table 3.

The Gz 2 values d e t e r m i n e d b y the s um peak m e t h o d and PAC m e a s u r e m e n t s are

in good agreement . The e x t e n t o f er rors in G22 can be decreased b y min imiz ing the

e r rors in the observed sum peak rat ios. This m e t h o d has some advantages over the

Table 3 Time integral attenuation coefficients G22

Material Present work SIDHU et al.6

BaC12 (solution) 0.887 + 0.105 1 BaC12 (solid) 0.642 + 0.078 - BaSO 4 0.524 + 0.064 0.59 + 0.12 Ba(NO3)2 0.938 + 0.112 1 Ba -EDTA 0.943 + 0.114 - Ba-MES 0.676 + 0.082 - Ba-BSA 0.962 + 0.118 -

PAC m e t h o d . I t is less t ime c o n s u m i n g and on ly w e a k radioac t ive sources are

required . Moreover , i t does n o t requi re c o m p l i c a t e d co inc idence circui ts as in the

case o f PAC m e t h o d .

The authors are grateful to Council of Scientific and Industrial Research (CSIR) for provid- ing a research project to carry out this work.

References

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Chem., 119 (1987) 131. 6. M. DE BRUIN, P. J. M. KORTHOVEN, Radiochem. Radional. Lett., 21 (1975) 287. 7. K YOSHIHARA, H. KAJI, T. MITSUGASHIRA, S. SUZUKI, Radiochem. Radioanal. Lett., 58

(1983) 9. 8. K. YOSHIHARA, H. KAJI, T. SHIOKAWA, Inorg. Chim. Aeta, 32 (1979) 287. 9. M. NAGAI, T. MIYOSHI, H. KAJI, K. YOSHIHARA, :F. SHIOKAWA, Proc. 37th Annual

Meeting of Chemical Society of Japan, 1973, p. 97. 10. Y. C. YEH, H. KAJI, T. SHIOKAWA, Radiochem. Radioanal. Lett., 26 (1976) 333. 11. N. P. S. SIDHU, Ph. D. Thesis, Punjabi University Patiala, 1987, unpublished. 12. A. P ARYA Phys. Rev., 122 (1961)549.

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