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Applied Radiation and Isotopes 64 (2006) 693–699

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Precision measurements in 124Te following the decay of 124Sb

Amol Patil, D. Santhosh, K. Vijay Sai�, M. Sainath, K. Venkataramaniah

Department of Physics, Sri Sathya Sai Institute of Higher Learning, Prasanthinilayam 515 134, India

Received 14 April 2004; received in revised form 12 December 2005; accepted 12 December 2005

Abstract

The decay of 124Sb (60 d half-life) to levels of 124Te has been studied using two HPGe detectors in singles and coincidence mode. We

identify 75 transitions in this decay, including 14 gamma rays, the emission of which are being reported here for the first time. In

confirming the existence of 26 well-established levels below 2900 keV excitation, we also introduce 5 other levels at 2490.5, 2618.4,

2747.05, 2834.99, and 2859.4 keV. The data on energies of gamma transitions and the levels are reported at high precision.

r 2006 Elsevier Ltd. All rights reserved.

Keywords: Radioactivity; 124Sb beta decay; Singles and coincidence studies; 124Te level scheme

1. Introduction

The even–even isotope 124Te has been the subject ofconsiderable interest (Auble and Ball, 1972; Lien et al.,1977) since it is the testing ground for different theoreticalmodels. Till now, no complete understanding of nuclearstructure of this nucleus has been achieved. Even manyaspects of the low-lying spectrum are still puzzling (Warret al., 1998). The level structure of 124Te has been investigatedthrough the study of 124Sb (t1=2 ¼ 60:2 days) decay as well asthrough nuclear reactions (Iimura et al., 1997).

Several levels in 124Te that were established in the decaystudies of various workers (Meyer et al., 1969; Johnson andMann, 1974; Sharma et al., 1979; Mardirosian and Stewart,1984; Jianming et al., 1988; Goswamy et al., 1993) have notbeen supported unambiguously and they have never beenreported by any of the reaction studies. Conversely, severallevels which in view of the decay energy might have beenstudied by 124Sb decay, have only been reported in reactionstudies (Bushnell et al., 1969; Christensen et al., 1970;Auble and Ball, 1972; Lien et al., 1977). Fourteen newgamma transitions and two new levels have been reportedby Iimura et al. (1997). Jianming et al. (1988) have studied

e front matter r 2006 Elsevier Ltd. All rights reserved.

radiso.2005.12.010

ing author. Tel.: +918555287235; fax: +91 8555287474.

ess: vjsai80@rediffmail.com (K. Vijay Sai).

this decay through singles and coincidence measurements,reporting nine new gamma transitions, also trying toestablish four new levels at 2512, 2550, 2808.8 and2814.5 keV. Based on their coincidence data, Jianminget al. (1988) ruled out the presence of 34 of the previouslyreported gammas (Lederer et al., 1978; Sharma et al., 1979;Mardirosian and Stewart, 1984). Goswamy et al. (1993)confirmed the levels at 2808 and 2814 keV and nine gammarays of energies 148.4, 189.7, 210.4, 291.5, 346.5, 530.3,571.6, 1565.9, and 2808.0 keV. Apart from the energies ofthe levels and the gamma transitions, the intensity valuesfor many weak gamma rays measured by different workersare inconsistent with each other.The present work attempts to: (i) clarify the above-

mentioned discrepancies and to confirm the new resultsof Jianming et al. (1988) and Goswamy et al. (1993);(ii) determine the energies and intensities of gammatransitions, and (iii) propose a revised level scheme for124Te by a reinvestigation of the decay of 124Sb aiming atprecision measurements (singles and coincidence studies).By looking for the weak transitions that could not be seenin earlier decay studies, an effort has been made to look forseveral of the energy levels that were proposed in particletransfer reaction studies (Auble and Ball, 1972; Lien et al.,1977) but which were not reported in the beta decaystudies. This becomes possible with present precision

ARTICLE IN PRESSA. Patil et al. / Applied Radiation and Isotopes 64 (2006) 693–699694

gamma spectroscopy systems and has lead to veryinteresting results for other nuclei (Sainath et al., 1999,2003).

2. Experimental procedure

2.1. Singles Gamma-ray measurements

A carrier-free sample has been obtained of the radio-active source 124Sb, being produced by thermal neutronirradiation of 123Sb at the Bhabha Atomic Research Centre(Mumbai) in the form of antimony chloride (SbCl3) indilute HCl solution. The 124Sb source was allowed to decayfor about 8 months, primarily to rid the source of anyshort-lived impurities. Sources for acquiring spectra wereprepared by drying the source solution on aluminizedmylar foil supported by thin aluminium discs of 1 cmdiameter. The count rate was kept at around 500 counts/s.

Table 1

Coincidence measurement results from decay of 124Sb

Energy (keV) Gate (keV)

603 646 709 714 723

183 |336 |444 | |511 |525 |603 | | | |646 | | |662 |670 |709 |715 | |722 | | |736 | |790 | |899 | |968 | | | |1045 | |1068 |1178 |1198 |1263 |1325 |1355 |1368 | | | |1376 | |1436 | |1445 | |1489 |1526 | |1580 |1690 | |1720 |1919 |2033 |2091 |2287 |

Singles gamma spectra were recorded with two 60 cm3

HPGe detectors (FWHM ¼ 1.80 keV at 1.33MeV) coupledto an 8k PC-based Multichannel Analyser. Gamma singlesspectra were acquired at a source to detector distance of25 cm. The counting period lasted an average of 4.5� 105 s/spectrum. Efficiency calibration for HPGe detectors wasdone using standard radioactive sources obtained from theInternational Atomic Energy Agency, Vienna. The low-energy spectrum was acquired using a Si(Li) detector(FWHM ¼ 180 eV at 5.9 keV). The gamma ray peaks wereanalysed using the computer codes FIT (Petkov andBakaltchev, 1990) and Gamma Vision (version 5.10 EG&GORTEC (1998)).

2.2. Gamma–gamma coincidence measurements

Coincidence measurements were performed with theabove mentioned two 60 cm3 HPGe detectors. A standardfast–slow coincidence system with the time resolution of20 ns was used. The source to detector distance wasmaintained at 10 cm. Coincidence spectra were taken bysetting gates at 602, 614, 709, 714, and 723 keV gammaenergies, as summarized in Table 1.

3. Results and discussion

Our typical gamma spectra are shown in Fig. 1(a–h). Weexplain the comparison with a ‘bench mark’ test toestablish the credibility of our identification of as yetunconfirmed weaker transitions and their precise energies.The most recent energy calibration standard for 125Sb(IAEA, 1995; Firestone and Shirley, 1996; IAEA–TEC-DOC-619, 1991) have been compared with our resultsobtained in Table 2(a); a similar comparison with theadditional transitions included in the ‘standardizationanalysis’ (Helmer, 1990) is presented in Table 2(b).It is seen that almost in all cases the deviations are

comparable to the assigned uncertainties. The averagedeviation for the 16 transition energies is less than 8 eV.The excellent agreement of our measured gamma energiesand accepted ‘benchmark values’ in the IAEA calibrationtables and other similar measurements provides us with afirm basis for the identification of new transitions and alsofor the use of our measured gamma ray energies to arrive ata revised level scheme for 124Te through application of theRitz combination principle (Mitropolsky I.A., 2003).A complete list of the energies and relative intensities of

75 gamma transitions observed in our study and shown inFig. 1(a–h) is given in Table 3. In addition to a comparisonof our intensity values, we also include results fromMardirosian and Stewart (1984); Jianming et al. (1988)and Goswamy et al. (1993). In accordance with the usualconvention, intensities in the table are quoted relative tothe intense 602.9 keV transition (in which it is assumedIg ¼ 1000). We do not see the 148.4, 189.6 and 346.5 and1054.0 keV transitions reported in a number of earlierstudies. On the other hand, we observe 14 new gamma

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Fig. 1. (a–h) Singles gamma-ray spectra. Fig 1(i) X-ray spectrum. Fig. 1(j) Coincidence spectrum (gate 602).

A. Patil et al. / Applied Radiation and Isotopes 64 (2006) 693–699 695

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Table 2

Comparison of our measured gamma energies with the corresponding

adopted values for the transitions (IAEA-95; IAEA-91) and for other

gamma energies precisely determined in ‘standardization’ studies by

Helmer (1990) in the decay of 125Sb

Gamma energies (keV)

Present (a) IAEA-95 Present (b) Helmer-90

176.308(2) 176.314(2) 35.489(4) 35.489(5)

380.454(8) 380.454(8)a 172.708(7) 172.719(8)

427.880(5) 424.874(4) 198.631(14) 198.654(11)

463.368(4) 463.365(4) 204.144(8) 204.139(8)

600.589(3) 600.597(2) 208.074(10) 208.079(4)

606.700(2) 606.713(2) 227.876(10) 227.891(10)

635.951(3) 635.950(3) 408.069(12) 408.065(10)

671.445(6) 671.441(6) 443.565(7) 443.554(9)

Numbers within the parentheses denote the uncertainties in last digit(s).aTaken from R.G. Helmer (1990).

Table 3

Intensities of gamma rays emitted following the decay of 124Sb

Eg (keV) Ig

Present Goswamy et al. (1993)

27.741(15) 3.681(55) 3.66

31.622(31) 0.852(15) 0.84

148.4 — 0.037(7)

186.100(185) 0.02(36) —

209.839(31) 0.147(5) 0.055(10)

254.529(48) 0.137(6) 0.163(8)

291.829(11) 0.070(6) 0.088(8)

336.220(16) 0.760(18) 0.75(2)

371.059(30) 0.257(15) 0.34(8)

400.339(21) 1.249(66) 1.24(13)

444.119(21) 1.830(10) 1.92(2)

469.089(25) 0.364(23) 0.47(3)

481.420(37) 0.205(10) 0.24(2)

525.510(21) 1.429(75) 1.4(2)

530.450(27) 0.421(12) 0.43(2)

572.070(57) 0.184(10) 0.193(13)

592.729(50) 0.14(2) —

602.900(25) 1000(10) 1000(10)

632.500(16) 0.990(9) 1.07(1)

646.070(9) 76.85(52) 75.5(8)

662.409(29) 0.148(10) 0.32(2)

709.590(42) 13.94(16) 13.4(2)

713.900(6) 22.88(24) 22.7(3)

722.849(8) 108.77(118) 107.7(14)

735.799(14) 1.399(19) 1.29(2)

743.200(82) 0.058(11) —

766.320(28) 0.039(3) 0.124(2)

775.270(73) 0.119(12) 0.093(18)

790.679(009) 7.664(89) 7.52(9)

795.310(15) 0.368(11) —

816.9 — 0.74(2)

856.679(35) 0.216(11) —

899.229(28) 0.200(12) 0.175(14)

968.320(13) 21.051(225) 19.2(2)

976.640(22) 0.841(10) 0.845(17)

1045.420(11) 20.257(95) 18.7(2)

1053.8 — 0.05(2)

1086.750(74) 0.358(16) 0.38(2)

A. Patil et al. / Applied Radiation and Isotopes 64 (2006) 693–699696

transitions not given in NDS (1997) or any other reportincluded in the table. Our measured energies and intensitiesfor K X-rays and gamma rays which are weighted averagesare found to be consistent and are found to be in generalagreement with Goswamy et al. (1993) and Jianming et al.(1988). However the intensity values for many weakgamma rays differ. A few of these additional gammaenergies had earlier been tentatively suggested, but they donot appear in the evaluated data set of NDS, 1997. Sevenof the 14 new gamma transitions pertain to already existinglevels and the other 7 gamma transitions are in connectionwith the 5 proposed levels.

4. Revised 124Te level scheme

Using the precisely determined transition energies asinput data for application of the Ritz combination

Jianming et al. (1988) Mardirosian et al. (1984)

— —

— —

0.061(20) —

— —

0.062(28) —

0.214(41) 0.3(66)

0.122(61) —

0.86(6) 0.78(7)

0.356(61) 0.239(61)

1.55(13) 1.68(12)

2.04(10) 2.26(15)

0.53(3) 0.79(5)

0.29(8) 0.3(5)

1.65(10) 1.78(12)

0.47(11) —

0.25(10) —

— —

1000(10) 1000

1.01(6) 1.18(7)

75.5(10) 78.2(22)

0.35(11) 0.43(5)

13.8(4) 14.9(7)

22.9(5) 24.6

109.9(15) 114.6(16)

1.45(21) 1.42(5)

— —

0.092(41) 0.09(5)

0.112(41) 0.112(41)

7.53(11) 7.66(8)

— —

0.74(7) 0.86(8)

— —

0.2(6) —

19.45(23) 20.38(24)

0.88(5) 0.88(12)

18.97(24) 20.13(23)

— 0.07(1)

0.43(5) 0.58(5)

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Table 3 (continued )

Eg (keV) Ig

Present Goswamy et al. (1993) Jianming et al. (1988) Mardirosian et al. (1984)

1263.489(69) 0.482(14) 0.42(2) 0.43(5) 0.54(10)

1301.119(86) 0.256(13) 0.35(1) 0.39(5) 0.61(8)

1325.800(8) 17.07(19) 16.1(2) 16.45(23) 16.9(29)

1355.420(58) 10.93(13) 10.5(1) 11.03(18) 11.08(22)

1368.369(32) 27.00(21) 26.4(3) 26.96(31) 27.58(69)

1376.089(9) 5.43 (5) 4.93(6) 4.96(10) 5.31(46)

1385.339(34) 0.64 (2) 0.62(3) 0.71(6) 0.79(25)

1418.599(124) 0.05(2) — — —

1436.859(37) 12.70(12) 12.5(1) 12.36(17) 13.4(27)

1445.189(49) 3.35 (32) 3.34(4) 3.46(10) 3.29(14)

1489.00(44) 6.92 (5) 6.87(6) 7.09(54) 7.23(20)

1509.630(151) 0.08 (1) — — —

1526.329(15) 4.51(4) 4.14(5) 4.34(9) 4.33(8)

1565.9 — 0.15(4) 0.13(4) —

1580.020(107) 4.60 (4) 4.27(5) 4.19(41) 2.38(7)

1621.670(19) 0.477(12) 0.42(1) 0.4(4) 0.47(4)

1691.089(13) 466.27 (45) 493.2(55) 487.3(61) 508.8(88)

1720.719(15) 0.97 (18) 0.96(2) 1.02(4) 1.01(5)

1757.9 — 0.049(23) — 0.188(35)

1852.170(42) 0.02 6(10) 0.062(9) 0.112(31) 0.025(25)

1918.829(28) 0.58 (16) 0.55(2) 0.6(3) 0.55(3)

2016.349(61) 0.090(9) 0.112(10) 0.124(7) 0.112(25)

2039.810(27) 0.661(19) 0.66(2) 0.68(2) 0.68(3)

2079.929(52) 0.741 (18) 0.268(14) 0.163(25) 0.371(87)

2091.350(22) 53.97 (52) 57.4(7) 56.9(9) 59.2(10)

2099.379(94) 0.572(12) — 0.46(2) 0.37(5)

2108.330(13) 0.501(7) 0.45(2) 0.44(2) 0.35(5)

2145.060(29) 0.0068(3) — — —

2172.2 — 0.021(5) 0.022 0.046(10)

2182.409(163) 0.36 (7) 0.44(1) 0.45(2) 0.48(2)

2204.260(13) 0.310 (6) — — —

2232.409(50) 0.01(3) — — —

2256.489(119) 0.006(2) — — —

2283.649(26) 0.422(9) 0.101(8) 0.076(14) 0.097(20)

2294.149(26) 0.56 (23) 0.76(5) 0.31(5) 0.45(2)

2323.479(79) 0.060(3) 0.027(3) 0.025(7) 0.04(1)

2373.790(596) 0.009(3) — — —

2386.139(1619) 0.0024(2) — — —

2455.300(108) 0.092(1) 0.081(2) 0.016(6) 0.01(5)

2490.600(199) 0.02 (1) — — —

2515.189(3209) 0.0049(1) — — —

2681.6 — 0.020(4) 0.018(6) 0.025(10)

2693.300(633) 0.003(1) 0.047(5) 0.026(16) 0.056(10)

2746.179(253) 0.01(1) — — —

2807.420(257) 0.093(4) 0.015(2) 0.020(8) —

2814.370(449) 0.035(2) — — —

A. Patil et al. / Applied Radiation and Isotopes 64 (2006) 693–699 697

principle, we now proceed to construct the 124Te levelscheme. Well-established undisputed features of thisscheme as seen in the latest nuclear data sheets NDS 97are used as cross checks in our procedure. Application ofthe energy sum rule using the software GTOL (programpackage, ENSDAT version 3.92 NNDC, Brookhaven,1994) in different loops leads us to the placement of theobserved transitions and to an evaluation of the levelenergies in the thus constructed level scheme. The results ofthis exercise are shown in Fig. 2, which incorporates all the75 observed transitions.

All the 22 levels in the adopted scheme of NDS, 1997and the 4 extra levels proposed by Jianming and Goswamyet al. appear in our level scheme with the excitationenergies agreeing in each case. Our level scheme includesfive additional levels with excitation energies 2490.5,2618.4, 2747.05, 2834.99, and 2859.4 keV. These new levelswere proposed in the particle transfer studies (Auble andBall, 1972; Lien et al., 1977) but were not reported in betadecay studies. Out of the 9 gamma rays observed byJianming et al. (1988) and Goswamy et al. (1993), only 6could be observed in the present work. The observed

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Fig. 2. 124Sb b� decay scheme.

A. Patil et al. / Applied Radiation and Isotopes 64 (2006) 693–699698

gamma rays at 1565.9 and 2808 keV confirm the proposedlevels at 2814.5 and 2807.427 keV. The level at 1747 keV ofthe NDS 97 could not be confirmed because of the absenceof the 498 keV gamma emission.

The newly observed 2490.6 keV gamma transition couldbe fitted as a transition to the ground state of 124Te from2490.5 keV new level. Two gammas with energies 2016.34and 1368.36 keV were reported by Goswamy et al. (1993)but the former does not find its place in their level schemewhile the later was fitted between the 2693.80 and1325.57 keV levels. However, in the present work boththe gammas have been observed but could be fitteddifferently by proposing a new level. The decay gammasof 1368.36 and 2016.34 keV transition from a new level to602.73 and 1248.0 keV levels yield an energy of 2618.4 keVfor the new level.

The 3rd level, proposed at 2747.05keV with the observa-tion of 2746.17 and 2145.06keV gamma transitions connectsthe ground state and the 602.73 keV level with the new level.The decay gammas 795.0, 1509.63, and 2232.4 keV could befitted using the GTOL program between 602.73, 1325.52,and 2039.303keV levels and a level at 2834.99keV energy.

A newly observed gamma emission of 2256.48 keV hasbeen observed and could be fitted between 602.73 keV anda level at 2859.4 keV. All these 5 levels have been proposedin the particle transfer reaction studies (Auble and Ball,1972; Lien et al., 1977). In the present work the precisionmeasurements of energies and intensities have made itpossible to establish and assign the exact level energies ofthe 5 new levels.

5. Summary

We have carried out precise measurements of the X-rayand the gamma-ray energies and intensities following the124Sb decay. The precision of our data is established bycomparing our results with the IAEA adopted interna-tional calibration standards and other similar bench-mark measurements. The revised level scheme for 124Teis constructed based on summed energy rules for variousloops incorporating 75 gamma transitions; the latterinclude 14 new transitions observed by us but not listedin the adopted data set of the latest (1997) Nuclear datasheets. The revised level scheme introduces 5 new levels at

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2490.5, 2618.4, 2747.05, 2834.99, and 2859.4 keV with7 out of 14 new transitions connecting these levelswith the earlier established levels. It is expected thatthe presently reported more extensive gamma-ray data andthe revised level scheme of 124Te taken together with theresults from reaction studies produces a better data basefor understanding the level structures in the transitionalnuclei.

Acknowledgements

The authors acknowledge financial support provided bythe Department of Atomic Energy, Government of Indiathrough the DAE-BRNS research project.

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