W.B. Walters

Decay scheme of 13.3 h 123I

Abstract The decay scheme of 13.3 h 123 I to levels of 123 Te has been determined with the use of Ge(Li) and NaI(Tl) γ-ray detectors and coincidence equipment. Sources were produced by the 121 Sb(α, 2n) 123 I reaction. A total of 14 γ-rays was observed and placed in the decay scheme. Excited states of 123 Te were established at 159, 248 (117 d 123m Te), 440, 506, 688, 698, 784 and 895 keV. The upper limit for position decay of 123 I is 0.01%. The 11 2 − isomer 123m Te is fed in 0.010±0.005% of the decays of 123 I. The levels of 123 Te are fitted considerably better by the recent predictions by Kisslinger and Kumar than by the older calculations of Kisslinger and Sorensen.

Decay of 19 min 67Ge to levels of 67Ga

Abstract The decay of 19 min 67 Ge to levels of 67 Ga has been studied with large Ge(Li) detectors and Ge(Li)-Ge(Li) coincidence experiments. A total of 56 γ-rays were observed and all but 8 have been placed in the decay scheme. Levels are observed in 67 Ga at 167, 359, 828, 911, 1082, (1203), (1556), 1640, 1810, 1976, 2527, 2620, 2731, 3162, 3225, 3402, 3632, 3655 and 3728 keV. The levels below 3600 keV have also been seen in one or more nuclear-reaction studies. We found no evidence for a level at 333 keV that was previously proposed to decay via a cascade of unresolved 166.5 keV γ-rays. Levels observed in odd-mass isotopes of Cu, Ga and As are discussed and compared with theoretical predictions.

Decay schemes of 70 min 129gTe and 33 d 129mTe

Abstract Gamma rays emitted in the decay of 70 min 129g Te and 33 d 129m Te have been investigated with Ge(Li) and NaI(Tl) detectors. Results of Ge(Li)-NaI(Tl) coincidence studies, coupled with relative intensity measurements for both isomers, suggest a decay scheme considerably different from those recently proposed by other workers. Excited levels are placed in 129 I at 27.7, 278.4, 487.4, 559.8, 696.0, 729.8, 829.8, 844.7, 1050, 1111.4, 1260, 1291, and 1402 keV. Beta decay of 129g Te feeds all of these except the ones at 696.0, 729.8, 768.9, 844.7, 1050 and 1402 keV. Beta transitions form 129m Te populate all of the latter set of levels and the ground state. The I.T. branching fraction of 129m Te is about 72%. With some exceptions the levels of 129 I agree rather well with those predicted by Kisslinger and Sorensen. Considerable evidence for the previously suggested hindrance of β-decay caused by phonon mixing of the wave functions has been observed.

Decay scheme of 3.9 d 127Sb

Abstract Beta and γ-rays emitted in the decay of 3.9 d 127 Sb have been studied with the use of Si(Li), Ge(Li) and NaI(Tl) detectors and coincidence equipment and the level scheme of 127 Te has been constructed. In order to check on interference from other antimony isotopes, sources were prepared by separating antimony directly from fission products, by milking antimony from separated tin fission products, and by use of the 128 Te(γ, p) 127 Sb reaction followed by chemical separation. A total of 33 γ-rays were observed, of which 32 were placed in the level scheme of 127 Te. Levels of 127 Te populated by decay of 127 Sb were observed at the following energies: 61, 88, 341, 473, 503, 631, 686, 764, 784, 786, 924, 1077, 1142, 1155, 1290, 1323 and 1378 keV. The properties of low-lying, even-parity levels of 127 Te are in reasonable agreement with the predictions of Kisslinger and Sorensen. Evidence for 9 2 − “intruder” state at 341 keV in 127 Te similar to that at 322 keV in 125 Te was found. Additional evidence for apparent hindrance of allowed β transitions was obtained.

The decay of 1.2 min 113mAg and 5.3 h 113gAg

Abstract The decay schemes of 1.2 min and 5.3 h 113Ag have been studied using Ge(Li) and NaI(Tl) detectors and a 4096-channel multiparameter pulse-height analyser system. The decay of 5.3 h 113Ag was found to involve 15 γ-rays and to produce 10 excited states in 113Cd at energies of 264.7, 298.0, 315.6, 583.9, 604.6, 681.1, 883.6, 936.9, 989.0 and 1195.2 keV. The italicized energies refer to negative parity states, through which 1.3% of the decays go to yield the 14y 111 m Cd ( 11 2 − ) isomer at 264.7 keV. The 604.6 keV level is thought to be a case|9/2− level similar for those found in several odd-mass Te and Xe isotopes. The 1.2 min 113mAg decay was found to populate several of the same levels in Cd and two additional levels at 452 and 689 keV. The 1.2 min 113Ag is the upper isomer with high spin, probably 7 2 + .

Decay schemes of 42 min 123Sn and 10 min 125mSn

Abstract The radioactive decay schemes of 42 min 123 Sn and 10 min 125m Sn have been studied with the aid of a Ge(Li) detector and coicidencee equipment. Levels in 123 Sb at 160, 542 and 712 keV were populated in the decay of 42 min 123 Sn and levels at 332, 643, 921, 1349, 1484, 1700, 1736, 1914, 1947 and 2112 were populated in 123 Sb in the decay of 10 min 125m Sn. The systematic behavior of low-lying levels of odd-mass Sb isotopes is discussed, and the levels observed in this study are compared to the levels calculated by Kisslinger and Sorensen.

Decay of 9.6 d 125Sn to levels of 125Sb

Abstract The decay scheme of 9.62 d 125g Sn has been investigated using NaI(Tl) and Ge(Li) detectors in conjunction with a 4096-channel multi-parameter pulse-height analyser system. Previously unreported γ-rays have been observed at 283, 652.6, 1087.4 and 1164.3 keV. Coincidence evidence indicates the presence of a new level at 2253.1 keV as well as a significant γ-ray branching to the 5 2 + level at 332.0 keV. The β-branching to the ground state has been redetermined to be 82.5±5% and new log ft values calculated. The pattern of levels is found to correspond closely with that predicted by the calculations of Kisslinger and Sorensen.

Decay of 40 d 103Ru and 17 d 103Pd to levels of 103Rh

Abstract The structure and properties of the levels of 103 Rh have been further characterized by studying the electrons and γ -rays emitted in the decay of 40 d 103 Ru and 17 d 103 Pd. K-conversion coefficients of 0.0043±0.0006 and 0.0025±0.0005 have been measured for the 497 and 610 keV γ -transitions respectively and indicate positive parity for the 537 and 650 keV levels. Using a time-to-amplitude conversion system, an upper limit of 0.4 ns has been determined for the lifetime of the 93 keV level. Angular correlations have been observed for the 444-53 and 557-53 keV cascades and indicate spins of 5 2 or 7 2 for the levels at 537 and 650 keV. A weak 242 keV γ - ray from the 537 keV level to the 3 2 − level at 295 keV establishes the spin and parity of the 537 keV level as 5 2 + . The log ft values for the β − decay and E. C. decay to the levels of 103 Pd have been determined and sizeable hindrances noted.

Decay of 56 min 69gZn, 14 h 69mZn and 39 h 69Ge to levels of 69Ga

Abstract The decay of 69mZn was found to have weak β-branches to the 574 (0.032±0.005%) and 872 keV (0.004±0.002%) levels of 69Ga in addition to the prominent (>99.9%) 439 keV isometric transition to 69gZn. Decay of the latter includes a weak (0.0015±0.0005%) β-branch to the 318 keV level of 69Ga. Ten of the 36 γ-rays assigned to the decay of 69Ge in this work had not previously been observed. Levels are established in 69Ga at 318, 574, 872, 1106, 1336, 1487, 1525, 1723, 1891, 1923, 2022 and 2043 keV. The recent level predictions by Kisslinger and Kumar are in better agreement with the observed levels of 69Ga than previous calculations although discrepancies in levels positions are still rather large. As the energies of the excited states of even nuclei in the vicinity of 69Ga do not vary smoothly with N and Z, it is doubtful that a generalized type of calculation (e.g. Kisslinger-Kumar) can provide a very good fit to levels in the region. The log ft value of 8.6 for the β− transition from 1 2 − 69gZn to the 1 2 − level at 318 keV in 69Ga is among the largest known for allowed transitions. The half-lives of the species studied were determined to be 69gZn, 55.6±1.6 min; 69mZn, 14.4±0.1 h and 69Ge, 39.05±0.10 h. A value of 0.102±0.004 was obtained for the isomer-yield ratio 69mZn/69gZn in the 68Zn(n,γ)69Zn reaction.

Ge(Li)NaI(Tl) studies of the decay of 117Te

Abstract Results of independent investigations performed at MSU and MIT on the decay of 1.1 h 117 Te suggest an energy level scheme for 117 Sb. Sources were produced at MIT via the 114 Sn(α, n) 117 Te reaction, while the MSU group bombarded natural antimony metal with 52 MeV protons. Ge(Li)NaI(Tl) coincidence experiments, γ-ray energy and relative intensity measurements, and positon end-point measurements were performed at both laboratories and produced results which were in excellent agreement. On the basis of these results, excited states in 117 Sb are placed at 719.7, 923.9, 1354.5, 1454.5, 1716.4, 1810.5, 2213, 2284.8 and 2300.0 keV. Additional levels, accommodating only very weak ground state transitions, may be present at 1596, 2380 and 2885 keV. No conclusive evidence for the existence of a possible 117m Te was obtained.