J.H. Hamilton

Rotation-aligned coupling and axial asymmetry in 189−195Au

Abstract Levels in 189, 191, 193Au have been studied by radioactive decay of isotopically separated 189, 191, 193Hg. The systematics of the levels are followed from 195Au to 189Au and show a remarkable insensitivity to neutron number. The h 1 1 2 bands are identified and provide a critical test of the model of a single-j nucleon subject to rotation-aligned coupling to an asymmetric core. Within the framework of the model the triaxial degree of freedom appears to be very stable.

The decay of 110mAg: Gamma-ray energy and intensity standardization

Abstract The energies and intensities of the transitions from the decay of 110mAg have been carefully measured with three different systems which use Ge(Li) detectors. The following energies in keV and intensities in parentheses were determined for standards: 446.77 ± 0.04 (3.5 ± 0.2), 620.22 ± 0.03 (2.9 ± 0.2), 657.71 ± 0.03 (100), 677.55 ± 0.03 (12.2 ± 0.7), 686.80 ± 0.03 (7.4 ± 0.6), 706.68 ± 0.04 (17.2 ± 07), 744.19 ± 0.04 (4.4 ± 0.4), 763.88 ± 0.04 (24.0 ± 0.8), 818.00 ± 0.04 (7.8 ± 0.3), 884.67 ± 0.04 (79.6 ± 2.0). 937.48 ± 0.04 (36.5 ± 1.1), 1384.22 ± 0.04 (27.7 ± 0.8) 1475.73 ± 0.04 (4.5 ± 0.2), 1504.90 ± 0.08 (14.8 ±0.4) and 1562.22 ± 0.06 (1.33 ± 0.06). All these transitions fit into the well-known decay scheme of 110mAg. Transitions previously reported at 566.0, 667.2, 753.0, 785.0 and 1443.0 keV were not observed, but weak new transitions at 626, 997 and 1334 keV were observed. Transitions of 434.00 ± 0.10, 614.37 ± 0.10 and 722.95 ± 0.08 keV were observed from the decay of 108mAg.

The decay of 99Mo

Abstract The radioactive decay of 67 h 99 Mo has been studied by measuring internal conversion spectra, single gamma-ray spectra and gamma-gamma coincidences. Large volume Ge(Li) detectors, a curved-crystal spectrometer, a sector field beta-ray spectrometer and a fast coincidence arrangement were employed in these experiments. The following gamma rays were observed (relative intensities are given in parentheses): 40.584 ± 0.002, 140.511 ± 0.006(100), 142.63 ± 0.03(0.03), 181.06 ± 0.04(7.5), 249 ± 1(0.006), 344 ± 2(0.0013), 366.4 ± 0.1(1.6), 380.7 ± 0.2(0.011), 409 ± 2(0.0016), 411.5 ± 0.5(0.027), 458 ± 1(0.006), 528.9 ± 0.2(0.06), 620.7 ± 0.2(0.027), 620.7 ± 0.2(0.005), 739.7 ± 0.1(15.4), 778.2 ± 0.1(5.4), 823.1 ± 0.1(0.16), 961.0 ± 0.2(0.12), 988.2 ± 0.5(0.002), 1001.7 ± 0.2(0.007) and 1016 ± 2 keV(0.001). The following energy levels are populated: 140.511 ± 0.006, 142.63 ± 0.03, 181.095 ± 0.007, 509.0 ± 0.1, 671.5 ± 0.2, 761.3 ± 0.2, 920.8 ± 0.1, 1004.2 ± 0.2, 1129.7 ± 0.2, 1142.1 ± 0.2, 1169.3 ± 0.5 and 1197 ± 2 keV. The levels at 671.5, 761.3, 1004.2, 1142.1, 1169.3 and 1197 keV have not been reported previously. The following K-conversion coefficients were determined: α K (140.5) = 0.104 ± 0.007, α K (142.6) = 23 ± 6, α K (181.1) = 0.130 ± 0.012 and α K (739.7) = (1.6 ± 0.4) × 10 −3 .

The K-conversion coefficient of the 279 keV transition in Tl203 by a coincidence technique and establishment as a standard

The K-conversion coefficient of the 279-kev transition in Tl/sup 203/ was measured by a coincidence technique. The Kconversion electrons and beta rays following the decay of Hg/sup 203/ were detected in a magnetic lens spectrometer in coincidence with x rays and gamma rays, respectively. From these data, the probability of K-conversion electron emission kappa /sub eK/ was determined to be 0.132 plus or minus 0.002. The Kconversion coefficient was calculated from epsilon /sub K/ = kappa /sub eK//STA1- kappa /sub e K/ (K + L + M + N)/K! to be 0.162 plus or minus 0.003. The consistent epsilon /sub K/ results from several different techniques suggest this is a useful standard for conversion coefficient measurements in this energy range. (auth)

The decay of 160Tb to levels in 160Dy

Abstract The gamma radiation associated with the beta decay of 160Tb to levels in 160Dy has been studied with curved-crystal and Ge(Li) spectrometers. Eight previously unreported transitions were observed with energies 237.638 ± 0.086 keV, 246.489 ± 0.016 keV, 349.94 ± 0.11 keV, 432.7 ± 0.6 keV, 1005 ± 1 keV, 1069.1 ± 0.4 keV and 1300.0 ± 0.8 keV. The existence of transitions at 176, 379, 486, 872 and 1286 keV has been confirmed. Gamma-gamma coincidence studies employing two Ge(Li) detectors have led to a decay scheme which is essentially that given by previous investigators with the addition of levels at 1155.8, 1288.7 and 1535.2 keV. The level at 1155.8 keV has been identified as the 4+ member of the gamma-vibrational band. No evidence was obtained for the population of any Kπ = 0+ beta-vibrational levels from the decay of 160Tb.

Mean life of the 854 keV 02+ state in 74Se and the coexistence model

Abstract The mean life of the first excited 0 2 + state in 74 Se, only 219 keV above the first excited 2 + state at 635 keV, was measured to be 1.2±0.2 nsec, with delayed coincidence techniques. The 0 2 + state was populated by the decay of 74 Br produced via the 60 Ni( 16 O, pn) 74 Br reaction. The extracted B (E2; 0 2 + → 20 1 + ) value is 14±2 s.p.u. which suggests that the 0 2 + state is collective. Application of a coexistence model in terms of spherical and deformed shapes is discussed for 74 Se.

Levels in 72Ge populated by 72Ga

Abstract The radioactive decay of 72 Ga has been investigated by means of Ge(Li) and Si(Li) detectors. The energies and intensities of 71 γ-rays have been determined from the γ-ray singles spectrum. Extensive γγ coincidence experiments were performed with two Ge(Li) detectors coupled to a two-parameter analyser. Internal conversion electron measurements were performed with a Si(Li) detector system. The electron-γ delayed coincidence experiments were carried out with an anthracene crystal and a 35 cm 3 Ge(Li) detector. These extensive coincidence relationships were used to identify the levels of 72 Ge populated by 72 Ga with excited states at 691.2, 834.02, 1463.88, 1728.24, 2064.80, 2402.0, 2463.74, 2514.65, 2583.5, 2754.1, 2943.45, 3035.41, 3094.7, 3324.92, 3341.68, 3439.3, 3455.2, 3566.0, 3678.1, 3707.1, 3758.6 and 3815.4 keV. The β − feedings and the log ƒt values were calculated from the relative γ-ray intensities.

Properties of levels in 132Ba and 132Xe populated by 132Cs

Abstract The energies and intensities of the transitions in the decay of 132 Cs have been determined with improved accuracy with a 30 cm 3 Ge(Li) detector and 4096-channel analyser. The following transitions were measured in 132 Xe (energies in keV and intensities in parentheses): 363.0±1.0(0.7±0.1), 505.7±0.4(8.3±0.8), 629.8±0.2(10.1±1.0), 667.65±0.09(1000), 772.4±0.4(0.79±0.07), 1135.8±0.2(5.0±0.4), 1297.7±0.5(0.48±0.04), 1317.65±0.15(6.1±0.5) and 1985.3±0.3(0.74±0.07) and 464.5±0.2(18.8±2.0), 567.0±0.8(2.6±0.3) and 1031.4±0.2(1.2±0.1) in 132 Ba . The level energies in 132 Xe determined from these results are 667.65±0.09, 1297.6±0.2, 1440.1±0.4, 1803.4±0.2 and 1985.30±0.15 keV. The first two excited states in 132 Ba are at 464.5±0.2 and 1031.4±0.2 keV.

Electron spectroscopy studies of the decay of 154Eu

Abstract The relative conversion electron intensities of 16 transitions between 440 and 1280 keV were measured in an iron-free double-focusing spectrometer. The K conversion coefficients of the nine strongest transitions were measured by the internal-external conversion method, and multipole assignments of these transitions were made. The conversion electron intensities of the 676 and 692 keV transition between the 4+ and 2+ levels of the K = 0 vibrational band and the 4+ and 2+ levels for the ground state rotational band, respectively, were found to be about 90% E0 radiation. Transitions of 534 and 681 keV are assigned to be pure E0.

A MAGNETIC LENS SPECTROMETER FOR ELECTRON-GAMMA AND ELECTRON-ELECTRON DIRECTIONAL CORRELATION MEASUREMENTS

Abstract A magnetic lens spectrometer has been adapted for electron-gamma and electron-electron directional correlation measurements. One electron channel has magnetic momentum selection provided by a medium short magnetic lens spectrometer. The lens spectrometer is iron-free with the exception of two steel end plates which decouple the already weak magnetic field in the lens from the electron detector and from the movable gamma or electron detector. The source sits outside the magnetic field and is accessable through 180° to a movable detector. Directional correlations of electrons with gamma-rays or electrons have been carried out by using a NaI(Tl) detector or an anthracene scintillation detector, respectively. A special source holder was designed for the electron-electron work. Electron energies down to 20 keV have been measured in the lens. A proportional counter may be used to lower energies. The maximum lens energy is ≈ 5 MeV. The spectrometer mean emission angle was chosen to be 13.5°. The resolution can then be varied from 1 to 5 per cent with a corresponding transmission of 0.4 to 1.5 per cent.