J. J. Pinajian

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 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.

Total and K conversion coefficient measurements in 54Cr, 65Cu and 88Sr for use as standards

Abstract Total and K-conversion coefficients were measured for the 835.0, 898.2 and 1115.6 keV transitions in 54 Cr, 88 Sr and 65 Cu, respectively ( α K × 10 6 = 224 ± 10, 301 ± 21, 166.4 ± 6.6, respectively). These isotopes provide useful α K calibration standards for decay scheme studies.

PRECISION GAMMA-RAY ENERGY MEASUREMENTS.

Abstract The energies of several transitions which are useful as calibration standards over the energy range 800–1850 keV have been measured with an accuracy of 0.10 keV.

Decay of 67Cu

Abstract The γ-rays following the β-decay of 67 Cu have been investigated with a high-resolution Ge(Li) detector. The 67 Cu was produced by double neutron capture on 65 Cu. Gamma rays of energies (and relative intensities) 91.26 (155), 93.25 (360), 184.53 (1000), 208.95 (2.4), 300.22 (15.7) and 393.60 (4.3) keV were observed. The γ-rays have been incorporated in a level scheme of 67 Zn with levels (and spins and parities) at 0( 5 2 − ), 93.3 ( 1 2 − ), 184.5 ( 3 2 − ) and 393.5 ( 3 2 − ) keV .

Precision gamma-ray spectroscopy on the decay of 168Tm

Abstract Precision gamma-ray energy and intensity measurements have been made on the decay of 87 d 168 Tm. The uncertainty in energy of the more prominent gamma rays ranged from 20 to 40 eV, and the uncertainty in the relative intensity varied from 1 to 5%. The available conversion electron intensity data were used with the data here to calculate internal conversion coefficients. A decay scheme consistent with these results is presented, and several ambiguities of the previous 168 Tm decay schemes have been resolved. The E2 branching ratios from the gamma vibrational band to the ground state band were calculated and, when compared to band-mixing theory, gave the following values for the vibration-rotation coupling parameter z 2 : 0.0278 ± 0.0055, 0.0284±0.0091, 0.0283±0.0056, 0.0314±0.0025 and 0.0329±0.0015. A weighted average of the values is 0.0320±0.0013.

The decay of 151Gd to the levels of 151Eu

Abstract The γ-rays of 151 Eu have been investigated with a 35 cm 3 Ge(Li) detector coupled to a 4096-channel analyser. Gamma rays of the following energies and intensities (in parenthesis) were found to decay with the half-life of 151 Gd: 106.51±0.06(1.29), 110.53±0.11(0.12), 153.57±0.06(100), 174.65±0.06(48.3), 196.46±0.09(0.45), 239.00±0.14(2.31), 243.22± 0.06(89.9), 260.39±0.09(0.84), 286.00±0.09(1.35), 307.43±0.09(16.5), 328.23±0.09(1.32), 332.13±0.12(0.17) and 353.51±0.09(2.04). Using the energy sum rules and coincidence relationships the levels at 21.54, 196.21, 196.46, 243.22, 260.44, 306.99, 307.47, 349.76 and 353.56 keV are proposed for 151 Eu. A decay scheme consistent with our results is presented. The present studies support the previously proposed collective states.

High spin rotational states in 154Dy, 164Er And 162Yb

Abstract High spin rotational states in 154 Dy, 164 Er and 162 Yb have been investigated with (α, 4nγ) and (α, 6nγ) reactions. The ground state rotational bands have been identified up to spin 14 for 154 Dy and 162 Yb and spin 16 for 164 Er. Anomalous behaviour of the moment of inertia has been observed in 164 Er.

Conversion electron measurements in the decay of156Tb

The conversion electron spectrum from the decay of156Tb to156Gd was measured with an iron, double-focusing spectrometer. TheK conversion coefficient of the 1222.4 keV transition was measured relative to theK conversion coefficient of the 661.6 keV transition in137Cs and found to be 0.00174±0.00013. This result was used to normalize electron and gamma-ray data to obtain theK conversion coefficients of 33 transitions in156Gd. The 1009.6 and 1040.6 keV transitions have largeE0 components.

The decay of 1.3 min 82Rb to levels in 82Kr

The γ-spectra from 82Rb (T12 = 1.3 min) have been measured with a 30 cm3 Ge(Li) detector in singles and in coincidence with a 12.7 cm × 12.7 cm Nal(Tl) scintillation detector. Ten γ-rays were observed. Portions of the γ-spectrum from 82Br(T12 = 35.5 h) were also studied. It is proposed that the decay of 82Rb (Jπ = 1+) populates levels in 82 Kr at 2171.8, 2480, 2945 and 3190 keV in addition to the known levels at 776.55 and 1474.9 keV. Limits on probable spin and parity values for the newly introduced levels have been established.