Seventy-nine γ-rays, three of which are reported here for the first time, have been observed in the decay of 231Pa. The internal conversion electron spectrum has been studied using a trochoidal spectrometer, and the internal conversion coefficients of transitions between 240 and 410 keV have been determined. The αK values for four of the transitions, viz. those at 243.15, 255.76, 277.10, and 407.80 keV are here reported for the first time. Two levels at 508.9 and 576.6 keV proposed by de Pinho et al. as higher spin states of the case12−(530) rotational band have been confirmed. Reduced transition probabilities of inter- and intra-band transitions have been determined and compared with theoretical predictions. An estimate of Q0, gR and gK is presented.

The decay of 233U was examined using Ge(Li) and Si(Li) gamma ray spectrometers in singles and coincidence configurations. Chemical separation of the contaminating daughter products was effected through anion exchange. Of the 117 gamma rays observed here, 26 are reported for the first time. Four new levels, having excitation energy 235, 340, 436.7 and 478.7 keV, are proposed for 229Th. The lowest-lying levels are discussed within the context of the Nilsson model including Coriolis mixing effects.

The decay of 233U was examined using Ge(Li) and Si(Li) gamma ray spectrometers in singles and coincidence configurations. Chemical separation of the contaminating daughter products was effected through anion exchange. Of the 117 gamma rays observed here, 26 are reported for the first time. Four new levels, having excitation energy 235, 340, 436.7 and 478.7 keV, are proposed for 229Th. The lowest-lying levels are discussed within the context of the Nilsson model including Coriolis mixing effects.

The decay of 237Np has been investigated from singles and coincidence γ-ray spectra acquired using Ge(Li) detectors. Forty-two γ rays have been observed and all but one have been placed in the level scheme of 233Pa. The presence of unobserved transitions of low energy has been confirmed by the coincidence data. Five new γ rays are reported here and a new level in 233Pa at 303.8 keV is proposed.

Twenty-eight γ-rays, ten of which are reported for the first time, have been observed in the decay of 235U, and all have been placed in a revised level scheme for 231Th. Three new levels at 390.27, 317.42 and 240.82 keV respectively have been proposed and the data are in accord with he results of coincidence studies. Reduced transition probabilities of inter-band γ-ray transitions are calculated from the data and compared with theory and an estimate of the intrinsic quadrupole moment, QO has been computed.

High-resolution γ-ray studies have shown the decay patterns of 203Bi and 204Bi to be very complex with 79 γ-rays assigned to the former decay and 169 to the latter. Conversion coefficients were calculated for 17 transitions in 203Pb and 56 in 204Pb and are compared with earlier results. Spin and parity assignments are given on the basis of the multipolarities of de-exciting transitions. Level schemes are discussed for both decays.

SynopsisThe shape factors of the partial β-spectra of highest end-point energy in the decay of 72Ga and 140La have been calculated and compared with the only previously reported determination of these quantities. For both isotopes the shape factor is consonant with the view that the Blj matrix element controls the decay. Shape factor analysis alone is insufficient to determine the cause of the predominance of a particular matrix element.

Fifty-five γ-rays have been observed in the decay of201Pb and levels in201Tl are indicated at 1134.87, 1330.24, 1419.96, 1639.52 and 1671.99 keV. Conversion coefficients have been calculated for many of the transitions and compared with earlier results. Spin and parity assignments to the levels of 201Tl were made on the basis of the multipolarity of de-exciting transitions. A level scheme is proposed.

Gamma-rays of energy 130.7, 222.0, 271.2, 294.0, 401.8, 516.5, and 677 keV and absolute intensity (%) 0.104, 0.028, 9.93, 0.059, 6.48, 0.022 and ≈ 0.006 respectively have been observed in the decay of 219Rn. Conversion electron studies show the 130.7 and 271.2 keV transitions to be M1 + 25 % E2 and 93.6 % E2 + 6.4 % M1 respectively. The 401.8, 294 and 222 keV transitions appear to be E2, M2 and E2 respectively. The 6.551 MeV α-271.2 keV γ directional correlation gave A22 = −0.108 ± 0.073 and A44 = −0.170 ± 0.056. The sequence 32−52−72 is proposed.