The lifetimes of eight lower spin levels of the yrast band in 168Yb, populated via the 154Sm(18O,4n) and 124Sn(48Ca,4n) reactions, were measured, six of them for the first time, by means of the recoil-distance Doppler-shift method. Two versions of the differential decay-curve method have been applied for the data analysis resulting in a very good agreement. The reduced transition probabilities indicate some reduction of the collectivity for states just above the 61+ level, i.e. well below the band-crossing. The reasons of this effect are discussed in terms of an interaction between the ground-state band and yet unknown part of the two-quasiparticle (ν13/2) spin-aligned S-band by invoking the shell-structure or alternatively/additionally, as changes in the internal structure/shape induced by the rotation.

A previously-unmeasured neutron-rich nucleus Ir-199 has been produced by the exotic transfer reaction Pt-198(O-18, F-17)Ir-199. A Q-value of -8.240 +/- 0.041 MeV has been determined for the ground state of this reaction. This result yields a mass excess for Ir-199 of -24.425 +/- 0.041 MeV. Excited states in this nucleus are indicated in the region of 160 and 240 keV. The new result for the mass excess, together with existing ones, has been used to investigate systematic trends in the n-p interaction strengh across the Z = 82 and N = 126 shell closures.

The decay of the yrast and near-yrast high-spin states in 161Tm has been observed following the reaction 128Te(37Cl,4n). Extension of the known level scheme reveals previously unobserved crossings in the bands built on the 72−[523], 72+[404] and 12−[541] Nilsson states. The use of both gold- and terbium-backed targets has enabled the measurement by the Doppler shift attenuation method of lifetimes of states in the h112 yrast band in the spin range 412 ⩽ I ⩽ 672. The results show little evidence for change in the nuclear deformation over this interval in spin (Qt ≈ 6 eb). From lifetime measurements and B(M1)B(E2) values in the h112 band, absolute B(M1) values for five transitions (for states with 412 ⩽ I ⩽ 512) were determined. These results provide some evidence for a reduction in the proton spin projection on the deformation axis relative to its value at low rotational frequency. The signature splitting in the Routhians and B(M1)B(E2) values for the h112 band is discussed in terms of the inclusion of non-axially-symmetric (γ-deformed) components in the nuclear wavefunction.

A Q-value of −8.240 ± 0.041 MeV has been determined for the exotic transfer reaction: 198Pt(18O, 17F) 199Ir. This result yields a value of −24.425 ± 0.041 MeV for the mass excess of the previously-unmeasured nucleus, 199Ir. Excited states in this nucleus are indicated in the region of 160 and 240 keV. The new result for the mass excess, together with existing ones, has been used to investigate systematic trends in the n-p interaction strength across the Z = 82 and N = 126 shell closures.

High-spin states of W-171,W-172 have been investigated using the reaction Nd-146 (Si-30,5n-4n) at a bombarding energy of 160 MeV. In W-171, four negative-parity and two(three) positive-parity bands have been established. A favoured (-, -1/2) configuration based on the (-, +1/2) configuration (E) coupled to the (+,1) configuration (AC) is suggested to be the nature of the continuation of the (-, -1/2) band above the AB crossing. This would be the first observation of the EAC configuration. The positive-parity decay sequences in W-171 provide an interesting extreme signature dependence for the interband M1 transition matrix elements, which is found to be well accounted for by theoretical expectations. In W-172 four negative-parity bands are established besides the positive-parity yrast sequence.

The level structure of 169Ta has been studied using the reactions 155Gd(19F,5n), E = 85.5–100 MeV and 122Sn(51V,4n), E = 223 MeV. Four rotational bands of 169Ta have been identified with assignments 12−[541], 92−[514], 52+[402], 12+[411] and a decoupled band was identified but not assigned to any configuration. Different configurations are observed to have different band-crossing frequencies and these differences are consistent with configuration-dependent deformation driving effects. The crossing frequency of the band based on the 12−[541] configuration is deduced to be 0.305MeV/ħ which is delayed by about 55 keV in comparison with the yrast bands of its even neighbours. The first band crossings of 169Ta are attributed to the alignment of a pair of i132 quasineutrons, while the second band crossings may correspond to h112 two-quasiproton alignment. The deformation driving effects of quasiparticle orbitais, B(M1)/B(E2) values of the 92−[514] and 52+[402] bands and the band crossings in 169Ta are discussed.

The two-quasiproton structure of 174Yb has been investigated in a study of the 175Lu(t,α)174Yb reaction. The reaction was performed using a 35.5 MeV triton beam delivered by the Daresbury tandem Van de Graaff accelerator. Magnetic analysis of ejectile ions was achieved using a QMG2 magnetic spectrometer and ion identification and detection employed a hybrid gas-filled, multielement, focal plane detector. Elements of the detailed nuclear structure of 174Yb are discussed in terms of the two-quasiproton configurations populated. Of particular interest is a low-lying Kπ = 3+ band, observed in this reaction and discussed in terms of hexadecapole collectivity. No Kπ = 1+ bands were observed, and the consequences of this for a microscopic description of the magnetic-dipole-strength distribution in 174Yb are discussed.

The two-quasiproton structure of 164Dy has been investigated in a study of the 165Ho(t, α) 164Dy reaction. The experiment was performed using a 37.3 MeV triton beam delivered by the Daresbury tandem Van de Graaff accelerator. Magnetic analysis of ejectile ions was achieved using a QMG/2 magnetic spectrometer, and ion identification and detection employed a hybrid gas-filled, multielement, focal-plane detector. The two-quasiproton strengths accessed in this reaction are discussed with reference to the detailed spectroscopy of 164Dy. In particular, a rotational band built on a Kπ = 1+ state, previously interpreted as a collective structure, was observed and assigned as a two-quasiproton excitation which at zero deformation is based on the spherical (h112)2 shell-model state. The structure of the octupole-vibrational band and that of other states in the final nucleus have been elucidated.

A new nucleus 199Ir has been produced using the exotic transfer reaction 198Pt(18O, 17F)199Ir at 140 MeV. The mass of 199Ir has been measured by the determination of the reaction Q value. Its mass excess is -24.424 ± 0.034 MeV.

High-spin states in 171Re have been studied using the reaction Sb-123(Cr-52,4n)171Re. A back-bend in the i13/2 band of a Re nucleus has been fully delineated for the first time. A new back-bend has also been observed in the 5/2+[402] band and other bands have been extended to higher spin and added to the level scheme. Band crossings are interpreted using the CSM and three-band mixing calculations. These appear to show evidence for shape coexistence and configuration-dependent neutron pairing.

Excited states in 167Ta and 168Ta, populated in the 142Nd(30Si, pxn) reaction, were investigated using the ESSA30 array with 29 Compton-suppressed Ge detectors. Several rotational decay sequences are identified and for the first time a high-spin level scheme is established for these nuclei. The results for 167Ta are discussed in comparison with existing data in the neighbouring nuclei and with cranked shell model calculations. The possible intrinsic structure and its consequences for the yrast band in 168Ta are also briefly discussed.

High-spin states of 174Os have been investigated by means of the 146Nd(32S,4n)174Os reaction using the ESSA30 multidetector system. The decay is dominated by the ground-state positive-parity band, two negative-parity 4− and 5− bands and another band starting at spin 9. Deformed shell-model calculations have been carried out to interpret the observed band structures. The role of the strongly shape-driving, non-aligned, πh92 configuration in the low-spin region of the ground-state band is discussed. The first band crossing is interpreted as due to the νi132 alignment. The two lowest side-bands are understood in terms of coupling to octupole excitations.

This paper presents the results of tests, both with sources and in-beam experiments, on prototype Ge and BGO detectors of the Eurogam array. Timing and energy resolution data are reported along with results for various methods of ballistic deficit correction. The first measurements with the new "shared suppression" technique are presented.

Preliminary results are presented from internal conversion electron and gamma decay measurements following 245Cm α-decay which are underway at the National Physical Laboratory, U.K. Multipole mixing ratios, from relative subshell intensities, have been established experimentally for the following transitions: 42, 54, 57, 79, 133, 136, 175 and 190 keV. This is the first time that mixing ratios have been determined experimentally for transitions following the parent decay. The measured values are compared with the previously adopted values. Relative gamma ray intensities are given for 12 transitions and these are also compared with the currently adopted values.

Excited states in 167W and 168W, populated in the 142Nd(30Si, xn) reaction, were investigated at high spins using the ESSA30 array with 29 Compton-suppressed Ge detectors. The level schemes are extended to higher spins and several new rotational bands are identified. The results are discussed in comparison with existing data on the neighbouring N = 93 and 94 isotones and on the Z = 74W isotopes. A theoretical analysis is presented within the framework of a pairing-self-consistent cranked shell model using shape parameters obtained from total-routhian-surface calculations.

For the first time, excited states of 175Ir have been observed. Remarkably different developments with rotation are found in bands built on the [541]1/2-, [505]11/2-, and [660]1/2+ orbitals. The data are analyzed within the deformed shell model. The pattern of the [505]11/2- band is interpreted as a combined stretching and alignment effect. For the [606]1/2+ band, an extremely strong interaction with the S band results in an almost entirely smeared out alignment process not explained by standard calculations. This feature might indicate a strong residual pn interaction.