The reaction64Ni(36S,34Si)66Zn atE=198 MeV has been used to measure the mass excess of34Si; a value of −19.971 −0.044 +0.037 MeV was obtained. This result which is in agreement with the previous value (−19.85±0.30 MeV) is in excellent agreement with recent shell-model mass predictions. The result is discussed within the context of the proposed region of deformation aroundZ=11,N=20.

The design, construction and performance of a modular, two pressure focal plane detector, 550 mm long, 1000 mm deep and with an active height of 60 mm are described. The detector has been operated with ions ranging from 50 MeV 1H to 200 MeV 36S. Typical results achieved are 0.5 mm and 0.3° for the spatial and angular resolutions, and 0.7% and 3% for the total energy and energy loss measurements. A height signal is also provided.

The 18O + 61,64Ni reactions at E = 150 MeV have been used to measure the mass excess of 21O; the value obtained was 8.057−0.020+0.010 MeV. Tentative evidence for excited states at excitation energies of 1.32 MeV and 2.23 MeV has also been found. The results are compared with current theoretical predictions.

Measurements are reported for the elastic and inelastic (478 keV excited state) scattering of 68 MeV7Li from a208Pb target. These are compared with coupled-channels and high-energy adiabatic model calculations, using an alpha-triton cluster structure description of7Li. In contrast to the results of fitting to the breakup cross sections, the purely nuclear contributions to the inelastic processes are too small in both models. Inclusion of a Coulomb amplitude in the coupled-channel calculation helps to fit the cross section at angles down to the grazing angle, but is too large at smaller angles. A DWBA Coulomb correction to the adiabatic model improves its ability to fit the data at angles except near grazing.

The direct breakup of 70-MeV $^{7}\mathrm{Li}$ scattered from a $^{120}\mathrm{Sn}$ target is investigated at forward angles. Inside the grazing angle, it is found that the breakup is dominated by the Coulomb interaction between projectile and target.

Cross sections, and for the first time analysing powers, have been measured in a kinematically complete determination of the 3He break-up on 12C, 27Al and 58Ni targets. A strong dependence of the 3He spin orientation has been found in the elastic channel, particularly for wide separation angles between the deuteron and proton.

An α-particle source and slotted entrance aperture has been used to investigate the optics of a magnetic spectrometer. The method described has proved to be a simple and accurate way of mapping out the focal plane, obtaining information about the aberrations, and hence determining the optimum field settings for some of the magnetic elements.

The effective field boundaries of a QMG/2 spectrometer have been experimentally determined and compared with the design. The results have been used to recalculate the ion-optics.

Two dimensional models of critical regions of the detector electrode geometry to the focal plane detector of the QMG/2 spectrometer have been studied numerically for a determination of the electric fields in these regions. The sensitivity of the charge collection to the geometry and bias potentials for several proposed designs was established, providing some general criteria for the operation of the detector.

Energy and angular correlations between α-particles and heavy ejectiles have been measured for 148 MeV 14N incident on 12C, 27Al and 58Ni targets. The coincidence cross sections for ejectiles with Z < 6 may be parametrised as a product of singles cross sections for the detection of α-particles and heavy ions. For 27Al and 58Ni targets, this indicates that the α-particles are emitted at an early stage of the reaction prior to the formation of the deep inelastic fragments. For the 12C target, however, kinematic effects are found to dominate the observed correlations. For Z ≧ 6 ejectiles the observed correlations appear consistent with the emission of α-particles from the recoiling nucleus produed in the reaction.

t a r g e t s o f 5 8 ~i , 2 7 ~~ 'AI I1'N Hl z I lLB MeV l d e g ) Fig.

Reactions induced by 105 MeV 13C ions on 52Cr have been investigated in the angular range 7°–20°. Optical model parameters derived from the elastic scattering data were used in a DWBA analysis of the inelastic scattering and single-nucleon transfer data. The DWBA calculations did not reproduce the shape of the angular distributions, unless an increase of 10% in the exit channel optical potential radius was introduced. A partial wave study of the total direct reaction cross section showed that, while these failures may be due to the neglect of two-step reaction processes, there is evidence that some of the fundamental assumptions of the DWBA may be invalid in these reactions.

In-plane angular and energy correlations between $\ensuremath{\alpha}$ particles and heavy ejectiles have been measured for the reaction $^{14}\mathrm{N}$ + $^{58}\mathrm{Ni}$ at 148 MeV. The coincidence cross sections may be parametrized as a product of singles cross sections for the detection of $\ensuremath{\alpha}$ particles and heavy ejectiles. The observed correlations indicate that the $\ensuremath{\alpha}$ particles are emitted at an early stage, prior to the formation of the deep-inelastic fragments.

In-plane angular correlations between α-particles and heavy ejectiles have been measured in the reactions 11B + 12C and 11B + 58Ni at 116 MeV incident energy. The observed correlations cannot be interpreted by a sequential mechanism.

It has been found that the timing resolution between two surface barrier detectors is degraded when they are separated to make a time-of-flight telescope. The degradation consists of a broadening of the peak with an asymmetric tail developing on the “early” time side of the peak. Measurement has shown that these effects vary progressively with the radial distance from the centre of the back detector. Ions which arrive closer to the edge of the detector produce a time peak which is shifted to earlier time than those which arrive in the centre. A further measurement has shown that only small changes in the pulse shape occur for these different events. The suggestion is made that the observed effect is predominantly due to different delays in the pulses which have to propagate different distances across the detector. The propagation velocity in this case was measured to be 20% that of light. An approximate treatment for the detector in terms of a simple delay line is capable of giving a reasonable description of the observed effects.

The tensor analysing power of the 27Al(d, 3He)26Mg reaction has been measured at Ed = 12.4 MeV. The results are reproduced by predictions of the DWBA including D-state components in the 3He wave function. The magnitude of the tensor analysing power provides information on the asymptotic D-state to S-state ratio in the 3He wave function. The value obtained for 3He is in agreement with the corresponding value for 3H.

States in 75Se have been excited by the reaction 72Ge(α, n)75Se and a level scheme built up from the observed γ-ray spectra. Gamma-ray angular distribution measurements have been analysed to yield spin assignments, mixing ratios and branching ratios. Comparison of the positive parity spectrum with the levels predicted by a Coriolis coupling calculation shows good agreement. In particular the model can successfully predict the occurrence of “anomalous” states with Jπ = 52+ and 72+ which lie close to the 92+ state in this nucleus, and which ar general feature of many neighbouring nuclei. Calculated E2 and M1 transition rates among these levels agree with available experimental data to within a factor of two. A strong case can therefore be made for regarding the low-lying levels in 75Se as arising from an odd neutron coupled to a deformed prolate core.