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The structure of 91Y has been studied using the 92Zr(t, α)91Y and 89Y(t, p)91Y reactions. The fact that the ground states of 92Zr and 89Y have spin-parities of 0+ and 1 2 − , respectively, made it possible to assign uniquely the spins and parities to nine levels in 91Y for which unambiguous determinations of the trasferred angular momenta were obtained in both the (t, α) and (t, p) experiments. A comparison of the experimental results with shell-model calculations in which 88Sr was considered a closed core shows significant disagreement, and it is concluded that there must be appreciable contributions of particle-hole excitations from at least the (2 p 3 2 ) and (1 f 5 2 ) shells.

A fast tape transport system has been developed for transporting samples collected from the ion beam of an isotope separator to a low background area. The unusual features of the system are its tape speed (up to 585 cm/s) and the fact that the tape system operates entirely in air except for the collection point on the tape at the end of the beam line.

Average radiation widths 〈Γ γ 〉 are calculated by a method that permits application to exotic nuclei where little spectroscopic information is available. The calculations are tested against 62 near-stable nuclei and - for the first time this has been possible - against 5 exotic nuclei for which 〈Γ γ 〉 has now been measured. Excellent results are obtained if level densities are calculated with the back-shifted Fermi gas model but not if Gilbert and Cameron densities are used.

In contradiction with a recent publication, we demonstrate that data on the β -decay of 145 Gd confirm in all respects the statistical conclusions derived in 1977 from a computer-simulated decay of the fictional nucleus, Pandemonium. Complex β -decay schemes based on singles spectra of β -delayed λ -rays must still be regarded as doubtful.

Experimental ƒt -values are used to examine various theoretical treatments of analogue symmetry breaking in superallowed Fermi β-decay. None of the fits to experiment in more than barely acceptable and, contrary to a previous analysis, we find no clear preference for one type of treatment over another.

The excitation energy of the lowest 0+ T = 2 state in 28Si was measured to be 15.206 ± 0.025 MeV. The state decays predominantly by isospin-forbidden α-particle emission. Its analogue in 28Al was also observed at 5.983 ± 0.025 MeV.

The first significant disagreement with recent “exact” shell-model calculations occurs in 17O(p, d)16O at Ep = 31 MeV. The 4+ level at 10.36 MeV has < 5% of its predicted intensity. Little 1p32 strength appears below 18 MeV excitation in agreement with the model.

Half-lives for 26 Al m , 34 Cl, 38 K m and 42 Sc are measured to be 6351 ± 10, 1534 ± 3, 929.2 ± 3.5 and 684.5 ± 1.2 ms, respectively. The results for 34 Cl and 38 K m are substantially lower than previously accepted values and tend to bring the ft -values into agreement with other superallowed decays. The mirror asymmetry for mass 34 becomes Δ = (−2.5 ± 1.7)%.

By consideration of the 28Si(t,p)30Si reaction, the sign of the interaction matrix element 〈d 3 2 2 ωVωs 1 2 2 〉 J=0 is determined to be negative, and the sign of 〈d 3 2 2 ωVωs 1 2 d 3 2 〉 J=2 to be positive. The method has quite general applications.

With the increasing accessibility of nuclei far from stability, experimenters find themselves faced more and more often with complex s-decay schemes: nuclei with over 5 MeV of s-decay energy, exhibiting hundreds and perhaps thousands of transitions. A detailed level-by-level exposition of such schemes - for example, by studying s-delayed γ-rays - is at best prohibitively time consuming, and at worst actually impossible with current techniques1. Furthermore, even if reliable schemes are obtained experimentally, their confrontation with theory is severely limited by the absence of theories sufficiently complete to account for such complex spectra. At best, it is the details of the first few excited states and the general features of the rest that are useful for comparison. From both points of view, experimental and theoretical, there is strong motivation to find a broader perspective, emphasizing these general features without being overwhelmed by a proliferation of detail.

Two new beta -delayed proton precursors, /sup 97,99/Cd, have been identified at the ISOLDE on-line isotope separator. The proton branching ratio for /sup 99/Cd is 1.7(+1.1, -0.5)*10/sup -3/. The /sup 99/Cd proton spectrum is discussed in terms of the statistical model with Porter-Thomas fluctuations. The half-life of /sup 99/Cd was determined to be 16+or-3 sec. A search for /sup 98/Cd was also performed and it was found to be a pure beta -emitter with a probable half-life of approximately=8 sec. (18 refs).

A new nuclide, /sup 35/K, has been identified and its decay has been studied. Its half-life was determined to be 190+or-30 ms. Spectra of beta -delayed protons and gamma -rays from the decay of this nuclide have been obtained. A decay scheme is proposed, taking into account 18 of the 19 observed gamma -rays and 5 of the 10 observed proton groups. Log ft values have been deduced for 11 beta -transitions populating excited states in /sup 35/Ar. These values and the level structure in /sup 35/Ar are compared with shell-model calculations. (19 refs).

The 10/sup -16/ second lifetimes of proton unstable states in /sup 73 /Br have been measured by using the particle X-ray coincidence technique. Comparison with statistical model calculations shows no significant evidence of lifetime anomalies that might be attributed to local properties of nuclear structure. (18 refs).

Lifetimes in the region of 10 −16 s have been measured for excited states between 4 and 6.6 MeV in 73 Br. The states were produced by the β + (EC) decay of a mass-separated source of 73 Kr, and they decayed by the emission of protons or γ-rays; their lifetimes were measured by the particle X-ray coincidence technique. The data yield information on both γ-ray and proton partial widths as well as on the level density, a level density parameter- a = 13.7 MeV −1 is obtained. With the level widths so determined, a statistical model calculation yields excellent agreement with the delayed proton spectrum if a smooth gaussian β-strength function is employed. It is concluded, however, that without the lifetime data, β-strength function information could not have been reliably extracted.

The branching ratio for the decay of /sup 35/Ar to the first excited state in /sup 35/Cl has been measured to be (1.34+or-0.08)% with the ISOLDE on-line isotope separator. Combining this result with previous data leads to the value (98.28+or-0.06)% for the branching ratio of the ground state (superallowed) transitions. This does not resolve the apparent anomalousness of the derived Cabibbo angle for this transition, which now stands at theta /sub v/

Gamma and electron spectroscopy have been used to study β‐ and γ‐decay of neutron‐deficient Gd and Eu because of the proposed 64−proton shell closure. The Gd isotopes were produced via the 144Sm(3He,xn)147−xGd and the 112Sn(32S,2pxn)142−xGd reactions at the Foster Radiation Laboratory (McGill University, Montreal) and the MP Tandem at the Chalk River Nuclear Laboratories, respectively. (AIP)

The reactions 36 Ar(p, t) 34 Ar, 36 Ar(p, 3 He) 34 Cl and 36 Ar(d, α) 34 Cl have been used to study energy levels in 34 Ar and 34 Cl. Excitation energies and J π values have been established for states up to 8 MeV in 34 Ar, and many of their T = 1 analogues have been identified in 34 Cl. These results exemplify the usefulness of the spin and isospin selection rules inherent in two-nucleon transfer reactions. The results are discussed in terms of the mass-34 T = 1 multiplet and the J -dependence of their Coulomb displacement energies.

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A fast gas-sweeping system has been developed which enables activities to be transported up to 5 m from the target position in 50–100 ms. It has been used along with a cooled semiconductor-counter telescope to obtain delayed-proton spectra in which the energy resolution was limited to 45 keV by kinematic effects. The remote counting location also permits use of a Ge(Li) detector without fear of radiation damage. Several different high-yield target configurations are described, including a sulfur target that is useful for prolonged high-intensity bombardments.

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The (V-A) structure of the weak interaction was put into the standard model by hand in order to obtain agreement with experiments. These experiments, however, do not rule out relatively large deviations from this structure. Muon decay provides an ideal laboratory to test this structure, being a purely leptonic process. The TRIUMF Weak Interaction Symmetry Test (TWIST) will measure both the energy and emission-angle distribution of positrons from the decay of polarized muons. This will provide a simultaneous determination of the Michel parameters Pμξ, ρ and δ describing muon decay with a precision of a few parts in 104. Stringent limits may then be placed on the coupling constants, as well as the mass and mixing angle of a possible right-handed W boson (WR). In this paper the formalism for muon decay is presented, TWIST is described, and the expected results are discussed.

A simple dual-mode conical horn has been developed and tested at 0.5, 1.4, 3.1, and 34.2 mm. The horn has nearly equal beam shape in the E and H plane far field patterns with a 3-dB half angle of 6°. At 34.2 mm, the waveguide reflection loss and the phase center have been determined.

The anomalous behaviour of 35 Ar decay could be consistent with the suggestion of Salam and Strathdee that the Cabibbo angle vanishes at high magnetic fields.

The structure of140Eu has been investigated through the decay of140Gd, which has a measured half-life of 16.2±0.8 s. A decay scheme is constructed, which comprises 22 transitions depopulating 16 excited states.