abstract

A number of rotational bands have been found in light-lead nuclei. But the transitions between the states are predominantly of M1 multipolarity rather than E2. In at least one case where the lifetimes were measured, the values of B(M1) found were among the largest known, while the values of B(E2) for two crossover transitions are relatively small, of order 15 single-particle units. These bands also show other interesting properties, and the connecting transitions to the lower bands in the nucleus have usually not been found.

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Suggestion of a more detiled analysis of the moments of inertia J(2) in varions rotational bands and their relations to other features of nuclear structure such as the nature of band-heads in odd-A nuclei, the variation of nuclear pairing, deformations, aligments etc.

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Main characteristics together with the first results obtained which are related to the decay out of the superdeformed band in the nucleus 133Nd is presented.

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The band structure observed in high-spin spectroscopy is illustrated through typical examples. The question whether observed alternating parity bands within a nucleus originate from a single intrinsic orbital is considered. Future directions in the experimental exploration of octupole deformed nuclei are suggested.

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A new device for the detection of evaporation residues in coincidence with \(\gamma \) rays in heavy-ion induced reactions is presented. This new detector mainly discriminates against fission and allows Doppler corrections of the \(\gamma \) spectra. As a first application, the level schemes of the neutron deficient lead isotopes \(^{188}\)Pb and \(^{186}\)Pb have been studied for the first time at the VICKSI accelerator. Both nuclei exhibit a structure different from heavier even–even Pb isotopes and show low-lying rotational bands.

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The nuclear structure studies of the neutron-rich nuclei represent a vibrant and fast progressing field. A review is given of a few regions of critical importance to nuclear structure that are now accessible exclusively by mass separation techniques of fission or spallation products. In particular, recent results on the doubly-magic \(^{132}\)Sn are discussed as well as those for the low-lying bands in the neutron-rich \(A \sim 100\) and \(A \sim 150\) regions: discrepancies between the shape-coexistence interpretation and the experimental results on the shape-coexistence regions of heavy Sr/Zr, Cd/Sn and Sm/Gd, the ‘correspondence interpretation’ of transitional Sm/Gd, suggestion that the \(\beta ^{\prime }\) band in the transitional Sm/Gd nuclei represents a new mode of intrinsic excitation in par with the \(\beta \) and \(\gamma \) modes, and the issue of ‘di-nature’ of the excited \(0^+\) bands. The latter, relates to a seemingly contradictory feature shown by the excited \(0^+\) bands, which behave like a weakly mixed (independent) second ground state with its individual properties (like moment of inertia) and at the same time like proper members of the g.s. structure.

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The features of the fission process which determine precisely what range of nuclei can be studied will be discussed.

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\(E1\), \(E2\) and \(E3\) matrix elements have been measured using Coulomb excitation for \(^{148,150}\)Nd and \(^{226}\)Ra. The behaviour of the quadrupole and octupole matrix elements is roughly consistent with that expected for a rotating axially symmetric shape, although deviations are seen for the Nd isotopes. The results are compared with theoretical expectations.

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We will discuss this important feature of the nucleus as a finite many-body system.

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Some of the phenomena which are observed and which provide new and basic information on the timescales associated with the hot compound nucleus will be discussed.

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In this lecture we shall concentrate on the research program around the two main instruments IGISOl and RITU under the construction in the laboratory.

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The status of research in double beta decay is reviewed. Double beta decay experiments yield at present the sharpest limits on the electron neutrino mass, right-handed coupling constants, the neutrino-Majoron coupling constant, and the best laboratory limit on the half-life of electron decay. A new era of second generation \(\beta \beta \)-experiments just started and will be dominated by use of enriched detectors. One of the most advanced projects is the HEIDELBERG–MOSCOW experiment having at its disposal 16.9 kg of enriched \(^{76}\)Ge. Concerning the calculations of nuclear matrix elements for \(\beta \beta \) decay, a major step beyond the frequently used QRPA model has been made by introducing the Operator Expansion Method.

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Is there some simple way of estimating \(\rho (\vec r)\) without going through the misery of numerically solving N partial differebtial Schrödinger equations for the N particles?