Exotic nuclei

All the classic methods apply here, nothing very new has appeared, although some exotic nuclei in NMR have been applied to the study of tautomerism. 

Matsson, O., Isotope Effects for Exotic Nuclei, in A. Kohen and H.H. Limbach, Eds. Isotope Effects in Chemistry and Biology, CRC Press/Taylor Francis, Boca Raton, FL, 2005. 

Exotic Nuclei and Their Decay. As reported by J.C. Hardy (Chalk River Nuclear Laboratories. Atomic Energy of Canada, Ltd.), recent advances in nuclear accelerators and experimental techniques have led to an increasing ability to synthesize new isotopes. As isotopes are produced with more and more extreme combinations of neutrons and protons in their nuclei, new phenomena are observed, and the versatility of the nucleus is increased as a laboratory for studying fundamental forces. Hardy reports that, among the newly discovered decay modes are (1) proton radioactivity, (2) triton, two-proton, two-neutron, and three-neutron decays that are beta-delayed, and (3) 14C emission m radioactive decay, Precise tests of the properties of the weak force have also been achieved. 

The fundamental usefulness of exotic nuclei and their decay assures a continuing interest in the field. New heavy-ion accelerators will ensure that... 

The population of high-lying unbound states by (3 decay is an important feature of nuclei near the driplines. 3-Delayed proton emission and (3-delayed neutron emission have been studied extensively and provide important insight into the structure of exotic nuclei. 

A continuing effort among experimentalists who study nuclei far from beta stability is the measurement of the atomic mass surface As a manifestation of the nuclear force and the nuclear many body system, atomic masses signal important features of nuclear structure on both a macroscopic and microscopic scale It has thus been a challenge to nuclear theorists to devise models which can reproduce the measured mass surface and to predict successfully the masses of new isotopes Both the measured mass surface and that beyond it which can be predicted by these models serve as important input to a variety of fundamental and applied problems, e g, nucleosynthesis calculations, predictions of decay modes of exotic nuclei far from stability, nuclear de-excitation by particle evaporation, decay heat simulations, etc ... 

The Tandem Accelerator Superconducting Cyclotron facility at Chalk River, which is nearing completion of phase 1, will be capable of accelerating all ions to at least 10 HeV/u. Together with the on-line isotope separator it will provide a powerful means of studying exotic nuclei ... 

Undoubtedly the Chalk River ISOL will be used, as others are, in the identification and spectroscopy of exotic nuclei. The nuclear chart in figure 5 illustrates the scope for such studies. However, the extreme purity of isotopes separated by our ISOL has been essential in the past to precision studies of the weak interaction, in one case the lifetimes of superallowed 0+ 0+ transitions [K.OS83], in another 8-v-a triple correlation coefficients in the decay of 2( Na [CLI83] both yielded measurements of the weak vector coupling constant. These types of measurements will be extended to other nuclei, since they exploit the best qualities of the accelerator and separator. 

We expect direct mass measurements to form an important component of the exotic-nuclei program at TASCC. Indeed, we already hope to upgrade our facilities through a proposal made in collaboration with the University of Manitoba to build a high-transmission mass spectrometer, which could accept beam from the ISOL directly without reionization, again making use of the ISOL s excellent beam quality. This could improve the precision of measurements to a level rivalling that now possible with stable isotopes. 

Chalk River is not the only laboratory with an isotope separator on-line to a heavy-ion accelerator, Berkeley, Oak Ridge and GSI Darmstadt have already proven the value of such a combination in studying exotic nuclei. We believe that the versatility and energy range of TASCC, together with the proven quality of separated beams from the ISOL, will make the Chalk River facility among the best in the field. 

In recent years there has been a rapid increase in our knowledge of the atomic-mass surface far from the valley of 0 stability [BEN80,CER8l]. However, even with these advances there remain more than 60 neutron-rich nuclei with A < 70 for which the only known information is that they are stable with respect to neutron emission. It is clear that more detailed information about these exotic nuclei is essential. Especially important are the measurements of ground state atomic masses, since the ground state mass is one of the most fundamental properties of a nucleus. 

Nuclear reactions producing exotic nuclei at the limits of stability are usually very non-specific. For the fast and efficient removal of typically several tens of interfering elements with several hundreds of isotopes from the nuclides selected for study mainly mass separation [Han 79, Rav 79] and rapid chemical procedures [Her 82] are applied. The use of conventional mass separators is limited to elements for which suitable ion sources are available. There exists a number of elements, such as niobium, the noble metals etc., which create problems in mass separation due to restrictions in the diffusion-, evaporation- or ionization process. Such limitations do not exist for chemical methods. Although rapid off-line chemical methods are still valuable for some applications, continuously operated chemical procedures have been advanced recently since they deliver a steady source of activity needed for measurements with low counting efficiencies and for studies of rare decay modes. The present paper presents several examples for such techniques and reports briefly actual applications of these methods for the study of exotic nuclei. 

The referencing of more exotic nuclei is generally less clear-cut than for those in common use and in many cases it is impractical to add reference materials to precious samples, and it is sometimes even difficult to identify what substance is the accepted reference standard. In such cases the S-scale can be used, which does not require use of a specific reference material. Instead this scheme defines the reference frequency for the referenee material of each nuclide at a field strength at whieh the proton signal of TMS resonates at exactly 100.000 MHz. The reference frequencies are scaled appropriately for the magnetic field in use and this then defines the absolute frequency at 0.0 ppm for the nuclide in question. The S values for selected nuclei are also summarised in Table 3.3, whilst more extensive tables are available [19]. 

Production and properties of exotic nuclei are the focus of another forefront development accelerators capable of producing, in a first step, beams of radioactive nuclei, which are then... 

Strutinsky VM (1967) Nucl Phys A 95 420 Strutinsky VM (1968) Nucl Phys A 122 1 Suzuki Y, Lovas RG, Yabana K, Varga K (2003) Structure and reactions oflight exotic nuclei. Taylor Francis, London... 

Nagame Y, Asai M, Haba H, Tsukada K, Goto S, Salima M, Nishinaka I, Toyoshima A, Akiyama K, Ichil wa S (2002b) J Nucl Radiochem See 3 129 Nal matsu H, Adachi H, Mukoyama T (1992) Bull Inst Chem Res Kyoto Univ 70 16 Nal matsu H (1995) Chem Phys 200 49 Nash KL, Choppin GR (eds) (1995) Separation of f-elements. Plenum Press, New York Ninov V, Gregorich KE, McGrath CA (1998) In Sherrill BM, Morrissey DJ, Davids CN (eds) Exotic nuclei and atomic masses, AlP conference proceedings 455, American Institute of Physics, Woodbury/New York, pp 704-707... 

His research field is nuclear theory reactions, clustering, cluster decay and light exotic nuclei. He is a coauthor of the monograph Structure and Reactions of Light Exotic Nuclei (2003). 

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