Direct Mass Measurements Of Light Neutron Rich Nuclei Using The Time Of Flight Isochronous Tofi Magnetic Spectrometer

The search for examples of proton radioactivity has resulted in the discovery of a large number of proton emitters in the region 50

This experiment has demonstrated that direct mass measurements can be performed (albeit of low precision in this first attempt) using the M proportional to ET2 method. This technique has the advantage that many particle-bound nuclei, produced in fragmentation reactions can be measured simultaneously, independent of their N or Z. The main disadvantage of this approach is that both energy and time-of-flight must be measured precisely on an absolute scale. Although some mass walk with N and Z was observed in this experiment, these uncertainties were largely removed by extrapolating the smooth dependence observed for known nuclei which lie closer to the valley of .beta.-stability. Mass measurements for several neutron-rich light nuclei ranging from 17C to 26Ne have been performed. In all cases these measurements agree with the latest mass compilation of Wapstra and Audi. The masses of 2°N and 24F have been determined for the first time.

Extensive new mass measurement capabilities have evolved with the development of recoil spectrometers. In the Z = 3 to 9 neutron-rich region alone, 12 neutron-rich nuclei have been determined for the first time by the fast-recoil direct mass measurement method. A recent experiment using the TOFI spectrometer illustrates this technique. A systematic investigation of nuclei that lie along or near the neutron-drip line has provided a valuable first glimpse into the nuclear structure of such nuclei. No evidence for a large single-particle energy gap at N = 14 is observed; however, a change in the two-neutron separation model calculations, and is interpreted in terms of the smaller 1s12 - 1s12 interaction compared to that of the 0d52 - 0d52 neutron-neutron interaction. 18 refs., 7 figs., 1 tab.

Proceedings of a NATO ARW held in Cargese, France, June 3-7, 1991

This project was directed toward the study of neutron-rich nuclei using the experimental facilities at LAMPF, which is a part of LANL. The principal results of the investigation include the discovery of many new isotopes along with a measurement of their masses and in particular those nuclides in the Z = 7--19 and 14 --26 regions of the chart of the nuclides. Thirty-four new nuclides were detected and studied with their masses being measured with relatively high accuracy, and an additional twenty-six that were previously known and measured were remeasured to an improved accuracy. Besides providing new information about the mass surface in new and extended redons of the chart of the nuclides, this investigation enabled properties and previously unknown structure of some of the nuclei to be determined such as nuclear deformation among some of the nuclides. Also a study of the neutron pairing gaps and the proton pairing gaps among these nuclides was made. Other developments also achieved included instrument (TOFI) improvements and upgrades and theoretical investigations into the masses of the hadrons.

Nuclei Far from Stability and Atomic Masses and Fundamental Constants 1992 presents a collection of 200 papers presented at two conferences that were held concurrently. Particular attention is paid to developments in the field of nuclear physics with energetic secondary beams and the increase of precision in the determination of atomic masses. Topics covered include nuclear spectroscopy and nuclear shapes, the heaviest elements, fission and cluster radioactivity, beta decay, coupling constants, neutrino mass, moments and radii, nuclei near the drip line and their structure, atomic masses, nuclear aspects in astrophysics, and experimental developments.