K. Ashktorab

COULOMB EXCITATION OF 8LI

We have observed the excitation of the first excited state ({ital E}{sub {ital x}}=0.98 MeV, {ital J}{sup {pi}}=1{sup +}) of the radioactive, neutron-rich nucleus {sup 8}Li ({ital J}{sub g.s.}{sup {pi}}=2{sup +}) from its inelastic scattering on {sup nat}Ni at {ital E}({sup 8}Li){congruent}14.6 MeV. Cross sections measured out to large {theta}{sub c.m.} agree well with Coulomb-excitation probabilities and have been used to deduce an {ital E}2{up arrow} transition rate for the 2{sub g.s.}{sup +}{r arrow}1{sup +} excitation in {sup 8}Li{sup *}. The latter ({ital B}({ital E}2{up arrow})=55{plus minus}15 {ital e}{sup 2} fm{sup 4}) is large relative to nearby stable nuclei, but comparable to the neighboring neutron-rich nucleus {sup 10}Be. The relevance of the data to predicted neutron-halo giant dipole resonances in unstable nuclear projectiles is considered.

Production and use of 6He, 7Be, 8Li, 12B and metastable nuclear beams

Abstract A low energy (few MeV/nucleon), modest flux ( 10 4 −10 7 s ) radioactive nuclear beam (RNB) facility has been in operation for approximately three years at the University of Notre Dame Van de Graaff accelerator. This facility utilizes a compact superconducting solenoid lens, designed at the University of Michigan, with adjustable apertures to produce momentum-analyzed secondary beams via the direct transfer and other methods. Useable beams of 6He, 7Be, 8Li, 12B, 18F and to our knowledge the first isomeric beam, 18mF, have been produced and a first generation of RNB experiments has been successfully completed.

Deuterated liquid scintillator (NE230) as a fast neutron detector for cold-fusion and other research

Unlike conventional liquid scintillators (e.g., NE213) deuterated scintillators (NE230) can provide, without time-of-flight, usable neutron energy spectra for neutrons E/sub n/>or=1 MeV. The authors have assembled and calibrated several of these detectors and have used them in experiments searching for d+d fusion-neutron emission (E/sub n/=2.5 MeV) in Pd+D/sub 2/O electrolysis and Ti+D/sub 2/ absorption at liquid nitrogen temperatures. The detectors yield direct fusion-neutron spectra and set limits in the Pd+D and Ti+D experiments of <7*10/sup -24/ fusion n/s/dd pair and <3*10/sup -24/ fusion n/s/dd pair, respectively. In addition, these detectors have been used for in-beam accelerator experiments requiring coincidence between fast neutrons and scattered ions.<<ETX>>

2H induced reactions on 8Li and primordial nucleosynthesis

Cross sections for the [sup 8]Li([ital d],[ital n])[sup 9]Be (ground state) and [sup 8]Li([ital d],[ital t])[sup 7]Li reactions, both important to primordial nucleosynthesis in the inhomogeneous models, have been measured using a radioactive beam technique. The cross section for the former reaction is found to be small, so it is important only for synthesis of [sup 9]Be. The cross section for the latter reaction, however, is found to be large enough to destroy significant quantities of [sup 8]Li, and thus could affect predictions of primordial nucleosynthesis yields.

Coulomb energies and the shell model

Phenomenological shell-model Coulomb energy equations with coefficients varying as A-3 are considered. The highly regular systematics of Coulomb displacement energies is presented and discussed. In a global fit with 22 adjustable parameters the equations reproduce 377 displacement energies with a standard deviation of 55 keV. The relations to other shell-model equations are discussed. The numerical values of the adjusted coefBcients are related to the charge radius and deformation parameters of the liquid drop model. The calculation of total Coulomb energies for ground states is considered. The total energy of the nucleus is a sum of nuclear and Coulomb energies. In a semi-empirical shell-model treatment the parameters describing them are statistically correlated. In order to obtain physically meaningful and statisticaily significant coefficients for mass equations one has to consider both ground state masses and Coulomb displacement energies (CDE). This was one of the main motivations for the present study. In the mass equation of ref. ) Coulomb energy coefficients were determined by using the Carlson-Talmi Coulomb energy equation *,) both for the ground state and for excited isobaric analog states (IAS), with coefficients varying like A-. The adjusted coefficients described ) experimental Coulomb displacement energies with a standard deviation of about one third of the deviation obtained for the masses. On the other hand, in the above procedure one neglects the dependence of the Coulomb energy in a given nucleus on the isospin T. In ref. ) the T-dependence of Coulomb displacement energies was calculated assuming the Carlson-Talmi equation for ground states. A variation of the coefficients with nucleon numbers was adopted, which reflects upon the isotope shifts of nuclear charge radii. The resulting equations were adjusted to the data simultaneously in all shell regions, resulting in a mean deviation smaller than that for the Carlson-Talmi equation.

Cross sections and reaction rates of d + 8Li reactions involved in Big Bang nucleosynthesis

Abstract We have measured angular distributions of the 2 H( 8 Li, 7 Li) 3 H and 2 H( 8 Li, 9 Be)n reactions at E c.m. = 1.5 to 2.8 MeV using an 8 Li- radioactive-beam technique. Astrophysical S -factors and reaction rates were calculated form the measured cross sections. Although the 2 H( 8 Li, 9 Be)n cross section is small, it can contribute to 9 Be synthesis. The 2 H( 8 Li, 7 Li) 3 H reaction has a sufficiently large cross section to destroy 8 Li, which may decrease the synthesis of heavier elements. No products from the 2 H( 8 Li, 9 Li)p reaction were detected. We also present the results of calculations using the inhomogeneous model of primordial nucleosynthesis in several regions of parameter space.

H2induced reactions onLi8and primordial nucleosynthesis

Cross sections for the [sup 8]Li([ital d],[ital n])[sup 9]Be (ground state) and [sup 8]Li([ital d],[ital t])[sup 7]Li reactions, both important to primordial nucleosynthesis in the inhomogeneous models, have been measured using a radioactive beam technique. The cross section for the former reaction is found to be small, so it is important only for synthesis of [sup 9]Be. The cross section for the latter reaction, however, is found to be large enough to destroy significant quantities of [sup 8]Li, and thus could affect predictions of primordial nucleosynthesis yields.

[sup 2]H induced reactions on [sup 8]Li and primordial nucleosynthesis

Cross sections for the [sup 8]Li([ital d],[ital n])[sup 9]Be (ground state) and [sup 8]Li([ital d],[ital t])[sup 7]Li reactions, both important to primordial nucleosynthesis in the inhomogeneous models, have been measured using a radioactive beam technique. The cross section for the former reaction is found to be small, so it is important only for synthesis of [sup 9]Be. The cross section for the latter reaction, however, is found to be large enough to destroy significant quantities of [sup 8]Li, and thus could affect predictions of primordial nucleosynthesis yields.

H 2 induced reactions on Li 8 and primordial nucleosynthesis

Cross sections for the [sup 8]Li([ital d],[ital n])[sup 9]Be (ground state) and [sup 8]Li([ital d],[ital t])[sup 7]Li reactions, both important to primordial nucleosynthesis in the inhomogeneous models, have been measured using a radioactive beam technique. The cross section for the former reaction is found to be small, so it is important only for synthesis of [sup 9]Be. The cross section for the latter reaction, however, is found to be large enough to destroy significant quantities of [sup 8]Li, and thus could affect predictions of primordial nucleosynthesis yields.

A Macintosh-II CAMAC multi-parameter data acquisition system for nuclear physics experiments

An Apple Macintosh-II CAMAC data acquisition system has been developed based on a Nubus crate controller with custom drivers and display software written in C. This system provides much enhancement performance (to several events/sec) relative to GPIB or RS232-based CAMAC systems. The software provides a user-friendly multiwindow environment with pull down menus, multiparameter grating, and event-mode recording. The MAC-II system has been effectively utilized in a number of experiments such as a search for cold-fusion from Ti+D/sub 2/ loading (and unloading) at cryogenic temperatures.<<ETX>>