622 research outputs found

### Ground--state energies and widths of $^5$He and $^5$Li

We extract energies and widths of the ground states of $^5$He and $^5$Li from
recent single--level R--matrix fits to the spectra of the $^3$H$({\rm
d},\gamma$)$^5$He and the $^3$He$({\rm d},\gamma$)$^5$Li reactions. The widths
obtained differ significantly from the formal R--matrix values but they are
close to those measured as full widths at half maxima of the spectra in various
experiments. The energies are somewhat lower than those given by usual
estimates of the peak positions. The extracted values are close to the
S--matrix poles calculated previously from the multi--term analyses of the
N-$^4$He elastic scattering data.Comment: 3 pages, no figures, uses revtex.sty, accepted for publication in
PRC, uuencoded postscript and tex-files available at
ftp://is1.kph.tuwien.ac.at/pub/ohu/fwidth.u

### E2 properties of nuclei far from stability and the proton-halo problem of 8B

E2 properties of A=6--10 nuclei, including those of nuclei far from
stability, are studied by a $(0+2)\hbar\omega$ shell-model calculation which
includes E2 core-polarization effects explicitly. The quadrupole moments and
the E2 transition strengths in A=6--10 nuclei are described quite well by the
present calculation. This result indicates that the relatively large value of
the quadrupole moment of $^8$B can be understood without introducing the
proton-halo in $^8$B. An interesting effect of the $2\hbar\omega$
core-polarization is found for effective charges used in the $0\hbar\omega$
shell model; although isoscalar effective-charges are almost constant as a
function of nucleus, appreciable variations are needed for isovector
effective-charges which play important roles in nuclei with high
isospin-values.Comment: (LaTeX, 23 pages

### Energy Levels of Light Nuclei A = 7

Abstract: An evaluation of A = 5-10 was published in Nuclear Physics 78 (1966), p. 1. This version of A = 7 differs from the published version in that we have corrected some errors discovered after the article went to press. Figures and introductory tables have been omitted from this manuscript. Reference key numbers have been changed to the TUNL/NNDC format

### Properties of $^{8}$Be and $^{12}$C deduced from the folding--potential model

The $\alpha$--$\alpha$ differential cross sections are analyzed in the
optical model using a double--folded potential. With the knowledge of this
potential bound and resonance--state properties of $\alpha$--cluster states in
$^{8}$Be and $^{12}$C as well as astrophysical S--factors of
$^{4}$He($\alpha$,$\gamma$)$^{8}$Be and $^{8}$Be($\alpha$,$\gamma$)$^{12}$C are
calculated. $\Gamma_{\gamma}$--widths and B(E2)--values are deduced.Comment: 2 pages LaTeX, 2 figures can be obtained from the author

### Isospin Effects in Nuclear Multifragmentation

We develop an improved Statistical Multifragmentation Model that provides the
capability to calculate calorimetric and isotopic observables with precision.
With this new model we examine the influence of nuclear isospin on the fragment
elemental and isotopic distributions. We show that the proposed improvements on
the model are essential for studying isospin effects in nuclear
multifragmentation. In particular, these calculations show that accurate
comparisons to experimental data require that the nuclear masses, free energies
and secondary decay must be handled with higher precision than many current
models accord.Comment: 46 pages, 16 figure

### Cluster states in nuclei as representations of a U(n+1) group

We propose a description of cluster states in nuclei in terms of
representations of unitary algebras U(n+1), where n is the number of space
degrees of freedom. Within this framework, a variety of situations including
both vibrational and rotational spectra, soft and rigid configurations,
identical and non-identical constituents can be described. As an example, we
show how the method can be used to study alpha-clustering configurations in 12C
with point group symmetry D(3h).Comment: 5 pages, 2 figures, Phys. Rev. C, in pres

### Nuclear halo and its scaling laws

We have proposed a procedure to extract the probability for valence particle
being out of the binding potential from the measured nuclear asymptotic
normalization coefficients. With this procedure, available data regarding the
nuclear halo candidates are systematically analyzed and a number of halo nuclei
are confirmed. Based on these results we have got a much relaxed condition for
nuclear halo occurrence. Furthermore, we have presented the scaling laws for
the dimensionless quantity $/R^{2}$ of nuclear halo in terms of the
analytical expressions of the expectation value for the operator $r^{2}$ in a
finite square-well potential.Comment: 14 pages, 3 figure

### An Attempt to Study T=2 States in 16-N

This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440

### Direct radiative capture of p-wave neutrons

The neutron direct radiative capture (DRC) process is investigated,
highlighting the role of incident p-wave neutrons. A set of calculations is
shown for the 12-C(n,gamma) process at incoming neutron energies up to 500 keV,
a crucial region for astrophysics. The cross section for neutron capture
leading to loosely bound s, p and d orbits of 13-C is well reproduced by the
DRC model demonstrating the feasibility of using this reaction channel to study
the properties of nuclear wave functions on and outside the nuclear surface. A
sensitivity analysis of the results on the neutron-nucleus interaction is
performed for incident s- as well as p-waves. It turned out that the DRC cross
section for p-wave neutrons is insensitive to this interaction, contrary to the
case of incident s-wave neutrons.
PACS number(s): 25.40Lw,21.10Gv,23.40.HcComment: 16 pages, REVTeX file, PostScript file, .dvi fil

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