S. Raman

Energy levels of light nuclei, A = 20

Abstract Compilation of energy levels of A = 20 nuclei, with emphasis on the review of material leading to information about the structure of the A = 20 systems.

Predictions of B(E2; 01+ → 21+) values for even-even nuclei☆

Abstract Adopted values (from a previous compilation) for the energy, E , and the reduced electric quadrupole transition probability, B ( E 2)↑, for the first-excited 2 + state of 276 even-even nuclei are tabulated. The adopted B ( E 2)↑ values are employed to test the various systematic, empirical, and theoretical relationships that have been proposed to exist among these B ( E 2)↑ values on a global, local, or regional basis. On the basis of these systematics, predictions of unmeasured B ( E 2)↑ values for 181 additional nuclei are made in the tabulation.

Density of discrete levels in 116Sn.

Model fits were made to the cumulative distribution of all known levels (with spins [ital J][le]10) in [sup 116]Sn below an excitation energy of 4.1 MeV identified in a variety of experiments, and simultaneously to the density of [ital J]=0 and [ital J]=1 resonances inferred from neutron capture and total cross-section measurements in [sup 115]Sn+[ital n]. Neither the back-shifted Fermi-gas model nor the constant-temperature model provides a satisfactory fit over the entire energy range. The generalized superfluid model, with a level-density parameter and a spin-cutoff factor that are both energy dependent, does give a good fit, and the resulting best-fit parameter values are consistent with those found in other applications of this model.

Density of discrete levels in [sup 116]Sn

Model fits were made to the cumulative distribution of all known levels (with spins [ital J][le]10) in [sup 116]Sn below an excitation energy of 4.1 MeV identified in a variety of experiments, and simultaneously to the density of [ital J]=0 and [ital J]=1 resonances inferred from neutron capture and total cross-section measurements in [sup 115]Sn+[ital n]. Neither the back-shifted Fermi-gas model nor the constant-temperature model provides a satisfactory fit over the entire energy range. The generalized superfluid model, with a level-density parameter and a spin-cutoff factor that are both energy dependent, does give a good fit, and the resulting best-fit parameter values are consistent with those found in other applications of this model.

Energy levels of 91Nb, 93Mo, 95Tc and 97Tc via (p, n) reactions and the reaction Q-values

Abstract The (p, n) reactions on isotopically enriched targets of 91Zr, 95Mo and 97Mo and monoisotopic 93Nb were investigated for a bombarding energy range 4 to 5.4 MeV. The neutron groups populating the low-lying excited states of 91Nb, 93Mo, 95Tc and 97Tc were studied by the use of a time-of-flight system. The reaction Q-values for 91Zr, 95Mo and 97Mo target nuclei were determined to be −2.045 ± 0.006, −2.490 ± 0.006 and −1.128 ± 0.008 MeV, respectively. Many low-lying states were populated by these reactions and their excitation energies determined with a high precision.

Decay of 67Cu

Abstract The γ-rays following the β-decay of 67 Cu have been investigated with a high-resolution Ge(Li) detector. The 67 Cu was produced by double neutron capture on 65 Cu. Gamma rays of energies (and relative intensities) 91.26 (155), 93.25 (360), 184.53 (1000), 208.95 (2.4), 300.22 (15.7) and 393.60 (4.3) keV were observed. The γ-rays have been incorporated in a level scheme of 67 Zn with levels (and spins and parities) at 0( 5 2 − ), 93.3 ( 1 2 − ), 184.5 ( 3 2 − ) and 393.5 ( 3 2 − ) keV .

Two-phonon J = 1 states in even-mass Te isotopes with A = 122–130☆

Abstract Excited states of the nuclei 122,126,130 Te were populated via the (γ, γ′) reaction at endpoint energies of the bremsstrahlung between 4.5 and 5.5 MeV. Gamma rays were detected with a EUROBALL CLUSTER detector and a single HPGe detector. In all investigated nuclei two or three prominent dipole transitions were identified at E γ ≈ 3 MeV. The corresponding low-lying J = 1 states are interpreted as two-phonon excitations. Quasiparticle-phonon-model calculations predict at about 3 MeV one 1 − state arising from the coupling of the first quadrupole and the first octupole phonon, and one 1 + state arising from the coupling of the first and the second quadrupole phonon, where the latter has isovector character. Such an excitation mode can be considered as an analogue of the scissors mode in vibrational nuclei. The calculated transition strengths are compatible with experimental ones within a factor of about 1.5.

Elastic scattering of 16O by 16O

Abstract The cross section for 16 O+ 16 O elastic scattering at 90° c.m. was measured from 35 to 88 MeV c.m. Pronounced structure was observed, as strong as seen earlier in the 20–30 MeV region. Several optical-model potentials derived from data at lower energies fail to predict the observed structure.

Thermal Neutron Capture Cross Sections of Zirconium-91 and Zirconium-93 by Prompt γ-ray Spectroscopy

A lower limit of 0.63 ± 0.02 b has been determined for the thermal neutron capture cross section (σ0) of 93Zr from a measurement of the prompt γ-rays emitted by the 93Zr (n th,γ) 94Zr reaction. The present result for 93Zr is much smaller than the single previously reported measurement as well as compiled and evaluated values for this cross section. This work also reports a lower limit for σ0 of 91Zr as 1.30 ± 0.04 b, which is consistent with the single previously reported measurement, as well as compiled and evaluated values for this cross section, within the quoted uncertainties.

Coulomb excitation of 117, 119Sn

Abstract A total of 5 states in 117Sn and 4 states in 119Sn were observed to be Coulomb excited with α-particle and 16O projectiles. Level energies, spins, B(E2) and B(M1) transition probabilities and mean-lives were obtained. For 117Sn, spin 3 2 + states were observed at 158.7 and 1005 keV and spin 5 2 + states were observed at 1020, 1180 and 1447 keV. For 119Sn, spin 3 2 + states were observed at 23.9 and 920.5 keV and spin 5 2 + states were observed at 921.4, 1090 and 1354 keV. A total of 20 B(E2) values were obtained and they varied in magnitude from 1 10 to 10 times the single-particle estimate. About 12 B(M1) values were obtained and they range from 10−1 to 10−4 of the single-particle estimate. Evidence was found for the existence of quadrupole collective states built on low-lying excited quasiparticle states.