Fast neutron scattering from rubidium

Abstract

A study was made of the (n, n), (n, n'), and (n, n'~,) reactions which occur when a natural rubidium scattering sample is exposed to mono-energetic neutron fluxes of energies ranging from 120 to 1910 keV. Total cross sections, elastic scattering angular distributions and excitation functions for inelastic scattering were measured with a neutron time-of-flight spectrometer. Results are compared with Hauser-Feshbach theory. A 40 cc Ge(Li) detector was used in the time-gated mode to measure ~-rays from the (n, n'~,) reaction. The latter measurements were used to refine and extend the energy level schemes derived from neutron spectroscopy. Several new levels were discovered in the low-lying (below 1900 keV) energy level spectra of 8SRb and 87Rb. Gamma decay schemes and branching ratios were determined for the low-lying levels of 85Rb and 87Rb.

The level structure of85Rb and87Rb from (n, n??) reaction measurements

“…We have attempted to establish the level structures and determine level parameters for 85Rb and 87Rb up to 2 MeV excitation. The low-lying levels of 87Rb have been studied previously using beta decay [9 11], inelastic proton scattering [12], pick-up reactions [6,13] and stripping reactions [14,15], coulomb excitation [16,17] and inelastic neutron scattering [18,19]. The present measurements are generally in good agreement with these data whilst resolving a few ambiguities in addition.…”

“…The SSRb nucleus lies in a transition region and exhibits a level structure more complex than that of STRb due to the two additional holes in the neutron shell. The low-lying levels of 85Rb have been studied by electron capture [20,21,22], coulomb excitation [17], single-particle transfer reactions [23,24], as well as by inelastic neutron scattering [18,19]. The present measurements, although again being in general agreement with previous data, have served to resolve several discrepancies, establish six new levels and assign more accurate level energies whilst also resolving spin assignment ambiguities in several cases.…”

The low-lying level structure of87Rb

“…Until 1972 STKr decay [1,2] was the source of most of the level structure of SVRb. Since then, (n,n'7) [3,4], (p,p') [5], Coulomb excitation [6], SSSr(d, 3He) [7,8], and S6Kr(3He, d) [9,10] experiments have confirmed much of the early structure information and added new information. As a result of these experiments, the energy levels of STRb and the spins, parities, and spectroscopic factors for the lowest lying levels have become reasonably well known.…”

“…The calculation predicts a 1/2-assignment for the state observed at 1893keV and from stripping strength considerations favors J~= 1/2-rather than 3/2-for the state at 2396keV. There is also a calculated 5/2-state at 1793 keV which may correspond to the state observed at 1740 _+_ 1 keV in 87Kr decay and the scattering experiments [3][4][5] and which is assigned J~=(5/2-). This state (1740keV) is not seen in the stripping reaction [10] but this may be partially explained by the small calculated strength and the fact that it is expected to be weak in this reaction.…”

“…The present theoretical study has been prompted by the accumulation of experimental data for this nucleus and the little theoretical information available [2,11]. The single particle transfer reaction data [7][8][9][10] and the scattering data [3][4][5] indicate the presence of coupling between the proton and collective motions of the core. The data of [7,10] and the 8VRb(d, 3He) experiment [15] also show that thefs/2, P3/2, and Pl/2 single particle orbitals are partially open.…”