Beta-delayed neutron emission from93?100Rb to excited states in the residual Sr isotopes

Abstract

Beta-delayed neutron emission from the precursors 93-1~176 to excited states in the residual nuclei 92-998r has been measured by means of 7-ray and neutron spectroscopy. In general, considerable neutron feeding of excited final states is observed. The experimental branching ratios (P,~) are compared to predictions from statistical model calculations. It is demonstrated that the main parameter affecting the Pj-values is the shape of the/3-strength function (Sp). For several Rb isotopes hindrance, respectively enhancement of neutron branches to specific final states is observed giving evidence for the persistence of intermediate structure of the neutron-emitting states. By the example of 98Rb it is shown that a few integral /3-delayed neutron properties may be sufficient to derive first estimates on the real shape of Se above the neutron binding energy. This result is of importance for exotic nuclei where detailed spectroscopic investigations are precluded.

β-decay half-lives andβ-delayed neutron emission probabilities of nuclei in the regionA≲110, relevant for the r process

“…Moreover, as discussed in Refs. [80,81,82], high-resolution spectroscopic studies of β-delayed neutron-emitter nuclei produced by fission showed that E βn was always much lower than Q β − S n (e.g. 199 keV for 87 Br, 450 keV for 98 Rb, and 579 keV for 137 I).…”

Relevance of β-delayed neutron data for reactor, nuclear physics and astrophysics applications

“…[4,5] and for later compilations [36,37]), in the early 1970's the focus was more directed to measuring energy spectra of fission-product nuclei by using different types of detectors (see, e.g. the review article of Kratz in [5], and [6,7,8,9,10,11,12,13,14,15,16]. As already mentioned in the introduction, among the most common experimental methods for β dn-spectroscopy was the use of 3 He filled proportional counters or ionization chambers.…”

“…The partial spectrum to the first excited state was obtained from a nγ-coincidence measurement with the γ-gate set on the 837 keV line (2 + 1 → 0 + ) in the final nucleus. The partial spectrum to the ground state was derived by subtracting all nγ-coincidence spectra weighted according to their integral P i n branching ratios [15]. By comparing the well resolved peaks in the singles neutron spectrum (upper left part of Fig.…”

“…Selected aspects of their applications for reactor control [50,51], nuclear structure far from stability (see, e.g. [15,16,17,19,52,53,54,55,56]) and astrophysics (see, e.g. [18,20,21]) will be presented in the following chapters.…”

“…[9,10,11,12,13]) led in the following years to a considerable extension of β dn spectroscopy to various problems in nuclear-structure physics (see, e.g. [13,14,15,16,17]) and astrophysics (see, e.g. [18,19,20,21]).…”