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Register a new userBeta-Delayed Proton Emission Branches in 43Cr
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The beta+ decay of very neutron deficient 43Cr has been studied by means of an imaging time projection chamber which allowed recording tracks of charged particles. Events of beta-delayed emission of one-, two-, and three protons were clearly identified. The absolute branching ratios for these channels were determined to be 81(4)%, 7.1(4)%, and 0.08(3)%, respectively. The 43Cr is thus established as the second case in which the beta-3p decay occurs. Although the feeding to the proton-bound states in 43V is expected to be negligible, the large branching ratio of 12(4)% for decays without proton emission is found.
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Beta-delayed proton emission from nuclides in the neighborhood of 100Sn was studied at the National Superconducting Cyclotron Laboratory. The nuclei were produced by fragmentation of a 120 MeV/nucleon 112Sn primary beam on a Be target. Beam purification was provided by the A1900 Fragment Separator and the Radio Frequency Fragment Separator. The fragments of interest were identified and their decay was studied with the NSCL Beta Counting System (BCS) in conjunction with the Segmented Germanium Array (SeGA). The nuclei 96Cd, 98Ing, 98Inm and 99In were identified as beta-delayed proton emitters, with branching ratios bp = 5.5(40)%, 5.5+3 -2%, 19(2)% and 0.9(4)%, respectively. The bp for 89Ru, 91,92Rh, 93Pd and 95Ag were deduced for the first time with bp = 3+1.9 -1.7%, 1.3(5)%, 1.9(1)%, 7.5(5)% and 2.5(3)%, respectively. The bp = 22(1)% for 101Sn was deduced with higher precision than previously reported. The impact of the newly measured bp values on the composition of the type-I X-ray burst ashes was studied.
Remarkable results have been published recently on the $beta$ decay of $^{56}$Zn. In particular, the rare and exotic $beta$-delayed $gamma$-proton emission has been detected for the first time in the $fp$ shell. Here we focus the discussion on this exotic decay mode and on the observed competition between $beta$-delayed protons and $beta$-delayed $gamma$ rays from the Isobaric Analogue State.
A common approach to studying $beta$-delayed proton emission is to measure the energy of the emitted proton and corresponding nuclear recoil in a double-sided silicon-strip detector (DSSD) after implanting the $beta$-delayed proton emitting ($beta$p) nucleus. However, in order to extract the proton-decay energy, the measured energy must be corrected for the additional energy implanted in the DSSD by the $beta$-particle emitted from the $beta$p nucleus, an effect referred to here as $beta$-summing. We present an approach to determine an accurate correction for $beta$-summing. Our method relies on the determination of the mean implantation depth of the $beta$p nucleus within the DSSD by analyzing the shape of the total (proton + recoil + $beta$) decay energy distribution shape. We validate this approach with other mean implantation depth measurement techniques that take advantage of energy deposition within DSSDs upstream and downstream of the implantation DSSD.
We report the observation of a very exotic decay mode at the proton drip-line, the $beta$-delayed $gamma$-proton decay, clearly seen in the $beta$ decay of the $T_z$ = -2 nucleus $^{56}$Zn. Three $gamma$-proton sequences have been observed after the $beta$ decay. Here this decay mode, already observed in the $sd$-shell, is seen for the first time in the $fp$-shell. Both $gamma$ and proton decays have been taken into account in the estimation of the Fermi (F) and Gamow Teller (GT) strengths. Evidence for fragmentation of the Fermi strength due to strong isospin mixing is found.
Background: The Doppler broadening of $gamma$-ray peaks due to nuclear recoil from $beta$-delayed nucleon emission can be used to measure the energies of the nucleons. This method has never been tested using $beta$-delayed proton emission or applied to a recoil heavier than $A=10$. Purpose: To test and apply this Doppler broadening method using $gamma$-ray peaks from the $^{26}$P($beta pgamma$)$^{25}$Al decay sequence. Methods: A fast beam of $^{26}$P was implanted into a planar Ge detector, which was used as a $^{26}$P $beta$-decay trigger. The SeGA array of high-purity Ge detectors was used to detect $gamma$ rays from the $^{26}$P($beta pgamma$)$^{25}$Al decay sequence. Results: Radiative Doppler broadening in $beta$-delayed proton-$gamma$ decay was observed for the first time. The Doppler broadening analysis method was verified using the 1613 keV $gamma$-ray line for which the proton energies were previously known. The 1776 keV $gamma$ ray de-exciting the 2720 keV $^{25}$Al level was observed in $^{26}$P($beta pgamma$)$^{25}$Al decay for the first time and used to determine that the center-of-mass energy of the proton emission feeding the 2720-keV level is 5.1 $pm$ 1.0 (stat.) $pm$ 0.6 (syst.) MeV, corresponding to a $^{26}$Si excitation energy of 13.3 $pm$ 1.0 (stat.) $pm$ 0.6 (syst.) MeV for the proton-emitting level. Conclusions: The Doppler broadening method has been demonstrated to provide practical measurements of the energies for $beta$-delayed nucleon emissions populating excited states of nuclear recoils at least as heavy as $A=25$.
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