Isospin-nonconserving particle decays in light nuclei

Beta-delayed proton emission from 21Mg

“…As many of the known partial and total decay widths have been measured in 20 Ne(p, p) scattering experiments after the work of [5], see [19,20], as well as a more recent measurement of γp coincidences, the present interpretation has a more solid foundation.…”

“…To further suppress the Na contamination we made use of the fact that the proton beam on the ISOLDE target is pulsed with pulse spacing a multiple of 1.2 s. This, together with the fact that 21 Mg and 21 Na have a large difference in half-lives, 122(2) ms and 22.49(4) s respectively [4], and that the timescale for Mg ions to diffuse out of the target, be ionized, and transported to the setup is of the order of 100 ms, provides a natural way of suppressing the isobaric contamination of Na by only letting the beam into the setup during the first 300 ms following proton impact on target. From measurements on mass 20, which show a similar difference in the half-lives of 20 Mg and 20 Na, a ratio of 20 …”

“…The observed line shape is much better described by replacing the one broad proton branch by two proton branches. However, the line shape may also be explained by interference effects, which would require proton emission from two close lying resonances in 21 Na with the same values of I π and going to the same resonance in the particle daughter 20 Ne. It is possible to have such interference with p 5 but it would mean a new interpretation of the peak p 2−4 .…”

“…In Sect. 4 we present an improved interpretation of the decay scheme based on the current measurement in combination with recent 20 Ne(p,p) scattering experiments.…”

“…The only other identified decay mode is β-delayed proton emission to states in 20 Ne, but βα, βαp, and βpα are all energetically allowed. As the separation energies for such decays are quite high, S α = 6561.3(4) keV and S pα = S αp = 7161.5(3) keV [4], it is most likely to observe such low intensity decay modes as emissions from the Isobaric Analog State, IAS, with T z = 3 2 at an excitation energy of 8975(4) keV, as this state is strongly fed in the β-decay due to the similarity a e-mail: mvl07@phys.au.dk of the structure with the ground state of 21 Mg and the position of the IAS inside the Q EC -window.…”