The decay characteristic of $^{22}$Si and its ground-state mass significantly affected by three-nucleon forces

Abstract

The decay of the proton-rich nucleus 22 Si was studied by a silicon array coupled with germanium clover detectors. Nine charged-particle groups are observed and most of them are recognized as β-delayed proton emission. A charged-particle group at 5600 keV is identified experimentally as β-delayed two-proton emission from the isobaric analog state of 22 Al. Another charged-particle emission without any β particle at the low energy less than 300 keV is observed. The half-life of 22 Si is determined as 27.5 ( 18) ms. The experimental results of β-decay of 22 Si are compared and in nice agreement with shell-model calculations. The mass excess of the ground state of 22 Si deduced from the experimental data shows that three-nucleon (3N) forces with repulsive contributions have significant effects on nuclei near the proton drip line.

Two-proton radioactivity with 2p halo in light mass nuclei A = 18–34

“…However, the result for 34 Ca is found albeit in difference for RMF theory where the charge radii is not much enlarged and also S 2p > 0 although the experimental data [49] and other theories show S 2p <0 and support energetically favoured 2p emission in 34 Ca which needs further investigation. Another remarkable feature of this work is to show the quasi bound state in two-proton emitter 22 Si studied recently experimentally [31] which indicates that it must have finite life time large enough to study such 2p unbound nucleus experimentally.…”

“…2p-radioactivity which is essentially the energetically allowed simultaneous two-proton emission is investigated by employing two simple and effective well established theoretical formalisms (i) Relativistic mean-field plus state dependent BCS (RMF+BCS) approach [32,33,34,35,36,37,38] and (ii) Macroscopic-microscopic approach (Mac-Mic) with Nilson Strutinsky (NS) prescription [30,39]. We calculate one-and two-proton separation energies of proton rich Mg, Si, S, Ar and Ca isotopes near proton drip-line and identify 19 Mg, 22 Si, 26 S, 30 Ar and 34 Ca as potential candidates of 2p-radioactivity in agreement with the available experimental data [20,21,31] for 19 Mg, 22 Si and 30 Ar. The structural evidences for the existence of halo are searched in the above identified 2p emitters within the RMF+BCS approach by investigating spatial density distribution, larger charge radius, wave functions and single particle energies that reveal a halo like structure of weakly bound protons which is the highlight of this work.…”

“…We study the charge density distribution and variation of proton single particle energies of sd shell (1d 5/2 , 2s 1/2 , 1d 3/2 ) within the spherical framework of RMF with NL3* parameter for the experimentally identified 2p emitter 22 Si [31]. From charge density distribution curves plotted in (Fig.…”

“…So far 2p-radioactivity has been observed in the decay of ground state 45 Fe [1,14], 54 Zn [15,16], 48 Ni [17,18], 67 Kr [19], 19 Mg [20], 30 Ar [21], 31 Ar * corresponding authors: Mamta Aggarwal, mamta.a4@gmail.com [22,23] 20 Mg [24,25,26], and excited states 22 Mg and 94 Ag (for 1p and 2p decay) [27,28] in experimental and theoretical [29,30] works have provided useful insights into this exotic decay mode of proton rich nuclei. Recent experimental observations of (i) β-delayed two-proton emission in the decay of 22 Si [31] (ii) 2p correlated emissions in 28,29 S but not in 27,28 P which indicated [8,9,10] that the diproton correlations may result from proton configuration in the initial state like 2p halo rather than the deformed orbit (iii) and the speculation [11] that the 2p halo plays an important role in the diproton emission, lack a precise theoretical description that has invoked the present study. The objective in this letter is to search for 2p halo and 2p unbound nuclear systems in even Z=12 to 20 in a theoretical framework and present for the first time an analysis to probe the interdependence between the weakly bound 2p halo like structure and the direct 2p emission.…”