[en] Recently an experiment has been carried out at RIKEN, Japan, using the projectile fragment separator RIPS to test a new approach of studying β-delayed proton emitters. The approach consists of reduction of contamination from neighbouring isotones and isotopes by using a set of Al absorbers at the RIPS focal plane and stopping the fragments of interest on a thin foil placed in front of a gas ΔE-Si E detector telescope for delayed proton measurement. These two together have led to a remarkable reduction of β-background in the delayed proton spectrum of ²⁴Si and a number of new levels in ²⁴Al decaying by proton emission to ²³Mg have been observed. The details of the technique and the results obtained from the β-delayed proton decay of ²⁴Si will be discussed. (author)

No abstract available

[en] We performed B(GT) measurement for the β decay of 2^4Si in order to investigate behavior of a weakly-bound s-wave proton. The behavior of a weakly-bound proton in a proton-rich nucleus is one of the interesting topics to explore exotic nuclear structures, in association with proton halo [1]. Mirror asymmetry on nuclear structure helps us to close up a characteristic behavior of such a weakly-bound proton in a proton-rich nucleus. One of the example is the Thomas-Ehrman (TE) shift [2] that is lowering of the Coulomb energy due to the spatially spreading of a s-wave proton. The TE shift is important for the spectra of nuclei near the proton-drip line. We should take into account another effect, that is the change of configuration in the wave function due to lowering of the single-particle energy of the s_1/2 orbit. 2^4Si is a nucleus near the proton-drip line and β-decays to 2^4Al. Since 2^4Al has 5 valence protons in the sd shell, a state dominated by s-wave protons is expected to appear in an excited states fed by the β decay. Indeed there is found a TE-type mirror asymmetry of energy level on the second 1⁺ states between 2^4Al and 2^4Na [3,4,5]. However the change of configuration also may be related to the asymmetry. Since B(GT) is a sensitive observable to the configuration of wave function, we can extract the contribution related to the change of configuration using mirror asymmetry of B(GT). The experiment was carried out at the RIPS facility in RIKEN. It included the measurements for the β-delayed γ rays which had not been measured so far, and for the β-delayed protons of 2^4Si. In this presentation, we will report the experimental results of the B(GT) measurement. Discussion on the comparison with theoretical calculations which takes into account the Coulomb force and the TE shift is also given in order to clarify the effect of the weakly-bound proton on the nuclear structure.(author)

[en] A new detection system with high detection efficiency and low detection threshold has been developed for charged-particle decay studies, including β-delayed proton, α decay or direct proton emission from proton-rich nuclei. The performance was evaluated by using the β-delayed proton emitter "2"4Si produced by projectile fragmentation at the First Radioactive Ion Beam Line in Lanzhou. Under a continuous-beam mode, the isotopes of interest were implanted into two double-sided silicon strip detectors, where the subsequent decays were measured and correlated to the preceding implantations by using position and time information. The system allows us to measure protons with energies down to about 200 keV without obvious β background in the proton spectrum. Further application of the detection system can be extended to the measurements of β-delayed proton decay and the direct proton emission of more exotic proton-rich nuclei.

[en] Ground-state masses of ¹²O, ¹⁶Ne, ²⁴Si, and ³²Ar, members of isospin quintets, were measured, and mass excesses are tabulated. Results were consistent with the quadratic nature of the isobaric multiplet mass equation. 2 tables

[en] We carried out the β-decay spectroscopy on ²⁴Si in order to investigate a change in configuration in the wave function induced by Thomas-Ehrman shift from a perspective of mirror asymmetry of B(GT). We observed two β transitions to low-lying bound states in ²⁴Al for the first time. In this proceeding, the B(GT) of ²⁴Si is compared with that of the mirror nucleus ²⁴Ne, and the mirror asymmetry of B(GT) is determined. Then the origin of the B(GT) asymmetry is discussed through the comparison with theoretical calculations.

No abstract available

[en] Two-neutron knockout reactions from nuclei in the proximity of the proton dripline have been studied using intermediate-energy beams of neutron-deficient ³⁴Ar, ³⁰S, and ²⁶Si. The inclusive cross sections, and also the partial cross sections for the population of individual bound final states of the ³²Ar, ²⁸S and ²⁴Si knockout residues, have been determined using the combination of particle and γ-ray spectroscopy. Similar to the two-proton knockout mechanism on the neutron-rich side of the nuclear chart, these two-neutron removal reactions from already neutron-deficient nuclei are also shown to be consistent with a direct reaction mechanism

[en] With using the quantum-chemical tight binding method the stabilities of hollow silicon clusters are investigated in the process of quasi-one-dimensional growth. The obtained hexagonal structures of clusters Si₂₄ and Si₂₆ can be the 'building units' of a silicon nanowire. (authors)

[en] In experiments at GANIL and at GSI, we explored the proton drip line to search for new isotopes and to study the decay modes of nuclei close to the drip line. Detailed studies of the decay of ²²Al and ²⁴Si yielded new decay branches for these nuclei, in particular a β-delayed α emission for ²²Al. Studies at GSI revealed the new isotopes ⁴²Cr, ⁴⁵Fe, and ⁴⁹Ni, ⁴⁵Fe being most probably the best candidate for the yet unobserved two-proton ground-state emission. Finally at GANIL, the fragmentation of ⁹²Mo showed clear evidence for the new isotopes ⁷⁷Y, ⁷⁹Zr, and ⁸³Mo, ⁷⁷Y being a good candidate for proton ground-state emission. The measurement of the half-lives of odd-odd N = Z nuclei in this region shows clearly the presence of a super-allowed β-decay branch. (author)