Decay of a New Isotope,S30

Abstract

Scintillation techniques were used to study the beta and gamma radiation from high-purity natural silicon targets after irradiation with 8-Mev He 3 ions. In addition to activities associated with well-known radioisotopes, an activity with a (1.35±0.10)-sec half-life was observed. A (677=kl0)-kev gamma ray was associated with the 1.35-sec half-life. Decomposition of decay curves constructed from data obtained by observing annihilation radiation revealed a component with the same half-life. Half-life measurements using positrons with energies in excess of 3.15 Mev also indicated the presence of a 1.35-sec activity. The beta spectrum in coincidence with two annihilation quanta extended to »5.0 Mev, a higher energy than can be accounted for by positrons from the known reaction products. The beta spectrum in coincidence with the (677=blO)-kev gamma ray had an end-point energy of (4.30±0.15) Mev. The assignment of the (1.35±0.10)-sec activity to the decay of S 30 produced in the reaction Si 28 (He 3 ,w)S 30 , and the proposed decay scheme are supported by arguments formulated from the known characteristics of reaction products, half-life studies using both beta and gamma radiation, the features of the experimental beta and gamma spectra, beta-gamma coincidence spectra, nuclear systematics, and nuclear theory. The decay of the ground state of S 30 takes place by at least two positron transitions: ft, a (4.98±0.15)-Mev superallowed transition to the 1+, T=0 ground state of P 30 ; 0 2 , a (4.30±0.15)-Mev superallowed transition to the 0+, T=l (0.677±0.010)-Mev first excited state of P 30 . No evidence was found for /3 3 , presumably an allowed transition to the 1+, (0.704±0.005)-Mev second excited state of P 30 , but an experimental upper limit of 25% is placed on its branching percentage. Branching percentages of (19±2)%, (73±7)%, and (8=1= 10)% for (3 h /3 2 , and & were calculated using the measured S 30 half-life, a S 30 -P 30 mass difference of (6.01 ±0.15) Mev, assumed charge independence of nuclear forces, and the fact that log ft for 0 + to 0 + positron transitions within T -1 charge multiplets is almost constant.

Discovery of the Isotopes with 11≤Z≤19

“…Robinson et al discovered30 S as described in the 1961 article "Decay of a new isotope, S 30 "[91]. Natural silicon targets were irradiated with an 8 MeV 3 He beam from the Purdue cyclotron 30.…”