No abstract

NUCLEAR £1 PEAK SPLITTING 815 initial and final states of the nucleus and does not deformation by one parameter only) for realistic directly reflect the properties of the summed-over intermediate states that constitute the El giant resonance. The literal connections among all these phenomena arising in a deformed i.h.o. model simply indicate that the model is too simplified (it expresses application to nuclei.The weak positron spectrum in the decay of Y 88 has been investigated using a 47r-positron-scintillation spectrometer. Two measurements of the spectrum yield experimental shape factors which are consistent above 250 keV with that expected for a unique once-forbidden transition. The average end-point energy obtained in these two measurements is 761 ±9 keV. The positron branching was measured and found to be 0.20db0.01%. The \ogft is 9.4, and logfit is 8.7. On the basis of recent measurements of the gamma-ray intensities in the Y 88 decay the electron capture branching to the 1840-keV level is determined to be 5.8±0.7%, which yields an electron capture to positron ratio of 29±4 for this transition.

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.

A series of measurements of nuclear beta and gamma radiation arising in neutron irradiation of a NaI(Tl) crystal is described. These measurements, which employ equipment items available in many advanced undergraduate physics laboratories, permit identification of prominent low-energy prompt gamma radiations produced in the I127(n,γ)I128 reaction as well as certain other radiations interpreted as arising in deexcitation of states in I127 excited by inelastic neutron scattering. In addition, a good determination of the Q value for beta-minus decay of I128 to Xe128 can be made, and the K capture branching to the Te128 ground state can be determined.