Haruhiko Morinaga

Some New Activities Produced by Fast Neutron Bombardments

Several new nuclides were produced in the internal target of the INS cyclotron from the fast neutron bombardments of Ge, Mo, Gd, Er, Yb and Hf. Their radiation characteristics were determined with the aid of beta and gamma ray scintillation spectrometers. The new activities observed are as follows:

New Activities in Rare Earth Region Produced by the (γ, p) Reactions

Several new activities in the rare earth region were identified and also the decay characteristics of some previously reported activities in this region were studied more in detail. They were produced by the (γ, p ) reactions and measurement was made with the aid of the scintillation spectrometers. Results were as follows:

Search for tri-neutrons

Abstract A search for bound tri-neutrons in the reaction 7 Li(n, 3 n) 5 Li has been made with neutrons produced by a 55 MeV proton beam incident on a thick metallic lithium target. The detection of the tri-neutron was attempted with the reaction 138 Ba( 3 n, n) 140 Ba, whose yield of 140 La, the β-decay product of 140 Ba, was measured with a low-background counting apparatus. No evidence for the existence of the bound tri-neutron was found within the limits of experimental error. The upper limit was determined at 1 mb for the total cross section of the reaction 7 Li (n, 3 n) 5 Li at the neutron energies E n ≈ 14–19 MeV, where its values were expected to become the highest.

Gamma rays following intermediate energy proton bombardments and collective states in Ba130

Abstract Low-energy gamma rays generated by bombardments with 27–50 MeV protons were studied. In a tantalum bombardment, the rotational states were observed up to the 10 + state in W 178 , the (p, 4n) product. In a series of bombardments of ceasium targets with different energy protons states were observed in Ba 130 with spin values up to 6. The results are compared with results in the neighbouring region studied with the aid of beta-gamma spectroscopy.

Decay of Ir195and Ir197

The beta energies of Ir>s1/sup >> /d Ir>s1/sup >> /e compared wit h those predicted by beta-decay systematics. The beta energies 1 Mev and 0.6 Mev were found for Ir>s1/sup >>;/o beta above 1 Mev with a half life of 2.3 hr was observed. 2.0 and 1.5 Mev beta rays were found and assigned to 7-min. Ir>s1/sup >>./ The energies and relative intensities of gamma rays following the decays are also tabularly given. (N.W.R.)

He3-Alpha Scattering

Differential cross sections for scattering of He 4 by He 3 have been measured at E α =27.7, 28.5, 29.4, 30.0, 32.0, 33.4, 34.7, 36.5, 38.4, 41.0 MeV using a scintillation counter spectrometer, at the center of mass angles from ∼30° to ∼150°. Three distinct minima were found at about 45°, 100°, and 140°. The absolute cross-section and the pattern of the angular distribution showed no appreciable change in the energy range investigated: thus, there was found no sharp resonance in the He 3 +He 4 system corresponding to an excited state of Be 7 between 13.4 and 19.2 MeV. Differential cross-sections of the protons from He 3 (α, p )Li 6 Li 6* were observed. Differential cross-sections of alpha-alpha scattering were also measured at E α =33.5 and 35.5 MeV.

A 4+–0+ Cross-Over Transition

A 4/sup +/ -0/sup +/ cross-ever transition is reported in the decay or Ni/sup 60/ at the 2.505-Mev level. The branching ratio of the direct ground state transition from the 4/sup +/state to the cascade transition was 4 x 10/sup - 7/,which compares favorably with the theoretical branching ratio 1.3 x 10/sup -7 obtained by using the Weisskopf single particle estimate. (C.J.G.)

DECAY OF Ir

The beta energies of Ir>s1/sup >> /d Ir>s1/sup >> /e compared wit h those predicted by beta-decay systematics. The beta energies 1 Mev and 0.6 Mev were found for Ir>s1/sup >>;/o beta above 1 Mev with a half life of 2.3 hr was observed. 2.0 and 1.5 Mev beta rays were found and assigned to 7-min. Ir>s1/sup >>./ The energies and relative intensities of gamma rays following the decays are also tabularly given. (N.W.R.)