Tsutomu Tohei

Observation of two-hole states at high excitation energy in (p, t) reactions

Abstract Bumps of two-hole states at high excitation energies were observed systematically in the triton spectra from (p, t) reactions with 52 MeV protons on nuclei in a broad range of masses. The cross sections of the bumps are almost equal for various targets with the same deep major shells. These cross sections vary discontinuously with variation of the corresponding deep major shell. About 20 to 50 % of the total expected strength is observed experimentally, if the bumps are assumed to arise from two-neutron pickup from the deep major shells. The centres of gravity of the bumps are located at excitation energies of about 7 to 9 MeV in all cases. On the other hand, the widths of the bumps change from about 3 MeV for 66 Zn to about 9 MeV for 230 Th.

The Be9(p, α)Li6 and Be9(p, d)Be8 reactions from 1 to 4.6 MeV

Abstract Excitation curves for the products of the Be9+p reaction and several angular distributions for the Be9(p, α0)Li6 and Be9(p, d0)Be8 reactions have been measured for bombarding energies from 1.00 to 4.60 MeV. Showing the typical behaviours for direct reaction mechanism, the results have been compared with the pick-up theory in plane-wave Born approximation.

Proton Widths of Excited States in 29P by the 28Si(3He, d)29P Reaction

The low-lying states in 29 P were excited by the reaction 28 Si( 3 He, d) 29 P. The analysis of the reaction in terms of the direct reaction process yielded the orbital angular momenta of the transferred protons and the relative values of the proton widths. The reduced proton width obtained from the experiment are generally in agreement with the values predicted on the Nilsson model with small deformation. A number of low-lying levels were found to have very small proton widths. This fact is accounted for as the effects of the rotational excitation and the band mixing of the excited levels. The measurement of the nucleon width may be useful to clarify the property of the excited level.

Structure of 14c studied by the 14c(p,d)13c reaction

Abstract Cross sections for the neutron pickup reaction 14 C(p, d) 13 C were measured at E p = 35.0 MeV for the states below E = 10 MeV, and at E p = 40.1 MeV for the states between E x = 11 and 18 MeV. Obtained angular distributions were compared with exact finite-range DWBA calculations to extract spectroscopic factors. Second-order DWBA calculations were also made in some cases. Almost full 0p 1 2 strength was found, while the observed 0p 3 2 strength was 80% of the simple sum-rule limit. The main part of the remaining strength was found in the 0d 5 2 orbit, and, in a lesser degree, in the 1s 1 2 and 0d 3 2 orbits. Small fractions of the 0f 5 2 and Og 9 2 strengths were also necessary to explain the angular-distribution shapes and the cross-section magnitudes of the predominantly multistep transitions to the 5− 2 and 5+ 2 states.

Effects of inelastic multistep processes on (p, t) reactions in a transition region between rare-earth nuclei and double-magic 208Pb

Abstract Effects of inelastic multistep processes on (p, t) reactions in a transition region between well-deformed rare-earth nuclei and the double-magic 208 Pb have been investigated by the 188 Os(p, t) 186 0s, 194, 196 Pt(p, t) 192, 194 Pt and 200, 202 Hg(p, t) 198, 200 Hg reactions at E p = 51.9 MeV. The observed ground 0 + , first excited 2 + and 4 + angular distributions together with those for the 206, 208 pb(p, t) 204, 206 pb reactions have been compared with CCBA and DWBA calculations, using transfer form factors based on the Nilsson, vibrational and shell models. It is found that the inelastic multistep processes play a very important role in reproducing both the shapes and magnitudes of the observed first excited 2 + angular distributions, contrasting to small contributions in the ground-state 0 + transitions. The effects of the inelastic multistep processes on the first excited 4 + transitions are also considered to be important.

Structure of Giant Resonance in Al27(p, γ) Reaction

The 90 deg yields of gamma radiation produced from proton capture by Al/ sup 27/ were measured at proton energies of 7.5 to 14.5 Mev. The relative cross section data combined with these of Canberra revealed a giant resonance of width on the order of 4 Mev and with many peaks. Three resonances at 7.61, 8.75, and 10.13 Mev can be attributed to the excited state of Si/sup 28/. The giant resonance is interpreted from the standpoint of spheroidal deformation of a compound nucleus. (D. L.C.)

The 9Be(d, n)10B reaction at 25 MeV

Abstract Differential cross sections for the 9Be(d, n)10B reaction have been measured at Ed=25 MeV using the time-of-flight technique. Experimental angular distributions for the states below Ex=6.57 MeV were analysed with the distorted-wave theory including the S-wave deuteron-breakup effects in the adiabatic approximation. The extracted spectroscopic factors were compared with previous data. Coupled-reaction-channel (CRC) calculations were also performed, and significant improvements were seen for weakly excited states.

ALPHA PARTICLE GROUPS FROM THE DEUTERON BOMBARDMENT ON

Calcium oxide targets were bombarded with 15.14-MeV deuterons from the INS cyclotron. Alpha-particle spectra were obtained at angles of 45°, 60° and 90° by means of a broad range magnetic spectrograph. In the 45° and 60° spectra none of the alpha-particle groups corresponding to T =1 levels in N 14 up to an excitation of l0 MeV was observed with an appreciable intensity with the only exception of the alpha-particle group leading to the 9.17-MeV level. In the 90° spectrum, however, alpha-particle groups leading to some of the T =1 levels in N 14 were observed evidently. Alpha-particle groups leading to somewhat doubtful levels in N 14 , i.e., 6.05-, 6.70-, 7.40- and 7.60-MeV levels were not observed with appreciable intensities in all the spectra. Alpha-particle groups from the Ca 40 ( d , α) K 38 reaction leading to several levels in K 38 below 4-MeV excitation and some He 3 groups from the Ca 40 ( d , He 3 ) K 39 reaction leading to the lowest levels in K 39 were observed.

sup 16

Abstract Evidence for the proximity 3 He(n, p) 3 H reaction in the final state of the sequential 6 Li(d, 3 He) 5 He(n) 4 He process was observed. The behaviour of the positions of the peaks in the two-dimensional spectra was consistent with kinematical predictions. It should be emphasized that the proximity scattering was extended to a rearrangement process. The strength of the process gave direct information on the lifetime of the ground state of 5 He. A classical estimate led to τ = 1.4 × 10 −21 sec, which is the shortest nuclear lifetime directly measured. The consistency of this value with the level width gives quantitative support for the occurrence of the proximity reaction.

O AND

Abstract In peeling off the thin target material from glass plate, which was prepared by vacuum-evaporation, glucose was used instead of Teepole. The advantages of this method are described.