Akira Uchida

Nuclear spin-spin effect in the total cross section for 1 MeV polarized neutrons on polarized 59Co nuclei

Abstract Measurements of the spin-spin effect, σ ss = (σ↑↑-σ↑↓) 2 P n · p I in the total cross section for polarized neutrons on polarized 59 Co are reported at neutron energies of 1.1 and 1.4 MeV. Target polarizations from 47 ± 5% to 30 ± 3% were obtained for a polycrystalline metal of Co 0.90 -Fe 0.10 alloy at demagnetization temperatures from 0.030 to 0.048°K. The results for σ ss are −0.21 ± 0.18 b at 1.1 MeV and −0.18 ± 0.23 b at 1.4 MeV, combined with experimental asymmetries obtained at 4.2° K. If σ ss is assumed to arise from a spin-spin term in the optical potential of the form − V ss f(r) σ · I , the upper limit of the strength is obtained as | V ss | σ ss at 7.90 MeV and assuming f ( r ) as a microscopic form factor. The obtained nature of V ss is qualitatively explained by a microscopic model.

The Spin-Spin Interaction of 0.92 MeV Polarized Neutrons with Polarized 165Ho Nuclei

In order to obtain a direct measure of the strength and form of the nuclear spin-spin interaction, the transmission of 0.92 MeV polarized neutrons by polarized 165 Ho was measured. The total cross section and relative scattering angular distribution of 0.92 MeV unpolarized neutrons through unpolarized 165 Ho nuclei were also measured in order to make a parameter search of the optical potential. The experimental results are analyzed with Davies and Satchlers DWBA formalism. The results show that the effective spin-spin interaction between a free neutron and a 165 Ho nucleus, is an attraction type and its strength has the order of one MeV, and the present experimental result together with other data obtained at ORNL and Stanford, can be fitted by the DWBA approach in either case of a volume and surface type of the form factor. For the further determination of the strength and the form of the spin-spin interaction, more precise similar experiments are needed for various different neutron energies.

NEUTRON DEPOLARIZATION IN ELASTIC SCATTERING.

The depolarization parameter D (θ) in elastic scattering of 1.36 MeV neutrons was measured at θ 2 =30°, 38°, 80°, 120° and 150° for 27 Al, 59 Co, 63,65 Cu, 209 Bi and Ni nuclei. The departure of D (θ) from unity for Al, Co, Cu and Bi was observed particularly at backward angles, but not observed for Ni. This fact shows that the spin flip of incident neutrons takes place along the normal to the scattering plane in the elastic scattering process for non-zero spin targets. These results are discussed in the light of different nuclear reaction mechanisms.

Crystal structure and thermodynamical behavior of tetrabenzo[de,hi,op,st]pentacene endoperoxide

Abstract The crystal structure of an endoperoxide of tetrabenzo[de,hi,op,st]pentacene (TBPA-O2) was determined by X-ray crystallography. The unusually long OO and CO bonds were rationalized by the characteristic molecular structure of TBPA-O2. The photochromic behavior between TBPA-O2 and TBPA was discussed based on the enthalpy difference between TBPA-O2 and TBPA + O2 and the thermodynamic parameters of the extrusion reaction of oxygen from TBPA-O2.

Elastic Scattering of 55 MeV Protons from Heavy Nuclei

Several targets, covering the spherical, deformed and transition regions of heavy nuclei, were bombarded with 55 MeV protons and angular distributions of the elastically scattered protons were measured. The diffraction structure of them are strongly damped for the deformed nuclei, as compared with that for the spherical nuclei and this feature changes gradually for nuclei of the transition region. The optical model analysis was also performed to discuss the details of the deformation effect.

A Liquid Helium, Time of Flight Neutron Polarimeter with a Spin Rotating Solenoid

A Liquid helium time of flight neutron polarimeter with a spin rotating solenoid has been developed to measure neutron polarization for the energies as low as 800 KeV. Energy selection is accomplished by time of flight techniques and accuracy of polarization measurement is improved by a spin rotating solenoid. Measurements of the neutron polarization for the Li7(p, n0)Be7 and C12(d, n0)N13 reactions were made for the proton and deutron energies at 2.8 MeV and 1.58 MeV at laboratory angles of 52° and 70°, respectively. The polarization of the neutron for the C12(d, n0)N13 reaction is -(40.5±2.7)%.

Low Energy (p, n) Reaction on 55Mn and the Low-Lying Excited States of 55Fe

The ( p , n ) reaction on 55 Mn was studied with the emphasis upon the investigation of the low-lying states of 55 Fe. The angular distributions of each neutron groups corresponding to energy states of 55 Fe lower than 0.93 MeV were measured at ten different proton energies in the energy range from 2.3 MeV to 2.8 MeV. New levels of 55 Fe at 0.51 and 0.68 MeV reported by Kim at ORNL were not observed at least with so much intensities as he claimed. The Integrated cross section of each group corresponding to the low-lying states of 55 Fe was analyzed by means of the statistical theory due to Hauser and Feshbach. As a Consequence, the spin and parity of 0.41 MeV level were assigned as (1/2) - ; (3/2) - was excluded. This assignment is consistent with that suggested by Schiffer et al. . The measurement of The life of the first excited state at 041 MeV was tried as a testing of core-excitation model.