Yozo Nogami

Excited states in 29P by the reaction 28Si(p, γ)29P

Abstract The excited states in 29P have been investigated using the reaction 28Si(p, γ)29P for proton energies between 1.3 MeV.and 3.2 MeV. Gamma rays from the resonances at 1.383±0.003 MeV 1.655±0.005 MeV, 2.086±0.006 MeV, 2.88±0.02 MeV and 3.111±0.006 MeV have been studied. These resonances correspond to the excited states in 29P at 4.082±0.01 MeV, 4.345±0.01 MeV, 4.761±0.01 MeV, 5.53 MeV and 5.751±0.01 MeV, respectively. Gamma rays from the 4.08 MeV state lead to the excited states at 1.38 MeV and 1.96 MeV. The radiation widths are 0.9±0.4 meV and 1.1±0.5 meV, respectively. The 4.35 MeV state de-excites to the ground state and the first excited state with radiation widths 1.8±0.4 eV and 0.26±0.1 eV, respectively. The 4.76 MeV state showed the gamma radiation feeding the excited state. The radiation width is 0.33±0.1 eV. Capture gamma rays were not observed at 2.88 MeV resonance. Gamma transition widths from the 5.75 MeV state to the first and the second excited states are estimated to be less than 0.06 eV and not more than 0.08 eV, respectively. The analysis of angular distributions of the de-excitation gamma rays are consistent with the assignment of J π = 7 2 + ( 5 2 + ) and 3 2 − to the 4.08 MeV and 4.35 MeV states. Proton widths Γp were obtained to be less than 3 keV, 56±6 keV, 18±5 keV and 4.5±1.5 keV for the states at 4.08 MeV, 4.35 MeV, 4.76 MeV and 5.75 MeV, respectively. Properties related to the collective motion as well as the individual particle motion are found in the low-lying excited states in 29P.

Experiment on Elastic Scattering of Protons by O18

The differential cross section for the elastic scattering of protons by O 18 has been measured for proton energies from 600 to 1450 keV at center-of-mass angles of 140.8° and 90.0°. Targets consisted of thin LiOH films on thin gold foils and BeO films on thick beryllium foils. The technique for the preparation of these thin O 18 targets is described. Protons scattered elastically from O 18 were selected by a 90°-magnetic spectrometer. Resonances were observed at 633, ∼680, ∼850, 987, 1169, 1239 and 1403 keV in proton energies, indicating the excitation of seven levels of the compound nucleus, F 19 . The resonance near 850 keV showed a marked anomaly with large width, and the resonance near 680 keV was a weakly excited one with large width. Other resonances had weakly excited anomalies with small widths.

A study of the n-p final state interaction in the 2H(α, pα)n reaction at 18 MeV☆

Abstract Absolute cross sections of the 2 H(α, pα)n reaction have been measured at an incident energy and angle suitable for observing the effects of the n-p final state interaction (n-p FSI). The data are analysed by a semi-phenomenological modified impulse approximation (MIA). In the energy range E np ⪅ 0.6 MeV, destructive interference is clearly seen between the MIA matrix elements and n-p FSI.

PHOTOREACTIONS IN

The structure of the giant resonance in 28 Si has been studied using monochromatic gamma-rays ( Δ E γ / E γ ≈1%) from proton capture reactions. A silicon solid-state detector served both as target and detector. Total cross sections for the 28 Si (γ, p 0 ), (γ, p 1 ), (γ, p 2 ), (γ, α 0 ) and (γ, α 1 ) reactions were obtained from 17.4 to 22.3 MeV and the integrated cross sections were 34.4, 18.9, 17.6, 1.6 and 2.7 mb·MeV, respectively. The excitation functions of proton emission showed many discernible fine structures. Most of the peaks of the cross sections for different exit channels occurred at the same gamma-ray energy and the number of resonance states involved in a peak seems to be a few. The (γ, α 0 )-reaction excitation functions revealed several humps which are possibly caused by an E 1 absorption. Isotopic-spin selection rule seems no longer to be valid for the present (γ, α 0 ) reaction. Comparisons were made with the calculated absorption probability from the Nilsson model.

sup 28

Absolute cross sections of the 4 He( d , p α) n reaction have been measured at E d =8.9 MeV in order to study the reaction mechanism at low energy. A gas target in a cell with very thin wall (0.25 mg/cm 2 ) is used to detect low energy α-particles. In the coincidence spectra, prominent peaks are observed corresponding to the strong n -α final state interaction. Shapes of the spectra are well reproduced by the simple impulse approximation and the single-level R-matrix theory, but the absolute values as well as the angular dependence of the experimental peakcross section can not be fitted by these calculations. Independence of the peakcross section from kinematical variables such as the spectator energy and the nucleon-α scattering angle indicates that effects of multiple processes in the reaction are dominant at this low energy. A simple physical picture of the processes is presented.

Si NUCLEUS BY MONOCHROMATIC GAMMA-RAYS

Abstract Excitation functions for elastic and inelastic scattering of protons from 110 Cd and 112 Cd have been measured in the energy ranges of 5.8–8.1 MeV in 110 Cd and 6.1–8.4 MeV in 112 Cd. Elastic resonance data have been analyzed using the many-level formula of modified R -matrix theory. Angular distributions have been measured at four prominent inelastic resonances- The results are compared with spectroscopic predictions deduced from calculations using the quasiparticle randomphase approximation (QRPA). The contributions of two different modes arising from the 2p-1h character of the analog state and from the particle-core coupling nature of the parent state were deduced in a microscopic picture. The interference between the resonance and direct scattering has a marked effect on the inelastic angular distributions.

4He(d, pα)n Reaction at Ed=8.9 MeV

The reations Si>s2/sup >(/ gamma )P>s2/sup >,/>s2/sup > / (p, gamma )P>s3/sup >,/nd Si>s3/sup >(/ gamma )P>s3/sup > / are studied in the region of proton energy from 300 to 1700 kev. Two new resonances were found in the reaction Si>s2/sup >(/ gamma )F>s3/sup > / proton energies 1307.5 plus or minus 3 and 1331.5 plus or minus 3 kev, and in the reaction Si>s3/sup >(/ gamma )P>s3/ sup > /ne new resonances were found at proton energies 1094, 1179.5, 1209.5, 1290.5, of plus or minus 3 kev. No definite resonant level was observed in the reaction Si>s2/sup >(/ gamma )P>s2/sup > / the range of proton energy between 570 and 1400 kev. (auth)The reactions 28 Si( p , γ) 29 P, 29 Si( p , γ) 30 P and 30 Si( p , γ) 31 P have been studied in the region of proton energy from 300 kev to 1700 kev. We have found in the reaction 29 Si( p , γ) 30 P two new resonances at proton energies 1307.5±3 kev and 1331.5±3 kev, and in the reaction 30 Si( p , γ) 31 P nine new resonances at proton energies 1094, 1179.5, 1209.5, 1290.5, 1300, 1302.5, 1324.5, 1394.5 and 1403 kev with the errors of ±3 kev. No definite resonant level has been observed in the reaction 28 Si( p , γ) 29 P in the range of proton energy between 570 kev and 1400 kev.

Proton inelastic scattering from 110Cd and 112Cd at isobaric analog resonances and analysis with the quasiparticle random-phase approximation

The reaction Fe/sup 54/(p, gamma )Co/sup 55/ was studied in the energy range of 770-110 kev. Resonance levels of Co/sup 55/ were observed at 883, 961, and 1107 kev. The energies and intensities of observed gamma rays are also presented. (C.E.S.)

Resonance Levels in the Reactions 28Si(p, γ)29P, 29Si(p, γ)30P and 30Si(p, γ)31P

Oxygen-18 was bombarded with protons having energies over a range from 570 to 1500 kev, and proton capture gamma rays were studied. Four resonance levels were observed at proton energies 628, 847, 1167, and 1397 kev, and their widths were estimated to be 2.7, 44, 0.6, and 3.7 kev, respectively. From an analysis of angular distributions of gamma rays emitted form the resonance level at Ep = 1167 kev, it was deduced that spin values of the 5/2, respectively. The results were compared with the theoretical predictions based on shell model and collective model calculations.

Experiment on Fe54 (p, γ) Co55 Reaction

Abstract Kinematically complete measurements of the 2 (α, pα)n reaction at 18 MeV lab energy have been performed at various pairs of angles θ p and θ α . The p-α quasi-free scattering peak cross sections show an angular dependence similar to that predicted in the plane wave impulse approximation. From the analysis in a modified impulse approximation, it is found that two correction terms reflecting the effects of the three-nucleon transfer reaction and 6 Li resonances are necessary to reproduce the data, as was the case for the 15 MeV 2 H(α, pα)n reaction.