Search

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.

The angular distributions of the reactions Ni 58 (p, α) Co 55 , Ni 60 (p, α) Co 57 and Fe 56 (p, α) Mn 53 leading to the ground and several excited states of the residual nuclei have been measured at 12.6–14.25 MeV, at 10.02–14.43 MeV and at 11.0 MeV, respectively, making use of solid state detectors. Levels have been found in Co 55 at 1.8 ± 0.2, 2.2 ± 0.2 and 2.45 ± 0.2 MeV and in Co 57 at 1.77 ± 0.02, 2.08 ± 0.03 and 2.21 ± 0.03 MeV. It was found that at about 14 MeV the forward peaks are predominant in the angular distributions for the reactions Ni 58 (p, α) Co 55 and Ni 60 (p, α) Co 57 leading to the ground states of the residual nuclei. The forward peaking disappears gradually with decreasing proton energy. The angular distributions of the reactions Ni 58 (p, α) Co 55 and Ni 60 (p, α) Co 57 leading to the several excited states of the residual nuclei have approximately 90° symmetry. The angular distributions of the reaction Ni 58 (p, α) Co 55 leading to the ground state of Co 55 have been measured at 28 energies between 8.96 and 10.32 MeV. Sharp variation of the shape of the angular distribution with the bombarding energy was obtained. The results of the measurements have been analysed with the theory of the compound nucleus developed by Ericson.

The thermal inactivation of stable and unstable (persistent lethal sectoring) lines of yeast was investigated at various temperatures. The temperature dependence of mortality rate was adequately described by the first-order chemical reaction formula. A semilog plot of temperature vs. life time of the stable line appeared as a straight line. On the other hand, that of the unstable line had two components: one had the same activation energy as the stable line and the other one had a different lower value. This new component may have originated in a mutated protein and caused the instability.

Thin /sup 29/Si targets were bombarded with protons in the energy range 1 --1.4 Mev and gamma rays were investigated at the proton resonance energies 1.309 and 1.333 Mev using sodium iodide scintillation counters. The two resonant levels correspond to the excited states in /sup 30/P at 6.835 plus or minus 0.03 and 6.86 plus or minus 0.03 Mev, respectively. Estimated values of spins, parities, isobaric spins and reduced gamma radiation widths were J/sup pi / = 1/ sup +/, T = 0, GAMMA gamma = 0.21 plus or minus 0.05 ev for the 6.835 Mev state and J/sup pi / = 2/sup plus or minus /, T = 1, GAMMA gamma = 0.28 plus or minus 0.05 ev fo r the 6.86 Mev state. The Q value of the reaction was measured to be Q = 5.57 plus or minus 0.03 Mev. Most of the gamma ray transitions from the resonant levels are in accord with the isobaric spin selection rule for seif-conjugate nuclei. A gamma transition, which is forbidden by the same selection rule, was also observed. This may be accounted for in terms of the isobaric spin impurity in the excited state. (auth)

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.

The angular distributions of the reaction Cu 63 (p, α) Ni 62 , Cu 65 (p, α) Ni 62 , As 75 (p, α) Ge 72 and Rh 103 (p, α) Ru 100 leading to the ground and several excited states of the residual nuclei have been measured in the proton energy range between 8 and 14 MeV. For the reactions Cu 63 (p, α) Ni 60 , Cu 65 (p, α) Ni 62 and As 75 (p, α) Ge 72 , the angular distributions are generally most forward peaked for the alpha particle group corresponding to the ground state of the residual nucleus at the highest proton energy, and then approach 90° symmetry when the proton energy is decreased. When one compares the angular distributions corresponding to the various states of the residual nucleus at a given incident proton energy, one observes in general for Cu and As that the forward peaking in the angular distribution is most prominent for the alpha particle group corresponding to the ground state and that this peaking gradually disappears with increasing excitation energy of the residual nucleus. For the reaction Rh 103 (p, α) Ru 100 , all the angular distributions are observed to be more or less forward peaked.