Kinuko Horie

Cosmogenic nuclides in the Kirin chondrite

Abstract Radioactive and stable cosmogenic nuclides have been determined in the various fragments of the Kirin chondrite (H5). Experimental results obtained from our samples are described and compared with similar data obtained in other laboratories. Cosmogenic 54 Mn, 22 Na, 60 Co, 26 Al, 53 Mn, 40 K (in the metal phase), and light noble gases were measured. Based on these data, the irradiation history of this meteorite can be explained in terms of (1) a multi-stage exposure which involves a first-stage irradiation for 10 7 years and a second stage for about 4×10 5 years, and (2) depth effects in the productions of the nuclides in 4π(second stage) and 2π(first stage) geometries. These conclusions are consistent with those of our previous work which was based on a limited number of samples.

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.

Applications of neutron activation method for 53Mn in meteoritic iron

Abstract A highly sensitive determination of 53Mn by a neutron activation method which was proposed by H. Millard (1965) was examined in detail. A reference source of 53Mn was extracted from an iron meteorite and the activity was standardized using X-ray and gamma counters. The cross-section and the interferences due to the Mn(n, 2n) and Fe(n,p) were studied under several different irradiation conditions. Appropriate chemical process before and after the irradiation was studied. Some applications of this method, especially the examination of local distibutions of 53Mn in iron and stone meteorites, were performed. The 53Mn content in an iron target bombarded by a high energy proton was determined in the presence of 54Mn. An artificial method was proposed for the preparation of a 53Mn source essentially free from 54Mn.

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

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.

Gamma rays from the reaction 29Si(p, γ)30P

Abstract Thin 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 MeV and 1.333 MeV using sodium iodide scintillation counters. The two resonant levels correspond to the excited states in 30 P at 6.835±0.03 MeV and 6.86±0.03 MeV, respectively. Estimated values of spins, parities, isobaric spins and reduced gamma radiation widths were J π = 1 + , T = 0, Γ γ = 0.21±0.05 eV for the 6.835 MeV state and J π = 2 ± , T = 1, Γ γ = 0.28±0.05 eV for the 6.86 MeV state. The Q value of the reaction was measured to be Q = 5.57±0.03 MeV. Most of the gamma ray transitions from the resonant levels are in accord with the isobaric spin selection rule for self-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.

ANGULAR DISTRIBUTIONS OF HIGH ENERGY GAMMA RAYS FROM THE F

The reaction F/sup 19(p, gamma )Ne/sup 20/ was studied for protein energies from 550 to l500 kev. The 1322-kev resonance reported previously was not observed. The angular distributions of the gamma rays from Ne/sup 20/ compound states corresponding to the E/sub p/ = 669 and l425-kev resonances to the first excited state were isotropic within 2% in both cases. The angular distribution of the gamma ray to the first excited state of Ne/sup 20/ at E/sup p/ = 1090 kev was W( theta ) = (1 plus or minus 0.028) + (0.363 plus or minus 0.051) P/sub 2/(cos theta ) -- (0.019 plus or minus 0.069) P/sub 4/ (cos THETA ). From this result the spin and parity of the l3.9l-Mev state of Ne/sub 20/ was determined to be 2/sup -/. (auth)