G. Murray

The accurate determination of some (p, n) thresholds in the proton energy range 5 to 10 MeV

Abstract The thresholds for the reactions Al 27 (p, n)Si 27 , S 34 p, n)Cl 34 , Fe 54 (p, n)Co 54 and Ni 58 (p,n) Cu 58 have been measured with an accuracy of ±5 keV or better. The residual nucleus being in each case a position emitter with a half-life in the range 4 to 0.2 sec, it has been found convenient to measure the reaction yields by the activation method, positions being detected between short periods of proton irradiation. The proton energies at the thresholds were measured in terms of the accurately known energies of alpha particle from ThC and ThC′ sources, by comparison in a broad-range magnetic spectrograph. The values obtained for the (p, n) thresholds were 5802.9±3.8 keV in Al 27 ; 6451.1±4.5 keV in S 34 ; 9202.7±4.8 keV in Fe 54 ; 9512.9±5.0 keV in Ni 58 .

The half-lives of Al26m, Cl34, Co54 and Cu58

Abstract The half-lives of Al26m, Cl34, Co54 and Cu58 have been measured with an accuracy of about 1 2 % . The activities were produced using (p,n) reactions on Mg26, S34, Fe54 and Ni58, respectively, at bombarding energies close to the reaction threshold. A beam chopping technique permitted a series of short irradiations of about one half-life interspersed with periods of several half-lives during which the activities were counted. The values of the half-lives obtained were 6.374±0.016 sec for Al26m, if1.565±0.007 sec for Cl34, 0.1937±0.0010 sec for Co54 and 3.204±0.007 sec for Cu58.

The beta end-point energy for the superallowed fermi decay 14O(β+) 14N

Abstract Accurate measurements of the threshold for the reaction 14 N(p,n) 14 O and of the energy of the first excited state of 14 N have provided a new value for the beta end-point energy in the Fermi decay of 14 O. The result is somewhat lower than the value currently used for ft calculations.

A study of the energy levels of 75Se

Abstract A level scheme has been established for 75Se by observing the γ-rays and internal conversion electrons following the decay of 75Br, and spins and parities have been assigned to some of the states. A search has been made for a low-lying 1 2 − state which systematically occurs in odd-A nuclei with N between 39 and 47, but no candidate has been found. It has been demonstrated that a doublet occurs at 286.5 keV, and that the two components probably possess J π = 3 2 − and 5 2 − .

An anomalous coupling 72+ state in 73Se

Abstract The existence of a 25.9 ± 0.3 keV E3 transition is reported in 73Se with a half-life of 42 min. This together with measurements on the β decay of the ground state and isomeric state of this nucleus, implies that the spins of these states are 7 2 + and 1 2 −, respectively.

Low-lying positive-parity states in 71Ge

Abstract The 20 ms 71 Ge isomeric activity has been positively identified with a 198.4 keV 9 2 + level, by measuring the conversion coefficient of the transition involved. The energies and relative intensities of the γ-rays following the decay of 71 As have been measured, and log ft values calculated. A level scheme for 71 Ge is proposed and compared with the schemes deduced from the (d, p) scattering measurements of Goldman and the (p, nγ) measurements of Malan. It is deduced that the first anomalous positive-parity state in 71 Ge is the 5 2 + 525.1 keV level.

The decay of 73Br

Abstract The energies and relative intensities of the γ-rays following the radioactive decay of 3.3 min 73Br produced by the 59Co(16O, 2n) reaction have been measured using Ge(Li) detectors. No isomeric transition with half-life greater than 1 ms has been observed in 73Br. A level scheme for 73Se is proposed. The results are discussed in the light of observed correlations of the variations in the B(E2) values and the excitation energies of the first 2+ states in doubly even nuclei and the excitation energies of the first 9 2 + states in odd-proton nuclei in the region Z, N = 28 and Z, N = 50.

The decay of 73Se

Abstract The energies and relative intensities of the γ-rays following the radioactive decay of 7.1 h 73Se and 42 min 73mSe produced by the 70Ge(α, n) reaction have been measured using Ge(Li) detectors. The excitation functions of the 11 most prominent γ-rays following the 73Se decays have been studied. A level scheme for 73As is proposed and compared with those of 75As and 75As.

THE POSITRON DECAY OF

Abstract The energies and relative intensities of the gamma rays following the positon decay of 10C to 10B have been studied in order to determine accurately the beta end-points and branching ratios in the decay. The energies of the first two excited states of 10B have been measured as 718.32±0.09 and 1740.16±0.17 KeV, respectively. The branching ratios for the positon decay to the first, second and third excited states have been found to be 98.48−0.02+0.03, 1.523−0.021+0.018 and 0−0.00+0.02%. The ft values for the Fermi and Gamow-Teller transitions have been deduced.

sup 10

Abstract The energies and relative intensities of the gamma rays following the positon decay of 10C to 10B have been studied in order to determine accurately the beta end-points and branching ratios in the decay. The energies of the first two excited states of 10B have been measured as 718.32±0.09 and 1740.16±0.17 KeV, respectively. The branching ratios for the positon decay to the first, second and third excited states have been found to be 98.48−0.02+0.03, 1.523−0.021+0.018 and 0−0.00+0.02%. The ft values for the Fermi and Gamow-Teller transitions have been deduced.