MeV Maximum Energy Research Articles

Directional correlation of the 0.845 and 1.24 MeV γ-rays of56Fe

The directional correlation of the 0.845 ÷ 1.24 MeV γ-γ cascade of the56Fe in coincidence with the β+ spectrum of 1.5 MeV maximum energy has been studied. The observed correlation function, after correction for the finite angular resolution of the detectors, is given byW(ϑ)=1+(0.1023±0.0027)P2(cosϑ)+(0.0015±0.0035)P4(cosϑ) according to a spin and multipolarity assignment 4(2)2(2)0.

Decay ofSc47

${\mathrm{Sc}}^{47}$ was milked from ${\mathrm{Ca}}^{47}$, prepared by proton irradiation of CaO, and its radiations were studied by coincidence and gamma-ray spectrometry. ${\mathrm{Sc}}^{47}$ was found to decay with the emission of beta rays of 0.46\ifmmode\pm\else\textpm\fi{}0.02 and 0.62\ifmmode\pm\else\textpm\fi{}0.03 Mev maximum energy. 66\ifmmode\pm\else\textpm\fi{}3% of the decay is accompanied by a 0.157\ifmmode\pm\else\textpm\fi{}0.007 Mev gamma ray in coincidence with the 0.46-Mev beta rays.

New Isotopes of Niobium:Nb89andNb89m

A new 1.9\ifmmode\pm\else\textpm\fi{}0.3-hour activity was found in niobium fractions isolated from proton irradiated niobium and zirconium metal foils. By identification of the 78-hour daughter activity, the mass assignment has been made to ${\mathrm{Nb}}^{89}$. Evidence indicates that the decay is a simple positron emission of 2.9\ifmmode\pm\else\textpm\fi{}0.4 Mev maximum energy. Evidence was also obtained for the existence of the \textonehalf{} - isomeric state in ${\mathrm{Nb}}^{89}$ which decays with a 0.8\ifmmode\pm\else\textpm\fi{}0.3-hour half-life by positron emission to the similar 4.4-minute state in ${\mathrm{Zr}}^{89}$.

Radiations of 53-MinI134and 86-SecI136

The radiations from 53-min ${\mathrm{I}}^{134}$ and 86-sec ${\mathrm{I}}^{136}$ were examined with a scintillation spectrometer and compared with known radiations. The former was found to emit beta rays of 1.5\ifmmode\pm\else\textpm\fi{}0.1 Mev and 2.5\ifmmode\pm\else\textpm\fi{}0.2 Mev maximum energy, and $\ensuremath{\gamma}$ rays of the following energies: 0.86\ifmmode\pm\else\textpm\fi{}0.01 Mev, 1.10\ifmmode\pm\else\textpm\fi{}0.03 Mev, and 1.78\ifmmode\pm\else\textpm\fi{}0.05 Mev. Coincidence measurements showed that the 2.5-Mev $\ensuremath{\beta}$ rays were followed by the 0.86-Mev $\ensuremath{\gamma}$ rays and that the first excited level in ${\mathrm{Xe}}^{134}$ is very likely at 0.86 Mev as predicted by the systematics of even-even nuclei. There is some evidence for two additional weak $\ensuremath{\gamma}$ rays at 120 kev and 200 kev.The ${\mathrm{I}}^{136}$ was found to decay by emission of a $\ensuremath{\beta}$-ray branch of 6.3\ifmmode\pm\else\textpm\fi{}0.3 Mev maximum energy leading to the ground state of ${\mathrm{Xe}}^{136}$, a 5.0\ifmmode\pm\else\textpm\fi{}0.3 Mev $\ensuremath{\beta}$-ray branch followed by 1.38\ifmmode\pm\else\textpm\fi{}0.05 Mev $\ensuremath{\gamma}$ rays, and a 3.7\ifmmode\pm\else\textpm\fi{}0.2 Mev $\ensuremath{\beta}$-ray branch followed by 2.9\ifmmode\pm\else\textpm\fi{}0.2 Mev $\ensuremath{\gamma}$ rays. A possible disintegration scheme is proposed. The first excited state at 1.38 Mev corresponds to that expected for the 82-neutron closed-shell nucleus, ${\mathrm{Xe}}^{136}$.

Radiations ofCe143

A spectrometric investigation of the radiations of ${\mathrm{Ce}}^{143}$ has revealed that there are beta-ray groups of 1.090\ifmmode\pm\else\textpm\fi{}0.005, 1.390\ifmmode\pm\else\textpm\fi{}0.005, and 0.710\ifmmode\pm\else\textpm\fi{}0.010 Mev maximum energy. In addition, there was evidence for a fourth lower energy group which could not be resolved. Electromagnetic radiations of energies 0.0349\ifmmode\pm\else\textpm\fi{}0.001, 0.126\ifmmode\pm\else\textpm\fi{}0.005, \ensuremath{\sim}0.160\ifmmode\pm\else\textpm\fi{}0.010, 0.289\ifmmode\pm\else\textpm\fi{}0.005, 0.356\ifmmode\pm\else\textpm\fi{}0.005, 0.660\ifmmode\pm\else\textpm\fi{}0.010, and 0.720\ifmmode\pm\else\textpm\fi{}0.010 Mev were found. A decay scheme for ${\mathrm{Ce}}^{143}$ is proposed.

The Radiations from 2.7-DayAu198

The radiations from the 2.7-day ${\mathrm{Au}}^{198}$ activity were investigated with a counter and photographically recording beta-ray spectrometer. The shape of the continuous beta-ray spectrum is essentially that of an allowed spectrum with some additional intensity in the region below 0.6 Mev. The maximum energy of the spectrum is 0.966\ifmmode\pm\else\textpm\fi{}0.010 Mev. Very strong conversion lines are observed from a gamma-ray of 0.408\ifmmode\pm\else\textpm\fi{}0.004 Mev, and weak conversion lines attributed to gamma-rays of 0.157\ifmmode\pm\else\textpm\fi{}0.002 and 0.208\ifmmode\pm\else\textpm\fi{}0.002 Mev were detected. These weak lines and the deviation of the spectrum from the theoretically permissable spectra suggest that the beta-ray spectrum may be complex with a component of 0.601\ifmmode\pm\else\textpm\fi{}0.016 Mev maximum energy occurring in 15 percent, or less, of the disintegrations. This suggested mode of decay is consistent with the theoretical analysis of the spectrum and half-life. In terms of this theory the 0.966-Mev transition is described by the polar-vector or pseudo-scalar interaction corresponding to a nuclear spin change of \ifmmode\pm\else\textpm\fi{}1, with no parity change.

On the Photodisintegration of Beryllium and Deuterium

High voltage x-rays have been used to redetermine the thresholds for the photodisintegration of beryllium and deuterium nuclei, giving 1.627\ifmmode\pm\else\textpm\fi{}0.010 Mv and 2.183\ifmmode\pm\else\textpm\fi{}0.012 Mv, respectively. The ratio of the two cross sections ($\frac{{\ensuremath{\sigma}}_{\mathrm{Be}}}{{\ensuremath{\sigma}}_{\mathrm{D}}}$) at 15 kv above the threshold voltage is approximately 10. The angular distribution of the neutrons from the photodisintegration of deuterium has been investigated, with x-rays of 2.43 Mev maximum energy, and found to be approximately isotropic. On the basis of these data, the value of the ratio of the photomagnetic to photoelectric cross section is estimated to be 6 to 1.

Two Radioactive Substances from Magnesium after Deuteron Bombardment

Under bombardment by 3.3 MEV deuterons, magnesium becomes radioactive with the emission of negative electrons and gamma-rays, and with two decay periods: 10\textonequarter{}\ifmmode\pm\else\textpm\fi{}\textonequarter{} min. and 15.8\ifmmode\pm\else\textpm\fi{}0.5 hours. These periods are characteristic of ${\mathrm{Mg}}^{27}$ (Fermi) and ${\mathrm{Na}}^{24}$ (Lawrence). The reactions producing these bodies are: ${_{12}\mathrm{Mg}^{26}+_{1}\mathrm{H}^{2},=_{12}\mathrm{Mg}^{27}+_{1}\mathrm{H}^{1}; _{12}\mathrm{Mg}^{27}=_{13}\mathrm{Al}^{27}+\ensuremath{\beta}+\ensuremath{\gamma}.}{_{12}\mathrm{Mg}^{26}+_{1}\mathrm{H}^{2},=_{11}\mathrm{Na}^{24}+_{2}\mathrm{He}^{4}; _{11}\mathrm{Na}^{24}=_{12}\mathrm{Mg}^{24}+\ensuremath{\beta}+\ensuremath{\gamma}.}$ The protons have not been looked for. The alpha-particles have a range of about 7 cm. The ${\mathrm{Mg}}^{27}$ beta-rays have 2.0 MEV maximum energy, and the accompanying hard gamma-ray has about 1.3 MEV energy. The voltage excitation functions of these two activities have been measured, and have been found to follow different laws. The ${\mathrm{Mg}}^{27}$ following the Oppenheimer and Phillips function and the ${\mathrm{Na}}^{24}$ the older Gamow function. At 3 MEV one atom becomes ${\mathrm{Na}}^{24}$ for each 9.6 atoms going to ${\mathrm{Mg}}^{27}$. The thick target yield of ${\mathrm{Mg}}^{27}$ atoms is about 5 per ${10}^{7}$ deuterons. The nuclear cross section (${\mathrm{Mg}}^{26}$) at 3 MEV is about 2.4\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}26}$.