Slow-Neutron Capture Gamma Rays from Sodium and Cadmium

Abstract

A thin-lens magnetic spectrometer has been used to observe the external conversion spectra of ${\mathrm{Na}}^{23}(n, \gamma ){\mathrm{Na}}^{24}$ and ${\mathrm{Cd}}^{113}(n, \gamma ){\mathrm{Cd}}^{114}$ and the internal conversion spectrum of ${\mathrm{Cd}}^{113}(n, \gamma ){\mathrm{Cd}}^{114}$ in the energy range of 300 kev to 3 Mev. An arrangement using an external neutron beam and one using a source located inside the reactor are compared. It is shown that target materials placed inside the reactor allow a better discrimination against background and permit the use of a $K$ x-ray-conversion-electron coincidence scheme for photoelectric conversion which greatly simplifies the observed conversion spectrum. Four of the nine gamma rays observed from sodium are assigned to transitions on the basis of the known energy levels from ${\mathrm{Na}}^{23}(d, p){\mathrm{Na}}^{24}$; the other five are assigned to probable transitions on an energy and intensity basis. The internal conversion spectrum of ${\mathrm{Cd}}^{114}$ has disclosed a 0+ level at 1308±3 kev and the de-excitation of this level by means of $E2\mathrm{}$ transitions to other states in ${\mathrm{Cd}}^{114}$ is also observed. Three other states in ${\mathrm{Cd}}^{114}$ are proposed in addition to the well-known 559-kev (2+) and 1286-kev (4+) states to explain the observed gamma-ray spectrum: 1212±3 kev (2+ or 1+), 1368±4 kev (2+ or 1+), and 1860+5 kev (4+ or 3+).