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Neutron Capture γ -Rays from Titanium, Chromium, Iron, Nickel, and Zinc

1953; American Institute of Physics; Volume: 89; Issue: 2 Linguagem: Inglês

10.1103/physrev.89.375

1536-6065

B. B. Kinsey, G. A. Bartholomew,

Radioactive Decay and Measurement Techniques

The neutron capture $\ensuremath{\gamma}$-rays emitted by the even-charge elements, from titanium to zinc, have been investigated with the aid of a pair spectrometer.Titanium emits a very simple spectrum. Two strong $\ensuremath{\gamma}$-rays, 6.756\ifmmode\pm\else\textpm\fi{}0.006 and 6.412\ifmmode\pm\else\textpm\fi{}0.006 Mev, are produced by capture in ${\mathrm{Ti}}^{48}$. Neither the direct transition to the ground state of ${\mathrm{Ti}}^{49}$, nor the transitions to the ground states of ${\mathrm{Ti}}^{48}$ and ${\mathrm{Ti}}^{50}$ were detected. From chromium the $\ensuremath{\gamma}$-rays corresponding to transitions to the ground state (9.716\ifmmode\pm\else\textpm\fi{}0.007 Mev) and to the first excited state (8.881\ifmmode\pm\else\textpm\fi{}0.007 Mev) of ${\mathrm{Cr}}^{54}$ are prominent and have intensities of 13 and 35 photons per 100 captures in ${\mathrm{Cr}}^{53}$. The direct transition to the ground state of ${\mathrm{Cr}}^{51}$ was not detected. The iron spectrum is dominated by a strong $\ensuremath{\gamma}$-ray with the energy 7.639\ifmmode\pm\else\textpm\fi{}0.004 Mev resulting from neutron capture in ${\mathrm{Fe}}^{56}$. This $\ensuremath{\gamma}$-ray is produced in the transition in ${\mathrm{Fe}}^{57}$ either to the ground state or to the excited state at 14 kev. Two weaker $\ensuremath{\gamma}$-rays with nearly equal energies close to 6 Mev are also produced in this isotope. The ground state $\ensuremath{\gamma}$-ray and the $\ensuremath{\gamma}$-rays leading to the first two excited states of ${\mathrm{Fe}}^{55}$ have been identified. Of these, the groundstate $\ensuremath{\gamma}$-ray (9.298\ifmmode\pm\else\textpm\fi{}0.007 Mev) is strong, about 50 photons per 100 captures in ${\mathrm{Fe}}^{54}$. A part of the counting rate ascribed to this $\ensuremath{\gamma}$-ray, however, may be due to the $\ensuremath{\gamma}$-ray producing the first excited state of ${\mathrm{Fe}}^{58}$ in a direct transition. The ground state $\ensuremath{\gamma}$-ray in ${\mathrm{Fe}}^{58}$ (10.16\ifmmode\pm\else\textpm\fi{}0.04 Mev) accounts for about 5 percent of all captures by ${\mathrm{Fe}}^{57}$. The nickel spectrum contains an intense $\ensuremath{\gamma}$-ray with an energy of 8.997\ifmmode\pm\else\textpm\fi{}0.005 Mev, which is produced in 50 percent of the captures in ${\mathrm{Ni}}^{58}$. Another prominent $\ensuremath{\gamma}$-ray at 8.532\ifmmode\pm\else\textpm\fi{}0.008 Mev may represent the transition to the ground state in ${\mathrm{Ni}}^{61}$; if so, it accounts for some 80 percent of captures in ${\mathrm{Ni}}^{60}$. From considerations of intensity, five of the remaining nickel $\ensuremath{\gamma}$-rays can be ascribed to transitions to excited states in ${\mathrm{Ni}}^{59}$. In the spectrum of zinc, few discrete $\ensuremath{\gamma}$-rays can be discerned above a background of unresolved radiations. Of these, a very strong $\ensuremath{\gamma}$-ray, with an energy to 7.876\ifmmode\pm\else\textpm\fi{}0.007 Mev, probably producing directly the ground state of ${\mathrm{Zn}}^{65}$, is emitted in 40 percent of neutron captures by ${\mathrm{Zn}}^{64}$.