Neutron-Capture Gamma Rays inCl36

Abstract

$\gamma -\gamma$ coincidences on the gamma rays following thermal neutron capture in ${\mathrm{Cl}}^{35}$ have been measured. Combining these results with the energy levels in ${\mathrm{Cl}}^{36}$ known from the ${\mathrm{Cl}}^{35}(d, p){\mathrm{Cl}}^{36}$ reaction and the ${\mathrm{Cl}}^{35}(n, \gamma ){\mathrm{Cl}}^{36}$ gamma-ray spectrum measured by other workers, a decay scheme is constructed which un-ambiguously places most of the known gamma rays in ${\mathrm{Cl}}^{36}$. An examination is made of the reduced widths of gamma rays emanating from the capturing state, and it is shown that the reduced widths for gamma rays of the same multipolarity can fluctuate widely, and that these fluctuations do not appear to be correlated with the final-state shell model configuration. It is also shown that the reduced widths for $E1\mathrm{}$ and $M1\mathrm{}$ transitions emanating from the capturing state are significantly smaller than those calculated from the single-particle estimate, and that $E1\mathrm{}$ transitions are more intense than $M1\mathrm{}$ transitions by about a factor of four. Evidence is presented for there being collective motion present in some of the higher excited states in ${\mathrm{Cl}}^{36}$.