Nuclear Energy Levels ofNa24in the Region from 630 to 860 kev

Abstract

An investigation of the nuclear level structure of ${\mathrm{Na}}^{24}$ for neutron energies in the range from 630 to 860 kev revealed the presence of 73 levels distributed throughout the range. Each of the two previously known large peaks was found to be composed of a set of levels. These levels are attributable to values of $J$ up to 7 for the first peak and up to $J=6\mathrm{}$ for the other one. No $s$-wave levels were identifiable in this region and it is doubtful that any $p$-wave levels are present. A set of parameters was determined for the levels by a best fit to the data. These levels were then grouped with those up to 630 kev to obtain a combined total of 230 levels up to 860 kev. The parameters of these levels show the following distributions: (a) an approximate exponential distribution for the level spacings, (b) an approximate exponential or Porter-Thomas distribution for the neutron widths with a tendency to favor the latter, and (c) a distribution of the angular momenta which agrees with the theoretical distribution given by Bloch. Reasonable values of the strength functions were obtained for $s$- and $p$-wave levels (0.035 and 0.27, respectively) but the values for $l>~2$ appear to be much too large. A plot of the number of levels having energies $<~E_n$ as a function of $E_n$ shows fluctuations about a linear trend, with no bending away from this trend at high energies to indicate a general missing of levels.