Neutron resonance spectroscopy: Chlorine

Results are presented of time of flight total $\sigma$ vs $E$ measurements for natural Cl to 400 keV. Resonance parameters were obtained for 35 resonances below 200 keV. Of these, 12 resonances were assigned to ${}_{}{}^{35}{}_{}{}^{}\mathrm{Cl}$, 6 to ${}_{}{}^{37}{}_{}{}^{}\mathrm{Cl}$, with 17 weak resonances for which isotope assignments could not be made. On the basis of our assignments as $s$ or $p$ resonances, $10{}_{}{}^4{}_{}{}^{}\mathrm{S}_0^{}{}_{}{}^{}=\left({0.12}_{-0.07\mathrm{}}^{+0.23\mathrm{}}\right)$ for ${}_{}{}^{35}{}_{}{}^{}\mathrm{Cl}$ and (${0.59}_{-0.28\mathrm{}}^{+0.66\mathrm{}}$) for ${}_{}{}^{37}{}_{}{}^{}\mathrm{Cl}$. For ${}_{}{}^{35}{}_{}{}^{}\mathrm{Cl}$, $10{}_{}{}^4{}_{}{}^{}\mathrm{S}_1^{}{}_{}{}^{}=\left({0.77}_{-0.29\mathrm{}}^{+0.53\mathrm{}}\right)$ with no $S_1$ determination for ${}_{}{}^{37}{}_{}{}^{}\mathrm{Cl}$. The anomalous behavior of $\sigma$ vs $E$ below ∼ 1000 eV for natural Cl, along with previously established thermal cross sections, are fitted by assigning a bound resonance in ${}_{}{}^{35}{}_{}{}^{}\mathrm{Cl}$ at - 130 eV, having $l=0\mathrm{}$, $J=2\mathrm{}$, ${\Gamma }_n^0=0.725\mathrm{}$ eV, and ${\Gamma }_{\gamma }=0.378\mathrm{}$ eV.