M1andE1transition strength near threshold inCe140

The ${}_{}{}^{140}{}_{}{}^{}\mathrm{Ce}(\gamma ,n){}_{}{}^{139}{}_{}{}^{}\mathrm{Ce}$ reaction has been studied near threshold with high energy resolution. The angular distribution of photoneutrons was measured at 90° and 135°, and the $M1\mathrm{}$ and $E1\mathrm{}$ strength functions at an excitation of approximately 9.1 MeV were determined. The measured integrated $M1\mathrm{}$ strength was found to be consistent with the existence of a giant $M1\mathrm{}$ resonance centered at 8.7 MeV as suggested both by calculation and previous electron scattering data. The integrated $E1\mathrm{}$ strength was also found to be consistent with what is known of the $E1\mathrm{}$ strength function in the threshold region.