Discrete deexcitations in 235U from Nuclear Resonance Fluorescence

Systematics of the even-even rare-earth nuclei suggest a concentration of $M1$ excitations peaking around 3 MeV with a $\sum{B(M1)\uparrow}$ strength of $\sim3\mu_N^2$. In addition, a linear dependence on the square of the ground-state deformation was observed in the systematics of the $\sum{B(M1)\uparrow}$ strengths. The actinide region is interesting for investigation of the ``scissors'' mode of $M1$ excitations because it has neutron-rich nuclei with large deformations. Evidence of $M1$ resonances concentrated around 2.0-2.5 MeV were found in $^{238}$U \& $^{232}$Th. A research program has been initiated at TUNL to measure dipole transitions in the actinide using HI$\gamma$S. Nearly monoenergic $\&$ circular polarized $\gamma$-ray beams below 3.0 MeV was used to measure transitions in $^{235}$U. More than 20 transitions were observed. The integrated cross sections, $B(M1)$ strengths \& branching transitions intensities will be presented and compared with previous measurements.