Resonance Fluorescence inRe187

The excited levels of ${\mathrm{Re}}^{187}$ which are populated in the decay of ${\mathrm{W}}^{187}$ have been investigated by the resonance-fluorescence method. Applying the centrifuge technique and a Li-drifted germanium counter as detector for the scattered radiation, resonance fluorescence from the levels at 880, 864, 773, 686, 618, and 512 keV has been identified. With the most likely spin values for these levels, the following mean lifetimes have been obtained: 880-keV level, 0.44±0.13 psec; 864-keV level, 2.7±0.9 psec; 773-keV level, 0.25±0.02 psec; 686-keV level, 8.6±0.5 psec; 618-keV level, 15.7±1.3 psec; and 512-keV level, 23±8 psec. No scattering has been observed from the levels at 589 and 625 keV. The investigation of the $\gamma$ spectrum emitted by the ${\mathrm{W}}^{187}$ source with a Li-drifted germanium detector revealed a new transition at 816.3±0.5 keV. The results are discussed on the basis of the Nilsson model.