Branching and Fragmentation of Dipole Strength in

In recent measurements of the scissors mode in radiative decay experiments, transition strengths were observed that were double that expected from theory and systematics well established from measurements on the radiative excitation channel, that is, using nuclear resonance fluorescence (NRF). Additional strength as measured with NRF can only be present as heretofore unobserved branching or fragmentation of the scissors mode. Such possibilities were investigated in a transmission NRF measurement on the deformed, odd-mass ^{181}Ta, using a quasimonoenergetic γ-ray beam at two beam energies. This measurement further influences applications using transmission NRF to assay or detect odd-mass fissile isotopes. A large branching, ≈75%, of small resonances to excited states was discovered. In contrast, previous studies using NRF of the scissors-mode strength in odd-mass nuclei assumed no branching existed. The presently observed branching, combined with the observed highly fragmented elastic strength, could reconcile the scissors-mode strength observed in NRF measurements with the expectations for enhanced scissors-mode strength from radiative decay experiments.

Method for determining individual deposition velocities of radon progeny.

The deposition velocity of radon progeny is used to model the removal of progeny from the air by surfaces in assessing indoor air quality. It can also be used to assess radon-induced background in sensitive, low-background experiments. A single value of the deposition velocity is typically used for all radon progeny for modeling purposes. This paper presents a method for uniquely determining the individual deposition velocities of radon progeny. Measurements demonstrating the method were carried out.

Measurement of excitation functions for the (nat)Mo(d,x)99Mo and (nat)Mo(p,x)99Mo reactions.

The excitation functions for proton and deuteron induced reactions on natural molybdenum for the production of 99Mo were measured. The proton induced reaction was measured in the energy range of 11.3-49.6 MeV, and the deuteron induced reaction was measured in the energy range of 9.7-58.5 MeV. Both beams were generated by the 88" cyclotron located at Lawrence Berkeley National Laboratory. The results are compared to previously published data. Thick target yields were obtained by direct measurement, in addition to being determined by integration of the measured cross sections.