State-Selective High-Energy Excitation of Nuclei by Resonant Positron   Annihilation
  In the annihilation of a positron with a bound atomic electron, the virtual gamma photon created may excite the atomic nucleus. We put forward this effect as a spectroscopic tool for an energy-selective excitation of nuclear transitions. This scheme can efficiently populate nuclear levels of arbitrary multipolarities in the MeV regime, including monopole transitions and giant resonances. In certain cases, it may have a higher cross sections than the conventionally used Coulomb excitation. 
N. A. Belov, Z. Harman
nucl-th physics.atom-ph quant-ph