This paper reports a new a-priori approach to the calibration of attenuations observed in Recoil-in-Vacuum angular distribution experiments which should allow extraction of g-factors for states of picosecond (ps) lifetime in many nuclei, of both odd-A and even-A without the need for extensive experimentally based calibration. The methods used and results for Ge and Mo isotopes are discussed, with outline applications to both on-line beam/target Coulomb excitation and fission fragment experiments.