Observation of an atomic Starkelectric-quadrupole interference

Abstract
An interference between electric quadrupole and Stark induced dipole amplitudes is observed for the first time. Measurement of this interference in atomic strontium permits the first experimental determination of the decay rate between the lowest P1 and metastable D1 levels in an alkaline-earth atom. We obtain the result A(5s5p-5s4d)=(3.85±0.94±0.5 3)×103 s1.