Interlevel transfer mechanisms and their application to grasers*

Within the gamma‐ray laser (GRASER) research community, much attention is being given to two‐step schemes that store energy in a long‐lived isomeric state and achieve lasing by transferring population to a short‐lived state. Because the electron system exhibits large multipole moments and is in the near field of the nucelus, it can be used as an intermediate mechanism for transferring energy, angular momentum, and parity change. Two distinct electron‐nucleus interaction mechanisms are discussed: (1) resonant electronic transitions and (2) collective outer‐shell excitations.