Large Contributions Of Negative-Energy States To Forbidden Magnetic-Dipole Transition Amplitudes In Alkali-Metal Atoms

The influence of negative-energy states (NES) on forbidden magnetic-dipole ns(1/2) - (n + 1)s(1/2) transitions in alkali-metal atoms is investigated. We find that the NES contributions are significant in almost all cases and, for rubidium. reduce the transition rate by a factor of 8. We tabulate magnetic-dipole (M-1) transition amplitudes for the alkalis. Our M-1 value for cesium, where accurate measurements are available, differs from experiment by 16%. We briefly discuss the feasibility of an experimental test of NES effects.