Hyperfine-Induced 1s2s 1S0-1s2p 3P0 Transition and Fine-Structure Measurement in Heliumlike Nitrogen

We have observed the 1{ital s}2{ital s}{sup 1}{ital S}{sub 0}-1{ital s}2{ital p}{sup 3}{ital P}{sub 0} transition in {sup 14}N{sup 5+} using Doppler-tuned fast-beam laser spectroscopy. This transition, absolutely forbidden for atoms with zero nuclear spin, occurs due to mixing of states of different {ital J} by the hyperfine interaction. By measuring the difference between the 2{sup 1}{ital S}{sub 0}-2{sup 3}{ital P}{sub 1,{ital F}} and 2{sup 1}{ital S}{sub 0}-2{sup 3}{ital P}{sub 0} transition energies, we have obtained a value for the 1{ital s}2{ital p}{sup 3}{ital P}{sub 1}-2{sup 3}{ital P}{sub 0} fine-structure splitting in N{sup 5+}. Our result will test quantum-electrodynamic corrections to recent high precision calculations [Z.-C. Yan and G.W.F. Drake, Phys. Rev. Lett. {bold 74}, 4791 (1995)]. {copyright} {ital 1996 The American Physical Society.}