Laser magnetic resonance measurement of the P-3(1)-P-3(0) fine-structure separation of P+

The far-infrared laser magnetic resonance spectrum associated with the J = 1 <-- 0 fine-structure transition of P-31(+) in its ground P-3 State has been recorded. This is the first laboratory observation of this magnetic dipole transition, and its frequency has been measured 2 orders of magnitude more accurately than the previous, indirect determination from optical spectroscopy. The frequency is Delta E(10) = 4944433.0 +/- 1.7 MHz. A small nuclear hyperfine splitting was also observed for the J = 1 level.