Hyperfine Structure of the Metastable Deuterium Atom

The hyperfine separation Δν(2S; D) of the metastable 2²S1/2 state of the deuterium atom has been measured by an atomic-beam magnetic-resonance method that has been described previously. We found that Δν(2S; D)=40924.439±0.020 kc/sec. From this result and the ground-state separation Δν(1S; D) we obtain $R(D){≡}{{Δ}{ν}(2S; D)}{{Δ}{ν}(1S; D)}=1/8(1.0000342±{}0.0000006)$. Comparison of this value with the corresponding quantity for hydrogen, $R(H)=1/8(1.0000346±{}0.0000003)$, confirms within experimental error the theoretical prediction that $R(D)=R(H)$.