Hyperfine Structure of Atomic Phosphorus

The spin-exchange optical polarization method was used to determine the sign and the magnitude of the hyperfine interaction constant in the ground (3p)³⁴S3/2 state of atomic P³¹. The measurements were made by monitoring the transmission of circularly polarized rubidium D₁ (5P1/2→5S1/2) resonance radiation through a flask containing rubidium, atomic phosphorus, and a buffer gas as a function of the frequency of an external radio-frequency field. The value for the hyperfine interaction constant of P³¹ obtained by extrapolation to zero pressure in a helium buffer gas is A(P³¹)=+(55055691±8) cps/sec. The pressure shifts in cycles/sec/mm Hg of the phosphorus hyperfine interaction constant for helium and neon buffer gases are +3.61±{}0.23 and +6.73±{}0.15, respectively.