Pressure Shifts of the Hyperfine Structure of Atomic Nitrogen

The hyperfine structure of atomic nitrogen in the (2p)³⁴S3/2 electronic ground state has been investigated by the spin-exchange optical polarization method. The transmission of circularly polarized rubidium D₁(5²P1/2↔5²S1/2) resonance radiation through a flask containing rubidium vapor, a buffer gas, and atomic nitrogen was observed as a function of the frequency of an applied radio-frequency field. Measurements were made at pressures ranging from 10 to 65 mm Hg in neon, argon, helium, and molecular nitrogen buffer gases. The extrapolated zero-pressure frequency intervals and their corresponding pressure shifts, as determined by the method of least squares, are Average values found for the hyperfine interaction constants are: ${A({N}¹⁴),=+10450930±{}8 cps}{B({N}¹⁴),=+ 1±{}5 cps}{A({N}¹⁵),={-}14645457±{}5 cps}$The quoted errors are based on the dispersion of the various extrapolated values of the zero-pressure intervals. In terms of the statistical variation of the data this error is equivalent to three standard deviations of the mean.The experimental pressure shifts are compared with a theory recently proposed by Adrian and an expression is derived for the Stark shift of the nitrogen hyperfine structure.