The hyperfine structure has been measured in several rotational states of the X${}^1$${\Sigma }_g^{+}$, v’’=0 ground state of ${\mathrm{Na}}_2$ with the aid of the laser-rf double-resonance technique on a molecular beam. The rotational states observed were especially chosen to avoid distortion of the line shapes by laser-induced coherence effects. The electric quadrupole, nuclear spin-rotation, tensor spin-spin, and scalar spin-spin hyperfine coupling constants are, respectively, eqQ=[-458.98(4)-0.007 28(25)J(J+1)] kHz, c=242.9(1.5) Hz, d=302.6(5.0) Hz, and δ=1066.7(6.5) Hz.

• Received 1 July 1985

DOI:https://doi.org/10.1103/PhysRevA.32.2595