Zeeman splitting of the methane 2947.912-${\mathrm{cm}}^{-1\mathrm{}}$ $F_1^{}{}_{}{}^{\mathrm{}\left(2\right)\mathrm{}}$ line was studied. The $g$ factor of the rotational magnetic moment of methane was measured to be $g_J=+0.311\mathrm{}\pm 0.006$ and it was found that $g_J({\nu }_3=1)$ is equal to $g_J({\nu }_3=0)$. A Doppler-generated "level-crossing" saturated absorption signal was observed and is described.

• Received 10 December 1970

DOI:https://doi.org/10.1103/PhysRevLett.26.289