Rf transitions characteristic of interaction between the electron spin and the molecular rotation have been observed in para-${\mathrm{H}}_2^{+}$. Values of the coupling coefficients ($\rho$- type doubling constant) are given for two vibrational states tentatively identified as $v=5\mathrm{}$ and $v=6\mathrm{}$. An approximate determination of the rotational magnetic moment in the rotational state $K=2\mathrm{}$ has also been made.

• Received 23 October 1967

DOI:https://doi.org/10.1103/PhysRevLett.20.39