Spin Rotation Constant and Rotational Magnetic Moment of 13C16O

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Abstract
13C16O has been studied by the molecular‐beam magnetic‐resonance method in the high‐field limit. Two different spectra were observed. These correspond, first, to the reorientation of the carbon‐13 nuclear spin with respect to the external field H, and second, to the reorientation of the rotational angular momentum with respect to H. By analyzing these spectra with third‐order perturbation theory, it was found that the carbon‐13 spin–rotation constant c = − (32.59 ± 0.15) kHz , and that the rotational gyromagnetic ratio gJ = −(0.25691 ± 0.00020) nm . From this measurement of gJ and the known value of the molecular quadrupole moment, the anisotropy constant f of the susceptibility tensor has been determined. It was shown that f / H2 = + (38.9 ± 3.9) × 10−5Hz G−2 . By combining the present results for c and gJ with Huo's ab initio calculations of the ground‐state electronic properties of the molecule, the average carbon‐13 shielding constant σa and the mean diamagnetic susceptibility ξa have been evaluated. These are: σa = 5.0 × 10−6 and ξa = − 203 × 10−31erg G−2·molecule−1 . A simple method of determining the sign of c in terms of the sign of gJ by inserting an obstacle into the molecular beam is described.