Rotational magnetic moment spectra of a series of tetrahedral molecules

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Abstract
The molecular beam magnetic resonance method has been used to study the rotational magnetic moment spectrum of each of a series of tetrahedral XY4 molecules in which nucleus X has no spin and nucleus Y has a spin of one‐half. The transitions observed involve the reorientation of the rotational angular momentum relative to an external magnetic field in the high‐field limit. It is shown that to excellent approximation the transition frequencies depend on only two molecular constants: the rotational g factor gJ and the average spin rotation constant ca of nucleus Y. For each molecule, both constants were determined. The results are for CH4 gJ=+0.31338(4) nm, ca=+10.5(5) kHz; for SiH4 gJ=−0.27036(50) nm, ca=+3.6(6) kHz; for GeH4 gJ=−0.10815(14) nm, ca=+4.0(3) kHz; for CF4 gJ=−0.03124(5) nm, ca=−6.78(6) kHz; for SiF4 gJ=−0.03193(4) nm, ca=−2.45(8) kHz; for GeF4 gJ=−0.02658(5) nm, ca=−1.85(5) kHz. For each tetrafluoride, the sign of ca was taken from earlier theoretical work; all other signs were determined experimentally here. In all cases where comparison values are available, the agreement is good. The application of these measurements to investigations of molecular electronic properties and of nuclear spin relaxation processes is discussed.