Rotational frequencies of methyl group tunneling.

Methyl tunnel frequencies, measured at 4 K, are found to be 455 +/- 8 kHz in methyl malonamide and 496 +/- 8 kHz in methyl ethyl ketone. The first is unaffected by deuteration of the amide groups. Measurements of the temperature dependence of the spin lattice relaxation time are also reported for methyl malonamide and a further test is made of a previously reported correlation between tunnel frequency and the temperature of the T1 minimum. The measurements are in good agreement with the universal correlation curve.