An avoidedhyphen;crossing RF resonance technique has been used to study methane (12CH4) in the (J=2) rotational state with a conventional molecularhyphen; beam magnetic resonance spectrometer. In zero external field the (I=1) levels are about 8 MHz above the (I=0) levels because of the tensor centrifugal distortion interaction. The (I=1) levels with negative nuclear Zeeman effect can be made nearly degenerate with corresponding (I=0) states by the application of a magnetic field of about 2 kG. Mixing of the levels by nuclear hyperfine interactions gives rise to avoided crossings. Electric and magnetic dipole transitions were observed near these avoided crossings. The method is discussed in detail. Values were obtained for the scalar and tensor spinndash;rotation constantscaandcd, and for the tensor spinndash;spin coupling constantd. By using a value of the tensor centrifugal distortion splitting Dgr;2=60 (DT+6H4T+36L4T) calculated from a combined doublehyphen;resonance and microwave absorption set of distortion constants, a value of the rotationalghyphen;factorgJwas obtained. Alternatively, the value ofgJmeasured in studies of the rotationalhyphen;moment molecularhyphen;beam spectrum can be used, in conjunction with the present work, to obtain Dgr;2. The values and their estimated uncertainties (90percnt; confidence limits) areca=10.372 (83) kHz,cd=18.370 (23) kHz,d=21.17 (32) kHz,gJ=0.31317 (28), and Dgr;2=7970.30 (66) kHz. These results for (J=2) are in agreement with previous determinations, which (except for Dgr;2) represent averages over many values ofJ. The application of the present measurements to calculations of the nuclear magnetic shielding constants and of the molecular magnetic susceptibility is discussed.
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