Magnetic Resonance Molecular-Beam Spectra of Methane

A detailed analysis of the hyperfine Hamiltonian for the protons in CH₄ is given using group-theoretical techniques, a generalized concept of irreducible tensor operators being introduced. Experimental results using the magnetic resonance molecular-beam technique are given and compared with the theoretical results. The average spin-rotational constant for the protons was found to be (+) 10. 400. 10 kc/sec, and the g value of the rotational magnetic moment for the CH₄ molecule was measured to be (+) 0. 31330. 0002. Neither sign was measured, but strong arguments are given that the signs in parentheses are the correct ones. The proton in CHD₃ was also investigated to give, with the CH₄ results, the spin-rotational constant for rotations perpendicular to a carbon-hydrogen band axis as (+) 17. 41. 6 kc/sec and for rotations about the axis as (-) 3. 6 3. 2 kc/sec. A measurement of the quadrupole moment of a substituted deuteron was attempted with inconclusive results.