Magnetic Resonance Molecular-Beam Spectra of Methane

Abstract

A detailed analysis of the hyperfine Hamiltonian for the protons in C${\mathrm{H}}_4$ 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 (+) 10.40±0.10 kc/sec, and the $g$ value of the rotational magnetic moment for the C${\mathrm{H}}_4$ molecule was measured to be (+)0.3133±0.0002. Neither sign was measured, but strong arguments are given that the signs in parentheses are the correct ones. The proton in CH${\mathrm{D}}_3$ was also investigated to give, with the C${\mathrm{H}}_4$ results, the spin-rotational constant for rotations perpendicular to a carbon-hydrogen band axis as (+)17.4±1.6 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.