Paper 2.14: "Direct Observation of Ortho–Para Transitions in Methane," I. Ozier, P. N. Yi, A. Khosla and N. F. Ramsey, Phys. Rev. Lett. 24, 642–646 (1970)
Reprinted with permission from Physical Review Letters. Copyright 1970, The American Physical Society.
Because of the great interest in methane (CH4) and other spherical top and tetrahedral molecules, we made a series of magnetic resonance measurements on these and similar molecules using the apparatus described in Paper 2.7 and its commentary. The first was by C. H. Anderson and me [Phys. Rev. 149, 14–24 (1966). We used the apparatus described in Paper 2.6. to study the spectrum associated with the reorientations of the total nuclear spin and the rotational angular momentum relative to a strong external magnetic field in CH4 and CHD3. We measured the average spinrotational constants for the protons and the g value of the rotational magnetic moments.
Paper 2.14 reports the first direct observation of the normally forbidden ortho–para transition in CH4. The ortho–para transitions result from spin conversion transitions in a magnetic field where there is an anticrossing between ortho and para levels, and the results give information on the distortion electric dipole moment.
W. Itano and I. Ozier [J. Chem. Phys. 72, 3700–3711 (1980)] have studied in our laboratory the avoided crossing spectrum of methane in the J = 2 rotational state and W. M. Itano and I [J. Chem. Phys. 72, 4941–4945 (1980)] have studied the corresponding spectrum of SiH4 and GeH4. The analysis of the experiments gave the hyperfine constants and rotational g factors of the molecules.
