OBSERVATION OF A PAKE DOUBLET IN THE H-1-NMR SPECTRUM OF CENIINHX

H-1 nuclear-magnetic-resonance (NMR) studies have been performed in CeNiInH(x) (x = 1.0 and 1.6) in the temperature range 140-300 K. Near 300 K, the H-1 NMR spectra show a single narrow line. Below about 210 K, the spectra look very much like a Pake doublet on which a central narrow line is superimposed. The experimental H-1 NMR spectrum of CeNiInH1.0 at 140 K has been fitted to a theoretical line shape consisting of a doublet and a central Lorentzian line. This fitting yields a proton-proton separation of about 1.48 angstrom +/- 0.02. The ordered arrangement of the paired protons in CeNiIn has been discussed in terms of the proposed hydrogen sites in isostructural systems.