title: The use of differential transverse relaxation to detect mobile species in solids.
abstract: Delayed acquisition of the proton NMR in selected organic molecular solids (L-alanine, durene, ethyl fumarate, and p-hydroxybenzoic acid) is shown to allow the observation of mobile species in the presence of relatively rigid bulk molecules. The mobility is found to be thermally activated. The combination of the thermally activated motion and magic-angle spinning leads to a fraction of these species moving nearly isotropically on the time scale of the inverse of the homonuclear dipolar splitting. In the case of ethyl fumarate and alanine, there exist populations with differing values of T1 and T1 row. This indicates the co-existence of relatively rigid and relatively mobile molecules in the same sample. The intensities under delayed acquisition cannot always be trusted to yield quantitative information. Comparison of spectra taken under delayed acquisition and under the CRAMPS (B.C. Gerstein, R.G. Pembleton, R.C. Wilson and L.M. Ryan, J. Chem. Phys., 66 (1977)361) technique is made.
authors.affiliation: Ames Laboratory, Iowa State University 50011-3020, USA.
authors.forename: B C
authors.initials: BC
authors.lastname: Gerstein
authors.forename: J Z
authors.initials: JZ
authors.lastname: Hu
authors.forename: J
authors.initials: J
authors.lastname: Zhou
authors.forename: C
authors.initials: C
authors.lastname: Ye
authors.forename: M
authors.initials: M
authors.lastname: Solum
authors.forename: R
authors.initials: R
authors.lastname: Pugmire
authors.forename: D M
authors.initials: DM
authors.lastname: Grant
mesh_terms: D000409:Alanine / Q000737:chemistry*; D001555:Benzene Derivatives / Q000737:chemistry*; D003461:Crystallography; D003890:Desiccation; D004578:Electron Spin Resonance Spectroscopy; D005650:Fumarates / Q000737:chemistry*; D006859:Hydrogen; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D010226:Parabens / Q000737:chemistry*; D011522:Protons; D013696:Temperature
chemical_list: D001555:Benzene Derivatives; D005650:Fumarates; D010226:Parabens; D011522:Protons; C023973:durene; D006859:Hydrogen; C038193:4-hydroxybenzoic acid; D000409:Alanine; C061175:ethyl fumarate