title: Low-field approach to double resonance in nuclear quadrupole resonance of spin-1 nuclei.
abstract: Using double-resonance conditions, in which the Larmor frequency of a spin-1/2 nucleus is matched to one of the nuclear quadrupole resonance frequencies of a spin-1 nucleus, the authors demonstrate increased cross relaxation between the two nuclear spin species. They calculate the cross-relaxation rate using the motionally averaged heterogeneous dipole Hamiltonian as a perturbation to the combined quadrupole and Zeeman Hamiltonians. Using this cross-relaxation rate, in addition to hydrogen and nitrogen autorelaxation rates, expressions governing spin-1/2 and spin-1 spin-lattice relaxation are determined. With ammonium nitrate, containing nitrogen (spin-1) and hydrogen (spin-1/2), increased nitrogen signal and spin-lattice relaxation are demonstrated, using fields less than 120 G. The cross-relaxation rate is also measured and an overall signal/noise improvement by a factor of 2.3+/-0.1 is attained.
authors.affiliation: Department of Physics and Astronomy, George Mason University, Fairfax, Virginia 22030, USA.
authors.forename: D W
authors.initials: DW
authors.lastname: Prescott
authors.forename: O
authors.initials: O
authors.lastname: Olmedo
authors.forename: S
authors.initials: S
authors.lastname: Soon
authors.forename: K L
authors.initials: KL
authors.lastname: Sauer