title: A new mechanism for electron spin echo envelope modulation.
abstract: Electron spin echo envelope modulation (ESEEM) has been observed for the first time from a coupled heterospin pair of electron and nucleus in liquid solution. Previously, modulation effects in spin-echo experiments have only been described in liquid solutions for a coupled pair of homonuclear spins in nuclear magnetic resonance or a pair of resonant electron spins in electron paramagnetic resonance. We observe low-frequency ESEEM (26 and 52 kHz) due to a new mechanism present for any electron spin with S > 12 that is hyperfine coupled to a nuclear spin. In our case these are electron spin (S = 32) and nuclear spin (I = 1) in the endohedral fullerene N@C(60). The modulation is shown to arise from second-order effects in the isotropic hyperfine coupling of an electron and (14)N nucleus.
authors.affiliation: Department of Materials, Oxford University, UK. john.morton@materials.ox.ac.uk
authors.forename: John J L
authors.initials: JJ
authors.lastname: Morton
authors.forename: Alexei M
authors.initials: AM
authors.lastname: Tyryshkin
authors.forename: Arzhang
authors.initials: A
authors.lastname: Ardavan
authors.forename: Kyriakos
authors.initials: K
authors.lastname: Porfyrakis
authors.forename: S A
authors.initials: SA
authors.lastname: Lyon
authors.forename: G Andrew D
authors.initials: GA
authors.lastname: Briggs