title: Spin mixing at level anti-crossings in the rotating frame makes high-field SABRE feasible.
abstract: A new technique is proposed to carry out Signal Amplification By Reversible Exchange (SABRE) experiments at high magnetic fields. SABRE is a method, which utilizes spin order transfer from para-hydrogen to the spins of a substrate in transient complexes using suitable catalysts. Such a transfer of spin order is efficient at low magnetic fields, notably, in the Level Anti-Crossing (LAC) regions. Here it is demonstrated that LAC conditions can also be fulfilled at high fields in the rotating reference frame under the action of an RF-field. Spin mixing at LACs allows one to polarize substrates at high fields as well; the achievable NMR enhancements are around 360 for the ortho-protons of partially deuterated pyridine used as a substrate and around 700 for H2 and substrate in the active complex with the catalyst. High-field SABRE effects have also been found for several other molecules containing a nitrogen atom in the aromatic ring.
authors.affiliation: International Tomography Center, Siberian Branch of the Russian Academy of Science, Institutskaya 3a, Novosibirsk, 630090, Russia. ivanov@tomo.nsc.ru.
authors.forename: Andrey N
authors.initials: AN
authors.lastname: Pravdivtsev
authors.forename: Alexandra V
authors.initials: AV
authors.lastname: Yurkovskaya
authors.forename: Hans-Martin
authors.initials: HM
authors.lastname: Vieth
authors.forename: Konstantin L
authors.initials: KL
authors.lastname: Ivanov