title: Long-lived heteronuclear spin-singlet states in liquids at a zero magnetic field.
abstract: We report an observation of long-lived spin-singlet states in a 13C-1H spin pair in a zero magnetic field. In 13C-labeled formic acid, we observe spin-singlet lifetimes as long as 37 s, about a factor of 3 longer than the T1 lifetime of dipole polarization in the triplet state. In contrast to common high-field experiments, the observed coherence is a singlet-triplet coherence with a lifetime T2 longer than the T1 lifetime of dipole polarization in the triplet manifold. Moreover, we demonstrate that heteronuclear singlet states formed between a 1H and a 13C nucleus can exhibit longer lifetimes than the respective triplet states even in the presence of additional spins that couple to the spin pair of interest. Although long-lived homonuclear spin-singlet states have been extensively studied, this is the first experimental observation of analogous singlet states in heteronuclear spin pairs.
authors.affiliation: Institute of Technical and Macromolecular Chemistry, RWTH Aachen University, Worringer Weg 1, 52074 Aachen, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Emondts
authors.affiliation: Department of Physics, University of California, Berkeley, California 94720, USA and AOSense, 767 North Mary Avenue, Sunnyvale, California 94085, USA.
authors.forename: M P
authors.initials: MP
authors.lastname: Ledbetter
authors.affiliation: Department of Physics, University of California, Berkeley, California 94720, USA and Center for Magneto-Optical Research, Institute of Physics, Jagiellonian University, Reymonta 4, PL-30-059 Kraków, Poland.
authors.forename: S
authors.initials: S
authors.lastname: Pustelny
authors.affiliation: Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA and Department of Chemistry, University of California, Berkeley, California 94720, USA.
authors.forename: T
authors.initials: T
authors.lastname: Theis
authors.affiliation: Department of Physics, University of California, Berkeley, California 94720, USA.
authors.forename: B
authors.initials: B
authors.lastname: Patton
authors.affiliation: Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA and Department of Chemistry, University of California, Berkeley, California 94720, USA.
authors.forename: J W
authors.initials: JW
authors.lastname: Blanchard
authors.affiliation: Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA and Department of Chemistry, University of California, Berkeley, California 94720, USA.
authors.forename: M C
authors.initials: MC
authors.lastname: Butler
authors.affiliation: Department of Physics, University of California, Berkeley, California 94720, USA and Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: D
authors.initials: D
authors.lastname: Budker
authors.affiliation: Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA and Department of Chemistry, University of California, Berkeley, California 94720, USA.
authors.forename: A
authors.initials: A
authors.lastname: Pines