Highly Efficient Polarization of Spin-1/2 Insensitive NMR Nuclei by Adiabatic Passage through Level Anticrossings.
A method is proposed to transfer spin order from para-hydrogen, that is, the H2 molecule in its singlet state, to spin-1/2 heteronuclei of a substrate molecule. The method is based on adiabatic passage through nuclear spin level anticrossings (LACs) in the doubly rotating frame of reference; the LAC conditions are fulfilled by applying resonant RF excitation at the NMR frequencies of protons and the heteronuclei. Efficient conversion of the para-hydrogen-induced polarization into net polarization of the heteronuclei is demonstrated; the achieved signal enhancements are about 6400 for (13)C nuclei at natural abundance. The theory behind the technique is described; advantages of the method are discussed in detail.
†International Tomography Center, Institutskaya 3a, Novosibirsk 630090, Russia.|‡Novosibirsk State University, Pirogova 2, Novosibirsk 630090, Russia.
Andrey N
AN
Pravdivtsev
†International Tomography Center, Institutskaya 3a, Novosibirsk 630090, Russia.|‡Novosibirsk State University, Pirogova 2, Novosibirsk 630090, Russia.
Alexandra V
AV
Yurkovskaya
†International Tomography Center, Institutskaya 3a, Novosibirsk 630090, Russia.|‡Novosibirsk State University, Pirogova 2, Novosibirsk 630090, Russia.
Nikita N
NN
Lukzen
†International Tomography Center, Institutskaya 3a, Novosibirsk 630090, Russia.|‡Novosibirsk State University, Pirogova 2, Novosibirsk 630090, Russia.
Konstantin L
KL
Ivanov
§Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany.
Hans-Martin
HM
Vieth
NMR; PHIP; avoided level crossings; heteronuclei; spin hyperpolarization