A nuclear magnetic resonance (NMR) method for singlet-state exchange
NMR-spectroscopy comprises steps of excitation of single-quantum in-phase
coherences, generation of single-quantum anti-phase coherences,
excitation of zero-quantum coherences ZQ.sub.x and/or longitudinal
two-spin order 2I.sub.zS.sub.z (="ZZ order") using a .pi./4 pulse,
reversal of the sign of the zero-quantum coherences ZZQ.sub.x under the
effect of the difference of the chemical shifts of the examined spins,
transformation of the zero-quantum coherences ZZQ.sub.x and/or
longitudinal two-spin ZZ order into singlet-state populations by means of
RF irradiation during a mixing period .tau..sub.m reconversion of the
singlet-state populations remaining at the end of the mixing period
.tau..sub.m into zero-quantum coherences ZZQ.sub.x and/or ZZ order,
reversal of the sign of the zero-quantum coherences ZZQ.sub.x under the
effect of the difference of the chemical shifts of the examined spins,
and reconversion of zero-quantum coherences ZZQ.sub.x and/or ZZ order
into single-quantum anti-phase coherences. With the broadband method for
the excitation of single state population, NMR can monitor correlations
between states that are connected through very slow processes