Abstract
The excitation and detection of multiple quantum transitions in systems of coupled spins offers, among other advantages, an increase in resolution over single quantum n.m.r. since the number of lines decreases as the order of the transition increases. This paper reviews the motivation for detecting multiple quantum transitions by a Fourier transform experiment and describes an experimental approach to high resolution multiple quantum spectra in dipolar systems along with results on some protonated liquid crystal systems. A simple operator formalism for the essential features of the time development is presented and some applications in progress are discussed.
Highlights
The excitation and detection of multiple quantum transitions in systems of coupled spins offers, among other advantages, an increase in resolution over single quantum n.m.r. since the number of lines decreases as the order of the transition increases
The alternative time domain experiment is the determination of multiple quantum transition frequencies by following the time development of multiple quantum coherences point by point.[5,6,7]
K,rx,q where T~ is the qth component of a spherical tensor operator of rank k. 10 The label ex. completes the specification of a complete basis of tensor operators
Summary
BY GARY DROBNY, ALEXANDER PINES, STEVEN SINTON, DANIEL P. The excitation and detection of multiple quantum transitions in systems of coupled spins offers, among other advantages, an increase in resolution over single quantum n.m.r. since the number of lines decreases as the order of the transition increases. The energy level diagram of a system of coupled spins 1/2 in high field is shown schematically in fig. Extension to high order transitions is not promising, since the transitions observed are a sensitive function of r.f. field strength. This leads to difficult spectral simulations and experimental problems of saturation and sample heating. Broken arrows indicate the forbidden types of transition observed in Fourier transform multiple quantum experiments. Point was DROBNY, PINES, SINTON, WEITEKAMP AND WEMMER experiments in which the irradiation consists of pulses at the Larmor frequency. Synthesis of 4-cyano-4'-[2H]11pentyl-biphenyl was by the procedure of Gray and Mosley. 8
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