Multiple-quantum and two-dimensional gas phase NMR

We introduce experiments designed to measure double- and zero-quantum frequencies and relaxation in the gas phase. We use a combination of phase cycling and gradients to achieve multiple quantum selectivity, and we note that conventional gradient strategies will not work because of the high diffusion constants of low-molecular-weight gases. We therefore choose the lengths of the gradients so that unwanted coherences fall at nodes in the integrated magnetization. We propose a related sequence that allows measurement of relaxation of either double- or zero-quantum coherence. Finally, we show T 2 relaxation curves for the 1H and 13C single-quantum relaxation, as well as the zero- and double-quantum relaxation, in 13C1-acetylene at natural abundance. © 2017 John Wiley & Sons, Ltd.