Radiation damping artifacts in 2D COSY NMR experiments

An experimental and theoretical analysis of multiple-quantum (MQ)-like artifacts in 2D NMR spectra of water is presented and discussed. During the t1 domain, either magnetic field gradients or Q-switching techniques, were used to minimize radiation damping effects. Nevertheless, a myriad of MQ artifacts, in excess of Δm = ± 20, were observed in the indirectly detected t1 domain. The source of these MQ-like artifacts has been traced, rather surprisingly, to radiation damping in the t2 domain. This conclusion was reached experimentally, using Q-switching experiments in both the t1 and t2 domains, and confirmed theoretically, using a modification of the radiation damping theory of Vlassenbroek et al., J. Chem. Phys. 103 (1995) 5886.