Evaluation of paramagnetic relaxation rates in a J-coupled two-spin system

The relaxation rates of zero quantum and double quantum transitions of two J-coupled spin-1/2 nuclei are calculated when the two nuclei are relaxed by an electron spin S through contact, dipolar and Curie interactions. Besides the paramagnetic relaxation for each nuclear spin, cross terms are present which are positive for double quantum and negative for zero quantum transitions. Therefore zero quantum transitions are less affected then double quantum transitions by a paramagnetic center. Sample calculations are performed to show that zero quantum experiments may be competitive with standard COSY experiments on paramagnetic compounds.