Refocused primary echo: A zero dead time detection of the electron spin echo envelope modulation

We report on the two-dimensional (2D) implementation of the refocused prima ry electron spin echo envelope modulation (ESEEM) technique, its theory and experimental application to a model system and a system of biological inte rest. This technique is virtually free of dead time along one time coordina te. The ESEEM obtained by integration of the 2D time-domain data of the ref ocused primary ESEEM over one of the time coordinates shows the intensity o f the sum combination harmonics proportional to k(2) for k much less than 1 and proportional to k for k similar to 1 (k is a usual notation for the mo dulation amplitude factor). This feature, in combination with the adjustmen t of k by means of variation of the operational frequency of the spectromet er, was found to be very useful for detection of protons with distributed h yperfine interaction parameters situated close to the electron spin. (C) 20 00 Academic Press.