Pseudo steady-state photo-CIDNP measurements with improved background suppression

Pulse sequences have been developed which considerably increase the background suppression in pseudo steady-state photo-CIDNP experiments (measurements of photochemically induced dynamic nuclear polarization in which several laser flashes are applied during a period smaller than the nuclear spin relaxation times). Quantitative estimates of the errors caused by pulse imperfections and nuclear spin relaxation are given. The feasibility of the schemes is demonstrated with an experimental example (photoreaction of benzophenone with triethylsilane).