Low magnetic field electron–nuclear resonance transitions detected by nuclear polarization of radical reaction products

The low magnetic field electron–nuclear resonance transitions, detected via changes in the nuclear polarization of radical reaction products, have been investigated. Due to the mixing of the wavefunctions in low magnetic fields such transitions are allowed as electron resonance transitions but at the same time lead to significant changes of nuclear polarization. The photolysis of 2,4,6-trimethylbenzoylphosphonic acid dimethyl ester has been used as a model reaction. It proceeds via the intermediate dimethoxyphosphonyl radical which has a large hyperfine constant (69.6–70 mT). It has been shown that this effect can be applied for the investigation of low field electron and nuclear polarization.