Dynamics and mechanism of radical formation in a highly sensitive oxime photoinitiator as revealed by time-resolved absorption and EPR measurements

•Radical formation of a photoinitiator was studied by time-resolved spectroscopies.•The S1 and T1 states undergo N-O bond cleavage leading to formation of radical pair.•Radical pair produced from the T1 state is effectively dissociated to free radicals.•Exchange interaction could suppress the dissociation process of the radical pair.