• diuron;
  • resonance Raman;
  • quantum chemistry calculation;
  • photodissociation dynamics

Resonance Raman spectra (RRs) and quantum chemical calculations were used to investigate the photodissociation dynamics of diuron in S2 state. The RRs indicate that the photorelaxation dynamics for the S0[RIGHTWARDS ARROW] S2 excited state is predominantly along nine motions: the ring C = C stretch vibration ν12 (1593 cm−1), Ph–N–H wag ν14 (1517 cm−1), CO–N(CH3)2 stretch ν23 (1365 cm−1), CCH wag in plane/ring C = C stretch ν24 (1297 cm−1), ring CH rock in plane/ring deformation ν27 (1233 cm−1), CCH wag in plane ν29 (1151 cm−1), Ph–Cl (para) stretch ν35 (1028 cm−1), Ph–N–H wag ν37 (913 cm−1) and ring breath ν44 (685 cm−1). Dissociation by Ph–Cl (para) cleavage at S2 state directly or relaxation to T2 state by internal conversion (S2[RIGHTWARDS ARROW] S1) and intersystem crossing (S1/T2) is expected by ~250 nm irradiation based on the RRS, complete active space self-consistent field, configuration interaction singles and time-dependent density functional theory calculations. Copyright © 2012 John Wiley & Sons, Ltd.