Abstract: | A theoretical study has been carried out on the allyl radical in its ground and first excited electronic states. Complete active space self‐consistent field (CASSCF) calculations show the presence of a conical intersection between the ground and first excited electronic states (~400 cm?1 above the adiabatic excited state energy), reached by decreasing the C? C? C angle and twisting the C? C bonds. The presence of this conical intersection provides a likely explanation for the very rapid predissociation in the excited electronic state. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 |