The photoluminescence spectrum and action spectrum for the photooxidation of orthovanadate- like (V = O)O-3 species exhibiting photoluminescence at 520 nm indicate that the triplet excited state T-1 of the orthovanadate- like species, which is formed from the singlet excited states S-1 and S-2 by intersystem crossing, is directly involved in the photooxidation of cyclohexane into cyclohexanone in the presence of molecular oxygen. (c) 2008 Elsevier B. V. All rights reserved.