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.