Sneaking up on the Criegee intermediate from below: Predicted photoelectron spectrum of the CH2OO- anion and W3-F12 electron affinity of CH2OO

High level ab initio calculations were undertaken on the CH2OO anion and neutral species to predict the electron affinity and anion photoelectron spectrum. The electron affinity of CH2OO, 0.567 eV, and barrier height for dissociation of CH2OO− to O− and CH2O, 16.5 kJ/mol, are obtained by means of the W3-F12 thermochemical protocol. Two major geometric differences between the anion and neutral, being the dihedral angle of the terminal hydrogen atoms with respect to C–O–O plane, and the O–O bond length, are reflected in the predicted spectrum as pronounced vibrational progressions.