Photodissociation spectroscopy and dynamics of CH3O and CD3O

The photodissociation spectroscopy and dynamics of the methoxy radical Ã( 2 A 1 ) ← X̃( 2 E) transition have been investigated using fast radical beam photofragment translational spectroscopy. The à state of both CH 3 O and CD 3 O is observed to predissociate via curve crossings with one or more repulsive electronic states. The photofragment yield spectrum consists of the C−O stretch progression and combination bands based on this mode. The major product channel is CH 3 (CD 3 ) + O, with a threshold 3775 cm -1 above the zero-point level of the à state. The product translational energy distributions reveal ν 2 umbrella excitation in CH 3 (CD 3 ), yielding considerable insight into the dissociation dynamics for this channel. CD 3 O shows a mode-specific dynamical effect in which energy deposited in parent umbrella motion preferentially populates umbrella motion in the fragment. The product channels CH 2 + OH (CD 2 + OD) and D + CD 2 O are also observed, with evidence that the methylene fragment is predominantly in the excited ã ( 1 A 1 ) state.