Nuclear spin state conservation in photodissociation of formaldehyde

Abstract Excitation of formaldehyde to the 2141 band of the S1 state leads to photodissociation with nuclear spin state conservation of the hydrogen. Dissociation of ortho-formaldehyde gives ortho-hydrogen as a product. Interconversion between ortho- and para-formaldehyde at 1 Torr occurs with a rate constant greater than 0.1 min−1.