Stepwise Excitation Processes in Photodissociation and Detection

Two‐photon processes in which stationary intermediates are involved in the excitation are discussed, and three processes are described in detail: (a) stepwise 2‐photon laser induced dissociation of NCNO at wavelengths 600–800 nm, followed by detection of the CN fragment via laser induced fluorescence (LIF); (b) detection of HONO via a 2‐frequency scheme, in which dissociation is induced at 355 nm and is followed by LIF detection of the OH fragment; (c) stepwise 2‐frequency 2‐photon ionization detection of nascent PO produced via the collision free IR photolysis of aliphatic phosphonates and phosphites. Absorption throughout the B 2 Σ + ‐ X 2 system of PO is followed by ionization using 266 nm radiation.