Ultrafast dissociation processes in the NO dimer studied with time-resolved photoelectron imaging

Ultraviolet photodissociation of the NO dimer is studied with femtosecond time-resolved photoelectron imaging (TR-PEI) spectroscopy. Pump pulses in the range 200-235 nm are employed, while probe pulses are kept at 300 nm. The time dependencies of the observed photoelectron kinetic energies and photoelectron angular distributions support a picture in which valence state optically excited in the dimer evolves on a time scale of <1 ps to the dimer 3s Rydberg state. This dimer Rydberg state then undergoes fragmentation on a time scale of a few ps. In this study we focus on dissociation into an NO ground state fragment and an NO fragment in its 3s Rydberg A2Σ+ state. Every stage of this continuous process, viz. the dimer valence state, the dimer 3s Rydberg state, the separating NO(X) + NO(A) fragments, and the isolated NO(A) fragment is interrogated with TR-PEI.