A time resolved study of S1/S2 electronic coupling in naphthalene

The relaxation dynamics of jet cooled naphthalene (NPH) has been studied by mass-resolved transient ionization, following excitation to the S1(Lb) and S2(La) states and further single/multi photon ionization at a variety of probe wavelengths. Time-dependent signals were collected from the parent C 10 H 8 + and the C 10 H 7 + fragment ions. The relaxation transients include two lifetimes of 30 and 800 fs. The short decay suggests the presence of a conical intersection nearby the La state surface minimum that is crossed in one single passage by most part of the population, whereas the long lifetime is tentatively assigned either to internal vibrational redistribution (IVR) within the Lb state, or to the decay of coherent recurrences.