Multiphoton ionisation (MPI) spectroscopy has been used to investigate the electronic structure of short-lived molecules in the gas-phase. Electronic transitions observed in the MPI spectra of the short-lived molecules studied were assigned by analysis of the rotational structure in the observed bands. In the main part of this work, the molecules chosen for study using MPI spectroscopy were NF and NC1, which are of interest as possible energy transfer agents in chemical laser systems. The observation of resolved bands involving triplet Rydberg states has allowed the determination of the first experimental values for the spin-orbit splitting in any state of NF and NC1. Finally, known two-photon resonant MPI transitions of atomic chlorine were used to measure the relative population of the C1(²P_3/2) and C1(²P_1/2) spin-orbit states resulting from the UV photolysis of HOC1, a species of importance in stratospheric ozone depletion. The results indicated a stronger preference for formation of ground state atomic (C1(²P_3/2)) than expected from statistical weights, and also that most of the energy available upon photolysis is converted into kinetic energy of the photofragments.