Following photoexcitation at 230 nm, population is transferred from the S0 state of conformer 1a to the S1 state of conformer 1a, above the ADE. The 230 nm photoelectron spectrum is reproduced in Fig. 6 and plotted as a function of electron binding energy, eBE = hν – eKE (bottom axis) and eKE (top axis). The MS-CASPT2 calculated VDEs and ADEs for motor conformers 1a and 1b and the VEE for conformer 1a are also marked on this plot. The calculated VDE for conformer 1a (4.91 eV) is very close to the maximum of the broad feature of the photoelectron spectrum (4.8 eV), supporting our assignment of this feature to direct detachment to the electronic continuum associated with the ground electronic state of the neutral radical, D0. However, the ADE for conformer 1a is very close to the VDE, so the photoelectrons observed with eBEs lower than the ADE must either result from direct detachment from vibrationally hot S0 to the D0 continuum associated with the 1a conformer, or to indirect detachment from S1 to D0 of the 1b conformer. Since the low eBE edge of the photoelectron spectrum is very close to the calculated ADE of the 1b conformer, it seems most likely that these lower eBE photoelectrons arise from autodetachment from the S1 state of the 1b conformer. Importantly, the observation of autodetachment from the S1 state of the 1b conformer as well as thermionic emission is indicative of competing relaxation processes. Thus, we can deduce that following excitation at 230 nm and relaxation on the S1 potential energy surface some population remains on the S1 potential energy surface and some population undergoes internal conversion back to S0. Thermionic emission is possible from both 1a and 1b conformers with the 5.39 eV of internal energy in S0 that comes from excitation at 230 nm. Our observations are consistent with recent time-resolved studies of second generation molecular rotary motors in solution which observed an initial relaxation out of the Franck–Condon region to a ‘dark state’, which subsequently decays back to the ground electronic state.22–24 The similarity between the gas and solution phases suggests that the mechanical motion associated with the initial photoisomerisation step of the rotary cycle is independent of the solvent environment.