Following photoexcitation at 320–298 nm, population is transferred from the S0 state of conformer 1a to the S1 state of conformer 1a, below the ADE. Since excitation is below the ADE, direct electron detachment is not possible. The molecule rotates around its axle as it relaxes along the S1 potential energy surface. Population then either remains on the S1 potential surface or it undergoes internal conversion to S0, returning to 1a or forming the rotated conformer 1b. Thermionic emission from the ground electronic state of conformer 1a is not possible because the internal energy is lower than the ADE; however, the ADE of conformer 1b is approximately 0.7 eV lower than that of conformer 1a, and thermionic emission from the ground electronic state of conformer 1b is possible. Thus, we assign the low eKE features in the photoelectron spectra recorded at 320–298 nm to thermionic emission from conformer 1b. Importantly, this indicates that the initial dynamical steps of the isolated deprotonated rotary motor are similar to those observed for rotary motors in solution, i.e. the motor rotates on the excited electronic state and undergoes internal conversion back to the electronic ground state.