A combined theoretical and experimental determination of the electronic spectrum of acetone

A combined ab initio and experimental investigation has been performed of the main features of the electronic spectrum of acetone. Vertical transition energies have been calculated from the ground to the n(y) --> pi*, pi --> pi*, sigma --> pi*, and the n = 3 Rydberg states. In addition, the (1)A(1) energy surfaces have been studied as functions of the CO bond length. The (1)A(1) 3p and 3d states were found to be heavily perturbed by the pi --> pi* state. Resonant multiphoton ionization and polarization-selected photoacoustic spectra of acetone have been measured and observed transitions were assigned on internal criteria. The calculated vertical transition energies to the n(y) --> pi* and all Rydberg states were found to be in agreement with experiment. This includes the 3s-, all three 3p-, and the A(1), B-1, and B-2 3d-Rydberg states. By contrast, there is little agreement between the calculated and experimental relative intensities of the A, and B, 3d-Rydberg transitions. In addition, anomalously intense high vibrational overtone bands of one of the 3p-Rydberg transitions have been observed. These results confirm the strong perturbation of the 3p- and 3d-Rydberg states by the pi --> pi* state found in the theoretical calculation and support the calculated position of this unobserved state. (C) 1996 American Institute of Physics.