Dissociative Electron Photodetachment vs. Anionic Photofragmentation of deprotonated Aromatic acid

G. A. PINO; R. JARA TORO; J. P. ARANGUREN; C. DEDONDER-LARDEUX; C. JOUVET

Tokyo

Simposio; WRHI International symposium on Advanced Laser Spectroscopy for soft molecular systems; 2018

The competition between dissociative electron photodetachment and anionic photofragmentation of cold benzoate and naphthoate anions was studied through measurement of the kinetic energy of the neutral fragments and intact parent benzoyloxy and naphtoyloxy radicals as well as by detecting the anionic fragments whenever they are produced. For the benzoate anion, there is no ionic fragmentation and the radical dissociation occurs near the vertical electron photodetachment energy. This is in agreement with DFT calculations showing that the dissociation energy in CO2 and C6H5 is very low. The dissociation barrier can be deduced from experimental results and calculations to be (0.67 ± 0.10) eV, which makes the benzoyloxy radical C6H5COO very unstable, although more stable than the acetyloxy radical. In the case of naphthoate, the observation of negative fragments at low excitation energies demonstrates the opening of the ionic fragmentation channel in the excited state of the naphthoate anion, whose yield decreases at higher energies when the dissociative electron photodetachment channel opens.