Evidence of ultrafast dissociation in the CHCl3 molecule

In the present work, we use tunable synchrotron radiation to investigate experimentally and theoretically the dissociation of a chlorinated methane, the CHCl3 molecule, by exciting a chlorine 2p core electron into the LUMO and LUMO + 1 orbitals. The Auger electron energy distribution measured at the Cl 2p3/2 → 10a1 resonance shows narrow lines which energies correspond to the Cl* → Cl+ atomic decay, a clear evidence that the Auger decay takes place after consummation of the dissociation, when the moieties were already far away from each other. Our experimental data are endorsed theoretically by a series of high-level ab initio quantum mechanical calculations. The excited states are calculated to be strongly repulsive in the Franck-Condon region (−dE/dy ∼ 0.15 a.u.) along the C-Cl bond direction.