Ion‐pair formation from saturated hydrocarbons through photoexcitation of an inner‐valence electron

Vacuum ultraviolet negative photoion spectroscopy of chloroform

Negative ions Cl(-), Cl(2)(-), CCl(-), CHCl(-), and CCl(2)(-) are observed in vacuum-ultraviolet ion-pair photodissociations of chloroform (CCl(3)H) using the Hefei synchrotron radiation facility, and their ion production efficiency curves are recorded in the photon energy range of 10.00-21.50 eV. Two similar spectra of the isotope anions (35)Cl(-) and (37)Cl(-) indicate the following: Besides the strong bands corresponding to the electron transitions from valence to Rydberg orbitals converging to the ionic states, some additional peaks can be assigned with the energetically accessible multibody fragmentations; a distinct peak at photon energy 14.55 eV may be due to a cascade process (namely, the Cl(2) neutral fragment at the highly excited state D'2(3)Π(g) may be produced in the photodissociation of CCl(3)H, and then the Cl(-) anions are produced in the pulsed-field induced ion-pair dissociations of Cl(2) (D'2(3)Π(g))); two vibrational excitation progressions, nν(2)(+) and nν(2)(+) + ν(3)(+), and nν(4)(+) and nν(4)(+) + ν(2)(+), are observed around C̃ (2)E and D̃ (2)E ionic states, respectively. The enthalpies of the multibody fragmentations to Cl(2)(-), CCl(-), CHCl(-), and CCl(2)(-) are calculated with the thermochemistry data available in the literature, and these multibody ion-pair dissociation pathways are tentatively assigned in the respective anion production spectra.