Dissociation dynamics of ion-pair states of Cl2 at principal quantum numbers beyond 1500

Long-lived ion-pair states of Cl-2 have been observed by delayed pulsed-field ionization in the vicinity of the Cl-(S-1(0)) + Cl+(P-3(2)) dissociation threshold following single-photon excitation from the X (1)Sigma(+)(g) (v = 0) ground state with a tunable vacuum-ultraviolet laser. The field-ionization spectra reveal a series of resonances corresponding to ion-pair states with effective principal quantum number n* between 1858 and 1876 belonging to a series converging to the Cl-(S-1(0)) + Cl+(P-3(0)) dissociation threshold. These states are observed by forced predissociation into the Cl-(S-1(0)) + Cl+(P-3(2)) ion-pair channel. This process is the ion-pair analog of the process of forced autoionization observed in Rydberg states. The analysis of the spectra and of the field-ionization behavior provides information on the couplings between the relevant ionization and dissociation channels and has enabled the determination of the ion-pair dissociation threshold [E-IPD(Cl-(S-1(0)) + Cl+(P-3(2))) = 95 449.8 +/- 1.0 cm(-1)] and of the dissociation energies of Cl-2 [D-0(X (1)Sigma(+)(g)) = 19 998.4 +/- 1.1 cm(-1)] and Cl-2(+) [D-0(X+ (2)Pi(u)) = 31 942.1 +/- 1.5 cm(-1)].