The REMPI spectroscopy of Cl-2; A bound-free-bound route to the 1(g)(D-1(2)) ion-pair state

The 1(g)(D-1(2)) ion-pair state of Cl-2 has been accessed via a two-photon, two-colour bound-free-bound route. An extensive vibrational progression is observed, overlapping high levels of the E0(g)(+) (P-3(2)) state. The absolute numbering is established from isotopic shifts and continuity with the known term values of v' = 0-6. The intermediate resonant state accessing the 1(g)(D-1(2)) state is the unbound C-1 Pi(1u). The final state classification as Ohm = 1 is confirmed by simulating the rotational band structure observed under perpendicular pump/probe polarization conditions using Honl-London factors from a coherent superposition of intermediate J(i)M(i) states, not those appropriate to well-defined J(i) and M(i) states. These Honl-London factors also reproduce the rotational linestrengths of the beta 1(g)(P-3(2)); v' = 65 <-- <-- X; v '' = 0 transition observed under parallel to and perpendicular to polarization conditions when the pump photon energy lies in the continuum of the C <-- X and B <-- X absorption.