Optical-optical double-resonance spectroscopy of the 1(u)(P-3(2)) and 2(u)(P-3(2)) states of I-2 through the A(3)Pi(1(u)) state

Optical-optical double-resonance spectroscopy is used to study the 1(u)(P-3 (2)) and 2(u)(P-3(2)) ion-pair states of I-2 correlating to the lowest ioni c state, I-(S-1)+I+(P-3(2)). In the (1+2) photoexcitation sequence, we gain access to the 1(u)(P-3(2)) ion-pair state through the A(3)II(1(u)) state. The 2(u)(P-3(2)) state is also identified from the occurrence of extra line s through heterogeneous coupling with the 1(u)(P-3(2)) State and an apparen t energy shift in the 1(u)(P-3(2)) state. The energy levels of the 1(u)(P-3 (2)) and 2(u)(P-3(2)) states were analyzed in detail by including the heter ogeneous interaction between these states. We have established the vibratio nal numbering of the 2(u)(P-3(2)) State in considering the 1(u)-2(u)(P-3(2) ) interaction terms under a pure precession approximation. Combined with ot her results, the present study has allowed us to characterize and map out t he ion-pair states of I-2 in the 5 eV region.