Observation of a substantially-bound excited-core Rydberg state in I-2 by optical triple resonance

A substantially-bound (D-e similar to 7000 cm(-1), R-e similar to 3.1 angstrom, T-e similar to 60 546 cm(-1)) 6s Rydberg state Of I-2 with 0(u)(+) symmetry based on the lowest excited state of the ion core, previously labelled a (4 Sigma(u,)(1/2)(-)), has been identified using optical triple resonance via the B(0(u)(+)) and E0(g)(+)(P-3(2)) states together with resonance ionization. The interactions with ground-core Rydberg states that the new state undergoes and the reasons why it is observed in the resonance ionization spectrum via the E0(g)(+)(P-3(2)) state, whilst the A[(2)Pi(u,1/2)](c); 6s0(u)(+) state is not, are explained in terms of its electronic configuration. (c) 2005 Elsevier B.V. All rights reserved.