Sequential two-photon excitation via repulsive intermediate states

Abstract

Large bond extensions ≈ 1 Å are reported in a two-photon bound-to-bound optical excitation via a repulsive intermediate electronic state. In a one-colour experiment on I 2, the ion-pair E state is accessed in the sequence E(0 + g( v′≈40–70) ← B(0 + u) ← X with the pump/probe wavelength scanned near the prominent red extremum of the E←B transition. At this wavelength the continuum of the B state is reached in the first step, rather than the bound levels conventionally used in OODR spectroscopy. The classical point of transition that conserves atomic momentum for the second step then occurs near R e of the ion-pair state.