Phase-controlled optical pulses and the adiabatic electronic sign change

It is shown that the time development of the electronic Berry phase predicted to accompany molecular pseudorotation around a conical degeneracy is accessible to measurement with pairs of vibrationally abrupt phase-controlled optical pulses. In the simplest case, an electronic sign change resulting from the induced vector potential will manifest itself as a delay-dependent oscillation in the interference signal with twice the period of pseudorotational motion.