A two-state vibrational wave packet is prepared in a low-lying 4d 1 or 2 Rydberg state of jet cooled Br2 (4d, v′ =3 and v′ =4) by two-photon excitation with 266.5 nm pulses from an ultrafast laser. The wave packet is detected by autoionization following excitation with time-delayed 800 nm pulses to the n=8 (v+ =4) and n=9 (v+ =3) Rydberg states in the Π 12 2 angular momentum core state. Autoionization of each state occurs to the Π 32 2 state of the ion through spin-orbit ionization. Photoelectron spectroscopy is used to differentiate between the n=8 and n=9 ejected photoelectrons. Detection of the wave packet recurrences via the n=8 and n=9 Rydberg states reveals a π phase-shift difference of the recurrences between the two final states. In each case, Δv0 transitions are observed since wave packet recurrences are detected. By fitting the observed phase change of the recurrences with a simple model for the overlap amplitudes and assumptions about the potentials, we estimate, within the context of the model, that approximately 0.6% of the transitions may be attributed to Δv=±1 transitions between the initial Rydberg superposition state and the final Rydberg detection state.
Bibliographical noteFunding Information:
The authors are happy to thank Professor Daniel Neumark and his group for providing us with the MB-TOFS. Helpful discussions with Dr. Jan Verlet are greatly appreciated. This work was supported by the director, Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division, U.S. Department of Energy under Contract No. DE-AC02-05CH11231.