Real-time observation of vibrational revival in the fastest molecular system

After preparing a coherent vibrational wave packet in the hydrogen molecular ion by ionizing neutral H-2 molecules with a 6.5 fs, 760 nm laser pulse at 3 x 10(14) W/cm(2), we map its spatio-temporal evolution by the fragmentation induced with a second 6.5 fs laser pulse of doubled intensity. In this proof-of-principle experiment, we visualize the oscillations of this most fundamental molecular system, observe a dephasing of the vibrational wave packet and its subsequent revival. Whereas the experimental data exhibit an overall qualitative agreement with the results of a simple numerical simulation, noticeable discrepancy is found in the characteristic revival time. The most likely reasons for this disagreement originate from the simplifications used in the theoretical model, which assumes a Franck-Condon transition induced by the pump pulse with subsequent field-free propagation of the H-2(+) vibrational wave packet, and neglects the influence of the rotational motion. (c) 2006 Elsevier B.V. All rights reserved.