Measuring Dissociating Wave Packets by Laser Coulome Explosion Imaging

摘要

From exact non-Born-Oppenheimer simulations of dynamics of H~+_2 in an intense (I > 10~(15) W/cm~2 ) , ultrashort laser pulse (t_p < 5 femtoseconds), we show that it is possible to measure the time evolution of the probability distribution |ψ/>(R, t)|~2 of a dissociating wave packet. In our simulation, a pump-probe technique is used: first, a weaker laser (I< 10~1 4), photo-dissociates the molecule, and next , with experimentally controlled time-delay t_0, a second, intense (I>10~(15) W/cm~2 ), ultrashort (t_p < 5 femtoseconds) laser is applied. The latter, ionizes, "instantaneously" the dissociating molecule. Measurement of the kinetic energy spectra of exploding fragments allows us, with the help of the inversion based on Coulomb's law and classical conservation of energy, to reconstruct the shape of the probability distribution at |ψ(R,t)|~2 time t = t_0. By repeating this experiment for many time delays t_0, we can obtain a detailed information about dynamics of the photo-induced dissociation. The theory of Coulomb explosion imaging of moving wave packets and limitations of the above classical inversion method are presented.