Preparation of a wave packet through a mixed level in Li2; predissociation of one member of the superposition

Stark-assisted population control of coherent CS2 4f and 5p Rydberg wave packets studied by femtosecond time-resolved photoelectron spectroscopy

A two-color (3+1(')) pump-probe scheme is employed to investigate Rydberg wave packet dynamics in carbon disulfide (CS(2) (*)). The state superpositions are created within the 4f and 5p Rydberg manifolds by three photons of the 400 nm pump pulse, and their temporal evolution is monitored with femtosecond time-resolved photoelectron spectroscopy using an 800 nm ionizing probe pulse. The coherent behavior of the non-stationary superpositions are observed through wavepacket revivals upon ionization to either the upper (12) or lower (32) spin-orbit components of CS(2) (+). The results show clearly that the composition of the wavepacket can be efficiently controlled by the power density of the excitation pulse over a range from 500 GWcm(2) to 10 TWcm(2). The results are consistent with the anticipated ac-Stark shift for 400 nm light and demonstrate an effective method for population control in molecular systems. Moreover, it is shown that Rydberg wavepackets can be formed in CS(2) with excitation power densities up to 10 TWcm(2) without significant fragmentation. The exponential 1e population decay (T(1)) of specific excited Rydberg states are recovered by analysis of the coherent part of the signal. The dissociation lifetimes of these states are typically 1.5 ps. However, a region exhibiting a more rapid decay ( approximately 800 fs) is observed for states residing in the energy range of 74 450-74 550 cm(-1), suggestive of an enhanced surface crossing in this region.

Electron correlation in the 3 (1)Sigma(g)+ and 2 (1)Sigma(u)+ excited state lithium molecule

Electron correlation effects in the two excited states of Li(2), 3 (1)Sigma(g) (+) and 2 (1)Sigma(u) (+), one with a shelf shape and another with double minima in their potential energy curves, have been studied with the aid of the calculated electron pair density distribution as a function of the internuclear distance and the analysis of the natural orbitals. Both states show increased electron pair densities at intermediate interelectronic distances around the second minimum of their potential energy curves. Since the bond breaks homolitically this observation runs contrary to regular expectations. Analysis of the electron pair density distributions and the natural orbitals provides mechanisms to account for this abnormal behavior.