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

Abstract

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.

Ultrafast dynamics and dissociative ionization of CS2 molecules studied via the femtosecond pump-probe method

“…The lifetime of the 4f-Rydberg state was found to be 830 fs (570 fs and 670 fs) by fitting the transient behavior of CS 2 + (S + , and CS + ). In the time-resolved photoelectron measurement studied by Knappenberger et al [27], the lifetime of the […”

“…They first used a short (100 fs), nonresonant (805 nm) laser pulse to align the molecule, and then followed this with a pumpprobe scheme with photoelectron imaging measurement. The dynamics of Rydberg states of CS 2 molecules were investigated by Liu et al [25] using time-resolved pumpprobe ion yield measurement, and by Knappenberger et al using TRPES technique [26,27].…”

Coherent Vibrational Dynamics of Au144(SC8H9)60 Nanoclusters

“…The dephasing time is determined by energy dissipation rates of the system. , For Au 144 (SC 8 H 9 ) 60 , energy dissipation from the nanocluster to the surrounding occurs in the 1–10 ps range, in good agreement with the dephasing times reported here. The decoherence behavior observed for the nanoclusters is in contrast to dephasing of molecular vibrational wavepackets, for which coherence dephasing times are frequently determined by the state-specific lifetimes and relative amplitudes of the various eigenstates that form the coherent superposition. , For condensed-phase molecules, these lifetimes are often on the time scale of internal conversion (≈100 fs) or dissociation. Still, several examples of molecular wavepackets persisting on picosecond and longer time scales are available .…”

Imaging the breakdown of molecular-frame dynamics through rotational uncoupling

“…We employ a ≈100 fs 400 nm excitation pulse with a peak intensity of ≈10 14 W/cm 2 . The pulse excites molecules to the 4f Rydberg manifold via a transient five-photon resonance due to the intensity-dependent ac Stark shift [26]. The elec-tron wave packet is subsequently probed through single photon ionization by a time-delayed, co-propagating 800 nm pulse of similar duration and intensity as the pump pulse.…”