Wavepacket compression

Dynamics. Cluster dynamics constitutes a rich held, which focused on nuclear dynamics on the time scale of nuclear motion—for example, dissociahon dynamics [181], transihon state spectroscopy [177, 181, 182], and vibrahonal energy redistribuhon [182]. Recent developments pertained to cluster electron dynamics [183], which involved electron-hole coherence of Wannier excitons and exciton wavepacket dynamics in semiconductor clusters and quantum dots [183], ultrafast electron-surface scattering in metallic clusters [184], and the dissipahon of plasmons into compression nuclear modes in metal clusters [185]. Another interesting facet of electron dynamics focused on nanoplasma formation and response in extremely highly ionized molecular clusters coupled to an... 

In contrast, we observe an increase of the probability density at distances shorter than the PA window, manifesting a compression of the wavepacket. A secondary maximum is created, which moves toward the repulsive wall of the lower state potential on a timescale of a few hundred picoseconds, typical of half the vibrational period... 

The compression effect is maximum at t = topt, and later the wavepacket is reflected on the inner wall of the potential. 

To explore the possibilities offered by the compression of the wavepacket, we have represented in Figure 7.14 the variation of the Franck-Condon overlap between g R,t = topt), when the compression effect is maximum, and various stationary wavefunctions (pe,v of the bound vibrational levels in the external well of the excited state. Important overlap is obtained with almost all levels in the outer well... 

FIGURE 7.14 The compression effect and its optimization various quantities are compared related to the initial wavepacket for two colliding atoms (dashed lines), and to the compressed wavepackets when the compression effect is maximum, at fopt = fp + 950 psec, after illuminating with the pulse (solid lines). Also displayed are the compressed wavepackets, now at fgpj = fp -I- 350 psec, after illuminating with the optimized pulse (shaded curves). 

From the conclusion of Section 7.5, a pulse has been designed to optimize the compression effect in the ground-state wavepacket. The new pulse, described as in Table 7.2, is obtained from by increasing the chirp rate x and therefore the duration. For this pulse, the duration xc = 376.13 psec is comparable to half the vibration period TVib in the excited state. The intensity was increased to obtain 24 Rabi oscillations, close to a (2n)n-pulse. The probability of excitation is markedly decreased (3 x 10 " instead of 2 x 10 ). As displayed in Figure 7.14, a spectacular compression effect, maximum at f p, = fp -F 350 psec, is observed. The compressed wavepacket is associated with large values for the time-dependent Franck-Condon factor with low-lying levels in the external well of the excited state, suited for PA with a second pulse red-detuned from and delayed by 350 psec. 

For the single proton transfer, the donor-acceptor distance of only one of the two H-chelate rings has to be compressed. This is achieved by an antisymmetric bending motion. This example demonstrates that different reaction channels result in different coherent wavepacket dynamics. BP(OH)2 exhibits inversion symmetry, and direct optical excitation of the antisymmetric bending mode is not possible because of selection rules for electronic dipole transitions [74]. This proves that the observed coherent wavepacket motions result from ultrafast intramolecular reactions. 

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