Fragmentation dynamics

The pump-probe scheme that we use is as follows the molecule is initially excited by a pump laser photon (htOj) to the first excited neutral state. The dynamics is then followed with a probe laser by one-photon ionization (hooa). Compared to a free diatomic, solvation by CH3CN brings two new factors come into play. Firstly, the potential energy curves of the diatomic are modified by the presence of the neighboring molecule. Secondly, the fragmentation dynamics of the diatomic is changed as there may be collisions with, and a transfer of energy to, the acetonitrile. 

The present analysis relies on - and extends - the comprehensive theoretical study of Refs. [23,24] on the multi-state interactions in the manifold of the X — E states of Bz+. Like this recent work, it utilizes an ab initio quantum-dynamical approach. In Refs. [23,24] we have, in addition, identified strong coupling effects between the B — C and B — D electronic states, caused by additional conical intersections between their potential energy surfaces. A whole sequence of stepwise femtosecond internal conversion processes results [24]. Such sequential internal conversion processes are of general importance as is evidenced indirectly by the fluorescence and fragmentation dynamics of organic closed-shell molecules and radical cations [49,50]. It is therefore to be expected that the present approach and results may be of relevance for many other medium-sized molecular systems. 

S(t) reflects the evolution of the wavepacket in the excited electronic state and therefore it reflects the fragmentation dynamics and the forces —dV/dQi in the upper state. 

According to Section 4.1.1 the wavepacket is a superposition of stationary wavefunctions corresponding to a relatively wide range of energies. This and the superposition of three apparently different types of internal vibrations additionally obscures details of the underlying molecular motion that causes the recurrences. A particularly clear picture emerges, however, if we analyze the fragmentation dynamics in terms of classical trajectories. 

Because of the very short lifetime the time-dependent approach provides the more illuminating explanation of diffuse structures. It allows the separation of the indirect part of the dissociation from the less interesting direct one, which dominates the overall fragmentation dynamics. 

Pernot, P., Atabek, O., Beswick, J.A., and Millie, Ph. (1987). A quantum mechanical model study of CH3NO2 fragmentation dynamics, J. Phys. Chem. 91, 1397-1399. 

In the reaction Rl the rupture of the first C-N bond is followed by the rupture of the first N-N02 bond (release of the nitrogroup), as one can see in the Fig. 2a. Then the rest of the molecule is gradually totally decomposed. Reaction R2 starts with the rupture of three C-N bonds and subsequent break up of the molecule into three CH2NN02 fragments (see Fig. 2b). Afterwards the N02 groups are released from these fragments. Dynamics trajectory enables the animation of molecular motion with the time resolution lfs and the visualization of the molecular decomposition process in real time. 

ELECTRONIC PROPERTIES AND FRAGMENTATION DYNAMICS OF ORGANIC SPECIES DEPOSITED ON SILICON SURFACES... 

Another molecule with mode-specific fragmentation dynamics is hypo-chlorous acid,... 

Note however, that the for the internal relaxation dynamics of the clusters this approach has to be used carefully as has been shown for the quantized fragmentation dynamics [28,38] revealed in kinematically complete experiments of collision induced dissociation [29]. 

S. S. Brown, Ph. D. Thesis, Spectroscopy and Bond-selected Fragmentation Dynamics in the Photodissociation of Highly Excited Isocyanic Acid University of Wisconsin-Madison, Madison, 1996. 

For the evaluation of the averaged induction-dispersion interaction -Ce/ " , we here accept based on the Slater-Kirkwood formnla valne Ce=23.2 from the work [23], In order to create more reliable estimations of the anisotropy of Ce term, one can again resort to the RSOF method by Meyer et al. [6] and to the related calculations of the fragment dynamic polarizabilities [20, 30], The FFC basis of Eq.25 consists of 36 functions transforming upon time inversion as... 

The systematically performed pump-probe spectroscopy on alkali clusters provided a good indication about suited candidates for a coherent control experiment. Among these, the fragmentation dynamics of the heteronu-clear trimer Na2K appeared to us the best. The corresponding pump-probe spectrum is shown in Fig. 14(a). It clearly exhibits — superimposed on an exponential decay with a time constant of 3.28 ps — an oscillatory behaviour with a period of roughly 500 fs. The Fourier-transform of this... 

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