Intermode coupling

Intermode coupling All of these experimental findings reveal the existence of internal pathways of energy transference between modes which eventually become efficient due to non-negiigible coupling between the excited internal mode and the mode directly actuating in the reaction coordinate. 

For example, a step index silica hber of 100-pm-diameter was excited at 10° off-axis. The 2D far-held pattern (MPD) and intensity prohle were scanned and recorded by a CCD camera as shown in Fig. 30a. When the hber was under perturbation, the recorded far-held pattern showed intermodal coupling and redistribution of the modal power (Fig. 30b). As the perturbation level was increased, considerable rearrangement of the modal power was recorded in a similar way. This experiment indicates that continuous variation of the applied perturbation results in a respective change in the MPD, in a very sensitive manner. 

In the second step we account for the essential physical effect of intermode couplings, as explained in the two-oscillator case. With three equal oscillators, such interactions will result in (1) the splitting of degeneracies associated with the purely local behavior and (2) the correspondingly specific symmetry of wavefunctions, under bond permu-... 

As discussed previously for bent molecules, the local model (4.54) is a poor approximation when intermode coupling occurs, so we now need to introduce the Majorana operator. The explicit analysis of this problem is perfectly analogous to the previous one, apart from the different conversion law between algebraic and vibrational quantum numbers. Moreover, in a linear molecule we expect to obtain vibrational wavefunctions... 

The intermode coupling has been calculated by constructing a model Hamiltonian based upon the nine zero-order states plus a 10th level that represents the zero-order vdW levels p and [Pg.284]

In an actual case, anharmonlclty and Intermode coupling allow more eigenstates to contribute to the trldlagonal matrix, but the above basic trends will still be observed ... 

Note that the simple and robust definition of the delta-funetion proposed by Krishna and Tully ° was used in the above expression, but this ehoiee is by no means restrictive. The anharmonicity and the intermode coupling of the vibrational states enter naturally the expression via the friction-like term, which modulates the strength of the non-... 

Fig. 4 Snapshots of the probability distribution evolution for two CO molecules on a copper(lOO) surface subject to non-adiabatic coupling. The dynamics is initiated with two quanta of vibrational excitation in one of the CO molecules, here the qi mode. The labels full and fact, refer to the choice of vibrational basis to represent the reduced density matrix in eqn (19). The left panels show the system in the absence of intermode coupling and the strong intermode coupling regime is depicted in the right panels. Reproduced with permission from ref. 97.

For more complex unimolecular dissociations like C2H5 H + C2H11. and C2H3F -> HF 4- C2H2, we expect that intermode couplings in the exit-channel will partition some of the potential energy released to vibrational and maybe rotational motion. 

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