Pump-dump scheme

Figure Al.6.30. (a) Two pulse sequence used in the Tannor-Rice pump-dump scheme, (b) The Husuni time-frequency distribution corresponding to the two pump sequence in (a), constmcted by taking the overlap of the pulse sequence with a two-parameter family of Gaussians, characterized by different centres in time and carrier frequency, and plotting the overlap as a fiinction of these two parameters. Note that the Husimi distribution allows one to visualize both the time delay and the frequency offset of pump and dump simultaneously (after [52a]).

The second example is the quadratically chirped pump-dump scheme. Since the pioneering work by Tannor and Rice [119], the pump-dump method has been widely used to control various processes. However, since it is not possible to transfer a wave packet from one potential energy surface to another nearly completely by using the ordinary transform limited or linear chirped pulses, the... 

Figure 57. Schematic potential energy profiles and the pump-dump scheme. Taken from Ref. [49].

Figure 58. Changes of the wavepacket populations on the respective states (upper panels) under the 3.5TWcm quadratically chirped pulses (lower panels) during the sequential pump-dump scheme via the (a) I A —> I B pumping at CHD and [(b) and (c)] 2 A I B —> I A pump...

In general, the results of the calculations establish that it is possible to guide the reaction to preferentially form one or the other product with high yield. Note that, unlike the original Tannor-Rice pump-dump scheme, in which the pulse sequences that favor the different products have different temporal separations, the complex optimal pulses occupy about the same time window. Indeed, the optimal pulse shape that generates one product is very crudely like a two-pulse sequence, which suggests that the mechanism of the enhancement of product formation in this case is that the time delay between the pulses is such that the wavepacket on the excited-state... 

D. J. Tannor I would like to point out that the Scherer-Fleming wavepacket interferometry experiment is very different from the Tannor-Rice pump-dump scheme, in that it exploits optical phase coherence of the laser light (optical phase coherence translates into electronic phase coherence between the wavepackets on different potential surfaces). However, there was a paragraph in the first paper of Tannor and Rice [7. Chem. Phys. 83, 5013 (1985), paragraph above Eq. (11)] that did in fact discuss the role of optical phase and suggested the possibility of experiments of the type performed by Scherer and Fleming. 

Figure 3.21 (a) Schematic diagram of a pump-dump scheme to control the mod... 

The pump-dump scheme described above has also been applied to the control off the... 

The conceptionally simplest approach for IR-driven HT, the pump-dump scheme [45], can be illustrated using a one-dimensional double minimum potential as shown in Fig. 4.1. First we notice that the potential is asymmetric which allows one to distinguish between the initial state S and the final state S f of the HT reaction. Initially a pump-pulse excites the system from the localized ground state S to a delocalized intermediate state which usually is energetically above the reaction barrier. From there a second pulse dumps the system into the product... 

Figure 4.1 Illustration of the pump-dump scheme for a slightly asymmetric one-dimensional double minimum potential. In a first step a pump pulse excites the system from the initial state an above-the-barrier state From there a second pulse dumps the population into the target state Pf.

Fig. 10.29. The pump-dump scheme for specific vibrational level population in the ground triplet state of Cs2 from Ref. 207.

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