Pump-probe spectrum

Figure8. (a) Pump-probe spectra of (NH3)2NH+ through the A (v= 0,1,2 corresponding to 214, 211, 208 nm, respectively) states the data reveal the influence of the vibrational level probed in the experiments, (b) Pump-probe spectrum of (NH3hH+ and (NH3)sH+ with pump pulses at 208 nm and probe pulses at 312 nm A (v = 2) of the ammonia molecule. The role of cluster size is evident. The delay time is the interval between the pump and probe laser, (a) Taken with permission from ref. 65 (b) Taken with permission from ref. 68.

Figure 2. Franck-Condon windows lVpc(Gi, r, v5) for the Na3(X) - N83(B) and for the Na3(B) Na3+ (X) + e transitions, X = 621 nm. The FC windows are evaluated as rather small areas of the lobes of vibrational wavefunctions that are transferred from one electronic state to the other. The vertical arrows indicate these regions in statu nascendi subsequently, the nascent lobes of the wavepackets move coherently to other domains of the potential-energy surfaces, yielding, e.g., the situation at t = 653 fs, which is illustrated in the figure. The snapshots of three-dimensional (3d) ab initio densities are superimposed on equicontours of the ab initio potential-energy surfaces of Na3(X), Na3(B), and Na3+ (X), adapted from Ref. 5 and projected in the pseudorotational coordinate space Qx r cos

Figure 6-4. Pump-probe spectrum of ammonia clusters with both pump and probe pulses at 624 nm C (v = 1) of the ammonia molecule.

Fig. 1.18. Spectrally resolved pump-probe spectrum of pristine MDMO-PPV compared to highly fullerene-loaded MDMO-PPV/PCBM composites at various delay times, (a) Absorption spectrum of a pure MDMO-PPV film (solid line) and AT/T spectrum at 200 fs pump-probe delay (dashed line), (b) AT/T spectra of the MDMO-PPV/PCBM blend (1 3 wt. ratio) at various time delays following resonant photoexcitation by a sub-10-fs optical pulse. The CW PA of the blend ( ) was measured at 80 K and 10-5 mbar. Excitation was provided by the 488 nm line of an argon ion laser, chopped at 273 Hz...

We already discussed the projection onto the co axis as being the pump-probe spectrum. The 45° projections can also be quite useful for analyzing the correlations in the inhomogeneous distributions. It is useful to note that Eq. (47) can be rewritten as... 

By stepping a over the duration of the pulse and collecting a pump-probe spectrum for each time value of a, the vibrational population transfer over the course of the pulse is assessed. To quantitatively extract relative vibrational populations from these pump-probe spectra, we fit peak intensities assuming a harmonic scaling law for the transition dipoles [e.g., (n + l) /xn n+i 2 = (n + 2)... 

The result of a pump-probe spectrum obtained from is shown in... 

Fig. 7. Pump-Probe spectrum for K5. The spectrum exhibits an oscillation of 6.5 ps superposed to a fast unimolecular decay of 5.6 ps.

A similar pump-probe spectrum obtained from a predissociated state of K5 is shown in Fig. 7. The duration of an oscillation period is 6.5 ps, the exponential decay of the particle occurs in 5.6 ps which is slightly faster than the decay of K3. 

Fig. 12. Pump-Probe spectrum of Nas obtained imder identical experimented conditions, as Fig. 5 with the only exception that the employed pump pulse was linearly downchirped to a duration of 400 fe. The resulting oscillation time of 230 fis corresponds to the symmetric stretch vibration of the electronic ground state of Nas. At negative times (i.e. unchirped pump, chirped probe), still the vibration of the B-state is observed (see Fig. 5).

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... 

Being mainly interested in the dynamics associated with the conical intersection of the and S2 excited electronic states, we focus in the following on the excited-state contribution to the pump-probe spectrum. Figures 2 and 3 compare three different excited-state pump-probe signals, namely the integral stimulated-emission spectrum (2b), the time-resolved fluorescence spectrum (3a), and the dispersed stimulated-emission spectrum (3b). As has been discussed above, the integral stimulated-emission spectrum and the time-resolved fluorescence spectrum are rather similar. Because of the... 

Another aspect of the high-power pump probe spectrum is the experimentally observed beat structure of 2.6 ps (Fig. 3.27b). Again the existence of two different ionization pathways is of decisive importance. The vibrational periods of the excited potential surfaces involved (A i7+, 4 17, and 2 77g) lie in the range 500 — 620 fs. Their beat frequency with the ground state oscillations of 380 fs has a period of 1.3 ps. Thus the experimentally observed beat frequency of 2.6 ps can only be caused by the influence of two additional ionization pathways. These may be located, for instance, at the inner and outer turning points, mirroring half the oscillation period of the wave packet in one of the excited states. The two states 4 17+ and 2 77g in combination just open the possibility of mirroring half the oscillation period of the wave packet in the state, i.e. the first-harmonic (via the... 

For this, various 3d quantum ab initio simulations of the wave packet dynamics in Naa B are presented here and compared to ultrashort laser pump probe experiments. In addition to exact QD calculations, an a > proximate QD method is suggested to simulate the main features of a pump probe spectrum. The simulations provide satisfactory results in comparison to exact QD calculations. By means of these two methods it is possible to reproduce and to explain the different experimental pump probe spectra. The 310 fs oscillation in the femtosecond pump probe experiment [62, 81] can clearly be assigned to the Qs vibration, while the 3ps oscillation of the picosecond pump probe experiment [306, 379] is caused by a slow pseudorotational wave packet motion. 

Figure 3.49 shows a comparison between the experimental (top) and the approximate QD pump probe spectrum (bottom). Both curves show an oscillation with a period of about 3ps, which can be identified with the vibration from the obtuse to the acute geometry as described above (including only V — I and 2, with an approximate energy spacing of 13cm of the (p mode). This is in accordance with an earlier study [380] where the 3ps oscillation was explained by a similar pseudorotational motion of the molecule,... 

This theorem can be used to determine the correct relative phase factor. The entire spectral interferometry analysis described in this section is performed, changing the relative phase factor used until the projection of the real 2DPE spectrum in energy matches the spectrally resolved pump probe spectrum. In all of the work presented in this chapter, a non-frequency-dependent phase factor... 

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