Chirp negative

Fig. 3.14. Left transient reflectivity change of Te obtained with transform limited, negatively chirped, and positively chirped pulses. Right coherent phonon amplitude as a function of the pulse chirp. Adapted from [42]...

A negative chirped pulse is shown in Figure 6.4c. Experiments and theoretical studies on coherent control of ultrafast electron dynamics by intense chirped laser pulses will be discussed in Sections 6.3.2.3 and 633.2. 

Fig. 2. Left Dissociation yield U for a positive chirp ( + ), no chirp ( 0 ), and negative chirp experiment (gray, left scale) and theory (light gray, right scale). Right The dissociation yield U is a steep function of negative chirp experiment (bars, left scale) and theory (open circles, right scale).

The Wigner distributions of harmonics obtained with laser intensity of 1 x 1015 W/cm2 are shown in Fig. 8.3. In this case, the harmonics are negatively chirped at the leading edge of the chirp-free pulses as shown in Fig. 8.3a. So the positively chirped laser pulses can compensate for the negative harmonic chirp, as shown in Fig. 8.3b. 

Fig. 8.3. Wigner distribution of harmonics after propagating through a 0.7-mm long neon medium of density 2 x 1018 cm 3. Laser intensity applied is 5 x 101BW/cm2. The laser intensity and laser pulse duration used in four different cases are a 1 x 101BW/cm2, chirp-free 25 fs, b positively chirped 35 fs from a, c 5 x 1015 W/cm2, chirp free 25fs, and d negatively chirped 100fs from c...

The spatial and temporal modifications of the laser profile during propagation are calculated for the case of a negatively chirped 42-fs pulse with 5-mJ energy. The gas medium is a 9-mm Ne gas jet with a density of 1.4xl018cm 3. 

Fig. 12.7. The pulse duration dependence of the mean ion energy measured at a fixed laser energy of 49 mJ and a laser contrast of 5 x 10 6 with positive and negative chirps...

Results for up-pumping W(CO)6 with chirped pulse excitation were compared to excitation of the Tlu manifold using transform-limited pulses with center frequencies all tuned to the peak vibrational mode absorption frequency. Figure 3 shows transient broadband absorption spectra taken at 40 ps time delay for the three different pulse types. As depicted, one readily observes that the relative population amplitudes in the CO-stretch v = 1 (at 1970 cm-1) and v = 2 (at 1955 cm ) levels are strongly affected by the chirp of the excitation pulse. Excitation with negatively chirped... 

Figure 3 Examples of transient infrared spectra obtained at 40 ps time delay for W(CO)6 in n -hexane using (top) positively chirped, (middle) no chirp, and (bottom) negatively chirped IR excitation pulses centered at 1983 cm-1. Note the suppression and increase in v = 1 —> 2 excited state absorption near 1950 cm-1. 

FIG. 2.5 Instantaneous frequencies of C-N and N=N stretching modes calculated from tfie spectrogram analysis of oscHlatit components of the AT/T(t) traces by usir (A) positii cNrped (PC) pulse and (B) negatively chirped (NC) pulse. Delay-tile dependence (upper) and Lissa)ou s figures (lovyer). 

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