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12  G. ROBERTS


















































                               Figure 1.5. Femtosecond spectroscopy of bimolecular collisions. The cartoon
                               shown in (a) illustrates how pump and probe pulses initiate and monitor the
                               progress of H CO →[HO . . . CO]→OH CO collisions. The build-up of OH
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                               product is recorded via the intensity of fluorescence excited by the probe laser as a
                               function of pump-probe time delay, as presented in (b). Potential energy curves
                               governing the collision between excited Na* atoms and H are given in (c); these
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                               show how the Na* H collision can proceed along two possible exit channels,
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                               leading either to formation of NaH H or to Na H by collisional energy
                                                                     2
                               exchange.
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