Coherent Control of Photofragmentation Product Branching Ratios

Theoretical calculations show that there is no coupling between dissociation and ionization continua in HC1 (see Fig. 5 of Lefebvre-Brion and Keller, 1989). 

13 Coherent Control of Photofragmentation Product Branching Ratios 

The coherence properties of laser radiation provide an opportunity to exert some external control over intramolecular dynamics. Control over photofragmentation product branching ratios has been achieved in both time and frequency domain experiments. 

An experiment on the Na2 molecule by Baumert and Gerber (1994) illustrates the Tannor-Rice scheme. A pair of ultrashort (70-110 fs) laser pulses is used to excite selectively either the 

Instead, the vibrational wavepacket created at zero pump/probe delay on the Nat X2Ej state is built from low-u+ levels centered near the intersection of the probe pulse dotted arrow with the X2E+-state potential. The excess energy from the probe pulse must go into the kinetic energy of the ejected electron (in even-1 partial waves). The excitation by the probe pulse at the outer turning point (solid vertical arrow) has good Franck-Condon overlap with the 2E+-state repulsive potential. The g +- u optical selection rule requires that the low kinetic energy ejected electron depart in odd-1 (i.e., u symmetry) partial waves. Both electronic and vibrational transition probability factors favor excitation at the outer turning point. 

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