Quantum control of the yield of a chemical reaction

Order of magnitude enhancement in the concerted elimination pathway leading to I-2 product formation in the photodissociation reaction of CH2I2 by the use of positively chirped 312 nm femtosecond laser pulses is demonstrated. The maximum yield is found for chirps of 2400 fs(2) while the minimum is found near -500 fs(2). Multiphoton excitation with 624 nm pulses results in the opposite effect, where the maximum yield is found near -500 fs(2). The enhancement as a function of chirp is found to depend on the wavelength and intensity of the laser pulses. These results offer new experimental evidence for quantum control of chemical reactions. (C) 1998 American Institute of Physics.