Coherent Control of Radiationless Transitions

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In this award, funded by the Experimental Physical Chemistry Program of the Chemistry Division, Professor Gordon and his students will use lasers to control the relaxation rate of electronically excited organic molecules. Such processes, known as "radiationless transitions," play an essential role in vision, mutagenesis, and carcinogenesis, as well as in many industrial processes. For example, a unique property of the four nucleotide building blocks of DNA is that their conversion of electronic to vibrational energy is faster than fragmentation, allowing these molecules to be stable in the presence of ultraviolet radiation. This property is essential for life to exist on the surface of the earth. The goal of this project is to use ultrashort femtosecond laser pulses either to accelerate or inhibit the rate of such radiationless transitions. By using a combination of theory and experiment, the temporal profile of the pulses will be optimized to achieve the desired goal. This research fits into the larger context of coherent control of chemical reactions, in which light pulses are designed to control the outcome of chemical and physical processes. The research will also provide a deeper understanding of the mechanism of this important class of chemical processes.