Laser chemistry: coherent control, aerosol chemistry, surface chemistry

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The research proposed for the coming five year period is in the general area of laser chemistry and laser spectroscopy. Within the research program, there are two main themes, one using short wavelength (vacuum ultraviolet) lasers for photoionization mass spectrometry of aerosol particles, the other using shaped femtosecond laser pulses to modify and control the spectral response and photochemistry of materials.The first general research theme is based on a newly constructed apparatus at UBC, an apparatus which has the capability to carry out detailed chemical analysis on single, sub-micron, aerosol particles. The heart of this analysis is a novel mass spectrometer, which uses a tunable vacuum ultraviolet laser to provide just enough photon energy to ionize a molecule (threshold photoionization), a process that prevents fragmentation of the parent ion, and allows for the determination of the ionization threshold of the m/e detected. This, coupled with high level ab-inito calculations, leads to an unambiguous identification of the detected species, something that is critical in studying complex oxidation processes. In an extension of this technique, it should be possible to use the same apparatus to record the mass spectrum of large molecules of biological interest, and exploit the ion trap mass spectrometer for structure determination.The second general theme is coherent control. This is a large and imprtant area within laser science, and our program will use shaped femtosecond laser pulses for non-linear spectroscopy, especially coherent anti-Stokes Raman spectroscopy (CARS), and for control of quantum state distributions in molecules, leading to a control over photochemiscla processes. The spectroscopic work will exploit new methodologies that we have been developing to study spectroscopy and photophysics of complex systems, and for spectrally resolved imaging. In the quantum state control, we hope to demonstrate the ability to carry out complex manipulations of molecular states, and to use these to prevent spontaneous emission and to carry out chiral purification.