Laser chemistry: coherent control, aerosol chemistry, surface chemistry

拟议在今后五年期间进行的研究是在激光化学和激光光谱学的一般领域。在研究计划中，有两个主要主题，一个是使用短波长（真空紫外）激光器用于气溶胶粒子的光电离质谱，另一个使用成形的飞秒激光脉冲来修改和控制材料的光谱响应和光化学。第一个一般研究主题是基于UBC新建的设备，一种能够对单个亚微米气溶胶颗粒进行详细化学分析的设备。这种分析的核心是一种新型的质谱仪，它使用可调谐真空紫外激光器提供刚好足够的光子能量来激发分子（阈值光电离），这是一个防止母离子碎裂的过程，并允许确定检测到的m/e的电离阈值。再加上高水平的ab-inito计算，可以明确识别检测到的物质，这在研究复杂的氧化过程中至关重要。在该技术的扩展中，应该可以使用相同的设备来记录生物感兴趣的大分子的质谱，并利用离子阱质谱仪进行结构测定。这是激光科学中的一个重要领域，我们的计划将使用成形的飞秒激光脉冲进行非线性光谱学，特别是相干反斯托克斯拉曼光谱学（汽车），并用于控制分子中的量子态分布，从而控制光化学过程。光谱学工作将利用我们一直在开发的新方法来研究复杂系统的光谱学和光谱物理学，以及光谱分辨成像。在量子态控制中，我们希望展示对分子态进行复杂操作的能力，并利用这些来防止自发辐射和进行手性纯化。

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.