Selection of photodissociation products using a laser phase control techique.

本论文研究了光解产物支化过程的激光相位控制。1996年，离子成像系统建成，使我们能够测量光碎片在特定电子、振动和转动状态下的平动能。在这个系统中，使用共振增强多光子电离技术电离的光碎片。产生的离子被电场加速，并在无场漂移管中转移。然后，通过二维探测器探测由于平移运动而扩散的离子云。1997年，我们用光解产物离子成像系统研究了ZONE和CH_3分子的光解过程。在280- 320 nm的Hartley和Huggins带中，监测了带分子光解产生的O（^3P）和O（^1D）原子。通过扫描光解激光波长和监测O（^3P）和O（^1D）原子的信号强度，测量了O（^3P）和O（^1D）产物的光碎片激发谱（PHOFEX）。在此光解离波长范围内，存在O（^3P）+O_2（X^3SIGMA^-_g）和O（^1D）+O_2（a^1DELTA_g）两种解离途径。发现O（^1P）原子的PHOFEX光谱具有离散的臭氧振动结构，而O（^1D）原子的PHOFEX光谱是平滑的。这表明产物的支化受臭氧上电子表面振动的影响，并暗示支化可能受激光相干相的控制。对于CH_3I分子，用308和616 nm激光监测I^+的离子图像，研究了单光子和双光子激发过程之间的相位差的影响。

In this research, the laser phase control of product branching in photodissociation processes was investigated. In 1996, the ion imaging system was constructed, which enabled us to measure the translational enegies of the photofragments in the specific electronic, vibrational and rotational states. In this system, the photofragments were ionized using a resonance-enhanced multiphoton ionization technique. The producted ions were accelerated by an electric field and transferred in a field free drift tube. Then, the clouds of the spread ions due to the translational their motions were detected by a 2-dimensional detector. In 1997, the photodissociation processes of zone and CH_3 molecules were studied using the ion imaging system for the photodissociation products. The O (^3P) and O(^1D) atoms produced by the photodissociation of zone molecules in the Hartley and Huggins bands around 280-320nm were monitored. The photofragment excitation (PHOFEX) spectra for the O (^3P) and O(^1D) products were measured by scanning photodissociation laser wavelength and monitoring the signal intensities of O (^3P) and O (^1D) atoms. There were two dissociation pathways, O (^3P)+O_2 (X^3SIGMA^-_g) and O (^1D) +O_2 (a^1DELTA_g), in this photodissociation wavelength range. The PHOFEX spectrum for the O (^1P) atoms was found to have discreet vibrational structure of ozone, while that for the O (^1D) atoms were smooth. This indicated that the product branching was affected by the vibrational motion in the upper electronic surface of ozone, and suggested that the branching might be controlled by the laser coherent phase. For the CH_3I molecules, the effects of the phase difference between the one-photon and two-photon excitation processes were studied by monitoring the ion images of I^+ with 308 and 616nm laser light.