Picosecond and Nanosecond Laser Pulse Shaping for State-Selective Chemistry

Warren S. Warren博士获得了物理化学项目的资助，致力于开发新的激光脉冲整形和脉冲测序技术，用于气体和凝聚态分子物种的光谱研究。这项工作的新颖方面来自于在各种应用中使用对激光辐射场的增强控制来产生简单和可解释的分子状态。沃伦已经从理论上和实验上证明，可以产生具有皮秒分辨率、高功率和完全相位控制的形状脉冲和脉冲序列。他还证明了需要哪些特征形状来解决特定的分子问题，如振动态的选择性激发，气体和分子晶体中的光密度和弛豫效应的补偿，在不使用分子束的情况下进行速度选择。这些技术被用于各种各样的研究。例如，两种不同颜色的形状脉冲被用来选择性地和完全地泵送碘中的高振动态，从而允许研究速度变化的碰撞和为氧碘激光器提供动力的反应的演变。形状深紫外脉冲加上可见脉冲被用来表征HCP的弯曲势和光化学性质。为了研究孤子在光纤中的传播，对1,4-二溴二萘的局部分子激发进行了泵浦。最后，在混合有机晶体中，光子回波序列正在被研究以获得不受光密度效应和分子相互作用影响的无畸变衰减。

Dr. Warren S. Warren is supported by a grant from The Physical Chemistry Program to develop new laser pulse shaping and pulse sequencing techniques for spectroscopic studies of molecular species in both gas and condensed phases. The novel aspect of this work comes from the use of enhanced control over the laser radiation field to produce simple and interpretable molecular states in a wide variety of applications. Warren has demonstrated both theoretically and experimentally that it is possible to produce shaped pulses and pulse sequences with picosecond resolution, high powers, and complete phase control. He has also demonstrated which characteristic shapes would be required to solve specific molecular problems such as selective excitation of vibrational states, compensation for optical density and relaxation effects in both gases and molecular crystals, and velocity selection without the use of molecular beams. These techniques are being used in a variety of studies. For example, two shaped pulses of different colors are being used to selectively and completely pump high vibrational states in iodine, thus permitting study of both velocity changing collisions and the evolution of the reaction which powers the oxygen-iodine laser. Shaped deep-UV pulses plus visible pulses are being used to characterize the bending potential and photochemistry of HCP. Localized molecular excitations of 1,4-dibromonaphthalene are being pumped in order to study soliton propagation in fibers. Finally, photon echo sequences are being studied to give undistorted decays independent of optical density effects and molecular interactions in mixed organic crystals.