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首页> 外文学位 >Vibrational wave packets: Molecular state reconstruction in the gas phase and mixed quantum/semiclassical descriptions of small-molecule dynamics in low-temperature solid media.
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Vibrational wave packets: Molecular state reconstruction in the gas phase and mixed quantum/semiclassical descriptions of small-molecule dynamics in low-temperature solid media.

机译：振动波包：气相中的分子状态重建以及低温固体介质中小分子动力学的混合量子/半经典描述。

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摘要

We explore the reconstruction of B-state vibrational wave packets in I2 from simulated two-color nonlinear wave packet interferometry data. As a simplification of earlier proposals, we make use of different vibrational energy ranges in the B-state---rather than different electronic potential surfaces---for the short-pulse preparation and propagation of both target and reference wave packets. Numerical results from noisy interferograms indicate that experimental reconstruction should be possible with high fidelity (>0.99).;Time-resolved coherent nonlinear optical experiments on small molecules in low-temperature host crystals are exposing valuable information on quantum mechanical dynamics in condensed media. We make use of generic features of these systems to frame two simple, comprehensive theories that will enable the efficient calculation of their ultrafast spectroscopic signals and support their interpretation in terms of the underlying chemical dynamics. Both treatments rely on the identification of normal coordinates to unambiguously partition the well-structured guest-host complex into a system and a bath and expand the overall wave function as a sum of product states between fully anharmonic vibrational basis states for the system and approximate Gaussian wave packets for the bath degrees of freedom. The theories exploit the fact that ultrafast experiments typically drive large-amplitude motion in a few intramolecular degrees of freedom of higher frequency than the crystal phonons, while these intramolecular vibrations indirectly induce smaller-amplitude---but still perhaps coherent---motion among the lattice modes. The equations of motion for the time-dependent parameters of the bath wave packets are fairly compact in a fixed vibrational basis/Gaussian bath (FVB/GB) approach. An alternative adiabatic vibrational basis/Gaussian bath (AVB/GB) treatment leads to more complicated equations of motion involving adiabatic and nonadiabatic vector potentials.;Numerical tests of the FVB/GB are presented. We consider two bilinearly coupled harmonic oscillators with varying coupling strengths and initial conditions and show that the mixed quantum/semiclassical theory compares favorably with the exact results. Linear absorption spectra and wave-packet interferometry signals calculated using the theory are presented.;This dissertation includes previously published coauthored material.
机译：我们从模拟的两色非线性波包干涉测量数据中探索了I2中B态振动波包的重建。为了简化先前的建议，我们在B态中使用了不同的振动能量范围-而不是在不同的电子势面-中进行了短脉冲准备以及目标波包和参考波包的传播。嘈杂干涉图的数值结果表明，应该能够以较高的保真度（> 0.99）进行实验重建。在低温基质晶体中对小分子进行时间分辨的相干非线性光学实验，揭示了有关凝聚介质中量子力学动力学的宝贵信息。我们利用这些系统的通用功能来构建两个简单而全面的理论，这将使它们能够快速计算其超快光谱信号并支持其对基本化学动力学的解释。两种处理都依赖于法向坐标的识别，以将结构良好的来宾-主体复合体明确划分为系统和浴，并扩展整体波函数，作为系统的完全非谐振动基态与近似高斯之间的乘积状态之和。波包为洗浴自由度。这些理论利用了以下事实：超快实验通常以比晶体声子高的几个分子内自由度来驱动大幅度运动，而这些分子内振动间接地引起了振幅较小的运动，但仍可能是相干运动。晶格模式。在固定的振动基础/高斯浴（FVB / GB）方法中，浴波包的时间相关参数的运动方程相当紧凑。另一种绝热振动基础/高斯浴（AVB / GB）处理导致涉及绝热和非绝热矢量势的更复杂的运动方程。;提出了FVB / GB的数值测试。我们考虑了两个具有不同耦合强度和初始条件的双线性耦合谐振子，并表明混合量子/半经典理论与精确结果相比具有优势。给出了利用该理论计算得到的线性吸收光谱和波包干涉测量信号。

著录项

  • 作者

    Chapman, Craig Thomas.;

  • 作者单位

    University of Oregon.;

  • 授予单位 University of Oregon.;
  • 学科 Chemistry Physical.;Physics Quantum.;Physics Molecular.
  • 学位 Ph.D.
  • 年度 2010
  • 页码 195 p.
  • 总页数 195
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
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