Scaling in Molecular Electronic Spectroscopy

麻省理工学院的Robert W. Field在实验物理化学计划的支持下，进一步发展和利用分子量子缺陷理论（MQDT），正在努力研究分子电子光谱中的缩放（用n*， l和ml）。具体来说，他将使用Stark开关光谱来研究核心非穿透分子的里德堡态，或者使用双色共振增强的多光子电离来研究碱土单卤化物的核心穿透里德堡系列。最初，他将专注于相对简单的系统，如碱土单卤化物，然后转向更复杂的系统，包括更大的多原子分子。他的总体目标是开发、揭示和测试非常规模型，这些模型可能最终描述整个分子家族的电子结构和动力学：所有属性、所有状态、所有动力学过程。对这些实验的实际意义作一些评论是有必要的。为什么我们要关心阳离子的电多极矩？所有的+1阳离子都有相同的单极子，所以阳离子与外界相互作用的主要方面是独立于分子的。另一方面，离子特异性的远程相互作用来源于更高的多极（及其法向坐标位移导数）。这些多极和导数控制了共振远程离子-分子，离子-电子，可能还有离子-表面能和角动量交换的机制和速率。从核心非穿透里德伯态的系统研究中获得的信息将对等离子体中发生的各种过程产生有价值的见解。

Robert W. Field of The Massachusetts Institute of Technology is supported by the Experimental Physical Chemistry Program to further develop and exploit molecular quantum defect theory (MQDT) in an ongoing effort to investigate scaling (with n*, l and ml) in molecular electronic spectroscopy. Specifically, he will use Stark switching spectroscopy to study core non-penetrating molecular Rydberg states or two-color resonance-enhanced multiphoton ionization to study the core-penetrating Rydberg series of alkaline earth monohalides. Initially, he will focus on relatively simple systems such as the alkaline earth monohalides, then gravitate to more complex systems including larger polyatomic molecules. His overall objective is to exploit, uncover, and test unconventional models which might eventually describe the electronic structure and dynamics of entire families of molecules: all properties, all states, all dynamical processes. A few comments about the practical significance of these experiments are warranted. Why should we care about the electric multipole moments of cations? All +1 cations have the same monopole, so this dominant aspect of the interaction of the cation with the outside world is independent of the molecule. Ion-specific long-range interactions, on the other hand, derive from the higher multipoles (and their normal coordinate displacement derivatives). These multipoles and derivatives control the mechanisms and rates of resonant long-range ion-molecule, ion-electron, and possibly ion-surface energy and angular momentum exchange. The information obtainable from systematic studies of core-nonpenetrating Rydberg states would yield valuable insights into a wide variety of processes occurring in plasmas.