Scaling in Molecular Electronic Spectroscopy

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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.