Colloquia

Joint Chemistry-Physics Colloquium
Friday, November 12, 2010
4:00 PM
Physics Building, Room 204
Note special time.

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"CaF: Just Large Enough, and Ca: Even Smaller"


Robert Field , MIT
[Host: Tom Gallagher]
ABSTRACT:
CaF is as “not-atom” as a diatomic molecule can be. The core-penetrating and core-nonpenetrating Rydberg states of CaF are observed by two-color Resonance Enhanced Ionization spectroscopy. The observed rovibronic energy levels are input to an energy- and internuclear distance-dependent Multichannel Quantum Defect Theory fit model. The fitted quantum defect matrix, μ(E,R), accounts for nearly all spectra and dynamics of CaF. A “zone of death” is observed, where selection-rule-shattering “indirect” interactions of all Rydberg states with each other, is caused by one repulsive electronic potential curve. A STIRAP-like, multiphoton, chirped pulse, millimeter wave scheme for “jumping over” this zone of death is being developed. Progress toward “pure electronic spectroscopy” and magnetic resonance-like manipulation of molecular Rydberg states requires taking a step that Arthur Schawlow would have liked, back from CaF, with its one atom too many, to the Ca atom. 5 kilo-Debye Rydberg-Rydberg transitions in Ca are directly detected by Free Induction Decay signals, rather than indirectly, via ions or UV fluorescence, in a pulsed supersonic jet.
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