Abstract

Structural dynamics in semi-quantum and quantum solids (Ne, H2 and D2) is reported, and compared to results in classical solids such as Ar. The structural dynamics is driven by excitation of the lowest Rydberg state of the NO impurity. The resulting charge redistribution induces a local radial deformation of the medium ('bubble' formation) around the impurity. The steady-=state spectroscopic signatures of this process are presented and analyzed in the configuration coordinate model and harmonic approxn. Intermol. potentials describing the impurity-medium interaction are obtained. The dynamics of bubble formation and the ensuing medium response are probed in real-time by femtosecond pump-probe spectroscopy. In the very soft H2 and D2 environments, bubble formation is a 1-way process without recurrence of the cage motion and is complete in .apprx.1-2 ps. In the case of solid Ne, the dynamics are characterized by an initial expansion of the matrix cage around the impurity, followed by a low frequency recurrence. Overall the trend obsd. is that the expansion becomes slower in the sequence Ar-Ne-hydrogens, which is counterintuitive. This is discussed in terms of the quantum (delocalized) character of the lighter medium, which introduces an addnl. microscopic friction. These results establish exptl. procedure based on the use of low-n Rydberg states as a novel method for probing structural and electronic solvation dynamics in nonpolar media. [on SciFinder (R)]

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