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A method to estimate intermolecular potential well depths for species in both ground and excited electronic states A relationship is developed from two distinct theoretical approaches to correlate the rate constants kM or cross sections O"M for a series of added gases M which coJlisionally induce a state transformation A' -lB. The correlation derived from theory iswhere C is a constant and EA'M is the intermolecular well depth between A* and M. We observe that experimental data can be described by a related correlation where f3 is a constant and EMM is the well depth between pairs of M molecules. This correlation is shown to be general. It works for electronic state deactivation in atoms, intersystem crossing and internal conversion in S, polyatomics, rotational and also vibrational relaxation in SI polyatomics. predissociation in diatomics and polyatomics, and vibrational relaxation in a free radical as well as in a molecular ion. The theory is appropriate only when attractive forces dominate the interaction, and this seems consistent with the experimental data. The correlation thus provides a simple means to distinguish between attractive and repulsive interactions. The correlation also reveals that collision partners do not substantialIy modify the intrinsic Sr T mixing during collision-induced intersystem crossing. 5442

This work explores the utility of attractor-based approaches in the field of vibration-based structural health monitoring. The technique utilizes the unique properties of chaotic signals by driving the structure directly with the output of a chaotic oscillator. Using the Kaplan-Yorke conjecture, the Lyapunov exponents of the driving signal may be tuned to the dominant eigenvalues of the structure, thus controlling the dimension of the structural response. Data are collected at various stages of structural degradation and a simple nonlinear model, constructed from the undamaged data, is used to make predictions for the damaged response data. Prediction error is then introduced as a "feature" for classifying the magnitude of the damage. Results are presented for an experimental cantilevered beam instrumented with fiber-optic strain sensors.

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