Efforts are being made to generate a general technological method of studying tunneling and energy transfer that is applicable to symmetric double wells as well as other dynamical structures. Such investigations should permit a new class of biodynamic processes to be observed. The method involves time resolved polarization spectroscopy (four-wave mixing). From a technical standpoint this experimental configuration involves a pump pulse polarized at l/4 to the vertical, that prepares electronic and Raman coherences in the system and creates a macroscopic anisotropic polarizability. The Raman coherences beat with each other and decay with vibrational T2 times whereas the latter decays by orientational relaxation of the molecules. A vertically polarized probe pulse generates the horizontally polarized signal field in this well characterized experiment involving nearly crossed polarizers. When the molecule undergoes overdamped or periodic motion changes in the nonlinear index occur because the polarizability tensor axes rotate in the laboratory frame. Superimposed on this decay (or oscillation) is the decay and oscillation of vibrational coherences introduced by the pump pulse. This experiment is equally well carried out with a transient grating configuration. To our knowledge these methods were not yet used to study biological processes. A 25 fs pulse is needed for these experiments.
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