Electron dephasing mechanisms

Thirdly, the collision-induced Raman resonances can expand the application of Raman spectroscopy to situations where the conventional Raman susceptibility vanishes. Andrews et al., for example, have demonstrated that sharp vibrational transitions in an initially unpopulated excited electronic state of a molecule can be observed as extra four-wave mixing resonances, even though they cannot be observed in absorption because of rapid dephasing of the electronic transition. In these experiments pentacene molecules were doped in a benzoic acid crystal, and phonon scattering rather than collisions provided the dephasing mechanism. CARS of equally-populated ground state rotational levels in molecules would also become possible by observing collision-induced resonances. 

MEG is intimately related to phonon-induced dephasing. Impact ionization assumes incoherent transitions from high-energy SE states to MEs. The loss of electronic coherence occurs by coupling to phonons and, in this case, should be faster than MEG. The dephasing mechanism " starts with a coherent superposition of single and ME states and associates MEG with dephasing of the... 

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