Coherent control of large molecules in liquids

To achieve quantmn control of simple molecules is a problem that is relatively simple to solve. Can we hope to control the quantum dynamics of large molecules, specifically macromolecules such as proteins and nucleic acids We should distinguish between the following two, rather different cases the gas phase or a molecular beam (Sections 12.4 and 12.5), and a condensed (liquid) medium. 

The fact that such an experimental window for coherent control in liquids does actually exist was verified in experiments on the selective multiphoton excitation of two distinct electronically and structurally complex dye molecules in solution (Brixner et al. 2001(b)). In these experiments, despite the failure of single-parameter variation (wavelength, intensity or linear chirp control), adaptive femtosecond pulse shaping revealed that complex laser fields could achieve chemically selective molecular excitation. These results prove, first, that the phase coherence of complex molecules persists for more than 100 fs in a solvent environment. Second, this is direct proof that it is the nontrivial coherent manipulation of the excited state and not of the frequency-dependent two-photon cross sections that is responsible for the coherent control of the population of the excited molecular state. 

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