title: Shaped and Feedback-Controlled Excitation of Single Molecules in the Weak-Field Limit.
abstract: Coherent control uses tailored femtosecond pulse shapes to influence quantum pathways and drive a light-induced process toward a specific outcome. There has been a long-standing debate whether the absorption properties or the probability for population to remain in an excited state of a molecule can be influenced by the pulse shape, even if only a single photon is absorbed. Most such experiments are performed on many molecules simultaneously, so that ensemble averaging reduces the access to quantum effects. Here, we demonstrate systematic coherent control experiments on the fluorescence intensity of a single molecule in the weak-field limit. We demonstrate that a delay scan of interfering pulses reproduces the excitation spectrum of the molecule upon Fourier transformation, but that the spectral phase of a pulse sequence does not affect the transition probability. We generalize this result to arbitrary pulse shapes by performing the first closed-loop coherent control experiments on a single molecule.
authors.affiliation: Physical and Theoretical Chemistry Laboratory, University of Oxford , South Parks Road, Oxford OX1 3QZ, United Kingdom.
authors.forename: Alexander
authors.initials: A
authors.lastname: Weigel
authors.affiliation: Physical and Theoretical Chemistry Laboratory, University of Oxford , South Parks Road, Oxford OX1 3QZ, United Kingdom.
authors.forename: Aleksandar
authors.initials: A
authors.lastname: Sebesta
authors.affiliation: Physical and Theoretical Chemistry Laboratory, University of Oxford , South Parks Road, Oxford OX1 3QZ, United Kingdom.
authors.forename: Philipp
authors.initials: P
authors.lastname: Kukura
keywords: genetic algorithm; single molecule dynamics; single molecule spectroscopy; single-molecule fluorescence excitation spectrum; wavepacket motion; weak-field coherent control