title: Variable-Temperature Tip-Enhanced Raman Spectroscopy of Single-Molecule Fluctuations and Dynamics.
abstract: Structure, dynamics, and coupling involving single-molecules determine function in catalytic, electronic or biological systems. While vibrational spectroscopy provides insight into molecular structure, rapid fluctuations blur the molecular trajectory even in single-molecule spectroscopy, analogous to spatial averaging in measuring large ensembles. To gain insight into intramolecular coupling, substrate coupling, and dynamic processes, we use tip-enhanced Raman spectroscopy (TERS) at variable and cryogenic temperatures, to slow and control the motion of a single molecule. We resolve intrinsic line widths of individual normal modes, allowing detailed and quantitative investigation of the vibrational modes. From temperature dependent line narrowing and splitting, we quantify ultrafast vibrational dephasing, intramolecular coupling, and conformational heterogeneity. Through statistical correlation analysis of fluctuations of individual modes, we observe rotational motion and spectral fluctuations of the molecule. This work demonstrates single-molecule vibrational spectroscopy beyond chemical identification, opening the possibility for a complete picture of molecular motion ranging from femtoseconds to minutes.
authors.affiliation: Department of Physics, Department of Chemistry, and JILA, University of Colorado , Boulder, Colorado 80309, United States.
authors.forename: Kyoung-Duck
authors.initials: KD
authors.lastname: Park
authors.affiliation: Department of Physics, Department of Chemistry, and JILA, University of Colorado , Boulder, Colorado 80309, United States.
authors.forename: Eric A
authors.initials: EA
authors.lastname: Muller
authors.affiliation: Department of Physics, Department of Chemistry, and JILA, University of Colorado , Boulder, Colorado 80309, United States.
authors.forename: Vasily
authors.initials: V
authors.lastname: Kravtsov
authors.affiliation: Department of Physics, Department of Chemistry, and JILA, University of Colorado , Boulder, Colorado 80309, United States.
authors.forename: Paul M
authors.initials: PM
authors.lastname: Sass
authors.affiliation: German Research School for Simulation Sciences, RWTH Aachen University and Forschungszentrum Jülich , D-52425 Jülich, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Dreyer
authors.affiliation: Department of Physics, Department of Chemistry, and JILA, University of Colorado , Boulder, Colorado 80309, United States.|Department of Chemistry, University of North Carolina , Chapel Hill, North Carolina 27599, United States.
authors.forename: Joanna M
authors.initials: JM
authors.lastname: Atkin
authors.affiliation: Department of Physics, Department of Chemistry, and JILA, University of Colorado , Boulder, Colorado 80309, United States.
authors.forename: Markus B
authors.initials: MB
authors.lastname: Raschke
keywords: Tip-enhanced Raman spectroscopy (TERS); low-temperature; molecular dynamics; molecular orientation; single molecule; vibrational dephasing