title: Imaging of tautomerism in a single molecule.
abstract: Fluorescence imaging is used to visualize directly the transfer of two inner hydrogen atoms in single porphycene molecules. This reaction leads to a chemically equivalent but differently oriented structure and hence results in a rotation of the transition dipole moments. By probing single immobilized molecules with an azimuthally polarized laser beam in the focal spot of a confocal microscope we observe ring-like emission patterns, possible only for a chromophore with two nearly orthogonal transition dipole moments. Numerical simulations of the observed emission patterns yield a value of 72 degrees for the angle between the S0-S1 transition moments in the two tautomeric forms.
authors.affiliation: Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland.
authors.forename: Hubert
authors.initials: H
authors.lastname: Piwoński
authors.forename: Clemens
authors.initials: C
authors.lastname: Stupperich
authors.forename: Achim
authors.initials: A
authors.lastname: Hartschuh
authors.forename: Jerzy
authors.initials: J
authors.lastname: Sepioł
authors.forename: Alfred
authors.initials: A
authors.lastname: Meixner
authors.forename: Jacek
authors.initials: J
authors.lastname: Waluk