Orientational imaging of single molecules by annular illumination
The absorption dipole orientation of single fluorescent molecules is determined by mapping the spatial distribution of the squared electric field components in a high-numerical-aperture laser focus. Annular illumination geometry and the vicinity of a plane dielectric/air interface strongly enhance the longitudinal field component and the transverse fields perpendicular to the polarization direction. As a result, all three excitation field components in the focus are of comparable magnitude. The scheme holds promise to monitor rotational diffusion of single molecules in complex environments.
Sick
B
Physical Chemistry Laboratory, Swiss Federal Institute of Technology, ETH-Z, CH-8092 Zurich, Switzerland.
Hecht
B
Novotny
L