Hochaufgelöste optische Spektroskopie einzelner Terrylen-Moleküle bei kryogenen Temperaturen mit einem Parabolspiegelmikroskop

A confocal microscope with a parabolic mirror objective (NA ≈ 1) is used at ensemble and single molecule level for fluorescence microscopy and spatially resolved spectroscopy of the organic dye terrylene, which is embedded in a Shpol´skii matrix of n-octadecane. Beside an efficient excitation and collection of light a spatial resolution close to the diffraction limit is achieved, both at room temperature and at 1.8 K. The focusing properties of the microscope are experimentally verified and show a value which is 1.5 times larger than the theoretical limit. By fluorescence excitation spectroscopy with a narrow band laser, excitation spectra are recorded at low temperatures and yield a natural linewidth of (42 ± 2) MHz. Homogeneous and inhomogeneous broadening is demonstrated. The orientation of single molecules can coarsely be concluded from fluorescence saturation and power broadening. Analyzed spectral jumps are found to be light induced. Fluorescence spectroscopy at low temperatures yield the energy of the highly resolved vibrational levels of the electronic ground state. Surface enhanced resonance Raman scattering at room temperature is compared with the lowtemperature data and reproduces some of the fluorescence lines. For forthcoming experiments a polarization converter with interferometer arrangement for generation of radially and azimuthally polarized light is set up and characterized in detail.