In this paper we present a rigorous and general theoretical model for the illumination point spread function of a confocal microscope that correctly reproduces the optical setup. The model uses vectorial theory and assumes that monochromatic light with a Gaussian intensity distribution (such as from a laser or a single-mode fiber) is focused by a microscope objective with high numerical aperture and passes through stratified media on its way to the sample. This covers the important practical case of illumination through up to three layers, which is the situation most commonly encountered in biological microscopy (immersion oil, glass coverslip, aqueous sample medium). It also accounts for objectives that are corrected for a certain coverslip thickness and refractive index but operated under non-design conditions. Furthermore, illumination with linearly, circularly, or elliptically polarized light is covered by introducing a Babinet-Soleil compensator into the beam path. The model leads to a set of analytical equations that are readily evaluated. Two-dimensional intensity distributions for particular cases of interest are presented and discussed.
By assuming that the conjugation length of a long polyene chain may be broken into segments (for example, by twists about the single bonds) and that the energy to create such a conjugation break is independent of where it occurs, a conjugation length distribution is derived. For long chains this distribution is dominated by short fragments, in agreement with conclusions drawn from measured absorption spectra.
We use fluorescent nanospheres as scalar detectors for the electric-field intensity in order to probe the near-field of an optical tip used in aperture-type near-field scanning optical microscopy (NSOM).
Surprisingly, the recorded fluorescence images show two intensity lobesif the sphere diameter is smaller that the aperture diameter, as expected only in the case of vector detectors like single molecules. We present a simple but realistic, analytical model for the electric field created by light emitted by a NSOM tip which is quantitative agreement with the experimental data.A crucial step towards the development of nanoscale optoelectronic devices from building blocks like single molecules, semiconductor nanocrystals, or quantum dots is the study of their behavior under optical stimulation. On these length scales, near-field effects and diffraction phenomena play a major role both for the interaction of such subwavelength structures with incident light as well as for the communication pathways
Recently we showed that internal electric fields for linear polyenes in n-alkane crystals could be determined by high-resolution optical hole burning spectroscopy in combination with a novel quantum mechanical approach to data analysis. Here we demonstrate that the same ideas can be applied to protoporphyrin IX substituted horse myoglobin to determine the two internal electric field components in the porphyrin plane. The orientation
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.