Modeling fluorescence collection from single molecules in microspheres: effects of position, orientation, and frequency

Abstract

We present calculations of fluorescence from single molecules (modeled as damped oscillating dipoles) inside a dielectric sphere. For an excited molecule at an arbitrary position within the sphere we calculate the fluorescence intensity collected by an objective in some well-defined detection geometry. We find that, for the cases we model, integration over the emission linewidth of the molecule is essential for obtaining representative results. Effects such as dipole position and orientation, numerical aperture of the collection objective, sphere size, emission wavelength, and linewidth are examined. These results are applicable to single-molecule detection techniques employing microdroplets.

Chemical Characterization of Flowing Polydisperse Aerosols by Raman Spectroscopy

“…For application to polydisperse aerosols, the intensity of the Raman signal should be proportional to the species mass concentration, as is the case for bulk materials. Complicating factors include the distribution of the targeted component with respect to particle size and its distribution pattern within individual particles (Druger and McNulty 1983;Hill et al 1996).…”

Enhanced Backward-Directed Multiphoton-Excited Fluorescence from Dielectric Microcavities

“…However, when these molecules are homogeneously imbedded in a dielectric microcavity (such as a sphere, spheroid, or cylinder), the emission can become anisotropic. The microcavity can concentrate the internal field intensity I͑r͒ of the incident radiation [1][2][3], and can introduce an angular-dependent reemission efficiency [4]. Because of the reciprocity principle [5,6], fluorescence from regions of high I͑r͒ tends to return toward the illuminating source.…”

Semiclassical scattering of an electric dipole source inside a spherical particle

“…(14). As ␣ increases toward ␣ TIR Ϫ for q Ͼ q c , the deflection angle ⌰ increases toward ⌰ TIR Ϫ , approaching it with infinite slope.…”

“…[7][8][9] The exact solution to the related electromagnetic boundary-value problem of scattering by an arbitrarily positioned, arbitrarily oriented electric dipole source inside a spherical particle has also been derived. [10][11][12][13][14][15][16] This situation describes, for example, a liquid droplet containing molecules that fluoresce. Although scattering in the short-wavelength limit by a sphere containing an interior source has been computed by using both wave theory 17 and ray theory, [18][19][20][21][22] a detailed physical interpretation of the angular dependence of the scattered intensity has not been given.…”