The effects of morphological resonances on radiative emission rates and on dipole–dipole energy transfer rates between molecules embedded in aerosol droplets are studied by developing and applying a theory based on electromagnetic solutions for a dielectric sphere. Expressions for the Mie-resonance contributions to the transfer and emission rates are obtained in terms of the experimentally measurable spectral shape functions for the donor and acceptor molecules in the bulk host medium. Mie resonances in droplets of about 10 μm diameter are found to cause only minor changes in the integrated radiative rate, while strongly enhancing the rate and quantum efficiency of energy transfer. Estimates of the enhancement effect and calculations of its dependence on donor/acceptor location yield results consistent with experiment, supporting our interpretation that the observed energy–transfer enhancement occurs via Mie resonances of the nearly spherical droplets, and providing further insight into the Mie-enhanced energy–transfer mechanism.

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A spectrometer for measuring the fluorescence emission from a single trapped aerosol particle is described. This device consists of a particle generator, an electrodynamic levitator, an excitation source, and detection optics and electronics. Provision is made to cool the sample chamber, and spectra can be obtained in real time. Typical spectra from particles containing organic laser dyes are presented.

Electron capture from an unfilled atomic s orbital is investigated theoretically.Analyses are carried out for two simple situations, a mirror transition of a nucleus with a nucleon in an outer sl/2 state and a Gamow-Teller transition decreasing the nuclear spin by one unit. It is shown that the hyperfine interaction between electron and nuclear spins has a great infIuence on the rate of electron capture at temperatures small compared to the hyperfine splitting. The possibility of inducing electron capture with resonant electromagnetic fields is discussed.

The theory of enhanced energy transfer within an aerosol particle based on donor coupling to morphological dependent resonances is tested for the first time to our knowledge. The correspondence between theory and experiment is good and allows one to obtain the photon lifetime within the longest-lived resonances. A comparison between this lifetime and the lifetime as obtained by Mie theory is discussed.