Dispersed particles, molecular photonics

In this review we have described some of the advances in the quantum electrodynamical formulation of theory for molecular photonics. We have shown how the framework described in an earlier review has now been extended to new areas of application, and reformulated for application to real dispersive media—as reflected in the new treatment of refractive, dissipative, and resonance properties. With all its conceptual splendor, conventional quantum optics has not generally been pursued at this level of detail on its dielectric host, and it is our hope that this work will help match its precepts with quantitative accuracy. Applications of the new theory have revealed new quantum optical features in two quite different aspects of the familiar process of second harmonic generation, one operating through local coherence within small particles and the other, a coherence between the quantum amplitudes for fundamental and harmonic excitation. Where the salient experiments have been performed, they exactly match the theoretical predictions. The theoretical foundation we have discussed therefore shows promise for the delivery of accurate insights into other optical processes yet to be characterized, and it should be well placed to facilitate the determination of meaningful data from the associated experiments. 

Atto-engineering for more than a whole century is in permanent and almost infinite development. Theoretical background is related to the surface physics and chemistry, quantum and wave mechanics, and quantum electrodynamics. Discrete and constrained discrete models are convenient for describing related events. Tools and equipment are nano- and atto-dispersions and beams (demons, ions, phonons, infons, photons, electrons), ultra-thin films and membranes, fullerenes and bucky tubules, Langmuir-Blodgett systems, molecular machines, nano-electronic devices, and various beam generators. Output is, generally, demonstrated as finely dispersed particles (plasma, fluosol-fog, fluosol-smoke, foam, emulsion, suspension, metal, vesicle, dispersoid). 

There are few methods suitable for on-line chemical analysis of aerosol particles. Raman spectroscopy offers the possibility of identifying the chemical species in aerosol particles because the spectrum is specific to the molecular. structure of the material, especially to the vibrational and rotational modes of the molecules. Raman spectra have been obtained for individual micron-sized particles placed on surfaces, levitated optically or by an eiectrodynamic balance, or by monodisperse aerosols suspended in a flowing gas. A few measurements have also been made for chemically mixed and poly disperse aerosols. The Raman spectrum of a spherical particle differs from that of the bulk material because of morphology-dependent resonances that re.su It when the Raman scattered photons undergo Mie scattering in the particle. Methods have been developed for calculating the modified spectra (McNulty el al., 1980). 

In more recent times, Clarke and Vincent (1981b) have extended the studies of Sieglaff on microgel particles. They used ethyl benzene and n-butyl formate, rather than toluene, as the dispersion medium. Their various samples of relatively narrow molecular weight free polystyrene spanned the molecular weight range 1-8 x 10 to 2 x 10 . The microgel particles when swollen had a diameter of between 500 and 1150 nm, as determined by photon correlation spectroscopy. 

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