Spectroscopic properties of a two-level atom interacting with a complex spherical nanoshell

Frequency shifts, radiative decay rates, the Ohmic loss contribution to the nonradiative decay rates, fluorescence yields, and photobleaching of a two-level atom radiating anywhere inside or outside a complex spherical nanoshell, i.e. a stratified sphere consisting of alternating silica and gold concentric spherical shells, are studied. The changes in the spectroscopic properties of an atom interacting with complex nanoshells are significantly enhanced, often more than two orders of magnitude, compared to the same atom interacting with a homogeneous dielectric sphere. The detected fluorescence intensity can be enhanced by 5 or more orders of magnitude. The changes strongly depend on the nanoshell parameters and the atom position. When an atom approaches a metal shell, decay rates are strongly enhanced yet fluorescence exhibits a well-known quenching. Rather contra-intuitively, the Ohmic loss contribution to the nonradiative decay rates for an atomic dipole within the silica core of larger nanoshells may be decreasing when the silica core - inner gold shell interface is approached. The quasistatic result that the radial frequency shift in a close proximity of a spherical shell interface is approximately twice as large as the tangential frequency shift appears to apply also for complex nanoshells. Significantly modified spectroscopic properties (see computer program (pending publication of this manuscript) freely available at http://www.wave-scattering.com) can be observed in a broad band comprising all (nonresonant) optical and near-infrared wavelengths.Comment: 20 pages plus 63 references and 11 figures, plain LaTex, for more information see http://www.wave-scattering.com (color of D sphere in figures 2-6 altered, minor typos corrected.

Quantification of α‐Chain Excess in Erythrocytes in β‐Thalassaemia by Microinterferometry

Summary: Microinterferometry was used to determine the dry mass of α‐chain precipitates in erythrocytes from four patients with homozygous β‐thalassaemia. α‐Chain precipitates represented on the average 40% of the total dry mass of cells with measurable amounts of precipitation. The maximum load of α‐chain inclusions in a single cell was 75% of the dry mass. A linear correlation was established between the amount of total haemoglobin and non‐α‐chains in individual cells, and the amount of α‐chain precipitation increased linearly with decreasing amounts of soluble haemoglobin, thus indicating an association between impaired haemoglobin production and lack of non‐α‐chains at undisturbed α‐chain production. The mean ratio of the quantity of α/(β+γ+δ) chain in individual patients varied between 2.3 and 3.0. These ratios are lower than expected from synthetic rate studies, thus indicating the possibility of some precipitate degradation in vivo. Copyright © 1972, Wiley Blackwell. All rights reserve