Optical properties atomic absorption

Abstract Silver clusters, composed of only a few silver atoms, have remarkable optical properties based on electronic transitions between quantized energy levels. They have large absorption coefficients and fluorescence quantum yields, in common with conventional fluorescent markers. But importantly, silver clusters have an attractive set of features, including subnanometer size, nontoxicity and photostability, which makes them competitive as fluorescent markers compared with organic dye molecules and semiconductor quantum dots. In this chapter, we review the synthesis and properties of fluorescent silver clusters, and their application as bio-labels and molecular sensors. Silver clusters may have a bright future as luminescent probes for labeling and sensing applications. 

The luminescence of diamonds is related to various defects in its structure. Almost always, luminescence centers in diamonds are related to N atoms. It is logical, because the atomic radii of C and N are nearly equal (approximately 0.77 A). Luminescence spectroscopy has proven to be the most widely used method in studies of diamonds even in comparison with optical absorption, ESR, IR and Raman spectroscopies. Himdreds of spectra have been obtained, fluorescence characteristics enter into diamond quality gemological certificates, a wide range of electronic and laser applications are based on diamond optical properties in excited states nitrogen center aggregation is controlled by the residence time of diamond in the mantle, distinction between natural... 

Temperature changes do not appreciably affect ultraviolet optical properties of both metals and insulators, although at low temperatures absorption bands associated with excitons and electron band transitions are usually sharper, and frequencies of peak absorption may shift slightly. In the soft x-ray region, transitions of core electrons buried in the interior of atoms hardly notice temperature changes. 

It is interesting to note the near-absence of absorption in the translational band of pure para-hydrogen. At the temperature of the measurement (20.8 K), all para-H2 molecules are in the rotational ground state (J = 0) which is optically isotropic. The optical properties of these molecules are thus much like those of He atoms. No translational ab-... 

In other respects, a bis(ferrocenyl)polymethine cation, in which two ferrocene end groups are connected by a polymethine spacer with up to 13 CH units, has been described by Tolbert et al. [14b]. The molecular-wire behavior is claimed, from the optical properties, in particular the absorption energy varying as the reciprocal of the chain length. In addition, separate oxidation potentials were observed for up to 13 carbon atoms between the metal centers. 

If the atomic frequency v has any real physical significance it should be possible to calculate it from various other physical properties. Thus Nemst supposed that the frequency of a body composed of electrically charged ions could be calculated from its optical properties. In agreement vdth this hypothesis he found that the frequencies of the ultra-red absorption bands of potassium and sodium chloride determined by Rubens were approximately equal to the values of v calculated from the specific heat. It is probable, however, that this agreement is purely accidental. 

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