Density effects, optical

Depending on the details of the structure, particularly on the confinement factor, the pump power density needed to achieve an effective optical gain of, say, 50 cm 1 is of the order of a few hundred kilowatts per square centimetre at room temperature [14-16],... 

Lately, quantum-classical molecular-dynamics simulations of an excess electron in water performed for wide ranges of temperature and pressure suggest that the observed red shift of the optical absorption spectrum is a density effect rather than a temperature effect. Indeed, by increasing the temperature, the mean volume of the cavity occupied by the solvated electron increases due to weakening of bonds between solvent molecules the electron is less confined in the cavity, and the potential well becomes less deep. 

Density effects. He I lines in the optical spectrum, particularly the triplets, are subject to collisional excitation because the 2 3S level is metastable. The contribution of collisional excitation depends on both electron density and electron temperature. It is debated whether electron densities typically derived from [S II] line ratios are appropriate for He I. Detailed studies of density structure in a few good H II regions would provide useful information on this. 

Polymer Film Photod radation Optical Density Effects... 

Optical density effects on photodegr ation in films have been considered in studies on cellulose ( ), poly(methyl isoprop-enyl ketone)(7), poly(ethylene terephthalate)( ), and poly(methyl methacrylate)T, ). More recently an attenqit was made to analyze the photosensitized gelation of poly(vinyl butyral) with correction for optical density effects (10). 

According to the EMT, the effective optical constants of an islandlike film depend on the packing density of the particles, the optical constants of the surroundings, and the polarizability of the mutually interacting metal islands... 

Figure 5.9. Effect of the silylation period on density and optical transmission (%) of the aerogel.

The closing of the effective optical gap and other changes in the optical absorption spectrum described in Sec. 4.2.1 correspond to nonlinear enhancement of the real part of the dielectric constant due to interatomic interactions. As they develop in the dilute vapor, these interactions represent the first stage of a process that eventually leads to a metallic state. Now the dielectric constant determines the total polarization P which, in turn, can be expanded at low densities in powers of the density p (Buckingham and Pople, 1955)... 

Electron densities n (in 10 cm ) of 1.53,2.05, and 2.3 have been derived from spectroscopic studies on Tm Se with x = 0.87, 1.0, and 1.05 at room temperature. These were compared with 1.5,2.05, and 2.3, calculated assuming one electron per Tm. The effective optical mass for all these samples is m = 1.65 mo- The effective number of electrons per formula unit for TmSe at 2.5 eV is neff = 0.86. A figure in the paper for the range -0 to-6.5 eV shows an increase from -0 at -0 eV to neff 2.5 at 6.5 eV, Batlogg [18], see also [19]. Electron mean free paths of 8.0 and 6.2 A are derived for nearly stoichiometric TmSe from the photoelectron spectrum induced by synchrotron radiation (UPS), Kaindl etal. [20, 21]. 

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