Optical absorption coefficient

Depth resolution depends on the (spectrally dependent) optical absorption coefficient of the material. Near-surface analysis (first 50 nm) frequendy can be per-... 

The significantly faster PuF6(g) fluorescence decay rate found using 532 nm excitation is unlikely to be due to a thermally induced effect (e.g. pyrolysis). The optical absorption coefficients of PuF6(g) at 532 nm is at most twice as large as at 1064 nm (15) Assuming the 1064 nm absorption... 

Ferroelectric materials are capable of being polarized in the presence of an electric field. They may exhibit considerable anomalies in one or more of their physical properties, including piezoelectric and pyroelectric coefficients, dielectric constant, and optoelectronic constant. In the latter case, the transmission of light through the material is affected by the electric field, which produces changes in refractive index and optical absorption coefficient. Varying the applied field changes the phase modulation. 

In amorphous semiconductors, information about the width of the band tail states (or disorder) may also be extracted from the optical absorption spectra. For photon energies near bandgap energy, the optical absorption coefficient of amorphous semiconductors exhibit an exponential dependence on the photon energy, following the so-called Urbach relationship ... 

Thin-film solar cell devices based on CIGS have already demonstrated an efficiency of 19.52%.40 The direct energy gap of CIGS results in a large optical absorption coefficient, which, in turn, permits the use of thin (-1 pm) layers of active material. CIGS solar cells are also known for their long-term stability.76... 

Melting Temperature. The double helix of polynucleotides described above becomes thermodynamically unstable at particular temperatures (with specified conditions of solute concentration, pH, etc.) and is transformed into the open random-coil arrangement. This transformation is rather sharp, and can be measured by the concurrent changes in a number of physical properties of the nucleic acid, such as the optical absorption coefficient. The midpoint of the transition region is called the melting point. 

A major advantage of DOAS is its high sensitivity for species that meet the requirement of having narrow absorption bands in the UV-visible. Furthermore, because the differential optical absorption coefficients are fundamental spectroscopic properties of the molecule, the measurements need not be calibrated in the field. 

Lindberg, J. D., 1975. The composition and optical absorption coefficient of atmospheric particulate matter, Opt. Quant. Electron., 7, 131-139. 

Figure 7.14 Imaginary part of the dielectric constant 62 as a function of photon energy, hv, for amorphous and crystalline silicon. (After Pierce Spicer, 1972.) Since Sj is proportional to the optical absorption coefficient a, Sj is a dimensionless measure of optical absorption.

However, the existence of such an effect can be demonstrated by the application of a recently proposed technique for the study of interband transitions having energies greater than the "optical" band gap (11). Standard procedures exist for the extraction of band-gap information from measurement of the optical absorption coefficient, which has been shown to be proportional to the quantum efficiency (photocurrent density divided by the incident... 

The dielectric constant e can be estimated to be of the order of 100, and the donor concentration N can be estimated from the measured conductivity, activation energy.and Hall mobility to be of the order of 10 cm. Then W = 10 cm and L is even smaller, so that expansion of the exponential yielSs a quantum efficiency porportional to the optical absorption coefficient even for large values of a. 

The optical absorption coefficient for a single injerband transition is related to the photon energy by a v (hv) (hv - Eg) where Eg is the band gap and n depends upon the character of the transition (n = 0.5 for allowed direct transitions n = 2 for allowed indirect ones). Thus, if experimental values for a are multiplied by hv and are plotted as (ahv) against hv, then a... 

Depends on optical absorption coefficients—all radiation may be absorbed by solute. Absorption of quantum is always complete. 

D0 the optical absorption length is the distance the infrared radiation can travel through the sample (cm), equal to 1/p where P is the optical absorption coefficient... 

Optically transparent D0 > D, the optical absorption coefficient is small... 

The typical polymer or rubber sample would be classified as optically transparent or opaque and thermally thick except possibly for the strongest bands. In this case the signal intensity would be proportional to the product of the optical absorption coefficient (P) and the thermal diffusion length and show a - 3/2 dependence on the modulation frequency (to). The angular modulation frequency is a product of the interferometer mirror velocity and the wavenumber ... 

Gordon et al. [59] proposed a figure of merit defined by the ratio of the electrical conductivity over the optical absorption coefficient in the visible spectral range. They tested many dopants for AP-CVD ZnO films, and obtained the highest figure of merit for fluorine-doped ZnO, which they used as TCO for amorphous silicon solar cells. 

Fig. 1. The optical absorption coefficient as a function of photon energy for undoped a-Si H (solid curve), p-type a-Si H (dashed curve), and p-type a-Si C H (dashed-dotted curve). Both p-type films contains a few atomic percent of boron, and the a-Si C H film also contains —20 at. % of carbon.

Evidently, the differential signal will have a line shape corresponding to the third derivative of the optical absorption coefficient. This third derivative spectroscopy has had a considerable impact on the development of electrore-... 

---