Absorption and Reflection Spectra

The reflectivity of TmSe is high and monotonically decreasing in the far infrared from nearly 100% at 100 cm to 90% at 400 cm The earlier reported strong frequency dependence (Ward etal. [9]) is superseded, Clayman etal. [10]. The reflection spectra of Tm Se with x = 0.87, 1.0, and 1.05 are studied between about 1 meV and 12 eV. Fig. 200, p. 378, shows the spectra at room temperature compared with that of TmS. The spectra for Tm oSe down to 1 meV at 77 and 300 Kina logarithmic scale are presented in the paper. The metallic lustrous color is caused by intraband absorption below 2 eV. The edge at 2 eV is due to a plasma oscillation interfering with interband excitations. The reflectivity of Tm oSe in the 100 meV 

---

Chapter 4, presents details of the absorption and reflectivity spectra of pure crystals. The first part of this chapter coimects the optical magnimdes that can be measured by spectrophotometers with the dielectric constant. We then consider how the valence electrons of the solid units (atoms or ions) respond to the electromagnetic field of the optical radiation. This establishes a frequency dependence of the dielectric constant, so that the absorption and reflectivity spectrum (the transparency) of a solid can be predicted. The last part of this chapter focuses on the main features of the spectra associated with metals, insulators, and semiconductors. The absorption edge and excitonic structure of band gap (semiconductors or insulator) materials are also treated. 

Dichroic behaviour of the polymer crystals with intense absorption and reflection spectra peaking at ca. 2 eV for light polarized parallel to the polymer chain. 

From the similarity of the electronic absorption and reflectance spectra (Figure 3) and al 4 of the position of the CsN stretching vibrations in the IR spectra of Ti02 powders treated with Fe (CN)6, (Table 1) we can conclude that the complexes formed on the Ti02 surfaces are of the same type. 

In general, AIN crystal samples of suitable size and of high quality have not been available for measurements of IR spectra. Only a limited number of experimental results have been published [12], In very small samples, Collins et al [13] measured the IR absorption and reflectivity spectra, and obtained TO = 666.7 cm 1, LO = 916.3 cm 1, e(oo) = 4.84, and s(0) = 9.14. Carlone et al [14] obtained Ei(LO) and Ei(TO) modes near 800 and 610 cm 1, respectively. MacMillan et al [15] reported IR reflectance of AIN thin fihns in the reststrahl region, and discussed their results using Lorenz oscillators. However, these data are not conclusive. Recently, Wetzel et al reported IR reflection in AlGaN heterostructures [16],... 

The synthesis of the iridium(III) azide complex (Bu N)3[Ir(N3)6] occurs via reaction (75). The visible and near-UV absorption and reflection spectra of this complex have been recorded the assignment of bands in this and rhodium(III) azide complexes has led to the location of the Nf ligand in the spectrochemical and nephelauxetic series.283... 

In Fig. 15 the measured low energy absorption and reflectance spectra are compared with the emission spectra of BaCP. At room temperature four bands can be resolved. 

We now determine the radiation width of the exciton state assuming that in (12.29) the wavevector k = 0. For normal incidence of light just the states with k = 0 determine the features of the absorption and reflection spectra and, in the presence of radiative decay, these states give rise to fluorescent photons. 

The dielectric parameters are tensors, and consequently it is essential to use polarized radiation when recording the infrared absorption and reflection spectra of all but cubic crystals. Thus, with an orthorhombic crystal the reflection has to be measured with the electric vector parallel to the a, Z , and c axes. When obtaining the reflection spectra from the be plane of a monoclinic crystal, it is necessary to rotate the plane of polarization of the electric vector. The longitudinal optic (LO) frequency [see discussion of Equation (4)] can be found for q = 0 by noting that it is the frequency for which = 0. It can be measured directly in cubic crystals by a method due to Berriman [114]. 

The results obtained by Glurdzhidze et al. (1978) by reflection spectra in the phonon energy range 0.06-2.3 eV have permitted the observation, for the first time, of the fine structure of the absorption and reflection spectra associated with the splitting of the initial and final electron states. The authors conclude that the spin-orbit interactions splits the 4f ( Hj), 4f ( Fj) and 5d t2g states. Moreover, there is an energy gap of 0.15 eV between the valence and conduction bands. 

ABSORPTION AND REFLECTION SPECTRA OF THE SOLID SOLUTION 0.7 InSb-0.3 InAs IN RELATION TO THE STRUCTURE OF THE ENERGY BANDS ... 

We studied the infrared absorption and reflection spectra for tellurium-doped specimens of the alloy 0.7 InSb-0.3 InAs, which belongs to the range of conqmsitions corresponding to the minimum values of the energy gap. This makes its study of considerable interest. 

In similar studies, Borisov and Ryzhenko (40) observed the absorption and reflection spectra (500-1700 cm" ) to vary with the SiOj Na20 ratio. In concentrated 1.5 ratio solution of (HO)2Si02, and (HO) (SiO)40 the cyclic tetramer ion predominated, but disappeared when more alkali was added or when the solution was diluted-. No dimer or trimer was mentioned. 

Measurements of optical absorption and reflection spectra permit the study of the real (fij and imaginary ( 2) parts of the dielectric function... 

From a reading of this chapter, which methods do you find are best suited, in terms of accuracy and economy of time, for computation of the following properties of CPs bandgaps band structures band structure evolutions rotational barriers UV-Vis-NIR absorption spectra far-IR absorption and Reflectance spectra Pauli susceptibility optical transition probabilities (intensities). 

Relative transmission, absorption, and reflection spectra of a 190 nm thick film of CLEVIOS PH 1000 including 5% DMSO deposited on quartz substrate with a conductivity of approximate 1000 S/cm. (Data from A. Elschner, H.C. Starck Clevios GmbH. Unpublished results.)... 

---