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This chapter lists many of the common physical properties that can be easily calculated using the OLCAO method discussed in Chapter 3. The most fundamental quantities are the band structures, density of states, interatomic bonding, effective charges, and optical excitations. Simple examples obtained by using the OLCAO method are presented here while modern practical applications of such calculations of more complex systems are described in later chapters. The details of how OLCAO is used for core-level spectroscopy are discussed separately in Chapter 11.

Efforts to verify or invalidate hypotheses on the structure of liquid water have been hampered by the lack of a general theory of the liquid state. In the absence of such a theory, conclusions about the structure of water have been based on two approaches. The first involves formulating a model for liquid water, treating the model in a particular fashion — involving massive approximations — using methods of statistical mechanics, and comparing the calculated values of macroscopic properties with those that are observed. This chapter focuses on the second approach, which is to deduce aspects of the structure of the liquid from the macroscopic properties of water.

The stability of metal clusters exhibits shell effects similar to that of nuclei. This chapter reviews how this feature is treated in the jellium model. The main focus is on optical properties described by the dielectric function, which is analyzed in greater detail, first for the Drude-Lorentz model then for a fully quantal treatment. With increasing volume of the clusters, only bulk properties typical for a metal are important. For smaller systems, quantum size effects come into play. This effect is studied, reporting on microscopic calculations within the jellium model. Of special interest is the damping width, for which finite values are obtained even at small frequencies if the quantal electronic states are treated as being quasi-continuous. This mechanism is often associated with Landau damping known to conserve entropy. The problem related to this fact is examined, together with the analogous one of wall friction in finite nuclei.

This chapter addresses defects with an extra degree of complexity, ones that raise important issues both in optical properties and in magnetic properties for simple oxides that are not usually magnetic (involving the V⁰ centre).

Two important problems facing the ocean optics research community in the coming decade concern optical model closure and inversion (see Chapter 3). We obtain model closure if we can describe the measured light environment by combining elementary measurements of the optical properties of the medium with radiative transfer theory. If we can accurately deduce the concentration of various constituents from a combination of measures of the submarine light field and inverse model calculations, we term this process model inversion. The most elementary measurements of the optical properties of the sea are those that are independent of the geometry of the light field, the inherent optical properties (Preisendorfer, 1961). Optical properties that are dependent on the geometry of the light field are termed apparent optical properties (AOP). Models of the submarine light field typically relate apparent optical properties to inherent optical properties (see Chapter 2). Examples include the relationship between the AOP irradiance reflectance R and a combination of inherent optical properties (backscattering coefficient bb and absorption coefficient a), and the relationship between the AOP downwelling diffuse attenuation coefficient kd and a combination of the absorption coefficient, backscattering coefficient, and downwelling average cosine μd (e.g., Gordon et al., 1975; Morel and Prieur, 1977; Smith and Baker, 1981; Morel, 1988; Kirk, 1984a). Under some circumstances these relationships work well enough that the absorption coefficient can be derived indirectly. This is important since measurement of the absorption coefficient by direct means has been difficult. Derived values for the absorption coefficient by model inversion methods are not easily verified by independent measurements, however, because of the difficulty of measuring the absorption coefficient. Model closure and model inversion both become more tenuous when the following phenomena are present: 1. Transpectral or inelastic scattering such as fluorescence (e.g., Gordon, 1979; Carder and Steward, 1985; Mitchell and Kiefer, 1988a; Spitzer and Dirks, 1985; Hawes and Carder, 1990) or water Raman scattering (Marshall and Smith, 1990; Stavn, 1990; Stavn and Weidemann, 1988a,b; Peacock et al, 1990; Chapter 12 this volume). 2. Particles that are large relative to the measurement volume for inherent optical property meters such as beam transmissometers, light-scattering photometers, fluorometers, and absorption meters.

It is shown how electronic transitions can be induced by the interaction with an electromagnetic wave of a suitable frequency. The rate of a transition between two electronic states induced by a time-dependent field is derived. The transition rate expression is used to calculate the absorption coefficient due to electronic transitions. The differential absorption coefficient for left and right circular polarized light is specific to chiral molecules and has different signs for a pair of enantiomers. The discussion then shifts to general functions describing the response of an atom or molecule to an external. The ideas developed thus far are then applied to the dynamic polarizability, molecular linear response functions in general, and the optical rotation. Linear response theory is set up within time-dependent molecular orbital theory. The Chapter concludes with a discussion of non-linear response properties and two-photon absorption.

Optical properties of photocathodes and their characterization in terms of absorptance, transparency, and reflectance in mixed dielectric media are presented. Photometric units and international standards are based on a specified white light source. The electromagnetic spectrum covers about a decade in wavelength and there is a relationship between photon energy and wavelength. Spectral responsivity can be specified in milliamps per watt or as quantum efficiency, η‎(λ‎), in terms of photoelectrons per incident photon. Empirical specifications, based on filtered light from a standard white light source give a measure of the photocathode response to blue, red, and infrared light. Bialkali photocathodes laid on a conducting substrate can operate at ultra-low temperatures approaching absolute zero, while others can survive operation at 200 °C. End window and side window photomultipliers are available in a range of diameters and photocathode types.

Thin-sections of rocks allow petrology to be characterized at a microscopic scale and enable mineral identification to be made with greater confidence than in hand-specimens. This chapter examines the methods used to produce drawings of rocks and minerals in thin-section for the analysis and interpretation of petrology. Crystal or component shapes should be drawn first and it is useful to work outwards from a single object. Four worked examples of thin-section drawings are described to illustrate different tactics used in creating these diagrams. Practical advice on identifying minerals in thin-section and the optical properties of minerals is also given. Crystal orientation diagrams, useful in recording the optical properties of individual minerals, are also discussed.

The Casimir force is an effect of quantum vacuum field fluctuations, with applications in many domains of physics. The ideal expression obtained by Casimir, valid for perfect plane mirrors at zero temperature, has to be modified to take into account the effects of the optical properties of mirrors, thermal fluctuations, and geometry. After a general introduction to the Casimir force and a description of the current state of the art for Casimir force measurements and their comparison with theory, this chapter presents pedagogical treatments of the main features of the theory of Casimir forces for one-dimensional model systems and for mirrors in three-dimensional space.

An experimental survey of the optical properties of linear polyenes and trans-polyacetylene is given, before the concepts of previous chapters are used to develop a theoretical interpretation of them. The key excited states, i.e. the 1Bu singlet and triplet, and the 2Ag singlet are discussed. DMRG calculations of the Pariser-Parr-Pople-Peierls model are used to interpret the data.

An experimental survey of the optical properties of the phenyl-based light emitting polymers (poly (para-phenylene) and poly (para-phenylene vinylene)) is given. These are then explained by developing a theoretical model of their excited states via a discussion of the excited states of benzene, biphenyl, stilbene and oligophenylenes. Results of DMRG and CI-S calculations of the Pariser-Parr-Pople model are shown to reliably explain the experimental data. Vibrational relaxation of the photo-excited states and the formation of exciton-polarons are described.