Solid surface parameters

In the thermal infrared the spectral intensity, / , measured by a radiometric instrument facing the opaque surface of an astronomical object can be written 

The simplest interpretation of the radiance measured by a single-channel radiometer is through the brightness temperature, which is the temperature of a black-body that emits the same intensity, Iv, at the wavenumber v as does the object of interest. To find the kinetic temperature of the surface from the brightness temperature one must know the emissivity of the material. Rarely are the composition and texture of the surface known well enough to permit computations of s. In reality 

We consider now measurements with a nonpolarizing radiometer, that is, with an instrument that averages over both planes of polarization. All infrared radiometers flown on planetary spacecraft to date are of this type. If we also exclude measurements at large emission angles, say larger than 45°, then the thermal emissivity of a smooth, polished surface can be approximated from Eqs. (1.6.15) and (1.6.16) as 

Several precautions can be taken to assure a good estimate of the tme surface temperature. As indicated in Eq. (8.5.1), the emissivity normally depends on the wavenumber. With a spectrometer or multichaimel radiometer one may search for a dispersion region of the surface material where the refractive index varies strongly with wavenumber (see Subsection 3.7.b). Near the index minimum the emissivity has a maximum. In addition to the composition the emissivity strongly depends on particle size and surface texture. A spectral search for an emissivity maximum is an improvement over the use of an arbitrarily chosen spectral interval. The maximum in the Martian brightness temperature near 1280 cm , shown in the upper spectrum of Fig. 6.2.8, may be an example of such a case. 

At wavenvunbers where the refractive index of the material equals that of the substance it is imbedded in (CO2 gas in the Martian case), the suspended atmospheric dust is least scattering, but still absorbing. The frequency where the index of the particles equals that of the environment is called the Christiansen frequency. If atmospheric gas and dust absorption are not excessive, the spectral region sim-rounding this frequency may provide a suitable window for a measurement of the surface temperature. 

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Solid surface parameters MERCURY LOCAL TIME (hourt)... 

The Good-Girifalco theory [77-82] was originally formulated to make an attempt to correlate the solid-liquid interfacial tension to the solid surface energy and the liquid surface tension through an interaction parameter, basic formulation of the theory is ... 

These studies have indicated that the independent parameters controlling the postulated solid-phase reactions significantly affect the resulting acoustic admittance of the combustion zone, even though these reactions were assumed to be independent of the pressure in the combustion zone. In this combustion model, the pressure oscillations cause the flame zone to move with respect to the solid surface. This effect, in turn, causes oscillations in the rate of heat transfer from the gaseous-combustion zone back to the solid surface, and hence produces oscillations in the temperature of the solid surface. The solid-phase reactions respond to these temperature oscillations, producing significant contributions to the acoustical response of the combustion zone. 

Another contributing mechanism is the direct cooling of hot propellant surface by contact with the injected fluid. The fluid should cause the decomposing surface to reduce its pyrolysis rate to a point where combustion cannot be sustained. In addition, the presence of water on the surface would obstruct heat transfer from the gas-phase reaction zones to the solid surface, thus augmenting the cooling of the surface. Proponents of these two approaches have correlated the injection data on the basis of mass of fluid required per unit area of surface, but theoretical justifications for the use of this particular correlating parameter have not been presented. 

Bockris and Parry-Jones were the first to carry out experiments with a pendulum to measure the friction between a wetted substrate and the pivot upon which the pendulum swung. It should be noted that Rebinder and Wenstrom199 used such a device for an objective similar to that of Bockris and Parry-Jones, but they claimed that the characteristics of the pendulum oscillations reflected the hardness of the solid surface. The plastic breakdown determining this would be a function of v and this is a potential-dependent value.100, 01 More extensive determinations were made later by Bockris and Argade200 the theoretical treatment was given by Bockris and Sen.201 In the absence of adjustable parameters in the theory, a good agreement between theory and experimental data was assumed.201 The studies by Bockris and Parry-Jones indicated that the... 

The combination of photocurrent measurements with photoinduced microwave conductivity measurements yields, as we have seen [Eqs. (11), (12), and (13)], the interfacial rate constants for minority carrier reactions (kn sr) as well as the surface concentration of photoinduced minority carriers (Aps) (and a series of solid-state parameters of the electrode material). Since light intensity modulation spectroscopy measurements give information on kinetic constants of electrode processes, a combination of this technique with light intensity-modulated microwave measurements should lead to information on kinetic mechanisms, especially very fast ones, which would not be accessible with conventional electrochemical techniques owing to RC restraints. Also, more specific kinetic information may become accessible for example, a distinction between different recombination processes. Potential-modulation MC techniques may, in parallel with potential-modulation electrochemical impedance measurements, provide more detailed information relevant for the interpretation and measurement of interfacial capacitance (see later discus-... 

As discussed already in Chapter 2 the work function, , of a solid surface is one of the most important parameters dictating its chemisorptive and catalytic properties. The work function, (eV/atom) of a surface is the minimum energy which an electron must have to escape from the surface when the surface is electrically neutral. More precisely is defined as the energy to bring an electron from the Fermi level, EF, of the solid at a distance of a few pm outside of the surface under consideration so that image charge interactions are negligible. 

The work function, O, of a solid surface (in eV) is the minimum energy required to extract an electron from that (neutral) surface.9 10,16 23 The parameter O/e (in V) is usually called the extraction potential. 

Doyen [158] was one who theoretically examined the reflection of metastable atoms from a solid surface within the framework of a quantum- mechanical model based on the general properties of the solid body symmetry. From the author s viewpoint the probability of metastable atom reflection should be negligibly small, regardless of the chemical nature of the surface involved. However, presence of defects and inhomogeneities of a surface formed by adsorbed layers should lead to an abrupt increase in the reflection coefficient, so that its value can approach the relevant gaseous phase parameter on a very inhomogeneous surface. 

Pattison, P. and Williams, B. (1976) Fermi surface parameters from fourier analysis of Compton profiles, Solid State Commun., 20, 585-588. 

By means of Equations 5 and 6, the adsorption process can be described in terms of the parameters and Ks. Since the effective area of solid surface available to polymer adsorption is not generally known in practice, Ng is a third parameter which must be fitted from experiment and Equations 5 and 6 define a three-parameter model for the process. 

In an effort to understand the mechanisms involved in formation of complex orientational structures of adsorbed molecules and to describe orientational, vibrational, and electronic excitations in systems of this kind, a new approach to solid surface theory has been developed which treats the properties of two-dimensional dipole systems.61,109,121 In adsorbed layers, dipole forces are the main contributors to lateral interactions both of dynamic dipole moments of vibrational or electronic molecular excitations and of static dipole moments (for polar molecules). In the previous chapter, we demonstrated that all the information on lateral interactions within a system is carried by the Fourier components of the dipole-dipole interaction tensors. In this chapter, we consider basic spectral parameters for two-dimensional lattice systems in which the unit cells contain several inequivalent molecules. As seen from Sec. 2.1, such structures are intrinsic in many systems of adsorbed molecules. For the Fourier components in question, the lattice-sublattice relations will be derived which enable, in particular, various parameters of orientational structures on a complex lattice to be expressed in terms of known characteristics of its Bravais sublattices. In the framework of such a treatment, the ground state of the system concerned as well as the infrared-active spectral frequencies of valence dipole vibrations will be elucidated. 

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