Reflectance function copper

Complex mean reflectance functions for aluminium, nickel, and copper are presented in Fig. 11.10. These represent a series of increasingly anisotropic... 

When electrons traverse an alloy rather than a pure metal, tire scattering of electrons is different at tire ion core of each chemical species and so the conductivity reflects a mixture of the effects due to each species. In a series of copper alloys it was found that the resistance, which is the reciprocal of the conductivity, is a parabolic function of tire concentration of the major element... 

Typical pressure and temperature histories computed are shown in Figs. 6.6 and 6.7. In Figs. 6.6, the pressure is shown as a function of position within the powder compact at various times. For the baratol explosive loading shown, an initial wave, whose pressure is 1.8 GPa, is shown moving slowly from right to left. Upon reflection from the rear interface with the copper, the pressure jumps to a much higher value and then quickly reverberates to a peak pressure of about 11.4 GPa. The shorter reverberation time reflects the higher wavespeed and the major reduction in thickness in the compressed powder. 

The dielectric function of a metal can be decomposed into a free-electron term and an interband, or bound-electron term, as was done for silver in Fig. 9.12. This separation of terms is important in the mean free path limitation because only the free-electron term is modified. For metals such as gold and copper there is a large interband contribution near the Frohlich mode frequency, but for metals such as silver and aluminum the free-electron term dominates. A good discussion of the mean free path limitation has been given by Kreibig (1974), who applied his results to interpreting absorption by small silver particles. The basic idea is simple the damping constant in the Drude theory, which is the inverse of the collision time for conduction electrons, is increased because of additional collisions with the boundary of the particle. Under the assumption that the electrons are diffusely reflected at the boundary, y can be written... 

The interaction of cupric ions with alumina supports has subsequently been studied more extensively as a function of the support surface area, metal loading, and calcination temperature (93,279) by means of EXAFS and X-ray absorption-edge shifts, in conjunction with XRD, EPR, XPS, and optical reflectance spectroscopy. These techniques, each sensitive to certain structural and electronic aspects, allow a unified picture of the phases present and the cation site location. Four Cu2 + ion sites are distinguished in the catalysts. In low concentrations (typically below about 4 wt. % Cu/100 m2/g support surface area) Cu2 + ions enter the defect spinel lattice of the A1203 support. The well-dispersed surface copper aluminate has Cu2+ ions predominantly occupying tetragonally (Jahn-Teller) distorted octahedral sites, although... 

The rate constants and the associated free-energy snrfaces available to the peroxide and native intermediates deserve comment since they differ overall by nearly 10 (or ca. Vkcalmol in absolnte valne). Given the relatively electronentral nature of electron transfers between the copper sites (the E° values for the three sites differ overall by only 60 mV), the differences in rate in the first instance reflect the difference in the E° value for le versus 2e reduction of dioxygen (leading to the peroxy intermediate) and peroxide (leading to the native intermediate). Second, the differences reflect the work available from the favorable 4e reduction that drives the turnover from native intermediate to fully reduced enzyme primed, now, to react with O2. This latter process, k 100 s (compare to k = 0.34s for decay of the native intermediate to fully oxidized enzyme), is functionally equivalent to the reductive release of Fe + from Fe +-transferrin catalyzed by the membrane metalloreductase, Dcytb in both cases, the lower valent metal species is more loosely coordinating. Whereas Fe + dissociates in the latter case, in MCO turnover the bound water(s) dissociate. 

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