EXHIBIT C Why Metals Are Shiny

The characteristic shine of metals is related to their ability to conduct electricity. In a simplified explanation, the bonding in a metal such as copper differs from that in covalent compounds such as H2 in that the valence shell electrons are shared by all of the metal atoms in a contiguous piece of the pure metal. The electrons are completely delocalized and move easily within the valence-bond bands that are available. When a photon of the appropriate wavelength is absorbed, an electron is easily promoted. The extinction coefficient for the transition is strong, and as a result, photons do not travel far into the metal. The absorption of a photon—a packet of electromagnetic energy—causes an electrical current to flow in the metal and emits a photon at the same wavelength. The collection of photons emitted is perceived by an observer as shine or luster. 

Source Nassau, K., Ch. 5 Color Caused by Transition Metals in a Ligand Field, in K. Nassau, The Physics and Chemistry of Color, 2nd Ed. New York John Wiley and Sons, 2001. 

Another group of mk delivery devices consists of those which operate via capillary action. Fiber-tipped pens, also called felt tips deliver inks with solvent bases that are aqueous, glycol based, or xylene based. Tlie inks are generally less viscous than ballpoint inks. Recently introduced gel pens are increasing in popularity and, as the name implies, deliver colorants via a gel rather than a comparatively thin solution. Colorants are primarily pigments, and once dry, the inks are virtually insoluble. As a result, forensic analyses are more complex, but still feasible, as is discussed later in the chapter. 

Two inks are to be compared, one extracted from a ransom note and one obtained from a pen recovered from a suspect. Both inks are a light-blue color. A reflectance spectrum of one reveals a single broad peak for one ink, while the spectrum of the other shows two peaks. Are the inks differentiated  

Answer Yes. The spectra indicate that, although they appear similar, the colors ue produced by two different compositions. The first is likely a single colorant, the second a mixture. The inks are not from a common source. 

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