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Exclusive Book Preview: The Encyclopedia of Ultraviolet Filters
Posted: February 12, 2007
page 2 of 5The energy absorbed from the UV radiation corresponds to the energy required to cause a “photochemical excitation” in the ultraviolet filter. The molecule is excited to a higher energy state from its ground state by absorbing this radiation.
As the excited molecule returns to the ground state, energy is emitted that is lower in magnitude than the energy initially absorbed to cause the excitation. Thus, the energy is emitted in the form of longer wavelengths since the energy is lower than the shorter wavelengths originally absorbed. If the loss in the energy is quite large, that is, the wavelength of the emitted radiation is of sufficient length that is in the infrared region, it may be perceived as a mild heat radiation on the skin. This minuscule heat effect is undetected because the skin receives a much larger heat effect from the direct exposure to the sun’s heat. If the emitted energy lies in the visible region, then it may be perceived as either a fluorescent or a phosphorescent effect. In the extreme case, the emitted radiation is sufficiently energetic (lower wavelength) that it may cause a fraction of the sunscreen molecule to react photochemically. Cis-Trans, Keto-Enol photochemical isomerization has been observed in some organic molecules.
Data on Ultraviolet Filters in Commerce Worldwide
Two compilations for all ultraviolet filters in commerce worldwide are included in this book. The first is comprised of Tables 17 – 19. Table 17 lists the regulatory data for the ultraviolet filters used worldwide. Table 18 contains the chemical and optical properties. Table 19 lists the manufacturers and distributors of ultraviolet filters worldwide. The second compilation is the “Compendium of Global Ultraviolet Filters,” which basically is a two-page summary of the data accumulated on each of the 55 ultraviolet filters used worldwide.
They are both designed for quick reference as follows:
1. The ultraviolet filters are alphabetically listed by their (INCI) name.