Spectroscopic scale protection factor (SSPF) of solar ultraviolet radiation molecular screens. I. Salicylidene compounds

We have found a new absolute scale of solar ultraviolet radiation protectio n factor for molecular screens, called spectroscopic scale protection facto r (SSPF). This scale, based on the solar-action spectra of these molecular screens, is obtained under a 20 degrees zenith angle of the sun actinic flu x spectra at the earth's surface. In order to compare this scale versus the usual sun protection factor (SPF) scale which uses homosalate (SPF = 4.2) as a standard compound, we have de termined the electronic absorption spectral properties of a salicylidene co mpound series. Since these aromatic compounds present a good photostability behavior, a broad absorption band and a high molar absorption coefficient in the W-A and W-B regions, we have established their potential use as a so lar ultraviolet radiation molecular screen according to the SSPF data. (C) 1998 Elsevier Science S.A. All rights reserved.