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Publication
The Journal of Chemical Physics
Paper
Reflection spectra of the first singlet transition of crystalline phenanthrene
Abstract
Reflection spectra in the range of the first singlet transition are reported for the (001) face of a phenanthrene crystal at 1.5 K and at several higher temperatures. The spectra were taken at near normal incidence with light polarized parallel and perpendicular to the monoclinic b axis. The (001) face was obtained by cleaving a crystal grown from the melt. For the a-polarized transition the reflectivity of the 0-0 component is 30% and the stopband is approximately 5 cm-1 wide. The 0-0b transition has a much lower reflectivity, close to 16%, and a stopband almost 40 cm-1 wide. The dielectric function was calculated for the 0-0 region by fitting the spectrum to that of a series of Lorentzian oscillators and also by using the Kramers-Kronig transformation. The factor group splitting in reflection is measured to be 41 cm-1, while the same splitting from the derived absorption spectra is 46 cm-1. This difference is due to a red shift of the a-polarized absorption peak and a blue shift of the b-polarized absorption peak from the corresponding peaks in the reflection spectrum. The absorption linewidths are narrower than previously reported. The temperature dependence of the linewidths is discussed. © 1978 American Institute of Physics.