THE FIRST SINGLET STATE OF PYRIDINE
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Date
1968
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Ohio State University
Abstract
High resolution spectra of the $2875 {\AA} (\pi^{\ast} \leftarrow n)$ singlet system of pyridine and perdeuteropyridine have been obtained in polycrystalline benzene and cyclohexane matrices at $4.2^{\circ}K$. These studies were undertaken with the hope of resolving several puzzling features of the pyridine vapor $specrum,^{1}$ most notably the appearance of a medium-strong band lying $139 cm^{-1}$ to the blue of the $\pi^{\ast}\leftarrow n$ origin. At low temperatures, this band is either absent or has shifted to higher energies: a band having comparable intensity appears at $352 cm^{-1}$ above the origin in benzene and at $331 cm^{-1}$ in cyclohexane. In addition, a weak band, having roughly $1/20$ the intensity of the origin band and scen only in the benzene host, appears at $186 cm^{-1}$ to the red of the $\pi^{\ast} \leftarrow n$ origin. Although the possibility of site effects or dimer lines cannot be completely ruled out as exmplanations for this weak band, it might also be interpreted as the origin of an electronically forbidden transition whose appearance results from crystal field perturbations. The results for perdeuteropyridine are analagous and will be presented.
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$^{1}$ H. Sponer and H. Stucklen, J. Chem. Phys. 14, 101 (1946).
Author Institution: Frick Chemical Laboratory, Princeton University
Author Institution: Frick Chemical Laboratory, Princeton University