Chemical Physics Letters, Vol.462, No.4-6, 178-182, 2008
Ultraviolet absorption spectra of pyridine-d(0) and -d(5) and their ring-bending potential energy function in the S-1(n,pi*) state
The ultraviolet absorption spectra of both pyridine and its pyridine-d(5) isotopomer have been recorded and assigned with a focus on the low-frequency vibrational modes in the S-1(n,pi*) electronic excited state. More than a dozen absorption bands associated with the nu(18) (formerly labeled nu(16b)) bending mode were observed. An energy map for the low-frequency modes was constructed and the data for the nu(18) mode allowed a highly anharmonic one-dimensional potential energy function to be determined for the S1 excited state. In this state pyridine is quasi-planar and very floppy with a barrier to planarity of 3 cm (1). (c) 2008 Elsevier B. V. All rights reserved.