Abstract
The rotational spectra for three conformers of 3,3-difluoropentane have been measured using both a newly constructed narrow bandwidth chirped-pulse Fourier-transform microwave spectrometer and a Balle-Flygare resonant cavity Fourier-transform microwave spectrometer. The chirped-pulse instrument produces a microwave pulse spanning up to 480 MHz bandwidth in the 7-18 GHz region by mixing a 1 mu s chirped pulse (of up to 240 MHz bandwidth) from an arbitrary function generator with the output from a microwave synthesizer.
Rotational spectra for the normal isotopic species and all possible C-13 single substitutions were observed for the gauche-gauche and anti-gauche conformers, allowing a Kraitchman substitution structure and an inertial fit structure to be determined. C-13 isotopic species and dipole moment components were not measurable for the less intense anti-anti species as a result of partially resolved fine splitting. Details of the new chirped-pulse instrument will be described and the structural results will be presented and compared with ab initio data for 3,3-difluoropentane. (C) 2010 Elsevier Inc. All rights reserved.