The ν6 parallel band of cyclopropane at 3100 cm−1

Abstract The ν 6 fundamental of cyclopropane has been recorded on a 4.5-m vacuum spectrometer. Deconvolution of the spectrum has revealed considerably more detail than found in previous investigations. New information of a qualitative nature has been learned about the highly perturbed upper state and improved values of the band center and the upper-state rotational constant have been obtained. A lower-state combination-difference analysis using J values up to J = 23 has resulted in values of B ″ and D ″ J which are in excellent agreement with recent investigations. The following values of molecular constants, in wavenumber units (cm −1 ), have been determined: B ″ = 0.67023, D ″ J = 0.93 × 10 −6 , ν 0 = 3101.529, and B ′ − B ″ = −0.0019. The present data have been used with data from recent Raman and infrared spectra of C 3 H 6 in a combined least-squares fit to the ground-state constants.