Perpendicular bands of cyclopropane in the 3.5 μm region

Abstract

The spectrum of the cyclopropane molecule was measured in the region 2898.5 to 3157.3 cm −1 with Doppler-limited resolution using a difference frequency laser spectrometer. Deconvolution was used to further enhance the effective resolution in the main part of the highly perturbed spectrum. The region below ∼3060 cm −1 contains perpendicular bands, including the ν 8 fundamental of species E′ in close anharmonic resonance with the E′ component of the state ν 7 + ν 9 + ν 14 and with other E′ states, and the ν 2 + ν 9 band which borrows its intensity from ν 8 via Fermi resonance. The ν 2 + ν 9 E′ state is also perturbed by anharmonic interactions with additional E′ states. A comprehensive analysis of this complex system of perpendicular bands based on a Hamiltonian model of the main interactions yielded much improved spectroscopic constants for the ν 8 fundamental, for the ν 2 + ν 9 combination, and for the newly observed ν 7 + ν 9 + ν 14 state, as well as information on seven tentatively identified perturbing states.