The structure and molecular parameters of camphene determined by Fourier transform microwave spectroscopy and quantum chemical calculations

Abstract

Camphene (C10H16) is a bicyclic monoterpene of atmospheric interest. The structure of the unique stable conformer was optimized using density functional theory and ab initio calculations. The rotational spectrum of camphene was recorded in a supersonic jet expansion with a Fourier transform microwave spectrometer over the range 2–20GHz. Signals from the parent species and from the ten 13C isotopomers were observed in natural abundance. The rotational and centrifugal distortion parameters were fitted to a Watson’s Hamiltonian in the A-reduction. Complex line-shapes resulting from a magnetic interaction associated with the pairs of hydrogen nuclei in the methylene groups was observed and modeled. The rotational constants were used together with equilibrium structure to determine the r0 and the rm(1) gas-phase geometries of the carbon skeleton. The present work provides the first spectroscopic characterization of camphene in the gas phase.