Ro-vibrational spectroscopy of 2,5-norbornadiene between 400 and 850 cm-1

Rotationally-resolved infrared absorption spectra of the two lowest-energy fundamental bands for each of the three infrared active symmetry species of 2,5-norbornadiene (C-2v point group symmetry; asymmetry parameter kappa = -0.2203), nu(11) (a(1)), nu(12)(a(1)), nu(28)(b(1)), nu(29)(b(1)), nu(38)(b(2)), and nu(39)(b(2)), have been measured, assigned and fit to a semi-rigid rotor Hamiltonian to produce a set of spectroscopic constants for each band. The fit band centers are nu(11)(a(1)), c-type transitions, 728.852357(3) cm(-1); nu(12) (a(1)), c-type transitions, 417.31604(1) cm(-1); nu(28)(b(1)), a-type transitions, 656.719741(3) cm(-1); nu(29) (b(1)), a-type transitions, 500.31425(1) cm(-1); nu(38) (b(2)), b-type transitions, 800.82243(2) cm(-1); and nu(39)(b(2)), b-type transitions, 539.23110(6) cm(-1). Using ground state combination differences from the nu(11) and v(28) bands and previously published microwave data, an improved set of ground state spectroscopic constants was fit for the parent isotopologue of the molecule. (C) 2020 Published by Elsevier Inc.