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

[Display omitted] •Infrared spectra of 2,5-norbornadiene were recorded using a hi-res FTIR.•First rotationally-resolved infrared spectra of six fundamental bands of 2,5-norbornadiene.•Ro-vibrational transitions were assigned and then fit using a semi-rigid rotor Hamiltonian.•This work provides improved ground state spectroscopic constants for the molecule.•Vibrational assignments for 2,5-norbornadiene have been confirmed. 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 (C2v point group symmetry; asymmetry parameter κ = −0.2203), ν11 (a1), ν12(a1), ν28(b1), ν29(b1), ν38(b2), and ν39(b2), 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 ν11 (a1), c-type transitions, 728.852357(3) cm−1; ν12 (a1), c-type transitions, 417.31604(1) cm−1; ν28 (b1), a-type transitions, 656.719741(3) cm−1; ν29 (b1), a-type transitions, 500.31425(1) cm−1; ν38 (b2), b-type transitions, 800.82243(2) cm−1; and ν39 (b2), b-type transitions, 539.23110(6) cm−1. Using ground state combination differences from the ν11 and ν28 bands and previously published microwave data, an improved set of ground state spectroscopic constants was fit for the parent isotopologue of the molecule.