Vibrational Spectroscopic Database of Formic Acid and its Isotopologs. I. Monomer, 1937–2025

The vibrational spectroscopy of isolated formic acid molecules, including both conformers and various isotopologs (H1, H2, C12, C13, O16), is compiled from the literature and critically reviewed. This work extends the previous database [Nejad and Sibert III, J. Chem. Phys. 154, 064301 (2021)] beyond 4000 cm−1 to include all available experimental band centers up to the near-infrared and visible regions. Assignments in the overtone region are reexamined using fc-CCSD(T) VPT2, resulting in five reassignments for HCOOH, three for its deuterated isotopologs, and one for H13COOH. The implications of the present work for the HITRAN database are discussed and directions for future work outlined.