Vibrational states of deuterated <i>trans</i>- and <i>cis</i>-formic acid: DCOOH, HCOOD, and DCOOD
Antoine Aerts, Philippe Carbonnière, F.‐W. Richter, Alex Brown
Abstract
The vibrational eigenenergies of the deuterated forms of formic acid (DCOOD, HCOOD, and DCOOH) have been computed using the block-improved relaxation method, as implemented in the Heidelberg multiconfiguration time-dependent Hartree package on a previously published potential energy surface [F. Richter and P. Carbonnière, J. Chem. Phys. 148, 064303 (2018)] generated at the CCSD(T)-F12a/aug-cc-pVTZ-F12 level of theory. Fundamental, combination band, and overtone transition frequencies of the trans isomer were computed up to ∼3000 cm−1 with respect to the zero point energy, and assignments were determined by visualization of the reduced densities. Root mean square deviations of computed fundamental transition frequencies with experimentally available gas-phase measurements are 8, 7, and 3 cm−1 for trans-DCOOD, trans-HCOOD, and trans-DCOOH, respectively. The fundamental transition frequencies are provided for the cis isomer of all deuterated forms; experimental measurements of these frequencies for the deuterated cis isotopologues are not yet available, and the present work may guide their identification.