On the vibrations of formic acid predicted from first principles

Abstract

In this article, we review recent first principles, anharmonic studies on the molecular vibrations of gaseous formic acid in its monomer form.

Vibrational infrared and Raman spectrum of HCOOH from variational computations

“…1 and has been motivated by a systematic experimental effort [2][3][4][5] to measure the infrared and Raman vibrational spectrum of the formic acid monomer to set experimental benchmarks and to challenge computational quantum dynamics methodologies. [6][7][8][9][10][11][12][13] In the present work, we aim to make progress with a complete quantum dynamical characterization of this five-atomic molecule. In the one hand, we elaborate on the basis pruning condition to be able to converge all vibrational energies up to and beyond the top of the cis-trans isomerization barrier with a convergence error less uncertainty introduced by the potential energy surface (PES) representation.…”

Vibrational dynamics of formic acid and its dimer: FTIR and Raman jet spectroscopy and theory

“…21 Very recently, the published anharmonic vibrational studies of formic acid have been reviewed in Ref. [97]. See also Refs.…”

“…Relating these selection rules to the symmetric top limit, we see how Δ ± 1 additionally becomes allowed due to symmetry lowering. 97 + -type bands are a mixture of totally symmetric and non-totally symmetric bands whereas + -type bands more resemble non-totally symmetric bands as they are missing the characteristic central branch --and -type bands usually exhibit a lower intensity towards the band centre. The identification of the central branch or verification of its absence thus unambiguously allows an assignment of the observed band type for the and 2ℎ point groups.…”

“…[212]. 97 It is noted that Herzberg, who discusses the theory for Raman bands in less detail (due to the sparse number of well-resolved Raman spectra at that time), writes that for near-symmetric top molecules of the point group, Δ = ±1 instead of ±2 applies for A ′′ −A ′ transitions [172, p. 443].…”

“…Again, we turn to CVPT6 energy levels which show that this spectral region is dominated by different 5 polyads. Overall, there are six A ′ symmetric energy levels in this region (states [92][93][94][95][96][97]Table D.6). When correcting the expected error using Eq.…”