A new “spectroscopic” potential energy surface for formaldehyde in its ground electronic state

Abstract

We report a new "spectroscopic" potential energy surface (PES) of formaldehyde (H(2)(12)C(16)O) in its ground electronic state, obtained by refining an ab initio PES in a least-squares fitting to the experimental spectroscopic data for formaldehyde currently available in the literature. The ab initio PES was computed using the CCSD(T)/aug-cc-pVQZ method at 30 840 geometries that cover the energy range up to 44 000 cm(-1) above equilibrium. Ro-vibrational energies of formaldehyde were determined variationally for this ab initio PES by means of the program TROVE [Theoretical ROtation-Vibration Energies; S. N. Yurchenko, W. Thiel, and P. Jensen, J. Mol. Spectrosc. 245, 126 (2007)]. The parameter values in the analytical representation of the PES were optimized in fittings to 319 ro-vibrational energies with J = 0, 1, 2, and 5. The initial parameter values in the fittings were those of the ab initio PES, the ro-vibrational eigenfunctions obtained from this PES served as a basis set during the fitting process, and constraints were imposed to ensure that the refined PES does not deviate unphysically from the ab initio one in regions of configuration space not sampled by the experimental data. The resulting refined PES, referred to as H(2)CO-2011, reproduces the available experimental J ≤ 5 data with a root-mean-square error of 0.04 cm(-1).

Ab initio computational spectroscopy and vibrational dynamics of polyatomic molecules: Applications to syn and anti-CH3CHOO and NO3

“…There has also been substantial progress in achieving this goal for general tetraatomics, see for example Refs. [5][6][7][8] and for some larger, albeit semi-rigid molecules, such as CH 4 [9,10], C 2 H 4 [11,12] and CH 3 OO [13]. There has also been significant progress in developing global, i.e., describing multiple minima and in some cases fragment channels, PESs for tetraatomics, based on strict mathematical fitting of tens of thousands of high-level electronic energies.…”

“…In recent applications the sum-of-products is expressed more generally in terms of exponential Morse variables (see below), bond angles, etc., see for example, Ref. [8]. Even with these advances in PES development, the rigorous calculation of high-lying ro-vibrational eigenstates and reactive scattering for tetraatomics remains a substantial challenge computationally.…”

Simulating electric field interactions with polar molecules using spectroscopic databases

“…These systems have been treated within the ExoMol framework19 and we refer the reader to the relevant publications for details of the ro-vibrational calculations51525354. Candidate ro-vibrational states were identified by sorting the  files according to upper state energy.…”

Rotational spectrum of formaldehyde reinvestigated using a photomixing THz synthesizer

“…Formaldehyde, H 2 CO, is a small model molecule used to test quantum mechanical computations [1,2], force field calculations [3], and vibration-rotation interactions [4,5]. It is also an important interstellar [6] and atmospheric [4] molecule.…”