Vibrational infrared and Raman spectra of HCOOH from variational computations.

Area of Science:

• * Quantum Chemistry
• * Molecular Spectroscopy
• * Computational Physics

Background:

• * Formic acid (HCOOH) exists in multiple forms, each with unique vibrational properties.
• * Accurate calculation of molecular vibrations is crucial for understanding chemical behavior and spectra.
• * Previous studies may lack comprehensive vibrational energy calculations for all formic acid conformers.

Purpose of the Study:

• * To compute highly accurate vibrational energies for formic acid conformers up to 4500 cm^-1.
• * To generate full-dimensional dipole and polarizability surfaces for HCOOH.
• * To simulate jet-cooled infrared and Raman spectra of formic acid.

Main Methods:

• * Employed the GENIUSH-Smolyak variational approach for vibrational energy calculations.
• * Utilized an *ab initio* potential energy surface derived from high-level electronic structure theory.
• * Fitted dipole and polarizability surfaces using coupled-cluster singles doubles with augmented correlation-consistent polarized valence triple zeta (CCSD/aug-cc-pVTZ) computations.

Main Results:

• * Converged vibrational energies for *trans*-, *cis*-, and *delocalized* formic acid were obtained.
• * Body-fixed vibrational dipole and polarizability transition moments were calculated.
• * Simulated infrared and Raman spectra of jet-cooled formic acid were generated.

Conclusions:

• * The computed data represents benchmark quality for vibrational energy and transition moments.
• * This work provides essential data for comparison with experimental vibrational spectroscopy.
• * The results will facilitate further advanced rovibrational computations and analyses.