A hybrid variational-perturbation calculation of the ro-vibrational spectrum of nitric acid

Abstract

Rotation-vibration spectra of the nitric acid molecule, HNO\3, are calculated for wavenumbers up to 7000~\cm. Calculations are performed using a Hamiltonian expressed in internal curvilinear vibrational coordinates solved using a hybrid variational-perturbation method. An initial potential energy surface (PES) and dipole moment function (DMF) are calculated {\it ab initio} at the CCSD(T)/aug-cc-pVQZ level of theory. Parameters of the PES and DMF are varied to minimize differences between the calculated and experimental transition frequencies and intensities. The average, absolute deviation between calculated and experimental values is 0.2~\cm\ for frequencies in the fundamental bands and 0.4~\cm\ for those in the first overtone and lowest combination bands. For the intensities, the calculated and experimental values differ by 0.3\% and 40\% for the fundamentals and overtones, respectively. The optimized PES and DMF are used to calculate the room-temperature ro-vibrational spectrum. These calculation reproduce both the form of the absorption bands, and fine details of the observed spectra, including the rotational structure of the vibrational bands and the numerous hot absorption band. Many of these hot bands are found to be missing from the compilation in HITRAN. A room temperature line list comprising $2\times 10^9$ lines is computed.

27 pages, 5 Tables. 7 Figures

References in corpus (2)

• Hybrid variation-perturbation method for calculating rovibrational energy levels of polyatomic molecules
• Visible line intensities of the triatomic hydrogen ion from experiment and theory

Cited by in corpus (6)

• Symmetry adapted ro-vibrational basis functions for variational nuclear motion calculations: TROVE approach
• The ExoMol project: Software for computing large molecular line lists
• ExoMol molecular line lists - XVII The rotation-vibration spectrum of hot SO${}_3$
• Ab initio effective rotational and rovibrational Hamiltonians for non-rigid systems via curvilinear second order vibrational Møller-Plesset perturbation theory
• An evaluation for geometries, formation enthalpies, and dissociation energies of diatomic and triatomic (C, H, N, O), NO3, and HNO3 molecules from the PAW DFT method with PBE and optB88-vdW functionals
• Exploring Synergies between Twinkle and Ariel: a Pilot Study