High resolution spectroscopy of the ν1+ν3 band of the 35ClO2 free radical: Spin-rotation-vibration interactions

O N Ulenikov; E S Bekhtereva; O V Gromova; A N Kakaulin; C Sydow; K Berezkin; S Bauerecker

doi:10.1016/j.saa.2022.121379

High resolution spectroscopy of the ν₁+ν₃ band of the ³⁵ClO₂ free radical: Spin-rotation-vibration interactions

Spectrochim Acta A Mol Biomol Spectrosc. 2022 Oct 5:278:121379. doi: 10.1016/j.saa.2022.121379. Epub 2022 May 14.

Authors

O N Ulenikov¹, E S Bekhtereva², O V Gromova², A N Kakaulin², C Sydow³, K Berezkin³, S Bauerecker⁴

Affiliations

¹ Research School of High-Energy Physics, National Research Tomsk Polytechnic University, Tomsk 634050, Russia. Electronic address: Ulenikov@mail.ru.
² Research School of High-Energy Physics, National Research Tomsk Polytechnic University, Tomsk 634050, Russia.
³ Institut für Physikalische und Theoretische Chemie, Technische Universität Braunschweig, D - 38106, Braunschweig, Germany.
⁴ Institut für Physikalische und Theoretische Chemie, Technische Universität Braunschweig, D - 38106, Braunschweig, Germany. Electronic address: s.bauerecker@tu-bs.de.

PMID: 35605358
DOI: 10.1016/j.saa.2022.121379

Abstract

The high resolution spectrum of the ν₁+ν₃ band of the ³⁵ClO₂ free radical was recorded with a Bruker IFS 125HR Fourier transform infrared spectrometer and theoretically analysed with an improved theoretical basis including the reduced effective spin-rotation Hamiltonian (which takes into account sixth order operators describing spin-rotational interactions) and a newly created computer code ROVDES for the ro-vibrational spectra of open-shell free radicals. About 2600 spin-ro-vibrational transitions with the values N^max=59 and K_a^max=17 (being about 2.4 times higher in comparison with the number of assigned transitions known in the literature) were assigned to the ν₁+ν₃ band of ³⁵ClO₂ and 1049 spin-ro-vibrational energies (produced only from unblended non-saturated and not very weak experimental lines) of the (101) upper vibrational state were obtained. A set of 30 varied parameters of the effective spin-rotation-vibration Hamiltonian of the (101) vibrational state (vibrational energy, 17 rotational and centrifugal distortion parameters and 12 are spin-rotational ones) was determined from the weighted fit of parameters of the effective spin-rotational Hamiltonian in A-reduction and I^r-representation. The obtained set of parameters reproduces the initial 1049 "experimental" upper state energies with the d_rms=2.5×10^-4 cm^-1 which is close to the experimental uncertainty of the recorded spectra and is almost 70 times higher in comparison with the analogous reproduction of the same initial upper energies with the use of parameters from (J.Mol.Spectrosc.,158,347-356(1993)).

Keywords: asymmetric top molecules in non-singlet electronic states; high resolution spectroscopy of ClO(2); spectroscopic parameters; spin-rotation interactions.