High resolution ro-vibrational analysis of molecules in doublet electronic states: the ν1 fundamental of chlorine dioxide (16O35Cl16O) in the X2B1 electronic ground state

Improved Theory of the Effective Dipole Moments and Absolute Line Strengths of the XY2 Asymmetric Top Molecules in the X2B1 Doublet Electronic States

A new effective dipole moment model for the XY2 (C2v-symmetry) molecule in a doublet electronic state is derived that includes (as special cases) all currently known models of effective dipole moments for such types of molecules, and allows us to take into account the influence of spin-rotation interactions on the effective dipole moment operator that were not considered in the preceding studies. Necessary for the analysis of absolute line strengths, the matrix elements of this dipole moment operator are derived. A comparison with the previous analog models is made and discussed. The efficiency of the obtained results is illustrated, which have been applied to a set of the "forbidden" ΔKa=2 transitions of the ν3 band of the OClO free radical molecule.

High resolution spectroscopy of asymmetric top molecules in nonsinglet electronic states: the ν3 fundamental of chlorine dioxide (16O35Cl16O) free radical in the X2B1 electronic ground state

Highly resolved spectra of the ¹⁶O³⁵Cl¹⁶O isotopologue of chlorine dioxide were recorded with a Bruker IFS 125HR Fourier transform infrared spectrometer in the region of the ν₃ band. The analysis was made in the frame of the spin-rotational effective Hamiltonian (in A-reduction and I^r-representation) taking into account spin-rotational coupling operators up to the sixth order and the corresponding reduction of the Hamiltonian. The mathematical description of the ro-vibrational spectra was implemented to the specially created computer program ROVDES. Under the present experimental conditions, we were able to assign more than 5200 spin-rotational transitions to the ν₃ band. This number is 2.4 times higher compared to the previous studies available from the literature. The vibrational ground state parameters were improved, and the 2220 upper spin-rotation-vibration energy levels were determined and used as initial data in the inverse spectroscopic problem with the derived effective spin-rotational Hamiltonian. A total of 37 fitted parameters were determined (22 rotational and centrifugal parameters and 15 parameters of spin-rotation coupling). The appearance of strong Coriolis resonance interactions between the (001) and (100) vibrational states in the sets of (001)[N,K_a = 9], (001)[N,K_a = 17], (001)[N,K_a = 18] and (001)[N,K_a = 19] spin-rotation-vibration levels was experimentally observed for the first time and explained. The d_rms = 1.4 × 10^-4 cm^-1 reproduction of the initial "experimental" upper ro-vibrational energy values was achieved which is considerably better compared to the use of parameters from a previous study ([J. Ortigoso et al., J. Mol. Spectrosc., 1992, 155, 25-43]).

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

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)).