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

Abstract

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.

Keywords: absolute line strengths; asymmetric top molecules in non-singlet electronic states; effective dipole moment operator; spin–rotation interactions.

Figure 1

Small portion of the experimental spectrum of ClO₂ compared with Ref. [36]. “Forbidden transitions” $\Delta K=\pm 2$ are marked by dark circles. Experimental conditions: resolution is 0.0015 cm⁻¹; number of scans is 400; source is a Globar; detector is a MCT313; beam-splitter is made from KBr; optical path length is 0.23 m; aperture is 1.15 mm; temperature is 22 ± 0.3 °C; pressure is 100 Pa; calibration was performed by CO₂ and H₂O spectral lines.