Accidental Interaction in the Torsional Spectrum of Singly Deuterated Hydrogen Peroxide HOOD

We extended previously recorded infrared spectra of singly deuterated hydrogen peroxide (HOOD) to the submm-wavelength region and derived accurate molecular parameters and a semi-empirical equilibrium structure. In total, more than 1500 ro-torsional HOOD transitions have been assigned between 6 and 120 cm$^{-1}$. We succeeded to analyze the accidental interaction between the torsional sub-states by measuring several perturbed transitions. In addition to the set of Watsonian parameters for each tunneling component, only two interaction constants were required to describe the spectrum. The $K_a$- and $J$-dependance of the torsional splitting could be determined also for the perturbed states.