Anharmonic effects in the vibrational spectra of radon-containing small molecules

Anharmonic vibrational frequencies were computed for radon-containing inorganic compounds. Structures of molecules HRnAH and HRnAF (A = O, S), HRnAH2 and HRnAF2 (A = N, P) were optimized in their ground electronic states and anharmonic vibrational frequencies computed with the correlation-corrected vibrational self-consistent-field method. Spectra of HRnSH and HRnPH2 are analyzed in detail and dominant features of each highlighted. The HRnSH spectrum includes the three IR active fundamentals, two overtones, and one combination band. The HRnPH2 spectrum features three high-intensity fundamentals and many intense combination bands and overtones. The quartic force field approximation has large errors with respect to the direct method in computation of overtones. Energy barriers to dissociation were found and kinetic stability is also discussed.