IR Spectrum of FHF–and FDF–Revisited Using a Spectral Method in Four Dimensions

Abstract

A four dimensional (4D) time-dependent calculation to obtain the first vibrational states of the hydrogen bifluoride ion, FHF–, and its deuterated counterpart, FDF–, has been performed using a spectral method in Cartesian coordinates. The corresponding potential energy surfaces have been computed at the CCSD(T)/aug-cc-pVTZ level of theory. The obtained values for the fundamental vibrational bands ν̃1 = 589 cm–1, ν̃2 = 1305 cm–1, and ν̃3 = 1372 cm–1 assigned to the symmetric stretch, bend, and asymmetric stretch modes, respectively (598, 943, and 972 cm–1 for FDF–, respectively) are in good agreement with available experimental and theoretical values. Selected overtones and mixed modes are also calculated. Infrared spectra have been simulated using the dipole approximation for two different polarization directions of the incident light.