Vibrational anharmonicity and reorientational dynamics of SO 42− anions isolated in an Ag 2SeO 4 matrix

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Room and low-temperature (∼100 K) FT-IR spectra of sulfate anions isolated in Ag 2SeO 4 matrix were recorded. The anharmonicity constants and harmonic vibrational frequencies for the ν 3 and ν 4 internal modes of the dopant anions were calculated, on the basis of the measured fundamental and second-order transitions. The appearance of the IR spectrum of the studied species may be explained in terms of D 2d effective symmetry. According to the magnitude of the splitting of ν 3 and ν 4 modes of the dopant anions, the bond length distortion of the sulfate impurities is lower, and the angular distortion is significantly higher in Ag 2SeO 4 than in all other matrices studied so far. The OSO angles calculated from the ratio of the intensities of B 2 and E ν 3 mode components are 111.6 and 108.4°. Using the transition dipole moment time correlation function approach, the period of essentially “undisturbed” rotational motion for the dopant anions about the pseudo- C 2 axes is estimated to be approximately 0.035 ps.