AB-INITIO CALCULATIONS AND HIGH-RESOLUTION INFRARED INVESTIGATION ON XEF4

Ab initio calculations employing effective core potentials and polariz ed triple-zeta basis sets have been carried out for XeF4 at the follow ing levels: self-consistent-field (SCF) theory, Moller-Plesset second- order perturbation theory (MP2), and coupled cluster theory with singl e and double excitations and a perturbational treatment of triple exci tations (CCSD(T)). Pronounced correlation effects are found, especiall y for the Xe-F bond length and the vibrational frequencies. The theore tical predictions for the harmonic and anharmonic force fields and the associated spectroscopic constants have guided the analysis of the ex perimental data. Fourier transform infrared spectra of monoisotopic (X eF4)-Xe-136 have been recorded between 100-1170 cm(-1) with an effecti ve resolution of 0.002-0.004 cm(-1), and a rotational analysis has bee n performed for the v(2) band. The high resolution results provide acc urate molecular parameters for the ground state and the v(2)=1 excited state of XeF4 and allow a precise determination of the ground state X e-F bond length, r(0)=193.487(3) pm. The agreement between the experim ental and the correlated theoretical results is generally quite good. (C) 1996 American Institute of Physics.