High-resolution FTIR spectroscopy and analysis of the K a = 0 ← 1 subbands of the fundamentals ν 3 and ν 6 of the dimer (HF)2

Abstract

We report new far-infrared spectra of (HF)2 obtained by high resolution long-path Fourier Transform-Infrared (FTIR) spectroscopy. The origins of the two tunneling components of the K a = 0 ← 1 subband of the in-plane symmetric bending fundamental ν 3 were found to be at 450.4546 cm − 1 (Γ t : A + ← B +) and at 451.4583 cm − 1 (B + ← A +), and of the K a = 0 ← 1 subband of the out-of-plane bending fundamental ν 6 at 382.0802 cm − 1 (A + ← A +) and at 383.2245 cm − 1 (B + ← B +). The K a = 0 term values with respect to the ground state Γ t = A + term are 486.9442 cm − 1 for the A + and 486.8834 cm − 1 for the B + tunneling levels of ν 3. They are 417.5053 cm − 1 for the A − and 419.7140 cm − 1 for the B − vibration-tunneling sublevels of ν 6. The results are discussed in relation to full-dimensional quantum dynamics and predictions based on recent ab initio calculations and our empirically refined potential energy hypersurfaces. Graphical abstract