Rotational predissociation, vibrational mixing, and van der Waals intermolecular potentials of NeDF

The near-infrared spectrum of NeDF formed in a slit free jet expansion is recorded with a high resolution, tunable laser spectrometer. Four bands, consisting of the DF stretching fundamental and three internal rotation and van der Waals stretch combination bands, are observed and analyzed for both the 20Ne and 22Ne isotopomers. All three combination bands reveal a sudden onset of rotational predissociation at modest J, which is modeled with effective one-dimensional potentials to determine the binding energy D0=34.7±0.8 cm−1 for 20NeDF (v=0) and D0=35.1±0.8 cm−1 for 20 NeDF (v=1). The experimental results are compared with predictions of a recently published ab initio anisotropic potential surface, and an improved potential is developed and tested. This refined potential has an absolute minimum of −86 cm−1 in the linear Ne–D–F geometry, a secondary minimum at −55 cm−1 in the inverted linear Ne–F–D geometry, and an intervening saddle point at −39 cm−1 near the perpendicular geometry. The lowest bound state lies ≊4 cm−1 above the saddle so internal DF rotation is only slightly hindered in this complex.