The translational energy dependence of the integral reaction cross sectionfor Li+HF(v=0)-> LiF+H

In a crossed molecular beam study we have measured the dependence of the re lative integral cross section for the reaction Li + HF(v = 0,(j) over bar = 1.4) --> LiF + H on the translational energy of the reactants (excitation function) within a range extending from 82 to 376 meV. We find an upper bou ndary for the translational energy threshold of < 82 meV. Only the potentia l energy surfaces of Palmieri and Lagana (J. Chem. Phys., 1989, 91, 7303; l atest version: Parker et al., J. Chem. Phys., 1995, 102, 1238) and Aguado e t al. (J. Chem. Phys., 1997, 107, 10085) are compatible with this result. I n the threshold region the excitation function exhibits a steep rise with d ecreasing collision energy which might be due to a peak located below the a ccessed energy range. Similar features have been found also in recent appro ximate quantum scattering calculations. Theoretical predictions for the int ermediate and high energy region agree well with the data.