Experimental Absolute Cross-Sections for the Reaction F + D2 at Collision Energies 90−240 meV

Absolute differential and integral cross-sections for the DF( v f =0−4) vibrational products of the F + D 2 ( v i =0, j i =0−2) → DF( v f ) + F reaction have been evaluated from the time-of-flight spectra measured in high-resolution crossed molecular beam scattering experiments at five collision energies within the range 90−240 meV. The observed rise of the total reactive cross-section with increasing collision energy can be fitted with an empirical, modified line-of-centers model, yielding an activation energy of 1.8 kcal·mol -1 . Remarkably pronounced angular structures are observed in the vibrationally resolved differential reactive cross-sections, especially for the largest accessible vibrations, v f = 3 and v f = 4. The experimental absolute cross-sections are compared with the results of previously reported quantum mechanical and quasiclassical trajectory calculations on the most recent potential energy surfaces for the F + D 2 system. An overall excellent agreement is found within the experimental uncertainty. However, some significant differences are also apparent, especially at the lowest collision energies studied.