High resolution relative integral cross sections were measured for the interactions of low-velocity H atoms with CF6 and SF+ In each system two maxima were resolved, and the lower peak occurs at relative velocities of about 450-500 m/s The shapes of the "spectra" are similar to those observed for H-rarpgas scattering but differ in details.
Resonances have now been observed in several wellcharacterized systems, including H f Ar, Kr, Xe [ I,2 3 , H + Hg [3], and H2 + Ar, Kr, Xe [4] _ The measured intensities, widths and positions have been brought into agreement with the theory of orbiting resonances, providing information on potential surfaces in the longrange attractive region. In addition, the demonstrated existence of these short-lived bi-and polyatomic quasibound systems is highly pertinent to understanding certain gas-phase chemicaI processes, such as recombination and termolecular reactions [S] . Since confidence can be placed in the experimental techniques, it was felt appropriate to proceed to the examination of some more complicated and less well-understood systems to see how widely such measurements might be useful.
The symmetric top molecules CF4 and SF6 were chosen for target beams. Since their chemical and physical properties are such that they resemble the noble gases [6], it was anticipated that little or no modification of the existing apparatus would be required, and since they are "spherical" it was hoped that the interpretation of the experimental data couid be at least partially carried out within the theoretical framework already successfully used for the noble gases. The possibIe fluorine abstraction reactions are exothermic [7] but have high activation barriers (30 kcallmole for H + SF, and 44 k&/mole for H + CF4 [S] ), and so were not expected to interfere. "P-ancnfaddress~ Depar~nentof(=h~.Brookhaven