EXPERIMENTAL-OBSERVATION OF STRUCTURE IN THE DISTRIBUTION OF FINAL ROTATIONAL STATES IN SMALL-ANGLE INELASTIC-SCATTERING OF LI+ FROM CO(EC.M.=4-7EV)

The energy loss of 5.3 eV Li+ ions scattered from CO molecules (Ec.m. = 4.28 eV) was measured in a time of flight apparatus. In the range of small scattering angles (Θlab=2° to 14°) a rainbow and a supernumerary rainbow maximum appear in the angular dependence of the total differential cross section at 5.5° and 2.5°, respectively. The time of flight measurements show a large amount of rotational excitation, even at the smallest measured scattering angle. In the range of 6° < Θlab < 10°, the time of flight spectra reveal several maxima in the distribution of final rotational states. For example in one spectrum at Θlab= 8°, four peaks at Δj=0, 13, 20 and 26 were resolved. Several possible explanations of the observed structure are discussed. © 1979.