Measurements of rotational and vibrational quantum transition probabilities in the scattering of Li+ from N2 and CO at center of mass energies of 4.23 and 7.07 eV

Abstract

Angular distributions and time of flight spectra for the scattering of Li⁺ ions from ground state N₂ and CO molecules have been measured over a range of scattering angles (0°⩽ϑ_c.m.⩽60°) and for E_c.m. =4.23 and 7.07 eV. The time of flight spectra show a number of maxima which have been attributed to unresolved rotational excitation superimposed upon vibrational quantum transitions corresponding to n=0→0, 0→1, and 0→2. The laboratory spectra have been transformed into the center of mass system to obtain relative inelastic differential cross sections. Significant differences between the vibrational inelastic cross sections for N₂ and CO are observed at large angles at the highest energy studied. The results are discussed in terms of the SCF potential hypersurfaces. The differences in the vibrational cross sections cannot be explained in terms of the infinite order sudden approximation and the vibrational matrix elements of the SCF hypersurfaces. This suggests that the inclusion of rotational–vibrational coupling % in the dynamics and/or an improved hypersurface are called for.