Collisional angular momentum mixing of Nandstates by CH4andC3H8

Measurements of collisional $l$-mixing cross sections for Na $\mathrm{nd}$ states have been extended to C${\mathrm{H}}_4$ and ${\mathrm{C}}_3$ ${\mathrm{H}}_8$. The measurements, which have been made using a time-resolved laser induced fluorescence approach, show that the cross section for C${\mathrm{H}}_4$ rises sharply from $n=7\mathrm{} \mathrm{to} 10$, and then decreases. The ${\mathrm{C}}_3$ ${\mathrm{H}}_8$ cross section is much larger than for previously studied collision partners, and rises monotonically from $n=7\mathrm{} \mathrm{to} 17$ with the exception of an unexpected dip at about $n=15\mathrm{}$. The measurements are in qualitative agreement with expectations based on low-energy $e-\mathrm{C}{\mathrm{H}}_4$ and $e-{\mathrm{C}}_3{\mathrm{H}}_8$ scattering, and suggest that the effect of internal structure and molecular geometry on the collision dynamics is relatively small.