Knowledge Bank

Crossed molecular beams have been used to study rotationally and vibrationally inelastic scattering from several vibrational-rotational initial levels of $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}A0(S1)$ glyoxal in collisions with He. The cross sections obtained in our spectroscopic experiments can now be compared to those predicted by ab initio calculations [Kroes, Rettschnick and Clary, Chem. Phys. 148, 359 (1990)]. The predictions show that substantial differences exist between the cross sections for rotationally inelastic scattering from the $00$ and $72$ initial levels. The calculations also show that there are differences between the rotationally inelastic scattering cross sections from the $00$ level for scattering by $H2$ and He. The emerging experimental data for inelastic scattering of glyoxal with He shows the same trends. The experimental cross sections for excitation (or de-excitation) are larger for scattering from $72$ than for $00$ and the rotationally inelastic cross sections for scattering from $00$ depend on whether $H2$ or He are used as the collision partners.