Two-dimensional model of rotationally inelastic collisions

State-to-state resolved differential cross sections for rotationally inelastic scattering of ND3with He

“…Only the 15 three lowest energy rotational levels j k = 0 0 , 1 1 and 1 0 are significantly populated, with just 0.7% of population in the higher rotational levels. The cooled ND 3 molecules were subjected to hexapole electrostatic state selection, in which states with k ≠ 0 experience a radial force due to an interaction of the electric field 20 with the molecular dipole moment. The direction of this force depends on the parity of the molecular state: molecules with symmetric umbrella inversion (+) diverge from the path along the hexapole axis, whereas molecules with antisymmetric inversion symmetry (−) experience a restoring force and are focussed into 25 the scattering region.…”

“…The ND 3 -collider system also has grea reduced mass than the NH 3 -collider system, so the dynamics evolving on the PES may be expected to differ. For example, from the classical results for rotational rainbow scattering of a homonuclear molecule with an atom, 20 the position of the 20 rotational rainbow for a given j and collision energy to shift towards larger scattering angles for the deuterated system.…”

“…These wavelengths were generated by frequency doubling the output of a tuneable pulsed dye laser (Lambda Physik ScanMate) operating with DCM dye using a BBO doubling crystal. The dye laser was pumped by a 20 Nd:YAG laser (Continuum Powerlite 9000) operating at 532 nm and with 10 Hz repetition rate. Typical ultraviolet (UV) laser energies were ~4.5 mJ/pulse in pulses of duration 7-9 ns.…”

Parity-dependent rotational rainbows in D2–NO and He–NO differential collision cross sections

“…In between these zero positions of b n there are two maximum values, one on each side of the molecule, that allow for maximum rotational excitation. 24 In the case of an ellipsoid 23 this is at b n = A − B where A and B are its major and minor axis, respectively. All together this implies that there are ͑except at b n = 0 and at its maximum value͒ four angles ͑␥ n ͒ that lead to the same value of b n .…”

“…The magnitude of the rotational excitation is proportional to the effective impact parameter b n at the point of impact. 23 This impact parameter is the shortest distance between the surface normal and the center of mass of the molecule. For a convex shell, there are three values of ␥ n at which b n = 0: two at each end of the molecule ͑␥ n = ␥ R =0, ͒ and one near the equator ͑␥ n = ␥ R Ϸ /2͒.…”