Molecular Beam Scattering of Nitrogen Molecules in Supersonic Seeded Beams: A Probe of Rotational Alignment

Abstract

Measurements of total integral cross sections for scattering of nitrogen molecules by Xe atoms in the glory collision energy range (40−600 meV) are reported under two different experimental conditions, using either a rotationally "hot" (most probable levels J = 8, 9) effusive beam of nitrogen (obtaining information on the isotropic component of the interaction potential) or rotationally "cold" N2 seeded beams emerging from supersonic expansions (obtaining quantitative information on rotational alignment of molecular nitrogen). The scattering results presented in this paper allow us to establish that the recently reported phenomenon of the strong correlation between the degree of collision-induced alignment and the speed of the molecules within a supersonic seeded velocity distribution, as previously observed for the first time in molecular oxygen, also occurs for the case of nitrogen molecules. Alignment parameters are reported for both the ortho and para forms of nitrogen, which are cooled down in the seeded supersonic expansion process to their lowest rotational levels J = 0, 1, 2.