Exploration of the van der Waals Region of the NO <i>A</i> ² Σ ⁺ + N ₂ <i>X</i> ¹ Σ _<i>g</i> ⁺ Collision Complex

High Resolution Image Download MS PowerPoint Slide The van der Waals (VdW) region of the potential energy surface (PES) of the collision complex of NO( A 2 Σ + ) and N 2 ( X 1 Σ g + ) was explored using explicitly correlated coupled-cluster methods. The Rydberg character of the NO( A 2 Σ + ) state necessitated a sufficiently large and diffuse basis set. Basis set superposition error endemic to such systems was mitigated by the use of an explicitly correlated method in addition to a counterpoise correction, subsequent benchmarking was performed via both energetics and molecular properties such as the dipole and quadrupole moment. The method ultimately used was CCSD(T)-F12a/t-aug-cc-pVTZ, with the full VdW PES constructed through a series of three-dimensional cuts exploring the space between key orientations. A broad main minimum well was observed surrounding the linear nitrogen-to-nitrogen (“LN”) orientation with a maximum depth of −239.51 cm –1 at an intermolecular separation of 4.2 ⁡ Å . This new PES is useful for interpretation of recent molecular beam scattering experiments.