An ab initio study of the Ar-NO(A 2Sigma+) intermolecular potential

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Spectroscopy

Background:

• Molecular dynamics simulations of photoexcited nitric oxide (NO) in solid argon (Ar) require accurate intermolecular potentials.
• The angular dependence of the Ar-NO interaction is critical for these simulations.

Purpose of the Study:

• To perform an ab initio study of the Ar-NO(A 2Sigma+) intermolecular potential.
• To provide an analytical representation of the potential energy surface (PES) for use in simulations.

Main Methods:

• Ab initio calculations using the CASSCF-MRCI level of theory with aug-cc-pVTZ basis sets.
• Investigation of the influence of quadruple excitations on the PES topology.
• Analytical fitting of the PES as a function of Jacobi coordinates.

Main Results:

• The PES is generally repulsive, with two shallow wells appearing at linear configurations (alpha=0 and 180 degrees).
• Inclusion of quadruple excitations shifts the well positions and deepens the well energies.
• For distances beyond 7 Å, the interaction becomes weakly attractive and tends towards isotropic behavior.

Conclusions:

• The calculated Ar-NO intermolecular potential provides essential data for more accurate molecular dynamics simulations.
• Understanding the PES is vital for interpreting spectroscopic data of NO in solid Ar matrices.