Testing standard basis sets for direct ionizations: H⁺ + H at E_Lab = 0.1-100 keV

Area of Science:

• Atomic and Molecular Physics
• Quantum Chemistry
• Computational Physics

Background:

• Accurate simulation of atomic collision processes is crucial for understanding fundamental physics.
• The Simplest-Level Electron Nuclear Dynamics (SLEND) method offers a novel approach to nonadiabatic dynamics.
• Standard basis sets like Slater-type-orbital/contracted-Gaussian-functions (STO/CGFs) are widely used in quantum chemistry.

Purpose of the Study:

• To test the efficacy of the SLEND method using STO/CGFs basis sets for simulating direct ionizations (DIs), charge transfers (CTs), and target excitations (TEs).
• To evaluate the performance of SLEND/STO/CGFs for challenging DI processes, which have not been previously tested.
• To assess the accuracy of SLEND/STO/CGFs in predicting integral cross-sections (ICSs) for these collision processes.

Main Methods:

• Utilized the Simplest-Level Electron Nuclear Dynamics (SLEND) method, a time-dependent, variational, on-the-fly, and nonadiabatic approach.
• Employed classical dynamics for nuclei and a Thouless single-determinantal state for electrons.
• Tested standard Slater-type-orbital/contracted-Gaussian-functions (STO/CGFs) basis sets for H+ + H collisions across a wide energy range (0.1-100 keV).

Main Results:

• SLEND/STO/CGFs simulations successfully reproduced all features of DIs, CTs, and TEs across all impact parameters and energies.
• Predicted charge transfer integral cross-sections (ICSs) accurately over the entire energy range.
• Achieved satisfactory predictions for direct ionization and target excitation ICSs within specific energy ranges.

Conclusions:

• The SLEND method, in conjunction with STO/CGFs basis sets, provides a reliable tool for simulating atomic collision processes.
• This study establishes the capability of SLEND/STO/CGFs for direct ionization simulations.
• Further strategies are proposed to enhance the accuracy of SLEND/STO/CGFs for direct ionization predictions.