Electron-Impact Ionization Cross Sections of Molecules Containing Heavy Elements (Z > 10)

Area of Science:

• Atomic and Molecular Physics
• Chemical Physics
• Quantum Chemistry

Background:

• The binary-encounter-Bethe (BEB) theory is a widely used model for calculating electron-impact ionization cross sections.
• For molecules with heavy atoms (valence principal quantum number n > 2), two BEB procedures exist: kinetic-energy correction and effective core potentials (ECPs).

Purpose of the Study:

• To compare the accuracy of two alternative BEB procedures for molecules containing heavy elements.
• To validate computational methods against experimental ionization cross-section data.
• To identify and correct previously reported inaccurate BEB calculations.

Main Methods:

• Application of two distinct BEB theoretical procedures to calculate electron-impact ionization cross sections.
• Comparison of calculated cross sections with experimental data for a range of molecules containing heavy elements.
• Prediction of dipole polarizability for Zn(C2H5)2 as an ancillary calculation.

Main Results:

• Both kinetic-energy correction and ECP methods provide good agreement with experimental ionization cross sections.
• The ECP method demonstrated slightly superior agreement with experimental measurements compared to the kinetic-energy correction method.
• Electron-impact ionization cross sections were computed for numerous molecules, including C2Cl6, CCl4, TiCl4, P4, As4, CS2, CH3I, and Zn(C2H5)2.
• Previously published incorrect BEB calculations for several molecules were identified.

Conclusions:

• The ECP approach is recommended for calculating electron-impact ionization cross sections of molecules with heavy atoms due to its improved accuracy.
• The study provides reliable cross-section data for various heavy-atom-containing molecules, aiding future research.
• Accurate theoretical calculations are crucial for understanding molecular ionization processes.