Fano-ADC(2,2) method for electronic decay rates.

Area of Science:

• Quantum Chemistry
• Theoretical Chemistry
• Atomic and Molecular Physics

Background:

• Fano-ADC methods predict electronic decay widths in excited atomic and molecular systems.
• Current Fano-ADC schemes have limitations in treating initial and final states, restricting accuracy and applicability to first-order decay processes.
• Unbalanced correlation treatment compromises numerical accuracy in existing Fano-ADC methods.

Purpose of the Study:

• To introduce an improved Fano-ADC approximation, ADC(2,2), for enhanced accuracy in predicting electronic decay widths.
• To extend the applicability of Fano-ADC methods to second-order decay processes, including double Auger decay (DAD).
• To address the limitations of unbalanced correlation treatments in previous Fano-ADC schemes.

Main Methods:

• Development of the ADC(2,2) approximation for singly ionized states, treating both initial and final states to second order.
• Construction of the Fano-ADC(2,2) approximation for decay width calculations.
• Application of the Fano-ADC(2,2) method to a series of decay processes.

Main Results:

• The Fano-ADC(2,2) approximation demonstrates superior accuracy for predicting electronic decay widths.
• The new scheme successfully calculates decay widths for processes previously beyond the scope of Fano-ADC.
• Access to second-order decay processes, such as double Auger decay (DAD), is now enabled.

Conclusions:

• The Fano-ADC(2,2) method represents a significant advancement in the ab initio prediction of electronic decay widths.
• This improved method enhances numerical accuracy and expands the range of accessible decay phenomena.
• Fano-ADC(2,2) is a powerful tool for studying complex electronic decay processes in ionized systems.