Intersystem Crossings in Late-Row Elements: A Perspective.

Area of Science:

• Photophysics
• Computational Chemistry
• Quantum Mechanics

Background:

• Intersystem crossing (ISC) is crucial for electronic and nuclear transitions in photophysics.
• ISC simulations are well-established for light elements and transition metals.
• ISC's importance increases with atomic number due to spin-orbit coupling (SOC), yet simulations in heavy elements are scarce.

Purpose of the Study:

• To investigate the challenges in simulating intersystem crossing (ISC) in heavy elements, specifically lanthanides and actinides.
• To highlight the necessity of advanced computational methods for accurate ISC modeling in these elements.

Main Methods:

• Exploration of challenges including the loss of spin as a good quantum number.
• Inclusion of spin-orbit coupling (SOC) variationally using two- or four-component electronic structure methods.
• Utilizing Density Functional Theory (DFT) calculations and a model Hamiltonian for simulations.

Main Results:

• Identified key challenges for ISC simulation in late-row elements.
• Demonstrated the impact of SOC and high density of states in these systems.
• Illustrated the importance of momentum rescaling in surface hopping simulations for strongly coupled states.

Conclusions:

• Accurate simulation of ISC in heavy elements requires addressing specific computational challenges.
• Advanced electronic structure methods and simulation techniques are essential for understanding ISC in lanthanides and actinides.