Role of Multistate Intersections in Photochemistry

Area of Science:

• Physical Chemistry
• Theoretical Chemistry
• Computational Chemistry

Background:

• Potential energy surface intersections facilitate nonadiabatic transitions, critical in photochemistry.
• While conical intersections of two electronic states are well-studied, multistate intersections in polyatomic molecules are increasingly recognized for their photochemical importance.

Purpose of the Study:

• To review algorithms for locating two- and three-state intersections, highlighting advances in general multistate intersection searches.
• To examine intersystem crossing (ISC) at multistate intersections, focusing on the influence of state-specific spin-orbit coupling.
• To emphasize the synergy between nonadiabatic dynamics simulations and electronic structure calculations.

Main Methods:

• Review of algorithms for identifying two- and three-state intersections.
• Focus on computational methods for locating general multistate intersections.
• Analysis of spin-orbit coupling effects on nonadiabatic intersystem crossing.

Main Results:

• Development of general algorithms for locating multistate intersections.
• Demonstration of the significant role of state-specific spin-orbit coupling in nonadiabatic ISC.
• Validation of combined electronic structure and dynamics simulations for studying these phenomena.

Conclusions:

• Multistate intersections are vital in photochemistry, particularly for intersystem crossing.
• Advanced computational algorithms are essential for their identification and study.
• The interplay of electronic structure and nonadiabatic dynamics is key to understanding photochemical reaction mechanisms.