Spin-Vibronic Mechanism for Intersystem Crossing.

Area of Science:

• Quantum Chemistry
• Molecular Spectroscopy
• Chemical Physics

Background:

• Intersystem crossing (ISC) is a key process in excited state decay, traditionally explained by spin-orbit coupling.
• Standard models often assume vibrational motion and internal conversion occur on different timescales than ISC.
• These assumptions are limiting, as spin, electronic, and vibrational dynamics are often coupled.

Purpose of the Study:

• To review the theory and principles of the spin-vibronic mechanism for ISC.
• To provide empirical rules for estimating ISC rates.
• To discuss recent advancements in experimental and theoretical methods for studying spin-vibronic ISC.

Main Methods:

• Theoretical framework development for spin-vibronic coupling.
• Empirical rule formulation for ISC rate estimation.
• Review of advanced femtosecond spectroscopy and high-level computational methods.

Main Results:

• The spin-vibronic mechanism reveals that spin, electronic, and vibrational dynamics are often interdependent.
• Spin-vibronic levels provide a more accurate description than simplified Jablonski diagrams.
• Recent advances enable detailed investigation of ISC in various molecular systems.

Conclusions:

• The spin-vibronic mechanism is essential for a comprehensive understanding of ISC, impacting chemistry, physics, and biology.
• Accurate ISC rate prediction requires considering the interplay of spin, electronic, and vibrational motions.
• Interdisciplinary research leveraging advanced theory and experiments continues to illuminate ISC phenomena.