Internal conversion induced by external electric and magnetic fields.

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Photophysics

Background:

• Internal conversion (k_IC) is a crucial photophysical process affecting molecular excited-state lifetimes.
• External electric and magnetic fields can potentially influence molecular electronic properties and dynamics.
• Understanding field-induced effects is vital for interpreting experiments involving strong fields.

Purpose of the Study:

• To develop a methodology for calculating electric and magnetic field contributions to internal conversion rate constants (k_IC).
• To quantify the impact of these fields on k_IC for representative molecules.
• To assess the relevance of these effects in various experimental contexts.

Main Methods:

• Development of a novel theoretical framework to compute field-induced contributions to k_IC.
• Application of the methodology to seven diverse molecular systems.
• Estimation of k_IC-E and k_IC-M contributions at varying field strengths.

Main Results:

• External electric fields (k_IC-E) can significantly enhance k_IC, often matching the field-free rate at 10^11 V m^-1.
• For specific molecules (e.g., indocyanine green), substantial k_IC-E effects are observed even at 10^9 V m^-1.
• Magnetic field contributions (k_IC-M) to k_IC are negligible under terrestrial conditions but significant in extreme astrophysical environments.

Conclusions:

• The influence of electric fields on k_IC must be considered in photophysical calculations for experiments using strong fields (e.g., plasmonics, laser-field studies).
• The impact of magnetic fields on k_IC is generally negligible on Earth but relevant for astrophysical phenomena near neutron stars and white dwarfs.
• This work provides a new tool for predicting and understanding field-dependent photophysical processes.