In the ever-evolving world of science, theories from the past sometimes need a modern revisit. A perfect example is the work of Atkins and Evans from 1975, which explored the interaction of magnetic fields with luminescent solutions. This theory has become more important in recent times, especially for the development of upconversion processes in solar energy and optoelectronic applications.
Upconversion is a process where two low energy photons of light combine to produce one high-energy photon. The science behind this involves molecules that are excited to higher energy states through the absorption of light. The intriguing part is that these molecular states have unique spin properties that are influenced by magnetic fields, providing scientists with a method to understand and optimise this process.
Back in the 1970s, Atkins and Evans created a groundbreaking theory describing how this upconversion worked in liquid solutions. Their theory explained how the brightness of the resulting light depended on the strength of a magnetic field.
Fast forward to the 21st century, and advancements in technology, such as the ability to demonstrate upconversion using sunlight instead of lasers, have brought renewed attention to this field. This fresh interest has also shed light on some discrepancies and limitations in the original Atkins & Evans theory.
Using contemporary tools and understanding of quantum mechanics, Exciton Science researchers based at RMIT University, led by PhD student Roslyn Forecast and Professor Jared Cole, have revisited and enhanced the Atkins & Evans model. This modern approach not only rectifies some of the issues from the original theory but also provides new insights.
While the original theory primarily focused on light emission during upconversion, the updated approach provides insights into "optically-dark states", which are harder to observe but can now be studied using advanced techniques such as electron spin resonance spectroscopy.
“We've reformulated the seminal theory of Atkins & Evans to make it more accessible to modern readers and extended the theory to describe magnetic field effects in dark states, which can now be interrogated experimentally,” Roslyn said.
“We’ve provided a simple set of equations which experimentalists can use to model magneto-photoluminescence experiments.”
The realm of upconversion processes is expanding, and thanks to Roslyn and her collaborators, so is our understanding of it.
By revisiting older theories with modern tools, scientists are paving the way for advancements in solar energy and lighting.
The magnetic field's influence on these processes remains a central theme, reinforcing its significance in the broader scientific landscape.
Dr Francesco Campaioli of the University of Padua in Italy, a co-author of the work, said: “Magnetic fields are one of the best ways we have to study these processes, and to understand if and how they are happening, so that we can improve them for a specific application.”
The results have been published in the Journal of Chemical Theory and Computation.