Researchers in Japan have captured an extraordinarily fast electronic transformation inside a metal-organic framework, observing a fleeting state and the hidden state that followed within just 30 femtoseconds. The team from Science Tokyo, Tohoku University, and Nagoya Institute of Technology combined ultrafast laser spectroscopy with theoretical calculations to uncover a previously unknown intermediate electronic state that helps drive the transformation. The discovery offers new clues about how light could eventually be used to rapidly control the properties of advanced materials.
Materials can behave in unexpected ways after absorbing light. In some cases, light pushes them into photoinduced states with properties that are very different from those they display under ordinary conditions. These states give researchers another way to alter material behavior beyond conventional approaches such as heating or cooling. Learning exactly how they form could be important for developing future photoresponsive materials and advanced optical technologies.
Capturing a Transformation in Femtoseconds
One of the biggest challenges is speed. The first steps in forming a photoinduced state can unfold on the femtosecond (fs) timescale (a millionth of a billionth of a second), making them exceptionally difficult to observe.
To investigate these earliest moments, a team led by Assistant Professor Tadahiko Ishikawa from the Department of Chemistry, School of Science, Institute of Science Tokyo (Science Tokyo), Japan, worked with then doctoral student Samiran Banu (currently a Special Postdoctoral Researcher at RIKEN) and collaborators at Tohoku University and Nagoya Institute of Technology, Japan.
The researchers focused on a metal-organic framework (MOF), a material constructed by connecting metal ions with organic molecules. Their goal was to determine exactly how a photoinduced hidden state develops. The findings were published in the journal Physical Review Letters.
"We found that the photoinduced hidden state forms within 30 fs through a previously unknown intermediate electronic state," says Ishikawa.
Ultrafast Lasers Reveal a Hidden State
