Scientists observe ultrafast chemistry in water caused by ionising radiation for the first time

An international research team jointly led by Nanyang Technological University, Singapore (NTU Singapore), the U.S. Department of Energy’s (DOE) Argonne National Laboratory and Germany’s Deutsches Elektronen-Synchrotron (DESY) has for the first time observed the ultrafast formation and then breakdown of the water ion that is created when water is exposed to ionising radiation.

The water ion plays a crucial role in many chemical reactions, but has never been directly observed due to its extremely short lifetime.

When ionising radiation with enough energy hits water molecules (H2O), it forcefully strips an electron away from them, creating the water ion known as the highly unstable radical cation (H2O+). The entire process occurs in just 50 femtoseconds (50 quadrillionths of a second, or 0.000 000 000 000 05 of a second).

Scientists believe that the H2O+ radical is the first chemical species in a long cascade of chain reactions that can eventually lead to radiation damage in biological tissue.

Published today in Science, the clocking of this chemical reaction in ionised water was the result of an international collaboration between NTU Singapore and partners.

Lead author NTU Associate Professor Loh Zhi-Heng, whose group at the School of Physical and Mathematical Sciences has studied the ultrafast dynamics of ionising molecules using ultrafast lasers for the past nine years, said, “What we are observing is like the prequel to radiation damage – the very first chemical reaction which leads to subsequent chemical reactions that lead to what scientists have classified as radiation damage. If we can fully understand how this chemical reaction happens, then finding a way to stop or reverse this reaction could pave the way towards stopping or reducing radiation damage in biological cells.”