For the first time, an international team has tracked at BESSY II how heavy molecules – in this case bromochloromethane – disintegrate into smaller fragments when they absorb X-ray light. Using a newly developed analytical method, they were able to visualise the ultrafast dynamics of this process. In this process, the X-ray photons trigger a “molecular catapult effect”: light atomic groups are ejected first, similar to projectiles fired from a catapult, while the heavier atoms – bromine and chlorine – separate more slowly.
When X-rays hit molecules, they can knock electrons out of certain orbitals and into extremely high-energy states, breaking chemical bonds. This often happens ultra rapidly, in just a few femtoseconds (10-15 s). While this phenomenon has been studied in light molecules such as ammonia, oxygen, hydrochloric acid or simple carbon compounds, it has hardly been studied in molecules with heavier atoms.
A team from France and Germany has now studied the rapid decay of molecules containing halogens. They focused on a molecule in which bromine and chlorine atoms are linked by a light bridge – an alkylene group (CH2). The measurements were made at the XUV beamline of BESSY II.
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Image: The X-ray photons trigger a ‘molecular catapult effect’: light atomic groups are ejected first, similar to projectiles shot from a catapult, while the heavier atoms – bromine and chlorine – separate much more slowly. The image was printed on the cover of “The Journal of Physical Chemistry Letters”.
Credit: The Journal of Physical Chemistry Letters