Scientists have used intense X-rays to visualize how powerful lasers cause the buckyball molecule, C60, to expand, fragment, and lose electrons. The experiment, conducted at the SLAC National Accelerator Laboratory, reveals key stages of molecular response at different laser intensities. Findings highlight gaps in current models for predicting molecular behavior under extreme light.
Researchers from the Max Planck Institute for Nuclear Physics in Heidelberg, the Max Planck Institute for the Physics of Complex Systems in Dresden, and the Max Born Institute in Berlin, along with international collaborators, exposed Buckminsterfullerene (C60) to strong infrared laser pulses. Using ultrashort X-ray pulses from the Linac Coherent Light Source (LCLS) at SLAC, they captured real-time diffraction patterns to track the molecule's transformation.
The analysis focused on two parameters from the X-ray diffraction: the average molecular radius R, indicating expansion or deformation, and the Guinier amplitude A, which relates to the squared effective number of scattering atoms and reveals fragmentation.
At low laser intensity, C60 first expands without immediate breakup, shown by an initial increase in R followed by a delayed drop in A as fragmentation begins modestly.
At intermediate intensity, expansion precedes a radius reduction in images, signaling scattering from smaller fragments, corroborated by a slightly delayed Guinier amplitude decline.
At the highest intensity, rapid expansion occurs alongside an immediate Guinier amplitude drop at the pulse's start, indicating swift stripping of outer valence electrons. Theoretical models replicate this 'kick' effect but fail to predict observed behaviors at lower intensities, such as absent oscillations from molecular 'breathing' motions. Incorporating ultrafast heating in models better aligns predictions with data, underscoring the need for refined quantum treatments of multi-electron dynamics in complex molecules.
These insights, detailed in a 2025 Science Advances paper, advance understanding of light-driven chemical reactions and test quantum processes in polyatomic systems.