Speaker
Description
Swift heavy ion (SHI) irradiation creates unique extreme conditions because each ion deposits a large amount of energy within a localized region [1,2]. Such intense excitation can induce local melting, amorphization, defect formation, phase transformations, and rapid recrystallization [1]. An important consequence is the modification of interatomic bonding and the local chemical environment, particularly in molecular crystals held together by weak intermolecular interactions. We have demonstrated that the combination of high pressure and SHI irradiation can strongly modify the bonding and structural configurations of molecular solids, such as carbon monoxide (CO), urea, and sulfur (S) [3]. Where SHI irradiation induced polymerization of CO, decomposition and disordering of urea, and ring-opening polymerization of S₈.
We have also investigated the effects of SHI irradiation on sp²-bonded conjugated systems, including benzene and graphite, under high pressure [4]. In benzene, we observed irradiation-induced amorphization of the molecular crystal at pressures substantially below those required for the corresponding phase transition without irradiation. In graphite, SHI irradiation resulted in the formation of amorphous carbon with grain sizes of only a few nanometers, accompanied by partial conversion of the carbon atoms from sp² to sp³ hybridization.
Overall, our results demonstrate that SHI irradiation provides a kinetically controlled pathway for driving molecular and carbon-based solids toward structural and chemical states that may not be accessible through pressure alone.
We acknowledge funding from the BMBF (05K22RF3, 05K25RF3) and the DFG (BA4020, WI1232).
[1] M. Lang et al., Comprehensive Nuclear Materials, 2020, 485-516
[2] I. Tzifas et al., Physical Review Research 8, 2026, 023054
[3] L. Jiaxu, et al., Phys. Chem. Chem. Phys., 2026, 28, 7835
[4] L. Jiaxu, et al., in preparation, 2026