Research
Enhanced multiple ionisation partial cross-sections for coronene (C24H12) in collisions with fast O ions- By Dr. A. N. Agnihotri
Multiple ionization and fragmentation of a large polycyclic aromatic hydrocarbon (PAH) molecule, i.e. coronene (C24H12) under the impact of fast (1.5–5.5 MeV/u) O ions are investigated as a function of the perturbation strength (charge state/velocity). The mass spectra from a Wiley-McLaren type time-of-flight mass spectrometer have been measured for different energy and charge state of the projectile. We have observed a dramatically large enhancement in the ratios (2+/1+) of doubly-to-singly charged parent recoil ion yields and similarly in the 3+/1+ recoil ion ratios which are discussed in the context of highly correlated electrons in the PAH and resulting collective excitations in coronene. These ratios are well-reproduced by a classical over-the-barrier (COB) model. The nearly linear dependence of the measured cross-sections on the projectile charge state is linked to the collective plasmon excitation in the coronene molecule based on a model originally developed for the fullerene. The measured absolute cross sections, obtained using a novel normalization technique, based on complementary electron spectroscopy experiments, are compared with the CTMC-COB (Classical trajectory Monte Carlo calculations including classical over-the-barrier model), as well as with a more sophisticated state-of-the-art quantum-mechanical CDW-EIS (continuum distorted wave eikonal initial state) model. The absolute partial cross sections for the singly, doubly and triply ionized recoil-ions exhibit a good quantitative agreement with the CDW-EIS calculations - a step toward the development of quantum mechanical model for such large molecule. The present observation will also have implications towards the study of astrochemistry of the interstellar medium.
Link : https://10.1088/1402-4896/ae26f3, 5 January 2026
Contact Details
ADITYA N. AGNIHOTRI
Department of Physics,
agnihotri@physics.iitd.ac.in