Aromatic molecules revisited under bare helium collision: experiment and theory

WANIA WOLFF; LUCIA H. COUTINHO; FABIO R. DE ALMEIDA; VOLKER DANGENDORF; GEHARD HILGERS; ULRICH GIESEN; ALEJANDRA MENDEZ; LÓPEZ, SEBASTIÁN; CLAUDIA MONTANARI

MATSUE, SHIMANE

Conferencia; HCI 2022; 2022

KUNIBIKI MESSE

Aromatic molecules are of multidisciplinary interest such as in bio-, atmospheric-, and astrochemistry, and are considered resistant to fragmentation to ion-impact in theintermediate energy range. Pyrimidine (C4 H4 N2), pyridine (C5 H5 N), and benzonitrile (C6 H5 CN) were selected respectively as representative molecules in the related fields.The relevance of measuring the ionization and subsequent fragmentation of suchmolecules has been stressed in many works associated with hadron-therapy [1] , cloudformation [2], and aromatic hydrocarbon formation in the interstellar medium [3] . Here, we report the ionization and fragmentation of aromatic molecules under bare helium collision over a wide range of impact energies, 700 up to 6000 keV, using pulsed beams and extraction fields combined with a high-resolution time-of-flight spectrometer. There are few fragmentations studies on aromatic molecules following energetic ion interaction.Previously, fragmentation cross sections were measured for pyrimidine under protonimpact for energies from 300 keV to 16000 keV 1. Searching for charge effects on theionization and break-up channels we compared the He2+ data with those measured of 50to 150 keV protons and 20 to 2000 keV electrons colliding on these aromatic molecules.To understand the general behaviour of ion-aromatic cross sections we includedtheoretical results for the single ionization and electron capture of these species bycombining the atomic cross section of its constituents with a stoichiometric approach [4] .These atomic values were obtained within CTMC and CDW-EIS methods and areexamined to probe the importance of the electron capture phenomena at impact energiesranging from 25 keV to 250 keV. The derived data from this study can help to improvethe estimates of astrophysical, biological and atmospheric models.[1] Rudek, B., Arndt, A., Bennett, D. et al. Ion induced fragmentation cross-sections of DNA constituents. Eur. Phys. J. D 69, 237 (2015). doi: 10.1140/epjd/e2015-60204-7[2] Bibang, P.C.J., Agnihotri, A.N., Boduch, P. et al. Radiolysis of pyridine in solidwater. Eur. Phys. J. D 75, 57 (2021). doi: 10.1140/epjd/s10053-021-00058-y[3] Brett A. Mcguire, Andrew M. Burkhardt, Sergei Kalenskii, Christopher N.Shingledecker et al. Detection of the aromatic molecule benzonitrile (c-C6H5CN) in theinterstellar medium, Science 359, 202 (2018) doi: 10.1126/science. aao4890[4] Mendez A. M. P., Montanari C. C., Miraglia J. E. Ionization of biological molecules by multicharged ions using the stoichiometric model, J. Phys. B: At. Mol. Opt. Phys. 53 (2020) 055201. https://doi.org/10.1088/1361-6455/ab6052