Theoretical investigations of collision dynamics of cytosine by low-energy (150–1000 eV) proton impact**Project supported by the National Natural Science Foundation of China (Grant Nos. 11905160 and 11635003) and the Natural Science Foundation of Jiangsu Province of China (Grant No. BK20160199).

Abstract

Using a real-space real-time implementation of time-dependent density functional theory coupled to molecular dynamics (TDDFT-MD) nonadiabatically, we theoretically study both static properties and collision process of cytosine by 150–1000 eV proton impact in the microscopic way. The calculated ground state of cytosine accords well with experiments. It is found that proton is scattered in any case in the present study. The bond break of cytosine occurs when the energy loss of proton is larger than 22 eV and the main dissociation pathway of cytosine is the breaks of C1N2 and N8H10. In the range of 150 eV ≤ Ek ≤ 360 eV, when the incident energy of proton increases, the excitation becomes more violent even though the interaction time is shortened. While in the range of 360 eV < Ek ≤ 1000 eV, the excitation becomes less violent as the incident energy of proton increases, indicating that the interaction time dominates mainly. We also show two typical collision reaction channels by analyzing the molecular ionization, the electronic density evolution, the energy loss of proton, the vibration frequency and the scattering pattern detailedly. The result shows that the loss of electrons can decrease the bond lengths of C3N8 and C5N6 while increase the bond lengths of C4H11, C5H12 and C4C5 after the collision. Furthermore, it is found that the peak of the scattering angle shows a little redshift when compared to that of the loss of kinetic energy of proton.