Fragmentation of methane molecules by antiproton impact

Extending previous work for proton impact [1], we have investigated the fragmentation of methane molecules due to collisions with antiprotons in the 25 keV to 5 MeV impact energy range. The multi-center nature of the problem is addressed by using a spectral representation of the molecular Hartree-Fock-level Hamiltonian and a single-center expansion of the initially populated molecular orbitals. The two-center basis generator method (TC-BGM) is used for orbital propagation. Electron-removal cross sections obtained from the TC-BGM solutions are complemented with a dynamical decay-route fragmentation model [2] to calculate cross sections for the production of fragment ions. Good agreement with the available experimental data [3] is observed for CH$_4^+$, CH$_3^+$, CH$_2^+$ and CH$^+$. [1] A. Salehzadeh and T. Kirchner, J. Phys. Conf. Ser. \textbf{635}, 032077 (2015). [2] H. Luna \textit{et al.}, J. Phys. B \textbf{36}, 4717 (2003). [3] H. Knudsen \textit{et al.}, J. Phys. B \textit{28}, 3569 (1995).