We present scaling laws for absolute cross sections for non-statistical fragmentation in collisions between Polycyclic Aromatic Hydrocarbons (PAH/PAH(+)) and hydrogen or helium atoms with kinetic energies ranging from 50 eV to 10 keV. Further, we calculate the total fragmentation cross sections (including statistical fragmentation) for 110 eV PAH/PAH(+) + He collisions, and show that they compare well with experimental results. We demonstrate that non-statistical fragmentation becomes dominant for large PAHs and that it yields highly reactive fragments forming strong covalent bonds with atoms (H and N) and molecules (C6H5). Thus nonstatistical fragmentation may be an effective initial step in the formation of, e.g., Polycyclic Aromatic Nitrogen Heterocycles (PANHs). This relates to recent discussions on the evolution of PAHNs in space and the reactivities of defect graphene structures.
In this paper, we establish an initial theory regarding the Second Order Asymptotical Regularization (SOAR) method for the stable approximate solution of ill-posed linear operator equations in Hilbert spaces, which are models for linear inverse problems with applications in the natural sciences, imaging and engineering. We show the regularizing properties of the new method, as well as the corresponding convergence rates. We prove that, under the appropriate source conditions and by using Morozov's conventional discrepancy principle, SOAR exhibits the same power-type convergence rate as the classical version of asymptotical regularization (Showalter's method). Moreover, we propose a new total energy discrepancy principle for choosing the terminating time of the dynamical solution from SOAR, which corresponds to the unique root of a monotonically non-increasing function and allows us to also show an order optimal convergence rate for SOAR. A damped symplectic iterative regularizing algorithm is developed for the realization of SOAR. Several numerical examples are given to show the accuracy and the acceleration affect of the proposed method. A comparison with other state-of-the-art methods are provided as well.
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