Alignment of H(2p) in collisions of protons and antiprotons with hydrogen atoms with screened Coulomb interaction

The effects of screened Coulomb interaction on the alignment of H(2p) state produced in collisions of hydrogen atoms with protons and antiprotons are investigated in the energy range 1–200 keV by using the two-center atomic orbital close-coupling (TC-AOCC) method. It is shown that the decrease of the binding energy of hydrogen nl-states and the reduction of the number of bound states with increasing the strength of the screening affect significantly the alignment degree and its energy dependence. In the case of antiproton-H collision the difference between the alignments with screened and unscreened Coulomb potential increases with increasing the strength of the screening in the entire energy range above 2 keV/u, while in the case of proton-H collision it does so only in the energy range 5–25 keV/u

Electron capture and excitation in H

The processes of state-selective electron capture and excitation in proton collisions with Li+(1s2 1S) and Li+(1s2s 1,3S) ions are studied by using the two-center atomic orbital close-coupling (TC-AOCC) methods in the energy range 2.5–800 keV. The interaction of the active electron with the Li2+ ion core is represented by model potentials that reproduce the energies of excited singlet and triplet states of Li+ with accuracy better than 2%. The expansion basis in the coupled state calculations includes all states with n ≤ 8 (in total 120 states) centered on each of the colliding centers. Total and state-selective electron capture and excitation cross sections to final states with n ≤ 4 are presented. The physical mechanisms involved in the dynamics of considered processes are discussed in detail. The reported cross sections should be useful in the kinetic modeling and diagnostics of fusion reactor plasmas with liquid lithium divertors

Electron capture, excitation and ionization processes in He

Electron capture, excitation and ionization processes in He2+–H collisions taking place in quantum plasmas are studied by employing the two-center atomic orbital close coupling (TC-AOCC) method. The Debye-Hückel-cosine (DHC) potential is used to describe the plasma screening effects on the Coulomb interaction between charged particles. The properties of eigenenergies of hydrogen-like atom with DHC potential are investigated as function of the screening length of the potential. It is found that the binding energies of nl states decrease with decreasing the screening length of the potential. The dynamics of excitation, electron capture and ionization processes in He2+–H collision system is investigated when the screening length of the potential varies for a wide collision energy range. The TC-AOCC cross sections are compared with those for the pure Coulomb potential and, for the total electron capture, with the results of classical trajectory Monte Carlo method

Collision processes of hydrocarbon species in hydrogen plasmas 3: The silane family

Cross sections are provided for most important collision processes of the Silicon-Hydrides from the "Silane-family": SiH$_{y}$ (y = 1 - 4) molecules and their ions SiH$^{+}_{y}$, with (plasma) electrons and protons. The processes include: electron impact ionization and dissociation of SiH$_{y}$, dissociative excitation, ionization and recombination of SiH$^{+}_{y}$ ions wich electrons, and charge - and atom - exchange in proton collisions with SiH$_{y}$. All important channels of dissociative processes are considered. Information is also provided an the energetics (reactants/products energy loss / gain) of each individual reaction channel. Total and partial cross sections are presented in compact analytic forms. The critical assessment of data, derivation of new data and presentation of results follow closely the concepts of the recently published related databases for Carbon-Hydrides, namely for the Methane family [1, 2], and for the Ethane- and the Propane families [3], respectively

Cross sections for electron capture and excitation in proton collisions with the metastable Be(2s2p

The two-center atomic orbital close-coupling method is employed to study electron capture and excitation processes in proton collisions with the metastable Be(1s2s2p P) atom. The interaction of the active electron with the Be ion core is represented by a model potential reproducing accurately (to within 3.5%) the energies of triplet excited states Be(1s2snl L) (at least up to n = 7). The excitation and state-selective electron capture cross sections up to the n = 5 shells of both centers are calculated in the energy range 1–200 keV/u using an expansion basis involving all the states with n ≤ 7 on H and all triplet states with n ≤ 7 on Be, augmented with a number of pseudostates. In the energy region below ~10 keV/u, the cross sections of both processes exhibit oscillatory structures, resulting from the multistate coupling accounted for in the dynamical model. It has been found that the magnitude of excitation cross sections above ~10 keV/u is dominated by the multipole interactions, while below this energy the excitation process proceeds through intermediate electron capture states

Collision processes of hydrocarbon species in hydrogen plasmas I : the methane family

Cross sections and rate coefficients are provided for collision processes of CH$_{y}$ and CH$^{+}_{y}$ (1$\le$y$\le$4) hydrocarbon species with electrons and protons in a wide range of collision energy and temperature. The considered processes include: electron impact ionisation and dissociation of CH$_{y}$, dissociative excitation, ionisation and recombination of CH$^{+}_{y}$ wich electrons, and charge- and atom exchange in proton collisions with CH$_{y}$. In dissociative processes all important reaction channels are considered separately. Information is also provided about the energetics for each individual reaction channel. The cross sections and rate coefficients are represented in analytic fit forms

Collision processes of hydrocarbon species in hydrogen plasmas II : the ethane and propane families

Cross sections and rate coefficients are provided for collision processes of electrons and protons with C$_{x}$H$_{Y}$ and C$_{x}$H$^{+}_{y}$ (x = 2,3; 1 $\le$ y $\le$ 2x + 2) hydrocarbon species in a wide range of collision energies and plasma (gas) temperatures. The considered processes include: electron-impact ionization and dissociation of C$_{x}$H$_{y}$, dissociative excitation, ionization and recombination of C$_{x}$H$_{y}$ with electrons, and both charge transfer and atom exchange in proton channels are considered separately. Information is also provided for the energies of each individual reaction channel. The cross sections and rate coefricients are presented in compact analytic forms

Collision processes in low-temperature hydrogen plasmas

Collision processes among the constituents of low-temperature hydrogen plasmas (e, H, H$^{+}$, H$^{-}$, H$_{2}$ , H$^{+}_{2}$, H$^{+}_{3}$) play a key role in technical plasma applications as well as in the boundary regions of magnetically confined fusion plasmas. In this work a review of the current knowledge on their cross sections is presented. Collision processes of electronically and vibrationally excited species are also included in the present review. The energy range in which these processes are considered extends from thermal energies to several hundreds electronvolts (and to the keV region for some heavy-particle collision processes). The available experimental and theoretical cross section information is critically assessed and presented in form of analytic fit functions, convenient for use in plasma applications

Antiproton-impact ionization of hydrogen atom with Yukawa interaction

The process of ionization of hydrogen atom by antiproton impact is studied when the interparticle interactions in the system are described by screened interactions of Yukawa type. The collision dynamics is described by the semiclassical atomic-orbital close-coupling method in which the bound atomic states and positive energy continuum pseudostates are determined by diagonalization of target Hamiltonian in a sufficiently large even-tempered basis to ensure convergence of the results at each value of the screening length λ of the interaction. With decreasing the screening length, the bound states in the Yukawa potential become unbound, thus increasing the number of continuum pseudostates. At low collision energies, this leads to the increase of the ionization cross section. It is observed that the energies of pseudostates, generated by the exit of nl bound states in the continuum, at certain critical values λnlc exhibit series of avoided crossings when λ is varied. The avoided crossings appear between the (n + k) l and (n + k + 1) l (n = 1, 2, 3, … ; k = 0, 1, 2, …) states at screening lengths close to the critical screening length λnlc. The avoided crossings become increasingly less pronounced with increasing n, k and l. The matrix elements for the (n + k) l - (n + k + 1) l transitions at the avoided crossings λx,(n+k)l(n+k+1)l exhibit maxima and are reflected in the structure of the cross sections for population of the lower nl pseudostates. These structures are, however, smeared out in the total ionization cross section