Resonance structure in charge transfer cross sections: an application to the N3++H to N2++H+reaction (original) (raw)
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Journal of Physics B Atomic and Molecular Physics
We have computed the cross section for charge transfer from atomic hydrogen to the excited 3s level of doubly charged nitrogen, triply charged nitrogen and atomic hydrogen at very low relative collision energies (mcv). A rich resonance structure is found and interpreted in terms of quasi-bound states associated with the classical phenomenon of orbiting. Possible experimental verification of the resonance structure is discussed.
Electron capture in collisions of with H and with C
Journal of Physics B: Atomic, Molecular and Optical Physics, 1998
Charge transfer processes due to collisions of N + with atomic hydrogen and H + with atomic nitrogen are investigated using the quantum-mechanical molecular-orbital close-coupling (MOCC) method. The MOCC calculations utilize ab initio adiabatic potentials and nonadiabatic radial and rotational couplings obtained with the multireference single-and double-excitation configuration interaction approach. Total and state-selective cross sections for the energy range 0.1 meV/u -1 keV/u are presented and compared with existing experimental and theoretical data. A large number of low-energy resonances are obtained for exoergic channels and near thresholds of endoergic channels. Rate coefficients are also obtained and comparison to previous calculations suggests nonadiabatic effects dominate for temperatures greater than 20,000 K, but that the spin-orbit interaction plays a major role for lower temperatures.
Resonant charge exchange involving electronically excited states of nitrogen atoms and ions
Physical Review A, 2006
Within the framework of the asymptotic theory the matrices for the exchange interaction potentials of the nitrogen ion, with electron shell p 2 , and nitrogen atom, with electron shell p 3 , are constructed. The hierarchy of interactions in the nitrogen molecular ion at large internuclear distances is constructed for different electronic states. On the basis of these interaction potentials, the cross sections of resonant charge exchange in slow collisions are evaluated for different values of electron momentum projections and then averaged over these momentum projections. The mobilities of nitrogen ions in atomic nitrogen are also derived.
Charge transfer in low-energy collisions of H with He+and H+with He in excited states
Journal of Physics B: Atomic, Molecular and Optical Physics, 2018
We present a theoretical study of charge transfer in collisions of excited (n = 2, 3) hydrogen atoms with He + and in collisions of excited (n = 2, 3) helium atoms with H +. A combination of a fully quantum-mechanical method and a semi-classical approach is employed to calculate the chargeexchange cross sections at collision energies from 0.1 eV/u up to 1 keV/u. These methods are based on accurate ab initio potential energy curves and non-adiabatic couplings for the molecular ion HeH +. Charge transfer can occur either in singlet or in triplet states, and the differences between the singlet and triplet spin manifolds are discussed. The dependence of the cross section on the quantum numbers n and l of the initial state is demonstrated. The isotope effect on the charge transfer cross sections, arising at low collision energy when H is substituted by D or T, is investigated. Finally, the impact of the present calculations on models of laboratory plasmas is discussed.
Charge transfer in H + He$^+$ and H$^+$ + He collisions in excited states
arXiv: Atomic Physics, 2018
We present a theoretical study of charge transfer in collisions of excited ($n=2,3$) hydrogen atoms with He$^+$ and in collisions of excited ($n=2,3$) helium atoms with H$^+$, extending the results of Phys. Rev. A 82 012708 (2010). A combination of quantum-mechanical and semi-classical approaches is employed to calculate the charge-exchange cross sections at collision energies from 0.1 eV/u up to 1 keV/u. These methods are based on accurate ab initio potential energy curves and non-adiabatic couplings for the molecular ion HeH$^+$. Charge transfer can occur either in singlet or in triplet states, and the differences between the singlet and triplet spin manifolds are discussed. The dependence of the cross section on the quantum numbers nnn and lll of the initial state is demonstrated. The isotope effect on the charge transfer cross sections, arising at low collision energy when H is substituted by D or T, is investigated. Finally, the impact of the present calculations on models of l...
Electron Capture in collisions of C+ with H and H+ with C
Journal of Physics B Atomic Molecular and Optical Physics
Charge transfer processes due to collisions of N + with atomic hydrogen and H + with atomic nitrogen are investigated using the quantum-mechanical molecular-orbital close-coupling (MOCC) method. The MOCC calculations utilize ab initio adiabatic potentials and nonadiabatic radial and rotational couplings obtained with the multireference single-and double-excitation configuration interaction approach. Total and state-selective cross sections for the energy range 0.1 meV/u -1 keV/u are presented and compared with existing experimental and theoretical data. A large number of low-energy resonances are obtained for exoergic channels and near thresholds of endoergic channels. Rate coefficients are also obtained and comparison to previous calculations suggests nonadiabatic effects dominate for temperatures greater than 20,000 K, but that the spin-orbit interaction plays a major role for lower temperatures.
The Journal of Chemical Physics
The non-adiabatic quantum dynamics of the H+H + 2 → H 2 + H + charge transfer reactions, and some isotopic variants, is studied with an accurate wave packet method. A recently developed 3×3 diabatic potential model is used, which is based on very accurate ab initio calculations and includes the long-range interactions for ground and excited states. It is found that for initial H + 2 (v=0), the quasi-degenerate H 2 (v'=4) non-reactive charge transfer product is enhanced, producing an increase of the reaction probability and cross section. It becomes the dominant channel from collision energies above 0.2 eV, producing a ratio, between v'=4 and the rest of v's, that increases up to 1 eV. H+H + 2 → H + 2 + H exchange reaction channel is nearly negligible, while the reactive and non-reactive charge transfer reaction channels are of the same order, except that corresponding to H 2 (v'=4), and the two charge transfer processes compete below 0.2 eV. This enhancement is expected to play an important vibrational and isotopic effect that need to be evaluated. For the three proton case, the problem of the permutation symmetry is discussed when using reactant Jacobi coordinates.
Physical Review A, 1995
Total cross sections for electron transfer, target excitation, and ionization processes are reported for the H++Na(3s) and H++Na(3p) systems at 1-100 keV impact energies. We have employed a twocenter coupled-Sturmian-pseudostate approach that has recently been developed and applied to several quasi-one-electron systems by Winter [Phys. Rev. A 48, 3706 (1993)]. The Sturmian basis set, together with an analytic Hartree-Fock potential, are chosen carefully so that all three channels (transfer, excitation, and ionization) are represented properly. We also discuss briefly the effects of the binding-energy correction on the calculated cross sections. We find that our various cross sections (0" p 0 p o p', and the A2o alignment pa~~met~~for Na{3s 3p)~o~p~~~very well with most of the available experimental data, as well as with previous theoretical results. For all the above quantities, when a comparison is made between theory and measurement, our results are equally good or better than the earlier calculations employing different theoretical approaches. We still find a persistent discrepancy between theory (present as well as previous calculations) and measurements for the electron transfer cross sections into the metastable state of the H atom (o."'"'). Our results for the orientation and alignment effects in the electron transfer process of H++Na(3p} collisions are in good qualitative accord with recent observations and previous theoretical studies. In particular, we see a strong enhancement for the H(n + 3) capture cross sections in the H++Na(3p) collisions. The H(n =2) production cross sections in the H++ Na(3p) collisons follow a roughly similar trend, as observed experimentally when plotted against the impact energy.
Electron capture from excited alkali atoms by H+ at low energies
Journal of Molecular Structure: THEOCHEM, 1996
Charge-transfer cross sections from the initially aligned np-state of alkali atoms by protons have been calculated in the 10 eV to 5 keV amu -1 energy region. The semiclassical impact-parameter method is employed wherein a coupled molecular states expansion, augmented by the plane wave electron translation factor, is used to represent the electronic wave functions. The dependence of the cross section for the formation of the first excited (n = 2/) states of H, on the orbital geometry and the alignment of the initial state, is discussed. The cross sections are sensitive to the variation of the spatial alignment of the electron charge distribution. The cross section decreases with increasing initial alignment at lower energies, and at higher energies, the situation is reversed. At E = 0.05 keV amu -1, the cross section is isotropically aligned. At this energy, the cross section is the same for both the initial states ~; and 1-I. The orientation of the excited H(2p) orbital resulting from electron capture is also given. * Corresponding author. resonant charge transfer processes. In surface scattering, a prior knowledge of these effects is very crucial.
Long-range interactions of hydrogen atoms in excited states. III. nS−1S interactions for n≥3
Physical review, 2017
The long-range interaction of excited neutral atoms has a number of interesting and surprising properties, such as the prevalence of long-range, oscillatory tails, and the emergence of numerically large van der Waals C6 coefficients. Furthermore, the energetically quasi-degenerate nP states require special attention and lead to mathematical subtleties. Here, we analyze the interaction of excited hydrogen atoms in nS states (3 ≤ n ≤ 12) with ground-state hydrogen atoms, and find that the C6 coefficients roughly grow with the fourth power of the principal quantum number, and can reach values in excess of 240 000 (in atomic units) for states with n = 12. The nonretarded van der Waals result is relevant to the distance range R ≪ a0/α, where a0 is the Bohr radius and α is the fine-structure constant. The Casimir-Polder range encompasses the interatomic distance range a0/α ≪ R ≪ c/L, where L is the Lamb shift energy. In this range, the contribution of quasi-degenerate excited nP states remains nonretarded and competes with the 1/R 2 and 1/R 4 tails of the pole terms which are generated by lower-lying mP states with 2 ≤ m ≤ n − 1, due to virtual resonant emission. The dominant pole terms are also analyzed in the Lamb shift range R ≫ c/L. The familiar 1/R 7 asymptotics from the usual Casimir-Polder theory is found to be completely irrelevant for the analysis of excited-state interactions. The calculations are carried out to high precision using computer algebra in order to handle a large number of terms in intermediate steps of the calculation, for highly excited states.