Under läsåret 2023/24 undervisar jag i kurserna Atom och molekylfysik (FK5023) och Avancerad Kvantmekanik (FK5027).

Jag har tidigare också undervisat i kurser såsom Kvantmekanik, Molekylfysik, Fysik på basåret samt akustik och fysik för adiologer.

Jag utför beräkningar av molekylära processer som har gemensamt att högt exciterade tillstånd är inblandade. De olika frihetsgraderna i systemet koppas då samman och molekyldynamiken blir alltmer komplex. Det är en utmaning att teoretiskt beskriva dessa till synes enkla reaktioner för relativt små molekylära system. För att testa mina teoretiska modeller arbetar jag i nära samarbete med experimentella grupper såsom DESIREE vid Stockholms universitet och CSR (Cryogenic Storage Ring) vid Max Planck Institutet för Kärnfysik (MPIK) i Heidelberg. Reaktioner som jag studerar inkluderar laddningsöverföringsreaktioner då motsatt laddade joner kolliderar (ömsesidig neutralisering), dissociativ rekombination som sker då molekylära joner fångar upp elektroner samt den molekyldynamik som sker då fotoner absorberas.

I urval från Stockholms universitets publikationsdatabas

• Dissociative recombination and resonant ion-pair formation in electron collisions with HD⁺

  2024. Johan Hörnquist, Ann E. Orel, Åsa Larson. Physical Review A: covering atomic, molecular, and optical physics and quantum information 109 (5)

  Artikel

  We have developed a method for which a variety of reactive scattering processes involving the H₂ reaction complex can be studied using the same set of potential curves and couplings. The method is based on a close coupling approach in a strict diabatic representation. By rigorously incorporating non-adiabatic couplings among bound states, we enable the computation of final state distributions. Loss into the ionization continuum is accounted for with a non-local complex potential matrix. The method has successfully been applied in the studies of H⁺ + H^- mutual neutralization and H(1s) + H(ns) associative ionization. In this paper, we investigate the applicability of this method to dissociative recombination and resonant ion-pair formation in electron collisions with HD⁺. The importance of a non-local description of autoionization is demonstrated. Calculated cross sections and final state distributions are compared with results from experiments and previous theoretical studies.

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• Mutual neutralization in collisions of Li⁺ with CN^-

  2024. Åsa Larson, Ann E. Orel. Physical Chemistry, Chemical Physics - PCCP 26 (3), 1977-1983

  Artikel

  The mutual neutralization reaction in collisions of Li⁺ with CN⁻ is a promising candidate for rigorous multi-dimensional ab initio studies of atom-molecule charge transfer processes. The reaction is driven by the non-adiabatic interaction between the lowest two ¹A′ electronic states at large Li–CN distances, resulting in a large cross section for mutual neutralization. As a first step, the relevant adiabatic potential energy surfaces and non-adiabatic interaction are computed ab initio, and the process is studied quantum mechanically using the vibrational sudden approximation, where the vibrational and rotational motions of the CN molecule are assumed to be frozen during the collision.

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• Associative ionization in collisions of H plus + H- and H(1s) + H(ns)

  2023. Johan Hörnquist (et al.). Physical Review A: covering atomic, molecular, and optical physics and quantum information 108 (5)

  Artikel

  Associative ionization in collisions of H+ + H- as well as H(1s) + H(ns) with n = 2, 3, 4 is studied theoretically. Relevant adiabatic potential curves and nonadiabatic couplings are calculated ab initio and the autoionization from the lowest electronic resonant states in the 11+g/u and 31+g/u symmetries are considered. The cross sections are obtained by solving the coupled Schrodinger equation, including a complex potential matrix, in a strict diabatic representation. The importance of using a nonlocal description of autoionization is investigated. Associative ionization is also studied for different isotopes of hydrogen. Calculated cross sections are compared with results from measurements.

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• Charge transfer in sodium iodide collisions

  2023. Patrik Hedvall, Michael Odelius, Åsa Larson. Journal of Chemical Physics 158 (1)

  Artikel

  Sodium iodide (NaI) has, over the years, served as a prototype system in studies of non-adiabatic dynamics. Here, the charge transfer collision reactions Na⁺ + I− ⇆ Na + I (mutual neutralization and ion-pair formation) are studied using an ab initio approach and the total and differential cross sections are calculated for the reactions. This involves electronic structure calculations on NaI to obtain adiabatic potential energy curves, non-adiabatic and spin–orbit couplings, followed by nuclear dynamics, treated fully quantum mechanically in a strictly diabatic representation. A single avoided crossing at 13.22 a₀ dominates the reactions, and the total cross sections are well captured by the semi-classical Landau–Zener model. Compared to the measured ion-pair formation cross section, the calculated cross section is about a factor of two smaller, and the overall shape of the calculated differential cross section is in reasonable agreement with the measured ion-pair formation differential cross section. Treating the Landau–Zener coupling as an empirical parameter of 0.05 eV, the measured total and differential cross sections are well captured when performing fully quantum mechanical cross section calculations including rotational coupling. A semi-empirical spin–orbit coupling model is also investigated, giving satisfactory estimation of the effects of spin–orbit interactions for the reactions. 

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• Stability and Cooling of the C²⁻₇ Dianion

  2023. P. K. Najeeb (et al.). Physical Review Letters 131 (11)

  Artikel

  We have studied the stability of the smallest long-lived all carbon molecular dianion () in new time domains and with a single ion at a time using a cryogenic electrostatic ion-beam storage ring. We observe spontaneous electron emission from internally excited dianions on millisecond timescales and monitor the survival of single colder molecules on much longer timescales. We find that their intrinsic lifetime exceeds several minutes—6 orders of magnitude longer than established from earlier experiments on . This is consistent with our calculations of vertical electron detachment energies predicting one inherently stable isomer and one isomer which is stable or effectively stable behind a large Coulomb barrier for →+e⁻ separation.

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• Fragmentation of and electron detachment from hot copper and silver dimer anions: A comparison

  2023. Emma K. Anderson (et al.). Physical Review A: covering atomic, molecular, and optical physics and quantum information 107 (6)

  Artikel

  We measured the spontaneous decays of internally hot copper and silver dimer anions, and , stored in one of the two ion-beam storage rings of the Double Electrostatic Ion Ring Experiment (DESIREE) at Stockholm University. A coincidence detection technique was utilized enabling essentially background-free measurements of -> Cu + Cu^- and -> Ag + Ag^- fragmentation rates. Furthermore, the total rates of neutral decay products (monomers and dimers) were measured and the relative contributions of fragmentation and electron emission ( -> Cu₂ + e^- and -> Ag₂ + e^-) were deduced as functions of storage time. Fragmentation is completely dominant at early times. However, after about 20 ms of storage, electron emission is observed and becomes the leading decay path after 100 ms for both dimer anions. The branching ratios between fragmentation and electron emission (vibrationally assisted autodetachment processes) are very nearly the same for and Ag-2 throughout the present storage cycle of 10 seconds. This is surprising considering the difference between the electron affinities of the neutral dimers, Cu₂ and Ag₂, and the difference between the and the dissociation energies.

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• Mutual neutralization in H⁺+H⁻ collisions: An improved theoretical model

  2022. Johan Hörnquist (et al.). Physical Review A: covering atomic, molecular, and optical physics and quantum information 106 (6)

  Artikel

  The total and differential cross sections of mutual neutralization in H⁺+H⁻ collisions are calculated ab initio and fully quantum mechanically for energies between 0.001 and 600 eV. Effects which have not previously been considered in studies on mutual neutralization (MN) for this system, such as inclusion of rotational couplings and autoionization, are investigated. Adiabatic potential curves corresponding to the relevant states of ¹Σ, ¹Σ, ¹Π_g and ¹Π_u symmetries as well as radial and rotational nonadiabatic couplings are computed ab initio. A quasidiabatic model is developed and applied in order to investigate the importance of higher excited states as well as the inclusion of autoionization. Molecular data for the lowest electronic resonant state in each symmetry are obtained by performing electron scattering calculations. It is shown that rotational couplings cause a significant increase of the total MN cross section while autoionization plays a minor role as a loss mechanism. Additionally, a differential cross section is obtained that is symmetric around θ=90^∘. This result is in disagreement with a previous theoretical calculation where it was found that the differential cross section is dominated by backwards scattering.

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• Pseudo–Jahn-Teller interaction among electronic resonant states of H₃

  2021. Patrik Hedvall, Åsa Larson. Physical Review A: covering atomic, molecular, and optical physics and quantum information 103 (3)

  Artikel

  We study the electronic resonant states of H₃ with energies above the potential energy surface of the H_3⁺ ground state. These resonant states are important for the dissociative recombination of H_3⁺ at higher collision energies, and previous studies have indicated that these resonant states exhibit a triple intersection. We introduce a complex generalization of the pseudo–Jahn-Teller model to describe these resonant states. The potential energies and the autoionization widths of the resonant states are computed with electron scattering calculations using the complex Kohn variational method, and the complex model parameters are extracted by a least-square fit to the results. This treatment results in a non-Hermitian pseudo–Jahn-Teller Hamiltonian describing the system. The nonadiabatic coupling and geometric phase are further calculated and used to characterize the enriched topology of the complex adiabatic potential energy surfaces.

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• Dissociative electron attachment to MgCN

  2020. Ann Orel, Åsa Larson. European Physical Journal D 74 (1)

  Artikel

  Dissociative electron attachment (DEA) to the molecule MgCN and its isomer MgNC has been proposed as a possible source of CN- in the interstellar media. We have carried out electron scattering calculations using the complex Kohn Variational Method as a function of the internal degrees of freedom of the molecule to obtain the resonance energy surfaces and autoionization widths. We use these data as input to form the Hamiltonian relevant to the nuclear dynamics. The multidimensional time-dependent Schrodinger equation is solved using the MultiConfiguration Time-Dependent Hartree (MCTDH) approach. We compute the DEA cross sections and discuss the implications for CN- formation in circumstellar envelopes.

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• Spontaneous Electron Emission from Hot Silver Dimer Anions: Breakdown of the Born-Oppenheimer Approximation

  2020. Emma K. Anderson (et al.). Physical Review Letters 124 (17)

  Artikel

  We report the first experimental evidence of spontaneous electron emission from a homonuclear dimer anion through direct measurements of Ag-2(-) -> Ag-2 + e(-) decays on milliseconds and seconds timescales. This observation is very surprising as there is no avoided crossing between adiabatic energy curves to mediate such a process. The process is weak, yet dominates the decay signal after 100 ms when ensembles of internally hot Ag-2(-) ions are stored in the cryogenic ion-beam storage ring, DESIREE, for 10 s. The electron emission process is associated with an instantaneous, very large reduction of the vibrational energy of the dimer system. This represents a dramatic deviation from a Born-Oppenheimer description of dimer dynamics.

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• Mutual neutralization in collisions of H+ with Cl-

  2019. Åsa Larson (et al.). Journal of Chemical Physics 151 (21)

  Artikel

  The cross section and final state distribution for mutual neutralization in collisions of H+ with Cl- have been calculated using an ab initio quantum mechanical approach. It is based on potential energy curves and nonadiabatic coupling elements for the six lowest (1)Sigma(+) states of HCl computed with the multireference configuration interaction method. The reaction is found to be driven by nonadiabatic interactions occurring at relatively small internuclear distances (R < 6 a(0)). Effects on the mutual neutralization cross section with respect to the asymptotic form of the potential energy curves, inclusion of closed channels, as well as isotopic substitution are investigated. The effect of spin-orbit interaction is investigated using a semiempirical model and found to be small. A simple two-state Landau-Zener calculation fails to predict the cross section.

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• Reactions of C+ + Cl-, Br-, and I--A comparison of theory and experiment

  2019. Jordan C. Sawyer (et al.). Journal of Chemical Physics 151 (24)

  Artikel

  Rate constants for the reactions of C+ + Cl-, Br-, and I- were measured at 300 K using the variable electron and neutral density electron attachment mass spectrometry technique in a flowing afterglow Langmuir probe apparatus. Upper bounds of <10(-8) cm(3) s(-1) were found for the reaction of C+ with Br- and I-, and a rate constant of 4.2 +/- 1.1 x 10(-9) cm(3) s(-1) was measured for the reaction with Cl-. The C+ + Cl- mutual neutralization reaction was studied theoretically from first principles, and a rate constant of 3.9 x 10(-10) cm(3) s(-1), an order of magnitude smaller than experiment, was obtained with spin-orbit interactions included using a semiempirical model. The discrepancy between the measured and calculated rate constants could be explained by the fact that in the experiment, the total loss of C+ ions was measured, while the theoretical treatment did not include the associative ionization channel. The charge transfer was found to take place at small internuclear distances, and the spin-orbit interaction was found to have a minor effect on the rate constant.

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• A theoretical study of mutual neutralization of He⁺+H^- collisions

  Åsa Larson, Sifiso Nkambule, Ann Orel.

  Total and differential cross sections for mutual neutralization in low energy (0.001 eV -100 eV) He + and H − collisions are calculated ab initio and fully quantum mechanically. Atomic final state distributions and isotope effects are investigated. The theoretical model includes dynamics on eleven coupled states of 2 Σ + symmetry where autoionization is incorporated. The potential energy curves, autoionization widths and non-adiabatic couplings of electronic resonant states of HeH are computed by combining structure calculations with electron scattering calculations. The nuclear dynamics is studied using a strict diabatic representation of the resonant states. Effects of rotational couplings between 2 Σ + and 2 Π electronic states are investigated in the pure precession approximation.

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• Dissociative recombination of BeH⁺

  Johanna Brinne Roos (et al.).

  The cross section for dissociative recombination of BeH⁺ is calculated by solution of the timedependent Schrödinger equation in the local complex potential approximation. The effects of couplings between resonant states and the Rydberg states converging to the ground state of the ionare studied. The relevant potentials, couplings and autoionization widths are extracted using abinitio electron scattering and structure calculations, followed by a diabatization procedure. Thecalculated cross sections shows a sizable magnitude at low energy, followed by a high-energy peakcentered around 1 eV. The electronic couplings between the neutral states induce oscillations in thecross section. Analytical forms for the cross sections at low collision energies are given.

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• Low-energy collisions between electrons and BeD+

  2018. S. Niyonzima (et al.). Plasma sources science & technology 27 (2)

  Artikel

  Multichannel quantum defect theory is applied in the treatment of the dissociative recombination and vibrational excitation processes for the BeD+ ion in the 24 vibrational levels of its ground electronic state (X (1)Sigma(+), v(i)(+) = 0 ... 23). Three electronic symmetries of BeD** states ((2)Pi, (2)Sigma(+), and (2)Delta) are considered in the calculation of cross sections and the corresponding rate coefficients. The incident electron energy range is 10(-5)-2.7 eV and the electron temperature range is 100-5000 K. The vibrational dependence of these collisional processes is highlighted. The resulting data are useful in magnetic confinement fusion edge plasma modeling and spectroscopy, in devices with beryllium based main chamber materials, such as ITER and JET, and operating with the deuterium-tritium fuel mix. An extensive rate coefficients database is presented in graphical form and also by analytic fit functions whose parameters are tabulated in the supplementary material.

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• Dissociative recombination of HCl+

  2017. Åsa Larson, Samantha Fonseca dos Santos, Ann E. Orel. Journal of Chemical Physics 147 (8)

  Artikel

  The dissociative recombination of HCl+, including both the direct and indirect mechanisms, is studied. For the direct process, the relevant electronic states are calculated ab initio by combining electron scattering calculations to obtain resonance positions and autoionization widths with multi-reference configuration interaction calculations of the ion and Rydberg states. The cross section for the direct dissociation along electronic resonant states is computed by solution of the time-dependent Schrodinger equation. For the indirect process, an upper bound value for the cross section is obtained using a vibrational frame transformation of the elements of the scattering matrix at energies just above the ionization threshold. Vibrational excitations of the ionic core from the ground vibrational state, v = 0, to the first three excited vibrational states, v = 1, v = 2, and v = 3, are considered. Autoionization is neglected and the effect of the spin-orbit splitting of the ionic potential energy upon the indirect dissociative recombination cross section is considered. The calculated cross sections are compared to measurements. Published by AIP Publishing.

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• Low-energy collisions between electrons and BeH+: Cross sections and rate coefficients for all the vibrational states of the ion

  2017. S. Niyonzima (et al.). Atomic Data and Nuclear Data Tables 115, 287-308

  Artikel

  We provide cross sections and Maxwell rate coefficients for reactive collisions of slow electrons with BeH+ ions on all the eighteen vibrational levels (X-1 Sigma(+), v(i)(+) = 0, 1, 2, ... , 17) using a Multichannel Quantum Defect Theory (MQDT)-type approach. These data on dissociative recombination, vibrational excitation and vibrational de-excitation are relevant for magnetic confinement fusion edge plasma modeling and spectroscopy, in devices with beryllium based main chamber materials, such as the International Thermonuclear Experimental Reactor (ITER) and the Joint European Torus (JET). Our results are presented in graphical form and as fitted analytical functions, the parameters of which are organized in tables.

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• Differential and total cross sections of mutual neutralization in low-energy collisions of isotopes of H+ + H-

  2016. Sifiso M. Nkambule (et al.). Physical Review A: covering atomic, molecular, and optical physics and quantum information 93 (3)

  Artikel

  Mutual neutralization in the collisions of H+ and H- is studied both theoretically and experimentally. The quantum-mechanical ab initio model includes covalent states associated with the H(1)+H(n <= 3) limits and the collision energy ranges from 1 meV to 100 eV. The reaction is theoretically studied for collisions between different isotopes of the hydrogen ions. From the partial wave scattering amplitude, the differential and total cross sections are computed. The differential cross section is analyzed in terms of forward- and backward-scattering events, showing a dominance of backward scattering which can be understood by examining the phase of the scattering amplitudes for the gerade and ungerade set of states. The isotope dependence of the total cross section is compared with the one obtained using a semiclassical multistate Landau-Zener model. The final state distribution analysis emphasizes the dominance of the n = 3 channel for collisions below 10 eV, while at higher collision energies, the n = 2 channel starts to become important. For collisions of ions forming a molecular system with a larger reduced mass, the n = 2 channel starts to dominate at lower energies. Using a merged ion-beam apparatus, the branching ratios for mutual neutralization in H+ and H- collisions in the energy range from 11 to 185 eV are measured with position- and time-sensitive particle detectors. The measured and calculated branching ratios satisfactorily agree with respect to state contributions.

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• Dissociative recombination of N2H+

  2016. S. Fonseca dos Santos (et al.). Physical Review A 94 (2)

  Artikel

  The direct and indirect mechanisms of dissociative recombination of N2H+ are theoretically studied. At low energies, the electron capture is found to be driven by recombination into bound Rydberg states, while at collision energies above 0.1 eV, the direct capture and dissociation along electronic resonant states becomes important. Electron-scattering calculations using the complex Kohn variational method are performed to obtain the scattering matrix as well as energy positions and autoionization widths of resonant states. Potential-energy surfaces of electronic bound states of N2H and N2H+ are computed using structure calculations with the multireference configuration interaction method. The cross section for the indirect mechanism is calculated using a vibrational frame transformation of the elements of the scattering matrix at energies just above the ionization threshold. Here vibrational excitations of the ionic core from v = 0 to v = 1 and v = 2 for all three normal modes are considered and autoionization is neglected. The cross section for the direct dissociation along electronic resonant states is computed with wave-packet calculations using the multiconfiguration time-dependent Hartree method, where all three internal degrees of freedom are considered. The calculated cross sections are compared to measurements.

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• Theoretical study of mutual neutralization in He+ + H- collisions

  2016. Åsa Larson, Sifiso M. Nkambule, Ann E. Orel. Physical Review A 94 (2)

  Artikel

  Total and differential cross sections for mutual neutralization in He+ and H- collisions at low to intermediate (0.001 eV to 100 eV) are calculated ab initio and fully quantum mechanically. Atomic final-state distributions and isotope effects are investigated. The theoretical model includes dynamics on eleven coupled states of (2)Sigma(+) symmetry, where autoionization is incorporated. The potential-energy curves, autoionization widths, and nonadiabatic couplings of electronic resonant states of HeH are computed by combining structure calculations with electron scattering calculations. The nuclear dynamics is studied using a strict diabatic representation of the resonant states. Effects of rotational couplings between (2)Sigma(+) and (2)Pi electronic states are investigated in the pure precession approximation.

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• Advances in the MQDT approach of electron/molecular cation reactive collisions: High precision extensive calculations for applications

  2015. O. Motapon (et al.). DR2013

  Konferens

  Recent advances in the stepwise multichannel quantum defect theory approach of electron/molecular cation reactive collisions have been applied to perform computations of cross sections and rate coefficients for dissociative recombination and electron-impact rovibrational transitions of H-2(+), BeH+ and their deuterated isotopomers. At very low energy, rovibronic interactions play a significant role in the dynamics, whereas at high energy, the dissociative excitation strongly competes with all other reactive processes.

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• Electronic and photonic reactive collisions in edge fusion plasma and interstellar space: application to H-2 and BeH systems

  2015. J. Zs Mezei (et al.). Light element atom, molecule and radical behaviour in the divertor and edge plasma regions

  Konferens

  Reactive collisional and radiative elementary processes rate coefficients have been either computed using multichannel-quantum-defect theory methods, or measured in merged-beam (storage ring) and crossed-beam experiments. The reaction mechanisms are explained and output data are displayed in ready-to-be-used form, appropriate for the modeling of the kinetics of the edge fusion plasma and of the interstellar molecular clouds.

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• Low-energy dissociative electron attachment to CF2

  2015. S. T. Chourou, Åsa Larson, A. E. Orel. Physical Review A. Atomic, Molecular, and Optical Physics 92 (2)

  Artikel

  We present the results of a theoretical study of dissociative electron attachment (DEA) of low-energy electrons to CF2. We carried out electron scattering calculations using the complex Kohn variational method at the static-exchange and relaxed self-consistent field (SCF) level at the equilibrium geometry and compare our differential cross sections to other results. We then repeated these calculations as a function of the three internal degrees of freedom to obtain the resonance energy surfaces and autoionization widths. We use this data as input to form the Hamiltonian relevant to the nuclear dynamics. The multidimensional wave equation is solved using the multiconfiguration time-dependent Hartree (MCTDH) approach within the local approximation.

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• Mutual neutralization in collisions of Li+ and F-

  2015. Sifiso M. Nkambule, Pietro Nurzia, Åsa Larson. Chemical Physics 462, 23-27

  Artikel

  Mutual neutralization in collisions of Li+ and F is driven by an avoided crossing between the two lowest (1)Sigma(+) electronic states of the LiF system. These electronic states are computed using the multi-reference configuration interaction method. We investigate how the adiabatic potential energy curves and the non-adiabatic coupling element depend on the choice of the reference configurations as well as the basis set. Using diabatic states, the total and differential cross sections for mutual neutralization are computed.

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• Potential-splitting approach applied to the Temkin-Poet model for electron scattering off the hydrogen atom and the helium ion

  2015. E. Yarevsky (et al.). Journal of Physics B 48 (11)

  Artikel

  The study of scattering processes in few body systems is a difficult problem especially if long range interactions are involved. In order to solve such problems, we develop here a potential-splitting approach for three-body systems. This approach is based on splitting the reaction potential into a finite range core part and a long range tail part. The solution to the Schrodinger equation for the long range tail Hamiltonian is found analytically, and used as an incoming wave in the three body scattering problem. This reformulation of the scattering problem makes it suitable for treatment by the exterior complex scaling technique in the sense that the problem after the complex dilation is reduced to a boundary value problem with zero boundary conditions. We illustrate the method with calculations on the electron scattering off the hydrogen atom and the positive helium ion in the frame of the Temkin-Poet model.

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• Reactive collisions involving the BeH molecular system

  2015. Åsa Larson (et al.). Light element atom, molecule and radical behaviour in the divertor and edge plasma regions

  Konferens

  In the divertor and fusion edge plasma regions reactive collisions involving the BeH molecular system are taking place. Theoretical ab initio quantum studies of electron collisions with BeH+ resulting in either dissociative recombination, vibrational excitation or dissociative excitation are performed for ions in different vibrational states as well for different isotopologues. Furthermore, the mutual neutralization reaction in collisions of H- with Be+ is studied semiclassically.

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• Studies of HeH: DR, RIP, VE, DE, PI, MN, ...

  2015. Åsa Larson (et al.). EPJ Web of Conferences 84

  Artikel

  The resonant states of HeH are computed by combining structure calculations at a full configuration interaction level with electron scattering calculations carried out using the Complex-Kohn variational method. We obtain the potential energy curves, autoionization widths, as well as non-adiabatic couplings among the resonant states. Using the non-adiabatic couplings, the adiabatic to diabatic transformation matrix can be obtained. A strict diabatization of the resonant states will be used to study various scattering processes where the resonant states are involved. These processes involve high energy dissociative recombination (DR) and ion-pair formation (RIP), resonant and direct dissociative excitation (DE), penning ionization (PI) as well as mutual neutralization (MN).

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• Theoretical study of the mechanism of H2O+ dissociative recombination

  2015. Sifiso M. Nkambule (et al.). Physical Review A. Atomic, Molecular, and Optical Physics 92 (1)

  Artikel

  By combining electronic structure and scattering calculations, quasidiabatic potential energy surfaces of both bound Rydberg and electronic resonant states of the water molecule are calculated at the multireference configuration-interaction level. The scattering matrix calculated at low collision energy is used to obtain explicitly all couplings elements responsible for the electronic capture to bound Rydberg states. These are used to estimate the cross section arising from the indirect mechanism of dissociative recombination. Additionally, the role of the direct capture and dissociation through the resonant states is explored using wave-packet propagation along one-dimensional slices of the multidimensional potential energy surfaces.

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