Åsa LarsonProfessor
Om mig
Jag är professor i teoretisk molekylfysik vid Fysikum på Stockholms universitet.
Undervisning
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.
Forskning
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.
Forskningsprojekt
Publikationer
I urval från Stockholms universitets publikationsdatabas

Dissociative recombination and resonant ionpair 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)
ArtikelWe have developed a method for which a variety of reactive scattering processes involving the H_{2} 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 nonadiabatic couplings among bound states, we enable the computation of final state distributions. Loss into the ionization continuum is accounted for with a nonlocal 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 ionpair formation in electron collisions with HD^{+}. The importance of a nonlocal description of autoionization is demonstrated. Calculated cross sections and final state distributions are compared with results from experiments and previous theoretical studies.

Mutual neutralization in collisions of Li^{+} with CN^{}
2024. Åsa Larson, Ann E. Orel. Physical Chemistry, Chemical Physics  PCCP 26 (3), 19771983
ArtikelThe mutual neutralization reaction in collisions of Li^{+} with CN^{−} is a promising candidate for rigorous multidimensional ab initio studies of atommolecule charge transfer processes. The reaction is driven by the nonadiabatic interaction between the lowest two ^{1}A′ 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 nonadiabatic 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.

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)
ArtikelAssociative 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.

Charge transfer in sodium iodide collisions
2023. Patrik Hedvall, Michael Odelius, Åsa Larson. Journal of Chemical Physics 158 (1)
ArtikelSodium iodide (NaI) has, over the years, served as a prototype system in studies of nonadiabatic dynamics. Here, the charge transfer collision reactions Na^{+} + I− ⇆ Na + I (mutual neutralization and ionpair 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, nonadiabatic and spin–orbit couplings, followed by nuclear dynamics, treated fully quantum mechanically in a strictly diabatic representation. A single avoided crossing at 13.22 a_{0} dominates the reactions, and the total cross sections are well captured by the semiclassical Landau–Zener model. Compared to the measured ionpair 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 ionpair 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 semiempirical spin–orbit coupling model is also investigated, giving satisfactory estimation of the effects of spin–orbit interactions for the reactions.

Stability and Cooling of the C^{2−}_{7 }Dianion
2023. P. K. Najeeb (et al.). Physical Review Letters 131 (11)
ArtikelWe have studied the stability of the smallest longlived all carbon molecular dianion () in new time domains and with a single ion at a time using a cryogenic electrostatic ionbeam 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.

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)
ArtikelWe measured the spontaneous decays of internally hot copper and silver dimer anions, and , stored in one of the two ionbeam storage rings of the Double Electrostatic Ion Ring Experiment (DESIREE) at Stockholm University. A coincidence detection technique was utilized enabling essentially backgroundfree 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 ( > Cu_{2} + e^{} and > Ag_{2} + 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 Ag2 throughout the present storage cycle of 10 seconds. This is surprising considering the difference between the electron affinities of the neutral dimers, Cu_{2} and Ag_{2}, and the difference between the and the dissociation energies.

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)
ArtikelThe 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 ^{1}Σ_{}, ^{1}Σ_{}, ^{1}Π_{g} and ^{1}Π_{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.

Pseudo–JahnTeller interaction among electronic resonant states of H_{3}
2021. Patrik Hedvall, Åsa Larson. Physical Review A: covering atomic, molecular, and optical physics and quantum information 103 (3)
ArtikelWe study the electronic resonant states of H_{3} 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–JahnTeller 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 leastsquare fit to the results. This treatment results in a nonHermitian pseudo–JahnTeller 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.

Dissociative electron attachment to MgCN
2020. Ann Orel, Åsa Larson. European Physical Journal D 74 (1)
ArtikelDissociative 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 timedependent Schrodinger equation is solved using the MultiConfiguration TimeDependent Hartree (MCTDH) approach. We compute the DEA cross sections and discuss the implications for CN formation in circumstellar envelopes.

Spontaneous Electron Emission from Hot Silver Dimer Anions: Breakdown of the BornOppenheimer Approximation
2020. Emma K. Anderson (et al.). Physical Review Letters 124 (17)
ArtikelWe report the first experimental evidence of spontaneous electron emission from a homonuclear dimer anion through direct measurements of Ag2() > Ag2 + 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 Ag2() ions are stored in the cryogenic ionbeam 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 BornOppenheimer description of dimer dynamics.

Mutual neutralization in collisions of H+ with Cl
2019. Åsa Larson (et al.). Journal of Chemical Physics 151 (21)
ArtikelThe 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 spinorbit interaction is investigated using a semiempirical model and found to be small. A simple twostate LandauZener calculation fails to predict the cross section.

Reactions of C+ + Cl, Br, and IA comparison of theory and experiment
2019. Jordan C. Sawyer (et al.). Journal of Chemical Physics 151 (24)
ArtikelRate 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 spinorbit 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 spinorbit interaction was found to have a minor effect on the rate constant.

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 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 Σ + and 2 Π electronic states are investigated in the pure precession approximation.

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 highenergy 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.

Lowenergy collisions between electrons and BeD+
2018. S. Niyonzima (et al.). Plasma sources science & technology 27 (2)
ArtikelMultichannel 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 1005000 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 deuteriumtritium 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.

Dissociative recombination of HCl+
2017. Åsa Larson, Samantha Fonseca dos Santos, Ann E. Orel. Journal of Chemical Physics 147 (8)
ArtikelThe 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 multireference 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 timedependent 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 spinorbit 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.

Lowenergy 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, 287308
ArtikelWe provide cross sections and Maxwell rate coefficients for reactive collisions of slow electrons with BeH+ ions on all the eighteen vibrational levels (X1 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 deexcitation 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.

Differential and total cross sections of mutual neutralization in lowenergy 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)
ArtikelMutual neutralization in the collisions of H+ and H is studied both theoretically and experimentally. The quantummechanical 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 backwardscattering 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 LandauZener 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 ionbeam 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 timesensitive particle detectors. The measured and calculated branching ratios satisfactorily agree with respect to state contributions.

Dissociative recombination of N2H+
2016. S. Fonseca dos Santos (et al.). Physical Review A 94 (2)
ArtikelThe 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. Electronscattering 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. Potentialenergy 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 wavepacket calculations using the multiconfiguration timedependent Hartree method, where all three internal degrees of freedom are considered. The calculated cross sections are compared to measurements.

Theoretical study of mutual neutralization in He+ + H collisions
2016. Åsa Larson, Sifiso M. Nkambule, Ann E. Orel. Physical Review A 94 (2)
ArtikelTotal 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 finalstate distributions and isotope effects are investigated. The theoretical model includes dynamics on eleven coupled states of (2)Sigma(+) symmetry, where autoionization is incorporated. The potentialenergy 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.

Advances in the MQDT approach of electron/molecular cation reactive collisions: High precision extensive calculations for applications
2015. O. Motapon (et al.). DR2013
KonferensRecent 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 electronimpact rovibrational transitions of H2(+), 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.

Electronic and photonic reactive collisions in edge fusion plasma and interstellar space: application to H2 and BeH systems
2015. J. Zs Mezei (et al.). Light element atom, molecule and radical behaviour in the divertor and edge plasma regions
KonferensReactive collisional and radiative elementary processes rate coefficients have been either computed using multichannelquantumdefect theory methods, or measured in mergedbeam (storage ring) and crossedbeam experiments. The reaction mechanisms are explained and output data are displayed in readytobeused form, appropriate for the modeling of the kinetics of the edge fusion plasma and of the interstellar molecular clouds.

Lowenergy dissociative electron attachment to CF2
2015. S. T. Chourou, Åsa Larson, A. E. Orel. Physical Review A. Atomic, Molecular, and Optical Physics 92 (2)
ArtikelWe present the results of a theoretical study of dissociative electron attachment (DEA) of lowenergy electrons to CF2. We carried out electron scattering calculations using the complex Kohn variational method at the staticexchange and relaxed selfconsistent 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 timedependent Hartree (MCTDH) approach within the local approximation.

Mutual neutralization in collisions of Li+ and F
2015. Sifiso M. Nkambule, Pietro Nurzia, Åsa Larson. Chemical Physics 462, 2327
ArtikelMutual 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 multireference configuration interaction method. We investigate how the adiabatic potential energy curves and the nonadiabatic 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.

Potentialsplitting approach applied to the TemkinPoet model for electron scattering off the hydrogen atom and the helium ion
2015. E. Yarevsky (et al.). Journal of Physics B 48 (11)
ArtikelThe 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 potentialsplitting approach for threebody 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 TemkinPoet model.

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
KonferensIn 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.

Studies of HeH: DR, RIP, VE, DE, PI, MN, ...
2015. Åsa Larson (et al.). EPJ Web of Conferences 84
ArtikelThe resonant states of HeH are computed by combining structure calculations at a full configuration interaction level with electron scattering calculations carried out using the ComplexKohn variational method. We obtain the potential energy curves, autoionization widths, as well as nonadiabatic couplings among the resonant states. Using the nonadiabatic 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 ionpair formation (RIP), resonant and direct dissociative excitation (DE), penning ionization (PI) as well as mutual neutralization (MN).

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)
ArtikelBy 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 configurationinteraction 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 wavepacket propagation along onedimensional slices of the multidimensional potential energy surfaces.
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