Ismanuel Rabadán

Ismanuel Rabadán
Universidad Autónoma de Madrid | UAM · Department of Chemistry

PhD

About

91
Publications
3,446
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985
Citations
Citations since 2017
10 Research Items
276 Citations
201720182019202020212022202301020304050
201720182019202020212022202301020304050
201720182019202020212022202301020304050
201720182019202020212022202301020304050
Additional affiliations
September 1998 - present
Universidad Autónoma de Madrid
March 1995 - September 1998
University College London

Publications

Publications (91)
Article
Full-text available
Cross sections for charge transfer and ionization in proton–uracil collisions are studied, for collision energies 0.05<E<2500 keV, using two computational models. At low energies, below 20 keV, the charge transfer total cross section is calculated employing a semiclassical close-coupling expansion in terms of the electronic functions of the supermo...
Article
Full-text available
Absolute cross sections for single electron capture by Sn3+ colliding with H2 and D2 have been measured and calculated in the energy range of 1–100 keV. The cross sections are determined by measuring the change in ion beam current with varying target density and by measuring the yields of charged target fragments by means of a time-of-flight spectr...
Article
Collisions of He²⁺, Li ³⁺ and C³⁺Cppp ions with water molecules are studied at energies ranging between 20 keV/u and 500 keV/u. Three methods are employed: the classical trajectory Monte Carlo (CTMC), the expansion of the scattering wave function in terms of asymptotic frozen molecular orbitals (AFMO) and a lattice method to numerically solve the t...
Article
Full-text available
Synopsis Total cross sections for ionization and electron capture in Li ³⁺ + H 2 O collisions are calculated at energies 20 ⩽ E ⩽ 750 keV/u. Three different models are applied: the classical trajectory Monte Carlo method, an expansion in terms of asymptotic-frozen-molecular-orbitals and the numerical solution of the time dependent Schrödinger equat...
Article
Full-text available
The fragmentation of the water cation from its B[combining tilde] 2B2 electronic state, allowing the participation of the X[combining tilde] 2B1, Ã 2A1 and C[combining tilde] 2B1 states in the process, is simulated using the extended capabilities of the collocation GridTDSE code to account for the nonadiabatic propagation of wave packets in several...
Article
Total cross sections for formation of H and H⁻, and electron production, in H⁺ + Ar collisions have been calculated at energies between 100 eV and 200 keV employing two methods: for E<10 keV, a semiclassical treatment with an expansion in a basis of electronic wave functions of the ArH⁺ quasimolecule and, for E>10 keV, the switching-Classical-Traje...
Article
Full-text available
The charge transfer process is studied in proton collisions with BeH. Given the anisotropy of the target molecule, two approaches are considered, and compared, in order to calculate orientation-averaged cross sections. The necessary molecular data (electronic energies and non-adiabatic couplings) are obtained from full configuration-interaction wav...
Article
We present calculations of electron-capture cross sections in collisions of H+ with BeH molecules in the energy range 25eV<E<10keV. We discuss the validity of the models employed to describe nonadiabatic ion-molecule collisions, specifically the eikonal approximation, the Franck-Condon approximation, and the isotropic approximation to obtain orient...
Article
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We present calculations of electron capture cross sections in proton collisions with BeH molecules in the energy range 25 eV/u < E <25 keV/u.
Article
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We present a semi-classical numerical integration method for studying electron loss processes in ion collisions with water molecules. Capture and ionization cross section are calculated in the intermediate-high energy range, and the kinetic energy distribution of the ejected electrons is analyzed. The results are compared with those obtained with a...
Article
Full-text available
A quantum-dynamical study of the fragmentation of H2O⁺(²B2) is carried out by using wave packet propagations on ab initio potential energy surfaces connected by nonadiabatic couplings assuming a Franck- Condon initial wave packet from the ground state of the water molecule. The simulations indicate that a conical intersection between the ²B2 and Ã...
Article
Full-text available
The 29th International Conference on Photonic, Electronic and Atomic Collisions (XXIX ICPEAC) was held at the Palacio de Congresos ''El Greco'', Toledo, Spain, on 22-28 July, 2015, and was organized by the Universidad Autónoma de Madrid (UAM) and the Consejo Superior de Investigaciones Científicas (CSIC). ICPEAC is held biannually and is one of the...
Article
Electron loss in proton-water collisions is studied in the energy range 100keV<E<1MeV by employing a three-center model potential. The electron-loss probabilities are calculated by applying a new lattice method that yields cross sections which are in good agreement with previous semiclassical close-coupling and classical calculations. The lattice m...
Article
Full-text available
The calculations of total cross sections of electron capture in collisions of C q + with H(1s) are reviewed. At low collision energies, new calculations have been performed, using molecular expansions, to analyze isotope effects. The Classical Trajectory Monte Carlo method have been also applied to discuss the accuracy of previous calculations and...
Article
Full-text available
A quantum-mechanical study of the predissociation of H2O+ ((B) over tilde B-2(2)) is carried out by using wave packet propagations on ab initio potential energy surfaces connected by nonadiabatic couplings. The simulations show that within the first 30 fs 80% of the initial wave packet is transferred from the (B) over tilde B-2(2) to the (A) over t...
Conference Paper
Full-text available
The single ionization of water molecules by collisions with photons, electrons or ions leaves H2O+ in several possible electronic states: X ^2B_1 , A ^2A_1 and B ^2B_2 . The first two states are obtained after removal of essentially non-bonding electrons from H2O, and the corresponding cations do not fragment; however, the energy of the third estat...
Conference Paper
Full-text available
We measure the vibrational distribution of Hj ions issued from charge transfer in H+ + H2 collisions to probe the details of the electron transfer mechanism from low to high impact energies. The experiments are accompanied by theoretical calculations. This joint experimental-theoretical study allows us to elicit the adequacy and accuracy of widely...
Article
Full-text available
Electron capture cross sections in collisions of protons with the nitrogen molecule are obtained with two semiclassical ab initio methods: one uses multireference configuration interaction wavefunctions while the other is based on monoelectronic wavefunctions and the independent particle approximation. The accuracy and usefulness of this last, simp...
Article
Full-text available
Total and singly differential (in the electron energy) cross section of electron emission in proton collisions with H2O are obtained at energies in the range 10 keV to 5 MeV. Two non-perturbative methods are employed, one classical and one semiclassical, both combining a multi-center target electron potential and an independent particle statistics....
Article
There is no consensus on the magnitude and shape of the charge transfer cross section in low-energy H^{+}+H_{2} collisions, in spite of the fundamental importance of these collisions. Experiments have thus been carried out in the energy range 15≤E≤5000 eV. The measurements invalidate previous recommended data for E≤200 eV and confirm the existence...
Article
We report both total and singly differential cross sections for ionization of water molecules by H+, He2+ and C6+ projectiles in the energy range of 15 keV/amu <= E <= 10 MeV/amu. We employ an independent-event model in the framework of the Classical Trajectory Monte Carlo method. Good agreement of calculated cross sections with the experiments is...
Article
Full-text available
Two nonperturbative methods are applied to obtain total and singly differential (in the electron energy) cross sections of electron emission in proton collisions with H2O at impact energies in the range 10 keV ≤Ep≤ 5 MeV. Both methods, one classical and one semiclassical, combine an independent particle treatment with a multicenter model potential...
Article
Total cross-sections for electron capture and electron production in proton collisions with N(2), CO and H(2)O, are evaluated using a classical trajectory Monte Carlo treatment for collision energies between 30 and 3000keV. A semiclassical close-coupling treatment has been also employed for proton collisions with H(2)O, to discuss the accuracy of t...
Chapter
We present calculations of cross sections for one- and two-electron processes in collisions of H+, He2+ and C6+ with water molecules. We employ two kind of methods: a classical trajectory Monte Carlo approach and a semiclassical treatment with expansions in terms of molecular wavefunctions. Anisotropy effects related to the structure of the target...
Article
Full-text available
We calculate the electron capture cross sections in collisions of protons with water dimers, using a simple ab initio approach. The formalism involves one-electron scattering wave functions and a statistical interpretation to evaluate many-particle cross sections. By comparing with proton-water collisions, we aim at identifying aggregation effects...
Article
Full-text available
We calculate electron capture cross sections in collisions of protons with water molecules, using two simple ab initio approaches. The formalism involves the calculation of one-electron scattering wave functions and the use of three-center pseudo potential to represent the electron H2O+ interaction. Several methods to obtain many-electron cross sec...
Article
Full-text available
The Classical Trajectory Monte Carlo method is applied to treat proton collisions with N2, CO and CH4 at collision energies 25< E < 2.5 × 103 keV. The calculation employs model potentials to describe the interaction of the active electron with the molecular core. General good agreement with available experimental data is found.
Article
Full-text available
We employ the independent event electron model in the framework of the classical trajectory Monte Carlo method to compute ionization and capture cross sections for one- and two- electron processes in collisions of H+, He2+ and C6+ with water molecules at intermediate impact energies. Subsequente fragmentation processes are also considered, as well...
Article
Full-text available
We present calculations of charge exchange and vibrational excitation cross sections in low energy p+H2 collisions. These cross sections are obtained by means of an hemiquantal treatment which uses Diatomics In Molecules (DIM) diabatic wavefunctions of the H3+ molecule. The hemiquantal approach allows to distinguish the nonreactive, dissociative an...
Article
Full-text available
Charge transfer cross sections in proton collisions with water dimers are calculated using an ab initio method based on molecular orbitals of the system. Results are compared with their counterpart in proton-water collisions to gauge the importance of intermolecular interactions in the cross sections.
Article
Total and partial charge transfer cross sections are calculated in collisions of protons with the nitrogen molecule at energies between 0.1 and 10 keV. Ab initio potential energy curves and nonadiabatic couplings have been obtained for a number of N2 bond lengths using a multireference configuration interaction method. The influence of the anisotro...
Article
Two simple ab initio methods based on one-electron wave functions are employed to calculate the single-electron capture and single ionization of H2O and CO molecules by ion impact. The anisotropy of the molecular targets is taken into account by using multicenter pseudopotentials to represent the interaction of the active electron with the ionic mo...
Article
Two simple ab initio methods based on one-electron wave functions are employed to calculate the single-electron capture and single ionization of H2O and CO molecules by ion impact. The anisotropy of the molecular targets is taken into account by using multicenter pseudopotentials to represent the interaction of the active electron with the ionic mo...
Article
We present calculations of cross sections for one- and two-electron processes in collisions of H{sup +}, He{sup 2+}, and C{sup 6+} with water molecules in the framework of the Franck-Condon approximation. We employ an independent-electron method and a classical trajectory Monte Carlo approach. Anisotropy effects related to the structure of the targ...
Article
Calculations of charge transfer total cross section in proton collisions with CH are presented at collision energies 10 eV < E < 6.25 keV. Two-state calculations using the sudden approximation for rotation and vibration do not show significant differences with respect to the simple Franck-Condon approximation, which is appropriate for energies abov...
Article
Tesis doctoral inédita. Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Química. Fecha de lectura: 12-11-2010 Bibliogr.: p.100-103
Article
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H(+)+H(2) collisions are studied by means of a semiclassical approach that explicitly accounts for nuclear rearrangement channels in nonadiabatic electron processes. A set of classical trajectories is used to describe the nuclear motion, while the electronic degrees of freedom are treated quantum mechanically in terms of a three-state expansion of...
Article
Single electron capture and single ionization total cross sections in collisions of proton with ethylene are calculated for an energy range 25 keV ≤ E ≤ 150 keV, using the classical trajectory Monte Carlo method. Multi-center model potentials are employed to represent the interaction of the active electron on each molecular orbital with the C2H cor...
Article
We explain the origin of the unusual large isotopic dependence found in charge-transfer cross sections for H(D,T){sup +}+Be collisions. We show that this large effect appears in a semiclassical treatment as a consequence of the mass dependence of the charge-transfer transition probabilities, which is due to the variation of the radial velocity in t...
Article
Quantal calculations of electron-capture and elastic cross sections have been carried out for collisions of C4+ and B5+ with H(1s) at collision energies 0.00025
Article
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We present a study of the ionization and capture processes in collisions of H+, He2+ and C6+ with water molecules. Single and total cross sections are obtained in the energy range 20 keV/amu
Article
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Charge transfer and ionization in collisions of H+ with H2O and (H2O)2 is obtained by using simple ab initio methods based on one-electron wave functions and multi-center pseudo-potentials and independent particle model treatments.
Article
Full-text available
Charge exchange in collisions of H+, D+ and T+ with beryllium is examined at impact energies from 2.5 × 10-4 and 10 eV/amu. The ab initio cross sections show a large isotopic dependence below 0.6 eV/amu that cannot be explain in terms of kinematical effects.
Article
Full-text available
We present semiclassical calculations of total cross section for electron capture, vibrational excitation, dissociation and nuclear exchange reactions in H++H2 collisions at energies 5 eV < E < 1 keV. Our results for electron capture agree with close-coupling calculations but not with the recommended data for this system.
Article
Electron capture, vibrational excitation, dissociation and nuclear exchange in collisions of H+ with H2 are studied at impact energies between 5 eV and 1 keV. Calculations are performed by employing classical trajectories for the nuclear evolution and a three-state expansion of the electronic wavefunction that uses the diatomics in molecules approa...
Article
Full-text available
We present calculations of electron capture cross sections in collisions of O2+ and N2+ with H(1s) for impact energies 0.001 eV < E < 10 keV and the corresponding rate coefficients for temperatures 102 K < T < 105 K. Our molecular close-coupling treatment leads to significant differences from the capture rates usually employed in the modeling of as...
Article
Full-text available
Classical (CTMC) calculations of single electron capture and single ionization cross sections are carried out for collisions of H+ and C6+ collisions with H2O molecules in the impact energy range 25< E < 5000keV/amu. The calculation employs a multi-center model potential for the interaction of the active electron with the H 2O+ core. The results ag...
Article
An ab initio study of charge exchange and excitation processes in collisions between protons and beryllium atoms is presented. State selective cross sections are obtained for collision energies between 2.5 × 10−7 and 16 keV/amu, using both quantum and semiclassical treatments. A very large isotopic dependence of the charge exchange cross section is...
Article
. The dynamics of collisional processes between Mg atoms and caesium ions is studied using the hemiquantal (HQ) approach with special attention to the collisional channels leading to Mg(3 1P) and Cs(6 2P) states, for which the corresponding emission excitation functions have been previously measured in our laboratory. The radial and angular non-adi...
Article
A semiclassical model is devised to shed light on the role of asymptotic transitions around conical intersections in the dynamics of ion-diatom collisions. We consider the fundamental H++H2 case, with vibrationally excited target, in the impact velocity range 10−4≤v≤5.10−2 a.u. The reliability of the sudden approximation for vibration and trajector...
Article
We report total cross sections for single ionization and electron capture in ${\mathrm{H}}^{+}$ collisions with water molecules at impact energies $25\phantom{\rule{0.3em}{0ex}}\mathrm{keV}<E<5\phantom{\rule{0.3em}{0ex}}\mathrm{MeV}$. Calculations have been carried out by applying the independent-particle model and the eikonal\char21{}classical tra...
Article
Full-text available
We have calculated charge transfer total cross sections in ion-H(1s) collisions at very low energies (E < 1 eV). These cross sections show a Langevin-type behaviour, although the corresponding transition probabilities are smaller than one, as obtained in the Landau-Zener model. The cross sections exhibit numerous spikes which are related to the exi...
Article
We present ab initio calculations of cross sections for vibrational excitation and electron capture in collisions of ${\mathrm{H}}^{+}$ with ${\mathrm{H}}_{2}$ and its isotopical variants at impact energies between $10\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ and $10\phantom{\rule{0.3em}{0ex}}\mathrm{keV}$. Calculations have been carried out by means...
Chapter
Ab initio total and partial cross sections for electron capture proccess in collisions of ground and metastable 14N2+ and 16O2+ with H(1s) are presented. Calculations are performed in a wide energy range from 1x10^-5 to 20 keV/amu, using both quantal and semiclassical treatments, and a molecular basis set that includes 80 and 39 states for NH2+ and...
Article
We present ab initio calculations of cross sections for electron capture by C2+ ions in their ground (1S) and metastablee (3P) states, from H and H2. We explain the difference between C2+–H2 collisions, where the content of metastable ions is critical, and C2+–H collisions, where it is less important. We also present preliminary results for electro...
Article
The vibrational distribution of H2+ (X2Σg+;v) after charge transfer in H++H2 and C2+(2s2p;3P)+H2 collisions is obtained using the SEIKON approach and ab initio molecular data. We also present H2 vibrational excitation cross sections in H++H2 collisions.
Article
We present ab initio quantal calculations of electron capture cross sections for collisions of ground and metastable states of ¹⁴N{sup 2+} and ¹⁶O{sup 2+} ions with H(1s), at collision energies 10⁻²
Article
Full-text available
A parametrization of the three asymptotic conical intersections between the energies of the H3(+) ground state and the first excited singlet state is presented. The influence of an additional, fourth conical intersection between the first and second excited states at the equilateral geometry on the connection between the three conical regions is st...
Article
We present an ab initio study of H2+ + H(1s) collisions at H2+ impact energies between 0.4 and 50 keV. Cross sections are obtained within the sudden approximation for rotation and vibration of the diatomic molecule. We have found that anisotropy effects are crucial to correctly describe this system in this energy range.
Article
Full-text available
The lowest two ab initio potential energy surfaces (PES), and the corresponding nonadiabatic couplings between them, have been obtained for the Hâ{sup +} system; the molecular data are compared to those calculated with the diatomic in molecules (DIM) method. The form of the couplings is discussed in terms of the topology of the molecular structure...
Article
An ab initio calculation of the electron capture cross sections for collisions of ground and metastable states of N2+ with H(1s) is presented. Total cross sections are evaluated for 14N impact energies from 2×10−3 to 300 keV, using both quantal and semiclassical treatments. The results are compared with experimental and previous theoretical data, a...
Article
Full-text available
A method to evaluate the sign consistency of dynamical couplings between ab initio three-center wave functions was discussed. The method was found to systemically diabatize avoided crossings between two potential surfaces, which also included conical intersections. The delayed overlap matrix (DOM), whose elements are overlaps between the molecular...
Article
Full-text available
We present ab initio calculations of cross sections for single and autoionizing double electron capture in collisions of N5+ with H2, for impact energies between 0.2 and 10 keV/amu. Calculations have been carried out by means of a close-coupling molecular treatment using the sudden approximation for rotation and vibration of the diatomic molecules....
Article
Full-text available
An ab initio calculation of the electron capture cross sections for collisions of ground and metastable states of N2+ with H(1s) is presented. Total cross sections are evaluated for N14 impact energies from 2×10−3to300keV, using both quantal and semiclassical treatments. The results are compared with experimental and previous theoretical data, and...
Article
Molecular R-matrix calculations are performed at a range of energies to give rotational and vibrational excitation and de-excitation cross-sections and, hence, rates for electron collisions with HeH+ up to electron temperatures of 20 000 K. Critical electron densities are also given. The rotational calculations include the Coulomb–Born completion o...
Article
Vibronic close-coupling calculations of charge transfer and ${\mathrm{H}}_{2}$ vibrational excitation total cross sections in ${\mathrm{H}}^{+}+{\mathrm{H}}_{2}{(}^{1}{$\Sigma${}}_{g}^{+},$\nu${}=0)$ collisions are presented and compared with experimental data in the energy range $50 \mathrm{eV}<E<2 \mathrm{keV}$. It is shown that the sudden approx...
Article
We present cross sections for electron capture in N5++H2 collisions in the energy range 100 eV/amu≤E≤6 keV/amu. We employ a model potential aproximation to treat the interaction of the active electron with the cores, and a recently proposed method, which applies the independent particle model to evaluate the Hamiltonian matrix elements. © 2001 John...
Article
We present an analysis of the characteristics of nonadiabatic couplings due to the existence of conical intersections between potential energy surfaces of triatomic systems in collinear configurations. We discuss the relative merits and performance of four techniques that we tested to remove the singularities, and illustrate our findings for a coni...
Article
Full-text available
Multichannel quantum defect calculations for NO+ dissociative recombination (DR) for electron energies from threshold to 8 eV are presented. The calculations use electronic energies and autoionization widths of valence states obtained from ab initio R-matrix calculations with the corresponding potential curves calibrated using available spectroscop...
Article
The vibrational distribution of H2+(X 2Σ+g; ν) after charge transfer in C2+(2s2p; 3P) + H2 collisions is obtained ab initio using the semiclassical eikonal method and the sudden approximation. Results are in good agreement with experiment (Leputsch et al 1997 J. Phys. B: At. Mol. Opt. Phys. 30 5009).
Article
Full-text available
An ab initio calculation, using the R-matrix method, of the cross sections for the electron impact vibrational excitation of NO+(X 1+,v = 0) up to v = 5 is presented. Calculations have been carried out in both an adiabatic and a non-adiabatic approximation. It is shown that these two approximations produce dramatically different results. This is du...
Article
New coupled-state R-matrix calculations are performed at energies up to 1 eV to give rotational excitation and de-excitation cross-sections for electron collisions with CH+. Rotational excitations with Δ j up to 7 are considered. Transitions with Δ j up to 6 are found to have appreciable cross-sections, those with Δ j = 2 being comparable to (indee...
Article
We report a study on electronic distributions obtained from a CTMC treatment of the reaction, which may be used as criteria to improve the quality of pseudostates within the framework of close-coupling molecular methods. By using the concept of molecular energy of classical electrons, an analysis of the mechanism at intermediate energies confirms t...
Article
Full-text available
Methods of computing rotational excitation cross sections for electron collisions with diatomic molecular ions are examined for impact energies up to 5 eV. The HeH and NO ions are used as test cases and calculations are performed at various levels of approximation. Previous studies have all used the Coulomb-Born approximation assuming only dipolar...
Article
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A 28-term molecular expansion is employed to calculate total and partial cross sections for charge exchange and excitation in Be++H collisions in the range of impact energies 0.1-25 keV amu-1, which are of predictive value.
Article
Full-text available
Cionga et al have employed the Kramers-Henneberger gauge when performing Floquet close-coupling calculations of electron-hydrogen scattering. It is shown that with their basis the effect of the laser on the target electron is described very inaccurately: their model assumes that the electron attached to the proton oscillates freely in the laser fie...
Article
Bound states and quasibound Rydberg states of NO are studied as a function of internuclear distances in the range . R-matrix calculations which include 12 configuration interaction target states in the close-coupling expansion are performed. Rydberg states of up to n = 10 are studied for the , and symmetries of NO. Intruder states, of both valence...
Article
The validity of the Kroll-Watson approximation to treat electron-atom collisions in the presence of a laser field is discussed. Numerical calculations have been carried out using classical mechanics and a model potential to describe electron-helium scattering for conditions of experimental interest. The effect of an additional polarization term, ar...