Feras Afaneh | Hashemite University (original) (raw)

Papers by Feras Afaneh

Instrumentation Science & Technology, 2015

Polymer International, 2003

Abstract Electrical properties of bis-ethylenediamine Co (II), Co (III) and Co (II–III) mixed val... more Abstract Electrical properties of bis-ethylenediamine Co (II), Co (III) and Co (II–III) mixed valence complexes and polyethylenediaminecarbosilazane (PEDCSZ)[Co (II), Co (III) and Co (II–III)] macromolecules were measured at room temperature in a frequency range between 1 Hz and 10 6 Hz. Electrical modulus, permittivity and ac conductivity were calculated using ac impedance and phase-angle measurements. It was found that the overall conductivity of PEDCSZ macromolecules with Co is much higher than that for Co ...

Phys. Chem. Chem. Phys., 2015

Nuclear motion in the N1s(-1)4a core-excited state of ammonia is investigated by studying the ang... more Nuclear motion in the N1s(-1)4a core-excited state of ammonia is investigated by studying the angular anisotropy of fragments produced in the decay of the highly excited molecule and compared with predictions from ab initio calculations. Two different fragmentation channels (H(+)/NH2(+) and H(+)/NH(+)/H) reveal complex nuclear dynamics as the excitation photon energy is tuned through the 4a1 resonance. The well-defined angular anisotropy of the fragments produced in the dissociation of the molecular dication species suggests a very rapid nuclear motion and the time scale of the nuclear dynamics is limited to the low fs timescale.

Nuclear Physics A, 2004

Correlated many-particle dynamics in Coulomb systems, which is one of the unsolved fundamental pr... more Correlated many-particle dynamics in Coulomb systems, which is one of the unsolved fundamental problems in AMO-physics, can now be experimentally studied with so far unprecedented completeness and precision of the momenta of all particles involved in the reaction. The recent development of the COLTRIMS technique (COLd Target Recoil Ion Momentum Spectroscopy) provides a coincident multi-fragment imaging technique for eV and sub eV particle detection (1,2). In its completeness, e.g. measuring the fully differential cross section of a reaction by detecting the particles in 47r for all energies up to a couple of 100 eV so far, it is as powerful as the bubble chamber in high energy physics. Based on state-of-the-art cooling techniques (super sonic jets, MOT etc.) and nuclear physics imaging methods, fragmentation processes of atoms, molecules, clusters, as well as the dynamics of electron emission from solid state surfaces which are induced by single photon or multi photon laser absorption, electron or ion impact can be explored completely in momentum space and, for ions, with micro eV resolution. In recent benchmark experiments quasi snapshots (duration as short as an attosec) of the correlated dynamics between electrons and nuclei are taken for atomic and molecular systems.

Radiation Protection Dosimetry, 2008

The activity concentrations of naturally occurring radionuclides ((238)U, (226)Ra, (228)Ra, (210)... more The activity concentrations of naturally occurring radionuclides ((238)U, (226)Ra, (228)Ra, (210)Pb and (40)K) in Jordanian phosphate ore, fertilizer material and phosphogypsum piles were investigated. The results show the partitioning of radionuclides in fertilizer products and phosphogypsum piles. The outcome of this study will enrich the Jordanian radiological map database, and will be useful for an estimation of the radiological impact of this industrial complex on the immediate environment. The activity concentration of (210)Pb was found to vary from 95 +/- 8 to 129 +/- 8 Bq kg(-1) with a mean value of 111 +/- 14 Bq kg(-1) in fertilizer samples, and from 364 +/- 8 to 428 +/- 10 Bq kg(-1) with a mean value of 391 +/- 30 Bq kg(-1) in phosphogypsum samples; while in phosphate wet rock samples, it was found to vary between 621 +/- 9 and 637 +/- 10 Bq kg(-1), with a mean value of 628 +/- 7 Bq kg(-1). The activity concentration of (226)Ra in fertilizer samples (between 31 +/- 4 and 42 +/- 5 Bq kg(-1) with a mean value of 37 +/- 6 Bq kg(-1)) was found to be much smaller than the activity concentration of (226)Ra in phosphogypsum samples (between 302 +/- 8 and 442 +/- 8 Bq kg(-1) with a mean value of 376 +/- 62 Bq kg(-1)). In contrast, the activity concentration of (238)U in fertilizer samples (between 1011 +/- 13 and 1061 +/- 14 Bq kg(-1) with a mean value of 1033 +/- 22 Bq kg(-1)) was found to be much higher than the activity concentration of (238)U in phosphogypsum samples (between 14 +/- 5 and 37 +/- 7 Bq kg(-1) with a mean value of 22 +/- 11 Bq kg(-1)). This indicates that (210)Pb and (226)Ra show similar behaviour, and are concentrated in phosphogypsum piles. In addition, both isotopes enhanced the activity concentration in phosphogypsum piles, while (238)U enhanced the activity concentration in the fertilizer. Due to the radioactivity released from the phosphate rock processing plants into the environment, the highest collective dose commitment for the lungs was found to be 1.02 person nGy t(-1). Lung tissue also shows the highest effect due the presence of (226)Ra in the radioactive cloud (0.087 person nGy t(-1)).

Radiation Protection Dosimetry, 2005

The natural radioactivity due to the presence of (226)Ra, (232)Th and (40)K in selected building ... more The natural radioactivity due to the presence of (226)Ra, (232)Th and (40)K in selected building materials used in Jordanian building constructions has been measured using gamma-ray spectrometer with a Hyper Pure germanium detector. The average activity concentrations observed in different building materials ranged from 27.7 +/- 7.5 to 70.4 +/- 2.8, 5.9 +/- 0.67 to 32.9 +/- 3.9 and 30.8 +/- 0.87 to 58.5 +/- 1.5 for (226)Ra, (232)Th and (40)K, respectively. The activity concentrations of (226)Ra measured in fine aggregates was found to be among the highest values obtained in this work. The ranges of the calculated Ra-equivalent were found to be lower than those values recommended for construction materials (370 Bq kg(-1)). The average internal and external hazard indices were found to be <1. The average of the calculated annual gonadal equivalent dose was found to be 198 microSv y(-1). Results indicate no significant radiological hazards arise from using such materials in building construction.

Journal of Physics B: Atomic, Molecular and Optical Physics, 2002

The transfer ionization of He and H 2 by incident He 2+ was investigated at 0.81 au impact veloci... more The transfer ionization of He and H 2 by incident He 2+ was investigated at 0.81 au impact velocity employing cold target recoil ion momentum spectroscopy. In addition to electrons in the saddle point region between the target and projectile forming two 'jets' separated by a valley along the projectile beam axis, we find a new group of electrons moving with a velocity greater than the projectile velocity. These new fast forward electrons result from a narrow range of impact parameters and contribute up to 40% to the total cross section of the transfer ionization process.

Journal of Physics B: Atomic, Molecular and Optical Physics, 2007

The zero-degree ejected-electron spectrum for protons incident on He at 25 keV is examined experi... more The zero-degree ejected-electron spectrum for protons incident on He at 25 keV is examined experimentally using the COLTRIMS technique. The momentum distribution of the emitted electrons for the transfer ionization (TI) reaction channel is measured in coincidence with the momentum vectors of the recoil ion and the scattered projectile. The momentum distribution of the electrons emitted around zero degree in the forward direction for the TI reaction channel shows two prominent structures: the electron-capture-to-the-continuum (ECC) peak and the saddle-point peak. From the measured fully differential electron emission cross sections with respect to the scattering plane we can deduce that the main ECC formation mechanism is electron promotion via quasimolecular orbitals.

We studied slow dissociative collisions between He and diatomic molecular ions using Cold Target ... more We studied slow dissociative collisions between He and diatomic molecular ions using Cold Target Recoil Momentum Spectroscopy (COLTRIMS) technique in combination with fragment imaging technique. All final state momentum components, as well as the masses of the molecular fragments were determined. As the complete information on the kinematics is available, we are able to calculate the final state binding energy as well as the kinetic energy of the molecular fragments in the molecular center of mass system (kinetic energy release). The results show that the probability of the reaction channels is strongly dependent on the relative geometric orientation of the participants.

Journal of Physics B-atomic Molecular and Optical Physics, 2000

We demonstrate experimentally the difference between a sequential interaction of a femtosecond la... more We demonstrate experimentally the difference between a sequential interaction of a femtosecond laser field with two electrons and a nonsequential process of double ionization mediated by electron-electron correlation. This is possible by observing the momentum distribution of doubly charged argon ions created in the laser field. In the regime of laser intensities where the nonsequential process dominates, an increase in laser power leads to an increase in the observed ion momenta. At the onset of the sequential process, however, a higher laser power leads to colder ions. The momentum distributions of the ions from the sequential process can be modelled by convolving the single-ionization distribution with itself.

Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2005

The single ionization (SI) and the transfer ionization (TI) of H 2 have been investigated utilizi... more The single ionization (SI) and the transfer ionization (TI) of H 2 have been investigated utilizing the Cold Target Recoil Ion Momentum Spectroscopy (COLTRIMS) reaction microscope. Continuum electron velocity spectra have been measured for experimentally determined nuclear motion. Electron velocity distributions for the SI of H 2 show that the ejected electrons lie mainly in the scattering plane where their velocities were found to lie between those of the recoiling target and the scattered projectile. In addition to a group of electrons seen in SI saddle electrons group, the electron velocity spectra for TI of H 2 unveiled the existence of another group of electrons with different structure. These electrons were emitted with velocities greater than the projectile velocity and found to result from a narrow range of impact parameters. These fast forward electrons reveal a substantial amount of out-of-plane scattering.

Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2002

A new spectrometer has been developed based on the combination of standard time-of-flight techniq... more A new spectrometer has been developed based on the combination of standard time-of-flight technique and position sensitive delay line detectors. The basic features of the spectrometer, particularly of the multi-hit capable detector, are described. To demonstrate the performance of this new system, the dynamic emission characteristics, i.e. the threedimensional velocity distribution, of desorbed H þ 2 from Al target by Ar 0 impact (570 keV) is presented. It is found that the desorption yield is maximum for radial and axial emission velocities at 1.2 and 12 km/s respectively, corresponding to 1.5 eV ions emitted at 57°to normal (following the projectile radial direction). The initial energy distribution spreads out over 16 eV. Ó

Physical Review Letters, 2008

The dissociative electron transfer from He into 10 keV H þ 2 was measured in a kinematically comp... more The dissociative electron transfer from He into 10 keV H þ 2 was measured in a kinematically complete experiment by using the cold target recoil ion momentum spectroscopy imaging technique in combination with a highly resolving molecular fragment imaging technique. The electron transfer into the dissociative b 3 AE þ u state of H 2 could be selected by kinematic conditions. We find a striking double slit interference pattern in the transverse momentum transfer which we can modify by selecting different internuclear distances. Compared to an optical double slit, interference minima and maxima are interchanged. The latter is the result of a phase shift in the electronic part of the wave function.

Journal of Physics: Conference Series, 2009

The dissociative electron transfer from He into 10 keV H þ 2 was measured in a kinematically comp... more The dissociative electron transfer from He into 10 keV H þ 2 was measured in a kinematically complete experiment by using the cold target recoil ion momentum spectroscopy imaging technique in combination with a highly resolving molecular fragment imaging technique. The electron transfer into the dissociative b 3 AE þ u state of H 2 could be selected by kinematic conditions. We find a striking double slit interference pattern in the transverse momentum transfer which we can modify by selecting different internuclear distances. Compared to an optical double slit, interference minima and maxima are interchanged. The latter is the result of a phase shift in the electronic part of the wave function.

Nuclear Physics A, 2004

Correlated many-particle dynamics in Coulomb systems, which is one of the unsolved fundamental pr... more Correlated many-particle dynamics in Coulomb systems, which is one of the unsolved fundamental problems in AMO-physics, can now be experimentally studied with so far unprecedented completeness and precision of the momenta of all particles involved in the reaction. The recent development of the COLTRIMS technique (COLd Target Recoil Ion Momentum Spectroscopy) provides a coincident multi-fragment imaging technique for eV and sub eV particle detection (1,2). In its completeness, e.g. measuring the fully differential cross section of a reaction by detecting the particles in 47r for all energies up to a couple of 100 eV so far, it is as powerful as the bubble chamber in high energy physics. Based on state-of-the-art cooling techniques (super sonic jets, MOT etc.) and nuclear physics imaging methods, fragmentation processes of atoms, molecules, clusters, as well as the dynamics of electron emission from solid state surfaces which are induced by single photon or multi photon laser absorption, electron or ion impact can be explored completely in momentum space and, for ions, with micro eV resolution. In recent benchmark experiments quasi snapshots (duration as short as an attosec) of the correlated dynamics between electrons and nuclei are taken for atomic and molecular systems.

Physical Review Letters, 2001

We report on the experimental observation of an abrupt rise in the longitudinal momentum distribu... more We report on the experimental observation of an abrupt rise in the longitudinal momentum distribution of recoil ions created in proton helium collision. The details of this structure can be related to electrons traveling with the velocity of the projectile [electron capture to the continuum (ECC)]. The longitudinal as well as the transverse distribution of the recoil ions can be explained as a continuation of the momentum distribution from ions resulting from electron capture illustrating the smooth transition from the capture to bound states of the projectile to the ECC.

Journal of Physics B-atomic Molecular and Optical Physics, 2007

We have used the cold target recoil ion momentum spectroscopy imaging technique to investigate di... more We have used the cold target recoil ion momentum spectroscopy imaging technique to investigate dissociative ionization of H 2 by 25 keV proton impact. A kinematically complete picture of the dissociative ionization dynamics for slow proton collision has been obtained. The results show a strong impactparameter dependence of the fragmentation process of H 2 . This clearly emerged in the energy distributions of the H + ions generated for different impact parameters. At large impact parameters the H + ions equally share the energy liberated in the collision whereas at small impact parameters, the energy sharing is quite asymmetric. We also observed a strong dependence of the electron emission on molecular alignment. The momentum distribution of the emitted electron generated for a fixed-in-space H 2 molecule displays that the electrons are more likely to be emitted perpendicular to the molecular axis.

We demonstrate experimentally the difference between a sequential interaction of a femtosecond la... more We demonstrate experimentally the difference between a sequential interaction of a femtosecond laser field with two electrons and a nonsequential process of double ionization mediated by electron-electron correlation. This is possible by observing the momentum distribution of doubly charged argon ions created in the laser field. In the regime of laser intensities where the nonsequential process dominates, an increase in laser power leads to an increase in the observed ion momenta. At the onset of the sequential process, however, a higher laser power leads to colder ions. The momentum distributions of the ions from the sequential process can be modelled by convolving the single-ionization distribution with itself.

Journal of Physics B-atomic Molecular and Optical Physics, 2000

The dynamics of singly ionizing proton-helium collisions have been studied experimentally for sev... more The dynamics of singly ionizing proton-helium collisions have been studied experimentally for several energies of the projectile (0.2, 0.5, 1.0 and 1.3 MeV) with the technique of cold target recoil-ion momentum spectroscopy (COLTRIMS). The complete final-state distribution in momentum space of all three particles was determined by measuring the three momentum components of the emitted electron and the coincident recoiling target ion. The momentum transfer and energy loss of the outgoing projectile was determined by momentum and energy conservation laws. Doubly differential cross sections of the kinematically complete experimental investigation are presented. The present data are compared with results from fast highly charged heavy-ion impact experiments.

Physical Review A, 2007

Using cold target recoil ion momentum spectroscopy ͑COLTRIMS͒ we have investigated the production... more Using cold target recoil ion momentum spectroscopy ͑COLTRIMS͒ we have investigated the production of one free electron in slow He 2+ +He͑1s 2 ͒ collisions. At projectile velocities between 0.6 and 1.06 a.u. ͑9-28 keV/ u͒, the fully differential cross section was measured state selective with respect to the second electron, which is bound either at the target or the projectile. We provide a comprehensive data set comprising state selective total cross section, scattering angle dependent single differential cross sections, and fully differential cross section. We show that the momentum distribution of the electron in the continuum image the relevant molecular orbitals for the reaction channel under consideration. By choosing the bound electron final state at the target or projectile and the impact parameter we can select these orbitals and manipulate their relative phase.

Instrumentation Science & Technology, 2015

Polymer International, 2003

Abstract Electrical properties of bis-ethylenediamine Co (II), Co (III) and Co (II–III) mixed val... more Abstract Electrical properties of bis-ethylenediamine Co (II), Co (III) and Co (II–III) mixed valence complexes and polyethylenediaminecarbosilazane (PEDCSZ)[Co (II), Co (III) and Co (II–III)] macromolecules were measured at room temperature in a frequency range between 1 Hz and 10 6 Hz. Electrical modulus, permittivity and ac conductivity were calculated using ac impedance and phase-angle measurements. It was found that the overall conductivity of PEDCSZ macromolecules with Co is much higher than that for Co ...

Phys. Chem. Chem. Phys., 2015

Nuclear motion in the N1s(-1)4a core-excited state of ammonia is investigated by studying the ang... more Nuclear motion in the N1s(-1)4a core-excited state of ammonia is investigated by studying the angular anisotropy of fragments produced in the decay of the highly excited molecule and compared with predictions from ab initio calculations. Two different fragmentation channels (H(+)/NH2(+) and H(+)/NH(+)/H) reveal complex nuclear dynamics as the excitation photon energy is tuned through the 4a1 resonance. The well-defined angular anisotropy of the fragments produced in the dissociation of the molecular dication species suggests a very rapid nuclear motion and the time scale of the nuclear dynamics is limited to the low fs timescale.

Nuclear Physics A, 2004

Correlated many-particle dynamics in Coulomb systems, which is one of the unsolved fundamental pr... more Correlated many-particle dynamics in Coulomb systems, which is one of the unsolved fundamental problems in AMO-physics, can now be experimentally studied with so far unprecedented completeness and precision of the momenta of all particles involved in the reaction. The recent development of the COLTRIMS technique (COLd Target Recoil Ion Momentum Spectroscopy) provides a coincident multi-fragment imaging technique for eV and sub eV particle detection (1,2). In its completeness, e.g. measuring the fully differential cross section of a reaction by detecting the particles in 47r for all energies up to a couple of 100 eV so far, it is as powerful as the bubble chamber in high energy physics. Based on state-of-the-art cooling techniques (super sonic jets, MOT etc.) and nuclear physics imaging methods, fragmentation processes of atoms, molecules, clusters, as well as the dynamics of electron emission from solid state surfaces which are induced by single photon or multi photon laser absorption, electron or ion impact can be explored completely in momentum space and, for ions, with micro eV resolution. In recent benchmark experiments quasi snapshots (duration as short as an attosec) of the correlated dynamics between electrons and nuclei are taken for atomic and molecular systems.

Radiation Protection Dosimetry, 2008

The activity concentrations of naturally occurring radionuclides ((238)U, (226)Ra, (228)Ra, (210)... more The activity concentrations of naturally occurring radionuclides ((238)U, (226)Ra, (228)Ra, (210)Pb and (40)K) in Jordanian phosphate ore, fertilizer material and phosphogypsum piles were investigated. The results show the partitioning of radionuclides in fertilizer products and phosphogypsum piles. The outcome of this study will enrich the Jordanian radiological map database, and will be useful for an estimation of the radiological impact of this industrial complex on the immediate environment. The activity concentration of (210)Pb was found to vary from 95 +/- 8 to 129 +/- 8 Bq kg(-1) with a mean value of 111 +/- 14 Bq kg(-1) in fertilizer samples, and from 364 +/- 8 to 428 +/- 10 Bq kg(-1) with a mean value of 391 +/- 30 Bq kg(-1) in phosphogypsum samples; while in phosphate wet rock samples, it was found to vary between 621 +/- 9 and 637 +/- 10 Bq kg(-1), with a mean value of 628 +/- 7 Bq kg(-1). The activity concentration of (226)Ra in fertilizer samples (between 31 +/- 4 and 42 +/- 5 Bq kg(-1) with a mean value of 37 +/- 6 Bq kg(-1)) was found to be much smaller than the activity concentration of (226)Ra in phosphogypsum samples (between 302 +/- 8 and 442 +/- 8 Bq kg(-1) with a mean value of 376 +/- 62 Bq kg(-1)). In contrast, the activity concentration of (238)U in fertilizer samples (between 1011 +/- 13 and 1061 +/- 14 Bq kg(-1) with a mean value of 1033 +/- 22 Bq kg(-1)) was found to be much higher than the activity concentration of (238)U in phosphogypsum samples (between 14 +/- 5 and 37 +/- 7 Bq kg(-1) with a mean value of 22 +/- 11 Bq kg(-1)). This indicates that (210)Pb and (226)Ra show similar behaviour, and are concentrated in phosphogypsum piles. In addition, both isotopes enhanced the activity concentration in phosphogypsum piles, while (238)U enhanced the activity concentration in the fertilizer. Due to the radioactivity released from the phosphate rock processing plants into the environment, the highest collective dose commitment for the lungs was found to be 1.02 person nGy t(-1). Lung tissue also shows the highest effect due the presence of (226)Ra in the radioactive cloud (0.087 person nGy t(-1)).

Radiation Protection Dosimetry, 2005

The natural radioactivity due to the presence of (226)Ra, (232)Th and (40)K in selected building ... more The natural radioactivity due to the presence of (226)Ra, (232)Th and (40)K in selected building materials used in Jordanian building constructions has been measured using gamma-ray spectrometer with a Hyper Pure germanium detector. The average activity concentrations observed in different building materials ranged from 27.7 +/- 7.5 to 70.4 +/- 2.8, 5.9 +/- 0.67 to 32.9 +/- 3.9 and 30.8 +/- 0.87 to 58.5 +/- 1.5 for (226)Ra, (232)Th and (40)K, respectively. The activity concentrations of (226)Ra measured in fine aggregates was found to be among the highest values obtained in this work. The ranges of the calculated Ra-equivalent were found to be lower than those values recommended for construction materials (370 Bq kg(-1)). The average internal and external hazard indices were found to be <1. The average of the calculated annual gonadal equivalent dose was found to be 198 microSv y(-1). Results indicate no significant radiological hazards arise from using such materials in building construction.

Journal of Physics B: Atomic, Molecular and Optical Physics, 2002

The transfer ionization of He and H 2 by incident He 2+ was investigated at 0.81 au impact veloci... more The transfer ionization of He and H 2 by incident He 2+ was investigated at 0.81 au impact velocity employing cold target recoil ion momentum spectroscopy. In addition to electrons in the saddle point region between the target and projectile forming two 'jets' separated by a valley along the projectile beam axis, we find a new group of electrons moving with a velocity greater than the projectile velocity. These new fast forward electrons result from a narrow range of impact parameters and contribute up to 40% to the total cross section of the transfer ionization process.

Journal of Physics B: Atomic, Molecular and Optical Physics, 2007

The zero-degree ejected-electron spectrum for protons incident on He at 25 keV is examined experi... more The zero-degree ejected-electron spectrum for protons incident on He at 25 keV is examined experimentally using the COLTRIMS technique. The momentum distribution of the emitted electrons for the transfer ionization (TI) reaction channel is measured in coincidence with the momentum vectors of the recoil ion and the scattered projectile. The momentum distribution of the electrons emitted around zero degree in the forward direction for the TI reaction channel shows two prominent structures: the electron-capture-to-the-continuum (ECC) peak and the saddle-point peak. From the measured fully differential electron emission cross sections with respect to the scattering plane we can deduce that the main ECC formation mechanism is electron promotion via quasimolecular orbitals.

We studied slow dissociative collisions between He and diatomic molecular ions using Cold Target ... more We studied slow dissociative collisions between He and diatomic molecular ions using Cold Target Recoil Momentum Spectroscopy (COLTRIMS) technique in combination with fragment imaging technique. All final state momentum components, as well as the masses of the molecular fragments were determined. As the complete information on the kinematics is available, we are able to calculate the final state binding energy as well as the kinetic energy of the molecular fragments in the molecular center of mass system (kinetic energy release). The results show that the probability of the reaction channels is strongly dependent on the relative geometric orientation of the participants.

Journal of Physics B-atomic Molecular and Optical Physics, 2000

We demonstrate experimentally the difference between a sequential interaction of a femtosecond la... more We demonstrate experimentally the difference between a sequential interaction of a femtosecond laser field with two electrons and a nonsequential process of double ionization mediated by electron-electron correlation. This is possible by observing the momentum distribution of doubly charged argon ions created in the laser field. In the regime of laser intensities where the nonsequential process dominates, an increase in laser power leads to an increase in the observed ion momenta. At the onset of the sequential process, however, a higher laser power leads to colder ions. The momentum distributions of the ions from the sequential process can be modelled by convolving the single-ionization distribution with itself.

Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2005

The single ionization (SI) and the transfer ionization (TI) of H 2 have been investigated utilizi... more The single ionization (SI) and the transfer ionization (TI) of H 2 have been investigated utilizing the Cold Target Recoil Ion Momentum Spectroscopy (COLTRIMS) reaction microscope. Continuum electron velocity spectra have been measured for experimentally determined nuclear motion. Electron velocity distributions for the SI of H 2 show that the ejected electrons lie mainly in the scattering plane where their velocities were found to lie between those of the recoiling target and the scattered projectile. In addition to a group of electrons seen in SI saddle electrons group, the electron velocity spectra for TI of H 2 unveiled the existence of another group of electrons with different structure. These electrons were emitted with velocities greater than the projectile velocity and found to result from a narrow range of impact parameters. These fast forward electrons reveal a substantial amount of out-of-plane scattering.

Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2002

A new spectrometer has been developed based on the combination of standard time-of-flight techniq... more A new spectrometer has been developed based on the combination of standard time-of-flight technique and position sensitive delay line detectors. The basic features of the spectrometer, particularly of the multi-hit capable detector, are described. To demonstrate the performance of this new system, the dynamic emission characteristics, i.e. the threedimensional velocity distribution, of desorbed H þ 2 from Al target by Ar 0 impact (570 keV) is presented. It is found that the desorption yield is maximum for radial and axial emission velocities at 1.2 and 12 km/s respectively, corresponding to 1.5 eV ions emitted at 57°to normal (following the projectile radial direction). The initial energy distribution spreads out over 16 eV. Ó

Physical Review Letters, 2008

The dissociative electron transfer from He into 10 keV H þ 2 was measured in a kinematically comp... more The dissociative electron transfer from He into 10 keV H þ 2 was measured in a kinematically complete experiment by using the cold target recoil ion momentum spectroscopy imaging technique in combination with a highly resolving molecular fragment imaging technique. The electron transfer into the dissociative b 3 AE þ u state of H 2 could be selected by kinematic conditions. We find a striking double slit interference pattern in the transverse momentum transfer which we can modify by selecting different internuclear distances. Compared to an optical double slit, interference minima and maxima are interchanged. The latter is the result of a phase shift in the electronic part of the wave function.

Journal of Physics: Conference Series, 2009

The dissociative electron transfer from He into 10 keV H þ 2 was measured in a kinematically comp... more The dissociative electron transfer from He into 10 keV H þ 2 was measured in a kinematically complete experiment by using the cold target recoil ion momentum spectroscopy imaging technique in combination with a highly resolving molecular fragment imaging technique. The electron transfer into the dissociative b 3 AE þ u state of H 2 could be selected by kinematic conditions. We find a striking double slit interference pattern in the transverse momentum transfer which we can modify by selecting different internuclear distances. Compared to an optical double slit, interference minima and maxima are interchanged. The latter is the result of a phase shift in the electronic part of the wave function.

Nuclear Physics A, 2004

Correlated many-particle dynamics in Coulomb systems, which is one of the unsolved fundamental pr... more Correlated many-particle dynamics in Coulomb systems, which is one of the unsolved fundamental problems in AMO-physics, can now be experimentally studied with so far unprecedented completeness and precision of the momenta of all particles involved in the reaction. The recent development of the COLTRIMS technique (COLd Target Recoil Ion Momentum Spectroscopy) provides a coincident multi-fragment imaging technique for eV and sub eV particle detection (1,2). In its completeness, e.g. measuring the fully differential cross section of a reaction by detecting the particles in 47r for all energies up to a couple of 100 eV so far, it is as powerful as the bubble chamber in high energy physics. Based on state-of-the-art cooling techniques (super sonic jets, MOT etc.) and nuclear physics imaging methods, fragmentation processes of atoms, molecules, clusters, as well as the dynamics of electron emission from solid state surfaces which are induced by single photon or multi photon laser absorption, electron or ion impact can be explored completely in momentum space and, for ions, with micro eV resolution. In recent benchmark experiments quasi snapshots (duration as short as an attosec) of the correlated dynamics between electrons and nuclei are taken for atomic and molecular systems.

Physical Review Letters, 2001

We report on the experimental observation of an abrupt rise in the longitudinal momentum distribu... more We report on the experimental observation of an abrupt rise in the longitudinal momentum distribution of recoil ions created in proton helium collision. The details of this structure can be related to electrons traveling with the velocity of the projectile [electron capture to the continuum (ECC)]. The longitudinal as well as the transverse distribution of the recoil ions can be explained as a continuation of the momentum distribution from ions resulting from electron capture illustrating the smooth transition from the capture to bound states of the projectile to the ECC.

Journal of Physics B-atomic Molecular and Optical Physics, 2007

We have used the cold target recoil ion momentum spectroscopy imaging technique to investigate di... more We have used the cold target recoil ion momentum spectroscopy imaging technique to investigate dissociative ionization of H 2 by 25 keV proton impact. A kinematically complete picture of the dissociative ionization dynamics for slow proton collision has been obtained. The results show a strong impactparameter dependence of the fragmentation process of H 2 . This clearly emerged in the energy distributions of the H + ions generated for different impact parameters. At large impact parameters the H + ions equally share the energy liberated in the collision whereas at small impact parameters, the energy sharing is quite asymmetric. We also observed a strong dependence of the electron emission on molecular alignment. The momentum distribution of the emitted electron generated for a fixed-in-space H 2 molecule displays that the electrons are more likely to be emitted perpendicular to the molecular axis.

We demonstrate experimentally the difference between a sequential interaction of a femtosecond la... more We demonstrate experimentally the difference between a sequential interaction of a femtosecond laser field with two electrons and a nonsequential process of double ionization mediated by electron-electron correlation. This is possible by observing the momentum distribution of doubly charged argon ions created in the laser field. In the regime of laser intensities where the nonsequential process dominates, an increase in laser power leads to an increase in the observed ion momenta. At the onset of the sequential process, however, a higher laser power leads to colder ions. The momentum distributions of the ions from the sequential process can be modelled by convolving the single-ionization distribution with itself.

Journal of Physics B-atomic Molecular and Optical Physics, 2000

The dynamics of singly ionizing proton-helium collisions have been studied experimentally for sev... more The dynamics of singly ionizing proton-helium collisions have been studied experimentally for several energies of the projectile (0.2, 0.5, 1.0 and 1.3 MeV) with the technique of cold target recoil-ion momentum spectroscopy (COLTRIMS). The complete final-state distribution in momentum space of all three particles was determined by measuring the three momentum components of the emitted electron and the coincident recoiling target ion. The momentum transfer and energy loss of the outgoing projectile was determined by momentum and energy conservation laws. Doubly differential cross sections of the kinematically complete experimental investigation are presented. The present data are compared with results from fast highly charged heavy-ion impact experiments.

Physical Review A, 2007

Using cold target recoil ion momentum spectroscopy ͑COLTRIMS͒ we have investigated the production... more Using cold target recoil ion momentum spectroscopy ͑COLTRIMS͒ we have investigated the production of one free electron in slow He 2+ +He͑1s 2 ͒ collisions. At projectile velocities between 0.6 and 1.06 a.u. ͑9-28 keV/ u͒, the fully differential cross section was measured state selective with respect to the second electron, which is bound either at the target or the projectile. We provide a comprehensive data set comprising state selective total cross section, scattering angle dependent single differential cross sections, and fully differential cross section. We show that the momentum distribution of the electron in the continuum image the relevant molecular orbitals for the reaction channel under consideration. By choosing the bound electron final state at the target or projectile and the impact parameter we can select these orbitals and manipulate their relative phase.