Application de la methode du titre a l'etude de la structure de C 4 . Observation pour la pre... more Application de la methode du titre a l'etude de la structure de C 4 . Observation pour la premiere fois d'un C 4 rhombique
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1988
The-ontent of this paper is divided Into two parts: I) Achievements of che last two years in stud... more The-ontent of this paper is divided Into two parts: I) Achievements of che last two years in studying molecular Ion structure with the aid of the newly developed Coulomb-Explosion (CE) method, and II) the understanding of the modern CS data in terms of an invariant density of nuclear coordinates of the studied molecule.
A solution is presented for the problem of interpreting measurements of data from many degrees of... more A solution is presented for the problem of interpreting measurements of data from many degrees of freedom where binning is prohibitive. A binninglike procedure is introduced in which data and theory are represented by a set of independent expectation values. A comparison between theory and experiment is then performed by a conventional procedure together with an additional test of the independence of the expectation values. Associated uncorrelated errors are derived as well. The application of this method to Coulomb-explosion imaging is discussed. The method is illustrated by the analysis of the bending angle distribution of the CH 2 ϩ molecule from Coulomb-explosion imaging measurements.
The effect of target polarization fields on the bond-angle distribution following the foil-induce... more The effect of target polarization fields on the bond-angle distribution following the foil-induced Coulomb explosion of CH 2 + has been measured. Incorporating a detailed model description of the polarization effects and other target effects into a Monte Carlo simulation of the experiment, a good description of the various observables is obtained. In particular, the bond-angle distribution is found to agree with existing ab initio calculations.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1995
Three dimensional imaging of the molecular dissociation process in fast collisions is presented w... more Three dimensional imaging of the molecular dissociation process in fast collisions is presented with two different setups. One setup is for a fast molecular beam from an accelerator colliding with a gas target. The second setup is for a molecular target system and the collision process is with highly ionized fast beam. The advantages of each system are discussed. The three dimensional imaging of the molecular fragments is done with special detectors that combine the CCD image with time of flight data. An example of the molecular beam measurement is given for an 11 MeV B, beam.
Some biological membranes are affected by weak magnetic fields.1 In particular, magnet-induced or... more Some biological membranes are affected by weak magnetic fields.1 In particular, magnet-induced orientation was observed in the outer segments of retinal rods,2 chloroplasts,3 bacterial chromatophores,4 purple membranes,5 and recently in black lipid membranes.6 The ...
The effect of the structure of organic films on their electronic band above the vacuum level is i... more The effect of the structure of organic films on their electronic band above the vacuum level is investigated. The ballistic transmission probability of secondary electrons emitted from metal substrates through organized organic thin films is found to decrease for electrons with kinetic energy higher than ca. 1 eV. The thicker and more ordered the adsorbed film is, the better defined is its band structure and the sharper is its transmission resonance.
Two-dimensional arrangements of molecules can show remarkable cooperative electronic effects. Suc... more Two-dimensional arrangements of molecules can show remarkable cooperative electronic effects. Such effects can serve to achieve direct electronic sensing of chemical and physical processes via electrostatic effects, i.e., without transfer of charge or matter between the locus of sensing and that of detection.
ABSTRACT The Coulomb Explosion Imaging (CEI) method was used to determine the structure and photo... more ABSTRACT The Coulomb Explosion Imaging (CEI) method was used to determine the structure and photochemistry of carbon clusters. The cyclic structure of C4 was found using a combination of laser photodetachment techniques and the CEI method. The cyclic C4 electron affinity was found to be 2.1 ± 0.1 eV, more than 1 eV lower than the electron affinity of the linear isomer.
Combined energy and angle distributions of protons resulting from Coulomb explosion of 11.2 Mev O... more Combined energy and angle distributions of protons resulting from Coulomb explosion of 11.2 Mev OH+ in carbon foils have been measured in simultaneous coincidence with different emerging oxygen charge-states. The measurements were made with targets of thickness ranging from 80 A to 740 A. The proton distributions show strong asymmetry effects due to the electronic wake produced by oxygen atoms in the solid, and there is also a marked dependence of the shape of the distributions on both the target thickness and the oxygen charge-state downstream from the target.
Nuclear Instruments and Methods in Physics Research
ABSTRACT Experiments involving the use of MeV molecular-ion beams have yielded new information on... more ABSTRACT Experiments involving the use of MeV molecular-ion beams have yielded new information on atomic collisions in solids. A central part of the analyses of such experiments is a knowledge of the distribution of internuclear separations contained in the incident beam. In an attempt to determine how these distributions depend on ion-source gas conditions, we have studied foil-induced dissociations of H2+, H3+, HeH+ and OH2+ ions. Although changes of ion-source gas compositions and pressure were found to have no measurable influence on the vibrational state populations of the beams reaching our target, for HeH+ we found that beams produced in our rf source were vibrationally “hotter” than beams produced in a duoplasmatron. This was also seen in studies of neutral fragments and transmitted molecules.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
The structure of small carbon clusters (C,, n = 3-8) has been studied using the Coulomb explosion... more The structure of small carbon clusters (C,, n = 3-8) has been studied using the Coulomb explosion imaging technique. The experimental system is based on the 14 MV Pelletron accelerator at the Weizmann Institute. Negative molecules are accelerated and photodetached by a laser beam inside the high voltage terminal of the accelerator. The neutral molecules are then electron stripped by passing through a thin Formvar target and the resulting atomic ions are collected by a new 3D multiparticle imaging detector. Nonlinear structures of C, and C, clusters were observed. New measurements of laser photodetachment thresholds for C, (n = 3-8) indicate that new compact isomers exist.
ABSTRACT We report the results of a series of experiments investigating the nature of very-highly... more ABSTRACT We report the results of a series of experiments investigating the nature of very-highly-excited states of fast ions emerging from thin foils. The yields of electrons produced by field ionization of these atoms are compared for different projectiles and beam energies. Various field arrangements were used. The consequences for related studies of fast-ion beams penetrating solids are discussed.
The authors report measurements of the joint distributions in energy and angle for fragments aris... more The authors report measurements of the joint distributions in energy and angle for fragments arising from the dissociation of 1.2-MeV Hâ/sup +/ and 3.0-MeV HeH/sup +/ in thin carbon foils and in a variety of gases at several pressures. From the foil measurements the distribution of initial internuclear separations in the incident projectiles is derived. These distributions are then used
ABSTRACT The structure of protonated acetylene (C2H+3), including correlations, is measured and a... more ABSTRACT The structure of protonated acetylene (C2H+3), including correlations, is measured and analyzed by an advanced Coulomb explosion imaging method. In the data analysis, it is essential to include large-amplitude motions of the nuclei within the molecule and many-body correlation features for revealing the correct structure. We find that the nuclear conformations in this molecule differ markedly from theoretical predictions and previous experimental findings.
Application de la methode du titre a l'etude de la structure de C 4 . Observation pour la pre... more Application de la methode du titre a l'etude de la structure de C 4 . Observation pour la premiere fois d'un C 4 rhombique
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1988
The-ontent of this paper is divided Into two parts: I) Achievements of che last two years in stud... more The-ontent of this paper is divided Into two parts: I) Achievements of che last two years in studying molecular Ion structure with the aid of the newly developed Coulomb-Explosion (CE) method, and II) the understanding of the modern CS data in terms of an invariant density of nuclear coordinates of the studied molecule.
A solution is presented for the problem of interpreting measurements of data from many degrees of... more A solution is presented for the problem of interpreting measurements of data from many degrees of freedom where binning is prohibitive. A binninglike procedure is introduced in which data and theory are represented by a set of independent expectation values. A comparison between theory and experiment is then performed by a conventional procedure together with an additional test of the independence of the expectation values. Associated uncorrelated errors are derived as well. The application of this method to Coulomb-explosion imaging is discussed. The method is illustrated by the analysis of the bending angle distribution of the CH 2 ϩ molecule from Coulomb-explosion imaging measurements.
The effect of target polarization fields on the bond-angle distribution following the foil-induce... more The effect of target polarization fields on the bond-angle distribution following the foil-induced Coulomb explosion of CH 2 + has been measured. Incorporating a detailed model description of the polarization effects and other target effects into a Monte Carlo simulation of the experiment, a good description of the various observables is obtained. In particular, the bond-angle distribution is found to agree with existing ab initio calculations.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1995
Three dimensional imaging of the molecular dissociation process in fast collisions is presented w... more Three dimensional imaging of the molecular dissociation process in fast collisions is presented with two different setups. One setup is for a fast molecular beam from an accelerator colliding with a gas target. The second setup is for a molecular target system and the collision process is with highly ionized fast beam. The advantages of each system are discussed. The three dimensional imaging of the molecular fragments is done with special detectors that combine the CCD image with time of flight data. An example of the molecular beam measurement is given for an 11 MeV B, beam.
Some biological membranes are affected by weak magnetic fields.1 In particular, magnet-induced or... more Some biological membranes are affected by weak magnetic fields.1 In particular, magnet-induced orientation was observed in the outer segments of retinal rods,2 chloroplasts,3 bacterial chromatophores,4 purple membranes,5 and recently in black lipid membranes.6 The ...
The effect of the structure of organic films on their electronic band above the vacuum level is i... more The effect of the structure of organic films on their electronic band above the vacuum level is investigated. The ballistic transmission probability of secondary electrons emitted from metal substrates through organized organic thin films is found to decrease for electrons with kinetic energy higher than ca. 1 eV. The thicker and more ordered the adsorbed film is, the better defined is its band structure and the sharper is its transmission resonance.
Two-dimensional arrangements of molecules can show remarkable cooperative electronic effects. Suc... more Two-dimensional arrangements of molecules can show remarkable cooperative electronic effects. Such effects can serve to achieve direct electronic sensing of chemical and physical processes via electrostatic effects, i.e., without transfer of charge or matter between the locus of sensing and that of detection.
ABSTRACT The Coulomb Explosion Imaging (CEI) method was used to determine the structure and photo... more ABSTRACT The Coulomb Explosion Imaging (CEI) method was used to determine the structure and photochemistry of carbon clusters. The cyclic structure of C4 was found using a combination of laser photodetachment techniques and the CEI method. The cyclic C4 electron affinity was found to be 2.1 ± 0.1 eV, more than 1 eV lower than the electron affinity of the linear isomer.
Combined energy and angle distributions of protons resulting from Coulomb explosion of 11.2 Mev O... more Combined energy and angle distributions of protons resulting from Coulomb explosion of 11.2 Mev OH+ in carbon foils have been measured in simultaneous coincidence with different emerging oxygen charge-states. The measurements were made with targets of thickness ranging from 80 A to 740 A. The proton distributions show strong asymmetry effects due to the electronic wake produced by oxygen atoms in the solid, and there is also a marked dependence of the shape of the distributions on both the target thickness and the oxygen charge-state downstream from the target.
Nuclear Instruments and Methods in Physics Research
ABSTRACT Experiments involving the use of MeV molecular-ion beams have yielded new information on... more ABSTRACT Experiments involving the use of MeV molecular-ion beams have yielded new information on atomic collisions in solids. A central part of the analyses of such experiments is a knowledge of the distribution of internuclear separations contained in the incident beam. In an attempt to determine how these distributions depend on ion-source gas conditions, we have studied foil-induced dissociations of H2+, H3+, HeH+ and OH2+ ions. Although changes of ion-source gas compositions and pressure were found to have no measurable influence on the vibrational state populations of the beams reaching our target, for HeH+ we found that beams produced in our rf source were vibrationally “hotter” than beams produced in a duoplasmatron. This was also seen in studies of neutral fragments and transmitted molecules.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
The structure of small carbon clusters (C,, n = 3-8) has been studied using the Coulomb explosion... more The structure of small carbon clusters (C,, n = 3-8) has been studied using the Coulomb explosion imaging technique. The experimental system is based on the 14 MV Pelletron accelerator at the Weizmann Institute. Negative molecules are accelerated and photodetached by a laser beam inside the high voltage terminal of the accelerator. The neutral molecules are then electron stripped by passing through a thin Formvar target and the resulting atomic ions are collected by a new 3D multiparticle imaging detector. Nonlinear structures of C, and C, clusters were observed. New measurements of laser photodetachment thresholds for C, (n = 3-8) indicate that new compact isomers exist.
ABSTRACT We report the results of a series of experiments investigating the nature of very-highly... more ABSTRACT We report the results of a series of experiments investigating the nature of very-highly-excited states of fast ions emerging from thin foils. The yields of electrons produced by field ionization of these atoms are compared for different projectiles and beam energies. Various field arrangements were used. The consequences for related studies of fast-ion beams penetrating solids are discussed.
The authors report measurements of the joint distributions in energy and angle for fragments aris... more The authors report measurements of the joint distributions in energy and angle for fragments arising from the dissociation of 1.2-MeV Hâ/sup +/ and 3.0-MeV HeH/sup +/ in thin carbon foils and in a variety of gases at several pressures. From the foil measurements the distribution of initial internuclear separations in the incident projectiles is derived. These distributions are then used
ABSTRACT The structure of protonated acetylene (C2H+3), including correlations, is measured and a... more ABSTRACT The structure of protonated acetylene (C2H+3), including correlations, is measured and analyzed by an advanced Coulomb explosion imaging method. In the data analysis, it is essential to include large-amplitude motions of the nuclei within the molecule and many-body correlation features for revealing the correct structure. We find that the nuclear conformations in this molecule differ markedly from theoretical predictions and previous experimental findings.
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Papers by Zeev Vager