Jozo Jureta

Bio: Jozo Jureta is an academic researcher from Université catholique de Louvain. The author has contributed to research in topics: Ionization & Electron ionization. The author has an hindex of 12, co-authored 44 publications receiving 531 citations. Previous affiliations of Jozo Jureta include University of Belgrade.

Intense-laser-field ionization of molecular hydrogen in the tunneling regime and its effect on the vibrational excitation of H2+.

Abstract: H2 molecules were ionized by Ti:sapphire (45 fs, 800 nm) and Nd-doped yttrium aluminum garnet lasers (6 ns, 1064 nm). The relative populations of the vibrational levels of the H+2 ions were determined and found to be concentrated in the lowest vibrational levels. Tunneling ionization calculations with exact field-modified potential curves reproduce the experimental results. The reason for the departure from conventional Franck-Condon-like distributions is the rapid variation of the ionization rate with internuclear distance.

Simulation of KrCl (222 nm) and XeCl (308 nm) excimer lamps with Kr/HCl(Cl2) and Xe/HCl(Cl2) binary and Ne/Kr/Cl2 ternary mixtures excited by glow discharge

Abstract: Based on the kinetic models of XeCl and KrCl active media in Kr/HCl(Cl 2 ), Xe/HCl(Cl 2 ), and Ne/Kr/Cl 2 mixtures, the simulation of XeCl and KrCl excimer lamps pumped by glow discharge is carried out. The optimum compositions of the mixtures are determined. The results obtained are compared with the available experimental data.

Electron impact dissociation and ionization of N-2(+)

Abstract: Absolute cross sections for electron impact ionization, dissociative excitation (DE) and dissociative ionization of N-2(+) ions are measured in the energy range from threshold to 2500 eV. The animated crossed electron-ion beam method has been employed. The individual contributions of ionization products (N-2(2+)) and dissociation fragments (N+), which have both identical mass-to-charge ratio and average velocity, are deduced from the analysis of product velocity distributions. Particular attention was paid to determining the transmission efficiency for dissociation fragments, since their collection was incomplete during the measurements. Threshold energies and kinetic energy released to dissociation fragments are measured. The role of states contributing to different reactions is discussed. For DE, the present results are found to be much smaller than the results of Peterson et al (1998). For ionization (single and dissociative), a satisfactory agreement with their result is obtained as well as with the prediction of Kim et al (2000) obtained in the binary-encounter Bethe approximation.

Total cross sections and kinetic energy release for the electron impact dissociation of H-2(+) and D-2(+)

Abstract: Absolute total cross sections have been measured for electron impact dissociative excitation and dissociative ionization of H-2(+) and D-2(+) in the energy range 5-3000 eV. The vibrational population of the primary H-2(+) beam has been analysed by dissociative charge exchange on a potassium target, and is in good agreement with the measurements of von Busch and Dunn (1972 Phys. Rev. A 5 1726). Kinetic energy release (KER) distributions have been extracted from momentum analysis of the released protons and deuterons at selected impact energies. A model calculation has been performed to interpret the different spectra. Below 100 eV, the distributions exhibit a sharp peak in the range 0-1 eV that is attributed to the dissociative excitation of high vibrational levels to the 2psigma(u) repulsive state in the vicinity of their outer turning point. This observation is consistent with the measured vibrational population extending up to upsilon = 13, as confirmed by the appearance threshold of the dissociative ionization (DI) channel. The KER distributions exhibit a second contribution peaking between 1 and 5 eV, resulting from the admixture of the (1ssigma(g) --> 2psigma(u)), (1ssigma(g) --> 2ppi(u)) and (1ssigma(g) --> 2ssigma(g)) electronic transitions. A distinctive hump is also present around 9 eV, that coincides both with the maximum of the DI contribution, and with the high-energy shoulder of the 2ppi(u) and 2ssigma(g) contributions. The present measurements are in qualitative agreement with the previous results of Caudano and Delfosse, and are fairly well reproduced by our first-order model.

A crossed-beam experiment for electron impact ionization and dissociation of molecular ions: its application to CO+

Abstract: A crossed electron-ion beam experimental set-up has been upgraded for the study of electron impact ionization and dissociation of molecular ions by means of ionic product detection. Both the experimental set-up and the data analysis procedures are described in detail for the estimation of ( i) absolute cross sections, ( ii) kinetic energy release distributions ( KERD) and ( iii) anisotropies of angular distributions. Absolute cross sections are obtained separately for dissociative excitation ( DE) and for dissociative ionization ( DI). A double focusing magnetic field analyser is used for the observation of product velocity distributions, in the laboratory frame, at selected electron energies. The KERD in the centre of mass frame is calculated from the measured velocity distribution as well as the anisotropy of the angular distribution with respect to the initial orientation of the molecular ions. Results are reported for dissociative ionization and dissociative excitation of CO+ to C+ and O+ fragments in the energy range from about 5 eV to 2.5 keV. Absolute cross sections for DE at maximum, i. e. for an electron energy around 35 eV, are found to be ( 9.69 +/- 2.08) x 10(-17) cm(2) and ( 6.24 +/- 1.33) x 10(-17) cm(2), for C+ and O+, respectively, and the corresponding threshold energies are found to be ( 8.5 +/- 0.5) eV and ( 14.8 +/- 0.5) eV. The DE process leading to C+ production is seen to dominate at low electron energies. For DI, the absolute cross section is found to be ( 12.56 +/- 2.38) x 10(-17) cm(2) around 125 eV and the corresponding threshold energy is ( 27.7 +/- 0.5) eV. KERDs, which extend from 0 to 24 eV both for C+ and O+, exhibit very different shapes at low electron energy but similar ones above 100 eV, confirming the role observed respectively for DE and DI. The groups of states contributing to the different processes are identified by comparing present energies thresholds values and the KERDs with theoretical values. Anisotropies are estimated to be in the range 3-6% for both C+ and O+.

Attosecond Physics

Abstract: Summary form only given. Fundamental processes in atoms, molecules, as well as condensed matter are triggered or mediated by the motion of electrons inside or between atoms. Electronic dynamics on atomic length scales tends to unfold within tens to thousands of attoseconds (1 attosecond [as] = 10-18 s). Recent breakthroughs in laser science are now opening the door to watching and controlling these hitherto inaccessible microscopic dynamics. The key to accessing the attosecond time domain is the control of the electric field of (visible) light, which varies its strength and direction within less than a femtosecond (1 femtosecond = 1000 attoseconds). Atoms exposed to a few oscillations cycles of intense laser light are able to emit a single extreme ultraviolet (XUV) burst lasting less than one femtosecond. Full control of the evolution of the electromagnetic field in laser pulses comprising a few wave cycles have recently allowed the reproducible generation and measurement of isolated sub-femtosecond XUV pulses, demonstrating the control of microscopic processes (electron motion and photon emission) on an attosecond time scale. These tools have enabled us to visualize the oscillating electric field of visible light with an attosecond "oscilloscope", to control single-electron and probe multi-electron dynamics in atoms, molecules and solids. Recent experiments hold promise for the development of an attosecond X-ray source, which may pave the way towards 4D electron imaging with sub-atomic resolution in space and time.

The dynamics of small molecules in intense laser fields

Abstract: In the past decade, the understanding of the dynamics of small molecules in intense laser fields has advanced enormously. At the same time, the technology of ultra-short pulsed lasers has equally progressed to such an extent that femtosecond lasers are now widely available. This review is written from an experimentalist's point of view and begins by discussing the value of this research and defining the meaning of the word 'intense'. It continues with describing the Ti: sapphire laser, including topics such as pulse compression, chirped pulse amplification, optical parametric amplification, laser-pulse diagnostics and the absolute phase. Further aspects include focusing, the focal volume effect and space charge. The discussion of physics begins with the Keldysh parameter and the three regimes of ionization, i.e. multi-photon, tunnelling and over-the-barrier. Direct-double ionization (non-sequential ionization), high-harmonic generation, above-threshold ionization and attosecond pulses are briefly mentioned. Subsequently, a theoretical calculation, which solves the time-dependent Schrodinger equation, is compared with an experimental result. The dynamics of H-2(+) in an intense laser field is interpreted in terms of bond-softening, vibrational trapping (bond-hardening), below-threshold dissociation and laser-induced alignment of the molecular axis. The final section discusses the modified Franck-Condon principle, enhanced ionization at critical distances and Coulomb explosion of diatomic and triatomic molecules.

Molecular imaging using recolliding electrons

Abstract: When molecules are subject to intense laser pulses, electrons can be detached, accelerated and driven back to the molecule, resulting in electron–ion recollisions. Recolliding electrons probe the structure and dynamics of molecules. We review the theoretical concepts and experimental achievements towards using recollisions to image molecules. We classify these methods by the choice of the observed signal, which can be one of high-harmonic radiation, electrons from high-order above-threshold ionization, or fragment kinetic energies from recollision-induced dissociation or Coulomb explosion. It is shown that sub-Angstrom and sub-femtosecond resolution is possible within these schemes.

Intense-field many-body S-matrix theory

Abstract: Intense-field many-body S-matrix theory (IMST) provides a systematic ab initio approach to investigate the dynamics of atoms and molecules interacting with intense laser radiation. We review the derivation of IMST as well as its diagrammatic representation and point out its advantage over the conventional 'prior' and 'post' expansions which are shown to be special cases of IMST. The practicality and usefulness of the theory is illustrated by its application to a number of current problems of atomic and molecular ionization in intense fields. We also present a consistent S-matrix formulation of the quantum amplitude for high harmonic generation (HHG) and point out some of the most general properties of HHG radiation emitted by a single atom as well as its relation to coherent emission from many atoms. Experimental results for single and double (multiple) ionization of atoms and the observed distributions of coincidence measurements are analysed and the dominant mechanisms behind them are discussed. Ionization of more complex systems such as diatomic and polyatomic molecules in intense laser fields is analysed as well using IMST and the results are discussed with special attention to the role of molecular orbital symmetry and molecular orientation in space. The review ends with a summary and a brief outlook.