Scientometrics and academia.

The social significance and quality of every human activity are proportional to its usefulness to the social community. Science belongs to the very top of the processes and events in the history of humankind that strongly influenced the development of society, which over time transformed it and contributed to the common good. Science produced new knowledge that made it possible for billions of people to rise out of poverty, develop industrialization and mass communication, eradicate many dangerous diseases for humankind, and enable humans to leave their footprints on the moon. Science is a human activity that produces new knowledge presented through innovations, patents, and publications, aimed at solving the problems facing humanity. Read more in the PDF.

High-order harmonic generation by aligned homonuclear diatomic cations.

We introduce the theory of high-order harmonic generation by aligned homonuclear diatomic cations using a strong-field approximation. The target cation is represented as a system which consists of two atomic (ionic) centres and one active electron, while the driving field is either a monochromatic or bichromatic field. For a linearly polarised driving field, we investigate the differences between the harmonic spectra obtained with a neutral molecule and the corresponding molecular cation. Due to the larger ionisation potential, the molecular cations can withstand much higher laser-field intensity than the corresponding neutral molecule before the saturation effects become significant. This allows one to produce high-order harmonics with energy in the water-window interval or beyond. Also, the harmonic spectrum provides information about the structure of the highest-occupied molecular orbital. In order to obtain elliptically polarised harmonics, we suggest that an orthogonally polarised two-colour field is employed as a driving field. In this case, we analyse the harmonic ellipticity as a function of the relative orientation of the cation in the laser field. We show that the regions with large harmonic ellipticity in the harmonic energy-orientation angle plane are the broadest for cations whose molecular orbital does not have a nodal plane. Finally, we show that the molecular cations exposed to an orthogonally polarised two-colour field represent an excellent setup for the production of elliptically polarised attosecond pulses with a duration shorter than 100 as.

Elliptic Dichroism in the Above-Threshold Ionization of Molecules Induced by a Strong Laser Field.

Using a strong-field-approximation theory, we investigate the high-order above-threshold ionization of diatomic molecules exposed to the monochromatic and bichromatic elliptically polarized fields. We devote particular attention to the difference between the photoelectron momentum distributions obtained with fields with opposite helicity. This difference is quantified using the elliptic-dichroism parameter, which represents the normalized difference between the differential ionization rates calculated with driving fields with opposite helicity. We find that this parameter strongly depends on the molecular orientation with respect to the laser field. In addition, this dependence is different for molecules with different types of highest-occupied molecular orbital. In other words, we show that the molecular structure is imprinted onto the elliptic-dichroism parameter for both monochromatic and bichromatic driving fields. This is explained by analyzing the interferences between various partial contributions to the differential ionization rate. In this way, elliptic dichroism also serves as a tool to analyze the electron dynamics. Finally, for heteronuclear diatomic molecules, we show that the elliptic dichroism is different from zero even for the direct electrons, i.e., the electrons that after liberation go directly to the detector. In this case, the dependence on the molecular orientation is far more pronounced for a bichromatic driving field.

Nondipole effects in terahetz-pulse-assisted strong-field ionization.

Nondipole effects in processes assisted by a THz field having the strength of a few MV/cm can be significant due to its long wavelength. We illustrate this for strong-laser-field-induced ionization assisted by a THz field. To this end, we generalize our strong-field-approximation theory so that it includes the first-order term in a 1/c expansion of the vector potential. We show that in this case, in addition to a shift of the maximum of the photoelectron momentum distribution, the differential ionization probability as well as the cutoff energy can be significantly increased. For an explanation of these unexpected results we use the saddle-point method adjusted to include nondipole effects.

Macroscopic effects in high-order harmonic generation - a focal-averaging method based on the integral solution of the wave equation.

A macroscopic theory of high-order harmonic generation (HHG) is presented, which applies a focal-averaging method based on the integral solution of the wave equation. The macroscopic high-harmonic yield is the coherent superposition of the single-atom contributions of all atoms of the generating medium, which are positioned at different spatial points of the laser focus and exposed to the space-time-dependent laser pulse. The HHG spectrum obtained in our macroscopic simulations is qualitatively different from the one obtained using the microscopic or single-atom theory of HHG. Coherent intensity focal averaging, the simpler and more approximate of two methods we introduced, gives the spectrum which forms a declining plateau with the same cutoff position as that of the microscopic spectrum. The second, more precise method, which we call coherent spatio-temporal focal averaging, shows that it is possible, changing the macroscopic conditions, to obtain an observable peak in the harmonic spectrum at an energy much lower than the microscopic cutoff energy. Generally, the high-harmonic yield appears to be dominated by the contributions of laser-pulse spatio-temporal regions with lower intensities as well as by interference, so that the high-energy plateau and its sharp cutoff are quenched in the theoretical simulation and, presumably, in the experiment. The height and position of this peak strongly depend on the macroscopic conditions. We confirmed these findings by applying our macroscopic theory to simulate two recent experiments with mid-infrared laser fields, one with a linearly polarized field and the other one with a bicircular field.

Strong-laser-field-induced ionization assisted by a terahertz pulse.

Extreme terahertz (THz) pulses can be generated via interaction of strong infrared ultrashort laser pulses with a suitable target. Inverting this scheme, we propose to use such THz pulses to control strong-laser-field-driven processes. In particular, we show that for THz-pulse-assisted strong-laser-field ionization the electron yield can be increased by one order of magnitude for some energies, and that the maximal emitted photoelectron energy can be a few times higher than that realized with the laser field alone. This can be achieved with the THz field intensity many orders of magnitude lower than that of the ionizing laser field. The only requirement is that the vector potential amplitude of the THz field, which governs the electron dynamics after the ionization by the laser field, be comparable with that of the used laser field. An important control parameter is the time delay between the THz pulse and the laser pulse. Strong-field ionization of Cs atoms is used for an illustration. The numerical results are obtained applying the improved strong-field approximation. For a physical explanation, we use quantum-orbit theory supported by the modified saddle-point method, as well as a classical model.

Elliptic dichroism in strong-field ionization of atoms subjected to tailored laser fields.

The differential ionization rate for strong-field ionization by tailored laser fields of atomic systems averaged over the magnetic quantum number satisfies particular inversion and reflection symmetries. The symmetries of the elliptic-dichroism parameter, which is related to the change of sign of the ellipticity of the laser field, are considered in detail, with particular emphasis on high-order above-threshold ionization. The general results are illustrated by the examples of an elliptically polarized laser field and a bi-elliptical orthogonally polarized two-color (BEOTC) field. For the BEOTC field the differential ionization rate and the elliptic-dichroism parameter are investigated for the ω-2ω and ω-3ω field combinations and for various relative phases between the laser-field components. The inversion and reflection symmetries of the photoelectron momentum distribution in the polarization plane of the field depend on the parities of r and s in the rω--sω BEOTC field combination and on the relative phase between the field components. We suggest that, by analyzing the symmetry properties of the measured momentum distribution of the elliptic-dichroism parameter, one can identify the mechanism of strong-field ionization. If the rescattering mechanism is dominant one can use these distributions to obtain information about the atomic and molecular structure and dynamics.

The First Mediterranean Seminar on Science Writing, Editing and Publishing, Sarajevo, December 2-3, 2016.

The First Mediterranean Seminar on Science Writing, Editing & Publishing (SWEP 2016) was held in Sarajevo, Bosnia & Herzegovina from 2nd to 3rd December 2016. It was organized by Academy of Medical Sciences of Bosnia and Herzegovina, running concurrent sessions as part of its Annual Meeting titled " "Days of AMNuBiH - Theory and Practice in Science Communication and Scientometrics". Hotel Bosnia in the city centre was the chosen venue. On the first day, nineteen presentations on various issues of science writing and publication ethics were delivered by speakers from Croatia, Serbia, Macedonia, Albania, Bosnia & Herzegovina and the UK (Asim Kurjak, Milivoj Boranic, Doncho Donev, Osman Sinanovic, Miro Jakovljevic, Enver Zerem, Dejan Milosevic, Silva Dobric, Srecko Gajovic, Izet Masic, Armen Yuri Gasparyan, Sekib Sokolovic, Nermin Salkic, Selma Uzunovic, Admir Kurtcehajic, Edin Begic and Floreta Kurti). Each presentation had a take-home message for novice and seasoned authors, encountering numerous problems in non-Anglophone research environment. Lecturers, who were internationally recognized editors of regional journals, generously shared their experience of adhering to the best ethical guidance. Elegant presentations by Srecko Gajovic (Editor-in-Chief of the Croatian Medical Journal) and Armen Yuri Gasparyan (past Chief Editor of the European Science Editing) showcased their accomplishments that strengthened ties between authors from all over the world. Gasparyan reflected on educational resources of editorial associations, such as the International Committee of Medical Journal Editors (ICMJE) and the Committee on Publication Ethics (COPE), and called not just to declare the adherence to, but also to enforce their ethical guidance in daily practice. Editors of Medical Archives, Croatian Medica Journal, Vojnosanitetski Pregled, Psychiatria Danubina, Acta Informatica Medica, Materia Socio-Medica, The Donald School Journal of Ultrasound in Obstretics and Gynecology, Acta Medica Saliniana and Medicinski Glasnik presented their editorial strategies aimed at attracting best authors and resolving problems with authorship, conflicts of interest, and plagiarism. Topical education on science writing and editing was considered as an inseparable part of continuing professional development in biomedicine. Armen Yuri Gasparyan (UK) was offered an opportunity to interact with more than 70 participants, attending the SWEP 2016 on the second day. The lecturer talked about author contributions, disclosures of conflicts of interests, plagiarism of ideas and words, research performance and impact indicators, and targeting ethical journals. Topics were presented in a way to help non-Anglophone authors, reviewers and editors avoid common ethical problems. Dr Gasparyan stressed the importance of regularly arranging such meetings across Balkan and Mediterranean countries to eradicate plagiarism and other forms research misconduct. The organizers of the SWEP 2016 awarded selected keynote speakers with certificates of lifetime achievement in journal editing, and decided to run the Seminar annually with support of Balkan and Mediterranean editors and publishers. The SWEP 2016 marked a turning point in the process of regional developments since all attending editors opted for nurturing enthusiasm of the organizers and launching the Mediterranean Association of Science Editors and Publishers (MASEP). The Seminar was a great success with its impressive scientific and social activities. It attracted more than 100 students, researchers, editors, and publishers from Bosnia & Herzegovina and neighbouring countries. Proceedings, in the form of short reports, were published in Acta Informatica Medica and archived in PubMed Central. New friendships were forged between regional experts in editing and young specialists during those unforgettable two days of intensive discussions and informal interactions (a-y).

Bright circularly polarized soft X-ray high harmonics for X-ray magnetic circular dichroism.

We demonstrate, to our knowledge, the first bright circularly polarized high-harmonic beams in the soft X-ray region of the electromagnetic spectrum, and use them to implement X-ray magnetic circular dichroism measurements in a tabletop-scale setup. Using counterrotating circularly polarized laser fields at 1.3 and 0.79 µm, we generate circularly polarized harmonics with photon energies exceeding 160 eV. The harmonic spectra emerge as a sequence of closely spaced pairs of left and right circularly polarized peaks, with energies determined by conservation of energy and spin angular momentum. We explain the single-atom and macroscopic physics by identifying the dominant electron quantum trajectories and optimal phase-matching conditions. The first advanced phase-matched propagation simulations for circularly polarized harmonics reveal the influence of the finite phase-matching temporal window on the spectrum, as well as the unique polarization-shaped attosecond pulse train. Finally, we use, to our knowledge, the first tabletop X-ray magnetic circular dichroism measurements at the N4,5 absorption edges of Gd to validate the high degree of circularity, brightness, and stability of this light source. These results demonstrate the feasibility of manipulating the polarization, spectrum, and temporal shape of high harmonics in the soft X-ray region by manipulating the driving laser waveform.

Generation of elliptically polarized attosecond pulse trains.

Stimulated by the recent demonstration of the first bright source of circularly polarized high harmonics, we examine the attosecond pulse trains generated by a group of such harmonics. For the s ground state of an atom, the polarization of generated pulses is close to linear, with three different orientations per cycle. However, for the p ground state of the inert gases used in the experiments, the polarization of the attosecond pulses is close to elliptical. We show that this is caused by the different intensities of the high harmonics of the opposite helicity.