Radmila Panajotovic

Institute of Physics Belgrade | IPB · Centre for solid state physics and new materials

Keywords: field effect; graphene; liquid-phase exfoliation; optoelectronics; photosynthetic reaction center. Abbreviations: AFM-atomic force microscopy; CNT-carbon nanotube; CVD-chemical vapor deposition; CWDL-continuous wave diode laser; DI-de-ionized; IDS-drain-source current; IR-infrared; LB-Langmuir-Blodgett; LBA-Langmuir-Blodgett assembly; LPE...

Tungsten disulfide, a transition metal dichalcogenide, has numerous applications as active components in gas- and chemical-sensing devices, photovoltaic sources, photocatalyst substrates, etc. In such devices, the presence of water in the sensing environment is a factor whose role has not been well-understood. To address this problem, the in situ p...

Background: Dental stem cells, which originate from the neural crest, due to their easy accessibility might be good candidates in neuro-regenerative procedures, along with graphene-based nanomaterials shown to promote neurogenesis in vitro. We aimed to explore the potential of liquid-phase exfoliated graphene (LPEG) film to stimulate the neuro-dif...

We report on experimental elastic differential and integral cross sections for electron scattering from zinc. The energy range of these measurements is 10–100 eV, while the scattered electron angular range in the differential cross-section data is 10∘–150∘. We also supplement our measured data with applications of our optical potential and relativi...

Aim: To characterize stem cells originating from different dental tissues (apical papilla [SCAP], dental follicle [DFSC], and pulp [DPSC]) and test the capacity of Raman microspectroscopy to distinguish between the three dental stem cell types. Methods: SCAP, DFSC, and DPSC cultures were generated from three immature wisdom teeth originating fro...

Stem cell‐based therapies are considered a promising treatment modality for many medical conditions. Several types of stem cells with variable differentiation potentials have been isolated from dental tissues, among them stem cells from apical papilla (SCAP). In parallel, new classes of biocompatible nanomaterials have also been developed, includin...

We demonstrate a facile fabrication technique for highly conductive and transparent thin graphene films. Sheet conductivity of Langmuir–Blodgett assembled multi-layer graphene films is enhanced through doping with nitric acid, leading to a five fold improvement while retaining the same transparency as un-doped films. Sheet resistivity of such chemi...

In cancer research the radiation dose delivered to different organs presents a critical parameter for destroying the cancer cells' DNA, but the biochemical pathways that bring cells to death in many cases start at the cell membrane whose major part consists of lipid molecules. In our XPS and NEXAFS experiment, we exposed a monolayer lipid film supp...

Chemical changes in phospholipid (DPPC -- 1,2-dipalmitoyl-sn-glycero-3-phosphocholine) monolayer films deposited on gold are studied in an X-ray photoelectron spectroscopy experiment. DPPC films have been irradiated by a monoenergetic electron beam in the energy range from 5 to 200 eV. The shifts in the binding energy of C 1s, O 1s, P 2p, and N 1s...

Since the first experiments of low-energy electron scattering from condensed DNA [1] have been performed, the interest in studying low-energy electron-biomolecule interactions has been increasing. Knowledge of effective cross sections for single- and double-strand breaks of DNA and for vibrational and electronic excitation of nucleic bases and nucl...

This article presents a new type of low-energy crossed-beam electron spectrometer for measuring angular differential cross sections of electron-impact excitation of atomic and molecular targets. Designed for investigations at energies close to excitation thresholds, the spectrometer combines a pulsed electron beam with the time-of-flight technique...

Extensive results from measurements on short DNA strands impinged on by 1-30 eV electrons indicate that the damage they induce is due to the chemical nature of the nucleic bases and/or their sequence. The strong variation of effective cross sections for plasmid DNA single-strand breaks with incident electron energy and the resonant enhancement at 1...

A new spectrometer is described for measuring the momentum distributions of scattered electrons arising from electron-atom and electron-molecule ionization experiments. It incorporates and builds on elements from a number of previous designs, namely, a source of polarized electrons and two high-efficiency electrostatic electron energy analyzers. Th...

Measurements of the vibrational and electronic excitation of a sub-monolayer up to a monolayer film of adenine were performed with a high resolution electron energy-loss (HREEL) spectrometer. The integral cross sections (over the half-space angle) for excitation of the normal vibrational modes of the ground electronic state and electronically excit...

Spin-resolved (e,2e) measurements provide stringent tests to the theory of electron impact-induced ionization and afford insight into the correlated many-body behaviour of systems of charged particles. Here we describe recent improvements made to our toroidal-sector (e,2e) electron spectrometer and demonstrate its enhanced instrumental sensitivity...

Recent progress in the measurement of absolute collision cross sections for electron molecule scattering is discussed in the context of measurements which have relevance to atmospheric phenomena and technological applications. Cross sections for low energy (< 5 eV) scattering from NO highlight the role of resonant processes in the excitation of thi...

The process of electron scattering from heavy target atoms is of considerable interest due to the enhanced role of relativistic effects and distortion of the electron trajectories resulting from the large value of nuclear charge. Here we present (e,2e) ionization measurements and distorted-wave Born approximation calculations for the scattering of...

It has been know for some time that the possibility for exchange between continuum electrons and bound electrons (normally called exchange distortion) can have an important effect on the outcome of electron-atom collisions particularly if the continuum electron is spin polarized. The proper way to treat this exchange would be through a Hartree-Fock...

We determined effective cross sections for production of single-strand breaks (SSBs) in plasmid DNA [pGEM 3Zf(-)] by electrons of 10 eV and energies between 0.1 and 4.7 eV. After purification and lyophilization on a chemically clean tantalum foil, dry plasmid DNA samples were transferred into a high-vacuum chamber and bombarded by a monoenergetic e...

The most detailed insight into the process of electron impact‐induced ionization of atomic species is provided by measurements in which both kinematical and quantum mechanical variables are determined. Here we describe recent (e,2e) experimental and theoretical studies involving the ionization of xenon and argon by spin‐polarized electrons in which...

We present results of a joint theoretical and experimental investigation of electron scattering from the $4{s}^{2}\phantom{\rule{0.3em}{0ex}}^{1}S$ ground state of zinc. The $4s4p\phantom{\rule{0.2em}{0ex}}^{1}P^{o}$ and $4s5p\phantom{\rule{0.2em}{0ex}}^{1}P^{o}$ differential cross sections were measured at scattering angles between 10\ifmmode^\cir...

We report experimental results for electron scattering from perfluorocyclobutane, c-C(4)F(8), obtained from measurements in our two laboratories. A set of differential, integral, and momentum transfer cross sections is provided for elastic scattering for incident electron energies from 1.5 to 100 eV. Inelastic scattering (vibrational excitation) cr...

We report experimental results for electron scattering from tetrafluoroethylene, C2F4, obtained from measurements in two laboratories. An extensive set of differential, integral, and momentum transfer cross sections is provided for elastic scattering for incident electron energies from 1 to 100 eV and inelastic (vibrational excitation) scattering f...

The interaction of electrons with water molecules has significance in a wide range of naturally occurring phenomena and many practical applications. A particularly relevant area of study is the effect of ionizing radiation in the human body, whose water content is approximately 60 percent. It is well recognized that high-energy particles produce a...

Fluorocarbons like C_2F4 and C_4F8 are very common processing gases in the plasma etching of silicon dioxide, which is an important step in the manufacture of semiconductor microelectronics. Understanding the reaction chemistry of these molecules is crucial for achieving production efficiency and stability of the etched surfaces. In order to explai...

Although only a minor constituent of the earth's upper atmosphere, nitric oxide (NO) plays a major role in infrared auroral emissions due to radiation from vibrationally excited (NO*) states. The main process leading to the production of these excited molecules was thought to be chemiluminescence, whereby excited nitrogen atoms interact with oxygen...

Electron impact excitation from the ground state to the and states of zinc has been experimentally investigated at incident energies from 15 to 100 eV and scattering angles up to 12°. The absolute generalized oscillator strengths and differential cross-sections are determined through normalization to the optical oscillator strengths. The present va...

A range of experimental and theoretical techniques have been applied to the study of transient negative ions (resonances) formed in electron scattering from the Group II metals Mg, Zn, Cd, and Hg at incident electron energies below the first ionization potential. A wealth of resonance structures have been observed and from the experimental observat...

NO is a molecule of significant interest because of its importance in areas as diverse as the chemistry of our atmosphere and many human biological processes. In particular NO plays an important role in the energy balance of the atmosphere through its IR emissions from fundamental and first and higher order overtones in its ground electronic state....

We have measured absolute elastic scattering cross sections for electron impact on ethylene. The experimental data have been obtained on two different, crossed-beam electron spectrometers and they cover the energy range from 1 to 15eV and scattering angles between 10° and 130°. Both differential (in angle) and energy dependent cross sections have b...

Absolute measurements of elastic scattering and vibrational excitation of the NO molecule by low energy electron impact (0.4-2.5 eV) are presented. They show that previous estimates of these cross sections may be in error by as much as a factor of 3 and provide compelling evidence for a reassessment of the balance between elastic scattering and vib...

We have measured absolute elastic scattering and vibrational excitation cross sections for electron impact on ethylene. The experimental data have been obtained on two different crossed-beam electron spectrometers and they cover the energy range from 1 to 100 eV and scattering angles between 10? and 130?. Both differential (in angle) and energy-dep...

A new electron coincidence spectrometer based around toroidal sector electrodes is described, whose design has been optimised for electron impact induced (e,2e) ionization studies. An improvement in data collection efficiency of more than three orders of magnitude compared to its predecessor has been achieved. The strengths and weaknesses of the de...

We have carried out independent measurements in our two laboratories of low energy (1-100 eV) electron scattering from ethylene, tetraflouroethylene and perfluorocyclobutane. The main motivation for the measurements in the fluorinated molecules are their applications in plasma processing, whilst for ethylene, it is interesting to compare the cross...

The measured relative electron differential cross sections (DCSs) for excitation of the 2 + and states of N2O (Marinkovic et al 1986 J. Phys. B: At. Mol. Phys. 19 2365) have been normalized through a recent forward scattering function for the generalized oscillator strength. Measurements were obtained at electron impact energies of 15, 20, 30, 50 a...

We determined experimentally two critical points in elastic electron scattering by argon where the differential cross section (DCS) attains its smallest values. The points were found to be at and at . Special attention was given to improve the angular resolution in order to determine the exact positions of the minima. These minima are important bec...

Relative differential electron impact cross sections sigma ( theta ) for elastic and inelastic scattering in mercury have been measured. The sigma ( theta ) are normalized to the optical oscillator strength for the 61S0-61P1 transition and put on an absolute scale. Results are presented at 15, 25, 35, 40, 50, 60 and 100 eV for elastic scattering an...

A new technique is described which is capable of observing the stability of specific states of doubly charged molecular ions with vibrational level resolution. The method is based on the process of double photoionization using synchrotron radiation. Pairs of threshold electrons identify the initial state, and the resulting ions are characterized by...