I. I. Popescu

Romanian Academy, Bucureşti, Romania

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Publications (57)

  • A Groza · A Surmeian · C Diplasu · [...] · I. I. Popescu
    [Show abstract] [Hide abstract] ABSTRACT: In this paper we demonstrate that negative and positive corona discharge in air at atmospheric pressure is a convenient physical method for generation of germanium oxides in polydimetylsiloxane based polymers layers during the polymerization processes. The dependence of content distribution of the different germanium oxides in the polymers layers with the electrodes polarity was investigated by infrared (IR) and Glow Discharge Optical Emission (GD-OES) spectroscopies. The results of the spectroscopic measurements show that in positive corona discharges, the germanium oxide diffuses in the polymers while in negative corona discharges, the germanium oxide layer formed at the polymersubstrate interface has a limited diffusion due to the formation of Si-O-Ge bonds.
    Article · Nov 2010 · OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS
  • A Surmeian · C Diplasu · A Groza · [...] · I. Iovitz Popescu
    [Show abstract] [Hide abstract] ABSTRACT: An absorption spectroscopy technique with temporal resolution using a conventional spectral source operating in pulsed mode has been used to determine the temporal distribution of neon metastable atoms density in the afterglow of a high voltage pulsed hollow cathode discharge plasma. The measured values for Neon 23P2 state density in the 40-120 μs temporal afterglow range are found to lay from 1.2 × 1012 ± 20% cm-3 to 3 × 1010 ± 20% cm-3.
    Article · Jun 2010 · OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS
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    S.A. Karamian · C.A. Ur · J. Adam · [...] · I. I. Popescu
    [Show abstract] [Hide abstract] ABSTRACT: Production of Hf and Lu high-spin isomers has been experimentally studied in spallation reactions induced by intermediate energy protons. Targets of enriched 179Hf (91%) and natHf were bombarded with protons of energy in the range from 90 to 650 MeV provided by the internal beam of the Dubna Phasotron synchrocyclotron. The activation yields of the reaction products were measured by using the γ-ray spectroscopy and radiochemistry methods. The production cross-sections obtained for the 179m2Hf, 178m2Hf and 177mLu isomers are similar to the previously measured values from the spallation of Ta, Re and W targets. Therefore, the reactions involving emission of only a few nucleons, like (p,p′), (p,p′n) and (p,2pn), can transfer high enough angular momentum to the final residual nuclei with reasonable large cross-sections. A significant gain in the isomeric yields was obtained when enriched 179Hf targets were used. The mass distribution of the residual nuclei was measured over a wide range of masses and the fission-to-spallation ratio could be deduced as a function of the projectile energy. Features of the reaction mechanism are briefly discussed.
    Full-text Article · Mar 2009 · Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment
  • S. Olariu · M. Sorescu · I.-I. Popescu · C. B. Collins
    [Show abstract] [Hide abstract] ABSTRACT: We consider the possibility that multiphoton sidebands to Mössbauer transitions should be produced for nuclei embedded in displacive-type ferroelectric crystals in the paraelectric phase, by modulating the hyperfine electric-field gradient acting at the nuclear sites with the aid of an electric radiofrequency field. It is calculated that the intensity of the first-order sideband to the 14.4 keV transition of 57Fe, incorporated in a BaTiO3 crystal having a dielectric constant of 3 103, becomes 9% of the intensity of the parent line when the crystal is polarized by a static electric field of 107 V/m and a parallel radiofrequency electric field of 3 106 V/m, oscillating at 2.9 MHz.
    Article · Jul 2007 · EPL (Europhysics Letters)
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    [Show abstract] [Hide abstract] ABSTRACT: A process for transferring energy from electron shells into nuclear excitation, NEET, has offered the promise for modulating nuclear properties at accessible levels of power. It had been proven recently by exciting a nuclear level of 197Au with synchrotron radiation, but measured couplings were far below theoretical objectives. Reported here is an extension of that approach for excitation to 178Hf m2 isomeric nuclei. Isomeric targets were irradiated with X-rays in the beamline BL01B1 at the synchrotron radiation source SPring-8. Energies were tuned from 9 to 13 keV. In this range an excitation branch attributed to NEET was found to have a probability of 2 × 10−3 relative to L-shell photoionization. The resulting emission of exoergic γ-photons was observed from the target at a rate approaching the theoretical maximum.
    Full-text Article · Jan 2007 · EPL (Europhysics Letters)
  • A. Groza · A. Surmeian · M. Ganciu · I. I. Popescu
    [Show abstract] [Hide abstract] ABSTRACT: In this paper we have demonstrated that the negative and positive corona discharge in air at atmospheric pressure is a convenient physical method for the initiation of the high-reaction-rate polymerization process of the linseed oil. The different stages of the polymerization process were investigated by infrared (IR) spectroscopy and the formation of the linseed oil polymer was evaluated by the presence of the C-O-C bands.
    Article · Jan 2007 · EPL (Europhysics Letters)
  • A Surmeian · C Diplasu · I.-Iovitz Popescu
    [Show abstract] [Hide abstract] ABSTRACT: The use of classical electric probes for studying plasma parameters of the high voltage pulsed discharges, encounters enormous difficulties. Besides the difficulty of a proper galvanic insulation of the probe required during the high voltage pulse, the probe can exert great influence over the plasma potential by the current that it draws from the plasma. In this paper, we proposed a new method for the determination of the electrical conductivity of the plasma in the afterglow of the high voltage pulsed discharges, using a low frequency RF plane probe. The application of a small low frequency signal to the plane probe could successfully eliminate all the disadvantages mentioned above.
    Article · Dec 2005
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    A Surmeian · C Diplasu · A Groza · [...] · II Popescu
    [Show abstract] [Hide abstract] ABSTRACT: We report a new population mechanism of Ar II energy levels in a high density current hollow cathode pulsed discharge which may be of practical interest in the investigation of population inversion and lasing of Ar II emission lines in the temporal afterglow plasmas.
    Full-text Conference Paper · Oct 2005
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    A. Groza · A. Surmeian · M. Ganciu · I. I. Popescu
    [Show abstract] [Hide abstract] ABSTRACT: The changes in the chemical structure of an organosilicon compound generated in a wire-to-plane corona discharge electrode configuration in air at atmospheric pressure are investigated by infrared spectral measurements. A comparison between the compounds obtained in negative and positive corona discharges, is made.
    Full-text Article · Oct 2005 · OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS
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    A. Groza · A. Surmeian · M. Ganciu · [...] · I. I. Popescu
    [Show abstract] [Hide abstract] ABSTRACT: This paper demonstrates that the coupling between negative and positive corona discharges in air at atmospheric pressure can be used as a physical method for SiO 2 thin films generation, having an organo-silicon compound (silicone oil) as precursor.
    Full-text Article · Aug 2005 · Journal of Optoelectronics and Advanced Materials
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    [Show abstract] [Hide abstract] ABSTRACT: The Hf-178m2 nuclear spin isomer stores 2.45 MeV of energy for a half life of 31 years. Unperturbed, such nuclei radiate away the stored energy through the emission of gamma photons from electromagnetic (EM) transitions occurring within the nuclei. It has been shown that the irradiation of samples containing such nuclei with pulsed X-rays can accelerate the rate of the EM transitions by relaxing the selection rules upon changes of angular momenta. To date, most work has been done with incident X-ray energies between 9 and 10 keV, and in such cases the acceleration of the rate of gamma emission is immediate. Reported here is a channel for deexcitation excited by more energetic X-rays that results in a cascade of gamma transitions that includes a 4 second statistical time lag. This more protracted release of the energy stored in samples of the Hf-178m2 nuclear isomers encourages consideration of potential mechanical and thermal applications.
    Full-text Article · Jun 2005 · Journal de Physique IV (Proceedings)
  • C. B. Collins · N. C. Zoita · F. Davanloo · [...] · I. I. Popescu
    [Show abstract] [Hide abstract] ABSTRACT: Induced release of the high energy densities stored in isomeric nuclear states may be important in the development of ultrashort wavelength lasers. Such a release could compensate the spontaneous power density radiated from the laser medium at threshold. The most promising candidate for such a role seems to be the 31-yr isomeric nucleus of Hf-178 that stores 1.3 GJ/g in the electromagnetic excitation of its constituent protons and neutrons. Successful studies of the induced release of energies from such isomeric states have required an extension of techniques for nuclear resonance spectroscopy using synchrotron radiation (SR) that had previously been applied only to ground state materials. In 2004, monochromatic X-rays from the SPring-8 SR source were used to identify one of the excited nuclear states that mediates the induced decay of the 31-yr isomer of Hf-178. That trigger level was found to lie at 2457.20(22) keV. It was excited when an isomeric nucleus absorbed an incident X-ray photon. We found that one branch of its subsequent decay consisted of a strong electromagnetic transition to the ground state of the nucleus. The energy of the γ-photon emitted was equal to the energy of the trigger level. Proximity in energy of that level to the energy of 2446.06 keV stored by the isomer makes it easy to induce a release of the stored energy and encourages prospects for the development of a gamma ray laser. (© 2005 by Astro, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA)
    Article · Mar 2005 · Laser Physics Letters
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    [Show abstract] [Hide abstract] ABSTRACT: A nuclear-XAFS effect occurs during the scattering of electrons or X-ray photons when the excitation of inner shell electrons couples both energy and angular momentum into nuclear channels of excitation. Nuclear transitions can be induced if the density of excited states of the nucleus enclosed by the electrons is high enough. The 31-yr isomeric state, 178m2Hf satisfies the condition for excitation by monochromatic X-rays from synchrotron sources. Strong effects upon such nuclei are studied.
    Full-text Article · Oct 2004 · Radiation Physics and Chemistry
  • S.A Karamian · J Adam · P Chaloun · [...] · C.A Ur
    [Show abstract] [Hide abstract] ABSTRACT: Yields and cross-sections of the radioactive nuclides produced after the irradiation of natural composition W and enriched 186W targets at the Dubna synchrocyclotron were measured using the γ-ray spectroscopy methods with high-resolution Ge detectors. Among the detected nuclides we identified the spallation and fission products. High-spin isomeric states in the Hf and Lu nuclides were populated and the isomer-to-ground state ratios could be estimated. The nuclide yields were calculated using the LAHET code at six different values of the proton energy in the range from 100 to 800 MeV both for the natW and enriched 186W targets. The measured isotope yields are in general good agreement with the calculations. A shortcoming of the code is the inability to predict isomer-to-ground state ratios. The experimental data show that the 177mLu, 178m2Hf and 179m2Hf high-spin isomers are produced with a 2.5 times higher yield in the 97% enriched 186W target as compared to the natW target under identical irradiation conditions. This makes significance for the creation of high-activity isomeric sources. The mass-distribution of the products and the fission-to-spallation ratio were also deduced and compared with theory prediction.
    Article · Jul 2004 · Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment
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    [Show abstract] [Hide abstract] ABSTRACT: Cited By (since 1996):13, Export Date: 27 April 2013, Source: Scopus
    Full-text Article · Feb 2004 · Laser Physics
  • A. Groza · M. Ganciu-Petcu · A. Surmeian · I. I. Popescu
    [Show abstract] [Hide abstract] ABSTRACT: High reaction rate mechanisms of oils polymerization are reported in a wire-to-plane corona discharge electrode configuration at atmospheric pressure. Spectral measurements are performed at different stages of the polymerization process, as well as optical investigation of the oil polymer layers.
    Article · Jan 2004 · Molecular Crystals and Liquid Crystals
  • E Badareu · I Popescu · C Ghita · O Zamfir
    [Show abstract] [Hide abstract] ABSTRACT: The effect of the addition of mercury to a conventional caesium neutralized diode is described. A pronounced Penning effect was found, the mercury 63P1-63D1,2 transitions being the most efficient for the volume ionization of caesium atoms. The increased electron scattering due to the introduction of mercury into the diode is to a large extent minimized by the low collision cross section, at 0.17 eV, due to the Ramsauer effect. Consequently, it appears that the performance of the diode operating under arc mode conditions may be significantly improved by the addition of mercury.
    Article · Nov 2002 · British Journal of Applied Physics
  • E Badareu · C Ghita · G Musa · [...] · O Zamfir
    [Show abstract] [Hide abstract] ABSTRACT: It is found that the volume ionization in caesium diodes may be improved by the addition of cadmium. This is due to collisions of the second kind of caesium with cadmium atoms excited on the resonance level. Some electrical and spectral characteristics of the low voltage arc in caesium-cadmium vapours are given.
    Article · Nov 2002 · British Journal of Applied Physics
  • [Show abstract] [Hide abstract] ABSTRACT: In this work a compact electron beam source, a preionized controlled open-ended hollow cathode discharge, is used for the ablation of an anodic target. Time-resolved spectroscopic measurements of the optical emission of the filamentary and plume plasmas, both created by the electron beam, are presented and electron beam parameters are given. These latter are compared to preliminary measurements in a channel-spark.
    Conference Paper · Aug 2002
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    [Show abstract] [Hide abstract] ABSTRACT: The productivity of the spallation reactions at proton energies of 100–660 MeV for accumulation of the radioactive isotopes and isomers has been studied experimentally. Spectra of Ta and Re targets activated at Dubna synchrocyclotron were measured using the methods of radiochemistry and gamma spectroscopy. Many radioactive products of the spallation and fission reactions are identified, and their yields are compared with the LAHET code simulations. Cross-sections σm and isomer-to-ground state ratios σm/σg are deduced for nuclear isomers, in particular, for high-spin isomers, as 178m2Hf, 179m2Hf and 177mLu. Spin distributions for the spallation-residue nuclei are estimated to understand the σm/σg ratios. Possibilities to optimize the methods for the long-lived isomers production are discussed, and it would be a necessary step on the way to accumulate such exotic radionuclides in milligram amount under reasonable cost and radiation safety conditions.
    Full-text Article · Aug 2002 · Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment

Publication Stats

574 Citations

Institutions

  • 2010
    • Romanian Academy
      Bucureşti, Romania
  • 2007
    • University of Bucharest
      Bucureşti, Bucureşti, Romania
  • 2000-2007
    • National Institute for Laser, Plasma and Radiation Physics
      Bucureşti, Bucureşti, Romania
    • University of Texas at Dallas
      Richardson, Texas, United States
  • 1999
    • Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering
      București, Bucureşti, Romania
  • 1998
    • Universitätsklinikum Erlangen
      Erlangen, Bavaria, Germany
  • 1996
    • Université Paris-Sud 11
      Orsay, Île-de-France, France