Svatopluk Civis

Academy of Sciences of the Czech Republic, Praha, Hlavni mesto Praha, Czech Republic

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Publications (40)87.76 Total impact

  • [show abstract] [hide abstract]
    ABSTRACT: In tables we present the QDT calculated the matrix elements (f- and A-values) for the transition involving the nd, nf, ng, and nh states of CaI and MgI in the 800-9000cm-1 range. The Ritz wavenumbers ν and air wavelengths λ are calculated using the energy level values from the cited references. (2 data files).
    VizieR Online Data Catalog. 04/2013;
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    ABSTRACT: Aims: While solar spectra contain a lot of Ca I and Mg I infrared (IR) lines, no laboratory-measured spectra of these atoms have been reported for wavenumbers below 2000 cm-1. This study reports Ca I spectra in the 1300-4500 cm-1 range and Mg I spectra in the 1300-4500 cm-1 range. Methods: We performed a time-resolved Fourier transform infrared spectroscopy study of a plasma created by the laser ablation of MgF2 and CaF2 targets in a vacuum. The oscillator strengths (f-values) were calculated using quantum defect theory (QDT), which shows good agreement with the available experimental and theoretical results. Results: We report several Ca I and Mg I IR lines that have not been measured previously in laboratory. The recorded spectra allow the excitation energies of some Ca I and Mg I states with high orbital momentum (l = 4,5) to be determined. We also provide a long list of QDT-calculated f-values for Ca I and Mg I in the range of 800-9000 cm-1. Tables 5 and 6 are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/554/A24
    Astronomy and Astrophysics 01/2013; 554:A24. · 5.08 Impact Factor
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    ABSTRACT: The formamide-based synthesis of nucleic acids is considered as a non-aqueous scenario for the emergence of biomolecules from inorganic matter. In the current study, we scrutinized the chemical composition of formamide ices mixed with an FeNi meteorite material treated with laser-induced dielectric breakdown plasma created in nitrogen buffer gas. These experiments aimed to capture the first steps of those chemical transformations that may lead to the formation of nucleobases during the impact of an extraterrestrial icy body containing formamide on an early Earth atmosphere. High-resolution FT-IR spectroscopy combined with quantum chemical calculations was used to analyze the volatile fraction of the products formed during such an event. We have found that the spectrum of the evaporated formamide ices is dominated by the spectral signatures of the dimeric form of formamide. Upon exposure to laser sparks new well-defined bands appear in the spectrum centered at ~820, ~995 and ~1650 cm-1. On the basis of quantum chemical calculations, these bands can be assigned to the absorptions of 2-amino-2-hydroxy-acetonitrile and to 2-amino-2-hydroxy-malononitrile, which are formed in a direct reaction between formamide and CN∙ radicals upon the high-energy impact event. We also show that there is an exergonic reaction route via these intermediates leading to diaminomaleonitrile, which is generally considered to play a key role in the synthesis of nucleobases.
    Journal of the American Chemical Society 11/2012; · 10.68 Impact Factor
  • S. Civis, V.E. Chernov, M. Ferus
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    ABSTRACT: High resolution time-resolved Fourier-transform infrared spectroscopy is be applied for observations of the emission arising after irradiation of a metal and metal oxides targets with a pulsed nanosecond ArF (λ = 193 nm) laser. The infrared emission spectra will be studied in the 800-8000 cm-1 spectral region. Although the spectra of the atoms were studied in various frequency ranges, our study points to the existence of spectral lines, which have not yet been observed. While the visible spectral lines are due to the transitions involving the ground and low-excited states, the IR lines in atoms correspond to the transitions between highly excited (Rydberg) levels. The transition probabilities and oscillator strengths for all transitions involving the reported levels are calculated.
    Transparent Optical Networks (ICTON), 2012 14th International Conference on; 01/2012
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    ABSTRACT: Aims. While solar spectra contain a lot of Ca I and Mg I infrared (IR) lines, no laboratory-measured spectra of these atoms have been reported for wavenumbers below 2000 cm-1. This study reports Ca I spectra in the 1300–4500 cm-1 range and Mg I spectra in the 1300–4500 cm-1 range. Methods. We performed a time-resolved Fourier transform infrared spectroscopy study of a plasma created by the laser ablation of MgF2 and CaF2 targets in a vacuum. The oscillator strengths (f-values) were calculated using quantum defect theory (QDT), which shows good agreement with the available experimental and theoretical results. Results. We report several Ca I and Mg I IR lines that have not been measured previously in laboratory. The recorded spectra allow the excitation energies of some Ca I and Mg I states with high orbital momentum (l = 4,5) to be determined. We also provide a long list of QDT-calculated f-values for Ca I and Mg I in the range of 800–9000 cm-1.
    Astronomy and Astrophysics 01/2012; 542:A35. · 5.08 Impact Factor
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    ABSTRACT: A novel high-energy explosive material, FOX-7 (1,1-diamino-2,2-dinitroethylene), was studied using a combination of laser-induced breakdown spectroscopy (LIBS) and selected ion flow tube mass spectrometry (SIFT-MS). The LIBS technique uses short laser pulses (an ArF excimer laser) as the energy source to convert small quantities of a sample into plasma and to induce the emission of its molecular fragments or atoms. SIFT-MS is a novel method for absolute quantification based on chemical ionization using three reagent ions, with the ability to determine concentrations of trace gases and vapors of volatile organic compounds in real time. SIFT-MS was used to study the release of NO, NO(2), HCN, HONO, HCHO, CH(3)CH(2)OH, and C(2)H(2) after laser ablation of the explosive compound FOX-7 in solid crystalline form. The radiation emitted after excitation was analyzed using a time-resolved UV-vis spectrometer with an ICCD detector. The electronic bands of CN (388 nm), OH (308.4 nm), and NO (237.1 nm) radicals and the atomic lines of C, N, and H were identified.
    Analytical Chemistry 01/2011; 83(3):1069-77. · 5.70 Impact Factor
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    ABSTRACT: The infrared emission spectra of Au, Ag and Cu resulting from the laser ablation of metal targets in a vacuum were recorded using time-resolved Fourier-transform spectroscopy in the 1200-1600, 1900-3600, 4100-5000 and 5200-7500 cm-1 ranges with a resolution of 0.017 cm-1. The majority of the observed lines correspond to transitions between low-excited Rydberg (Nd10)nlj states of Cu (N = 3), Ag (N = 4) and Au (N = 5) with a principal quantum number n = 4, ..., 10; the most prominent lines being due to transitions between the states with high orbital momenta l = 3, ..., 5. This study reports 32 new lines of Au, 12 of Ag and 20 of Cu (with uncertainties of 0.0003-0.03 cm-1). From the lines observed here and in our previous works, we extract revised energy values for 85 energy levels (uncertainty 0.01-0.03 cm-1) of which eight levels of Au, three of Ag and four of Cu are reported for the first time. These newly reported levels have high orbital momentum l = 3, 4, 5.
    Journal of Physics B Atomic Molecular and Optical Physics 01/2011; 44(10). · 2.03 Impact Factor
  • Svatopluk Civis, Martin Ferus
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    ABSTRACT: Titanium dioxide is an attractive material for (photo)catalysis, solar cells, electrochromics and batteries, while various fundamental studies would benefit from the accessibility of a totally 18O exchanged material. For instance, O-isotope labeling would allow deeper discussion of Raman spectra, because the presence of heavier oxygen atom in the crystal lattice of titania (anatase, rutile) influences differently various Raman active vibrations of the lattice. Second motivation for synthesis of Ti18O2 was the investigation of surface effects during titania/gas interaction. Here we report, for the first time, the preparation of pure Ti18O2 both in anatase and rutile forms. Raman spectroscopy indicated various isotope shifts for the known vibration modes of titania (anatase, rutile). The interaction with carbon dioxide was investigated with the aim to explore oxygen isotope exchange at the Ti18O2/CO2 interface. For this purpose, high-resolution Fourier transform infrared spectroscopy of the gas phase was adopted.
    01/2011;
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    ABSTRACT: Four types of explosives were studied using a combination of Laser Induced Breakdown Spectroscopy (LIBS) and Selected Ion Flow Tube Mass Spectrometry (SIFT-MS). The LIBS technique uses short laser pulses (ArF excimer laser) as the energy source to convert small amounts samples into plasma and to produce the emission from their molecular fragments or atoms. SIFT-MS is a novel method for absolute quantification based on chemical ionization using three precursor ions, with the capability to determine concentrations of trace gases and vapours of volatile organic compounds in real time. This is the first time that SIFT-MS has been used to study the release of NO, NO(2), HCN, HNO(3), HONO, HCHO and C(2)H(2) after a laser-induced breakdown of pure explosive compounds HMX (1,3,5,7-tetranitro-1,3,5,7-tetraazacyclo-octane), RDX (1,3,5-trinitro-2-oxo-1,3,5-triazacyclo-hexane), PETN (pentaerithrityl-tetranitrate) and TNT (2,4,6-trinitrotoluene) in solid form. The radiation emitted after excitation was analysed using a time resolving UV-Vis spectrometer with a ICCD detector. Electronic bands of the CN radical (388 nm), the Swan system of the C(2) radical (512 nm), the NH radical (336 nm), the OH radical (308.4 nm) and atomic lines of oxygen, nitrogen and hydrogen were identified. Vibrational and excitation temperatures were determined from the intensity distributions and a scheme of chemical reactions responsible for the formation of the observed species was proposed.
    The Analyst 05/2010; 135(5):1106-14. · 4.23 Impact Factor
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    ABSTRACT: 5,10,15,20-tetrakis(4-N-methylpyridyl)porphyrin, 5,10,15,20-tetrakis(2-N-methylpyridyl)porphyrin, and 5,10,15,20-tetrakis(4-trimethylammoniophenyl)porphyrin form self-assemblies with single-walled carbon nanotubes (SWNT) functionalized by polyaminobenzene sulfonic acid. Both steady-state and time-resolved emission studies revealed efficient quenching of the excited singlet states of the porphyrins. Atomic force microscopy, fluorescence confocal microscopy, and fluorescence lifetime imaging allowed the visualization of individual bundles of SWNTs and the differentiation of porphyrin molecules at specific binding sites of SWNT.
    Journal of Nanoscience and Nanotechnology 10/2009; 9(10):5795-802. · 1.15 Impact Factor
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    ABSTRACT: The distribution of pollutants in two urban scale models (point emission source and street canyon with extensive transport) was investigated by means of CO(2) laser photoacoustic spectroscopy in the region of the atmospheric window (9-10 mum). The experimental results of physical modeling are in a good agreement with the numerical calculations performed in the frame of computational fluid dynamic (CFD) modeling. Methanol, ethanol, and ozone (examples of light pollutants), as well as sulfur hexafluoride and 1,2 dichlorethane (examples of heavy pollutants), were selected on the basis of their high resolution spectra acquired by Fourier transform and laser diode spectroscopy.
    Applied Spectroscopy 05/2009; 63(4):430-6. · 1.94 Impact Factor
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    ABSTRACT: A large-scale plasma was created in CO–N2–H2O gas mixtures by high-power laser-induced dielectric breakdown. The composition of the mixtures used corresponded to a cometary and/or meteoritic impact into the Earth’s early atmosphere. A multiple-centimeter-sized fireball was created by focusing near-infrared laser pulse into the centre of cell. The laser–plasma formation in the mixtures mainly leads to a production of CO2. The competition of the CO+CO→CO2+C and CO+OH→CO2+H reactions in the CO2 production was investigated using 18O labeled water. An analysis of the isotopomers was carried out by means of high-resolution FTIR spectroscopy.
    Chemical Physics Letters 01/2009; 472(1):14-18. · 2.15 Impact Factor
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    ABSTRACT: The MQW GaInAsSb/AlGaAsSb lasers are monomodal throughout almost the whole temperature range of its operation, and they can be tuned in a wide spectral range. With the combination of the Fourier transform spectrometer and the diode lasers as sources of coherent radiation, we compared the spectra measured with a FTIR spectrometer in its absorption arrangement using a 50 W halogen lamp, with a laser emission by a current with different amplitudes. This technique proved to be very promising for the detection of weak absorption signals in a narrow spectral range of laser emission. The main target of our work is focused on the modally characterization and the measurement of the basic properties (threshold current, spectral region of the laser emission, laser width and the area of tunability) of the three similar VCSEL diode based on GaSb matrix, which are emitting in the infrared region around 4250 cm-1. We used FTIR spectrometer Bruker IFS 120 HR with the maximum resolution 0.0035 cm-1 in the emission setup for the laser diagnostic research. The first measurement of the high resolution absorption spectra of several gases (methane, carbon monoxide and ammonia) has been achieved.
    01/2009;
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    ABSTRACT: Large-scale plasma was created in gas mixtures containing carbon monoxide by high-power laser-induced dielectric breakdown (LIDB). The composition of the mixtures used corresponded to a cometary and/or meteoritic impact into the Earth's early atmosphere. A multiple-centimeter-sized fireball was created by focusing a single 85 J, 450 ps near-infrared laser pulse into the center of a 15 L gas cell. The excited reaction intermediates that formed in various stages of the LIDB plasma chemical evolution were investigated by optical emission spectroscopy (OES) with temporal resolution. Special attention was paid to any OES signs of molecular ions. However, carbon monoxide cations were registered only if their production was enhanced by Penning ionization, i.e., excess He was added to the CO. The chemical consequences of laser-produced plasma generation in a CO-N 2-H 2O mixture were investigated using high resolution Fourier-transform infrared absorption spectroscopy (FTIR) and gas chromatography (GC). Several simple inorganic and organic compounds were identified in the reaction mixture exposed to ten laser sparks. H 2 (18)O was used to avoid possible contamination. The large laser spark triggered more complex reactivity originating in carbon monoxide than expected, when taking into account the strong triple bond of carbon monoxide causing typically inefficient dissociation of this molecule in electrical discharges.
    The Journal of Physical Chemistry A 08/2008; 112(31):7162-9. · 2.77 Impact Factor
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    ABSTRACT: The industrial production of poly (ethylene terephthalate), PET, continues to increase and thus it is important to understand the composition of fumes resulting from its disposal as a part of incinerated waste. In this study samples of PET material were combusted in a furnace corresponding to the German standard DIN 53,436 at temperatures of 500 degrees C, 800 degrees C (in an air flow) and also uncontrolled combustion in air. The gaseous products were then analysed using three different analytical methods: high resolution Fourier transform infrared spectroscopy (FTIR), selected ion flow tube mass spectrometry (SIFT-MS) and gas chromatography mass spectrometry (GC-MS). Carbon dioxide, methane, ethylene, acetylene, formaldehyde (methanal) and acetaldehyde (ethanal) were detected by FTIR. Water, methane, acetaldehyde, ethylene, formaldehyde, methanol, acetone, benzene, terephthalic acid, styrene (ethenylbenzene), ethanol, toluene (methylbenzene), xylene (dimethylbenzene), ethylbenzene, naphthalene, biphenyl and phenol concentrations were all quantified by both SIFT-MS and GC-MS. Additionally, the fumes resulting from uncontrolled combustion in air were analysed by FTIR which resolves the rotation-vibration structure of the absorption bands of formaldehyde (2779.90 and 2778.48 cm(-1)) and propane, which was identified from characteristic vibrations of CH(3) groups at 2977.00 and 2962.00 cm(-1). The spectra were compared with reference standards.
    Molecular Physics 05/2008; 106(9-10, SI):1205-1214. · 1.67 Impact Factor
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    ABSTRACT: The spectrum of formaldehyde was studied in the 4350 - 4361 cm<sup>-1</sup> region using photoacoustic detection in combination with a semiconductor GalnAsSb/AlGaAsSb diode laser as a radiation source. This laser operates at laboratory and higher temperatures in the 4342 - 4362 cm<sup>-1</sup> region with an output of about 1 mW. The spectrum of formaldehyde was measured photoacoustically and this was compared with other techniques, such as laser absorption in a single path 0.4 m long cell and Fourier transform spectroscopy. The dependence of the photoacoustic signal on the pressure of the measured gas was recorded. The same technique was employed to determine the detection limit (less than 0.1 ppmV) of formaldehyde diluted with nitrogen for the strongest absorption line in the emission region of the diode laser.
    ICTON Mediterranean Winter Conference, 2007. ICTON-MW 2007; 01/2008
  • [show abstract] [hide abstract]
    ABSTRACT: The industrial production of poly (ethylene terephthalate), PET, continues to increase and thus it is important to understand the composition of fumes resulting from its disposal as a part of incinerated waste. In this study samples of PET material were combusted in a furnace corresponding to the German standard DIN 53,436 at temperatures of 500 degrees C, 800 degrees C (in an air flow) and also uncontrolled combustion in air. The gaseous products were then analysed using three different analytical methods: high resolution Fourier transform infrared spectroscopy (FTIR), selected ion flow tube mass spectrometry (SIFT-MS) and gas chromatography mass spectrometry (GC-MS). Carbon dioxide, methane, ethylene, acetylene, formaldehyde (methanal) and acetaldehyde (ethanal) were detected by FTIR. Water, methane, acetaldehyde, ethylene, formaldehyde, methanol, acetone, benzene, terephthalic acid, styrene (ethenylbenzene), ethanol, toluene (methylbenzene), xylene (dimethylbenzene), ethylbenzene, naphthalene, biphenyl and phenol concentrations were all quantified by both SIFT-MS and GC-MS. Additionally, the fumes resulting from uncontrolled combustion in air were analysed by FTIR which resolves the rotation-vibration structure of the absorption bands of formaldehyde (2779.90 and 2778.48 cm(-1)) and propane, which was identified from characteristic vibrations of CH3 groups at 2977.00 and 2962.00 cm(-1). The spectra were compared with reference standards.
    Molecular Physics. 01/2008; 106(9-10):1205-1214.
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    Svatopluk Civis, Libor Juha
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    ABSTRACT: Large laser sparks created by a single shot of a high-power laser system were used for the laboratory simulation of the chemical consequences of high-energy-density events (lightning, high-velocity impact) in planetary atmospheres, e.g., the early Earth's atmosphere.
    Proceedings of the International Astronomical Union 01/2008; 251:473-474.
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    ABSTRACT: A large-scale, double-stream gas puff target has been illuminated by sub-kJ, near-infrared (NIR) focused laser pulses at the PALS facility (Prague Asterix Laser System) to produce high-energy pulses of soft X rays from hot, dense plasma. The double-puff arrangement ensures high gas density and conversion efficiency from NIR to X rays approaching that typical for solid targets. In addition, its major advantage over solid targets is that it is free of debris and has substantially suppressed charged-particle emission. The X-ray emission characteristics of the source were determined for a range of gases that included krypton, xenon, N(2), CO and N(2)-CO. A demonstrated application of the xenon-based source is a single-shot damage induction to plasmid DNA. The yields of single-strand breaks (SSBs) and double-strand breaks (DSBs) were determined as a function of energy fluence adjusted by varying distance of sample from the source and thickness of aluminum filters.
    Radiation Research 10/2007; 168(3):382-7. · 2.70 Impact Factor
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    ABSTRACT: We report on an electrochemical conversion of N2 to NH3 at ambient pressure and 60 degrees C, which is mediated by reduced C(60) inside the molecular cavity of gamma-cyclodextrin.
    Chemical Communications 07/2007; · 6.38 Impact Factor