Svatopluk Civis

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

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Publications (52)113.89 Total impact

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    ABSTRACT: The spontaneous isotopic exchange of oxygen atoms between dry powdered Ti16O2-containing minerals and gaseous C18O2 was studied using gas-phase high-resolution Fourier transform infrared absorption spectroscopy (FTIR) of carbon dioxide isotopologues. The absorption rovibrational spectra of all measured carbon dioxide isotopologues were assigned and then used for quantification of the time-dependent isotope exchange of oxygen atoms (16O) from the surface crystalline lattice of the solid mineral samples with (18O) oxygen atoms from gaseous C18O2. Similar to our previous studies devoted to the isotopic exchange activity of titanium dioxide, we determined that rutile, montmorillonite, siderite, calcite, and basaltic minerals also exhibit unexpectedly significant oxygen mobilities between solid and gas phases. The rate of formation of gaseous C16O2 is found to be highly dependent on the nature of the mineral sample. Our previous studies together with the results presented here suggest that such crystal–surface oxygen isotope mobilities can be explained by two mechanisms: the cluster-like structure of finely powdered materials or the existence of oxygen-deficiency sites in the structure of the surface crystal lattice.
    No preview · Article · Dec 2015 · The Journal of Physical Chemistry C
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    ABSTRACT: Context. The Ne i spectrum in the 800-1800 cm-1 (5.55-14.3 μm) domain has not been previously investigated. Aims. To address this spectral gap, we performed high-resolution laboratory measurements of the Ne i emission spectrum over the 800-7000 cm-1 (1.43-14.3 μm) range. Methods. The Ne i laboratory spectra were obtained from a pulsed discharge plasma and recorded using time-resolved Fourier transform spectroscopy. The identification of the spectral lines was performed according to the transition probability values calculated using the quantum defect method. Results. Based on these measurements, we report the wavenumbers of 151 Ne i lines and energy values for 14 Ne i levels that are not listed in the available databases.
    No preview · Article · Aug 2015 · Astronomy and Astrophysics
  • Svatopluk Civis · Martin Ferus
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    ABSTRACT: Spontaneous isotopic exchange of oxygen atoms between gaseous C18O2 and Ti16O2 nanoparticles has been studied using high-resolution Fourier transform infrared absorption and first principles density functional theory calculations. The rate of formation of gaseous C16O2 is found to be highly dependent on the nature of the titania sample, growing with increasing calcination temperature for both amorphous and crystalline nanoparticles. This is attributed to an increase in the population of oxygen atom defects and for uncoordinated sites at higher calcination temperatures. Additional support for the experimental observations is provided by calculations of the activation barriers for oxygen exchange on crystalline anatase and on a (TiO2)10 cluster. Photoirradiated Ti16O2 is known to reduce carbon dioxide to methane. This multistep reaction is commonly represented as a sequence of proton-coupled two-electron reactions leading from carbon dioxide to formate to formaldehyde to methanol and to methane. The actual reaction mechanism is more complex catalytic cycle together with the radical chemistry. The implications of these reactions for photocatalytic methanogenesis and photosynthetic fixation of atmospheric carbon in prebiotic nature are discussed.
    No preview · Article · Aug 2015
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    ABSTRACT: Laser-induced breakdown spectroscopy (LIBS) in combination with time-resolved Fourier-transform technique was applied to obtain spectra of In I in the infrared spectral region. This method was proven to be suitable for measuring the weak energy transitions between highly excited Rydberg atomic levels. The advantage comes from the possibility of selecting an optimal time-delay after the laser pulse, when the low intensity spectral lines are near their maximum intensity and can filter out the disturbing high intensity lines with different emission time profiles. The time-resolved spectra were recorded in the 700-1000, 900-1300, 1200-1680, 1800-4000, 4100-5000 and 5000-7700 cm-1 ranges with a resolution of 0.017 cm-1. Using this technique, we obtained five g- and h-levels of In I that have never been measured previously. We demonstrate a close similarity of wavenumbers for the 7s1/2-7p1/2 and 4f-5g transitions of the In atom.
    Full-text · Article · Jul 2014 · Journal of Analytical Atomic Spectrometry
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    ABSTRACT: 1310 nm wavelength VCSELs produce single mode emission in excess of 1 mW in the temperature range of 20-70°C with a very low relative intensity noise of -148 dB/Hz. These devices have a broad tuning range of ~50 cm-1 with variable temperature and current, which covers multiple absorption lines of methane, ammonia and hydrogen fluoride. With these VCSELs, we report optical absorption spectroscopy of several gases near 1310 nm wavelength. In particular, we report for the first time detection of HF using the absorption line in the vicinity of 7568 cm-1 with an estimated low-pressure detection limit at the level of several ppm.
    No preview · Conference Paper · Jul 2014
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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
    Full-text · Article · Jun 2013 · Astronomy and Astrophysics
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    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).
    No preview · Article · Apr 2013
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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.
    No preview · Article · Nov 2012 · Journal of the American Chemical Society
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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.
    Preview · Article · Jun 2012 · Astronomy and Astrophysics
  • 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.
    No preview · Conference Paper · Jan 2012
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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.
    Preview · Article · May 2011 · Journal of Physics B Atomic Molecular and Optical Physics
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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.
    No preview · Article · Feb 2011 · Analytical Chemistry
  • 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.
    No preview · Article · Jan 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.
    No preview · Article · May 2010 · The Analyst
  • S. Civis
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    ABSTRACT: The main target of this work is focused on characterization and measurement of the basic properties of laser emission (laser width) of several VCSEL diode based on GaSb matrix, which are emitting in the infrared region around 4250 cm-1. High resolution Fourier transform Bruker IFS 120 HR spectrometer with maximum resolution 0.003 cm-1 was used for the laser diagnostic research.
    No preview · Article · Dec 2009
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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.
    Full-text · Article · Oct 2009 · Journal of Nanoscience and Nanotechnology

  • No preview · Article · Aug 2009 · Origins of Life and Evolution of Biospheres

  • No preview · Article · Aug 2009 · Origins of Life and Evolution of Biospheres
  • Svatopluk Civis · Jaroslav Cihelka · Irena Matulkova
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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.
    No preview · Article · Jun 2009
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    ABSTRACT: VCSEL (Vertical-Cavity Surface-Emitting Laser) diodes are the youngest members of the semiconductor laser diode family. The main target of our work is focused on the modally characterization and the measurement of the basic properties (threshold current, spectral range of the laser emission, the current tunability) of the three VCSEL diode based on GaSb matrix, which are emitting in the infrared region around 4250 cm-1. We used high resolution FTIR spectrometer Bruker IFS 120 HR with the maximum resolution 0.0035 cm-1 in the emission setup for the laser diagnostic research. The spectra of atmospheric pollutants like methane, carbon mono-oxide and ammonia, which have several absorption lines in studied spectral range have been measured using vertical cavity surface emitting lasers for the first time. Lasers were also used for investigation of these gases by absorption spectroscopy.
    No preview · Conference Paper · Jun 2009