S. Civi - Academia.edu (original) (raw)
Papers by S. Civi
Journal of Molecular Spectroscopy, 1989
ABSTRACT
Proceedings of the National Academy of Sciences of the United States of America, Jan 20, 2015
The coincidence of the Late Heavy Bombardment (LHB) period and the emergence of terrestrial life ... more The coincidence of the Late Heavy Bombardment (LHB) period and the emergence of terrestrial life about 4 billion years ago suggest that extraterrestrial impacts could contribute to the synthesis of the building blocks of the first life-giving molecules. We simulated the high-energy synthesis of nucleobases from formamide during the impact of an extraterrestrial body. A high-power laser has been used to induce the dielectric breakdown of the plasma produced by the impact. The results demonstrate that the initial dissociation of the formamide molecule could produce a large amount of highly reactive CN and NH radicals, which could further react with formamide to produce adenine, guanine, cytosine, and uracil. Based on GC-MS, high-resolution FTIR spectroscopic results, as well as theoretical calculations, we present a comprehensive mechanistic model, which accounts for all steps taking place in the studied impact chemistry. Our findings thus demonstrate that extraterrestrial impacts, wh...
The Analyst, 1999
ABSTRACT Laser photoacoustic spectrometry and a line permeation pollution source were used in a s... more ABSTRACT Laser photoacoustic spectrometry and a line permeation pollution source were used in a study of the dispersion of pollution in an urban agglomerate using simulation in a wind tunnel. Applications of this measuring technique utilize the high sensitivity and broad dynamic range (3 orders of magnitude in this case) of the photoacoustic detection method. The minimum detected absorbance in the photoacoustic detection method employed in this work was at the level of 4.3 3 10 26 (8 mg m 23 CH 3 OH). The effectiveness and flexibility of the permeation method for generation of various concentrations of gases were verified for simulation of emission pollution sources in a wind tunnel. The line permeation pollution source developed in this work, with a concentration flux of (8.3 3 10 25 ± 2 3 10 26) g s 21 at 20 °C, generated a concentration level in the model used from a background value of 80–90 mg m 23 up to values of 1000 mg m 23 of methanol. A simple model street canyon together with the pollution source was employed to carry out a number of measurements of spatial profiles. The dispersion of the pollutant was studied at the bottom and on the walls of the street canyon together with the concentration variation with changes in the wind speed. The laboratory model was used to demonstrate the differences in ventilation of the street canyon.
The Analyst, 2010
Four types of explosives were studied using a combination of Laser Induced Breakdown Spectroscopy... more 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.
Chemical Physics, 1994
Threecompletelydiff~nt l~line~a~sfortherovibrationallinesofArH+ andArD+ ionsindiffemntexperi~cond... more Threecompletelydiff~nt l~line~a~sfortherovibrationallinesofArH+ andArD+ ionsindiffemntexperi~conditions were detected in an ac discharge using a tm@le diode laser and a velocity modulation technique. The lineshapes of these ions were studied under various experimental conditions and also by on4f and freqency modulation techniques. A simple theoretical model has been proposed that permits explanation of the observed effects on the basis of a Gaussian distribution of the ion velocities in an ac field with constant frequency at various partial pressures of the buffering gas. The radial distribution of the intensities and widths at half maxi-in the plasma discharge were studied for all thtee types of lines of the ArH+ ion and their agreement with the Schottky form was checked.
Journal of Molecular Structure, 2004
The Fourier transform emission spectrum of 20NeH+ in its 1Σ+ ground electronic state was observed... more The Fourier transform emission spectrum of 20NeH+ in its 1Σ+ ground electronic state was observed in the infrared spectral region at an apodized resolution of 0.02 cm−1. The wavenumbers of the observed lines were assigned and fitted within the framework of the Dunham expansion and reduced potential curve (RPC) methods making use of ab initio potentials calculated to high accuracy.
Journal of Molecular Structure, 2004
ABSTRACT The Fourier transform emission spectrum of 20NeH+ in its 1Σ+ ground electronic state was... more ABSTRACT The Fourier transform emission spectrum of 20NeH+ in its 1Σ+ ground electronic state was observed in the infrared spectral region at an apodized resolution of 0.02 cm−1. The wavenumbers of the observed lines were assigned and fitted within the framework of the Dunham expansion and reduced potential curve (RPC) methods making use of ab initio potentials calculated to high accuracy. Of the total of 122 lines observed, 40 lines are newly assigned, including the new 4→3 vibrational band. The global potential energy function arising from the RPC analysis provides a very close description of the mobility data for H+ and D+ ions in Ne gas and of the long-range induction interaction data thus indicating high reliability of its predictive power.
Journal of Molecular Spectroscopy, 1989
ABSTRACT
Proceedings of the National Academy of Sciences of the United States of America, Jan 20, 2015
The coincidence of the Late Heavy Bombardment (LHB) period and the emergence of terrestrial life ... more The coincidence of the Late Heavy Bombardment (LHB) period and the emergence of terrestrial life about 4 billion years ago suggest that extraterrestrial impacts could contribute to the synthesis of the building blocks of the first life-giving molecules. We simulated the high-energy synthesis of nucleobases from formamide during the impact of an extraterrestrial body. A high-power laser has been used to induce the dielectric breakdown of the plasma produced by the impact. The results demonstrate that the initial dissociation of the formamide molecule could produce a large amount of highly reactive CN and NH radicals, which could further react with formamide to produce adenine, guanine, cytosine, and uracil. Based on GC-MS, high-resolution FTIR spectroscopic results, as well as theoretical calculations, we present a comprehensive mechanistic model, which accounts for all steps taking place in the studied impact chemistry. Our findings thus demonstrate that extraterrestrial impacts, wh...
The Analyst, 1999
ABSTRACT Laser photoacoustic spectrometry and a line permeation pollution source were used in a s... more ABSTRACT Laser photoacoustic spectrometry and a line permeation pollution source were used in a study of the dispersion of pollution in an urban agglomerate using simulation in a wind tunnel. Applications of this measuring technique utilize the high sensitivity and broad dynamic range (3 orders of magnitude in this case) of the photoacoustic detection method. The minimum detected absorbance in the photoacoustic detection method employed in this work was at the level of 4.3 3 10 26 (8 mg m 23 CH 3 OH). The effectiveness and flexibility of the permeation method for generation of various concentrations of gases were verified for simulation of emission pollution sources in a wind tunnel. The line permeation pollution source developed in this work, with a concentration flux of (8.3 3 10 25 ± 2 3 10 26) g s 21 at 20 °C, generated a concentration level in the model used from a background value of 80–90 mg m 23 up to values of 1000 mg m 23 of methanol. A simple model street canyon together with the pollution source was employed to carry out a number of measurements of spatial profiles. The dispersion of the pollutant was studied at the bottom and on the walls of the street canyon together with the concentration variation with changes in the wind speed. The laboratory model was used to demonstrate the differences in ventilation of the street canyon.
The Analyst, 2010
Four types of explosives were studied using a combination of Laser Induced Breakdown Spectroscopy... more 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.
Chemical Physics, 1994
Threecompletelydiff~nt l~line~a~sfortherovibrationallinesofArH+ andArD+ ionsindiffemntexperi~cond... more Threecompletelydiff~nt l~line~a~sfortherovibrationallinesofArH+ andArD+ ionsindiffemntexperi~conditions were detected in an ac discharge using a tm@le diode laser and a velocity modulation technique. The lineshapes of these ions were studied under various experimental conditions and also by on4f and freqency modulation techniques. A simple theoretical model has been proposed that permits explanation of the observed effects on the basis of a Gaussian distribution of the ion velocities in an ac field with constant frequency at various partial pressures of the buffering gas. The radial distribution of the intensities and widths at half maxi-in the plasma discharge were studied for all thtee types of lines of the ArH+ ion and their agreement with the Schottky form was checked.
Journal of Molecular Structure, 2004
The Fourier transform emission spectrum of 20NeH+ in its 1Σ+ ground electronic state was observed... more The Fourier transform emission spectrum of 20NeH+ in its 1Σ+ ground electronic state was observed in the infrared spectral region at an apodized resolution of 0.02 cm−1. The wavenumbers of the observed lines were assigned and fitted within the framework of the Dunham expansion and reduced potential curve (RPC) methods making use of ab initio potentials calculated to high accuracy.
Journal of Molecular Structure, 2004
ABSTRACT The Fourier transform emission spectrum of 20NeH+ in its 1Σ+ ground electronic state was... more ABSTRACT The Fourier transform emission spectrum of 20NeH+ in its 1Σ+ ground electronic state was observed in the infrared spectral region at an apodized resolution of 0.02 cm−1. The wavenumbers of the observed lines were assigned and fitted within the framework of the Dunham expansion and reduced potential curve (RPC) methods making use of ab initio potentials calculated to high accuracy. Of the total of 122 lines observed, 40 lines are newly assigned, including the new 4→3 vibrational band. The global potential energy function arising from the RPC analysis provides a very close description of the mobility data for H+ and D+ ions in Ne gas and of the long-range induction interaction data thus indicating high reliability of its predictive power.