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Examination of thermal decomposition of street samples of cocaine and methamphetamine shows that typical products detected in previous studies are accompanied by a wide palette of simple volatile compounds easily detectable by spectral techniques. These molecules increase smoke toxicity and their spectral detection can be potentially used for identification of drug samples by well-controlled laboratory thermolysis in temperature progression. In our study, street samples of cocaine and methamphetamine have been thermolyzed under vacuum over the temperature range of 350–650 °C. The volatile products (CO, HCN, CH4, C2H4, etc.) have been monitored by high-resolution Fourier-transform infrared (FTIR) spectrometry in this temperature range. The decomposition mechanism has been additionally examined theoretically by quantum-chemical calculations for the highest temperature achieved experimentally in our study and beyond. Prior to analysis, the street samples have also been characterized by FTIR, Raman spectroscopy, energy-dispersive X-ray spectroscopy, and melting point determination.

In this work we present a time-resolved FTIR spectroscopic study on kinetics of atomic and molecular species, specifically CO, CN radical, N

Two sets of NH3 absorption spectra covering the 0.793 μm region are recorded using two Bruker IFS 125 HR Fourier transform spectrometers. Three unapodized absorption spectra are recorded in Brussels over the range 11000−14500 cm−1 and the positions and intensities of 1114 ammonia lines observed in the 12491−12810 cm−1 region are measured using a multi-spectrum least squares fitting algorithm. 367 additional lines are identified in an ammonia absorption spectrum recorded in two steps at the J. Heyrovsky Institute of Physical Chemistry in Prague, using two different interference filters covering the 12000−12500 and 12400−13000 cm−1 ranges. The 1481 measured ammonia lines are analyzed using an empirical line list computed using variational nuclear motion calculations and ground state combination differences. Transitions are assigned to vibrational states with 4νNH stretching excitation (v1+v3=4). 278 out of the 1481 measured lines are assigned to 300 transitions and 119 upper state energy levels are derived from the frequencies of the assigned transitions., SCOPUS: ar.j, info:eu-repo/semantics/published

All the spectra presented in this atlas were measured with the time-resolved Fourier-transform infrared (FTIR) spectrometer at the Department of Spectroscopy, J. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences. The original purpose in constructing time-resolved hardware was to directly observe the excitation and de-excitation of atomic and molecular species as well as follow chemical processes in periodically-excited systems.

The era of fossil fuels is slowly nearing its inevitable end and the urgency of alternative energy sources basic research, exploration and testing becomes ever more important. Storage and alternative production of energy from fuels, such as methane, represents one of the many alternative approaches. Natural gas containing methane represents a powerful source of energy producing large volume of greenhouse gases. However, methane can be also produced in closed, CO2-neutral cycles. In our study, we compare detailed chemical composition of CH4 fuel produced in two different processes: Classical production of biogas in a rendering station, industrial wastewater treatment station and landfill gas station together with novel approach of artificial photosynthesis from CO2 over acidic anatase TiO2 in experimental apparatus developed in our laboratory. The analysis of CH4 fuel produced in these processes is important. Trace gaseous traces can be for example corrosive or toxic, low quality of the mixture suppresses effectivity of energy production, etc. In this analysis, we present a combination of two methods: High resolution Fourier transform infrared spectroscopy (HR-FTIR) suitable for the main component analysis; and the complementary extremely sensitive method of Selected Ion Flow Tube Mass Spectrometry (SIFT-MS) and gas chromatography (GC–MS), which are in turn best suited for trace analysis. The combination of these methods provides more information than any single of them would be able to and promises a new possible analytical approach to fuel and gaseous mixture analysis.

The intensity ratio of the D 1 and D 2 sodium-doublet emission lines varies both across spectra of astronomical sources and in laboratory plasmala. This article probes the behaviour of this ratio under controlled laboratory conditions. In order to study this variation, we have recorded microwave discharge spectra of sodium vapour in range of 15000 to 18000 cm − 1 . Emission bands of the molecular nitrogen buffer gas and kinetic broadening of nitrogen and sodium lines have been used in a characterisation of the discharge temperature. We show that the relative intensity of doublet lines is determined by self-absorption and depends on the buffer-gas pressure and discharge power. The ratio and line shapes can be explained by a two-temperature model of sodium emission and foreground absorption. Line ratios estimated for spectra with various strength of the self-absorption of electric discharges can be used for characterising their temperatures and densities. In contemporary astronomical observation of exoplanetary atmospheres, this effect has not been resolved yet. To observe this effect, at least 0.01 - 0.05 cm − 1 resolution (resolving power 1 600 000) is required. We make a connection to stellar Na emission and possible absorption processes for future observations of exoplanetary atmospheres.

Capillary electromigration techniques have proven their capabilities in detection of variety of analytes from inorganic ions and small organic molecules through bio(macro)molecules to large analytes such as cells or nano/micro particles. Also broad range of potential applications includes food and environmental analysis, biomedical and pharmaceutical investigations or even diagnostics. In this work, it was demonstrated that capillary micellar electrokinetic chromatography is an excellent tool extremely helpful in investigations focused on prebiotic synthesis of molecules essential for formation of life on early Earth – nucleobases. In particular, rapid separation of nucleobases (

Endohedral fullerenes with paramagnetic encapsulated atoms are new magnetic materials of interest for numerous applications from medicine to quantum computers. An important phenomenon with endohedral fullerenes is the appearance of new vibrational frequencies not associated with empty fullerenes. The vibrational spectra of the lanthanide endohedral fullerenes La@C60 and Ce@C60 in various spin states are calculated using the density functional method. Most of the spectral lines lie in the 300–1600 cm - 1 range, and their intensities change dramatically depending on the molecule’s symmetry and spin state, which are determined by the encapsulated lanthanide atom. The average frequency shift of the carbon cage vibrations caused by spin transition is only 5 cm - 1 . The calculated frequencies of the coupled “metal–carbon cage” vibrations of the lanthanide endohedral fullerenes La@C60 and Ce@C60 in various spin states lie in the 10–170 cm - 1 range. The computational results for both the frequencies and intensities of the metal–cage modes depend considerably on the spin state. The changes in these vibrational modes are due to the changes in the molecular symmetry and the metal–carbon bond lengths. Such dependence can be used as a basis for controlling the spin state of metallofullerenes by measuring the vibration frequencies in the far-infrared zone, which could be important for nanoelectronics and quantum informatics.

This paper presents an extension to our knowledge of ∆v = 1 and ∆v = 2 bands of carbon monoxide in the ground state, measured by Fourier transform infrared spectroscopy of glow discharge of formamide-nitrogen mixture. Lines in declared bands are measured up to v = 30 for ∆v = 1 and up to v = 24 for ∆v = 2 band, by use of both InSb and MCT detectors, which have not been measured in the laboratory before. Dunham parameters obtained by fitting our lines are presented as well as comparison to other authors. The paper also demonstrates the interesting impossibility of sufficient population of ∆v = 2 band of CO when only pure CO is used in the glow discharge, instead of formamide-based mixture. Additionally, we present a non-LTE model to describe the intensity pattern of the ∆v = 1 and the ∆v = 2 bands of 12C16O experimental spectra by simulating the corresponding non-LTE vibrational populations of CO.

Time-resolved infrared emission spectra of atomic helium have been measured using a high-resolution Fourier transform spectrometer in the spectral range of 700–15000 cm − 1 with a maximum resolution of 0.01 cm − 1 . A total of 74 spectral lines have been observed, of which 47 lines are detected for the first time. Most of the observed transitions are from highly excited levels ( n = 8, 7 and 6). The time profiles of the spectral line’s emission intensities observed under the current experimental conditions have been plotted, and the decay times have been obtained. The level energy values are extracted from the list of spectral lines, and their consistency is justified by the obtained ionization potential of the He atom and the dipole polarizability of He + .

Recently, many studies have demonstrated that carbon dioxide can be converted to methane on TiO 2 surface by a photocatalytic process. We show that such a photo-reduction can be significantly affected by the presence of an acidic proton in powder samples of titania. Using in situ absorption gas-phase rovibrational spectroscopic detection of CH 4 , CO and CO 2 , we demonstrate that proton enhancement positively affects transformation of intermediate derivatives to methane during the photo-irradiation process via several reactions in which the electron transfer inside titania is coupled to oxygen transfer to the Ti 3+ centers of TiO 2 structure. The yield of CH 4 or CO depends on the surface conditioning of titania: the formation of CH 4 is boosted by a presence of adsorbed HCl, while the formation of CO is boosted by adsorbed H 2 SO 4 .

Using the high-resolution time-resolved Fourier transform infrared spectroscopy of a plasma created in a positive column discharge cell, we record Kr I spectrum in the 700–7600 cm − 1 range. We report 88 new Kr I lines in the 700–2800 cm − 1 range previously not accessed by laboratory observations. This allows us to extract the excitation energies of the 6h, and 7h, 7i levels of Kr I, which have not been measured before. We include these newly measured lines into the level optimisation together with the results of other high-resolution measurements to obtain an updated system of Kr I levels which is internally consistent to within 0.0019 cm − 1 .

An ammonia absorption spectrum recorded at room temperature in the region 8800–10,400 cm−1 is analysed using a variational line list, BYTe, and ground state energies determined using the MARVEL procedure. BYTe is used as a starting point to initialise assignments by combination differences and the method of branches. Assignments are presented for the region 9400–9850 cm−1. 642 lines are assigned to 6 previously unobserved vibrational bands, ( 2 v 1 + 2 v 4 2 ) ± , ( 2 v 1 + v 3 1 ) ± and ( v 1 + v 3 1 + 2 v 4 2 ) ± , leading to 428 new energy levels with 208 confirmed by combination differences. A recently calculated purely ab initio NH3 PES is also used to calculate rovibrational energy levels. Comparison with assigned levels shows better agreement between observed and calculated levels than for BYTe for higher vibrational bands.

Important features in meteor spectra are usually interpreted by synthetic convolution of lines extracted from databases. For such an assignment, in our study, we employed experimental technique of meteorite specimen laser ablation spectroscopy. The spectra are recorded by high resolution laboratory Echelle spectrograph and simultaneously using novel high resolution Meteor Spectral Camera for meteor observation. The data are subsequently evaluated via calibration-free method alongside with analysis of real meteor emission spectra. Additionally, spectral features related to airglow plasma are compared with the spectra of the Laser Induced Breakdown in the air. In this manner, we show that instead of theoretical spectra simulation, laboratory experiments can be applied in evaluation of the observational data.

We study spectra of a plasma created by the laser ablation of ZnS targets in a vacuum and report 47 (not observed previously) Zn I lines in the range of 1300–6400 cm −1 . From the recorded spectra we determine energies of 5 g , 6 g , 7 f , 6 h , 7 h and 8 h Zn I levels. We also calculate a large list of transition probabilities and oscillator strengths for Zn I in the observed spectral range.

High-resolution FT-IR spectroscopy combined with quantum chemical calculations was used to study the chemistry of OCS-disproportionation over the reduced surface of isotopically labelled, nanocrystalline TiO2. Analysis of the isotopic composition of the product gases has revealed that the reaction involves solely OCS molecules from the gas-phase. Using quantum chemical calculations we propose a plausible mechanistic scenario, in which two reduced Ti(3+) centres mediate the reaction of the adsorbed OCS molecules.

Laser-induced breakdown spectroscopy (LIBS) in combination with a 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.

Context. Meteor spectra are commonly interpreted using data from databases and tables. Several studies have demonstrated very sophisticated calculations of elemental compositions of meteoroid bodies based on the computation of synthetic meteor spectra or on the spectral analysis of airglow plasma containing evaporated, atomized, and ionized meteoroid matter. However, considering accuracy, reliability of computations, lack of laboratory experimental data in this field, as well as the complicated physical structure of meteor plasma, such qualitative assignment or quantitative calculations are still extensively discussed in the scientific community. Even on the laboratory level, many studies have shown the high complexity of the acquisition and interpretation of the data that are recorded with techniques of emission spectroscopy that are in fashion and philosophy similar to the spectral analysis of meteor plasma, that is, detection and quantification of the elements that are ablated from complicated multicomponent matrices. Aims. The current study is focused on the application of terawatt-class laser-induced breakdown spectroscopy (TC-LIBS) of real samples of chondritic meteorites. We recorded emission spectra with high resolution and high precision that contain spectral lines that are typical for real meteoric spectra. Experimental data were compiled in a form that is convenient for the meteoric spectra interpretation and calibration. Methods. TC-LIBS was carried out by a high-power terawatt-class laser facility, the Prague Asterix Laser System (PALS). The spectra were simultaneously recorded by an echelle high-resolution spectrograph in the UV/VIS spectral ranges and by a low-resolution spectrograph that was used for real observation of meteor spectra. We also present calculated synthetic spectra based on data from the NIST atomic spectra database. Results. We assembled etalon qualitative tables of major meteoric spectral features that can be used both for the spectral wavelength calibration of low-resolution observational instruments and for the exact interpretation of meteor spectra. The data are compared with real meteor spectra.

The main motivation for the synthesis of Ti18O2 was the investigation of surface effects during titania/gas interaction. The interaction with carbon dioxide was investigated with the aim to explore oxygen isotope exchange at the Ti18,17O2/CO2 interface. For this purpose, high-resolution Fourier transform infrared spectroscopy of the gas phase was adopted. In the present study, we have explored the oxygen isotope exchange between gaseous C16O2 and solid Ti18O2 or Ti17O2. The present measurement in dark mixtures has, as its primary goal, the determination of the time-scale of the spontaneous isotope exchange between carbon dioxide and solid TiO2. The profiles of the individual lines of selected isotopologues (isolated lines in the spectrum) were fitted and quantified. The quantification of the spectra was carried out on the basis of calibration measurements of the absorption spectra of individual isotopologues (reference gases) of carbon dioxide at different pressures. The concentrations of individual isotopologues determined from the intensity profiles of the individual rotation–vibration lines are characterized by the exponential decrease of the 16O–C–16O isotopologue and the exponential increase of the 18O–C–18O isotopologue. The 18O–C–16O acts as an intermediate in the mixture and its concentration remains almost constant.

We study spectra of a plasma created by the laser ablation of SrF 2 targets in a vacuum and report 19 Sr I lines in the range of 1300–5000 cm −1 which have not been observed before. From the recorded spectra we determine the previously unknown excitation energies of 5 g, 6 g and 6 h states of Sr I. We also calculate a large list of transition probabilities and oscillator strengths for Sr I in the observed spectral range. These A - and f -values are calculated using quantum defect theory which shows good agreement with the available experimental and theoretical results.

Large-scale plasma was created in gas mixtures containing methane using high-power laser-induced dielectric breakdown (LIDB). The composition of the mixtures corresponded to a cometary and/or meteoritic impact into the early atmosphere of either Titan or Earth. A multiple-centimeter-sized fireball was created by focusing a single 100 J, 450 ps near-infrared laser pulse into the center of a 15 L gas cell. The excited reaction intermediates formed during the various stages of the LIDB plasma chemical evolution were investigated using optical emission spectroscopy (OES) with temporal resolution. The chemical consequences of laser-produced plasma generation in a CH4–N2–H2O mixture were investigated using high resolution Fourier-transform infrared absorption spectroscopy (FTIR) and gas selected ion flow tube spectrometry (SIFT). Several simple inorganic and organic compounds were identified in the reaction mixture exposed to ten laser sparks. Deuterated water (D2O) in a gas mixture was used to separate several of the produced isotopomers of acetylene, which were then quantified using the FTIR technique.

The photoinduced isotope exchange between 18O atoms in the lattice of vacuum-calcinated solid Ti18O2 and 16O atoms of formic acid and its photoproducts was studied with gas-phase high-resolution Fourier transform infrared absorption spectroscopy. The rotation–vibration absorption spectra of all products from the photochemical reactions of formic acid were measured over a broad infrared spectral range and used to quantify the time-dependent isotope exchange between the oxygen atoms on solid Ti18O2 and the oxygen atoms in gaseous HC16O16OH and the isotopologues of CO2, CO, and H2O. It was found that formic acid did not exchange oxygen with titania during adsorption and decomposition processes; strongly bonded formate species blocked active sites and thereby inhibited the exchange between CO2 and Ti18O2. Similar blocking was observed by adsorbed water. The isotopologues C16O18O and C18O2 are the products of the spontaneous exchange of oxygen atoms in C16O2 and the active sites on Ti18O2 that are unblocked du...

High-resolution FT-IR spectroscopy was used for the analysis of the products of formamide dissociation using a high-energy Asterix laser. In the experiment, the detected products of the formamide LIDB dissociation were hydrogen cyanide, ammonia, carbon monoxide, carbon dioxide, nitrous oxide, hydroxylamine, and methanol. The molecular dynamics of the process was simulated with the use of a chemical model. The chemistry shared by formamide and the products of its dissociation is discussed with the respect to the formation of biomolecules.

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.

The room temperature operating GaInAsSb/AlGaAsSb based diode laser and 66 K InAsSb/InAsSbP laser diode both operating in spectral range of formaldehyde absorption 4350–4361 cm −1 and 2821–2823 cm −1 have been characterized and compared. Very precise arrangement of laser absorption together with high resolution Fourier transform technique was tested. The photoacoustic technique was employed to determine the detection limit of formaldehyde (less than 1 ppmV) diluted by nitrogen for the strongest absorption line of the ν 3 + ν 5 band in the emission region of the GaInAsSb/AlGaAsSb diode laser. The detection limit (less than 10 ppbV) of formaldehyde was achieved in the 2820 cm −1 spectral range in case of InAsSb/InAsSbP laser (fundamental bands of ν 1 , ν 5 ) .

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-N2-H2O 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. H2 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. I. Introduction The standard theories of chemical evolution in the Earth’s early atmosphere presume that the organic molecules necessary for life formation on Earth (like amino acids, nitrogen bases, sugars, lipids, etc.) were formed by the action of, for example, lightning discharge plasma or an extraterrestrial body impact. The laboratory simulations of the high-energy-density processes have been carried out in various models of the Earth’s early atmosphere, from highly reducing 1–3 to the slightly reducing and neutral. 4–6 The simulations used both laser plasma and electric discharges; their comparison can be found in ref 7. Chemical physics investigates primarily the relations between the parameters of such laboratory plasma and its chemical actions in mixtures simulating the chemistry of the Earth’s early atmosphere. The identification of the reaction products and intermediates, together with the measuring of their concentrations in a time scale, gives us an idea of the mechanisms and yields of these reactions in different gaseous mixtures. Geochemists are provided in this way with information on the probability of the formation of organic molecules via the high-energycontent phenomena, within their considered models of the Earth’s early atmosphere. These models can be assessed from the point of view of life formation probability. In addition to this, the purpose of the chemical-physics research into the described phenomenon is also to find the conditions under which the laboratory plasma is at its closest to the natural conditions. In this article, we focus on the chemical manifestations of

The A2Π–X2Σ+Δv = −3 bands of the 12C14N radical have been observed by time-resolved Fourier transform spectroscopy in the 1850–3100 cm−1 region with a wavenumber resolution of 0.025 cm−1. The radical was produced in a pulsed positive column discharge in a cyanogene and helium mixture. Seven bands of v = 0–3, 1–4, 2–5, 3–6, 4–7, 5–8, and 6–9 were analyzed to give the molecular constants of each state by least-squares fitting of 801 lines. The pulsed discharge was found to be efficient for production of CN in the excited A2Π state. The vibrational excitation temperature was determined to be 6680 ± 835 K and 6757 ± 534 K for the A2Π and X2Σ+ states, respectively. The population of the A2Π was found to be 4% of that of the X2Σ+ state in the time after turning off the discharge.

The Fourier transform emission spectrum of 20 NeH + in its 1 Σ + 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.

An investigation of photoacoustic detection using 3.2-3.6 and 5 mum diode lasers is described. An inexpensive resonant photoacoustic system was developed based, on a simple glass cell and condenser and electret microphone (BrüelKjaer type 4144/Sennheiser type K6P). The system was tested on the single rotation-vibration lines of C(2)H(2), CO, COS, and NH(3) gases. The best detection limits obtained are 300 ppm V for C(2)H(2) and 20 ppm V for COS. Potential applications of infrared diode laser photoacoustic detection lie in the areas of analytical chemistry, atmospheric research, and investigation of the kinetics of reactive species.

The three lowest vibrational bands 1← 0, 2← 1 and 3← 2 of 20 NeH + in the 1 Σ + ground electronic state are recorded from IR emission of a positive column discharge with a Fourier transform Bruker 120 spectrometer between 1800 and 3000 cm −1 . Accurate integrated intensities have been measured for 75 vibration rotation transitions. The diagonalisation procedure first developed by T. Tanaka et al. [ J. Mol. Struct. 153, 413 (1997)] was applied for the determination of the transition dipole moment of NeH + . With the reported theoretical value of the permanent dipole moment taken as 3.004 D, the vibrational transition moment μ 1−0 is determined to be 0.314±0.026D, with one standard deviation.

A method was used to measure the width of emission lines of a type of semiconductor laser with composition InAsSb/InAsSbP. This type of laser was manufactured specially for absorption high-resolution spectroscopy of gases absorbing in the 2800–3100 cm−1 region. Parameters used for calculation of spectral emission linewidths were obtained using selected rotation-vibration lines of the gaseous molecules N2O, CH3Cl, and OCS. The estimated spectral emission linewidths varied in the range 10–30 MHz in dependence of the current passing and the type of laser.

CO 2 laser photoacoustic spectroscopy was used for quantitative analysis of a multicomponent gaseous mixture of pollutants with similar chemical structures (toluene, ortho -, para - and meta -xylenes) in trace concentrations (50–700 ppm). The agreement with the results of gravimetric measurements was better than 5% in most cases. The following detection limits were found for this method in the given arrangement: 3.57±0.04 ppm for toluene, 1.82±0.02 ppm for o -xylene, 1.00±0.01 ppm for p -xylene and 2.86±0.04 ppm for m -xylene. Determination of the concentration using the classical least squares method was compared with a method based on the principle of calculation of the lowest component entropy. While the least squares method yielded the most selective analysis when four lines were used for four-components mixture, introduction of the component entropy yielded an increase in the selectivity level by measurement of six lines.

The concept of the Allan variance has been utilized to test the detection abilities of two powerful experimental methods for trace gas monitoring: IR diode–laser and CO 2 laser photo-acoustic spectroscopy. The detection of stable molecules (OCS, allene, CH 3 OH), and unstable species (ozone, short-lived free radical CN and molecular ion ArD + ) have been compared. An approach for studies of the influence of the reactivity on the optimal averaging time for the minimum detectable concentration is demonstrated.

The current dependence of the output frequency of InAsSb/InAsSbP diode lasers at wavelengths near 3.6 µm is studied. It is found that in these lasers the number of lasing modes can be reduced without introducing crystallographic defects. It is shown that the photon momentum aids in suppressing the spectral modes closest to the dominant mode. Two-mode laser spectroscopy is done over an interval of 2 cm−1 for two gases, N2O and CH3Cl.

Absolute line intensities of sixteen rovibrational transitions in the ν4 band of 14NH3 were measured around 1800 cm−1 using a tunable diode laser spectrometer with a sweep modulation of the laser frequency. Individual laser scans over the line region were recorded to disk storage separately and the spectrum accumulation was performed off-line using a computer to reduce a significant line broadening because of a lower accuracy of the hardware on-line accumulation. From integrated absorption coefficients obtained by the numerical analysis of the measured line profile, the effective transition moments of individual rovibrational lines were derived. Using the second order perturbation theory of the transition moment of rovibrational transitions of the symmetric top molecules, the effective vibrational transition moments for the ν4 fundamental band of 14NH3 were estimated.

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 × 10–6 (≅ 8 µg m–3 CH3OH). 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 × 10–5 ± 2 × 10–6) g s–1 at 20 °C, generated a concentration level in the model used from a background value of 80–90 µg m–3 up to values of ≅ 1000 µg m–3 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.

An investigation of the sub-millimeter-wave spectra of the ionic complexes Ar.H+3 and Ar.D+3 is presented. These complexes were produced in a negative glow electric discharge, in mixtures of argon with either H2 or D2. About 80 new transitions were assigned in the 485-680 GHz frequency range using a sub-millimeter-wave spectrometer built with Russian made backward wave oscillators (BWO) sources. These measurements enabled us to observe the first Ka = 2 transitions for Ar.H+3 and the first Ka = 3 transitions for Ar.D+3. Analyses of the line frequencies were carried out using an IAM-like approach, which accounts for the large amplitude internal rotation motion displayed by both species. Insights into the geometry of the intermediate configuration for this large amplitude motion were gained. Copyright 1998 Academic Press.

The performance of the InAsSbP/InAs lasers for absorption spectroscopy of ammonia at 3370–3660 cm−1 was first shown. These continuous wave lasers based on the III–V semiconductor are alternative to a widespread utilised Pb-salt device and were first investigated in closed-cycle He-cryostat at temperatures of 32–85 K. The spectral and tuning characteristics of the laser were considered versus both heatsink temperatures and drive currents in viewpoint of applications in molecular laser spectroscopy, with best device performance being found at 45–65 K. The preliminary experiments to record spectra of the ammonia absorption with the diode were undertaken.

The infrared diode laser spectrum of the nu2 + nu5 - nu2 hot band of acetylene has been observed within the discharge plasma of acetylene diluted in He. The concentration of acetylene in the nu2 state was modulated by applying a few kHz of ac current, and the spectrum of the hot band was recorded selectively by the discharge modulation technique. In total, 46 P, R, and Q-branch lines have been assigned to the nu2 + nu5 - nu2 hot band and molecular constants including the band origin 727.59318(27) cm-1 were derived. The lifetime of acetylene in the nu2 state was measured to be about 1 ms, proving that the nu2 state is metastable. The collisional relaxation rate constant of acetylene in the nu2 state by helium was measured to be k = 8.01plusmn; 0.19 x 10(-14) cm3 molec-1 s-1. Copyright 1998 Academic Press. Copyright 1998Academic Press

The rotational spectra of H 2 13 COH + and D 2 COD + were observed in the 110–224 GHz frequency region using a magnetically confined negative glow discharge as ion production source. Analysis of the spectra allowed determination of the ground state rotational and quartic centrifugal distortion constants. These new data, together with those of Dore et al. [ Chem. Phys. Lett. 244, 145 (1995)] concerning H 2 COH + , allow an estimate of the molecular structure of protonated formaldehyde.

SO was created by electric discharge in a mixture of SO2and Ar and by UV-laser photolysis of Cl2SO. The two methods are compared. The pure rotational spectrum of theX3Σ−electronic ground state was measured in highly excited vibrational states up tov= 17, that of thea1Δ excited state up tov= 13, and that of theb1Σ+excited state up tov= 11. Measurements up to 900 GHz without harmonic generation were possible thanks to the use of Russian-constructed BWOs.

Bi(Pb)–Sr–Ca–Cu–O layers were prepared by laser ablation in air, that is without using a vacuum chamber. At this method a much higher density of pulse energy of laser beam is required (10–30 J cm−2) in comparison with the standard method (1–3 J cm−2). The mentioned condition has specific effects on the nature of the transport of material from the target. As follows from the electron microprobe analysis of the layers, the starting composition of the transported material is identical with that of the superconducting phase sintered in the target; one exception represents Pb, the content of which in the transported material is lower. The image of the process is complemented by UV/VIS spectroscopy scans of the plasma plume.

The perpendicular band of the fourfold degenerate C–H stretching vibration of dimethylacetylene (2-butyne) occurring in the region 2955–3065 cm −1 has been measured with Doppler-limited resolution at a temperature of ∼195 K on a difference-frequency laser spectrometer, and on a high-resolution Fourier transform instrument at room temperature as well as in a molecular jet at ∼20 K. From a detailed rotational analysis of this complex band, based on an extension of the model of the rotational–torsional interactions described by P. R. Bunker and C. di Lauro ( Chem. Phys. 190, 159–169, 1995), accurate spectroscopic constants were determined for the upper CH stretching state, along with values for the first three components of the Fourier expansion for the torsional potential in the ground state, and for six components of this potential in the upper state. Over 700 lines assigned to 37 well-resolved subbands plus 25 additional unresolved line-like Q -branches were fitted with an overall standard deviation of 0.0024 cm −1 . The results yield a value of 6.316 ± 0.034 cm −1 for the barrier to internal rotation in the ground state, and 6.643 ± 0.006 cm −1 for the C–H stretching state. This value for the ground state barrier is somewhat higher than that recently determined from an analysis of the CH 3 rocking band by P. R. Bunker et al. ( J. Mol. Spectrosc. 162, 142–151, 1993).

We have developed several methods of diode laser spectroscopy and have applied them for high-resolution spectroscopy and kinetic studies of molecular ions. For these purposes we have used a special high-voltage modulation technique for generation of ions in the plasma of a gas discharge. This modulator enables the studies of the formation and decay processes of ions. The modulator can also alternately switch the polarity of a high voltage and can be used for experimental measurement of velocity modulation of ions in the gas discharge. It was found that this spectrometer can be successfully used in the following regions: • -velocity modulation spectroscopy of molecular ions (ArD+, SD−), • -distinction between the velocity modulation signal of cation and anion (due to the reverse phase of both signals), • -measurement of Doppler shifts of ions (information about the velocity and mobilities of ions), • -ion kinetics (measurement of times of formation and decay of ions in the gas discharge).

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.

A combination of nuclear quadrupole resonance spectroscopy (NQR) and mass spectrometry (MS) has been used to observe trends in electronic structure in three titanocenes: bis(cyclopentadienyl) titanium dichloride (η(5)-C(5)H(5))(2)TiCl(2), bis(pentamethylcyclopentadienyl) titanium dichloride (η(5)-C(5)(CH(3))(5))(2)TiCl(2) and dimethylsilylene-bridged ansa bis(cyclopentadienyl) titanium dichloride Si(CH(3))(2)(η(5)-C(5)H(5))(2)TiCl(2). Using MS, electron ionisation mass spectra of these compounds are presented within the context of the entire homologous series with one to five methyl groups on each cyclopentadienyl ligand. A dedicated NQR spectrometer was constructed for this study with a sensitivity sufficient to precisely determine the NQR resonant frequency of (35)Cl atoms using 3 g samples of these titanocenes. The observed frequencies are thus 11.784, 11.930 and 10.863 MHz at 298 K. The results demonstrate that NQR using a relatively simple apparatus can be used as a sensitive and cost effective probe into the molecular structure of organometallic chlorides, which complements the information inferred from the mass spectra.

Three completely different 1f lineshapes for the rovibrational lines of ArH+ and ArD+ ions in different experimental conditions were detected in an discharge using a tunable diode laser and a velocity modulation technique. The lineshapes of these ions were studied under various experimental conditions and also by on-off and frequency 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 maximum in the plasma discharge were studied for all three types of lines of the ArH+ ion and their agreement with the Schottky form was checked.