Study of lattice vibrational modes in CuGaS2 by using fourier transform spectroscopy

The lattice dynamics of a single crystal of CuGaS₂, grown by iodine transport technique, have been studied by using far IR absorption spectroscopy. All the absorption maxima caused by the phonon excitation are compared with the lattice vibrational modes obtained by Raman spectroscopy and by IR reflection techniques. An absorption maximum located at 175 cm^?1 cannot be explained with the help of phonon excitation; however this peak can be attributed to the defect frequency originating from the replacement of gallium atom by sulphur in the v₁₇ mode of vibration. The frequency of this defect-induced vibrational mode is calculated by taking a modified molecular model approach, and is found to be 166.9 cm^?1, which is in reasonably good agreement with the experimentally observed value of 175 cm^?1.     

The structure and vibrational features of proton disolvates in water–ethanol solutions of HCl: the combined spectroscopic and theoretical study

The infrared (IR) spectra of water–ethanol (EtOH) solutions of HCl are measured over a wide range of acid concentration at fixed H₂O―EtOH ratios (1 : 1, 1 : 2, and 1 : 40). In these systems, different proton disolvates with (quasi)symmetrical H‐bonds are formed. Their structure and vibrational features are revealed by the density functional theory method coupled with the polarizable continuum model of solvation. In dilute acidic solutions, the Zundel‐type H₅O₂⁺ ion is mainly formed. In concentrated HCl solutions, the ions (H₂O···H···O(H)Et)⁺ and (Et(H)O···H···O(H)Et)⁺ with the quasi‐symmetrical O···H⁺···O unit having O···O separation <2.45 Å appear. The first ion characterized by the IR‐intensive band around 1800 cm^?1 is mainly formed in the 1 : 1 water–ethanol systems. The second ion exists in the 1 : 2 and 1 : 40 water–ethanol systems. Its spectroscopic signatures are the groups of the IR‐intensive bands around 800 and 1050 cm^?1. In highly concentrated HCl solutions with the 1 : 40 water–ethanol ratio, a neutral Et(H)O···H⁺···Cl^? complex exists. Copyright © 2013 John Wiley & Sons, Ltd.     

Low-frequency spectroscopy of four-photon scattering of laser radiation in aqueous solutions of biopolymers

Four-photon scattering (FPS) spectroscopy is used to record rotational resonances of H₂O and H₂O₂ molecules in aqueous solutions of DNA and denatured DNA within a range of ±10 cm^-1 with a spectral resolution of 3 GHz. The resonance contribution of rotational transitions of these molecules in solutions was found to be considerably larger than that in distilled water. This fact is interpreted as a manifestation of the specific properties of a hydrate layer at the interface between water and DNA or denatured DNA molecules. An analysis of the FPS spectra shows that the concentration of H₂O₂ molecules in the hydrate layer of the DNA molecule increases threefold after denaturation. In addition, the FPS spectra of aqueous solutions of α-chymotrypsin protein with concentrations of 0-20 mg cm^-3 were measured in the spectral range of ±7 cm^-1. It is found that the velocity of hypersound in the protein aqueous solution, which is measured by the shift of the Mandelstam—Brillouin scattering spectrum components, is a cubic function of the concentration and reaches 3000 m/s at 20 mg/cm³.     

中子辐照含氢FZ-Si的红外吸收研究

对于中子辐照的n-FZSi(H₂),利用红外吸收光谱研究了由于辐照所产生的各种与氢有关的缺陷态。在未辐照的样品和辐照的样品中分别发现了未曾报道的1992cm^{-1和1857cm-1吸收峰。对于在n-FZSi(H₂)所引起的本征吸收峰和辐照损伤吸收峰,进行了讨论和指派。2150cm-1吸收峰则被认为是由于氢施主所引起的。 关键词：}     

Optical properties of BiFeO<Subscript>3</Subscript> ceramics in the frequency range 0.3–30.0 THz

Reflection and transmission infrared spectra of BiFeO₃ ceramic samples have been measured using submillimeter spectroscopy (on a backward-wave tube spectrometer) and Fourier-transform infrared spectroscopy in the frequency range from 5 to 1000 cm⁻¹ at temperatures in the range from 10 to 500 K. New resonant modes (probably, magnetic in nature) with the eigenfrequencies decreasing with an increase in the temperature have been recorded in the range 10–30 cm⁻¹ by IR spectroscopy for the first time. An additional absorption with a fairly large dielectric contribution has been revealed in the range 30–60 cm⁻¹. It has been demonstrated that the corresponding oscillators couple with both the lowest frequency phonon mode and the magnetic subsystem.     

Ions with strong symmetric H-bonds and their solvation in aqueous-ethanolic solutions of HCl

Ion-molecular interactions in the HCl-EtOH-H₂O system are studied by means of multiple frustrated total internal reflection IR spectroscopy over a wide range of concentrations of the components. It is demonstrated that, in the investigated solutions, the acid is fully bound into ions and uncharged complexes formed by strong symmetric or quasi-symmetric H-bonds. There is a competition between H₂O and EtOH molecules during the formation of the (H₅C₂(H)O…H…O(H)C₂H₅)⁺, (H₂O…H…OH₂)⁺, and (H₂O…H…O(H)C₂H₅)⁺ proton disolvates. In dilute solutions of HCl in 2: 1 and 1: 1 EtOH-H₂O mixtures, (H₂O…H…OH₂)⁺ proton dihydrates are mainly formed, whereas in concentrated HCl solutions, under conditions of a partial solvation of ions by solvent molecules, predominantly (H₂O…H…O(H)C₂H₅)⁺ mixed proton disolvates arise. In concentrated solutions of HCl in EtOH with low water content, the acid is partially bound into (H₅C₂(H)O…H⁺…Cl^?) uncharged complexes with the participation of the Cl^? anion.     

Initiation of nuclear reactions under laser irradiation of Au nanoparticles in the aqueous solution of Uranium salt

Laser exposure of a suspension of either gold or palladium nanoparticles in aqueous solutions of UO₂Cl₂ of natural isotope abundance was experimentally studied. Picosecond Nd:YAG lasers at peak power of 10¹¹–10¹³ W/cm² at the wavelength of 1.06–0.355 μm were used as well as a visible-range Cu vapor laser at a peak power of 10¹⁰ W/cm². The composition of colloidal solutions before and after laser exposure was analyzed using atomic absorption and gamma spectroscopy in the 0.06–1 MeV range of photon energy. Real-time gamma spectroscopy was used to characterize the kinetics of nuclear reactions during laser exposure. It was found that laser exposure initiated nuclear reactions involving both ²³⁸U and ²³⁵U nuclei via different channels in H₂O and D₂O. The influence of saturation of both the liquid and nanoparticles by gaseous H₂ and D₂ on the kinetics of nuclear transformations was found. Possible mechanisms of observed processes are discussed.     

Simultaneous measurement of two compounds in aqueous solution with dual quantum cascade laser absorption spectroscopy

Two pulsed Fabry–Pérot quantum cascade lasers (QCL) have been employed for the simultaneous measurement of two analytes in aqueous solutions. Two laser beams (1393 and 1080 cm^-1) were combined by an optical system of parabolic mirrors and a ZnSe-beam splitter. Measurements were made in transmission using a 41 μm CaF₂-flow cell and a mercury-cadmium-telluride (MCT) detector. Using glucose and sodium acetate as model analytes, the measurements show the potential of dual QCL absorption spectroscopy for analyte specific detection and background compensation. The use of the two lasers gives quantitative information about the analytes, even when they show overlapping absorption bands typically found in condensed phase. PACS 42.55.Px; 42.62.Fi     

H<Subscript>3</Subscript>O<Stack><Subscript>2</Subscript><Superscript>-</Superscript></Stack> ions with a strong quasi-symmetrical H-bond and their hydration in aqueous solutions of NaOH and KOH

Ion-molecular interactions in aqueous solutions of NaOH (0–47.8%) and KOH (0–51.95%) are studied by multiple frustrated total internal reflection IR spectroscopy. Interpretation of the spectra and analysis of the spectral data are performed based on the results of DFT calculations (B3LYP/6-31++G(d, p)) of the characteristics of the free and double hydrated H₃O ₂ ^- ion. It is established that the changes in the IR spectra of NaOH and KOH aqueous solutions caused by increasing alkali concentration are due to the formation of H₃O ₂ ^- ions with a strong quasi-symmetrical hydrogen bond and their subsequent hydration by one or two water molecules. The influence of the cation nature on the degree of hydration of H₃O ₂ ^- ions is demonstrated. The equilibrium concentrations of monohydrate (H₃O ₂ ^- ? H₂O) and dihydrate (H₃O ₂ ^- ? 2H₂O) are calculated and their IR continuous absorption spectra are isolated.     

Raman spectroscopic study of the hydrogen‐arsenate mineral pharmacolite Ca(AsO3OH)·2H2O—implications for aquifer and sediment remediation

The removal of arsenate anions from aqueous media, sediments and wasted soils is of environmental significance. The reaction of gypsum with the arsenate anion results in pharmacolite mineral formation, together with related minerals. Raman and infrared (IR) spectroscopy have been used to study the mineral pharmacolite Ca(AsO₃OH)· 2H₂O. The mineral is characterised by an intense Raman band at 865 cm⁻¹ assigned to the ν₁ (AsO₃)²⁻ symmetric stretching mode. The equivalent IR band is found at 864 cm⁻¹. The low‐intensity Raman bands in the range from 844 to 886 cm⁻¹ provide evidence for ν₃ (AsO₃) antisymmetric stretching vibrations. A series of overlapping bands in the 300‐450 cm⁻¹ region are attributed to ν₂ and ν₄ (AsO₃) bending modes. Prominent Raman bands at around 3187 cm⁻¹ are assigned to the OH stretching vibrations of hydrogen‐bonded water molecules and the two sharp bands at 3425 and 3526 cm⁻¹ to the OH stretching vibrations of only weakly hydrogen‐bonded hydroxyls in (AsO₃OH)²⁻ units. Copyright © 2009 John Wiley & Sons, Ltd.     

Spectroscopic studies of the lanthanide(III) ions with pyridine carboxylic acid N-oxide ligands and in mixed ligand complexes

A series of Ln(III) complexes with pyridine carboxylic acid-N-oxides (L) Ln-L, and mixed ligand complexes of Ln-L plus bipyridine (bipy) or 1,10-phenanthroline (O-phen) (X) Ln-L-X have been studied. These complexes were characterized in solution using Nd(III) absorption in the spectral range of the ⁴I_9/2 → ⁴G_5/2 transition corresponding to the hypersensitive band, and in the solid state with the use of IR and Eu(III) luminescence spectroscopy. In solutions a series of Nd(III) complexes and mixed ligand complexes has been examined and the formation of binary LnL and LnL₂ complexes and mixed ligand LnL₂X complexes evidenced. Solid complexes of Eu(III) with nicotinic acid N-oxide and ternary with nicotinic acid N-oxide plus phen were studied with the use of Eu(III) luminescence lifetime measurements and IR spectroscopy, proving the formation of binary [Eu(nicN-oxide)₃(H₂O)₂].2H₂O and ternary [Eu(nicN-oxide)₃phen].H₂O complexes.     

Low frequency four-wave mixing spectroscopy of biopolymer hydration layers in aqueous solutions

Four-wave mixing (FWM) spectroscopy has been applied to detection of H₂O₂ molecules rotational resonances in both DNA and denatured DNA aqueous solutions in the range ±100 cm⁻¹. A considerable growth of rotational lines intensity of H₂O and H₂O₂ has been observed in comparison with distilled water. This fact was interpreted as an exhibition of specific property of a hydration layer formation at DNA/water and denatured DNA/water interfaces. The fitting of four-wave mixing spectra shows the increasing of the H₂O₂ rotational line’s amplitude by a factor of ∼3 in DNA solutions due to denaturizing. The shifting of FWM Brillouin resonances in opposite way in protein solution and SWNT (single wall carbon nanotube) suspension to comparison with water was observed and discussed.     

Local structural order in carbonic acid polymorphs: Raman and FT‐IR spectroscopy

Two different polymorphs of carbonic acid, α‐ and β‐H₂CO₃, were identified and characterized using infrared spectroscopy (FT‐IR) previously. Our attempts to determine the crystal structures of these two polymorphs using powder and thin‐film X‐ray diffraction techniques have failed so far. Here, we report the Raman spectrum of the α‐polymorph, compare it with its FT‐IR spectrum and present band assignments in line with our work on the β‐polymorph [Angew. Chem. Int. Ed. 48 (2009) 2690–2694]. The Raman spectra also contain information in the wavenumber range ∼90–400 cm⁻¹, which was not accessible by FT‐IR spectroscopy in the previous work. While the α‐polymorph shows Raman and IR bands at similar positions over the whole accessible range, the rule of mutual exclusion is obeyed for the β‐polymorph. This suggests that there is a center of inversion in the basic building block of β‐H₂CO₃ whereas there is none in α‐H₂CO₃. Thus, as the basic motif in the crystal structure we suggest the cyclic carbonic acid dimer containing a center of inversion in case of β‐H₂CO₃ and a catemer chain or a sheet‐like structure based on carbonic acid dimers not containing a center of inversion in case of α‐H₂CO₃. This hypothesis is strengthened when comparing Raman active lattice modes at < 400 cm⁻¹ with the calculated Raman spectra for different dimers. In particular, the intense band at 192 cm⁻¹ in β‐H₂CO₃ can be explained by the inter‐dimer stretching mode of the centrosymmetric RC(OHO)₂ CR entity with ROH. The same entity can be found in gas‐phase formic acid (RH) and in β‐oxalic acid (RCOOH) and produces an intense Raman active band at a very similar wavenumber. The absence of this band in α‐H₂CO₃ confirms that the difference to β‐H₂CO₃ is found in the local coordination environment and/or monomer conformation rather than on the long range. Copyright © 2011 John Wiley & Sons, Ltd.     

CO2 pressure broadening and shift coefficients for the 1–0 band of HCl and DCl

CO₂ broadened spectra of the 1–0 band of H³⁵Cl and H³⁷Cl, observed near 2886 cm^?1, and the 1–0 band of D³⁵Cl and D³⁷Cl, located near 2089 cm^?1, have been recorded at room temperature and five total pressures between 150 and 700 Torr, using a Bruker IFS125HR Fourier transform spectrometer. Spectra of pure HCl were also recorded. CO₂ broadening and shift coefficients of HCl and DCl have been measured using multi-spectrum non-linear least squares fitting of Voigt profiles. The analysis of the 1–0 band of DCl was complicated by the presence of overlapping CO₂ bands, which were included in the treatment as absorption coefficients calculated taking line-mixing effects into account.     

不同含氮量的a-Si:H/a-SiNx:H超晶格界面性质的研究

通过电调制吸收、光热偏转谱、光致发光及红外吸收谱等实验技术,研究了不同含氮量的a-Si:H/a-SiN_x:H超晶格的界面性质。由电调制吸收测试得出的界面电荷密度Q_s～10¹²cm^-2。Q_s比由光热偏转谱所获得的界面态密度N_i～10¹¹cm^-2大出约半个数量级。N_i,Q_s,及光致发光相对峰值 关键词：     

Detection of C2H2 and HCl using mid-infrared degenerate four-wave mixing with stable beam alignment: towards practical in situ sensing of trace molecular species

A stable and convenient optical system to realize the forward phase-matching geometry for degenerate four-wave mixing (DFWM) is demonstrated in the mid-infrared spectral region by measuring DFWM signals generated in acetylene (C₂H₂) and hydrogen chloride (HCl) molecules by probing the fundamental ro-vibrational transitions. IR laser pulses tunable from 2900 cm^?1 to 3350 cm^?1 with a 0.025 cm^?1 linewidth were obtained using a laser system composed of an injection seeded Nd:YAG laser, a dye laser, and a frequency mixing unit. At room temperature and atmospheric pressure, a detection limit of 35 ppm (～ 9.5×10¹⁴ molecules/cm³) for C₂H₂ was achieved in a gas flow of a C₂H₂/N₂ mixture by scanning the P(11) line of the (010(11)⁰)–(0000⁰0⁰) band. The detection limit of the HCl molecule was measured to be 25 ppm (～6.8×10¹⁴ molecules/cm³) in the same environment by probing the R(4) line. The dependences of signal intensities on molecular concentrations and laser pulse energies were demonstrated using C₂H₂ as the target species. The variations of the signal line shapes with changes in the buffer gas pressures and laser intensities were recorded and analyzed. The experimental setup demonstrated in this work facilitates the practical implementation of in situ, sensitive molecular species sensing with species-specific, spatial and temporal resolution in the spectral region of 2.7–3.3 μm (3000–3700 in cm^?1), where various molecular species important in combustion have absorption bands.     

Cavity ring-down spectroscopy of H2O in the range 16 570-17 125 cm

Following previous investigations on H₂¹⁶O and H₂¹⁸O by cavity ring-down spectroscopy, this method has now been applied to investigate the energy region of the 5ν polyad in the absorption spectrum of H₂¹⁷O. In the range 16 570-17 125 cm⁻¹, the highest energy range investigated for the H₂¹⁷O isotopologue so far, 516 lines are attributed to H₂¹⁷O and assigned from a newly generated line list.     

The near infrared cavity-enhanced absorption spectrum of methyl cyanide

The absorption spectrum of methyl cyanide (CH₃CN) has been measured in the near IR between 6000 and 8000 cm^?1 with a resolution of 0.12 cm^?1 using Fourier transform incoherent broadband cavity-enhanced absorption spectroscopy. The spectrum contains several weakly perturbed spectral regions; potential vibrational combination bands contributing to the spectrum are outlined. Line positions and cross-sections of CH₃CN between 6814 and 7067 cm^?1 have been measured at high-resolution of 0.001 cm^?1 using diode laser based off-axis cavity-enhanced absorption spectroscopy. A total of 4630 new absorption lines of CH₃CN are identified in this region. A value for the self-broadening coefficient has determined to be (3.3±0.2)×10^?3 cm^?1 mbar^?1 for one isolated line at 7034.171 cm^?1. Several line series have been identified in these regions and an autocorrelation analysis performed with a view to aiding future assignments of the rotational-vibrational transitions.     

The absorption spectrum of 12C2H2 IV. The regions 7600–9200 cm−1 and 10600–11500 cm−1

The absorption spectrum of ¹²C₂H₂ has been recorded by intracavity laser absorption spectroscopy (ICLAS) in the 10600–11 500 cm^?1 spectral region, where no absorption bands were previously reported. Fifteen bands starting from the vibrational ground state are observed and rotationally analysed. All corresponding excited vibrational levels were assigned using the polyad model, the so-called cluster model (El Idrissi, M.I., Liévin, J., Campargue, A., and Herman, M., 1999, J. chem. Phys., 110, 2074) which allows vibrational energies, rotational B_v constants and, to some respect, relative band intensities to be predicted. Additional data and constants are also provided in the range 7600–9200cm^?1, whenever improving the literature results, from spectra recorded previously at ULB using Fourier transform spectroscopy. The assignment procedure in the range recorded by ICLAS is detailed, leading to a deeper understanding of vibration-rotation and intensity features of the absorption bands within the frame of the cluster model.     

Observation of a forbidden vibrational absorption band of H2 in nanoporous aerogel

Room-temperature absorption spectra of H₂ in nanoporous aerogel with a pore diameter of ～20 nm have been studied on a Fourier spectrometer in the spectral range of 4000–4800 cm^?1. Absorption at the forbidden transitions of the 0–1 vibrational band has been observed. The recorded spectra of H₂ in aerogel have been compared with the spectra of free high-pressure H₂.