IR absorption spectrum (4200–3100 cm) of H2O and (H2O)2 in CCl4. Estimates of the equilibrium constant and evidence that the atmospheric water absorption continuum is due to the water dimer

IR absorption spectra, 4200–3100 cm⁻¹, of water in CCl₄ solutions are presented. It is shown that for saturated solutions significant amounts of water are present as dimer (ca. 2%). The IR spectra of the monomer and dimer are retrieved. The integrated absorption coefficients of the monomer absorption are significantly enhanced relative to the gas phase values. The dimer spectrum consists of 5 bands, of which 4 were expected from data from cold beams and cold matrices. The origin of the “extra” band is discussed. In addition it is argued that the dimer absorption bands intensities must be enhanced relative to the gas phase values. Based on recent calculations of band strengths, and observed frequency shifts relative to the gas phase, the intensity enhancement factors are estimated as well as the monomer/dimer equilibrium constant in CCl₄ solution at T=296 K (K_c=1.29 mol⁻¹ L). It is noted that the observed dimer spectrum has a striking resemblance with the water vapour continuum determined by Burch in 1985 which was recently remeasured by Paynter et al. and it is concluded that the atmospheric water absorption continuum in the investigated spectral region must be due to water dimer. Based on the newly published spectral data a revised value of the gas phase equilibrium constant is suggested (K_p=0.035 atm⁻¹ at T=296 K) as well as a value for the standard enthalpy of formation, ΔH⁰=15.4 kJ mol⁻¹.     

Absorptions of the ϱστ, 0.8 μm and a bands of the water vapor

Absorptions of the ?στ, 0.8 μm and a bands of water vapor were measured using a long pathlength, multiple-traversal absorption cell. The band intensities were found to be 842.3, 53.2, and 50.12 cm^-1/g-cm^-2 at 334 K for the ?στ, 0.8 μm and a bands, respectively. The measured equivalent widths gradually exceed calculated values for the Lorentz line profile and the self-broadening coefficients of 5 with increasing absorber amounts. Possible causes of this excess absorption are discussed.     

Confirming Sγ products by blending isotopic doublets of HCl

Experimental confirmation is reported of a published technique, ⁽²⁾ applicable to the square root region which specifies the degree to which two Lorentz absorption lines, not necessarily equal, overlap. It also specifies the deficiency, γ, of the aggregate equivalent width of the blend from its value when the two lines are completely independent. The experiment was conducted at room temperature using pure HCl gas in a 3·34 m path at pressures from 2 to 750 torr. It consisted of sequentially pressure blending fundamental band isotopic doublets. The blended equivalent width of each doublet was compared to predictions from the aforementioned theory as a function of pressure, using previously published values of S and γ as the basis for its application.Published line strength values for the HCl fundamental band agree well only in the upper R (J≥7) branch. These were used to test the procedure. Predictions based upon divergent line strengths in the remainder of the band were then compared to the experimental results and confirm the accuracy of the Sγ products of Benedictet al.⁽¹⁾A polynomial representation of the Ladenburg-Reiche function is given which is useful in extending the procedure of Ref. (2) to the linear region.Finally, a new experiment is described, based upon the confirmed theory, which allows the validity of the Lorentz shape to be assessed as a function of pressure for various foreign broadeners and interaction potentials. Application to cometary abundance determinations is also discussed.     

Investigation of the temperature dependence for the spectra of supercooled water in the middle infrared

The temperature dependence of the bending ν₂, combination ν₂ + ν _L , and stretching (ν₁, ν₃, 2ν₂) absorption bands in the infrared spectra of supercooled water with a temperature-change step Δt from 2 to 2.5°C was studied using an advanced infrared Fourier spectrometer. It was found that the frequency of the maximum of the stretching absorption band (2700–3700 cm^?1) decreases with the reduction of the water temperature from ?0.5 to ?5.0°C. The frequency of the maximum of the combination absorption band (2130 cm^?1) increases with the reduction of the water temperature in a range from ?3.0 to ?5.0°C. The frequency of the maximum of the absorption band of bending oscillation (1640 cm^?1) is invariable with a reduction of the water temperature from ?0.5 to ?5.0°C.     

The ν9 fundamental of ethane: Integrated intensity and band absorption measurements with application to the atmospheres of the major planets

Measurements of the absolute intensity and integrated band absorption have been performed for the ν₉ fundamental band of ethane. The intensity is found to be 34 ± 1.6 cm^-2 atm^-1 at STP, and this is significantly higher than previous estimates. It is shown that a Gaussian profile provides an empirical representation of the apparent spectral absorption coefficient. Employing this empirical profile, a simple expression is derived for the integrated band absorption, which is in excellent agreement with experimental values. The band model is then employed to investigate the possible role of ethane as a source of thermal infrared opacity within the atmospheres of Jupiter and Saturn, and to interpret qualitatively observed brightness temperatures for Saturn.     

Excess attenuation of millimeter waves at window region due to atmospheric water vapor

The attenuation of 245.52 GHz millimeter wave was measured through a near ground horizontal path in order to study the anomalous water vapor absorption at the window region. The result demonstrates that the attenuation coefficient includes the quadratic dependence on the water vapor density. The quadratic component of the water vapor density in the expression of the attenuation was assumed to arises from the contribution of water dimers alone, then the concentration of water dimers was estimated adopting the published theoretical water dimers absorption coefficient. The obtained concentration was 0.062% of monomers in number when the water vapor density is 7.5 g/m³. This concentration is in agreement with the published result obtained by way of another method.     

Shallow center in AgBr: Theoretical investigation by sum rules

In AgBr, an absorption band at 168 cm^?1 can be attributed to absorption by an electron bound in an electrostatic potential. The comparison between the experimental values of the moments of the absorption coefficient and their theoretical expressions gives the ground state mean radius, mean kinetic energy and mean charge density seen by the electron. The ionization energy and electron charge distribution of this center are also obtained.     

The Fundamental Infrared Spectrum of the Ammonium Ion in Aqueous Solutions

The infrared absorptions of NH₄ ⁺ of aqueous solutions of NH₄ ⁺ salt solutions were recently considered in some detail and, based on changes in the contour of the water band, the effect of anions of the water absorption were discussed.¹ We find, however, that differences of the contours of absorptions of pure water and of aqueous solutions can easily produce an artifact.     

Systematic study of the relationships between energy levels of Tl(1), Tl centers and the crystalline environment

In this paper, we present the first systematic study of the relationships between energy levels of Tl⁰(1) and Tl²⁺ centers in alkali halides and the crystalline environment by using dielectric theory of chemical bond for complex crystals. It is found that the coordination number of the central ion, the bond volume polarizability, and the fractional covalence of the chemical bond between the central ion and the nearest anion are the three determinative parameters for the absorption band energy. Four empirical formulas are proposed. The calculated results are in good agreement with the experimental values. The current model can serve as a prediction tool and can be applied to assign the absorption band energy of Tl⁰(1) and Tl²⁺ centers.     

Optical characterisation of CuInSe2 thin films prepared by two-stage process

Optical absorption spectra of CuInSe₂ chalcopyrite semiconductor films prepared using a two-stage technique were investigated. In addition to absorption measurements, energy-dispersive analysis of X-rays (EDAX) and X-ray diffraction measurements (XRD) were also performed. Direct bandgap energy values for the CuInSe₂ films were derived from the variation of (αhν)² with energy. All the measurements were performed on samples with various Cu/In ratios. It was determined from the absorption measurements that the materials have strong absorption at the fundamental band edge. The E_g values showed an increasing trend with decreasing Cu/In ratios. Received: 26 May 2000 / Accepted: 31 October 2000 / Published online: 10 January 2001     

IR spectroscopic manifestations of hydration of poly(diphenyl sulfophthalide) during its storage

IR spectroscopy measurements show that films of poly(diphenyl sulfophthalide) (PDSP), a cardo polymer, interact with atmospheric moisture during storage at room conditions. A total of 15 absorption bands were isolated in spectra of PDSP hydrated during storage, which belong to sorbed water and hydrolysis products. A number of absorption bands (within 1500–1800 cm⁻¹ and 980–1100 cm⁻¹) were obtained by subtracting the spectrum of the film after heating from that of the initial hydrated film. At least six individual bands in the region of the O-H bond stretching vibration were isolated by decomposing a broad complex band (3700–2000 cm⁻¹) into Gaussian components. The isolated bands were tentatively assigned based on the available literature data and quantum-chemical calculations of the characteristics of a number of complexes of a diphenyl sulfophthalide model compound with water molecules. The IR spectra and energies of the hydrogen bonds formed were calculated at the B3LYP/6-311G(d, p) level. In particular, the absorption bands at 1010 and 1079 cm⁻¹ were assigned to the symmetric stretching vibrations of the S=O bonds in the −SO₃⁻ anion, the 1062-cm⁻¹ absorption band, to ν(C-OH), and the absorption bands at 3646, 3586, and 3475 cm⁻¹, to complexes of water with sulfophthalide cycles of the polymer. After a long storage, PDSP largely transforms into a polymeric oxonium salt, and its spectrum becomes similar to that of a polymeric salt prepared by alkaline hydrolysis. A general mechanism of the interaction of PDSP with water is proposed, according to which the hydrolysis of the sulfophthalide cycles (SPC) by sorbed water yields new hydrophilic groups, sulfoacid, and hydroxyl groups. A further sorption of water by the sulfoacid results in its ionization and the formation of various hydroxonium forms. Sorption and hydrolysis are reversible processes: water is desorbed and the SPC is recovered when the polymer is heated to 100–150°C, as can be judged from an increase in the intensity of the S=O bond vibrations of the sulfophthalide cycle at 1352 and 1192 cm⁻¹. The possibility of using strongly hydrated PDSP for manufacturing proton-conducting membranes is discussed.     

表面修饰的二氧化钛纳米材料的结构相变和光吸收性质

采用胶体化学法制备表面修饰的二氧化钛纳米材料，并使用XRD，TEM，UV-vis光谱等手段研究表面修饰的二氧化钛纳米微粒的结构相变和光吸收性质.结果表明，表面修饰可以改变二氧化钛的晶化行为、加快锐钛矿→金红石的相变进程、引起二氧化钛纳米粒子的光吸收带边大幅度红移.光吸收系数与光子能量之间关系的计算分析显示，在吸收带边附近，二氧化钛纳米微粒溶胶及二氧化钛纳米薄膜的(αhν)^1/2vs hν(间接)和(αhν)² vs hν(直接)均呈线性关系，其间接和直接光学带隙能可以分别通过外推这种线性关系来测量. 关键词： 二氧化钛纳米材料 结构相变 表面改性 光吸收     

Mid-infrared absorption cross-sections and temperature dependence of CFC-113

The temperature dependence of the infrared absorption cross-sections of CFC-113 (1,1,2-trichlorotrifluoroethane) in a pure vapor phase has been recorded in the 600-1250 cm⁻¹ spectral region using Fourier transform spectroscopy. Spectra at 0.05 cm⁻¹ resolution have been used to derive the integrated band strengths of the five main absorption bands over a range of temperatures from 223 to 283 K. Our results show good agreement with previously published data. The new cross-sections will allow more accurate retrieval of atmospheric CFC-113 concentrations using infrared spectroscopic techniques.     

Shape of the IR bands of CH4: The CH4-Kr system in different phase states

The IR absorption spectrum of mixtures of CH₄ with Kr in the range 800–6000 cm^?1 is studied in the region of the gas-liquid and liquid-crystal phase transitions. It is found that, as the system density increases, the ratio of the ν₄ band intensity to that of the ν₃ band becomes larger and the measured values of the second spectral moment of the ν₄ band become smaller than the corresponding calculated values. The quantum counterpart of the generalized J-diffusion model was used to describe the shape of the ν₃ and ν₄ bands, and the rotational relaxation times of CH₄ in solutions were obtained. It was shown that, as the density increases, a broad 1470-cm^?1 band appears in the region of the “forbidden” (induced by a Coriolis interaction) ν₂ band (ν_Q=1535 cm^?1) detected in a low-density gas. The intensity of this band is appreciably higher than that of the ν₂ band.     

CdxHg1-xTe混晶声子谱的远红外光谱研究

在温度4.2—300K和波数15—5OOcm^-1的范围内研究了x=0.18到0.45的不同组分的Cd_xHg_1-xTe的远红外吸收光谱。除剩余射线吸收带两侧的双声子吸收结构外,实验首次观察到一个位于波数20—50cm^-1的低频吸收带。用面间力常数的密度函数法等估计了Cd_xHg_1-xTe混晶的声子谱,并将上述低频吸收带归之于混晶导致的无序和“掺杂”诱发TA声子带模吸收效应。 关键词：     

Mid-infrared diode laser spectroscopy of SO

The absorption spectrum of the fundamental band of SO⁺ (X²Π) has been recorded using a mid-infrared tunable diode laser spectrometer with the velocity modulation technique in an AC glow discharge of He/SO₂. Forty-two lines of SO⁺ were identified in the spectral range of 1230-1330 cm⁻¹. The observed rovibrational transitions together with the microwave data published previously were fitted to a standard effective Hamiltonian for ²Π states. Molecular constants for the ground and υ = 1 vibrational states were derived. The band origin was determined to be 1291.5299(27) cm⁻¹.     

First experiments on field photodesorption IR spectroscopy

The ion current of adsorbed water molecules is studied experimentally as a function of the frequency of near-IR radiation incident on a surface at frequencies in the intrinsic vibrational bands of the water molecule. The ions are produced by nonequilibrium field surface ionization. The observed band (near one of the combination frequencies) has a width of 100 cm⁻¹ and is shifted relative to the free molecular band by 130 cm⁻¹. Estimates show that the cross section for absorption of the radiation by the adsorbed molecules is 3–4 orders of magnitude larger than for free molecules, as is typical of surface processes. Zh. Tekh. Fiz. 69, 123–127 (September 1999)     

Optical properties of Sm-doped CaF2 bismuth borate glasses

Sm³⁺-doped calcium fluoride bismuth borate glasses were prepared and characterized optically and the oscillator strengths and Judd–Ofelt parameters for the glass containing 1.5 mol% of Sm₂O₃ were calculated. Density and optical absorption, transmission and the emission spectra were measured. The values of Judd–Ofelt parameters suggested an increase in the degree of asymmetry the local ligand field at Sm³⁺ sites. The optical band gap energy, band tailing parameter and Urbach's energy were calculated for all glass samples. It was found that with increasing the concentration of Sm₂O₃ content the values of the optical band gap energy decrease whereas Urbach's energy increases. Absorption and excitation spectra indicate that commercial UV and blue laser diodes, blue and bluish-green LEDs and Ar⁺ optical laser are powerful excitation sources for Sm³⁺ visible fluorescence in the glass.     

Diode-laser study of the torsional overtone in CH3SiH3

A tunable diode-laser spectrometer has been used to study the (v = 2 ← 0) torsional band in methyl silane at Doppler-limited resolution with an absorption path of 64 m. Between 330 and 380 cm⁻¹, 87 transitions have been measured to an accuracy ∼0.0015 cm⁻¹. A good fit to a torsion-rotation Hamiltonian involving 21 constants has been obtained by analyzing these measurements along with frequencies from previously reported experiments including an earlier interferometer study of the (v = 2 ← 0) band at substantially lower resolution. In the course of calibrating the spectra, experimental determinations to ∼0.0015 cm⁻¹ have been made for 16 very weak water lines for which only calculated frequencies were previously available.