Raman and infrared spectra of ethylene glycol

The Raman spectrum of ethylene glycol has been investigated in the liquid and solid states and also in aqueous solutions. The infrared absorption spectrum of the liquid has been recorded. 27 Raman lines and 17 infrared maxima in the liquid state and 20 Raman lines in the solid state have been reported. Detailed vibrational assignments have been given. Two strong polarised Raman lines of the liquid which have no corresponding infrared absorption bands, and which disappear on solidification, have been attributed to the trans configuration of the glycol molecule. From a comparative study of the various spectra, it is concluded that in the liquid state, glycol exists as a mixture of the two rotational isomers (trans and gauche) whereas in the solid state only the gauche form is present. In very dilute aqueous solutions, the predominant molecular form is the gauche form.     

Mathematical modeling and numerical simulation of CO2 transport through hollow-fiber membranes

Chemical absorption of carbon dioxide was studied theoretically using hollow-fiber membrane contactors in this work. A 2D mathematical model was developed to study CO₂ transport through hollow-fiber membrane contactors. The model considers axial and radial diffusion in the membrane contactor. It also considers convection in the tube and shell side with chemical reaction. The finite element method (FEM) was used to solve the model equations. Modeling predictions were validated with the experimental data obtained from literature for CO₂ absorption in amine aqueous solutions as solvent. The modeling predictions were in good agreement with the experimental data for different values of gas and liquid velocities. The liquid solvents considered for this study include aqueous solutions of monoethanolamine (MEA), diethanolamine (DEA), N-methyldiethanolamine (MDEA), 2-amino-2-methyl-1-propanol (AMP) and potassium carbonate (K₂CO₃). The simulation results indicated that amine aqueous solutions were better than K₂CO₃ aqueous solution for CO₂ absorption. Also simulation results revealed that the removal of CO₂ with aqueous solution of MEA was the highest among the amines solvents. The hollow-fiber membrane contactors showed a great potential in the area of CO₂ absorption.     

Infra-red spectra of fluoroxylenes

The infra-red spectra of four fluoroxylenes (1, 2, 6-, 1, 2, 3-, 1, 3, 4-and 1, 2, 5-isomers) have been recorded in the 2–15 µ region on a Perkin-Elmer Model 21 spectrophotometer. From among the bands recorded, those which could be correlated to the fundamental vibration of the constituent benzene and methyl groups are discussed in detail and compared with particular reference to the type of substitutions.     

N.M.R. and I.R. studies of 1, 1, 1 trifluoroacetone in proton donor solvents

Interactions of 1, 1, 1 trifluoroacetone with proton donor solvents of the type RH [where R=HO, CH₃S, CH₃CH₂CH₂CH₂S, CH₃O, (CH₃)₂N, (C₂H₅)₂N] have been investigated using NMR and infra-red techniques. Evidence of the formation of addition products of the type CF₃.C(OH)R.CH₃ where OH group is hydrogen-bonded with the fluorine of the CF₃ group has been obtained.     

Optical absorption spectrum of Ni2+ in Garnierite

The results obtained in the study of the absorption spectrum of Ni²⁺ in two samples of Garnierite are described. Both the samples of Garnierite have been studied by preparing their mineral oil mulls. One of these samples could however be studied in its crystal form as well. From the observed features, the absorption bands in both the samples of Garnierite have been attributed to an ion of Ni²⁺ in tetrahedral symmetry. The observed and calculated energies for the bands are found to be in close agreement with one another justifying the assumption that the site symmetry of Ni²⁺ ion is tetrahedral. For one of the Garnierite samples both the crystal and mineral oil mull spectra could be recorded and it is interesting to find that they are identical with one another. It has therefore been suggested that the absorption spectrum of any mineral can be studied by preparing its mineral oil mull in case it cannot be cut and polished into a thin crystal suitable for absorption work. The crystal field parameters derived for the two samples of Garnierite are identical and they are B = 845 cm^?1, C = 3.9 B, Dq = 422 cm^?1 and λ = ? 275 cm^?1.     

Rotational analysis of the C2Σ+ — X2Σ+ system of AlO

The 2-0, 1-0, 0-0 and 0-1 bands of the C²Σ⁺-X²Σ⁺ system of AlO, lying at 2391.88 Å, 2438.35 Å, 2487.32 Å and 2548.51 Å respectively were excited in a low pressure arc and photographed on a 6.6-metre concave grating spectrograph in the third order at a dispersion of 0.37 Å/mm. From the rotational analysis of these bands, the following constants have been determined: B_e′ = 0.565₃ cm.^?1 a_e′ = 0.004₈ cm.^?1 T_e =40267.0 cm.^?1 B_e″ = 0.641₃ cm.^?1 a_{″ = 0.005 7} cm.^?1     

Preparation and properties of peroxy titanium malonate

The method of preparation and physicochemical properties of peroxy titanium malonate, TiO₂(OOC)₂CH₂·3H₂O are given. The reasons for the poor complexing tendency of malonic acid are discussed. The nature of the bonds between titanium and the peroxy as well as malonate groups is assigned from spectrophotometric and infra-red absorption studies.     

Studies on the relation between chemical constitution and ultraviolet absorption spectra of optically active and racemic compounds

The ultraviolet absorption spectra of camphor-β-sulphonyl-phenyl, (o-, m- andp-) tolyl, (α- and β-) naphthylamides have been determined in methyl alcohol, ethyl alcohol, and chloroform. The absorption spectra of all the compounds show two absorption bands: one varying from 267 to 284 mμ, the longer absorption maximum (λ_max) due to selective absorption of the keto group, and the other shorter one, ranging from 226 to 230 mμ, due to general absorption of the saturated molecules. The values of the characteristic wavelengths, λ₀₈ obtained from Drude’s one-term equation, have been compared with the absorption maxima, λ_max obtained by direct measurements. There are marked discrepancies in the values of λ₀ and λ_max. An explanation of the discrepancies is given. The nature of racemic modifications of the compounds has also been discussed.     

Emission spectrum of bismuth monochloride

Bismuth chloride has been excited in flowing condition with an uncondensed transformer discharge. About 390 bands are observed in the present experiments of which only 140 were recorded by earlier workers. The vibrational constants obtained are the same as those obtained by Morgan from obsorption experiments except for the addition of a cubic term for the upper state. It appears quite likely that the upper state of the system dissociates into Bi (⁴S_3/2) + Cl (²P_1/2) while the lower state, which is probably the ground state, dissociates into Bi (⁴S_3/2) + Cl (²P_3/2). The rough values of the dissociation energies obtained by extrapolations are D₀′=3750 cm.^?1 and D₀″=24614 cm.^?1     

Rotational analysis of some bands of C1 Σ u + -X1 Σ g + system of P2 molecule involving lowν′,ν″ values

Ten ultraviolet bands of the C¹ Σ _u ⁺ -X¹ Σ _g ⁺ system of P₂ involving lowv′ andv″ values have been photographed at dispersion of 0·38 and 0·56 Å/mm. and analysed for their rotational structure. While four of these bands were analysed earlier, six of them,viz., 0–10, 1–12, 2–7, 2–14, 4–8 and 6–9 have been analysed for the first time during the present studies. The rotational constants, B _v S with lowv″ quantum numbers are obtained from which value of B _θ ^″ has been derived. The value of B _θ ^″ is found to be in agreement with the value obtained by Douglas and Rao from their study of A¹ Π _g-X¹ Σ _g ⁺ bands of P₂. Earlier findings on the perturbation ofν′=2 level of the C¹ Σ _u ⁺ state have been confirmed from the analysis of the 2–7, 2–14 and 2–15 bands. Theν ₀₀ values of the bands show large deviations from the expected values.     

F2Δr−A2Πi band system of CN

The spectrum of CN has been studied in condensed electrical discharge through flowing CH₃CN vapour. Ten new bands of F²?,?A²Π_i system in the region 2100–2700 Å are obtained. The vibrational constantsω ₀′ = 1229.7 cm.^?1 and ω₀′χ₀′= 14.0 cm.^?1 are obtained for the first time for the²Δ state of CN.     

The near ultraviolet emission spectrum of tetralin (tetrahydronaphthalene)

An emission spectrum of tetralin (tetrahydronaphthalene) in the near ultraviolet excited by a transformer discharge through flowing vapour has been studied and about twenty-nine bands in emission have been photographed and measured on suitable instruments. Vibrational analysis of the bands in terms of the fundamental frequencies of the molecule is proposed and is compared with those obtained in the corresponding absorption spectrum of tetrahydronaphthalene studied by the author.² The results afford further confirmation of the correctness of the analysis and particularly the assignment of the (0,0) band proposed in the absorption spectrum of the molecule.     

Electron paramagnetic resonance studies of VO2+ in single crystals of NaCl,KCl and RbCl

Electron paramagnetic resonance (EPR) of VO²⁺ radicals incorporated in face-centred single crystals of NaCl, KC1 and RbCl has been studied in the temperature range of 77° K to 330° K. At liquid nitrogen temperature, anisotropic spectra have been recorded in each case while spectra recorded at room and higher temperatures are isotropic suggesting the existence of a fast readjustment of VO²⁺ molecular ions in the crystals at higher temperature while this motion gets hindered at liquid nitrogen temperatures. Spin-Hamiltonian constants are calculated from the recorded isotropic and anisotropic spectra. The line widths in each case are found to obey a parabolic law originally proposed by Kivelson. The constants which give a close fit have been evaluated. The random orientation and readjustment of V-0 bond in these alkali chloride crystals is explained on the assumption that the medium exhibits a “liquid-like” nature for VO²⁺ molecular ion as far as the electron paramagnetic resonance absorption is concerned.     

Electron paramagnetic resonance of Mn2+ in NaF single crystals

The electron paramagnetic resonance of Mn²⁺ in NaF single crystals is investigated at different temperatures from 573° K to 93° K. Four different spectra designated as I, II, III₂ and III₄ are observed. Spectrum I consists of a single broad resonance corresponding to precipitated Mn²⁺ ions. Spectrum II is isotropic and centred nearg = 2.00. This spectrum corresponds to substitutional Mn²⁺ ions with remote charge compensating sites and therefore with local cubic symmetry. Spectrum III₂ withg = 2.014 and spectrum III₄ withg = 1.995 are also due to substitutional Mn²⁺ ions but subjected to tetragonal crystalline fields and are the same as those reported by earlier workers. Superhyperfine structure has been observed in spectra II, III₂ and III₄. The analysis of that structure in spectra II and III₂ has been carried out for the first time and the constants A_s, and A_σ are given. The spectra are analysed by the usual spin-Hamiltonian method.     

Infrared spectrum of ferroelectric lithium hydrazinium sulphate [Li (N2H5) SO4]

Dielectric observations on lithium hydrazinium sulphate have shown earlier that it is ferroelectric over a range of temperatures from below ?15° C. to above 80° C. and a new type of hydrogen bond rearrangement which would allow the protons to migrate along the chain has also been suggested by others. The infrared spectrum of LiH _z S in the form of mull and as single crystal sections parallel and perpendicular to the ‘C’ axis exhibit about 21 well-defined absorption maxima. The position and the width of the maxima agree with the known structure of the crystal according to which the hydrazine group exists in the form of the hydrazinium ion, NH₂·NH ₃ ⁺ and the observed N⁺-H frequencies agree better with the new correlation curve given by R. S. Krishnan and K. Krishnan (1964). However it has been pointed out that from a comparative study of the new infrared spectra of hydrazonium sulphate and lithium ammonium sulphate that the absorption band at 969 cm.^?1 is due to N-N stretching vibration and that the fairly intense band between 2050–2170 cm.^?1 is due to the bending vibrations of the NH ₃ ⁺ group.     

The nuclear magnetic resonance spectra of four spin systems

High resolution H¹ and F¹⁹ nuclear magnetic resonance spectra of 1-fluoro, 2, 4-dinitrobenzene were obtained and analyzed to determine all the parameters involved. As the spectrum of one of the protons is well separated from that of the other two, the secular equation has been solved in the first approximation. The analysis gives the following spin-spin coupling constants: J₀ ^HH = 8.7 ± 0.3 cps., J_m ^HH = 2.9 ± 0.2 cps., J_p ^HH = 0.6 ± 0.3 cps., J₀ ^HH = 10.4 ± 0.2 cps., and the two meta H-F coupling constants were found to be considerably different being 6.5 ± 0.3 cps. and 3.8 ± 0.3 cps. It has been found that theortho andmeta H-F coupling constants have the same sign as theortho andpara H-H coupling constants.     

Optical properties of nanocrystalline silicon embedded in SiO2

Nanocrystalline silicon embedded SiO₂ matrix has been formed by annealing the a-SiO_x films fabricated by plasma enhanced chemical vapor deposition technique. Absorption and photoluminescence spectra of the films have been studied in conjunction with micro-Raman scattering spectra. It is found that absorption presents an exponential dependence of absorption coefficient to photon energy in the range of 1.5–3.0 eV, and a sub-band appears in the range of 1.0–1.5 eV. The exponential absorption is due to the indirect band-to-band transition of electrons in silicon nanocrys-tallites, while the sub-band absorption is ascribed to transitions between surfaces and/or defect states of the silicon nanocrystallites. The existence of Stokes shift between absorption and photoluminescence suggests that the phonon-assisted luminescence would be enhanced due to the quantum confinement effects.     

The near ultraviolet absorption spectra ofortho- andmeta-thiocresols

The absorption spectra ofortho- andmeta-thiocresols have been studied in the present investigation. The ortho-thiocresol spectrum consists of about forty-five bands of rather a diffuse nature and in general low intensity in the region from 2873 Å to 2600 Å. The maximum number of bands is obtained by using a path length of 330 cm. for absorption, the temperature of the bulb being maintained at 14°C. Several of these bands are assigned as due tov-v-transitions. The (0, 0) band is chosen at 35386 cm.^?1 which is the strongest band on the longer wavelength side. Vibrational frequencies in the excited state have values 729, 957 and 1159 and combinations and overtones of these are present. Themeta-thiocresol spectrum consists of about forty bands of rather a diffuse nature and very weak intensities in the region from 2900 Å to 2590 Å. The maximum number of bands is obtained by using a path length 200 cm. for absorption and by keeping the temperature of the bulb at 20° C. The (0, 0) band is chosen to be that at 34793 cm.^?1 which is the strongest band on the longer wavelength side. Vibrational frequencies in the excited state have values 492, 611, 720, 845, 965, 1016 and 1155 cm.^?1 and combinations and overtones of these are present.     

Hydrogen bonding and solvolysis of alkyl sulphonate esters and related compounds

Hydrogen bonding between alkyl sulphonyl compounds andp-chlorophenol in carbon tetrachloride solution has been investigated by infra-red spectrometry. Analysis of the intensity of the bonded O-H stretching absorption indicates that, under the conditions employed, only 1:1 complexes are formed in significant concentration. Equilibrium constants for the complex formation have been determined at 15, 25, 35 and 45° C., and the corresponding enthalpy values derived. The strengths of the hydrogen bonds have been estimated from the positions of the bonded O-H stretching bands, and these frequencies correlate with the normal electronic effect of substitution in aryl and alkyl groups attached to the sulphonyl group. The rate of solvolysis of the methyl sulphonates in water is shown to vary inversely as the strength of the hydrogen bond formed. The possible bearing of these observations on certain aspects of the detailed mechanism of solvolysis is discussed.     

Urey-bradley force field: SF4 molecule

The force constants of SF₄ molecule have been evaluated using the Urey-Bradley force field and compared with those obtained by F-G matrix method. Using the Urey-Bradley constants, the fundamental vibrational frequencies are calculated and compared with the observed frequencies.