Vibrational spectra and rotational isomerism of allyl amine

The infrared spectra of allyl amine in the vapour, liquid and solid phases have been measured from 250 to 4000 cm⁻¹. The laser-Raman spectrum in the liquid state has also been recorded photoelectrically and qualitative depolarization measurements have been made. The interpretation of the spectral data suggests the presence of two rotational isomers (‘cis and trans”, and ‘ganche and trans’) in the vapour and liquid phases whereas the form having asymmetrical structure (‘gauche and trans’, C₁ symmetry) gets stabilized in the solid state at low temperature.     

Infrared and Raman Spectra,conformations, ab initio calculations and spectral assignments of 1,3‐disilabutane (SiH3CH2SiH2CH3)

Raman spectra of 1,3‐disilabutane (SiH₃CH₂SiH₂CH₃) as a liquid were recorded at 293 K and as a solid at 78 K. In the Raman cryostat at 78 K an amorphous phase was first formed, giving a spectrum similar to that of the liquid. After annealing to 120 K, the sample crystallized and large changes occurred in the spectra since more than 20 bands present in the amorphous solid phase vanished. These spectral changes made it possible to assign Raman bands to the anti or gauche conformers with confidence. Additional Raman spectra were recorded of the liquid at 14 temperatures between 293 and 137 K. Some Raman bands changed their peak heights with temperature but were countered by changes in linewidths, and from three band pairs assigned to the anti and gauche conformers, the conformational enthalpy difference Δ_confH(gauche–anti) was found to be 0 ± 0.3 kJ mol⁻¹ in the liquid. Infrared spectra were obtained in the vapor and in the liquid phases at ambient temperature and in the solid phases at 78 K in the range 4000–400 cm⁻¹. The sample crystallized immediately when deposited on the CsI window at 78 K, and many bands present in the vapor and liquid disappeared. Additional infrared spectra in argon matrixes at 5 K were recorded before and after annealing to temperatures 20–34 K. Quantum chemical calculations were carried out at the HF, MP2 and B3LYP levels with a variety of basis sets. The HF and DFT calculations suggested the anti conformer as the more stable one by ca 1 kJ mol⁻¹, while the MP2 results favored gauche by up to 0.4 kJ mol⁻¹. The Complete Basis Set method CBS‐QB3 gave an energy difference of 0.1 kJ mol⁻¹, with anti as the more stable one. Scaled force fields from B3LYP/cc‐pVQZ calculations gave vibrational wavenumbers and band intensities for the two conformers. Copyright © 2007 John Wiley & Sons, Ltd.     

Phase Dependence of the IR Spectra of Nitrobenzene

The IR spectra of nitrobenzene-d₀ and -d₅ were recorded in gas and liquid phases at 25°C and in amorphous solid phase at -170°C. The appearance of new bands and intensity changes going from liquid to solid phase spectrum, are interpreted in terms of molecular symmetry modifications. A normal coordinates analysis was performed and the potential energy distribution agrees well with previous assigments.     

Coherent laser spectroscopy of RF resonances in liquid

Four-photon polarization spectra of double distilled water subjected to a special treatment in a cavitation chamber and 20% aqueous solution of hydrogen peroxide were recorded in the range ±8 cm⁻¹. All recorded spectra contain narrow (< 0.3 cm⁻¹) resonances corresponding to the frequencies of the rotational spectrum of ortho and para spin isomers of the H₂O molecule. Numerical simulation of the spectra obtained made it possible to quantitatively estimate the contribution of the rotational spectrum to the coherent scattering signal. It was found that the contribution of the para spin isomer of the H₂O molecule to the rotational line spectrum decreases in an aqueous solution of the α-chymotrypsin protein. Apparently, this decrease indicates the selectivity of interaction of biopolymer molecules with different spin isomers.     

Rotational isomers of methyl trans-cinnamate: A Raman study

The Raman and infrared spectra of methyl trans-cinnamate were measured as a function of temperature in the liquid and solid phases. The temperature dependence of the band intensities established the presence of two conformers in the liquid phase (the s-cis and s-trans forms, with CC CO dihedral angles equal to 0° and 180°, respectively; ΔH_{(s-trans)-(s-cis)} = 3.43 ± 0.84 kJ mol⁻¹) and led to the conclusion that the thermodynamically most stable s-cis form is the only form present in the solid.     

Vibrational spectroscopic studies,conformations and ab initio calculations of 1,2‐bis(trifluorosilyl)ethane (SiF3CH2CH2SiF3)

Infrared spectra of 1,2‐bis(trifluorosilyl)ethane (SiF₃CH₂CH₂SiF₃) were obtained in the vapour and liquid phases, in argon matrices and in the solid phase. Raman spectra of the compound as a liquid were recorded at various temperatures between 293 and 270 K and spectra of an apparently crystalline solid were observed. The spectra revealed the existence of two conformers (anti and gauche) in the vapour, liquid and in the matrix. When the vapour was chock‐frozen on a cold finger at 78 K and annealed to 150 K, certain weak Raman bands vanished in the crystal. The vibrational spectra of the crystal demonstrated mutual exclusion between IR and Raman bands in accordance with C_2h symmetry. Intensity variations between 293 and 270 K of pairs of various Raman bands gave ΔH(gauche—anti) = 5.6 ± 0.5 kJ mol⁻¹ in the liquid, suggesting 85% anti and 15% gauche in equilibrium at room temperature. Annealing experiments indicate that the anti conformer also has a lower energy in the argon matrices, is the low‐energy conformer in the liquid and is also present in the crystal. The spectra of both conformers have been interpreted, and 34 anti and 17 gauche bands were tentatively identified. Ab initio and density functional theory (DFT) calculations were performed giving optimized geometries, infrared and Raman intensities and anharmonic vibrational frequencies for both conformers. The conformational energy difference derived in CBS‐QB3 and in G3 calculations was 5 kJ mol⁻¹. Copyright © 2009 John Wiley & Sons, Ltd.     

Revised molecular constants and term values for the XΣ and AΠ states of NH

The vibration–rotation spectra of NH have been reinvestigated using laboratory spectra and infrared solar spectra recorded from orbit by the ACE and ATMOS instruments. In addition to identifying the previously unobserved 6–5 vibration–rotation band in the laboratory spectra, many additional high N rotational lines have been observed. By combining the new observations with the previously published data and recent far infrared data, an improved set of molecular constants and term values have been derived for the X³Σ⁻ and A³Π states.     

Dipole moment and far infra-red absorption of quinuclidine (1-aza-bicyclo-[2-2-2]-octane)

Incoherent quasi-elastic neutron-scattering spectra have been measured on powder samples of D-BPBAC in its smectic E, B and A phases using the high-resolution backscattering technique. The data have been analysed in terms of translational diffusion and a localized rotational motion. It has been found that the apparent translational diffusion constant has a temperature dependent value of ～1 × 10^-6 cm² s^-1 in the smectic A phase but is smaller by at least an order of magnitude in the smectic B and E phases. Comparison of the widths of the rotational components of the spectra with other measurements suggests that simple rotational models are not adequate to explain the experimental data.     

Density functional theory calculations and vibrational spectra of 3,5 dichloro hydroxy benzaldehyde and 2,4 dichloro benzaldehyde

The solid‐phase Fourier transform infrared (FT‐IR) and FT‐Raman spectra of 3,5 dichloro hydroxy benzaldehyde (DHB) and 2,4 dichloro benzaldehyde (DB) have been recorded in the regions 4000–400 and 4000–0 cm⁻¹, respectively. Theoretical information on the optimized geometry, harmonic vibrational wavenumbers as well as infrared and Raman intensities were obtained by means of density functional theory (DFT) using standard B3LYP/6–31G** level. This information was used in the assignment of the various fundamentals. Comparison of the simulated spectra with the experimental spectra provides important information about the ability of the computational method to describe the vibrational modes. Copyright © 2008 John Wiley & Sons, Ltd.     

Infrared spectroscopy of a dense potassium vapor jet

In this paper we report the development of new apparatus for the containment and study of dense alkali metal vapors, and the use of the apparatus to study the infrared spectra of potassium vapor. The apparatus is the first to employ aerodynamic confinement of a dense alkali vapor. We have recorded absorption spectra, thermal emission spectra, and laser-induced emission spectra of dense potassium vapor. These techniques all reveal a spectral feature near 1.1 μm which we believe originates in ³Σ⁺_g→³Σ⁺_u transitions of the K₂ molecule.     

Millimeter- and submillimeter-wave spectroscopy of HBS and DBS in vibrationally excited states

Normal and deuterated isotopic variants of thioborine have been produced in the gas phase by a high temperature reaction between crystalline boron and hydrogen sulfide. Millimeter- and submillimeter-wave rotational spectra have been recorded in the frequency range from 75 to 730 GHz for vibrational ground and excited states of the H^10/11B³²S and D^10/11B³²S isotopic species. The spectra of all the excited states which lie below 1500 cm⁻¹, that are 01¹0, 00⁰1, 02⁰0, and 02²0, have been observed and analyzed for each of the four isotopologues investigated. High-order Fermi resonance parameters were found important to analyze properly the spectra of the 00⁰1 and 02⁰0 interacting states. The improved rotational data in conjunction with earlier infrared spectroscopy results have been employed to calculate more precise anharmonic force constants and equilibrium bond lengths.     

The microwave,Raman, far infrared,and NMR spectra and structure of methylchloroformate

The microwave spectra of six isotopic species of methylchloroformate, ClCO₂CH₃, have been recorded from 18.0 to 40.0 GHz. Structural parameters have been determined, and it is shown that the only stable conformer at ambient temperature is the s-trans. The Raman and far infrared spectra of the vapor are reported. Four cases of Fermi resonance have been observed in the Raman effect. Both the methyl and methoxy torsions have been observed in the far infrared, and the methyl barrier to internal rotation has been determined to be 1.15 kcal/mole (1.19 kcal/mole for the CD₃ rotor), which is in agreement with the 1.23 kcal/mole obtained from the microwave splitting method. It is shown from both the ¹³C and ¹H NMR spectra along with the far-infrared data that only one conformer exists, which is contrary to what was previously reported. The vibrational spectrum of the solid is also reported and discussed.     

FTIR spectroscopy of 2-0 band of carbon monoxide confined in silica aerogels with different pore sizes

The absorption spectra of carbon monoxide confined in three aerogel samples with different pore sizes have been recorded within the 4100–4400?cm^-1 spectral region at room temperature. The measurements were made using a Bruker IFS 125HR Fourier-transform infrared spectrometer. Lineshift and half-width values for CO were obtained. The influence of pore sizes on dependence of CO line half-width values on rotational quantum numbers was studied.     

FT‐Raman,FT‐IR spectra and DFT calculations on monomeric and dimeric structures of 5‐fluoro‐ and 5‐chloro‐salicylic acid

The experimental and theoretical study on the structures and vibrations of 5‐fluoro‐salicylic acid and 5‐chloro‐salicylic acid (5‐FSA and 5‐ClSA, C₇H₅FO₃ and C₇H₅ClO₃) is presented. The Fourier transform infrared spectra (4000–400 cm⁻¹) and the Fourier transform Raman spectra (4000–50 cm⁻¹) of the title molecules in the solid phase were recorded. The molecular structures, vibrational wavenumbers, infrared intensities, Raman intensities and Raman scattering activities were calculated for a pair of molecules linked by the intermolecular O H···O hydrogen bond. The geometrical parameters and energies of 5‐FSA and 5ClSA were obtained for all eight conformers/isomers from density functional theory (DFT) (B3LYP) with 6‐311++G(d,p) basis set calculations. The computational results identified the most stable conformer of 5‐FSA and 5‐ClSA as the C1 form. The complete assignments were performed on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. The spectroscopic and theoretical results were compared with the corresponding properties for 5‐FSA and 5‐ClSA monomers and dimer of C1 conformer. The optimized bond lengths, bond angles and calculated wavenumbers showed the best agreement with the experimental results. Copyright © 2010 John Wiley & Sons, Ltd.     

Thermal conductivities of solid and liquid phases for neopentylglycol, aminomethylpropanediol and their binary alloy

The variations of thermal conductivities of solid phases versus temperature for neopentylglycol (NPG), 2-amino-2-methyl-1,3-propanediol (AMPD) and AMPD-42.2 mol% NPG alloy were measured with a radial heat flow apparatus. From the graphs of the solid phases thermal conductivity variations versus temperature, the thermal conductivities of the solid phases at their melting temperature and temperature coefficients for same materials were also found to be 0.22±0.01, 0.45±0.02 and 0.32±0.02 W/Km and 0.0047, 0.0031 and 0.0043 K⁻¹, respectively. The thermal conductivity ratios of liquid phase to solid phase for the same materials at their melting temperature are found to be 1.07, 1.12 and 0.74 with a Bridgman type directional solidification apparatus, respectively. Thus, the thermal conductivities of liquid phases for pure NPG, pure AMPD and AMPD-42.2 mol% NPG alloy at their melting temperature were evaluated to be 0.24, 0.50 and 0.23 W/Km, respectively, by using the values of solid phase thermal conductivities and the thermal conductivity ratios of liquid phase to solid phase.     

Infrared and Raman Study of the Local Anesthetic Procaine

The infrared and Laser Raman spectra of procaine with free basis in the solid state were obtained. The characteristic vibrational frequencies of their different modes were identified and assigned from isotope shifts and theoretical calculations. An infrared study in the liquid phase was also carried out. The corresponding rotation and inversion barriers in p-amino group were computed by means of different optimization procedures.     

Pure Rotational Raman Spectra of Vapor Phase Methanols

Abstract

The rotational Raman spectra of four vapor phase isotopic methanols, CH₃OH, CH₃OD, CD₃OH and CD₃OD, have been reported for the first time in the wavenumber regions from 5 to 100–120 cm^?1. The major parts of the spectra consist of bands equispaced at 3.19, 3.04, 2.56 and 2.46 cm^?1 intervals, respectively, and have been interpreted as the pure rotational S-branch transitions.     

Structural nonuniformity of detonation-produced diamond-containing material

Raman backscattering spectra (RBS), infrared spectra, and X-ray diffraction intensity curves for various fractions of ultradispersed diamond-containing material (UDDCM) were recorded. The RBS and XRD curves obtained suggest that UDDCM is characterized by sharp variations in the ratio between the diamond and nondiamond components, a factor that makes it possible to consider this phase as an individual product and determines the scale of variations in the main characteristics. Fine UDDCM fractions contain only small amounts diamond-like (sp ³ carbon) grains, if any. One possible reason for changes in the ratio between the phases is density fluctuations under nonequilibrium conditions of synthesis.     

The Infrared Spectra of Diiodosilane

Abstract

The IR spectra of SiH₂I₂ was recorded in the gaseous, liquid and solid phases, in the range 4000-250 cm^?1. An assignment of the observed bands is proposed and the measured frequencies are compared with the existing data for the other members of the series SiH₂X₂ (X: halogen).     

Atom-solid 3p level binding energy shift of transition metals Cr,Mn, Fe,Co, and Ni

Binding energy shifts between atomic and solid phases for transition metals Cr, Mn, Fe, Co, and Ni have been obtained for 3p subshells from simultaneously recorded atomic vapor and solid state spectra. This experimental technique provides higher accuracy in comparison to separate measurements and allows direct determination of the shifts. The observed shift values are compared to values obtained using the semiempirical Born–Haber cycle method and the peak structures of the solid state photoelectron spectra are compared to atomic 3p spectra. The binding energy shift of Cr is found to be much smaller than that of the other studied elements.