Argon Solutions Research Articles

Absorption spectrum of the (CF4) dimer in liquid argon solution

The concentration dependence of the shape of absorption bands in the spectrum of CF4 in liquid argon is studied in the concentration range (0.01–17)×10−3 molar fractions at 93 K. In all spectral regions related to ν3, the shape of the spectral function is determined, along with the Fermi resonance 〈νi,ν3+1,ν4|≈〈νi,ν3,ν 4+2|, by the resonance dipole-dipole interaction. In the spectral region of the Fermi doublet ν 1+ν3≈ ν1+2ν4, the spectrum of the contact (CF4)2 dimer is identified. Agreement between this spectrum and the calculated spectrum is achieved by simultaneously taking intramolecular and intermolecular resonances into account. The distance R C-C in the dimer is 4.85(15) A. The calculations of the spectra of (12CF4)2 and (13CF4−12CF4) dimers with this value of R C-C in the region ν 3≈2ν4 agree with the experiment.

Solvent isotope effects on the solubility of argon and pair interactions in aqueous solution of hexamethylenetetramine

The solubilities of gaseous argon in solutions of hexamethylenetetramine (hmta) in H2O and D2O were measured at different concentrations, at five temperatures in the range of 283–318 K, and at a partial gas pressure of 101325 Pa by microvolumetry with an accuracy of ≤0.3%. The standard Setchenov coefficients for argon solutions and the thermodynamic parameters of Ar-hmta pairwise interactions were calculated from the data on the solubility. Interactions between hydrated Ar and hmta molecules are characterized by mutual repulsions. The structural states of water in the hydration sphere of hmta and in the bulk of solution are substantially different. Due to the difference in the mechanisms of hydration of hmta and Ar, the addition of the first component leads to a decrease in the solubility of the second component.

Vibrational Analysis of the van der Waals Complex between Cyclopropane and Boron Trifluoride in Liquefied Inert Gases

A weakly bound van der Waals complex is formed between cyclopropane and boron trifluoride dissolved in liquid argon or liquid nitrogen. A complexation enthalpy of −7.8(6) kJ mol−1 was determined by analysis of infrared spectra recorded at several temperatures between 93 and 125 K of a solution in liquid argon. Ab initio calculations at the MP2/6-31 + G(d) level gave insight into the structure of the complex, shown here, and supported the assignment of the vibrational spectra.

Vibrational energy transfer between the isotopomers of carbon monoxide at low temperatures

Rate constants have been measured for vibration to vibration energy transfer from C12O16(v=1) to the first vibrationally excited state of both C13O16 (Δν̄=47 cm−1) and C13O18 (Δν̄=100 cm−1) using the infrared laser fluorescence technique over the temperature range 50 to 270 K in the gas phase and in liquid neon, deuterium and argon solutions. Fluorescence from C12O16(v=1) was filtered out, and the time-dependence of the fluorescence intensity from the other isotopomer used to determine the rate constants for energy transfer. The results for the two isotopomeric systems are markedly different. For that with the smaller energy mismatch, C12O16–C13O16, the rate constants increase with decrease in temperature from 270 to 80 K. This is shown to be consistent with near-resonant energy transfer mediated by transition dipole-transition dipole couplings. Below 80 K, the temperature dependence of the rate constants flattens. For the C12O16–C13O18 system, the rate constants decrease with decrease in temperature from 270 to 100 K, below which they increase with further decrease in temperature. The temperature dependence in the range 270 to 100 K is shown to be consistent with energy transfer mediated by a combination of by long range and short range forces. Below 100 K, the temperature dependence of the rate constants is governed by attractive forces which influence the collision pair during their encounter. The rate constants are compared with previous studies of near-resonant vibrational energy transfer in other systems at low temperatures.

Cis- and trans-3-hexene: infrared spectrum in liquid argon solution, ab initio calculations of equilibrium geometry, normal coordinate analysis, and vibrational assignments

The infrared spectra of cis-3-hexene and trans-3-hexene dissolved in liquid argon have been obtained at temperatures from 93 to 120 K. The absorptions were observed with a low-temperature cell and a Fourier transform infrared spectrophotometer. Ab initio molecular orbital calculations were performed to obtain the equilibrium geometry, vibrational frequencies, force fields, and infrared intensities. The calculations were done at the Hartree-Fock level using 6-31G basis set. The Cartesian force fields from ab initio calculations have been converted to the force field in symmetry coordinates. The scale factors of ab initio calculated force fields were determined. Normal coordinate calculations were performed using a scaled quantum mechanical (SQM) force field. Vibrational normal modes calculated for the lowest energy rotamers of cis- and trans-3-hexene have been assigned to infrared absorption bands observed in liquid argon solution. The assignments were based on calculated frequencies and potential energy distributions. The equilibrium geometries of the two lowest energy rotamers (symmetry C 2 and C s ) of cis-3-hexene and of the three lowest energy rotamers (symmetry C i , C 2, and C 1) of trans-3-hexene were calculated. Variable temperature studies of the infrared spectrum of cis- and trans-3-hexenes dissolved in liquid argon were done to obtain the ΔH of conversion between the rotamers C 2 and C s of cis-3-hexene and between the rotamers C i , C 2, and C 1 of trans-3-hexene.

The van der Waals Complex between Boron Trifluoride and Methyl Fluoride: An Infrared and ab Initio Study

Mixtures of CH3F and BF3 have been investigated, using infrared spectroscopy, at low temperatures in the gas phase (170−210 K) and in solution in liquid argon (85−110 K) and in liquid krypton (115−165 K). In all cases, the formation of a 1:1 complex CH3F·BF3 was observed. The complexation enthalpy was measured to be −16.8(5) kJ mol-1 in liquid argon and −18.0(3) kJ mol-1 in liquid krypton. Structural, energetic, and spectroscopic properties of the complex were calculated using ab initio methods at the MP2/6-31+G** level and are compared with the experimental data.

Vibrational overtone spectroscopy of methane in liquid argon solutions

The spectra of the fundamental, and first and second overtones (Δ ν = 1,2,3) around the C-H stretch of methane in liquid argon solutions have been measured at approximately 95 K. Combination bands involving one quantum of a bending mode in the region 3500–5000 cm -1 and three quanta of bending modes in the region 6500–7600 cm -1 were also measured. The near-infrared (IR) spectra of pure liquid methane was recorded between 6500 and 12 000 cm -1 at 94 K. Measurements were made using a cryostat, a low-temperature cell, and a Fourier transform IR and near-IR spectrometer. Visible spectra of the fourth (Δ ν = 5) and fifth (Δ ν = 6) overtones of liquid methane and methane in liquid argon solutions were measured at 95 K. Visible spectra were recorded with a photoacoustic spectrometer employing resonant continuous-wave excitation and piezoelectric detection. Spectra in solutions are greatly simplified compared with the gas phase. This simplification is attributed to a narrowing of the rotational distribution at low temperatures and partial hindering of the rotational motion of sample molecules. Peak positions are systematically red shifted with respect to the gas phase, and the magnitude of the shift increases with the vibrational quantum number. The harmonic frequency and anharmonicity were obtained from a Birge–Sponer fit of the C–H vibrations. Previously reported assignments in normal-mode notation and local-mode calculations of energy levels of methane were used to assign the vibrational transitions observed in our experiments. The local mode notation is based on the harmonically coupled anharmonic oscillator model. Linewidths of the pure overtones increase proportionally as a function of the vibrational quantum number ν. There is indication that, for transitions with Δ ν = 5 and 6, the bandwidths are due to a dephasing mechanism in the slow modulation limit.

Solvent effects on non-resonant vibrational deactivation: N 2( ν = 1) deactivated by CH 4 in liquid Ar/liquid N 2 mixtures

New measurements have been made of rate constants for the vibrational deactivation of N 2( ν = 1) by CH 4 in liquid Ar/liquid N 2 mixtures. The ratio of the liquid phase rate constants, k L,M for the liquid mixture over k L,Ar for liquid argon solution, varies non-linearly with composition. The results imply a saturation effect which occurs when one solvent N 2 molecule is present in the first solvation shell of the excited molecule. It is proposed that this is due to the formation of a N 2( ν = 1) … N 2 collision complex.

Vibrational overtone spectroscopy of CH2D2 in liquid argon solutions

Abstract The spectra of the fundamental and overtones of the CH ( ν = 1–5) and CD ( Δν = 1, 2, 3) stretches of CH 2 D 2 have been measured in liquid argon solutions at temperatures between 94 and 101 K. Absorption in the visible was obtained with a low temperature cell and a resonant continuous wave laser technique with acoustic detection. Absorptions in the IR and near-IR were observed with a Fourier transform spectrophotometer. To interpret the experimental results, overtone transitions are described in terms of the local mode model. The harmonically coupled anharmonic oscillator (HCAO) model was used to determine the overtone energy levels and assign the absorption bands to vibrational transitions. The linewidths of the fundamental and overtone transitions are discussed in terms of rotational relaxation for the fundamental bands and vibrational relaxation in the form of dephasing for the overtones.

Vibrational spectra of phosphine and arsine in the gas phase, the liquid phase, and in the solution of liquefied argon

The IR spectra of phosphine and arsine in the gas phase, in the liquid phase and in liquefied argon solution have been investigated (spectral range 400–5700 cm −1). The vibrational frequencies and the integrated absorption coefficients of the fundamental and overtone bands have been measured. The possibility of self-association of the hydrides in the liquid phase is discussed.

Near-Infrared and Visible Spectroscopy of CH3D in Liquid Argon Solutions

The near-infrared and visible spectra of CH3D in liquid argon solutions have been measured around 95 K. The fundamental and overtones, Δv = 1, 2, 3, 4, and 5 around the C−H stretch and Δv = 1, 2, a...

Infrared spectroscopy of 2-methyl-2-butene in liquid argon solution and ab initio calculated vibrational frequencies

Abstract The infrared spectrum of 2-methyl-2-butene dissolved in liquid argon has been measured at 90 K. The absorption was obtained with a low-temperature cell and a Fourier transform spectrophotometer. The solubility of 2-methyl-2-butene in liquid argon was measured. Ab initio molecular orbital calculations were performed to obtain the equilibrium geometry, vibrational frequencies, and infrared intensities. The calculations were done at the Hartree-Fock level using the 6-31G ∗ split-valence basis set. A normal coordinate analysis was performed using a scaled force field determined from the 6-31G ∗ basis set. The potential energy distribution was also obtained.

Overtone Spectroscopy of CHD3 in Liquid Argon Solutions

AbstractThe vibrational overtone spectrum of CHD3 has been obtained in liquid argon solutions at temperatures around 94 K. The spectra of C‐H and C‐D overtones below 10000 cm−1 were obtained with a Fourier transform spectrophotometer operating in the near‐infrared region and a low temperature cell. The C‐H spectrum around Δv = 5 was recorded using a resonant photoacoustic technique at cryogenic temperatures. The absorption bands were computer deconvoluted to obtain the peak absorption frequency, the band‐width, and the area of some important bands. Due to the small frequency shift of the absorption bands in solution with respect to the gas phase frequencies, the assignment of the transitions was made by comparison with experimental and calculated gas phase frequencies. The calculation of gas phase frequencies and vibrational states was made using the pure local mode model for the isolated C‐H bond and the Harmonically Coupled Anharmonic Oscillator (HCAO) model for the three equivalent C‐D bonds. In order to test the Fermi resonance interaction between C‐H stretching and bending vibrations, the absorption bands and relative intensities in solution were used to obtain the parameters of an effective Fermi resonance Hamiltonian. The values of the parameters obtained in solution and gas phase are very close in magnitude. The optimized parameters of the Fermi resonance Hamiltonian give a good description of the frequencies and relative intensities of the C‐H absorption bands in solution.

Molecular simulation study of solvation structure in supercritical aqueous solutions

We report new molecular dynamics simulations of aqueous solutions that consist of various solutes (xenon, NaCl, benzene, toluene, and benzonitrile) at infinite dilution in supercritical water at two thermodynamic states: one at the critical density and at 5% above the critical temperature, the other at 50% above the critical density and along the critical isotherm. These new simulations complement our previous simulations of infinitely dilute supercritical aqueous solutions of argon, Na +, Cl −, and methanol at the same state points. The aim of this work is to determine the solvation structure around various solutes in supercritical water with the goal of developing a molecular understanding of the solubility of nonpolar noble gases, ionic fluids and organics in supercritical water. Such an understanding can provide important insight into fundamental aspects of supercritical water oxidation of organic wastes. In addition, we report thermodynamic properties and solute—solvent structural quantities for the various solutes.

Isosteric and isothermal studies of the Raman depolarization ratios in an argon-methane mixture at 298 K and 323 K

Raman depolarization ratios (RDRs) have been measured for a 10 mole % methane solution in argon at 298 and 323 K over a wide range of densities corresponding to pressures from 49 to 2200 bars. In addition, the anistropic Raman time correlation functions (TCFs) at these conditions have been recorded. The results are in striking contrast to previous work on pure methane and 10% methane in carbon dioxide where there was strong evidence for angular dependency of the intermolecular potential functions. In argon, apparently, the isotropic atomic potential gave rise to little change in either the RDR or the TCF values as might have been expected, but had to be confirmed in order to understand the process involved.

Vibrational Spectroscopy of C-H Bonds of C2H4 Liquid and C2H4 in Liquid Argon Solutions

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTVibrational Spectroscopy of C-H Bonds of C2H4 Liquid and C2H4 in Liquid Argon SolutionsAnsgar Brock, Nairmen Mina-Camilde, and Carlos ManzanaresCite this: J. Phys. Chem. 1994, 98, 18, 4800–4808Publication Date (Print):May 1, 1994Publication History Published online1 May 2002Published inissue 1 May 1994https://doi.org/10.1021/j100069a006RIGHTS & PERMISSIONSArticle Views150Altmetric-Citations31LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (887 KB) Get e-Alerts

Electronic absorption spectra of large benzene ⋅Arn clusters

We report the mass resolved resonant two-photon ionization spectra of C6D6⋅Arn clusters up to n=70. Shifts of the benzene S1←S0 610 vibronic band were studied as a function of both cluster size and expansion conditions. We find that clusters in different size ranges exhibit remarkably different spectra, which also depend on expansion conditions and, hence, cluster internal energy. Below n=16, spectral features trend toward the blue with increasing size. Above n=16, all features exhibit weak size dependence over wide size ranges. In the n=20–40 range, four distinct bands were found, which we suggest could be due to fully enclosed fluxional (−55 cm−1 vs free C6D6), partially enclosed rigid (−43 cm−1), and one-sided rigid (−32 cm−1) or one-sided fluxional (also −32 cm−1, broader) structural types. Above n=40, only one band was definitely identified (at −26 cm−1), which may be due to a one-sided rigid structural type. The trends in spectral shift vs size give no indication of approaching bulk-like solvation of the benzene. Only one subpopulation between n=20 and 40 may show similarity to macroscopic benzene–argon solutions.

Vibrational spectroscopy of CH bonds of methane and tetramethylsilane in liquid argon solutions

The liquid phase spectra of the fundamental and first overtone (Δ v = 1, 2) around the CH stretch of methane and tetramethylsilane in liquid argon solutions have been measured using Fourier transform IR and near-IR techniques. The fourth overtone (Δ v = 5) of the CH stretch has been measured in methane pure at 116 K and in liquid argon solutions at 100 K using laser excitation with acoustic detection. The results indicate that absorption bands, which normally present extensive inhomogeneous congestion, could be simplified by studying the absorptions in diluted solutions at low temperatures with inert liquefied gases as solvents.

On the apparent molar volumes of nonelectrolytes in water

Apparent molar volumes of aqueous solutions of argon and xenon have been calculated using a previously developed comprehensive equation of state for nonelectrolyte systems. The equation consists of a virial expansion truncated after the fourth virial coefficient and a closed-form term approximating higher coefficients. Mixing rules are based on the composition dependence of virial coefficients, which is known from statistical mechanics. The equation accurately represents vapor-liquid and gas-gas equilibria for the Ar+H2O and Xe+H2O systems over wide ranges of pressure and temperature using two binary parameters. With the binary parameters determined from phase equilibrium data, the equation accurately predicts apparent molar volumes Vϕ in the near-critical and far-from-critical regions. Apart from reproducing experimental Vϕ data, the equation reveals remarkable maxima of Vϕ as a function of pressure and temperature in the near-critical region. The implications of this equation with respect to the Ar−H2O potential are discussed via the second virial coefficient.

Femtosecond chemical dynamics in solution. Wavepacket evolution and caging of I 2

Theoretical and experimental studies are discussed for the femtosecond wavepacket dynamics and reaction of iodine in compressed argon solution and in the collision-free gas phase limit. Classical and quantum calculations are compared with experiment and are used to demonstrate the influence of the solvent on wavepacket nuclear motion dephasing, on the caging and recombination of the separating iodine atoms, and on iodine vibrational relaxation. It is shown that these phenomena are observed on the time scale in which they occur.