Obtention des bandes de cameron par photo excitation de co en matrices d'argon de krypton et de xenon

CO trapped in solid matrices of argon, krypton and xenon has been excited by 10 eV photons. Cameron bands v′=0, v″=0,1,2,3,4 are observed during the irradiation. If red shifts are observed in argon and krypton matrices, the transition in xenon shows no differences with gas phase data.     

Studies of intermolecular interactions by matrix isolation vibrational spectroscopy: Self-association of water

The mid- and far-infrared spectra of water in argon and nitrogen matrices have been reinvestigated. The water molecule rotates in an argon matrix, but in a nitrogen matrix two low-frequency bands are attributed to libration of the water monomer about its A and C rotational axes. Combinations of these modes with the stretching and bending modes of the water monomer were observed. A detailed concentration-dependence study enabled bands to be attributed to dimer, trimer, and tetramer or higher multimers. The dimer and trimer were both found to have open chain structures, whereas tetramer or higher multimer species appear to be predominantly cyclic. Intermolecular modes, observed for dimer and trimer in the far-infrared spectra, are tentatively assigned.     

The ultraviolet absorption spectra of GeO in rare gas matrices

The absorption spectra of GeO isolated in rare gas matrices have been investigated in the wavelength region 1150–3000 Å using the 2.5-GeV synchrotron in Bonn as a continuum light source. Two vibrational progressions of bands have been found in each of the matrices, in neon, argon, krypton, and xenon. These progressions are situated in the regions 2400–2700 and 1800–2100 Å. They have been analyzed as corresponding to gas-phase bands of the A¹Π-X¹Σ⁺ and the E¹Σ⁺-X¹Σ⁺ systems, respectively. Absorption lines of matrix-isolated GeO were also found in the region 1180–1500 Å.     

Matrix isolation spectrum of the 2491 Å system of NO2

The absorption spectrum of the 2491 Å NO₂ bands (${}^2\text{B}{}_2\text{←}\text{X}\text{?}{}^2\text{A}{}_1$) has been observed in neon and argon matrices at 6 K. Evidence for two distinct matrix sites is confirmed by the doubling of the electronic origin. The bands are shifted slightly to the blue (～ + 60 cm^?1) in neon and to the red (～ ?64 cm^?1) in argon. The excited state vibrational frequencies are reported.     

Resonance Raman and fluorescence spectra of chlorine dioxide in argon,krypton, xenon,and nitrogen matrices at 16 K

Laser excitation studies of matrix-isolated ClO₂ at 16 K using the 4579, 4765, 4880, and 5145 Å argon ion lines and argon, krypton, xenon, and nitrogen matrices were conducted. Quenching of fluorescence by the matrix was evidenced by the observation of displaced bands in the Ar, Kr, and N₂ work and increased background in the Xe studies. An intense progression in ν₁ of ClO₂ with regularly decreasing intensities out to 6ν₁ observed in solid Ar with 4579 Å excitation was attributed to the resonance Raman effect. Shorter resonance Raman progressions were observed in Xe and N₂ matrices.     

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.     

Vibrational spectroscopy of trans and cis deuterated formic acid (HCOOD): Anharmonic calculations and experiments in argon and neon matrices

The absorption spectra of trans and cis conformers of deuterated formic acid (HCOOD) isolated in argon and neon matrices are analyzed in the mid-infrared and near-infrared spectral regions (7900-450 cm⁻¹). Vibrational excitation by narrow-band IR radiation is used to convert the lower-energy trans conformer to the higher-energy cis form. A large number of overtone and combination bands are identified. The results of anharmonic vibrational calculations (CC-VSCF) for both conformers are reported and compared to the experimental spectra.     

Studies of intermolecular interactions by matrix isolation vibrational spectroscopy and normal coordinate analysis: Self-association of hydrogen cyanide

A detailed study of the infrared spectra of hydrogen and deuterium cyanide in noble gas, nitrogen and carbon monoxide matrices at 4 K and 20 K has enabled the bands observed to be assigned to monomer, dimer, trimer, tetramer and higher multimer species. Force constants calculated for the linear dimer are used to predict the spectrum of the trimer. The nature of the trapping sites occupied by the monomer and linear dimer, and the structure and trapping site of a second type of dimer observed only in argon matrices, are discussed.     

Matrix isolation studies and potential function for perfluorocyclobutane

The infrared and Raman spectra of perfluorocyclobutane isolated in argon matrices at 1:100 and 1:200 mole ratios have been measured between 200 and 2000 cm^?1. Although the ring-puckering fundamental (ν₁₆) was not observed directly, an assignment for the 2 ← 1 (30 cm^?1) transition of ν₁₆ has been deduced from sum and difference bands resolved in the infrared spectrum. Potential functions based upon valence force models are considered in detail and correlated with those of similar ring systems. By using the frequency of the 2 ← 1 transition for ν₁₆ and a vibrational reduced mass of 1501 amu, an approximate model potential function calculation yields a slightly puckered equilibrium conformation with a barrier on the order of 124 cm^?1. The vibrational assignment for perfluorocyclobutane is discussed in terms of the new matrix isolation spectra.     

Infrared spectra of matrix-isolated sodium and potassium cyanides

The infrared spectra of matrix-isolated sodium and potassium cyanides in neon, argon, krypton, and nitrogen matrices were examined over the range 4000 cm^?1 to 33 cm^?1. The effect of temperature cycling, which normally results in migration of trapped molecules to generate polymeric species, has been pursued. A careful study of the effect of superheating the vapor species on the spectra has also been carried out. By these means it has been possible to identify the bands in the spectrum due to monomeric and polymeric species. Isotopic frequency shifts were measured for a ¹³C-enriched sample of sodium cyanide and ¹³C- and ¹⁵N-enriched samples of potassium cyanide. From the measured isotopic shifts it was possible to determine the structure of these two compounds as being linear NaCN and KCN. Accurate force constants were calculated using the measured frequency values for the three fundamental vibrational modes of the different isotopic molecules of NaCN and KCN. Bands due to sodium and potassium cyanates were also identified in some of these systems. ¹³C and ¹⁵N isotopic frequency shifts were also observed for NaOCN and KOCN.     

Absorption and emission spectra of matrix-isolated GeTe

Systems of broad bands have been observed in the absorption and laser-induced emission spectra of the GeTe molecule in solid argon and krypton matrices. Hitherto unreported electronic states have been characterized: a, ν₀₀ = 15 500 cm^?1; B, ν₀₀ = 20 070, ω_e = 190 cm^?1; C, ν₀₀ = 23 500, ω_e = 270 cm^?1. Higher energy states are also reported as well as an emission system in the red which is probably due to the Ge₂Te₂.     

Matrix isolation of Mg2 and Mgn molecules in neon,argon, and nitrogen hosts

The Mg₂ and Mg_n molecules have been formed and studied in neon, argon, and nitrogen matrices at approximately 4° and 12 K. Bands observed between 2000 and 3500 Å have been investigated as a function of gradual changes in trapping conditions and assigned to various stages of magnesium atom polymerization. The A¹Σ_u⁺ ← X¹Σ_g⁺ system of Mg₂ relative to the gas exhibits a pronounced red shift which increases with the polarizability of the matrix host. A band at 2653 Å in argon was observed which can be tentatively assigned to another Mg₂ system.     

Confirmation of Complex Formation Between Ethylene and Mercury Halides by Matrix-Isolation Infrared Spectroscopy

Since DeKock¹ first prepared the Ni(CO)_n (n = 1,2,3 and 4) series in argon matrices, a number of unstable and transient coordination compounds have been synthesized by reacting metal vapor directly with the ligand in inert gas matrices at low temperatures. These include metals such as Pt, Pd and Ni, and ligands such as CO, N₂′ NO, O₂ and PF₃. Van Leirsburg and DeKock² prepared the MX₂-L type complexes by reacting metal halide vapor such as NiF₂ and NiCl₂ directly with ligands such as CO, NO and N₂ in argon matrices. Thus far, no reports are available on the synthesis of metal halid-ethylene complexes in inert gas matrices. In this letter, we wish to report the confirmation of such complex formation by matrix-isolation infrared spectroscopy.     

Observation of stokes and anti-stokes vibrational sidebands in the optical emission spectrum of Eu atoms isolated in an argon matrix

The 4f⁶5d6s² → 4f⁷ 6s² emission spectrum of Eu atoms isolated in an argon matrix shows (a) zero-phonon lines and (b) Stokes vibrational sidebands due to resonance modes in the $\text{Ar}$: Eu phonon spectrum. In addition, unexpected anti-Stokes vibrational side bands are observed, which might be due to “hot luminescence”.     

Particular features of the ν(OH) absorption band of strongly hydrogen-bonded complexes in the gas phase,low-temperature matrices,and crystalline films at 12–600 K

The particular features of the ν(OH) absorption band of dimers with a strong hydrogen bond (ΔH = 24–50 kcal/mol = 8000–17000 cm^?1/molecule) formed by molecules of phosphinic acids R₂POOH N₂ are studied in the gas phase, low-temperature argon and nitrogen matrices, and crystalline films. It is found that, irrespective of the type of the acid, the ν(OH) IR absorption bands of dimers are broad (Δν_1/2 ～ 1000 cm^?1) and similar in shape, exhibiting a characteristic ABC structure. The formation of these anomalously broad absorption bands is shown to be primarily associated with vibrations of the ?POOH fragments, participating in the hydrogen bonding. A change in the temperature in the range 12–600 K and the passage from cyclic dimers in the gas phase to helical chains with hydrogen bonds in the crystalline state cause no significant changes in the shape, width, or structure of the dimer band. The contribution to the formation of the broad absorption band of the (R₂POOH)₂ dimers made by anharmonic interactions between the high-frequency ν(OH) vibration and the low-frequency intermolecular vibrations is estimated. The absorption spectra of weak complexes R₂POOH...N₂ in matrices at 12 K are discussed.     

Raman spectroscopy of melamine‐formaldehyde resin microparticles exposed to processing in complex plasma

We explore the characterization of melamine formaldehyde resin (MF‐R) micron‐sized particles, immersed in argon, neon and argon–oxygen plasmas, using Raman spectroscopy. It is shown that plasma treatment of MF‐R results in modification of its chemical composition. Particularly, a decrease in the intensities of the Raman scattering bands, corresponding to both formaldehyde C―H and melamine C―N and N―H bonds, is observed. The band at 980–990 cm⁻¹, associated with breathing vibrations of the triazine rings, undergoes the most significant changes, and the greatest modifications of the spectra are observed after exposure to Ar and Ar–O₂ plasma, whilst for the MF‐R particles exposed to Ne plasma these modifications are less pronounced. Copyright © 2016 John Wiley & Sons, Ltd.     

The problem of the Mössbauer isomer shift calibration for the119Sn resonance from rare-gas matrix isolation experiments

Data of new rare-gas matrix isolation experiments are presented and discussed in connection with the problem of the Mössbauer isomer shift calibration for¹¹⁹Sn. These experiments are: (i) A Mössbauer source experiment with^119mSn in solid xenon yielding the isomer shift of Sn⁺ with the atomic configuration 4d¹⁰5s²5p; (ii) Mössbauer absorption studies of isolated Sn(II) halide molecules (SnX₂, X-F, Cl, Br, I) in argon matrices; and (iii) Mössbauer absorption experiments with isolated¹²⁵Te atoms and molecules in argon and krypton matrices.This work was supported in part by a grant from the National Science Foundation and from the Bundesministerium für Forschung und Technologie     

Vibronic spectra of matrix-isolated lead sulfide

Vibronic spectra are reported for lead sulfide in argon, krypton and SF₆ matrices at low temperatures. Emission stimulated by laser line irradiation of PbS is observed from the v′ = 0 level of three electronic states lying at about 14 500, 18 500 and 21 500 cm^?1 above the ground state. Emission is also observed from an excited state of Pb₂S₂ at about 17 000 cm^?1. In addition, the laser radiation gives rise to the vibrational Raman spectrum of PbS in argon at 423.2 cm^?1 and to a very weak Raman band at 297 ± 2 cm^?1 which we attribute to Pb₂S₂.The effects of temperature on the matrix spectra, of matrix material on the band origins, and of matrix concentration on the vibrational relaxation process, and the apparent degrees of coupling among the electronic states have all been examined. The electronic absorption spectrum of PbS in Ar is reported and the matrix data are compared with available information on gaseous PbS.     

Effects of neon matrix environment on three vibronic emission systems of PbS

Laser sources have been used to explore three emission band systems of the PbS molecule in solid neon matrices. The D → X emission (origin near 29 630 cm^?1), excited biphotonically, consists of broad bands originating from V′ = 0. With laser excitation tuned into the region of the band system origin near 21 860 cm^?1, the B → X system shows emission narrowing of inhomogeneously broadened absorption. Hot luminescence from the B state is also reported. In the a → X system near 14 625 cm^?1 the intensities of phonon sidebands on the high-frequency side of the zero-phonon lines are found to be very sensitive to laser power. Lifetimes of the a, A, and B states of PbS in solid argon have been measured as 260, 0.95, and 1.8 μsec.     

Measurements of pressure-induced shifts in the 1-0 and 2-0 bands of HF and in the 2-0 bands of H35Cl and H37Cl

Fourier absorption spectra of HCl and HF measured at room temperature and low pressures were found to show evidence of pressure-induced shifts of the spectral lines at gas pressures of only 10 torr. Self-induced shifts were measured for the HF 2-0 band and for the H³⁵Cl and H³⁷ 2-0 bands. There were also measured in the same spectra shifts in the HF 2-0 band due to HCl and shifts in both HCl bands due to HF, with indications of shift oscillation due to near-resonant dipole-dipole interactions between HCl and HF. Separate measurements were made of pressure-induced shifts in the HF 1-0 and 2-0 bands and in both isotopic HCl bands, using separately argon, neon, nitrogen and carbon dioxide as the perturbing gases.