Nitrogen-Broadening Parameters for Atmospheric Spectra Modelling of the ν Band of SF.

The infrared absorption of the ν band region of SF at temperatures spanning the 130 to 297 K range, has been reexamined using improved instrumentation with one goal: to estimate the broadening of parameters by nitrogen gas. These parameters are compared to previous literature predictions and an extended set of IR cross-sections is proposed and compared to other existing datasets.

A Theoretical Study of HF-CHCl and (HF)-CHCl Complexes.

The equilibrium geometries, relative stabilities, and vibrational properties (frequencies and intensities) of the HF-CHCl (1:1) and (HF)-CHCl (1:2) complexes were reinvestigated at the MP2/Aug-cc-pVTZ level. The results are discussed in light of the results obtained in solid argon matrices by L. Andrews and co-workers and related to the bonding analysis.

Improved mid infrared detector for high spectral or spatial resolution and synchrotron radiation use.

When using bright, small effective size sources, such as synchrotron radiation light beam, for broadband spectroscopy at spectral or spatial high resolution for mid-IR FTIR measurements, a marked detectivity improvement can be achieved by setting up a device matching the detector optical étendue to that of the source. Further improvement can be achieved by reducing the background unmodulated flux and other intrinsic noise sources using a lower temperature cryogen, such as liquid helium. By the combined use of cooled apertures, cold reimaging optics, filters and adapted detector polarization, and preamplification electronics, the sensitivity of a HgCdTe photoconductive IR detector can be improved by a significant factor with respect to standard commercial devices (more than one order of magnitude on average over 6-20 μm region) and the usable spectral range extended to longer wavelengths.

On the electronic structure and photochemistry of coordinatively unsaturated complexes: the case of nickel bis-dinitrogen, Ni(N2 )2.

The electronic ground and excited states of the coordinatively unsaturated complex Ni(η(1) -N2 )2 , isolated in an Ar matrix, are analyzed in detail by vibrational and electronic absorption and emission spectroscopies allied with quantum chemical calculations. The bond force constants are determined from a normal coordinate analysis and compared with those of the isoelectronic carbonyl complex. The consequences for the bond properties are discussed, and the trend in the force constants is compared with the standard formation enthalpies.

A rugged, high precision capacitance diaphragm low pressure gauge for cryogenic use.

In order to carry out precise laboratory measurements of infrared absorption intensities, line profiles of molecules and organic volatile compounds for atmospheric chemistry in planetary and upper earth atmospheric layers, precise gas pressure measurement between 10(-3) and a few mbars in the 77-300 K temperature range is necessary. A prototype, rugged, precision capacitive pressure gauge for cryogenic use has been designed, built at SOLEIL and tested down to 77 K. The design includes corrosion-resistant materials and has been tailored to operate on a differential measurement scheme based on a simple, precision capacitance-to-digital converter chip, instead of high precision floating capacitive bridges, as are used in other designs.

A new, low temperature long-pass cell for mid-infrared to terahertz spectroscopy and synchrotron radiation use.

A new cell has been designed for accurate spectroscopic measurements in the 80-400 K temperature range with variable path lengths from 3 to more than 141 m. The spectral coverage at these temperatures ranges from the visible to less than 10 cm(-1), thanks to the use of diamond windows. The design of the cryostat and vacuum setups allows vibration-free operation.

High-resolution spectroscopy and structure of osmium tetroxide. A benchmark study on 192OsO4.

Osmium tetroxide (OsO(4)) is a heavy tetrahedral molecule that constitutes a benchmark for quantum chemistry calculations. Its favorable spin statistics (due to the zero nuclear spin of oxygen atoms) is such that only A(1) and A(2) (T(d) symmetry) rovibrational levels are allowed, leading to a dense but quite easily resolvable spectrum. We reinvestigate here the ν(1)/ν(3) stretching fundamental (940-980 cm(-1)) dyad region and perform new assignments and effective Hamiltonian parameter fits for the main isotopologue ((192)OsO(4)).

Vibrational spectrum and structure of CoO6: a model compound for molecular oxygen reversible binding on cobalt oxides and salts; a combined IR matrix isolation and theoretical study.

The formation and structure of a novel species, a disuperoxo-cobalt dioxide complex (CoO(6)), has been investigated using matrix isolation in solid neon and argon, coupled to infrared spectroscopy and by quantum chemical methods. It is found that CoO(6) can be formed by successive complexation of cobalt dioxide by molecular oxygen without activation energy by diffusion of ground state O(2) molecules at 9K in the dark. The IR data on one combination and seven fundamentals, isotopic effects, and quantum chemical calculations are both consistent with an asymmetrical structure with two slightly nonequivalent oxygen ligands complexing a cobalt dioxide subunit.

Formation and structure of Co₂O₄: a combined IR matrix isolation and theoretical study.

The formation and structure of dicobalt tetroxide (Co₂O₄) has been investigated using matrix isolation in solid neon and argon coupled to infrared spectroscopy and quantum chemical methods. It is found that Co₂O₄ can be formed by dimerization of cobalt dioxide without activation energy by diffusion of ground state CoO₂ molecules at 9 K in the dark. The IR data on eight fundamentals, isotopic effects and quantum chemical calculations are both consistent with a centro-symmetrical structure with two pairs of equivalent oxygen atoms, engaged in a stronger terminal Co-O bond and in a weaker bridging Co-O-Co position.

Evaluation of CO coordination energies from spectroscopic data: on the use of vibrational isotopic effects.

For molecules containing a linearly coordinated carbonyl group, relationships linking 13C and 18O isotopic effects on the CO stretching vibration to the force constant of the M-C coordination bond are proposed. These relationships are rationalized by simple considerations involving the mechanical coupling of the CO and M-C oscillators, tested on model triatomic molecules, and generalized to larger systems. Previous theoretical considerations and several examples presented here show that the long-accepted relation between the shift in the stretching frequency of the coordinated CO with respect to that of isolated CO and the coordination strength has no general predictive power.

The Ni2+O2 reaction: the IR spectrum and structure of Ni2O2. A combined IR matrix isolation and theoretical study.

The formation of Ni2O2 can be observed from the condensation of effusive beams of Ni and O2 in neon or argon matrices. Observation of 58Ni(2)16O2, 58Ni60Ni16O2, 60Ni2(16)O2, Ni(2)18O2 and Ni(2)16O18O isotopic data for five fundamental transitions enable a discussion of structural parameters for matrix-isolated Ni2O2 in its cyclic ground state. Analysis of the nickel isotopic effects on the 58,60Ni2(16)O18O fundamentals suggest an elongated rhombic structure with a Ni-O bond force constant (240+/-10 N m-1) and NiONi bond angles around 79 degrees.

Characterization of ground and low-lying excited states of CoO4: a combined matrix isolation and DFT study.

The nature of the reaction products between CoO(2) and molecular O(2), isolated in rare gas matrices, have been investigated using IR absorption spectroscopy. In this paper, we report on the vibrational spectrum of the CoO(4) molecule in its ground and first low-lying excited states. Isotopic substitutions using (16)O(2) and (18)O(2) precursors, as well as (16)O(2) + (18)O(2) and (16)O(2) +( 16)O(18)O + (18)O(2) mixtures in either excess argon or neon, enable demonstration of C(2)(v)() and C(s)() structures for the respective states.

Reactivity of atomic cobalt with molecular oxygen: a combined IR matrix isolation and theoretical study of the formation and structure of CoO2.

The reactivity of atomic cobalt toward molecular oxygen in rare gas matrices has been reinvestigated. Experiments confirm that Co atoms in their a(4)F ground state are inert toward O(2) in solid argon and neon but reactive in the b(4)F first excited state, in agreement with the previous gas-phase study of Honma and co-workers. The formation of CoO(2) starting from effusive beams of Co and O(2) has been followed by IR absorption spectroscopy, both in neon and argon matrices.

Absorption spectra of ground-state and low-lying electronic States of copper nitrosyl: a rare gas matrix isolation study.

The reaction of ground-state Cu atoms with NO during condensation in solid argon, neon, and binary argon/neon mixtures has been reinvestigated. In addition to the ground-state already characterized in rare gas matrixes by its nu1 mode in reactions of laser-ablated Cu with nitric oxide, another very low lying electronic state is observed for CuNO in solid argon. Photoconversion and equilibrium processes are observed between the two lowest lying electronic states following photoexcitations to second and third excited states in the visible and near-infrared.

A combined electron paramagnetic resonance and fourier transform infrared study of the co(c(6)h(6))(1,2) complexes isolated in neat benzene or in cryogenic matrixes.

The products obtained in the reaction of cobalt atoms in neat benzene or in a benzene/argon mixture at low temperature have been reinvestigated. At least three cobalt-containing species were detected by IR, namely, Co(C(6)H(6)), Co(C(6)H(6))(2), and Co(x)(C(6)H(6)), x>1. The IR bands were assigned to these complexes by monitoring their behavior as a function of (a) Co and C(6)H(6) concentration, (b) isotopic substitution, and (c) photoirradiation.

Reactivity of titanium dimer and molecular nitrogen in rare gas matrices. Vibrational and electronic spectra and structure of Ti2N2.

The reactivity of diatomic titanium with molecular nitrogen has been investigated in rare gas matrices. The formation of Ti2N2 from the condensation of effusive beams of Ti and N2 in neon and argon matrices is observed after sample deposition. Our results also show that the in situ formation results from the spontaneous reaction at 9 K of ground state Ti2 with N2.

The Ni + O2 reaction: a combined IR matrix isolation and theoretical study of the formation and structure of NiO2.

The reaction of Ni atoms with molecular oxygen has been reinvestigated experimentally in neon matrices and theoretically at the DFT PW91PW91/6311G(3df) level. Experimental results show that i) the nature of the ground electronic state of the superoxide metastable product is the same in neon and argon matrices, ii) two different photochemical pathways exist for the conversion of the superoxide to the dioxide ground state (involving 1.6 or 4 eV photons) and iii) an important matrix effect exists in the Ni + O(2)--> Ni(O(2)) or ONiO branching ratios.

Ni(N2)4 revisited: an analysis of the Ni-N2 bonding properties of this benchmark system on the basis of UV/Vis, IR and Raman spectroscopy.

Matrix isolation of Ni atoms in an N2 matrix leads to the formation of Ni(N2)4. This compound, being isoelectronic with the well known Ni(CO)4, represents an important bench-mark system. It has been characterised experimentally by UV/Vis, IR and Raman spectra.

Reactivity of cobalt dimer and molecular oxygen in rare gas matrices. IR spectrum, photophysics and structure of Co2O2.

The reactivity of cobalt dimer towards molecular oxygen has been investigated in rare gas matrices. If the formation of Co2O2 from the condensation of effusive beams of Co and O2 in neon and argon matrices is observed after sample deposition, our results show that the in situ formation does not result from the reaction of ground state Co nor Co2 with molecular oxygen. One reaction channel has been evidenced through reaction of Co2 in excited states, close or above the dissociation limit.

IR and theoretical studies of monocarbonyl Ni complexes formed by adsorption of CO at low pressure on silica-supported Ni(II) ions.

This work reports on the reactivity of coordination vacancies of Ni(II) ions grafted onto the tridentate silica support (Ni(II)(3c) ions) with respect to CO used as a probe molecule. The adsorption of CO at 77 K in the 0.3 to 3.

Formation and characterization of the gallium and indium subhydride molecules Ga2H2 and In2H2: a matrix isolation study.

Ga2 reacts spontaneously with H2 in solid Ar matrixes at 12 K to form the cyclic molecule Ga(mu-H)2Ga. In2 does not react with H2 under similar conditions, but irradiation at wavelengths near 365 nm induces the formation of the corresponding indium hydride, In(mu-H)2In. The molecules have been identified and characterized by the IR spectra displayed by matrixes containing the metal and H2, D2, HD, or H2 + D2; they each have planar, dihydrido-bridged structures with D2h symmetry, as endorsed by comparison of the measured spectra (i) with the properties forecast by quantum chemical calculations and (ii) with the spectra of known gallium and indium hydrides.