Matrix isolation infrared spectroscopy was used to characterize a 1:1 complex of carbon dioxide (CO₂) with hexaflourobenzene (C₆F₆). Co-deposition experiments with CO₂ and C₆F₆ were performed at 20 K using argon as the matrix gas. New infrared peaks attributable to the CO₂-C₆F₆ complex were observed near the O-C-O antisymmetric stretching vibration of the CO₂ monomer and near the C-F stretching vibration of the C₆F₆ monomer. The initial identification of the newly observed infrared peaks to those of a CO₂-C₆F₆ complex was established by performing several concentration studies in which the sample-to-matrix ratios of the monomers were varied between 1:100 to 1:1600, by comparing the resulting co-deposition spectra with the spectra of the individual monomers, and by matrix annealing experiments (30 – 35 K). Co-deposition experiments were also performed using isotopically labeled carbon dioxide (¹³CO₂) and the analogous peaks for the ¹³CO₂-C₆F₆ complex were observed. Quantum chemical calculations were performed for the CO₂-C₆F₆ complex at the MP2/aug-cc-pVDZ level of theory in order to explore the intermolecular potential energy surface of the complex and to obtain optimized complex geometries and predicted vibrational frequencies of the complex. The calculations for the exploration of the potential energy surface involved rigid scans along the intermolecular distance and various angle coordinates for several general orientations of the two monomers. Based on these calculations, full geometry optimizations were then performed and two stable complex minima were found: one in which the CO₂ is perpendicular and centered to the C₆F₆ ring (∆E_int = -7.9 kJ/mol) and one in which the CO₂ is parallel to the C₆F₆ ring but displaced from the center (∆E_int = -6.0 kJ/mol). Comparing the predicted vibrational spectra for both complexes to the observed experimental spectra, particularly for the O-C-O antisymmetric stretching region, it is concluded that both structures are present in the solid argon matrices.

About 11 C₃Ar bands near the 0 4⁻ 0-000 and 0 2⁺ 0-000 transitions of the ùΠ_u−~X¹Σ⁺_g system of C₃ have been studied by both laser-induced fluorescence and wavelength-resolved emission techniques. Two prominent pairs of C₃Ar features were observed to the red of each of these two C₃ transitions. Each pair consists of a type A band and a type C band, with the type C band lying about 3 cm⁻¹ above the type A band. Rotational analysis showed that three of the bands are comparatively sharp, with line widths of 0.035 cm⁻¹, but the pair at 25504 and 25507 cm⁻¹ shows clear evidence of diffuseness. The spectral widths of the rotational lines do not depend on the excitation energies in any simple way. Most of the features in the wavelength-resolved emission spectra can be assigned as emission from vibrationally excited levels of the à state of the C₃ fragments down to the ground electronic state. Two different types of vibrational excitation of the C₃ fragments have been found: pure C₃-bending and antisymmetric C-C stretching. The branching ratios of the C₃ product states, the C₃-Ar vdW binding energy, and propensity rules for vibrational predissociation processes will be presented.

The ν₃ fundamental vibrational band of carbon subsulfide, SCCCS, first studied by Holland and collaboratorsF. Holland, M. Winnewisser, C. Jarman, H. W. Kroto, and K. M. T. Yamada 1988, J. Mol. Spectrosc. 130, 344^,F. Holland and M. Winnewisser 1991, J. Mol. Spectrosc. 147, 496as been reinvestigated using a combination of laser ablation production, free−jet expansion and quantum cascade laser spectroscopy. In addition to the fundamental band (located at 2100 cm^-1) and associated hot bands originating from the lowest bending mode _7, the hot bands from the two energetically higher−lying bending modes _5 and _6 have been observed for the first time as has the S^13 F. Holland and M. Winnewisser 1991, J. Mol. Spectrosc. 147, 496h

We report infrared photodissociation spectra of [Sn(CO₂)_n] (n=2-6) clusters. We explore core ion geometries through quantum chemical calculations and assign our experimental spectra through comparison with calculated vibrational frequencies. We discuss our results in the context of heterogeneous catalytic reduction of CO₂, and compare our results with previous work on other post-transition metal species.

The rovibrational spectrum of both parallel and perpendicular bands of the SF₆ dimer near the ν₃ band of SF₆ monomer was reinvestigatedR.-D. Urban and M. Takami, J. Chem. Phys. 103, 9132 (1995).sing high resolution jet-cooled infrared laser spectroscopy to provide deeper insight on its conformational landscape. Taking advantage of our versatile set-upP. Asselin, Y. Berger, T. R. Huet, R. Motiyenko, L. Margulès, R. J. Hendricks, M. R. Tarbutt, S. Tokunaga, B. Darquié, PCCP 19, 4576 (2017). jet-cooled spectra were recorded by combining different geometries of supersonic expansions, SF₆ concentrations seeded in a carrier gas and axial distances. Relaxation effects could be evidenced at very low rotational temperature leading to different conformational populations. Three spectral features (noted #1, #2 and #3) belonging to three dimer conformers are unambiguously identified on the grounds of 3 distinct S-S distances derived from the rovibrational analysis of parallel band contours in the 932-935 cm⁻¹range. Symmetry assignment, a priori accessible from the perpendicular band structure of a spherical top dimer, could not be clearly proved. The dependence of such conformational infrared signatures as a function of expansion conditions provides additional information about population dependence and interconversion processes taking place between these three forms predicted to be nearly isoenergetic by theoretical calculationsT. Vazhappilly, A. Marjolin and K. J. Jordan, J. Phys. Chem. B 120, 1788 (2016). Based on experimental considerations, a qualitative picture of the nearly flat potential energy surface of the SF₆ dimer is proposed which could explain the dominant presence of #1 and #3 populations in fast/cold axisymmetric expansions and that of #1 and #2 populations in slow/hot planar ones.

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Footnotes:

R.-D. Urban and M. Takami, J. Chem. Phys. 103, 9132 (1995).u P. Asselin, Y. Berger, T. R. Huet, R. Motiyenko, L. Margulès, R. J. Hendricks, M. R. Tarbutt, S. Tokunaga, B. Darquié, PCCP 19, 4576 (2017)., T. Vazhappilly, A. Marjolin and K. J. Jordan, J. Phys. Chem. B 120, 1788 (2016)..

r0pt Figure Cerium oxide is known for its use in solid oxide fuel cells due to its high ionic conductivity. The doping of trivalent samarium atoms into cerium oxide is known to enhance the ionic conductivity through the generation of additional oxygen vacancies. This study probes the electronic structure of Sm_xCe_yO_z (x+y=3, z=2-4) anion and neutral clusters. Anion photoelectron spectra of these mixed metal clusters exhibit additional spectral features not present in the previously studied cerium oxide clusters. Density functional theory calculations have been used to aid interpretation of collected spectra. The results of this work can be used to inform the design of materials used for solid oxide fuel cells.

Taking advantage of our sensitive laser spectrometer coupled to a pulsed slit jetP. Asselin, Y. Berger, T. R. Huet, R. Motiyenko, L. Margulès, R. J. Hendricks, M. R. Tarbutt, S. Tokunaga, B. Darquié, PCCP 19, 4576 (2017),e recorded near the ν₂ vibration a series of rovibrational transitions of the NH₃−Ar van der Waals (vdW) complex. These transitions involve in the ground vibrational state several internal rotor states corresponding to the orthoNH₃ and paraNH₃ spin modifications of the complex. They are labeled by Σ_a(j,k), Σ_s(j,k), Π_a(j,k) and Π_s(j,k) where Σ(K=0) and Π(K=1) indicate the projection K of the total rotational angular momentum J on the vdW axis, the superscripts s and a designate a symmetric or antisymmetric NH₃ inversion wave function, and j, k quantum numbers indicate the correlation between the internal-rotor state of the complex and the j, k rotational state of the free NH₃ monomer. Five bands have been identified, only one of which was partly observed beforeG. T. Fraser, A.S. Pine and W. A. Kreiner, J. Chem. Phys. 94, 7061 (1991). They include transitions starting from the Σ_a(j=0 or j=1) state without any internal angular momentum, consequently they can be assigned from the band contour of a linear-molecule-like K=0, ∆J=1 transition. The energies and splittings of the rovibrational levels of the ν₂=1←0 spectrum derived from the analysis of the Π_s, Σ_s(j=1)← Σ_a(j=0), k=0 bands and mostly of the Σ_s, Π_s and Σ_a(j=1)←Σ_a(j=1), k=1 bands bring relevant information about the ν₂ dependence of the NH₃−Ar interaction, the rovibrational dynamics of the NH₃−Ar complex and provide a sensitive test of a recently developed 4D potential energy surface that includes explicitly its dependence on the umbrella motionJ. Loreau, J. Liévin, Y. Scribano and A. van der Avoird, J. Chem. Phys. 141, 224303 (2014).

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Footnotes:

P. Asselin, Y. Berger, T. R. Huet, R. Motiyenko, L. Margulès, R. J. Hendricks, M. R. Tarbutt, S. Tokunaga, B. Darquié, PCCP 19, 4576 (2017),w G. T. Fraser, A.S. Pine and W. A. Kreiner, J. Chem. Phys. 94, 7061 (1991).. J. Loreau, J. Liévin, Y. Scribano and A. van der Avoird, J. Chem. Phys. 141, 224303 (2014)..

Measurements of the vibrational distribution function of carbon monoxide produced via a reaction between carbon vapor and molecular oxygen has shown a total population inversion on vibrational levels 4-7. Carbon vapor, produced using an arc discharge to sublimate graphite, is mixed with an argon oxygen flow. The excited carbon monoxide is vibrationally populated up to level v=14, at low temperatures, T=400-450 K, in a collision-dominated environment, 15-20 Torr, with total population inversions between v=4-7. The average vibrational energy per CO molecule formed by the reaction is 0.6-1.2 eV/molecule, which corresponds to 10-20% of the reaction enthalpy. Kinetic modeling of the flow reactor, including state specific vibrational processes, was performed to infer the vibrational distribution of the products of the reaction. The results show viability of developing of a new chemical CO laser from the reaction of carbon vapor and oxygen.