Raman Spectra Of CO2 Research Articles

IR and Raman spectra of two layered aluminium phosphates Co(en) 3Al 3P 4O 16 · 3H 2O and [NH 4] 3[Co(NH 3) 6] 3[Al 2(PO 4) 4] 2 · 2H 2O

The FT IR and FT Raman spectra of Co(en) 3Al 3P 4O 16 · 3H 2O (compound I) and [NH 4] 3[Co(NH 3) 6] 3[Al 2(PO 4) 4] 2 · 2H 2O (compound II) are recorded and analysed based on the vibrations of Co(en) 3 3+, Co(NH 3) 6 3+, NH 4 +, AlOP, PO 3, PO 2 and H 2O. The observed splitting of bands indicate that the site symmetry and correlation field effects are appreciable in both the compounds. In compound I, the overtone of CH 2 deformation Fermi resonates with its symmetric stretching vibration. The NH 4 ion in compound II is not free to rotate in the crystalline lattice. Hydrogen bonding of different groups is also discussed.

Raman Studies on Solid CO2 and N2 with Excess He at Pressures up to 40GPa.

Raman spectra of CO2 and the van-der-Waals compound He (N2) 11 were obtained under nearly hydrostatic pressures up to 40 GPa. The pressure induced changes of the librational spectra suggest that solid CO2 does not transform directly from phase-I (cubic Pa3) to phase-III (orthorhombic Cmca). An intermediate phase-IV. which may involve only minor modifications of phase-I, is formed prior to the transition to Cmca structure. P hases IV and III coexist over some pressure range. The pressure shifts of all four Raman active librons of phase-III were determined over a wide pressure range and are compared to previous theoretical results. Spectra of external and internal modes of the van-der-Waals compound He (N2) 11 are very similar to those of e-N2 and imply a close relationship between the structures of He (N2) 11 and e-N2. The observed splitting of the main vibron of isotopic species 14N-15N indicates that in addition to factor-group interactions site effects are responsible for the observed splittings of the 14N2 main vibron of He (N2) 11.

Collapse of Vibrational Structure in the Auger Resonant Raman Spectrum of CO by Frequency Detuning

Observations made in the $\mathrm{C}1s\ensuremath{\rightarrow}{\ensuremath{\pi}}^{*}$ Auger resonant Raman spectra of carbon monoxide demonstrate that the vibrational structure in such spectra is strongly frequency dependent. In the limit of narrow bandpass photon excitation, the vibrational excitations of the $5\ensuremath{\sigma}$ participator transition collapse to one single line within a sub-eV detuning range. The effect is explained in terms of a generalized duration time for the resonance process, in which the lifetime of the core excited state and the inverse of the detuning frequency play equal roles.

Raman spectroscopic analyses of the growth process of CO 2 hydrates

CO 2 hydrate crystals with polyhedral facet were observed to grow from CO 2 solution. For both CO 2 hydrates and CO 2 solution, raman spectroscopic analyses were carried out. Raman spectra of CO 2 and H 2O molecules in CO 2 hydrate were different from those in CO 2 solution. We presented an attempt to estimate the density of CO 2 hydrate by the raman intensity ratio, and found that the densities of CO 2 hydrates were considerably smaller than those used in some modeling studies.

Vibrational modes of CO adsorbed on disordered copper films

AbstractThe Raman spectrum of CO adsorbed on copper films featuring atomic‐scale roughness reveals four vibrational modes: a CO stretching mode at 2102 cm−1, a restricted rotation at 282 cm−1 and restricted translations normal and parallel to the local surface at 355 and 24 cm−1. The spectrum originates from a minority of CO molecules adsorbed at surface defect sites via a single coordination bond. The bond strength is increased compared with adsorption at facet sites, presumably owing to increased σ‐donation promoted by a local depletion of conduction electron density. A splitting of the translational mode into two separate frequencies, expected for adsorption sites with rotational symmetry less than C3v, is not observed. The intensities and line shapes of the SERS bands are sensitive to a thermally induced rearrangement of the molecules within the adsorbate layer. Spectra from annealed substrate films indicate dominant excitation of the rotational mode on surfaces with a lesser degree of atomic‐scale roughness. This is explained by the relevance of Herzberg‐Teller contributions to the inelastic scattering of photoexcited electrons by the surface molecules.

CO2-Based Thermometry of Supercritical Water Oxidation

We have demonstrated the suitability of CO2 Raman spectra as a thermometry probe of the fluid mixtures encountered in supercritical water oxidation. Measured temperature accuracies of ±6% are presented. Measurements were made of the v1 2 v2 Fermi resonance features of CO2 in a supercritical water environment. Over the temperature range of interest to researchers of supercritical water oxidation, ∼400–650°C, hot bands appear in the Raman spectrum of CO2 with sufficient spectral intensity to serve as a convenient measure of the fluid temperature. We have analyzed these hot bands by taking the ratio of their integrated intensity with the integrated intensity of the fundamental. Over the temperature range of 390 to 540°C, the intensity ratio of the first pure hot band feature to the fundamental of v1 shows a very nearly linear dependence on temperature. The experimental ratio measurements are well explained by standard Raman theory if the Fermi resonance is accounted for. As discussed, the CO2 spectral line shape is affected by the high pressure ( P > 22.1 MPa) used in supercritical work, but these changes do not affect the extraction of a fluid temperature from the spectra.

Surface‐induced substitution reaction on cobalt(III) and manganese(III) tetrakis (4‐N‐methylpyridyl)porphyrins probed by surface‐enhanced Raman spectroscopy

AbstractThe Surface‐enhanced Raman spectra of Co(III)TMPyP(4)Cl and Mn(III)TMPyP(4)Cl [where TMPyP(4) = tetrakis (4‐N‐methylpyridyl)porphyrin] demonstrate the formation of Ag(II)TMPyP(4) on the silver surface. The reaction is not photon assisted but is dependent on the sol activity and time. The effect of NaCl on the sol activity and the surface‐induced reaction was investigated. It was observed that the metal substitution reaction of Mn(III)TMPyP(4)Cl was more efficient than that of Co(III)TMPyP(4)Cl.

Collisional narrowing of the rotational Raman spectrum of CO_2 near the critical point

The density dependence of the linewidth of the collisionally narrowed, pure rotational Raman band of CO2 has been measured at 32.7°C or 1.7°C above its critical temperature. Analysis of the results and comparison with other observations indicate that rotational spectra showing collisional narrowing are not sensitive to density fluctuations. The observed spectral asymmetry is discussed.

Raman Spectra of Carbon Dioxide and its Isotopic Variants in the Fermi Resonance Region. Part IV: Temperature Dependence on Q-Branch Intensities from 300 K to 650 K

The temperature dependence of the intensities of the Q-branches in the Raman spectrum of gaseous CO2 in the Fermi resonance region was measured in the range from 300 K to 650 K. The intensity contours were reproduced by computer simulation, taking into account energy levels up to ( v1 v21 v3) = (30°0) as final states. Calibration curves are given for the determination of temperatures from the intensity distribution in the hot bands of the Raman spectrum of CO2.

Normal unenhanced Raman spectra of CO adsorbed on Ni(100) at liquid-nitrogen temperature and at room temperature

Normal unenhanced Raman spectra (NURS) of CO adsorbed on Ni(100) after an exposure of 10 6 L CO have been recorded at both liquid-nitrogen temperature and room temperature at pressures below 10 −8 Torr. At both temperatures three models are presented to explain the observed spectra in the CO stretch region and the NiC stretch region. These models are based upon the electronic sharing of the adsorbed CO in different configurations (linear, two-fold bridge and four-fold bridge) with both the Ni surface atoms and co-adsorbed species (like H and oxygen) present in the residual gas in the chamber.

Normal unenhanced raman spectra of CO adsorbed on Ni(100) at liquid-nitrogen temperature and at room temperature

Normal unenhanced raman spectra of CO adsorbed on Ni(100) at liquid-nitrogen temperature and at room temperature

Normal Unenhanced Raman Spectra of CO and CH4Adsorbed on Cobalt(poly)

Abstract Normal unenhanced Raman spectra (NURS) of low-polarizability CO molecules were observed for the first time on cobalt at R. T. and residual gas pressure. We assign five bands observed between 2030–2130 cm−1 to linear chemisorbed CO species, while those observed between 1840–2010 cm−1 have been ascribed to the 2-fold chemisorbed species. The three bands observed between 1740–1830 cm−1 we believe are due to the 3-fold species. The corresponding fourteen Co-C stretches were observed and assigned. A model based upon electron backdonation is proposed for each of the three structures. NURS were also observed at R. T. for physisorbed CH4 and assignments are made to the four frequencies of CH4.

Normal unenhanced Raman spectra of CO and residual gas adsorbed on Ni(111)

Normal unenhanced Raman spectra of CO and residual gas adsorbed on Ni(111)

Normal unenhanced Raman spectra of CO and residual gas adsorbed on Ni(111)

Normal unenhanced Raman spectra (NURS) of low-polarizability molecules adsorbed on Ni(111) at 98 K. have been recorded at residual gas pressure. This is the first observation of Raman spectra from low-polarizability molecules adsorbed at low pressure onto a poor Raman signal enhancer. Raman bands were also recorded from Ni(111) at 98 and 298 K after exposing the crystal to 10 6 L CO. Assignments of CO stretches and their corresponding Ni-C stretches are discussed for both linear and bridge CO adsorbed with different neighboring species. Two low-lying vibrational modes of CO were recorded at 80 and 185 cm −1 and assigned to the CNiNi bend (on-top) and the OCNi bend (bridged), respectively. Other Raman bands are assigned to vibrations of oxygen, ozone, and hydrogen adsorbed on Ni(111).

Raman spectra of Co(NH3)6X3 (X = Cl, Br, I) complexes

Etude des spectres Raman entre 310 et 40 K. La structure fine vers 500 cm −1 s'explique par la presence de sites non equivalents. Etude des intensites polarisees pour les vibrations A 1g , T 1u et E g . Lorsque X=I, le complexe passe de la phase cubique a la phase polydomaniale monoclinique vers 280 K

UHV cell for Raman studies of gases adsorbed on metals

We describe a UHV Raman cell for the study by laser Raman spectroscopy of gases adsorbed at low coverages on smooth metal surfaces. Provision is made for three samples, and the sample temperature is controlled from 100 to 800 K. The cell also contains a residual gas analyzer, an argon-ion sputter gun for cleaning the samples, and ports for observation of right-angle and oblique Raman scattering. Displayed are Raman spectra of CO on Ni(111) adsorbed from the chamber residual gases and Raman spectra of CH3COCH3 adsorbed on the same single crystal at 10 L exposure.

The collision induced contribution to the depolarized Raman spectrum of compressed HCl, CO, N2 and CO2

The depolarized Raman spectrum of compressed HCl at 60 and 55 °C was measured at a number of densities. Several theoretical calculations and an analysis of the spectra support the view that the spectrum at densities above 80 amagat is dominated by a collision induced component. The calculations also show that the neglect of a collision induced contribution to the depolarized Raman spectrum of CO, N2, and CO2 is justified.

Study of the Fermi doublet ν 1 — 2ν 2 in the Raman spectra of CO 2 in different phases

The relation between the intensity ratio R and the frequency separation Δ of the Fermi doublet components ν + and ν − in the Raman spectra of CO 2 in dense gas, liquid, solid and aqueous solutions is used to establish the correct assignment of the levels to ν 1 and 2ν 2. The unperturbed fundamental ν 0 1 is at higher frequency than 2ν 0 2 in all the phases studied. The values of ν 0 1 increase and of 2ν 0 2 decrease with pressure. The values of W and K 122 are nearly constant for the dense gas, liquid and solid in the pressure range of 6–44 kbars, but decrease in the solid for pressures up to 100 kbars and also in aqueous solutions.

Infrared and Raman Spectra and Lattice Vibrations of Some Oxide Spinels

The infrared transmission and reflection spectra of Co II Co III 2 O 4 , CoAl 2 O 4 , ZnFe 2 O 4 and MnFe 2 O 4 and the single crystal Raman spectra of Co II Co III 2 O 4 and CoAl 2 O 4 have been measured. The frequencies of the transverse (TO) and longitudinal (LO) modes of the infrared active species have been obtained from the observed reflectivities. The TO-LO splitting supplies a criterion for the ionic character. The lattice dynamical analysis of the optically active vibrations has been made for Co II Co III 2 O 4 , CoAl 2 O 4 and ZnFe 2 O 4 , in which the rigid ion model for the long-range Coulomb potential and the central force field for the short-range potential have been used. The obtained short-range potential constants have been discussed, in relation to the bond character.

Raman Spectra of CO Adsorbed on Ni(100)

Abstract Experimental results are discussed for laser Raman spectra of CO adsorbed on Ni(100) at -131C. Raman shifts are observed at 2050, 2028, 466 and 419 cm−1. Assignments are made for the modes based upon C2v and C4v. point groups. The assignments are compared with earlier experimental and theoretical work.