High-resolution CARS spectroscopy of small carbon dioxide clusters: investigation of the CO2 dimer in the Fermi dyad

Raman spectroscopy and crystal-field split rotational states of photoproducts CO and H2 after dissociation of formaldehyde in solid argon J. Chem. Phys. 137, 164310 (2012) The links between translational, rotational, and vibrational temperatures of supersonic molecular jets, and their density and degree of condensation, are discussed in terms of quantitative Raman scattering experimental data. Such links are established as the result of energy and momentum conservation laws, and of the collisional regime in the jet. Four representative supersonic expansions of CO 2 , generated at different stagnation pressures are analyzed, showing the potential of quantitative Raman spectroscopy for a complete characterization of the jet.

Section: Resultsmentioning

confidence: 57%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Raman spectroscopy of supersonic jets of CO2: Density, condensation, and translational, rotational, and vibrational temperatures

Maté¹,

Tejeda²,

Montero³

1998

“…In gaseous phase, investigations have been mainly devoted to the analysis of the Fermi resonance coupling of vibrational modes of the isolated molecule, [1][2][3] and to the characterisation of the structure of weakly bounded clusters. [4][5][6][7][8][9][10][11][12][13][14][15][16][17] In dense phase, the aim was to provide insight on the nature and time scale of the intermolecular interactions from "allowed" vibrational spectra or from the analysis of collision induced (CI) spectra which are unique probes of the multi-body interactions. [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] The study of the interaction of carbon dioxide with molecular liquids and complex fluids as ionic liquids is a field of current interest, motivated not only from the fundamental point of view but mainly under the impetuous motivation of understanding the interactions of CO 2 in the field of environmental studies.…”

Section: Introductionmentioning

confidence: 99%

Assessing the non-ideality of the CO2-CS2 system at molecular level: A Raman scattering study

Besnard

Cabaço²,

Coutinho

et al. 2013

The dense phase of CO 2 -CS 2 mixtures has been analysed by Raman spectroscopy as a function of the CO 2 concentration (0.02-0.95 mole fractions) by varying the pressure (0.5 MPa up to 7.7 MPa) at constant temperature (313 K). The polarised and depolarised spectra of the induced (ν 2 , ν 3 ) modes of CS 2 and of the ν 1 -2ν 2 Fermi resonance dyad of both CO 2 and CS 2 have been measured. Upon dilution with CO 2 , the evolution of the spectroscopic observables of all these modes displays a "plateau-like" region in the CO 2 mole fraction 0.3-0.7 never previously observed in CO 2 -organic liquids mixtures. The bandshape and intensity of the induced modes of CS 2 are similar to those of pure CS 2 up to equimolar concentration, after which variations occur. The preservation of the local ordering from pure CS 2 to equimolar concentration together with the non-linear evolution of the spectroscopic observables allows inferring that two solvation regimes exist with a transition occurring in the plateau domain. In the first regime, corresponding to CS 2 concentrated mixtures, the liquid phase is segregated with dominant CS 2 clusters, whereas, in the second one, CO 2 monomers and dimers and CO 2 -CS 2 hetero-dimers coexist dynamically on a picosecond time-scale. It is demonstrated that the subtle interplay between attractive and repulsive interactions which provides a molecular interpretation of the non-ideality of the CO 2 -CS 2 mixture allows rationalizing the volume expansion and the existence of the plateau-like region observed in the pressure-composition diagram previously ascribed to the proximity of an upper critical solution temperature at lower temperatures.

“…Dimer features in the ν 1 /2ν 2 Fermi-doublet region (∼1300 cm −1 ) received much attention, [12][13][14][15][16][17] but have not been very informative, partly because these experiments are performed at relatively high temperatures (>180 K) and gas pressures. Larger clusters have been probed using a number of techniques, [18][19][20][21][22][23][24][25][26][27] but (CO 2 ) 3 remained the largest cluster for which explicit infrared band assignments were supported by resolved rotational structure. Very recently, we reported 28 assignments of specific vibration-rotation bands in the ν 3 region to medium-size carbon dioxide clusters, (CO 2 ) N , with N = 6, 7, 9, 10, 11, 12, and 13.…”

Section: Introductionmentioning

confidence: 99%

High resolution infrared spectroscopy of carbon dioxide clusters up to (CO2)13

Oliaee

Dehghany

McKellar

et al. 2011

Thirteen specific infrared bands in the 2350 cm −1 region are assigned to carbon dioxide clusters, (CO 2 ) N , with N = 6, 7, 9, 10, 11, 12 and 13. The spectra are observed in direct absorption using a tuneable infrared laser to probe a pulsed supersonic jet expansion of a dilute mixture of CO 2 in He carrier gas. Assignments are aided by cluster structure calculations made using two reliable CO 2 intermolecular potential functions. For (CO 2 ) 6 , two highly symmetric isomers are observed, one with S 6 symmetry (probably the more stable form), and the other with S 4 symmetry. (CO 2 ) 13 is also symmetric (S 6 ), but the remaining clusters are asymmetric tops with no symmetry elements. The observed rotational constants tend to be slightly (≈2%) smaller than those from the predicted structures. The bands have increasing vibrational blueshifts with increasing cluster size, similar to those predicted by the resonant dipole-dipole interaction model but significantly larger in magnitude.