High-resolution infrared diode laser spectroscopy of (CO2)3: Vibrationally averaged structures, resonant dipole vibrational shifts, and tests of CO2–CO2 pair potentials

Abstract

High-resolution infrared spectra of (CO2)3 formed in a slit jet supersonic expansion are obtained via direct absorption of a tunable diode laser in the ν3 asymmetric stretch region of CO2. Over 100 distinct transitions are recorded in the trimer spectrum, which can be modeled as a perpendicular band of a planar symmetric top with C3h symmetry and no observable tunneling splittings. Results from the spectroscopic fit indicate that the complex is vibrationally averaged planar, with a carbon–carbon atom separation of RCC=4.0376(2) Å. An analysis of the vibrational blue shift for (CO2)3 of 2.5755(2) cm−1 via a resonant dipole–dipole interaction model yields an angular orientation for each CO2 axis of β=33.8(5)° away from a line tangent to the vertex and parallel to the opposite side of the equilateral triangle connecting the centers of mass of each CO2 monomer. Several model CO2–CO2 interaction potentials are tested against the vibrationally averaged structural parameters for (CO2)3. In particular, the potential of Murthy et al. [Mol. Phys. 50, 531 (1983)] reproduces RCC for the complex, but similar to all potentials tested, does not accurately predict the angular orientation β of the monomers within the trimer. Lastly, spectral evidence and model predictions suggest that there is an asymmetric top isomer of the trimer that is energetically comparable to the observed cyclic isomer.

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

“…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.…”

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

“…41 The deviations of rotational temperature in the jet from the isentropic prediction have been measured by means of intracavity Raman spectroscopy; 16,17 Rayleigh scattering has proved useful to track the onset of condensation in some detail. 17 As far as the detailed structure of the condensed fraction of the jet is concerned, high resolution IR spectroscopy has been successful in establishing the geometry of the CO 2 dimers 42,43 and trimers 44,45 formed in the jet. Large clusters have been investigated by Fourier transform infrared spectroscopy ͑FTIR͒.…”

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

“…Results of such calculations are shown in Tables II and III. We used an experimental CO 2 transition dipole value 51 (the same as Weida et al 7 ) and the SAPT-s structures (M-O-M structures give similar results). For the asymmetric top clusters in Table II (N = 7-12), only the three strongest of the N allowed infrared bands are listed.…”

“…More generally, clusters represent the "missing" link between single molecules or molecular pairs and the bulk liquid or solid phases, and intermolecular forces play a key role in this transition region. Carbon dioxide dimers [1][2][3][4][5] and trimers [6][7][8] were extensively studied by high-resolution infrared spectroscopy in the period from 1984 to 1996. The dimer was shown to have a planar slipped-parallel structure, with centrosymmetric C 2h symmetry.…”

“…[33][34][35][36] An older but noteworthy and widely accepted empirical function is the M-O-M or Murthy potential, 37,38 which was based on solid CO 2 elastic constants but has also been shown to work rather well in predicting dimer and trimer structures, vibrational shifts, and transition moment orientations. 7,8 …”