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 Title: Collision-induced Spectra: An Avenue To Investigate Microscopic-scale Diffusion In Fluids Author(s): Kouzov, Alexander Contributor(s): van der Veken, Benjamin J.; Herrebout, Wouter A. Subject(s): Linelists, Lineshapes, Collisions Abstract: New data on the IR spectra induced by intermolecular interactions in liquid cryogenic mixtures at T=89 K (O$_{2}$ in LAr and LN$_{2}$ and binary O$_{2}$-Ar solutions in LN$_{2}$) are reported. \ The induced fundamental bands appear as diffuse pedestals (with FWHH$\approx$100 cm$^{-1}$) on which weak, paradoxically sharp lines (FWHH$\approx$2 cm$^{-1}$) develop at the 2326 and 1552 cm$^{-1}$ frequencies of the free-molecule vibrational transitions in N$_{2}$ and O$_{2}$, respectively. In LAr and LN$_{2}$ these lines were carefully separated and studied at varied O$_{2}$ concentrations up to $c=$0.23 mole fractions (mf). While the 1552 cm$^{-1}$ line scales as $c$[O$_{2}$]$^{2}$ and thus is induced by the O$_{2}$-O$_{2}$ interactions in a bulk of cryosolvent (Ar, N$_{2}$), the 2326 cm$^{-1}$ feature varies linearly with $c$[O$_{2}$] and hence is caused by interaction of a guest (O$_{2}$) with a vibrating host (N$_2$). \ The impurity induction mechanism was further supported by our data on the binary O$_{2}$-Ar solutions in LN$_{2}$ %for which the spectra were recorded at the fixed $c$[O$_{2}$] (0.03 and 0.06 mf) and the varied $c$% [Ar]$\leq0.2$ mf. Both series revealed the same (linear) enhancement of the sharp N$_{2}$ line by argon, in an accord with our previous studies of the Ar-LN$_{2}$ system\footnote{W.A. Herrebout, A.A. Stolov, E.J. Sluyts, and B.J. van der Veken, Chem. Phys. Lett. \textbf{295,} 223 (1998).}. The results suggest that the resonance 2326 cm$^{-1}$ feature is primarily due to the local distortion of the first coordination sphere around a vibrating N$_2$ by a guest molecule. We also notice that the resonance lines should be due to the dispersion- and overlap-induced dipole moments independent on the rotational degrees of freedom\footnote{J.E. Bohr and K.L.C. Hunt , J. Chem. Phys. \textbf{86}, 5441 (1987).}. As our previous studies of the H$_{2}$-LNe system showed%\footnote{W. A. Herrebout, B. J. van der Veken, and A. P. Kouzov, Phys.Rev. Lett. \textbf{101}, 093001 (2008).}, \footnote{W. A. Herrebout, B. J. van der Veken, and A. P. Kouzov, J. Chem. Phys. \textbf{137}, 084509 (2012).}, the unusual line sharpness is a conspicuous manifestation of the relative solvent-solute and solute-solute translations dramatically retarded in a liquid by a fast velocity relaxation, an effect directly related to the microscopic-scale diffusion. The collision-induced spectra thus open up new vistas for studies of microscopic liquid dynamics. Issue Date: 2014-06-16 Publisher: International Symposium on Molecular Spectroscopy Citation Info: Kouzov, A.; van der Veken, B.J.; Herrebout, W.A. COLLISION-INDUCED SPECTRA: AN AVENUE TO INVESTIGATE MICROSCOPIC-SCALE DIFFUSION IN FLUIDS. Proceedings of the International Symposium on Molecular Spectroscopy, Urbana, IL, June 16-21, 2014. DOI: 10.15278/isms.2014.MK15 Genre: CONFERENCE PAPER/PRESENTATION Type: Text Language: English URI: http://hdl.handle.net/2142/51099 DOI: 10.15278/isms.2014.MK15 Rights Information: Copyright 2014 by the authors. Licensed under a Creative Commons Attribution 4.0 International License. http://creativecommons.org/licenses/by/4.0/ Date Available in IDEALS: 2014-09-172015-04-14
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