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Atomistic Simulations of CO Vibrations in Ices Relevant to Astrochemistry
Author(s) -
Plattner Nuria,
Meuwly Markus
Publication year - 2008
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200800030
Subject(s) - anharmonicity , multipole expansion , chemical physics , astrochemistry , molecule , molecular dynamics , chemistry , quadrupole , absorption (acoustics) , infrared , monatomic gas , carbon monoxide , infrared spectroscopy , absorption spectroscopy , spectral line , libration (molecule) , molecular physics , physics , atomic physics , computational chemistry , condensed matter physics , interstellar medium , astrophysics , optics , biochemistry , organic chemistry , quantum mechanics , galaxy , catalysis , point (geometry) , geometry , mathematics , astronomy
The experimental absorption band of carbon monoxide (CO) in mixed ices has been extensively studied in the past. The astrophysical interest in this band is related to its characteristic shape, which appears to depend on the surrounding ice structure. Herein, molecular dynamics simulations are carried out to analyze the relationship between the structure of the ice and the infrared (IR) spectrum of embedded CO molecules at different concentrations. Instead of conventional force fields, anharmonic potentials are used for the bonded interactions. The electrostatic interactions are more accurately described by means of fluctuating atomic multipole moments (up to quadrupole). The experimentally observed splitting of the CO absorption band (gas phase: 2143 cm −1 ) into a blue‐ (2152 cm −1 ) and a red‐shifted (2138 cm −1 ) signal is also found in the simulations. Complementary atomistic simulations allow us to relate the spectra with the structural features. The distinction between interstitial and substitutional CO molecules as the origin of this splitting is found to be qualitatively correct. However, at increasing CO concentrations, additional effects—such as mutual interactions between CO molecules—become important, and the simplistic picture needs to be revised.