ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
Two isomers of N2O3, asym-N2O3 and sym-N2O3, are identified with infared (IR) absorption when mixtures of NO–NO2–Ar or NO–O2–Ar are deposited onto a target at 13 K. Upon irradiation with a XeCl excimer laser at 308 nm, asym-N2O3 is converted to sym-N2O3 and a new form of N2O3, trans-cis N2O3; the latter is readily converted to sym-N2O3 upon further irradiation with red light. Assignments of IR absorption lines to each conformer in its isotopic variants are based on 18O-isotopic substitution and photoconversion experiments. For asym-N2O3, we observed 18O-isotopic shifts of a few vibrational modes previously unresolved in a N2 matrix, confirming that O-atoms in the NO2 moiety are inequivalent. For sym-N2O3, a more nearly complete set of isotopic shifts for absorption lines at 1688.6, 971.0, and 704.6 cm−1 enables us to provide refined assignments. In addition, lines at 1722.5 and 1721.1 cm−1 are assigned to symmetric stretching modes of two terminal N(Double Bond)O groups of 18ON16ON16O and 18ON18ON16O; they gain IR activity because C2V symmetry is broken. Trans-cis N2O3 with an asymmetric ONONO structure is identified with absorption lines at 1704.5, 1665.7, 877.8, and 243.0 cm−1. Isotopic experiments indicate that this species contains two nearly isolated N(Double Bond)O groups. Spectral assignments are supported by theoretical calculations with density-functional theories (BLYP and B3LYP); previous assignments of low-energy vibrational modes of asym-N2O3 and sym-N2O3 are revised based on comparison with calculations. Photoconversion among these isomers is discussed. © 1998 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.477700
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