ROTATIONAL SPECTRA AND STRUCTURE OF THE HCN TRIMER
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Date
1986
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Ohio State University
Abstract
The ground state structure of the HCN trimer has been characterized by Fourier transform microwave observations of its $J = 4 - 5$ to $J = 7 - 8$ transitions, using Ar and Ne as carrier gases in a pulsed nozzle system. The trimer is found to be linear. The rotational constants $B_{O}, D_{J}$ and a $6^{th}$ order term H have been determiend for five $^{14}N/^{15}N$ isotopically substituted species. An approximate analysis neglecting torsional oscillations of the subunits, gives their separations $r_{1}$ and $r_{2}$ to be 3.26 and 3.22 A, respectively, as shown: $HCN\ldots {^{r}}1.HCN\ldots{^{r}}2.HCN$. These values are approximately midway between the intermolecular separation of 3.18 A in the crystalline $solid^{1}$ and of 3.28 A in the gas-phase $dimer.^{2}$ The $^{14}N$ quadrupole coupling constants have been determined for each of the three sites in the complex by observations of the $mono-HC^{14}N, di-HC^{15}N$ species. Further work with HCN is in progress, including a search for the HCN tetramer. The implications of such work will be discussed.
Description
Work supported by NSF and PRF. $^{1}$ W. J. Dalmage and W. N. Lipscomb, Acta Cryst, 4, 330 (1951). $^{2}$ L. W. Buxton, E. J. Campbell, and W. H. Flygare, Chem. Phys. 56, 399 (1981). Address: Noyes Chemical Laboratory, University of Illinois, Urbans, IL 61801.
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