STRUCTURE OF THE CARBON-CHAIN RADICALS CCCN AND CCCCH
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Date
1995
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Publisher
Ohio State University
Abstract
The millimeter-wave rotational spectra of $CCC^{15}N$ and the single $^{13}C$ isotopic species of the CCCN and CCCCH radicals were measured and the same set of rotational, centrifugal distortion, and spin-rotation constants used to describe the normal species [Gottlieb et al., Astrophys. j. 275, 916 (1983)] were determined. Owing to a large Fermi-contact interaction at the terminal carbon, hyperfine structure was resolved in $^{13}CCCCH.$ Measurements of the fundamental $N = 1 \rightarrow 0$ rotational transition of CCCCH with a Fourier transform spectrometer described in the accompanying talk by $Chen et al.^{1}$ yielded precise values of the Fermi-contact and dipole-dipole hyperfine coupling constants in all four $^{13}C$ species. The Fermi-contact interaction is of order a factor of two larger in CCCN, allowing determination of hyperfine coupling constant b in $^{13}CCCN$ and $C^{13}CCN$ from the millimeter-wave rotational spectra. Substitution $(r_{s})$ structures were determined for both radicals. The equilibrium geometry of CCCN has been determined both from large-scale coupled cluster calculations including connected triple substitutions [RCCSD(T)] as well as by a mixed experimental-theoretical procedure. Less extensive RCCSD(T) calculations were also carried out for CCCCH.
Description
1. W. Chen. S.T. Novick, M. C. McCarthy, C.A. Gottlieb, and P. Thaddeus, accompanying paper presented during this Symposium.
Author Institution: Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138; Harvard University, Cambridge, MA 02138.; Universität Göttingen, Tammannstr. 6, D-37077 Göttingen, Germany.
Author Institution: Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138; Harvard University, Cambridge, MA 02138.; Universität Göttingen, Tammannstr. 6, D-37077 Göttingen, Germany.