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The microwave spectra of symmetric top polyacetylenes

1978; Elsevier BV; Volume: 70; Issue: 1 Linguagem: Inglês

10.1016/0022-2852(78)90011-5

1096-083X

A. J. Alexander, Harold W. Kroto, M. Maier, David R. M. Walton,

Astrophysics and Star Formation Studies

The rotational spectra of 1,3,5-heptatriyne, CH3(CC)3H and 1-cyano-2,4-pentadiyne, CH3(CC)2CN have been studied in detail between 26.5 and 40.0 GHz. The molecules have long linear chains of heavy atoms and show characteristic C3v symmetric top spectra consisting of groups of R-branch lines at regular intervals separated by approximately 2B0. Six isotopic modifications of CH3(CC)2CN have been detected in natural abundance allowing rs substitution structural data to be derived for this species. Long linear polyacetylenic chains are quite flexible and this dynamic property manifests itself in the appearance of extended sequences of complex vibrational satellites associated with the bending of the chain. The vibrational ground state spectra as well as several low frequency vibrational satellites have been analyzed yielding various vibration-rotation parameters. For CH3(CC)3H B0 = 778.2445 ± 0.0007 and for CH3(CC)2CN B0 = 778.040 ± 0.001 MHz.