15min:

CHRISTOPHER T. DEWBERRY, GARRY S. GRUBBS II AND STEPHEN A. COOKE, The Department of Chemistry, University of North Texas, P.O. Box 305070, Denton, TX, 76203-5070.

Using both chirped pulse-, and low frequency cavity-based Fourier transform spectroscopy over 700 transitions have been recorded for the title molecule for the first time. The C₁, C₂ and C₃ carbon-13 species have been observed in natural abundance allowing a substitution structure for the CCC backbone to be determined. Nearly all the transitions observed were either a-type R branches or b-type Q branches. No c-type transitions were observed. The _aa, _bb, _cc and _ab components of the iodine nuclear quadrupole coupling tensor have been determined. Of note, several forbidden transitions were also observed, such as J_k_-1,k₊₁ F = 14_4,10 23/2 12_5,7 21/2. In this particular case it seems that the upper energy level is nearly degenerate with a level connected to the lower energy level by a µ_a dipole component term, but the lower energy level is also nearly degenerate with a second level connected to the upper energy level, again by a µ_a dipole component term. The two intermediate energy levels are themselves connected by a µ_b dipole component term. Near degeneracies such as these, together with a large _ab value (~ 1 GHz) mean that certain J = 2 transitions become allowed. This phenomena has been previously observed for 1-iodopropane by Fujitake and Hayashi (J. Mol. Spect, 127, (1988), 112-124).