Analysis of rotational structure in the high-resolution infrared spectrum and assignment of vibrational fundamentals of butadiene-2,3-13C2

The 2,3-C-13(2) isotopomer of butadiene was synthesized, and its fundamental vibrational fundamentals were assigned from a study of its infrared and Raman spectra aided with quantum chemical predictions of frequencies, intensities, and Raman depolarization ratios. For two C-type bands in the high-resolution (0.002 cm(-1)) infrared spectrum., the rotational structure was analyzed. These bands are for nu(11)(a(u)) at 907.17 cm(-1) and for nu(12)(a(u)) at 523.37 cm(-1). Ground state and upper state rotational constants were fitted to Watson-type Hamiltonians with a full quartic set of centrifugal distortion constants and two sextic ones. For the ground state, A(0) = 1.3545088(7) cm(-1), B-0 = 0.1469404(1) cm(-1), and C-0 = 0.1325838(2) cm(-1). The small inertial defects of butadiene and two C-13(2) isotopomers, as well as for five deuterium isotopomers as previously reported, confirm the planarity of the s-trans rotamer of butadiene. (C) 2005 Elsevier Inc. All rights reserved.