Carbon-13 Isotopic Species of H2C3, H2C4, and H2C5: High-Resolution Rotational Spectra

Abstract

The microwave rotational spectra of the carbon-13 isotopic species of H2C3, H2C4, and H2C5 have been observed in a pulsed supersonic molecular beam by Fourier transform microwave spectroscopy. At high resolution all of the rotational lines exhibit hyperfine structure produced by the magnetic interaction between the nuclear spin of 13C and the overall rotation of the molecule. The component of the nuclear spin–rotation tensor along the a-inertial axis is large for most isotopic species, especially at the carbene carbon; at this position Caa is two to three times larger than at other substituted positions along the chain. In contrast to both H2C3 and H2C3, in H2C4Caa exhibits a pronounced alternation along the carbon chain backbone. Following detection of the five carbon-13 isotopic species and D2C5, an experimental structure (r0) has been determined to high accuracy for H2C5.