Rotational spectroscopy of singly $^{13}$C substituted isotopomers of
  propyne and determination of a semi-empirical equilibrium structure
  Submillimeter spectra of three isotopomers of propyne containing one $^{13}$C
atom were recorded in natural isotopic composition in the region of 426 GHz to
785 GHz. Additional measurements were carried out near 110 GHz. Combining these
with earlier data resulted in greatly improved spectroscopic parameters which
permit reliable extrapolations up to about 1.5 THz. Coupled cluster
quantum-chemical calculations were carried out in order to assess the
differences between equilibrium and ground state rotational parameters of these
and many other isotopic species to evaluate semi-empirical equilibrium
structural parameters. In addition, we estimated the main spectroscopic
parameters of the isotopomers of propyne with two $^{13}$C atoms, which have
not yet been studied in the laboratory, but which may be detectable in
astronomical sources with a large amount of $^{13}$C compared to the dominant
$^{12}$C.
