AB INITIO CALCULATIONS FOR $C_{5}S$

$C_{5}S$ was recently detected in them $laboratory^{1}$ and possibly also in the circumstellar envelope of IRC+$10126^{2}$. Making use of the CEPA = $1^{3}$ method and a basis set of 184 contracted Gaussian type orbitals we arrive at a linear equilibrium structure with the following bond lengths: $R_{1e} = 1.2855$ {\\AA}, $R_{2e} = 1.2924$ {\\AA}, $R_{se}=1.2707$ {\\AA}, $R_{ae}=1.2800$ {\\AA} and $R_{5e} = 1.5582$ {\\AA} with the bonds ordered according to the chemical formula. The corresponding equilibrium rotational constant $B_{e}= 917.1$ MHz compares well with the experimental $B_{0}$ $value^{1}$ of 922.7 MHz. The equilibrium dipole moment calculated by CCSD (T)$^{4}$ is as high as 5.38 D. The wave numbers and IR intensities of the stretching vibrations were determined using a well established anharmonic model. The $\\nu_{1}$ band with origin at $2085 cm^{-1}$ was calculated ton have a very large integrated IR intensity of 4000 km/mol. The $\\nu_{3} 1615.2 cm^{-1}$ is also very intense with $A_{3}$ = 613 km/mol.