On the electron affinity of SiN and spectroscopic constants of SiN(-)

Accurate spectroscopic constants and energetics were calculated for the two lowest-lying states of SiN and SiN- employing the coupled cluster methodology and very large basis sets (up to doubly augmented sextuple-zeta quality) accounting also for core/valence correlation, one-electron Douglas-Kroll-Hess relativistic effects, and atomic spin-orbit couplings. Our best estimate for the adiabatic electron affinity of SiN is 3.002 eV, in very good agreement with the recent, experimentally determined value of 2.949(8) eV. However, the calculated bond length of the SiN- X 1sigma+ state at the same level, r(e) = 1.5904 angstroms, is smaller than the indirectly extracted experimental value of 1.604(5) angstroms, pointing out that the latter value is either a bit overestimated or not as accurate as the +/- 0.005 angstroms error bar indicates. For the neutral SiN, all calculated data are in excellent agreement with previous accurate experimental results.