A singlet potential energy surface (PES) of the [Si, N C, S](+) system is investigated by means of MP2 and QCISD(T) (single-point) methods. Four linear isomers of [Si, N, C, S](+) system are found to be kinetically stable and should be experimentally observable. The linear isomer SiNCS+ is the thermodynamically most stable, followed by SSiCN+, SSiNC+ and SiCNS+. No cyclic kinetically stable isomers are found. For the isomer SiNCS+, several isomerizations call very favorably compete with its direct dissociation, and thus, the very recent mass spectrometric experiment can reasonably be interpreted by analyzing the structures and bonding. (C) 2002 Elsevier Science B.V. All rights reserved.