  Electronic transitions of the title molecules were measured between 250 and
710 nm using a mass-resolved 1+1' resonant two-photon ionization technique at a
resolution of 0.1 nm. Calculations at the B3LYP/aug-cc-pVQZ level of theory
support the analyses. Because of their spectral properties, SiC$_2$, linear
Si$_2$C$_2$, Si$_3$C, and SiC$_6$H$_4$ are interesting target species for
astronomical searches in the visible spectral region. Of special relevance is
the Si--C$_2$--Si chain, which features a prominent band at 516.4 nm of a
strong transition ($f=0.25$). This band and one from SiC$_6$H$_4$ at 445.3 nm
were also investigated at higher resolution (0.002 nm).
