A kinetic study of electronically excited silicon atoms, Si[3p2(1S0)], 1.909 eV above the 3p2(3P0) ground state is presented. Si(31S0) was generated by the repetitive pulsed irradiation of SiCl4 in a flow system, and the optically metastable atom was monitored photoelectrically by time-resolved resonance line absorption at λ= 390.53 nm [4s(1P°1)â†� 3p2(1S0)]. Absolute quenching rate constants (kQ, cm3 molecule–1 s–1, 300 K) are reported for the following collision partners : He ( 1.3 × 10–15), H2( 10–14), N2( 10–14), O2(1.5 ± 0.2 × 10–11), Cl2(7.3 ± 0.1 × 10–11), CO( 10–14), NO (1.2 ± 0.05 × 10–9), CO2(1.7 ± 0.3 × 10–11), N2O(4.3 ± 0.4 × 10–11), CH4(9.4 ± 1.2 × 10–11), CF4(4.3 ± 0.8 × 10–12), C2H2(1.0 ± 0.1 × 10–10), C2H4(2.5 ± 0.3 × 10–10) and SiCl4(9.1 ± 1.4 × 10–11). A rough correlation (in the classical sense) is observed between kQ and the ionisation potential of the collision partners.