Kinetic study of electronically excited silicon atoms, Si(3p 2( 1S 0)), by time-resolved attenuation of atomic resonance radiation

Abstract

The collisional behaviour of electronically excited silicon atoms in the 3p 2( 1S 0) state, 1.909 eV above the 3p 2( 3P 0) ground state, is investigated by time-resolved attenuation of atomic resonance radiation at λ = 390.53 nm (4s( 1P o 1)←3p 2 ( 1S 0)). The optically metastable Si(3 1S 0) atoms were generated by the repetitive pulsed irradiation of SiCl 4 and their decay monitored in the presence of added gases. Absolute quenching rate constants ( k Q, cm 3 molecule −1 s −1, 300 K) are reported for the following collision partners: He (⩽1.3 × 10 −15), SiCl 4 ((9.1 ± 1.4) × 10 −11), O 2 ((1.5 ± 0.2) × 10 −11) and N 2O ((4.3 ± 0.4) × 10 −11). The results for O 2 and N 2O are compared with analogous data reported hitherto for Si(3p 2( 3P J )) and with those for the other np 2( 1S 0) states of the group IV atoms C, Ge, Sn and Pb. The rate data for the silicon atoms are considered in terms of the nature of the potential surfaces arising from symmetry arguments based on the weak spin orbit coupling approximation.