Collisional quenching of electronically excited silicon atoms, Si[3p2(1D2)], by atomic absorption spectroscopy

Abstract

A kinetic study of electronically excited silicon atoms, Si[3p²(¹D₂)], 0.781 eV above the 3p²(³P₀) ground state is presented. The optically metastable Si(3¹D₂) was generated by repertitive pulsed irradiation in a flow system from the photolysis of an SiCl₄+ He mixture and monitored photoelectrically in absorption at λ= 288.16 nm [4s(¹P^°₁)â†� 3p²(¹D₂)]. The spectroscopic source comprised data handling system comprising a fast response transient recorder interfaced to a signal averager, the resulting output being analysed by means of an IBM 370 computer. Absolute second-order rate constants for the removal of Si(3¹D₂) are reported for the gases He, Kr, Xe, H₂, N₂, O₂, Cl₂, CO, NO, CO₂, N₂O, CH₄, CF₄, C₂H₂, C₂H₄ and SiCl₄. The results are compared with analogous data described hitherto for Si[3p²(³P_J)] and Si[3p²(¹S₀)], and discussed, where appropriate, within the context of symmetry arguments on the nature of the potential surfaces involved using the weak spin orbit coupling approximation. Attempts at the construction of pulsed photodissociation lasers, operating on the transitions np²(¹S₀→¹D₂) for the atoms Si, Ge, Sn and Pb are described.