The rate constant of self-reaction of silyl radicals, SiH 3 + SiH 3 f products (1), was measured at 300 K over an extended buffer gas pressure range (1-100 bar, He) using excimer laser pulsed photolysis combined with the transient UV spectroscopy. Silyl radicals were produced in fast reaction of chlorine atoms with silane, Cl + SiH 4 f SiH 3 + HCl. Oxalyl chloride, (COCl) 2 , and phosgene, COCl 2 , were used as "clean" photodissociation sources of Cl atoms at 193 nm (ArF laser). Silyl radicals were monitored using UV absorption. The absorption cross-sections of SiH 3 radicals are determined using the measured photodepletion of the precursor, (COCl) 2 , via its transient absorption at 210 nm. The UV absorption of silyl radical has maximum at 218 nm with the absorption cross-section, σ SiH3 (218 nm) ) (2.01 ( 0.11) × 10 -17 cm 2 molecule -1 . No pressure dependence of the overall rate constant of reaction 1 was found over the range 1-100 bar (He). The measured rate constant is: k 1 ) (8.25 ( 1.05) × 10 -11 cm 3 molecule -1 s -1 at 300 K. Observed residual UV absorption, tentatively assigned to the dissociation products of the vibrationally excited Si 2 H 6 * molecules formed in reaction 1, is quenched by the buffer gas at 100 bar pressure due to the collisional stabilization of excited disilane molecules.