The à 1 B 1 -X 1 A 1 absorption spectrum of SiH 2 has been observed using intracavity laser absorption spectroscopy with an equivalent path length of up to 13.0 km and the à 1 B 1 (0, 0, 0)-X 1 A 1 (0, 0, 0) band near 640 nm recorded for the first time. The silylene radical was generated in a continuous discharge in a flowing mixture of silane in argon, giving a concentration of the order of 10 10 SiH 2 /cm 3 . The spectrum spans the region between 15350 and 16100 cm Ϫ1 . Rotational transitions have been assigned to levels up to Jϭ16 and K a ϭ9, with ⌬K a up to 5, ⌬K c up to 4. Perturbations have been detected in the spectrum, due to Renner-Teller and spin-orbit interactions between both electronic states and the 3 B 1 state, predicted to be between them. However, the strength of the irregular perturbations affecting the rotational states of à 1 B 1 ͑0,0,0͒ state is found to be much weaker than that affecting the other (0, v 2 Ј, 0) levels previously studied. The analysis of the spectrum has allowed the determination of the rotational constants of the 1 B 1 ͑0,0,0͒ level, and a new estimation of those of the vibrational and electronic ground state. The geometry of the excited electronic level has also been determined for the first time from accurate experimental data. A change in the structure of this molecule takes place with this transition, the equilibrium angle opening from 92°to 122.4°, while the bond distance is reduced from 1.51 to 1.485 Å.