“…Silylene, SiH 2 , the prototype radical in silylene family, plays an important role in the organic silicon chemistry, [1][2][3] and it is postulated as a reactive intermediate in the manufacturing process of amorphous silicon lms by chemical vapor deposition. [4][5][6][7] The studies of SiH 2 started as early as 1967, when Dubois and co-workers observed electronic absorption spectra belonging to theX 1 A 1 -Ã 1 B 1 transition of this radical for the rst time. 8 It was not ascertained that whether the lower 1 A 1 state of the observed transition was the ground state or there was a lower-lying triplet state, as in CH 2 , would be the ground state until Milligan and Wirsam's work conrmed that the lower state of the previously observed electronic transition of singlet SiH 2 , is the ground state 9,10 and Apeloig and co-workers explained why CH 2 is a ground state triplet while SiH 2 is a ground state singlet.…”