The Band Spectrum of Silicon Monofluoride, SiF

The emission spectrum of SiF has been examined in the Schumann and infra-red regions. The system B-A (ν 0, 0 = 11850.8 cm -1 ) is strong, and rotational analysis shows that both states are 2 Σ. A new rotational analysis of the 0, 0 band of the α-system, A-X 2 π, although in substantial agreement with earlier work, confirms the view that state A is 2 Σ + , and not 2 π (case- b ), as has previously been supposed. Violet degraded bands which have tentatively been ascribed to five systems, all with X 2 π as the ground state, are found, partly superimposed, in the region 51 000 to 53 500 cm -1 . Three of the excited states of SiF appear to form a Rydberg series of 2 Σ + states leading to the ground state... π 4 σ 2 , 1 Σ + of SiF + . The ionization potential is found to be 7.2 8 eV. Evidence about the dissociation energy is briefly considered; the best value seems to be D 0 double prime(SiF) similar 125 kcal.