Kinetics and spectroscopy of electronically excited BiO obtained by energy transfer from metastable O₂. I. Dependence of excitation on [O ₂ ]

Excitation of electronic states of the BiO molecule in a mixture of Bi vapor and O₂ ( ¹Δ¹Σ) was monitored as a function of the density of the O₂ singlet states. Emission in the 300-900 nm wavelength region was studied under low resolution and assigned to the A(²Π_1/2 ), B(⁴Σ.) and C( ²Δ_3/2 ) states of BiO. The intensity of the emission from the A (ν≥14), B and C states increased while that from A(ν≤ 12) decreased with increasing O₂ (¹Δ) density suggesting that the excitation mechanism for these higher levels involves multiple collisions with O₂ ( ¹Δ ). Emission from BiO C and from several A,ν' and B,ν' states has been observed here for the first time. In addition, emission in the 1400-1600 nm region was observed and studied for the reaction of Bi and low density of O₂ ( ¹Δ) via Fourier transform spectroscopy and is tentatively assigned to previously unobserved low lying 1/2 and 3/2 states of BiO. It is suggested that these states may play a crucial role in the excitation mechanism of the higher states.