Excited state, charge transfer absorption spectrym of HgBr in the blue (λ∼447 nm)

Absorption from the lowest-lying ion pair state of HgBr (i.e., Hg ⁺-Br^-:B ²Σ_1/2⁺) has been observed by transient absorption spectroscopy in a pulsed, transverse discharge containing a mixture of Ne, N₂, and HgBr₂ vapor. A highly structured band peaking at ∼447 nm is shown to be associated with charge-transfer transitions from the B ²Σ_1/2 ⁺ state to a higher-lying, covalently bonded (Hg*-Br) state. By pumping the 447 nm transition with a pulsed dye laser while simultaneously monitoring gain on the HgBr (B ²Σ_1/2 ⁺→X ²Σ_1/2⁺) band at 502 nm, the absorption cross section for the blue band was measured to be (3.0±1.5)×10^-17 cm² and the saturation intensity for the transition at 447 nm was determined to be 710±50 kW cm^-2.