First observation of a collisionally induced diffuse band of ⁷Li₂ around 452 nm

We report on the first clear observation of a collisionally induced diffuse band of lithium dimer around 452.0 nm in direct single photon excitation using 337.1 nm (N₂) laser radiation from an excimer laser. The band, which is being tentatively assigned to the 2 ¹Σ⁺_u → X ¹Σ⁺_g transition and could only be observed at buffer gas pressures of ≥ 75 mbar, had been theoretically pre dicted. We also report on the other violet band of Li₂ around 458.0 nm, already assigned to the 2 ³Π_g → a ³Σ⁺_u transition. Parametr ic dependences for the two bands are presented. Together with these continuum emissions, a number of strong atomic lithium lines are also observed. A possible correlation between the atomic and continuum emissions is presented which may help in a better understanding of the kinetics of the system.