Coupling of the green (506-nm) and ultraviolet (342-nm) emission bands of i₂

Collisional coupling between the electronic excited states of I2 that are responsible for the green and ultraviolet (D' → A') bands of the molecule (centered at 506 and 342 nm, respectively) has been studied in electron-beam-pumped mixtures of argon and hydrogen iodide (HI). The dependence of the temporal decay of the green and UV fluorescence waveforms on the buffer-gas pressure demonstrates that the two bands do not originate from a common upper state. The interdependence of the two bands, however, is clear from the disappearance of gain at 506 nm, when an optical cavity having a high Q at 342 nm is installed around the excited medium (Iuv ˜ 30 MW cm^-2). Also, the peak intensity of the UV band is suppressed by more than 40% when a green dye-laser pulse (λ= 503 nm, I ≥ 5 MW cm^-2) is directed along the axis of the active medium.