Enhancement of stimulated Raman scattering by E-V energy transfer and laser deexcitation

The third harmonic of a YAG laser with wavelength at 355 nm dissociated PbI₂ and induced Raman Stokes and anti-Stokes scattering between two photolytic atomic metastable states of Pb. Because of the energy transfer from the 6p²³P₂ to the high vibrational state of molecules such as N₂, CO₂, the final state of Raman scattering 6p²³P₂ was emptied, while the initial state 6p²³P₁ was more populated. This process led to increasing the intensity of Raman scattering. Especially, the 2nd-order Stokes component at 444 nm increased by three orders of magnitude. Furthermore, the 2nd harmonic of the YAG laser was used to exhaust directly the 6p²³P₂ state. Those two desxcitation methods were compared. Besides, an anomalous emission with wavelength at 712 nm was discussed.