Population transfer by multiple stimulated Raman scattering

We present results of density matrix calculations describing population transfer in a four level system via stimulated Raman scattering with three laser pulses whose frequencies are in (or nearly in) resonance with the transitions between the levels. A high degree of transfer to the terminal level is possible via transitions through the two intermediate excited levels, despite the large decay rates of both levels compared with the inverse of the laser pulse durations, provided that the pulse timing sequences are correctly adjusted. Hence multiple stimulated Raman scattering can be an efficient method of moving population into a given molecular level.