Effect of the phase modulation of a light pulse on three-photon absorption in a system without intermediate resonance states

The effect of phase modulation of a femtosecond light pulse on three-photon absorption in a diatomic system is studied. Direct three-photon transitions between the initial and final electronic states are considered. The total populations of the final electronic state are calculated for different modulation types as functions of the parameter describing modulation. It is found that the effect of modulation on the three-photon excitation probability substantially depends on the modulation regime. The results of calculations are compared with available experimental data.