The effect of pump-2 laser on Autler–Townes splitting in photoelectron spectra of K2 molecule

Abstract

We theoretically investigated Autler–Townes (AT) splitting in the photoelectron spectra of a four-level ladder K₂ molecule driven by pump1–pump2–probe pulses by employing the time-dependent wave packet approach. The effect of pump-2 laser intensity and wavelength on AT splitting was studied for the first time. Triple splitting with asymmetric profiles arises because of the non-resonant excitation. The triple splitting transforms to double splitting when pump-2 detuning approaches ±1/2 times of pump-1 Rabi frequency. The splitting between two side band peaks in the triplet or doublet does not change with the pump-2 laser wavelength. The three peaks shift to a lower energy with a different shift as pump-2 wavelength increases. The magnitude of AT splitting increases with increasing pump-2 laser intensity. The asymptotic behavior of AT splitting with the pump-2 laser intensity are interesting at the threshold point of the near resonant region and far-off resonant region.