Effect of pump-1 laser on Autler–Townes splitting in photoelectron spectrum of K2 molecule**Project supported by the National Natural Science Foundation of China (Grant Nos. 41104094 and 11174119), the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20114324120002), the Research Foundation of Education Bureau of Hunan Province, China (Grant No. 12C0370), and the Scientific Research Foundation

Abstract

We theoretically investigate the Autler–Townes (AT) splitting in the photoelectron spectrum of four-level ladder K2 molecule driven by a pump 1-pump 2-probe pulse via employing the time-dependent wave packet approach. The effects of the pump-1 laser intensity and wavelength on AT splitting are studied for the first time. The magnitude of AT splitting increases with increasing the pump-1 laser intensity. The triple splitting with asymmetric profile occurs due to the nonresonant excitation. The triple structure is transformed into a double structure (near-resonant region), and then becomes a peak (far-off resonant region) progressively as the pump-1 laser is detuned from the resonance wavelength, which can be explained in terms of the asymmetric excitation/population of dressed states. The splitting between adjacent peaks and the splitting between the two sideband peaks in the triplet do not change with the pump-1 pulse wavelength. The three peaks shift toward lower energy with the same shift 1/4*Δ1 as the pump-1 wavelength changes in near-resonant region. The asymptotic behaviors of AT splitting with the pump-1 laser intensity are interesting in the threshold points of the near-resonant region and the far-off resonant region.