We theoretically investigate two-time intensity–intensity correlation spectroscopy in three-level atoms, a spectroscopic method that allows for direct detection of energy level structures and resonances in complex molecules. We show that in three-level Λ or V -systems, a richer spectroscopic signature is obtained when the applied fields are detuned from the transitions to values other than the typical zero-detuning or two-photon detuning settings. This allows us to identify, in the limit in which the overall decoherence rate from an excited state is much smaller than the Rabi frequency of the driving field, areas of parameter space for a three-level V -system in which low-frequency quantum beats can be generated while still maintaining significant signal amplitude. This may prove advantageous in improving the quality and ease of measurements in quantum beat spectroscopy as this type of experimental technique requires a high degree of time resolution.

中文翻译：

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三能级系统中的强度-强度相关性和低频量子搏动

我们从理论上研究了三能级原子的两次强度-强度相关光谱，该光谱法可直接检测能级结构和复杂分子的共振。我们表明，在三能级Λ或V系统中，当将应用的场从过渡点转变为不同于典型的零失谐或两光子失谐设置的值时，可以获得更丰富的光谱特征。这使我们能够在与激发场的整体去相干率远小于驱动场的拉比频率的极限范围内，识别出三级V系统的参数空间区域，其中低频量子拍可以产生信号，同时仍然保持明显的信号幅度。