The frequency-resolved correlations of the fluorescence emitted by a four-level system in the J = 1/2 to J = 1/2 transition driven by a linearly polarized laser field are theoretically investigated. In the cross two-photon correlation of the pi and sigma(+) transitions, we show that VICs can induce the interference of time orderings between the two-photon paths with different dipole moments, which can serve as a good scheme to exhibit the effects of vacuum-induced coherences (VICs). An external magnetic field can cause frequency differences between two-photon paths with different time ordering...
