Coherence effects in a spin-orbit mixed four-level molecular system coupled by three lasers

We study the EIT and Autler-Townes effect in a spin-orbit mixed four-level molecular system coupled by three lasers. The spin-orbit mixed rovibrational levels are ubiquitous in molecules, which have been widely used in laser spectroscopy. The mixed levels’ characteristics depend on the degree of spin-orbit mixing. The mixing coefficient varies from case to case. The spin–orbit mixed states in such as diatomic molecules have been used as gateways to access some triplet transitions that are not possible in a lot of situations in laser spectroscopy of diatomic molecules. In this study, we show that the mixing coefficients of the singlet-triplet states can be modified using a laser to couple the mixed pair to an auxiliar level. We use density matrix equations for a spin-orbit mixed four-level molecular system to show that the EIT and Autler-Townes can be controlled by a coupling laser.