Quantum control of isotope-selective molecular orientation

We investigate quantum control of isotope-selective molecular orientation using optimal control theory. The target in this study is to inversely orient two isotopologues, 7Li37Cl and 7Li35Cl, along the field polarization vector. The Hamiltonian includes dipole and polarization interactions and we prepare two laser sources, one of which is responsible for resonant transitions through the dipole interaction and the other is stronger and responsible for nonresonant transitions through the polarization interaction. Total time of the control pulse is set to twice the rotational period that is defined as the inverse of the J = 1 ← 0 transition frequency (J: the rotational quantum number). As a result of the calculation at 0 K, an optimal field leads to the expectation values of cosθ (θ: the angle between the field polarization vector and the molecular axis) for the two isotopologues, 0.76 and -0.78, indicating that the control is successful. It is found that in the optimal field the resonant and nonresonant pulses cooperatively interact with the molecules to enhance the control efficiency.