【摘要】：Single-loop cyclic three-level(?-type) configuration of chiral molecules was used for enantio-separation in many theoretical works [1-5]. Considering the effect of molecular rotation, this simple single-loop configuration is generally replaced by a complicated multiple-loop configuration containing multiple degenerated magnetic sub-levels and the ability of the enantio-separation methods is suppressed [6]. For chiral asymmetric top molecules, we propose a scheme to construct a real single-loop ?-type configuration with no connections to other states by applying three microwave fields with appropriate polarization vectors and frequencies. With our scheme, the previous theoretical proposals for enantio-separation based on single-loop ?-type configurations can be experimentally realized when the molecular rotation is considered.