We propose a theoretical model used for dynamically manipulating an ultracold weakly bound heteronuclear alkali-metal diatomic molecule by a nonresonant single-cycle THz laser pulse. Taking the ${}^6\mathrm{Li}{}^{23}\mathrm{Na}$ molecule as an example, we first calculate the variation of the weakly bound state and quasibound state as a function of external electric field, and then reveal abundant interference patterns during and after the laser pulse due to the superpositions between states involving weakly bound state, scattering state, and quasibound state. Moreover, one can map out the nodes of the probability density of the weakly bound molecules by measuring the wavepacket dynamics.

We establish a theoretical model to analyze the photoassociative spectroscopy of 85Rb 133Cs molecules in the (3)3Σ+ state. The vibrational energy, spin–spin coupling constant, and hyperfine interaction constant of the (3)3Σ+ state are determined based on nine observed vibrational levels. Consequently, the Rydberg–Klein–Rees potential energy curve of the (3)3Σ+ state is obtained and compared with the ab initial potential energy curve. Our model can be adopted to analyze the photoassociative spectroscopy of other heteronuclear alkali-metal diatomic molecules in the (3)3Σ+ state.

We study exotic orbits in the photoassociation process by considering both the vibrational and rotational motions in a classical model. In the presence of rotational motion, the exotic orbits possess regular bound segments even when the total energy exceeds the threshold energy of the interaction potential. Such features of the exotic orbits are interpreted by introducing an effective potential. We employ Lagrangian descriptors and escape time to characterize the phase-space structure and show that exotic orbits are distributed around the stable region in the short-range phase space. We further calculate the photoassociation probability. Our work provides new insights into the dynamical mechanisms of photoassociation processes.