Isotope-selective dissociation of diatomic molecules by terahertz optical pulses

We propose a method for isotope-selective dissociation of diatomic molecules in the gas phase by using two kinds of terahertz-pulse fields. The first field consists of a train of pulses, composing a frequency comb, which excites only the selected isotope into a highly rotationally-excited state. The second field dissociates the excited molecules by further rovibrational excitations. We numerically demonstrate the applicability of the proposed scheme by molecular wave-packet computations using the lithium chlorides Li7Cl35 and Li7Cl37. Nearly 20% of the Li7Cl37 in the lowest rovibrational state is dissociated in a single interaction of the designed terahertz fields, while the dissociation probability is negligible in Li7Cl35. This scheme is expected to be applicable to the molecular ensemble whose rotational states spread in energy.