Theory and Spectroscopy for Ultracold KRb Molecules

摘要

The KRb molecule is of interest in part because its two component atoms are quite similar. In particular, the attraction of an outer electron for the K~+ and Rb~+ ion cores is very similar, with the ionization potentials of K and Rb being 35009.8140 and 33690.81 cm~(-1), respectively. Likewise, the first resonant D lines (ns-np) are very similar, 12985.186 and 13042.896 cm~(-1) for K and 12578.950 and 12816.545 cm~(-1) for Rb. Thus an electronic structure calculation must carefully balance the quality of the representations around the two distinct ion cores. The calculation of the electric dipole moment, for example, is very sensitive to this balance [1]. Fortunately, there are several well-balanced calculations of high quality for the potential energy curves of the ground X ~1Σ~+, the metastable a ~3Σ~+, and many other electronic states of KRb [2]- [4], as discussed in [5]-[6]. Experimental observations of KRb are also challenging since normally in a heat pipe oven or molecular beam, the KRb spectra are overlapped with the spectra of K_2 and Rb_2. This difficulty can often be overcome with high resolution laser spectroscopic techniques. In the past 20 years, many such studies of KRb have been carried out, emphasizing the internuclear distance region near R_e, the equilibrium internuclear distance of the X state, as also reviewed and discussed in [5]-[6].