Analysis of the Alkali Metal Diatomic Spectra

This e-book illustrates the complementarity of molecular beam (MB) spectra and ultracold molecule (UM) spectra in unraveling the complex electronic spectra of diatomic alkali metal molecules, using KRb as the prime example. The book goes on to show, somewhat remarkably, that in the case of the diatomic alkali metal molecules such as KRb, the spectroscopic assignments of the ultracold molecule spectra are completely assignable given the spectroscopic assignments of the molecular beam spectra. This is shown explicitly in the case of KRb. It is expected that there will be similar advantages for more complex diatomic molecules. Also, a new type of comparison spectrum is discussed here: the MB × UM spectrum, in which case the MB spectrum and the UM spectrum are plotted as a function of the energy of the excited electronic level being excited, and then the spectra are simply multiplied at each excited level energy. Finally it is noted that the comparison spectrum provides powerful insight even when the detailed assignments of the spectra are uncertain. In particular, the Stimulated Raman Adiabatic Passage (STIRAP) method transfers a molecule from an initial state to a final state by a stimulated Raman transition. In the case of ultracold molecules, usually prepared in weakly bound rovibrational levels near the dissociation limit to two ground-state atoms, there is a desire to efficiently transfer these molecules to the lowest rovibrational level of the Xground electronic state. Not only will there be no rovibrationally inelastic collisions for molecules in the lowest rovibrational level, but also it becomes possible to produce a quantum degenerate gas of either Boson molecules (Bose–Einstein condensation) or Fermion molecules.