Laser-assisted ultracold lithium-hydride molecule formation:: stimulated versus spontaneous emission

We investigate the feasibility of forming ultracold LiH from a mixture of the ultracold atomic gases, by using B-1 Pi as an intermediate state in the photoassociation process. Using accurate molecular potential energy curves and dipole transition moments, we calculate and compare two possible schemes to populate vibrational levels of the ground electronic state, X-1 Sigma(+): (1) two-photon stimulated radiative association and (2) excitation to bound levels of the B-1 Pi state, followed by spontaneous emission to the X-1 Sigma(+) state. With laser intensities and atomic densities that are easily attainable experimentally, we find that significant quantities of molecules can be formed in various v, J levels of the electronic ground state. We examine the spontaneous emission cascade which takes place from the upper vibrational levels on a time scale of milliseconds. We discuss the issue of back-stimulation for the two-photon process and ways to mitigate it. Because photon emission in the cascade process does not contribute to trap loss, a sizable population of molecules in v = 0 can be achieved.