Theoretical treatment of channel mixing in excited Rb₂ and Cs₂ ultracold molecules: determination of predissociation lifetimes with coordinate mapping

An overview is given on the calculations of the predissociation lifetimes for vibrational levels of an excited ultracold molecule, when the vibrational motion extends out to large distances in a potential with asymptotic R^-3 behavior. For demonstration purposes, application to predissociation effects in the O_u⁺ spectrum of Rb₂ and Cs₂ between the ns+np²P _1/2 and ²P_3/2 dissociation limits is discussed in the framework of two-coupled-channel calculations.