  Starting from a mean-field model of the Bose-Einstein condensate dimer, we
reintroduce classically forbidden tunneling through a Bohr-Sommerfeld
quantization approach. We find closed-form approximations to the tunneling
frequency more accurate than those previously obtained using different
techniques. We discuss the central role that tunneling in the self-trapped
regime plays in a quantitatively accurate model of a dissipative dimer leaking
atoms to the environment. Finally, we describe the prospects of experimental
observation of tunneling in the self-trapped regime, both with and without
dissipation.
