Optical Shielding of Destructive Chemical Reactions between Ultracold Ground-State NaRb Molecules

We propose a method to suppress the chemical reactions between ultracold bosonic ground-state (NaRb)-Na-23-Rb-87 molecules based on optical shielding. By applying a laser with a frequency blue-detuned from the transition between the lowest rovibrational level of the electronic ground state X-1 Sigma(+)(v(X) = 0; j(X) = 0), and the long-lived excited level b(3)Pi(0)(v(b) = 0; j(b) = 1), the long-range dipole-dipole interaction between the colliding molecules can be engineered, leading to a dramatic suppression of reactive and photoinduced inelastic collisions, for both linear and circular laser polarizations. We demonstrate that the spontaneous emission from b(3)Pi(0)(v(b) = 0; j(b) = 1) does not deteriorate the shielding process. This opens the possibility for a strong increase of the lifetime of cold molecule traps and for an efficient evaporative cooling. We also anticipate that the proposed mechanism is valid for alkali-metal diatomics with sufficiently large dipole-dipole interactions.