Predissociation induced by ungerade-gerade symmetry breaking in the B 1Πu state of the 6Li7Li molecule

Unlike the ⁶Li⁶Li and ⁷Li⁷Li isotopomers, the ⁶Li⁷Li molecule exhibits surprisingly high dissociation rates for the levels that lie just above the dissociation limit of the B ¹Π_u state. As shown by Cacciani and Kokoouline [Phys. Rev. Lett. 84, 5296 (2000)] they can be attributed to a coupling between the B ¹Π_u and 1 ¹Π_g states, through the breaking of the ungerade-gerade symmetry. Systematic measurements of these dissociation rates have been performed by discriminating atomic fluorescence from molecular fluorescence in a sub-Doppler experiment involving a beam of lithium dimers and a cw tunable laser beam. Calculations of dissociation rates have been performed in the framework of a perturbative approach, by solving the coupled Schrödinger equations through the use of the mapped Fourier grid representation method. Measured and calculated dissociation rates are in excellent agreement for a unique value of the coupling strength h=0.144 cm^-1.