Double Resonance Spectroscopy of the $B"\overline B { }^1\Sigma _u^+ $state of H$_{2 }$above the double well barrier.*

Double resonance spectroscopy via the$EF{ }^1\Sigma _g^+ ,v'_{EF} =6,J'$ state has been used to probe the rovibrational the \textit{ungerade} double-well $B"\overline B { }^1\Sigma _u^+ $state of H$_{2}$. Many transitions to levels of the outer-well and the combined inner and outer-well above the barrier have been observed for the first time by detecting both molecular and atomic ion production as a function of energy by using a time of flight mass spectrometer. While significant perturbations are observed in the energy region above the double-well barrier, assignments to states with dominant inner and outer-well characteristics can still be made. Distinct dynamical behaviors of the levels below, at and above the barrier have also been observed.