Determination of the ionization and dissociation energiesof the hydrogen molecule

The transition wave number from the EF Σ 1 g + ( v = 0 , N = 1 ) energy level of ortho- H 2 to the 54 p 1 1 ( 0 ) Rydberg state below the X + Σ 2 g + ( v + = 0 , N + = 1 ) ground state of ortho- H 2 + has been measured to be 25 209.997 56 ± ( 0.000 22 ) statistical ± ( 0.000 07 ) systematic cm − 1 . Combining this result with previous experimental and theoretical results for other energy level intervals, the ionization and dissociation energies of the hydrogen molecule have been determined to be 124 417.491 13 ( 37 ) and 36 118.069 62 ( 37 ) cm − 1 , respectively, which represents a precision improvement over previous experimental and theoretical results by more than one order of magnitude. The new value of the ionization energy can be regarded as the most precise and accurate experimental result of this quantity, whereas the dissociation energy is a hybrid experimental-theoretical determination.