Heavy Atom- and Deuterium Isotope Effect in Bis-(Phenylethinyl)-Mercury

The influence of mercury as a heavy atom on the spin orbit coupling is investigated in bis(phenylethinyl)-mercury and its deuterated derivative. From the experimental results we draw the following conclusions: a) the symmetry of the molecule is D2 , b) the large spin orbit coupling of the mercury atom is introduced via djr p^-interaction, c) local a jr-transitions and vibronic coupling are of no importance, d) the weak deuterium effect in the radiationless decay is a consequence of the fact that the triple bonds act as strong energy acceptors.