  The recently observed transient absorption of the lowest excited state of the
special pair P* at 2710 cm-1 is assigned as a singlet which arises from the
coupling of the two lowest triplets from the two dimer halves. INDO
calculations are used to predict its intensity. The analogy of the coupling
mechanism to the trip-doublet spectrum from P+ is shown and the influence of
the double triplet on the Stark effect of P* is investigated.
