Platt’s notation

We (fl) have reported the photophysical processes of a series of model esters of PET, and tentatively assigned the fluorescence and phosphorescence of the aromatic esters as (n, tt ) transitions, respectively. We (9) also performed an extensive study of the photophysical processes available to dimethyl terephthalate (DMT) in order to relate this monomeric species to the PET polymer. In 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) (Table I), DMT has three major,absorptions which are according to Platt, s notation 191 nm, A- B, e = 40,620 1 mole" cm"1 244 nm, A-dLaT e = 23,880 1 mole-) cm" 289 nm, A U, e = 1780 1 mole")cm. ... 

La and types in Platt s notation. The first state has the excited w-electron distributed on the atoms, i.e-, its nodal planes are across bonds whereas the latter state has its excited ir-electron distributed between atoms with its nodal planes containing the atoms. 

Platt s notation for molecular states is N M lt,pl,c lyStateSymmelry, where N labels the first, second, third, etc., states of the same type, the multiplicity is (25 + 1), A and B states are non-degenerate and degenerate, respectively, and g and u identify symmetric (gerade) and antisymmetric (ungerade) states, respectively. 

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