ELECTRONIC STRUCTURES OF EXCITED AROMATIC COMPOUNDS

Open shell (restricted and unrestricted) SCF MO calculations have been carried out for the lowest triplet states of some aromatic compounds. Their lowest excited singlet states have been calculated by SCF MO CI method for closed shell. All of the calculations have been performed within the framework of the variable $\\beta$ approximation. In addition to the two center electron repulsion integrals, the so-called NM integrals, normally utilized $(\\gamma_{\\mu \\nu} = 14.395/(r_{\\mu \\nu}+a_{\\mu \\nu}) e.v.)$, a second set, the N integrals, has also been tested. The results are summarized as follows: 1). The lowest triplet state energies can be calculated reliably with the restricted open shell SCF MO method when N-integrals are used. 2). The electron population matrix associated with the lowest excited singlet state $(S_{1})$ tells that the molecular geometry is not greatly varied by $S_{0} \\rightarrow S_{1}$ transition. 3). The electron population matrix associated with the lowest triplet state is remarkably dependent on the method, either closed shell or open shell SCF MO scheme.