EXCITED-STATE ABSORPTION AND HYPERPOLARIZABILITY IN SILICON NAPHTHALOCYANINES

The excited-state absorption (ESA) from the first excited singlet, S-1 , and lowest energy excited triplet, T-1, state of a model silicon nap hthalocyanine has been calculated using a multiconfiguration-interacti on (MECI) procedure, in conjunction with semiempirical molecular orbit al theory. The calculations indicate that the ESA from these states ef fectively covers the whole of the visible region when bandwidths are t aken into consideration, thus making silicon naphthalocyanines attract ive candidates for optical limiting applications. The nonlinear optica l susceptibility (molecular second hyperpolarizability) of the ground state, and the S-1 and T-1 excited states, was also calculated, with t he excited slates exhibiting a considerable enhancement in the magnitu de of the calculated nonlinear susceptability, in comparison with the value obtained for the ground state.