HOLE-BURNING STARK SPECTROSCOPY OF J-AGGREGATES

We performed comparative hole burning Stark effect experiments on the monomer and aggregate absorption of PIG-I. The linear Stark effect in the J band is reduced by more than two orders of magnitude as compared to the monomer. Although this result does not comply with straightfor ward exciton theories, it can be explained by imposing structural cons traints on the aggregate. The quadratic Stark effect is significant in the aggregate. At field strengths of about 300 kV/cm, it is as large as the linear contribution.