Higher-order Stark effect on single-molecules

Stark effect experiments have been performed on terrylene (Tr) and 2.3.7.8-di-(peri-naphthylen)-pyren (DPNP) molecules, both, in a n-hexadecane Shpol'skii matrix by single molecule spectroscopy technique at low temperatures. Electric field was applied to the samples in a range of up to 20 kV/cm. The differences between the dipole moments in the ground and first excited states have been calculated from the experimental data. The molecules showed mostly a linear shift in an external electric field and the contribution of the quadratic shift was rather small. A few molecules have demonstrated higher than linear or quadratic Stark effect, their spectra are presented and discussed. (C) 2002 Elsevier Science B.V. All rights reserved.