Full anisotropy of the stark effect on the 1B2u←1Ag electronic transitions of tetracene and pentacene in a ρ-terphenyl host crystal

Abstract

The results of a low temperature Stark-effect study on the vis~le short axis polarized singlet transitions of tetracene and pentacene are presented and discussed.The full anisotropy of the Stark effect could be obtained reliably only by using bipolar electric field modulation together with an optical multichannel detection system. This system is also briefly described in this paper.Using the anisotropic Lorentz approximation the difference polarizability tensor components are found to be: for tetracene AaLL = 29 +-3 A s, Ac~t/L~/= 25 • 4 A s, AaNN = 5 • 5 A s; and for pentacene ACXLL = 53 • 4 A s, Ac~z~/Lt//= 90 • 8 A s, and AaNN = -11 +-9 A s. The paper emphasizes that these numbers, due to the inherent approximations of the Lorentz approximation, should be handled with great caution.

Recent Results of Single‐Molecule Spectroscopy in Solids

“…14, the position of a molecular absorption line varies quadratically with the applied field strength, i.e., the system exhibits a second-order Stark effect. This is in agreement with earlier measurements on the whole inhomogeneous absorption band [51]. The physical reason is that both the dye and the matrix molecules are centrosymmetric and that the dye molecules have an ordered, symmetrical environment in the crystal.…”

“…Hence, they still perform averages over large numbers of molecules. This becomes obvious, for instance, when an external field is applied to a hole-burning spectrum: Under the influence of an electric field or pressure the hole spectrum is subjected to inhomogeneous broadening [4, 51, since the accidental degeneracy of the lines is lifted.…”

Stark Spectroscopy of Rubrene. I. Electroabsorption Spectroscopy and Molecular Parameters

“…42 The value of Δα ̅ for rubrene (Table 1) has the same order of magnitude to these values but is larger than those for tetracene, unless the correction for the internal field factor f is made. In EA measurements in condensed phase systems, an estimation of the internal field is often an annoying problem in 28 In a simple model to calculate the internal field, it is assumed that the molecule resides in a spherical cavity in a dielectric medium, and then f is given by f = 3ε/(2ε + 1), where ε is the dielectric constant.…”

Optical Stark spectroscopy of solids

“…For a centrosymmetric molecule such as tetracene or pentacene in a centrosymmetric crystal such as p-terphenyl, the Stark effect is predominantly quadratic. In experiments on bulk crystals [83] only the quadratic effect was seen. With the higher resolution and sensitivity of single-molecule techniques [26] a small dipole moment is observed for many of the molecules but the overall effect is dominantly quadratic.…”