Apparent vibrational side-bands in pi-conjugated systems: the case of distyrylbenzene

TL;DR

This paper investigates the temperature-dependent vibrational side-bands in the photoluminescence spectra of distyrylbenzene, revealing an effective single-mode behavior explained by a time-dependent damping model.

Contribution

It introduces a time-dependent damping model to explain the apparent vibrational modes in PL spectra of pi-conjugated systems, highlighting temperature effects.

Findings

Temperature influences vibronic structures in PL spectra.

Effective single-mode behavior emerges at high damping levels.

Vibrational side-bands do not match Raman frequencies of distyrylbenzene.

Abstract

The photoluminescence (PL) spectra of dilute solution and single crystals of distyrylbenzene show unique temperature dependent vibronic structures. The characteristic single frequency progression at high temperatures is modulated by a low frequency progression series at low temperatures. None of the series side band modes corresponds to any of the distyrylbenzene Raman frequencies. We explain these PL properties using a time dependent model with temperature dependent damping, in which the many-mode system is effectively transformed to two- and then to a single "apparent" mode as damping increases.