Search results

Sort By:

Limit search:

Excited-State Equilibration and the Fluorescence-Absorption Ratio

100%

Knox R.

Acta Physica Polonica A

1999

vol. 95

issue 1

85-103

In any complex system at temperature T the absorption cross-section and fluorescent power at a given photon energy are connected by a simple relation if the system is in thermal equilibrium while occupying one particular electronic excited state. Although this situation is impossible in principle because of finite excited-state lifetimes, it is often approximated to the extent that the simple relation, which is expressed as a linear function of energy with slope -1/k_{B}T, holds in a variety of cases. (The usual symbols for Boltzmann's constant and absolute temperature are used.) Observed deviations are of two principal kinds: a slope characteristic of some temperature T* other than ambient, and departures from a single pure straight line. The latter may include seemingly random variations and in some cases multiple regions of straight-line behavior. We have recently introduced an effective temperature T*(E), derived from the actual local slope of the putative straight line at energy E, which turns out to be a very sensitive detector of deviations from the ideal and, we believe, from equilibrium in the excited state. Plots of T*(E) display a variety of features. An anomaly in the T*(E) spectrum of chlorophyll a can be analyzed on this model, indicating a second weakly fluorescent state about 70 meV below the well-known Q_{y} band. The cases of chlorophyll and many others are included in a selective review of applications of the universal relation to fluorescent systems.

Refine search results

1 Acta Physica Polonica A

1 1999

1 Knox R.

Search results

Excited-State Equilibration and the Fluorescence-Absorption Ratio