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Turkish Journal of Physics

Abstract

An exact analytical solution to a three-state photophysical model is presented to explicitly map the time-resolved fluorescence dynamics of a fluorophore under pulsed excitation. As distinct from earlier analytical treatments that primarily focused on transient absorption and total ground-state depletion, the proposed eigenvalue-eigenvector framework captures both transient and steady-state emission responses. The photophysical model accounts for electronic transitions between the singlet ground state, the excited singlet state and a long-lived triplet state, enabling a treatment of excitation, radiative decay, intersystem crossing, together with triplet-state relaxation. By diagonalizing the rate matrix consisting of phenomenological transition rates, closed-form expressions for the time-dependent and steady-state populations are obtained, revealing a clear separation of time scales governing fluorescence dynamics. The analytical solution is then applied to the rhodamine-based CF640R dye with an aim to investigate population redistribution as a function of arbitrary pulse duration and excitation irradiance in the nanosecond-to-millisecond time window. The computational results demonstrate that pulsed excitation enables the resolution of triplet-state dynamics, which strongly influence the excitation-dependent fluorescence behavior arising from the singlet excited state. Beyond the specific case of CF640R, the presented analytical treatment establishes a general and physically adaptive framework for analyzing excitation-duration and irradiance-dependent fluorescence behavior of diverse fluorescent chromophores with long-lived, nonemissive electronic states in condensed phases.

Author ORCID Identifier

BARIŞ DEMİRBAY: 0000-0002-5454-7437

DOI

10.55730/1300-0101.2812

Keywords

Photophysics, chromophore, nonluminescent states, time-resolved fluorescence, analytical solution, eigenvalue-eigenvector analysis

First Page

192

Last Page

203

Publisher

The Scientific and Technological Research Council of Türkiye (TÜBİTAK)

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

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