Temperature Dependence of Fluorescence

This repository provides MATLAB (live) scripts for analyzing the temperature dependence of laser-induced fluorescence (LIF) signals in gas-phase species, with a particular focus on NO and OH. It simulates excitation and absorption spectra across a defined temperature range and evaluates the temperature sensitivity of selected absorption transitions using simulated flame data.

Description

The repository contains two MATLAB (live) scripts where the temperature dependence of the absorption spectrum (tempDependenceABS.mlx) and fluorescence excitation spectrum (tempDependenceFLUO.mlx) are calculated for a single species (e.g., NO, OH). More specifically, the scripts perform the following steps:

• Loads flame conditions and species concentration profiles.
• Defines a temperature range and calculates the absorption or the fluorescence excitation spectrum for each temperature.
• Filters spectral lines based on laser and detection parameters.
• Calculates the temperature sensitivity ($dI/dT$) of the most intense transitions.
• Outputs the least temperature dependent transitions for experimental targeting.

The final result is a colored excitation spectrum map with overlayed labels for the least temperature sensitive peaks.

History

• First public release: May 2025.

Author(s)

👤 André Silva Correia, 0009-0004-6075-4530, Technische Universiteit Delft – Author and Maintainer

Contributors

👤 Francesca De Domenico, 0000-0002-5922-0118, Technische Universiteit Delft – Reviewer

👤 Arvind Gangoli Rao, 0000-0002-9558-8171, Technische Universiteit Delft – Reviewer

👤 Francesco Mazza, 0000-0003-4406-8034, Technische Universiteit Delft – Reviewer

👤 Leonardo Castellanos, Technische Universiteit Delft – Reviewer

Table of Contents

• Description
• History
• Author(s)
• Requirements
• Structure
• Usage
• License
• References
• Citation
• Would you like to contribute?

Requirements

• MATLAB R2020b or later
• LIFSIM v4.0 library (required and initialized via init.m)

The MATLAB (live) scripts (.mlx) have run on MATLAB R2025a with the following MATLAB add-ons: - Signal Processing Toolbox
- Deep Learning Toolbox
- Statistics and Machine Learning Toolbox

Structure

This repository contains the following structure:

. ├── LICENSE ├── README.md ├── init.m ├── input-data │   ├── filters │   │   ├── NO.LaVision.xlsx │   │   └── OH.LaVision.xlsx │   └── gas-compositions │   └── F_PLIF_OH_NO.mat ├── output-data │   ├── tempDependenceABS.png │   └── tempDependenceFLUO.png │   ├── dIdT_ABS.mat │   └── dIdT_FLUO.mat └── src ├── tempDependenceABS.mlx └── tempDependenceFLUO.mlx

The ./src/directory contains the MATLAB (live) scripts where the temperature dependence of the absorption spectrum (tempDependenceABS.mlx) and fluorescence excitation spectrum (tempDependenceFLUO.mlx) are calculated for a single species (e.g., NO, OH, ...).

The ./input-data/ directory contains the filter data and gas-composition data to be provided as input to the MATLAB (live) scripts found in ./src/. ./input-data/filters/*.xlsx include the detection filters to be used with the same format that LIFSIM requires (first collumn - wavelength, second collumn - transmissivity). ./input-data/gas-compositions/F_PLIF_OH_NO.mat includes the following data for a 1D CH4/air free-flame simulation: - Tflame - flame temperature - Y_NO - NO molar concentration - Y_OH - OH molar concentration - z - simulation grid in m - phi - equivalence ratios used for the free-flame simulations (phi).

The ./output-data/ directory contains the expected outputs when running the default settings in the MATLAB (live) scripts. These outputs are also displayed in the MATLAB live scripts themselves. ./output-data/dIdT_ABS.mat and ./output-data/dIdT_FLUO.mat contain the data to reconstruct the output: - Tset includes the set of temperatures used - dI includes the temperature dependence of each excitation lines - excWnum or absWnum include wavenumbers (cm-1) used - spec includes the spectrum intensity within the wavenumbers (cm-1) at the different temperatures used - excWnum_peak or absWnum_peak include wavenumbers (cm-1) of the evaluated excitation lines - spec_peak includes the spectrum intensity (cm-1) of the evaluated excitation lines at the different temperatures used

Usage

In order to run the scripts make sure to specify: - path to where LIFSIM is (LIFSIM_path)
- path to LIFSIM air+NO.csv file (colls_path) - when installing LIFSim, this file would be located in LIFSim/input-data/gas-compositions/ directory
- path to the flame data - e.g., input-data/gas-compositions/F_PLIF_OH_NO.mat
- path to the filter data (pathFilter) - e.g., input-data/filters/NO.LaVision.xlsx

When running the scripts with the default provided values for NO, the expected output are the files found in ./output-data/ directory.

License

The contents of this repository are licensed under a GNU Affero General Public License 3.0 (see LICENSE file).

Copyright notice:

Technische Universiteit Delft hereby disclaims all copyright interest in the program “LIFTempDependence”. It is a Matlab code for analyzing the temperature dependence of laser-induced fluorescence (LIF) signals in gas-phase species written by the Author(s).
Henri Werij, Dean of Faculty of Aerospace Engineering, Technische Universiteit Delft.

© 2025, A. Silva Correia.

References

A. El Moussawi, S. Karaminejad, J. Menser, W. G. Bessler, T. Dreier, T. Endres, C. Schulz, LIFSim, a modular laser-induced fluorescence code for concentration and temperature analysis of diatomic molecules, Appl. Phys. B 131, p-TBD, (2025), in press.

LaVision Spectral Data: https://www.lavision.de

Fundings

This code is part of the project file 20312 of the research programme NWO Talent Programme Veni AES 2022 which is (partly) financed by the Dutch Research Council (NWO).

Citation

If you use this repository in your work, please cite:
A. Silva Correia (2025) LIFTempDependence. Version 1. 4TU.ResearchData. software. https://doi.org/10.4121/dd222007-8c0f-4cde-a642-5e4580324af6 (DOI will become active upon article publication)

Would you like to contribute?

Contributions are welcome! Please open an issue or submit a pull request. Feel free to fork the repository and suggest improvements.