A modular laser-induced fluorescence code

LIFSim 4.0

An open-source MATLAB-based tool, simulates absorption, excitation, and emission spectra of diatomic molecules, incorporating effects such as line broadening and quenching based on spectroscopic data. It enables multi-line LIF thermometry for images or single spectra. These tools also enable temperature sensitivity analysis and fitting of excitation spectra.

Version 4.0 achieves a transparent implementation of the models through MATLAB scripts, which are open-source. This implementation targets two audience groups, the first group are researchers with limited programming skills, using livescripts, enabling easy access to individually simulated spectra. The second group are researchers with programming skills for which we provide the documentation of the functions and scripts to enable embedding in complex data analysis workflows.

Terms of use

Using LIFSim via web browser or via downloading the source code is free (license here)! If you used the code (as is or modified) or web-tool in your work, please cite: 

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-72, (2025).

Multi-line LIF temperature imaging

Multi-line laser-induced fluorescence (LIF) spectroscopy is a powerful non-invasive optical diagnostic technique used to measure gas-phase species concentrations and temperature in reactive media. This method is essential for understanding reaction and transport processes in environments such as flames and chemically reacting flows. LIFSim is a modular software for simulating and analyzing LIF spectra of diatomic molecules like NO, SiO, OH, O₂, and more.

LIF species concentration 

The LIF signal intensity depends on a set of spectroscopic and physical constants and variables, which is proportional to the excited species concentration. The measurement strategy involves the excitation of molecules with a laser at specific wavelengths, causing them to fluoresce. By analyzing the emitted fluorescence spectra and spectral intensities, we can determine species concentrations and potential interference. Multi-line LIF enhances this technique by using multiple excitation wavelengths to capture the temperature-dependent population distribution of quantum states to determine the gas temperature. This method is particularly useful for species such as NO, SiO, OH, O₂, and more, which are prevalent in reactive flows and indicative of, e.g., pollutant formation and reaction zones.

Studies used LIFSim 4.0

Multi-line OH-LIF for gas-phase temperature and concentration imaging in the SpraySyn burner

S.Karaminejad, A. El Moussawi, T. Dreier, T. Endres, C. Schulz, Appl. Energy Combust. Sci. 16,  100222 (2023), DOI: 10.1016/j.jaecs.2023.100222 

Time-averaged temperature fields inferred via multi-line OH-LIF thermometry for a laminar pilot flame (left) and spray flame (right)

Analyzing 3D fields of refractive index, emission and temperature in spray-flame nanoparticle synthesis via tomographic imaging using multi-simultaneous measurements (TIMes)

F. Martins, C. T. Foo, A. Unterberger, S. Karaminejad, T. Endres, K. Mohri, Appl. Energy Combust. Sci. 16,  100213 (2023), DOI: 10.1016/j.jaecs.2023.100213

Averaged 2D fields of temperature based on two-color tomographic salt emission thermometry using TIMes (left half) and relative absolute difference from multi-line OH PLIF temperature measurements (right half)

LIF-imaging of temperature and iron-atom concentration in iron nitrate doped low-pressure aerosol flat flames

S Apazeller, S. Karaminejad, M. Nanjaiah, H. Wiggers, T. Endres, I. Wlokas, C. Schulz, Appl. Energy Combust. Sci. 16, 100199 (2023), DOI: 10.1016/j.jaecs.2023.100199

2D temperature distribution of the CH₄/O₂ flame with precursor aerosol of 0.2 mol/l INN in BuOH. OH-LIF thermometry (left), 3D simulation (right).

A hydrogen-based burner concept for pilot-scale spray-flame synthesis of nanoparticles: Investigation of flames and iron oxide product materials

M. Unterberg, M. Prenting, M. Sieber, S. Schimek, C. Paschereit, T. Hülser, T. Endres, C. Schulz, H. Wiggers, S. Schnurre, Appl. Energy Combust. Sci. 15,  100165 (2023), DOI: 10.1016/j.jaecs.2023.100165

 Spatially resolved time-averaged gas-temperature maps using multi-line NO-LIF thermometry of pilot scale flames 

Multi-line SiO fluorescence imaging in the flame synthesis of silica nanoparticles from SiCl₄

History

LIFSim was developed by Bessler et al. [1, 2] and originally tailored for simulating and fitting NO and O₂ emission/LIF excitation spectra. One focus of LIFSim was to enable selective and quantitative LIF measurements at elevated pressure conditions relevant for pollutant formation in practical combustion. Therefore, line-broadening and -shift were related to experimental measurements in high-pressure flames. As interference of hot O₂ can be relevant for selective NO detection [1, 3, 4], this species was also included from the beginning. LIFSim 1 was developed 1995–1996 by Volker Sick [5]; it included basic functionality for simulating LIF excitation spectra for the NO gamma bands. For LIFSim 2 (1999 by Wolfgang Bessler), the usability of the original code was improved. Key functionalities were added for LIFSim 3 (2000-2004 by Wolfgang Bessler). This included the simulation of UV absorption spectra and LIF emission spectra of NO and O₂, and various tools such as fitting functionalities and sensitivity analysis. It also considered newer quenching data based on the work of Settersten et al. [6]. In 2004, LIFSim 3 was introduced as an online version through a web interface that provided easy access to simulating spectra under various practically relevant conditions, frequently applied in the community. For all these versions, the source code was not available to a larger community and therefore, interruptions in the operation of the website sometimes affected the usability.

References

[1] W.G. Bessler, C. Schulz, T. Lee, J.B. Jeffries, R.K. Hanson, Strategies for laser-induced fluorescence detection of nitric oxide in high-pressure flames. I. A-X(0,0) excitation, Appl. Opt. 41, 3547-3557 (2002)
[2] W.G. Bessler, C. Schulz, V. Sick, J.W. Daily, A versatile modeling tool for nitric oxide LIF spectra, Proceedings of the Third Joint Meeting of the U.S. Sections of The Combustion Institute, Chicago, 2003.
[3] W.G.Bessler, C. Schulz, T. Lee, J.B. Jeffries, R.K. Hanson, Strategies forlaser-induced fluorescence detection of nitric oxide in high-pressure flames.II. A-X(0,1) excitation, Appl. Opt. 42, 2031-2042 (2003)
[4] W.G.Bessler, C. Schulz, T. Lee, J.B. Jeffries, R.K. Hanson, Strategies forlaser-induced fluorescence detection of nitric oxide in high-pressure flames.III. Comparison of A-X excitation schemes, Appl. Opt. 42,  4922-4936 (2003)
[5] V. Sick, M. Szabadi,Einstein coefficients for oxygen B-X transitions used in LIF experiments withtunable KrF excimer lasers, J. Quant. Spectros. Radiat. Transfer 54,  891-898 (1995)
[6] T.B. Settersten, B.D. Patterson, W.H. Humphries, IV, Radiative lifetimes of NO A²Σ⁺(v′ = ,1,2) and the electronic transition moment of the A²Σ⁺−X²Π system, J. Chem. Phys. 131,  104309 (2009)