Luis Bonah

Workgroup of Prof. Schlemmer

I. Physikalisches Institut, Universität zu Köln
Zülpicher Straße 77, 50937 Köln, Germany

Research Interests

DM-DR Spectroscopy

Double modulation double resonance spectroscopy opens up new and innovative ways of analyzing molecules

DM-DR Spectroscopy

The most basic abbsorption experiment consists of a source, an absorption cell and a detector. For each frequencies the transmission is measured resulting in a spectrum. However, the assignment of the obtained lines can be complicated, especially for complex and complicated molecules which have a dense spectrum.

The Double Resonance (DR) and Double-Modulation Double-Resonance (DM-DR) techniques are two possible solutions for this problem. They use a second frequency source, the so-called pump source. The pump source allows to manipulate the levels of a known transition. By comparing the spectra with and without the pump source we can identify transitions sharing an energy level of the known transition. The DM-DR technique does this comparison in real-time, resulting in a spectrum that only consists of transitions sharing an energy level with the pumped transition. This drastically simplifies assigning quantum numbers to the lines in the spectrum and allows to unambiguously assign transitions in complicated and dense spectra.

See our paper Millimeter-millimeter-wave double-modulation double-resonance spectroscopy for more information on this topic.

Automation

Automating repetitive tasks to allow for spending more time on the interesting tasks

Automation

To allow myself to spend more time on new and exciting things I like to automate or speed up tasks that are already undersood. Some projects in this direction are a new measurement software for our absorption experiments or tools for the analysis of spectra, which can be found in the projects area.

LLWP is a software for the analysis of spectra that uses Loomis-Wood plots to enhance the efficiency and confidence of the assignment process. In addition to its main functionality, the software provides multiple modules for an extended analysis.

Pyckett is a Python package for reading and writing to formats of Herb Picketts SPFIT/SPCAT suite of programs. Additionally, the package can be used to run SPFIT and SPCAT. This allows to create artificial spectra fully automatically, to test different new parameters and many other cool things that are quite teadious by hand.

Picture showing typical molecular pattern

High-Precision Spectroscopy

Performing high-precision spectroscopy of complex organic molecules

High-Precision Spectroscopy

In space, there are places so far away that no human would survive traveling there, at least not with our current forms of traveling. Nonetheless, we have a good understanding of some of these places. How do we obtain information about these places without ever having been there? The answer is, that these places send information towards us via the light emitted from them. Here on earth, we detect this light and extract the information from the light spectrum. The basic principle is, that each atom or molecule has its own distinctive spectrum which identifies it unambiguously. This is why we call these spectra the spectroscopic fingerprints of the molecule.

To record these spectroscopic fingerprints we use high-precision spectroscopy in our laboratories. Then we can analyze the measured spectra and construct a matching quantum mechanical model. With these models we can predict transitions for these molecules. This allows astronomers to find the molecules in space and, due to the quantum mechanical model, to also identify various physical conditions in these places, like the pressure or temperature.

The predictions and models are available in our own Cologne Database for Molecular Spectroscopy (CDMS).

Publications

High-Resolution Infrared Spectroscopy and ASAP Analysis of Cyclopentadiene: The Vibrational Modes below 860 cm⁻¹ and the ν₂₁ Mode at 961 cm⁻¹ L. Bonah, M.-A. Martin-Drumel, O. Pirali, F. Tonolo, M. Nonne, M. Melosso, L. Bizzocchi, C. Puzzarini, J.-C. Guillemin, C.P. Endres, S. Schlemmer, and S. Thorwirth ACS Earth Space Chem. 9, XXX (2026) arXiv

Analyzing Rotational Spectra of Complex Organic Molecules L. Bonah PhD Thesis, Universität zu Köln KUPS

Leveraging MMW–MMW Double Resonance Spectroscopy to Understand the Pure Rotational Spectrum of Glycidaldehyde and 17 of Its Vibrationally Excited States L. Bonah, J.-C. Guillemin, A. Belloche, S. Thorwirth, H.S.P. Müller, and S. Schlemmer ACS Earth Space Chem. 9, 864 (2025) arXiv

Extending the rotational spectrum of cyclopentadiene towards higher frequencies and vibrational states L. Bonah, B. Helmstaedter, J.-C. Guillemin, S. Schlemmer, and S. Thorwirth J. Mol. Spectrosc. 408, 111967 (2025) arXiv

On the Spectroscopy of Phosphaalkynes: Millimeter- and Submillimeter-Wave Study of C₂H₅CP L. Bonah, S. Schlemmer, J.-C. Guillemin, M.E. Harding, and S. Thorwirth J. Phys. Chem. A 128, 4859 (2024) arXiv

Hyperfine-Resolved Rotational Spectroscopy of HCNH⁺ W.G.D.P. Silva, L. Bonah, P.C. Schmid, S. Schlemmer, and O. Asvany J. Chem. Phys. 160, 071101 (2024) arXiv

Gas-Phase Infrared Action Spectroscopy of CH₂Cl⁺ and CH₃ClH⁺: Likely Protagonists in Chlorine Astrochemistry S. Thorwirth, K. Steenbakkers, T. Danowski, P.C. Schmid, L. Bonah, O. Asvany, S. Brünken, and S. Schlemmer Molecules 29, 665 (2024) Molecules

Astronomical CH₃⁺ rovibrational assignments P.B. Changala, N.L. Chen, H.L. Le, B. Gans, K. Steenbakkers, T. Salomon, L. Bonah, I. Schroetter, A. Canin, M.-A. Martin-Drumel, U. Jacovella, E. Dartois, S. Boyé-Péronne, C. Alcaraz, O. Asvany, S. Brünken, S. Thorwirth, S. Schlemmer, J.R. Goicoechea, G. Rouillé, A. Sidhu, R. Chown, D. Van De Putte, B. Trahin, F. Alarcón, O. Berné, E. Habart, and E. Peeters Astron. Astrophys. 680, A19 (2023) HAL

LLWP—A new Loomis-Wood software at the example of Acetone-¹³C₁ L. Bonah, O. Zingsheim, H.S.P. Müller, J.-C. Guillemin, and S. Schlemmer J. Mol. Spectrosc. 388, 111674 (2022) arXiv

Rotational spectroscopy of n-propanol: Aa and Ag conformers O. Zingsheim, J. Maßen, H.S.P. Müller, B. Heyne, M. Fatima, L. Bonah, A. Belloche, F. Lewen, and S. Schlemmer Astron. Astrophys. 662, A111 (2022) arXiv

(Sub-)millimeter-wave spectroscopy of gauche-propanal O. Zingsheim, H.S.P. Müller, L. Bonah, F. Lewen, S. Thorwirth, and S. Schlemmer J. Mol. Spectrosc. 384, 111565 (2022) arXiv

Internal rotation arena: Program performances on the low barrier problem of 4-methylacetophenone S. Herbers, O. Zingsheim, H.V.L. Nguyen, L. Bonah, B. Heyne, N. Wehres, and S. Schlemmer J. Chem. Phys. 155, 224302 (2021) HAL

Millimeter-millimeter-wave double-modulation double-resonance spectroscopy O. Zingsheim, L. Bonah, F. Lewen, S. Thorwirth, H.S.P. Müller, and S. Schlemmer J. Mol. Spectrosc. 381, 111519 (2021) arXiv

SOLEIL and ALMA views on prototypical organic nitriles: C₂H₅CN M.-A. Martin-Drumel, O. Zingsheim, L. Bonah, O. Pirali, T. Zhang, A. Sanchez-Monge, T. Möller, N. Wehres, P. Schilke, M.C. McCarthy, S. Schlemmer, P. Caselli, and S. Thorwirth J. Mol. Spectrosc. 375, 111392 (2021) HAL

High-Resolution Infrared Spectroscopy and ASAP Analysis of Cyclopentadiene

The spectroscopic fingerprints of vibrationally excited states of astronomical molecules are interesting for multiple reasons. They are excellent temperature probes of the corresponding astronomical ...

LLWP — A new Loomis-Wood Software at the Example of Acetone-¹³C₁

Acetone-¹³C₁ is a complex organic molecule with two internal methyl (-CH₃) rotors having relatively low effective barriers to internal rotation of about 249 cm^-1 ...

Teaser image for paper on DM-DR spectroscopy

Millimeter-millimeter-wave double-modulation double-resonance spectroscopy

A new millimeter- to millimeter-wave double-modulation double-resonance scheme has been applied to record spectra of two astronomically relevant complex organic molecules ...