Ibrahim Sadiek

HNC Formation Revealed in Low-Temperature Plasmas (LTP)

We report the first experimental observation of hydrogen isocyanide (HNC), the high-energy isomer of HCN, in low-temperature N₂/H₂/CH₄ plasmas. The results were puplished in Physical Chemistry Chemical Physics (January 2026).

Using combined optical frequency comb and quantum cascade laser spectroscopy, we detect both isomers and find HNC concentrations ~10,000 times lower than HCN. This strong suppression of HNC, in contrast to cold interstellar chemistry, reflects plasma kinetics dominated by radical-driven reactions and rapid isomerization. The [HNC]/[HCN] ratio provides a sensitive benchmark for validating plasma chemical models, with implications for plasma-assisted synthesis and surface processing.

HNO Dimerization Validated as a δ¹⁵N Site-Preference Reference

Our recent JACS study shows that nitroxyl (HNO) dimerization under acidic conditions has strong potential as a reproducible chemical reference for N₂O isotopic site preference (δ¹⁵N^SP). Using mid-infrared frequency comb spectroscopy combined with ab initio calculations, we validated the cis-hyponitrous acid pathway as the dominant N₂O formation route at low pH.

This study represents an important step toward standardized, absolute isotopic calibration of N₂O sources, with implications for environmental, atmospheric, and biogeochemical research.

Save the Date: Optica Sensing Congress 2025, July 20 – 24, 2025 at Hilton Long Beach, Long Beach, California, USA

We are excited to announce that Dr. Ibrahim Sadiek will be presenting an invited talk at the Fourier Transform Spectroscopy (FTS) Topical Meeting during the Optica Sensing Congress 2025. His talk, titled: ‘Precision Frequency Comb Spectroscopy: From Complex Halogenated Compounds to Reactive Plasmas’.

Join us to explore how optical frequency comb spectroscopy enhances our understanding of complex halogenated species and reactive molecular plasmas!

We report on an air-spaced virtually imaged phased array (VIPA) spectrometer that resolves the modes of a mid-infrared frequency comb with a repetition rate of 250 MHz, without an optical filter cavity.

With a record spectral resolution of 94 MHz for VIPA, the spectrometer enables precision molecular spectroscopy with high resolution, broad spectral coverage and fast data acquisition.

Tested in low-pressure plasmas, it captured absorption spectra of methane (around 3017 cm⁻¹), hydrogen cyanide, and ammonia (around 3240 cm⁻¹) across 290 cm⁻¹ (8.7 THz). Performance metrics, including Allan-Werle deviation and noise-equivalent absorption, highlight its potential for atmospheric and astrophysical spectroscopy.

Save the dates: The German Physical Society meeting is scheduled for 26 – 29 February at the University of Greifswald, Greifswald, Germany.

Dr. Ibrahim Sadiek is invited to give a talk at the meeting. The talk, titled ‘Insights into the Non-Thermal Character of Molecular Plasmas from Optical Frequency Comb Spectroscopy,’ is scheduled for Wednesday, Feb. 28, 2024, from 11:00 to 11:30, at WW1:HS.

 

If you are attending the DPG, join us in exploring how detailed insights into the non-thermal nature of molecular plasmas are enabled by state-of-the-art optical frequency comb technology. Students from the region, as well as international students, are welcome to explore potential training and work opportunities.

Save the dates: Technical Conference: 05 – 10 May 2024 and The CLEO Hub: 07 – 09 May 2024, at the Charlotte Convention Center in Charlotte, North Carolina, USA.

We are thrilled to announce that Dr. Ibrahim Sadiek, will be presenting an invited talk on ‘Precision Frequency Comb Spectroscopy of Reactive Molecular Plasmas‘ at the ‘S&I 13: Active Optical Sensing; during CLEO 2024’.

 

If you are joining CLEO, join us in exploring how optical frequency comb spectroscopy can help understand the intricate chemistry of non-thermal molecular plasmas.

Two Species–One Wavelength Method Defeats Cross-Sensitivity. This article tackles cross-sensitivity challenges in species concentration detection, a common hurdle in many sensor technologies.

We present a proof-of-principle study to overcome cross-sensitivity by taking advantage of the distinct optical saturation characteristics of different gas mixture components. By controlling the absorption contribution of a selected species by intentional optical saturation, simultaneous and quantitative detection of two interfering species becomes possible even without the need for spectral scanning.

Demonstrated with direct absorption and cavity-ringdown setups, the method offers a new opportunity to further enhance laser-based analyzers for complex gas mixture analysis in environmental and other applications.

2nd “Carbon Recycling Energy Research CenteRecently (CRERC)” International Seminar.

Dr. Ibrahim Sadiek delivered an exclusive presentation at the 2nd Carbon Recycling Energy Research Center (CRERC) International Seminar, held at Ibaraki University in Japan. He showcased the power of absorption spectroscopy with frequency comb lasers, emphasizing their wide bandwidth and exceptional spectral resolution for diagnosing non-thermal quantum states in plasma-generated chemical species.

The seminar sparked discussions on using frequency combs for simultaneous measurements of multiple chemical species in CRERC’s combustion chambers.

Mid-infrared frequency comb spectroscopy shines the way to dynamic process control of plasma nitriding.

In a collaboration between experts from the Leibniz Institute for Plasma Science and Technology (INP), neoplas control, RÜBIG, and Menlo Systems, we’ve achieved a remarkable milestone. Together, we successfuly developed and applied frequency comb-based VIPA (Virtually Imaged Phased Array) diagnostics for precise measurements in plasma nitriding, even under challenging industrial conditions.

Our achievement recently earned recognition in an an article published in Laser Focus World. Stay tuned for further advancements in this dynamic field!

Broadband, High-Resolution Trace Gas Detection Using OFC-PAS

We report optical frequency comb photoacoustic spectroscopy (OFC-PAS), the first photoacoustic detection scheme based on an optical frequency comb. OFC-PAS uniquely combines broadband spectral coverage and high resolution with cantilever-enhanced photoacoustic detection in a small sample volume.

The technique is demonstrated through high-resolution measurements of methane rovibrational spectra, achieving a spectral resolution two orders of magnitude better than previous broadband PAS implementations, along with excellent linearity over a wide dynamic range. OFC-PAS significantly advances multispecies trace gas sensing for environmental and analytical applications.

Dr. Ibrahim Sadiek has received the prestigious “Faculty Prize” for the best PhD thesis from the Faculty of Mathematics and Natural Sciences, Kiel University, Germany.

Dr. Sadiek’s thesis brilliantly bridges spectrometer development, high-resolution spectroscopy, and trace gas detection. Notably, his work introduces an innovative detection scheme for trace gases, with the potential to enhance absorption-based spectrometers significantly.

This achievement was made possible through support from the HOSST program and Kiel’s “Future Ocean” cluster of excellence, both dedicated to interdisciplinary marine sciences research.