A mid-IR laser diagnostic for HCN detection

Ali Elkhazraji, Mohammad Adil, Mhanna Mhanna, Nawaf Abualsaud, Ahmed Ayidh Alsulami, Mohammad Khaled Shakfa, Marco Marangoni, Binod Giri, Aamir Farooq*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


Hydrogen cyanide (HCN) is a major source of prompt-NOx formation especially in fuel-bound nitrogen systems. To date, there is still a significant disagreement between experimental data and theoretical predictions of the rate coefficients of combustion reactions involving HCN as a prompt-NOx precursor. Accurate modeling of NOx formation would greatly benefit from a diagnostic capable of performing high-fidelity measurements of HCN formation/consumption time-histories. In this study, a laser diagnostic is developed for sensitive and selective HCN sensing by probing its most intense absorption feature in the mid-infrared (MIR). The diagnostic is based on difference-frequency generation (DFG) between a CO2 gas laser and an external-cavity quantum cascade laser in a nonlinear orientation-patterned gallium arsenide crystal which results in a DFG laser tunable over 11.56 − 15 µm. HCN measurements were carried out at the peak of the Q-branch of its strong ν2 vibrational band near 14 µm. Pressure dependence of the absorption cross-section was investigated at room temperature over the pressure range of 0.07 − 1.07 bar. Temperature-dependent absorption cross-section measurements were conducted behind reflected shock waves over the temperature range of 850 − 3000 K. The diagnostic was demonstrated in reactive experiments in a shock tube where HCN mole fraction time-histories were measured during the thermal decomposition of isoxazole (C3H3NO) and the first-order rate coefficients of C3H3NO → HCN + CH2CO reaction were determined.

Original languageEnglish (US)
Pages (from-to)1485-1493
Number of pages9
JournalProceedings of the Combustion Institute
Issue number1
StatePublished - Jan 2023


  • Absorption cross-section
  • Difference-frequency generation
  • HCN, Isoxazole decomposition
  • Shock tube

ASJC Scopus subject areas

  • General Chemical Engineering
  • Mechanical Engineering
  • Physical and Theoretical Chemistry


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