A2: Ro-vibrational distribution measurement in transient discharges by coherent anti-Stokes Raman scattering

Principal Investigators: U. Czarnetzki, D. Luggenhölscher

Team

Czarnetzki, Uwe (Principal Investigator)

Luggenhölscher, Dirk (Principal Investigator)

Kuhfeld, Jan (PhD)

Busch, Christian (PhD)

Description

Vibrational (and rotational) excited molecules play a key role in plasma chemistry since due to their high internal energy they strongly affect the chemical processes. An open question is the role of excited states in catalytic reactions. The excitation of the molecules occurs by collisions with energetic electrons present in the plasma and by excitation transfer from already excited molecules. The detailed physical mechanisms and rate constants are often not known or have not been validated in experiments. Further, simulations are generally very involving, in particular in connection with highly transient discharges at atmospheric pressures, where time scales stretch from ps for the electron interaction to μs or even ms for collision transfer and chemical reactions. Therefore, this project aims at the measurement of the ro-vibrational excitation of CO2 and N2 by coherent anti-Stokes Raman scattering (CARS). In addition to the experimental setup also a new analysis procedure has been developed that allows addressing non-equilibrium distribution functions. Further, an analytical model allows ab-initio prediction of the population distributions with electric field data and current measurements taken from project A1. Independent control on plasma density and electric field in ns-discharges is demonstrated. This allows an optimized coupling of almost the entire energy of the electrons in the plasma bulk into vibrational excitation.

Publications

• PIC/MCC simulation for a ns-pulsed glow discharge in nitrogen at sub-atmospheric pressure and analysis of its quasi-steady state physics
  J. Kuhfeld, N. D. Lepikhin, D. Luggenhölscher, U. Czarnetzki, Z. Donkó
  Plasma Sources Sci. Technol. 32 084001 (2023)
  
• Breakdown and quasi-DC phase of a nanosecond discharge. Comparison of Optical Emission Spectroscopy measurements with numerical simulations
  N. D. Lepikhin, J. Kuhfeld, Z. Donkó, D. Luggenhölscher, U. Czarnetzki
  Plasma Sources Sci. Technol. 32 084002 (2023)
  
• Vibrational CARS measurements in a near-atmospheric pressure plasma jet in nitrogen: I. Measurement procedure and results
  J. Kuhfeld, N. Lepikhin, D. Luggenhölscher, U. Czarnetzki
  J. Phys. D: Appl. Phys. 54 305204 (2021)
  
• Vibrational CARS measurements in a near-atmospheric pressure plasma jet in Nitrogen: II. Analysis
  J. Kuhfeld, D. Luggenhölscher, U. Czarnetzki
  J. Phys. D: Appl. Phys. 54 305205 (2021)
  
• Time evolution of CO₂ ro-vibrational excitation in a nanosecond ​discharge measured with quantum cascade laser absorption spectroscopy
  Y. Du, Ts. V. Tsankov, D. Luggenhölscher, U. Czarnetzki
  J. Phys. D: Appl. Phys. 54 365201 (2021)
  
• Nanosecond resolved ro-vibrational CO₂ excitation measurement
  Y. Du, Ts. V. Tsankov, D. Luggenhölscher, U. Czarnetzki
  J. Phys. D: Appl. Phys. 54 34LT02 (2021)
  

Thesis

• Jan Kuhfeld, PhD thesis - 12/2022
  Ro-vibrational distribution measurement in transient discharges by coherent anti-Stokes Raman scattering
• Jutta Püttmann, Bachelor thesis - 09/2019
  Electric Field Measurementsvia EFISH in a CARS Setup

Further reading

• Sensitive Electric Field Measurement by Fluorescence-Dip Spectroscopy of Rydberg States of Atomic Hydrogen
  U. Czarnetzki, D. Luggenhölscher and H.F. Döbele,
  Physical Review Letters 81 (1998) 4592
• Electric field measurement in an atmospheric or higher pressure gas by coherent Raman scattering of nitrogen
  T. Ito, K. Kobayashi, S. Müller, D. Luggenhölscher, U. Czarnetzki, and S. Hamaguchi
  J. Phys. D: Appl. Phys. 42 (2009) 092003