Simultaneous single-shot rotation-vibration non-equilibrium thermometry using pure rotational fs/ps CARS coherence beating. Academic Article uri icon


  • We report the development of a simple and sensitive two-beam hybrid femtosecond/picosecond pure rotational coherent anti-Stokes Raman scattering (fs/ps CARS) method to simultaneously measure the rotational and vibrational temperatures of diatomic molecules. Rotation-vibration non-equilibrium plays a key role in the chemistry and thermalization in low-temperature plasmas as well as thermal loading of hypersonic vehicles. This approach uses time-domain interferences between ground state and vibrationally excited N2 molecules to intentionally induce coherence beating that leads to apparent non-Boltzmann distributions in the pure rotational spectra. These distortions enable simultaneous inference of both the rotational and vibrational temperatures. Coherence beating effects were observed in single-shot fs/ps CARS measurements of a 75 Torr N2 DC glow discharge and were successfully modeled for rotational and vibrational temperature extraction. We show that this method can be more sensitive than a pure rotational fs/ps CARS approach using a spectrally narrow probe pulse. Lastly, we experimentally measured the beat frequencies via Fourier transform of the time-domain response and obtained excellent agreement with the model.

published proceedings

  • Opt Lett

author list (cited authors)

  • Chen, T. Y., Liu, N., Kliewer, C. J., Dogariu, A., Kolemen, E., & Ju, Y.

complete list of authors

  • Chen, Timothy Y||Liu, Ning||Kliewer, Christopher J||Dogariu, Arthur||Kolemen, Egemen||Ju, Yiguang

publication date

  • March 2022