Simultaneous single-shot rotation-vibration non-equilibrium thermometry using pure rotational fs/ps CARS coherence beating

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

Research output: Contribution to journalArticlepeer-review

Abstract

We report the development of a simple and sensitive twobeam 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 nonequilibrium plays a key role in the chemistry and thermalization in low-temperature plasmas aswell 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/psCARSmeasurements of a 75TorrN2 DCglowdischarge andwere 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.

Original languageEnglish (US)
Pages (from-to)1351-1354
Number of pages4
JournalOptics Letters
Volume47
Issue number6
DOIs
StatePublished - Mar 15 2022

All Science Journal Classification (ASJC) codes

  • Atomic and Molecular Physics, and Optics

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