Title: Time-domain self-broadened and air-broadened nitrogen S-branch Raman linewidths at 80–200 K recorded in an underexpanded jet

Abstract

We report pure-rotational N₂–N₂, N₂–air, and O₂–air S-branch linewidths for temperatures of 80–200 K by measuring the time-dependent decay of rotational Raman coherences in an isentropic free-jet expansion from a sonic nozzle. We recorded pure-rotational hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering (fs/ps CARS) spectra along the axial centerline of the underexpanded jet, within the barrel shock region upstream of the Mach disk. The dephasing of the pure-rotational Raman coherence was monitored using probe-time-delay scans at different axial positions in the jet, corresponding to varying local temperatures and pressures. The local temperature was obtained by fitting CARS spectra acquired at zero probe time delay, where the impact of collisions was minimal. The measured decay of each available Raman transition was fit to a dephasing constant and corrected for the local pressure, which was obtained from the CARS-measured static temperature and thermodynamic relationships for isentropic expansion from the known stagnation state. Nitrogen self-broadened transitions decayed more rapidly than those broadened in air for all temperatures, corresponding to higher Raman linewidths. In general, the measured S-branch linewidths deviated significantly in absolute and relative magnitudes from those predicted by extrapolating the modified exponential gap model to low temperatures. The temperature dependence of the Ramanmore » linewidth for each measured rotational state of nitrogen (J ≤ 10) and oxygen (N ≤ 11) was fit to a temperature-dependent power law over the measurable temperature domain (80–200 K) and extrapolated to both higher rotational states and room temperature. Furthermore, the measured and modeled low-temperature linewidth data provided here will aid low temperature gas-phase pressure measurements with fs/ps CARS.« less

Authors:

Retter, Jonathan E.  ^[1];

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• Search DOE PAGES for ORCID "0000-0002-6812-163X"

Koll, Matthew ^[2]; Richardson, Daniel R.  ^[3];

• Search DOE PAGES for author "Richardson, Daniel R."
• Search DOE PAGES for ORCID "0000-0001-7852-5657"

Kearney, Sean P. ^[3]

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+ Show Author Affiliations

1. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); National Inst. of Aerospace, Hampton, VA (United States)
2. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Univ. of Illinois at Urbana-Champaign, IL (United States)
3. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

Publication Date:

Thu Apr 28 00:00:00 EDT 2022

Research Org.:

Univ. of Illinois at Urbana-Champaign, IL (United States); Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

Sponsoring Org.:

USDOE National Nuclear Security Administration (NNSA)

OSTI Identifier:

1870160

Alternate Identifier(s):

OSTI ID: 1867912; OSTI ID: 1872025

Report Number(s):

SAND2022-6678J
Journal ID: ISSN 0021-9606; TRN: US2306498

Grant/Contract Number:  

NA0003969; NA0003525; NA0002374; NA0003963

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Chemical Physics

Additional Journal Information:

Journal Volume: 156; Journal Issue: 19; Journal ID: ISSN 0021-9606

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Coherent anti Stokes Raman scattering; Temperature metrology; Ultrafast laser spectroscopy; Collisional broadening; Measuring instruments; Raman spectroscopy; Spectrograms; Rotational spectra; coherent anti Stokes Raman scattering; temperature metrology; ultrafast laser spectroscopy; collisional broadening; measuring instruments; spectrograms; rotational spectra