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A tomographic laser absorption spectroscopy technique, using mid-wave infrared light sources, is presented as a quantitative method to spatially resolve the mole fraction and temperature in small-diameter reacting flows relevant to the combustion of nitrogen-based fuels and propellants, with particular applicability to the study of green propulsion concepts. Tunable quantum and interband cascade lasers are used to spectrally resolve multiple rovibrational transitions near 4.42 and 5.18 µm to measure N2O, NO, and H2O mole fractions, as well as gas temperature in an axially symmetric H2-N2O premixed jet flame. Signal processing methods for direct N2O thermometry utilizing a Boltzmann regression are detailed for the experiment, including considerations for the tomographic reconstruction of axial and radial profiles of thermochemical structure for the flame. The tomographic absorption spectroscopy technique is demonstrated to recover radially resolved N2O, NO, and H2O mole fractions for multiple planes at different heights above the jet exit, revealing distinct reaction zones in the jet flame associated with the production of each H2O and NO surrounding the relatively cool reactant core containing N2O.
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Rovibrational quantum state resolution of the C 60 fullerene
The unique physical properties of buckminsterfullerene, C60, have attracted intense research activity since its original discovery. Total quantum state–resolved spectroscopy of isolated C60molecules has been of particularly long-standing interest. Such observations have, to date, been unsuccessful owing to the difficulty in preparing cold, gas-phase C60in sufficiently high densities. Here we report high-resolution infrared absorption spectroscopy of C60in the 8.5-micron spectral region (1180 to 1190 wave number). A combination of cryogenic buffer-gas cooling and cavity-enhanced direct frequency comb spectroscopy has enabled the observation of quantum state–resolved rovibrational transitions. Characteristic nuclear spin statistical intensity patterns confirm the indistinguishability of the 60 carbon-12 atoms, while rovibrational fine structure encodes further details of the molecule’s rare icosahedral symmetry.
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- Award ID(s):
- 1734006
- PAR ID:
- 10082715
- Publisher / Repository:
- American Association for the Advancement of Science (AAAS)
- Date Published:
- Journal Name:
- Science
- Volume:
- 363
- Issue:
- 6422
- ISSN:
- 0036-8075
- Page Range / eLocation ID:
- p. 49-54
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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