Chirped-pulse millimeter-wave spectroscopy for dynamics and kinetics studies of pyrolysis reactions
A Chirped-Pulse millimeter-Wave (CPmmW) spectrometer is applied to the study of chemical reaction products that result from pyrolysis in a Chen nozzle heated to 1000 – 1800 K. Millimeter-wave rotational spectroscopy unambiguously determines, for each polar reaction product, the species, the conforme...
| Main Authors: | , , , , , , , , , , , |
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| Other Authors: | |
| Format: | Article |
| Language: | en_US |
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Royal Society of Chemistry (RSC)
2018
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| Online Access: | http://hdl.handle.net/1721.1/114506 https://orcid.org/0000-0002-7609-4205 |
| _version_ | 1826192850389303296 |
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| author | Vasiliou, AnGayle K. Oldham, James M. David, Donald E. Muenter, John S. Stanton, John F. Suits, Arthur G. Barney Ellison, G. Field, Robert W. Prozument, Kirill Park III, George Barratt Shaver, Rachel Glyn Field, Robert W |
| author2 | Massachusetts Institute of Technology. Department of Chemistry |
| author_facet | Massachusetts Institute of Technology. Department of Chemistry Vasiliou, AnGayle K. Oldham, James M. David, Donald E. Muenter, John S. Stanton, John F. Suits, Arthur G. Barney Ellison, G. Field, Robert W. Prozument, Kirill Park III, George Barratt Shaver, Rachel Glyn Field, Robert W |
| author_sort | Vasiliou, AnGayle K. |
| collection | MIT |
| description | A Chirped-Pulse millimeter-Wave (CPmmW) spectrometer is applied to the study of chemical reaction products that result from pyrolysis in a Chen nozzle heated to 1000 – 1800 K. Millimeter-wave rotational spectroscopy unambiguously determines, for each polar reaction product, the species, the conformers, relative concentrations, conversion percentage from precursor to each product, and, in some cases, vibrational state population distributions. A chirped-pulse spectrometer can, within the frequency range of a single chirp, sample spectral regions of up to ~10 GHz and simultaneously detect many reaction products. Here we introduce a modification to the CPmmW technique in which multiple chirps of different
spectral content are applied to a molecular beam pulse that contains the pyrolysis reaction products. This technique allows for controlled allocation of its sensitivity to specific molecular transitions and effectively doubles the bandwidth of the spectrometer. As an example, the pyrolysis reaction of ethyl nitrite, CH[subscript 3]CH[subscript 2]ONO, is studied at different
temperatures of the Chen reactor, and CH[subscript 3]CHO, H[subscript 2]CO, and HNO products are simultaneously observed, exploiting the multi-chirp CPmmW technique. Rotational and vibrational temperatures of some product molecules are determined. Subsequent to supersonic expansion from the heated nozzle, acetaldehyde molecules display a rotational
temperature of 4 ± 1 K. Vibrational temperatures are found to be controlled by the collisional cooling in the expansion, and to be both species- and vibrational mode-dependent. Rotational transitions of vibrationally excited formaldehyde in levels ν[subscript 4], 2ν[subscript 4], 3ν[subscript 4], ν[subscipt 2], ν[subscript 3], and ν[subscript 6] are observed and effective vibrational temperatures for modes 2, 3, 4, and 6 are determined and
discussed. Keywords: millimeter wave spectroscopy, microwave spectroscopy, broadband rotational spectroscopy, chirped pulse, free induction decay, fast passage, flash pyrolysis, branching, concentration of reaction products, kinetics, dynamics, thermal decomposition, ethyl nitrite,
CH[subscript 3]CH[subscript 2]ONO, C[subscript 2]H[subscript 5]ONO, methyl nitrite, CH[subscript 3]ONO, formaldehyde, acetaldehyde, nitroxyl, H[subscript 2]CO, CH[subscript 2]O, CH[subscript 3]CHO, HNO, multi-chirp, Chen nozzle, pulsed valve, tubular reactor, vibrational relaxation, collisional cooling, vibrational temperature, vibrational population distribution, rotational temperature, Coriolis interaction, ortho, para, nuclear spin statistics. |
| first_indexed | 2024-09-23T09:30:10Z |
| format | Article |
| id | mit-1721.1/114506 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T09:30:10Z |
| publishDate | 2018 |
| publisher | Royal Society of Chemistry (RSC) |
| record_format | dspace |
| spelling | mit-1721.1/1145062022-09-30T14:51:55Z Chirped-pulse millimeter-wave spectroscopy for dynamics and kinetics studies of pyrolysis reactions Vasiliou, AnGayle K. Oldham, James M. David, Donald E. Muenter, John S. Stanton, John F. Suits, Arthur G. Barney Ellison, G. Field, Robert W. Prozument, Kirill Park III, George Barratt Shaver, Rachel Glyn Field, Robert W Massachusetts Institute of Technology. Department of Chemistry Field, Robert, W. Prozument, Kirill Park III, George Barratt Shaver, Rachel Glyn Field, Robert W A Chirped-Pulse millimeter-Wave (CPmmW) spectrometer is applied to the study of chemical reaction products that result from pyrolysis in a Chen nozzle heated to 1000 – 1800 K. Millimeter-wave rotational spectroscopy unambiguously determines, for each polar reaction product, the species, the conformers, relative concentrations, conversion percentage from precursor to each product, and, in some cases, vibrational state population distributions. A chirped-pulse spectrometer can, within the frequency range of a single chirp, sample spectral regions of up to ~10 GHz and simultaneously detect many reaction products. Here we introduce a modification to the CPmmW technique in which multiple chirps of different spectral content are applied to a molecular beam pulse that contains the pyrolysis reaction products. This technique allows for controlled allocation of its sensitivity to specific molecular transitions and effectively doubles the bandwidth of the spectrometer. As an example, the pyrolysis reaction of ethyl nitrite, CH[subscript 3]CH[subscript 2]ONO, is studied at different temperatures of the Chen reactor, and CH[subscript 3]CHO, H[subscript 2]CO, and HNO products are simultaneously observed, exploiting the multi-chirp CPmmW technique. Rotational and vibrational temperatures of some product molecules are determined. Subsequent to supersonic expansion from the heated nozzle, acetaldehyde molecules display a rotational temperature of 4 ± 1 K. Vibrational temperatures are found to be controlled by the collisional cooling in the expansion, and to be both species- and vibrational mode-dependent. Rotational transitions of vibrationally excited formaldehyde in levels ν[subscript 4], 2ν[subscript 4], 3ν[subscript 4], ν[subscipt 2], ν[subscript 3], and ν[subscript 6] are observed and effective vibrational temperatures for modes 2, 3, 4, and 6 are determined and discussed. Keywords: millimeter wave spectroscopy, microwave spectroscopy, broadband rotational spectroscopy, chirped pulse, free induction decay, fast passage, flash pyrolysis, branching, concentration of reaction products, kinetics, dynamics, thermal decomposition, ethyl nitrite, CH[subscript 3]CH[subscript 2]ONO, C[subscript 2]H[subscript 5]ONO, methyl nitrite, CH[subscript 3]ONO, formaldehyde, acetaldehyde, nitroxyl, H[subscript 2]CO, CH[subscript 2]O, CH[subscript 3]CHO, HNO, multi-chirp, Chen nozzle, pulsed valve, tubular reactor, vibrational relaxation, collisional cooling, vibrational temperature, vibrational population distribution, rotational temperature, Coriolis interaction, ortho, para, nuclear spin statistics. United States. Army Research Office (Award 58245-CH-11) 2018-04-03T15:33:26Z 2018-04-03T15:33:26Z 2014-03 Article http://purl.org/eprint/type/JournalArticle 1463-9076 1463-9084 http://hdl.handle.net/1721.1/114506 Prozument, Kirill, et al. “Chirped-Pulse Millimeter-Wave Spectroscopy for Dynamics and Kinetics Studies of Pyrolysis Reactions.” Phys. Chem. Chem. Phys., vol. 16, no. 30, 2014, pp. 15739–51. https://orcid.org/0000-0002-7609-4205 en_US http://dx.doi.org/10.1039/c3cp55352c Physical Chemistry Chemical Physics Creative Commons Attribution-Noncommercial-Share Alike http://creativecommons.org/licenses/by-nc-sa/4.0/ application/pdf Royal Society of Chemistry (RSC) Prof. Field |
| spellingShingle | Vasiliou, AnGayle K. Oldham, James M. David, Donald E. Muenter, John S. Stanton, John F. Suits, Arthur G. Barney Ellison, G. Field, Robert W. Prozument, Kirill Park III, George Barratt Shaver, Rachel Glyn Field, Robert W Chirped-pulse millimeter-wave spectroscopy for dynamics and kinetics studies of pyrolysis reactions |
| title | Chirped-pulse millimeter-wave spectroscopy for dynamics and kinetics studies of pyrolysis reactions |
| title_full | Chirped-pulse millimeter-wave spectroscopy for dynamics and kinetics studies of pyrolysis reactions |
| title_fullStr | Chirped-pulse millimeter-wave spectroscopy for dynamics and kinetics studies of pyrolysis reactions |
| title_full_unstemmed | Chirped-pulse millimeter-wave spectroscopy for dynamics and kinetics studies of pyrolysis reactions |
| title_short | Chirped-pulse millimeter-wave spectroscopy for dynamics and kinetics studies of pyrolysis reactions |
| title_sort | chirped pulse millimeter wave spectroscopy for dynamics and kinetics studies of pyrolysis reactions |
| url | http://hdl.handle.net/1721.1/114506 https://orcid.org/0000-0002-7609-4205 |
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