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Prozument K, Barratt Park G, Shaver RG, Vasiliou AK, Oldham JM, David DE, Muenter JS, Stanton JF, Suits AG, Barney Ellison G, Field RW. Chirped-Pulse millimeter-Wave spectroscopy for dynamics and kinetics studies of pyrolysis reactions. Phys Chem Chem Phys 2015; 16:15739-15751. [PMID: 24756159 DOI: 10.1039/c3cp55352c] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
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, CH3CH2ONO, is studied, and CH3CHO, H2CO, and HNO products are simultaneously observed and quantified, 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 ν4, 2ν4, 3ν4, ν2, ν3, and ν6 are observed and effective vibrational temperatures for modes 2, 3, 4, and 6 are determined and discussed.
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Affiliation(s)
- Kirill Prozument
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139, USA. and Department of Chemistry, Wayne State University, 5101 Cass Ave, Detroit, MI 48202, USA
| | - G Barratt Park
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139, USA.
| | - Rachel G Shaver
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139, USA.
| | - AnGayle K Vasiliou
- Department of Chemistry and Biochemistry, Middlebury College, 276 Bicentennial Way, Middlebury, VT 05753, USA
| | - James M Oldham
- Department of Chemistry, Wayne State University, 5101 Cass Ave, Detroit, MI 48202, USA
| | - Donald E David
- Department of Chemistry and Biochemistry, University of Colorado at Boulder, Cristol Chemistry 58, Boulder, CO 80309, USA
| | - John S Muenter
- Department of Chemistry, University of Rochester, 120 Trustee Road, Rochester, NY 14627, USA
| | - John F Stanton
- Department of Chemistry, The University of Texas at Austin, 1 University Station A5300, Austin, TX 78712-0165, USA
| | - Arthur G Suits
- Department of Chemistry, Wayne State University, 5101 Cass Ave, Detroit, MI 48202, USA
| | - G Barney Ellison
- Department of Chemistry and Biochemistry, University of Colorado at Boulder, Cristol Chemistry 58, Boulder, CO 80309, USA
| | - Robert W Field
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139, USA.
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Kable SH, Knight AEW. Semiempirical Model of Vibrational Relaxation for Estimating Absolute Rate Coefficients. J Phys Chem A 2003. [DOI: 10.1021/jp035516u] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Scott H. Kable
- School of Chemistry, University of Sydney, Sydney, NSW, 2006 Australia
| | - Alan E. W. Knight
- Molecular Dynamics Laboratory, School of Science, Griffith University, Brisbane, QLD, 4111 Australia
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Fernández JA, Puyuelo P, Husain D, Sánchez Rayo MN, Castaño F. Removal rates for the collisional quenching of various vibronic levels of ground state NCO by simple molecules (N2, O2, NO, CO2, N2O, and SO2). J Chem Phys 1997. [DOI: 10.1063/1.473731] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Repond P, Sigrist MW. Photoacoustic spectroscopy on trace gases with continuously tunable CO(2) laser. APPLIED OPTICS 1996; 35:4065-4085. [PMID: 21102812 DOI: 10.1364/ao.35.004065] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
A novel photoacoustic (PA) system that uses a continuously tunable high-pressure CO(2) laser as radiation source is presented. A minimum detectable absorption coefficient of 10(-6) cm(-1) that is limited mainly by the desorption of absorbing species from the cell walls and by residual electromagnetic perturbation of the microphone electronics has currently been achieved. Although a linear dependence of the PA signal on the gas concentration has been observed over 4 orders of magnitude, the dependence on energy exhibits a nonlinear behavior owing to saturation effects in excellent agreement with a theoretical model. The calibration of the laser wavelength is performed by PA measurements on low-pressure CO(2) gas, resulting in an absolute accuracy of ± 10(-2) cm(-1). PA spectra are presented for carbon dioxide (CO(2)), ammonia (NH(3)), ozone (O(3)), ethylene (C(2)H(4)), methanol (CH(3)OH), ethanol (C(2)H(5)OH), and toluene (C(7)H(8)) in large parts of the laser emission range. The expected improvement in detection selectivity compared with that of studies with line-tunable CO(2) lasers is demonstrated with the aid of multicomponent trace-gas mixtures prepared with a gas-mixing unit. Good agreement is obtained between the known concentrations and the concentrations calculated on the basis of a fit with calibration spectra. Finally, the perspectives of the system concerning air analyses are discussed.
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Kapitanov VA, Tikhomirov BA. Pulse photoacoustic technique for the study of vibrational relaxation in gases. APPLIED OPTICS 1995; 34:969-972. [PMID: 21037618 DOI: 10.1364/ao.34.000969] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Characteristic peculiarities of the formation of the photoacoustic-detector signal from excitation of absorbing gas molecules by a short laser pulse (τ(p) « τ(vt)) that allows for the natural oscillations of the microphone membrane are considered. A technique for τ(vt) measurement is proposed on the strength of the finding that the signal form is determined by the microphone membrane oscillation under low pressure (P ≤ 10 Torr). The results of measurement of the τ(vt) of the vibrational state ν(1) + 3ν(3) in H(2)O for the collisions H(2)O-(2)O and H(2)O-air are presented.
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