The Experts below are selected from a list of 228 Experts worldwide ranked by ideXlab platform
Arthur G Suits - One of the best experts on this subject based on the ideXlab platform.
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a chirped pulse fourier transform microwave Pulsed uniform Flow spectrometer ii performance and applications for reaction dynamics
Journal of Chemical Physics, 2014Co-Authors: Chamara Abeysekera, James M Oldham, Baptiste Joalland, Lindsay N Zack, Kirill Prozument, Ian R Sims, Barratt G Park, Robert W Field, Nuwandi M Ariyasingha, Arthur G SuitsAbstract:This second paper in a series of two reports on the performance of a new instrument for studying chemical reaction dynamics and kinetics at low temperatures. Our approach employs chirped-pulse Fourier-transform microwave (CP-FTMW) spectroscopy to probe photolysis and bimolecular reaction products that are thermalized in Pulsed uniform Flows. Here we detail the development and testing of a new Ka-band CP-FTMW spectrometer in combination with the Pulsed Flow system described in Paper I [J. M. Oldham, C. Abeysekera, B. Joalland, L. N. Zack, K. Prozument, I. R. Sims, G. B. Park, R. W. Field, and A. G. Suits, J. Chem. Phys.141, 154202 (2014)]. This combination delivers broadband spectra with MHz resolution and allows monitoring, on the μs timescale, of the appearance of transient reaction products. Two benchmark reactive systems are used to illustrate and characterize the performance of this new apparatus: the photodissociation of SO2 at 193 nm, for which the vibrational populations of the SO product are monitored, and the reaction between CN and C2H2, for which the HCCCN product is detected in its vibrational ground state. The results show that the combination of these two well-matched techniques, which we refer to as chirped-pulse in uniform Flow, also provides insight into the vibrational and rotational relaxation kinetics of the nascent reaction products. Future directions are discussed, with an emphasis on exploring the low temperature chemistry of complex polyatomic systems.
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a chirped pulse fourier transform microwave Pulsed uniform Flow spectrometer i the low temperature Flow system
Journal of Chemical Physics, 2014Co-Authors: James M Oldham, Chamara Abeysekera, Baptiste Joalland, Lindsay N Zack, Kirill Prozument, Ian R Sims, Barratt G Park, Robert W Field, Arthur G SuitsAbstract:We report the development of a new instrument that combines chirped-pulse microwave spectroscopy with a Pulsed uniform supersonic Flow. This combination promises a nearly universal detection method that can deliver isomer and conformer specific, quantitative detection and spectroscopic characterization of unstable reaction products and intermediates, product vibrational distributions, and molecular excited states. This first paper in a series of two presents a new Pulsed-Flow design, at the heart of which is a fast, high-throughput Pulsed valve driven by a piezoelectric stack actuator. Uniform Flows at temperatures as low as 20 K were readily achieved with only modest pumping requirements, as demonstrated by impact pressure measurements and pure rotational spectroscopy. The proposed technique will be suitable for application in diverse fields including fundamental studies in spectroscopy, kinetics, and reaction dynamics.
Chamara Abeysekera - One of the best experts on this subject based on the ideXlab platform.
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a chirped pulse fourier transform microwave Pulsed uniform Flow spectrometer ii performance and applications for reaction dynamics
Journal of Chemical Physics, 2014Co-Authors: Chamara Abeysekera, James M Oldham, Baptiste Joalland, Lindsay N Zack, Kirill Prozument, Ian R Sims, Barratt G Park, Robert W Field, Nuwandi M Ariyasingha, Arthur G SuitsAbstract:This second paper in a series of two reports on the performance of a new instrument for studying chemical reaction dynamics and kinetics at low temperatures. Our approach employs chirped-pulse Fourier-transform microwave (CP-FTMW) spectroscopy to probe photolysis and bimolecular reaction products that are thermalized in Pulsed uniform Flows. Here we detail the development and testing of a new Ka-band CP-FTMW spectrometer in combination with the Pulsed Flow system described in Paper I [J. M. Oldham, C. Abeysekera, B. Joalland, L. N. Zack, K. Prozument, I. R. Sims, G. B. Park, R. W. Field, and A. G. Suits, J. Chem. Phys.141, 154202 (2014)]. This combination delivers broadband spectra with MHz resolution and allows monitoring, on the μs timescale, of the appearance of transient reaction products. Two benchmark reactive systems are used to illustrate and characterize the performance of this new apparatus: the photodissociation of SO2 at 193 nm, for which the vibrational populations of the SO product are monitored, and the reaction between CN and C2H2, for which the HCCCN product is detected in its vibrational ground state. The results show that the combination of these two well-matched techniques, which we refer to as chirped-pulse in uniform Flow, also provides insight into the vibrational and rotational relaxation kinetics of the nascent reaction products. Future directions are discussed, with an emphasis on exploring the low temperature chemistry of complex polyatomic systems.
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a chirped pulse fourier transform microwave Pulsed uniform Flow spectrometer i the low temperature Flow system
Journal of Chemical Physics, 2014Co-Authors: James M Oldham, Chamara Abeysekera, Baptiste Joalland, Lindsay N Zack, Kirill Prozument, Ian R Sims, Barratt G Park, Robert W Field, Arthur G SuitsAbstract:We report the development of a new instrument that combines chirped-pulse microwave spectroscopy with a Pulsed uniform supersonic Flow. This combination promises a nearly universal detection method that can deliver isomer and conformer specific, quantitative detection and spectroscopic characterization of unstable reaction products and intermediates, product vibrational distributions, and molecular excited states. This first paper in a series of two presents a new Pulsed-Flow design, at the heart of which is a fast, high-throughput Pulsed valve driven by a piezoelectric stack actuator. Uniform Flows at temperatures as low as 20 K were readily achieved with only modest pumping requirements, as demonstrated by impact pressure measurements and pure rotational spectroscopy. The proposed technique will be suitable for application in diverse fields including fundamental studies in spectroscopy, kinetics, and reaction dynamics.
James M Oldham - One of the best experts on this subject based on the ideXlab platform.
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a chirped pulse fourier transform microwave Pulsed uniform Flow spectrometer ii performance and applications for reaction dynamics
Journal of Chemical Physics, 2014Co-Authors: Chamara Abeysekera, James M Oldham, Baptiste Joalland, Lindsay N Zack, Kirill Prozument, Ian R Sims, Barratt G Park, Robert W Field, Nuwandi M Ariyasingha, Arthur G SuitsAbstract:This second paper in a series of two reports on the performance of a new instrument for studying chemical reaction dynamics and kinetics at low temperatures. Our approach employs chirped-pulse Fourier-transform microwave (CP-FTMW) spectroscopy to probe photolysis and bimolecular reaction products that are thermalized in Pulsed uniform Flows. Here we detail the development and testing of a new Ka-band CP-FTMW spectrometer in combination with the Pulsed Flow system described in Paper I [J. M. Oldham, C. Abeysekera, B. Joalland, L. N. Zack, K. Prozument, I. R. Sims, G. B. Park, R. W. Field, and A. G. Suits, J. Chem. Phys.141, 154202 (2014)]. This combination delivers broadband spectra with MHz resolution and allows monitoring, on the μs timescale, of the appearance of transient reaction products. Two benchmark reactive systems are used to illustrate and characterize the performance of this new apparatus: the photodissociation of SO2 at 193 nm, for which the vibrational populations of the SO product are monitored, and the reaction between CN and C2H2, for which the HCCCN product is detected in its vibrational ground state. The results show that the combination of these two well-matched techniques, which we refer to as chirped-pulse in uniform Flow, also provides insight into the vibrational and rotational relaxation kinetics of the nascent reaction products. Future directions are discussed, with an emphasis on exploring the low temperature chemistry of complex polyatomic systems.
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a chirped pulse fourier transform microwave Pulsed uniform Flow spectrometer i the low temperature Flow system
Journal of Chemical Physics, 2014Co-Authors: James M Oldham, Chamara Abeysekera, Baptiste Joalland, Lindsay N Zack, Kirill Prozument, Ian R Sims, Barratt G Park, Robert W Field, Arthur G SuitsAbstract:We report the development of a new instrument that combines chirped-pulse microwave spectroscopy with a Pulsed uniform supersonic Flow. This combination promises a nearly universal detection method that can deliver isomer and conformer specific, quantitative detection and spectroscopic characterization of unstable reaction products and intermediates, product vibrational distributions, and molecular excited states. This first paper in a series of two presents a new Pulsed-Flow design, at the heart of which is a fast, high-throughput Pulsed valve driven by a piezoelectric stack actuator. Uniform Flows at temperatures as low as 20 K were readily achieved with only modest pumping requirements, as demonstrated by impact pressure measurements and pure rotational spectroscopy. The proposed technique will be suitable for application in diverse fields including fundamental studies in spectroscopy, kinetics, and reaction dynamics.
Aviv Amirav - One of the best experts on this subject based on the ideXlab platform.
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Pulsed Flow modulation two dimensional comprehensive gas chromatography tandem mass spectrometry with supersonic molecular beams
Journal of Chromatography A, 2008Co-Authors: Marina Poliak, Alexander B Fialkov, Aviv AmiravAbstract:Abstract Pulsed Flow modulation (PFM) two-dimensional comprehensive gas chromatography (GC × GC) was combined with quadrupole-based mass spectrometry (MS) via a supersonic molecular beam (SMB) interface using a triple-quadrupole system as the base platform, which enabled tandem mass spectrometry (MS-MS). PFM is a simple GC × GC modulator that does not consume cryogenic gases while providing tunable second GC × GC column injection time for enabling the use of quadrupole-based mass spectrometry regardless its limited scanning speed. The 20-ml/min second column Flow rate involved with PFM is handled, splitless, by the SMB interface without affecting the sensitivity. The combinations of PFM GC × GC–MS with SMB and PFM GC × GC–MS-MS with SMB were explored with the analysis of diazinon and permethrin in coriander. PFM GC × GC–MS with SMB is characterized by enhanced molecular ion and tailing-free fast ion source response time. It enables universal pesticide analysis with full scan and data analysis with reconstructed single ion monitoring on the enhanced molecular ion and another prominent high mass fragment ion. The elimination of the third fragment ion used in standard three ions method results in significantly reduced matrix interference. GC × GC–MS with SMB improves the GC separation, and thereby our ability for sample identification using libraries. GC–MS-MS with SMB provides better reduction (elimination) of matrix interference than GC × GC–MS. However, it is a target method, which is not always applicable. GC × GC–MS-MS does not seem to further reduce matrix interferences over GC–MS-MS and unlike GC × GC–MS, it is incompatible with library identification, but it is beneficial to have both GC × GC and MS-MS capabilities in the same system.
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Pulsed Flow modulation comprehensive two dimensional gas chromatography
Journal of Chromatography A, 2008Co-Authors: Marina Poliak, Maya Kochman, Aviv AmiravAbstract:Abstract Pulsed Flow modulation (PFM) is based on higher Flow rate time compression of the first GC column effluent, which prior to the injection into the second column is stored for a few seconds in a standard fused silica wide bore transfer line. We constructed the PFM device with two standard 1/16 in. brass compression fittings with the insertion of the two columns inside the wide bore 0.53 mm i.d. fused silica storage transfer line for the elimination of dead volumes. This simple arrangement provides a combination of flexibility in the length of the sample storage transfer line hence comprehensive two-dimensional gas chromatography (GC × GC) cycle time, inert sample path and full elimination of cooling gas consumption. A record short second column injection time of 20 ms is demonstrated. Practical injection times are the sample collection time (such as 4 s) divided by the second to first column Flow rate ratio (such as 20/0.7), which is typically around 150 ms. Due to the low cost of the device it can also be considered for use with non comprehensive time segmented GC × GC to remove a few accidental coelutions. PFM-GC × GC excels with high second column capacity due to the use of 0.32 mm i.d. columns with high Flow rates as the second dimension GC × GC column. As a result, PFM-GC × GC can have up to two orders of magnitude higher second column sample capacity and linear dynamic range for improved reduction of adverse matrix interference effects due to column overloading.
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gas chromatography mass spectrometry with supersonic molecular beams
Journal of Mass Spectrometry, 2008Co-Authors: Aviv Amirav, Marina Poliak, Alexander Gordin, Alexander B FialkovAbstract:Gas chromatography-mass spectrometry (GC-MS) with supersonic molecular beams (SMBs) (also named Supersonic GC-MS) is based on GC and MS interface with SMBs and on the electron ionization (EI) of vibrationally cold analytes in the SMBs (cold EI) in a fly-through ion source. This ion source is inherently inert and further characterized by fast response and vacuum background filtration capability. The same ion source offers three modes of ionization including cold EI, classical EI and cluster chemical ionization (CI). Cold EI, as a main mode, provides enhanced molecular ions combined with an effective library sample identification, which is supplemented and complemented by a powerful isotope abundance analysis method and software. The range of low-volatility and thermally labile compounds amenable for analysis is significantly increased owing to the use of the contact-free, fly-through ion source and the ability to lower sample elution temperatures through the use of high column carrier gas Flow rates. Effective, fast GC-MS is enabled particularly owing to the possible use of high column Flow rates and improved system selectivity in view of the enhancement of the molecular ion. This fast GC-MS with SMB can be further improved via the added selectivity of MS-MS, which by itself benefits from the enhancement of the molecular ion, the most suitable parent ion for MS-MS. Supersonic GC-MS is characterized by low limits of detection (LOD), and its sensitivity is superior to that of standard GC-MS, particularly for samples that are hard for analysis. The GC separation of the Supersonic GC-MS can be improved with Pulsed Flow modulation (PFM) GC x GC-MS. Electron ionization LC-MS with SMB can also be combined with the Supersonic GC-MS, with fast and easy switching between these two modes of operation.
Lindsay N Zack - One of the best experts on this subject based on the ideXlab platform.
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a chirped pulse fourier transform microwave Pulsed uniform Flow spectrometer ii performance and applications for reaction dynamics
Journal of Chemical Physics, 2014Co-Authors: Chamara Abeysekera, James M Oldham, Baptiste Joalland, Lindsay N Zack, Kirill Prozument, Ian R Sims, Barratt G Park, Robert W Field, Nuwandi M Ariyasingha, Arthur G SuitsAbstract:This second paper in a series of two reports on the performance of a new instrument for studying chemical reaction dynamics and kinetics at low temperatures. Our approach employs chirped-pulse Fourier-transform microwave (CP-FTMW) spectroscopy to probe photolysis and bimolecular reaction products that are thermalized in Pulsed uniform Flows. Here we detail the development and testing of a new Ka-band CP-FTMW spectrometer in combination with the Pulsed Flow system described in Paper I [J. M. Oldham, C. Abeysekera, B. Joalland, L. N. Zack, K. Prozument, I. R. Sims, G. B. Park, R. W. Field, and A. G. Suits, J. Chem. Phys.141, 154202 (2014)]. This combination delivers broadband spectra with MHz resolution and allows monitoring, on the μs timescale, of the appearance of transient reaction products. Two benchmark reactive systems are used to illustrate and characterize the performance of this new apparatus: the photodissociation of SO2 at 193 nm, for which the vibrational populations of the SO product are monitored, and the reaction between CN and C2H2, for which the HCCCN product is detected in its vibrational ground state. The results show that the combination of these two well-matched techniques, which we refer to as chirped-pulse in uniform Flow, also provides insight into the vibrational and rotational relaxation kinetics of the nascent reaction products. Future directions are discussed, with an emphasis on exploring the low temperature chemistry of complex polyatomic systems.
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a chirped pulse fourier transform microwave Pulsed uniform Flow spectrometer i the low temperature Flow system
Journal of Chemical Physics, 2014Co-Authors: James M Oldham, Chamara Abeysekera, Baptiste Joalland, Lindsay N Zack, Kirill Prozument, Ian R Sims, Barratt G Park, Robert W Field, Arthur G SuitsAbstract:We report the development of a new instrument that combines chirped-pulse microwave spectroscopy with a Pulsed uniform supersonic Flow. This combination promises a nearly universal detection method that can deliver isomer and conformer specific, quantitative detection and spectroscopic characterization of unstable reaction products and intermediates, product vibrational distributions, and molecular excited states. This first paper in a series of two presents a new Pulsed-Flow design, at the heart of which is a fast, high-throughput Pulsed valve driven by a piezoelectric stack actuator. Uniform Flows at temperatures as low as 20 K were readily achieved with only modest pumping requirements, as demonstrated by impact pressure measurements and pure rotational spectroscopy. The proposed technique will be suitable for application in diverse fields including fundamental studies in spectroscopy, kinetics, and reaction dynamics.
