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Dudek J, Kędziorski A, Zobel J, Krośnicki M, Urbańczyk T, Puczka K, Koperski J. Bound→free and bound→bound multichannel emission spectra from selectively excited Rydberg states in the ZnAr and CdAr van der Waals complexes. J Mol Struct 2020. [DOI: 10.1016/j.molstruc.2020.128840] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Dudás E, Suas-David N, Brahmachary S, Kulkarni V, Benidar A, Kassi S, Charles C, Georges R. High-temperature hypersonic Laval nozzle for non-LTE cavity ringdown spectroscopy. J Chem Phys 2020; 152:134201. [PMID: 32268744 DOI: 10.1063/5.0003886] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A small dimension Laval nozzle connected to a compact high enthalpy source equipped with cavity ringdown spectroscopy (CRDS) is used to produce vibrationally hot and rotationally cold high-resolution infrared spectra of polyatomic molecules in the 1.67 µm region. The Laval nozzle was machined in isostatic graphite, which is capable of withstanding high stagnation temperatures. It is characterized by a throat diameter of 2 mm and an exit diameter of 24 mm. It was designed to operate with argon heated up to 2000 K and to produce a quasi-unidirectional flow to reduce the Doppler effect responsible for line broadening. The hypersonic flow was characterized using computational fluid dynamics simulations, Pitot measurements, and CRDS. A Mach number evolving from 10 at the nozzle exit up to 18.3 before the occurrence of a first oblique shock wave was measured. Two different gases, carbon monoxide (CO) and methane (CH4), were used as test molecules. Vibrational (Tvib) and rotational (Trot) temperatures were extracted from the recorded infrared spectrum, leading to Tvib = 1346 ± 52 K and Trot = 12 ± 1 K for CO. A rotational temperature of 30 ± 3 K was measured for CH4, while two vibrational temperatures were necessary to reproduce the observed intensities. The population distribution between vibrational polyads was correctly described with Tvib I=894±47 K, while the population distribution within a given polyad (namely, the dyad or the pentad) was modeled correctly by Tvib II=54±4 K, testifying to a more rapid vibrational relaxation between the vibrational energy levels constituting a polyad.
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Affiliation(s)
- Eszter Dudás
- Univ Rennes, CNRS, IPR (Institut de Physique de Rennes) - UMR 6251, F-35000 Rennes, France
| | - Nicolas Suas-David
- Univ Rennes, CNRS, IPR (Institut de Physique de Rennes) - UMR 6251, F-35000 Rennes, France
| | - Shuvayan Brahmachary
- Department of Mechanical Engineering, Indian Institute of Technology Guwahati, Guwahati, India
| | - Vinayak Kulkarni
- Department of Mechanical Engineering, Indian Institute of Technology Guwahati, Guwahati, India
| | - Abdessamad Benidar
- Univ Rennes, CNRS, IPR (Institut de Physique de Rennes) - UMR 6251, F-35000 Rennes, France
| | - Samir Kassi
- Université Grenoble Alpes, LIPhy, F-38000 Grenoble, France and CNRS, LIPhy, F-38000 Grenoble, France
| | - Christine Charles
- Space Plasma, Power and Propulsion Laboratory (SP3), Research School of Physics, The Australian National University, Canberra, ACT 2601, Australia
| | - Robert Georges
- Univ Rennes, CNRS, IPR (Institut de Physique de Rennes) - UMR 6251, F-35000 Rennes, France
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