State-Resolved Collisional Energy Transfer in Highly Vibrationally Excited Polyatomic Molecules PDF Download
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Author: Publisher: ISBN: Category : Languages : en Pages : 17
Book Description
The transfer of energy in isolated or colliding molecules is a fundamental process with practical consequences for complex phenomena occurring in atmospheric chemistry, combustion, molecular lasers, plasmas, and a host of other environments containing energetic species. We have developed a technique that combines vibrational overtone excitation, to prepare highly vibrationally excited initial states, and time-resolved spectroscopic detection, to probe the evolution of the prepared state, for studying energy transfer in vibrationally energized molecules. We have used this approach to determine directly, for the first time, the frequencies of the three ungerade vibrations in the first electronically excited state of acetylene. Using this information we have characterized highly vibrationally excited states of acetylene and directly the frequencies and rotational constants of the perturbing vibrational states at these energies. Combining these spectroscopic insights on the vibrationally and electronically excited states of acetylene has allowed us to determine the energy transfer rates and pathways in the collisional relaxation of a polyatomic molecule containing 10,000 cm-1 of vibrational energy, Rotational energy transfer is very rapid, occurring on about every other collision, but is essentially unaffected by the identity of the vibrational state in which the rotational relaxation occurs.
Author: Publisher: ISBN: Category : Languages : en Pages : 17
Book Description
The transfer of energy in isolated or colliding molecules is a fundamental process with practical consequences for complex phenomena occurring in atmospheric chemistry, combustion, molecular lasers, plasmas, and a host of other environments containing energetic species. We have developed a technique that combines vibrational overtone excitation, to prepare highly vibrationally excited initial states, and time-resolved spectroscopic detection, to probe the evolution of the prepared state, for studying energy transfer in vibrationally energized molecules. We have used this approach to determine directly, for the first time, the frequencies of the three ungerade vibrations in the first electronically excited state of acetylene. Using this information we have characterized highly vibrationally excited states of acetylene and directly the frequencies and rotational constants of the perturbing vibrational states at these energies. Combining these spectroscopic insights on the vibrationally and electronically excited states of acetylene has allowed us to determine the energy transfer rates and pathways in the collisional relaxation of a polyatomic molecule containing 10,000 cm-1 of vibrational energy, Rotational energy transfer is very rapid, occurring on about every other collision, but is essentially unaffected by the identity of the vibrational state in which the rotational relaxation occurs.
Author: F. F. Crim Publisher: ISBN: Category : Languages : en Pages : 22
Book Description
The three objectives of this work are to determine the nature of highly vibrationally excited polyatomic molecule, to determine the rate constants and pathways for the collisional relaxation of these molecules, and to probe the electronic spectroscopy of these molecules. We have created and implemented approaches for accomplishing these objectives and have demonstrated their feasibility by studying the collisional energy transfer in highly vibrational excited acetylene. We have found that the collisional self relaxation rates of single angular momentum states with 10,000/cm of vibrational energy are a substantial fraction of the gas kinetic collision rates. The rate constant is about a factor of two smaller for relaxation by atomic partners. Molecular energy transfer, Vibrational energy transfer. (MJM).
Author: Trevor C. Brown Publisher: ISBN: Category : Languages : en Pages : 338
Book Description
This thesis describes the studies made on several unimolecular reaction systems in order to obtain collisional energy transfer information on highly excited polyatomic molecules. Pressure-dependant very low-pressure pyrolysis (VLPP) and infrared multiphoton decomposition (IRMPD) experimental techniques are used.
Author: Publisher: ISBN: Category : Languages : en Pages : 130
Book Description
The vibrational to translational (V-->T) energy transfer in collisions between large highly vibrationally excited polyatomics and rare gases was investigated by time-of-flight techniques. Two different methods, UV excitation followed by intemal conversion and infrared multiphoton excitation (IRMPE), were used to form vibrationally excited molecular beams of hexafluorobenzene and sulfur hexafluoride, respectively. The product translational energy was found to be independent of the vibrational excitation. These results indicate that the probability distribution function for V-->T energy transfer is peaked at zero. The collisional relaxation of large polyatomic molecules with rare gases most likely occurs through a rotationally mediated process. Photodissociation of nitrobenzene in a molecular beam was studied at 266 nm. Two primary dissociation channels were identified including simple bond rupture to produce nitrogen dioxide and phenyl radical and isomerization to form nitric oxide and phenoxy radical. The time-of-flight spectra indicate that simple bond rupture and isomerization occurs via two different mechanisms. Secondary dissociation of the phenoxy radicals to carbon monoxide and cyclopentadienyl radicals was observed as well as secondary photodissociation of phenyl radical to give H atom and benzyne. A supersonic methyl radical beam source is developed. The beam source configuration and conditions were optimized for CH3 production from the thermal decomposition of azomethane. Elastic scattering of methyl radical and neon was used to differentiate between the methyl radicals and the residual azomethane in the molecular beam.
Author: James Yardley Publisher: Elsevier ISBN: 0323156037 Category : Science Languages : en Pages : 321
Book Description
Introduction to Molecular Energy Transfer intends to provide an elementary introduction to the subject of molecular energy transfer and relaxation. The book covers the foundation of molecular energy transfer such as quantum mechanics; the vibrational state of molecules; and vibrational energy transfer and the experimental methods for its study. Coverage also includes the different kinds of energy transfer in gases; vibrational relaxation in condensed phases; electronic states and interactions; electronic energy as a result of intermolecular interaction; radiationless electronic transition; and rotational energy transfer. The text is recommended for students, graduates, and researchers in the fields of physics and chemistry, especially those who would like to know more about molecular energy transfer.
Author: B. S. Rabinovitch Publisher: ISBN: Category : Languages : en Pages : 7
Book Description
The report summarizes the experimental and theoretical accomplishment under a program which dealing with collisional activation and deactivation of polyatomic molecules at the levels of vibrational excitation which correspond to chemical reaction. (Author).
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Author: F. F. Crim
Author: Kieran Fergus Lim
Author: Trevor C. Brown
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Author: Todd Andrew Stone
Author: Brian Stevens
Author: James Yardley
Author: Pamela Mei-Ying Chu
Author: B. S. Rabinovitch