Download or read book UV Photodissociation Dynamics of Polyatomic Free Radicals Using High n Rydberg Atom Time of Flight Spectroscopy written by Michael Scott Lucas and published by . This book was released on 2016 with total page 222 pages. Available in PDF, EPUB and Kindle. Book excerpt: Chapter 7 will briefly discuss the results of a related system, 3-cyclohexenyl radical, and general conclusions.
Download or read book UV photodissociation Dynamics of Small Molecules and Free Radicals Studied by High n Rydberg H Atom Time of Flight Spectroscopy written by Gabriel Alejandro Amaral and published by . This book was released on 2001 with total page 406 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Photodissociation Dynamics of Free Radicals Using High n Rydberg Atom Time of flight Technique written by Yu Song and published by . This book was released on 2011 with total page 253 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first chapter discusses the photodissociation dynamics as well as its experimental methodology. The experimental setup of the HRTOF technique is explained in detail.
Download or read book Photodissociation and Reaction Dynamics of Small Molecules and Free Radicals Via High n Rydberg Hydrogen Atom Time of Flight Spectroscopy written by Kesheng Xu and published by . This book was released on 2001 with total page 390 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dynamics Studies of Free Radical Reactions Using Hydrogen Rydberg Time of flight Spectroscopy written by Mariví Ortiz-Suárez and published by . This book was released on 2007 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Coincidence and Noncoincidence Studies of the Photodissociation Dynamics of Free Radicals written by Ann Elise Faulhaber and published by . This book was released on 2005 with total page 238 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Photodissociation Spectroscopy and Dynamics of Free Radicals Clusters and Ions written by Hyeon Choi and published by . This book was released on 1999 with total page 340 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Polyatomic Free Radicals written by J. M. Brown and published by Springer. This book was released on 2005-09-21 with total page 526 pages. Available in PDF, EPUB and Kindle. Book excerpt: Volume II/24 presents the rotationally resolved high resolution spectroscopic data on diamagnetic and paramagnetic molecules as well as on molecular ions and radicals up to date considering the publications up to and partly including 1997. For subvolume II/24D2 covering the polyatomic radicals, publications up to the year 2000 are taken into account. The spectroscopic information collected has been obtained principally from gas phase microwave , mm-wave and sub-mm wave measurements. In addition, gas phase data have been included derived from methods related to microwave spectroscopy by employing a coherent radiation source. These are molecular beam techniques, radio frequency spectroscopy, electron resonance spectroscopy, laser spectroscopy, double resonance and saturation techniques. Some other methods are considered if the accuracy of the derived molecular parameters is comparable to that of microwave spectroscopy owing to a good statistics in the analysis of data, and no microwave data are available. Examples would be Fourier infrared spectroscopy or laser induced fluorescence.
Download or read book Photodissociation Dynamics and Spectroscopy of Free Radical Combustion Intermediates written by and published by . This book was released on 1996 with total page 422 pages. Available in PDF, EPUB and Kindle. Book excerpt: The photodissociation spectroscopy and dynamics of free radicals is studied by the technique of fast beam photofragment translational spectroscopy. Photodetachment of internally cold, mass-selected negative ions produces a clean source of radicals, which are subsequently dissociated and detected. The photofragment yield as a function of photon energy is obtained, mapping out the dissociative and predissociative electronic states of the radical. In addition, the photodissociation dynamics, product branching ratios, and bond energies are probed at fixed photon energies by measuring the translational energy, P(E{sub T}), and angular distribution of the recoiling fragments using a time- and position-sensitive detector. Ab initio calculations are combined with dynamical and statistical models to interpret the observed data. The photodissociation of three prototypical hydrocarbon combustion intermediates forms the core of this work.
Download or read book Photoisomerization and Photodissociation Dynamics of Reactive Free Radicals written by Ryan Tyler Bise and published by . This book was released on 2000 with total page 404 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Photodissociation Studies of Polyatomic Free Radicals written by and published by . This book was released on 1993 with total page 147 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental program in gas phase polyatomic photochemistry and photophysics has been extablished in the Department of Chemistry at the University of Puerto Rico. Real time dynamics of sulfur monoxide photoelimination reactions have been studied by laser induced fluorescence spectroscopy of the nascent SO fragment on the B3 sigma ( - ) -X3 sigma ( - ) transition in the region of 237-295 nm. The group of molecules under investigation are Sulfur dioxide (SO2), dimethyl sulfoxide (CH3)2SO), and the thionyl halides (SOX2; where X = F, Cl or Br). In all of these experiments, the parent molecule is irradiated with an excimer laser (either 193 or 248 nm) and the energy disposal into the nascent SO photofragment is determined, and used as a mechanistic probe. The experiments indicate that the several of these parent molecules undergo three body dissociations. A second set of experiments measures kinetic decay constants of the C2H3O, both in the ground state and in the excited state. The temperature (295-374K) and pressure (2.5-100 torr) dependences for the rate constant of the C2H30 + N02 reaction have been measured by laser flash photolysis/laser induced fluorescence kinetic spectroscopy. The temperature dependent reaction for the decay of C2H3O in the presence of N02 is characterized over the measured region by the rate expression, k sub II = (1.48 +/-0.70)xlO(exp-11) exp(80.7 +/- 23.4K/T)cu cm/molecule/s. Fluorescence decay rates were determined in the presence to ten collision partners: He, Ar, N2, 02, CO, H2, HCl, C02, C2H4, and CH30CH = CH2. The measured electronic quenching cross-sections vary from 0.01 - 66.5 A2. A vibrational level dependence was found for the radiative lifetimes.
Download or read book Photoisomerization and Photodissociation Dynamics of Reactive Free Radicals written by and published by . This book was released on 2000 with total page 198 pages. Available in PDF, EPUB and Kindle. Book excerpt: The photofragmentation pathways of chemically reactive free radicals have been examined using the technique of fast beam photofragment translational spectroscopy. Measurements of the photodissociation cross-sections, product branching ratios, product state energy distributions, and angular distributions provide insight into the excited state potential energy surfaces and nonadiabatic processes involved in the dissociation mechanisms. Photodissociation spectroscopy and dynamics of the predissociative {tilde A}2A1 and {tilde B}2A2 states of CH3S have been investigated. At all photon energies, CH3 + S(3P{sub j}), was the main reaction channel. The translational energy distributions reveal resolved structure corresponding to vibrational excitation of the CH3 umbrella mode and the S(3P{sub j}) fine-structure distribution from which the nature of the coupled repulsive surfaces is inferred. Dissociation rates are deduced from the photofragment angular distributions, which depend intimately on the degree of vibrational excitation in the C-S stretch. Nitrogen combustion radicals, NCN, CNN and HNCN have also been studied. For all three radicals, the elimination of molecular nitrogen is the primary reaction channel. Excitation to linear excited triplet and singlet electronic states of the NCN radical generates resolved vibrational structure of the N2 photofragment. The relatively low fragment rotational excitation suggests dissociation via a symmetric C{sub 2V} transition state. Resolved vibrational structure of the N2 photofragment is also observed in the photodissociation of the HNCN radical. The fragment vibrational and rotational distributions broaden with increased excitation energy. Simple dissociation models suggest that the HNCN radical isomerizes to a cyclic intermediate (c-HCNN) which then dissociates via a tight cyclic transition state. In contrast to the radicals mentioned above, resolved vibrational structure was not observed for the ICNN radical due to extensive fragment rotational excitation, suggesting that intermediate bent states are strongly coupled along the dissociation pathway. The measurements performed in this Thesis have additionally refined the heats of formation and bond dissociation energies of these radicals and have unambiguously confirmed and added to the known electronic spectroscopy.
Download or read book Photodissociation of Small Molecules and Photoionization of Free Radicals Using the VUV Velocity map Imaging Photoion and Photoelectron Method written by Hong Gao and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The tunable vacuum ultraviolet (VUV) laser generated through the two-photon resonance-enhanced four-wave mixing scheme is combined with the newly developed time-slice velocity map imaging photoion method to study the photodissociation of small molecules in the VUV region, and with the velocity map imaging photoelectron method to study the photoionization of free radicals. The photodissociation dynamics of NO in the energy region around 13.5 eV has been investigated. Branching ratios of the three lowest dissociation channels of 12C16O that produce C(3P) + O(3P), C(1D) + O(3P) and C(3P) + O(1D) are measured for the first time in the VUV region from 102,500 cm−1 to 110,500 cm−1, valuable information of the dissociation dynamics for this prototype system has been deduced. We demonstrated an experiment that has two independently tunable VUV lasers and a time-slice velocity map imaging setup, this provides us a global way to perform systematic state-selected photodissociation of small molecules via state-selected detection of the atomic products in the VUV region. The velocity map imaging photoelectron method was successfully used to obtain the photoelectron spectrum of the propargyl radical (C3H3) via a single VUV photoionization process. The propargyl radical is generated by the 193 nm laser photodissociation of the precursor C3H3Cl. This is the first time that the velocity map imaging photoelectron method is used to get the photoelectron spectra of free radicals, indicating that it is a powerful technique for studying the photoionization of free radicals which are always hard to be produced with high enough number densities for spectroscopic studies.
Download or read book Photodissociation Spectroscopy and Dynamics of Free Radicals Clusters and Ions written by and published by . This book was released on 1999 with total page 169 pages. Available in PDF, EPUB and Kindle. Book excerpt: The photodissociation spectroscopy and dynamics of free radicals and ions is studied to characterize the dissociative electronic states in these species. To accomplish this, a special method of radical production, based on the photodetachment of the corresponding negative ion, has been combined with the technique of fast beam photofragment translational spectroscopy. The photofragment yield as a function of photon energy is obtained, mapping out the dissociative and predissociative electronic states. Branching ratios to various product channels, the translational energy distributions of the fragments, and bond dissociation energies are then determined at selected photon energies. The detailed picture of photodissociation dynamics is provided with the aid of ab initio calculations and a statistical model to interpret the observed data. Important reaction intermediates in combustion reactions have been studied: CCO, C2H5O, and linear C{sub n} (n = 4--6).
Download or read book Polyatomic Photodissociation Dynamics written by Stephen J. Riley and published by . This book was released on 1975 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt: During the contract period photofragment spectroscopy studies of several small halide molecules were carried out. In two cases evidence for novel free radical dissociation processes was found. (Author).
Download or read book Photodissociaion Dynamics of Neutral Free Radicals written by Bogdan Negru and published by . This book was released on 2012 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt: Photofragment translational spectroscopy was used to study the photodissociation dynamics of the phenyl and tert-butyl radicals. These radicals were produced in a collisionless environment from the flash pyrolysis of the appropriate precursor, nitrosobenzene for phenyl and azo-tert-butane for the tert-butyl radical. The photodissociation dynamics of the phenyl radical (C6H5) were investigated at 248 and 193 nm. At 248 nm, the only dissociation products observed were from hydrogen atom loss, attributed primarily to H + o-C6H4 (ortho-benzyne). The observed translational energy distribution was consistent with statistical decay on the ground state surface. At 193 nm, dissociation to H + C6H4 and C4H3 + C2H2 was observed. The C6H4 fragment can be either o-C6H4 or l-C6H4 resulting from opening of the phenyl ring. The C4H3 + C2H2 products dominate over the two H loss channels. Attempts to reproduce the observed branching ratio by assuming ground state dynamics were unsuccessful. This discord, between the experimentally observed branching ratio and the theoretically predicted branching ratio led us to reinvestigate the dissociation dynamics of the phenyl radical at 193 nm, while producing the radical under different source conditions. The photodissociation dynamics of the tert-butyl radical (t-C4H9) were investigated at 248 nm. Two distinct channels of approximately equal importance were identified: dissociation to H + 2-methylpropene (C4H8), and CH3 + dimethylcarbene (C3H6). Neither the translational energy distributions that describe these two channels nor the product branching ratio are consistent with statistical dissociation on the ground state, and instead favor a mechanism taking place on excited state surfaces. The studies presented in this dissertation show that although hydrogen atom loss is sometimes expected to be the only major dissociation pathway in the photodissociation of hydrocarbon radicals this is not always a justified assumption.
Download or read book Constants for Radicals written by W. Hüttner and published by . This book was released on 2005 with total page 526 pages. Available in PDF, EPUB and Kindle. Book excerpt: Volume II/24 presents the rotationally resolved high resolution spectroscopic data on diamagnetic and paramagnetic molecules as well as on molecular ions and radicals up to date considering the publications up to and partly including 1997. For subvolume II/24D2 covering the polyatomic radicals, publications up to the year 2000 are taken into account. The spectroscopic information collected has been obtained principally from gas phase microwave , mm-wave and sub-mm wave measurements. In addition, gas phase data have been included derived from methods related to microwave spectroscopy by employing a coherent radiation source. These are molecular beam techniques, radio frequency spectroscopy, electron resonance spectroscopy, laser spectroscopy, double resonance and saturation techniques. Some other methods are considered if the accuracy of the derived molecular parameters is comparable to that of microwave spectroscopy owing to a good statistics in the analysis of data, and no microwave data are available. Examples would be Fourier infrared spectroscopy or laser induced fluorescence.
