Photodissociation Studies with Vacuum Ultraviolet Lasers by Means of Ion Velocity Imaging PDF Download

Author: Roosevelt Jerome Price
Publisher:
ISBN:
Category :
Languages : en
Pages : 356

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Author: Zhou Lu
Publisher:
ISBN: 9781321806731
Category :
Languages : en
Pages :

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By employing two independently tunable vacuum ultraviolet (VUV) laser radiations in tandem with the velocity-map imaging photoion (VMI-PI) apparatus, state-to-state photodissociation of CO2 has been investigated in the VUV energy range between 101.5 and 107.2 nm. The spin-allowed CO + O product channels, CO(X1[Sigma]+) + O(1D), CO(X1[Sigma]+) + O(1S), and CO(a3[Pi]) + O(3P) and the spin-forbidden dissociation channel, CO(X1[Sigma]+) + O(3P), were directly observed VMI-PI images. By detecting photofragment atoms of O(3P2,1,0), O(1D), and O(1S) via VMI-PI detection scheme, we have determined the vibrational-state distributions of the CO fragments. The total kinetic energy release spectra of the CO(X1[Sigma]+) + O(1D) and CO(X1[Sigma]+) + O(1S) reveal substantial differences in the CO vibrational-state distribution produced from different CO2 predissociative states. By using the VUV-Visible photoionization scheme of O(3P2,1,0) atoms, we have measured the spin-orbit branching ratios between the spin-allowed CO(a3[Pi]) + O(3P2,1,0) and spin-forbidden CO(X1[Sigma]+) + O(3P2,1,0) channels from O(3P2,1,0) ion images. We have directly detected all the thermodynamically available CO + O dissociation channels (eq. 1-3, and 5) between 101.5 and 107.2 nm in CO2 photodissociation. Besides the CO + O products for the photodissociation of CO2 molecule, we provided the first experimental evidence for the formation of C(3P) + O2(X3[Sigma](g-)) product mixtures between 101.5 and 107.2 nm in CO2 photodissociation. Our results indicate that all the energetically accessible channels (eq. 1-5) should be included in the CO2 photochemcial reaction networks. We have also combined the VUV laser with VMI method to measure the photoionization energies and vibrational energies of the cationic transient radical species, including C3H3, C3H5, CH2Cl, and CH2Br. This newly developed technique has been proved to achieve higher detection efficiency and comparable resolution compared to the traditional pulsed-field ionization photoelectron (PFI-PE) method, making it an ideal alternative to record high-resolution photoelectron spectra of transient radical species with superior resolution and signal to noise ratio.

Author: Hong Gao
Publisher:
ISBN: 9781303442544
Category :
Languages : en
Pages :

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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.

Author: Cheuk-yiu Ng
Publisher: World Scientific
ISBN: 9814506575
Category : Science
Languages : en
Pages : 582

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This monograph reviews the recent progress in vacuum ultraviolet (VUV) photoionization and photodissociation processes. Photoionization, photoelectron, and fluorescence spectroscopic techniques have played an important role in revealing the photoionization and photodissociation dynamics of molecules in the vacuum ultraviolet region and in providing accurate energetic and spectroscopic information of ions as well as neutral molecules. The book represents the first detailed review of major experimental developments in the studies of single vacuum ultraviolet photon ionization and dissociation processes of gaseous molecules and clusters.

Author: Kai-Chung Lau
Publisher:
ISBN:
Category :
Languages : en
Pages : 368

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Author: Lei Yang
Publisher:
ISBN: 9781267663399
Category :
Languages : en
Pages :

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By detecting the central signal of the photoelectron image as a function of vacuum ultraviolet (VUV) laser energy, we have obtained a high-resolution threshold photoelectron spectrum for the ground state of chlorobenzene cation (C6H5Cl) using the velocity-map imaging-photoelectron method. By employing the vacuum ultraviolet (VUV) laser velocity-map imaging (VMI) photoelectron scheme to discriminate energetic photoelectrons, we have measured the VUV-VMI-threshold photoelectrons (VUV-VMI-TPE) spectra of propargyl radical [C3H3 (X̃2B1)] near its ionization threshold at photoelectron energy bandwidths of 3 and 7 cm−1 (full-width at half-maximum, FWHM). The photoionization efficiency (PIE) and pulsed field ionization-photoion (PFI-PI) spectra for oxygen atoms O(3P2, 1, 0) resulting from the 193.3 nm photodissociation of SO2 have been measured using tunable vacuum ultraviolet (VUV) laser radiation in the frequency range of 109200 - 109900 cm−1. By coupling a tunable vacuum ultraviolet (VUV) laser system with the velocity-map imaging system, we have measured the photoionization efficiency (PIE) and the pulsed field ionization-photoion (PFI-PI) spectra for chlorine atoms Cl(2P[subscript 3/2, 1/2]) produced from the 193.3nm photodissociation of C6H5Cl in the VUV wavenumber range of 103,580 to 105,600 cm−1. The predissociation of N2 from the rotational levels in the o1[Pi subscript u] (v'=2) and b' 1[Sigma subscript u] (v'=8) bands have been studied in the wavelength range from 109,350 cm−1 (13.5577 eV) to 109,580 cm−1 (13.5862 eV) by time-sliced velocity-map imaging technique with VUV photoionization detection of the fragments.

Author: Elsayed Abdellah Abd Elaal Hassanein
Publisher:
ISBN:
Category :
Languages : en
Pages : 272

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Author: Michael Aaron Todt
Publisher:
ISBN:
Category :
Languages : en
Pages : 216

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Author: Cheuk-Yiu Ng
Publisher: World Scientific
ISBN: 9810238924
Category : Science
Languages : en
Pages : 731

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Owing to the advances of vacuum ultraviolet and ultrafast lasers and third generation synchrotron sources, the research on photoionization, photoelectrons, and photodetachment has gained much vitality in recent years. These new light sources, together with ingenious experimental techniques, such as the coincidence imaging, molecular beam, pulsed field ionization photoelectron, mass-analyzed threshold ion, and pulsed field ion pair schemes, have allowed spectroscopic, dynamic, and energetic studies of gaseous species to a new level of detail and accuracy. Profitable applications of these methods to liquids are emerging.This invaluable two-volume review consists of twenty-two chapters, focusing on recent developments in photoionization and photodetachment studies of atoms; molecules, transient species, clusters, and liquids.

Author: S.P. McGlynn
Publisher: Springer Science & Business Media
ISBN: 9400952694
Category : Science
Languages : en
Pages : 953

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This volume contains the texts of the Invited Lectures pre sented at the NATO Advanced Study Institute PHOTOPHYSICS AND PHOTOCHEMISTRY IN THE VACUUM ULTRAVIOLET, which was held at the Interlaken Lodge in Lake Geneva, Wisconsin USA, August 15-28, 1982. This ASI was the third in a series of NATO Institutes de voted to a study of the physical and chemical transformations undergone by atoms and molecules after absorption of high-energy (VUV