Photoelectron Spectroscopy of Supersonic Molecular Beams PDF Download

Author: James Edward Pollard
Publisher:
ISBN:
Category :
Languages : en
Pages : 338

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Languages : en
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A new technique for performing high resolution molecular photoelectron spectroscopy is described, beginning with its conceptual development, through the construction of a prototypal apparatus, to the initial applications on a particularly favorable molecular system. The distinguishing features of this technique are: (1) the introduction of the sample in the form of a collimated supersonic molecular beam; and (2) the use of an electrostatic deflection energy analyzer which is carefully optimized in terms of sensitivity and resolution. This combination makes it possible to obtain photoelectron spectra at a new level of detail for many small molecules. Three experiments are described which rely on the capability to perform rotationally-resolved photoelectron spectroscopy on the hydrogen molecule and its isotopes. The first is a measurement of the ionic vibrational and rotational spectroscopic constants and the vibrationally-selected photoionization cross sections. The second is a determination of the photoelectron asymmetry parameter, .beta., for selected rotational transitions. The third is an investigation of the rotational relaxation in a free jet expansion, using photoelectron spectroscopy as a probe of the rotational state population distributions. In the closing chapter an assessment is made of the successes and limitations of the technique, and an indication is given of areas for further improvement in future spectrometers.

Author:
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Languages : en
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From chemical spectroscopy and photochemistry in the vacuum ultraviolet conference; Valmorin, Quebec, Canada (5 Aug 1973). The development of the field of photoelectron spectroscopy and the intensities and angular distributions from which one can infer transition probabilities and phase shifts are discussed. (JFP).

Author: Baohua Niu
Publisher:
ISBN:
Category :
Languages : en
Pages : 392

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Languages : en
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The use of supersonic molecular beams in photoionization mass spectroscopy and photoelectron spectroscopy to assist in the understanding of photoexcitation in the vacuum ultraviolet is described. Rotational relaxation and condensation due to supersonic expansion were shown to offer new possibilities for molecular photoionization studies. Molecular beam photoionization mass spectroscopy has been extended above 21 eV photon energy by the use of Stanford Synchrotron Radiation Laboratory (SSRL) facilities. Design considerations are discussed that have advanced the state-of-the-art in high resolution vuv photoelectron spectroscopy. To extend gas-phase studies to 160 eV photon energy, a windowless vuv-xuv beam line design is proposed.

Author:
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Category :
Languages : en
Pages : 15

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A high temperature molecular beam source with electron bombardment heating has been built for high resolution photoelectron spectroscopic studies of high temperature species and clusters. This source has the advantages of: producing an intense, continuous, seeded molecular beam, eliminating the interference of the heating mechanism from the photoelectron measurement. Coupling the source with our hemispherical electron energy analyzer, we can obtain very high resolution HeI[alpha] (584Å) photoelectron spectra of high temperature species. Vibrationally-resolved photoelectron spectra of PbSe, As2, As4, and ZnCl2 are shown to demonstrate the performance of the new source. 25 refs., 8 figs., 1 tab.

Author:
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ISBN:
Category :
Languages : en
Pages : 192

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High resolution He I[alpha] photoelectron spectroscopy of formaldehyde and ketene and their deuterated compounds, are reported. The combination of a (H2CO) double-pass high-resolution electron-energy analyzer and effective rotational cooling of the sample by supersonic expansion enable the spectroscopy of these molecular cations. The vibrational autocorrelation functions are calculated from the high-resolution photoelectron spectra, shedding light on the ultrafast intramolecular dynamics of the molecular cations. This study reveals much more vibrational structural detail in the first electronic excited state of H2CO cations. The first electronic excited state of H2CO cations may have nonplanar equilibrium geometry. Strong isotope effects on vibronic (vibrational) coupling are observed in the second electronic excited state of H2CO. Vibrational autocorrelation functions are calculated for all four observed electronic states of H2CO. The correlation function of the first electronic excited state of H2CO shows a slow decay rate on the femtosecond time scale. The ultrafast decay of the H2CO cations in the third electronic excited state implies that dissociation and intramolecular processes are the main decay pathways. The present spectra of the ground states of ketene cations have more fine structure than before. The AIEs of the first and fifth excited states are determined unambiguously more accurately. The doublet-like fine structures present in the lint excited state of ketene implies the excitation of a soft'' mode not observed before. The vibrational autocorrelation functions are calculated for 4 of the 6 observed electronic states. The dynamics of the ground states of the cations are characterized by a wave packet oscillating with small amplitude around the minimum on the upper PES. The decay dynamics of the first and the fifth excited states of ketene are characterized by ultra-fast intramolecular processes like predissociation.

Author: Dennis James Trevor
Publisher:
ISBN:
Category :
Languages : en
Pages : 300

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Author: Bretislav Friedrich
Publisher: Springer Nature
ISBN: 3030639630
Category : Science
Languages : en
Pages : 639

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This Open Access book gives a comprehensive account of both the history and current achievements of molecular beam research. In 1919, Otto Stern launched the revolutionary molecular beam technique. This technique made it possible to send atoms and molecules with well-defined momentum through vacuum and to measure with high accuracy the deflections they underwent when acted upon by transversal forces. These measurements revealed unforeseen quantum properties of nuclei, atoms, and molecules that became the basis for our current understanding of quantum matter. This volume shows that many key areas of modern physics and chemistry owe their beginnings to the seminal molecular beam work of Otto Stern and his school. Written by internationally recognized experts, the contributions in this volume will help experienced researchers and incoming graduate students alike to keep abreast of current developments in molecular beam research as well as to appreciate the history and evolution of this powerful method and the knowledge it reveals.

Author: Immanual Estermann
Publisher: Elsevier
ISBN: 0323160344
Category : Technology & Engineering
Languages : en
Pages : 199

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Recent Research in Molecular Beam is a collection of scientific papers that have been inspired by Otto Stern, the founder of Molecular Beam Research. This book is composed of 10 chapters and begins with discussions on the early history of molecular beam research. The next chapters describe the velocity distribution measurements made on potassium molecular beams with a fixed-frequency, variable phase velocity selector, along with a brief consideration of the principles and concepts of electron magnetic moment and atomic magnetism. A chapter presents the atomic beam spectroscopic experiments on the metastable state of the hydrogen-like atoms that depend on a wholly different principle for the detection of transitions. This text further explores the effects of variations in the oscillatory field amplitudes, perturbations by neighboring resonances, perturbations by oscillatory fields, variations in the fixed field amplitudes, and phase shifts of the oscillatory fields. These topics are followed by a comparison of advantages and limitations of various techniques for spin property measurement as they apply in particular to radioactive nuclei, such as optical and molecular gas microwave spectroscopy, nuclear and paramagnetic resonance, and atomic beams. The remaining chapters examine fluid friction in a rarefied gas flow; some applications of molecular beam techniques to chemistry; and the polarized neutrons based on a Stern-Gerlach experiment. This work will be of great value to workers and researchers in molecular beam field.