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Atomic, Molecular and Optical Physics

Series

1995

Articles 1 - 11 of 11

Full-Text Articles in Physics

Measured Stark Widths Of A 425,94 Nm Ari Spectral Line, Ljiljana Skuljan, Vladimir Milosavljevic, Aleksandar Sreckovic, Stevan Djenize Dec 1995

Measured Stark Widths Of A 425,94 Nm Ari Spectral Line, Ljiljana Skuljan, Vladimir Milosavljevic, Aleksandar Sreckovic, Stevan Djenize

Articles

No abstract provided.

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Strong X-Ray Emission From High-Temperature Plasmas Produced By Intense Irradiation Of Clusters, T. Ditmire, Thomas D. Donnelly, R. W. Falcone, M. D. Perry Oct 1995

Strong X-Ray Emission From High-Temperature Plasmas Produced By Intense Irradiation Of Clusters, T. Ditmire, Thomas D. Donnelly, R. W. Falcone, M. D. Perry

All HMC Faculty Publications and Research

The interaction of an intense laser pulse with large (∼100Å) clusters present in pulsed gas jets is shown to produce novel plasmas with electron temperatures far in excess of that predicted by above-threshold ionization theory. The enhanced absorption of the laser light by the dense clusters results in the production of high ion charge states via collisional ionization resulting in strong x-ray emission from the hot plasma.

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Angle-Resolved Photoelectron Spectroscopy Of C60, T. Liebsch, O. Plotzke, Franz Heiser, U. Hergenhahn, Oliver Hemmers, R. Wehlitz, J. Viefhaus, B. Langer, S. B. Whitfield, U. Becker Jul 1995

Angle-Resolved Photoelectron Spectroscopy Of C60, T. Liebsch, O. Plotzke, Franz Heiser, U. Hergenhahn, Oliver Hemmers, R. Wehlitz, J. Viefhaus, B. Langer, S. B. Whitfield, U. Becker

Environmental Studies Faculty Publications

Angle-resolved photoelectron spectra of gaseous C60 were recorded in the photon energy regions from 21 to 108 eV and from 295 to 320 eV. Partial cross sections σ and the angular distribution anisotropy parameter β vary significantly with photon energy, particularly in the near-threshold region of the valence and the core ionization regimes. Some of these effects may be attributed to scattering of the outgoing photoelectron by the atoms of the ionized C60 molecule. Our results indicate that the observed satellites of the C(1s) main line are most likely of shake-up character. Low-energy electrons emitted below the shake-off …

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Vibrational-State-Dependent Decay Of The Co C(1s) Excitation, N. Saito, Franz Heiser, Oliver Hemmers, A. Hempelmann, K. Wieliczek, J. Viefhaus, U. Becker Jun 1995

Vibrational-State-Dependent Decay Of The Co C(1s) Excitation, N. Saito, Franz Heiser, Oliver Hemmers, A. Hempelmann, K. Wieliczek, J. Viefhaus, U. Becker

Environmental Studies Faculty Publications

Molecular ionization and ionic fragmentation of core excited CO valence and Rydberg states are studied by partial-ion-yield spectroscopy at vibrational resolution. The vibrational intensities of the Rydberg excitations differ significantly depending on the ionization and/or fragmentation channel. The observed intensity variations are explained by nondissociative excited final ionic states of the subsequent molecular Auger decay. The vibrational levels of these final states become selectively depopulated due to interaction with dissociative decay channels leading to ionic fragmentation.

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Dynamics Of Optical-Field-Ionized Plasmas For X-Ray Lasers, Thomas D. Donnelly, R. W. Lee, R. W. Falcone Apr 1995

Dynamics Of Optical-Field-Ionized Plasmas For X-Ray Lasers, Thomas D. Donnelly, R. W. Lee, R. W. Falcone

All HMC Faculty Publications and Research

The success of recombination-pumped x-ray laser schemes is determined by the kinetics of ions in plasmas with relatively dense, cold-electron distributions. We examine how laser gain in such systems is affected by a multipeaked electron distribution generated by sequential ionization of atoms using high-intensity, ultrashort-pulse lasers. We also investigate the role of heating processes that modify electron energy distributions during the recombination and the accompanying collisional cascade. We find that conditions for the success of these schemes are critically modified by the inclusion of these effects.

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Observation Of Parity-Unfavored Transitions In The Nonresonant Photoionization Of Argon, B. Langer, J. Viefhaus, Oliver Hemmers, A. Menzel, R. Wehlitz, U. Becker Feb 1995

Observation Of Parity-Unfavored Transitions In The Nonresonant Photoionization Of Argon, B. Langer, J. Viefhaus, Oliver Hemmers, A. Menzel, R. Wehlitz, U. Becker

Environmental Studies Faculty Publications

Single-photon ionization of an atom or molecule can be subdivided into parity-favored and -unfavored transitions, the latter characterized by electron emission, preferentially perpendicular to the electric vector. The nonresonant existence of these transitions is shown experimentally and studied over an extended energy range for a variety of satellite transitions in atomic argon. The spectra exhibit several clearly resolved satellite lines with strongly negative β values close to -1, independent of the photon energy. The results confirm the corresponding predictions of angular-momentum transfer theory.

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Design And Performance Of The Advanced-Light-Source Double-Crystal Monochromator, G. Jones, S. Ryce, Dennis W. Lindle, B. A. Karlin, J. C. Woicik, Rupert C. Perera Feb 1995

Design And Performance Of The Advanced-Light-Source Double-Crystal Monochromator, G. Jones, S. Ryce, Dennis W. Lindle, B. A. Karlin, J. C. Woicik, Rupert C. Perera

Chemistry and Biochemistry Faculty Research

A new “Cowan type” double-crystal monochromator, based on the boomerang design used at National Synchrotron Light Source (NSLS) beamline X-24A, has been developed for beamline 9.3.1 at the Advanced Light Source (ALS), a windowless ultrahigh vacuum beamline covering the 1-6 keV photon-energy range. Beamline 9.3.1 is designed to simultaneously achieve the goals of high energy resolution, high flux, and high brightness at the sample. The mechanical design of the monochromator has been simplified, and recent developments in technology have been included. Measured mechanical precision of the monochromator shows significant improvement over existing designs. In tests with x-rays at NSLS beamline …

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High-Brightness Beamline For X-Ray Spectroscopy At The Advanced Light Source, Rupert C. Perera, G. Jones, Dennis W. Lindle Feb 1995

High-Brightness Beamline For X-Ray Spectroscopy At The Advanced Light Source, Rupert C. Perera, G. Jones, Dennis W. Lindle

Chemistry and Biochemistry Faculty Research

Beamline 9.3.1 at the Advanced Light Source (ALS) is a windowless beamline, covering the 1-6 keV photon-energy range, designed to achieve the goals of high energy resolution, high flux, and high brightness at the sample. When completed later this year, it will be the first ALS monochromatic hard-x-ray beamline, and its brightness will be an order-of-magnitude higher than presently available in this energy range. In addition, it will provide flux and resolution comparable to any other beamline now in operation. To achieve these goals, two technical improvements, relative to existing x-ray beamlines, were incorporated. First, a somewhat novel optical design …

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Implications Of Fumi’S Theorem For Auxiliary Particle Methods, S. E. Barnes Jan 1995

Implications Of Fumi’S Theorem For Auxiliary Particle Methods, S. E. Barnes

Physics Articles and Papers

Fumi’s theorem in conjunction with some general theorems associated with auxiliary particle methods dictates the functional form of the on-shell auxiliary particle self-energy Σ for a certain class of impurity scattering problems. An explicit calculation which confirms the result is described and the implications for various approaches to the Kondo effect discussed.

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Scanning-Tunneling-Microscopy Study Of Pb On Si(111), D. Tang, H. E. Elsayed-Ali, J. Wendelken, J. Xu Jan 1995

Scanning-Tunneling-Microscopy Study Of Pb On Si(111), D. Tang, H. E. Elsayed-Ali, J. Wendelken, J. Xu

Electrical & Computer Engineering Faculty Publications

Scanning-tunneling microscopy has been used to study temperature and coverage dependence of the structure of lead on the Si(111)-7×7 surface. For low Pb coverage, the Pb atoms favored the faulted sites. The ratio between the number of Pb atoms on faulted to unfaulted sites increased after sample annealing. An energy difference of 0.05 eV associated with a Pb atom on these two sites is estimated. The mobility of Pb atoms on Si(111) was observed at a temperature as low as 260°C for a coverage of 0.1 and 1 ML. © 1995 The American Physical Society.

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Femtosecond Laser-Produced Plasma X-Rays From Periodically Modulated Surface Targets, J. C. Gautheir, S. Bastiani, P. Audebert, J. P. Geindre, K. Neuman, Thomas D. Donnelly, M. Hoffer, R. W. Falcone, R. Shepherd, D. Price, B. White Jan 1995

Femtosecond Laser-Produced Plasma X-Rays From Periodically Modulated Surface Targets, J. C. Gautheir, S. Bastiani, P. Audebert, J. P. Geindre, K. Neuman, Thomas D. Donnelly, M. Hoffer, R. W. Falcone, R. Shepherd, D. Price, B. White

All HMC Faculty Publications and Research

We have studied theoretically and experimentally the x-ray production above 1 keV from femtosecond laser plasmas generated on periodically modulated surface targets. Laser energy coupling to plasma surface waves has been modeled using a numerical differential method. Almost total absorption of incident laser radiation is predicted for optimized interaction conditions. Silicon gratings have been irradiated by a 120fs Ti:sapphire laser at irradiances in excess of 1016 W/cm2. X-ray intensities above 1.5 keV (K-shell lines) have been measured as a function of the incidence angle. Results show a distinct x-ray emission maximum for the first order diffraction …

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