Open Access. Powered by Scholars. Published by Universities.®

Physics Commons™

Open Access. Powered by Scholars. Published by Universities.®

Series

Atomic, Molecular and Optical Physics

Institution
Keyword
Publication Year
Publication
File Type

Articles 1051 - 1080 of 1178

Full-Text Articles in Physics

Role Of Spontaneous Emission In Ultracold Two-Color Optical Collisions, C. I. Sukenik, T. Walker Jan 1999

Role Of Spontaneous Emission In Ultracold Two-Color Optical Collisions, C. I. Sukenik, T. Walker

Physics Faculty Publications

We have observed violet photon emission resulting from energy-pooling collisions between ultracold Rb atoms illuminated by two colors of near-resonant infrared laser light. We have used this emission as a probe of doubly excited state ultracold collision dynamics. By varying the detuning of the lasers, we have clearly identified the effect of spontaneous emission on the collision process.

Go to article

Photofragmentation Of Third-Row Hydrides Following Photoexcitation At Deep-Core Levels, D. L. Hansen, M. E. Arrasate, J. Cotter, G. R. Fisher, Oliver Hemmers, K. T. Leung, Jon C. Levin, R. Martin, Paul Neill, Rupert C. Perera, I. A. Sellin, Marc Simon, Y. Uehara, B. Vanderford, S. B. Whitfield, Dennis W. Lindle Nov 1998

Photofragmentation Of Third-Row Hydrides Following Photoexcitation At Deep-Core Levels, D. L. Hansen, M. E. Arrasate, J. Cotter, G. R. Fisher, Oliver Hemmers, K. T. Leung, Jon C. Levin, R. Martin, Paul Neill, Rupert C. Perera, I. A. Sellin, Marc Simon, Y. Uehara, B. Vanderford, S. B. Whitfield, Dennis W. Lindle

X-Ray Atomic and Molecular Science Program

The relaxation dynamics of HCl, DCl, H2S, and D2S following photoexcitation in the vicinities of the Cl and S K-shell thresholds (~2.8 keV for Cl, ~2.5 keV for S) were studied by means of ion time-of-flight mass spectroscopy. In all cases, the onset of pre-edge core-shell photoionization precedes the formation on resonance of a significant amount of neutral hydrogen as well as postcollision-interaction effects above threshold. Examination of the width of the H+ peak in spectra taken with the analyzer parallel and perpendicular to the polarization vector of the incident light indicates that on resonance, …

Go to article

Photofragmentation Of Third-Row Hydrides Following Photoexcitation At Deep-Core Levels, D. Hansen, M. E. Arrasate, J. Cotter, G. R. Fisher, Oliver Hemmers, K. T. Leung, Jon C. Levin, R. Martin, Paul Neill, Rupert C. Perera, I. A. Sellin, Marc Simon, Y. Uehara, B. Vanderford, S. B. Whitfield, Dennis W. Lindle Nov 1998

Photofragmentation Of Third-Row Hydrides Following Photoexcitation At Deep-Core Levels, D. Hansen, M. E. Arrasate, J. Cotter, G. R. Fisher, Oliver Hemmers, K. T. Leung, Jon C. Levin, R. Martin, Paul Neill, Rupert C. Perera, I. A. Sellin, Marc Simon, Y. Uehara, B. Vanderford, S. B. Whitfield, Dennis W. Lindle

Environmental Studies Faculty Publications

The relaxation dynamics of HCl, DCl, H2S, and D2S following photoexcitation in the vicinities of the Cl and S K-shell thresholds (∼2.8keV for Cl, ∼2.5 keV for S) were studied by means of ion time-of-flight mass spectroscopy. In all cases, the onset of pre-edge core-shell photoionization precedes the formation on resonance of a significant amount of neutral hydrogen as well as postcollision-interaction effects above threshold. Examination of the width of the H+ peak in spectra taken with the analyzer parallel and perpendicular to the polarization vector of the incident light indicates that on resonance, the …

Go to article

High-Resolution Electron Time-Of-Flight Apparatus For The Soft-X-Ray Region, Oliver Hemmers, S. B. Whitfield, P. Glans, H. Wang, Dennis W. Lindle, R. Wehlitz, I. A. Sellin Nov 1998

High-Resolution Electron Time-Of-Flight Apparatus For The Soft-X-Ray Region, Oliver Hemmers, S. B. Whitfield, P. Glans, H. Wang, Dennis W. Lindle, R. Wehlitz, I. A. Sellin

Environmental Studies Faculty Publications

A gas-phase time-of-flight (TOF) apparatus, capable of supporting as many as six electron-TOF analyzers viewing the same interaction region, has been developed to measure energy- and angle-resolved electrons with kinetic energies up to 5 keV. Each analyzer includes a newly designed lens system that can retard electrons to about 2% of their initial kinetic energy without significant loss of transmission; the analyzers can thus achieve a resolving power (E/ΔE) greater than 104 over a wide kinetic-energy range. Such high resolving power is comparable to the photon energy resolution of state-of-the-art synchrotron–radiation beamlines in the soft …

Go to article

Parity Nonconservation In Neutron Capture On 113cd, S J. Seestrom, J D. Bowman, Bret E. Crawford, P P J. Delheij, C M. Frankle, C R. Gould, D G. Haase, M Iinuma, J N. Knudsen, P E. Koehler, L Y. Lowie, A Masaike, Y Matsuda, G E. Mitchell, S I. Penttila, Y P. Popov, H Postma, N R. Roberson, E I. Sharapov, H M. Shimizu, D A. Smith, Sharon L. Stephenson, Y-F Yen, V W. Yuan Nov 1998

Parity Nonconservation In Neutron Capture On 113cd, S J. Seestrom, J D. Bowman, Bret E. Crawford, P P J. Delheij, C M. Frankle, C R. Gould, D G. Haase, M Iinuma, J N. Knudsen, P E. Koehler, L Y. Lowie, A Masaike, Y Matsuda, G E. Mitchell, S I. Penttila, Y P. Popov, H Postma, N R. Roberson, E I. Sharapov, H M. Shimizu, D A. Smith, Sharon L. Stephenson, Y-F Yen, V W. Yuan

Physics and Astronomy Faculty Publications

Parity nonconservation was studied for 23 p-wave resonances in 113Cd up to En=500eV at the LANSCE pulsed neutron source using a longitudinally polarized neutron beam and the time-of-flight method. The helicity dependence of the total neutron capture cross section was measured with an enriched 113Cd target and with a target of natural cadmium. Parity violating effects were observed for several resonances in 113Cd and 111Cd. A root-mean-square value of the parity nonconserving matrix element MJ=1=2.9-0.9+1.3meV was obtained for the spin J=1 levels in the compound nucleus 114Cd. This …

Go to article

Auger Resonance Decay Process In Ar 2p Shell Excitation And Ionization, Y. Lu, Wayne C. Stolte, J.A. R. Samson Oct 1998

Auger Resonance Decay Process In Ar 2p Shell Excitation And Ionization, Y. Lu, Wayne C. Stolte, J.A. R. Samson

Chemistry and Biochemistry Faculty Research

The production and subsequent autoionization of the Ar+ (1D2)6d1 satellite state that is formed either by shake-up or recapture during the Auger decay of a 2p vacancy in Ar has been studied by photoelectron spectroscopy in the energy region from 243 to 256 eV. The creation of near zero energy electrons below and immediately above the Ar 2p ionization threshold is discussed. Some ambiguous points in previous studies are clarified.

Go to article

Measured Stark Widths And Shifts Of Several Niii Sectral Lines: Temperature Dependence, Stevan Djenize, Vladimir Milosavljevic Aug 1998

Measured Stark Widths And Shifts Of Several Niii Sectral Lines: Temperature Dependence, Stevan Djenize, Vladimir Milosavljevic

Articles

Stark parameters (width and shift) of four doubly ionized nitrogen spectral lines, that belong to 3s-3p and 3p-3d transitions (lower multiplets), have been measured in a linear pulsed, low pressure, arc discharge in the nitrogen-oxygen and helium-nitrogen-oxygen plasmas in a (30 000 - 54 000) K electron temperature and a (0.75 1023 - 2.8 1023) electron density ranges. The measured values have been compared to the existing experimental and calculated data.

Go to article

Parity Nonconservation In Neutron Resonances In 232th,, Sharon L. Stephenson, J D. Bowman, Bret E. Crawford, P P J. Delheij, C M. Frankle, M Iinuma, J N. Knudsen, L Y. Lowie, A Masaike, Y Matsuda, G E. Mitchell, S I. Penttila, H Postma, N R. Roberson, S J. Seestrom, E I. Sharapov, Y-F Yen, V W. Yuan Aug 1998

Parity Nonconservation In Neutron Resonances In 232th,, Sharon L. Stephenson, J D. Bowman, Bret E. Crawford, P P J. Delheij, C M. Frankle, M Iinuma, J N. Knudsen, L Y. Lowie, A Masaike, Y Matsuda, G E. Mitchell, S I. Penttila, H Postma, N R. Roberson, S J. Seestrom, E I. Sharapov, Y-F Yen, V W. Yuan

Physics and Astronomy Faculty Publications

Parity nonconservation (PNC) was measured for 24 p-wave resonances from 8 to 300 eV in 232Th by measuring the helicity dependence of the total neutron cross section for epithermal neutrons with an improved experimental system. Ten resonances show statistically significant parity violation. For these ten resonances the analyzing powers are all positive, thus confirming the previously observed sign correlation. The data are fit to the sum of two terms, a constant asymmetry and a fluctuating asymmetry. With this ansatz the root-mean-square PNC matrix element M=1.12 meV, which corresponds to a weak spreading widthΓw=4.7×10-7 eV. For the …

Go to article

Parity Nonconservation In Neutron Resonances In 238u, Bret E. Crawford, J D. Bowman, P P J. Delheij, C M. Frankle, M Iinuma, J N. Knudsen, L Y. Lowie, A Masaike, Y Matsuda, G E. Mitchell, S I. Penttila, H Postma, N R. Roberson, S J. Seestrom, E I. Sharapov, Sharon L. Stephenson, Y-F Yen, V W. Yuan Aug 1998

Parity Nonconservation In Neutron Resonances In 238u, Bret E. Crawford, J D. Bowman, P P J. Delheij, C M. Frankle, M Iinuma, J N. Knudsen, L Y. Lowie, A Masaike, Y Matsuda, G E. Mitchell, S I. Penttila, H Postma, N R. Roberson, S J. Seestrom, E I. Sharapov, Sharon L. Stephenson, Y-F Yen, V W. Yuan

Physics and Astronomy Faculty Publications

Parity nonconservation (PNC) was studied for 24 p-wave neutron resonances in 238U from 10 to 300 eV by measuring the helicity dependence of the total neutron cross section with an improved experimental apparatus. Six resonances show statistically significant (greater than 2.9σ) parity violation. An analysis treating the PNC matrix elements as random variables yields a root-mean-square PNC matrix element M=0.67-0.16+0.24 meV. The corresponding weak spreading width Γw=(1.35-0.64+0.97)×10-7 eV.

Go to article

Neutron Resonance Spectroscopy Of 106pd, And 108pd From 20–2000 Ev, Bret E. Crawford, J D. Bowman, P P J. Delheij, T Haseyama, J N. Knudsen, L Y. Lowie, A Masaike, Y Matsuda, G E. Mitchell, S I. Penttila, H Postma, N R. Roberson, S J. Seestrom, E I. Sharapov, Sharon L. Stephenson, V W. Yuan Aug 1998

Neutron Resonance Spectroscopy Of 106pd, And 108pd From 20–2000 Ev, Bret E. Crawford, J D. Bowman, P P J. Delheij, T Haseyama, J N. Knudsen, L Y. Lowie, A Masaike, Y Matsuda, G E. Mitchell, S I. Penttila, H Postma, N R. Roberson, S J. Seestrom, E I. Sharapov, Sharon L. Stephenson, V W. Yuan

Physics and Astronomy Faculty Publications

Parity nonconserving asymmetries have been measured in p-wave resonances of 106Pd and 108Pd. The data analysis requires knowledge of the neutron resonance parameters. Transmission and capture γ-ray yields were measured for En=20–2000 eV with the time-of-flight method at the Los Alamos Neutron Science Center (LANSCE). A total of 28 resonances in 106Pd and 32 resonances in 108Pd were studied. The resonance parameters for 106Pd are new for all except one resonance. In 108Pd six new resonances were observed and the precision improved for many of the resonance parameters. A Bayesian analysis was …

Go to article

Low Saturation Intensities In Two-Photon Ultracold Collisions, C. I. Sukenik, D. Hoffman, S. Bali, T. Walker Jul 1998

Low Saturation Intensities In Two-Photon Ultracold Collisions, C. I. Sukenik, D. Hoffman, S. Bali, T. Walker

Physics Faculty Publications

We have observed violet photon emission resulting from energy-pooling collisions between ultracold Rb atoms illuminated by two colors of near-resonant infrared laser light. We have used this emission as a probe of doubly excited state ultracold collision dynamics. We have observed the lowest saturation intensity for light-induced ultracold collisions seen to date which we identify as due to depletion of incoming ground state flux. We have also varied the detuning of the lasers which allows us to clearly identify the effect of spontaneous emission and optical shielding.

Go to article

Neutral Dissociation Of Hydrogen Following Photoexcitation Of Hcl At The Chlorine K Edge, D. L. Hansen, J. Cotter, G. R. Fisher, K. T. Leung, R. Martin, Paul Neill, Rupert C. Perera, I. A. Sellin, Marc Simon, Y. Uehara, B. Vanderford, S. B. Whitfield Apr 1998

Neutral Dissociation Of Hydrogen Following Photoexcitation Of Hcl At The Chlorine K Edge, D. L. Hansen, J. Cotter, G. R. Fisher, K. T. Leung, R. Martin, Paul Neill, Rupert C. Perera, I. A. Sellin, Marc Simon, Y. Uehara, B. Vanderford, S. B. Whitfield

Chemistry and Biochemistry Faculty Research

Time-of-flight mass spectroscopy was used to study the relaxation dynamics of HCl following photoexcitation in the vicinity of the Cl K edge (~2.8 keV) using monochromatic synchrotron radiation. At the lowest resonant excitation to the 6ơ* antibonding orbital, almost half of the excited molecules decay by emission of a neutral H atom, mostly in coincidence with a highly charged Cln1 ion. The present work demonstrates that neutral-atom emission can be a significant decay channel for excited states with very short lifetimes (1 fs). [S1050-2947(98)03604-X]

Go to article

Double Photoionization Of Helium, James A.R. Samson, Wayne C. Stolte, Z. X. He, Y. Lu, J. N. Cutler, R. J. Bartlett Mar 1998

Double Photoionization Of Helium, James A.R. Samson, Wayne C. Stolte, Z. X. He, Y. Lu, J. N. Cutler, R. J. Bartlett

Chemistry and Biochemistry Faculty Research

The cross sections for double photoionization of helium and the ratios of double to single ionization have been measured from the double-ionization threshold to 820 eV. The results are in very good agreement with several recent calculations.

Go to article

Electron Attachment Energies Of The Dna Bases, Kayvan Aflatooni, Gordon A. Gallup, Paul Burrow Jan 1998

Electron Attachment Energies Of The Dna Bases, Kayvan Aflatooni, Gordon A. Gallup, Paul Burrow

Paul Burrow Publications

Injection of electrons into the empty π* molecular orbitals of uracil and the DNA bases creates short-lived anion states whose energies have been determined by electron scattering. A common range of attachment energies into the lowest orbitals is observed in all the bases. Evidence for nuclear motion during the lifetimes of the anions is found in all the compounds except adenine. These properties of the bases as bridge sites along the π-stack of DNA, namely, the effective degeneracy of the anion energies and the strong excitation of vibration, are key parameters for theories of electron-transfer rate, some of …

Go to article

Emission Of Excimer Radiation From Direct Current, High-Pressure Hollow Cathode Discharge, Ahmed El-Habachi, Karl H. Schoenbach Jan 1998

Emission Of Excimer Radiation From Direct Current, High-Pressure Hollow Cathode Discharge, Ahmed El-Habachi, Karl H. Schoenbach

Bioelectrics Publications

A novel, nonequilibrium, high-pressure, direct current discharge, the microhollow cathode discharge, has been found to be an intense source of xenon and argon excimer radiation peaking at wavelengths of 170 and 130 nm, respectively. In argon discharges with a 100 μm diam hollow cathode, the intensity of the excimer radiation increased by a factor of 5 over the pressure range from 100 to 800 mbar. In xenon discharges, the intensity at 170 nm increased by two orders of magnitude when the pressure was raised from 250 mbar to 1 bar. Sustaining voltages were 200 V for argon and 400 V …

Go to article

Superfluorescence From Optically Trapped Calcium Atoms, Xianming Han Jan 1998

Superfluorescence From Optically Trapped Calcium Atoms, Xianming Han

Scholarship and Professional Work - LAS

We have studied superfluorescence (SF) under highly unfavorable conditions of rapid collisional and radiative distribution in a Doppler-broadened medium. Nanosecond SF pulses at 5.5 μm were generated on the Ca 4s4p1P1–3d4s1D2 transition from a column of calcium vapor buffered with Ar by optically pumping the 4s21S0–4s4p1P1 transition. The Rabi frequency associated with the intense pump pulse prevents the occurrence of SF while the pump laser is on. As a result, the predicted scaling laws that describe the properties of SF in a transversely excited system, such as peak heights, pulse widths, and delay times, are shown to apply in our …

Go to article

Aspects Of Postcollision Interactions (Pci) Near The Ar L-Shell, James A.R. Samson, Y. Lu, Wayne C. Stolte Oct 1997

Aspects Of Postcollision Interactions (Pci) Near The Ar L-Shell, James A.R. Samson, Y. Lu, Wayne C. Stolte

Chemistry and Biochemistry Faculty Research

In the present work we are interested in near-threshold photoionization experiments involving postcollision effects related to the Auger decay of a vacancy in the Ar L shell. In particular, we have measured the photoelectron energy spectrum resulting from the above postcollision interaction effects and have observed electrons produced by the process of electron capture and reemission.

Go to article

Neutron Resonance Spectroscopy Of 107ag, And 109ag, L Y. Lowie, J D. Bowman, Bret E. Crawford, P P J. Delheij, T Haseyama, J N. Knudsen, A Masaike, Y Matsuda, G E. Mitchell, S I. Penttila, H Postma, N R. Roberson, S J. Seestrom, E I. Sharapov, Sharon L. Stephenson, Y-F Yen, V W. Yuan Jul 1997

Neutron Resonance Spectroscopy Of 107ag, And 109ag, L Y. Lowie, J D. Bowman, Bret E. Crawford, P P J. Delheij, T Haseyama, J N. Knudsen, A Masaike, Y Matsuda, G E. Mitchell, S I. Penttila, H Postma, N R. Roberson, S J. Seestrom, E I. Sharapov, Sharon L. Stephenson, Y-F Yen, V W. Yuan

Physics and Astronomy Faculty Publications

Parity violation has been observed in a number of previously unreported neutron resonances in silver. Analysis of these parity violation data requires improved neutron resonance spectroscopy. The neutron total cross section for natural silver was measured for En=10–800 eV with the time-of-flight method at the Los Alamos Neutron Scattering Center. The neutron capture reaction was studied with both a natural silver target and a highly enriched sample (98.29%) of 107Ag. A total of 38 previously unreported resonances were observed. The combination of the two measurements allowed assignment of the newly observed resonances to 107Ag or to …

Go to article

Nondipole Resonant X-Ray-Raman Spectroscopy: Polarized Inelastic Scattering At The K Edge Of Cl2, J. D. Mills, J. A. Sheehy, T. A. Ferrett, S. H. Southworth, R. Mayer, Dennis W. Lindle, P. W. Langhoff Jul 1997

Nondipole Resonant X-Ray-Raman Spectroscopy: Polarized Inelastic Scattering At The K Edge Of Cl2, J. D. Mills, J. A. Sheehy, T. A. Ferrett, S. H. Southworth, R. Mayer, Dennis W. Lindle, P. W. Langhoff

Chemistry and Biochemistry Faculty Research

Experimental and theoretical studies are reported on the inelastic (Raman) scattering of wavelength-selected polarized x rays from the K edge of gas-phase chlorine molecules. The polarized emission spectra exhibit prominent nondipole features consequent of phase variations of the incident and emitted radiation over molecular dimensions, as predicted by the Kramers-Heisenberg scattering formalism. Issues pursuant to the detection of core-hole localization by resonant Raman scattering from homonuclear diatomic molecules are critically examined. [S0031-9007(97)03486-8]

Go to article

Core Scattering Of Stark Wave Packets, M. L. Naudeau, C. I. Sukenik, P. H. Bucksbaum Jul 1997

Core Scattering Of Stark Wave Packets, M. L. Naudeau, C. I. Sukenik, P. H. Bucksbaum

Physics Faculty Publications

We investigate the wave packet dynamics of electrons bound in the nonseparable potential of cesium in a static electric field using time-domain Ramsey interferometry. Specially shaped wave packets with low radial dispersion enable us to view the interaction between the wave packet and the atomic core. Experiments in cesium, together with quantum defect calculations of cesium and hydrogen, demonstrate changes in the motion and shape of these wave packets due to core scattering.

Go to article

On The Stark Broadening Parameters Of The Two Nii Spectral Lines Of The 3d-4f Transition, Vladimir Milosavljevic, Stevan Djenize Jun 1997

On The Stark Broadening Parameters Of The Two Nii Spectral Lines Of The 3d-4f Transition, Vladimir Milosavljevic, Stevan Djenize

Articles

Stark parameters (width and shift) of two singly ionized nitrogen spectral lines, that belong to 3d-4f transition have been measured in a linear pulsed, low pressure, arc discharge in the nitrogen-oxygen plasma at a 54000 K electron temperature and at a 2.8×10 23 m−3 electron density. The measured values have been compared to the existing experimental and calculated data

Go to article

Breakdown Of The Independent Particle Approximation In High-Energy Photoionization, E. W. B. Dias, H. S. Chakraborty, P. C. Deshmukh, S. T. Manson, Oliver Hemmers, P. Glans, D. Hansen, H. Wang, S. B. Whitfield, Dennis W. Lindle, R. Wehlitz, Jon C. Levin, I. A. Sellin Jun 1997

Breakdown Of The Independent Particle Approximation In High-Energy Photoionization, E. W. B. Dias, H. S. Chakraborty, P. C. Deshmukh, S. T. Manson, Oliver Hemmers, P. Glans, D. Hansen, H. Wang, S. B. Whitfield, Dennis W. Lindle, R. Wehlitz, Jon C. Levin, I. A. Sellin

Environmental Studies Faculty Publications

The independent particle approximation is shown to break down for the photoionization of both inner and outer nℓ (ℓ>0) electrons of all atoms, at high enough energy, owing to interchannel interactions with the nearby ns photoionization channels. The effect is illustrated for Ne 2p in the 1 keV photon energy range through a comparison of theory and experiment. The implications for x-ray photoelectron spectroscopy of molecules and condensed matter are discussed.

Go to article

Roughening And Preroughening Of Diamond-Cubic {111} Surfaces, Donald L. Woodraska, John A. Jaszczak Jan 1997

Roughening And Preroughening Of Diamond-Cubic {111} Surfaces, Donald L. Woodraska, John A. Jaszczak

Department of Physics Publications

A solid-on-solid model for {111} surfaces of diamond-cubic materials that correctly takes into account the diamond-cubic crystal structure has been developed for Monte Carlo simulation. In addition to a roughening transition at temperature TR, a distinct preroughening transition at TPR≈0.43TR is indicated by divergences in the surface specific heat and order-parameter susceptibility. Preroughening appears to arise naturally in our nearest-neighbor bond model from the entropic freedom available in the nontrivial crystal structure. Preroughening is shown to dramatically lower the nucleation barrier for growth and etching at low driving forces.

Go to article

Quantum Coherence In Small Antiferromagnets, S. E. Barnes, R. Ballou, B. Barbara, J. Strelen Jan 1997

Quantum Coherence In Small Antiferromagnets, S. E. Barnes, R. Ballou, B. Barbara, J. Strelen

Physics Articles and Papers

An antiferromagnetic particle with an excess spin j⃗ has 2 degrees of freedom. The one associated with j⃗ is ferromagnetic, while the antiferromagnetic behavior involves Néel vector n⃗. It is shown that the spin-parity effect described by Loss et al. has to do with the ferromagnetic degree of freedom and does not imply the localization of n⃗ for small enough particles for half-integer spin. It is also shown that the tunnel splitting associated with n⃗ is insensitive to applied fields.

Go to article

Kinetic-Energy- And Angular-Resolved Fragmentation Of Co In Vibrational-Resolved C 1s Excitation, N. Saito, Franz Heiser, Oliver Hemmers, K. Wieliczek, J. Viefhaus, U. Becker Sep 1996

Kinetic-Energy- And Angular-Resolved Fragmentation Of Co In Vibrational-Resolved C 1s Excitation, N. Saito, Franz Heiser, Oliver Hemmers, K. Wieliczek, J. Viefhaus, U. Becker

Environmental Studies Faculty Publications

Angular distributions of C++O+ from CO were measured, following vibrationally resolved C 1s excitations into the 2pπ, 3sσ, and 3pπ orbitals as well as into higher unresolved orbitals. A time-of-flight mass spectrometer, with a multihit-type position-sensitive anode, was used for the measurements. The anisotropy parameters (β) of C++O+ approach their theoretically expected values as the released kinetic energy in the fragmentation increases. The value of the β parameters remains constant for all vibrational states within each orbital.

Go to article

First Results From The High-Brightness X-Ray Spectroscopy Beamline 9.3.1 At Als, W. Ng, G. Jones, Rupert C. Perera, D. Hansen, J. Daniels, Oliver Hemmers, P. Glans, S. B. Whitfield, H. Wang, Dennis W. Lindle Sep 1996

First Results From The High-Brightness X-Ray Spectroscopy Beamline 9.3.1 At Als, W. Ng, G. Jones, Rupert C. Perera, D. Hansen, J. Daniels, Oliver Hemmers, P. Glans, S. B. Whitfield, H. Wang, Dennis W. Lindle

Environmental Studies Faculty Publications

Beamline 9.3.1 at the Advanced Light Source (ALS) is a windowless beamline, covering the 1–6 keV photon energy range. This beamline is designed to achieve the goal of high brightness at the sample for use in the x‐ray atomic and molecular spectroscopy (XAMS) science, surface and interface science, biology and x‐ray optical development programs at ALS. X‐ray absorption and time‐of‐flight photoemission measurements in 2–5 keV photon energy range along with the flux, resolution, spot size and stability of the beamline will be discussed. Prospects for future XAMS measurements will also be presented.

Go to article

Post-Collision Interactions In The Auger Decay Of The Ar L-Shell, James A.R. Samson, Wayne C. Stolte, Z. X. He, J. N. Cutler, D. Hansen Sep 1996

Post-Collision Interactions In The Auger Decay Of The Ar L-Shell, James A.R. Samson, Wayne C. Stolte, Z. X. He, J. N. Cutler, D. Hansen

Chemistry and Biochemistry Faculty Research

The photoionization cross sections for Ar+ through Ar4+, produced by the Auger decay of a 2p hole in argon, have been measured between 242 eV and 253 eV by the use of synchrotron radiation. The high resolution of the monochromator has allowed a detailed study of the postcollision interactions that occur in this spectral region. The concept of photoelectron recapture by Ar2+ to produce the Ar+ continuum is studied. The relative values of the quantum-mechanical calculations of the photoelectron recapture probability are shown to be in excellent agreement with the present data. The magnitude …

Go to article

Cross Sections For The Production Of He+ (Np) 2p0 States By 50 To 150 Kev Proton Impact On Helium, Wayne C. Stolte, R. Bruch Sep 1996

Cross Sections For The Production Of He+ (Np) 2p0 States By 50 To 150 Kev Proton Impact On Helium, Wayne C. Stolte, R. Bruch

Chemistry and Biochemistry Faculty Research

Cross sections have been measured for the production of He+ (np) 2Po states, n=2,3,4, by proton impact on helium over a projectile velocity range of 1.42–2.45 a.u. (50 ≤E≤150 keV). Cross sections were determined by measuring the extreme ultraviolet photons emitted from excited He1 ions. The data indicate a lower energy than expected for the maximum cross section. A comparison of the present results in terms of projectile energy dependance with the cross sections for excitation to He (1snp) 1Po, ionization, and total electron capture suggests the primary mechanism …

Go to article

Nuclear Reaction Studies With Radioactive {Sup 18}F Beams At Atlas, K. E. Rehm, M. Paul, Andrew D. Roberts, C. L. Jiang, D. Blumenthal, C. N. Davids, P. Decrock, S. M. Fischer, J. Gehring, D. Henderson, C. J. Lister, Robert J. Nickles, J. Nolen, R. C. Pardo, J. P. Schiffer, R. E. Segel Jul 1996

Nuclear Reaction Studies With Radioactive {Sup 18}F Beams At Atlas, K. E. Rehm, M. Paul, Andrew D. Roberts, C. L. Jiang, D. Blumenthal, C. N. Davids, P. Decrock, S. M. Fischer, J. Gehring, D. Henderson, C. J. Lister, Robert J. Nickles, J. Nolen, R. C. Pardo, J. P. Schiffer, R. E. Segel

Physics and Astronomy Department Publications

The contribution of the {sup 18}F(p,{gamma}) reaction to the production of {sup 19}Ne which is the crucial isotope for the breakout from the hot CNO cycle into the rp process, has been investigated in experiments with {sup 18}F beams. Measurements of the cross sections for the {sup 18}F(p,{alpha}){sup 15}O and the {sup 18}F(p,{gamma}){sup 19}Ne reactions indicate that the contribution from the (p,{gamma}) route to the formation of {sup 19}Ne is small.

Go to article

Observation Of A Large Parity Nonconserving Analyzing Power In Xe, J J. Szymanski, W M. Snow, J D. Bowman, B Cain, Bret E. Crawford, P P J. Delheij, R D. Hartman, T Haseyama, C D. Keith, J N. Knudsen, A Komives, M Leuschner, L Y. Lowie, A Masaike, Y Matsuda, G E. Mitchell, S I. Penttila, H Postma, D Rich, N R. Roberson, S J. Seestrom, E I. Sharapov, Sharon L. Stephenson, Y-F Yen, V W. Yuan Jun 1996

Observation Of A Large Parity Nonconserving Analyzing Power In Xe, J J. Szymanski, W M. Snow, J D. Bowman, B Cain, Bret E. Crawford, P P J. Delheij, R D. Hartman, T Haseyama, C D. Keith, J N. Knudsen, A Komives, M Leuschner, L Y. Lowie, A Masaike, Y Matsuda, G E. Mitchell, S I. Penttila, H Postma, D Rich, N R. Roberson, S J. Seestrom, E I. Sharapov, Sharon L. Stephenson, Y-F Yen, V W. Yuan

Physics and Astronomy Faculty Publications

A large parity nonconserving longitudinal analyzing power was discovered in polarized-neutron transmission through Xe. An analyzing power of 4.3±0.2% was observed in a p-wave resonance at En=3.2 eV. The measurement was performed with a liquid Xe target of natural isotopic abundance that was placed in the polarized epithermal neutron beam, flight path 2, at the Manuel Lujan Neutron Science Center. This apparatus was constructed by the TRIPLE Collaboration, and has been used for studies of parity symmetry in compound nuclear resonances. Part of the motivation of the experiment was to discover a nucleus appropriate for a sensitive test …

Go to article

First Prev Next Last