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Full-Text Articles in Physics

A Cylindrically Symmetric “Micro-Mott” Electron Polarimeter, Nathan B. Clayburn, Evan M. Brunkow, S. J. Burtwistle, George H. Rutherford, Timothy J. Gay May 2016

A Cylindrically Symmetric “Micro-Mott” Electron Polarimeter, Nathan B. Clayburn, Evan M. Brunkow, S. J. Burtwistle, George H. Rutherford, Timothy J. Gay

Timothy J. Gay Publications

A small, novel, cylindrically symmetric Mott electron polarimeter is described. The effective Sherman function, Seff , or analyzing power, for 20 kV Au target bias with a 1.3 keV energy loss window is 0.16 ± 0.01, where uncertainty in the measurement is due primarily to uncertainty in the incident electron polarization. For an energy loss window of 0.5 keV, Seff reaches its maximum value of 0.24 ± 0.02. The device’s maximum efficiency, I/Io, defined as the detected count rate divided by the incident particle rate, is 3.7 ± 0.2 ...


Anomalously Large Chiral Sensitivity In The Dissociative Electron Attachment Of 10-Iodocamphor, J. M. Dreiling, F. W. Lewis, J. D. Mills, Timothy J. Gay Jan 2016

Anomalously Large Chiral Sensitivity In The Dissociative Electron Attachment Of 10-Iodocamphor, J. M. Dreiling, F. W. Lewis, J. D. Mills, Timothy J. Gay

Timothy J. Gay Publications

We have studied dissociative electron attachment (DEA) between low energy (≤ 0.6 eV) longitudinally polarized electrons and gas-phase chiral targets of 3-bromocamphor (C10H15BrO), 3-iodocamphor (C10H15IO), and 10-iodocamphor. The DEA rate depends on the sign of the incident electron helicity for a given target handedness, and it varies with both the atomic number (Z) and location of the heaviest atom in the molecule. While simple dynamic mechanisms can account for the asymmetry dependence on Z, they fail to explain the large asymmetry variation with the heavy atom location.


Orientation Of Doubly Excited States In N2, John E. Furst, Timothy J. Gay, Joshua Machacek, David Kilkoyne, Kenneth W. Mclaughlin Jan 2012

Orientation Of Doubly Excited States In N2, John E. Furst, Timothy J. Gay, Joshua Machacek, David Kilkoyne, Kenneth W. Mclaughlin

Timothy J. Gay Publications

We have measured the total fluorescent intensity and circular polarization of light emitted in 3p 4Po → 3s4P transitions of excited neutral nitrogen atoms created by the photofragmentation of the N2 molecule with circularly polarized light having energies between 21 and 26 eV. The intensity measurements show the effect of predissociation of the N2 Rydberg series R(C) 1Σ+u states by non-Rydberg doubly excited resonances (NRDERs), while nonzero values of circular polarization allow us to unambiguously identify the presence of a directly excited NRDER with 1Πu symmetry in this ...


Detecting An Extended Light Source Through A Lens, E. T. Litaker, J. R. Machacek, Timothy J. Gay Jan 2011

Detecting An Extended Light Source Through A Lens, E. T. Litaker, J. R. Machacek, Timothy J. Gay

Timothy J. Gay Publications

We present a Monte Carlo simulation of a cylindrical luminescent volume and a typical lens–detector system. The results of this simulation yield a graphically simple picture of the regions within the cylindrical volume from which this system detects light. Because the cylindrical volume permits large angles of incidence, we use a modification of the thin-lens approximation for ray tracing. We compare simulation results with concepts from imaging optics, and comment on implications for experimental design.


Measurement Of Electron Beam Polarization From Unstrained Bulk Gaas Via Two Photon Photoemission, J L Mccarter, Timothy J. Gay, J Hansknecht, M Poelker, M L Stutzman Jan 2011

Measurement Of Electron Beam Polarization From Unstrained Bulk Gaas Via Two Photon Photoemission, J L Mccarter, Timothy J. Gay, J Hansknecht, M Poelker, M L Stutzman

Timothy J. Gay Publications

This paper describes measurements of the beam polarization and quantum efficiency for photo-emission using two-photon excitation from unstrained bulk GaAs illuminated with pulsed, high intensity 1560nm laser light. Quantum efficiency is linearly proportional to 1560nm peak laser intensity, which was varied in three independent ways, indicating that the emitted electrons are promoted from the valence to the conduction band via two-photon absorption. Beam polarization was measured using a microMott polarimeter, with a value of 16.8(4)% polarization at 1560nm, which is roughly half the measured value of 33.4(8)% using 778 nm light.


Production Of Excited Atomic Hydrogen And Deuterium From H2, Hd And D2 Photodissociation, J R. Machacek, V M. Andrianarijaona, J. E. Furst, A L D Kilcoyne, A L Landers, E T Litaker, K W Mclaughlin, Timothy J. Gay Jan 2011

Production Of Excited Atomic Hydrogen And Deuterium From H2, Hd And D2 Photodissociation, J R. Machacek, V M. Andrianarijaona, J. E. Furst, A L D Kilcoyne, A L Landers, E T Litaker, K W Mclaughlin, Timothy J. Gay

Timothy J. Gay Publications

We have measured the production of Lyman α and Balmer α fluorescence from atomic H and D for the photodissociation of H2, HD and D2 by linearly-polarized photons with energies between 22 and 64 eV. We discuss systematic uncertainties associated with our data, and compare our results with previous experimental results and ab initio calculations of the dissociation process. We comment on the discrepancies.


Alignment And Orientation Of Diatomic Molecules Induced By Polarized Electron Impact, Jack W. Maseberg, Timothy J. Gay Jan 2010

Alignment And Orientation Of Diatomic Molecules Induced By Polarized Electron Impact, Jack W. Maseberg, Timothy J. Gay

Timothy J. Gay Publications

We report measurements of linear and circular fluorescence polarizations for molecular transitions in H2, D2, and N2 induced by spin-polarized electron impact. Circular polarizations resulting from some Fulcher-α transitions in H2 and D2 are found to be significant, while the null results from nitrogen’s second positive system are consistent with an earlier measurement by the Münster group. We compare this nitrogen data to that from our previous study of nitrogen’s first negative system. Emphasis is placed on understanding the mechanisms that cause the values of circular polarization from N2 to be relatively ...


A Low-Voltage Retarding-Field Mott Polarimeter For Photocathode Characterization, J.L. Mccarter, M.L. Stutzman, K.W. Trantham, Timothy G. Anderson, A.M. Cook, Timothy J. Gay Jan 2010

A Low-Voltage Retarding-Field Mott Polarimeter For Photocathode Characterization, J.L. Mccarter, M.L. Stutzman, K.W. Trantham, Timothy G. Anderson, A.M. Cook, Timothy J. Gay

Timothy J. Gay Publications

Nuclear physics experiments at Thomas Jefferson National Accelerator Facility’s CEBAF rely on high polarization electron beams. We describe a recently commissioned system for prequalifying and studying photocathodes for CEBAF with a load-locked, low-voltage polarized electron source coupled to a compact retarding-field Mott polarimeter. The polarimeter uses simplified electrode structures and operates from 5 to 30 kV. The effective Sherman function for this device has been calibrated by comparison with the CEBAF 5 MeV Mott polarimeter. For elastic scattering from a thick gold target at 20 keV, the effective Sherman function is 0.201(5). Its maximum efficiency at 20 ...


Electron-Spin-Reversal Phenomenon In Optically Pumped Rubidium, E. B. Norrgard, D. Tupa, J. M. Dreiling, Timothy J. Gay Jan 2010

Electron-Spin-Reversal Phenomenon In Optically Pumped Rubidium, E. B. Norrgard, D. Tupa, J. M. Dreiling, Timothy J. Gay

Timothy J. Gay Publications

We have studied the optical pumping of mixtures of Rb vapor and N2 buffer gas by laser light tuned to the D1 transition having a spectral width of ∼500 MHz. The Rb densities are of the order of 1013 cm−3, while the buffer-gas pressures range from 0.1 to 10 torr. As the frequency of the right-hand circularly polarized laser is varied across the D1 absorption profile, the electron spin polarization of the Rb is found to take on negative values for small negative values of pump detuning from the absorption profile center. This occurs for ...


Spin Torque On Molecular Rotation Induced By Polarized Electrons, J. W. Maseberg, Timothy J. Gay Jan 2009

Spin Torque On Molecular Rotation Induced By Polarized Electrons, J. W. Maseberg, Timothy J. Gay

Timothy J. Gay Publications

We have measured the linear and circular polarization of 391.4 nm N2+ B 2Σu+(υ’=0) → X2Σg+n=0) P-branch fluorescence produced by spin-polarized electron impact excitation of N2 X1 Σg+(υ=0) ground states. The resulting nonzero values of the circular polarization indicate that spin-rotation coupling, in conjunction with electron exchange excitation, acts to produce oriented rotational angular momenta in the excited molecular state prior to decay.


Use Of Partial-Wave Decomposition To Identify Resonant Interference Effects In The Photoionization–Excitation Of Argon, Timothy J. Gay, Chris H. Greene, J. R. Machacek, K. W. Mclaughlin, H. W. Van Der Hart, Orhan Yenen, Duane H. Jaecks Jan 2009

Use Of Partial-Wave Decomposition To Identify Resonant Interference Effects In The Photoionization–Excitation Of Argon, Timothy J. Gay, Chris H. Greene, J. R. Machacek, K. W. Mclaughlin, H. W. Van Der Hart, Orhan Yenen, Duane H. Jaecks

Timothy J. Gay Publications

We have studied simultaneous photoionization and excitation of Ar in the range of incident photon energies between 36.00 and 36.36 eV, where the resonant production of doubly excited neutral Ar states imbedded in the ionization continuum is dominant. By measuring the relative Stokes parameters of the fluorescence from residual Ar+∗ (3p4 [3P] 4p) ions (2P1/2, 465.8 nm transition; 2P3/2, 476.5 nm; 2D3/2, 472.7 nm; 2D5/2, 488.0 nm; 4P5/2, 480.6 nm; 4D5/2, 514.5 ...


Active Feedback Scheme For Minimization Of Helicity-Dependent Instrumental Asymmetries, M. I. Fabrikant, K. W. Trantham, V. M. Andrianarijaona, Timothy J. Gay May 2008

Active Feedback Scheme For Minimization Of Helicity-Dependent Instrumental Asymmetries, M. I. Fabrikant, K. W. Trantham, V. M. Andrianarijaona, Timothy J. Gay

Timothy J. Gay Publications

A method for the active feedback reduction of optical instrumental intensity asymmetries is presented. It is based on the fast chopping of two spatially separated beams of light with orthogonal linear polarizations that are recombined and passed through a quarter-wave plate to yield a single beam with rapidly flipping helicity. Active electro-optic feedback has been successfully employed to maintain this asymmetry below 10−5.


Radiation Trapping In Rubidium Optical Pumping At Low Buffer-Gas Pressures, Mark A. Rosenberry, J. P. Reyes, D. Tupa, Timothy J. Gay Feb 2007

Radiation Trapping In Rubidium Optical Pumping At Low Buffer-Gas Pressures, Mark A. Rosenberry, J. P. Reyes, D. Tupa, Timothy J. Gay

Timothy J. Gay Publications

We have made a systematic study of rubidium optical pumping in a simple cylindrical cell geometry with a high-power 10 W diode laser array, low magnetic fields, and buffer-gas pressures of less than 50 torr. We have determined rubidium polarizations experimentally for H2, N2, He, and Ar buffer gases, with Rb number densities from 1012 to 1013 cm-3. Comparison to a relatively simple optical pumping model allows us to extract useful information about radiation trapping and quenching effects.


Fluorescence Polarization Of Helium Negative-Ion Resonances Excited By Polarized Electron Impact, J. W. Maseberg, Timothy J. Gay Nov 2006

Fluorescence Polarization Of Helium Negative-Ion Resonances Excited By Polarized Electron Impact, J. W. Maseberg, Timothy J. Gay

Timothy J. Gay Publications

We have investigated helium (1s3d) 3D → (1s2p) 3P (588 nm) fluorescence produced by electron impact excitation in the vicinity of the (2s22p) 2P and (2s2p2) 2D negative-ion resonances at 57.2 and 58.3 eV, respectively. In contrast to previous work, we use spin-polarized incident electrons and report the relative Stokes parameters P1, P2, and P3 in the 55–60 eV region. Our failure to see discernable resonance effects in P2 indicates that even though the lifetime of these resonances is significant (~10 fs), magnetic forces acting on the ...


Production Of Excited Atomic Hydrogen And Deuterium From H2 And D2 Photodissociation, J. D. Bozek, J. E. Furst, Timothy J. Gay, H. Gould, A. L. D. Kilcoyne, J. R. Machacek, F. Martin, K. W. Mclaughlin, J. L. Sanz-Vicario Nov 2006

Production Of Excited Atomic Hydrogen And Deuterium From H2 And D2 Photodissociation, J. D. Bozek, J. E. Furst, Timothy J. Gay, H. Gould, A. L. D. Kilcoyne, J. R. Machacek, F. Martin, K. W. Mclaughlin, J. L. Sanz-Vicario

Timothy J. Gay Publications

We have measured the production of both Lyα and Hα fluorescence from atomic H and D for the photodissociation of H2 and D2 by linearly polarized photons with energies between 24 and 60 eV. In this energy range, excited photofragments result primarily from the production of doubly excited molecular species which promptly autoionize or dissociate into two neutrals. Our data are compared with ab initio calculations of the dissociation process, in which both doubly excited state production and prompt ionization (non resonant) channels are considered. Agreement between our experimental data and that of earlier work, and with our ...


Angular Momentum Partitioning In The Dissociation Of Diatomic Molecules, Timothy J. Gay, J. D. Bozek, J. E. Furst, Gordon A. Gallup, A. S. Green, A. L. D. Kilcoyne, J. R. Machacek, J. W. Maseberg, K. W. Mclaughlin, Mark A. Rosenberry Jan 2006

Angular Momentum Partitioning In The Dissociation Of Diatomic Molecules, Timothy J. Gay, J. D. Bozek, J. E. Furst, Gordon A. Gallup, A. S. Green, A. L. D. Kilcoyne, J. R. Machacek, J. W. Maseberg, K. W. Mclaughlin, Mark A. Rosenberry

Timothy J. Gay Publications

We discuss recent experiments that study the transfer of angular momentum from a projectile to the residual target in collisions between the simple diatomic molecules H2 and N2 and spin-polarized electrons or circularly-polarized photons. We observe the fluorescence of both the atomic fragments and excited molecular states, and measure the circular polarization fraction of this light, P3. The incident electron energies range from 10 to 100 eV; the incident photon energies from 33 to 38 eV.


Angular Momentum Partitioning And The Subshell Multipole Moments In Impulsively Excited Argon Ions, H. M. Al-Khateeb, B. G. Birdsey, Timothy J. Gay Mar 2005

Angular Momentum Partitioning And The Subshell Multipole Moments In Impulsively Excited Argon Ions, H. M. Al-Khateeb, B. G. Birdsey, Timothy J. Gay

Timothy J. Gay Publications

We have investigated collisions between transversely polarized electrons and Ar, in which the Ar is simultaneously ionized and excited to the Ar+*[3p4(+D)4p] states. The Stokes parameters of the fluorescence emitted in the following transitions was measured: (+D)4s 2D5/2−(1D)4p 2F7/2 (461.0 nm), (1D)4s 2D5/2 −(1D)4p 2F5/2 (463.7 nm), (1P)3d 2D5/2−(1D)4p 2D5/2 (448.2 nm), and (1 ...


Angular Momentum Partitioning And The Subshell Multipole Moments In Impulsively Excited Argon Ions, H. M. Al-Khateeb, B. G. Birdsey, Timothy J. Gay Mar 2005

Angular Momentum Partitioning And The Subshell Multipole Moments In Impulsively Excited Argon Ions, H. M. Al-Khateeb, B. G. Birdsey, Timothy J. Gay

Timothy J. Gay Publications

We have investigated collisions between transversely polarized electrons and Ar, in which the Ar is simultaneously ionized and excited to the Ar+*[3p4(+D)4p] states. The Stokes parameters of the fluorescence emitted in the following transitions was measured: (+D)4s 2D5/2−(1D)4p 2F7/2 (461.0 nm), (1D)4s 2D5/2 −(1D)4p 2F5/2 (463.7 nm), (1P)3d 2D55/2−(1D)4p 2D5/2 (448.2 nm), and ...


Angular Momentum Partitioning And The Subshell Multipole Moments In Impulsively Excited Argon Ions, H. M. Al-Khateeb, B. G. Birdsey, Timothy J. Gay Mar 2005

Angular Momentum Partitioning And The Subshell Multipole Moments In Impulsively Excited Argon Ions, H. M. Al-Khateeb, B. G. Birdsey, Timothy J. Gay

Timothy J. Gay Publications

We have investigated collisions between transversely polarized electrons and Ar, in which the Ar is simultaneously ionized and excited to the Ar+*[3p4(+D)4p] states. The Stokes parameters of the fluorescence emitted in the following transitions was measured: (+D)4s 2D/2−(1D)4p 2F7/2 (461.0 nm), (1D)4s 2D5/2 −(1D)4p 2F5/2 (463.7 nm), (1P)3d 2D5/2−(1D)4p 2D5/2 (448.2 nm), and (1D ...


Spin-Exchange-Induced Circularly Polarized Molecular Fluorescence, A. S. Green, Gordon A. Gallup, Mark A. Rosenberry Mar 2004

Spin-Exchange-Induced Circularly Polarized Molecular Fluorescence, A. S. Green, Gordon A. Gallup, Mark A. Rosenberry

Timothy J. Gay Publications

We have measured the circular polarization of light emitted from both atomic H and molecular H2 after bombarding H2 with longitudinally polarized electrons. For both atomic and molecular fluorescence near threshold we observe a circular polarization as great as 10% of the electron polarization. This represents the first direct observation of spin transfer in electron-molecule collisions.


Effect Of Relativistic Many-Electron Interactions On Photoelectron Partial Wave Probabilities, K. W. Mclaughlin, Orhan Yenen, Duane H. Jaecks, Timothy J. Gay, M. M. Sant'anna, D. Calabrese, B. Thaden-Jordan Mar 2002

Effect Of Relativistic Many-Electron Interactions On Photoelectron Partial Wave Probabilities, K. W. Mclaughlin, Orhan Yenen, Duane H. Jaecks, Timothy J. Gay, M. M. Sant'anna, D. Calabrese, B. Thaden-Jordan

Timothy J. Gay Publications

We obtain relative cross sections for the production of photoelectrons with specific angular momentum quantum numbers. These cross sections are obtained from the polarization analysis of the visible fluorescence of ions produced when circularly polarized vacuum ultraviolet radiation photoionizes ground state Ar. The ratio of cross sections for the production of photoelectrons with the same orbital angular momentum but different total angular momenta shows strong deviations from the statistical ratio, demonstrating the importance of relativistic interactions in many-electron photoionization dynamics.


Progress With Optically Pumped Sources Of Polarized Electrons, Mark A. Rosenberry, Herman Batelaan, J. P. Reyes, Timothy J. Gay Jan 2002

Progress With Optically Pumped Sources Of Polarized Electrons, Mark A. Rosenberry, Herman Batelaan, J. P. Reyes, Timothy J. Gay

Timothy J. Gay Publications

We report our work in developing new "turn-key" sources of polarized electrons. These sources operate by extracting the electrons from a discharge and polarizing them through optical pumping. Preliminary work demonstrates that beams of 4 μA with greater than 20% polarization are possible. Such devices could enormously simplify the running of many experiments in the fields of atomic structure, magnetic materials and biophysics.


Determination Of Hexadecapole Moments For The 3p4(1D) Core Of Argon Ii Excited In Polarized E--Ar Collisions, B. G. Birdsey, H. M. Al-Khateeb, Timothy J. Gay Jan 2002

Determination Of Hexadecapole Moments For The 3p4(1D) Core Of Argon Ii Excited In Polarized E--Ar Collisions, B. G. Birdsey, H. M. Al-Khateeb, Timothy J. Gay

Timothy J. Gay Publications

We report on measurements of the integrated Stokes parameters of the light emitted from four well-LS coupled states of the 3p4(1D)4p manifold of Aril, following the simultaneous ionization and excitation of neutral argon by polarized electrons. As for all states, the state multipoles of J can be expanded in terms of the total orbital (L ) and the total spin (S) state multipoles. By splitting each L and S state multipole into multipoles for the core and outer electron, we have experimentally obtained for the first time the normalized integrated state multipole of rank 4 (hexadecapole moment ...


Monte Carlo Studies Of Mott Scattering Asymmetries From Gold Foils, M. A. Khakoo, D. Roundy, C. Hicks, N. Margolis, E. Yeung, A. W. Ross, Timothy J. Gay Oct 2001

Monte Carlo Studies Of Mott Scattering Asymmetries From Gold Foils, M. A. Khakoo, D. Roundy, C. Hicks, N. Margolis, E. Yeung, A. W. Ross, Timothy J. Gay

Timothy J. Gay Publications

We present the results of a series of model Monte Carlo calculations of the scattering of spin-polarized electrons from gold foil targets. Our calculations examine the behavior of the left-right scattering asymmetry A as a function of various parameters conventionally used in extrapolation of the left-right asymmetry to single atom and/or elastic scattering conditions. These parameters include target thickness, scattered count rate, and the maximum energy that an electron can have lost in the target and still be detected. Data are obtained at incident electron energies of 10–120 keV, with detector-subtended half-cone angles of 5°, 10°, and 20 ...


A Theoretical Study Of The Effects Of Insulators On Electron Transport Through Electrostatic Tube Lenses, T. G. Anderson, B. G. Birdsey, S. M. Woeher, Mark A. Rosenberry, Timothy J. Gay Jul 2001

A Theoretical Study Of The Effects Of Insulators On Electron Transport Through Electrostatic Tube Lenses, T. G. Anderson, B. G. Birdsey, S. M. Woeher, Mark A. Rosenberry, Timothy J. Gay

Timothy J. Gay Publications

Using the computer program SIMION 6, we have studied the effects of spurious insulator charging on the trajectories of electrons through electrostatic tube lenses. We considered lens elements with flat ends, spaced a distance g apart, whose inner diameter D=10g. For the standard cases of drift tubes, two-element lenses, and einzel lenses, we found that charging effects are eliminated if t/g>3.5, where t is the distance between the lens inner diameter and the charged spacing insulator.


Angular Momentum Partitioning And Hexacontatetrapole Moments In Impulsively Excited Argon Ions, H. M. Al-Khateeb, B. G. Birdsey, Timothy J. Gay Nov 2000

Angular Momentum Partitioning And Hexacontatetrapole Moments In Impulsively Excited Argon Ions, H. M. Al-Khateeb, B. G. Birdsey, Timothy J. Gay

Timothy J. Gay Publications

We have studied polarized electron collisions with Ar in which the target is simultaneously ionized and excited to form Ar+(3p4(1D)4p) states. We measured the integrated Stokes parameters of the subsequent fluorescence emitted by the 2F7/2, 2F5/2, 2D5/2, and 2P3/2 states along the direction of electron polarization. The Rubin-Bederson hypothesis is shown to hold for the L and S multipoles of these states. The electric quadrupole and hexadecapole of the 1D core are derived. By recoupling these moments with the electric ...


A Simplified Gaas Polarized Electron Source, H. M. Al-Khateeb, B. G. Birdsey, T. C. Bowen, A. S. Green, M. E. Johnston, Timothy J. Gay Oct 1999

A Simplified Gaas Polarized Electron Source, H. M. Al-Khateeb, B. G. Birdsey, T. C. Bowen, A. S. Green, M. E. Johnston, Timothy J. Gay

Timothy J. Gay Publications

We report operational and construction details of a simplified GaAs polarized electron source. It is contained in a modified 4.63 in. Conflat four-way cross, and uses a single 56 ℓ /s turbomolecular pump. The design incorporates multiple cesiators to extend source lifetime, a new spring-clamp GaAs crystal mounting design to provide uniform crystal heating, and a very simple tubular 90° electrostatic deflector. We also discuss matters related to preparing, heat cleaning, and activating the GaAs crystal.


Near-Threshold Measurement Of Integrated Stokes Parameters For Kr Excited By Polarized Electrons, B. G. Birdsey, H. M. Al-Khateeb, M. E. Johnston, T. C. Bowen, Timothy J. Gay, V. Zeman, K. Bartschat Aug 1999

Near-Threshold Measurement Of Integrated Stokes Parameters For Kr Excited By Polarized Electrons, B. G. Birdsey, H. M. Al-Khateeb, M. E. Johnston, T. C. Bowen, Timothy J. Gay, V. Zeman, K. Bartschat

Timothy J. Gay Publications

We have made high-accuracy measurements of the integrated Stokes parameters for resonance fluorescence from polarized electron-impact excitation of the 4p55p[5/2] 3D3 and 4p55p [5/2] 3D2 states of Kr. We report measurements in the region within 0.6 eV of threshold, which is below the first cascade threshold. We also present theoretical calculations of these Stokes parameters using a recently developed relativistic Breit-Pauli Rmatrix code. In well LS-coupled systems, nonzero values of the integrated Stokes parameter P2 signal relativistic effects (like continuum spin-orbit coupling ...


Optically Pumped Electron Spin Filter, Herman Batelaan, A. S. Green, B. A. Hitt, Timothy J. Gay May 1999

Optically Pumped Electron Spin Filter, Herman Batelaan, A. S. Green, B. A. Hitt, Timothy J. Gay

Timothy J. Gay Publications

This paper reports the first experimental demonstration of an optically pumped electron spin filter. Unpolarized electrons produced in a cold-cathode discharge drift through a mixture of spin-polarized Rb and a nitrogen or helium buffer gas. Through spin-exchange collisions with the Rb, the drifting electrons become polarized along the optical pumping axis. We study the role of the buffer gas in both the optical pumping and the spin transfer to the free electrons. This spin filter produces electron beams with currents and polarizations comparable to first-generation GaAs polarized electron sources.


Batelaan And Gay Reply, Herman Batelaan, Timothy J. Gay Nov 1998

Batelaan And Gay Reply, Herman Batelaan, Timothy J. Gay

Timothy J. Gay Publications

In their Comment [1] to our Letter [2], Rutherford and Grobe first disagree with our conclusion that “a tabletop Stern-Gerlach filter is feasible.” Given our estimate of the throughput for such a device, ~0.3 electrons/s, we were clearly not proposing it as an alternative to standard polarized electron sources (~1015 electrons/s). The main argument for “feasibility” is based on the relatively low currents required to establish the solenoidal magnetic field (5 A)—hence the use of the word “tabletop” in the abstract. In retrospect, a better statement would have been that “experimental demonstration of such a ...