Spin asymmetries in the low-energy electron impact excitation of 2S to 2P transitions in lithium atoms

Baum, G.; Frost, L. S.; Raith, Wilhelm; Sillmen, U.

doi:10.1088/0953-4075/22/10/019

Cited by 15 publications

(6 citation statements)

References 20 publications

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“…These results have been analyzed to give generalized oscillator strengths and zero-angle differential cross sections for several transitions from the ground state including the 2 2 P transition. Baum et al ͓11,12͔ reported a series of experiments involving polarized electrons and polarized lithium atoms. The spin asymmetry parameter A was measured at several scattering angles for elastic scattering ͓11͔ and for the excitation of the 2 2 P state ͓12͔ for incident electron energies from 1 eV to 30 eV.…”

Section: Introductionmentioning

confidence: 99%

Electron scattering from optically pumped lithium atoms

1999

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A series of superelastic scattering experiments is described in which electrons are scattered from lithium atoms optically pumped to the 2 P excited state. The incident electron energies were 5.2, 12.2, and 20 eV and superelastically scattered electrons with energies of 7, 14, and 21.8 eV were detected over the angular range from 0°to 140°. Both differential cross sections and the orientation and alignment parameters were deduced from the same measurements. A complete set of the four spin-averaged parameters, which fully characterize the electron impact excitation of the 2S-2 P transition in lithium, is presented. The experimental results are compared with those predicted from convergent-close-coupling ͑CCC͒ calculations and two distorted-wave calculations. Excellent agreement is found with the CCC calculations. ͓S1050-2947͑99͒06406-9͔

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Section: Introductionmentioning

confidence: 99%

Electron scattering from optically pumped lithium atoms

1999

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“…Figure 3 displays the spin asymmetry (A ex ) for excitation of p-states at 10 eV and 40 eV. The 10 eV experimental measurements of A ex are for 2p excitation (Baum et al 1989). Again, surprisingly, the spin asymmetry scaling is approximately valid at all scattering angles, even at rather low energies of 10 eV, but the scaling starts with N = 4 as opposed to N = 2 as was found for electron-hydrogen scattering.…”

Section: Lithiummentioning

confidence: 73%

“…The theoretical curves for different N -values are labelled in the same manner as in the upper part of figure 1. The circles are the 2p experimental results ofBaum et al (1989).…”

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confidence: 99%

Improvement in Thermal Stability and Temperature Dependence of Diffractivity in Low-T_g Photorefractive Polymers Dispersed with Plasticizers

Tanaka¹,

Kurihara²,

Nagayama³

et al. 2004

Jpn. J. Appl. Phys.

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Over the last two decades, there has been considerable interest in the electron-atom scattering problem. Most of this work has concentrated on elastic scattering and excitation of the lowest energy states. However, due to recent technological advances, it is now becoming possible to examine the excitation of higher lying states experimentally. The important question then concerns whether these higher states contain new information. We have recently examined the N dependence for electron-hydrogen scattering. The purpose of this work is to examine the N dependence for electron scattering from alkali atoms. The second-order distorted-wave method has been used to calculate scattering amplitudes for excitation of the higher lying levels of Li, Na and K atoms up to N = 7. The N dependence of the differential cross section and angular correlation parameter are discussed for energies from threshold to 250 eV.

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“…In the past we measured A for the total electronimpact ionization of various atoms [3,5,6], the autoionization of lithium ^P states [7], and for differential elastic as well as inelastic electron scattering from lithium atoms [8,9]. The techniques for producing and monitoring polarized beams of electrons and alkali atoms have now been combined in the present experiment with the coin-cidence technique required for the study of triple-differential scattering.…”

Section: A"=|/p (4)mentioning

confidence: 99%

Spin asymmetries for triple-differential electron-impact ionization of lithium at 54.4 eV

et al. 1992

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Up to now, all triple-differential cross-section measurements were performed with unpolarized electrons and atoms and, consequently, averaged over direct and exchange scattering. In our crossed-beam experiment, spin-polarized lithium atoms were ionized by spin-polarized electrons of 54.4 eV energy. In coplanar, asymmetric coincidence detection of scattered and ejected electrons, combined with electronenergy analysis, we measured a spin asymmetry which gives new information about the ionization process. Results are compared with recent calculations based on the distorted-wave Born approximation.PACS numbers: 34.80.Dp, 34.8aNzThe triple-differential cross section (TDCS), d^a/dClA y^dflsdEA, of electron-impact ionization of atoms depends on the angles of the outgoing electrons A and B and on the partition of the energy between them, described by EA andwhere Eo is the incident electron energy and Ejon the ionization energy for the ejected atomic electron. By adopting nuclear-physics terminology, this process is usually called {e,2e) scattering.Most {e,2e) experiments belong to one of two categories. (1) (e,2e) spectroscopy, typically performed with noncoplanar, symmetric ±45° detector geometry and energies in the keV range for which the first-order theory is expected to be valid. Here the goal is to measure the momentum distributions of the bound electrons in atoms and molecules [1]. (2) Ehrhardt-type experiments, usually performed with asymmetric geometry at lower energies and with simple target atoms such as H, He, or Li. Here the goal is to test theories of electron-impact ionization [2]. Such tests have shown that first-order approximations suffice at high energies and manageable secondorder approximations are satisfactory at intermediate energies. Therefore, the current experimental efforts are concentrated at low energies where exchange effects are known to be important. Results from this laboratory on the total ionization of lithium and other alkali atoms near threshold show pronounced effects of exchange scattering [3]. This is the reason we developed an (e,2e) experiment with spin-polarized electrons and spin-polarized ^Li atoms. We chose lithium because it is-aside from the experimentally more demanding atomic hydrogen-the simplest one-electron atom. The isotope ^Li is used for technical reasons: It has a small hfs splitting of the ground state which insures an efficient high-field state selection in the hexapole magnet.

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Spin asymmetries in the low-energy electron impact excitation of 2S to 2P transitions in lithium atoms

Cited by 15 publications

References 20 publications

Electron scattering from optically pumped lithium atoms

Electron scattering from optically pumped lithium atoms

Improvement in Thermal Stability and Temperature Dependence of Diffractivity in Low-T_g Photorefractive Polymers Dispersed with Plasticizers

Spin asymmetries for triple-differential electron-impact ionization of lithium at 54.4 eV

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Spin asymmetries in the low-energy electron impact excitation of 2S to 2P transitions in lithium atoms

Cited by 15 publications

References 20 publications

Electron scattering from optically pumped lithium atoms

Electron scattering from optically pumped lithium atoms

Improvement in Thermal Stability and Temperature Dependence of Diffractivity in Low-Tg Photorefractive Polymers Dispersed with Plasticizers

Spin asymmetries for triple-differential electron-impact ionization of lithium at 54.4 eV

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Improvement in Thermal Stability and Temperature Dependence of Diffractivity in Low-T_g Photorefractive Polymers Dispersed with Plasticizers