Observation of molecular frame (e,2e) cross section using an electron–electron-fragment ion triple coincidence apparatus

Takahashi, Masahiko; Watanabe, Noboru; Khajuria, Yugal; Nakayama, K.; Udagawa, Yasuo; Eland, J. H. D.

doi:10.1016/j.elspec.2004.08.002

Cited by 51 publications

(63 citation statements)

References 48 publications

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“…Third, the present (e,2e+M) method 179,180 is to be advanced. Although it has pioneered molecular frame EMS, there is ample room for improvements mainly in collection efficiency, which could be achieved by the detection of the two outgoing electrons in the momentum dispersive plane around the full 2³ azimuth and detection of the fragment ion over the full 4³ solid angle.…”

Section: Discussionmentioning

confidence: 99%

“…Very recently, this type of experiment has been proposed and realized by Takahashi et al 179,180 In this section, we will see the working principle and details of the (e,2e+M) spectrometer of Takahashi et al as well as their showcase experiment that has successfully observed molecular frame (e,2e) cross sections for the first time. 179,180 6.1 Principle. Let us recall the symmetric noncoplanar geometry discussed in Section 2.1.…”

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confidence: 99%

“…As examples of the experimental results, 179,180 let us see first the three-dimensional time spectrum in Figure 21, which represents the number of the triple coincidence events as a function of arrival time difference between the two outgoing electrons ¦t ee and that between either of the two electrons and the H + fragment ¦t eM . Since the three charged particles to be detected are produced in a single event, they must have correlation in their arrival times.…”

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confidence: 99%

“…The show case (e,2e+M) measurements 179,180 have been made for the 2s· g and 2p· u ionizationexcitation processes of H 2 , under experimental conditions where a retarding voltage (V ret ) of 2.5 V and an incident electron energy (E 0 ) of 1.2 keV have been employed. There are three motivations behind this.…”

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confidence: 99%

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Looking at Molecular Orbitals in Three-Dimensional Form: From Dream to Reality

Takahashi¹

2009

Bulletin of the Chemical Society of Japan

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Over the last four decades an experimental method has been developed for looking at electron orbitals in momentum space. The method, called electron momentum spectroscopy (EMS), is based on the electron-impact ionizing reaction near the Bethe ridge at incident electron energies of the order of 1 keV or higher. This account reviews frontiers of the field, involving the first approach to molecular frame EMS that enables one to look at molecular orbitals in three-dimensional form.

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Section: Discussionmentioning

confidence: 99%

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Looking at Molecular Orbitals in Three-Dimensional Form: From Dream to Reality

Takahashi¹

2009

Bulletin of the Chemical Society of Japan

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“…8,9 More recently, third generation spectrometers have been developed whose analyzers incorporate two-dimensional positionsensitive detectors, enabling a range of emission angles and energies to be measured in parallel. [10][11][12][13][14][15][16] From the measured arrival positions of electrons at the detectors, their energies and emission angles are deduced.…”

Section: Introductionmentioning

confidence: 99%

Invited Article: An improved double-toroidal spectrometer for gas phase (e,2e) studies

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Panajotović

Bellm

et al. 2007

Review of Scientific Instruments

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A new spectrometer is described for measuring the momentum distributions of scattered electrons arising from electron-atom and electron-molecule ionization experiments. It incorporates and builds on elements from a number of previous designs, namely, a source of polarized electrons and two high-efficiency electrostatic electron energy analyzers. The analyzers each comprise a seven-element retarding-electrostatic lens system, four toroidal-sector electrodes, and a fast position-and-time-sensitive two-dimensional delay-line detector. Results are presented for the electron-impact-induced ionization of helium and the elastic scattering of electrons from argon and helium which demonstrate that high levels of momentum resolution and data-collection efficiency are achieved. Problematic aspects regarding variations in collection efficiency over the accepted momentum phase space are addressed and a methodology for their correction presented. Principles behind the present design and previous designs for electrostatic analyzers based around electrodes of toroidal-sector geometry are discussed and a framework is provided for optimizing future devices.

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