Observation of a Molecular Frame(e,2e)Cross Section: An(e,2e+M

Masahiko Takahashi

¹

,

Noboru Watanabe

²

,

Yugal Khajuria

³

et al.

Abstract

We report the first experimental results showing transition-specific anisotropy of molecular frame (e, 2e) cross sections. Vector correlations between the two outgoing electrons and the fragment ion have been measured for specific ionization-excitation processes of H2. The results enable us to obtain molecular frame (e, 2e) cross sections for transitions to the 2ssigma(g) and 2psigma(u) excited states of H(2)(+), thereby making stereodynamics of the electron-molecule collisions directly visible.

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

“…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.…”

“…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.…”

“…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.…”

“…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.…”

Second Order Born Effects in the Perpendicular Plane Ionization of Xe (5p) Atoms

“…The (e, 2e) processes, have become a powerful tool to investigate the dynamics of the ionization process. The (e, 2e) on hydrogen atom may now be considered to be a solved problem [1][2][3][4][5][6]. Following the single ionization, complex processes such as double ionization, simultaneous excitation ionization and auto ionization [7][8][9] have also been investigated.…”