68th Annual Gaseous Electronics Conference/9th International Conference on Reactive Plasmas/33rd Symposium on Plasma Processing
Volume 60, Number 9
Monday–Friday, October 12–16, 2015;
Honolulu, Hawaii
Session OR4: Electron-Impact Ionization
10:00 AM–12:00 PM,
Thursday, October 15, 2015
Room: 303 AB
Chair: Allison Harris, Illinois State University
Abstract ID: BAPS.2015.GEC.OR4.1
Abstract: OR4.00001 : Progress in (e, 2e) electron momentum spectroscopy: from the static to the time-resolved regime
10:00 AM–10:30 AM
Preview Abstract
Abstract
Author:
Masahiko Takahashi
(Institute of Multidisciplinary Research for Advanced Materials, Tohoku University)
Electron momentum spectroscopy (EMS) is a kinematically-complete
electron-impact ionization experiment performed under the high-energy Bethe
ridge conditions, where the collision kinematics can be described by
electron Compton scattering that most nearly corresponds to the collision of
two free electrons with the residual ion acting as a spectator. The
remarkable feature of this technique is its ability to measure momentum
distributions of each electron bound in matter or to look at molecular
orbitals in momentum space. We have been exploring atomic and molecular
science using EMS, such as 3D orbital imaging for a stable gaseous molecule
[Takahashi et al., PRL 2005], observation of the giant resonance phenomenon
in the 2nd order projectile-target interactions [Takahashi et al., PRL
2007], and determination of spatial orientation of the constituent atomic
orbitals in molecular orbitals [Watanabe et al., PRL 2012].
Recently, we have started to direct our efforts also towards expanding
frontiers of EMS, through development of time-resolved EMS (TR-EMS) that
employs ultrashort laser (120 fs) and electron (1 ps) pulses in a pump-probe
scheme [Yamazaki et al., RSI 2013]. In spite of the low data statistics as
well as of the limited time-resolution due to velocity mismatch, our
experimental results on the deuterated acetone molecule in its second
excited singlet state with a lifetime of 13.5 ps [Yamazaki et al., PRL 2015]
have represented the first time that EMS measurements of short lived
transient species are feasible, opening the door to time-resolved orbital
imaging in momentum space. With further technical development, TR-EMS could
eventually enable one to take a series of snapshots of molecular orbitals
changing rapidly during chemical reaction, thereby making it possible to
exploit a new area for studies of ultrafast molecular dynamics as well as
the nature of molecular excited states; it is electrons that bind atoms into
molecules, and chemical reactions are all about the rearrangement of these
electrons or the change in spatial patterns of the corresponding molecular
orbitals.
In this contribution, some results of our recent studies will be presented,
which may examine the current status and future prospects of EMS.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2015.GEC.OR4.1