A Time- and Position-Sensitive Detector using a Resistive Film Anode Combined with a “Modified Backgammon with Weighted Capacitors” Readout Pad

Soft X-rays (90-173 eV) from the 3 rd generation Canadian Light Source have been used in conjunction with a multi coincidence time and position sensitive detection apparatus to observe the dissociative ionization of OCS. By varying the X-ray energy we can compare dynamics from direct and Auger ionization processes, and access ionization channels which result in two or three body breakup, from 2+ to 4+ ionization states. We make several new observations for the 3+ state such as kinetic energy release limited by photon energy, and using Dalitz plots we can see evidence of timescale effects between the direct and Auger ionization process for the first time. Finally, using Dalitz plots for OCS 4+ we observe for the first time that breakup involving an O 2+ ion can only proceed from out of equilibrium nuclear arrangement for S(2p) Auger ionization.

Section: Methodsmentioning

confidence: 99%

Ultrafast molecular dynamics of dissociative ionization in OCS probed by soft x-ray synchrotron radiation

Ramadhan

Wales

Karimi

et al. 2016

“…Fragment ions hit Chevron-arrangement micro-channel plates (MCP) and the ejected electrons are detected by a multiple backgammon weighted capacitor (MBWC) anode with a resistive film anode (Optima Corporation, [22]). With a MCP diameter of 40 mm φ, we are able to detect O + ions with a momentum perpendicular to the TOF axis of ∼300 × 10 3 amu m s −1 and C + ions with a momentum perpendicular to the TOF axis of ∼260 × 10 3 amu m s −1 .…”

Section: Methodsmentioning

confidence: 99%

Ultrafast imaging of multielectronic dissociative ionization of CO₂in an intense laser field

Brichta

Walker

Helsten

et al. 2006

Momentum vectors of fragment ions produced by the Coulomb explosion of CO2z+ (z = 3–6) in an intense laser field (∼50 fs, 1 × 1015 W cm−2) are determined by the triple coincidence imaging technique. The molecular structure from symmetric and asymmetric explosion channels is reconstructed from the measured momentum vectors. The channel-dependent mean C–O bond length of ⟨r⟩ = 2.14–3.89 Å and the O–C–O bend angle of ⟨θ⟩ = 170–175° confirm substantial deformation of the molecular skeleton during the laser-molecule interaction. The channel-dependent bond length data are qualitatively described using a classical enhanced ionization model. The kinetic energy spectra reveal interesting structure which is attributed to the existence of excited states in the fragment ions.

“…Projectile ions are measured by a two-dimensional position-sensitive-detector (PSD) system placed at the exit plane of the energy analyser. The PSD system is composed of a tandem MCP, a resistive anode [44], a thin insulation sheet and a backgammon electrode [45]. The insertion of the insulation sheet between the resistive anode and the backgammon anode makes it possible to detect signals at the ground potential without isolation of the amplifier even when high bias voltages are supplied to the MCP.…”

Section: Methodsmentioning

confidence: 99%

Collision dynamics of the Kr⁸⁺+ N₂system studied by a multi-coincidence technique

Kaneyasu¹,

Azuma²,

Okuno³

2005

We have developed a multi-coincidence technique to study MCI–molecule collisions. Using this technique, complicated reaction processes and collision dynamics in Kr8+ + N2 collisions have been successfully revealed in the energy region below 200 eV/u. The reaction processes in the single-, double-, triple- and quadruple-charge changing collisions are resolved and three low-energy collision phenomena, ‘peak-shifting’ of molecular ions, ‘peak-splitting’ and ‘anisotropic fragmentation’ of fragment ion pairs, are found in the time-of-flight spectra of target ions. By careful analysis of kinematics of all the products, it is concluded that the charge transfer in the Kr8+ + N2 collisions is dominated by multi-electron capture processes followed by electron emission and the collision dynamics is characterized by the transverse momentum transfer from the ion to the molecule and the appearance of the ‘anisotropic fragmentation’.