(a) Schematic of the low-field velocity-map imaging setup. The two μ-metal electrodes and the resistive glass tube connected to the front of the position sensitive detector, create an electrostatic lens at the center of the electrodes and the glass tube creates a constant field gradient. Photoelectrons are guided by this field and VMI focused by the lens onto the detector. The low electric fields in the arrangement lead to minimal deflection of the ion beam. (b) Construction drawing of the VMI extractor plate manufactured from μ-metal, all dimensions are given in mm.
SimIon 8.0 simulation of the contour lines present in our VMI setup. A central slice through the detector is shown for (a) traditional imaging with a potential (−75 V) applied to the electrodes and the detector front at 0 V and (b) imaging in which the electrodes are at 0 V while the front of the detector is held at a potential (+75 V). Red field lines are spaced by 1 V, blue field lines are spaced by 5 V. In (b), the fringe fields present at the edges of the electrodes seen in (a) are completely avoided.
SimIon 8.0 simulation of electron trajectories corresponding to kinetic energies of 0.0, 0.25, 0.5, 0.75, and 1.0 eV, imaged with a VMI voltage of −75 V.
Photoelectron spectrum for the photodetachment from iodide at 4.63 eV (268 nm) with a femtosecond laser. Shown inset is the raw (left half) and deconvoluted reconstructed (right half) photoelectron image. The laser polarization is indicated by ɛ.
Photoelectron spectra of iodide at 3.496 eV (355 nm) using (a) the traditional imaging in which the electrodes are held at a potential (−75 V) and (b) imaging in which the electrodes are held at near-ground potential (<−2 V) and the detector front plate at a positive potential (+75 V). Shown inset are the raw (left half) and deconvoluted reconstructed (right half) photoelectron images. The laser polarization is indicated by ɛ.
Photoelectron spectrum for the photodetachment from bromide at 3.496 eV (355 nm). Inset is the raw photoelectron image. The extraction field was created solely by the potential supplied from a 9 V battery connected to the electrodes, while the front of the detector was held at 0 V. The laser polarization is indicated by ɛ.
Article metrics loading...
Full text loading...