Velocity Map Imaging
Low energy electron and ion imaging
In Velocity Map Imaging (VMI), charged fragments generated after laser ionization of parent molecules will fly toward to detectors. Due to different masses, ions will have different time-of-flights (TOF). Therefore, ions with different mass can be separated in time domain to form corresponding ion images.
Replacing the old CCD/CMOS camera with ASI TPX3CAM detector, to be able to obtain full momenta of charged particles. Normally, ions in the VMI requires nanosecond time resolution, while electrons in the VMI requires picosecond time resolution.
All ions are recorded during one single measurements. Each ion, velocity map images can be provided. The image above shows ion TOF mass spectrum of BrCH2I recorded with TimepixCam, a previous model of the TPX3CAM, at the FLASH light source at the German Synchrotron, Hamburg after strong-field ionization with an intense laser pulse along with the camera images for each of the peaks in the TOF spectrum. Adapted from M.Fisher-Levine et al, J. Synchrotron Rad. (2018) 25, 336-345
“In TPX3CAM all individual pixels function independently and are able to time stamp incident ‘events’. This transforms the imaging sensor into an array of fast digitizers with both spatial and temporal resolutions acting in parallel so multiple ion species can be registered simultaneously allowing for coincidence and covariance analyses.”