Account: An Introduction to Velocity-Map Imaging Mass Spectrometry (VMImMS)

Abstract

This account introduces a new variant of time-of-flight mass spectrometry, termed velocity-map imaging mass spectrometry (VMImMS).While the ion abundances recorded in conventional ToF-MS measurements are highly useful for molecular quantification and structure determination, the final parent and fragment ion yields are largely blind to the dynamics of the processes in which the ions were formed inside the mass spectrometer. By recording the velocity distribution of each ion in tandem with the mass spectrum, not only can the details of the dissociative ionisation dynamics be unravelled, but the extra dimensions of information can be used for enhanced molecular fingerprinting, separating contributions from ions with identical mass-to-charge ratio and resolving components within mixtures, to name but a few examples. Measuring ion-velocity distributions within a mass spectrometry measurement is not new, but incorporating imaging techniques developed within the reaction dynamics community provides vastly improved velocity resolution for all ions simultaneously in a single-stage instrument. This account provides an introduction to VMImMS, outlines the fundamental instrumentation and detector requirements and the challenges associated with developing the method further, and details proof-of-concept work from our laboratory on a number of potential applications of the technique.

Velocity map images from surface-hopping; reactive scattering of OH (2Σ+) + H2 (1Σ+g)

“…8,9 Velocity Map imagining is a mature and popular method for obtaining simultaneous angles and velocities (and a wealth of other implicit information) from scattering experiments. 10 The popularity of this method makes it a natural choice for computational scientist to simulate, to effectively communicate results with experimentalist. We performed semi-classical trajectories on the potential energy surface (PES), used in similar systems to study quenching 11,12 and angular and velocity distributions.…”

Optimizing time resolution and power consumption in a current-mode circuit for SiPMs

“…The time resolution allows improving vertex identification, improved transverse momentum resolution, and reducing pile up. Other applications include Light Detection and Ranging (LIDAR) [5] or ToF Mass Spectrometry [6].…”

The kinetic energy of PAH dication and trication dissociation determined by recoil-frame covariance map imaging

“…From this dataset, dissociative pathways from PAH 2+ and PAH 3+ are isolated using recoil-frame covariance analysis. [19][20][21][22][23][24][25] Fitting the resulting covariance map images allows an accurate determination of the magnitude of the momentum of each fragment ion and, by extension, the TKER of the dication and trication dissociation processes. The results are supported by Born-Oppenheimer molecular dynamics (BOMD) theoretical simulations.…”