A novel "Correlated Ion and Neutral Time Of Flight" Method: event-by-event detection of neutral and charged fragments in Collision Induced Dissociation (CID) of mass selected ions

accepté dans Rev. Sci. Instrum.A new mass spectrometric MS-MS method based on Time Of Fight measurements performed on an event-by-event detection technique is presented. This "COrrelated Ion and Neutral Time of Flight (COINTOF)" method allows to explore CID fragmentation processes by directly identifying not only all ions and neutral fragments produced but also their arrival time correlations within each single fragmentation event from a dissociating molecular ion. This constitutes a new step in the characterization of molecular ions. The method will be illustrated here for a prototypical case involving Collision Induced Dissociation (CID) of protonated water clusters H+(H2O)n=1-5 upon collisions with argon atoms

Collision induced cluster fragmentation: From fragment size distributions to the caloric curve

IPMInternational audienceWe report on a cluster fragmentation study involving collisions of high-energy (60 keV/amu) H3+(H2)m hydrogen cluster ions (m=9, 11) with atomic helium or fullerenes. The experimental characterisation of the cluster fragmentation not only by the average fragment size distribution but also by a statistical analysis of the fragmentation events has become possible owing to a recently developed multi-coincidence technique in which all the fragments of all collisions occurring in the experiment are mass analysed on an event-by-event basis. By selecting specific decay reactions we can start after the energizing collision with a microcanonical cluster ion ensemble of fixed excitation energy. From the respective fragment distributions for these selected decay reactions we derive corresponding temperatures of the decaying cluster ions. The relation between this temperature and the excitation energy (caloric curve) exhibits the typical prerequisites of a first order phase transition in a finite system, in the present case signalling the transition from a bound cluster type situation to the free gas phase

High resolution studies of low-energy electron attachment to SF5Cl: Product anions and absolute cross sections

Low energy electron attachment to SF$_5$Cl was studied at high energy resolution by mass spectrometric detection of the product anions. Two variants of the laser photoelectron attachment (LPA) technique (Kaiserslautern) were used for determining the threshold behaviour of the yield for SF$_5^-$ formation at about 1 meV resolution, and to investigate the relative cross sections for Cl$^-$, FCl$^-$, and SF$_5^-$ formation towards higher energies (up to 1 eV) at about 20 meV resolution. Thermal swarm measurements (Birmingham) were used to place the relative LPA cross sections on an absolute scale. A trochoidal electron monochromator (Innsbruck) was used for survey measurements of the relative cross sections for the different product anions over the energy range of 0-14 eV with a resolution of 0.30 eV. Combined with earlier beam data (taken at Berlin, J. Chem. Phys. 88 (1988) 149), the present experimental results provide a detailed set of partial cross sections for anion formation in low-energy electron collisions with SF$_5$Cl

Low energy electron attachment to formic acid

Using a high resolution electron energy monochromator low energy electron attachment to formic acid is studied for the first time by means of mass spectrometric detection of the product anions. The largest dissociative electron attachment (DA) cross-section produces HCOO-+H with weaker channels for OH- and O- becoming apparent at higher incident energies

Proton transfer reaction mass spectrometry (PTR-MS) implementation in the dairy industry: new perspectives in quality control of fermented milks

In the present study, Proton Transfer Reaction-Mass Spectrometry (PTR-MS) has been successfully used for the monitoring of flavor formation during milk fermentation. Moreover, the impact of both milk base compositional and processing factors on flavor and off-flavor compounds formation were evaluated