Anisotropic Coulomb Explosion of CO Ligands in Group 6 Metal Hexacarbonyls: Cr(CO)6, Mo(CO)6, W(CO)6

Coulomb Explosion Dynamics of Multiply Charged para-Nitrotoluene Cations

This work explores Coulomb explosion (CE) dissociation pathways in multiply charged cations of para-nitrotoluene (PNT), a model compound for nitroaromatic energetic molecules. Experiments using strong-field ionization and mass spectrometry indicate that metastable cations PNT²⁺ and PNT³⁺ undergo CE to produce NO₂⁺ and NO⁺. The experimentally measured kinetic energy release from CE upon formation of NO₂⁺ and NO⁺ agrees qualitatively with the kinetic energy release predicted by computations of the reaction pathways in PNT²⁺ and PNT³⁺ using density functional theory (DFT). Both DFT computations and mass spectrometry identified additional products from CE of highly charged PNT^q+ cations with q > 3. The dynamical timescales required for direct CE of PNT²⁺ and PNT³⁺ to produce NO₂⁺ were estimated to be 200 and 90 fs, respectively, using ultrafast disruptive probing measurements.

Coulomb Explosion of Multi-charged Atomic Alkaline Metal Clusters

In the present work, a computational study of the Coulomb explosions of atomic metal clusters of the type X₈²⁺ was carried out, X = (Li-Cs). The work was done within the Kohn-Sham methodology using the Born-Oppenheimer molecular dynamics approximation. The dominant fission channels were established and the electron bonding patterns were analyzed with the help of the Electron Localization Function (ELF). A simple theoretical model was developed to understand and describe, in a qualitatively way, the main physical mechanism involved in the fission of these multicharged clusters. It has been found that the most possible fragments after explosion are the same considering the dynamics or the thermodynamics results. The bonds breaking and formation are well depicted by the ELF, and the main physical effects are well described by the developed model.

Selection of a Single Isotope of Multiply Charged Xenon (A Xez+ , A=128-136, z=1-6) by Using a Bradbury-Nielsen Ion Gate

The inclusion of an ion gate in a tandem mass spectrometer allows a specific precursor ion to be selected, and the fragment ions are then used for structure analysis and to investigate chemical reactions. However, the performance of an ion gate has been judged simply by whether or not the target ion was selected. In this study, we designed, manufactured, constructed, and characterized a Bradbury-Nielsen ion gate (BNG). The actual ion selection ability, i.e. the gate function, of the BNG was measured for isotopes of Xe^z+ (z=1-6). The gate function of the BNG was 36.5±0.5 ns in width and 3-13 ns in rise and fall times. The BNG provides a simple way to select multiply charged molecular cations of small organic molecules as well as large molecules such as proteins and peptides.

Interactions of low-energy electrons with the FEBID precursor chromium hexacarbonyl (Cr(CO)6)

Interactions of low-energy electrons with the FEBID precursor Cr(CO)₆ have been investigated in a crossed electron-molecular beam setup coupled with a double focusing mass spectrometer with reverse geometry. Dissociative electron attachment leads to the formation of a series of anions by the loss of CO ligand units. The bare chromium anion is formed by electron capture at an electron energy of about 9 eV. Metastable decays of Cr(CO)₅^- into Cr(CO)₄^-, Cr(CO)₄^- into Cr(CO)₃^- and Cr(CO)₃^- into Cr(CO)₂^- are discussed. Electron-induced dissociation at 70 eV impact energy was found to be in agreement with previous studies. A series of Cr(CO) _n C⁺ (0 ≤ n ≤ 3) cations formed by C-O cleavage is described for the first time. The metastable decay of Cr(CO)₆⁺ into Cr(CO)₅⁺ and collision-induced dissociation leading to bare Cr⁺, are discussed. In addition, doubly charged cations were identified and the ration between doubly and singly charged fragments was determined and compared with previous studies, showing considerable differences.