The charge loss due to initial recombination was measured for various therapy level ionization chamber types. Different methods were applied. Measurements were performed in Co beams, pulsed high-energy photon beams and pulsed high-energy electron beams. The results are mutually consistent within less than 0.05 %. Within this uncertainty initial recombination and diffusion do not depend on the r...

We present velocity map imaging measurements of photoelectrons in coincidence with ions produced via strong field molecular ionization. Our measurements, in conjunction with electronic structure and Stark shift calculations, allow us to assign several features in the low energy portion of the photoelectron spectrum to different molecular electronic continua (ionic states). Furthermore, we are a...

We have measured momentum spectra and branching ratios of charged ionic fragments emitted in the double ionization of D2 (and H2) molecules by short intense laser pulses. We find high-energy coincident D+ (and H+) ion pairs with kinetic energy releases between 8 and 19 eV which appear for linearly polarized light but are absent for circularly polarized light. The dependence on the polarization,...

The electron impact ionization cross section of H2 is calculated using a distortedwave approximation. The calculated cross section is compared to the experimental results of Peart and Dolder. The simplicity of the system allows an assessment of the accuracy of the distorted-wave approximation without complications from inaccuracies in the target state, initial continuum state, or final continuu...

Electronic properties of phosphorus donors in hydrogenated silicon nanocrystals are investigated using a real-space ab initio pseudopotential method for systems with up to 500 atoms. We present calculations for the ionization energy, binding energy, and electron density associated with the doped nanocrystal. We find that the ionization energy for the nanocrystal is virtually independent of size...

RATIONALE Although several reaction models have been proposed in the literature to explain matrix-assisted laser desorption/ionization (MALDI), further study is still necessary to explore the important ionization pathways that occur under the high-temperature environment of MALDI. 2,4,6-Trihydroxyacetophenone (THAP) is an ideal compound for evaluating the contribution of thermal energy to an in...

In this thesis the electron ionization of a number of small gas phase molecules is investigated using pulsed time-of-flight mass spectrometry coupled with a 2-D ion coincidence technique. The simultaneous acquisition of conventional TOF mass spectra and ion coincidence mass spectra, enables fragment ions formed by dissociative single, double, and triple ionization, to be distinguished and quant...

Experimental results are presented from an experiment in which ionization created by a highenergy x-ray synchrotron radiation beam intersecting an ethylene diffusion flame is measured.The ionization signal is believed to arise from x-ray absorption by aggregated soot particles.Comparisons are made between these ionization profiles and those due to natural flameionization. Visibl...

We have simulated ionization of purine nucleic acid components in the gas phase and in a water environment. The vertical and adiabatic ionization processes were calculated at the PMP2/aug-cc-pVDZ level with the TDDFT method applied to obtain ionization from the deeper lying orbitals. The water environment was modeled via microsolvation approach and using a nonequilibrium polarizable continuum m...

This review addresses the determination of the internal energy of ions produced by electrospray ionization (ESI) sources, and the influence of the internal energy on analyte fragmentation. A control of the analyte internal energy is crucial for several applications of electrospray mass spectrometry, like structural studies, construction of reproducible and exportable spectral libraries, analysi...