Intense laser light was focussed on the surface of a metal substrate (Nb or Cu) in vacuum, and a molecular beam of Mn2(CO)10 was injected nearby. Product ions resulting from the reaction of substrate metal ions or electrons with Mn2(CO)10 were analyzed by mass-spectroscopy. This method provides a simple and versatile diagnosis for the reactions of metal ions and/or electrons with molecules in the gas phase.
Laser photoelectron energy measurements in a molecular beam of trimethylamine were carried out at the laser wavelengths 192.1, 208.8, 228.7, and 252.7 nm. The photoelectron spectra observed at 192.1 and 208.8 nm can be attributed to two ionization processes competing with each other: one from the optically prepared S2 state and the other from the vibrationally excited SI state (S,t) produced from the internal conversion S2* --SI$.
IntroductionLaser excited-state photoelectron spectroscopy with a resonant two-or multiphoton ionization technique is very useful for characterization of various electronically excited states of molecules in the gas phase.' This technique makes it possible to provide information about excited states which cannot be detected by optical emission spectroscopy.When photoionization occurs at a specific excited state in competition with some intramolecular relaxation such as internal conversion and intramolecular vibrational redistribution, photoelectrons can be ejected from relaxed states as well as from the optically prepared excited state under appropriate laser irradiating conditions. The molecule in the initially prepared state is either ionized directly with the rate constant lai ( I is the laser fluence and u, is the ionization cross section) or relaxed to another state with the rate constant k (which is a molecular constant) and then
Increased accuracy in radiation delivery to a patient provided by scanning particle beams leads to high demands on quality assurance (QA). To meet the requirements, an extensive quality assurance programme has been implemented at the Heidelberg Ion Beam Therapy Center. Currently, highresolution radiographic films are used for beam spot position measurements and homogeneity measurements for scanned fields. However, given that using this film type is time and equipment demanding, considerations have been made to replace the radiographic films in QA by another appropriate device. In this study, the suitability of the flat-panel detector RID 256 L based on amorphous silicon was investigated as an alternative method. The currently used radiographic films were taken as a reference. Investigations were carried out for proton and carbon ion beams. The detectors were irradiated simultaneously to allow for a direct comparison. The beam parameters (e.g. energy, focus, position) currently used in the daily QA procedures were applied. Evaluation of the measurements was performed using newly implemented automatic routines. The results for the flat-panel detector were compared to the standard radiographic films. Additionally, a field with intentionally decreased homogeneity was applied to test the detector's sensitivities toward possible incorrect scan parameters. For the beam position analyses, the flat-panel detector results showed good agreement with radiographic films. For both detector types, deviations between measured and planned spot distances were found to be below 1% (1 mm). In homogeneously irradiated fields, the flatpanel detector showed a better dose response homogeneity than the currently used radiographic film. Furthermore, the flat-panel detector is sensitive to field irregularities. The flat-panel detector was found to be an adequate replacement 0031-9155/12/010051+18$33.00
Laser light (the second or third harmonics from an Nd:YAG laser) was focussed on the metal substrate in vacuum. A pulsed molecular beam of an organometallic compound, a metal carbonyl, or an organic molecule was introduced in the entrance region (the region in front of the ion-lens assembly) of a quadrupole mass filter which was located near the metal substrate. The reaction of the molecules in the beam with either the electrons or ions from the metal substrate was studied by monitoring the product ions by the mass spectrometer.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.