Search results for "IONIZATION"
showing 10 items of 1255 documents
Search for the Rare Leptonic Decay B+→μ+νμ
2004
A search for the rare leptonic decay with data collected at the resonance by the BABAR experiment was carried out. The decay rate was sensitive to the product of the Cabibbo Kobayashi Maskawa matrix element (Vub and the B decay constant fb, which was propotional to the wave function for zero separation between the quarks. The data used in the analysis was collectd with BABAR detector at the PEP-II storage ring and the sample consisted of an integrity luminosity of 81.4 fb-1. The systematic uncertainty in the signal efficiency was evaluated which included the muon candidate selection and the reconstruction efficiency of the companion B.
Theoretical determination of the geometric and electronic structures of oligorylenes and poli(peri‐naphthalene)
1992
We present a theoretical investigation of the electronic structure of oligorylenes (from perylene to heptarylene, including also the naphthalene molecule) and their corresponding polymer poly(peri‐naphthalene) (PPN) using the nonempirical valence effective (VEH) method. The geometry of the unit cell used to generate the polymer is extrapolated from the PM3‐optimized molecular geometries of the longest oligorylenes. That geometry shows some bond alternation along the perimeter carbon chains and a bond length of ≊1.46 Å is calculated for the peri bonds connecting the naphthalene units. The VEH one‐electron energy level distributions calculated for oligorylenes are used to interpret the experi…
Theoretical study of the effect of substituent and backbone conformation on the electronic properties of symmetrically substituted poly(di‐n‐alkylsil…
1994
We present the results of ab initio 3‐21G∗ geometry optimizations and valence effective Hamiltonian (VEH) band structure calculations aimed at determining the evolution of the geometric and electronic (ionization potential, electron affinities, and band gaps) properties of all‐trans poly(dimethylsilane), poly(diethylsilane), poly(di‐n‐propylsilane), and poly(di‐n‐butylsilane) when increasing the size of the alkyl group. In the latter polymer, we have also studied the 7/3 conformation, in order to analyze the effect of the backbone conformation on the geometric and electronic structure. The VEH ionization potentials of all‐trans poly(di‐n‐alkylsilanes) are almost equal, and as experimental p…
Rational computing of energy levels for organic electronics: the case of 2-benzylidene-1,3-indandiones
2016
Device engineering in organic electronics, an active area of research, requires knowledge of the energy levels of organic materials (traditionally but ambiguously denoted as HOMO and LUMO). These can be effectively determined by electrochemical investigation, but yet more effective would be quantum chemical (QC) computation of these quantities. However, there is no consensus on the computational method in the research community. Ongoing discussions often focus on choosing the right density functional method, but neglect other model parameters, in particular, the basis set. This study considers comparison of various methodologies and parameters for predicting ionization energy I and electron…
Assaying multiple 125 I seeds with the well-ionization chamber SourceCheck 4π 33005 and a new insert
2015
PURPOSE To provide a practical solution that can be adopted in clinical routine to fulfill the AAPM-ESTRO recommendations regarding quality assurance of seeds used in prostate permanent brachytherapy. The aim is to design a new insert for the well-ionization chamber SourceCheck(4π) 33005 (PTW, Germany) that allows evaluating the mean air-kerma strength of up to ten (125)I seeds with one single measurement instead of measuring each seed individually. MATERIAL AND METHODS The material required is: a) the SourceCheck(4π) 33005 well-ionization chamber provided with a PTW insert to measure the air-kerma strength S K of one single seed at a time; b) a newly designed insert that accommodates ten s…
Lower Rydberg series of methane: a combined coupled cluster linear response and molecular quantum defect orbital calculation.
2006
Vertical excitation energies as well as related absolute photoabsorption oscillator strength data are very scarce in the literature for methane. In this study, we have characterized the three existing series of low-lying Rydberg states of CH4 by computing coupled cluster linear response (CCLR) vertical excitation energies together with oscillator strengths in the molecular-adapted quantum defect orbital formalism from a distorted Cs geometry selected on the basis of outer valence green function calculations. The present work provides a wide range of data of excitation energies and absolute oscillator strengths which correspond to the Rydberg series converging to the three lower ionization p…
Measurement of the first ionization potential of astatine by laser ionization spectroscopy
2013
The radioactive element astatine exists only in trace amounts in nature. Its properties can therefore only be explored by study of the minute quantities of artificially produced isotopes or by performing theoretical calculations. One of the most important properties influencing the chemical behaviour is the energy required to remove one electron from the valence shell, referred to as the ionization potential. Here we use laser spectroscopy to probe the optical spectrum of astatine near the ionization threshold. The observed series of Rydberg states enabled the first determination of the ionization potential of the astatine atom, 9.31751(8) eV. New ab initio calculations are performed to sup…
A comparative analysis of electron spectroscopy and first-principles studies on Cu(Pd) adsorption on MgO
2006
Ultrathin MgO films were grown on a W(1 1 0) substrate while metastable impact electron (MIES) and photoelectron (UPS) spectra were measured in situ; apart from the valence band emission, no additional spectral features were detected. The oxide surface was exposed to metal atoms (Cu, Pd) at RT. A comparison with the DOS extracted from first-principles DFT calculations shows that the metal-induced intensity developing above the top of the O 2p valence band in the UP spectra under Cu(Pd) exposure is caused by Cu 3d (Pd 4d) emission. The emission seen in the MIES spectra is attributed to the ionization of Cu 3d and 4s states of adsorbed neutral Cu atoms in an Auger process, Auger neutralizatio…
Observation of low temperature VUV tungsten emission in JET divertor plasmas
2022
| openaire: EC/H2020/633053/EU//EUROfusion Funding Information: This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014–2018 and 2019–2020 under grant agreement No 633053 and from the RCUK Energy Programme [grant number EP/I501045]. The views and opinions expressed herein do not necessarily reflect those of the European Commission. Publisher Copyright: © 2022 The Author(s). Published by IOP Publishing Ltd. The properties of tungsten make it ideal for use as a plasma facing surface in the divertor of large plasma machines such as JET and ITER. However, the intense heat and particle fluxes …
SELDI-TOF-MS ProteinChip array profiling of tears from patients with dry eye.
2005
Protein and peptides in tears play an important role in ocular surface diseases. In previous studies, changes have been demonstrated in the electrophoretic protein profiles of patients with dry eye. The purpose of this work was to determine the usefulness of surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF-MS) ProteinChip Array (Ciphergen Biosystems, Inc., Fremont, CA) technology for the automated analysis of proteins and peptides in tear fluid.Patients with dry eye (DRY, n = 88) and healthy subjects (CTRL, n = 71) were examined. Their tear proteins were analyzed using SELDI-TOF-MS ProteinChip Arrays with three different chromatographic surfaces (CM10…