One-dimensional non-nearest-neighbor random walks in the presence of traps

A one-dimensional lattice random walk in the presence ofm equally spaced traps is considered. The step length distribution is a symmetric exponential. An explicit analytic expression is obtained for the probability that the random walk will be trapped at thejth trapping site.     

Tests of quantum electrodynamics using ion traps

Experiments in ion traps on the g factors for the free and the bound electron in low-Z, hydrogen-like ions have provided the most accurate tests of quantum-electrodynamics calculations. Moreover they have been used to determine new and precise values for fundamental constants. Extensions to more stringent tests using ions of higher values of the nuclear charge Z are on the way. Also other QED tests such as Lamb shifts or hyperfine structures in H-like ions using traps will be feasible in the near future. The tests in bound systems, however, will be limited by nuclear structure effects which are difficult to calculate. Assuming the QED calculations as correct, the experimental results may be used to determine nuclear contributions and thus support nuclear models. Contribution presented at the TCP06, Vancouver Island, 2006.     

The HITRAP project at GSI: trapping and cooling of highly-charged ions in a Penning trap

A decelerator will be installed at GSI in order to provide and study heavy nuclei without or with only few electrons at very low energies or even at rest. Highly-charged ions will be produced by stripping at relativistic energies. After electron cooling and deceleration in the Experimental Storage Ring (ESR) the ions are ejected out of the storage ring at 4 MeV/u and further decelerated in a combination of linear accelerator structures operated in reverse. Finally, they are injected into a Penning trap where the ions are cooled to 4 K by electron cooling in combination with resistive cooling. From here, the ions can be transferred in a quasi DC or in a pulsed mode to different experimental setups. This article describes the technical concepts of this project focused on the Penning trap.      

A high-current electron beam ion trap as an on-line charge breeder for the high precision mass measurement TITAN experiment

The precision of atomic mass measurements in a Penning trap is directly proportional to the charge state q of the ion and, hence, can be increased by using highly charged ions (HCI). For this reason, charge breeding with an electron beam ion trap (EBIT) is employed at TRIUMF’s Ion Trap for Atomic and Nuclear science (TITAN) on-line facility in Vancouver, Canada. By bombarding the injected and trapped singly charged ions with an intense beam of electrons, the charge state of the ions is rapidly increased inside the EBIT. To be compatible with the on-line requirements of short-lived isotopes, very high electron beam current densities are needed. The TITAN EBIT includes a 6 Tesla superconducting magnet and is designed to have electron beam currents and energies of up to 5 A and 60 keV, respectively. Once operational at full capacity, most species can be bred into a He-like configuration within tens of ms. Subsequently, the HCI are extracted, pass a Wien filter to reduce isobaric contamination, are cooled, and injected into a precision Penning trap for mass measurement. We will present the first results and current status of the TITAN EBIT, which has recently been moved to TRIUMF after assembly and commissioning at the Max-Planck-Institute (MPI) for Nuclear Physics in Heidelberg, Germany.     

Investigation of the effect of CdCl2 processing on vacuum deposited CdS/CdTe thin film solar cells by DLTS

Thin film CdS/CdTe solar cells have been prepared by conventional vacuum deposition technique. Deep level transient spectroscopy (DLTS), temperature and frequency dependent capacitance-voltage (C-V) measurements were utilised to investigate the performance limiting defect states in the CdTe layer subjected to the post deposition treatments such as CdCl₂-dipping and/or annealing in air. Five hole traps, all of which have been previously reported in the literature, were identified in as-grown CdTe at 0.19, 0.20, 0.22, 0.30 and 0.40 eV above the valence band. A single hole trap level has been evidenced at 0.45 eV after both post deposition heat and CdCl₂ treatments.     

Q value related mass determinations using a Penning trap

We report here about measurements of reaction and decay Q values by precise determination of pairs of atomic masses. These were performed with the Penning trap mass spectrometer SMILETRAP. Measurements with Penning traps give reliable and accurate masses, in particular Q values, due to the fact that certain systematic errors to a great deal cancel in the mass difference between the two atoms defining the Q value. Some Q values that are of fundamental interest will be discussed here, for example, a new Q value for the ⁶Li (n,γ) ⁷Li reaction, for the β-decay of tritium, related to properties of the electron neutrino mass, and for the neutrino-less double β-decay of ⁷⁶Ge, related to the question of whether the neutrino is a Majorana particle or not. In case of the latter two we report the most accurate Q values, namely 18,589.8(12) eV for the tritium decay and 2,038.997(46) keV for the neutrino-less double β-decay of ⁷⁶Ge.     

Identification of radicals spin-trapped in autoxidized linoleic acids: A high performance liquid chromatography and electron spin resonance study

Radicals generated in linoleic acid and deuterated linoleic acid have been trapped by the spin trap 2-methyl-2-nitroso-propane (MNP) and identified by electron spin resonance (ESR) and ENDOR spectroscopy. The formation of two distinct secondary alkyl radical adducts (one conjugated, the other non-conjugated, as shown by their UV absorption spectra) was demonstrated by 11, 11-dideuterio-9-cis-12-cis-linoleic acid using HPLC and ESR spectroscopy.     

Random walks on inhomogeneous lattices

For lattices with two kinds of points (black and white), distributed according to a translation-invariant joint probability distribution, we study statistical properties of the sequence of consecutive colors encountered by a random walker moving through the lattice. The probability distribution for the single steps of the walk is considered to be independent of the colors of the points. Several exact results are presented which are valid in any number of dimensions and for arbitrary probability distributions for the coloring of the points and the steps of the walk. They are used to derive a few general properties of random walks on lattices containing traps.Presented at the Symposium on Random Walks, Gaithersburg, MD, June 1982.     

Sample decomposition in an electrically heated cold-trap inlet system for high speed gas chromatography

Thermal decomposition of some hydrocarbon and chlorinated hydrocarbon compounds in metal capillary tubes used in an inlet system for high speed gas chromatography has been investigated. The metal tube is cooled to about ?75°C by a flow of cold nitrogen gas in order to focus a vapor sample cryogenically. A capacitive discharge power supply is then used to heat the metal tube resistively in order to revaporize the sample and introduce it to the separation column as a plug 5-10 ms wide. The effects of tube temperature, tube material, sample vapor residence time, and type of carrier gas on thermal cracking are described. Use of a copper-nickel alloy tube resulted in less cracking than either pure platinum or pure nickel. Cracking is more significant with hydrogen as carrier gas than with helium. Cracking also increases with increasing sample residence time in the hot tube. Quantitative sample injection with minimum decomposition can be obtained for a variety of aliphatic and aromatic hydrocarbons and chlorinated hydrocarbon compounds.     

Stabilization of an excess electron on molecular surfaces by a pair of HF molecules

This work presents the results of solvation of electrons on several hypothetical cyclooctane and cyclohexane molecular surfaces, using the hydrogen fluoride (HF) dimer. These complexes were constructed with extensive OH groups on one side of a hydrocarbon surface (i.e., cyclohexane sheets), which creates hydrogen‐bonded networks that can form, increasing the dipole moment of the system. Concurrently, the hydrogen atoms on the opposite side of the surface form a pocket of positive charge that can attract excess electrons. Two possible orientations for HF dimer solvation on eight molecular surfaces that have been demonstrated to be stable toward electron detachment are examined. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007