Results 1 - 10 of 3710
Results 1 - 10 of 3710. Search took: 0.035 seconds
|Sort by: date | relevance|
[en] The retrapping of highly charged Xe44+ and Th68+,72+ ions extracted from an open-quotes Electron Beam Ion Trapclose quotes (EBIT) is demonstrated after injection of the ions into RETRAP, a cryogenic Penning trap (up to 6 Tesla magnetic field) currently with an open cylinder design. Ion extraction in a short pulse (5-20 μsec) from EBIT, essential for efficient retrapping, is employed. The ions are slowed down upon entering a deceleration tube mounted above the trap within the magnetic field. The potential is then rapidly (100 ns) decreased, enabling low energy ions to enter the trap. Capture efficiencies up to 25% are observed via detection of the delayed ion release pulse with a detector below the trap. Signal voltages induced in a tuned circuit due to single and multiple ions have been observed by tuning the ion resonant axial oscillation frequencies for different ions. Results from transporting and retrapping of the ions, as well as their detection, are described and the trapping efficiency is discussed, The motivation for these studies is to cool the trapped very highly charged ions to low temperatures (< 4 K) in order to perform ultrahigh resolution precision spectroscopy, collision studies at ultra low energies and to observe phase transitions in Coulomb clusters of highly charged ions
[en] We have observed the variation in ion signal as a function of intensity within a focused laser spot. Using an aperture detector, the ion signals from narrow bands of the laser focus have been observed. By moving the laser focus along the direction of propagation, regions of different intensities are exposed to the detector. This has allowed detailed measurements to be made of ion signals as a function of laser intensity. (orig.)
[en] Lifetimes of seven levels belonging to the 5p46d configuration of Xe II have been measured by high frequency deflection technique with a delayed coincidence single photon counting arrangement. The results have been compared with other experimental and theoretical values. (orig.)
[en] The NIST Electron Beam Ion Trap (EBIT) has been modified to be used as a source of low kinetic energy, highly-charged ions. It can produce, for example, a continuous beam of Xe44+ ions with more than a million counts per second or 7 pA. This beam has been used to bombard surfaces such as mica, CR-39 (polymer) and self-assembled monolayers. The authors characterized the surfaces using techniques including AFM and SEM, and observed single-ion features approximately 15 nm in diameter
[en] Lifetimes of ions confined by a radio frequency quadrupole field in the presence of a buffer gas are measured. The results are in good agreement with a hard sphere collision model
[fr]On mesure la duree de vie d'ions Xenon confines par un piege quadrupolaire en fonction de la densite d'un gaz tampon. Les resultats sont en accord avec un modele theorique de collision a spheres dures
[en] The secondary electron yields as a result of highly charged ions impinging on clean Au(111) and thin films of C60 on Au have been measured. This has been done for film thicknesses of one to five monolayers and several charge states of Ar and Xe ions. For all ions an increase of 35% in the secondary electron yield is observed when going from Au(111) to multiple C60 layers. The increase remains constant for a wide range (7-26) of charge states. Possible scenarios are given to explain the increase in electron yield.
[en] Using molecular-dynamics simulation, we study the impact of 0.5 keV Xe ions at glancing incidence (80° from the surface normal) on a graphene flake supported on a (0 0 0 1) graphite substrate. The step forming at the ascending edge of the flake allows the entrance of glancing-incidence ions into a subsurface channel between graphene layers. We find that subsurface-channeled ions have a high probability to lift the flake off the substrate, while non-channeled projectiles rather damage the flake leading eventually to welding the flake to the substrate by the formation of sp3 bonds.
[en] Visible and UV laser emission from a highly ionized pulsed Xe plasma was studied in relation to the ionic assignment of the laser lines. Time-resolved spectroscopy was used to determine the ionic origin of the studied lines. The results are in agreement with an intensity versus pressure analysis performed over the same wavelength range. From the temporal behaviour of the spontaneous emission, a probable classification can be obtained. (author). 7 refs, 7 figs, 1 tab
[en] The intriguing electronic properties of graphene have renewed the interest in other 2D materials such as transition metal di-chalcogenides (TMDCs) monolayers. TMDCs, similar to graphite, have a layered structure with an indirect bandgap which becomes direct when only a monolayer is present. This leads to strongly enhanced photoluminescence (PL). However, unavoidable defects affect the opto-electronic properties of TMDC monolayers drastically, which makes it necessary to study and characterize their optical related properties. In this contribution, we present highly sensitive, non-destructive, temperature and power dependent PL measurements to study the defects present in tungsten di-sulfide (WS2) monolayers. For this purpose, pristine samples of WS2 were irradiated with Xe30+ ions to additionally create defects in the monolayers. Low temperature spectra of pristine samples show two different peaks associated with free and defect-bound excitons recombinations. For higher temperature or power, only the free exciton recombinations dominate the spectrum. For the different defect densities created in the monolayers, we observed changes in the PL spectrum with regard to intensity and FWHM, which will be discussed and compared to data published in literature.
[en] We present a revised analysis of the spectrum of singly ionized xenon, Xe II. This spectrum has been reanalyzed on the basis of the wavelength material published by Drs J. C. Boyce and C. J. Humphreys. The latter has kindly placed the original wavelength list covering the wavelength range 10220-390 A at our disposal. We report 161 energy levels which have been identified on the basis of classifications of 950 lines. We report first f and g levels in Xe II. Also a number of g-factors have been determined for the first time and we give in total 75 g-factors. We have carried out least-squares fits to the even configurations and report the resulting parameter values and eigenvector compositions. A least-squares fit to the 5p46p configuration is also reported. The levels have been named in jK and for many levels also in LS coupling. The former is the better coupling scheme for Xe II. We present an analysis of the 5s photoelectron satellite spectrum of Xe based on our calculated eigenvector compositions and calculations of transition probabilities for ground state transitions as well as lifetimes for the 6p levels. The latter are compared to recent experimental measurements. A list of wavelengths for observed laser transitions showing the present classifications and a discussion of the determination of the ionization potential of Xe II concludes the paper. (orig.)