Search results for " atom"
showing 10 items of 1526 documents
Work fluctuations in bosonic Josephson junctions
2016
We calculate the first two moments and full probability distribution of the work performed on a system of bosonic particles in a two-mode Bose-Hubbard Hamiltonian when the self-interaction term is varied instantaneously or with a finite-time ramp. In the instantaneous case, we show how the irreversible work scales differently depending on whether the system is driven to the Josephson or Fock regime of the bosonic Josephson junction. In the finite-time case, we use optimal control techniques to substantially decrease the irreversible work to negligible values. Our analysis can be implemented in present-day experiments with ultracold atoms and we show how to relate the work statistics to that…
Atom-field dressed states in slow-light waveguide QED
2015
We discuss the properties of atom-photon bound states in waveguide QED systems consisting of single or multiple atoms coupled strongly to a finite-bandwidth photonic channel. Such bound states are formed by an atom and a localized photonic excitation and represent the continuum analog of the familiar dressed states in single-mode cavity QED. Here we present a detailed analysis of the linear and nonlinear spectral features associated with single- and multi-photon dressed states and show how the formation of bound states affects the waveguide-mediated dipole-dipole interactions between separated atoms. Our results provide a both qualitative and quantitative description of the essential strong…
Comparative Theoretical Analysis of BN Nanotubes Doped with Al, P, Ga, As, In, and Sb
2013
SUMMARY AND CONCLUDING REMARKS We have performed large-scale first-principles calculations ofthe electronic structure of (5,5) boron nitride nanotubescontaining the following substitutional impurity atoms: Al, P,Ga, As, In, and Sb. Calculations have been performed using thetwo methods: (i) linear combination of atomic orbitals(LCAO) with the atomic-centered Gaussian-type functions asa basis set and (ii) linearized augmented cylindrical wave(LACW) accompanied with the local density functional andmuffin-tin approximations for the electronic potential. In arelatively good qualitative agreement, both methods predict lowformation energies and, thus, relative stability of point defectsthat are assoc…
The α and γ plasma modes in plasma-enhanced atomic layer deposition with O2-N2 capacitive discharges
2017
Two distinguishable plasma modes in the O2–N2 radio frequency capacitively coupled plasma (CCP) used in remote plasma-enhanced atomic layer deposition (PEALD) were observed. Optical emission spectroscopy and spectra interpretation with rate coefficient analysis of the relevant processes were used to connect the detected modes to the α and γ modes of the CCP discharge. To investigate the effect of the plasma modes on the PEALD film growth, ZnO and TiO2 films were deposited using both modes and compared to the films deposited using direct plasma. The growth rate, thickness uniformity, elemental composition, and crystallinity of the films were found to correlate with the deposition mode. In re…
Optimization of a laser ion source for $^{163}$Ho isotope separation
2019
To measure the mass of the electron neutrino, the “Electron Capture in Holmium-163” (ECHo) collaboration aims at calorimetrically measuring the spectrum following electron capture in 163Ho. The success of the ECHo experiment depends critically on the radiochemical purity of the 163Ho sample, which is ion-implanted into the calorimeters. For this, a 30 kV high transmission magnetic mass separator equipped with a resonance ionization laser ion source is used. To meet the ECHo requirements, the ion source unit was optimized with respect to its thermal characteristics and material composition by means of the finite element method thermal-electric calculations and chemical equilibrium simulation…
Ab initio calculations of structural, electronic and vibrational properties of BaTiO3 and SrTiO3 perovskite crystals with oxygen vacancies
2020
The first-principles (ab initio) computations of the structural, electronic, and phonon properties have been performed for cubic and low-temperature tetragonal phases of BaTiO3 and SrTiO3 perovskite crystals, both stoichiometric and non-stoichiometric (with neutral oxygen vacancies). Calculations were performed with the CRYSTAL17 computer code within the linear combination of atomic orbitals approximation, using the B1WC advanced hybrid exchange-correlation functional of the density-functional-theory (DFT) and the periodic supercell approach. Various possible spin states of the defective systems were considered by means of unrestricted (open shell) DFT calculations. It was demonstrated that…
Charge breeding time investigations of electron cyclotron resonance charge breeders
2018
To qualify electron cyclotron resonance charge breeders, the method that is traditionally used to evaluate the charge breeding time consists in generating a rising edge of the injected beam current and measuring the time in which the extracted multicharged ion beam reaches 90% of its final current. It is demonstrated in the present paper that charge breeding times can be more accurately measured by injecting short pulses of 1 + ions and recording the time resolved responses of N + ions. This method is used to probe the effect of the 1 + ion accumulation in the plasma known to disturb the buffer gas plasma equilibrium and is a step further in understanding the large discrepancies reported in…
Ultrasonic nebulization inductively coupled plasma optical emission spectrometry method for wine analysis
2020
Abstract A methodology was developed to determine mineral elements in wines using Inductively Coupled Plasma Optical Emission Spectrometry combined with ultrasonic nebulization. The concentration of 36 elements (Al, B, Ba, Bi, Ca, Cd, Ce, Co, Cr, Dy, Er, Eu, Fe, Gd, K, La, Lu, Mg, Mn, Mo, Na, Nd, Ni, Pb, Pr, Sb, Sc, Sm, Sr, Tb, Ti, Tm, V, Y, Yb, and Zn) was determined in 59 wine samples and used to distinguish between Brazilian and Spanish wines. The best conditions for the plasma were selected using a two-level factorial design: radiofrequency power 1500 W; plasma gas flow rate 15 L min−1; auxiliary 0.70 L min−1; and nebulizer 0.40 L min−1. An exploratory multivariate analysis by Principal…
Multi-scale multireference configuration interaction calculations for large systems using localized orbitals: Partition in zones
2012
A new multireference configuration interaction method using localised orbitals is proposed, in which a molecular system is divided into regions of unequal importance. The advantage of dealing with local orbitals, i.e., the possibility to neglect long range interaction is enhanced. Indeed, while in the zone of the molecule where the important phenomena occur, the interaction cut off may be as small as necessary to get relevant results, in the most part of the system it can be taken rather large, so that results of good quality may be obtained at a lower cost. The method is tested on several systems. In one of them, the definition of the various regions is not based on topological considerati…
Dynamics of the excited-state hydrogen transfer in a (dG)·(dC) homopolymer: intrinsic photostability of DNA
2018
Multiscale molecular dynamics simulations reveal out-of-plane distortions that favour DNA photostability. A novel photostability mechanism involving four proton transfers and triggered by a nearby Na+ ion is also unveiled.