Search results for "Sapphire"

Structural characterization of a-plane Zn1−xCdxO (0 < x <0.085) thin films grown by metal-organic vapor phase epitaxy.

2006

Zn1−xCdxO(11math0) films have been grown on (01math2) sapphire (r–plane) substrates by metal-organic vapor phase epitaxy. A 800-nm-thick ZnO buffer, deposited prior to the alloy growth, helps to prevent the formation of pure CdO. A maximum uniform Cd incorporation of 8.5 at. % has been determined by Rutherford backscattering spectrometry. Higher Cd contents lead to the coexistence of Zn1−xCdxO alloys of different compositions within the same film. The near band-edge photoluminescence emission shifts gradually to lower energies as Cd is incorporated and reaches 2.93 eV for the highest Cd concentration (8.5 at. %). The lattice deformation, due to Cd incorporation, has been described using a n…

Double-resonance-ionization mapping of the hyperfine structure of the stable Cu isotopes using pulsed narrowband Ti:sapphire lasers

2015

We present two approaches to enhance the resolving power for measuring hyperfine structure constants using resonance ionization spectroscopy. The first method employs a 2D-resonance ionization spectroscopy scanning technique with pulsed, narrowband Ti:sapphire lasers (1 GHz linewidth), allowing us to resolve hyperfine components that cannot be separated using the standard 1D-scanning method across only one optical transition. In a second refinement, the resolving power is further enhanced through the use of a ring design of the laser cavity. This layout leads to a reduction of the laser linewidth from 1 GHz to below 50 MHz, resulting in experimental linewidths of about 150 MHz. Motivated by…

2018

Abstract This article presents a pulsed narrowband injection-locked Titanium:Sapphire laser aimed for high-resolution in-jet resonance ionization spectroscopy at the SLOWRI/PALIS at RIKEN. The laser has been integrated into the PALIS laser laboratory enabling it to be utilized with the existing broadband Titanium:Sapphire and dye lasers. The seed efficiency has been evaluated to be close to unity over the master laser wavelength range ∼ 753 to 791 nm, and the slope efficiency, namely the ratio of the pump power to the output power, was determined to be ∼ 30 % at 780 nm. A two-step ionization scheme with 386.4016 nm first step and 286.731 nm second step into an autoionizing state was develop…

A hot cavity laser ion source at IGISOL

2008

A development program is underway at the IGISOL (Ion Guide Isotope Separator On-Line) facility, University of Jyvaskyla, to efficiently and selectively produce low-energy radioactive ion beams of silver isotopes and isomers, with a particular interest in N=Z 94Ag. A hot cavity ion source has been installed, based on the FEBIAD (Forced Electron Beam Induced Arc Discharge) technique, combined with a titanium:sapphire laser system for selective laser ionization. The silver recoils produced via the heavy-ion fusion-evaporation reaction, 40Ca(58Ni, p3n)94Ag, are stopped in a graphite catcher, diffused, extracted and subsequently ionized using a three-step laser ionization scheme. The performance…

Extreme increase in atomic transition probability of the Cs D_2 line in strong magnetic fields under selective reflection

2016

Selective reflection of 852-nm laser radiation from the interface between cesium vapor and the sapphire window of a 30-micrometer-thick microcell was used to record an extreme increase in the probability of the Fg=3→Fe=5 transitions associated with the Cs-atom D2 lines in magnetic fields with inductions ranging from 300 to 3200 Gauss. We showed that a group of seven transitions Fg=3, mF=−3, −2, −1, 0, +1, +2, +3→Fe=5, mF=−2, −1, 0, +1, +2, +3, +4 was formed in accordance with the selection rules ΔmF=+1 for σ+-circularly-polarized radiation. These seven transitions have much higher probabilities in 500–1000 Gauss magnetic fields, with three of the transitions having probabilities higher than…

Development of an array of calorimetric low-temperature detectors for heavy ion physics

2006

Abstract Calorimetric low-temperature detectors have been investigated for several applications in heavy ion physics within the last 15 years. The detectors used consist of sapphire absorbers of 2×3×0.33 mm 3 and superconducting aluminum transition edge sensors operated at T ≈1.5 K. To fully exploit the potential of such detectors for heavy ion physics, a detector array is developed. For this purpose, a specially adapted 4 He bath cryostat with a base temperature of 1.2 K, which allows an active detector area of 30×80 mm 2 , was constructed. As different detectors have different transition temperatures, each detector pixel has to be adjusted to its specific working point and temperature sta…

First application of calorimetric low-temperature detectors in accelerator mass spectrometry

2004

Abstract For the first time, calorimetric low-temperature detectors were applied in accelerator mass spectrometry, a well-known method for determination of very small isotope ratios with high sensitivity. The aim of the experiment was to determine with high accuracy the isotope ratio of 236U/238U for several samples of natural uranium, 236U being known as a sensitive monitor for neutron flux. Measurements were performed at the VERA tandem accelerator at Vienna, Austria. The detectors consist of sapphire absorbers and superconducting transition edge thermometers operated at T≈ 1.5 K. The relative energy resolution obtained for 17.39 MeV 238U is ΔE/E=4–9×10−3, depending on the experimental co…

Development of High Resolution Resonance Ionization Mass Spectrometry for Neutron Dosimetry Technique with93Nb(n,n')93mNb Reaction

2016

We have proposed an advanced technique to measure the 93mNb yield precisely by Resonance Ionization Mass Spectrometry, instead of conventional characteristic X-ray spectroscopy. 93mNb-selective resonance ionization is achievable by distinguishing the hyperfine splitting of the atomic energy levels between 93Nb and 93mNb at high resolution. In advance of 93mNb detection, we could successfully demonstrate high resolution resonant ionization spectroscopy of stable 93Nb using an all solid-state, narrowband and tunable Ti:Sapphire laser system operated at 1 kHz repetition rate. peerReviewed

Characterization of non-polar ZnO layers with positron annihilation spectroscopy

2008

We applied positron annihilation spectroscopy to study the effect of growth polarity on the vacancy defects in ZnO grown by metal-organic vapor phase deposition on sapphire. Both c-plane and a-plane ZnO layers were measured, and Zn vacancies were identified as the dominant defects detected by positrons. The results are qualitatively similar to those of earlier experiments in GaN. The Zn vacancy concentration decreases in c-plane ZnO by almost one order of magnitude (from high 10 cm−3 to low 10 cm−3) when the layer thickness is increased from 0.5 to 2 μm. Interestingly, in a-plane ZnO the Zn vacancy concentration is constant at a level of about 2×10 cm−3 in all the samples with thicknesses v…

Development of accelerator mass spectrometry assisted by isotope-selective laser photodetachment for monitoring 129I

2013

Abstract A prototype system was developed to investigate an isotope-selective laser photodetachment technique for a 129 I accelerator mass spectrometer. A pulsed ion source for negative iodine ions (I − ) that employed laser ablation proved to be suitable for isotope-selective laser photodetachment. Laser photodetachment of pulsed negative iodine ions was estimated to have an efficiency of about 81% based on a model calculation for the prototype system with a tunable pulsed Ti:sapphire laser.