Search

We present a method for retrieving of single-active electron potential in an atom or molecule from a given momentum distribution of photoelectrons ionized by a strong laser field. In this method the potential varying within certain limits is found as the result of the optimization procedure aimed at reproducing the given momentum distribution. The optimization using numerical solution of the time-dependent Schrödinger equation for ionization of a model one-dimensional atom shows the good accuracy of the potential reconstruction method. This applies to different ways used for representing of the potential under reconstruction, including a parametrization and determination of the potential by specifying its values on a spatial grid.

Erbium 169Er is one of the most interesting radiolanthanides for new potential receptor-targeted β− therapy applications due to its low energy β− emissions, very low intensity ɣ rays and the possibility to use 68Ga or 44Sc as companion for diagnostic in a theranostics approach. Currently it can be produced in reactors through the neutron activation of highly enriched 168Er. The low specific activity of the produced carrier-added 169Er is limiting its use for receptor-targeted therapy. Nonetheless it is used for radiosynoviorthesis of small joints. The aim of this work is to develop a new large-scale production method for the supply of very high specific activity 169Er. Highly enriched 168Er target has been irradiated at ILL nuclear reactor and shipped to CERN-MEDICIS. There, the irradiated sample has been mass separated in order to isolate 169Er from the high amount of remaining stable 168Er. The proof of principle for a preclinical dose production has been demonstrated with a collection of ≈17 MBq. The specific activity obtained was ≈240 GBq/mg (≈200 times higher than the product obtained at End of Bombardment – EOB) and the overall separation efficiency was ≈0.2%. Several improvements for the future have been identified and are promising. One of them is the installation of the new laser laboratory at CERN-MEDICIS that will allow to improve the selective ionization of erbium atoms leading to an increase of the efficiency of the method. This method can provide the supply of high specific activity 168Er, first for preclinical studies, and opens also the potential for future large-scale supply. © 2019

Two lowest-energy odd-parity atomic levels of actinium, 7s27pP21/2o, 7s27pP23/2o, were observed via two-step resonant laser-ionization spectroscopy and their respective energies were measured to be 7477.36(4) and 12 276.59(2) cm-1. The lifetimes of these states were determined as 668(11) and 255(7) ns, respectively. In addition, we observed the effect of the hyperfine structure on the line for the transition to P23/2o. These properties were calculated using a hybrid approach that combines configuration interaction and coupled-cluster methods, in good agreement with the experiment. The data are of relevance for understanding the complex atomic spectra of actinides and for developing efficient laser cooling and ionization schemes for actinium, with possible applications for high-purity medical-isotope production and future fundamental physics experiments. © 2020 American Physical Society.

Atom laser experiments with Bose-Einstein condensates (BECs) performed in ground-based laboratories feature a coherent and directed beam of atoms which is accelerated by gravity. In microgravity the situation is fundamentally different because the dynamics is entirely determined by the repulsive interaction between the atoms and not by the gravitational force. As a result, the output of a space atom laser is a spherical wave slowly expanding away from the initial BEC. We present a thorough theoretical study of this new source of matter waves based on rf outcoupling which exhibits an isotropic distribution both in position and momentum even for an initially anisotropic trap. The unique geometry of such a freely expanding, shell-shaped BEC offers new possibilities for matter waves in microgravity and is complementary to other matter-wave sources prepared by delta-kick collimation or adiabatic expansion. Our work paves the way for the upcoming experimental realization of a space atom laser making use of NASA's Cold Atom Laboratory on the International Space Station.

As an energy-preserving variant of laser hybrid welding, laser-assisted arc welding uses laser powers of less than 1 kW. Recent studies have shown that the electrical conductivity of a TIG welding arc changes within the arc in case of a resonant interaction between laser radiation and argon atoms. This paper presents investigations on how to control the position of the arc root on the workpiece by means of the resonant interaction. Furthermore, the influence on the welding result is demonstrated. The welding tests were carried out on a cooled copper plate and steel samples with resonant and non-resonant laser radiation. Moreover, an analysis of the weld seam is presented.

Efficient preparation and detection of the motional state of trapped ions is important in many experiments ranging from quantum computation to precision spectroscopy. We investigate the stimulated Raman adiabatic passage (STIRAP) technique for the manipulation of motional states in a trapped ion system. The presented technique uses a Raman coupling between two hyperfine ground states in 25Mg+, implemented with delayed pulses, which removes a single phonon independent of the initial motional state. We show that for a thermal probability distribution of motional states the STIRAP population transfer is more efficient than a stimulated Raman Rabi pulse on a motional sideband. In contrast to previous implementations, a large detuning of more than 200 times the natural linewidth of the transition is used. This approach renders STIRAP suitable for atoms in which resonant laser fields would populate nearby fluorescing excited states and thus impede the STIRAP process. We use the technique to measure the wavefunction overlap of excited motional states with the motional ground state. This is an important application for force sensing applications using trapped ions, such as photon recoil spectroscopy, in which the signal is proportional to the depletion of motional ground state population. Furthermore, a determination of the ground state population enables a simple measurement of the ion's temperature.

Quantum metrology enables new applications in geodesy, including relativistic geodesy. The recent progress in optical atomic clocks and in long-distance frequency transfer by optical fiber together pave the way for using measurements of the gravitational frequency redshift for geodesy. The remote comparison of frequencies generated by calibrated clocks will allow for a purely relativistic determination of differences in gravitational potential and height between stations on Earth surface (chronometric leveling). The long-term perspective is to tie potential and height differences to atomic standards in order to overcome the weaknesses and inhomogeneity of height systems determined by classical spirit leveling. Complementarily, gravity measurements with atom interferometric setups, and satellite gravimetry with space borne laser interferometers allow for new sensitivities in the measurement of the Earth's gravity field.

This consortium established a focused collaborative program to advance matter wave sensors. We combined atom interferometry with atom lasers and atom waveguides with the prospect of improving the sensitivity of such sensors by orders of magnitude as compared with existing state-of-the-art sensors. We identified, explored and exploited fundamental scientific possibilities surrounding the production, manipulation and detection of ultra-cold atoms for a variety of sensing applications. Such sensors include gravimeters, gravity gradiometers, gyroscopes, magnetometers and frequency standards and have applications in science and technology and within the DoD. Sensitive and accurate inertial force sensors can be used in covert/passive navigation, precision guidance, underground structure detection, gravitational mapping, etc. They are non-emanating and capable of operating in a jammed-GPS environment. We sought to build awareness of DoD needs critical to national defense at the graduate training level, and to establish a dialogue between DoD and industrial researchers/managers and PhD trainees., Consortium members: University of Arizona, Harvard University, Massachusetts Institute of Technology, and Stanford University. The original document contains color images.

We study both numerically and analytically the possibility of using an adiabatic passage control method to construct a Mach-Zehnder interferometer (MZI) for Bose-Einstein condensates in the time domain, in exact one-to-one correspondence with the traditional optical MZI that involves two beam splitters and two mirrors. The interference fringes one obtains from such a minimum-disturbance setup clearly demonstrates that, fundamentally, an atom laser is not monochromatic due to interatomic interactions. We also consider how the amount of entanglement in the system correlates to the interference fringes.

Our goal is to pursue atom interferometry and advances of the atom laser using Bose-Einstein condensates. Condensates will be moved from a vacuum chamber where they were produced into a science chamber where a great variety of experiments can be carried out without the severe limitations imposed by the cooling and trapping techniques applied in the first chamber. The new chamber has been constructed, and first Bose-Einstein condensates were produced in the spring of 2001. A large-volume optical trap which will be used for translating condensates was successfully tested. In this trap, condensates in lower dimensions and in the upper hyperfine state of sodium were produced. One important element for atom interferometry is the transfer of momentum by simulated light scattering. This scattering can be self-amplified and is accompanied by the amplification of atoms and light. Both processes were studied in detail.

The general goal of this research was the generation, manipulation and characterization of coherent and non-classical matter waves, including atom lasers. The research involved both a theoretical and an experimental component. Major achievements from the Meystre group include the theory of a binary-collision atom laser, new proposals in nonlinear atom optics, in particular the optical control of matter waves, matter-wave superradiance and coherent matter-wave amplification. These are applications of the nonlinear mixing between optical and matter waves, which have recently seen their first experimental verifications by groups at MIT, NIST and U. Tokyo. This work has also lead to a new proposal for atom holography. In addition, we have started to develop the coherence theory of matter waves and of the cross-coherence between optical and matter waves. Major results from the Jessen group include an in-depth study of practical avenues for single-atom quantum state engineering, and development of a novel proposal for entanglement engineering and quantum logic in optical lattices. Our most noteworthy experimental achievements include the development of efficient methods to load and trap atoms in far-of-resonant optical lattices, and the first demonstration of Raman sideband cooling of neutral Cs atoms to the ground state of an optical lattice. Most recently we have completed an experiment on coherent quantum tunneling and macroscopic quantum coherence in optical double-well potentials, and have initiated a new experiment to reconstruct the complete internal state of ultracold atomic wavepackets.

Our long-term goals are twofold. First, to explore the new properties of gaseous Bose-Einstein condensates and advance our understanding of quantum gases. Second, we want to use Bose condensed gases as new atom sources of unprecedented brightness ("atom lasers") for precision atom optics and precision metrology.

Long-term Research Objective: This program supports theoretical investigations of the quantum degenerate systems of trapped and interacting atomic gas. Primary topics being addressed are: (1) To understand the properties of atomic Bose-Einstein condensates, in particular, the low energy excitations, dynamics of Bose-Einstein condensation, vortex states creation and detection. (2) Theoretical prospects for quantum degeneracy and the realization of BCS states for interacting fermionic atoms, and the understanding their properties. (3) Theoretical proposals for realizing practical coherent matter wave creation and output devices, the physics of atom lasers. S&T Objectives: Theoretical understanding of the quantum statistical behavior of trapped low temperature atom cloud and the development of atom laser theory. Approach: The theoretical studies require us to combine theoretical tools developed in the area of atomic physics, many-body statistical physics, and quantum optics. Numerical methods are developed for the solution of the low energy atomic scattering in the presence of an anisotropic interaction potential.

The proposal contained the following goals: Development of a new dc magnetic trap, Bose-Einstein condensation of a large number of atoms, Study of dynamics of condensate formation and collective excitations

The program objectives are to develop an intensive source of Bose condensed sodium atoms and to study the properties of Bose-Einstein condensates.