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1

Some new trends in laser isotope separation in atomic vapours  

Microsoft Academic Search

New approaches to the methods of laser isotope separation are considered and realised which substantially extend the possibilities of the methods. To narrow down an absorption line and decrease parasitic absorption at transitions in isotope atoms that do not belong to an isotope being separated, two-photon excitation of atoms was used both in collinear and counterpropagating light beams. By using

P A Bokhan; D E Zakrevskii; M M Kalugin; N V Fateev; V V Buchanov; M A Kazaryan; A M Prokhorov

2002-01-01

2

Laser Isotope Separation in Atomic Vapour:. PhotoChemical Method VS. PhotoIonization One  

Microsoft Academic Search

Two methods of laser isotope separation in atomic vapour are compared. The first of them is a well developed Photo-ionization method. The other method is based on isotope-selective excitation of long-living atomic states and subsequent chemical reaction of excited atom with special reagents. It is shown that this method has some principal advantages compared to Photo-ionization method.

P. A. Bokhan; N. V. Fateyev; D. E. Zakrevskiy; V. V. Buchanov; M. A. Kazaryan

2010-01-01

3

SPECTROSCOPIC DATA FOR LASER ISOTOPE SEPARATION BY ATOMIC VAPOUR ROUTE: A CASE STUDY IN (U-234, U-235) ISOTOPIC SYSTEM  

Microsoft Academic Search

A b s t r a c t Involvement of atomic physics in the development of Laser Isotope Separation (LIS) technology with atomic vapour route is discussed with a case study in (U-234, U-235) isotopic system. Importance of atomic data, i.e. isotope shift, hyperfine structure and transition strength in configuration of an isotope selective three-step photoionisation sequence is discussed. Spectroscopic

A. P. Marathe; K. G. Manohar; B. N. Jagatap

4

Production of a highly enriched ¹Yb isotope in weight amounts by the atomic-vapour laser isotope separation method  

Microsoft Academic Search

The production of a highly enriched ¹Yb isotope in weight amounts by the atomic-vapour laser isotope separation method is reported. The content of ¹Yb achieved in the experimental samples of the enriched material was 99%. For a commercial production of about 20 mg h¹, the concentration of this isotope is about 88% with about 5% of the 'harmful' isotope ¹Yb.

O I Andreev; V I Derzhiev; V M Dyakin; A G Egorov; L A Mikhaltsov; V A Tarasov; A I Tolkachev; Yu G Toporov; S A Chaushanskii; Sergei I Yakovlenko

2006-01-01

5

INVITED PAPER: Some new trends in laser isotope separation in atomic vapours  

Microsoft Academic Search

New approaches to the methods of laser isotope separation are considered and realised which substantially extend the possibilities of the methods. To narrow down an absorption line and decrease parasitic absorption at transitions in isotope atoms that do not belong to an isotope being separated, two-photon excitation of atoms was used both in collinear and counterpropagating light beams. By using

P. A. Bokhan; V. V. Buchanov; D. E. Zakrevskii; M. A. Kazaryan; M. M. Kalugin; A. M. Prokhorov; N. V. Fateev

2002-01-01

6

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Production of a highly enriched 176Yb isotope in weight amounts by the atomic-vapour laser isotope separation method  

Microsoft Academic Search

The production of a highly enriched 176Yb isotope in weight amounts by the atomic-vapour laser isotope separation method is reported. The content of 176Yb achieved in the experimental samples of the enriched material was 99%. For a commercial production of about 20 mg h-1, the concentration of this isotope is about 88% with about 5% of the 'harmful' isotope 174Yb.

O. I. Andreev; V. I. Derzhiev; V. M. Dyakin; A. G. Egorov; L. A. Mikhal'tsov; V. A. Tarasov; A. I. Tolkachev; Yu G. Toporov; S. A. Chaushanskii; Sergei I. Yakovlenko

2006-01-01

7

Light propagation through atomic vapours  

NASA Astrophysics Data System (ADS)

This tutorial presents the theory necessary to model the propagation of light through an atomic vapour. The history of atom-light interaction theories is reviewed, and examples of resulting applications are provided. A numerical model is developed and results presented. Analytic solutions to the theory are found, based on approximations to the numerical work. These solutions are found to be in excellent agreement with experimental measurements.

Siddons, Paul

2014-05-01

8

Copper vapour laser pumped by a relativistic electron beam  

SciTech Connect

Experimental and theoretical investigations were made of the pumping of a copper vapour laser by a relativistic electron beam ({var_epsilon} {approximately}500 keV, I{approximately}3 KA, {tau} {approximately} 60 ns). The results obtained (energy of laser pulses {approximately} 30mJ, efficiency {approximately} 1.5%-3% at a neon pressure of {approximately}0.02 bar) were far from those expected. An analysis of the experimental and calculated data showed that the required concentration of the copper vapour in the atomic state was not reached in the active zone and that the process of pumping under these conditions was uncoventional: the energy was transferred from the electron beam to the medium not by collisions with gas atoms (ionisation losses) but by the interaction of a beam-induced eddy electric field with the beam plasma. 14 refs., 6 figs.

Arlantsev, S.V.; Borovich, B.L.; Molodykh, E.I. [Granat Special Design Bureau, Moscow (Russian Federation)] [and others] [Granat Special Design Bureau, Moscow (Russian Federation); and others

1994-11-01

9

Use of a Faraday modulator in a laser polarimeter for optical forward-wave level-crossing experiments in atomic vapours  

Microsoft Academic Search

Detection of level-crossings in forward-wave scattering of light by atomic vapours is normally accomplished by placing the sample of interest between crossed polarisers. The addition of a birefringence (Faraday) modulator between the polarisers allows not only optimisation of the signal-to-noise ratio in such experiments, but enhances the real part of the atomic susceptibility relative to the imaginary part. This has

T. D. Wolfenden; P. E. G. Baird; J. A. Deeny; M. Irie

1990-01-01

10

Collisional thulium vapour gas-discharge laser  

SciTech Connect

A collisional laser on a system of atomic levels based on the principle proposed by Gould is built for the first time. The population of the upper laser level and relaxation of the lower level occur upon inelastic collisions of excited thulium atoms with helium atoms. The lower-level relaxation occurs in a reaction with an energy defect of > 13000 cm{sup -1}. (active media. lasers)

Gerasimov, V A; Pavlinskii, A V [Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences, Tomsk (Russian Federation)

2004-01-31

11

Capacitive-discharge-pumped copper bromide vapour laser  

SciTech Connect

A copper bromide vapour laser pumped by a high-frequency capacitive discharge is developed. It is shown that, by using of a capacitive discharge, it is possible to built a sealed off metal halide vapour laser of a simple design allowing the addition of active impurities into the working medium. (letters)

Sukhanov, V B; Fedorov, V F; Troitskii, V O [Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences, Tomsk (Russian Federation); Gubarev, F A; Evtushenko, Gennadii S [Tomsk Polytechnical University, Tomsk (Russian Federation)

2007-07-31

12

Mechanisms of vapour plume formation in laser deep penetration welding  

NASA Astrophysics Data System (ADS)

We analysed the dynamic shape of the metal vapour plume during deep penetration laser welding by means of high speed imaging. Our studies show that besides the inclination also the elongation of the vapour plume is determined by the evaporation processes inside the keyhole. When welding stainless steel sheets, the shape of the vapour plume as well as the shape of its origin, the keyhole, significantly vary with laser power and feed rate settings in a consistent way. This rather deterministic relationship allows for estimating how evaporation is distributed along the keyhole surface in different welding regimes. Based on the evaluation of the high speed sequences and corresponding microsections we propose a model of the vapour plume formation. The model indicates that, depending on the keyhole shape, the generation of the vapour plume is either governed by the vapour formed at the bottom of the keyhole or by the vapour formed at the inclined front keyhole surface, resulting in a very different shape of the plume in each case.

Brock, C.; Hohenstein, R.; Schmidt, M.

2014-07-01

13

Diode laser spectroscopy: Water vapour detection in the atmosphere  

Microsoft Academic Search

Summary  Diode laser spectroscopy of water vapour has been performed in the near IR and the pressure broadening coefficients in nitrogen\\u000a and in air have been measured for one rotovibrational line. Detection of water vapour in the atmosphere has been obtained\\u000a and an evaluation of the sensitivity of our apparatus is reported. Discussion for further improvements is made.

A. Lucchesini; L. Dell'Amico; I. Longo; C. Gabbanini; S. Gozzini; L. Moi

1991-01-01

14

Copper bromide vapour laser with a pulse repetition rate up to 700 kHz  

SciTech Connect

The results of the experimental study of a copper bromide vapour laser at high repetition rates of regular pump pulses are presented. A record-high pulse repetition rate of 700 kHz is attained for lasing at self-terminating transitions in copper atoms. To analyse the obtained results, use is made of the data of numerical modelling of the plasma kinetics in the phase of pumping and discharge afterglow. (lasers)

Nekhoroshev, V O; Fedorov, V F; Evtushenko, Gennadii S; Torgaev, S N

2012-10-31

15

Resonance laser-induced ionisation of sodium vapour taking radiative transfer into account  

SciTech Connect

The problem of ionisation of atomic sodium in the field of resonance laser radiation is numerically solved taking radiative transfer into account. Seed electrons are produced due to the mechanism of associative ionisation, then they gain energy in superelastic processes (collisions of the second kind) and initiate the avalanche ionisation of the medium by electron impact. We studied the effect of secondary radiation on the laser pulse propagation upon competition between the ionising and quenching electron collisions with excited atoms, on the kinetics of ionisation-induced vapour bleaching, and the plasma channel expansion in the form of a halo. (interaction of laser radiation with matter)

Kosarev, N I [Siberian Juridical Institue, Ministry of Internal Affairs, Krasnoyarsk (Russian Federation); Shaparev, N Ya [Krasnoyarsk Scientific Center, Russian Academy of Sciences, Krasnoyarsk (Russian Federation)

2006-04-30

16

Enhanced Raman sideband cooling of caesium atoms in a vapour-loaded magneto-optical trap  

E-print Network

We report enhanced three-dimensional degenerated Raman sideband cooling (3D DRSC) of caesium (Cs) atoms in a standard single-cell vapour-loading magneto-optical trap. Our improved scheme involves using a separate repumping laser and optimized lattice detuning. We load $1.5 \\times 10^7$ atoms into the Raman lattice with a detuning of -15.5 GHz (to the ground F = 3 state). Enhanced 3D DRSC is used to cool them from 60 $\\mu$K to 1.7 $\\mu$K within 12 ms and the number of obtained atoms is about $1.2 \\times 10^7$. A theoretical model is proposed to simulate the measured number of trapped atoms. The result shows good agreement with the experimental data. The technique paves the way for loading a large number of ultracold Cs atoms into a crossed dipole trap and efficient evaporative cooling in a single-cell system.

Li, Y; Feng, G; Nute, J; Piano, S; Hackermuller, L; Ma, J; Xiao, L; Jia, S

2015-01-01

17

Laser spectroscopy of sub-micrometre- and micrometre-thick caesium-vapour layers  

SciTech Connect

We present high resolution laser spectroscopy of Cs vapours confined in a unique optical cell of sub-micrometric and micrometric thickness, where a strong spatial anisotropy is present for the time of interaction between the atoms and laser radiation. Similarly to the spectra of selective specular reflection, the Doppler-free spectra of absorption and fluorescence are observed, not revealing cross-over resonances that will be useful for frequency stabilisation, provided the cell is cheap and compact. A new resonance in the fluorescence of closed transition is studied, demonstrating its high sensitivity to elastic atom – atom and atom – dielectric surface collisions. The theoretical modelling performed is in agreement with the experimental observations. (laser spectroscopy)

Cartaleva, S; Krasteva, A; Slavov, D; Todorov, P; Vaseva, K [Institute of Electronics, Bulgarian Academy of Sciences, boul. Tzarigradsko shosse 72, 1784 Sofia (Bulgaria); Moi, L [CNISM and Physics Department, University of Siena, via Roma 56, 53100 Siena - Italy (Italy); Sargsyan, A; Sarkisyan, D [Institute for Physical Research, National Academy of Sciences of Armenia, Ashtarak-0203 (Armenia)

2013-09-30

18

Optimal repetition rates of excitation pulses in a Tm-vapour laser  

SciTech Connect

The optimal excitation pulse repetition rates (PRRs) for a gas-discharge Tm-vapour laser with indirect population of upper laser levels are determined. It is shown that, under the same excitation conditions, the optimal PRRs increase with a decrease in the energy defect between the upper laser acceptor level and the nearest resonant donor level. The reasons for the limitation of the optimal PRRs in Tm-vapour laser are discussed. It is shown that the maximum average power of Tm-vapour laser radiation may exceed several times the Cu-vapour laser power under the same excitation conditions and in identical gas-discharge tubes. (lasers)

Gerasimov, V A; Gerasimov, V V; Pavlinskii, A V

2011-01-31

19

Infrared Laser Optoacoustic Detection Of Gases And Vapours  

NASA Astrophysics Data System (ADS)

Mid-infrared laser optoacoustic spectroscopy has been used to detect a variety of gases and vapours. Performance was calibrated using the signal from a known concentration of ethene, and then the method applied to the perfume alcohol geraniol. Detection limits were found to be 1 ppb for ethene and 70 ppb for geraniol on their strongest absorption lines for a few seconds measurement time.

Johnson, S. A.; Cummins, P. G.; Bone, S. A.; Davies, P. B.

1988-10-01

20

Ionization of Heavy Water Vapour by Intense Carbon Dioxide Laser Pulses  

NASA Astrophysics Data System (ADS)

The goal of this study was the optimisation and stabilisation of a high-power CO_2 laser oscillator-amplifiers system for its efficient utilisation in intense CO_2 laser-matter interaction experiments, and its application. One such study, namely the investigation of the fundamental processes involved in the ionisation of molecules, is presented. The ionisation of heavy water vapour by intense nanosecond CO _2 laser pulses, in the neighborhood of 10 mum, was observed. The wavelength and intensity of these laser pulses allow the observation of ionisation in the tunnelling regime. A qualitative model explaining the experimental results is presented. Following the improvements to the laser system, the laser chain produces pulses in excess of 1 GW on a routine daily basis with minimal adjustments. The laser chain also includes a simple provision against amplified retroreflections, which has been developed in order to reduce potential damage to the system. Our experiments involve the measurement of ions emanating from the region of interaction of the focused, intense laser beam with heavy water vapour. Data are taken at two different laser wavelengths. The ionisation of the heavy water molecule occurs at a lower laser intensity than that which would be expected for an atom of the same ionisation potential. Mercury vapour has also been used in our experiment. The latter results are shown to be in good agreement with the tunnelling theory of Ammosov, Delone and Krainov (1986) (ADK). A qualitative model explaining the observation of D_2O^+ and (D_2O)_sp{2 }{+} resulting from the heavy water vapour ionisation is presented. The characteristics of the heavy water vapour ionisation experiment are such that it is performed largely within the tunnel ionisation regime. The model explaining our results is based on tunnel ionisation from the molecule which is in an electronically excited state. In comparing the experimental data for D _2O^+ and (D _2O)_sp{2}{+ } with ADK theory, the probability of attaining the electronically excited state prior to ionisation is estimated. Ionisation processes in (D_2 O)_2 and Hg_2 are also briefly discussed.

Decker, Jennifer Elizabeth

1992-01-01

21

Experimental study of multipass copper vapour laser amplifiers  

SciTech Connect

Repetitively pulsed multipass copper vapour amplifiers are studied experimentally. A considerable increase in the peak power of laser pulses was achieved by using a special scheme of the amplifier. It is found that the main reasons preventing an increase in the peak power during many passages of the beam are the competitive development of lasing from spontaneous seeds in a parasitic resonator formed by the fold mirrors of a multipass amplifier, a decrease in the amplification during the last passages, and an increase in the pulse width at the amplifier output. (lasers. amplifiers)

Karpukhin, Vyacheslav T; Malikov, Mikhail M [Scientific Association for High Temperatures, Russian Academy of Sciences, Moscow (Russian Federation)

2008-12-31

22

Laser-induced atomic adsorption: A mechanism for nanofilm formation  

NASA Astrophysics Data System (ADS)

We demonstrate and interpret a technique of laser-induced formation of thin metallic films using alkali atoms on the window of a dense-vapour cell. We show that this intriguing photo-stimulated process originates from the adsorption of Cs atoms via the neutralization of Cs+ ions by substrate electrons. The Cs+ ions are produced via two-photon absorption by excited Cs atoms very close to the surface, which enables the transfer of the laser spatial intensity profile to the film thickness. An initial decrease of the surface work function is required to guarantee Cs+ neutralization and results in a threshold in the vapour density. This understanding of the film growth mechanism may facilitate the development of new techniques of laser-controlled lithography, starting from thermal vapours.

Martins, Weliton S.; Passerat de Silans, Thierry; Oriá, Marcos; Chevrollier, Martine

2013-11-01

23

Resonance enhanced multiphoton ionisation probing of H atoms in a hot lament chemical vapour deposition reactor  

E-print Network

Resonance enhanced multiphoton ionisation probing of H atoms in a hot Ðlament chemical vapour multiphoton ionisation (MPI) spectroscopy, resonance enhanced at the two photon energy by the state, to detect

Bristol, University of

24

Studies of laser selective excitation of atoms  

NASA Astrophysics Data System (ADS)

Sample preparation through laser ablation of a solid target under vacuum has been combined with short-pulsed laser selective excitation to create a new and convenient experimental technique for measuring atomic radiative lifetimes. The lifetimes of the three resonance states of chromium determined in this way compare very favourably with those found through other experimental means. In addition, the technique has been extended to demonstrate experimentally the potential for plasma diagnostics using two-wavelength selective excitation with short laser pulses. The ratio of population densities of two energy states of chromium atoms has been measured as a function of time during the expansion of the ablation plasma. Extended saturation pumping of the resonance transition in sodium vapour has been investigated theoretically. Rate equations for 20 energy levels in the sodium atom, and the rate equations for the free electrons, were integrated numerically. It has been found that multiphoton ionization, combined with superelastic heating of free electrons can account for the rapid and complete ionization of an un-ionized vapour, as reported in the literature. The detailed theoretical results have led to the development of a simple model which accurately predicts the temporal variation of electron density.

Drewell, N.

1979-12-01

25

INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Dynamics of laser deposition of metals from the vapour phase on insulators  

NASA Astrophysics Data System (ADS)

Laser deposition of metals from the vapour phase on insulator surfaces by the action of cw laser radiation is investigated theoretically. Changes in the surface morphology during deposition and the temperature dependence of the vapour medium are taken into account. It is shown that during the initial stage the deposit may be mushroom-shaped, whereas later it becomes rod-shaped. If a moving laser beam is employed, the deposit may assume the form of a series of rods (fibres) tilted relative to the substrate surface.

Kirichenko, N. A.; Nikolaeva, E. G.

1997-03-01

26

Application of copper vapour lasers for controlling activity of uranium isotopes  

SciTech Connect

Beryllium nanoparticles are generated upon ablation of a beryllium target in water by a copper vapour laser. The average size of single crystalline nanoparticles is 12 nm. Ablation of a beryllium target in aqueous solutions of uranyl chloride leads to a significant (up to 50 %) decrease in the gamma activity of radionuclides of the uranium-238 and uranium-235 series. Data on the recovery of the gamma activity of these nuclides to new steady-state values after laser irradiation are obtained. The possibility of application of copper vapour lasers for radioactive waste deactivation is discussed. (laser applications and other topics in quantum electronics)

Barmina, E V; Sukhov, I A; Lepekhin, N M; Priseko, Yu S; Filippov, V G; Simakin, Aleksandr V; Shafeev, Georgii A

2013-06-30

27

Application of copper vapour lasers for controlling activity of uranium isotopes  

NASA Astrophysics Data System (ADS)

Beryllium nanoparticles are generated upon ablation of a beryllium target in water by a copper vapour laser. The average size of single crystalline nanoparticles is 12 nm. Ablation of a beryllium target in aqueous solutions of uranyl chloride leads to a significant (up to 50 %) decrease in the gamma activity of radionuclides of the uranium-238 and uranium-235 series. Data on the recovery of the gamma activity of these nuclides to new steady-state values after laser irradiation are obtained. The possibility of application of copper vapour lasers for radioactive waste deactivation is discussed.

Barmina, E. V.; Sukhov, I. A.; Lepekhin, N. M.; Priseko, Yu S.; Filippov, V. G.; Simakin, Aleksandr V.; Shafeev, Georgii A.

2013-06-01

28

Evolution of polarization in an atomic vapour with negative refractive index  

NASA Astrophysics Data System (ADS)

A three-level Lambda-configuration atomic vapour may exhibit simultaneously negative permittivity and permeability in the optical frequency band, and an isotropic left-handed vapour medium could therefore be realized within the framework of quantum optics. One of the most remarkable features of the present scheme is that both the refractive index and the photon helicity reversal inside the vapour can be controllably manipulated by an external coupling light field. The phenomenological Hamiltonian that describes the process of helicity reversal is constructed and the time-dependent Schrödinger equation governing the time evolution of the polarization states of the lightwave is solved by means of the Lewis-Riesenfeld invariant theory. The transition between the polarization states (and hence the accompanied photon helicity reversal), which is exactly analogous to the transition operation between bits in digital circuit, may be valuable for the development of new techniques in quantum optics and would have potential applications in information technology.

Zhuang, Fei; Shen, Jianqi

2006-08-01

29

Direct mercury determination in aqueous slurries of environmental and biological samples by cold vapour generation–electrothermal atomic absorption spectrometry  

Microsoft Academic Search

Direct cold vapour generation from aqueous slurries of environmental (marine sediment, soil, coal) and biological (human hair, seafood) samples have been developed using a batch mode generation system coupled with electrothermal atomic absorption spectroscopy. The effects of several variables affecting the cold vapour generation efficiency from solid particles (hydrochloric acid and sodium tetrahydroborate concentrations, argon flow rate, acid solution volume

Jorge Moreda-Piñeiro; Purificación López-Mah??a; Soledad Muniategui-Lorenzo; Esther Fernández-Fernández; Dar??o Prada-Rodr??guez

2002-01-01

30

Lasers, Understanding the Atom Series.  

ERIC Educational Resources Information Center

This booklet is one of the booklets in the "Understanding the Atom Series" published by the U. S. Atomic Energy Commission for high school science teachers and their students. Basic information for understanding the laser is provided including discussion of the electromagnetic spectrum, radio waves, light and the atom, coherent light, controlled…

Hellman, Hal

31

Atoms, Light, and Lasers  

NASA Astrophysics Data System (ADS)

Up to now, the spatial properties of quantum particles played no more than a secondary role: we only needed the de Broglie relation (1.4) which gives the quantum particles wavelength, and our discussion of the quantum properties of photons was based mainly on their polarization, which is an internal degree of freedom of the photon. The probability amplitudes which we used did not involve the positions or velocities of the particles, which are spatial, or external degrees of freedom. In the present chapter, we shall introduce spatial dependence by defining probability amplitudes a(?c r) that are functions of the position ?c r. In full generality, a(?c r) is a complex number, but we shall avoid this complication and discuss only cases where the probability amplitudes may be taken real. For simplicity, we also limit ourselves to particles propagating along a straight line, which we take as the Ox axis: x will define the position of the particle and the corresponding probability amplitude will be a function of x, a(x). In our discussion, we shall need to introduce the so-called potential well, where a particle travels back and forth between two points on the straight line. One important particular case is the infinite well, where the particle is confined between two infinitely high walls over which it cannot pass. This example is not at all academic, and we shall meet it again in Chapter 6 when explaining the design of a laser diode! Furthermore, it will allow us to introduce the notion of energy level, to write down the Heisenberg inequalities, to understand the interaction of a light wave with an atom and finally to explain schematically the principles of the laser.

Bellac, Michel Le

2014-11-01

32

Model of the radial gas-temperature distribution in a copper bromide vapour laser  

SciTech Connect

An analytic model is proposed to calculate the buffer-gas temperature in the discharge-tube cross section of the copper bromide vapour laser. The model is the generalisation of the previous models developed by the authors. Assuming that the volume electric power is arbitrary distributed over the tube radius, the general solution of the quasi-stationary heat conduction equation with the boundary conditions of the first and second kinds is presented. Application of the model is considered by the example of a copper bromide vapour laser emitting at 510.6 and 578.2 nm at different specific radial distributions of the volume power. The obtained results are compared with the temperature profiles known to date. Application of this model to molecular lasers is also discussed. (lasers)

Iliev, I P [Department of Physics, Technical University of Plovdiv, Plovdiv (Bulgaria); Gocheva-Ilieva, S G [Department of Applied Mathematics and Modelling, Faculty of Mathematics and Informatics, Paisii Hilendarski University of Plovdiv (Bulgaria)

2010-08-27

33

Atomic Vapor Laser Isotope Separation  

Microsoft Academic Search

This paper gives a brief history of the scientific considerations leading to the development of laser isotope separation (LIS) processes. The close relationship of LIS to the broader field of laser-induced chemical processes is evaluated in terms of physical criteria to achieve an efficient production process. Atomic-vapor LIS processes under development at Livermore are reviewed.

James I. Davis

1983-01-01

34

Atomic vapor laser isotope separation process  

DOEpatents

A laser spectroscopy system is utilized in an atomic vapor laser isotope separation process. The system determines spectral components of an atomic vapor utilizing a laser heterodyne technique. 23 figs.

Wyeth, R.W.; Paisner, J.A.; Story, T.

1990-08-21

35

Atomic vapor laser isotope separation process  

Microsoft Academic Search

A laser spectroscopy system is utilized in an atomic vapor laser isotope separation process. The system determines spectral components of an atomic vapor utilizing a laser heterodyne technique. 23 figs.

R. W. Wyeth; J. A. Paisner; T. Story

1990-01-01

36

Laser-Driven Atomic Pump  

NASA Astrophysics Data System (ADS)

We propose a laser-driven pump for atomic transport through carbon nanotubes. A two beam coherent control is used to inject carrier population into the lowest unoccupied nanotube bands, which is anisotropic in momentum space. The resulting electron current moves intercalated atoms along the tube. This system is a unique prototype of a single atom deposition machine which overcomes the loading problem of the scanning tunneling microscope.

Král, Petr; Tománek, David

1999-06-01

37

Nonlinear absorption of femtosecond laser pulses (800 nm) by atmospheric air and water vapour  

SciTech Connect

Quantitative data on the nonlinear absorption cross sections of femtosecond Ti : Sapphire laser pulses in air and water vapour have been obtained. A photoacoustic spectrometer calibrated based on the calculated value of linear absorption of laser pulses with a wavelength of 800 nm and a spectral width of 17.7 nm is used to find the nonlinear absorption cross sections of water vapour and air: {sigma}{sub 2}{sup w} = (2.6{+-}0.4) Multiplication-Sign 10{sup -55} cm{sup 4} s and {sigma}{sub 2}{sup a} = (8.7{+-}1.0) Multiplication-Sign 10{sup -56} cm{sup 4} s, respectively. Based on measuring the absorption of femtosecond Ti : Sapphire laser pulses with a photoacoustic detector calibrated with the known linear absorption of ruby laser radiation by water vapour in air, the air nonlinear absorption cross section is found to be (8.2{+-}0.9) Multiplication-Sign 10{sup -56} cm{sup 4} s.

Kiselev, A M; Ponomarev, Yu N; Stepanov, A N; Tikhomirov, A B; Tikhomirov, B A

2011-11-30

38

Atomic-based stabilization for laser-pumped atomic clocks  

Microsoft Academic Search

We describe a novel technique for stabilizing frequency shifts in laser-interrogated vapor-cell atomic clocks. The method suppresses frequency shifts due to changes in the laser frequency, intensity, and modulation index as well as atomic vapor density. The clock operating parameters are monitored by using the atoms themselves, rather than by using conventional schemes for laser frequency and cell temperature control.

V. Gerginov; V. Shah; S. Knappe; L. Hollberg; J. Kitching

2006-01-01

39

Atomic vapor laser isotope separation  

Microsoft Academic Search

Atomic Vapor Laser Isotope Separation (AVLIS) is a general and powerful technique applicable to many elements. A major present application to the enrichement of uranium for lightwater power reactor fuel has been under development at the Lawrence Livermore National Laboratory since 1973. In June 1985, the Department of Energy announced the selection of AVLIS as the technology to meet future

J. A. Paisner

1988-01-01

40

Hydride vapour phase epitaxy assisted buried heterostructure quantum cascade lasers for sensing applications  

NASA Astrophysics Data System (ADS)

Buried heterostructure (BH) lasers are routinely fabricated for telecom applications. Development of quantum cascade lasers (QCL) for sensing applications has largely benefited from the technological achievements established for telecom lasers. However, new demands are to be met with when fabricating BH-QCLs. For example, hetero-cascade and multistack QCLs, with several different active regions stacked on top of each other, are used to obtain a broad composite gain or increased peak output power. Such structures have thick etch ridges which puts severe demand in carrying out regrowth of semi-insulating layer around very deeply etched (< 10 ?m) ridges in short time to realize BH-QCL. For comparison, telecom laser ridges are normally only <5 ?m deep. We demonstrate here that hydride vapour phase epitaxy (HVPE) is capable of meeting this new demand adequately through the fabrication of BH-QCLs in less than 45 minutes for burying ridges etched down to 10-15 ?m deep. This has to be compared with the normally used regrowth time of several hours, e.g., in a metal organic vapour phase epitaxy (MOVPE) reactor. This includes also micro-stripe lasers resembling grating-like ridges for enhanced thermal dissipation in the lateral direction. In addition, we also demonstrate HVPE capability to realize buried heterostructure photonic crystal QCLs for the first time. These buried lasers offer flexibility in collecting light from the surface and relatively facile device characterization feasibility of QCLs in general; but the more important benefits of such lasers are enhanced light matter interaction leading to ultra-high cavity Q-factors, tight optical confinement, possibility to control the emitted mode pattern and beam shape and substantial reduction in laser threshold.

Lourdudoss, S.; Metaferia, W.; Junesand, C.; Manavaimaran, B.; Ferré, S.; Simozrag, B.; Carras, M.; Peretti, R.; Liverini, V.; Beck, M.; Faist, J.

2015-01-01

41

Effect of strong ligand on mercury analysis by cold vapour atomic absorption spectrometry  

NASA Astrophysics Data System (ADS)

The influence of ligands (halogens, sulphur-containing ligands and organic ligands) on the determination of Hg by cold vapour atomic absorption spectrometry (CVAAS) was studied. The principle of the cold vapour technique is to break the Hg-ligand structure under oxidative and pH stress to generate Hg(II) as Hg^{2+} cation which is then reduced to atomic Hg(O) by Sn(II). The presence of chemical species, which can strongly complex Hg^{2+} or Sn^{2+}, can partially or totally inhibit the Hg or Sn can partially or totally inhibit the Hg reduction. The aim of this study was to evaluate the effect of ligands (Cl^-, I^-, S^{2-}, SO3^{2-}, S2O3^{2-}, S2O3^{2-}, cysteine, EDTA) on the Hg detection by CVAAS for different ligand concentration ([L]) and pH. The conditional constants, K', taking into account both complex formation and redox equilibrium were calculated. The log K' decreases strongly in the presence of strong ligands (I^-, S^{2-} and S2O{3}^{2-}) due to the formation of very stable complexes even at low pH (pH < 1). These assumptions were verified experimentally. In fact the presence of strong ligands strongly decreased the Hg signal. The decrease depended on L and Sn(II) concentrations and pH. The reduction kineties decreases as the ligand concentration increases, the Sn(Il) concentration decreases and the pH decreases for I^- and increases for S^{2-} and S2O3^{2-}.

Wernert, V.; Ehrhardt, J.-J.; Behra, P.

2003-05-01

42

Resonance enhanced multiphoton ionization probing of H atoms and CH3 radicals in a hot lament chemical vapour deposition reactor  

E-print Network

reactor used for diamond chemical vapour deposition (CVD). Parameters varied include the hydrocarbon (CH4 to reinforce the consensus view that H atom production during diamond CVD in a hot ®lament reactor arises as a result of dissociative adsorption on the hot ®lament surface, whereas CH3 radical formation is dominated

Bristol, University of

43

Manipulation of Atoms by Laser Light  

Microsoft Academic Search

Laser cooling and laser manipulation of free neutral atoms have reached a level of sophistication not foreseen just a few years ago. This concerns trapping of neutral atoms at muK temperatures as well as the precise preparation of extreme dense and ultra cold atomic beams. These techniques offer plenty of new experiments answering basic physical questions or allowing totally new

W. Ertmer

1992-01-01

44

Photo-acoustic laser spectroscopy of water vapour and cloud content onboard passenger aircraft  

NASA Astrophysics Data System (ADS)

Water in form of water vapour and clouds is one of the most important trace species in the upper troposphere and lower stratosphere (UTLS), as it is responsible for ~75% (or ~25 K) of the natural greenhouse effect (Schmidt et al., JGR, 2010) and carries huge amounts of latent heat. Better climate models and realistic future predictions are therefore depending on how well the global hydrological cycle is understood and described in the models. Accurate measurements of water vapour and cloud water/ice in the UTLS are one essential step towards this goal. Here, we describe the technical set-up of a 2-channel photo-acoustic laser spectrometer (PAS) that was designed for fully unattended use aboard the CARIBIC passenger aircraft. The instrument makes use of an accurate frost-point hygrometer for in-flight calibration of two fast-responding PA channels to measure water vapour and cloud water, respectively. The efforts that were necessary to achieve high-precision (low acoustic noise) photo-acoustic signals within a noisy environment are described. Detailed system analyses were carried out prior and during the operational phase of this instrument. The precision of the instrument is ~0.8 ppmv at 3 sec integration time, and can be improved to 85 ppbv when averaging the data for 300 s. The accuracy is determined by the frost-point hygrometer, and is found to be better than ~0.5 ppmv. With its capability to accurately measure both water vapour and cloud water, this instrument provides unique insight in the hydrological cycle. It is operated since 2005 for four intercontinental flights per month aboard the CARIBIC passenger aircraft. Some scientific results gained during its airborne operation are presented. These include (i) a flight through ice clouds which demonstrates the performance of the device, (ii) the seasonal variation of water vapour from the UT up to 5 km above above the (mid-latitude) tropopause, or (iii) the distribution of the supersaturation inside and outside of clouds.

Sanati, Shahrokh; Zahn, Andreas; Dyroff, Christoph

2013-04-01

45

An ultra-bright atom laser  

NASA Astrophysics Data System (ADS)

We present a novel, ultra-bright atom laser and an ultra-cold thermal atom beam. Using rf-radiation we strongly couple the magnetic hyperfine levels of 87Rb atoms in a trapped Bose-Einstein condensate. The resulting time-dependent adiabatic potential forms a trap, which at low rf-frequencies opens just below the condensate and thus allows an extremely bright well-collimated atom laser beam to emerge. As opposed to traditional atom lasers based on weak coupling of the magnetic hyperfine levels, this technique allows us to outcouple atoms at an arbitrarily large rate. We achieve a flux of 4×107 atom s-1, a seven fold increase compared to the brightest atom lasers to date. Furthermore, we demonstrate by two orders of magnitude the coldest thermal atom beam (200 nK).

Bolpasi, V.; Efremidis, N. K.; Morrissey, M. J.; Condylis, P. C.; Sahagun, D.; Baker, M.; von Klitzing, W.

2014-03-01

46

Atom Skimmers and Atom Lasers Utilizing Them  

NASA Technical Reports Server (NTRS)

Atom skimmers are devices that act as low-pass velocity filters for atoms in thermal atomic beams. An atom skimmer operating in conjunction with a suitable thermal atomic-beam source (e.g., an oven in which cesium is heated) can serve as a source of slow atoms for a magneto-optical trap or other apparatus in an atomic-physics experiment. Phenomena that are studied in such apparatuses include Bose-Einstein condensation of atomic gases, spectra of trapped atoms, and collisions of slowly moving atoms. An atom skimmer includes a curved, low-thermal-conduction tube that leads from the outlet of a thermal atomic-beam source to the inlet of a magneto-optical trap or other device in which the selected low-velocity atoms are to be used. Permanent rare-earth magnets are placed around the tube in a yoke of high-magnetic-permeability material to establish a quadrupole or octupole magnetic field leading from the source to the trap. The atoms are attracted to the locus of minimum magnetic-field intensity in the middle of the tube, and the gradient of the magnetic field provides centripetal force that guides the atoms around the curve along the axis of the tube. The threshold velocity for guiding is dictated by the gradient of the magnetic field and the radius of curvature of the tube. Atoms moving at lesser velocities are successfully guided; faster atoms strike the tube wall and are lost from the beam.

Hulet, Randall; Tollett, Jeff; Franke, Kurt; Moss, Steve; Sackett, Charles; Gerton, Jordan; Ghaffari, Bita; McAlexander, W.; Strecker, K.; Homan, D.

2005-01-01

47

Atomic physics: An almost lightless laser  

E-print Network

Lasers are often described in terms of a light field circulating in an optical resonator system. Now a laser has been demonstrated in which the field resides primarily in the atomic medium that is used to generate the light.

Vuletic, Vladan

48

Tunable dye laser amplifier chain for laser isotope separation  

Microsoft Academic Search

A tunable dye laser amplifier chain developed for experiments on atomic vapour laser isotope separation (AVLIS) is described. The system, pumped by copper vapour lasers, consists of a master oscillator and an amplifier stage including a preamplifier and three main amplifiers working in the saturation mode. The master oscillator of the stage is a dye laser with a grazing incidence

Igor S Grigoriev; Aleksei B Dyachkov; Valerii P Labozin; Sergei M Mironov; Sergei A Nikulin; Valerii A Firsov

2004-01-01

49

LASERS. AMPLIFIERS: Tunable dye laser amplifier chain for laser isotope separation  

Microsoft Academic Search

A tunable dye laser amplifier chain developed for experiments on atomic vapour laser isotope separation (AVLIS) is described. The system, pumped by copper vapour lasers, consists of a master oscillator and an amplifier stage including a preamplifier and three main amplifiers working in the saturation mode. The master oscillator of the stage is a dye laser with a grazing incidence

Igor'S. Grigoriev; Aleksei B. D'yachkov; Valerii P. Labozin; Sergei M. Mironov; Sergei A. Nikulin; Valerii A. Firsov

2004-01-01

50

Scaling mechanisms of vapour/plasma shielding from laser-produced plasmas to magnetic fusion regimes  

NASA Astrophysics Data System (ADS)

The plasma shielding effect is a well-known mechanism in laser-produced plasmas (LPPs) reducing laser photon transmission to the target and, as a result, significantly reducing target heating and erosion. The shielding effect is less pronounced at low laser intensities, when low evaporation rate together with vapour/plasma expansion processes prevent establishment of a dense plasma layer above the surface. Plasma shielding also loses its effectiveness at high laser intensities when the formed hot dense plasma plume causes extensive target erosion due to radiation fluxes back to the surface. The magnitude of emitted radiation fluxes from such a plasma is similar to or slightly higher than the laser photon flux in the low shielding regime. Thus, shielding efficiency in LPPs has a peak that depends on the laser beam parameters and the target material. A similar tendency is also expected in other plasma-operating devices such as tokamaks of magnetic fusion energy (MFE) reactors during transient plasma operation and disruptions on chamber walls when deposition of the high-energy transient plasma can cause severe erosion and damage to the plasma-facing and nearby components. A detailed analysis of these abnormal events and their consequences in future power reactors is limited in current tokamak reactors. Predictions for high-power future tokamaks are possible only through comprehensive, time-consuming and rigorous modelling. We developed scaling mechanisms, based on modelling of LPP devices with their typical temporal and spatial scales, to simulate tokamak abnormal operating regimes to study wall erosion, plasma shielding and radiation under MFE reactor conditions. We found an analogy in regimes and results of carbon and tungsten erosion of the divertor surface in ITER-like reactors with erosion due to laser irradiation. Such an approach will allow utilizing validated modelling combined with well-designed and well-diagnosed LPP experimental studies for predicting consequences of plasma instabilities in complex fusion environment, which are of serious concern for successful energy production.

Sizyuk, Tatyana; Hassanein, Ahmed

2014-02-01

51

Nanosecond pulsed excimer laser machining of chemical vapour deposited diamond and highly oriented pyrolytic graphite: Part I An experimental investigation  

Microsoft Academic Search

A laser beam offers the benefits of high precision, contamination-free, high speed, and low bulk temperature for machining\\u000a of chemically vapour deposited (CVD) diamond thin films that in turn enable ultrafine finishing of diamond coated cutting\\u000a tool inserts and drills, and for finishing and drilling of diamond coated multichip module applications. In this work, laser\\u000a hole drilling and polishing of

R. WINDHOLZ; P. A. MOLIAN

1997-01-01

52

Atom Laser with a cw Output Coupler  

Microsoft Academic Search

We demonstrate a continuous output coupler for magnetically trapped atoms. Over a period of up to 100 ms, a collimated and monoenergetic beam of atoms is continuously extracted from a Bose-Einstein condensate. The intensity and kinetic energy of the output beam of this atom laser are controlled by a weak rf field that induces spin flips between trapped and untrapped

Immanuel Bloch; Theodor W. Hänsch; Tilman Esslinger

1999-01-01

53

Resonant character of laser-induced formation of particles in a Cs-H2 vapour J. L. Picqu, J. Vergs and R. Vetter  

E-print Network

], of isotope separation by the present pheno- menon [1]. However, from the study of the dependence of laserL-305 Resonant character of laser-induced formation of particles in a Cs-H2 vapour J. L. Picqué, J formation de particules induite par laser dans une vapeur Cs-H2 est résonnante vis-à- vis des secondes raies

Paris-Sud XI, Université de

54

Atomic vapour deposition (AVD) of SrBi 2Ta 2O 9 using an all alkoxide precursor  

Microsoft Academic Search

A “single-source” Sr–Ta heterometal alkoxide precursor, Sr[Ta(OEt)5(dmae)]2 (dmae=OCH2CH2NMe2), has been used for atomic vapour deposition (AVD) of SrBi2Ta2O9 (SBT). This single-source precursor is designed to alleviate the mismatch between conventional Sr and Ta sources. Strontium tantalate thin films were deposited on silicon using the Sr[Ta(OEt)5(dmae)]2, and the optimum temperatures for deposition of strontium tantalate with a Sr:Ta ratio of 0.5

Paul R. Chalker; Richard J. Potter; John L. Roberts; Anthony C. Jones; Lesley M. Smith; Marcus Schumacher

2004-01-01

55

Atomic vapour deposition (AVD) of SrBi2Ta2O9 using an all alkoxide precursor  

Microsoft Academic Search

A ``single-source'' Sr Ta heterometal alkoxide precursor, Sr[Ta(OEt)5(dmae)]2 (dmae=OCH2CH2NMe2), has been used for atomic vapour deposition (AVD) of SrBi2Ta2O9 (SBT). This single-source precursor is designed to alleviate the mismatch between conventional Sr and Ta sources. Strontium tantalate thin films were deposited on silicon using the Sr[Ta(OEt)5(dmae)]2, and the optimum temperatures for deposition of strontium tantalate with a Sr:Ta ratio of

Paul R. Chalker; Richard J. Potter; John L. Roberts; Anthony C. Jones; Lesley M. Smith; Marcus Schumacher

2004-01-01

56

Laser modification of ultracold atomic collisions: Theory  

Microsoft Academic Search

Specific molecular mechanisms are proposed for associative ionization collisions of ultracold sodium atoms in a hybrid optical trap. When an intense, strongly detuned optical trap laser is on, the ionization rate is modulated by molecular bound-state resonances which are strongly affected by field dressing. When the weak, slightly detuned optical molasses lasers are on to provide cooling, an excitation mechanism

Paul S. Julienne; Robert Heather

1991-01-01

57

Laser Cooled Atomic Clocks in Space  

NASA Technical Reports Server (NTRS)

The goals of the Glovebox Laser-cooled Atomic Clock Experiment (GLACE) are: (1) first utilization of tunable, frequency-stabilized lasers in space, (2) demonstrate laser cooling and trapping in microgravity, (3) demonstrate longest 'perturbation-free' interaction time for a precision measurement on neutral atoms, (4) Resolve Ramsey fringes 2-10 times narrower than achievable on Earth. The approach taken is: the use of COTS components, and the utilization of prototype hardware from LCAP flight definition experiments. The launch date is scheduled for Oct. 2002. The Microgravity Science Glovebox (MSG) specifications are reviewed, and a picture of the MSG is shown.

Thompson, R. J.; Kohel, J.; Klipstein, W. M.; Seidel, D. J.; Maleki, L.

2000-01-01

58

Molecular laser isotope separation versus atomic vapor laser isotope separation  

Microsoft Academic Search

In this work, the competitive molecular and atomic laser isotope separation methods are investigated to evaluate the potential of each une for more economical fuel fabrication of enriched uranium celas which can be practically used in light water reactors (LWR). The advantages, drawbacks and feasibility of various techniques of laser isotope separation including AVLIS and the main MLIS methods such

P. Parvin; B. Sajad; K. Silakhori; M. Hooshvar; Z. Zamanipour

2004-01-01

59

High-intensity laser-atom interactions  

NASA Astrophysics Data System (ADS)

Following a historical introduction on the nature of light and its interaction with matter, a survey is given of the development of lasers capable of delivering short pulses of very intense radiation. The peak intensities of these laser pulses are so high that the corresponding laser fields can compete with, or even dominate, the Coulomb field in governing the dynamics of atomic systems. As a result, new phenomena, known as multiphoton processes, can occur. An outline is given of the basic properties found in the study of three important multiphoton processes. Firstly, the multiphoton ionization of atoms and the phenomenon of “above-threshold ionization”. Secondly, the emission by atoms of high-order harmonics of the frequency of the driving laser and their use to generate laser pulses having durations in the attosecond range. Thirdly, laser-assisted electron-atom collisions. A review is then given of the main non-perturbative methods which have been used to perform theoretical studies of multiphoton processes.

Joachain, Charles J.

2014-11-01

60

Influence of the voltage pulse front shortening on the pulse repetition rate in a copper vapour laser  

SciTech Connect

The lasing characteristics of a copper vapour laser are investigated in the regime of a pulse train excited in the internalheating tube with the diameter of 2 cm and length of 48 cm. Two power supply schemes are compared: a conventional scheme with a storage capacitor discharged through a thyratron connected to a peaking capacitor and the scheme in which the peaking capacitor is connected to the laser active element through a kivotron – a fast switch based on the 'open discharge' with a turn-on time of less than 1 ns. It is shown that in the considered range of the pulse repetition rates f = 2 – 16 kHz in the first case we deal with a typical energy dependence on frequency having a maximum near 4 – 5 kHz. In the second case, the lasing energy is frequency-independent; hence, the average power in this range is proportional to f. The results obtained are explained by the neutralised influence of the initial electron concentration on energy characteristics of the copper vapour laser. (control of laser radiation parameters)

Bokhan, P A; Gugin, P P; Zakrevskii, D E; Lavrukhin, M A [A.V. Rzhanov Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk (Russian Federation); Kazaryan, M A [P N Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Lyabin, N A [Research and production corporation 'Istok', Fryazino, Moscow region (Russian Federation)

2013-08-31

61

Conservation laws and laser cooling of atoms  

E-print Network

The straightforward application of energy and linear momentum conservation to the absorption/emission of photons by atoms--first outlined by Schr\\"odinger in 1922--allows to establish the essential features of laser cooling of two levels atoms at low laser intensities. The minimum attainable average kinetic energy of the atoms depends on the ratio $\\Gamma/E_R$ between the natural linewidth and the recoil energy and tends to $E_R$ as $\\Gamma/E_R$ tends to zero. This treatment is valid for any value of the ratio $\\Gamma/E_R$ and contains the semiclassical theory of laser cooling as the limiting case in which $E_R\\ll \\Gamma$.

Giuliani, Giuseppe

2015-01-01

62

Prospects of laser cooling in atomic thallium  

NASA Astrophysics Data System (ADS)

One of the most precisely determined upper limits for the electron electric dipole moment (EDM) is set by the thallium (Tl) atomic beam experiment. One way to enhance the sensitivity of the atomic beam setup is to laser cool the Tl atoms to reduce the EDM-like phase caused by the E×v effect. In this report, a cooling scheme based on the 6P3/2(F=2)?6D5/2(F'=3) transition in Tl is proposed. The absolute frequency measurement of this nearly closed-cycle transition was performed in an atomic beam apparatus. Two Ti:sapphire lasers were frequency-doubled using enhancement cavities in X-type configurations to provide the needed 377- and 352-nm light sources for the optical pumping and cooling transitions, respectively. The absolute frequency of this cooling transition is determined to be 851 634 646(56) MHz.

Fan, Isaac; Chen, Tzu-Ling; Liu, Yu-Sheng; Lien, Yu-Hung; Shy, Jow-Tsong; Liu, Yi-Wei

2011-10-01

63

Prospects of laser cooling in atomic thallium  

SciTech Connect

One of the most precisely determined upper limits for the electron electric dipole moment (EDM) is set by the thallium (Tl) atomic beam experiment. One way to enhance the sensitivity of the atomic beam setup is to laser cool the Tl atoms to reduce the EDM-like phase caused by the Exv effect. In this report, a cooling scheme based on the 6P{sub 3/2}(F=2){r_reversible}6D{sub 5/2}(F{sup '}=3) transition in Tl is proposed. The absolute frequency measurement of this nearly closed-cycle transition was performed in an atomic beam apparatus. Two Ti:sapphire lasers were frequency-doubled using enhancement cavities in X-type configurations to provide the needed 377- and 352-nm light sources for the optical pumping and cooling transitions, respectively. The absolute frequency of this cooling transition is determined to be 851 634 646(56) MHz.

Fan, Isaac; Chen, Tzu-Ling; Liu, Yu-Sheng; Lien, Yu-Hung; Liu, Yi-Wei [Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Shy, Jow-Tsong [Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Institute of Photonics Technologies, National Tsing Hua University, Hsinchu 30013, Taiwan (China)

2011-10-15

64

Laser trapping of {sup 21}Na atoms  

SciTech Connect

This thesis describes an experiment in which about four thousand radioactive {sup 21}Na (t{sub l/2} = 22 sec) atoms were trapped in a magneto-optical trap with laser beams. Trapped {sup 21}Na atoms can be used as a beta source in a precision measurement of the beta-asymmetry parameter of the decay of {sup 21}Na {yields} {sup 21}Ne + {Beta}{sup +} + v{sub e}, which is a promising way to search for an anomalous right-handed current coupling in charged weak interactions. Although the number o trapped atoms that we have achieved is still about two orders of magnitude lower than what is needed to conduct a measurement of the beta-asymmetry parameter at 1% of precision level, the result of this experiment proved the feasibility of trapping short-lived radioactive atoms. In this experiment, {sup 21}Na atoms were produced by bombarding {sup 24}Mg with protons of 25 MeV at the 88 in. Cyclotron of Lawrence Berkeley Laboratory. A few recently developed techniques of laser manipulation of neutral atoms were applied in this experiment. The {sup 21}Na atoms emerging from a heated oven were first transversely cooled. As a result, the on-axis atomic beam intensity was increased by a factor of 16. The atoms in the beam were then slowed down from thermal speed by applying Zeeman-tuned slowing technique, and subsequently loaded into a magneto-optical trap at the end of the slowing path. The last two chapters of this thesis present two studies on the magneto-optical trap of sodium atoms. In particular, the mechanisms of magneto-optical traps at various laser frequencies and the collisional loss mechanisms of these traps were examined.

Lu, Zheng-Tian

1994-09-01

65

Steering neutral atoms in strong laser fields  

NASA Astrophysics Data System (ADS)

The seminal strong-field tunnelling theory introduced by L V Keldysh plays a pivotal role. It has shaped our understanding of atomic strong-field processes, where it represents the first step in complex ionisation dynamics and provides reliable tunnelling rates. Tunnelling rates, however, cannot be necessarily equated with ionisation rates. Taking into account the electron dynamics in the Coulomb potential following the tunnelling process, the process of frustrated tunnelling ionisation has been found to lead to excited Rydberg atoms. Here, we excite He atoms in the strong-field tunnelling regime into Rydberg states. A high percentage of these Rydberg atoms survive in high intensity laser fields. We exploit this fact together with their high polarisability to kinematically manipulate the Rydberg atoms with a second elliptically polarised focused strong laser field. By varying the spatial overlap of the two laser foci, we are able to selectively control the deflection of the Rydberg atoms. The results of semi-classical calculations, which are based on the frustrated tunnelling model and on the ponderomotive acceleration, are in accord with our experimental data.

Eilzer, S.; Eichmann, U.

2014-10-01

66

Strain and structure heterogeneity in MoS2 atomic layers grown by chemical vapour deposition  

NASA Astrophysics Data System (ADS)

Monolayer molybdenum disulfide (MoS2) has attracted tremendous attention due to its promising applications in high-performance field-effect transistors, phototransistors, spintronic devices and nonlinear optics. The enhanced photoluminescence effect in monolayer MoS2 was discovered and, as a strong tool, was employed for strain and defect analysis in MoS2. Recently, large-size monolayer MoS2 has been produced by chemical vapour deposition, but has not yet been fully explored. Here we systematically characterize chemical vapour deposition-grown MoS2 by photoluminescence spectroscopy and mapping and demonstrate non-uniform strain in single-crystalline monolayer MoS2 and strain-induced bandgap engineering. We also evaluate the effective strain transferred from polymer substrates to MoS2 by three-dimensional finite element analysis. Furthermore, our work demonstrates that photoluminescence mapping can be used as a non-contact approach for quick identification of grain boundaries in MoS2.

Liu, Zheng; Amani, Matin; Najmaei, Sina; Xu, Quan; Zou, Xiaolong; Zhou, Wu; Yu, Ting; Qiu, Caiyu; Birdwell, A. Glen; Crowne, Frank J.; Vajtai, Robert; Yakobson, Boris I.; Xia, Zhenhai; Dubey, Madan; Ajayan, Pulickel M.; Lou, Jun

2014-11-01

67

Laser manipulation of atomic and molecular flows  

NASA Astrophysics Data System (ADS)

The continuing advance of laser technology enables a range of broadly applicable, laser-based flow manipulation techniques. The characteristics of these laser-based flow manipulations suggest that they may augment, or be superior to, such traditional electro-mechanical methods as ionic flow control, shock tubes, and small scale wind tunnels. In this study, methodology was developed for investigating laser flow manipulation techniques, and testing their feasibility for a number of aerospace, basic physics, and micro technology applications. Theories for laser-atom and laser-molecule interactions have been under development since the advent of laser technology. The theories have yet to be adequately integrated into kinetic flow solvers. Realizing this integration would greatly enhance the scaling of laser-species interactions beyond the realm of ultra-cold atomic physics. This goal was realized in the present study. A representative numerical investigation, of laser-based neutral atomic and molecular flow manipulations, was conducted using near-resonant and non-resonant laser fields. To simulate the laser interactions over a range of laser and flow conditions, the following tools were employed: a custom collisionless gas particle trajectory code and a specifically modified version of the Direct Simulation Monte Carlo statistical kinetic solver known as SMILE. In addition to the numerical investigations, a validating experiment was conducted. The experimental results showed good agreement with the numerical simulations when experimental parameters, such as finite laser line width, were taken into account. Several areas of interest were addressed: laser induced neutral flow steering, collimation, direct flow acceleration, and neutral gas heating. Near-resonant continuous wave laser, and non-resonant pulsed laser, interactions with cesium and nitrogen were simulated. These simulations showed trends and some limitations associated with these interactions, used for flow steering and collimation. The use of one of these interactions, the induced dipole force, was extended beyond a single Gaussian laser field. The interference patterns associated with counter-propagating laser fields, or "optical lattices," were shown to be capable of both direct species acceleration and gas heating. This study resulted in predictions for a continuous, resonant laser-cesium flow with accelerations of 106 m/s2. For this circumstance, a future straightforward proof of principle experiment has been identified. To demonstrate non-resonant gas heating, a series of pulsed optical lattices were simulated interacting with neutral non-polar species. An optimum time between pulses was identified as a function of the collisional relaxation time. Using the optimum time between pulses, molecular nitrogen simulations showed an increase in gas temperature from 300 K to 2470 K at 1 atm, for 50 successive optical lattice pulses. A second proof of principle experiment was identified for future investigation.

Lilly, Taylor C.

68

Optogalvanic effect in a self-terminating copper atomic laser  

SciTech Connect

The optogalvanic effect in a copper-vapour pulsed laser as well as the optothermal effects due to a hysteresis of the optogalvanic effect were observed for the first time. The generalised rate constant for the deexcitation of a resonant level to the ionisation state of the active medium was estimated to be <{sigma}{nu}>{approx}(3 {+-} 1) x 10{sup -7} cm{sup 3} s{sup -1} . (laser applications and other topics in quantum electronics)

Yudin, Nikolai A [Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk (Russian Federation); Klimkin, V M [Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences, Tomsk (Russian Federation); Prokop'ev, V E [Institute of High Current Electronics, Siberian Branch, Russian Academy of Sciences, Tomsk (Russian Federation)

1999-09-30

69

Resonant laser ionization of radioactive atoms*1  

NASA Astrophysics Data System (ADS)

Intense radioactive ion beams are produced by the isotope separation on-line method. The resonance ionization laser ion source (RILIS) can provide the chemical selectivity to separate beams with reduced isobaric contamination. The hot cavity RILIS at ISOLDE (CERN) uses copper vapor laser pumped dye lasers for the resonant transitions. Up to now 22 elements have been ionized with efficiencies of the order of 10%. Additional elements have been ionized with similar RILIS set-ups at the Institute of Spectroscopy (Troitsk), IRIS (Gatchina), Mainz University and TIARA (Takasaki). Ideas are discussed for future developments of this type of RILIS, which could further improve the efficiency, selectivity, rapidity of release and stability of the operation. The RILIS can also be applied for atomic spectroscopy studies of exotic radioactive isotopes, which are produced at rates of few atoms per second only. An interesting parallel is shown to the atomic vapor laser isotope separation (AVLIS), a large-scale application of resonance ionization, which could be used for the isotope enrichment of macroscopic amounts: tens of kg per h.

Köster, U.; Fedoseyev, V. N.; Mishin, V. I.

2003-06-01

70

Analysis of Laser Beam Propagation Effects in Atomic Laser Isotope Separation  

Microsoft Academic Search

In the atomic laser isotope separation process, the laser beams propagate through the atomic vapor over a long distance. It has been shown that the laser-atom interactions significantly modify the laser pulse shape and propagation velocity, resulting in degradation of the isotope separation efficiency. These propagation effects have been analyzed quantitatively, and a simple scaling formula has been derived to

Yen-Wei Chen; Yasukazu Izawa; Sadao Nakai; Chiyoe Yamanaka

1995-01-01

71

Laser cooling and trapping of atomic ytterbium  

Microsoft Academic Search

This dissertation reports an experimental study of laser cooled and magneto-optically trapped atomic Ytterbium (Yb). Studies focus on cooling Yb by driving the strong 398.9 nm (6s2)1 S0-(6s6p) 1P1 transition and probing the resulting cold samples by weakly exciting the spectrally narrow 555.8 nm (6 s2)1S0-(6 s6p)3P1 transition. Apparatus required for these experiments, including a 398.9 nm laser system, a

Thomas Howard Loftus

2001-01-01

72

Entangling many atomic ensembles through laser manipulation  

E-print Network

We propose an experimentally feasible scheme to generate Greenberger-Horne-Zeilinger (GHZ) type of maximal entanglement between many atomic ensembles based on laser manipulation and single-photon detection. The scheme, with inherent fault tolerance to the dominant noise and efficient scaling of the efficiency with the number of ensembles, allows to maximally entangle many atomic ensemble within the reach of current technology. Such a maximum entanglement of many ensembles has wide applications in demonstration of quantum nonlocality, high-precision spectroscopy, and quantum information processing.

L. -M. Duan

2002-04-24

73

Laser cooling and trapping of atomic mercury  

NASA Astrophysics Data System (ADS)

The level structure of the Hg atom is similar to other alkaline earth-like atoms, offering the possibility to realize an extremely high quality resonance factor (Q) on the ``clock'' transition (^1S0- ^3P0) when confined in an optical lattice at the Stark-shift free wavelength. A key feature of the Hg system is the reduced uncertainty due to black-body induced Stark shifts, making it an interesting candidate as an optical frequency standard. For cooling on the ^1S0- ^3P1 transition at 253.7 nm, we employ an optically pumped semiconductor laser (OPSEL) operating at 1015 nm. The OPSEL frequency is quadrupled, generating over 120 mW at 253.7 nm. With this laser source we have trapped Hg^199 from a background vapor in a standard MOT. We trap up to 2 x 10^6 atoms with a 1/e^2 radius of our MOT of ˜310 microns, corresponding to a density of 1.28 x10^11 atoms/cm^3. Using the time- of-flight method, we have measured a doppler-limited temperature of 46?K for the MOT. We have also generated 10 mW at the 266 nm clock transition using a frequency-quadrupled fiber laser. This light will be referenced to an iodine standard for assisting in high-precision spectroscopy of the ^1S0- ^3P0 transition. We present updated results on the MOT and the probe laser system.

Paul, Justin; Lytle, Christian; Jones, Jason

2011-10-01

74

Studies of laser selective excitation of atoms  

NASA Astrophysics Data System (ADS)

Sample preparation through laser ablation of a solid target under vacuum was combined with short-pulsed laser selective excitation to create a technique for measuring atomic radiative lifetimes. The lifetimes of the three resonance states of chromium compare very favorably with those found through other experimental means. The technique was extended to demonstrate the potential for plasma dianostics using two-wavelength selective excitation with short laser pulses. The ratio of population densities of two energy states of chromium atoms was measured as a function of time during the expansion of the ablation plasma. Extended saturation pumping of the resonance transition in sodium vapor was also investigated. Rate equations for 20 energy levels in the sodium atom, and the rate equations for the free electrons ,were integrated numerically. It was found that multiphoton ionization, combined with superelastic heating of free electrons can account for the rapid and complete ionization of an un-ionized vapor. The theoretical results led to the development of a simple model which accurately predicts the temporal variation of electron density.

Drewell, N.

1979-12-01

75

Evidence for laser cooling in a magnesium atomic beam.  

PubMed

Laser cooling in a Mg atomic beam is reported for the first time to our knowledge. Previous cooling experiments were performed by using visible or infrared lasers. The Mg atoms were cooled by using an intracavity frequency-doubled dye laser at 285 nm to reach the resonant (1)S(0)-(1)P(1) transition. Evidence of laser cooling was obtained even with the limited available laser power ( approximately 1-2 mW). PMID:19749917

Beverini, N; De Pascalis, S; Maccioni, E; Pereira, D; Strumia, F; Vissani, G; Wang, Y Z; Novero, C

1989-04-01

76

Evidence for laser cooling in a magnesium atomic beam  

Microsoft Academic Search

Laser cooling in a Mg atomic beam is reported for the first time to our knowledge. Previous cooling experiments were performed by using visible or infrared lasers. The Mg atoms were cooled by using an intracavity frequency-doubled dye laser at 285 nm to reach the resonant ¹Sâ--¹P⁠transition. Evidence of laser cooling was obtained even with the limited available laser

N. Beverini; S. de Pascalis; E. Maccioni; D. Pereira; F. Strumia; G. Vissani; Y. Z. Wang; C. Novero

1989-01-01

77

Evidence for laser cooling in a magnesium atomic beam  

SciTech Connect

Laser cooling in a Mg atomic beam is reported for the first time to our knowledge. Previous cooling experiments were performed by using visible or infrared lasers. The Mg atoms were cooled by using an intracavity frequency-doubled dye laser at 285 nm to reach the resonant /sup 1/S/sub 0/--/sup 1/P/sub 1/ transition. Evidence of laser cooling was obtained even with the limited available laser power (approx. =1--2 mW).

Beverini, N.; De Pascalis, S.; Maccioni, E.; Pereira, D.; Strumia, F.; Vissani, G.; Wang, Y.Z.; Novero, C.

1989-04-01

78

Comments to the note by G.G. Petrash on the paper 'On the simulation of a copper vapour laser with hydrogen admixtures'  

SciTech Connect

The remarks on the results published in [1-4] on the simulation of a copper vapour laser with hydrogen admixtures are analysed. It is shown that these remarks do not affect the conclusions made in our papers, and many of them are simply erroneous. (discussion)

Boichenko, Aleksandr M; Evtushenko, Gennadii S; Zhdaneev, O V; Yakovlenko, Sergei I [A.M. Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2005-06-30

79

Laser-modified electron scattering from a slowly ionising atom  

NASA Technical Reports Server (NTRS)

When an electron scatters from an atom in the presence of a laser field which is resonant with an atomic transition, off-shell effects enter into the cross section. These only become significant at higher laser intensities where the atom may also be ionised by the laser. Cross-sections are obtained for electron-atom scattering in which these off-shell effects appear and in which the slow ionisation of the atom by the laser is included. Experiments are suggested in which simplifications can occur and which still retain these 'exotic' effects.

Fiordilino, E.; Mittleman, M. H.

1983-01-01

80

Separation of Li isotopes by laser defection of atomic beams  

Microsoft Academic Search

Separation of Li isotopes by laser deflection of atomic beams has been carried out. An atomic beam apparatus with a collimating ratio of 450\\/1 generates are Li atomic beam of 10⁹ atoms\\/cm³ at the oven temperature of 600 °C. The CW tunable dye laser crossing the atomic beam at a right angle has a linewidth of 6 MHz and its

L. Li; Y. Wang; M. Li

1983-01-01

81

Gravitational Wave Detection with Single-Laser Atom Interferometers  

NASA Technical Reports Server (NTRS)

A new design for a broadband detector of gravitational radiation relies on two atom interferometers separated by a distance L. In this scheme, only one arm and one laser are used for operating the two atom interferometers. The innovation here involves the fact that the atoms in the atom interferometers are not only considered as perfect test masses, but also as highly stable clocks. Atomic coherence is intrinsically stable, and can be many orders of magnitude more stable than a laser.

Yu, Nan; Tinto, Massimo

2011-01-01

82

ArF-excimer laser induced chemical vapour deposition of amorphous hydrogenated SiGeC films  

NASA Astrophysics Data System (ADS)

The growing interest in the development of silicon germanium carbon (SiGeC) based devices for micro- and optoelectronics provoked an increasing attention in alternative low thermal budget techniques capable to produce such alloys on large areas as well as on small selected regions. Excimer laser-induced chemical vapour deposition (LCVD) in parallel configuration is a "soft" alternative deposition technique that has already proved to be a feasible method for the production of various thin film semiconductors. This contribution will investigate the possibility to exploit the technique for producing the ternary SiGeC alloy and demonstrate that coatings with uniform composition, structure and thickness can be deposited at low substrate temperature. The samples have been extensively analysed by different techniques for identifying the most important experimental parameters determining the growth rate, and the homogeneity in stoichiometry and structure.

López, E.; Chiussi, S.; Serra, C.; Serra, J.; González, P.; León, B.; Pérez-Amor, M.

2003-03-01

83

Increasing the output power of single 808-nm laser diodes using diamond submounts produced by microwave plasma chemical vapour deposition  

NASA Astrophysics Data System (ADS)

We have designed and fabricated submounts from synthetic diamond grown by microwave plasma chemical vapour deposition and developed an economical process for metallising such submounts. Laser diode chips having an 808-nm emission wavelength, 3-mm-long cavity and 130-mm-wide stripe contact were mounted on copper heat sinks with the use of diamond submounts differing in quality. The devices were tested for more than 150 h in continuous mode at an output power of 8 W on diamond with a thermal conductivity of 700 W m-1 K-1, and no changes in their output power were detected. On diamond with a thermal conductivity of 1600 W m-1 K-1, stable cw operation for 24 h at an output power of 12 W was demonstrated.

Ashkinazi, E. E.; Bezotosnyi, V. V.; Bondarev, Vadim Yu; Kovalenko, V. I.; Konov, Vitalii I.; Krokhin, Oleg N.; Oleshchenko, V. A.; Pevtsov, Valerii F.; Popov, Yurii M.; Popovich, A. F.; Ral'chenko, Viktor G.; Cheshev, E. A.

2012-11-01

84

Increasing the output power of single 808-nm laser diodes using diamond submounts produced by microwave plasma chemical vapour deposition  

SciTech Connect

We have designed and fabricated submounts from synthetic diamond grown by microwave plasma chemical vapour deposition and developed an economical process for metallising such submounts. Laser diode chips having an 808-nm emission wavelength, 3-mm-long cavity and 130-mm-wide stripe contact were mounted on copper heat sinks with the use of diamond submounts differing in quality. The devices were tested for more than 150 h in continuous mode at an output power of 8 W on diamond with a thermal conductivity of 700 W m{sup -1} K{sup -1}, and no changes in their output power were detected. On diamond with a thermal conductivity of 1600 W m{sup -1} K{sup -1}, stable cw operation for 24 h at an output power of 12 W was demonstrated. (letters)

Ashkinazi, E E; Bezotosnyi, V V; Bondarev, Vadim Yu; Kovalenko, V I; Konov, Vitalii I; Krokhin, Oleg N; Oleshchenko, V A; Pevtsov, Valerii F; Popov, Yurii M; Popovich, A F; Ral'chenko, Viktor G; Cheshev, E A

2012-11-30

85

Stimulated IR emission in an optically pumped cesium vapour  

SciTech Connect

It is demonstrated that the optical pumping of a Cs vapour with light pulses of a dye laser tunable within the range of 15390-17920 cm{sup -1} gives rise to high-power stimulated IR emission on several atomic transitions. Analysis of threshold, energy, and spectral characteristics of this emission allowed the mechanism underlying this effect to be explained. (active media. lasers)

Sitnikov, M G; Znamenskiy, Nikolay V; Manykin, Eduard A; Petrenko, Evgenii A [Institute of Superconductivity and Solid-State Physics, Russian Research Centre 'Kurchatov Institute', Moscow (Russian Federation); Grigoryan, Grigorii G [Institute of Physics Research, Armenian Academy of Sciences, Ashtarak-2 (Armenia)

2000-03-31

86

Isotope separation by laser deflection of an atomic beam  

Microsoft Academic Search

Separation of isotopes of barium was accomplished by laser deflection of a single isotopic component of an atomic beam. With a tunable narrow linewidth dye laser, small differences in absorption frequency of different barium isotopes were exploited to deflect atoms of a single isotopic component of an atomic beam through an angle large enough to physically separate them from the

A. F. Bernhardt

1975-01-01

87

Laser cooling of Mg and Ca atomic beams  

SciTech Connect

Laser deceleration was achieved by irradiating thermal calcium and magnesium atomic beams with a counterpropagating laser beam in resonance with the {sup 1}S{sub 0}--{sup 1}P{sub 1} transition. Zeeman tuning of the atomic absorption was used to enhance the population of cooled atoms. (AIP)

Beverini, N.; Maccioni, E.; Pereira, D.; Strumia, F.; Vissani, G. (Dipartimento di Fisica dell'Universita di Pisa (CISM) and INFN, Sezione di Pisa, P. Torricelli 2, 56126 Pisa, Italy (IT))

1989-10-20

88

Laser cooling of Mg and Ca atomic beams  

Microsoft Academic Search

Laser deceleration was achieved by irradiating thermal calcium and magnesium atomic beams with a counterpropagating laser beam in resonance with the 1S0-1P1 transition. Zeeman tuning of the atomic absorption was used to enhance the population of cooled atoms. (AIP)

N. Beverini; E. Maccioni; D. Pereira; F. Strumia; G. Vissani

1989-01-01

89

Stable 85Rb micro vapour cells: fabrication based on anodic bonding and application in chip-scale atomic clocks  

NASA Astrophysics Data System (ADS)

We describe the microfabrication of 85Rb vapour cells using a glass-silicon anodic bonding technique and in situ chemical reaction between rubidium chloride and barium azide to produce Rb. Under controlled conditions, the pure metallic Rb drops and buffer gases were obtained in the cells with a few mm3 internal volumes during the cell sealing process. At an ambient temperature of 90 °C the optical absorption resonance of 85Rb D1 transition with proper broadening and the corresponding coherent population trapping (CPT) resonance, with a signal contrast of 1.5% and linewidth of about 1.7 kHz, have been detected. The sealing quality and the stability of the cells have also been demonstrated experimentally by using the helium leaking detection and the after-9-month optoelectronics measurement which shows a similar CPT signal as its original status. In addition, the physics package of chip-scale atomic clock (CSAC) based on the cell was realized. The measured frequency stability of the physics package can reach to 2.1 × 10-10 at one second when the cell was heated to 100 °C which proved that the cell has the quality to be used in portable and battery-operated devices.

Su, Juan; Deng, Ke; Guo, Deng-Zhu; Wang, Zhong; Chen, Jing; Zhang, Geng-Min; Chen, Xu-Zong

2010-11-01

90

A new method for preconcentration and determination of mercury in fish, shellfish and saliva by cold vapour atomic absorption spectrometry.  

PubMed

The development of a method using solid phase extraction for preconcentration and determination of mercury by cold vapour atomic absorption spectrometry is described. Hg (II) ions are sorbed on a minicolumn packed with Amberlite XAD-4 sorbent functionalised with 2-(2'-benzothiazolylazo)-p-cresol (BTAC). Then, a reducing solution was used for desorption and the transport of the analyte for subsequent detection. The assay presented a limit of detection of 0.011 ?g L?¹ (0.011 ?g g?¹, for solid samples), a limit of quantification of 0.038 ?g L?¹ (0.038 ?g g?¹, for solid samples), a precision of 0.50% (1.000 ?g L?¹ Hg solution) and an enrichment factor of 46. The proposed method was applied to the determination of mercury in human saliva (0.055-0.200 ?g L?¹). The following seafood collected in Todos os Santos Bay, Brazil was also analysed: bass (0.169-0.195 ?g g?¹), mullet (0.043-0.361 ?g g?¹), shrimp (0.075-0.374 ?g g?¹) and mussel (0.206-0.397 ?g g?¹). PMID:24295696

Lemos, Valfredo Azevedo; dos Santos, Liz Oliveira

2014-04-15

91

Linear Atom Guides: Guiding Rydberg Atoms and Progress Toward an Atom Laser  

NASA Astrophysics Data System (ADS)

In this thesis, I explore a variety of experiments within linear, two-wire, magnetic atom guides. Experiments include guiding of Rydberg atoms; transferring between states while keeping the atoms contained within the guide; and designing, constructing, and testing a new experimental apparatus. The ultimate goal of the atom guiding experiments is to develop a continuous atom laser. The guiding of 87Rb 59D5/2 Rydberg atoms is demonstrated. The evolution of the atoms is driven by the combined effects of dipole forces acting on the center-of-mass degree of freedom as well as internal-state transitions. Time delayed microwave and state-selective field ionization, along with ion detection, are used to investigate the evolution of the internal-state distribution as well as the Rydberg atom motion while traversing the guide. The observed decay time of the guided-atom signal is about five times that of the initial state. A population transfer between Rydberg states contributes to this lengthened lifetime, and also broadens the observed field ionization spectrum. The population transfer is attributed to thermal transitions and, to a lesser extent, initial state-mixing due to Rydberg-Rydberg collisions. Characteristic signatures in ion time-of-flight signals and spatially resolved images of ion distributions, which result from the coupled internal-state and center-of-mass dynamics, are discussed. Some groups have used a scheme to make BECs where atoms are optically pumped from one reservoir trap to a final state trap, irreversibly transferring those atoms from one trap to the other. In this context, transfer from one guided ground state to another is studied. In our setup, before the atoms enter the guide, they are pumped into the | F = 1, mF = --1> state. Using two repumpers, one tuned to the F = 1 ? F' = 0 transition (R10) and the other tuned to the F = 1 ? F' = 2 transition (R12), the atoms are pumped between these guided states. Magnetic reflections within the guide are also studied. Design and construction of a new linear magnetic atom guide is detailed. This guide beta has many improvements over the original guide alpha: a Zeeman slower, magnetic injection, a physical shutter, and surface adsorption evaporative cooling are some of the main changes. Testing of this new system is underway. It is hoped that the improvements to guide beta will yield an atom density sufficient to reach degeneracy, thereby forming a continuous BEC at the end of the guide. The BEC, which will be continuously replenished by the atoms within the guide, will be outcoupled to form a continuous atom laser.

Traxler, Mallory A.

92

Narrow linewidth single laser source system for onboard atom interferometry  

E-print Network

We present an original compact and robust laser system for atom interferometry based on a frequency-doubled telecom laser. Thanks to an original stabilization architecture on a saturated absorption, we obtain a frequency agile laser system allowing fast tuning of the laser frequency over 1 GHz in few ms using only a single laser source. The different laser frequencies used for atom interferometry are created by changing dynamically the frequency of the laser and by creating sidebands using a phase modulator. We take advantage of the maturity of fiber telecom technology to reduce the number of free-space optical components, which are intrinsically less stable, and to make the setup compact, much less sensitive to vibrations and thermal fluctuations. This source provides spectral linewidth below 2.5 kHz required for precision atom interferometry, and particularly for an high performance atomic inertial sensor.

Theron, Fabien; Renon, Geoffrey; Bidel, Yannick; Zahzam, Nassim; Cadoret, Malo; Bresson, Alexandre

2014-01-01

93

Dual-Beam Atom Laser Driven by Spinor Dynamics  

NASA Technical Reports Server (NTRS)

An atom laser now undergoing development simultaneously generates two pulsed beams of correlated Rb-87 atoms. (An atom laser is a source of atoms in beams characterized by coherent matter waves, analogous to a conventional laser, which is a source of coherent light waves.) The pumping mechanism of this atom laser is based on spinor dynamics in a Bose-Einstein condensate. By virtue of the angular-momentum conserving collisions that generate the two beams, the number of atoms in one beam is correlated with the number of atoms in the other beam. Such correlations are intimately linked to entanglement and squeezing in atomic ensembles, and atom lasers like this one could be used in exploring related aspects of Bose-Einstein condensates, and as components of future sensors relying on atom interferometry. In this atom-laser apparatus, a Bose-Einstein condensate of about 2 x 10(exp 6) Rb-87 atoms at a temperature of about 120 micro-K is first formed through all-optical means in a relatively weak singlebeam running-wave dipole trap that has been formed by focusing of a CO2-laser beam. By a technique that is established in the art, the trap is loaded from an ultrahigh-vacuum magnetooptical trap that is, itself, loaded via a cold atomic beam from an upstream two-dimensional magneto-optical trap that resides in a rubidium-vapor cell that is differentially pumped from an adjoining vacuum chamber, wherein are performed scientific observations of the beams ultimately generated by the atom laser.

Thompson, Robert; Lundblad, Nathan; Maleki, Lute; Aveline, David

2007-01-01

94

An improved model of gas temperature in a copper bromide vapour laser  

SciTech Connect

A new analytic model is proposed for calculating the temperature profile of gas in the transverse section of the discharge tube of copper bromide lasers emitting at 510.6 and 578.2 nm. The model is described by the quasi-stationary heat conduction equation with the boundary conditions of the third and fourth kinds taking into account the alternating volume electric power along the tube radius. The exact solution of the problem is obtained. The model was used to calculate the temperature profiles of the discharge in the case of natural and forced convection cooling. The obtained results are compared with previously known temperature distributions. The improved model proposed in the paper can be used to analyse existing lasers and develop new lasers. (lasers and amplifiers)

Iliev, I P [Department of Physics, Technical University of Plovdiv, Plovdiv (Bulgaria); Gocheva-Ilieva, S G [Department of Applied Mathematics and Modelling, Faculty of Mathematics and Informatics, Paisii Hilendarski University of Plovdiv (Bulgaria); Sabotinov, N V [Metal Vapour Lasers Department, Georgi Nadjakov Institute of Solid State Physics, Bulgarian Academy of Sciences, Sofia (Bulgaria)

2009-05-31

95

Measuring the Temporal Coherence of an Atom Laser Beam  

Microsoft Academic Search

We report on the measurement of the temporal coherence of an atom laser beam extracted from a 87Rb Bose-Einstein condensate. Reflecting the beam from a potential barrier creates a standing matter wave structure. From the contrast of this interference pattern, observed by magnetic resonance imaging, we have deduced an energy width of the atom laser beam which is Fourier limited

Michael Köhl; Theodor W. Hänsch; Tilman Esslinger

2001-01-01

96

Generating Controllable Atom-Light Entanglement with a Raman Atom Laser System S. A. Haine,1  

E-print Network

Generating Controllable Atom-Light Entanglement with a Raman Atom Laser System S. A. Haine,1 M. K. Olsen,2 and J. J. Hope1 1 Australian Centre for Quantum-Atom Optics, The Australian National University, Canberra, 0200, Australia 2 Australian Centre for Quantum-Atom Optics, University of Queensland, Brisbane

Queensland, University of

97

Cooling and Trapping Atoms Atoms are slowed and cooled by radiation pressure from laser light  

E-print Network

Cooling and Trapping Atoms Atoms are slowed and cooled by radiation pressure from laser light and then trapped in a bottle whose "walls" are magnetic fields. Cooled atoms are ideal for exploring basic. research has traditionally been the study of the intrinsic prop erties of isolated atoms. In the early part

Johannesson, Henrik

98

Design and prototyping of Stark atom chip for electric trapping of laser-cooled atoms  

Microsoft Academic Search

An electric trapping of laser-cooled neutral strontium (Sr) atoms on a chip with micro-electrodes has been successful. The device is called “Stark atom chip” since it makes use of Stark effects on neutral atoms in electric fields. In this paper, our design and prototyping of the Stark atom chip with high aspect ratio electrodes precisely built on a surface are

Keisuke Nagato; Takeshi Ooi; Tetsuo Kishimoto; Hidekazu Hachisu; Hidetoshi Katori; Masayuki Nakao

2006-01-01

99

Chaotic scattering of atoms at a standing laser wave  

E-print Network

Atoms, propagating across a detuned standing laser wave, can be scattered in a chaotic way even in the absence of spontaneous emission and any modulation of the laser field. Spontaneous emission masks the effect in some degree, but the Monte Carlo simulation shows that it can be observed in real experiments by the absorption imaging method or depositing atoms on a substrate. The effect of chaotic scattering is explained by a specific behavior of the dipole moments of atoms crossing the field nodes and is shown to depend strongly on the value of the atom-laser detuning.

S. V. Prants

2012-05-20

100

Comparison of the Er,Cr:YSGG laser with a chemical vapour deposition bur and conventional techniques for cavity preparation: a microleakage study  

Microsoft Academic Search

The aim of this study was to compare the effects of the Er,Cr:YSGG laser using chemical vapour deposition (CVD) bur cavity\\u000a preparation with conventional preparation methods including a diamond bur and a carbide bur on the microleakage with two different\\u000a adhesive systems. A total of 40 extracted human premolars were randomly assigned to four experimental groups according to\\u000a the cavity

A. Rüya Yazici; Zeren Y?ld?r?m; Sibel A. Antonson; Evren Kilinc; Daniele Koch; Donald E. Antonson; Berrin Dayangaç; Gül Özgünaltay

101

Development of laser excited atomic fluorescence and ionization methods  

SciTech Connect

Progress report: May 1, 1988 to December 31, 1991. The research supported by DE-FG05-88ER13881 during the past (nearly) 3 years can be divided into the following four categories: (1) theoretical considerations of the ultimate detection powers of laser fluorescence and laser ionization methods; (2) experimental evaluation of laser excited atomic fluorescence; (3) fundamental studies of atomic and molecular parameters in flames and plasmas; (4) other studies.

Winefordner, J.D.

1991-01-01

102

Isotope separation by laser deflection of an atomic beam  

Microsoft Academic Search

Separation of isotopes of barium has been accomplished by laser deflection of a single isotopic component of an atomic beam.\\u000a With a tunable narrow linewidth dye laser, small differences in absorption frequency of different barium isotopes on the 6s2\\u000a 1S0? 6s6p1P1 5536 ? resonance were exploited to deflect atoms of a single isotopic component of an atomic beam through an

Anthony F. Bernhardt

1976-01-01

103

Isotope separation by laser deflection of an atomic beam  

Microsoft Academic Search

Separation of isotopes of barium has been accomplished by laser deflection of a single isotopic component of an atomic beam. With a tunable narrow linewidth dye laser, small differences in absorption frequency of different barium isotopes on the 6s2 1S0- 6s6p1P1 5536 Å resonance were exploited to deflect atoms of a single isotopic component of an atomic beam through an

Anthony F. Bernhardt

1976-01-01

104

Preparation, characterisation and optimisation of lithium battery anodes consisting of silicon synthesised using Laser assisted Chemical Vapour Pyrolysis  

NASA Astrophysics Data System (ADS)

Suitability of silicon prepared using Laser assisted Chemical Vapour Pyrolysis (LaCVP) as a potential anode material in lithium batteries is systematically investigated. Its compositional, morphological, physical-chemical and electrochemical properties are compared to a current benchmark commercial silicon. Important differences in particle size and particle composition are found which, as shown, affect critically the rheological properties of the corresponding electrode slurries. In order to overcome the rheological problems of prepared nanosilicon, we introduce and optimise a spraying method instead of using the usual casting technique for slurry application. Interestingly, the optimised electrodes show similar electrochemical performance, regardless of the particle size or composition of nanosilicon. This unexpected result is explained by the unusually high resistance of electrochemical wiring in silicon-based electrodes (about 60 Ohm per 1 mg cm-2 of active material loading). Despite that, the optimised material still shows a capacity up to 1200 mA h g-1 at a relatively high loading of 1.6 mg cm-2 and after 20 cycles. On the other hand, by decreasing the loading to below ca. 0.9 mg cm-2 the wiring problems are effectively overcome and capacities close to theoretical values can be obtained.

Veliscek, Ziga; Perse, Lidija Slemenik; Dominko, Robert; Kelder, Erik; Gaberscek, Miran

2015-01-01

105

High performance liquid chromatography coupled to atomic fluorescence spectrometry for the speciation of the hydride and chemical vapour-forming elements As, Se, Sb and Hg: A critical review  

Microsoft Academic Search

We present the most recent applications of high performance liquid chromatography (HPLC) hyphenated to hydride generation or chemical vapour generation and atomic fluorescence spectrometry (HG\\/CVG-AFS), for the determination and speciation of the selected hydride-forming elements arsenic (As), selenium (Se) and antimony (Sb) and the chemical vapour-forming metal Hg. The review focuses on sample preparation, post-column treatments and on the applications

Yu-Wei Chen; Nelson Belzile

2010-01-01

106

Tunable dye laser amplifier chain for laser isotope separation  

SciTech Connect

A tunable dye laser amplifier chain developed for experiments on atomic vapour laser isotope separation (AVLIS) is described. The system, pumped by copper vapour lasers, consists of a master oscillator and an amplifier stage including a preamplifier and three main amplifiers working in the saturation mode. The master oscillator of the stage is a dye laser with a grazing incidence diffraction grating. Longitudinal pumping of the amplifiers is used. The efficiency of the main amplifiers is 50 % - 55 %. The average power of laser radiation at the output of the last amplifier is 100 W. (lasers. amplifiers)

Grigoriev, Igor' S; D'yachkov, Aleksei B; Labozin, Valerii P; Mironov, Sergei M; Nikulin, Sergei A; Firsov, Valerii A [Russian Research Centre 'Kurchatov Institute', Moscow (Russian Federation)

2004-05-31

107

Laser-Ranging Long Baseline Differential Atom Interferometers for Space  

E-print Network

High sensitivity differential atom interferometers are promising for precision measurements in science frontiers in space, including gravity field mapping for Earth science studies and gravitational wave detection. We propose a new configuration of twin atom interferometers connected by a laser ranging interferometer (LRI-AI) to provide precise information of the displacements between the two AI reference mirrors and a means to phase-lock the two independent interferometer lasers over long distances, thereby further enhancing the feasibility of long baseline differential atom interferometers. We show that a properly implemented LRI-AI can achieve equivalent functionality to the conventional differential atom interferometer measurement system. LRI-AI isolates the laser requirements for atom interferometers and for optical phase readout between distant locations, thus enabling optimized allocation of available laser power within a limited physical size and resource budget. A unique aspect of LRI-AI also enables...

Chiow, Sheng-wey; Yu, Nan

2015-01-01

108

A superradiant Raman laser as an atomic sensor  

NASA Astrophysics Data System (ADS)

We have realized an atomic sensor that combines active, wideband sensing with passive measurement periods using dynamic control of a cold-atom, superradiant Raman laser. Superradiant lasers have been proposed as highly stable optical frequency references for next generation precision measurement experiments. Collective emission of the atomic gain medium maps the quantum phase of the atomic ensemble onto the detected cavity field. This quantum phase can also be sensitive to the environment, allowing the laser to function as a sensor in addition to a frequency reference. We discuss the fundamental precision of the superradiant mapping and show that the non-demolition measurement can theoretically approach the standard quantum limit on phase estimation for a coherent spin state. Finally, we present experimental demonstrations of a superradiant Raman laser operated as a hybrid active/passive atomic measurement device.

Bohnet, Justin G.; Chen, Zilong; Weiner, Joshua M.; Cox, Kevin C.; Thompson, James K.

2013-04-01

109

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Dynamics of a plasma formed by a surface optical-discharge in a metal vapour interacting with a cw CO2 laser beam  

NASA Astrophysics Data System (ADS)

A surface optical-discharge plasma was formed in a metal vapour under normal conditions by steady-state irradiation with a cw CO2 laser delivering radiation of moderate (2-4.5 MW cm-2) intensity. This plasma strongly screened the irradiated surface. Under the selected experimental conditions the optical discharge was not a continuous (steady-state) process. The plasma cloud was displaced along the beam out of the waist to a region where the laser radiation intensity was almost an order of magnitude less than the threshold for excitation of the optical-discharge plasma in the vapour. A strong screening of the metal surface, which could even completely stop evaporation of the metal, was observed. Self-oscillations of the optical-discharge plasma were observed for the first time in a vapour interacting with cw CO2 radiation: this was attributed to screening of the target surface. Within one period of the self-oscillations there were additional hf plasma pulsations which led to stratification of the plasma cloud. The results obtained were interpreted.

Zaikin, A. E.; Levin, A. V.; Petrov, A. L.

1995-02-01

110

Narrow linewidth single laser source system for onboard atom interferometry  

NASA Astrophysics Data System (ADS)

A compact and robust laser system for atom interferometry based on a frequency-doubled telecom laser is presented. Thanks to the original stabilization architecture on a saturated absorption setup, we obtain a frequency agile laser system allowing fast tuning of the laser frequency over 1 GHz in few ms using a single laser source. The different laser frequencies used for atom interferometry are generated by changing dynamically the frequency of the laser and by creating sidebands using a phase modulator. A laser system for Rubidium 87 atom interferometry using only one laser source based on a frequency-doubled telecom fiber bench is then built. We take advantage of the maturity of fiber telecom technology to reduce the number of free-space optical components (which are intrinsically less stable) and to make the setup compact and much less sensitive to vibrations and thermal fluctuations. This source provides spectral linewidth below 2.5 kHz, which is required for precision atom interferometry and particularly for a high performance atomic inertial sensor.

Theron, Fabien; Carraz, Olivier; Renon, Geoffrey; Zahzam, Nassim; Bidel, Yannick; Cadoret, Malo; Bresson, Alexandre

2015-01-01

111

Investigations of laser pumped gas cell atomic frequency standard  

NASA Technical Reports Server (NTRS)

The performance characteristics of a rubidium gas cell atomic frequency standard might be improved by replacing the standard rubidium discharge lamp with a single mode laser diode. Aspects of the laser pumped gas cell atomic clock studied include effects due to laser intensity, laser detuning, and the choice of the particular atomic absorption line. Results indicate that the performance of the gas cell clock may be improved by judicious choice of the operating parameters of the laser diode. The laser diode also proved to be a valuable tool in investigating the operation of the conventional gas cell clock. Results concerning linewidths, the light shift effect and the effect of isotopic spin exchange in the conventional gas cell clock are reported.

Volk, C. H.; Camparo, J. C.; Fueholz, R. P.

1982-01-01

112

Recent progress of laser cooling for neutral mercury atom  

NASA Astrophysics Data System (ADS)

Mercury is the heaviest stable atom that could be laser cooled, and have a large nuclear charge number. So it has a distinct advantage in quantum precision measurement such as fine-structure constant ? and permanent electric dipole moment. Due to its insensitivity of black body radiation, atomic mercury is a good candidate of optical clock. Here we report our recent development of laser cooling of neutral mercury atom. By cooling the mercury source to about -70°C, an ultra-high vacuum system was realized to produce ultracold mercury atoms. The commercial frequency quadrupled semiconductor laser is locked on the cooling transition (1S0-3P1 transition, wavelength of 253.7 nm) by sub-Doppler frequency modulation spectroscopy. By the modification with feed-forward method, the UV laser becomes faster tunable and more stable. A folded beam configuration was used to realize the magneto-optical trap (MOT) because of the shortage of cooling laser power, and the ultracold mercury atoms were observed by fluorescence detection. All of six rich abundant isotopes have been observed, and the atom number is about 1.5×106 with density of 3.5×109 /cm3 for 202Hg. With optical shutter and the programmable system to control the time sequence, the temperature of ultracold atoms can be measured by time of flight method. To enhance the laser power, a 1014.8 nm fiber laser amplifier was developed, which can work at room temperature. After two stages of frequency doubling, about 75 mW of 253.7 nm UV laser were generated, and the saturated absorption spectroscopy of mercury atom was also observed. More power of UV laser could help to trap more atoms in the future. These works laid a good foundation to realize the mercury lattice clock.

Liu, Kang-Kang; Zhao, Ru-Chen; Fu, Xiao-Hu; Hu, Jin-Meng; Feng, Yan; Xu, Zhen; Wang, Yu-Zhu

2014-11-01

113

Laser-stimulated migration of adsorbed atoms on solid surfaces  

NASA Technical Reports Server (NTRS)

This paper presents a unified theory of the coherent, multiple-photon excitation and laser-stimulated migration of atoms adsorbed on solid surfaces. We show that under steady-state excitation the migration of the adsorbed atom on the surface is diffusional, with diffusion constant dependent upon field intensity, surface temperature, relaxation constants, dipole moment strength, laser frequency, and the vibrational frequency of the adsorbed atom. In particular, it is shown that the rate of diffusion is proportional to the field intensity. Finally, we discuss the utility of laser-stimulated migration in the enhancement of surface chemical reactions, as well as in the analysis of surface relaxational processes.

Slutsky, M. S.; George, T. F.

1979-01-01

114

Loading atom lasers by collectivity-enhanced optical pumping  

SciTech Connect

The effect of collectivity on the loading of an atom laser via optical pumping is discussed. In our model, atoms in a beam are laser-excited and subsequently spontaneously decay into a trapping state. We consider the case of sufficiently high particle density in the beam such that the spontaneous emission is modified by the particle interaction. We show that the collective effects lead to a better population of the trapping state over a wide range of system parameters, and that the second-order correlation function of the atoms can be controlled by the applied laser field.

Macovei, Mihai A.; Evers, Joerg [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany)

2010-01-15

115

Search for a permanent EDM using laser cooled radioactive atom  

NASA Astrophysics Data System (ADS)

The search for the electric-dipole moment (EDM) of laser-cooled francium (Fr) atoms could lead to a measurement for the electron EDM. It is predicted that the electron EDM would be enhanced by approximately three orders of magnitude in heavy atoms such as Fr. Laser-cooling and trapping techniques are expected to suppress statistical and systematic errors in precision measurements. The magneto-optical trap was achieved using stable rubidium in a developing factory of laser-cooled radioactive atoms. In light of the results from the rubidium experiments, we found that an upgrade of each apparatus is preferred for Fr trapping.

Kawamura, Hirokazu; Ando, S.; Aoki, T.; Arikawa, H.; Ezure, S.; Harada, K.; Hayamizu, T.; Inoue, T.; Ishikawa, T.; Itoh, M.; Kato, K.; Kato, T.; Nataraj, H. S.; Sato, T.; Uchiyama, A.; Aoki, T.; Furukawa, T.; Hatakeyama, A.; Hatanaka, K.; Imai, K.; Murakami, T.; Shimizu, Y.; Wakasa, T.; Yoshida, H. P.; Sakemi, Y.

2014-03-01

116

WHEN ATOMS BEHAVE AS WAVES: BOSE-EINSTEIN CONDENSATION AND THE ATOM LASER  

E-print Network

WHEN ATOMS BEHAVE AS WAVES: BOSE-EINSTEIN CONDENSATION AND THE ATOM LASER Nobel Lecture, December 8, 2001 by WOLFGANG KETTERLE* Department of Physics, MIT-Harvard Center for Ultracold Atoms, and Re cooling. The approach into the kelvin range was rewarded with the discovery of superconductivity in 1911

117

Nobel lecture: When atoms behave as waves: Bose-Einstein condensation and the atom laser*  

E-print Network

Nobel lecture: When atoms behave as waves: Bose-Einstein condensation and the atom laser* Wolfgang Ketterle Department of Physics, MIT-Harvard Center for Ultracold Atoms, and Research Laboratory cooling. The approach into the kelvin range was rewarded with the discovery of super- conductivity in 1911

118

Theoretical tools for atom-laser-beam propagation  

Microsoft Academic Search

We present a theoretical model for the propagation of non-self-interacting atom laser beams. We start from a general propagation integral equation and we use the same approximations as in photon optics to derive tools to calculate the atom-laser-beam propagation. We discuss the approximations that allow one to reduce the general equation whether to a Fresnel-Kirchhoff integral calculated by using the

J.-F. Riou; Y. Le Coq; F. Impens; W. Guerin; C. J. Bordé; A. Aspect; P. Bouyer

2008-01-01

119

Progress towards laser spectroscopy of atomic and molecular positronium  

NASA Astrophysics Data System (ADS)

The production of molecular positronium and the existence of excited states of this molecule make it natural to consider performing laser spectroscopy on this four-particle matter-antimatter system. We report here progress towards this goal, including the production of a more intense positron beam and the development and testing of laser systems suitable for spectroscopy of atomic and molecular positronium.

Cassidy, D. B.; Hisakado, T. H.; Meligne, V. E.; Tom, H. W. K.; Mills, A. P., Jr.

2009-11-01

120

Optical dipole traps for cold atoms using diffracted laser light  

SciTech Connect

We theoretically investigate the feasibility of using intensity distributions of light of a single laser beam diffracted by a circular aperture as optical dipole traps for cold neutral atoms. Localized and cylindrically symmetric traps on the central axis of the circular aperture exist for both blue- and red-detuned laser light. Experimental mapping of the spots of interest using CO{sub 2} laser light demonstrates the existence of these light distributions for laboratory conditions and their agreement with theoretical predictions.

Gillen, Glen D.; Guha, Shekhar; Christandl, Katharina [Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson Air Force Base, Dayton, Ohio 45433 (United States); Department of Physics, Ohio State University, Columbus, Ohio 43210 (United States)

2006-01-15

121

Desorption of metal atoms with laser light: Mechanistic studies  

Microsoft Academic Search

Results on laser-induced desorption of metal atoms from small metal particles are presented. Experiments have been performed on sodium, potassium, and silver particles supported on a LiF(100) single-crystal surface under ultrahigh vacuum conditions. Measurements include the determination of the desorption rate as a function of laser wavelength, laser intensity, average particle size, and substrate temperature, the determination of the kinetic

W. Hoheisel; M. Vollmer; F. Träger

1993-01-01

122

Atom Optics and Interferometry with Laser Cooled Atoms  

Microsoft Academic Search

A short review about recent developments of coherent atom optics and atom interferometry is given. The paper mainly concentrates on light fields as optical elements for de Broglie waves. Ramsey type interferometers for measurements of fundamental constants as well as for the study of pure quantum mechanical phase shifts are discussed in more detail. As an example measurements of the

J. H. Müller; D. Bettermann; V. Rieger; F. Ruschewitz; K. Sengstock; U. Sterr; M. Christ; M. Schiffer; A. Scholz; W. Ertmer

1994-01-01

123

A source of atomic oxygen for a chemical CO laser  

Microsoft Academic Search

A supersonic chemical CO laser employing a CS2\\/O2 mixture is proposed in which the equilibrium products of the combustion of sulfur in oxygen are used as a source of atomic oxygen. Theoretical calculations are presented which show that supersonic flows containing about 15 percent of oxygen atoms can be generated by this method over a wide range of pressures and

T. V. Bystrova; Iu. L. Chizhov

1985-01-01

124

Coupling of non-selective adsorption with selective elution for novel in-line separation and detection of cadmium by vapour generation atomic absorption spectrometry.  

PubMed

Non-selective adsorption of Cd(2+) ions on a cation exchange fiber and subsequent selective elution with a KI solution has been strategically utilized to develop a highly selective in-line separation of Cd(2+) ions from other metal ions for its rapid and reliable quantification by cold vapour-atomic absorption spectrometry. After retention of Cd(2+) with a high efficiency on cation exchange fiber, selective elution of the retained Cd(2+) was subsequently accomplished with 0.3M KI. Vapour generation of Cd for in-line CV-AAS determination was then achieved by merging the eluate with HCl and NaBH4. Interferences from most base metals with the vapour generation of Cd were eliminated by this approach, with the exception of Pb(2+)ions which was removed by co-precipitation with BaSO4 prior to the in-line separation. Substantial improvement in sensitivity of the in-line CV-AAS determination of Cd was achieved by increasing the sample loading time. A detection limit of 0.6ngL(-1) (3?) was obtained with sample loading time of 120s, corresponding to a consumption of 24mL of sample solution. Application of the method to the determination of Cd in certified sediment and fish samples gave a good agreement with the certified values. Further validation by recovery study in real fish sample digests and water gave average Cd recoveries of 98.7±1.0% for fish and 92±3% for water with RSD of 1.5% for fish and 4% for water, respectively. PMID:25770618

Zhang, Yanlin; Adeloju, Samuel B

2015-05-01

125

COMBUSTION DRIVEN ATOMIC FLUORINE GENERATORS FOR DF CHEMICAL LASERS Abstract -Conventional high pressure corabustors delivering atomic fluorine for DF chemical  

E-print Network

COMBUSTION DRIVEN ATOMIC FLUORINE GENERATORS FOR DF CHEMICAL LASERS Abstract - Conventional high pressure corabustors delivering atomic fluorine for DF chemical lasers have been designed and tested been obtained between the maximum laser power and the predicted best conditions of atomic fluorine

Paris-Sud XI, Université de

126

Four-level atom interferometer with trichromatic laser fields  

SciTech Connect

A four-level atom interferometer comprised of three excited states and one ground state with trichromatic fields coupled between them is investigated using Zeeman sublevels of {sup 3}P{sub 1} and {sup 1}S{sub 0} states of a calcium atom. A theoretical description of the interaction of four-level atoms with trichromatic laser fields is presented and compared with the experimental results of the interference fringes which are generated by the three excited states.

Honda, Kazuhito; Kobayashi, Yoshiyuki; Morinaga, Atsuo [Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda-shi, Chiba 278-8510 (Japan)

2007-02-15

127

Cold Collisions between Laser-Cooled Magnesium Atoms  

Microsoft Academic Search

Light-assisted inelastic cold collisions are the main loss process for neutral atoms trapped and laser cooled in magneto-optical traps. Alkaline earth atoms do not have hyperfine structure, which is expected to make the comparison between theoretical predictions and experimental results much easier, compared to the case of alkali-metal atoms. We present here a numerical calculation for the loss rates in

Kalle-Antti Suominen; Mette Machholm; Paul S. Julienne

2001-01-01

128

Plateau Effects in Laser-Assisted Electron-Atom Scattering  

Microsoft Academic Search

A quasienergy state analysis of electron-atom scattering in an intense, elliptically-polarized laser field is presented, modeling the atom by a zero-range potential. We obtain exact analytic expressions for the differential cross section dsigman for electron scattering with emission or absorption of n-photons [1]. Well-known approximate results [2] follow from our exact results in the limit that the atomic potential is

M. V. Frolov; Anthony F. Starace; A. V. Flegel; N. L. Manakov

2003-01-01

129

Solar-simulator-pumped atomic iodine laser kinetics  

NASA Technical Reports Server (NTRS)

The literature contains broad ranges of disagreement in kinetic data for the atomic iodine laser. A kinetic model of a solar-simulator-pumped iodine laser is used to select those kinetic data consistent with recent laser experiments at the Langley Research Center. Analysis of the solar-simulator-pumped laser experiments resulted in the following estimates of rate coefficients: for alkyl radical (n-C3F7) and atomic iodine (I) recombination, 4.3 x 10 to the 11th power (1.9) + or - cu cm/s; for n-C3F7I stabilized atomic iodine recombination (I + I) 3.7 x 10 to the -32nd power (2.3) + or -1 cm to the 6th power/s; and for molecular iodine (I2) quenching, 3.1 x 10 to the -11th power (1.6) + or - 1 cu cm/s. These rates are consistent with the recent measurements.

Wilson, H. W.; Raju, S.; Shiu, Y. J.

1983-01-01

130

Laser Assisted Free-Free Transition in Electron - Atom Collision  

NASA Technical Reports Server (NTRS)

Free-free transition is studied for electron-Hydrogen atom system in ground state at very low incident energies in presence of an external homogeneous, monochromatic and linearly polarized laser field. The incident electron is considered to be dressed by the laser in a non perturbative manner by choosing the Volkov solutions in both the channels. The space part of the scattering wave function for the electron is solved numerically by taking into account the effect of electron exchange, short range as well as of the long range interactions. Laser assisted differential as well as elastic total cross sections are calculated for single photon absorption/emission in the soft photon limit, the laser intensity being much less than the atomic field intensity. A strong suppression is noted in the laser assisted cross sections as compared to the field free situations. Significant difference is noted in the singlet and the triplet cross sections.

Sinha, C.; Bhatia, A. K.

2011-01-01

131

hal-00195321,version2-9Jan2008 Guided atom laser : a new tool for guided atom optics  

E-print Network

hal-00195321,version2-9Jan2008 Guided atom laser : a new tool for guided atom optics J. Billy, V: January 9, 2008) Abstract We present a guided atom laser. A Bose-Einstein condensate (BEC) is created in a crossed hybrid magnetic and an elongated optical trap, which acts as a matterwave guide. Atoms

Paris-Sud XI, Université de

132

An output coupler for Bose condensed atoms The observations of BEC have stimulated interest in atom lasers, coherent sources of  

E-print Network

An output coupler for Bose condensed atoms The observations of BEC have stimulated interest in atom lasers, coherent sources of atomic matter waves. The build-up of atoms in the ground state of a magnetic. We demonstrated a scheme for doing this with Bose condensed atoms [1]. A variable fraction of atoms

133

Infiltrating a thin or single-layer opal with an atomic vapour: Sub-Doppler signals and crystal optics  

NASA Astrophysics Data System (ADS)

Artificial thin glass opals can be infiltrated with a resonant alkali-metal vapour, providing novel types of hybrid systems. The reflection at the interface between the substrate and the opal yields a resonant signal, which exhibits sub-Doppler structures in linear spectroscopy for a range of oblique incidences. This result is suspected to originate in an effect of the three-dimensional confinement of the vapour in the opal interstices. It is here extended to a situation where the opal is limited to a few- or even a single-layer opal film, which is a kind of bidimensional grating. We have developed a flexible one-dimensional layered optical model, well suited for a Langmuir-Blodgett opal. Once extended to the case of a resonant infiltration, the model reproduces quick variations of the lineshape with incidence angle or polarization. Alternately, for an opal limited to a single layer of identical spheres, a three-dimensional numerical calculation was developed. It predicts crystalline anisotropy, which is demonstrated through diffraction on an empty opal made of a single layer of polystyrene spheres.

Moufarej, Elias; Maurin, Isabelle; Zabkov, Ilya; Laliotis, Athanasios; Ballin, Philippe; Klimov, Vasily; Bloch, Daniel

2014-10-01

134

Cold Atoms and Stable Lasers: The Clocks of the Future Today  

E-print Network

Cold Atoms and Stable Lasers: The Clocks of the Future Today Leo Hollberg National Institute laser and length metrology Richard Fox #12;Types of Clocks Ruler Clock Decay Stable Oscillator Atomic 158 Counter Generic Atomic Clock Atoms #12;Atomic Beam Clock Ramsey Method Cs Signal # of Atoms d

Van Stryland, Eric

135

Automated continuous monitoring of inorganic and total mercury in wastewater and other waters by flow-injection analysis and cold-vapour atomic absorption spectrometry  

PubMed Central

An automated continuous monitoring system for the determination of inorganic and total mercury by flow-injection analysis followed by cold-vapour atomic absorption spectrometry is described. The method uses a typical flow-injection manifold where digestion and reduction of the injected sample takes place. Mercury is removed by aeration from the flowing stream in a specially designed air-liquid separator and swept into a silica cell for absorption measurement at a wavelength of 253.7 nm. A calibration curve up to 10 ?g Hg ml-1 using three different path length cells is obtained with a detection limit of 0.02 ?g Hg ml-1. The sampling rate of an injection every 3 min produces 20 results per hour from a flowing stream. PMID:18925201

Birnie, S. E.

1988-01-01

136

Recirculation of Laser Power in an Atomic Fountain  

NASA Technical Reports Server (NTRS)

A new technique for laser-cooling atoms in a cesium atomic fountain frequency standard relies on recirculation of laser light through the atom-collection region of the fountain. The recirculation, accomplished by means of reflections from multiple fixed beam-splitter cubes, is such that each of two laser beams makes three passes. As described below, this recirculation scheme offers several advantages over prior designs, including simplification of the laser system, greater optical power throughput, fewer optical and electrical connections, and simplification of beam power balancing. A typical laser-cooled cesium fountain requires the use of six laser beams arranged as three orthogonal pairs of counter-propagating beams to decelerate the atoms and hold them in a three-dimensional optical trap in vacuum. Typically, these trapping/cooling beams are linearly polarized and are positioned and oriented so that (1) counter-propagating beams in each pair have opposite linear polarizations and (2) three of the six orthogonal beams have the sum of their propagation directions pointing up, while the other three have the sum of their propagation directions pointing down. In a typical prior design, two lasers are used - one to generate the three "up" beams, the other to generate the three "down" beams. For this purpose, the output of each laser is split three ways, then the resulting six beams are delivered to the vacuum system, independently of each other, via optical fibers. The present recirculating design also requires two lasers, but the beams are not split before delivery. Instead, only one "up" beam and one oppositely polarized "down" beam are delivered to the vacuum system, and each of these beams is sent through the collection region three times. The polarization of each beam on each pass through the collection region is set up to yield the same combination of polarization and propagation directions as described above. In comparison with the prior design, the present recirculating design utilizes the available laser light more efficiently, making it possible to trap more atoms at a given laser power or the same number of atoms at a lower laser power. The present design is also simpler in that it requires fewer optical fibers, fiber couplings, and collimators, and fewer photodiodes for monitoring beam powers. Additionally, the present design alleviates the difficulty of maintaining constant ratios among power levels of the beams within each "up" or "down" triplet.

Enzer, Daphna G.; Klipstein, WIlliam M.; Moore, James D.

2007-01-01

137

Miniature laser-pumped cesium cell atomic clock oscillator  

Microsoft Academic Search

Our approach to a low-power compact atomic oscillator is based on the use of a diode laser to excite a small cell (~0.1 cm3) containing cesium vapor and buffer gases. Laser wavelength and power are controlled solely with current and temperature, providing a compact, low-power, rugged, spectrally-pure, collimated optical source. A succession of physics packages, when operated with analog laboratory

P. J. Chantry; I. Liberman; W. R. Verbanets; C. F. Petronio; R. L. Cather; W. D. Partlow

1996-01-01

138

Search for electron EDM with laser cooled radioactive atom  

NASA Astrophysics Data System (ADS)

The permanent electric dipole moment (EDM) of the elementary particle has the sensitivity to the CP violation in the theories beyond the standard model (SM). The search for the EDM constitutes the stringent test to discriminate between the SM and beyond it. We plan to perform the electron EDM search by using the laser cooled francium (Fr) atom which has the largest enhancement factor of the electron EDM in the alkali atoms. In this paper, the present status of the laser cooled Fr factory that is being constructed at Cyclotron and Radioisotope Center (CYRIC), Tohoku University are reported.

Inoue, T.; Arikawa, H.; Ezure, S.; Harada, K.; Hayamizu, T.; Ishikawa, T.; Itoh, M.; Kato, T.; Kawamura, H.; Nataraj, H. S.; Sato, T.; Aoki, T.; Furukawa, T.; Hatakeyama, A.; Hatanaka, K.; Imai, K.; Murakami, T.; Shimizu, Y.; Wakasa, T.; Yoshida, H. P.; Sakemi, Y.

2013-05-01

139

Cold-atom dynamics in crossed-laser-beam waveguides  

SciTech Connect

We study the dynamics of neutral cold atoms in an L-shaped crossed-beam optical waveguide formed by two perpendicular red-detuned lasers of different intensities and a blue-detuned laser at the corner. The motion in one sense is optimized, and the motion in the other sense may be suppressed even if it is energetically allowed. Quantum and classical simulations are performed and give similar results. Complemented with a vibrational cooling process we find a range of parameters for which this setting works as a one-way device or 'atom diode'.

Torrontegui, E.; Muga, J. G. [Departamento de Quimica-Fisica, Universidad del Pais Vasco - Euskal Herriko Unibertsitatea, Apartado 644, E-48080 Bilbao (Spain); Echanobe, J. [Departamento de Ingenieria Electronica, Universidad del Pais Vasco - Euskal Herriko Unibertsitatea, Apartado 644, E-48080 Bilbao (Spain); Ruschhaupt, A. [Institut fuer Theoretische Physik, Leibniz Universitaet Hannover, Appelstrasse 2, D-30167 Hannover (Germany); Guery-Odelin, D. [Laboratoire Collisions Agregats Reactivite, CNRS UMR 5589, IRSAMC, Universite Paul Sabatier, 118 Route de Narbonne, F-31062 Toulouse CEDEX 4 (France)

2010-10-15

140

Continuous beam of laser-cooled Yb atoms  

NASA Astrophysics Data System (ADS)

We demonstrate the launching of laser-cooled Yb atoms in a continuous atomic beam. The continuous cold beam has significant advantages over the more-common pulsed fountain, which was also demonstrated by us recently. The cold beam is formed in the following steps: i) atoms from a thermal beam are first Zeeman-slowed to a small final velocity; ii) the slowed atoms are captured in a two-dimensional magneto-optic trap (2D-MOT); and iii) atoms are launched continuously in the vertical direction using two sets of moving-molasses beams, inclined at ±15° to the vertical. The cooling transition used is the strongly allowed {^1S}_0 \\rightarrow {^1P}_1 transition at 399 nm. We capture about 7 × 106 atoms in the 2D-MOT, and then launch them with a vertical velocity of 13 m/s at a longitudinal temperature of 125(6) mK.

Rathod, K. D.; Singh, Alok K.; Natarajan, Vasant

2013-05-01

141

Laser-induced nonresonant nuclear excitation in muonic atoms  

E-print Network

Coherent nuclear excitation in strongly laser-driven muonic atoms is calculated. The nuclear transition is caused by the time-dependent Coulomb field of the oscillating charge density of the bound muon. A closed-form analytical expression for electric multipole transitions is derived and applied to various isotopes; the excitation probabilities are in general very small. We compare the process with other nuclear excitation mechanisms through coupling with atomic shells and discuss the prospects to observe it in experiment.

A. Shahbaz; C. Müller; T. J. Buervenich; C. H. Keitel

2008-12-13

142

Collisions of cold magnesium atoms in a weak laser field  

Microsoft Academic Search

We use quantum scattering methods to calculate the light-induced collisional loss of laser-cooled and trapped magnesium atoms for detunings up to 30 atomic linewidths to the red of the 1S0-1P1 cooling transition. Magnesium has no hyperfine structure to complicate the theoretical studies. We evaluate both the radiative and nonradiative mechanisms of trap loss. The radiative escape mechanism via allowed 1Sigmau

Mette Machholm; Paul S. Julienne; Kalle-Antti Suominen

1999-01-01

143

Sub-Doppler laser cooling of potassium atoms  

NASA Astrophysics Data System (ADS)

We investigate the sub-Doppler laser cooling of bosonic potassium isotopes, whose small hyperfine splitting has so far prevented cooling below the Doppler temperature. We find instead that the combination of a dark optical molasses scheme that naturally arises in this kind of system and an adiabatic ramping of the laser parameters allows us to reach sub-Doppler temperatures for small laser detunings. We demonstrate temperatures as low as 25±3 ?K and 47±5 ?K in high-density samples of the two isotopes 39K and 41K, respectively. Our findings should find application to other atomic systems.

Landini, M.; Roy, S.; Carcagní, L.; Trypogeorgos, D.; Fattori, M.; Inguscio, M.; Modugno, G.

2011-10-01

144

Injection locking of a high power ultraviolet laser diode for laser cooling of ytterbium atoms  

E-print Network

We developed a high-power laser system at a wavelength of 399 nm for laser cooling of ytterbium atoms with ultraviolet laser diodes. The system is composed of an external cavity laser diode providing frequency stabilized output at a power of 40 mW and another laser diode for amplifying the laser power up to 220 mW by injection locking. The systematic method for optimization of our injection locking can also be applied to high power light sources at any other wavelengths. Our system, which does not depend on complex nonlinear frequency-doubling, has great importance for implementing transportable optical lattice clocks, and is also useful for investigations on condensed matter physics or quantum information processing using cold atoms.

Toshiyuki Hosoya; Martin Miranda; Ryotaro Inoue; Mikio Kozuma

2014-12-02

145

Recoil-induced gain and collective atomic recoil laser  

NASA Astrophysics Data System (ADS)

Recoil-induced resonances have been observed in pump-probe spectroscopy with cold atoms. On the other hand, a model for collective atomic recoil laser has been developed by R. Bonifacio and co-workers. These two systems rely on the recoil effect due to the absorption or the emission of a photon by an atom and share may features. In this paper, we shall investigate the relationship between the two models and clarify the underlying physics. We'll review also the experimental results.

Verkerk, Philippe

1998-07-01

146

Collisions of cold magnesium atoms in a weak laser field  

E-print Network

We use quantum scattering methods to calculate the light-induced collisional loss of laser-cooled and trapped magnesium atoms for detunings up to 30 atomic linewidths to the red of the 1S_0-1P_1 cooling transition. Magnesium has no hyperfine structure to complicate the theoretical studies. We evaluate both the radiative and nonradiative mechanisms of trap loss. The radiative escape mechanism via allowed 1Sigma_u excitation is dominant for more than about one atomic linewidth detuning. Molecular vibrational structure due to photoassociative transitions to bound states begins to appear beyond about ten linewidths detuning.

Machholm, M; Suominen, K A; Machholm, Mette; Julienne, Paul S.; Suominen, Kalle-Antti

1999-01-01

147

Guiding cold atoms in a hollow laser beam  

NASA Astrophysics Data System (ADS)

The theory of atom guiding in a far blue-detuned hollow laser beam (HLB) is developed for the dipole interaction scheme described by a three-level ? model. The complete kinetic description of atomic motion based on the Fokker-Planck equation for the atomic distribution function is presented. The dipole gradient force, radiation pressure force, and momentum diffusion tensor are then derived. It is found that even for a far-detuned laser beam, the optical potential for a three-level ? atom is not generally reduced to a sum of two independent potentials associated with the two two-level interactions in the ? scheme. The theory developed here is also compared with the experimental guiding of cold 85Rb atoms in the HLB. The experimental results are found to be in good agreement with the Monte Carlo simulations based on the three-level ? model. We observe that the guiding efficiency depends strongly on the intensity and the detuning of the HLB and the initial temperature of atoms. In particular, the experimental results show that, at small detunings, the guiding efficiency is deteriorated strongly by the radiation pressure force. The Monte Carlo simulations also indicate that the efficiency of guiding versus detuning depends strongly on the direction of the HLB propagation with respect to that of atomic motion. Under optimal conditions, the guiding efficiency was found to be about 20%.

Xu, Xinye; Minogin, V. G.; Lee, Kwanil; Wang, Yuzhu; Jhe, Wonho

1999-12-01

148

Intensity-resolved Above Threshold Ionization Yields of Atoms with Ultrashort Laser Pulses  

E-print Network

The above threshold ionization (ATI) spectra provide a diversity of information about a laser-atom ionization process such as laser intensity, pulse duration, carrier envelope phase, and atomic energy level spacing. However, the spatial distribution...

Hart, Nathan Andrew

2012-10-19

149

Atomic vapor laser isotope separation using resonance ionization  

Microsoft Academic Search

Atomic vapor laser isotope separation (AVLIS) is a general and powerful technique. A major present application to the enrichment of uranium for light-water power-reactor fuel has been under development for over 10 years. In June 1985, the Department of Energy announced the selection of AVLIS as the technology to meet the nation's future need for enriched uranium. Resonance photoionization is

B. Comaskey; J. Crane; G. Erbert; C. Haynam; M. Johnson; J. Morris; J. Paisner; R. Solarz; E. Worden

1986-01-01

150

Experiments on a semiconductor laser pumped rubidium atomic clock  

Microsoft Academic Search

Experiments designed to improve the performance of a commercial Rb-87 atomic clock by using a semiconductor laser are described. Two resonance gas cells were compared: gas cell A (natural Rb and buffer gases) and gas cell B (Rb-87 and buffer gases). Although the values of the highest microwave frequency stability obtained by using these cells were very similar, the magnitudes

Minoru Hashimoto; Motoichi Ohtsu

1987-01-01

151

Rescattering effects in laser-assisted electron–atom bremsstrahlung  

NASA Astrophysics Data System (ADS)

Rescattering effects in non-resonant spontaneous laser-assisted electron–atom bremsstrahlung (LABrS) are analyzed within the framework of time-dependent effective-range (TDER) theory. It is shown that high energy LABrS spectra exhibit rescattering plateau structures that are similar to those that are well-known in strong field laser-induced processes as well as those that have been predicted theoretically in laser-assisted collision processes. In the limit of a low-frequency laser field, an analytic description of LABrS is obtained from a rigorous quantum analysis of the exact TDER results for the LABrS amplitude. This amplitude is represented as a sum of factorized terms involving three factors, each having a clear physical meaning. The first two factors are the exact field-free amplitudes for electron–atom bremsstrahlung and for electron–atom scattering, and the third factor describes free electron motion in the laser field along a closed trajectory between the first (scattering) and second (rescattering) collision events. Finally, an extension of these TDER results to the case of LABrS in a Coulomb field is discussed.

Zheltukhin, A. N.; Flegel, A. V.; Frolov, M. V.; Manakov, N. L.; Starace, Anthony F.

2015-04-01

152

Rescattering effects in laser-assisted electron-atom bremsstrahlung  

E-print Network

Rescattering effects in nonresonant spontaneous laser-assisted electron-atom bremsstrahlung (LABrS) are analyzed within the framework of time-dependent effective-range (TDER) theory. It is shown that high energy LABrS spectra exhibit rescattering plateau structures that are similar to those that are well-known in strong field laser-induced processes as well as those that have been predicted theoretically in laser-assisted collision processes. In the limit of a low-frequency laser field, an analytic description of LABrS is obtained from a rigorous quantum analysis of the exact TDER results for the LABrS amplitude. This amplitude is represented as a sum of factorized terms involving three factors, each having a clear physical meaning. The first two factors are the exact field-free amplitudes for electron-atom bremsstrahlung and for electron-atom scattering, and the third factor describes free electron motion in the laser field along a closed trajectory between the first (scattering) and second (rescattering) co...

Zheltukhin, A N; Frolov, M V; Manakov, N L; Starace, Anthony F

2015-01-01

153

Rescattering effects in laser-assisted electron-atom bremsstrahlung  

E-print Network

Rescattering effects in nonresonant spontaneous laser-assisted electron-atom bremsstrahlung (LABrS) are analyzed within the framework of time-dependent effective-range (TDER) theory. It is shown that high energy LABrS spectra exhibit rescattering plateau structures that are similar to those that are well-known in strong field laser-induced processes as well as those that have been predicted theoretically in laser-assisted collision processes. In the limit of a low-frequency laser field, an analytic description of LABrS is obtained from a rigorous quantum analysis of the exact TDER results for the LABrS amplitude. This amplitude is represented as a sum of factorized terms involving three factors, each having a clear physical meaning. The first two factors are the exact field-free amplitudes for electron-atom bremsstrahlung and for electron-atom scattering, and the third factor describes free electron motion in the laser field along a closed trajectory between the first (scattering) and second (rescattering) collision events. Finally, a generalization of these TDER results to the case of LABrS in a Coulomb field is discussed.

A. N. Zheltukhin; A. V. Flegel; M. V. Frolov; N. L. Manakov; Anthony F. Starace

2015-02-01

154

Heteronuclear collisions between laser-cooled metastable neon atoms  

E-print Network

We investigate heteronuclear collisions in isotope mixtures of laser-cooled metastable 3P2 neon. Experiments are performed with spin-polarized atoms in a magnetic trap for all two-isotope combinations of the stable neon isotopes 20Ne, 21Ne, and 22Ne. We determine the rate coefficients for heteronuclear ionizing collisions to beta_{21,20}=(3.9+/-2.7) x 10^{-11} cm^3/s, beta_{22,20}=(2.6+/-0.7) x 10^{-11} cm^3/s, and beta_{21,22}=(3.9+/-1.9) x 10^{-11} cm^3/s. We also study heteronuclear elastic collision processes and give upper bounds for heteronuclear thermal relaxation cross sections. This work significantly extends the limited available experimental data on heteronuclear ionizing collisions for laser-cooled atoms involving one or more rare gas atoms in a metastable state.

Jan Schütz; Thomas Feldker; Holger John; Gerhard Birkl

2012-08-28

155

Development of a chemical oxygen - iodine laser with production of atomic iodine in a chemical reaction  

SciTech Connect

The alternative method of atomic iodine generation for a chemical oxygen - iodine laser (COIL) in chemical reactions with gaseous reactants is investigated experimentally. The influence of the configuration of iodine atom injection into the laser cavity on the efficiency of the atomic iodine generation and small-signal gain is studied. (lasers)

Censky, M; Spalek, O; Jirasek, V; Kodymova, J [Institute of Physics, Czech Academy of Sciences, Prague (Czech Republic); Jakubec, I [Institute of Inorganic Chemistry, Czech Academy of Sciences, Rez (Czech Republic)

2009-11-30

156

Dual-wavelength laser source for onboard atom interferometry V. Menoret1,  

E-print Network

Dual-wavelength laser source for onboard atom interferometry V. M´enoret1, , R. Geiger1,4 , G present a compact and stable dual-wavelength laser source for onboard atom interferometry with two laser source for onboard atom inter- ferometry with two species. It is based on two telecom Distributed

Paris-Sud XI, Université de

157

A Scheme of Generating and Spatially Separating Two-Component Entangled Atom Lasers  

E-print Network

Entanglement of remote atom lasers is obtained via quantum state transfer technique from lights to matter waves in a five-level $M$-type system. The considered atom-atom collisions can yield an effective Kerr susceptibility for this system and lead to the self- and cross- phase modulation between the two output atom lasers. This effect results in generation of entangled states of output fields. Particularly, under different conditions of space-dependent control fields, the entanglement of atom lasers and of atom-light fields can be obtained, respectively. Furthermore, based on the Bell-state measurement, an useful scheme is proposed to spatially separate the generated entangled atom lasers.

Xiong-Jun Liu; Hui Jing; Xin Liu; Ming-Sheng Zhan; Mo-Lin Ge

2005-11-14

158

Laser separation of uranium chosen for scaleup. [Atomic vapor laser isotope separation, molecular laser isotope separation, and plasma separation process  

Microsoft Academic Search

Atomic vapor laser isotope separation (AVLIS) has been selected by the Department of Energy to go into large-scale engineering development and demonstration over two other advanced technologies, molecular laser isotope separation and plasma separation. DOE will continue to support development of another uranium enrichment technology, gas centrifugation. By or around 1990, the most promising gas centrifuge technique will be compared

Rawls

1982-01-01

159

Laser separation of uranium chosen for scaleup. [Atomic vapor laser isotope separation, molecular laser isotope separation plasma separation process  

Microsoft Academic Search

Atomic vapor laser isotope separation (AVLIS) has been selected by the Department of Energy to go into large-scale engineering development and demonstration over two other advanced technologies, molecular laser isotope separation and plasma separation. DOE will continue to support development of another uranium enrichment technology, gas centrifugation. By or around 1990, the most promising gas centrifuge technique will be compared

Rawls

1982-01-01

160

Cs 728 nm Laser Spectroscopy and Faraday Atomic Filter  

NASA Astrophysics Data System (ADS)

We mainly present the 728 nm laser spectroscopy and Faraday atomic filter of Cs atoms with 650 MHz linewidth and 2.6% transmission based on an electrodeless discharge vapor lamp, compared with Rb 728 nm laser spectroscopy. Accidentally, this remarkably strong Cs 728 nm transition from the 6F7/2 state to the 5D5/2 state is only about 2.5 GHz away from the Rb 728 nm transition of the future potential four-level active optical clock, once laser cooled and trapped from the 7S1/2 state to the 5P1/2 state, as we proposed previously. A Faraday atomic filter stabilized 728 nm laser using a Cs electrodeless discharge vapor lamp with a power of 10mW will provide a frequency reference to evaluate the performance of the potential Rb four-level active optical clock at 728 nm with power less than 1 nW by 2.5 GHz heterodyne measurements.

Liu, Zhong-Zheng; Tao, Zhi-Ming; Jiang, Zhao-Jie; Chen, Jing-Biao

2014-12-01

161

Laser cooling of a magnetically guided ultracold atom beam  

NASA Astrophysics Data System (ADS)

We report on the transverse laser cooling of a magnetically guided beam of ultracold chromium atoms. Radial compression by a tapering of the guide is employed to adiabatically heat the beam. Inside the tapered section, heat is extracted from the atom beam by a two-dimensional (2D) optical molasses perpendicular to it, resulting in a significant increase in atomic phase space density. A magnetic offset field is applied to prevent optical pumping to untrapped states. Our results demonstrate that, by a suitable choice of the magnetic offset field, the cooling beam intensity and detuning, atom losses and longitudinal heating can be avoided. Final temperatures below 65 ?K have been achieved, corresponding to an increase in phase space density in the guided beam by more than a factor of 30.

Aghajani-Talesh, A.; Falkenau, M.; Volchkov, V. V.; Trafford, L. E.; Pfau, T.; Griesmaier, A.

2010-06-01

162

Velocity measurements by laser resonance fluorescence. [single atom diffusional motion  

NASA Technical Reports Server (NTRS)

The photonburst correlation method was used to detect single atoms in a buffer gas. Real time flow velocity measurements with laser induced resonance fluorescence from single or multiple atoms was demonstrated and this method was investigated as a tool for wind tunnel flow measurement. Investigations show that single atoms and their real time diffusional motion on a buffer gas can be measured by resonance fluorescence. By averaging over many atoms, flow velocities up to 88 m/s were measured in a time of 0.5 sec. It is expected that higher flow speeds can be measured and that the measurement time can be reduced by a factor of 10 or more by careful experimental design. The method is clearly not ready for incorporation in high speed wind tunnels because it is not yet known whether the stray light level will be higher or lower, and it is not known what detection efficiency can be obtained in a wind tunnel situation.

She, C. Y.; Fairbank, W. M., Jr.

1980-01-01

163

Atomic electron correlations in intense laser fields  

SciTech Connect

This talk examines two distinct cases in strong optical fields where electron correlation plays an important role in the dynamics. In the first example, strong coupling in a two-electron-like system is manifested as an intensity-dependent splitting in the ionized electron energy distribution. This two-electron phenomenon (dubbed continuum-continuum Autler-Townes effect) is analogous to a strongly coupled two-level, one-electron atom but raises some intriguing questions regarding the exact nature of electron-electron correlation. The second case examines the evidence for two-electron ionization in the strong-field tunneling limit. Although their ability to describe the one-electron dynamics has obtained a quantitative level of understanding, a description of the two (multiple) electron ionization remains unclear.

DiMauro, L.F.; Sheehy, B.; Walker, B. [Brookhaven National Lab., Upton, NY (United States); Agostini, P.A. [SPAM, Gif Sur Yvette (France). Centre d`Etudes de Saclay; Kulander, K.C. [Lawrence Livermore National Lab., CA (United States)

1998-11-01

164

Mercury(II) and methyl mercury determinations in water and fish samples by using solid phase extraction and cold vapour atomic absorption spectrometry combination.  

PubMed

A method has been developed for mercury(II) and methyl mercury speciation on Staphylococcus aureus loaded Dowex Optipore V-493 micro-column in the presented work, by using cold vapour atomic absorption spectrometry. Selective and sequential elution with 0.1 molL(-1) HCl for methyl mercury and 2 molL(-1) HCl for mercury(II) were performed at the pH range of 2-6. Optimal analytical conditions including pH, amounts of biosorbent, sample volumes were investigated. The detection limits of the analytes were 2.5 ngL(-1) for Hg(II) and 1.7 ngL(-1) for methyl mercury. The capacity of biosorbent for mercury(II) and methyl mercury was 6.5 and 5.4 mgg(-1), respectively. The validation of the presented procedure is performed by the analysis of standard reference material. The speciation procedure established was successfully applied to the speciation of mercury(II) and methyl mercury in natural water and microwave digested fish samples. PMID:19394391

Tuzen, Mustafa; Karaman, Isa; Citak, Demirhan; Soylak, Mustafa

2009-07-01

165

Blast waves in atomic cluster media using intense laser pulses.  

NASA Astrophysics Data System (ADS)

We report on the progress of experimental and numerical investigations of the dynamics of strong (>Mach 50) blast waves driven by focusing sub-ps laser pulses into an extended medium of atomic clusters. A gas of atomic clusters is an extraordinarily efficient absorber of intense laser light and can be used to create high energy density plasmas with tabletop laser systems. These HED plasmas can launch shocks and strongly radiative blast waves with dimensionless parameters scalable to astrophysical objects such as supernova remnants, and have been used by us in a number of shock evolution and collision studies. To date such experiments have been conducted with modest laser energies of <1J. In order to study processes such as the Vishniac overstability and cooling instability in these systems significantly more input energy may be required due to the weak variation of blast wave velocity with deposited energy Vb E^1/4. We report on the scaling of cluster blast wave experiments to laser energies up 0.5kJ using the Vulcan laser at RAL. An extensive suite of diagnostics including multi-frame optical probe systems, streaked Schlieren imaging and keV imaging and spectroscopy was fielded in order to study the growth of spatial and temporal instabilities. To better match astrophysical scenarios with strong radiative pre-heat of material upstream of the shock an additional radiation field was also introduced using a secondary laser heated gold foil target and grazing incidence XUV guiding structure. This allowed us to compare blast wave propagation into cold versus hot ionized upstream gases. These experimental systems provide a useful test bed against which to benchmark numerical simulations, and have been compared to the 3D magnetoresistive hydrocode GORGON and radiation-hydrodynamics code NYM.

Smith, Roland

2008-04-01

166

Strong-field atomic ionization in elliptically polarized laser fields  

NASA Astrophysics Data System (ADS)

We experimentally investigate strong-field ionization of noble-gas atoms in elliptically polarized laser fields with the Keldysh parameter ? ˜1, which is typical for most current strong-field experiments. Our data show that the single-ionization yields exhibit a rapid decrease with increasing elipticity and, moreover, the decrease becomes more dramatic for lower laser intensity. The experimental results are compared with the simulations of the Ammosov-Delone-Krainov (ADK) theory based on the quasistatic tunneling ionization picture and the strong-field approximation (SFA) theory, which involves the nonadiabatic effect in the tunneling ionization process. Our results show that although both the ADK simulations and the SFA calculations can qualitatively reproduce the experimental results, the SFA calculations are in a better agreement with the experimental data than the ADK simulations, which implies a nonadiabatic effect during strong-field atomic ionization for elliptical polarization with ? ˜1.

Wang, ChuanLiang; Lai, XuanYang; Hu, ZiLong; Chen, YongJu; Quan, Wei; Kang, HuiPeng; Gong, Cheng; Liu, XiaoJun

2014-07-01

167

Strong Field Atomic Dynamics Driven by Shaped Ultrafast Laser Pulses  

NASA Astrophysics Data System (ADS)

We demonstrate coherent control of atomic dynamics in strong laser fields including a phenomenon very similar to electromagnetically induced transparency (EIT) and population transfer in a multilevel system with multiphoton coupling between states. Ultrafast pulse shaping allows us to produce probe and coupling pulses for our EIT measurements with arbitrary intensities and time delays from a single ultrafast laser pulse. We compare our results to more traditional implementations of EIT. In our population transfer measurements we find that sequential population transfer is generally more efficient than adiabatic passage on ultrafast timescales with multiphoton coupling between states. Behind these experiments lies a simple time domain picture which draws upon the atom-field phase evolution in strong fields.

Clow, Stephen; Holscher, Uvo; Trallero, Carlos; Weinacht, Thomas

2009-05-01

168

Effect of Laser Power on Atom Probe Tomography of Silicates  

NASA Astrophysics Data System (ADS)

Atom probe tomography (APT) is an emerging analytical method that has the potential to produce nm-scale spatial resolution of atom positions with ppm-level detection limits. Until recently, APT has been limited to analysis of conducting samples due to the high pulsed electrical fields previously required. The recent development of laser-assisted APT now allows much lower laser powers to be used, opening the door to analysis of geologic minerals. The potential applications are many, ranging from diffusion profiles to the distribution of nano-phases to grain boundary chemical properties. We reported the first analysis of natural olivine using APT last year (Parman et al, 2010). While the spatial resolution was good (nm-scale), the accuracy of the compositional analysis was not. Two of the primary barriers to accurate ion identification in APT are: 1) Specimen overheating - This is caused by the interaction of the laser with the low thermal conductivity insulating specimens. Ions are assumed to have left the surface of the sample at the time the laser is pulsed during the analysis (laser pulse width = 12 ps). If the laser power is too high, the surface remains heated for an appreciable time (greater than 5 ns in some cases) after the laser pulse, causing atoms to field evaporate from the surface well after the laser pulse. Since they hit the detector later than the atoms that were released during the pulse, they are interpreted to be higher mass. Thus overheating appears in the analysis as a smearing of mass/charge peaks to higher mass/charge ratios (thermal tails). For well separated peaks, this is not a substantial problem, but for closely spaced peaks, overheating causes artificial mass interferences. 2) Molecular evaporation or clustering - This is also caused by overheating by the laser. Ideally, atoms are field evaporated individually from the surface of the cylindrical specimen. However, if the absorbed energy is high enough, clusters of atoms will be formed via surface diffusion and subsequently evaporated. Identifying clusters in the TOF data is problematic and may result in uncounted or misidentified ions. This problem appears to be exacerbated in high oxygen content materials like silicates due to the overlap of O+ and O2++. Both of these factors contributed to the high errors on the initial olivine APT analyses. Here, we report the results of using a laser with 100 times lower power than our previous analyses (500 pJ vs. 5 pJ). As expected, this yields a substantial improvement in both overheating and clustering, resulting in improved accuracy of the compositional analyses. In terms of mass resolution, the improvement is observable as a notable decrease in the full peak width at 1/10th peak maximum, from 5 ns to 0.4 ns.

Parman, S. W.; Gorman, B.; Jackson, C.; Cooper, R. F.; Diercks, D.

2011-12-01

169

Ultracold Atom Collisions Probed with Short Laser Pulses  

NASA Astrophysics Data System (ADS)

We have used short laser pulses to examine the process by which two ground state sodium atoms cooled to 0.5 mK in a magnetooptic trap absorb two photons tuned to the atomic 3S arrow 3P transition to produce a molecular ion by associative ionization. The 10 ps pulses are split into two pulses with the second pulse delayed up to T = 12 ns relative to the first. For T < 4 ns we see an enhancement of the ion signal, while for T > 4 ns the signal decays with a time constant of roughly 10 ns. The first laser pulse excites the atom pair at long range to an attractive R-3 potential from the 3S + 3P asymptote. The second pulse promotes the pair to an attractive R-5 potential from the 3P + 3P asymptote, where associative ionization can occur at short internuclear distances. We have simulated the behavior with a conceptually simple yet accurate model that predicts an enhancement of the flux of atoms caused by longer times spent on the intermediate potential.

Jones, Kevin; Fatemi, Fredrik; Lett, Paul

2000-06-01

170

Direct observation of electron emission from the grain boundaries of chemical vapour deposition diamond films by tunneling atomic force microscopy  

NASA Astrophysics Data System (ADS)

The emission of electrons from diamond in vacuum occurs readily as a result of the negative electron affinity of the hydrogenated surface due to features with nanoscale dimensions, which can concentrate electric fields high enough to induce electron emission from them. Electrons can be emitted as a result of an applied electric field (field emission) with possible uses in displays or cold-cathode devices. Alternatively, electrons can be emitted simply by heating the diamond in vacuum to temperatures as low as 350 °C (thermionic emission), and this may find applications in solar energy generation or energy harvesting devices. Electron emission studies usually use doped polycrystalline diamond films deposited onto Si or metallic substrates by chemical vapor deposition, and these films have a rough, faceted morphology on the micron or nanometer scale. Electron emission is often improved by patterning the diamond surface into sharp points or needles, the idea being that the field lines concentrate at the points lowering the barrier for electron emission. However, there is little direct evidence that electrons are emitted from these sharp tips. The few reports in the literature that have studied the emission sites suggested that emission came from the grain boundaries and not the protruding regions. We now present direct observation of the emission sites over a large area of polycrystalline diamond using tunneling atomic force microscopy. We confirm that the emission current comes mostly from the grain boundaries, which is consistent with a model for emission in which the non-diamond phase is the source of electrons with a threshold that is determined by the surrounding hydrogenated diamond surface.

Chatterjee, Vijay; Harniman, Robert; May, Paul W.; Barhai, P. K.

2014-04-01

171

Direct observation of electron emission from the grain boundaries of chemical vapour deposition diamond films by tunneling atomic force microscopy  

SciTech Connect

The emission of electrons from diamond in vacuum occurs readily as a result of the negative electron affinity of the hydrogenated surface due to features with nanoscale dimensions, which can concentrate electric fields high enough to induce electron emission from them. Electrons can be emitted as a result of an applied electric field (field emission) with possible uses in displays or cold-cathode devices. Alternatively, electrons can be emitted simply by heating the diamond in vacuum to temperatures as low as 350?°C (thermionic emission), and this may find applications in solar energy generation or energy harvesting devices. Electron emission studies usually use doped polycrystalline diamond films deposited onto Si or metallic substrates by chemical vapor deposition, and these films have a rough, faceted morphology on the micron or nanometer scale. Electron emission is often improved by patterning the diamond surface into sharp points or needles, the idea being that the field lines concentrate at the points lowering the barrier for electron emission. However, there is little direct evidence that electrons are emitted from these sharp tips. The few reports in the literature that have studied the emission sites suggested that emission came from the grain boundaries and not the protruding regions. We now present direct observation of the emission sites over a large area of polycrystalline diamond using tunneling atomic force microscopy. We confirm that the emission current comes mostly from the grain boundaries, which is consistent with a model for emission in which the non-diamond phase is the source of electrons with a threshold that is determined by the surrounding hydrogenated diamond surface.

Chatterjee, Vijay [School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS (United Kingdom); Department of Physics, Birla Institute of Technology, Mesra, Ranchi 835215 (India); Harniman, Robert; May, Paul W., E-mail: paul.may@bristol.ac.uk [School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS (United Kingdom); Barhai, P. K. [Department of Physics, Birla Institute of Technology, Mesra, Ranchi 835215 (India)

2014-04-28

172

Search for a permanent EDM using laser cooled radioactive atom  

NASA Astrophysics Data System (ADS)

An Electric Dipole Moment (EDM) of the elementary particle is a good prove to observe the phenomena beyond the Standard Model. A non-zero EDM shows the violation of the time reversal symmetry, and under the CPT invariance it means the CP violation. In paramagnetic atoms, an electron EDM results in an atomic EDM enhanced by the factor of the 3rd power of the charge of the nucleus due the relativistic effects. A heaviest alkali element francium (Fr), which is the radioactive atom, has the largest enhancement factor K ~ 895. Then, we are developing a high intensity laser cooled Fr factory at Cyclotron and Radioisotope Center (CYRIC), Tohoku University to perform the search for the EDM of Fr with the accuracy of 10-29 e · cm. The important points to overcome the current accuracy limit of the EDM are to realize the high intensity Fr source and to reduce the systematic error due to the motional magnetic field and inhomogeneous applied field. To reduce the dominant component of the systematic errors mentioned above, we will confine the Fr atoms in the small region with the Magneto-Optical Trap and optical lattice using the laser cooling and trapping techniques. The construction of the experimental apparatus is making progress, and the new thermal ionizer already produces the Fr of ~106 ions/s with the primary beam intensity 200 nA. The developments of the laser system and optical equipments are in progress, and the present status and future plan of the experimental project is reported.

Sakemi, Y.; Harada, K.; Hayamizu, T.; Itoh, M.; Kawamura, H.; Liu, S.; Nataraj, H. S.; Oikawa, A.; Saito, M.; Sato, T.; Yoshida, H. P.; Aoki, T.; Hatakeyama, A.; Murakami, T.; Imai, K.; Hatanaka, K.; Wakasa, T.; Shimizu, Y.; Uchida, M.

2011-07-01

173

Nuclear-driven flashlamp pumping of the atomic iodine laser  

SciTech Connect

This report is a study of the atomic iodine laser pumped with nuclear- excited XeBr fluorescence. Preliminary experiments, conducted in the TRIGA reactor investigated the fluorescence of the excimer XeBr under nuclear pumping with {sup 10}B and {sup 3}He, for use as a flashlamp gas to stimulate the laser. These measurements included a determination of the fluorescence efficiency (light emitted in the wavelength region of interest, divided by energy deposited in the gas) of XeBr under nuclear pumping, with varying excimer mixtures. Maximum fluorescence efficiencies were approximately 1%. In order to better understand XeBr under nuclear excitation, a kinetics model of the system was prepared. The model generated the time-dependant concentrations of 20 reaction species for three pulse sizes, a TRIGA pulse, a fast burst reactor pulse, and an e-beam pulse. The modeling results predicted fluorescence efficiencies significantly higher (peak efficiencies of approximately 10%) than recorded in the fluorescence experiments. The cause of this discrepancy was not fully determined. A ray tracing computer model was also prepared to evaluate the efficiency with which nuclear-induced fluorescence generated in one cavity of a laser could be coupled into another cavity containing an iodine lasant. Finally, an experimental laser cell was constructed to verify that nuclear-induced XeBr fluorescence could be used to stimulate a laser. Lasing was achieved at 1.31 micron in the TRIGA using C{sub 3}F{sub 7}I, a common iodine lasant. Peak laser powers were approximately 20 mW. Measured flashlamp pump powers at threshold agreed well with literature values, as did lasant pressure dependency on laser operation.

Miley, G.H.

1992-03-01

174

Atomic mass dependent electrostatic diagnostics of colliding laser plasma plumes  

SciTech Connect

The behaviours of colliding laser plasma plumes (C{sub p}) compared with single plasma plumes (S{sub p}) are investigated for 14 different atomic mass targets. A Faraday cup, situated at the end of a drift tube (L = 0.99 m), is employed to record the time-of-flight (TOF) current traces for all elements and both plume configurations, for a fixed laser intensity of I{sub p} = 4.2 × 10{sup 10} W cm{sup ?2} (F = 0.25 kJ cm{sup ?2}). The ratio of the peak current from the C{sub p} relative to twice that from the S{sub p} is designated as the peak current ratio while the ratio of the integrated charge yield from the C{sub p} relative to twice that from the S{sub p} is designated as the charge yield ratio. Variation of the position of the Faraday cup within the drift tube (L = 0.33, 0.55, and 0.99 m) in conjunction with a lower laser fluence (F = 0.14 kJ cm{sup ?2}) facilitated direct comparison of the changing TOF traces from both plasma configurations for the five lightest elements studied (C, Al, Si, Ti, and Mn). The results are discussed in the frame of laser plasma hydrodynamic modelling to approximate the critical recombination distance L{sub CR}. The dynamics of colliding laser plasma plumes and the atomic mass dependence trends observed are presented and discussed.

Yeates, P. [National Centre for Plasma Science and Technology (NCPST), Dublin City University (DCU), Dublin 7 (Ireland)] [National Centre for Plasma Science and Technology (NCPST), Dublin City University (DCU), Dublin 7 (Ireland); Fallon, C. [School of Physical Sciences, Dublin City University (DCU), Dublin 7 (Ireland)] [School of Physical Sciences, Dublin City University (DCU), Dublin 7 (Ireland); Kennedy, E. T.; Costello, J. T. [National Centre for Plasma Science and Technology (NCPST), Dublin City University (DCU), Dublin 7 (Ireland) [National Centre for Plasma Science and Technology (NCPST), Dublin City University (DCU), Dublin 7 (Ireland); School of Physical Sciences, Dublin City University (DCU), Dublin 7 (Ireland)

2013-09-15

175

Pilis: Post-ISOCELE laser isobar separation — an apparatus for laser spectroscopic studies of laser-desorbed atoms  

NASA Astrophysics Data System (ADS)

An apparatus for laser spectroscopic studies of laser-desorbed radioactive atoms has been installed on-line at the ISOCELE isotope separator (IPN, Orsay). Mass-separated gold ions were first implanted onto a substrate, and then thermally desorbed by a Nd-YAG laser pulse. A three-step, two-resonance scheme was used to selectively ionize the desorbed gold atoms. The ions created were then mass-identified through a time-of-flight technique. The laser system used has a linewidth of 130 MHz, and an actual experimental resolution of 170 MHz for the stable 197Au was obtained. It has been demonstrated that with 10 10 total implanted ions, several laser scans can be performed, and that a 5 × 10 -5 ion conversion efficiency for the desorbed gold atoms was reached at resonance. On-line measurements of the isotope shift (IS) and hyperfine structure (HFS) for several gold isotopes were carried out. With the high-resolution capability, a negative sign for the magnetic moment of 192Au was obtained. The HFS of 187Au confirms an earlier laser spectroscopic study, and the sudden variation of IS between 187Au and 186Au was reproduced.

Lee, J. K. P.; Savard, G.; Crawford, J. E.; kkadath, G.; Duong, H. T.; Pinard, J.; Liberman, S.; Le Blanc, F.; Kilcher, P.; Obert, J.; Oms, J.; Putaux, J. C.; Roussiére, B.; Sauvage, J.; Isocele Collaboration

1988-08-01

176

APS/123-QED Guided atom laser: transverse mode quality and longitudinal momentum distribution  

E-print Network

APS/123-QED Guided atom laser: transverse mode quality and longitudinal momentum distribution F the outcoupling of a matter wave into a guide by a time-dependent spilling of the atoms from an initially trapped to interactions in the mode quality of a guided atom laser. This study is consistent with recent experimental

177

Laser cooling and trapping of atomic particles. (Latest citations from the NTIS data base). Published Search  

SciTech Connect

The bibliography contains citations concerning theory and experiments on laser cooling and laser trapping of neutral atoms and atomic ions. Atoms and ions are cooled by laser radiation pressure to very low Kelvin temperatures and confined in electromagnetic traps of very high density. Atomic particles discussed include sodium atoms, mercury ions, beryllium ions, magnesium ions, and hydrogen. Applications for high performance spectroscopy, atomic clocks, microwave and optical frequency standards, relativistic neutral particle beam weapons, exotic fuels, cooling of electron beams, and space propulsion are examined. (Contains a minimum of 151 citations and includes a subject term index and title list.)

Not Available

1992-04-01

178

Laser cooling and trapping of atomic particles. (Latest citations from the NTIS bibliographic database). Published Search  

SciTech Connect

The bibliography contains citations concerning theory and experiments on laser cooling and laser trapping of neutral atoms and atomic ions. Atoms and ions are cooled by laser radiation pressure to very low Kelvin temperatures and confined in electromagnetic traps of very high density. Atomic particles cover sodium atoms, mercury ions, beryllium ions, magnesium ions, and hydrogen. Citations discuss applications in high performance spectroscopy, atomic clocks, microwave and optical frequency standards, relativistic neutral particle beam weapons, exotic fuels, cooling of electron beams, and space propulsion. (Contains a minimum of 204 citations and includes a subject term index and title list.)

Not Available

1994-12-01

179

Laser cooling and trapping of atomic particles. (Latest citations from the NTIS bibliographic database). Published Search  

SciTech Connect

The bibliography contains citations concerning theory and experiments on laser cooling and laser trapping of neutral atoms and atomic ions. Atoms and ions are cooled by laser radiation pressure to very low Kelvin temperatures and confined in electromagnetic traps of very high density. Atomic particles cover sodium atoms, mercury ions, beryllium ions, magnesium ions, and hydrogen. Citations discuss applications in high performance spectroscopy, atomic clocks, microwave and optical frequency standards, relativistic neutral particle beam weapons, exotic fuels, cooling of electron beams, and space propulsion. (Contains a minimum of 185 citations and includes a subject term index and title list.)

NONE

1994-02-01

180

Low-threshold short-cavity diode laser for a miniature atomic clock  

SciTech Connect

Short-cavity diode lasers (SCDLs) emitting at the 894-nm D{sub 1} line of caesium are developed. Low threshold currents and power consumption will make it possible to use these lasers in chip-size atomic clocks (CSACs) and magnetometers. The SCDL parameters are comparable with the parameters of surface-emitting lasers. (lasers)

Kargapol'tsev, Sergei V; Velichansky, Vladimir L; Vasil'ev, V V [P.N. Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Kobyakova, M Sh; Morozyuk, A V; Shiryaeva, N V; Konyaev, V P [M.F. Stel'makh Polyus Research and Development Institute, Moscow (Russian Federation)

2009-06-30

181

Optical pumping and laser cooling of magnesium atomic beam in metastable states  

Microsoft Academic Search

Here we report some initial results in the study of optical pumping and laser cooling of metastable Mg atomic beam. Eighty-five percent of optical pumping efficiency and laser cooling effect have been observed. We have successfully used frequency doubled diode laser in the experiments as a velocity analysis light source because diode laser is important for making a practical magnesium

Weiquan Cai; N. Beverini; S. del Tredici; J. V. Gomide; Enrico Maccioni; A. M. Messina; Franco Strumia

1992-01-01

182

Search for permanent EDM using laser cooled Fr atoms  

NASA Astrophysics Data System (ADS)

The existence of a non-zero electric dipole moment (EDM) implies the violation of time reversal symmetry. As the time-reversal symmetry violation predicted by the Standard Model (SM) for the electron EDM is too small to be observed with current experimental techniques and any a non-zero EDM would indicate new physics beyond the SM. The tiny signal from the electron EDM is enhanced in the heavy atoms such as francium (Fr). We are constructing the laser-cooled Fr factory to search for the electron EDM.

Kawamura, Hirokazu; Aoki, T.; Arikawa, H.; Ezure, S.; Furukawa, T.; Harada, K.; Hatakeyama, A.; Hatanaka, K.; Hayamizu, T.; Imai, K.; Inoue, T.; Ishikawa, T.; Itoh, M.; Kato, T.; Murakami, T.; Nataraj, H. S.; Sato, T.; Shimizu, Y.; Wakasa, T.; Yoshida, H. P.; Sakemi, Y.

2013-03-01

183

Research and development prospects for the atomic uranium laser isotope separation process. Research report 442  

Microsoft Academic Search

Research and development activities are being conducted on many aspects of the atomic uranium laser isotope separation process. Extensive laser spectroscopy studies have been made in order to identify attractive multi-step selective ionization schemes. Using low density (10¹° atoms\\/cm³) apparatus, the excited state spectra of atomic uranium have been investigated via multiple step laser excitation and photoionization studies using two,

G. S. Janes; H. K. Forsen; R. H. Levy

1977-01-01

184

Frustrated Quantum Magnetism with Laser-Dressed Rydberg Atoms  

E-print Network

We show how a broad class of lattice spin-1/2 models with angular- and distance-dependent couplings can be realized with cold alkali atoms stored in optical or magnetic trap arrays. The effective spin-1/2 is represented by a pair of atomic ground states, and spin-spin interactions are obtained by admixing van der Waals interactions between fine-structure split Rydberg states with laser light. The strengths of the diagonal spin interactions as well as the "flip-flop", and "flip-flip" and "flop-flop" interactions can be tuned by exploiting quantum interference, thus realizing different spin symmetries. The resulting energy scales of interactions compare well with typical temperatures and decoherence time-scales, making the exploration of exotic forms of quantum magnetism, including emergent gauge theories and compass models, accessible within state-of-the-art experiments.

Alexander W. Glaetzle; Marcello Dalmonte; Rejish Nath; Christian Gross; Immanuel Bloch; Peter Zoller

2014-10-13

185

Ionization of atomic hydrogen by an intense resonant laser pulse  

NASA Astrophysics Data System (ADS)

The ionization of atomic hydrogen by an intense laser field resonant with the transition ls-Spo is studied. The intensity of the field is strong enough to make the Rabi oscillations important. The theoretical treatment of this work is based on a modified form of the Coulomb-Volkov approximation. The decay to the continuum is accounted by coupling the initial and the excited resonant states to the continuum part of the atomic spectrum. A system of integro-differential equations numerically solved is obtained. The results obtained in this work have been tested against the numerical solution of the time-dependent Schrodinger equation. Good agreement has been obtained. ATI peaks splitting related to the Autler-Townes effect is discussed.

Bustamante, M. G.; Rodríguez, V. D.

2009-11-01

186

Ultrarelativistic quasiclassical wave functions in strong laser and atomic fields  

NASA Astrophysics Data System (ADS)

The problem of an ultrarelativistic charge in the presence of an atomic and a plane-wave field is investigated in the quasiclassical regime by including exactly the effects of both fields. Starting from the quasiclassical Green's function obtained by Di Piazza and Milstein [Phys. Lett. B 717, 224 (2012), 10.1016/j.physletb.2012.09.043], the corresponding in- and out-wave functions are derived in the experimentally relevant case of the plane wave counterpropagating with respect to the initial momentum of the particle. The knowledge of these electron wave functions opens the possibility of investigating a variety of problems in strong-field QED, where both the atomic field and the laser field are strong enough to be taken into account exactly from the beginning in the calculations.

Di Piazza, A.; Milstein, A. I.

2014-06-01

187

Frequency tuning of a CW atomic iodine laser via the Zeeman effect  

Microsoft Academic Search

A continuously operating, C3F7I photolytic 1.315-?m atomic iodine laser has been used to make the first precise observations of frequency tuning of an atomic iodine laser by means of the Zeeman effect. Application of a uniform magnetic field to the gain region of the photolytic iodine laser causes the laser to operate at different frequencies as a function of the

M. A. Kelly; J. K. McIver; R. F. Shea; G. D. Hager

1991-01-01

188

Entanglement on macroscopic scales in a resonant-laser-field-excited atomic ensemble  

NASA Astrophysics Data System (ADS)

We show that two groups of slow two-level atoms in a weak resonant laser field are entangled. The considered groups can be separated by a macroscopic distance, and be parts of a larger atomic ensemble. In a dilute regime, for two very distant groups of atoms, in a plane-wave laser beam, we determine the maximum attainable entanglement negativity, and a laser intensity below which they are certainly entangled. They both decrease with increasing distance between the two groups, but increase with enlarging groups sizes. As a consequence, for given laser intensity, far separated groups of atoms are necessarily entangled if they are big enough.

Camalet, S.

2015-03-01

189

A spectrometer on chemical vapour deposition-diamond basis for the measurement of the charge-state distribution of heavy ions in a laser-generated plasma  

SciTech Connect

This article reports on the development and the first applications of a new spectrometer which enables the precise and time-resolved measurement of both the energy loss and the charge-state distribution of ion beams with 10 < Z < 30 at energies of 4-8 MeV/u after their interaction with a laser-generated plasma. The spectrometer is based on five 20 Multiplication-Sign 7 mm{sup 2} large and 20 {mu}m thick polycrystalline diamond samples produced via the Chemical Vapour Deposition (CVD) process and was designed with the help of ion-optical simulations. First experiments with the spectrometer were successfully carried out at GSI using {sup 48}Ca ions at an energy of 4.8 MeV/u interacting with a carbon plasma generated by the laser irradiation of a thin foil target. Owing to the high rate capability and the short response time of the spectrometer, pulsed ion beams with 10{sup 3}-10{sup 4} ions per bunch at a bunch frequency of 108 MHz could be detected. The temporal evolution of the five main charge states of the calcium ion beams as well as the corresponding energy loss values could be measured simultaneously. Due to the outstanding properties of diamond as a particle detector, a beam energy resolution ({Delta}E/E) Almost-Equal-To 0.1% could be reached using the presented experimental method, while a precision of 10% in the energy loss and charge-state distribution data was obtained.

Cayzac, Witold; Frank, Alexander; Schumacher, Dennis; Roth, Markus [Institut fuer Kernphysik, Technische Universitaet Darmstadt, Schlossgartenstr. 9, 64289 Darmstadt (Germany); Blazevic, Abel; Wamers, Felix; Traeger, Michael; Berdermann, Eleni; Voss, Bernd; Hessling, Thomas [GSI Helmholtzzentrum fuer Schwerionenforschung, Planckstr. 1, 64291 Darmstadt (Germany)

2013-04-15

190

Laser-induced fluorescence with an OPO system. Part II: direct determination of lead content in seawater by electrothermal atomization-laser-excited atomic fluorescence (ETA-LEAF).  

PubMed

Fluorescence was induced by coupling a laser with an optical parametric oscillator (OPO) to develop an analytical method for the direct determination of lead content, at ultra-trace level, in seawater by electrothermal atomization-laser-excited atomic fluorescence (ETA-LEAF). The optimization of atomization conditions, laser pulse energy, and mainly temporal parameters allowed us to reach a 3 fg detection limit (0.3 ng L(-1)) despite the low repetition rate of the device. The expected error on predicted concentrations of lead, at trace levels, in seawater was below 15%. PMID:12664183

Le Bihan, A; Lijour, Y; Giamarchi, P; Burel-Deschamps, L; Stephan, L

2003-03-01

191

Atomic fountain of laser-cooled Yb atoms for precision measurements  

SciTech Connect

We demonstrate launching of laser-cooled Yb atoms in a cold atomic fountain. Atoms in a collimated thermal beam are first cooled and captured in a magneto-optical trap (MOT) operating on the strongly allowed {sup 1}S{sub 0}{yields}{sup 1}P{sub 1} transition at 399 nm (blue line). They are then transferred to a MOT on the weakly allowed {sup 1}S{sub 0}{yields}{sup 3}P{sub 1} transition at 556 nm (green line). Cold atoms from the green MOT are launched against gravity at a velocity of around 2.5 m/s using a pair of green beams. We trap more than 10{sup 7} atoms in the blue MOT and transfer up to 70% into the green MOT. The temperature for the odd isotope {sup 171}Yb is {approx}1 mK in the blue MOT, and reduces by a factor of 40 in the green MOT.

Pandey, Kanhaiya; Rathod, K. D.; Singh, Alok K.; Natarajan, Vasant [Department of Physics, Indian Institute of Science, Bangalore 560 012 (India)

2010-10-15

192

Experimental Effects of Atomic Oxygen on the Development of an Electric Discharge Oxygen Iodine Laser  

E-print Network

Experimental Effects of Atomic Oxygen on the Development of an Electric Discharge Oxygen Iodine of the electric discharge iodine laser continues, the role of oxygen atoms downstream of the discharge region of atomic iodine where the O2(a1 ) was produced in a flowing electric discharge. Excess atomic oxygen

Carroll, David L.

193

Linear Stark Effect for a Sulfur Atom in Strong High-Frequency Laser Fields  

NASA Astrophysics Data System (ADS)

Current trends in laser technology have reached the regime of studying atoms stabilized against ionization, going beyond the perturbation theory. In this work, properties of a laser-dressed sulfur atom are examined in this stabilization regime. The electronic structure of a sulfur atom changes dramatically as it interacts with strong high-frequency laser fields. Degenerate molecularlike states are obtained for the ground state triplet of the laser-dressed sulfur atom for high-frequency and moderate intensity laser parameters. The degenerate ground state is obtained for a laser intensity which is smaller by more than one order of magnitude than the intensity required for hydrogen atoms due to many electron screening effects. An infinitesimally weak static field mixes these degenerate states to give rise to asymmetric states with large permanent dipole moments. Hence, a strong linear Stark effect rather than the usual quadratic one is obtained.

Balanarayan, P.; Moiseyev, Nimrod

2013-06-01

194

Optically pumped external-cavity semiconductor lasers for precision spectroscopy and laser cooling of atomic Hg  

NASA Astrophysics Data System (ADS)

We demonstrate the utility of optically pumped semiconductor lasers (OPSLs) in the eld of precision atomic spectroscopy. We have constructed an OPSL for the purpose of laser-cooling and trapping neutral Hg atoms. The OPSL lases at 1015 nm and is frequency quadrupled to provide the trapping light for the ground state cooling transition. We report up to 1.5 W of stable, single-frequency output power with a linewidth of < 70 kHz with active feedback. From the OPSL we generate deep-UV light at 253.7 nm used to form a neutral Hg magneto-optical trap (MOT). We present details of the MOT. We also report initial results for spectroscopy of the 61S0 - 63P0 clock transition in the Hg199 isotope.

Paul, Justin R.; Lytle, Christian R.; Kaneda, Yushi; Moloney, Jerome; Wang, Tsuei-Lian; Jones, R. Jason

2013-02-01

195

Autler-Townes effect for an atom in a 100% amplitude-modulated laser field. I. A dressed-atom approach  

E-print Network

Autler-Townes effect for an atom in a 100% amplitude-modulated laser field. I. A dressed-atom probe field couples this strongly driven transition to a third atomic state. We obtain analytic When a sufficiently intense monochromatic laser field drives a two-level atomic resonance the resonant

Stroud Jr., Carlos R.

196

Laser frequency stabilization using Zeeman effect  

Microsoft Academic Search

We describe a new and easy to handle method to stabilize the laser frequency on an atomic transition. This method, based on Zeeman effect, involves the circular dichroism of an atomic vapour submitted to a magnetic field. It is applied to the frequency stabilization of a single frequency LNA laser on (2 (2 ^3S1-2 ^3P0) helium transition. Nous décrivons une

B. Chéron; H. Gilles; J. Hamel; O. Moreau; H. Sorel

1994-01-01

197

Studies on laser defocusing effects on laser ablation inductively coupled plasma-atomic emission spectrometry using emission signals from a laser-induced plasma  

Microsoft Academic Search

The effect of laser defocusing on analytical performance of laser ablation inductively coupled plasma atomic emission spectrometry (LA-ICP-AES) was studied by varying laser focus conditions with respect to the surface of a low-alloy steel and a powdered sediment pellet. Laser-induced plasma (LIP) and LA-ICP-AES emission signals and LIP excitation temperatures (LIP Tex) were determined and compared for different laser defocus

Masaki Ohata; Yoshihiro Iwasaki; Naoki Furuta; Isaac B. Brenner

2002-01-01

198

Counting radioactive noble gas atoms: Lasers, accelerators or decay counters?  

NASA Astrophysics Data System (ADS)

Radon-220 and Radon-222 in environmental air samples can be measured on-line with high temporal resolution by state-of-the-art alpha counting. Argon-37, Krypton-85 and Argon-39 are measured routinely by low level decay counting using high-pressure gas proportional counters in an underground laboratory. For Krypton-81 decay counting is not possible in environmental samples. Therefore, various attempts have been made to use atom counting techniques for this isotope. Laser Resonance Ionization Spectroscopy was used to count Kr-81 atoms from old groundwater samples. In a more recent study groundwater dating in the Great Artesian Basin in Australia was accomplished using Cyclotron Accelerator Mass Spectroscopy. Collinear Beam Spectroscopy using Photon Burst Detection and Atom Trap Trace Analysis were successfully used to detect both Kr-81 and Kr-85 in natural Kr samples. Most of these new techniques, however, need to be further improved to become routine tools in environmental studies. 2001 American Institute of Physics.

Lehmann, Bernhard E.

2001-08-01

199

Low temperature corneal laser welding investigated by atomic force microscopy  

NASA Astrophysics Data System (ADS)

The structural modifications in the stromal matrix induced by low-temperature corneal laser welding were investigated by atomic force microscopy (AFM). This procedure consists of staining the wound with Indocyanine Green (ICG), followed by irradiation with a near-infrared laser operated at low-power densities. This induces a local heating in the 55-65 °C range. In welded tissue, extracellular components undergo heat-induced structural modifications, resulting in a joining effect between the cut edges. However, the exact mechanism generating the welding, to date, is not completely understood. Full-thickness cuts, 3.5 mm in length, were made in fresh porcine cornea samples, and these were then subjected to laser welding operated at 16.7 W/cm2 power density. AFM imaging was performed on resin-embedded semi-thin slices once they had been cleared by chemical etching, in order to expose the stromal bulk of the tissue within the section. We then carried out a morphological analysis of characteristic fibrillar features in the laser-treated and control samples. AFM images of control stromal regions highlighted well-organized collagen fibrils (36.2 +/- 8.7 nm in size) running parallel to each other as in a typical lamellar domain. The fibrils exhibited a beaded pattern with a 22-39 nm axial periodicity. Laser-treated corneal regions were characterized by a significant disorganization of the intralamellar architecture. At the weld site, groups of interwoven fibrils joined the cut edges, showing structural properties that were fully comparable with those of control regions. This suggested that fibrillar collagen is not denatured by low-temperature laser welding, confirming previous transmission electron microscopy (TEM) observations, and thus it is probably not involved in the closure mechanism of corneal cuts. The loss of fibrillar organization may be related to some structural modifications in some interfibrillar substance as proteoglycans or collagen VI. Furthermore, AFM imaging was demonstrated to be a suitable tool for attaining three-dimensional information on the fibrillar assembly of corneal stroma. The results suggested that AFM analyses of resin-embedded histological sections subjected to chemical etching provide a rapid and cost-effective response, with an imaging resolution that is quite similar to that of TEM.

Matteini, Paolo; Sbrana, Francesca; Tiribilli, Bruno; Pini, Roberto

2009-02-01

200

Request for Support for the Conference on Super Intense Laser Atom Physics  

SciTech Connect

The Conference on Super Intense Laser Atom Physics (SILAP) was held in November 2003 in Dallas, Texas. The venue for the meeting was South Fork Ranch in the outskirts of Dallas. The topics of the meeting included high harmonic generation and attosecond pulse generation, strong field interactions with molecules and clusters, particle acceleration, and relativistic laser atom interactions.

Todd Ditmire

2004-10-21

201

HIGH RESOLUTION OPTICAL SPECTROSCOPY IN NEON USING A TUNABLE LASER AND AN EXCITED ATOMIC BEAM  

E-print Network

L-161 HIGH RESOLUTION OPTICAL SPECTROSCOPY IN NEON USING A TUNABLE LASER AND AN EXCITED ATOMIC BEAM absorption lines of neon have been investigated using a single mode tunable dye laser illuminating an atomic or near U.V.) the method cannot be applied. Neon and other noble gases are examples of this situation

Boyer, Edmond

202

Some Non-Perturbative and Non-Linear Effects in Laser-Atom Interaction  

E-print Network

We show that if the laser is intense enough, it may always ionize an atom or induce transitions between discrete energy levels of the atom, no matter what is its frequency. It means in the quantum transition of an atom interacting with an intense laser of circular frequency $\\omega$, the energy difference between the initial and the final states of the atom is not necessarily being an integer multiple of the quantum energy $\\hbar\\omega$. The absorption spectra become continuous. The Bohr condition is violated. The energy of photoelectrons becomes light intensity dependent in the intense laser photoelectric effect. The transition probabilities and cross sections of photo-excitations and photo-ionizations are laser intensity dependent, showing that these processes cannot be reduced to the results of interactions between the atom and separate individual photons, they are rather the processes of the atom interacting with the laser as a whole. The interaction of photons on atoms are not simply additive. The effects are non-perturbative and non-linear. Some numerical results for processes between hydrogen atom and intense circularly polarized laser, illustrating the non-perturbative and non-linear character of the atom-laser interaction, are given.

Qi-Ren Zhang

2006-08-06

203

Dipole and quadrupole forces exerted on atoms in laser fields: The nonperturbative approach  

NASA Astrophysics Data System (ADS)

Manipulation of cold atoms by lasers has so far been studied solely within the framework of the conventional dipole approximation, and the atom-light interaction has been treated using low order perturbation theory. Laser control of atomic motions has been ascribed exclusively to the corresponding light-induced dipole forces. In this work, we present a general theory to derive the potential experienced by an atom in a monochromatic laser field in a context analogous to the Born-Oppenheimer approximation for molecules in the field-free case. The formulation goes beyond the dipole approximation and gives rise to the field-atom coupling potential terms which so far have not been taken into consideration in theoretical or experimental studies. Contrary to conventional approaches, our method is based upon the many electron Floquet theory and remains valid also for high intensity laser fields (i.e., for a strongly nonperturbative atom-light interaction). As an illustration of the developed theory, we investigate the trapping of cold atoms in optical lattices. We find that for some atoms for specific laser parameters, despite the absence of the dipole force, the laser trapping is still possible due to the electric quadrupole forces. Namely, we show that by using realistic laser parameters one can form a quadrupole optical lattice which is sufficiently strong to trap Ca and Na atoms.

Šindelka, Milan; Moiseyev, Nimrod; Cederbaum, Lorenz S.

2006-11-01

204

Superelastic electron scattering from laser-excited cesium atoms  

SciTech Connect

We present results from a joint experimental and theoretical investigation of superelastic electron scattering from laser-excited Cs atoms in the (6p){sup 2}P{sub 3/2} state. Comparison of the measured pseudo-Stokes parameters P{sub 1}, P{sub 2}, and P{sub 3} and the total degree of polarization P{sup +} for incident energies of 5.5 eV and 13.5 eV, respectively, with theoretical predictions based upon a nonrelativistic convergent close-coupling method and a 24-state semirelativistic Breit-Pauli R-matrix approach indicates that driving channel coupling to convergence for these observables is more important than accounting for relativistic effects.

Slaughter, D. S.; Karaganov, V.; Brunger, M. J.; Teubner, P. J. O. [School of Chemistry, Physics and Earth Sciences, Flinders University, GPO Box 2100, Adelaide, 5001 (Australia); Bray, I. [ARC Centre for Antimatter-Matter Studies, Curtin University, Perth, 6845 (Australia); Bartschat, K. [Department of Physics and Astronomy, Drake University, Des Moines, Iowa 50311 (United States)

2007-06-15

205

Clock Technology Development for the Laser Cooling and Atomic Physics (LCAP) Program  

NASA Technical Reports Server (NTRS)

The Time and Frequency Sciences and Technology Group at Jet Propulsion Laboratory (JPL) has developed a laser cooling capability for flight and has been selected by NASA to support the Laser-Cooling and Atomic Physics (LCAP) program. Current work in the group includes design and development for tee two laser-cooled atomic clock experiments which have been selected for flight on the International Space Station.

Klipstein, W. M.; Thompson, R. J.; Seidel, D. J.; Kohel, J.; Maleki, L.

1998-01-01

206

Production of doubly charged ions in the ionisation of Ba atoms in two laser fields  

SciTech Connect

The production of doubly charged ions is studied upon multiphoton ionisation of Ba atoms exposed simultaneously to two radiation fields: the fundamental radiation of a colour centre laser ({omega} = 8800 - 8880 cm{sup -1}) and its second harmonic. A two-electron mechanism was shown to be responsible for the production of these ions. (interaction of laser radiation with matter. laser plasma)

Bondar', I I; Suran, V V [Department of Physics, Uzhgorod State University, Uzhgorod (Ukraine)

2001-12-31

207

Ordered many-electron motions in atoms and x-ray lasers. [Subpicosecond ultraviolet laser radiation  

SciTech Connect

Subpicosecond ultraviolet laser technology is enabling the exploration of nonlinear atomic interactions with electric field strengths considerably in excess of an atomic unit. As this regime is approached, experiments studying multiple ionization, photoelectron energy spectra, and harmonically produced radiation all exhibit strong nonlinear coupling. Peak total energy transfer rates on the order of approx.2 x 10/sup -4/ W/atom have been observed at an intensity of approx.10/sup 16/ W/cm/sup 2/, and it is expected that energy transfer rates approaching approx.0.1 to 1 W/atom will occur under more extreme conditions for which the ultraviolet electric field E is significantly greater than e/a/sub 0//sup 2/. In this high intensity regime, a wide range of new nonlinear phenomena will be open to study. These will include the possibility of ordered driven motions in atoms, molecules, and plasmas, mechanisms involving collisions, and relativistic processes such as electron-positron pair production. An understanding of these physical interactions may provide a basis for the generation of stimulated emission in the x-ray range. 100 refs., 8 figs.

Rhodes, C.K.

1986-01-01

208

Neutral atomic jet generation by laser ablation of copper targets  

SciTech Connect

This work aimed the obtainment of a neutral atomic jet departing from a plume generated by laser ablation of copper targets. A pair of electrodes together with a transducer pressure sensor was used to study the ablated plume charge composition and also to measure the ion extraction from the plasma plume. The neutral beam was produced with this setup and the relative abundance of neutrals in the plasma was measured, it decreases from 30% to 8% when the laser fluence is varied from 20 J/cm{sup 2} to 32 J/cm{sup 2}. The necessary voltage to completely remove the ions from the plume varied from 10 V to 230 V in the same fluence range. TOF analysis resulted in center of mass velocities between 3.4 and 4.6 km/s, longitudinal temperature in the range from 1 × 10{sup 4} K to 2.4 × 10{sup 4} K and a Mach number of M = 2.36, calculated using purely hydrodynamic expansion approximation.

Matos, J. B. de; Rodrigues, N. A. S. [Department of Physics, Technological Institute for Aeronautics – ITA/DCTA, São José dos Campos, P.O. Box 6050, 12.228-900 Sao Paulo (Brazil); Destro, M. G.; Silveira, C. A. B. da [Photonics Division, Institute for Advanced Studies – IEAv/DCTA, São José dos Campos, P.O. Box 6044, 12.231-970 Sao Paulo (Brazil)

2014-08-15

209

Laser sculpting of atomic sp, sp(2) , and sp(3) hybrid orbitals.  

PubMed

Atomic sp, sp(2) , and sp(3) hybrid orbitals were introduced by Linus Pauling to explain the nature of the chemical bond. Quantum dynamics simulations show that they can be sculpted by means of a selective series of coherent laser pulses, starting from the 1s orbital of the hydrogen atom. Laser hybridization generates atoms with state-selective electric dipoles, opening up new possibilities for the study of chemical reaction dynamics and heterogeneous catalysis. PMID:25257703

Liu, Chunmei; Manz, Jörn; Yang, Yonggang

2015-01-12

210

Radiative collisional heating at the Doppler limit for laser-cooled magnesium atoms  

Microsoft Academic Search

We report Monte Carlo wave function simulation results on cold collisions between magnesium atoms in a strong red-detuned laser field. This is the normal situation, e.g., in magneto-optical traps (MOT). The Doppler limit heating rate due to radiative collisions is calculated for Mg24 atoms in an MOT based on the S01-P11 atomic laser cooling transition. We find that radiative heating

J. Piilo; E. Lundh; K.-A. Suominen

2004-01-01

211

Detection of nickel atom by laser induced fluorescence during carbon nanotube formation in a laser produced plume  

NASA Astrophysics Data System (ADS)

In situ monitoring of catalyst nickel atoms by laser induced fluorescence during carbon nanotube formation in a laser-produced plume was performed at the Johnson Space Center nanotube production laboratory. The results indicate that ablation of nickel and plume dynamics are strongly related to the oven temperature. Nickel atoms have a long lifetime of several milliseconds and have an electronic temperature of at least 1500 K during carbon nanotube formation.

De Boer, G.; Arepalli, S.; Holmes, W.; Nikolaev, P.; Range, C.; Scott, C.

2001-05-01

212

Atomic photoionization with synchronized X-ray and optical lasers  

NASA Astrophysics Data System (ADS)

Photoionization is the dominant processes after the interaction of atoms with photons of short wavelength. New possibilities to obtain dynamical information about this extremely fast process were opened up in the last years due to the development of Free Electron Lasers, such as FLASH in Hamburg and LCLS in Stanford, with their unprecedented characteristics, especially the ultra-short temporal width of the pulses, which can be as short of a few femtoseconds, and the extremely high number of photons per pulse (about 10^12-10^13 photons/pulse) [1,2]. In a series of experiments at FLASH, the combination of XUV FEL radiation and synchronized NIR laser pulses was used to study the Above Threshold Ionization (ATI) in rare gases for the first time in a regime free from unwanted interference effects. Especially, the polarization dependence of the sideband structures in the electron spectra yields detailed insights into the photoionization dynamics, in particular into the distribution of angular momenta for the outgoing electrons [3]. Recent experiments at the LCLS have taken advantage of the very short (2-5fs) pulse durations, which are delivered by this new X-ray Free Electron Laser. This temporal width coincides with the lifetime of core hole states governing the dynamics of the Auger decay, and with the temporal width of one cycle of the electric field in the optical wavelength regime. By applying angle-resolved electron spectroscopy, the KLL Auger decay in atomic Ne was studied after excitation with few-fs X-ray (1 keV) pulses in the presence of an optical (800 nm) dressing field. The experimental spectra are marked by strong interference effects caused by the coherent emission of electrons produced during one cycle of the superimposed optical dressing field, in excellent agreement with recent theoretical work.[4pt] [1] C. Bostedt et al., Nucl. Instrum. Meth. A 601, 108 (2009).[0pt] [2] N. Berrah et al., J. Mod. Opt. 52, 1015 (2010).[0pt] [3] M. Meyer et al., Phys. Rev. Lett. 101, 193002 (2008).[0pt] [4] Y. Ding et al., Phys. Rev. Lett. 102, 254801 (2009).[0pt] [5] A.K. Kazansky, N.M. Kabachnik, J.Phys.B 42, 121002 (2009); 43, 035601 (2010).

Meyer, Michael

2011-06-01

213

Generation of laser-pulse-field harmonics in a gas upon impact ionisation of atoms  

Microsoft Academic Search

The generation of harmonics of a high-power-laser-pulse field in a gas during impact ionisation of atoms by oscillating electrons is studied theoretically. Fields are considered under conditions when the oscillation energy of electrons in the radiation field, remaining nonrelativistic, considerably exceeds the ionisation potential of an atom. In addition, the radiation field was assumed weak compared to the atomic field

M V Kuzelev; A A Rukhadze

2007-01-01

214

VCSEL Laser System for Atomic Clocks Nathan Belcher REU program, College of William and Mary  

E-print Network

VCSEL Laser System for Atomic Clocks Nathan Belcher REU program, College of William and Mary I of my project is to create a prototype atomic clock, and this summer's research has been all about modulation with rf signals, and use in miniature atomic clocks. This paper will describe the theory behind

Novikova, Irina

215

Laser microprobe and resonant laser ablation for depth profile measurements of hydrogen isotope atoms contained in graphite  

Microsoft Academic Search

We measured the depth profile of hydrogen atoms in graphite by laser microprobing combined with resonant laser ablation. Deuterium-implanted graphite was employed for the measurements. The sample was ablated by a tunable laser with a wavelength corresponding to the resonant wavelength of1S-2S of deuterium with two-photon excitation. The ablated deuterium was ionized by a 2 + 1 resonant ionization process.

Masafumi Yorozu; Tatsuya Yanagida; Terunobu Nakajyo; Yasuhiro Okada; Akira Endo

2001-01-01

216

Electron-impact excitation of holmium atoms  

SciTech Connect

The electron-impact excitation of holmium atoms was studied by the method of extended crossing beams. The cross sections and the optical excitation functions were obtained for odd levels of Ho I, including the 22014 cm{sup -1} laser level. Over 99% of the atoms were shown to reside in the ground level prior to collisions with electrons. Also measured were the excitation cross sections for six even levels, which presumably participate in the formation of inversion population in a gas-discharge holmium vapour laser. (laser applications and other topics in quantum electronics)

Smirnov, Yu M [Moscow Power Engineering Institute, Moscow (Russian Federation)

2000-06-30

217

Laser-induced fluorescence detection strategies for sodium atoms and compounds in high-pressure combustors  

NASA Technical Reports Server (NTRS)

A variety of laser-induced fluorescence schemes were examined experimentally in atmospheric pressure flames to determine their use for sodium atom and salt detection in high-pressure, optically thick environments. Collisional energy transfer plays a large role in fluorescence detection. Optimum sensitivity, at the parts in 10 exp 9 level for a single laser pulse, was obtained with the excitation of the 4p-3s transition at 330 nm and the detection of the 3d-3p fluorescence at 818 nm. Fluorescence loss processes, such as ionization and amplified spontaneous emission, were examined. A new laser-induced atomization/laser-induced fluorescence detection technique was demonstrated for NaOH and NaCl. A 248-nm excimer laser photodissociates the salt molecules present in the seeded flames prior to atom detection by laser-induced fluorescence.

Weiland, Karen J. R.; Wise, Michael L.; Smith, Gregory P.

1993-01-01

218

A self-injected, diode-pumped, solid-state ring laser for laser cooling of Li atoms  

E-print Network

We have constructed a solid-state light source for experiments with laser cooled lithium atoms based on a Nd:YVO$_4$ ring laser with second-harmonic generation. Unidirectional lasing, an improved mode selection, and a high output power of the ring laser was achieved by weak coupling to an external cavity which contained the lossy elements required for single frequency operation. Continuous frequency tuning is accomplished by controlling two PZTs in the internal and the external cavities simultaneously. The light source has been utilized to trap and cool fermionic lithium atoms into the quantum degenerate regime.

Miake, Yudai; O'Hara, Kenneth M; Gensemer, Stephen

2015-01-01

219

Charge states of high Z atoms in a strong laser field  

SciTech Connect

We present a numerical solution of the Thomas-Fermi atom in the presence of a static electric field as a model of the adiabatic response of a heavy atom in the presence of a strong laser field. In this semiclassical approach, we calculate the resulting charge state of the atom and its induced dipole moment after the field is turned on. Due to the scaling properties of the Thomas-Fermi approach, the resulting total atomic charge and dipole moment can be expressed as a universal function of the field. We compare our results with recent ionization experiments performed on noble gases using laser fields. 7 refs., 5 figs.

Susskind, S.M.; Valeo, E.J.; Oberman, C.R.; Bernstein, I.B. (Princeton Univ., NJ (USA). Plasma Physics Lab.; Yale Univ., New Haven, CT (USA))

1989-11-01

220

Testing Lorentz Invariance with Laser-Cooled Cesium Atomic Frequency Standards  

NASA Technical Reports Server (NTRS)

This slide presentation reviews the Lorentz invariance testing during the proposed PARCS experiment. It includes information on the primary atomic reference clock in space (PARCS), cesium, laser cooling, and the vision for the future.

Klipstein, William M.

2004-01-01

221

Non-additivity in laser-illuminated many-atom systems.  

PubMed

We show that atoms subject to laser radiation may form a non-additive many-body system on account of their long-range forces, when the atoms are trapped in the vicinity of a fiber with a Bragg grating. When the laser frequency is inside the grating's bandgap but very close to its edge, we find that the range and strength of the laser-induced interaction becomes substantially enhanced, due to the large density of states near the edge, while the competing process of scattering to the fiber is inhibited. The dynamics of the atomic positions in this system conforms to a prominent model of statistical physics which exhibits slow relaxation. This suggests the possibility of using laser-illuminated atoms to study the characteristics of non-additive systems. PMID:24978565

Shahmoon, Ephraim; Mazets, Igor; Kurizki, Gershon

2014-06-15

222

Quantum control of qubits and atomic motion using ultrafast laser pulses  

NASA Astrophysics Data System (ADS)

Pulsed lasers offer significant advantages over continuous wave (CW) lasers in the coherent control of qubits. Here we review the theoretical and experimental aspects of controlling the internal and external states of individual trapped atoms with pulse trains. Two distinct regimes of laser intensity are identified. When the pulses are sufficiently weak that the Rabi frequency ? is much smaller than the trap frequency ? trap, sideband transitions can be addressed and atom-atom entanglement can be accomplished in much the same way as with CW lasers. By contrast, if the pulses are very strong ? ? ? trap, impulsive spin-dependent kicks can be combined to create entangling gates which are much faster than a trap period. These fast entangling gates should work outside of the Lamb-Dicke regime and be insensitive to thermal atomic motion.

Mizrahi, J.; Neyenhuis, B.; Johnson, K. G.; Campbell, W. C.; Senko, C.; Hayes, D.; Monroe, C.

2014-01-01

223

Laser-pumped atomic clock exploiting pressure-broadened optical transitions  

Microsoft Academic Search

The alkali-vapor-cell atomic clock, of either the conventional or the coherent population trapping type, offers one of the most viable approaches to making ultraminiature and chip-scale devices. Unfortunately, this atomic clock suffers from two laser-induced noise processes: conversion of laser phase noise (PM) to amplitude noise (AM) and ac-Stark-shift fluctuations. Here we demonstrate a method for circumventing these problems in

James Camparo; John Coffer; Jeremy Townsend

2005-01-01

224

Determination of the concentrations of magnesium and aluminum in alloys by laser produced atomic emission spectroscopy  

E-print Network

DETERMINATION OF THE CONCENTRATIONS OF MAGNESIUM AND ALUiiINUM IN ALLOYS BY LASER PRODUCED ATOMIC EMISSION SPECTROSCOPY A Thesis by WILLIAM MONROE ASHE Submitted to the Office of Graduate Studies of Texas A&M University in partial... fulfillment of the reqmrements for the degree of MASTER OF SCIENCE December 1997 Major Subject: Physics DETERMINATION OF THE CONCENTRATIONS OF MAGNESIUM AND ALUMINUM ALLOYS BY LASER PRODUCED ATOMIC EMISSION SPECTROSCOPY A Thesis by WILLIAM MONROE ASHE...

Ashe, William Monroe

1997-01-01

225

Strongly correlated growth of Rydberg aggregates in a vapour cell  

E-print Network

The observation of strongly interacting many-body phenomena in gaseous samples typically requires ultracold atomic gases. Here we show that the very strong interaction potentials between Rydberg atoms enable the observation of many body effects in an atomic vapour, even at room temperature. We excite Rydberg atoms in caesium vapour and observe in real-time excitation dynamics far from resonance consistent with the formation of aggregates composed of several 10,000 Rydberg atoms. The experimental observations show qualitative and quantitative agreement with a microscopic theoretical model. Numerical simulations reveal that the strongly correlated growth of the emerging aggregates is reminiscent of soft-matter type systems.

Urvoy, A; Lesanovsky, I; Booth, D; Shaffer, J P; Pfau, T; Löw, R

2014-01-01

226

Direct atomic flux measurement of electron-beam evaporated yttrium with a diode-laser-based atomic absorption monitor at 668 nm  

E-print Network

Direct atomic flux measurement of electron-beam evaporated yttrium with a diode-laser-based atomic May 1997 A direct measurement of atomic flux in e-beam evaporated yttrium has been demonstrated den- sity and velocity, and thus the atomic flux in an e-beam evaporated yttrium system with a diode

Fejer, Martin M.

227

Atomic/Molecular-Level Simulations of LaserMaterials Interactions  

E-print Network

in the investigations of the laser-induced generation and accumulation of crystal defects, mechanisms of laser melting], and artwork restoration [6, 7], and to the exploration of the conditions for inertial confinement fusion-temperature/high-pressure region of the laser energy deposition (melting/denaturation/charring, gen- eration of crystal defects

Zhigilei, Leonid V.

228

Measurement of depth profile of hydrogen isotope atom contained in solid material using resonant laser ablation  

Microsoft Academic Search

The depth profile of hydrogen isotope atoms was measured by using mass spectrometry combined with resonant laser ablation. A graphite sample was implanted with deuterium by a cyclotron and was employed for the measurements. The graphite sample was ablated by a tunable laser which wavelength was corresponding to the resonant wavelength of 1S - 2S for deuterium with two- photon

Masafumi Yorozu; Yasuhiro Okada; Terunobu Nakajyo; Akira Endo

1999-01-01

229

Reactions of pulsed laser produced boron and nitrogen atoms in a condensing argon stream  

E-print Network

Reactions of pulsed laser produced boron and nitrogen atoms in a condensing argon stream Lester dilution in argon favored diboron species. At low laser power with minimum radiation, the dominant reaction for argon matrix reactions; instead intense new infrared ab- sorptions, with boron isotopic multiplets, were

Martin, Jan M.L.

230

High-order harmonic generation on atoms and ions with laser fields of relativistic intensities  

SciTech Connect

High-order harmonic generation (HHG) by hydrogenlike atoms or ions in the field of counterpropagating laser beams of standing-wave configuration, with linear polarizations and relativistic intensities, is studied. The relativistic quantum theory of HHG in such field configurations (homogeneous), at which the impeding factor of relativistic magnetic drift of superstrong laser fields can be eliminated, is presented.

Avetissian, H. K.; Markossian, A. G.; Mkrtchian, G. F. [Centre of Strong Fields Physics, Yerevan State University, 1 A. Manukian, Yerevan 0025 (Armenia)

2011-07-15

231

Some Non-Perturbative and Non-Linear Effects in Laser-Atom Interaction  

E-print Network

We show that if the laser is intense enough, it may always ionize an atom or induce transitions between discrete energy levels of the atom, no matter what is its frequency. It means in the quantum transition of an atom interacting with an intense laser of circular frequency $\\omega$, the energy difference between the initial and the final states of the atom is not necessarily being an integer multiple of the quantum energy $\\hbar\\omega$. The absorption spectra become continuous. The Bohr condition is violated. The energy of photoelectrons becomes light intensity dependent in the intense laser photoelectric effect. The transition probabilities and cross sections of photo-excitations and photo-ionizations are laser intensity dependent, showing that these processes cannot be reduced to the results of interactions between the atom and separate individual photons, they are rather the processes of the atom interacting with the laser as a whole. The interaction of photons on atoms are not simply additive. The effect...

Zhang, Q R

2006-01-01

232

Modulation transfer spectroscopy for two-level atoms at high laser intensity  

NASA Astrophysics Data System (ADS)

We present a theoretical study of lineshapes in modulation transfer spectroscopy for two-level atoms at high laser intensity. We consider the interaction involving photon numbers up to seven when calculating the density matrix equations and compare the lineshapes for different photon numbers, by changing the laser intensity and its modulation frequency. As the modulation frequency becomes smaller or the laser intensities become stronger, interactions involving higher photon numbers are required to generate accurate modulation transfer spectra.

Noh, Heung-Ryoul; Park, Sang Eon

2015-02-01

233

Selective laser sintering of gas atomized M2 high speed steel powder  

Microsoft Academic Search

Selective laser sintering of the gas atomized M2 high speed steel powder was performed using laser powers of 2.5–100 W, scan rates of 1–30 mm\\/s and scan line spacings of 0.15–0.75 mm. With increasing laser power, the sintered surface varied from open\\/closed pores to a fully dense structure. Large lateral pores were found in the sintered surface of samples using

H. J. Niu; I. T. H. Chang

2000-01-01

234

Fluctuation properties of laser light after interaction with an atomic system: comparison between two-level and multilevel atomic transitions  

E-print Network

The complex internal atomic structure involved in radiative transitions has an effect on the spectrum of fluctuations (noise) of the transmitted light. A degenerate transition has different properties in this respect than a pure two-level transition. We investigate these variations by studying a certain transition between two degenerate atomic levels for different choices of the polarization state of the driving laser. For circular polarization, corresponding to the textbook two-level atom case, the optical spectrum shows the characteristic Mollow triplet for strong laser drive, while the corresponding noise spectrum exhibits squeezing in some frequency ranges. For a linearly polarized drive, corresponding to the case of a multilevel system, additional features appear in both optical and noise spectra. These differences are more pronounced in the regime of a weakly driven transition: whereas the two-level case essentially exhibits elastic scattering, the multilevel case has extra noise terms related to sponta...

Lezama, A; Kastberg, A; Tanzilli, S; Kaiser, R

2015-01-01

235

Laser-Excited Atomic Fluorescence Techniques For Temperature Measurements In Flames: A Summary  

NASA Astrophysics Data System (ADS)

Twelve laser-excited atomic fluorescence methods suitable for absolute temperature measurements in flames and other atomic and/or ionic reservoirs are reviewed and summarized. The different characteristics of the techniques are discussed. Several important parameters that need to be evaluated experimentally and the assumptions that need to be made in order to obtain meaningful temperature data from the selected method are emphasized.

Zizak, G.; Omenetto, N.; Winefordner, J. D.

1984-12-01

236

Separation of isotopes by laser deflection of atomic beam. I. Barium  

Microsoft Academic Search

Spatial separation of isotopes of barium in an atomic beam has been demonstrated, using radiation pressure of light from a tunable dye laser which resolved the unusually narrow isotopic hyperfine structure of the Ba (I) 5535.7-Å resonance line. Observations of the deflected monoisotopic beam indicate an average of 25 photons scattered per atom in the deflected beam.

A. F. Bernhardt; D. E. Duerre; J. R. Simpson; L. L. Wood

1974-01-01

237

A cold atom pyramidal gravimeter with a single laser beam Q. Bodart,1  

E-print Network

A cold atom pyramidal gravimeter with a single laser beam Q. Bodart,1 S. Merlet,1 N. Malossi,1 F pyramidal configuration allows to achieve all functions: trapping, interferometer and detection that an atom interferometer based on Raman transitions [7] can be realized exploiting an hollow pyramid

Boyer, Edmond

238

Laser-cooled atoms inside a hollow-core photonic-crystal fiber  

E-print Network

We describe the loading of laser-cooled rubidium atoms into a single-mode hollow-core photonic-crystal fiber. Inside the fiber, the atoms are confined by a far-detuned optical trap and probed by a weak resonant beam. We ...

Bajcsy, M.

239

Laser Optogalvanic Analysis in a Radiofrequency Plasma: Detection of Iodine Atoms and Molecules  

Microsoft Academic Search

The optogalvanic effect (OGE) may be used to detect specific species in a plasma (ions, atoms, radicals, or molecules) by selective laser excitation of the plasma. The plasma itself is merely the reservoir of electronically excited, ionized, and atomized species. Compared with conventional ICP-AES, OGE has many advantages: no external detector, zero background, no interferences, and greater versatility. Since the

Xuan Yao; Sean P. McGlynn; Rama C. Mohanty

1999-01-01

240

Impact of Actin Rearrangement and Degranulation on the Membrane Structure of Primary Mast Cells: A Combined Atomic Force and Laser  

E-print Network

: A Combined Atomic Force and Laser Scanning Confocal Microscopy Investigation Zhao Deng, Tiffany Zink, Huan.g., poly-L-lysine) was investigated by combined atomic force micros- copy (AFM) and laser scanning confocal cells in their living and hydrated states. In this investigation we demonstrate that a combined laser

Liu, Gang-yu

241

Laser safety information for the Atomic, Molecular and Optical (AMO) Physics Labs at Lehigh University modified from the laser safety program developed by the office of Environmental  

E-print Network

1 Laser safety information for the Atomic, Molecular and Optical (AMO) Physics Labs at Lehigh University modified from the laser safety program developed by the office of Environmental Health and Safety Support III. Industrial Laser Safety Course Rockwell Laser Industries 7754 Camargo Road Cincinnati, Ohio

Huennekens, John

242

A pumped atom laser NICHOLAS P. ROBINS*, CRISTINA FIGL, MATTHEW JEPPESEN, GRAHAM R. DENNIS AND JOHN D. CLOSE  

E-print Network

ARTICLES A pumped atom laser NICHOLAS P. ROBINS*, CRISTINA FIGL, MATTHEW JEPPESEN, GRAHAM R. DENNIS AND JOHN D. CLOSE ARC Centre for Quantum-Atom Optics, Physics Department, Australian National University.1038/nphys1027 The atom laser, a bright, coherent matter wave derived from a Bose­Einstein condensate, holds

Loss, Daniel

243

Autler-Townes effect for an atom in a 100% amplitude-modulated laser field. II. Experimental results  

E-print Network

Autler-Townes effect for an atom in a 100% amplitude-modulated laser field. II. Experimental We report the observation of the Autler-Townes absorption spectrum of a two-level atom in a 100% amplitude-modulated optical field. Two frequency-stabilized dye lasers interact with a three-level atomic

Stroud Jr., Carlos R.

244

PARCS: NASA’s laser-cooled atomic clock in space  

Microsoft Academic Search

The Primary Atomic Reference Clock in Space (PARCS) mission is designed to perform certain tests of relativity theory, to study the performance of individual GPS space-vehicle clocks, to study the dynamics of atom motion in microgravity, to advance the state-of-the art for space clocks, and to serve as a pathfinder for precision instruments based on laser cooling of atoms. After

D. B. Sullivan; N. Ashby; E. A. Donley; T. P. Heavner; L. W. Hollberg; S. R. Jefferts; W. M. Klipstein; W. D. Phillips; D. J. Seidel

2005-01-01

245

Photoionisation of a helium atom involving autoionisation states coupled by a circularly polarised laser field  

SciTech Connect

The rotating wave approximation is used to obtain parametric expressions for the resonance cross section for the atomic ground state ionisation by linearly polarised probe radiation in the vicinity of an autoionisation state coupled resonantly to another autoionisation state through circularly polarised laser radiation. Calculations are made for the 2s2p {sup 1}P and 2s3d {sup 1}D states of the helium atom. It is shown that the structure of the photoionisation cross-section spectrum formed for circularly polarised laser radiation differs qualitatively from the structure formed in the case of linear polarisation. The dependence of this structure on the intensity and frequency of laser radiation and the direction of polarisation of the probe radiation is studied. (interaction of laser radiation with matter. laser plasma)

Gryzlova, E V [Department of Physics, M.V. Lomonosov Moscow State University, Moscow (Russian Federation); Magunov, A I [A.M. Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Rotter, I [Max-Planck-Institut fur Physik komplexer Systeme (Germany); Strakhova, S I [D.V. Skobel'tsyn Institute of Nuclear Physics, M.V. Lomonosov Moscow State University, Moscow (Russian Federation)

2005-01-31

246

Pulsed-laser atom probe studies of a precipitation hardened maraging TRIP steel.  

PubMed

A precipitation hardened maraging TRIP steel was analyzed using a pulsed laser atom probe. The laser pulse energy was varied from 0.3 to 1.9 nJ to study its effect on the measured chemical compositions and spatial resolution. Compositional analyses using proximity histograms did not show any significant variations in the average matrix and precipitate compositions. The only remarkable change in the atom probe data was a decrease in the ++/+ charge state ratios of the elements. The values of the evaporation field used for the reconstructions exhibit a linear dependence on the laser pulse energy. The adjustment of the evaporation fields used in the reconstructions for different laser pulse energies was based on the correlation of the obtained cluster shapes to the TEM observations. No influence of laser pulse energy on chemical composition of the precipitates and on the chemical sharpness of their interfaces was detected. PMID:21215524

Dmitrieva, O; Choi, P; Gerstl, S S A; Ponge, D; Raabe, D

2011-05-01

247

Orbital alignment in atoms generated by photodetachment in a strong laser field  

NASA Astrophysics Data System (ADS)

A pump-probe laser scheme is employed to investigate orbital alignment and its dynamics in the ground state of laser-generated neutral atoms. The alignment is initiated by electron photodetachment of an atomic negative ion in a strong laser pulse. The electron density distribution in the ground state of the residual atom is probed by means of strong-field ionization in a second laser pulse at a delayed time. The principle of the probe method relies on the fact that the portion of the electron density distribution oriented along the laser polarization axis constitutes the ionization yield in the high-energy jets of emitted electrons. A systematic study is carried out on C, Si, and Ge atoms, which possess two electrons in an open p shell. A pronounced temporal modulation in the yield of high-energy electrons is observed for C and Si, revealing a periodic spatial rearrangement of the electron density distribution in these atoms. Its period is defined by the beat between the J=1 and J=2 spin-orbit components of the ground state.

Eklund, Mikael; Hultgren, Hannes; Hanstorp, Dag; Kiyan, Igor Yu.

2013-08-01

248

Differential cross sections for ionization and excitation of laser-aligned atoms by electron impact  

NASA Astrophysics Data System (ADS)

Differential cross section measurements will be presented for electron impact ionization and excitation of atoms prepared using high resolution continuous wave laser radiation. In the case of ionization, low energy coplanar asymmetric (e,2e) experiments were performed from laser excited Mg atoms that were aligned using radiation around 285nm. The atoms were subjected to linearly polarized radiation whose polarization vector was varied from in the plane to perpendicular to the scattering plane. Ionization measurements were then conducted from the laser-excited 3P state, and the differential cross section determined. By careful analysis of the laser pumping, these measurements were directly compared to those from the ground state. Such experiments provide valuable information on the ionization of aligned targets. In the second experiment to be described here, a resonant enhancement cavity has been placed around the interaction region and super-elastic scattering measurements have been carried out from laser-excited atoms inside the cavity. This new technique opens up many new targets for study, since the cavity increases the effective intensity of the laser radiation that is exciting the atoms by a factor of up to 50. As such, new ionization and excitation measurements are possible using deep UV radiation where the laser power is only a few mW. Results from calcium will be presented, and progress towards studies from silver, copper and gold will be discussed. We are also advancing this new technique to allow simultaneous excitation from the hyperfine levels of different targets (such as Rb), which will allow the method to be adopted in different fields, such as laser cooling and trapping.

Murray, Andrew

2012-06-01

249

Laser Cooling and Trapping of Neutral Mercury Atoms Using an Optically-Pumped External-Cavity Semiconductor Laser  

NASA Astrophysics Data System (ADS)

The level structure of the Hg atom is similar to other alkaline earth-like atoms, offering the possibility to realize an extremely high quality resonance factor (Q) on the ``clock'' transition (^1S0- ^3P0) when confined in an optical lattice at the Stark-shift free wavelength. A key feature of the Hg system is the reduced uncertainty due to black-body induced Stark shifts, making it an interesting candidate as an optical frequency standard. One challenge to laser-cooling neutral Hg atoms is finding a reliable source for cooling on the ^1S0-^3P1 transition at 253.7 nm. We employ an optically pumped semiconductor laser (OPSEL) operating at 1015 nm, whose frequency is quadrupled in two external-cavity doubling stages to generate over 120 mW at 253.7 nm. With this new laser source we have trapped Hg^199 from a background vapor in a standard MOT. We trap up to 2 x 10^6 atoms with a 1/e^2 radius of our MOT of ˜310 microns, corresponding to a density of 1.28 x 10^10 atoms/cm^3. We report on the progress of our Hg system and plans for precision lattice-based spectroscopy of the clock transition.

Paul, Justin; Lytle, Christian; Jones, R. Jason

2011-06-01

250

Laser-cooled atoms inside a hollow-core photonic-crystal fiber  

SciTech Connect

We describe the loading of laser-cooled rubidium atoms into a single-mode hollow-core photonic-crystal fiber. Inside the fiber, the atoms are confined by a far-detuned optical trap and probed by a weak resonant beam. We describe different loading methods and compare their trade-offs in terms of implementation complexity and atom-loading efficiency. The most efficient procedure results in loading of {approx}30,000 rubidium atoms, which creates a medium with an optical depth of {approx}180 inside the fiber. Compared to our earlier study this represents a sixfold increase in the maximum achieved optical depth in this system.

Bajcsy, M.; Hofferberth, S.; Balic, V.; Zibrov, A. S.; Lukin, M. D. [Harvard-MIT Center for Ultracold Atoms, Department of Physics, Harvard University, Cambridge, Massachusetts 02138 (United States); Peyronel, T.; Liang, Q.; Vuletic, V. [MIT-Harvard Center for Ultracold Atoms, Department of Physics, MIT, Cambridge, Massachusetts 02139 (United States)

2011-06-15

251

Laser-cooled atoms inside a hollow-core photonic-crystal fiber  

E-print Network

We describe the loading of laser-cooled rubidium atoms into a single-mode hollow-core photonic-crystal fiber. Inside the fiber, the atoms are confined by a far-detuned optical trap and probed by a weak resonant beam. We describe different loading methods and compare their trade-offs in terms of implementation complexity and atom-loading efficiency. The most efficient procedure results in loading of ~30,000 rubidium atoms, which creates a medium with optical depth ~180 inside the fiber. Compared to our earlier study this represents a six-fold increase in maximum achieved optical depth in this system.

M. Bajcsy; S. Hofferberth; T. Peyronel; V. Balic; Q. Liang; A. S. Zibrov; V. Vuletic; M. D. Lukin

2011-04-28

252

Thermogravimetric analysis for boiling points and vapour pressure  

Microsoft Academic Search

A TGA instrument has been adapted for rapid measurement of boiling points and vapour pressure at temperatures from ambient up to 400°C and pressures from ambient down to 20 mm Hg. Samples were contained in sealed holders having a laser-drilled aperture. Several organic liquids in the 100 to 300 gMW range showed good agreement with reference vapour pressure data. Sample

J. W. Goodrum; E. M. Siesel

1996-01-01

253

Search for a permanent EDM using laser cooled radioactive atom  

Microsoft Academic Search

An Electric Dipole Moment (EDM) of the elementary particle is a good prove to observe the phenomena beyond the Standard Model. A non-zero EDM shows the violation of the time reversal symmetry, and under the CPT invariance it means the CP violation. In paramagnetic atoms, an electron EDM results in an atomic EDM enhanced by the factor of the 3rd

Y. Sakemi; K. Harada; T. Hayamizu; M. Itoh; H. Kawamura; S. Liu; H. S. Nataraj; A. Oikawa; M. Saito; T. Sato; H. P. Yoshida; T. Aoki; A. Hatakeyama; T. Murakami; K. Imai; K. Hatanaka; T. Wakasa; Y. Shimizu; M. Uchida

2011-01-01

254

Helium in chirped laser fields as a time-asymmetric atomic switch  

SciTech Connect

Tuning the laser parameters exceptional points in the spectrum of the dressed laser helium atom are obtained. The weak linearly polarized laser couples the ground state and the doubly excited P-states of helium. We show here that for specific chirped laser pulses that encircle an exceptional point one can get the time-asymmetric phenomenon, where for a negative chirped laser pulse the ground state is transformed into the doubly excited auto-ionization state, while for a positive chirped laser pulse the resonance state is not populated and the neutral helium atoms remains in the ground state as the laser pulse is turned off. Moreover, we show that the results are very sensitive to the closed contour we choose. This time-asymmetric state exchange phenomenon can be considered as a time-asymmetric atomic switch. The optimal time-asymmetric switch is obtained when the closed loop that encircles the exceptional point is large, while for the smallest loops, the time-asymmetric phenomenon does not take place. A systematic way for studying the effect of the chosen closed contour that encircles the exceptional point on the time-asymmetric phenomenon is proposed.

Kaprálová-Ž?ánská, Petra Ruth, E-mail: kapralova@jh-inst.cas.cz [Department of Radiation and Chemical Physics, Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague 8 (Czech Republic); J. Heyrovsky Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Dolejškova 3, 182 23 Prague 8 (Czech Republic); Moiseyev, Nimrod, E-mail: nimrod@tx.technion.ac.il [Schulich Faculty of Chemistry and Faculty of Physics, Technion – Israel Institute of Technology, Haifa 32000 (Israel)

2014-07-07

255

Combined quantum state preparation and laser cooling of a continuous beam of cold atoms  

E-print Network

We use two-laser optical pumping on a continuous atomic fountain in order to prepare cold cesium atoms in the same quantum ground state. A first laser excites the F=4 ground state to pump the atoms toward F=3 while a second pi-polarized laser excites the F=3 -> F'=3 transition of the D2 line to produce Zeeman pumping toward m=0. To avoid trap states, we implement the first laser in a 2D optical lattice geometry, thereby creating polarization gradients. This configuration has the advantage of simultaneously producing Sisyphus cooling when the optical lattice laser is tuned between the F=4 -> F'=4 and F=4 -> F'=5 transitions of the D2 line, which is important to remove the heat produced by optical pumping. Detuning the frequency of the second pi-polarized laser reveals the action of a new mechanism improving both laser cooling and state preparation efficiency. A physical interpretation of this mechanism is discussed.

Gianni Di Domenico; Laurent Devenoges; Claire Dumas; Pierre Thomann

2010-11-07

256

Combined quantum-state preparation and laser cooling of a continuous beam of cold atoms  

SciTech Connect

We use two-laser optical pumping on a continuous atomic fountain in order to prepare cold cesium atoms in the same quantum ground state. A first laser excites the F=4 ground state to pump the atoms toward F=3 while a second {pi}-polarized laser excites the F=3{yields}F{sup '}=3 transition of the D{sub 2} line to produce Zeeman pumping toward m=0. To avoid trap states, we implement the first laser in a two-dimensional optical lattice geometry, thereby creating polarization gradients. This configuration has the advantage of simultaneously producing Sisyphus cooling when the optical lattice laser is tuned between the F=4{yields}F{sup '}=4 and F=4{yields}F{sup '}=5 transitions of the D{sub 2} line, which is important to remove the heat produced by optical pumping. Detuning the frequency of the second {pi}-polarized laser reveals the action of a mechanism improving both laser cooling and state-preparation efficiency. A physical interpretation of this mechanism is discussed.

Di Domenico, Gianni; Devenoges, Laurent; Dumas, Claire; Thomann, Pierre [Laboratoire Temps-Frequence, Universite de Neuchatel, Avenue de Bellevaux 51, CH-2009 Neuchatel (Switzerland)

2010-11-15

257

Characterization of laser - induced plasmas by atomic emission spectroscopy  

NASA Astrophysics Data System (ADS)

In this work, Laser-induced breakdown spectroscopy (LIBS) has been applied to characterization of plasmas generated in air at atmospheric pressure from a calcium hydroxide sample with a known concentration of Mg by using an infrared Nd:YAG laser. The influence of laser irradiance on plasma morphology and emission intensity was studied. Spatially-integrated intensities of Mg I-II lines along the line-of-sight were measured for different laser energies and delay times. The plasma temperature and the electron density were determined in each case by using and algorithm that calculates the optical thickness of the spectral lines and reproduces their experimental profiles in a framework of an homogeneous plasma in LTE that takes into account the effects of self-absorption. The results obtained showed the usefulness of this approach to provide additional information retrieved from the optical thickness of spectral lines for plasma characterization in LIBS experiments.

Díaz Pace, Diego M.; Bertuccelli, Graciela; D'Angelo, Cristian A.

2011-01-01

258

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: On the feasibility of raising the density and the extension of atomic ensembles in laser cooling  

NASA Astrophysics Data System (ADS)

The ways of raising the limiting density of cooled atoms and the extension of the volume occupied by them are considered. These include raising the laser beam intensity above the saturation intensity of the working transition, the use of a noncollinear geometry of the laser beam and the atomic medium, and coherent cooling by sequences of counterpropagating ?-pulses.

Rivlin, Lev A.; Yakubovich, S. D.

2000-11-01

259

Electronic state detection/partitioning of atomic nickel during resonant laser ablation  

NASA Astrophysics Data System (ADS)

Resonance ionization mass spectrometry studies of atomic species originating from a thermal source have been used to produce intensity/population calibration factors in the 2 + 1 (photons to resonance + photons to ionize) ionization of Ni. In Ni, several low lying excited electronic states provide ionization pathways facilitating measurement of the electronic temperature of the probed atoms. This detection scheme has been used to determine the electronic temperature of laser ablated Ni atoms from an electroplated nickel surface. Assuming Boltzmann behavior, temperatures of approximately 2600 K have been observed. The production of such high temperatures during laser ablation results in significant population of a variety of electronic states, thereby decreasing the overall sensitivity of any state-specific analysis technique that follows such laser sampling.

Rothschopf, G.; Zoller, J.; Lewis, R.; Grant, C.; Schur, R.; Estler, R.

1995-12-01

260

Active and passive sensing of collective atomic coherence in a superradiant laser  

NASA Astrophysics Data System (ADS)

We study the nondemolition mapping of collective quantum coherence onto a cavity light field in a superradiant, cold-atom 87Rb Raman laser. We show theoretically that the fundamental precision of the mapping is near the standard quantum limit on phase estimation for a coherent spin state, ??=1/N, where N is the number of atoms. The associated characteristic measurement time scale ?W?1/N is collectively enhanced. The nondemolition nature of the measurement is characterized by only 0.5 photon recoils deposited per atom due to optical repumping in a time ?W. We experimentally realize conditional Ramsey spectroscopy in our superradiant Raman laser, compare the results to the predicted precision, and study the mapping in the presence of decoherence, far from the steady-state conditions previously considered. Finally, we demonstrate a hybrid mode of operation in which the laser is repeatedly toggled between active and passive sensing.

Bohnet, Justin G.; Chen, Zilong; Weiner, Joshua M.; Cox, Kevin C.; Thompson, James K.

2013-07-01

261

Optical Clocks with Cold Atoms and Stable Lasers  

NASA Astrophysics Data System (ADS)

The performance and prospects for neutral-atom optical frequency standards are discussed based on our recent progress with a calcium optical frequency standard. Second stage narrow-line cooling to microkelvin (and even 300 nK) temperatures, combined with launched atoms, should reduce Doppler frequency errors to about 1×10-16. Advanced femtosecond optical frequency combs allow direct comparisons between the Ca optical standard, the Hg+ optical standard and the Cs primary standard. These comparisons provide independent "reality checks" on both the stability and accuracy. Relative frequency measurements also constrain the possible time variation of atomic energy levels and fundamental constants.

Hollberg, L.; Oates, C. W.; Wilpers, G.; Curtis, E. A.; Hoyt, C. W.; Diddams, S. A.; Bartels, A.; Ramond, T. M.

2004-12-01

262

New energy levels of atomic niobium by laser induced fluorescence spectroscopy in the near infrared  

NASA Astrophysics Data System (ADS)

Laser-induced fluorescence spectroscopy was applied in order to find new energy levels of the niobium atom. A continuous wave tuneable titanium–sapphire laser in the wavelength range from 750 to 865 nm and a hollow-cathode lamp were used. We discovered four energy levels of even parity, three lying levels below 19 000 cm?1 and one at much higher energy. Additionally hyperfine structure data of six levels of odd parity were determined.

Öztürk, I. K.; Ba?ar, Gö; Er, A.; Güzelçimen, F.; Ba?ar, Gü; Kröger, S.

2015-01-01

263

Spectroscopy of atom and nucleus in a strong laser field: Stark effect and multiphoton resonances  

NASA Astrophysics Data System (ADS)

The consistent relativistic energy approach to atoms in a strong realistic laser field, based on the Gell-Mann and Low S-matrix formalism, is applied in the study of resonant multiphoton ionization of krypton by intense uv laser radiation and for the computation of the resonance shift and width in krypton. The approach to the treatment of the multiphoton resonances in nuclei is outlined for the 57Fe nucleus.

Glushkov, A. V.

2014-11-01

264

Nonlinear dynamics of ionization stabilization of atoms in intense laser fields  

E-print Network

We revisit the stabilization of ionization of atoms subjected to a superintense laser pulse using nonlinear dynamics. We provide an explanation for the lack of complete ionization at high intensity and for the decrease of the ionization probability as intensity is increased. We investigate the role of each part of the laser pulse (ramp-up, plateau, ramp-down) in this process. We emphasize the role of the choice for the ionization criterion, energy versus distance criterion.

Michael Norman; C. Chandre; T. Uzer; Peijie Wang

2014-12-06

265

Clock Technology Development in the Laser Cooling and Atomic Physics (LCAP) Program  

NASA Technical Reports Server (NTRS)

This paper presents the Laser Cooling and Atomic Physics (LCAP) program. It focuses on clock technology development. The topics include: 1) Overview of LCAP Flight Projects; 2) Space Clock 101; 3) Physics with Clocks in microgravity; 4) Space Clock Challenges; 5) LCAP Timeline; 6) International Space Station (ISS) Science Platforms; 7) ISS Express Rack; 8) Space Qualification of Components; 9) Laser Configuration; 10) Clock Rate Comparisons: GPS Carrier Phase Frequency Transfer; and 11) ISS Model Views. This paper is presented in viewgraph form.

Seidel, Dave; Thompson, R. J.; Klipstein, W. M.; Kohel, J.; Maleki, L.

2000-01-01

266

Experimental search for the electron electric dipole moment with laser cooled francium atoms  

NASA Astrophysics Data System (ADS)

A laser cooled heavy atom is one of the candidates to search for the permanent electric dipole moment (EDM) of the electron due to the enhancement mechanism and its long coherence time. The laser cooled francium (Fr) factory has been constructed to perform the electron EDM search at the Cyclotron and Radioisotope Center, Tohoku University. The present status of Fr production and the EDM measurement system is presented.

Inoue, T.; Ando, S.; Aoki, T.; Arikawa, H.; Ezure, S.; Harada, K.; Hayamizu, T.; Ishikawa, T.; Itoh, M.; Kato, K.; Kawamura, H.; Uchiyama, A.; Aoki, T.; Asahi, K.; Furukawa, T.; Hatakeyama, A.; Hatanaka, K.; Imai, K.; Murakami, T.; Nataraj, H. S.; Sato, T.; Shimizu, Y.; Wakasa, T.; Yoshida, H. P.; Yoshimi, A.; Sakemi, Y.

2014-12-01

267

Dynamics of recollisions for the double ionization of atoms in intense laser fields  

SciTech Connect

We investigate the dynamics of electron-electron recollisions in the double ionization of atoms in strong laser fields. The statistics of recollisions can be reformulated in terms of an area-preserving map from the observation that the outer electron is driven by the laser field to kick the remaining core electron periodically. The phase portraits of this map reveal the dynamics of these recollisions in terms of their probability and efficiency.

Mauger, F.; Chandre, C. [Centre de Physique Theorique, CNRS-Aix-Marseille Universite, Campus de Luminy, case 907, F-13288 Marseille cedex 09 (France); Uzer, T. [School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332-0430 (United States)

2010-06-15

268

Evolution of dark state of an open atomic system in constant intensity laser field  

SciTech Connect

We studied experimentally and theoretically the evolution of open atomic systems in the constant intensity laser field. The study is performed by analyzing the line shapes of Hanle electromagnetically induced transparency (EIT) obtained in different segments of a laser beam cross section of constant intensity, i.e., a {Pi}-shaped laser beam. Such Hanle EIT resonances were measured using a small movable aperture placed just in front of the photodetector, i.e., after the entire laser beam had passed through the vacuum Rb cell. The laser was locked to the open transition F{sub g}=2{yields}F{sub e}=1 at the D{sub 1} line of {sup 87}Rb with laser intensities between 0.5 and 4 mW/cm{sup 2}. This study shows that the profile of the laser beam determines the processes governing the development of atomic states during the interaction. The resonances obtained near the beam center are narrower than those obtained near the beam edge, but the significant changes of the linewidths occur only near the beam edge, i.e., right after the atom enters the beam. The Hanle EIT resonances obtained near the beam center exhibit two pronounced minima next to the central maximum. The theoretical model reveals that the occurrence of these transmission minima is a joint effect of the preparation of atoms into the dark state and the optical pumping into the uncoupled ground level F{sub g}=1. The appearance of the transmission minima, although similar to that observed in the wings of a Gaussian beam [A. J. Krmpot et al., Opt. Express 17, 22491 (2009)], is of an entirely different nature for the {Pi}-shaped laser beam.

Krmpot, A. J.; Radonjic, M.; Cuk, S. M.; Nikolic, S. N.; Grujic, Z. D.; Jelenkovic, B. M. [Institute of Physics, University of Belgrade, Pregrevica 118, RS-11080 Belgrade (Serbia)

2011-10-15

269

Quasistatic limit of the strong-field approximation describing atoms in intense laser fields: Circular polarization  

SciTech Connect

In the recent work of Vanne and Saenz [Phys. Rev. A 75, 063403 (2007)] the quasistatic limit of the velocity gauge strong-field approximation describing the ionization rate of atomic or molecular systems exposed to linearly polarized laser fields was derived. It was shown that in the low-frequency limit the ionization rate is proportional to the laser frequency {omega} (for a constant intensity of the laser field). In the present work I show that for circularly polarized laser fields the ionization rate is proportional to {omega}{sup 4} for H(1s) and H(2s) atoms, to {omega}{sup 6} for H(2p{sub x}) and H(2p{sub y}) atoms, and to {omega}{sup 8} for H(2p{sub z}) atoms. The analytical expressions for asymptotic ionization rates (which become nearly accurate in the limit {omega}{yields}0) contain no summations over multiphoton contributions. For very low laser frequencies (optical or infrared) these expressions usually remain with an order-of-magnitude agreement with the velocity gauge strong-field approximation.

Bauer, Jaroslaw H. [Katedra Fizyki Teoretycznej Uniwersytetu Lodzkiego, Ul. Pomorska 149/153, PL-90-236 Lodz (Poland)

2011-03-15

270

Lithium atomic beam spectroscopy and phase sensitive detection using a diode laser  

NASA Astrophysics Data System (ADS)

We describe spectroscopy of a collimated lithium atomic beam using a home-built external cavity diode laser (ECDL) at 671 nm. The atomic beam is formed from an effusive oven containing Li at T 450^oC and a series of apertures. The ECDL light is split into two beams that counter-propagate at right angles to the atomic beam. Fluorescence spectra from the unresolved 2S1/2 F=2 -> 2P3/2 D2 line of ^7Li were recorded over a large range of saturation parameters (0.1 s0 - 50 s0, where s0 is the ratio of laser intensity to the saturation intensity). We modeled the effects of transverse atomic velocities (residual Doppler broadening), power broadening, and the saturation feature at high s0. We calibrated the spectra by modulating the laser current at ˜110 MHz and observing the sideband spectra. We locked the frequency of the ECDL to the transition at low and high values of s0 by phase sensitive detection in the fluorescence. The laser beam was electro-optically modulated at 100 kHz and the fluorescence signal was demodulated with a lock-in amplifier. The locked ECDL will be used for laser cooling and trapping experiments.

Houlton, Jack; Peplinski, Brandon; Otto, Lauren; Klemme, Daniel; Greenlee, Tom; Hoyt, Chad

2011-04-01

271

Two-stage laser cooling and optical trapping of thulium atoms  

NASA Astrophysics Data System (ADS)

We propose to use the magnetic-dipole transition at ? = 1.14 ?m coupling two ground state fine-structure components of thulium (Tm), as a ‘clock transition’ in optical clocks. We have demonstrated first stage laser cooling of Tm atoms down to a temperature of 25??K using a strong transition at ? = 410.6 nm and we have also shown preliminary results for second stage cooling using a weaker transition at ? = 530.7 nm (natural linewidth ?G = 350?kHz). Laser cooled atoms have been trapped in an optical dipole trap and in a 1D optical lattice operating near 532?nm.

Vishnyakova, G. A.; Kalganova, E. S.; Sukachev, D. D.; Fedorov, S. A.; Sokolov, A. V.; Akimov, A. V.; Kolachevsky, N. N.; Sorokin, V. N.

2014-07-01

272

Laser-assisted ionization of atomic hydrogen by electrons in the second Born approximation  

SciTech Connect

Electron-impact ionization of atomic hydrogen in the presence of a linearly polarized laser field is studied in the second Born approximation. The state of fast electron in the laser field is described by the Volkov state, while the dressed state of the ejected slow electron and atomic hydrogen is treated perturbatively to the first order. We calculate the triple differential cross section in the Ehrhardt asymmetric coplanar geometry. Numerical results show that the triple differential cross sections of the first Born approximation are significantly improved when the second-order corrections are taken into account.

Zheng Mingyang [Department of Modern Physics, University of Science and Technology of China, P. O. Box 4, Hefei, Anhui 230026 (China); Li Shumin [Department of Modern Physics, University of Science and Technology of China, P. O. Box 4, Hefei, Anhui 230026 (China); Institut fuer Theoretische Physik, Universitaet Heidelberg, Philosophenweg 16, D-69120 Heidelberg (Germany)

2010-08-15

273

Theoretical study on isotope separation of an ytterbium atomic beam by laser deflection  

NASA Astrophysics Data System (ADS)

Isotope separation by laser deflecting an atomic beam is analyzed theoretically. Interacting with a tilted one-dimensional optical molasses, an ytterbium atomic beam is split into multi-beams with different isotopes like 172Yb,173Yb, and 174Yb. By using the numerical calculation, the dependences of the splitting angle on the molasses laser intensity and detuning are studied, and the optimal parameters for the isotope separation are also investigated. Furthermore, the isotope separation efficiency and purity are estimated. Finally a new scheme for the efficient isotope separation is proposed. These findings will give a guideline for simply obtaining pure isotopes of various elements.

Zhou, Min; Xu, Xin-Ye

2014-01-01

274

Generation of laser-pulse-field harmonics in a gas upon impact ionisation of atoms  

SciTech Connect

The generation of harmonics of a high-power-laser-pulse field in a gas during impact ionisation of atoms by oscillating electrons is studied theoretically. Fields are considered under conditions when the oscillation energy of electrons in the radiation field, remaining nonrelativistic, considerably exceeds the ionisation potential of an atom. In addition, the radiation field was assumed weak compared to the atomic field (E{sub a} = 5.1x10{sup 9} V cm{sup -1}), which allowed us to neglect the field ionisation of atoms, taking into account only the impact ionisation of atoms by oscillating electrons. Under such conditions, along with the elastic scattering of electrons, the inelastic scattering of oscillating electrons accompanied by ionisation of gas atoms can make a significant contribution to a nonlinear current induced in the plasma. (special issue devoted to the 25th anniversary of the a.m. prokhorov general physics institute)

Kuzelev, M V; Rukhadze, A A [A.M. Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2007-10-31

275

Making optical atomic clocks more stable with $10^{-16}$ level laser stabilization  

Microsoft Academic Search

The superb precision of an atomic clock is derived from its stability. Atomic\\u000aclocks based on optical (rather than microwave) frequencies are attractive\\u000abecause of their potential for high stability, which scales with operational\\u000afrequency. Nevertheless, optical clocks have not yet realized this vast\\u000apotential, due in large part to limitations of the laser used to excite the\\u000aatomic resonance.

Y. Y. Jiang; A. D. Ludlow; N. D. Lemke; R. W. Fox; J. A. Sherman; L.-S. Ma; C. W. Oates

2011-01-01

276

Calculations of collisions between cold alkaline-earth-metal atoms in a weak laser field  

Microsoft Academic Search

We calculate the light-induced collisional loss of laser-cooled and trapped magnesium atoms for detunings up to 50 atomic linewidths to the red of the 1S0-1P1 cooling transition. We evaluate loss rate coefficients due to both radiative and nonradiative state-changing mechanisms for temperatures at and below the Doppler-cooling temperature. We solve the Schrödinger equation with a complex potential to represent spontaneous

Mette Machholm; Paul S. Julienne; Kalle-Antti Suominen

2001-01-01

277

Suppression of thermal atomic interdiffusion in InGaAs\\/AlGaAs QW laser structures  

Microsoft Academic Search

Titanium dioxide (TiO2) cap layers were deposited onto C-doped InGaAs\\/AlGaAS QW laser structures by electron-beam evaporation in order to investigate their effect on atomic interdiffusion. In comparison to the as-grown sample, a negligible shift of the photoluminescence peak was observed after annealing at 900°C, indicating that the atomic interdiffusion was greatly suppressed by TiO2 capping layers. For the uncapped sample,

Paulus L. Gareso; Lan Fu; Manuela Buda; Hark H. Tan; Chennupati Jagadish

2004-01-01

278

Search for laser-induced formation of antihydrogen atoms.  

PubMed

Antihydrogen can be synthesized by mixing antiprotons and positrons in a Penning trap environment. Here an experiment to stimulate the formation of antihydrogen in the n = 11 quantum state by the introduction of light from a CO2 continuous wave laser is described. An overall upper limit of 0.8% with 90% C.L. on the laser-induced enhancement of the recombination has been found. This result strongly suggests that radiative recombination contributes negligibly to the antihydrogen formed in the experimental conditions used by the ATHENA Collaboration. PMID:17155742

Amoretti, M; Amsler, C; Bonomi, G; Bowe, P D; Canali, C; Carraro, C; Cesar, C L; Charlton, M; Ejsing, A M; Fontana, A; Fujiwara, M C; Funakoshi, R; Genova, P; Hangst, J S; Hayano, R S; Jørgensen, L V; Kellerbauer, A; Lagomarsino, V; Lodi Rizzini, E; Macrì, M; Madsen, N; Manuzio, G; Mitchard, D; Montagna, P; Posada, L G C; Pruys, H; Regenfus, C; Rotondi, A; Telle, H H; Testera, G; Van der Werf, D P; Variola, A; Venturelli, L; Yamazaki, Y; Zurlo, N

2006-11-24

279

Synchronization of internal and external degrees of freedom of atoms in a standing laser wave  

E-print Network

We consider dissipative dynamics of atoms in a strong standing laser wave and find a nonlinear dynamical effect of synchronization between center-of-mass motion and internal Rabi oscillations. The synchronization manifests itself in the phase space as limit cycles which may have different periods and riddled basins of attraction. The effect can be detected in the fluorescence spectra of atoms as equidistant sideband frequencies with the space between adjacent peaks to be inversely proportional to the value of the period of the respective limit cycle. With increasing the intensity of the laser field, we observe numerically cascades of bifurcations that eventually end up in settling a strange chaotic attractor. A broadband noise is shown to destroy a fine structure of the bifurcation scenario, but prominent features of period-1 and period-3 limit cycles survive under a weak noise. The character of the atomic motion is analyzed with the help of the friction force whose zeroes are attractor or repellor points in the velocity space. We find ranges of the laser parameters where the atomic motion resembles a random but deterministic walking of atoms erratically jumping between different wells of the optical potential. Such a random walking is shown to be fractal in the sense that the measured characteristic of the motion, time of exit of atoms from a given space of the standing wave, is a complicated function that has a self-similar structure with singularities on a Cantor set of values of one of the control parameters.

V. Yu. Argonov; S. V. Prants

2004-09-17

280

Laser frequency offset locking scheme for high-field imaging of cold atoms  

E-print Network

We present a simple and flexible frequency offset locking scheme developed for high-field imaging of ultra-cold atoms which relies on commercially available RF electronics only. The main new ingredient is the use of the sharp amplitude response of a home-made RF filter to provide an error signal for locking the lasers. We were able to offset lock two independent diode lasers within a capture range of 200 MHz, and with a tuning range of up to 1.4GHz. The beat-note residual fluctuations for offset locked lasers are bellow 2MHz for integration times of several hundreds of seconds.

Puentes, Graciana

2011-01-01

281

Laser wavelength effects on ionic and atomic emission from tin plasmas  

SciTech Connect

We investigated the effects of laser wavelength on atomic and ionic emission from Sn plasmas. Plasmas were produced using planar Sn targets excited with 10.6 mum carbon dioxide (CO{sub 2}) and 1.06 mum neodymium-doped yttrium aluminum garnet (Nd:YAG) lasers. Two-dimensional spectral imaging of visible emission showed that continuum emission was significantly more intense in the CO{sub 2} laser produced plasma (LPP) whereas line emission was considerably more extensive in the Nd:YAG LPP. Faraday cup analysis showed that ion profiles were narrower with CO{sub 2} LPPs although they possessed higher kinetic energies.

Campos, D.; Harilal, S. S.; Hassanein, A. [School of Nuclear Engineering and Center for Materials Under Extreme Environment, Purdue University, 400 Central Drive, West Lafayette, Indiana 47907 (United States)

2010-04-12

282

Calibrating laser beam deflection systems for use in atomic force microscopes and cantilever sensors  

SciTech Connect

Most atomic force microscopes and cantilever-based sensors use an optical laser beam detection system to monitor cantilever deflections. We have developed a working model that accurately describes the way in which a position sensitive photodetector interprets the deflection of a cantilever in these instruments. This model exactly predicts the numerical relationship between the measured photodetector signal and the actual cantilever deflection. In addition, the model is used to optimize the geometry of such laser deflection systems, which greatly simplifies the use of any cantilever-based instrument that uses a laser beam detection system.

Beaulieu, L.Y.; Godin, Michel; Laroche, Olivier; Tabard-Cossa, Vincent; Gruetter, Peter [Department of Physics and Physical Oceanography, Memorial University, St. John's, Newfoundland, A1B 37X (Canada); Division of Biological Engineering, Media Laboratory, Massachusetts Institute of Technology, 20 Ames Street, Cambridge, Massachusetts 02139 (United States); Physics Department, McGill University, Montreal, Quebec, H3A 2T8 (Canada)

2006-02-20

283

Velocity and electronic state distributions of sputtered Fe atoms by laser-induced fluorescence spectroscopy  

SciTech Connect

Velocity distributions and relative populations in the fine-structure levels of the a/sup 5/D/sub J/ ground state of Fe atoms, produced by sputtering with 3 keV argon ions, have been investigated by Doppler shifted laser induced fluorescence. The laser system employs a single-mode, scanning ring dye laser, amplified by a sequence of three excimer-pumped flowing-dye cells. Frequency doubling in a KD*P crystal was used to produce high energy (> .5 mJ) pulses of narrowband tunable UV output near 300 nm. Laser power influence on effective velocity bandwidth was investigated. Favorable light-collection geometry minimized distortion of the velocity spectra from apparatus-averaging effects. In impurity flux diagnostic applications in fusion devices, substantial spatial averaging may occur. In the latter case, the narrow velocity bandwidth (70 m/s, transform limit) of the present laser system is particularly useful.

Young, C.E.; Calaway, W.F.; Pellin, M.J.; Gruen, D.M.

1983-01-01

284

The History of Laser Trapping of Atoms and Particles  

Microsoft Academic Search

This subject began in 1970 with the demonstration of relatively large radiation pressure forces on small transparent macroscopic particles. Two components of the force were identified: a scattering force in the direction of the incident laser beam and a gradient component in the direction of the intensity gradient. This led to the discovery of stable optical trapping and manipulation of

Arthur Ashkin

2003-01-01

285

One-atom correlated-emission laser RID C-6638-2008  

E-print Network

One-atom correlated-emission laser Ho-Joon Kim,1,2 Ashfaq H. Khosa,1 Hai-Woong Lee,1,2 and M. Suhail Zubairy1,3 1Centre for Quantum Physics, COMSATS Institute of Information Technology, Islamabad, Pakistan 2Department of Physics, Korea Advanced..., Qatar #1;Received 31 October 2007; published 14 February 2008#2; We study a four-level double-#1; atomic configuration working as a two photon linear amplifier where two atomic transitions independently interact with cavity mode, while the other...

Kim, Ho-Joon; Khosa, Ashfaq H.; Lee, Hai-Woong; Zubairy, M. Suhail

2008-01-01

286

Laser-induced fluorescence of metal-atom impurities in a neutral beam  

SciTech Connect

The need to limit impurities in fusion devices to low levels is well known. We have investigated, by the technique of laser-induced fluorescence, the concentration of heavy-metal atoms in a neutral beam caused by their evaporation from the hot filaments in a conventional high-current multifilament hydrogen-ion source.

Burrell, C.F.; Pyle, R.V.; Sabetimani, Z.; Schlachter, A.S.

1984-10-01

287

Site evaluations for the uranium-atomic vapor laser isotope separation (U-AVLIS) production plant  

Microsoft Academic Search

This report describes a uranium-atomic vapor laser isotope separation (U-AVLIS) production plant siting study conducted during 1990 to identify alternative plant sites for examination in later environmental impact studies. A siting study methodology was developed in early 1990 and was implemented between June and December. This methodology had two parts. The first part -- a series of screening analyses that

T. Wolsko; M. Absil; R. Cirillo; S. Folga; J. Gillette; L. Habegger; R. Whitfield

1991-01-01

288

LETTER TO THE EDITOR: Double ionization of atomic negative ions in an intense laser field  

Microsoft Academic Search

In recent years there have been many studies of multiple ionization of closed shell rare gas atoms by intense laser fields. Until now no similar work has been done in the study of more diverse targets such as negative ions where low binding energies and strong electron correlations could yield distinctive behaviour. We present the first results of ionization of

J. B. Greenwood; G. F. Collins; J. Pedregosa-Gutierrez; J. McKenna; A. Murphy; J. T. Costello

2003-01-01

289

PHYSICAL REVIEW A 86, 022713 (2012) Heteronuclear collisions between laser-cooled metastable neon atoms  

E-print Network

PHYSICAL REVIEW A 86, 022713 (2012) Heteronuclear collisions between laser-cooled metastable neon-cooled metastable (3 P2) neon. Experiments are performed with spin-polarized atoms in a magnetic trap for all two-isotope combinations of the stable neon isotopes 20 Ne, 21 Ne, and 22 Ne. We determine the rate coefficients

Birkl, Gerhard

290

Modulation transfer and optical Stark effect in a rubidium atomic clock pumped by a semiconductor laser  

Microsoft Academic Search

Novel spectral line shapes of optical-microwave double resonance with an extremely narrow linewidth were observed in a rubidium atomic clock pumped by a semiconductor laser. It was confirmed that these novel spectral line shapes of double resonance were due to the modulation-transfer effect. These spectral line shapes were calculated by solving the equation of motion of the density matrix that

Minoru Hashimoto; Motoichi Ohtsu

1989-01-01

291

Development of laser excited atomic fluorescence and ionization methods. Final technical progress report, May 1, 1988--December 31, 1991  

SciTech Connect

Progress report: May 1, 1988 to December 31, 1991. The research supported by DE-FG05-88ER13881 during the past (nearly) 3 years can be divided into the following four categories: (1) theoretical considerations of the ultimate detection powers of laser fluorescence and laser ionization methods; (2) experimental evaluation of laser excited atomic fluorescence; (3) fundamental studies of atomic and molecular parameters in flames and plasmas; (4) other studies.

Winefordner, J.D.

1991-12-31

292

Estimation of the detection limits for cobalt in a solid base in laser atomic-fluorescence analysis  

Microsoft Academic Search

Laser ablation as a method of atomization is widely used for spectral analysis of solid samples. Some of the important advantages of the method involve the possibility of conducting a rapid analysis of the sample without its preliminary preparation. With the use of laser ablation at atmospheric pressure and recording of the emission spectrum of the laser torch detection limits

A. V. Zybin; A. V. Kunets

1993-01-01

293

Velocity selective bipolarization spectroscopy for laser cooling of metastable krypton atoms  

NASA Astrophysics Data System (ADS)

We report a velocity selective bi-polarization spectroscopy (VS-BPS) technique to generate a background-free, dispersion-like reference signal which is tunable over a wide range of frequency. In this technique, a pair of linearly polarized weak probe beams passing through a gas cell of metastable Krypton (Kr*) atoms, overlaps with a pair of counter-propagating circularly polarized strong pump beams derived from an independently tunable control laser. The polarization spectroscopy signals from the two probe beams, after subtraction, result in VS-BPS signal. The spectral shifting in VS-BPS signal can be achieved by tuning the frequency of the control laser. The dependence of the amplitude and slope of the VS-BPS signal on the RF power used for excitation of Kr atoms in the gas cell and on the power of pump beams has been studied. The frequency stability of a diode laser locked with VS-BPS signal has been found to be better than the frequency stability of the laser locked with a saturated absorption spectroscopy (SAS) signal. The VS-BPS signal is finally used for stabilization and tuning of the cooling laser frequency for a magneto-optical trap (MOT) for Kr* atoms.

Kale, Y. B.; Tiwari, V. B.; Singh, S.; Mishra, S. R.; Rawat, H. S.

2014-11-01

294

Entropy Driven Atomic Motion in Laser-Excited Bismuth  

NASA Astrophysics Data System (ADS)

We introduce a thermodynamical model based on the two-temperature approach in order to fully understand the dynamics of the coherent A1g phonon in laser-excited bismuth. Using this model, we simulate the time evolution of (111) Bragg peak intensities measured by Fritz et al. [Science 315, 633 (2007)SCIEAS0036-807510.1126/science.1135009] in femtosecond x-ray diffraction experiments performed on a bismuth film for different laser fluences. The agreement between theoretical and experimental results is striking not only because we use fluences very close to the experimental ones but also because most of the model parameters are obtained from ab initio calculations performed for different electron temperatures.

Giret, Y.; Gellé, A.; Arnaud, B.

2011-04-01

295

Atomic vapor laser isotope separation of lead-210 isotope  

DOEpatents

An isotopically selective laser process and apparatus for removal of Pb-210 from natural lead that involves a one-photon near-resonant, two-photon resonant excitation of one or more Rydberg levels, followed by field ionization and then electrostatic extraction. The wavelength to the near-resonant intermediate state is counter propagated with respect to the second wavelength required to populate the final Rydberg state. This scheme takes advantage of the large first excited state cross section, and only modest laser fluences are required. The non-resonant process helps to avoid two problems: first, stimulated Raman Gain due to the nearby F=3/2 hyperfine component of Pb-207 and, second, direct absorption of the first transition process light by Pb-207. 5 figs.

Scheibner, K.F.; Haynam, C.A.; Johnson, M.A.; Worden, E.F.

1999-08-31

296

Characterization of laser cooling in a high-magnetic-field atom trap  

NASA Astrophysics Data System (ADS)

We describe cooling and trapping of both 85Rb and 87Rb in a range of magnetic fields up to 2.6 T. Atoms are injected from a low-field pyramidal magneto-optical trap and recaptured in a high-magnetic-field atom trap. The atoms are cooled and trapped by a six-beam optical molasses via the 5S1/2|mI,mJ= 1/2>? 5P3/2|mI,mJ= 3/2> transition (mI= 5/2 for 85Rb and mI= 3/2 for 87Rb). We study the trap fluorescence spectra, atom temperatures, density distributions, and lifetimes as a function of magnetic field and detuning parameters. The trap fluorescence spectra are both narrow and asymmetric, as is characteristic for laser cooling of atoms in an external trapping potential. The trap is modeled using a Monte Carlo trajectory simulation technique.

Paradis, E.; Zigo, S.; Hu, K. Z.; Raithel, G.

2012-08-01

297

Accurate measurement of tunneling ionization rates of atoms in a high-intensity laser field  

NASA Astrophysics Data System (ADS)

Tunneling ionization of noble gas atoms is important for understanding the physics of strongly driven atoms and for developing new technologies such as ultrafast coherent x-ray sources and laser-based electron accelerators. Measurements of tunneling rates for atoms ionized by a high-intensity laser pulse have achieved a factor-of-ten improvement in accuracy over previous experiments, providing unprecedented detail about high- intensity laser-atom interactions. The measurements employ a circularly polarized, 2-ps, 1053-nm laser pulse with a peak intensity of 1.5 × 1017 W/cm2 to ionize low charge states of helium and neon. Under these conditions, electrons produced during ionization are ponderomotively scattered out of the laser focus and gain an amount of energy proportional to the intensity at the moment of ionization. The measured electron energy (0-4 keV) is insensitive to variations in the peak laser intensity, allowing the ionizing electric fields to be determined with an accuracy better than 2%. Detailed Monte Carlo simulations of electron motion in the focus, which calibrate the ionizing fields to the electron energies, confirm the accuracy of the measurements. The inferred ionization rates provide rigorous tests of available tunneling theories. The helium data show excellent agreement with the semiclassical theory of Ammosov, Delone, and Krainov (ADK). The results for hydrogenic helium (He1+), in particular, agree well with analytic and numerical solutions of the Schrödinger equation. The measurements verify both the importance of the long-range nature of the Coulomb potential and the effect of multielectron interactions in determining the ionization rate. The neon data show a small but significant breakdown of the ADK theory, which is attributed to polarization of the atom by the laser field prior to ionization. Atom polarization may imply that tunneling ionization intensities are described by a universal scaling relation. The neon data also provide tentative evidence for the DC Stark shift of the atomic ground state and its effect on tunneling ionization rates.

Buerke, Brian Joseph

2000-08-01

298

Comparing Laser Interferometry and Atom Interferometry Approaches to Space-Based Gravitational-Wave Measurement  

NASA Technical Reports Server (NTRS)

Thoroughly studied classic space-based gravitational-wave missions concepts such as the Laser Interferometer Space Antenna (LISA) are based on laser-interferometry techniques. Ongoing developments in atom-interferometry techniques have spurred recently proposed alternative mission concepts. These different approaches can be understood on a common footing. We present an comparative analysis of how each type of instrument responds to some of the noise sources which may limiting gravitational-wave mission concepts. Sensitivity to laser frequency instability is essentially the same for either approach. Spacecraft acceleration reference stability sensitivities are different, allowing smaller spacecraft separations in the atom interferometry approach, but acceleration noise requirements are nonetheless similar. Each approach has distinct additional measurement noise issues.

Baker, John; Thorpe, Ira

2012-01-01

299

Energy Approach to Atoms, Ions and Nuclei in a Super Strong Laser Field  

NASA Astrophysics Data System (ADS)

A consistent relativistic energy approach is applied to studying the interaction of the atoms and ions of plasma with an super intense electromagnetic (laser) field. Method bases on description of atom in a field by the k- photon emission and absorption lines. The lines are described by the QED moments of different orders, which can be calculated with the use of the Gell-Mann and Low S-matrix adiabatic formalism. In relativistic version the Gell-Mann and Low formulae expresses an imaginary part of the energy shift ImE through the QED scattering matrix, including interaction of atom with electromagnetic field and field of the photon vacuum. We present QED S-matrix energy formalism for calculation of the spectral lines shape in dense plasma. For any atomic level we calculate Im E as function of the laser pulse central frequency and further the moments of lines. Numerical modelling carried out for H, Cs, Ar, Yb, Tm atoms and H-, Li- and Ne-like ions. Especial interest attracts new relativistic treating of the drastic broadening effect of widths for the autoionization resonances in lanthanides. The direct interaction of super intense laser fields in the optical frequency domain with nuclei is studied and the AC Stark effect for nuclei is described within the operator perturbation theory and the relativistic mean-field model for the ground-state calculation of the nuclei 49Sc, 171Yb and compared with other available data.

Glushkov, Alexander

2011-11-01

300

Synchronization of internal and external degrees of freedom of atoms in a standing laser wave  

NASA Astrophysics Data System (ADS)

We consider dissipative dynamics of atoms in a strong standing laser wave and find a nonlinear dynamical effect of synchronization between center-of-mass motion and internal Rabi oscillations. The synchronization manifests itself in the phase space as limit cycles, which may have different periods and riddled basins of attraction. The effect can be detected in fluorescence spectra of atoms as equidistant sideband frequencies with the space between adjacent peaks to be inversely proportional to the value of the period of the respective limit cycle. With increasing intensity of the laser field, we numerically observe cascades of bifurcations that eventually end up in settling a strange chaotic attractor. A broadband noise is shown to destroy a fine structure of the bifurcation scenario, but prominent features of period-1 and period-3 limit cycles survive under a weak noise. The character of the atomic motion is analyzed with the help of the friction force whose zeroes are attractor or repellor points in the velocity space. We find ranges of the laser parameters where the atomic motion resembles a random but deterministic walking of atoms erratically jumping between different wells of the optical potential. Such a random walking is shown to be fractal.

Argonov, V. Yu.; Prants, S. V.

2005-05-01

301

Modeling and control of entanglement dynamics in laser cooling of trapped atoms  

E-print Network

We discuss the dynamical behavior of the entanglement between the internal and the external degrees of freedom of a trapped atom in electromagnetically-induced transparency (EIT) laser cooling. It is shown that essential features of the intricate entanglement dynamics observed in full numerical simulations of the underlying quantum master equation can be understood in terms of a two-state model on the basis of Landau-Zener splittings in the atom-laser field Hamiltonian. An extension of this model to an effective non-Hermitian Hamiltonian is constructed which describes the decay of entanglement by spontaneous emission processes. We also discuss schemes for the control of entanglement and demonstrate that a permanent entanglement can be imprinted on trapped atoms through a rapid switch off of the driving fields. Finally, we point out fundamental distinctions between the entanglement created in EIT cooling and in the cooling scheme based on velocity-selective coherent population trapping.

Maryam Roghani; Heinz-Peter Breuer; Hanspeter Helm

2011-08-01

302

Modeling and control of entanglement dynamics in laser cooling of trapped atoms  

E-print Network

We discuss the dynamical behavior of the entanglement between the internal and the external degrees of freedom of a trapped atom in electromagnetically-induced transparency (EIT) laser cooling. It is shown that essential features of the intricate entanglement dynamics observed in full numerical simulations of the underlying quantum master equation can be understood in terms of a two-state model on the basis of Landau-Zener splittings in the atom-laser field Hamiltonian. An extension of this model to an effective non-Hermitian Hamiltonian is constructed which describes the decay of entanglement by spontaneous emission processes. We also discuss schemes for the control of entanglement and demonstrate that a permanent entanglement can be imprinted on trapped atoms through a rapid switch off of the driving fields. Finally, we point out fundamental distinctions between the entanglement created in EIT cooling and in the cooling scheme based on velocity-selective coherent population trapping.

Roghani, Maryam; Helm, Hanspeter

2011-01-01

303

Radiative collisional heating at the Doppler limit for laser-cooled magnesium atoms  

SciTech Connect

We report Monte Carlo wave function simulation results on cold collisions between magnesium atoms in a strong red-detuned laser field. This is the normal situation, e.g., in magneto-optical traps (MOT). The Doppler limit heating rate due to radiative collisions is calculated for {sup 24}Mg atoms in an MOT based on the {sup 1}S{sub 0}-{sup 1}P{sub 1} atomic laser cooling transition. We find that radiative heating does not seem to affect the Doppler limit in this case. We also describe a channeling mechanism due to the missing Q branch in the excitation scheme, which could lead to a suppression of inelastic collisions, and find that this mechanism is not present in our simulation results due to the multistate character of the excitation process.

Piilo, J. [Department of Physics, University of Turku, FIN-20014 Turun yliopisto (Finland); Institute of Solid State Physics, Bulgarian Academy of Sciences, Tsarigradsko chaussee 72, 1784 Sofia (Bulgaria); School of Pure and Applied Physics, University of KwaZulu-Natal, Durban 4041 (South Africa); Lundh, E. [Helsinki Institute of Physics, PL 64, FIN-00014 Helsingin yliopisto (Finland); Department of Physics, KTH, SE-10691 Stockholm (Sweden); Suominen, K.-A. [Department of Physics, University of Turku, FIN-20014 Turun yliopisto (Finland); Helsinki Institute of Physics, PL 64, FIN-00014 Helsingin yliopisto (Finland)

2004-07-01

304

Radiative collisional heating at the Doppler limit for laser-cooled magnesium atoms  

E-print Network

We report Monte Carlo wave function simulation results on cold collisions between magnesium atoms in a strong red-detuned laser field. The Doppler limit heating rate due to radiative collisions is calculated for Mg-24 atoms in a magneto-optical trap based on the singlet S_0 - singlet P_1 atomic laser cooling transition. We find that radiative heating does not seem to affect the Doppler limit in this case. We also describe a channelling mechanism due to the missing Q branch in the excitation scheme, which could lead to a suppression of inelastic collisions, and find that this mechanism is not present in our simulation results due to the multistate character of the excitation process.

Piilo, J; Suominen, K A

2003-01-01

305

Four-level atomic interferometer driven by shaped ultrafast laser pulses  

NASA Astrophysics Data System (ADS)

We analyze the behavior of a four-state, two-path atomic interferometer driven by shaped ultrafast laser pulses. The laser pulses interact with atomic rubidium, exciting the atoms to the 5D state via two intermediate resonances (the 5P1/2 and 5P3/2). The relative phase of the two paths can be modified by applying a varying spectral phase at the wavelength corresponding to one of the resonant transitions for each pathway. We trace out the behavior of the system from the simplest case of weak-field excitation with resonant fields to strong-field excitation with a broadband source. Our measurements and analysis reveal that while interference is observed for all field strengths and spectral widths, the character of the interference changes substantially.

Clow, Stephen; Weinacht, Thomas

2010-08-01

306

A proposed method of efficient laser trapping of neutral radium atoms  

NASA Astrophysics Data System (ADS)

We report theoretical studies of an efficient accumulation of 225Ra atoms in a magneto-optical trap (MOT) from an atomic beam. The number of atoms in the trap is limited due to the large leakage into metastable D states from the cooling transition and the loss mechanism from collisions with the background gases and with other elements in the atomic beam. We propose a setup consisting of an efficient Zeeman slower, an optical atomic beam deflector, and an Egg-MOT, which provides a large capture velocity, e.g. the Zeeman slower capture velocity of 581 ms?1 and the MOT capture velocity of 46 ms?1. Furthermore, the pure slow atomic beam produced by the optical atomic beam deflector can maximize the number of trapped atoms and their lifetime in a ultra high vacuum chamber by minimizing the collisional loss. Our proposed setup allows for the search for a permanent electric dipole moment based on laser-cooled and trapped radium atoms with improved sensitivity.

Jong Park, Sung; Kim, Young Jin; Shin, Taeksu; Kim, Yong Kyun; Kim, Sun Kee

2014-12-01

307

Quantum-mechanical theory including angular momenta analysis of atom-atom collisions in a laser field  

NASA Technical Reports Server (NTRS)

The problem of two atoms colliding in the presence of an intense radiation field, such as that of a laser, is investigated. The radiation field, which couples states of different electronic symmetry, is described by the number state representation while the electronic degrees of freedom (plus spin-orbit interaction) are discussed in terms of a diabatic representation. The total angular momentum of the field-free system and the angular momentum transferred by absorption (or emission) of a photon are explicitly considered in the derivation of the coupled scattering equations. A model calculation is discussed for the Xe + F collision system.

Devries, P. L.; George, T. F.

1978-01-01

308

Atomic oxygen effects on thin film space coatings studied by spectroscopic ellipsometry, atomic force microscopy, and laser light scattering  

NASA Technical Reports Server (NTRS)

The University of Nebraska is currently evaluating Low Earth Orbit (LEO) simulation techniques as well as a variety of thin film protective coatings to withstand atomic oxygen (AO) degradation. Both oxygen plasma ashers and an electron cyclotron resonance (ECR) source are being used for LEO simulation. Thin film coatings are characterized by optical techniques including Variable Angle Spectroscopic Ellipsometry, Optical spectrophotometry, and laser light scatterometry. Atomic Force Microscopy (AFM) is also used to characterize surface morphology. Results on diamondlike carbon (DLC) films show that DLC degrades with simulated AO exposure at a rate comparable to Kapton polyimide. Since DLC is not as susceptible to environmental factors such as moisture absorption, it could potentially provide more accurate measurements of AO fluence on short space flights.

Synowicki, R. A.; Hale, Jeffrey S.; Woollam, John A.

1992-01-01

309

Time-resolved diffraction profiles and atomic dynamics in short-pulse laser-induced structural transformations: Molecular dynamics study  

E-print Network

Time-resolved diffraction profiles and atomic dynamics in short-pulse laser-induced structural on the atomic-level structural rearrangements available from the simulations to the diffraction spectra measured of the irradiated surface and provides limited direct information on atomic structural rearrangements. Recent

Zhigilei, Leonid V.

310

Detection of slow atoms confined in a Cesium vapor cell by spatially separated pump and probe laser beams  

E-print Network

Detection of slow atoms confined in a Cesium vapor cell by spatially separated pump and probe laser distribution of atoms in a thermal gas is usually described through a Maxwell-Boltzman distribution of energy, and assumes isotropy. As a consequence, the probability for an atom to leave the surface under an azimuth

Boyer, Edmond

311

A cesium beam atomic clock using laser optical pumping. Preliminary tests (*) Institut d'Electronique Fondamentale, Universit Paris-Sud,  

E-print Network

L-379 A cesium beam atomic clock using laser optical pumping. Preliminary tests (*) M. Arditi as an atomic clock have been performed. J. Physique - LETTRES 41 (1980) L-379 - L-3811 15 AOUT 1980 4-3- F = 4, mF = 0 of the ground state of the cesium atom 133Cs (at 9192 631770 Hz by definition

Boyer, Edmond

312

Continuous-wave laser oscillation on the 1315 nm transition of atomic iodine pumped by O2,,a1  

E-print Network

Continuous-wave laser oscillation on the 1315 nm transition of atomic iodine pumped by O2,,a11/2 I 2 P3/2 transition of atomic iodine is conventionally obtained by a near-resonant energy nm transition of atomic iodine where the O2 a1 used to pump the iodine was produced by a radio

Carroll, David L.

313

The effects of He addition on the performance of the fission-fragment excited Ar/Xe atomic xenon laser  

E-print Network

The effects of He addition on the performance of the fission-fragment excited Ar/Xe atomic xenon September 1990; accepted for publication 8 November 1990) The intrinsic power efficiency of the atomic xenon of a fission-fragment excited atomic xenon laser. Adding He increases the heat capacity without appreciably

Kushner, Mark

314

CO/sub 2/ laser sustained CW discharge atomic beam source  

SciTech Connect

A high pressure, supersonic, laser sustained plasma nozzle beam source has been developed for the production of intense (>10/sup 19/ particles s/sup 1/-sr/sup -1/) beams of atomic and/or radical species having kinetic energies in the range of 1 to 10 eV. A high plasma temperature (10 to 30,000 K) is produced in the throat of a hydrodynamic expansion nozzle by sustaining a cw optical discharge in a gas using a high power cw CO/sub 2/ laser. Gas mixtures are expanded through the nozzle/discharge region creating energetic atoms and molecules. An oxygen atom beam has been produced with a kinetic energy of 2 to 3 eV and an intensity of approx. 10/sup 18/ O-atoms s/sup -1/sr/sup -1/. O-atom collisions (1 eV) from an uncharacterized nickel surface shows strong specular scattering with approximately 50% energy loss to the surface. Argon beams having kinetic energies between 5 to 10 eV with intensities of >10/sup 19/ atoms s/sup -1/sr/sup -1/ have also been produced. 13 refs., 8 figs.

Cross, J.B.; Cremers, D.A.; Spangler, L.H.; Hoffbauer, M.A.; Archuleta, F.A.

1986-01-01

315

Correlated multielectron dynamics in mid-infrared laser pulse interactions with neon atoms.  

PubMed

The multielectron dynamics in nonsequential triple ionization (NSTI) of neon atoms driven by mid-infrared (MIR) laser pulses is investigated with the three-dimensional classical ensemble model. In consistent with the experimental result, our numerical result shows that in the MIR regime, the triply charged ion longitudinal momentum spectrum exhibits a pronounced double-hump structure at low laser intensity. Back analysis reveals that as the intensity increases, the responsible triple ionization channels transform from direct (e, 3e) channel to the various mixed channels. This transformation of the NSTI channels leads to the results that the shape of ion momentum spectra becomes narrow and the distinct maxima shift towards low momenta with the increase of the laser intensity. By tracing the triply ionized trajectories, the various ionization channels at different laser intensities are clearly identified and these results provide an insight into the complex dynamics of the correlated three electrons in NSTI. PMID:24104018

Tang, Qingbin; Huang, Cheng; Zhou, Yueming; Lu, Peixiang

2013-09-01

316

THERMAL EFFECTS ON MASS AND SPATIAL RESOLUTION DURING LASER PULSE ATOM PROBE TOMOGRAPHY OF CERIUM OXIDE  

SciTech Connect

Cerium oxide (CeO2) is an ideal surrogate material for trans-uranic elements and fission products found in nuclear fuels due to similarities in their thermal properties; therefore, cerium oxide was used to determine the best run condition for atom probe tomography (APT). Laser pulse APT is a technique that allows for spatial resolution in the nm scale and isotopic/elemental chemical identification. A systematic study of the impact of laser pulse energy and specimen base temperature on the mass resolution, measurement of stoichiometry, multiples, and evaporation mechanisms are reported in this paper. It was demonstrated that using laser pulse APT stoichiometric field evaporation of cerium oxide was achieved at 1 pJ laser pulse energy and 20 K specimen base temperature.

Rita Kirchhofer; Melissa C. Teague; Brian P. Gorman

2013-05-01

317

Relativistic effects of the interaction of an intense femtosecond laser pulse with atomic clusters  

SciTech Connect

The effects of the interaction of an intense femtosecond laser pulse with large atomic clusters are considered. The pulse intensity is of the order of 10{sup 18} W cm{sup -2}. New effects appear when the magnetic component of the Lorentz force is taken into account. The second harmonic of laser radiation is generated. The second harmonic generation (SHG) efficiency is proportional to the square of the number of atoms in a cluster and the square of the laser radiation intensity. The resonance increase in the SHG efficiency at the Mie frequencies (both at the second-harmonic frequency and fundamental frequency) proved to be insignificant because of a fast passage through the resonance during the cluster expansion. The mechanisms of the expansion and accumulation of energy by electrons and ions in the cluster are discussed in detail. The energy accumulation by electrons mainly occurs due to stimulated inverse bremsstrahlung upon elastic reflection of the electrons from the cluster surface. The equations describing the cluster expansion take into account both the hydrodynamic pressure of heated electrons and the Coulomb explosion of the ionised cluster caused by outer shell ionisation. It is assumed that both inner shell and outer shell ionisation is described by the over-barrier mechanism. It is shown that atomic clusters are more attractive for generation of even harmonics than compared to solid and gas targets. (superstrong laser fields)

Rastunkov, V S; Krainov, Vladimir P [Moscow Institute of Physics and Technology (State University), Dolgoprudnyi, Moscow Region (Russian Federation)

2005-06-30

318

High kinetic energy (1-10 eV) laser sustained neutral atom beam source  

NASA Astrophysics Data System (ADS)

Development of high energy (1-10eV) neutral atom beams has relied primarily on the use of charge exchange or DC/RF discharge techniques. A new source is described which uses a laser sustained plasma technique for producing high intensity (?0 15/cm 2s) and high translational energy (?1 eV) atomic beam species for use in gas-surface scattering experiments. Laser sustained plasmas have demonstrated temperatures of 10 000 K in xenon, 18 000 K in argon, and a predicted temperature of 30 000 K in helium. Combining this plasma with hydrodynamic expansion techniques should produce atomic beam velocities greater than 10 km/s for many species. Initial experiments with xenon using 70 W of CO 2 laser power have demonstrated beam kinetic temperatures of 8-9000 K with Mach numbers of 4-6 resulting in peak velocities for xenon of 1.5 km/s (1.5 eV). Extrapolation of these results to helium predicts that velocities in excess of 10 km/s are possible but will require laser powers in excess of 1.3 kW.

Cross, Jon B.; Cremers, David A.

1986-03-01

319

Laser supported detonation wave source of atomic oxygen for aerospace material testing  

NASA Astrophysics Data System (ADS)

A pulsed high flux source of nearly monoenergetic atomic oxygen has been developed at Physical Sciences Inc. (PSI) to perform accelerated erosion testing of spacecraft materials in a simulated low earth orbit (LEO) environment. Molecular oxygen is introduced into an evacuated conical expansion nozzle at several atmospheres pressure through a pulsed molecular beam valve. A laser induced breakdown is generated in the nozzle throat by a pulsed CO2 TEA laser focused to intensities ?109 W/cm2. The resulting plasma is heated in excess of 20,000 K by the ensuing laser supported detonation wave, and then rapidly expands and cools. The nozzle geometry confines the expansion to promote rapid electron-ion recombination into atomic oxygen. The source generates an atomic oxygen beam with fluxes ?1018 atoms per pulse at 8±1.6 km/s with an ion content below 1% for LEO testing. For other applications the beam velocity can be varied over a range from 5 to 13 km/s by changing the discharge conditions. Materials testing has obtained the same surface oxygen enrichment in polyethylene samples as observed on the STS-8 mission, and scanning electron micrographs of the irradiated polymer surfaces reveal an erosion morphology similar to that obtained on low earth orbit.

Krech, Robert H.; Caledonia, George E.

1990-07-01

320

Quantitative analysis of carbon in cementite using pulsed laser atom probe.  

PubMed

Carbon quantification and the standardisation in a pure cementite were conducted using pulsed-laser atom probe tomography (APT). The results were analysed to investigate a dependence on three distinct experimental parameters; the laser pulse energy, the cryogenic specimen temperature and the laser pulse frequency. All the measurements returned an apparent carbon content of 25.0±1.0at%. Carbon content measurements showed no clear dependence on the cryogenic temperature or the laser pulse frequency. However, the results did demonstrate a strong correlation with the laser pulse energy. For lower laser pulse energies, the analysis returned carbon contents higher than the stoichiometric ratio. It was suggested that this effect is due to pile up of (56)Fe(++) at the detector and as a consequence there is a systematic preferential loss of these ions throughout the course of the experiment. Conversely, in experiments utilising higher laser pulse energies, it was found that the carbon contents were smaller than the stoichiometric ratio. In these experiments an increasing fraction of the larger carbon molecular ions (e.g., C5 ions) were detected as part of a multiple detection events, which could affect the quantification measurements. PMID:25048825

Kitaguchi, H S; Lozano-Perez, S; Moody, M P

2014-12-01

321

High-stability compact atomic clock based on isotropic laser cooling  

SciTech Connect

We present a compact cold-atom clock configuration where isotropic laser cooling, microwave interrogation, and clock signal detection are successively performed inside a spherical microwave cavity. For ground operation, a typical Ramsey fringe width of 20 Hz has been demonstrated, limited by the atom cloud's free fall in the cavity. The isotropic cooling light's disordered properties provide a large and stable number of cold atoms, leading to a high signal-to-noise ratio limited by atomic shot noise. A relative frequency stability of 2.2x10{sup -13{tau}-1/2} has been achieved, averaged down to 4x10{sup -15} after 5x10{sup 3} s of integration. Development of such a high-performance compact clock is of major relevance for on-board applications, such as satellite-positioning systems. As a cesium clock, it opens the door to a new generation of compact primary standards and timekeeping devices.

Esnault, Francois-Xavier; Holleville, David; Rossetto, Nicolas; Guerandel, Stephane; Dimarcq, Noel [LNE-SYRTE, Observatoire de Paris, CNRS UPMC, 61 Avenue de l'Observatoire, 75014 Paris (France)

2010-09-15

322

Non-exponential tunneling ionization of atoms by an intense laser field  

NASA Astrophysics Data System (ADS)

We discuss the possibility of non-exponential tunneling ionization of atoms irradiated by intense laser field. This effect can occur at times which are greater than the lifetime of a system under consideration. The mechanism for non-exponential depletion of an initial quasi-stationary state is the cutting of the energy spectrum of final continuous states at long times. We first consider the known examples of cold emission of electrons from metal, tunneling alpha-decay of atomic nuclei, spontaneous decay in two-level systems, and the single-photon atomic ionization by a weak electromagnetic field. The new physical situation discussed is tunneling ionization of atoms by a strong low-frequency electromagnetic field. In this case the decay obeys ?1/t power-law dependence on the (long) interaction times.

Ishkhanyan, A. M.; Krainov, V. P.

2015-04-01

323

A Technology Demonstration Experiment for Laser Cooled Atomic Clocks in Space  

NASA Technical Reports Server (NTRS)

We have been developing a laser-cooling apparatus for flight on the International Space Station (ISS), with the intention of demonstrating linewidths on the cesium clock transition narrower than can be realized on the ground. GLACE (the Glovebox Laser- cooled Atomic Clock Experiment) is scheduled for launch on Utilization Flight 3 (UF3) in 2002, and will be mounted in one of the ISS Glovebox platforms for an anticipated 2-3 week run. Separate flight definition projects funded at NIST and Yale by the Micro- gravity Research Division of NASA as a part of its Laser Cooling and Atomic Physics (LCAP) program will follow GLACE. Core technologies for these and other LCAP missions are being developed at JPL, with the current emphasis on developing components such as the laser and optics subsystem, and non-magnetic vacuum-compatible mechanical shutters. Significant technical challenges in developing a space qualifiable laser cooling apparatus include reducing the volume, mass, and power requirements, while increasing the ruggedness and reliability in order to both withstand typical launch conditions and achieve several months of unattended operation. This work was performed at the Jet Propulsion Laboratory under a contract with the National Aeronautics and Space Administration.

Klipstein, W. M.; Kohel, J.; Seidel, D. J.; Thompson, R. J.; Maleki, L.; Gibble, K.

2000-01-01

324

Toward atomic resolution diffractive imaging of isolated molecules with x-ray free-electron lasers  

E-print Network

We give a detailed account of the theoretical analysis and the experimental results of an x-ray-diffraction experiment on quantum-state selected and strongly laser-aligned gas-phase ensembles of the prototypical large asymmetric rotor molecule 2,5-diiodobenzonitrile, performed at the Linac Coherent Light Source [Phys. Rev. Lett. 112, 083002 (2014)]. This experiment is the first step toward coherent diffractive imaging of structures and structural dynamics of isolated molecules at atomic resolution, i. e., picometers and femtoseconds, using x-ray free-electron lasers.

Stern, Stephan; Filsinger, Frank; Rouzée, Arnaud; Rudenko, Artem; Johnsson, Per; Martin, Andrew V; Barty, Anton; Bostedt, Christoph; Bozek, John D; Coffee, Ryan N; Epp, Sascha; Erk, Benjamin; Foucar, Lutz; Hartmann, Robert; Kimmel, Nils; Kühnel, Kai-Uwe; Maurer, Jochen; Messerschmidt, Marc; Rudek, Benedikt; Starodub, Dmitri G; Thøgersen, Jan; Weidenspointner, Georg; White, Thomas A; Stapelfeldt, Henrik; Rolles, Daniel; Chapman, Henry N; Küpper, Jochen

2014-01-01

325

High-power Ti:sapphire lasers for spectroscopy of antiprotonic atoms and radioactive ions  

NASA Astrophysics Data System (ADS)

The ASACUSA collaboration has developed injection-seeded Ti:sapphire lasers of linewidth ?pl ˜ 6 MHz, pulse energy 50-100 mJ, and output wavelength ? = 726-941 nm. They are being used in two-photon spectroscopy experiments of antiprotonic helium atoms at the Antiproton Decelerator (AD) of CERN. Ti:sapphire lasers of larger linewidth ?pl ˜ 100 MHz but more robust design will also be used in collinear resonance ionization spectroscopy (CRIS) experiments of neutron-deficient francium ions at the ISOLDE facility.

Hori, M.; Dax, A.; Soter, A.

2012-12-01

326

High-power Ti:sapphire lasers for spectroscopy of antiprotonic atoms and radioactive ions  

NASA Astrophysics Data System (ADS)

The ASACUSA collaboration has developed injection-seeded Ti:sapphire lasers of linewidth ?pl ˜ 6 MHz, pulse energy 50-100 mJ, and output wavelength ? = 726-941 nm. They are being used in two-photon spectroscopy experiments of antiprotonic helium atoms at the Antiproton Decelerator (AD) of CERN. Ti:sapphire lasers of larger linewidth ?pl ˜ 100 MHz but more robust design will also be used in collinear resonance ionization spectroscopy (CRIS) experiments of neutron-deficient francium ions at the ISOLDE facility.

Hori, M.; Dax, A.; Soter, A.

327

Stabilization of circular Rydberg atoms by circularly polarized infrared laser fields  

SciTech Connect

The ionization dynamics of circular Rydberg states in strong circularly polarized infrared (800 nm) laser fields is studied by means of numerical simulations with the time-dependent Schroedinger equation. We find that at certain intensities, related to the radius of the Rydberg states, atomic stabilization sets in, and the ionization probability decreases as the intensity is further increased. Moreover, there is a strong dependence of the ionization probability on the rotational direction of the applied laser field, which can be understood from a simple classical analogy.

Askeland, S.; Soerngaard, S. A.; Nepstad, R.; Foerre, M. [Department of Physics and Technology, University of Bergen, N-5007 Bergen (Norway); Pilskog, I. [Department of Physics and Technology, University of Bergen, N-5007 Bergen (Norway); Laboratoire de Chimie Physique - Matiere et Rayonnement, Universite Pierre et Marie Curie - CNRS (UMR 7614), F-75231 Paris Cedex 05 (France)

2011-09-15

328

Laser Irradiated Enhancement of the Atomic Electron Capture Rate in search of New Physics  

E-print Network

Electron capture processes are important in the search for new physics. In this context, a high capture rate is desired. We investigate the possibility of enhancing the electron capture rate by irradiating laser beam to ''atom''. The possibility of such enhancement can be understood as a consequence of an enhancement of the electron wave function at the origin, $\\Psi (0)$, through an increased effective mass of the electron. We find that an order of magnitude enhancement can be realized by using a laser with intensity on the order of $10^{10}$ W/mm$^2$ and a photon energy on the order of $10^{-3}$ eV.

Takaaki Nomura; Joe Sato; Takashi Shimomura

2007-06-16

329

Toward atomic resolution diffractive imaging of isolated molecules with X-ray free-electron lasers.  

PubMed

We give a detailed account of the theoretical analysis and the experimental results of an X-ray-diffraction experiment on quantum-state selected and strongly laser-aligned gas-phase ensembles of the prototypical large asymmetric rotor molecule 2,5-diiodobenzonitrile, performed at the Linac Coherent Light Source [Phys. Rev. Lett.112, 083002 (2014)]. This experiment is the first step toward coherent diffractive imaging of structures and structural dynamics of isolated molecules at atomic resolution, i.e., picometers and femtoseconds, using X-ray free-electron lasers. PMID:25415561

Stern, S; Holmegaard, L; Filsinger, F; Rouzée, A; Rudenko, A; Johnsson, P; Martin, A V; Barty, A; Bostedt, C; Bozek, J; Coffee, R; Epp, S; Erk, B; Foucar, L; Hartmann, R; Kimmel, N; Kühnel, K-U; Maurer, J; Messerschmidt, M; Rudek, B; Starodub, D; Thøgersen, J; Weidenspointner, G; White, T A; Stapelfeldt, H; Rolles, D; Chapman, H N; Küpper, J

2014-01-01

330

Model for atomic dielectric response in strong, time-dependent laser fields  

NASA Astrophysics Data System (ADS)

A nonlocal quantum-mechanical model is presented for calculating the atomic dielectric response to a strong laser electric field. By replacing the Coulomb potential with a nonlocal potential in the Schrödinger equation, a 3 + 1-dimensional calculation of the time-dependent electric dipole moment can be reformulated as a 0 + 1-dimensional integral equation that retains the three-dimensional dynamics, while offering significant computational savings. The model is benchmarked against an established ionization model and ab initio simulation of the time-dependent Schrödinger equation. The reduced computational overhead makes the model a promising candidate to incorporate full quantum-mechanical time dynamics in laser pulse propagation simulations.

Rensink, T. C.; Antonsen, T. M.; Palastro, J. P.; Gordon, D. F.

2014-03-01

331

Model for the Atomic Dielectric Response in Time Dependent Laser Fields  

E-print Network

A nonlocal quantum model is presented for calculating the atomic dielectric response to a strong laser electric field. By replacing the Coulomb potential with a nonlocal potential in the Schrodinger equation, a 3+1D calculation of the time-dependent electric dipole moment can be replaced with a 0+1D integral equation, offering significant computational savings. The model is benchmarked against an established ionization model and \\textit{ab initio} simulation of the time-dependent Schrodinger equation. The reduced computational overhead makes the model a promising candidate to incorporate full quantum mechanical time dynamics in laser pulse propagation simulations.

Rensink, T C; Palastro, J P; Gordon, D

2013-01-01

332

Observation of picosecond superfluorescent pulses in rubidium atomic vapor pumped by 100-fs laser pulses  

SciTech Connect

We study the superfluorescence (SF) from a gas of rubidium atoms. The atoms of a dense vapor are excited to the 5D state from the 5S state by a two-photon process driven by 100-fs laser pulses. The atoms decay to the 6P state and then to the 5S state. The SF emission at 420 nm on the 6P-5S transition is recorded by a streak camera with picosecond time resolution. The time duration of the generated SF is tens of picoseconds, which is much shorter than the time scale of the usual relaxation processes, including spontaneous emission and atomic coherence dephasing. The dependence of the time delay between the reference input pulse and SF is measured as a function of laser power. The experimental data are described quantitatively by a simulation based on the semiclassical atom-field interaction theory. The observed change in scaling laws for the peak intensity and delay time can be elucidated by an SF theory in which the sample length is larger than the cooperation length.

Ariunbold, Gombojav O. [Institute for Quantum Studies and Department of Physics, Texas A and M University, College Station, Texas 77843 (United States); Department of Physics, National University of Mongolia, 210646 Ulaanbaatar (Mongolia); Kash, Michael M. [Institute for Quantum Studies and Department of Physics, Texas A and M University, College Station, Texas 77843 (United States); Department of Physics, Lake Forest College, Lake Forest, Illinois 60045 (United States); Sautenkov, Vladimir A. [Institute for Quantum Studies and Department of Physics, Texas A and M University, College Station, Texas 77843 (United States); Lebedev Institute of Physics, Moscow 119991 (Russian Federation); Li, Hebin; Welch, George R. [Institute for Quantum Studies and Department of Physics, Texas A and M University, College Station, Texas 77843 (United States); Rostovtsev, Yuri V. [Institute for Quantum Studies and Department of Physics, Texas A and M University, College Station, Texas 77843 (United States); Department of Physics, University of North Texas, 1155 Union Circle 311427, Denton, Texas 76203 (United States); Scully, Marlan O. [Institute for Quantum Studies and Department of Physics, Texas A and M University, College Station, Texas 77843 (United States); Applied Physics and Materials Science Group, Princeton University, Princeton, New Jersey 08544 (United States); Max-Planck-Institute fuer Quantenoptik, D-85748 Garching (Germany)

2010-10-15

333

Measurements of sulfur compounds in CO 2 by diode laser atomic absorption spectrometry  

NASA Astrophysics Data System (ADS)

Two simple methods for the analysis of the total concentration of sulfur in CO 2 by diode laser atomic absorption spectrometry of excited, metastable sulfur atoms in a direct current discharge are presented. In the first method, the CO 2 sample gas is mixed with the plasma gas (Ar or He) while the second is based on reproducible measurements of the sulfur released from the walls in a helium discharge after being deposited as a result of operating the discharge in pure CO 2 sample gas. The detection limits obtained satisfy the requirements for the control of sulfur compounds in CO 2 used in the food and beverage industry.

Franzke, J.; Stancu, D. G.; Niemax, K.

2003-07-01

334

Nuclear Signatures in High-Order Harmonic Generation from Laser-Driven Muonic Atoms  

SciTech Connect

High-order harmonic generation from muonic atoms exposed to intense laser fields is considered. Our particular interest lies in effects arising from the finite nuclear mass and size. We numerically perform a fully quantum mechanical treatment of the muon-nucleus dynamics by employing modified soft-core and hard-core potentials. It is shown that the position of the high-energy cutoff of the harmonic spectrum depends on the nuclear mass, while the height of the spectral plateau is sensitive to the nuclear radius. We also demonstrate that {gamma}-ray harmonics can be generated from muonic atoms in ultrastrong VUV fields, which have potential to induce photonuclear reactions.

Shahbaz, A.; Mueller, C.; Staudt, A.; Keitel, C. H. [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, 69117 Heidelberg (Germany); Buervenich, T. J. [Frankfurt Institute for Advanced Studies, Johann Wolfgang Goethe University, Max-von-Laue-Strasse 1, 60438 Frankfurt (Germany)

2007-06-29

335

Survival of Rydberg atoms in intense laser fields and the role of nondipole effects  

NASA Astrophysics Data System (ADS)

We consider the interaction of Rydberg atoms with strong infrared laser pulses using an approach based on the Magnus expansion of the time evolution operator. First-order corrections beyond the electric dipole approximation are also included in the theory. We illustrate the dynamics of the interaction at the parameters of the experiment [Eichmann et al., Phys. Rev. Lett. 110, 203002 (2013), 10.1103/PhysRevLett.110.203002]. It emerges that the depletion of Rydberg atoms in this regime comes predominantly from the nondipole effects.

Klaiber, Michael; Dimitrovski, Darko

2015-02-01

336

New metal atom laser transitions in As, Bi, Ga, Ge, Hg, In, Pb, Sb, and Tl  

NASA Technical Reports Server (NTRS)

A double discharge technique was used in the investigation. An initial discharge established between parallel arrays of tungsten pin electrodes was followed, after a variable time delay, by a high voltage (180 kV), short duration (50 nsec) secondary discharge between two aluminum main electrodes. Metal compounds, including metal alkyls, hydrides, and halides, were used to obtain the required metal atom concentrations. Twenty-four new laser transitions involving 9 different metal atoms were observed. The observed relations are shown in a number of partial energy-level diagrams.

Chou, M. S.; Cool, T. A.

1976-01-01

337

TUDE DE LA LUMIRE DE FLUORESCENCE D'ATOMES EXCITS EN INTERACTION RSONNANTE AVEC UN LASER  

E-print Network

443. �TUDE DE LA LUMI�RE DE FLUORESCENCE D'ATOMES EXCIT�S EN INTERACTION R�SONNANTE AVEC UN LASER.N.R.S. (Reçu le 22 septembre 1967.) Résumé. 2014 La lumière de fluorescence émise par des atomes de néon d modifications sur les raies de fluorescence émises par le niveau 2p4 permet de vérifier les prévisions

Boyer, Edmond

338

Determination of mercury in microwave-digested soil by laser-excited atomic fluorescence spectrometry with electrothermal atomization.  

PubMed

A sample digestion procedure was developed which employs microwave heating of soil and sediment in concentrated nitric acid in a high-pressure closed vessel. Complete dissolution of mercury into the sample solution occurs within 5 min at 59 W/vessel without loss of analyte through overpressurization. Laser-excited atomic fluorescence spectrometry with electrothermal atomization (LEAFS-ETA) was used as the detection method. The scheme uses a two-step excitation, with lambda(1) = 253.7 nm and lambda(2) = 435.8 nm. Direct line fluorescence was measured at 546.2 nm. The absolute instrumental limit of detection was 14 fg; 1.4 pg/ml with a 10 mul sample injection. The recoveries of mercury in two spiked samples were 94 and 98%. The SRM 8406 (Mercury in River Sediment) was digested and analyzed for mercury, and the results (58.4 +/- 1.8 ng/g) agreed well with the reference value of 60 ng/g. The results obtained by LEAFS-ETA with microwave sample digestion are in good agreement with those found by cold vapor atomic absorption spectrometry with EPA Series Method 245.5 sample digestion, which is one of the most commonly used methods for the determination of mercury in soil. PMID:18966173

Pagano, S T; Smith, B W; Winefordner, J D

1994-12-01

339

Interaction of laser-cooled 87Rb atoms with higher order modes of an optical nanofibre  

NASA Astrophysics Data System (ADS)

Optical nanofibres are used to confine light to sub-wavelength regions and are very promising tools for the development of optical fibre-based quantum networks using cold, neutral atoms. To date, experimental studies on atoms near nanofibres have focussed on fundamental fibre mode interactions. In this work, we demonstrate the integration of a few-mode optical nanofibre into a magneto-optical trap for 87Rb atoms. The nanofibre, with a waist diameter of ˜700 nm, supports both the fundamental and first group of higher order modes (HOMs) and is used for atomic fluorescence and absorption studies. In general, light propagating in higher order fibre modes has a greater evanescent field extension around the waist in comparison with the fundamental mode. By exploiting this behaviour, we demonstrate that the detected signal of fluorescent photons emitted from a cloud of cold atoms centred at the nanofibre waist is larger if HOMs are also included. In particular, the signal from HOMs appears to be about six times larger than that obtained for the fundamental mode. Absorption of on-resonance, HOM probe light by the laser-cooled atoms is also observed. These advances should facilitate the realization of atom trapping schemes based on HOM interference.

Kumar, Ravi; Gokhroo, Vandna; Deasy, Kieran; Maimaiti, Aili; Frawley, Mary C.; Phelan, Ciarán; Chormaic, Síle Nic

2015-01-01

340

Multi-element analysis by ArF laser excited atomic fluorescence of laser ablated plumes: Mechanism and applications  

NASA Astrophysics Data System (ADS)

A new multi-element analysis technique based on laser-excited atomic fluorescence was reviewed. However, the one-wavelength-one-transition constraint was overcome. Numerous elements were induced to fluoresce at a single excitation wavelength of 193 nm. This was possible provided that the analytes were imbedded in dense plumes, such as those produced by pulsed laser ablation. The underlying mechanism of the technique was explained and corroborated. Analytical applications to metals, plastics, ceramics and their composites were discribed. Detection limits in the ng/g range and mass limits of atto moles were demonstrated. Several real-world problems, including the analysis of paint coating for trace lead, the non-destructive analysis of potteries and ink, the chemical profiling of electrode-plastic interfaces, and the analysis of ingestible lead colloids were discussed.

Cai, Yue; Chu, Po-Chun; Ho, Sut Kam; Cheung, Nai-Ho

2012-12-01

341

Laser-induced fluorescence of atomic hydrogen in an arcjet thruster  

NASA Technical Reports Server (NTRS)

A diagnostic has been developed to measure gas kinetic temperature and velocity in a 1 kW hydrogen fueled arcjet thruster. The technique is based on laser-induced fluorescence of the Balmer alpha transition (656 nm) in atomic hydrogen. A narrowband CW ring dye laser scans the excitation spectrum, permitting accurate determination of the atomic line shape and position. The velocity is inferred from the Doppler shift of the transition while the temperature is obtained from the shape. Near the exit plane, measured axial velocity varies between 4 and 14 km/s; measured radial velocity varies from 0 to 4 km/s. Temperatures were measured in the range from 1000 K near the edge of the plume to 5000 K at the centerline. Relevant broadening mechanisms are discussed.

Liebeskind, John G.; Hanson, Ronald K.; Cappelli, Mark A.

1992-01-01

342

Optimal Control of Atomic, Molecular and Electron Dynamics with Tailored Femtosecond Laser Pulses  

Microsoft Academic Search

With the invention of the laser, the dream was realized to actively exert control over quantum systems. Active control over\\u000a the dynamics of quantum mechanical systems is a fascinating perspective in modern physics. Cleavage and creation of predetermined\\u000a chemical bonds, selective population transfer in atoms and molecules, and steering the dynamics of bound and free electrons\\u000a have been important milestones

Tobias Brixner; Thomas Pfeifer; Gustav Gerber; Matthias Wollenhaupt; Thomas Baumert

343

Precise laser spectroscopy of the antiprotonic helium atom and CPT test on antiproton mass and charge  

E-print Network

We have measured twelve transition frequencies of the antiprotonic helium atom (pbar-He+) with precisions of 0.1--0.2 ppm using a laser spectroscopic method. The agreement between the experiment and theories was so good that we can put a limit on the proton-antiproton mass (or charge) difference. The new limit is expected to be much smaller than the already published value, 60 ppb.

H. Yamaguchi; J. Eades; R. S. Hayano; M. Hori; D. Horvath; T. Ishikawa; B. Juhasz; J. Sakaguchi; H. A. Torii; E. Widmann; T. Yamazaki

2003-03-19

344

Intense terahertz emission from atomic cluster plasma produced by intense femtosecond laser pulses  

SciTech Connect

Terahertz (THz) emission from argon cluster plasma, generated by intense femtosecond laser pulses in the energy range of 10-70 mJ, has been investigated. THz polarization, energy dependence, and angular distribution were measured to provide an initial discussion on the mechanisms of THz emission. THz pulses of much higher energy were generated from argon clusters than from argon gas, which indicates that plasma produced from atomic clusters holds considerable promise as an intense THz source.

Jahangiri, Fazel; Hashida, Masaki; Tokita, Shigeki; Sakabe, Shuji [Advanced Research Center for Beam Science, ICR, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan and Department of Physics, GSS, Kyoto University, Kitashirakawa, Sakyo, Kyoto 606-7501 (Japan); Nagashima, Takeshi; Hangyo, Masanori [Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871 (Japan)

2011-12-26

345

Charge states of many-electron atoms in a strong laser field  

SciTech Connect

The nonresonant, multiphoton ionization of many-electron atoms is explained theoretically within the Thomas-Fermi model with the inclusion of an electromagnetic field. Numerical results are presented for the charge state and induced dipole moment versus the strength of the applied electric field, which, because of the scaling properties of the model, can be expressed as universal functions of the field. Our results compare favorably with those from recent ionization experiments performed on noble gases using laser fields.

Susskind, S.M.; Valeo, E.J.; Oberman, C.R. (Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, New Jersey (US)); Bernstein, I.B. (Section of Applied Physics, Yale University, New Haven, Connecticut (US))

1991-03-01

346

Synthesis and behavior of metallic glasses via gas atomization and laser deposition  

Microsoft Academic Search

Al-based and Fe-used bulk metallic glasses (MGs) are of engineering and scientific interest due to their unique combination of attributes. The objective of the present dissertation is to provide fundamental insight into the influence of synthesis on the microstructure and physical behavior of Al-based and Fe-based MGs. Two non-equilibrium synthesis techniques are selected for study, gas atomization and laser deposition

Baolong Zheng

2006-01-01

347

Optical Ramsey interferences on laser cooled and trapped atoms, detected by electron shelving  

Microsoft Academic Search

Based on a new detection scheme optical Ramsey fringes on the magnesium intercombination transition (lambda=457 nm) have been demonstrated with a resolution of 4 kHz and an accuracy of 1 Hz (Deltav\\/v ~2×10-15)using laser cooled and trapped atoms. Applying a pulsed excitation scheme to the trapped ensemble, the Ramsey signals are nearly undisturbed by the relativistic Doppler effect and phase

K. Sengstock; U. Sterr; G. Hennig; D. Bettermann; J. H. Müller; W. Ertmer

1993-01-01

348

Wave packet dynamics of excited atomic electrons in intense laser fields  

SciTech Connect

Dynamics of muliphoton ionization in the tunneling (long wavelength, high intensity) regime is described. Photoemission by tunnel ionized atoms is dominated by the odd harmonics of the driving laser field. Excitation by ultra short ({similar_to} 10-20 fs) pulses produces hiogh harmonics with characteristics which will alow them to be compressed to given coherent sources of VUV and possibly XUV radiation with pulse lengths near or below 1 fs.

Kulander, K.C. [Lawrence Livermore National Lab., CA (United States); Schafer, K.J. [Louisiana State Univ., Baton Rouge, LA (United States). Dept. of Physics and Astronomy

1996-08-01

349

Predictions of laser-cooling temperatures for multilevel atoms in three-dimensional polarization-gradient fields  

SciTech Connect

We analyze the dynamics of atom-laser interactions for atoms having multiple, closely spaced, excited-state hyperfine manifolds. The system is treated fully quantum mechanically, including the atom's center-of-mass degree of freedom, and motion is described in a polarization gradient field created by a three-dimensional laser configuration. We develop the master equation describing this system, and then specialize it to the low-intensity limit by adiabatically eliminating the excited states. We show how this master equation can be simulated using the Monte Carlo wave function technique, and we provide details on the implementation of this procedure. Monte Carlo calculations of steady state atomic momentum distributions for two fermionic alkaline earth isotopes, {sup 25}Mg and {sup 87}Sr, interacting with a three-dimensional lin-perpendicular-lin laser configuration are presented, providing estimates of experimentally achievable laser-cooling temperatures.

Dunn, Josh W.; Greene, Chris H. [JILA, University of Colorado and National Institute of Standards and Technology, and Department of Physics, University of Colorado, Boulder, Colorado 80309-0440 (United States)

2006-03-15

350

Ground state bromine atom density measurements by two-photon absorption laser-induced fluorescence  

NASA Astrophysics Data System (ADS)

Ground state bromine atom detection by two-photon absorption laser-induced fluorescence (TALIF) is demonstrated. The (4p5) {^2Po3/2} bromine atoms are excited by two-photon absorption at 252.594 nm to the (5p) {^4So3/2} state and detected by 635.25 nm fluorescence to the (5s) 4P5/2 state. The atoms are generated in a radio-frequency inductively-coupled plasma in pure HBr. The excitation laser also causes some photodissociation of HBr molecules, but this can be minimized by not focussing the laser beam, still giving adequate signal levels. We determined the natural lifetime of the emitting (5p) {^4So3/2} state, ?f^Br*=30.9 +/- 1.4 ns and the rate constant for quenching of this state by collision with HBr molecules, k_HBrQ = 1.02 +/- 0.07× 10-15 m3 s-1 .

Sirse, N.; Foucher, M.; Chabert, P.; Booth, J.-P.

2014-12-01

351

Non-thermal laser-induced desorption of metal atoms with bimodal kinetic energy distribution  

NASA Astrophysics Data System (ADS)

Laser-induced desorption of metal atoms at low rate has been studied for pulsed excitation with wavelengths of ?=266, 355, 532 and 1064 nm. For this purpose sodium adsorbed on quartz served as a model system. The detached Na atoms were photo-ionized with the light of a second laser operating at ?=193 nm and their kinetic energy distribution was determined by time-of-flight measurements. For ?=1064 nm a distribution typical of thermal bond breaking is observed. If desorption, however, is stimulated with light of ?=266 or 532 nm, the kinetic energy distribution is non-thermal with a single maximum at E kin=0.16±0.02 eV. For ?=355 nm the non-thermal distribution is even bimodal with maxima appearing at E kin=0.16±0.02 and 0.33±0.02 eV. These values of the kinetic energies actually remain constant under variation of all experimental parameters. They appear to reflect the electronic and geometric properties of different binding sites from which the atoms are detached and thus constitute fingerprints of the metal surface. The non-thermal desorption mechanism is discussed in the framework of the Menzel-Gomer-Redhead scenario. The transition from non-thermal to thermal desorption at large fluences of the laser light could also be identified.

Götz, T.; Bergt, M.; Hoheisel, W.; Träger, F.; Stuke, M.

1996-09-01

352

Diode-laser-based sensor for ultraviolet absorption measurements of atomic mercury  

NASA Astrophysics Data System (ADS)

A new sensor has been developed for measuring atomic mercury using absorption spectroscopy with 254-nm radiation generated from two sum-frequency-mixed diode lasers. Beams from a 375-nm external-cavity diode laser and a 784-nm distributed feedback diode laser are mixed in a beta-barium-borate crystal to generate approximately 4 nW of ultraviolet radiation. The development of the sensor is described along with extensive characterization experiments in a mercury vapor cell in the laboratory. An accuracy of ±6% in the absolute concentration of atomic mercury has been demonstrated by comparison with equilibrium vapor pressure calculations. The detection limit is approximately 0.1 parts per billion of atomic mercury in a meter path length for 300-K gas and a 10-s integration time. The insensitivity of the sensor to broadband attenuation is demonstrated. Measurements of collision-broadening coefficients for air, N2, Ar, and CO2 are reported, and implementation of wavelength-modulation spectroscopy with the sensor is demonstrated. Finally, results are presented from measurements with the sensor in situ in the exhaust stream of an actual coal-fired combustor.

Anderson, T. N.; Magnuson, J. K.; Lucht, R. P.

2007-04-01

353

Low phase noise diode laser oscillator for 1S-2S spectroscopy in atomic hydrogen  

E-print Network

We report on a low-noise diode laser oscillator at 972 nm actively stabilized to an ultra-stable vibrationally- and thermally compensated reference cavity. To increase the fraction of laser power in the carrier we designed a 20 cm long external cavity diode laser with an intra-cavity electro-optical modulator. The fractional power in the carrier reaches 99.9% which corresponds to a rms phase noise of $\\phi^2_\\textrm{rms}=1\\,\\textrm{mrad}^2$ in 10\\,MHz bandwidth. Using this oscillator we recorded 1S-2S spectra in atomic hydrogen and have not observed any significant loss of the excitation efficiency due to phase noise multiplication in the three consecutive 2-photon processes.

N. Kolachevsky; J. Alnis; C. G. Parthey; A. Matveev; R. Landig; T. W. Haensch

2011-07-08

354

Laser-excitation technique for the measurement of absolute transition probabilities of weak atomic lines  

NASA Technical Reports Server (NTRS)

A new technique is presented for the measurement of transition probabilities for weak allowed, intersystem, and forbidden lines. The method exploits the fact that oscillator strength is proportional to the number of stimulated absorptions and emissions produced by a narrow-band laser pulse of known energy which is in resonance with an atomic transition. The method is tested for a particular transition of Mg I with a known oscillator strength value and of appropriate magnitude. The number densities are measured using a Mach-Zehnder interferometer and the hook method for the lower level population and by measuring an absorption-equivalent width for the other. The apparatus consisted of a high-power tunable laser and a magnesium oven to produce excited Mg vapor, and a laser-plasma background continuum. The results are in good agreement with theoretical and other experimental data.

Kwong, H. S.; Smith, P. L.; Parkinson, W. H.

1982-01-01

355

Velocity selective bi-polarization spectroscopy for laser cooling of metastable Krypton atoms  

E-print Network

We report a velocity selective bi-polarization spectroscopy (VS-BPS) technique to generate a background-free, dispersion-like reference signal which is tunable over a wide range of frequency. In this technique, a pair of linearly polarized weak probe beams passing through a gas cell of metastable Krypton (Kr*) atoms, overlaps with a pair of counter-propagating circularly polarized strong pump beams derived from an independently tunable control laser. The polarization spectroscopy signals from the two probe beams, after subtraction, result in VS-BPS signal. The spectral shifting in VS-BPS signal can be achieved by tuning the frequency of the control laser. The dependence of the amplitude and slope of the VS-BPS signal on the RF power used for excitation of Kr atoms in the gas cell and on the power of pump beams has been studied. The frequency stability of a diode laser locked with VS-BPS signal has been found to be better than the frequency stability of the laser locked with a saturated absorption spectroscopy...

Kale, Y B; Singh, S; Mishra, S R; Rawat, H S

2014-01-01

356

Nondipole ionization dynamics in atoms induced by intense xuv laser fields  

NASA Astrophysics Data System (ADS)

Solving the time-dependent Schrödinger equation from first principles, the laser-induced breakup dynamics of hydrogen is studied beyond the electric dipole approximation, at very high laser intensities. It is assumed that the atom is being irradiated by an extreme ultraviolet laser light pulse at a wavelength of 13 nm, corresponding to a photon energy of 95 eV. It has already been experimentally demonstrated that the free-electron laser (FEL) FLASH in Hamburg can deliver irradiance levels up to about 1016W/cm2 in this wavelength range. Although we will go to even higher intensities in the present work, in order to spot nondipole effects, this merely demonstrates that ultrahigh light intensities can be achieved with present FEL technologies. Furthermore, with new seeding techniques the laser power is expected to go even higher in the future. In our study the atom is exposed to a short attosecond laser pulse, and the role of higher-order corrections to the electric dipole approximation is studied systematically. The main findings are that higher-order corrections beyond the leading first-order term, to a good approximation, can be neglected for all intensities within the nonrelativistic regime, provided the pulse duration is not too long. This means that the effect of second- and higher-order corrections only needs to be accounted for when entering the relativistic regime, within the scope of the Dirac equation. It is further found that the leading first-order correction to the dipole approximation has a great impact on the angular emission pattern of the low-energy photoelectrons.

Førre, Morten; Simonsen, Aleksander Skjerlie

2014-11-01

357

Exploring Ramsey-coherent population trapping atomic clock realized with pulsed microwave modulated laser  

SciTech Connect

A scheme for a Ramsey-coherent population trapping (CPT) atomic clock that eliminates the acousto-optic modulator (AOM) is proposed and experimentally studied. Driven by a periodically microwave modulated current, the vertical-cavity surface-emitting laser emits a continuous beam that switches between monochromatic and multichromatic modes. Ramsey-CPT interference has been studied with this mode-switching beam. In eliminating the AOM, which is used to generate pulsed laser in conventional Ramsey-CPT atomic clock, the physics package of the proposed scheme is virtually the same as that of a conventional compact CPT atomic clock, although the resource budget for the electronics will slightly increase as a microwave switch should be added. By evaluating and comparing experimentally recorded signals from the two Ramsey-CPT schemes, the short-term frequency stability of the proposed scheme was found to be 46% better than the scheme with AOM. The experimental results suggest that the implementation of a compact Ramsey-CPT atomic clock promises better frequency stability.

Yang, Jing; Yun, Peter [Key Laboratory of Atomic Frequency Standards, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071 (China); Tian, Yuan; Tan, Bozhong [Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074 (China); Gu, Sihong, E-mail: shgu@wipm.ac.cn [Key Laboratory of Atomic Frequency Standards, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071 (China); Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074 (China)

2014-03-07

358

Preparation of nanowire specimens for laser-assisted atom probe tomography  

NASA Astrophysics Data System (ADS)

The availability of reliable and well-engineered commercial instruments and data analysis software has led to development in recent years of robust and ergonomic atom-probe tomographs. Indeed, atom-probe tomography (APT) is now being applied to a broader range of materials classes that involve highly important scientific and technological problems in materials science and engineering. Dual-beam focused-ion beam microscopy and its application to the fabrication of APT microtip specimens have dramatically improved the ability to probe a variety of systems. However, the sample preparation is still challenging especially for emerging nanomaterials such as epitaxial nanowires which typically grow vertically on a substrate through metal-catalyzed vapor phase epitaxy. The size, morphology, density, and sensitivity to radiation damage are the most influential parameters in the preparation of nanowire specimens for APT. In this paper, we describe a step-by-step process methodology to allow a precisely controlled, damage-free transfer of individual, short silicon nanowires onto atom probe microposts. Starting with a dense array of tiny nanowires and using focused ion beam, we employed a sequence of protective layers and markers to identify the nanowire to be transferred and probed while protecting it against Ga ions during lift-off processing and tip sharpening. Based on this approach, high-quality three-dimensional atom-by-atom maps of single aluminum-catalyzed silicon nanowires are obtained using a highly focused ultraviolet laser-assisted local electrode atom probe tomograph.

Blumtritt, H.; Isheim, D.; Senz, S.; Seidman, D. N.; Moutanabbir, O.

2014-10-01

359

Interaction of atomic systems with X-ray free-electron lasers.  

PubMed

The planned construction of an X-ray free-electron laser (XFEL) will provide new opportunities for research in various areas of physics, chemistry and biology. The proposed design of the XFELs at DESY (Deutsches Elektronen-Synchrotron) and SLAC (Stanford Linear Accelerator Center) is built on the concept of a fourth-generation synchrotron source and will provide an intense pulse (I(0) approximately 10(16) W cm(-2), tau(gamma) approximately 100 fs) for photon wavelengths down to 1 A. Some guidelines for applications of these sources pertaining to atomic physics are presented here. Issues such as the onset of strong photon-field effects, multiple ionization and hollow-atom formation are analyzed. Attention is especially given to studying the interaction with rare-gas atoms, for which some numerical estimates are provided. PMID:12200573

Kornberg, M A; Godunov, A L; Itza-Ortiz, S; Ederer, D L; McGuire, J H; Young, L

2002-09-01

360

MOLECULARPHYSICS, 1984, VOL. 52, No. 3, 541-566 An investigation of the laser optogalvanic effect for atoms  

E-print Network

in a laser-induced impedance M.P. S #12;542 J. Pfaff et al. change. Particularly, the mechanisms responsible lasers operating at visible wavelengths. In addition, we report the first definitive detection by this method of atomic ions having high second ionization energies (He+, At+). The objective of this research

Cohen, Ronald C.

361

The influence of and molecules on discharge equilibrium and F-atom production in a phototriggered HF laser using  

Microsoft Academic Search

The discharge equilibrium and the F-atom production kinetics in a phototriggered HF laser using gas mixtures containing Ne and with hydrogen or ethane have been investigated. Coupled experimental and theoretical studies have been carried out, through a 0D discharge modelling and measurements of the current, of the voltage and of the extracted laser energy, together with emission spectroscopy on F

L Richeboeuf; S Pasquiers; M Legentil; V Puech

1998-01-01

362

Relativistic Angular Distribution of Photoelectrons in the Tunneling Ionization of Atoms by a Linearly Polarized Laser Field  

NASA Astrophysics Data System (ADS)

In this paper, the angular distribution of the ejected photoelectrons during relativistic tunneling ionization of atoms by linearly polarized laser field is discussed. The effect of shifted ionization potential has been taken into account. The influence of two different spatial profiles of an intense laser pulse is studied.

Miladinovi?, Tatjana B.; Petrovi?, Violeta M.

2015-04-01

363

A Simple LIBS (Laser-Induced Breakdown Spectroscopy) Laboratory Experiment to Introduce Undergraduates to Calibration Functions and Atomic Spectroscopy  

ERIC Educational Resources Information Center

This laboratory experiment introduces students to a different type of atomic spectroscopy: laser-induced breakdown spectroscopy (LIBS). LIBS uses a laser-generated spark to excite the sample; once excited, the elemental emission is spectrally resolved and detected. The students use LIBS to analyze a series of standard synthetic silicate samples…

Chinni, Rosemarie C.

2012-01-01

364

Experimental demonstration of a compact and high-performance laser-pumped rubidium gas cell atomic frequency standard  

Microsoft Academic Search

The authors present a compact high-performance laser-pumped Rubidium atomic frequency standard exploiting the advantages of laser optical pumping for improved stability. The clock is based on an industrial Rb clock with the lamp assembly removed and optically pumped by light from a compact frequency-stabilized laser head. The modification of the buffer gas filling in the clock resonance cell reduces instabilities

Christoph Affolderbach; Fabien Droz; Gaetano Mileti

2006-01-01

365

Effects of laser linewidth on an effective method for excitation in three-level atomic systems by two optimally detuned counterpropagating pulsed lasers  

SciTech Connect

Population transfer in three-level atomic systems with high efficiency and selectivity is desirable for practical applications in laser spectroscopy, trace analysis, and isotope separation. The effective excitation method for achieving this population transfer in three-level atomic systems using coherent two-photon excitation with two optimally detuned counterpropagating pulsed lasers, initially investigated analytically assuming monochromatic lasers and Doppler-free systems, is studied numerically by solving the density matrix equations incorporating finite laser linewidth and effective Doppler width. A three-level Yb system is chosen for illustration of numerical results. The effects of laser linewidth and effective Doppler width on the values of optimal detunings and maximum third-level population are discussed.

Gupta, G. P.; Suri, B. M. [Laser and Plasma Technology Division, Bhabha Atomic Research Centre, Mumbai - 400085 (India)

2008-02-15

366

Millikelvin Reactive Collisions between Sympathetically Cooled Molecular Ions and Laser-Cooled Atoms in an Ion-Atom Hybrid Trap  

NASA Astrophysics Data System (ADS)

We report on a study of cold reactive collisions between sympathetically cooled molecular ions and laser-cooled atoms in an ion-atom hybrid trap. Chemical reactions were studied at average collision energies ?Ecoll?/kB?20mK, about 2 orders of magnitude lower than has been achieved in previous experiments with molecular ions. Choosing N2++Rb as a prototypical system, we find that the reaction rate is independent of the collision energy within the range studied, but strongly dependent on the internal state of Rb. Highly efficient charge exchange four times faster than the Langevin rate was observed with Rb in the excited (5p) P3/22 state. This observation is rationalized by a capture process dominated by the charge-quadrupole interaction and a near resonance between the entrance and exit channels of the system. Our results provide a test of classical models for reactions of molecular ions at the lowest energies reached thus far.

Hall, Felix H. J.; Willitsch, Stefan

2012-12-01

367

Measurement method for the nuclear anapole moment of laser-trapped alkali-metal atoms E. Gomez,1,  

E-print Network

for the hyperfine anomaly measurements in Fr. Current plans at the Isotope Separator and Accelerator ISAC at TRIUMFMeasurement method for the nuclear anapole moment of laser-trapped alkali-metal atoms E. Gomez,1 transition between the ground hy- perfine levels in a chain of isotopes of an alkali-metal atom. Alkali

Orozco, Luis A.

368

Reduction of Charge Transfer Loss in Atomic Laser Isotope Separation by Production of Excited Ions through Autoionization Levels  

Microsoft Academic Search

A new technique to reduce charge transfer loss when extracting ions from photoionized plasma has been developed, thereby increasing the efficiency of atomic vapor laser isotope separation (AVLIS). By selecting autoionization levels, specific isotopes are ionized to the excitation levels of the ions. Cross sections for charge transfer between specific excited ions and ground state atoms are smaller than those

Masahiro TOOMA; Manabu UENO; Kinya KOBAYASHI; Kazuki TSUCHIDA; Kazumichi SUZUKI

1996-01-01

369

Atomic force microscopy visualization of injuries in Enterococcus faecalis surface caused by Er,Cr:YSGG and diode lasers  

PubMed Central

Aim: To visualize by Atomic Force Microscopy the alterations induced on Enterococcus. faecalis surface after treatment with 2 types of laser: Erbium chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser and Diode laser. Material and Methods: Bacterial suspensions from overnight cultures of E. faecalis were irradiated during 30 seconds with the laser-lights at 1 W and 2 W of power, leaving one untreated sample as control. Surface alterations on treated E. faecalis were visualized by Atomic Force Microscopy (AFM) and its surface roughness determined. Results: AFM imaging showed that at high potency of laser both cell morphology and surface roughness resulted altered, and that several cell lysis signs were easily visualized. Surface roughness clearly increase after the treatment with Er,Cr:YSGG at 2W of power, while the other treatments gave similar values of surface roughness. The effect of lasers on bacterial surfaces visualized by AFM revealed drastic alterations. Conclusions: AFM is a good tool to evaluate surface injuries after laser treatment; and could constitute a measure of antimicrobial effect that can complete data obtained by determination of microbial viability. Key words:Atomic force microscopy, Er,Cr:YSGG laser, diode laser, Enterococcus faecalis, surface roughness. PMID:25475770

López-Jiménez, Lidia; Viñas, Miguel; Vinuesa, Teresa

2015-01-01

370

Nuclear-driven flashlamp pumping of the atomic iodine laser. Final report  

SciTech Connect

This report is a study of the atomic iodine laser pumped with nuclear- excited XeBr fluorescence. Preliminary experiments, conducted in the TRIGA reactor investigated the fluorescence of the excimer XeBr under nuclear pumping with {sup 10}B and {sup 3}He, for use as a flashlamp gas to stimulate the laser. These measurements included a determination of the fluorescence efficiency (light emitted in the wavelength region of interest, divided by energy deposited in the gas) of XeBr under nuclear pumping, with varying excimer mixtures. Maximum fluorescence efficiencies were approximately 1%. In order to better understand XeBr under nuclear excitation, a kinetics model of the system was prepared. The model generated the time-dependant concentrations of 20 reaction species for three pulse sizes, a TRIGA pulse, a fast burst reactor pulse, and an e-beam pulse. The modeling results predicted fluorescence efficiencies significantly higher (peak efficiencies of approximately 10%) than recorded in the fluorescence experiments. The cause of this discrepancy was not fully determined. A ray tracing computer model was also prepared to evaluate the efficiency with which nuclear-induced fluorescence generated in one cavity of a laser could be coupled into another cavity containing an iodine lasant. Finally, an experimental laser cell was constructed to verify that nuclear-induced XeBr fluorescence could be used to stimulate a laser. Lasing was achieved at 1.31 micron in the TRIGA using C{sub 3}F{sub 7}I, a common iodine lasant. Peak laser powers were approximately 20 mW. Measured flashlamp pump powers at threshold agreed well with literature values, as did lasant pressure dependency on laser operation.

Miley, G.H.

1992-03-01

371

Direct analysis of solid samples by laser excited atomic fluorescence spectrometry with sample atomization by ion sputtering in a planar magnetron discharge  

NASA Astrophysics Data System (ADS)

A specially designed planar magnetron for direct atomization of solid materials by ion sputtering for laser excited atomic fluorescence spectrometry (LEAFS) was investigated. This atomizer provides a much higher atomic flux than the previously used hollow cathode type. The potential of the atomizer was examined through the analysis of Si traces in high-purity In and Ga. Theoretically simulated calibration curves for a particular geometry of the atomizer were compared with those that were experimentally obtained. For both matrices, the deviations of the experimental and simulated calibration curves were by less than a factor of three. The limits of detection (3?) of 0.4 ng/g for In and of 1 ng/g for Ga were obtained.

Dashin, S. A.; Mayorov, I. A.; Bolshov, M. A.

1993-03-01

372

Liquid/Vapour visualization of common rail diesel sprays in different ambient conditions with visible and UV laser light scattering and PLIF  

NASA Astrophysics Data System (ADS)

In this paper UV-visible elastic light scattering and Planar Laser Induced Fluorescence (PLIF) have been applied for measuring the vaporization process of a diesel fuel in an optically accessible vessel at engine ambient conditions. The spray has been generated by an electronically controlled Common Rail injection system and emerged from an axial single-hole electroinjector, 0.18 mm in diameter (L/d = 5.55). The injected fluid has been a commercial Diesel fuel and a single strategy (1.0 ms in duration) has been implemented at the injection pressure of 60.0 MPa. The measurements have been carried out in a quiescent bomb filled with SF6 gas at pressures of 0.39 MPa and temperature ranging between 293 to 533 K. The ambient gas densities has varied from 12.64 kg/m3 to 23.0 kg/m3, equivalent to the diesel engine conditions between the Start of Injection (SOI) and the Start of Combustion (SOC). A Nd-YAG pulsed laser sheet has been used for excitation of the spray along its axis at two wavelengths: 532 and 355 nm; the sheet thickness and light pulse duration have been 0.10 mm and 12 ns, respectively. The scattered light has been collected and synchronized at different instant from the SOI. The comparison of the images of the fuel at different instant from the SOI has permitted the analysis of the spray characteristics in terms of tip penetration, cone angle and spray fragmentation. Elastic visible and UV scattering radiation have allowed investigations on the size of the droplets along a plane centered on the spray axis. Planar Laser Induced Fluorescence (PLIF) measurements on the same plane have been carried out exciting the droplets at 355 nm and collecting the light through an interference filter centered at 430 nm. PLIF has allowed a correlation between the liquid and the vapor structures of the jets in all the examined ambient conditions.

Allocca, L.; De Vita, A.; Merola, S. S.; Vaglieco, B. M.

2005-08-01

373

High-Precision Measurement of the Laser-Trapping Frequencies for $^{209,210,211}$Fr Atoms  

E-print Network

We present the accurate measurement of the frequency of the $7S-7P$ laser-trapping transition for three francium isotopes. Our approach is based on an interferometric comparison to deduce the unknown laser frequency from a secondary laser frequency-standard. After careful investigation of systematics, with samples of about 100 atoms the final accuracy reaches 8 MHz, an order of magnitude better than the best previous measurement for $^{210}$Fr, and opens the way to improved tests of the theoretical computation of Fr atomic structure.

Sanguinetti, S; Corradi, L; Dainelli, A; Khanbekyan, A; Mariotti, E; de Mauro, C; Minguzzi, P; Moi, L; Stancari, G; Tomassetti, L; Veronesi, S

2008-01-01

374

Optimization of feed flow parameters in separation of neodymium isotopes by atomic vapor selective laser photoionization and analysis of results  

Microsoft Academic Search

Experimental data for separation of neodymium isotopes by atomic vapor selective laser photoionization are analyzed. Atom\\u000a scattering in the working volume and the Doppler shift of the atom absorption line are shown to be the basic deselecting processes\\u000a in the experimental cell studied. A data processing technique that allows one to determine the effect of either deselecting\\u000a process on the

S. K. Kovalevich; V. P. Labozin; G. O. Tsvetkov

2005-01-01

375

Comment on "Generation of cold low divergent atomic beam of indium by laser ablation" [Rev. Sci. Instrum. 76, 113302 (2005)].  

PubMed

We present measurements of the velocity distribution of calcium atoms in an atomic beam generated using a dual-stage laser back-ablation apparatus. Distributions are measured using a velocity selective Doppler time-of-flight technique. They are Boltzmann-like with rms velocities corresponding to temperatures above the melting point for calcium. Contrary to a recent report in the literature, this method does not generate a subthermal atomic beam. PMID:19405705

Denning, A; Booth, A; Lee, S; Amonson, M; Bergeson, S D

2009-04-01

376

Oxygen assisted iodine atoms production in an RF discharge for a cw oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

Results of experiments and modeling of CH3I dissociation in a 40 MHz RF discharge in a discharge chamber of original design to produce iodine atoms for cw oxygen-iodine laser are presented. In experiments a substantial increase in CH3I dissociation efficiency due to addition of oxygen into Ar:CH3I mixture was observed. Complete CH3I dissociation in Ar:CH3I:O2 mixture occurred at 200 W discharge power. Fraction of discharge power spent on iodine atoms production was equal to 16% at 0.17 mmol/s CH3I flow rate. The rate of carbon atoms production as a function of molecular oxygen and water contents in CH3I:Ar mixtures was studied with the help of numerical modeling. It was found that addition of water vapor resulted in increase while addition of molecular oxygen and HI in decrease of the rate of carbon atoms production. Due to diffusion most of carbon atoms had enough time to deposit on the walls of the discharge chamber. However, contrary to the situation in a DC discharge, in the RF discharge accumulation of carbon on the walls of the discharge chamber did not hamper discharge stability and iodine production, as it was observed in our experiments.

Mikheyev, Pavel A.; Demyanov, Andrey V.; Ufimtsev, Nikolay I.; Kochetov, Igor V.; Azyazov, Valeriy N.; Napartovich, Anatoly P.

2015-02-01

377

Ionization and excitation of the excited hydrogen atom in strong circularly polarized laser fields  

NASA Astrophysics Data System (ADS)

In the recent work of Herath et al. [T. Herath, L. Yan, S. K. Lee, and W. Li, Phys. Rev. Lett. 109, 043004 (2012), 10.1103/PhysRevLett.109.043004] the first experimental observation of a dependence of strong-field ionization rate on the sign of the magnetic quantum number m [of the initial bound state (n ,l ,m )] was reported. The experiment with nearly circularly polarized light could not distinguish which sign of m favors faster ionization. We perform ab initio calculations for the hydrogen atom initially in one of the four bound substates with the principal quantum number n =2 , and irradiated by a short circularly polarized laser pulse of 800 nm . In the intensity range of 1012-1013W /c m2 excited bound states play a very important role, but also up to some 1015W /c m2 they cannot be neglected in a full description of the laser-atom interaction. We explore the region that with increasing intensity switches from multiphoton to over-the-barrier ionization and we find, unlike in tunneling-type theories, that the ratio of ionization rates for electrons initially counter-rotating and corotating (with respect to the laser field) may be higher or lower than 1.

Bauer, Jaros?aw H.; Mota-Furtado, Francisca; O'Mahony, Patrick F.; Piraux, Bernard; Warda, Krzysztof

2014-12-01

378

Molecular and atomic ultra trace analysis by laser induced fluorescence with OPO system and ICCD camera.  

PubMed

This paper presents a synthesis of some analytical potentialities of an equipment designed for both laser induced molecular and atomic fluorescence in the field of ultra-trace analysis (ng l(-1)). Excitation of fluorescence was performed with a pulsed Nd:Yag laser coupled to an optical parametric oscillator (OPO). Fluorescence spectra were recorded with a spectrograph and an intensified charge-coupled device (ICCD). The high energy and the tunability of the excitation combined with the sensitivity of the ICCD and the time-resolution provide better limit of detection (LOD) and selectivity. By molecular fluorescence, some major organic contaminants in the environment were studied, i.e. polycyclic aromatic hydrocarbons (PAHs) (benzo[a]pyrene and hydroxypyrene) and a pesticide (carbaryl). The LODs achieved by direct analysis were far below the restricted European values for tap water. Analysis was performed in water containing humic acids using time resolution to avoid the matrix fluorescence. By electro thermal atomisation-laser excited atomic fluorescence (ETA-LEAF), we detected traces of aluminium and lead in seawater. Some general considerations about the signal to noise ratio optimisation are reported. LODs reached the femtogram level. PMID:18969052

Burel, L; Giamarchi, P; Stephan, L; Lijour, Y; Le Bihan, A

2003-06-13

379

Laser cooling and trapping of atomic particles. January 1970-September 1989 (Citations from the NTIS data base). Report for Jan 70-Sep 89  

SciTech Connect

This bibliography contains citations concerning theory and experiments on laser cooling and laser trapping of neutral atoms and atomic ions. Atoms and ions are cooled by laser radiation pressure to very low Kelvin temperatures and confined in electromagnetic traps with very high density. Atomic particles discussed include sodium atoms, mercury ions, beryllium ions, magnesium ions, and hydrogen. Applications include high performance spectroscopy, atomic clocks, microwave and optical frequency standards, relativistic neutral particle beam weapons, exotic fuels, cooling of electron beams, and space propulsion. (Contains 97 citations fully indexed and including a title list.)

Not Available

1989-11-01

380

Laser spectroscopy of Ag and Au atoms immersed in superfluid helium and its applications to investigate nuclear structures  

NASA Astrophysics Data System (ADS)

We have been developing a new nuclear laser spectroscopic method “OROCHI” for determining spins and moments of exotic RIs. It is the method based on the combination of superfluid helium as a stopper of radioactive isotope (RI) beam and in situ laser spectroscopy of RI atoms. This unique method will enable us to measure nuclear spins and electromagnetic moments of extremely low yield RI (less than 1 particle per second). For applying this method to stable Ag and Au isotopes, we have measured optical absorption spectra of these elements. Optical pumping of those atoms has also been attempted with pumping lasers tuned to the measured absorption lines. Details of this laser spectroscopy method in He II “OROCHI” and the development for applying OROCHI to Ag and Au atoms are presented.

Furukawa, Takeshi; Matsuo, Yukari; Hatakeyama, Atsushi; Kobayashi, Tohru; Asahi, Koichiro; Shimoda, Tadashi; Orochi Collaboration

2011-01-01

381

High-order harmonic cut-off frequency in atomic silver irradiated by femtosecond laser pulses: theory and experiment  

NASA Astrophysics Data System (ADS)

The results of theoretical and experimental study of high-order optical harmonic generation in the ensemble of silver atoms irradiated by intense femtosecond pulses of Ti:Sapphire laser are presented. It is shown that the photoemission spectra exhibit unusual behavior when the laser field strength approaches near-atomic values. In subatomic field strength the cut-off frequency increases linearly with laser pulse intensity. However, when the field strength approaches near-atomic region firstly cut-off frequency slows down and then saturates. To give new interpretation of such kind of photoemission spectrum behavior we have proposed the light-atom interaction theory based on the use of eigenfunctions of boundary value problem for "the atom in an external field" instead of the traditional basis of the "free atom" eigenfunctions. The results of computer simulations clearly demonstrate saturation of the cut-off frequency at near-atomic strength of a laser field. The problem of angular divergence of a harmonic emission is analyzed.

Andreev, Anatoly V.; Ganeev, Rashid A.; Kuroda, Hiroto; Stremoukhov, Sergey Yu; Shoutova, Olga A.

2013-01-01

382

Optical field ionization of atoms and ions using ultrashort laser pulses  

SciTech Connect

This dissertation research is an investigation of the strong optical field ionization of atoms and ions by 120-fs, 614-run laser pulses and 130-fs, 800-nm laser pulses. The experiments have shown ionization that is enhanced above the predictions of sequential tunneling models for He{sup +2}, Ne{sup +2} and Ar{sup +2}. The ion yields for He{sup +l}, Ne{sup +l} and Ar{sup +l} agree well with the theoretical predictions of optical tunneling models. Investigation of the polarization dependence of the ionization indicates that the enhancements are consistent with a nonsequential ionization mechanism in which the linearly polarized field drives the electron wavefunction back toward the ion core and causes double ionization through inelastic e-2e scattering. These investigations have initiated a number of other studies by other groups and are of current scientific interest in the fields of high-irradiance laser-matter interactions and production of high-density plasmas. This work involved: (1) Understanding the characteristic nature of the ion yields produced by tunneling ionization through investigation of analytic solutions for tunneling at optical frequencies. (2) Extensive characterization of the pulses produced by 614-nm and 800-ran ultrashort pulse lasers. Absolute calibration of the irradiance scale produced shows the practicality of the inverse problem--measuring peak laser irradiance using ion yields. (3) Measuring the ion yields for three noble gases using linear, circular and elliptical polarizations of laser pulses at 614-nm and 800-nm. The measurements are some of the first measurements for pulse widths as low as 120-fs.

Fittinghoff, D.N.

1993-12-01

383

Experimental scaling laws for mass-ablation rate, ablation pressure in planar laser-produced plasmas with laser intensity, laser wavelength, and target atomic number  

Microsoft Academic Search

Layered-target experiments at 1.06 ?m for carbon and silicon materials have been carried out to measure mass-ablation rate m˙ and ablation pressure Pa as a function of absorbed laser intensity Ia, laser wavelength ?L, and target atomic number Z at irradiances of 1013–1015 W\\/cm2. The results can be put in the forms m˙(kg\\/s cm2)&bartil;55 [Ia(W\\/cm2)\\/1014]1\\/3?L?4\\/3(?m) Z3\\/8 and Pa(Mbar)&bartil;7.4 [Ia(W\\/cm2)\\/1014]2\\/3?L?2\\/3(?m) Z3\\/16.

Faiz Dahmani; Boulevard Frantz Fanon

1993-01-01

384

Optimal Control of Atomic, Molecular and Electron Dynamics with Tailored Femtosecond Laser Pulses  

NASA Astrophysics Data System (ADS)

With the invention of the laser, the dream was realized to actively exert control over quantum systems. Active control over the dynamics of quantum mechanical systems is a fascinating perspective in modern physics. Cleavage and creation of predetermined chemical bonds, selective population transfer in atoms and molecules, and steering the dynamics of bound and free electrons have been important milestones along this way. A promising tool for this purpose is available with femtosecond laser technologies. In this chapter we review some of our work on adaptive femtosecond quantum control where a learning algorithm and direct experimental feedback signals are employed to optimize user-defined objectives. Femtosecond laser pulses are modified in frequency-domain pulse shapers, which apart from phase- and intensity-modulation can also modify the polarization state as a function of time. We will highlight the major advances in the field of optimal control by presenting our own illustrative experimental examples such as gas-phase and liquid-phase femtochemistry, control in weak and strong laser fields, and control of electron dynamics.

Brixner, Tobias; Pfeifer, Thomas; Gerber, Gustav; Wollenhaupt, Matthias; Baumert, Thomas

385

Atom-probe tomography of nickel-based superalloys with green or ultraviolet lasers: a comparative study.  

PubMed

Recent developments in the technology of laser-pulsed local-electrode atom-probe (LEAP) tomography include a picosecond ultraviolet (UV) laser system having a 355 nm wavelength and both external and in-vacuum optics. This approach ensures focusing of the laser beam to a smaller spot diameter than has heretofore been obtained using a green (532 nm wavelength) picosecond laser. We compare the mass spectra acquired, using either green or UV laser pulsing, from nickel-based superalloy specimens prepared either electrochemically or by lifting-out from bulk material using ion-beam milling in a dual-beam focused ion beam microscope. The utilization of picosecond UV laser pulsing yields improved mass spectra, which manifests itself in higher signal-to-noise ratios and mass-resolving power (m/?m) in comparison to green laser pulsing. We employ LEAP tomography to investigate the formation of misoriented defects in nickel-based superalloys and demonstrate that UV laser pulsing yields better accuracy in compositional quantification than does green laser pulsing. Furthermore, we show that using a green laser the quality of mass spectra collected from specimens that were lifted-out by ion milling is usually poorer than for electrochemically-sharpened specimens. Employing UV laser pulsing yields, however, improved mass spectra in comparison to green laser pulsing even for ion-milled microtips. PMID:23046701

Amouyal, Yaron; Seidman, David N

2012-10-01

386

A study of isotopically selective photoionization of ytterbium atoms for laser isotope separation  

Microsoft Academic Search

Atomic-vapor laser isotope separation (AVLIS) is studied experimentally and theoretically for ytterbium vapors. The optimum ionization scheme and the process dynamics are determined. The photoionization scheme uses the transitions\\u000a$$6^1 S_0 \\\\mathop \\\\to \\\\limits^{555.648nm} 6^3 P_1 \\\\mathop \\\\to \\\\limits^{581.067nm} (7\\/2,3\\/2)_2 \\\\mathop \\\\to \\\\limits^{582.79nm} (52353cm^{ - 1} ).$$\\u000a For a numerical study of photoionization dynamics, the mathematical model of the AVLIS

S. K. Borisov; M. A. Kuz'mina; V. A. Mishin

1996-01-01

387

Using Lasers and X-rays to Reveal the Motion of Atoms and Electrons  

ScienceCinema

July 7, 2009 Berkeley Lab summer lecture: The ultrafast motion of atoms and electrons lies at the heart of chemical reactions, advanced materials with exotic properties, and biological processes such as the first event in vision. Bob Schoenlein, Deputy Director for Science at the Advanced Light Source, will discuss how such processes are revealed by using laser pulses spanning a millionth of a billionth of a second, and how a new generation of light sources will bring the penetrating power of x-rays to the world of ultrafast science

Bob Schoenlein

2010-01-08

388

Isotope effects in the harmonic response from hydrogenlike muonic atoms in strong laser fields  

E-print Network

High-harmonic generation from hydrogenlike muonic atoms exposed to ultraintense high-frequency laser fields is calculated. Systems of low nuclear charge number Z are considered where a nonrelativistic description applies. By comparing the radiative response for different isotopes we demonstrate characteristic signatures of the finite nuclear mass and size in the harmonic spectra. In particular, for Z>1, an effective muon charge appears in the Schr\\"odinger equation for the relative particle motion, which influences the position of the harmonic cutoff. Cutoff energies in the MeV domain can be achieved, offering prospects for the generation of ultrashort coherent gamma-ray pulses.

Shahbaz, Atif; Müller, Carsten

2010-01-01

389

Inner-shell ionization of potassium atoms ionized by a femtosecond laser  

SciTech Connect

With a femtosecond laser pulse we rapidly ionize potassium atoms (K{sup 0}) in the gas phase, generating potassium ions (K{sup +}), and monitor the altered energy-level scheme with a subsequent hard x-ray pulse. Removal of the potassium 4s valence electron increases the binding energies of both the valence and the 1s core levels, and induces an ultrafast change of the 1s-4p x-ray transition energy by about 2.8 eV. We simultaneously observe a 50% increase in oscillator strength of K{sup +} over K{sup 0} for that transition.

Hertlein, M. P.; Adaniya, H.; Amini, J.; Feinberg, B.; Prior, M. H.; Belkacem, A. [Lawrence Berkeley National Laboratory, Berkeley, California (United States); Bressler, C.; Kaiser, M. [Laboratoire de Spectroscopie Ultrarapide, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne (Switzerland); Neumann, N. [Lawrence Berkeley National Laboratory, Berkeley, California (United States); Institut fuer Kernphysik, J.W. Goethe-Universitaet, Frankfurt am Main, D-60486 Frankfurt (Germany)

2006-06-15

390

Refraction and absorption of x rays by laser-dressed atoms.  

SciTech Connect

X-ray refraction and absorption by neon atoms under the influence of an 800 nm laser with an intensity of 10{sup 13} W/cm{sup 2} is investigated. For this purpose, we use an ab initio theory suitable for optical strong-field problems. Its results are interpreted in terms of a three-level model. On the Ne 1s {yields} 3p resonance, we find electromagnetically induced transparency (EIT) for x rays. Our work opens novel perspectives for ultrafast x-ray pulse shaping.

Buth, C.; Santra, R.; Young, L. (Chemical Sciences and Engineering Division)

2010-06-01

391

Atomic Oxygen Sensors Based on Nanograin ZnO Films Prepared by Pulse Laser Deposition  

SciTech Connect

High-quality nanograin ZnO thin films were deposited on c-plane sapphire (Al{sub 2}O{sub 3}) substrates by pulse laser deposition (PLD). Scanning electron microscopy (SEM) and x-ray diffraction (XRD) were used to characterize the samples. The structural and morphological properties of ZnO films under different deposition temperature have been investigated before and after atomic oxygen (AO) treatment. XRD has shown that the intensity of the (0 0 2) peak increases and its FWHM value decreases after AO treatment. The AO sensing characteristics of nano ZnO film also has been investigated in a ground-based atomic oxygen simulation facility. The results show that the electrical conductivity of nanograin ZnO films decreases with increasing AO fluence and that the conductivity of the films can be recovered by heating.

Wang Yunfei; Chen Xuekang; Li Zhonghua; Zheng Kuohai; Wang Lanxi; Feng Zhanzu; Yang Shengsheng [National Key Laboratory of Vacuum and Cryogenics Technology and Physics, Lanzhou Institute of Physics, Lanzhou 730000 (China)

2009-01-05

392

Laser sampling system for an inductively-coupled atomic emission spectrometer. Final report  

SciTech Connect

A laser sampling system was attached to a Perkin Elmer Optima 3000 inductively-coupled plasma, atomic emission spectrometer that was already installed and operating in the Chemistry and Geochemistry Department at the Colorado School of Mines. The use of the spectrometer has been highly successful. Graduate students and faculty from at least four different departments across the CSM campus have used the instrument. The final report to NSF is appended to this final report. Appendices are included which summarize several projects utilizing this instrument: acquisition of an inductively-coupled plasma atomic emission spectrometer for the geochemistry program; hydrogen damage susceptibility assessment for high strength steel weldments through advanced hydrogen content analysis, 1996 and 1997 annual reports; and methods for determination of hydrogen distribution in high strength steel welds.

NONE

1998-02-15

393

General approach to few-cycle intense laser interactions with complex atoms  

SciTech Connect

A general ab initio and nonperturbative method to solve the time-dependent Schroedinger equation (TDSE) for the interaction of a strong attosecond laser pulse with a general atom, i.e., beyond the models of quasi-one-electron or quasi-two-electron targets, is described. The field-free Hamiltonian and the dipole matrices are generated using a flexible B-spline R-matrix method. This numerical implementation enables us to construct term-dependent, nonorthogonal sets of one-electron orbitals for the bound and continuum electrons. The solution of the TDSE is propagated in time using the Arnoldi-Lanczos method, which does not require the diagonalization of any large matrices. The method is illustrated by an application to the multiphoton excitation and ionization of Ne atoms. Good agreement with R-matrix Floquet calculations for the generalized cross sections for two-photon ionization is achieved.

Guan Xiaoxu; Zatsarinny, O.; Bartschat, K. [Department of Physics and Astronomy, Drake University, Des Moines, Iowa 50311 (United States); Schneider, B. I. [Physics Division, National Science Foundation, Arlington, Virginia 22230 (United States); Feist, J. [Institute for Theoretical Physics, Vienna University of Technology, A-1040 Vienna (Austria); Noble, C. J. [Department of Physics and Astronomy, Drake University, Des Moines, Iowa 50311 (United States); Computational Science and Engineering Department, Daresbury Laboratory, Warrington WA4 4AD (United Kingdom)

2007-11-15

394

Sub-doppler laser cooling of thulium atoms in a magneto-optical trap  

NASA Astrophysics Data System (ADS)

Sub-Doppler laser cooling in a magneto-optical trap for thulium atoms at a wavelength of 410.6 nm has been experimentally studied. Without any dedicated molasses period of sub-Doppler cooling, the cloud of 3 × 106 atoms at a temperature of 25(5) ?K was observed. The measured temperature is significantly lower than the Doppler limit of 240 ?K for the cooling transition at 410.6 nm. The high efficiency of the sub-Doppler cooling process is due to a near-degeneracy of the Landé g-factors of the lower 4 f 136 s 2 ( J = 7/2) and the upper 4 f 125 d 3/26 s 2 ( J = 9/2) cooling levels.

Sukachev, D.; Sokolov, A.; Chebakov, K.; Akimov, A.; Kolachevsky, N.; Sorokin, V.

2010-11-01

395

Proposed method for laser spectroscopy of pionic helium atoms to determine the charged-pion mass  

E-print Network

Metastable pionic helium ($\\pi{\\rm He}^+$) is a three-body atom composed of a helium nucleus, an electron occupying the $1s$ ground state, and a negatively charged pion $\\pi^-$ in a Rydberg state with principal- and orbital angular momentum quantum numbers of $n\\sim \\ell+1\\sim 16$. We calculate the spin-independent energies of the $\\pi{\\rm ^3He}^+$ and $\\pi{\\rm ^4He}^+$ isotopes in the region $n=15$--19. These include relativistic and quantum electrodynamics corrections of orders $R_{\\infty}\\alpha^2$ and $R_{\\infty}\\alpha^3$ in atomic units, where $R_{\\infty}$ and $\\alpha$ denote the Rydberg and fine structure constants. The fine-structure splitting due to the coupling between the electron spin and the orbital angular momentum of the $\\pi^-$, and the radiative and Auger decay rates of the states are also calculated. Some states $(n,\\ell)=(16,15)$ and $(17,16)$ retain nanosecond-scale lifetimes against $\\pi^-$ absorption into the helium nucleus. We propose to use laser pulses to induce $\\pi^-$ transitions from these metastable states, to states with large ($\\sim 10^{11}$ s$^{-1}$) Auger rates. The $\\pi{\\rm He}^{2+}$ ion that remains after Auger emission of the $1s$ electron undergoes Stark mixing with the $s$, $p$, and $d$ states during collisions with the helium atoms in the experimental target. This leads to immediate nuclear absorption of the $\\pi^-$. The resonance condition between the laser beam and the atom is thus revealed as a sharp spike in the rates of neutrons, protons, deuterons, and tritons that emerge....(continued)

Masaki Hori; Anna Sótér; Vladimir I. Korobov

2014-04-30

396

Proposed method for laser spectroscopy of pionic helium atoms to determine the charged-pion mass  

NASA Astrophysics Data System (ADS)

Metastable pionic helium (?He+) is a three-body atom composed of a helium nucleus, an electron occupying the 1s ground state, and a negatively charged pion ?- in a Rydberg state with principal and orbital angular momentum quantum numbers of n ˜?+1˜16. We calculate the spin-independent energies of the ?3He+ and ?4He+ isotopes in the region n =15-19. These include relativistic and quantum electrodynamics corrections of orders R??2 and R??3 in atomic units, where R? and ? denote the Rydberg and fine structure constants. The fine-structure splitting due to the coupling between the electron spin and the orbital angular momentum of the ?- and the radiative and Auger decay rates of the states are also calculated. Some states (n,?)=(16,15) and (17,16) retain nanosecond-scale lifetimes against ?- absorption into the helium nucleus. We propose the use of laser pulses to induce ?- transitions from these metastable states to states with large (˜1011 s-1) Auger rates. The ?He2+ ion that remains after Auger emission of the 1s electron undergoes Stark mixing with the s, p, and d states during collisions with the helium atoms in the experimental target. This leads to immediate nuclear absorption of the ? -. The resonance condition between the laser beam and the atom is thus revealed as a sharp spike in the rates of neutrons, protons, deuterons, and tritons that emerge. A resonance curve is obtained from which the ?He+ transition frequency can in principle be determined with a fractional precision of 10-8-10-6 provided the systematic uncertainties can be controlled. By comparing the measured ?He+ frequencies with the calculated values, the ?- mass may be determined with a similar precision. The ?He+ will be synthesized by allowing a high-intensity (>108 s-1) beam of ?-produced by a cyclotron to come to rest in a helium target. The precise time structure of the ?- beam is used to ensure a sufficient rate of coincidence between the resonant laser pulses and the ?He+ atoms.

Hori, Masaki; Sótér, Anna; Korobov, Vladimir I.

2014-04-01

397

Quantum control of multilevel atoms with rotational degeneracy using short laser pulses  

SciTech Connect

We study the quantum control of multilevel atoms with rotationally degenerate levels using short laser pulses. Various control schemes are considered, ones using {pi} pulses, frequency-chirped pulses, two consecutive pulses, or two pulses that overlap each other partially. We study the possibilities of controlling the quantum state of an ensemble of atoms distributed randomly over one or more rotationally degenerate levels initially. For the sake of concreteness we use the hyperfine level scheme of the {sup 85}Rb D line, but the results can easily be generalized for any of the alkali-metal atoms used in cooling and trapping experiments. We find that even though a number of difficulties arise, such as unequal coupling constants between rotational sublevels or dephasing between different hyperfine levels during the interaction, control schemes using simple or multiphoton adiabatic passage can be used to control the internal states of the atoms effectively as well as the center-of-mass motion. Furthermore, it is shown that in some cases it is possible to exploit the inequality of the coupling constants to entangle the rotational substates with specific distinct translational quantum states and hence separate these substates in momentum space.

Demeter, G. [Institute for Particle and Nuclear Physics of the Hungarian Academy of Sciences, Konkoly-Thege Miklos ut 29-33, H-1121 Budapest (Hungary)

2010-10-15

398

Quantum control of multilevel atoms with rotational degeneracy using short laser pulses  

NASA Astrophysics Data System (ADS)

We study the quantum control of multilevel atoms with rotationally degenerate levels using short laser pulses. Various control schemes are considered, ones using ? pulses, frequency-chirped pulses, two consecutive pulses, or two pulses that overlap each other partially. We study the possibilities of controlling the quantum state of an ensemble of atoms distributed randomly over one or more rotationally degenerate levels initially. For the sake of concreteness we use the hyperfine level scheme of the Rb85 D line, but the results can easily be generalized for any of the alkali-metal atoms used in cooling and trapping experiments. We find that even though a number of difficulties arise, such as unequal coupling constants between rotational sublevels or dephasing between different hyperfine levels during the interaction, control schemes using simple or multiphoton adiabatic passage can be used to control the internal states of the atoms effectively as well as the center-of-mass motion. Furthermore, it is shown that in some cases it is possible to exploit the inequality of the coupling constants to entangle the rotational substates with specific distinct translational quantum states and hence separate these substates in momentum space.

Demeter, G.

2010-10-01

399

Development of laser-plasma diagnostics using ultrafast atomic-scale dynamics. 96-ERD-046 final report  

SciTech Connect

Ultrashort laser pulse systems allow examination of intense, ultrafast laser-plasma interactions. More specifically, intense laser irradiation can induce short xuv/x-ray bursts from the surface of condensed phase targets. Ultrafast xuv/x-ray detection is needed to understand laser-plasma interactions in this dynamic regime. Support of the Stockpile Stewardship and Management Program requires this critical understanding. Our effort here has been to extend understanding of atomic-scale dynamics in such environments with the goal of developing next generation ultrafast xuv/x-ray diagnostics where the sensors will be the atoms and ions themselves and the time resolution will approach that of the induced atomic transitions ({approx} a few femtoseconds). Pivotal contributions to the rapidly developing field of highly nonperturbative interactions of ultrashort pulse lasers with atoms/ions have been made at this laboratory. In the visible/infrared wavelength regions the temporal and spectral content of ultrashort laser pulses are now reliably monitored within a single pulse using frequency resolved optical gating (FROG) which is based on rapid nonlinear optical processes such as the Kerr effect. New applications of this basic concept are still being developed. Corresponding detection for the xuv/x-ray wavelengths does not exist and is urgently needed in many laboratory programs. The FROG technique cannot be applied in the xuv/x-ray region. Current x-ray streak camera technology is limited to {approx}0.5 picosecond resolution.

Bolton, P.R.; Kulander, K.C. [Lawrence Livermore National Lab., CA (United States); Boreham, B.W. [Central Queensland Univ., Rockhampton, QLD (Australia). Dept. of Applied Physics

1997-03-01

400

Angular distribution of atoms ejected by laser ablation of different metals  

SciTech Connect

Angular distributions of 13 different metals ejected by laser ablation using fourth harmonics (wavelength=266 nm) of neodymium doped yttrium aluminum garnet laser and a fluence close to near-threshold value (2.3 J/cm{sup 2}) have been investigated with a high angular resolution. The angular distribution which is characterized by the exponent n of cos{sup n} theta distribution showed very broad range of values between 3 and 24 for different metals. A simple relation that the exponent n is proportional to the square root of particle atomic weight as reported previously has not been observed. Instead, a general trend has been found that the metals with higher sublimation energy such as Ta and Zr show narrower angular distribution than those with lower sublimation energy such as Sn and In. While the sublimation energy of metals has a great influence on the angular distribution of ejected atoms, a simple consideration suggests that their thermal conductivity and specific heat have little effect on it.

Konomi, I.; Motohiro, T. [Toyota Technological Institute, 2-12-1 Hisakata, Tempaku-ku, Nagoya 468-8511 (Japan); Toyota Central Research and Development Laboratories, Inc., 41-1 Yokomichi, Nagakute, Aichi 480-1192 (Japan); Asaoka, T. [Toyota Central Research and Development Laboratories, Inc., 41-1 Yokomichi, Nagakute, Aichi 480-1192 (Japan)

2009-07-01

401

Controllable optical bistability in photonic-crystal one-atom laser  

SciTech Connect

We investigate the property of optical bistability in a photonic-crystal one-atom laser when nonlinear microcavity is present. The physical system consists of a coherently driven two-level light emitter strongly coupled to a high-quality microcavity which is embedded within a photonic crystal and another coherent probing field which has incident into the microcavity. In our case, the microcavity is fabricated by nonlinear material and placed as an impurity in photonic crystal. This study reveals that such a system can exhibit optical bistability. The dependence of threshold value and hysteresis loop on the photonic band gap of the photonic crystal, driving field Rabi frequency and dephasing processes, are studied. Our results clearly illustrate the ability to control optical bistability through suitable photonic-crystal architectures and external coherent driving field, and this study suggests that in a photonic-crystal nonlinear microcavity, the one-atom laser acts as an effective controllable bistable device in the design of all-light digital computing systems in the near future.

Guo Xiaoyong; Lue Shuchen [Heilongjiang Key Laboratory for Advanced Functional Material and Excited State Process, School of Physics and Electronic Engineering, Harbin Normal University, Harbin 150025 (China)

2009-10-15

402

Comparison of recoil-induced resonances and the collective atomic recoil laser  

NASA Astrophysics Data System (ADS)

The theories of recoil-induced resonances (RIR) [J. Guo, P. R. Berman, B. Dubetsky, and G. Grynberg, Phys. Rev. A 46, 1426 (1992)] and the collective atomic recoil laser (CARL) [R. Bonifacio and L. De Salvo, Nucl. Instrum. Methods Phys. Res. A 341, 360 (1994)] are compared. Both theories can be used to derive expressions for the gain experienced by a probe field interacting with an ensemble of two-level atoms that are simultaneously driven by a pump field. It is shown that the underlying formalisms of the RIR and CARL are equivalent. Differences between the RIR and CARL arise because the theories are typically applied for different ranges of the parameters appearing in the theory. The RIR limit is one in which the time derivative of the probe field amplitude, dE2/dt, depends locally on E2(t) and the gain depends linearly on the atomic density, while the CARL limit is one in which dE2/dt=?t0f(t,t')E2(t')dt', where f is a kernel, and the gain has a nonlinear dependence on the atomic density. Validity conditions for the RIR or CARL limits are established in terms of the various parameters characterizing the atom-field interaction. The probe gain for a probe-pump detuning equal to zero is analyzed in some detail, in order to understand how gain arises in a system which, at first glance, appears to have a symmetry that would preclude the possibility for gain. Moreover, it is shown that these calculations, carried out in perturbation theory, have a range of applicability beyond the recoil problem. Experimental possibilities for observing CARL are discussed.

Berman, P. R.

1999-01-01

403

Polarization-based isotope-selective two-color photoionization of atomic samarium using broadband lasers  

NASA Astrophysics Data System (ADS)

An isotope separation method based on polarization selection rules is applied to atomic samarium by using two-color resonance ionization spectroscopy with broadband lasers. In this method, odd isotopes with nonzero nuclear spin are selectively excited, while even isotopes with zero nuclear spin are prohibited from excitation using two parallel linearly polarized lasers. We have identified a two-color excitation scheme 0 cm-1 ( J = 0) ? 15650.5 cm-1 ( J = 1) ? 33116.8 cm-1 ( J = 1) ? Sm+ for selective excitation of the odd isotopes of Sm I. Using this scheme, selective excitation of odd isotopes of Sm I (147Sm and 149Sm) with an isotopic selectivity better than 40 has been demonstrated. In addition, the effect of different polarization states of the excitation lasers and relative polarization angle between them on the selectivity of odd isotopes has also been studied. The dependence of the even mass isotope signal on the relative polarization angle followed sin2 ?, which is in excellent agreement with theoretical predictions.

Seema, A. U.; Rath, Asawari D.; Mandal, P. K.; Dev, Vas

2015-03-01

404

CCMR: Atomic Scale Theory of Real-Time X-ray Signatures in Pulsed Laser Deposition  

NSDL National Science Digital Library

Pulsed laser deposition (PLD) uses timed laser pulses to blast a target surface causing a plume of material to be discharged from the target. The plume of material then collides with the substrate surface on which the material is being grown. One thing pulsed laser deposition is used for is growing thin films of complex oxide crystals. In an experiment by Aaron Fleet, et al., a smoothing mechanism is found to be present during PLD of SrTiO3. Via real time x-ray diffraction data from the G3 facility at CHESS, the smoothing mechanism is found to vary with the step density of the thin film. These findings are the inspiration for this theoretical research project designed to study these step phenomena on the atomic level. The project focuses on two possibilities for the experimentally observed trend. One is the possibility of a difference in behavior of the collisions when hitting near a step, as opposed to a flat surface, and two is the possibility that there is a difference in the x-ray signatures only due to the presence of steps on a relaxed surface. These two possibilities are studied and compared to determine if they are relevant to the smoothing mechanism.

Handford, Christina G.

2005-08-17

405

Selective laser pumping of magnetic sublevels in the hyperfine structure of the cesium atom  

NASA Astrophysics Data System (ADS)

The evolution of the populations of the magnetic sublevels of the cesium atom (133Cs isotope) in resonant laser fields with linear polarization is analyzed using the equations for the density matrix. Analytic expressions are derived for stationary populations resulting from laser-induced optical transitions on the hyperfine structure components F g = 3 ? F e = 2, 3 and F f = 4 ? F e = 3, 4 of lines D 1 (62 S 1/2 ? 62 P 1/2) and D 2 (62 S 1/2 ? 62 P 3/2) depending on the initial values of the populations. The numerical solution of the evolution equations gives the characteristic times of stabilization of the steady regime as functions of laser field intensities and detuning from optical resonance. We determine the sequences of optical transitions increasing (by more than an order of magnitude) the population of the lower sublevel 62 S 1/2 F g = 3 M = 0 of the "clock" microwave transition F g = 3 M = 0 ? F f = 4 M = 0 in the cesium frequency standard, which increases the signal intensity in the recording system by the same proportion.

Magunov, A. I.; Palchikov, V. G.

2014-05-01

406

Slow light in paraffin-coated Rb vapour cells M. KLEIN*yz, I. NOVIKOVAy, D. F. PHILLIPSy and  

E-print Network

vapour cells, spin state lifetimes are often limited by wall collisions, which thermalize internal atomic & Francis http://www.tandf.co.uk/journals DOI: 10.1080/09500340600952135 #12;1. Cell coating procedure thoroughly cleaning the vapour cell manifold and attaching it to the vacuum system (see figure 1(a)), we bake

Walsworth, Ronald L.

407

Single-mode vertical-cavity surface emitting lasers for {sup 87}Rb-based chip-scale atomic clock  

SciTech Connect

The results of numerical simulation and study of lasing characteristics of semiconductor verticalcavity surface-emitting lasers based on Al{sub x}Ga{sub 1-x}As alloys are presented. Lasers exhibit stable single-mode lasing at a wavelength of 795 nm at low operating currents {approx}1.5 mA and an output power of 350 {mu}W, which offers prospects of their applications in next-generation chip-scale atomic clocks

Derebezov, I. A., E-mail: derebezov@thermo.isp.nsc.ru; Haisler, V. A.; Bakarov, A. K.; Kalagin, A. K.; Toropov, A. I.; Kachanova, M. M.; Gavrilova, T. A.; Semenova, O. I.; Tretyakov, D. B.; Beterov, I. I.; Entin, V. M.; Ryabtsev, I. I. [Russian Academy of Sciences, A.V. Rzhanov Institute of Semiconductor Physics, Siberian Branch (Russian Federation)

2010-11-15

408

Charge transfer between a laser-cooled ion and a thermal atom in a radio-frequency trap  

Microsoft Academic Search

The charge transfer process between a laser-cooled magnesium ion and a thermal barium atom in a radio-frequency ion trap in extremely low energy regime is observed. The merit of using the trap is that the generated ions are also confined in the trap. The occurrence of the charge transfer process is confirmed by the detection of the laser-induced fluorescence from

Taro Hasegawa; Tadao Shimizu

2000-01-01

409

Frequency-stable and ultranarrow-linewidth semiconductor laser locked directly to an atomic-cesium transition.  

PubMed

We describe a new method for semiconductor laser FM noise reduction. A Doppler-free Faraday resonance in Cs vapor provided optical feedback, and FM sideband saturation spectroscopy in a second Cs cell provided electronic feedback. The combined optical and electronic feedback allowed us to reduce the low-frequency FM noise power by more than 6 orders of magnitude, which resulted in a sub-100-Hz-linewidth semiconductor laser locked directly to an atomic transition frequency. PMID:18084548

Shevy, Y; Deng, H

1998-03-15

410

Cavity-mediated cooling of a trapped ?-type three-level atom using a standing-wave laser field  

NASA Astrophysics Data System (ADS)

We propose a ground-state cavity-mediated cooling scheme for a trapped atom, which is in the ? configuration and confined inside a high-finesse optical cavity, using a standing-wave cooling laser. The carrier transition can be prohibited by placing the atom at the node of the cavity field, and the blue-sideband transition can be simultaneously eliminated by exploiting quantum interference via tuning the frequency of the cooling laser. As a consequence, the ground-state cooling for the trapped atom can be achieved. Moreover, we numerically demonstrate the superiority by placing the atom at the antinode of the standing-wave cooling laser as compared with the running-wave cooling laser, and the robustness of the scheme using the standing-wave laser. Meanwhile, the cooling rate can reach the same order of magnitude as that obtained in the cavity-electromagnetically-induced-transparency cooling scheme, and the explicit expression for the final phonon number in higher order is also presented.

Yi, Zhen; Li, Gao-xiang; Yang, Ya-ping

2013-05-01

411

High-coherence electron and ion bunches from laser-cooled atoms.  

PubMed

Cold atom electron and ion sources produce electron bunches and ion beams by photoionization of laser-cooled atoms. They offer high coherence and the potential for high brightness, with applications including ultra-fast electron-diffractive imaging of dynamic processes at the nanoscale. The effective brightness of electron sources has been limited by nonlinear divergence caused by repulsive interactions between the electrons, known as the Coulomb explosion. It has been shown that electron bunches with ellipsoidal shape and uniform density distribution have linear internal Coulomb fields, such that the Coulomb explosion can be reversed using conventional optics. Our source can create bunches shaped in three dimensions and hence in principle achieve the transverse spatial coherence and brightness needed for picosecond-diffractive imaging with nanometer resolution. Here we present results showing how the shaping capability can be used to measure the spatial coherence properties of the cold electron source. We also investigate space-charge effects with ions and generate electron bunches with durations of a few hundred picoseconds. Future development of the cold atom electron and ion source will increase the bunch charge and charge density, demonstrate reversal of Coulomb explosion, and ultimately, ultra-fast coherent electron-diffractive imaging. PMID:24758916

Sparkes, Ben M; Thompson, Daniel J; McCulloch, Andrew J; Murphy, Dene; Speirs, Rory W; Torrance, Joshua S J; Scholten, Robert E

2014-08-01

412

Towards an Atomic Parity Violation Measurement with Laser Trapped Francium at ISAC  

NASA Astrophysics Data System (ADS)

The neutral atom trap for parity violation measurements at TRIUMF has recently accepted its first radioactive beam. The longest lived francium isotopes have half-lives of minutes, requiring us to produce them with the online mass separator of the ISAC facility. The ion beam is embedded into a catcher made of yttrium foil where it is neutralized. Subsequently, the foil is rotated and heated to release a pulse of atomic francium into the laser trap cell. Francium isotopes 207, 209 and 221 have successfully been cooled and confined in a magneto-optical trap, a crucial first step for later experiments. The next online measurements are planned for November 2012 where two physics goals will be pursued. Firstly, the hyperfine anomaly will be probed via high precision spectroscopy on the atomic D1 transition in order to investigate the nuclear magnetization distribution. This will be followed by ionization cross-section measurements from the 7p3/2 state to evaluate this as a potential problematic trap loss mechanism for future parity violation measurements.

Collister, R.; Tandecki, M.; Gwinner, G.; Zhang, J.; Orozco, L.; Behr, J. A.; Pearson, M. R.; Gomez-Garcia, E.; Aubin, S.

2012-10-01

413

Calculations of collisions between cold alkaline earth atoms in a weak laser field  

E-print Network

We calculate the light-induced collisional loss of laser-cooled and trapped magnesium atoms for detunings up to 50 atomic linewidths to the red of the ^1S_0-^1P_1 cooling transition. We evaluate loss rate coefficients due to both radiative and nonradiative state-changing mechanisms for temperatures at and below the Doppler cooling temperature. We solve the Schrodinger equation with a complex potential to represent spontaneous decay, but also give analytic models for various limits. Vibrational structure due to molecular photoassociation is present in the trap loss spectrum. Relatively broad structure due to absorption to the Mg_2 ^1Sigma_u state occurs for detunings larger than about 10 atomic linewidths. Much sharper structure, especially evident at low temperature, occurs even at smaller detunings due to of Mg_2 ^1Pi_g absorption, which is weakly allowed due to relativistic retardation corrections to the forbidden dipole transition strength. We also perform model studies for the other alkaline earth species...

Machholm, M; Suominen, K A; Julienne, Paul S.

2001-01-01

414

Nd:YLF laser at 1.3 m for calcium atom optical clocks and precision spectroscopy of hydrogenic systems  

E-print Network

Nd:YLF laser at 1.3 m for calcium atom optical clocks and precision spectroscopy of hydrogenic the silver atom clock transition.11,12 It can also emit at Y. Louyer, M. D. Plimmer plimmer@cnam.fr , P.9­1317.2 nm. It can be used for the interrogation of the clock transition in calcium 1314.0 nm or spectroscopy

Boyer, Edmond

415

Experiment to measure the electric dipole moment (edm) of the electron using laser-cooled Cs atoms  

Microsoft Academic Search

The electron edm de is known to be smaller in magnitude than 1.6x10-27e.cm [1]. We will describe progress on an ongoing experiment designed to be sensitive to an electron EDM de as small as 10-29e.cm. The experiment will search for the resulting edm of the Cs atom, proportional to de, using laser-cooled Cs atoms held in an optical dipole force

Yong-Sup Ihn; Daniel Heinzen

2010-01-01

416

Deep laser cooling of magnesium atoms using a 33P2?33D3 dipole transition  

NASA Astrophysics Data System (ADS)

We present the theoretical analysis of sub-Doppler laser cooling of 24Mg atoms using dipole transition 33P2?33D3 under two counterpropagating light waves with opposite circular polarizations (one-dimensional ?+?– configuration). For numerical calculations the standard semi-classical approach based on the Fokker–Planck equation for linear momentum distribution of atoms is exploited. The distributions are gained beyond the limits of slow atoms approximation and for an arbitrary light field intensity. The absence of these limits allows us to determine the optimal parameters of the light field to maximize a fraction of ultracold atoms (T ~ 10??K) in a whole atomic cloud. In particular, under certain conditions the fraction can reach a value of 50%. Solution of the existing problems in deep laser cooling of magnesium atoms has obvious prospects for atomic optics and quantum metrology: for instance, in designing new-generation optical frequency and time standards based on cold atoms in optical lattices.

Brazhnikov, D. V.; Bonert, A. E.; Goncharov, A. N.; Taichenachev, A. V.; Yudin, V. I.

2014-07-01

417

High-resolution X-ray spectroscopy of hollow atoms created in plasma heated by subpicosecond laser radiation  

SciTech Connect

The investigations of ultrashort (0.4-0.6 ps) laser pulse radiation interaction with solid targets have been carried out. The Trident subpicosecond laser system was used for plasma creation. The X-ray plasma emission was investigated with the help of high-resolution spectrographs with spherically bent mica crystals. It is shown that when high contrast ultrashort laser pulses were used for plasma heating its emission spectra could not be explained in terms of commonly used theoretical models, and transitions in so called {open_quotes}hollow atoms{close_quotes} must be taken into account for adequate description of plasma radiation.

Faenov, A.Ya.; Magunov, A.I.; Pikuz, T.A. [Multicharged Ions Spectra Data Center of VNIIFTRI, Moscow (Russian Federation)] [and others

1997-10-01

418

Photoionization and Optical Spectroscopy of Atomic Clusters Generated via Laser Ablation.  

NASA Astrophysics Data System (ADS)

Laser ablation, combined with a pulsed-nozzle gas source, has been used to generate atomic clusters of three different classes: metal clusters, metal-doped rare gas clusters, and carbon molecules. Resonant and non-resonant photoionization spectroscopy, with mass spectrometric detection, has been used to characterize these species as described below. The ionization thresholds (IPs) for Al _{n} (n = 1 - 70) and In_{n} (n = 1 - 30) clusters have been measured, and fail to conform to the behavior predicted by the spherical jellium model. In the small-size regime, to n = 6, the initial increase in the observed IPs agrees with previous ab initio calculations and provides evidence for the hybridization of the s and p electronic bands. The size-evolution of IPs beyond n = 6 exhibits an electronic shell structure, although the apparent ordering of the shells does not follow the prediction of the spherical jellium model. The most plausible explanation which may account for the observed electronic level pattern is lowering of structural symmetry due to the ion core lattice. The synthesis and spectroscopy of metal containing rare-gas atomic clusters Al cdot Ar_{n} and Al cdot (N_2)_{n} for n = 1 - 200 has also been studied. The mass spectra of the neutral and ionized clusters are shown to be consistent with the icosahedral shell-structure sequence. The size-evolution of the photoionization and optical excitation properties of the core metal atom have been measured by photoionization spectroscopy and resonant two-photon ionization spectroscopy. The use of microscopic theory to calculate vertical and adiabatic ionization energies gives reasonable agreement with experiment. Dielectric continuum theory gives general agreement with the experiment if the strong short-range interactions in the neutral cluster is included. Finally, a new and unique application of laser desorption mass spectrometry has been demonstrated in which a simple carbon cluster, C_{18} , is generated in a molecular beam and detected using multiphoton ionization. The generation of a specific sized carbon cluster is accomplished by using a unique precursor molecule which is predisposed to fragment with the generation of C_{18}. The feasibility of using laser desorption on weakly bound molecules and for inducing chemical reactions in the desorption step has been demonstrated, providing the groundwork for generating cluster beams containing a single, well-characterized species.

Schriver, Kenneth Edward

1990-01-01

419

Cold collisions of ground-state calcium atoms in a laser field: A theoretical study Beatrice Bussery-Honvault and Jean-Michel Launay  

E-print Network

number s : 34.20.Cf, 34.50.Rk, 32.80.Pj I. INTRODUCTION Recent developments in laser cooling and trapping that it is possible to trap and cool alkali-earth metal atoms, such as magnesium 3 , calcium 4,5 , and strontium 4Cold collisions of ground-state calcium atoms in a laser field: A theoretical study Be

Bussery-Honvault, Béatrice

420

Gain and continuous-wave laser oscillation on the 1315 nm atomic iodine transition pumped by an air-helium electric discharge  

E-print Network

Gain and continuous-wave laser oscillation on the 1315 nm atomic iodine transition pumped by an air on the 1315 nm transition of atomic iodine using the energy transferred to I 2 P1/2 from O2 a1 produced American Institute of Physics. DOI: 10.1063/1.2957678 The classical chemical oxygen iodine laser COIL re

Carroll, David L.

421

Vapour Intrusion into Buildings - A Literature Review  

EPA Science Inventory

This chapter provides a review of recent research on vapour intrusion of volatile organic compounds (VOCs) into buildings. The chapter builds on a report from Tillman and Weaver (2005) which reviewed the literature on vapour intrusion through 2005. Firstly, the term ?vapour intru...

422

Synthesis and behavior of metallic glasses via gas atomization and laser deposition  

NASA Astrophysics Data System (ADS)

Al-based and Fe-used bulk metallic glasses (MGs) are of engineering and scientific interest due to their unique combination of attributes. The objective of the present dissertation is to provide fundamental insight into the influence of synthesis on the microstructure and physical behavior of Al-based and Fe-based MGs. Two non-equilibrium synthesis techniques are selected for study, gas atomization and laser deposition via laser engineered net shaping (LENSRTM), which provide different thermal and solidification conditions. Thermal behavior studies involving numerical simulation and experimental validation, microstructure characterization, and mechanical behavior studies are combined in an effort to understand the influence of process parameters as well as to optimize microstructure and performance. Details of the approach used in the present dissertation are described below. First, a numerical approach was implemented to simulate and analyze heat transfer and cooling rates of individual droplets during flight in gas atomization. The calculated results, along with the experimental validation, were used to interpret the formation of amorphous structure and crystal phase development in the atomized powders of different sizes, and to optimize process parameters. Second, four different types of Al-based MG powders were gas-atomized with distinct process parameters. The microstructure, thermal stability, phase transformation sequences and micro-hardness were investigated with SEM, XRD, TEM, and DSC as a function of powder size. Fully amorphous powders were nominally <25mum in diameter. With increasing of powder size, nanocrystalline fcc-Al particles precipitated in an amorphous matrix. The micro-hardness increases with increasing volume fraction of amorphous phase. Third, the thermal behavior and cooling rate during LENSRTM process was simulated numerically using the alternate-direction explicit (ADE) finite difference method (FDM) and the results were compared to those obtained experimentally. The thermal history associated with the LENS RTM process involves numerous reheating cycles. The evolution of microstructure was analyzed as a function of the deposition conditions. Fourth, LENSRTM was implemented to fabricate net shaped Fe-based MG components. The glass transition, crystallization behavior, and physical properties of the glassy alloy, as processed under different process parameters, are analyzed to provide fundamental insight into the underlying physical mechanisms.

Zheng, Baolong

423

Water Vapour, Sonoluminescence and Sonochemistry  

Microsoft Academic Search

Sonoluminescence is the production of light from acoustically forced bubbles; sonochemistry is a related chemical processing technique. The two phenomena share a sensitive dependence on the liquid phase. The present work is an investigation of the fate and consequences of water vapour in the interior of strongly forced argon micro–bubbles. Due to the extreme nonlinearity of the volume oscillations, excess

Brian D. Storey; Andrew J. Szeri

2000-01-01

424

Diagnostics of Carbon Nanotube Formation in a Laser Produced Plume: An Investigation of the Metal Catalyst by Laser Ablation Atomic Fluorescence Spectroscopy  

NASA Technical Reports Server (NTRS)

Carbon nanotubes, elongated molecular tubes with diameters of nanometers and lengths in microns, hold great promise for material science. Hopes for super strong light-weight material to be used in spacecraft design is the driving force behind nanotube work at JSC. The molecular nature of these materials requires the appropriate tools for investigation of their structure, properties, and formation. The mechanism of nanotube formation is of particular interest because it may hold keys to controlling the formation of different types of nanotubes and allow them to be produced in much greater quantities at less cost than is currently available. This summer's work involved the interpretation of data taken last summer and analyzed over the academic year. The work involved diagnostic studies of carbon nanotube formation processes occurring in a laser-produced plume. Laser ablation of metal doped graphite to produce a plasma plume in which carbon nanotubes self assemble is one method of making carbon nanotube. The laser ablation method is amenable to applying the techniques of laser spectroscopy, a powerful tool for probing the energies and dynamics of atomic and molecular species. The experimental work performed last summer involved probing one of the metal catalysts, nickel, by laser induced fluorescence. The nickel atom was studied as a function of oven temperature, probe laser wavelength, time after ablation, and position in the laser produced plume. This data along with previously obtained data on carbon was analyzed over the academic year. Interpretations of the data were developed this summer along with discussions of future work. The temperature of the oven in which the target is ablated greatly influences the amount of material ablated and the propagation of the plume. The ablation conditions and the time scale of atomic and molecular lifetimes suggest that initial ablation of the metal doped carbon target results in atomic and small molecular species. The metal atoms survive for several milliseconds while the gaseous carbon atoms and small molecules nucleate more rapidly. Additional experiments and the development of in situ methods for carbon nanotube detection would allow these results to be interpreted from the perspective of carbon nanotube formation.

deBoer, Gary; Scott, Carl

2003-01-01

425

Breakthrough: X-ray Laser Captures Atoms and Molecules in Action  

ScienceCinema

The Linac Coherent Light Source at SLAC is the world's most powerful X-ray laser. Just two years after turning on in 2009, breakthrough science is emerging from the LCLS at a rapid pace. A recent experiment used the X-rays to create and probe a 2-million-degree piece of matter in a controlled way for the first time-a significant leap toward understanding the extreme conditions found in the hearts of stars and giant planets, and a finding which could further guide research into nuclear fusion, the mechanism that powers the sun. Upcoming experiments will investigate the fundamental, atomic-scale processes behind such phenomena as superconductivity and magnetism, as well as peering into the molecular workings of photosynthesis in plants.

Bergmann, Uwe

2014-05-21

426

Site evaluations for the uranium-atomic vapor laser isotope separation (U-AVLIS) production plant  

SciTech Connect

This report describes a uranium-atomic vapor laser isotope separation (U-AVLIS) production plant siting study conducted during 1990 to identify alternative plant sites for examination in later environmental impact studies. A siting study methodology was developed in early 1990 and was implemented between June and December. This methodology had two parts. The first part -- a series of screening analyses that included exclusionary and other criteria -- was conducted to identify a reasonable number of candidates sites. This slate of candidate sites was then subjected to more rigorous and detailed comparative analysis for the purpose of developing a short list of reasonable alternative sites for later environmental examination. To fully appreciate the siting study methodology, it is important to understand the U-AVLIS program and site requirements. 16 refs., 29 figs., 54 tabs.

Wolsko, T.; Absil, M.; Cirillo, R.; Folga, S.; Gillette, J.; Habegger, L.; Whitfield, R.

1991-07-01

427

Development of laser optogalvanic spectroscopy as a probe of alkali atoms in an MHD environment  

SciTech Connect

Application of Laser Optogalvanic Spectroscopy (LOGS) to MHD combustion systems requires selection of an appropriate alkali atom electronic transition to monitor. These studies suggest that in MHD combustion systems, it is desirable to use cesium, which occurs as an impurity in potassium compounds, as a surrogate for potassium rather than to directly monitor potassium in order to obtain reliable determinations of seed concentration. Studies were also performed to investigate the effect of electrode corrosion on the normalized LOGS signal intensity at a fixed wavelength (578.238 nm). During six-hour experiments in a near-stoichiometric flame, the normalized LOGS signal intensity decreased by 40-50% for a -960 V rod electrode and by 10-20% for a -500 V rod electrode. These changes are attributed to buildup of an oxide coating on the electrode, reducing the collection efficiency of the electrode.

Monts, D.L.; Qian, S.; Cook, R.L.; Shepard, W.S.

1995-02-01

428

Breakthrough: X-ray Laser Captures Atoms and Molecules in Action  

SciTech Connect

The Linac Coherent Light Source at SLAC is the world's most powerful X-ray laser. Just two years after turning on in 2009, breakthrough science is emerging from the LCLS at a rapid pace. A recent experiment used the X-rays to create and probe a 2-million-degree piece of matter in a controlled way for the first time-a significant leap toward understanding the extreme conditions found in the hearts of stars and giant planets, and a finding which could further guide research into nuclear fusion, the mechanism that powers the sun. Upcoming experiments will investigate the fundamental, atomic-scale processes behind such phenomena as superconductivity and magnetism, as well as peering into the molecular workings of photosynthesis in plants.

Bergmann, Uwe

2012-04-26

429

Spinor dynamics-driven formation of a dual-beam atom laser.  

PubMed

We demonstrate a novel dual-beam atom laser formed by outcoupling oppositely polarized components of an all-optical F = 1 spinor Bose-Einstein condensate whose Zeeman sublevel populations have been coherently evolved through spin dynamics. The condensate is formed through all-optical means using a single-beam running-wave dipole trap. We create a condensate in the magnetic field-insensitive m(F) = 0 state, and drive coherent spin-mixing evolution through adiabatic compression of the initially weak trap. Such dual beams, number-correlated through the angular momentum-conserving reaction 2m(0) ?m(+1) +m(-1), have been proposed as tools to explore entanglement and squeezing in Bose-Einstein condensates, and have potential use in precision phase measurements. PMID:19529412

Lundblad, N; Thompson, R J; Aveline, D C; Maleki, L

2006-10-30

430

Distribution of Fe atom density in a dc magnetron sputtering plasma source measured by laser-induced fluorescence imaging spectroscopy  

Microsoft Academic Search

Magnetron sputtering discharge is widely used as an efficient method for thin film fabrication. In order to achieve the optimized fabrication, understanding of the kinetics in plasmas is essential. In the present work, we measured the density distribution of sputtered Fe atoms using laser-induced fluorescence imaging spectroscopy. A dc magnetron plasma source with a Fe target was used. An area

K. Shibagaki; N. Nafarizal; K. Sasaki; H. Toyoda; S. Iwata; T. Kato; S. Tsunashima; H. Sugai

2003-01-01

431

Analysis of geological samples by atomic emission spectroscopy of plasmas induced by laser ablation at low pressures  

NASA Astrophysics Data System (ADS)

Elemental analysis of geologic samples based on atomic emission spectroscopy is currently considered for several future space lander missions to planets, moons and asteroids in solar system. The spectroscopic techniques, called laser-induced plasma (breakdown) spectroscopy (LIBS), provides quantitatively the microscopic in-situ abundances of all major and many trace elements of surfaces of solar system bodies. Excitation and evolution of the plasmas induced by lasers depend on the properties of the investigated material and on environmental conditions. This study focuses on the feasibility of spectroscopy of plasmas induced by low-energy laser (below 1 mJ per pulse) for the exploration of solar system bodies with thin atmospheres (pressures below 1 mPa). At such low pressures the excited plasmas have small plumes and expand very rapidly, which limits both the LIBS signal intensity and the available acquisition time. This, in turn, requires usually relatively powerful laser sources to create a detectable LIBS plasma. The low pressure conditions are simulated in a dedicated chamber at the DLR-Berlin Institute of Planetary Research, that can hold the Martian-like atmosphere or high vacuum conditions. Two infrared Q-switched lasers are used for comparative investigation of atomic emission spectra: Firstly, a Nd:YAG laser (Inlite, Continuum) operating at 1064 nm and at 10 Hz, pulse energy up to 230 mJ at 8-10 ns pulse duration and, secondly, developed for future planetary missions Nd:YLF laser (NeoLASE) operating at 1053 nm and at 10-50 Hz, pulse energy up to 3 mJ at 3-5 ns pulse duration. The emitted light of the laser-induced plasma is analysed by an echelle spectrometer (LTB Aryelle Butterfly) covering the wavelength range of 280-900 nm with a spectral resolution of around 104. Identification of atomic transitions is performed using the LTB built-in spectrometer software by comparison with the NIST spectral database. Several basaltic rock and sediment standards were crushed to powder and pressed into pellets. Reduction of both pressure and laser excitation energy results in a significant decrease of the signal-to-noise ratio for most atomic lines (an exception are the widely broadened lines of H). However, the detection of atomic emission lines of elements with relative abundances above 10-3 (0.1 wt%) - Al, Ca, Cr, H, K, Mg, Mn, Na, Ni, O, Si, Ti, - is possible down to a laser excitation energy of 0.9 mJ (laser irradiance on the sample surface 46 MW/mm2). Additionally, the detection of carbon and sulphur, having strong atomic transitions in ultraviolet range, can be expected by extension of the spectral range of the LIBS spectrometer to 190 nm. Atomic doublet and triplet transitions, broadened by atomic collisions at ambient pressures (100 kPa), become spectrally resolved and are identified below 1 mPa. This demonstrates the feasibility of miniaturized laser-induced breakdown spectrometry for space missions to solar bodies with absent or thin atmospheres.

Pavlov, S.; Schröder, S.; Jessberger, E.; Hübers, H.

2011-12-01

432

A new time-frequency method to reveal quatum dynamics of atomic hydrogen in intense laser pulses: Synchrosqueezing transform  

E-print Network

T)), where n = 60 is the pulse length measured in optical cycles (T = 2?/?0), ?0 ? 0.0428278 in atomic units (a.u.) corresponds to laser wavelength 1064 nm, and E0 ? 0.0169 in a.u. corresponds to the laser intensity of I0 = 1013 W/cm2. Figure 1(b) presents...AIP ADVANCES 4, 117138 (2014) A new time-frequency method to reveal quantum dynamics of atomic hydrogen in intense laser pulses: Synchrosqueezing transform Yae-lin Sheu,1 Liang-Yan Hsu,2,a Hau-tieng Wu,3,b Peng-Cheng Li,1,4 and Shih-I Chu1,5,c 1...

Sheu, Yae-lin; Hsu, Liang-Yan; Wu, Hau-tieng; Li, Peng-Cheng; Chu, Shih-I

2014-11-26

433

No sodium in the vapour plumes of Enceladus.  

PubMed

The discovery of water vapour and ice particles erupting from Saturn's moon Enceladus fuelled speculation that an internal ocean was the source. Alternatively, the source might be ice warmed, melted or crushed by tectonic motions. Sodium chloride (that is, salt) is expected to be present in a long-lived ocean in contact with a rocky core. Here we report a ground-based spectroscopic search for atomic sodium near Enceladus that places an upper limit on the mixing ratio in the vapour plumes orders of magnitude below the expected ocean salinity. The low sodium content of escaping vapour, together with the small fraction of salt-bearing particles, argues against a situation in which a near-surface geyser is fuelled by a salty ocean through cracks in the crust. The lack of observable sodium in the vapour is consistent with a wide variety of alternative eruption sources, including a deep ocean, a freshwater reservoir, or ice. The existing data may be insufficient to distinguish between these hypotheses. PMID:19553993

Schneider, Nicholas M; Burger, Matthew H; Schaller, Emily L; Brown, Michael E; Johnson, Robert E; Kargel, Jeffrey S; Dougherty, Michele K; Achilleos, Nicholas A

2009-06-25

434

Performance predictions of a focused ion beam from a laser cooled and compressed atomic beam  

NASA Astrophysics Data System (ADS)

Focused ion beams are indispensable tools in the semiconductor industry because of their ability to image and modify structures at the nanometer length scale. Here, we report on performance predictions of a new type of focused ion beam based on photo-ionization of a laser cooled and compressed atomic beam. Particle tracing simulations are performed to investigate the effects of disorder-induced heating after ionization in a large electric field. They lead to a constraint on this electric field strength which is used as input for an analytical model which predicts the minimum attainable spot size as a function of, amongst others, the flux density of the atomic beam, the temperature of this beam, and the total current. At low currents (I < 10 pA), the spot size will be limited by a combination of spherical aberration and brightness, while at higher currents, this is a combination of chromatic aberration and brightness. It is expected that a nanometer size spot is possible at a current of 1 pA. The analytical model was verified with particle tracing simulations of a complete focused ion beam setup. A genetic algorithm was used to find the optimum acceleration electric field as a function of the current. At low currents, the result agrees well with the analytical model, while at higher currents, the spot sizes found are even lower due to effects that are not taken into account in the analytical model.

ten Haaf, G.; Wouters, S. H. W.; van der Geer, S. B.; Vredenbregt, E. J. D.; Mutsaers, P. H. A.

2014-12-01

435

Analysis of atomic distribution in as-fabricated Zircaloy-2 claddings by atom probe tomography under high-energy pulsed laser  

NASA Astrophysics Data System (ADS)

The properties of second-phase particles (SPPs) in Zircaloy-2 claddings are key factors influencing the corrosion resistance of the alloy. The chemical compositions of Zr (Fe, Cr)2 and Zr2(Fe, Ni) SPPs were investigated by means of pulsed laser atom probe tomography. In order to prevent specimen fracture and to analyse wide regions of the specimen, the pulsed laser energy was increased to 2.0 nJ. This gave a high yield of average of 3 × 107 ions per specimen. The Zr (Fe, Cr)2 SPPs contained small amounts of Ni and Si atoms, while in Zr2(Fe, Ni) SPPs almost all the Si was concentrated and the ratio of Zr: (Fe + Ni + Si) was 2:1. Atomic concentrations of the Zr-matrix and the SPPs were identified by two approaches: the first by using all the visible peaks of the mass spectrum and the second using the representative peaks with the natural abundance of the corresponding atoms. It was found that the change in the concentration between the Zr-matrix and the SPPs can be estimated more accurately by the second method, although Sn concentration in the Zr2(Fe, Ni) SPPs is slightly overestimated.

Sawabe, T.; Sonoda, T.; Kitajima, S.; Kameyama, T.

2013-11-01

436

Parameters of an electric-discharge generator of iodine atoms for a chemical oxygen-iodine laser  

SciTech Connect

Laser-induced fluorescence is used for measuring the concentration of iodine molecules at the output of an electric-discharge generator of atomic iodine. Methyl iodide CH{sub 3}I is used as the donor of atomic iodine. The fraction of iodine extracted from CH{sub 3}I in the generator is {approx}50%. The optimal operation regimes are found in which 80%-90% of iodine contained in the output flow of the generator was in the atomic state. This fraction decreased during the iodine transport due to recombination and was 20%-30% at the place where iodine was injected into the oxygen flow. The fraction of the discharge power spent for dissociation was {approx}3%. (elements of laser setups)

Azyazov, V N; Vorob'ev, M V; Voronov, A I; Kupryaev, Nikolai V; Mikheev, P A; Ufimtsev, N I [Samara Branch of the P.N. Lebedev Physics Institute, Russian Academy of Sciences, Samara (Russian Federation)

2009-01-31

437

Continuous-wave laser oscillation in subsonic flow on the 1315 nm atomic iodine transition pumped by electric discharge produced O2,,a 1  

E-print Network

Continuous-wave laser oscillation in subsonic flow on the 1315 nm atomic iodine transition pumped in subsonic flow on the 1315 nm transition of atomic iodine using the energy transferred to I 2 P1/2 from O2 density and lower the temperature of the continuous gas flow to shift the equilibrium of atomic iodine

Carroll, David L.

438

Non-contact quantification of laser micro-impulse in water by atomic force microscopy and its application for biomechanics  

NASA Astrophysics Data System (ADS)

We developed a local force measurement system of a femtosecond laser-induced impulsive force, which is due to shock and stress waves generated by focusing an intense femtosecond laser into water with a highly numerical aperture objective lens. In this system, the force localized in micron-sized region was detected by bending movement of a cantilever of atomic force microscope (AFM). Here we calculated the bending movement of the AFM cantilever when the femtosecond laser is focused in water at the vicinity of the cantilever and the impulsive force is loaded on the cantilever. From the result, a method to estimate the total of the impulsive force at the laser focal point was suggested and applied to estimate intercellular adhesion strength.

Hosokawa, Yoichiroh

2011-12-01

439

Laser excited analytical atomic and ionic fluorescence in flames, furnaces and inductively coupled plasmas—I. General considerations  

NASA Astrophysics Data System (ADS)

Several important parameters for the analytical use of laser excited fluorescence spectrometry in flames, graphite furnaces and inductively coupled plasmas are discussed in some detail. These parameters include the laser characteristics such as peak power, pulse duration, spectral bandwidth and repetition rate, the choice of the excitation line, the optical arrangement and the detection system, this last one centred on the widespread use of the boxcar averager. It is shown that, if the ultimate sensitivity is the goal to be achieved, then the choice must be the electrothermal atomization. However, even for flames and inductively coupled plasmas, excellent results are possible provided that: (i) the laser system allows complete spectral coverage in the ultraviolet: (ii) saturation of the fluorescence signal can be approached over a large sample volume; and (iii) the gated detection parameters and the laser repetition frequency are optimized with respect to each other so as to reach the maximum signal-to-noise ratio.

Omenetto, N.; Human, H. G. C.

440

Theoretical study of terahertz generation from atoms and aligned molecules driven by two-color laser fields  

E-print Network

We study the generation of terahertz radiation from atoms and molecules driven by an ultrashort fundamental laser and its second harmonic field by solving time-dependent Schr\\"odinger equation (TDSE). The comparisons between one-, two-, and three- dimensional TDSE numerical simulations show that initial ionized wave-packet and its subsequent acceleration in the laser field and rescattering with long-range Coulomb potential play key roles. We also present the dependence of the optimum phase delay and yield of terahertz radiation on the laser intensity, wavelength, duration, and the ratio of two-color laser components. Terahertz wave generation from model hydrogen molecules are further investigated by comparing with high harmonic emission. It is found that the terahertz yield is following the alignment dependence of ionization rate, while the optimal two-color phase delays varies by a small amount when the alignment angle changes from 0 to 90 degrees, which reflects alignment dependence of attosecond electron d...

Chen, Wenbo; Meng, Chao; Liu, Jinlei; Zhou, Zhaoyan; Zhang, Dongwen; Yuan, Jianmin; Zhao, Zengxiu

2015-01-01

441

Self-injection and acceleration of electrons during ionization of gas atoms by a short laser pulse  

SciTech Connect

Using a relativistic three-dimensional single-particle code, acceleration of electrons created during the ionization of nitrogen and oxygen gas atoms by a laser pulse has been studied. Barrier suppression ionization model has been used to calculate ionization time of the bound electrons. The energy gained by the electrons peaks for an optimum value of laser spot size. The electrons created near the tail do not gain sufficient energy for a long duration laser pulse. The electrons created at the tail of pulse escape before fully interacting with the trailing part of the pulse for a short duration laser pulse, which causes electrons to retain sufficient energy. If a suitable frequency chirp is introduced then energy of the electrons created at the tail of the pulse further increases.

Singh, K.P. [Computational Plasma Dynamics Laboratory, Kettering University, Flint, Michigan 48504 (United States)

2006-04-15

442

Characterization of energetic and thermalized sputtered tungsten atoms using tuneable diode-laser induced fluorescence in direct current magnetron discharge  

NASA Astrophysics Data System (ADS)

In this study a tuneable diode-laser induced fluorescence (TD-LIF) technique (?0 = 407.4358 nm) is used to determine the atoms' velocity distribution function (AVDF) of energetic and thermalized sputtered tungsten (W) atoms in direct current magnetron discharge. The AVDF is characterized by probing the plasma above the centre of the target racetrack along the magnetron cathode axis in an argon–helium (Ar–He) mixture. Quantitative absorption measurements corroborated by deposition on silicon substrates are used to calibrate the TD-LIF relative measurements. Density, flux, temperature, AVDF and the flux velocity distribution function are derived from fitting the TD-LIF signals with four Gaussians (thermalized atoms) and four (energetic atom) functions (Stepanova and Dew 2004 Nucl. Instrum. Methods Phys. Res. B 215 357) taking into account the natural abundance and resonance wavelength shifts of the four main isotopes. Measurements show transport improvement for W atoms and an increase of the ratio of Ar ions to Ar neutrals with the increase of the percentage of He. All measurements are performed at 0.4 Pa and 100 W. The mean velocity of energetic W atoms typically ranges from 1900 to 2200 m s?1. The densities of thermalized and energetic atoms are in the same order of magnitude (˜109 cm?3) and their corresponding fluxes are several tens of times higher for energetic atoms (˜1015 cm?2 s?1).

Desecures, M.; de Poucques, L.; Bougdira, J.

2015-02-01

443

Principal physical problems in laser separation of weighable amounts of a rare ytterbium isotope  

SciTech Connect

A review is provided of the work on laser separation of Yb isotopes, carried out at the Institute of General Physics of the Russian Academy of Sciences and at the 'Lad' Scientific - Production Enterprise during the last 4 - 5 years. The processes of Yb isotope separation by the AVLIS (atomic vapour laser isotope separation) method were investigated both theoretically (by computer simulation) and experimentally. The main topics considered in the review are the ionisation selectivity, the formation of laser beams and of vapour flow in the cavity, and the extraction of ions from a plasma. A facility for producing highly enriched {sup 168}Yb on an industrial scale is described. The rate of production of the enriched ytterbium is now 5 - 10 mg h{sup -1} (over 1 g per month). Commercially viable production of the enriched {sup 168}Yb isotope by the AVLIS method was achieved for the first time anywhere in the world. (review)

Yakovlenko, Sergei I [A.M. Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

1998-11-30

444

Improved production of Br atoms near zero speed by photodissociating laser aligned Br{sub 2} molecules  

SciTech Connect

We theoretically investigated the improvement on the production rate of the decelerated bromine (Br) atoms near zero speed by photodissociating laser aligned Br{sub 2} precursors. Adiabatic alignment of Br{sub 2} precursors exposed to long laser pulses with duration on the order of nanoseconds was investigated by solving the time-dependent Schrödinger equation. The dynamical fragmentation of adiabatically aligned Br{sub 2} precursors was simulated and velocity distribution of the Br atoms produced was analyzed. Our study shows that the larger the degree of the precursor alignment, ?cos{sup 2}???, the higher the production rate of the decelerated Br atoms near zero speed. For Br{sub 2} molecules with an initial rotational temperature of ?1 K, a ?cos{sup 2}??? value of ?0.88 can result in an improvement factor of over ?20 on the production rate of the decelerated Br atoms near zero speed, requiring a laser intensity of only ?1 × 10{sup 12} W/cm{sup 2} for alignment.

Deng, L. Z., E-mail: lzdeng@phy.ecnu.edu.cn; Yin, J. P., E-mail: jpyin@phy.ecnu.edu.cn [State Key Laboratory of Precision Spectroscopy, Department of Physics, East China Normal University, Shanghai 200062 (China)

2014-10-28

445

Angular distribution of atoms emitted from a SrZrO{sub 3} target by laser ablation under different laser fluences and oxygen pressures  

SciTech Connect

Angular distributions of atoms emitted by laser ablation of perovskite-type oxide SrZrO{sub 3} have been investigated using electron probe microanalysis with wavelength-dispersive spectroscopy and charge-coupled device photography with an interference filter. Each constituent element has been analyzed as a two-modal distribution composed of a broad cos{sup m} {theta} distribution and a narrow cos{sup n} {theta} distribution. The exponent n characterizes the component of laser ablation while the exponent m characterizes that of thermal evaporation, where a larger n or m means a narrower angular distribution. In vacuum, O (n=6) showed a broader distribution than those of Sr (n=16) and Zr (n=17), and Sr{sup +} exhibited a spatial distribution similar to that of Sr. As the laser fluence was increased from 1.1 to 4.4 J/cm{sup 2}, the angular distribution of Sr became narrower. In the laser fluence range of 1.1-4.4 J/cm{sup 2}, broadening of the angular distribution of Sr was observed only at the fluence of 1.1 J/cm{sup 2} under the oxygen pressure of 10 Pa. Monte Carlo simulations were performed to estimate approximately the energy of emitted atoms, focusing on the broadening of the angular distribution under the oxygen pressure of 10 Pa. The energies of emitted atoms were estimated to be 1-20 eV for the laser fluence of 1.1 J/cm{sup 2}, and more than 100 eV for 2.2 and 4.4 J/cm{sup 2}.

Konomi, I.; Motohiro, T.; Azuma, H.; Asaoka, T.; Nakazato, T.; Sato, E.; Shimizu, T.; Fujioka, S.; Sarukura, N.; Nishimura, H. [Toyota Technological Institute, 2-12-1 Hisakata, Tempaku-ku, Nagoya 468-8511, Japan and Toyota Central Research and Development Laboratories, Inc., 41-1 Yokomichi, Nagakute, Aichi 480-1192 (Japan); Toyota Central Research and Development Laboratories, Inc., 41-1 Yokomichi, Nagakute, Aichi 480-1192 (Japan); Institute of Laser Engineering, Osaka University, 2-6 Yamada-oka, Suita, Osaka 565-0871 (Japan)

2010-05-15

446

Lasers.  

ERIC Educational Resources Information Center

Examines the nature of laser light. Topics include: (1) production and characteristics of laser light; (2) nine types of lasers; (3) five laser techniques including holography; (4) laser spectroscopy; and (5) laser fusion and other applications. (SK)

Schewe, Phillip F.

1981-01-01

447

High efficiency coherent optical memory with warm rubidium vapour  

PubMed Central

By harnessing aspects of quantum mechanics, communication and information processing could be radically transformed. Promising forms of quantum information technology include optical quantum cryptographic systems and computing using photons for quantum logic operations. As with current information processing systems, some form of memory will be required. Quantum repeaters, which are required for long distance quantum key distribution, require quantum optical memory as do deterministic logic gates for optical quantum computing. Here, we present results from a coherent optical memory based on warm rubidium vapour and show 87% efficient recall of light pulses, the highest efficiency measured to date for any coherent optical memory suitable for quantum information applications. We also show storage and recall of up to 20 pulses from our system. These results show that simple warm atomic vapour systems have clear potential as a platform for quantum memory. PMID:21285952

Hosseini, M.; Sparkes, B.M.; Campbell, G.; Lam, P.K.; Buchler, B.C.

2011-01-01

448

Aluminium atom density and temperature in a dc magnetron discharge determined by means of blue diode laser absorption spectroscopy  

NASA Astrophysics Data System (ADS)

Diode laser absorption studies of aluminium atoms produced in a direct current (dc) magnetron discharge with argon as well as argon/nitrogen and argon/oxygen mixtures as working gas are reported. The measured Al atom density increases with increasing discharge power. The observed temperature being in the range of 340-420 K rises with increasing power but shows little pressure dependence. A small admixture of oxygen gas leads to a complete disappearance of the absorption signal, a result which is not yet fully understood.

Wolter, Matthias; Do, Hoang Tung; Steffen, Hartmut; Hippler, Rainer

2005-07-01

449

Interference-induced enhancement of field entanglement in a microwave-driven V-type single-atom laser  

E-print Network

We investigate the generation and the evolution of two-mode continuous-variable (CV) entanglement from system of a microwave-driven V-type atom in a quantum beat laser. By taking into account the effects of spontaneously generated quantum interference between two atomic decay channels, we show that the CV entanglement with large mean number of photons can be generated in our scheme, and the property of the filed entanglement can be adjusted by properly modulating the frequency detuning of the fields. More interesting, it is found that the entanglement can be significantly enhanced by the spontaneously generated interference.

Wen-Xing Yang; Ai-Xi Chen; Ting-Ting Zha; Yanfeng Bai; Ray-Kuang Lee

2014-04-04

450

An electrostatic glass actuator for ultrahigh vacuum: A rotating light trap for continuous beams of laser-cooled atoms.  

PubMed

This article describes the design, characterization, and performance of an electrostatic glass actuator adapted to an ultrahigh vacuum environment (10(-8) mbar). The three-phase rotary motor is used to drive a turbine that acts as a velocity-selective light trap for a slow continuous beam of laser-cooled atoms. This simple, compact, and nonmagnetic device should find applications in the realm of time and frequency metrology, as well as in other areas of atomic, molecular physics and elsewhere. PMID:17979408

Füzesi, F; Jornod, A; Thomann, P; Plimmer, M D; Dudle, G; Moser, R; Sache, L; Bleuler, H

2007-10-01

451

Fifty Years of Atomic Frequency Standards  

Microsoft Academic Search

This brief review of the history of atomic frequency standards includes: atomic beam magnetic resonance, microwave absorption and optical pumping, atomic masers, lasers, laser cooling and laser cooled atoms and ions at optical frequencies.

Norman F. Ramsey

2002-01-01

452

[Atomic Vapor Laser Isotope Separation (AVLIS) program]. Final report, [January--July 1992  

SciTech Connect

This report summarizes work performed for the Atomic Vapor Laser Isotope Separation (AVLIS) program from January through July, 1992. Each of the tasks assigned during this period is described, and results are presented. Section I details work on sensitivity matrices for the UDS relay telescope. These matrices show which combination of mirror motions may be performed in order to effect certain changes in beam parameters. In Section II, an analysis is given of transmission through a clipping aperture on the launch telescope deformable mirror. Observed large transmission losses could not be simulated in the analysis. An EXCEL spreadsheet program designed for in situ analysis of UDS optical systems is described in Section III. This spreadsheet permits analysis of changes in beam first-order characteristics due to changes in any optical system parameter, simple optimization to predict mirror motions needed to effect a combination of changes in beam parameters, and plotting of a variety of first-order data. Optical systems may be assembled directly from OSSD data. A CODE V nonsequential model of the UDS optical system is described in Section IV. This uses OSSD data to build the UDS model; mirror coordinates may thus be verified. Section V summarizes observations of relay telescope performance. Possible procedures which allow more accurate assessment of relay telescope performance are given.

Not Available

1992-12-04

453

Half-cycle-like field-enhanced harmonic radiation by femtosecond laser-atom interaction  

NASA Astrophysics Data System (ADS)

A manipulatable half-cycle-like field (HCLF), homochromy with the driving femtosecond laser, is applied to enhance the harmonic emission by optimizing their relative delay time. We find that, by numerical computation, the HCLF can deliver a substantial momentum to the accelerated electrons as they return to their parent ions by a suitable phase delay, and also significantly increase the atomic ionization rate supplementarily. The results show that the harmonic order of the maximum or cut-off photon energy emitted in the presence of a half-cycle manipulating light pulse is risen to the 177th order, which is a significant increase compared with the 53rd order harmonics in the case of a single driving light pulse. To understand the essence from the wave-packet kinetics of the return electrons and their relation to the harmonic emission, we utilize the phase-space analysis of the coordinate momentum of an electronic wave packet by using a Gabor transformation, by which the presented numerical conclusions are further confirmed.

Yu, Cheng-Xin; Liu, Shi-Bing; Song, Hai-Ying

2013-06-01

454

Presynaptic structure of Aplysia single live neuron by atomic force and confocal laser scanning microscope.  

PubMed

The structural and functional plasticity of Aplysia mechanosensory presynaptic neurons has been studied in relation with the mechanism underlying learning and memory. Long-term facilitation (LTF), which is a well-known cellular model for long-term memory in Aplysia, is accompanied by new synaptic structural growth or change. We developed a combined atomic force microscope and confocal laser scanning microscope (AFM-CLSM) system integrated with a MATLAB routine for image processing to concurrently obtain high-resolution 3-dimensional (3D) outer-surface morphological images and 3D interior fluorescence images. With our combined AFM-CLSM system, volumetric changes in the presynaptic structures (varicosities) of Aplysia live sensory-motor neuron cocultures were observed. The spatial distribution of synaptic vesicle molecules in the preexisting varicosities was monitored together with a volumetric change in the varicosities. Our combined AFM-CLSM system is successfully adapted for measuring learning-related structural changes and the movement of synaptic molecules in the single live neuron through interaction force and fluorescence imaging. PMID:23594081

Park, Aee-Young; Chae, Yeon-Su; Lee, Seung-Hee; Kaang, Bong-Kiun; Lee, Seonghoon

2013-05-01

455

REVIEWS OF TOPICAL PROBLEMS: Tunnel and multiphoton ionization of atoms and ions in a strong laser field (Keldysh theory)  

NASA Astrophysics Data System (ADS)

The theoretical description of the nonlinear photoionization of atoms and ions exposed to high-intensity laser radiation is underlain by the Keldysh theory proposed in 1964. The paper reviews this theory and its further development. The discussion is concerned with the energy and angular photoelectron distributions for the cases of linearly, circularly, and elliptically polarized laser radiation, with the ionization rate of atomic states exposed to a monochromatic electromagnetic wave and to ultrashort laser pulses of various shape, and with momentum and angular photoelectron spectra in these cases. The limiting cases of tunnel (? ll 1) and multiphoton (? gg 1) ionization are discussed, where c is the adiabaticity parameter, or the Keldysh parameter. The probability of above-barrier ionization is calculated for hydrogen atoms in a low-frequency laser field. The effect of a strong magnetic field on the ionization probability is discussed. The process of Lorentz ionization occurring in the motion of atoms and ions in a constant magnetic field is considered. The properties of an exactly solvable model—the ionization of an s-level bound by zero-range forces in the field of a circularly polarized electromagnetic wave—are described. In connection with this example, the Zel'dovich regularization method in the theory of quasistationary states is discussed. Results of the Keldysh theory are compared with experiment. A brief discussion is made of the relativistic ionization theory applicable when the binding energy of the atomic level is comparable with the electron rest mass (multiply charged ions) and the sub-barrier electron motion can no longer be considered to be nonrelativistic. A similar process of electron-positron pair production from a vacuum by the field of high-power optical or X-ray lasers (the Schwinger effect) is considered. The calculations invoke the method of imaginary time, which provides a convenient and physically clear way of calculating the probability of particle tunneling through time-varying barriers. Discussed in the Appendices are the properties of the asymptotic coefficients of the atomic wave function, the expansions for the Keldysh function, and the so-called 'ADK theory'.

Popov, Vladimir S.

2004-09-01

456

Energy transfer among distant quantum systems in spatially shaped laser fields: Two H atoms with an internuclear separation of 5.29 nm (100 a.u.)  

SciTech Connect

The quantum dynamics of two distant H atoms excited by ultrashort and spatially shaped laser pulses is studied by the numerical solution of the non-Born-Oppenheimer time-dependent Schroedinger equation within a three-dimensional (3D) model, including the internuclear distance R and the two z coordinates of the electrons z{sub 1} and z{sub 2}. The two one-dimensional (1D) H atoms, A and B, are assumed to be initially in their ground states with a large (but otherwise arbitrary) internuclear separation of R=100 a.u. (5.29 nm). Two types of a spatial envelope of a laser field linearly polarized along the z axis are considered: (i) a broad Gaussian envelope, such that atom A is excited by the laser field predominantly, and (ii) a narrow envelope, such that practically only atom A is excited by the laser field. With the laser carrier frequency {omega}=1.0 a.u. and the pulse duration t{sub p}=5 fs, in both cases an efficient energy transfer from atom A to atom B has been found. The ionization of atom B achieved mostly after the end of the laser pulse is close to or even higher than that of atom A. It is shown that with a narrow spatial envelope of the laser field, the underlying mechanisms of the energy transfer from A to B and the ionization of B are the Coulomb attraction of the laser driven electron by the proton of atom B and a short-range Coulomb repulsion of the two electrons when their wave functions significantly overlap in the domain of atom B. In the case of a broad Gaussian spatial envelope of the laser field, the opposite process also occurs, but with smaller probability: the energy is transferred from the weakly excited atom B to atom A, and the ionization of atom A is also induced by the electron-electron repulsion in the domain of atom A due to a strong overlap of the electronic wave functions.

Paramonov, Guennaddi K.; Kuehn, Oliver; Bandrauk, Andre D. [Institut fuer Physik, Universitaet Rostock, D-18051 Rostock (Germany); Laboratorie de Chimie Theorique, Faculte des Sciences, Universite de Sherbrooke, Sherbrooke, Quebec, J1K 2R1 (Canada)

2011-01-15

457

Generation of isolated sub-20-attosecond pulses from He atoms by two-color midinfrared laser fields  

NASA Astrophysics Data System (ADS)

We propose an efficient method for the generation of ultrabroadband supercontinuum spectra and isolated ultrashort attosecond laser pulses from He atoms with two-color midinfrared laser fields. High-order harmonic generation (HHG) is obtained by solving the time-dependent Schrödinger equation accurately by means of the time-dependent generalized pseudospectral method. We found that the optimizing two-color midinfrared laser pulse allows the HHG cutoff to be significantly extended, leading to the production of an ultrabroadband supercontinuum. As a result, an isolated 18-attosecond pulse can be generated directly by the superposition of the supercontinuum harmonics. To facilitate the exploration of the ultrashort attosecond generation mechanisms, we perform both a semiclassical simulation and a wavelet time-frequency transform.

Li, Peng-Cheng; Laughlin, Cecil; Chu, Shih-I.

2014-02-01

458

Sensitivity function analysis of gravitational wave detection with single-laser and large-momentum-transfer atomic sensors  

NASA Astrophysics Data System (ADS)

Recently, a configuration using atomic interferometers (AIs) had been suggested for the detection of gravitational waves. A new AI with some additional laser pulses for implementing large momentum transfer was also put forward, in order to reduce the effect of shot noise and laser frequency noise. We use a sensitivity function to analyze all possible configurations of the new AI and to distinguish how many momenta are transferred in a specific configuration. By analyzing the new configuration, we further explore a detection scheme for gravitational waves, in particular, that ameliorates laser frequency noise. We find that the amelioration occurs in such a scheme, but novelly, in some cases, the frequency noise can be canceled completely by using a proper data processing method. Supported by the National Natural Science Foundation of China.

Tang, Biao; Zhang, Bao-Cheng; Zhou, Lin; Wang, Jin; Zhan, Ming-Sheng

2015-03-01

459

Generation of Attosecond X-ray Pulses Beyond the Atomic Unit of Time Using Laser Induced Microbunching in Electron Beams  

SciTech Connect

Ever since the discovery of mode-locking, efforts have been devoted to reducing the duration of laser pulses since the ultrashort pulses are critical to explore the dynamics occurred on a ever-shorter timescale. In this paper we describe a scheme that's capable of generating intense attosecond x-ray pulses with duration beyond the atomic unit of time ({approx}24 attoseconds). The scheme combines the echo-enabled harmonic generation technique with the bunch compression which allows one to generate harmonic numbers of a few hundred in a microbunched beam through up-conversion of the frequency of a UV seed laser. A few-cycle intense IR laser is used to generate the required energy chirp in the beam for bunch compression and for selection of an attosecond x-ray pulse. Using a representative realistic set of parameters, we show that 1 nm x-ray pulse with peak power of a few hundred MW and duration as short as 20 attoseconds (FWHM) can be generated from a 200 nm UV seed laser. The proposed scheme may enable the study of electronic dynamics with a resolution beyond the atomic unit of time and may open a new regime of ultrafast sciences.

Xiang, D.; Huang, Z.; Stupakov, G.; /SLAC

2009-12-11

460

Two-color, two-photon laser-induced polarization spectroscopy (LIPS) measurements of atomic hydrogen in near-adiabatic, atmospheric pressure hydrogen\\/air flames  

Microsoft Academic Search

Two-color, two-photon laser-induced polarization spectroscopy (LIPS) of atomic hydrogen has been demonstrated and applied in atmospheric pressure hydrogen\\/air flames. Fundamental and frequency-doubled beams from a single 486-nm dye laser were used in the experiments. The 243-nm pump beam in the measurements was tuned to the two-photon n=1?n=2 resonance of the hydrogen atom. The 486-nm probe beam was tuned to the

Waruna D. Kulatilaka; Robert P. Lucht; Sherif F. Hanna; Viswanath R. Katta

2004-01-01

461

Possibility of using Zn as the quantum absorber for a laser-cooled neutral atomic optical frequency standard  

SciTech Connect

In this paper, we present a detailed investigation of the laser cooling and trapping of the Zn atom, and various schemes employing the {sup 1}S{sub 0}-{sup 3}P{sub 0} transition, induced by nuclear magnetic moment or applied fields, as the clock transition. Using numerical simulations, the deceleration of Zn by a Zeeman slower and its capture by a magneto-optical trap (MOT) are analyzed, and the corresponding parameters are determined. The linear loss rate and the coefficient for two-body collisional loss in the MOT are discussed. To prove the feasibility of the intercombination line cooling, one-dimensional semiclassical Monte Carlo simulations are performed. Multiconfiguration Hartree-Fock and multiconfiguration Dirac-Fock approaches are employed to calculate the hyperfine-induced {sup 1}S{sub 0}-{sup 3}P{sub 0} transition. Up to now, various schemes inducing the {sup 1}S{sub 0}-{sup 3}P{sub 0} transition in bosonic isotopes have been proposed for alkaline-earth-metal atoms and Yb. Their applicability for Zn are investigated, and the corresponding parameters of Zn are calculated. Our results show that the Zn atom, either fermionic or bosonic, is a potential candidate for the quantum absorber used in laser-cooled neutral atomic optical frequency standard.

Wang Guangfu; Ye Anpei [Institute of Quantum Electronics, School of Electronics Engineering and Computer Science, Peking University, Beijing 100871 (China)

2007-10-15