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1

Laser optical pumping in Rb vapour-cell atomic clocks (Invited Paper)  

NASA Astrophysics Data System (ADS)

We discuss the basic physical principles of laser optical pumping double-resonance spectroscopy, which form the basis of state-of-the-art vapour-cell atomic frequency standards using laser optical pumping of Rb atoms. The main effects limiting the frequency stability of Rb vapour-cell atomic clocks are identified, and their impact on the development of high-performance frequency standars and their transfer from research laboratories to industry and space is discussed. As examples, the impact of the AC stark effect and the realated issue of laser frequency stabilisation are dealt with in more detail. The main features of the present state-of-the-art Rb atomic frequency standards will be illustrated using the example of the development of atomic clocks for satellite navigation and positioning systems (GPS, GLONAS, GALILEO, etc.) as well as some directions for further improvements that could overcome present day limitations. Such compact Rb clocks find their applications in, for example, telecommunications, local timekeeping and synchronisation, and space applications like satellite navigation and science missions. An overview of other, alternative clock schemes is given and critical issues for future developments towards further performance improvement or device miniaturisation in the field of vapour-cell atomic clocks are discussed.

Mileti, Gaetano; Affolderbach, C.

2005-04-01

2

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

3

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

4

Photonic metamaterials by direct laser writing and silver chemical vapour  

E-print Network

LETTERS Photonic metamaterials by direct laser writing and silver chemical vapour deposition online: 11 May 2008; doi:10.1038/nmat2197 Metamaterials are artificial materials that--unlike natural metamaterials4,5 has been fabricated by electron-beam lithography and evaporation of metal films, both of which

5

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 atomatom 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

6

Strontium vapour laser with a pulse repetition rate of up to 1 MHz  

SciTech Connect

For the first time it has been shown that the pulse repetition rate of the lasers on the self-terminating transitions of metal atoms may be as high as {approx}1 MHz. The highest pulse repetition rate equal to {approx}830 kHz was realised on self-terminating IR transitions in Sr I atoms ({lambda} = 6.456 {mu}m and {approx}3 {mu}m) and in Sr II ions ({lambda} {approx} 1 {mu}m) in a strontium vapour laser operating in a self-heating pulse periodic regime. The energy yield of a Sr laser was found to be proportional to the energy input into the active medium in a wide range of excitation pulse repetition frequencies; in this case, the average total specific output laser power is equal to 30 - 40 mW cm{sup -3}. (lasers)

Soldatov, Anatolii N; Yudin, Nikolai A; Vasilieva, Anna V; Kolmakov, E A; Polunin, Yurii P; Kostyrya, I D

2012-01-31

7

INTERACTION OF LASER RADIATION WITH MATTER: Resonance laser-induced ionisation of sodium vapour taking radiative transfer into account  

NASA Astrophysics Data System (ADS)

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.

Kosarev, N. I.; Shaparev, N. Ya

2006-04-01

8

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

9

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

NASA Astrophysics Data System (ADS)

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.

Cartaleva, S.; Krasteva, A.; Moi, L.; Sargsyan, A.; Sarkisyan, D.; Slavov, D.; Todorov, P.; Vaseva, K.

2013-09-01

10

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

11

Modelling of vapour flow in deep penetration laser welding  

NASA Astrophysics Data System (ADS)

The pressure induced by vapour flow during keyhole wall evaporation in deep penetration laser welding could have a more significant role in stabilizing keyhole walls, compared to that due to ablation pressure induced by local wall evaporation. In this paper, vapour flow modelling in a blind keyhole is presented by considering both simple geometries such as straight or inclined cylinders and more realistic profiles deduced from a self-consistent equilibrium calculation. The numerical approach used in the discretization is based on the finite element method that allows us to solve a two-dimensional Navier-Stokes set of equations assuming incompressible flow. In our model, the laser beam aperture and multiple reflections effects are taken into account. A ray-tracing procedure allows one to obtain absorbed intensities and thus the local surface temperature on the keyhole walls. The deduced local gas ejection velocities on the edge of the Knudsen layer are thus the boundary conditions of the Navier-Stokes problem.

Amara, E. H.; Bendib, A.

2002-02-01

12

Spatial homogeneity criteria for active media of cataphoresis repetitively pulsed metal vapour lasers  

SciTech Connect

The formation of the transverse distribution of the metal vapour concentration in repetitively pulsed lasers is analysed. The criterion for the homogeneity of this distribution is found. The optimal conditions for excitation of the active media of cataphoresis repetitively pulsed metal vapour lasers are determined under which a high degree of both longitudinal and transverse homogeneity is achieved. (active media)

Chebotarev, Gennady D; Prutsakov, Oleg O; Latush, Evgeny L [Department of Physics, Rostov State University, Rostov-on-Don (Russian Federation)

2005-07-31

13

ACTIVE MEDIA: Spatial homogeneity criteria for active media of cataphoresis repetitively pulsed metal vapour lasers  

Microsoft Academic Search

The formation of the transverse distribution of the metal vapour concentration in repetitively pulsed lasers is analysed. The criterion for the homogeneity of this distribution is found. The optimal conditions for excitation of the active media of cataphoresis repetitively pulsed metal vapour lasers are determined under which a high degree of both longitudinal and transverse homogeneity is achieved. Bibtex entry

Gennady D. Chebotarev; Oleg O. Prutsakov; Evgeny L. Latush

2005-01-01

14

Spatial homogeneity criteria for active media of cataphoresis repetitively pulsed metal vapour lasers  

Microsoft Academic Search

The formation of the transverse distribution of the metal vapour concentration in repetitively pulsed lasers is analysed. The criterion for the homogeneity of this distribution is found. The optimal conditions for excitation of the active media of cataphoresis repetitively pulsed metal vapour lasers are determined under which a high degree of both longitudinal and transverse homogeneity is achieved.

Gennady D Chebotarev; Oleg O Prutsakov; Evgeny L Latush

2005-01-01

15

Spatial homogeneity criteria for active media of cataphoresis repetitively pulsed metal vapour lasers  

Microsoft Academic Search

The formation of the transverse distribution of the metal vapour concentration in repetitively pulsed lasers is analysed. The criterion for the homogeneity of this distribution is found. The optimal conditions for excitation of the active media of cataphoresis repetitively pulsed metal vapour lasers are determined under which a high degree of both longitudinal and transverse homogeneity is achieved. (active media)

Gennady D Chebotarev; Oleg O Prutsakov; Evgeny L Latush

2005-01-01

16

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

17

High-power metal halide vapour lasers oscillating in deep ultraviolet, visible and middle infrared spectral ranges  

NASA Astrophysics Data System (ADS)

Middle infrared and deep ultraviolet high-power high-beam-quality stable-operating He-SrBr2 and Cu+ Ne-CuBr lasers excited in nanosecond pulsed longitudinal discharge are developed, patented and studied. Optimal discharge conditions, such as active zone diameter, vapour pressure, buffer-gas pressure, electrical excitation scheme parameters, average input power and pulse repetition frequency, are found. The highest output laser parameters are obtained for the Sr atom and Cu+ lasers, respectively. These lasers equipped with optical systems for the control of laser radiation parameters are used in a large variety of applications, such as precise material microprocessing, including biological tissues, determination of linear optical properties of different newly developed materials, laser-induced modification of conductive polymers and laser-induced fluorescence in wide-gap semiconductors, instead of free electron and excimer lasers, respectively. A master oscillator-power amplifier system, which is based on a high-beam-quality high-power CuBr vapour laser and is equipped with an optic system for laser beam control and with the X-Y stage controlled by adequate software as well, is developed and used in high-precision micromachining of samples made of nickel and tool steel.

Temelkov, K. A.; Slaveeva, S. I.; Kirilov, V. I.; Kostadinov, I. K.; Vuchkov, N. K.

2012-05-01

18

Atoms in Intense Laser Fields  

NASA Astrophysics Data System (ADS)

Part I. Basic Concepts: 1. High-intensity laser-atom physics; 2. Theory of laser-atom interactions; Part II. Theoretical Methods: 3. Perturbation theory; 4. Floquet theory; 5. Numerical integration of the wave equations; 6. The low-frequency regime; 7. The high-frequency regime; Part III. Multiphoton Atomic Physics: 8. Multiphoton ionization; 9. Harmonic generation and attosecond pulses; 10. Laser-assisted electron-atom collisions; Appendix; Index.

Joachain, C. J.; Kylstra, N. J.; Potvliege, R. M.

2014-07-01

19

Two-wavelength interferometry on excimer laser induced vapour/plasma plumes during the laser pulse  

NASA Astrophysics Data System (ADS)

Ablation-using short-pulse lasers, e.g., excimer lasers and solid state lasers, is becoming an important technology for micro-machining, thin film formation and fine particle generation. Hence, there is a great interest to understand the interaction mechanisms between the radiation field and the evaporated material. Especially the laser-induced material vapour influences the efficiency and the quality of the ablation, as shown in earlier contributions [G. Callies, P. Berger, J. Kästle, H. Hügel, Proc. SPIE, Vol. 2502, p. 706; G. Callies, H. Schittenhelm, P. Berger, F. Dausinger, H. Hügel, Proc. SPIE, Vol. 2246, p. 126]. Two-wavelength interferometry, shadowgraphy and resonance absorption photography allowed us to investigate the whole laser induced region with each probe-laser pulse. The experiments were performed in ambient air, helium and argon at a pressure of 10 5 Pa. Earlier, shadowgraphy experiments indicated several discontinuities within the plume arising during the laser pulse. To get more information about the nature of these discontinuities and their expansion behaviour and to obtain the free electron density distributions within the shock wave, interferometry with two wavelengths was applied. The results show spatially-separated regions of high free electron densities and therefore, high temperatures within the plasma plume. The observed regions correspond to those found by shadowgraphy and resonance absorption photography: the region of material vapour directly behind the contact front, the plasma core near the target surface with high electron densities, and two more regions separated by discontinuities. A variation of the ambient gas causes a drastic change in the electron density. In an argon atmosphere, a formation of a laser supported detonation wave, instead of a shock wave, arises for energy densities higher than 20-25 J/cm 2. The interferometry yields, for this case, a very high electron density within the material vapour near the contact front. A comparison of the electron density distribution with ablation rates in helium and nitrogen indicate the independence of the interaction of the excimer laser radiation with the electrons.

Schittenhelm, H.; Callies, G.; Berger, P.; Hügel, H.

1998-05-01

20

MEMS caesium vapour cell for european micro-atomic-clock  

Microsoft Academic Search

We described the technology of MEMS caesium cell for European Micro-Atomic-Clock. The technology utilize new caesium introduction method with use of the pill-like solid-state caesium dispenser. Optical measurements and results of accelerated aging tests were described.

Pawel Knapkiewicz; Jan Dziuban; Rafa? Walczak; Luca Mauri; Piotr Dziuban; Cristophe Gorecki

2010-01-01

21

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

22

High-power copper vapour lasers and applications  

SciTech Connect

Expanded applications of copper vapor lasers has prompted increased demand for higher power and better beam quality. This paper reports recent progress in laser power scaling, MOPA operation, beam quality improvement, and applications in precision laser machining. Issues such as gas heating, radial delay, discharge instability, and window heating will also be discussed.

Chang, J.J.; Warner, B.E.; Boley, C.D.; Dragon, E.P.

1995-08-01

23

Atom projector: atom manipulation by laser  

NASA Astrophysics Data System (ADS)

The problems of neutral atom beam formation and its application to the microelectronic manufacturing are considered. The plant using the focused neutral atom beam is presented. This high-vacuum plant is designed for complex CIP's processing. The scheme of this plant is given. It is divided into the following sections: atom generation, beam preparing, its structuring, compression, and surface treatment. The preparing section is described in detail. The beam is controlled by laser radiation resonant to basic transition in the atom absorption spectrum. The plant forms precisely structured low-temperature atom beams and controls atom density distribution in flow by rather simple projective methods. It allows discussing the possibility of the new, effective and high-automated manufacturing and analysis of micro-object surfaces. Resolution of the suggested method of treatment is proved to be limited only by characteristics of the equipment used. Calculation shows that at modern level of laser technique the spatial resolution of such a process can reach about 10 nm. The resolution of surface analysis is evaluated to be about 1 nm. Probable applications of the presented new technological process for integrated manufacturing, analysis and in-line reconstruction of the IC of super high integration by methods of liquid-free in-situ processing are considered.

Sovetov, Nikolay M.; Nikonov, Anatoly V.; Grigoriev, Dmitry A.; Khobotov, Andrey V.; Moscovsky, Victor A.; Naumova, Elena V.

1999-03-01

24

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

25

Atomic and molecular spectra of vapours evolved in a graphite furnace. Part 2: Magnesium chloride  

NASA Astrophysics Data System (ADS)

Electrothermal atomic and molecular absorption spectrometry was applied to investigate the vaporization of magnesium chloride. Using a CCD linear array detector, atomic and molecular absorption spectra were simultaneously measured in the range 200-400 nm. Vaporization was performed from pyrocoated and tantalum-lined graphite tubes; Ar and He were employed as furnace gas. A broad molecular band was first observed at 210 nm and attributed to MgCl 2(g). The signal was followed by a partially resolved system at 266, 269, 273 nm and a three bands at 369, 376 and 382 nm, which are characteristic of MgCl(g). The release of MgCl vapours was accompanied by Mg atomic absorption and by light scattering. MgCl 2·6H 2O partially vaporizes as MgCl 2(g) and partially reacts with the water of crystallization (hydrolysis reaction), leading to a mixture of magnesium hydroxychloride and hydroxide. By further heating of the condensed phase MgO(s) and MgCl vapours are formed. The hydrolysis process was favoured by long pyrolysis treatments or by stopping the gas flow during the pyrolysis step. In He atmosphere or when a tantalum-lined tube was used, the fraction of salt vaporized as MgCl 2 was increased, while scattering effects were not observed.

Daminelli, G.; Katskov, D. A.; Mofolo, R. M.; Kántor, T.

1999-05-01

26

Vapour phase growth and grain boundary structure of molybdenum disulphide atomic layers  

NASA Astrophysics Data System (ADS)

Single-layered molybdenum disulphide with a direct bandgap is a promising two-dimensional material that goes beyond graphene for the next generation of nanoelectronics. Here, we report the controlled vapour phase synthesis of molybdenum disulphide atomic layers and elucidate a fundamental mechanism for the nucleation, growth, and grain boundary formation in its crystalline monolayers. Furthermore, a nucleation-controlled strategy is established to systematically promote the formation of large-area, single- and few-layered films. Using high-resolution electron microscopy imaging, the atomic structure and morphology of the grains and their boundaries in the polycrystalline molybdenum disulphide atomic layers are examined, and the primary mechanisms for grain boundary formation are evaluated. Grain boundaries consisting of 5- and 7- member rings are directly observed with atomic resolution, and their energy landscape is investigated via first-principles calculations. The uniformity in thickness, large grain sizes, and excellent electrical performance signify the high quality and scalable synthesis of the molybdenum disulphide atomic layers.

Najmaei, Sina; Liu, Zheng; Zhou, Wu; Zou, Xiaolong; Shi, Gang; Lei, Sidong; Yakobson, Boris I.; Idrobo, Juan-Carlos; Ajayan, Pulickel M.; Lou, Jun

2013-08-01

27

Determination of mercury in rice by MSFIA and cold vapour atomic fluorescence spectrometry.  

PubMed

In the present paper the use of a MSFIA system for determination of mercury in rice by cold vapour atomic fluorescence spectrometry (CV AFS) is proposed. The sample digestion is performed in a microwave oven using nitric acid and hydrogen peroxide. The experimental conditions for vapour generation were determined using a full two-level factorial design involving the following factors: nitric acid and tin chloride concentrations and sample flow rate. Employing the conditions optimised, the method allows the determination of mercury using the external calibration technique with aqueous standards. The reached limits of detection and quantification were 0.48 and 1.61 ng g?¹ respectively, and the precision (as relative standard deviation) was 3.28% and 1.56% for rice samples with a mercury content of 3.63 and 5.81 ng g?¹, respectively. The method accuracy was confirmed analysing a certified reference material of rice flour furnished by National Institute of Standard and Technology. The interference of nitrous acid and nitrous oxides are removed using potassium dichromate. The method was applied to mercury determination in twelve rice samples acquired in Palma de Mallorca (Spain) between the months of January and April of 2012. The mercury content found varied from 2.15 to 7.25 ng g?¹. These results agree with those reported by others authors. PMID:23200004

da Silva, Douglas G; Portugal, Lindomar A; Serra, Antonio M; Ferreira, Sergio L C; Cerdà, Victor

2013-04-15

28

Thin film semiconductor nanomaterials and nanostructures prepared by physical vapour deposition: An atomic force microscopy study  

NASA Astrophysics Data System (ADS)

Amorphous/nanocrystalline SiOx/CdSe, GeS2/CdSe, SiOx/ZnSe and Se/CdSe amorphous multilayers (MLs) were grown by consecutive physical vapour deposition of the constituent materials at room substrate temperature. A step-by-step manner of deposition was applied for the preparation of each layer (2 10nm thick) of MLs. Surface morphology has been investigated by atomic force microscopy (AFM) in order to get information about ML interfaces. For a scanned area of 3.4×4?mSiOx/CdSe and GeS2/CdSe MLs showed surface roughness which is around three times greater than the roughness of SiOx/ZnSe MLs. This observation has been connected with effects of both film composition and deposition rate. For a scanned area of 250×250nm the roughness determined in all MLs displayed close values and a similar increase with the ML period. The latter has been related to the flexible structure of amorphous materials. The AFM results, in good agreement with previous X-ray diffraction and high resolution electron microscopy data, indicate that the application of step-by-step physical vapour deposition makes possible fabrication of various amorphous/nanocrystalline MLs with smooth interfaces and good artificial periodicity at low substrate temperatures.

Nesheva, D.; Petrova, A.; Stavrev, S.; Levi, Z.; Aneva, Z.

2007-05-01

29

Excimer laser recrystallization of nanocrystalline-Si films deposited by inductively coupled plasma chemical vapour deposition at 150°C  

NASA Astrophysics Data System (ADS)

Polycrystalline silicon thin film transistors (poly-Si TFTs) fabricated at low temperature (under 200°C) have been widely investigated for flexible substrate applications such as a transparent plastic substrate. Unlike the conventional TFT process using glass substrate, the maximum process temperature should be kept less than 200°C in order to avoid thermal damage on flexible substrates. We report the characteristics of nanocrystalline silicon (nc-Si) irradiated by an excimer laser. Nc-Si precursors were deposited on various buffer layers by inductively coupled plasma chemical vapour deposition (ICP-CVD) at 150°C. We employed various buffer layers, such as silicon nitride (SiNX) and silicon dioxide (SiO2), in order to report recrystallization characteristics in connection with a buffer layer of a different thermal conductivity. The dehydrogenation and recrystallization was performed by step-by-step excimer laser annealing (ELA) (XeCl,?=308 nm) in order to prevent the explosive release of hydrogen atoms. The grain size of the poly-Si film, which was recrystallized on the various buffer layers, was measured by scanning electron microscopy (SEM) at each laser energy density. The process margin of step-by-step ELA employing the SiNX buffer layer is wider than SiO2 and the maximum grain size slightly increased.

Park, Joong-Hyun; Han, Sang-Myeon; Park, Sang-Geun; Han, Min-Koo; Shin, Moon-Young

2006-09-01

30

Microfabricated rubidium vapour cell with a thick glass core for small-scale atomic clock applications  

NASA Astrophysics Data System (ADS)

This paper presents a new fabrication method to manufacture alkali reference cells having dimensions larger than standard micromachined cells and smaller than glass-blown ones, for use in compact atomic devices such as vapour-cell atomic clocks or magnetometers. The technology is based on anodic bonding of silicon and relatively thick glass wafers and fills a gap in cell sizes and technologies available up to now: on one side, microfabrication technologies with typical dimensions ? 2 mm and on the other side, classical glass-blowing technologies for typical dimensions of about 6-10 mm or larger. The fabrication process is described for cells containing atomic Rb and spectroscopic measurements (optical absorption spectrum and double resonance) are reported. The analysis of the bonding strength of our cells was performed and shows that the first anodic bonding steps exhibit higher bonding strengths than the later ones. The spectroscopic results show a good quality of the cells. From the double-resonance signals, we predict a clock stability of ?3 × 10-11 at 1 s of integration time, which compares well to the performance of compact commercial Rb atomic clocks.

Pétremand, Y.; Affolderbach, C.; Straessle, R.; Pellaton, M.; Briand, D.; Mileti, G.; de Rooij, N. F.

2012-02-01

31

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

32

An ultra-bright atom laser  

E-print Network

We present a novel, ultra-bright atom-laser and ultra-cold thermal atom beam. Using rf-radiation we strongly couple the magnetic hyperfine levels of 87Rb atoms in a magnetically trapped Bose-Einstein condensate. At low rf-frequencies gravity opens a small hole in the trapping potenital and a well collimated, extremely bright atom laser emerges from just below the condensate. As opposed to traditional atom lasers based on weak coupling, this technique allows us to outcouple atoms at an arbitrarily large rate. We demonstrate an increase in flux per atom in the BEC by a factor of sixteen compared to the brightest quasi-continuous atom laser. Furthermore, we produce by two orders of magnitude the coldest thermal atom beam to date (200 nK).

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

2013-11-25

33

Determination and characterization of phytochelatins by liquid chromatography coupled with on line chemical vapour generation and atomic fluorescence spectrometric detection  

Microsoft Academic Search

Liquid chromatography (LC) coupled on line with UV\\/visible diode array detector (DAD) and cold vapour generation atomic fluorescence spectrometry (CVGAFS) has been developed for the speciation, determination and characterization of phytochelatins (PCs). The method is based on a bidimensional approach, e.g. on the analysis of synthetic PC solutions (apo-PCs and Cd2+-complexed PCs) (i) by size exclusion chromatography coupled to UV

Emilia Bramanti; Daniel Toncelli; Elisabetta Morelli; Leonardo Lampugnani; Roberto Zamboni; Keith E. Miller; Joseph Zemetra; Alessandro D’Ulivo

2006-01-01

34

Characterization of denatured metallothioneins by reversed phase coupled with on-line chemical vapour generation and atomic fluorescence spectrometric detection  

Microsoft Academic Search

A new analytical hyphenated technique is proposed for determination and characterization of thiolic proteins, based on reverse phase chromatography (RPC) coupled on-line with cold vapour generation atomic fluorescence spectrometry (CVGAFS). Proteins are pre-column simultaneously denatured and derivatized in phosphate buffer solution containing 8.0moll?1 urea and p-hydroxymercurybenzoate (PHMB). The derivatized proteins are separated on a C4 Vydac Reverse Phase column. Post-column

Emilia Bramanti; Cristina Lomonte; Alvaro Galli; Massimo Onor; Roberto Zamboni; Giorgio Raspi; Alessandro D’Ulivo

2004-01-01

35

Generation of 10 mW tunable narrowband radiation around 210 nm using a 6.5 kHz repetition rate copper vapour laser pumped dye laser  

NASA Astrophysics Data System (ADS)

A reliable laser system, capable of generating 10 mW average power of tunable narrowband deep UV radiation around 210 nm is demonstrated. The system is based on a 6.5 kHz repetition rate copper vapour laser pumped dye laser. The dye laser emission is subsequently tripled by phasematched second harmonic generation and sum-frequency mixing in two BBO crystals. An application of the present system for high resolution excitation around 213 nm of the 1B 2( 1? +u) state of the CS 2 molecule and a resultant total fluorescence spectrum is given as an example.

Koprinkov, I. G.; Naylor, G. A.; Pique, J. P.

1994-01-01

36

Growth of SnO 2 thin films by atomic layer deposition and chemical vapour deposition: A comparative study  

Microsoft Academic Search

Thin films of the tetragonal rutile-type SnO2 phase have been deposited by both atomic layer deposition (ALD) and chemical vapour deposition (CVD) using the SnI4–O2 precursor combination. Depositions were carried out in the temperature region of 350–750°C on ?-Al2O3(0 1 2) substrates. In both cases the films were found to grow epitaxially with the in-plane orientation relationships [0 1 0]SnO2

Jonas Sundqvist; Jun Lu; Mikael Ottosson; Anders Hårsta

2006-01-01

37

Reactions of xenon difluoride and atomic hydrogen at chemical vapour deposited diamond surfaces  

Microsoft Academic Search

X-ray photoelectron spectroscopy has been used to investigate the interaction of xenon difluoride at chemical vapour deposited, polycrystalline diamond surfaces. Dissociative chemisorption, resulting in the formation of adsorbed fluorine up to monolayer coverages, occurs on the clean surface with a sticking probability of approximately 10?4. Prehydrogenation of the diamond, increases the initial reactive sticking probability, but reduces the saturation fluorine

J. S. Foord; N. K. Singh; R. B. Jackman; A. Gutierrez-Sosa; S. Proffitt; K. B. Holt

2001-01-01

38

Design for an optical cw atom laser.  

PubMed

A new type of optical cw atom laser design is proposed that should operate at high intensity and high coherence and possibly record low temperatures. It is based on an "optical-shepherd" technique, in which far-off-resonance blue-detuned swept sheet laser beams are used to make new types of high-density traps, atom waveguides, and other components for achieving very efficient Bose-Einstein condensation and cw atom laser operation. A shepherd-enhanced trap is proposed that should be superior to conventional magneto-optic traps for the initial collection of molasses-cooled atoms. A type of dark-spot optical trap is devised that can cool large numbers of atoms to polarization-gradient temperatures at densities limited only by three-body collisional loss. A scheme is designed to use shepherd beams to capture and recycle essentially all of the escaped atoms in evaporative cooling, thereby increasing the condensate output by several orders of magnitude. Condensate atoms are stored in a shepherd trap, protected from absorbing light, under effectively zero-gravity conditions, and coupled out directly into an optical waveguide. Many experiments and devices may be possible with this cw atom laser. PMID:15302937

Ashkin, Arthur

2004-08-17

39

Atomic stabilization by super-intense lasers.  

PubMed

Supercomputer simulations predict the creation of an unexpectedly stable form of atomic matter when ordinary atoms are irradiated by very intense, high-frequency laser pulses. In the rising edge of a very intense pulse of ionizing radiation, the atom's wave function distorts adiabatically into a distribution with two well-separated peaks. As the intensity increases, the peak spacing increases so that the atomic electron spends more time far from the nucleus and the ionization rate decreases. This leads to the surprising and counter-intuitive result that the atom becomes more stable as the ionizing radiation gets stronger. PMID:17772644

Eberly, J H; Kulander, K C

1993-11-19

40

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

41

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

42

Active narrowband filtering, line narrowing and gain using ladder electromagnetically induced transparency in an optically thick atomic vapour  

E-print Network

Electromagnetically induced transparency (EIT) resonances using the $5\\rm{S}_{1/2}\\rightarrow5\\rm{P}_{3/2}\\rightarrow5\\rm{D}_{5/2}$ ladder-system in optically thick Rb atomic vapour are studied. We observe a strong line narrowing effect and gain at the $5\\rm{S}_{1/2}\\rightarrow5\\rm{P}_{3/2}$ transition wavelength due to an energy-pooling assisted frequency conversion with characteristics similar to four-wave mixing. As a result it is possible to observe tunable and switchable transparency resonances with amplitude close to $100\\%$ and a linewidth of 15 MHz. In addition, the large line narrowing effect allows resolution of $^{85}$Rb $5\\rm{D}_{5/2}$ hyperfine structure even in the presence of strong power broadening.

James Keaveney; Armen Sargsyan; David Sarkisyan; Aram Papoyan; Charles S. Adams

2014-01-24

43

Active narrowband filtering, line narrowing and gain using ladder electromagnetically induced transparency in an optically thick atomic vapour  

NASA Astrophysics Data System (ADS)

Electromagnetically induced transparency (EIT) resonances using the 5S1/2 ? 5P3/2 ? 5D5/2 ladder-system in optically thick Rb atomic vapour are studied. We observe a strong line narrowing effect and gain at the 5S1/2 ? 5P3/2 transition wavelength due to an energy-pooling assisted frequency conversion with characteristics similar to 4-wave mixing. As a result it is possible to observe tunable and switchable transparency resonances with amplitude close to 100% and a linewidth of 15 MHz. In addition, the large line narrowing effect allows resolution of 85Rb 5D5/2 hyperfine structure even in the presence of strong power broadening.

Keaveney, James; Sargsyan, Armen; Sarkisyan, David; Papoyan, Aram; Adams, Charles S.

2014-04-01

44

Active narrowband filtering, line narrowing and gain using ladder electromagnetically induced transparency in an optically thick atomic vapour  

E-print Network

Electromagnetically induced transparency (EIT) resonances using the $5\\rm{S}_{1/2}\\rightarrow5\\rm{P}_{3/2}\\rightarrow5\\rm{D}_{5/2}$ ladder-system in optically thick Rb atomic vapour are studied. We observe a strong line narrowing effect and gain at the $5\\rm{S}_{1/2}\\rightarrow5\\rm{P}_{3/2}$ transition wavelength due to an energy-pooling assisted frequency conversion with characteristics similar to four-wave mixing. As a result it is possible to observe tunable and switchable transparency resonances with amplitude close to $100\\%$ and a linewidth of 15 MHz. In addition, the large line narrowing effect allows resolution of $^{85}$Rb $5\\rm{D}_{5/2}$ hyperfine structure even in the presence of strong power broadening.

Keaveney, James; Sarkisyan, David; Papoyan, Aram; Adams, Charles S

2013-01-01

45

Atomic fluorine source for chemical lasers  

NASA Astrophysics Data System (ADS)

We present results from the early development of an F atom source appropriate for HF and AGIL chemical laser research. The system uses high power microwaves to produce a high enthalpy plasma that thermally dissociates molecular species such as SF6 and F2. Results of the characterization of the flow are presented.

Davis, Steven J.; Oakes, David B.; Read, Michael E.; Gelb, Alan H.

2002-05-01

46

Interaction of cold atoms with short laser pulses  

Microsoft Academic Search

We present a powerful diagnostic system to observe the interaction of ultrafast laser pulses with trapped ^87Rb atoms. The ionization of cold atoms and the formation of cold molecules in an intense laser field in the muK temperature range open new branches of research in chemistry, metrology, and quantum physics. However, the interaction of cold atoms with short laser pulses

Karen Chamberlin; Derek Lilla; Kyle Taylor; Kevin Zick; Greg Taft; Hai Nguyen

2006-01-01

47

Broadband laser cooling of trapped atoms with ultrafast pulses  

E-print Network

and can sufficiently localize trapped atoms to produce near diffraction- limited atomic images. © 2006Broadband laser cooling of trapped atoms with ultrafast pulses B. B. Blinov,* R. N. Kohn, Jr., M. J January 11, 2006; posted February 6, 2006 (Doc. ID 64946) We demonstrate broadband laser cooling of atomic

Blinov, Boris

48

Photoassociation of Laser-cooled Ytterbium Atoms  

NASA Astrophysics Data System (ADS)

We report photoassociation of laser-cooled ytterbium (Yb) atoms. By detecting the trap loss of 174Yb atoms in the FORT due to the photoassociation beam, we could observe more than 90 photoassociation resonances of vibrational levels in the {}1? u^ + state which connects asymptotically to the 1S0+1P1 atomic state in the dissociation limit. From the observed resonance frequencies we could precisely determine the atomic radiative lifetime of the 1P1 state to 5.464 ± 0.005 ns. We have also observed linebroadening of photoassociation resonances, which is ascribed to the predissociation to the triplet states, and determined the transition probability to be 0.2. Furthermore, we have observed the decrease of the intensity of photoassiciation signal at 435 GHz detuning from the 1S0+1P1 asymptote, from which the scattering length is estimated to be equal to or less than 3 nm.

Takahashi, Y.; Takasu, Y.; Komori, K.; Honda, K.; Kumakura, M.; Yabuzaki, T.

2003-04-01

49

Atom-laser coherence via multiloop feedback control  

NASA Astrophysics Data System (ADS)

Coherence control is the key to success in the applications of atom-laser beams. A multiloop measurement feedback control scheme is proposed to improve atom-laser coherence. The first loop aims to cancel the decohering effects of the nonlinear atom-atom interactions via direct measurement feedback. However, there are nonlinear interactions with the optical probe field used in the measurement scheme which may also contribute to a degradation in atom-laser performance. Accordingly, a second feedback loop is used to reduce these effects based on linear quadratic Gaussian control. The multiloop design achieves improved atom-laser coherence.

Yanagisawa, M.; James, M. R.

2009-02-01

50

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

51

Atom interferometric gravitational wave detection using heterodyne laser links  

E-print Network

We propose a scheme based on a heterodyne laser link that allows for long baseline gravitational wave detection using atom interferometry. While the baseline length in previous atom-based proposals is constrained by the need for a reference laser to remain collimated as it propagates between two satellites, here we circumvent this requirement by employing a strong local oscillator laser near each atom ensemble that is phase locked to the reference laser beam. Longer baselines offer a number of potential advantages, including enhanced sensitivity, simplified atom optics, and reduced atomic source flux requirements.

Hogan, Jason M

2015-01-01

52

Laser-phase and frequency stabilization using atomic coherence  

NASA Astrophysics Data System (ADS)

We present a simple method of stabilizing the laser phase and frequency by polarization spectroscopy of an atomic vapor. In analogy to the Pound-Drever-Hall method, which uses a cavity as a memory of the laser phase, this method uses atomic coherence (dipole oscillations) as a phase memory of the transmitting laser field. A preliminary experiment using a distributed feedback laser diode and a rubidium vapor cell demonstrates a shot-noise-limited laser linewidth reduction (from 2 MHz to 20 kHz). This method would improve the performance of gas-cell-based optical atomic clocks and magnetometers and facilitate laser-cooling experiments using narrow transitions.

Torii, Yoshio; Tashiro, Hideyasu; Ohtsubo, Nozomi; Aoki, Takatoshi

2012-09-01

53

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

54

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

NASA Astrophysics Data System (ADS)

A "single-source" Sr-Ta heterometal alkoxide precursor, Sr[Ta(OEt) 5(dmae)] 2 (dmae=OCH 2CH 2NMe 2), has been used for atomic vapour deposition (AVD) of SrBi 2Ta 2O 9 (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 was found to be ˜510 °C. Deposition of Bi-oxide films using Bi(mmp) 3 (mmp=OCMe 2CH 2OMe) indicates similar decomposition behaviour to the Sr-Ta alkoxide precursor, demonstrating its suitability as a complementary source of Bi for SBT. The co-incorporation of Bi and Sr within the SBT films is promoted through the deposition of bismuth oxide/strontium tantalate super lattices. After post-growth annealing the super lattices are converted to strontium bismuth tantalate thin films.

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

2004-12-01

55

Determination of total mercury in foods of plant origin in Poland by cold vapour atomic absorption spectrometry.  

PubMed

Total mercury concentrations were determined in 573 samples of agricultural crops and foods of plant origin which included cereals, fruit and vegetables and their products commercially available on the Polish market. The method of cold vapour atomic absorption spectrometry (CVAAS) after a wet-acid digestion in a closed-vessels and microwave oven was used and the reliability of the procedure demonstrated. Mercury concentrations in the agricultural crops and plant foods were generally below the maximum permissible limits in Poland and rarely exceeded 5 microg x kg(-1). Values ranged from <0.1 to 14 microg x kg(-1), mean 2.4 +/- 2.3 microg x kg(-1) in wheat and rye grains; from <0.1 to 2.4 microg x kg(-1), mean 0.5 +/- 0.4 microg x kg(-1) in nine varieties of vegetables; from <0.1 to 5.1 microg x kg(-1), mean 1.1 +/- 0.9 microg x kg(-1) in seven varieties of fruit; from <0.1 to 5.6 microg x kg(-1) in cereal products and jams; and from <0.1 to 3.0 microg x l(-1) in fruit and vegetable juices, nectars and beverages. The contribution of the mercury in the analysed agricultural crops and foods of plant origin to the weekly dietary intake of total mercury was 8 microg/person, which represents only 3% of the provisional tolerable weekly intake (PTWI) for this metal. PMID:12443563

Jedrzejczak, R

2002-10-01

56

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

57

Atomic and molecular spectra of vapours evolved in a graphite furnace. Part 1. Alkali halides  

NASA Astrophysics Data System (ADS)

Molecular Absorption Spectrometry (MAS) with electrothermal vaporization was applied to the measurement of absorption by alkali halides. The MAS system, consisting of a deuterium lamp primary source, a tubular graphite furnace, a grating polychromator and a linear array of Charge-Coupled-Device (CCD) detectors, allowed the simultaneous determination of atomic and molecular absorption in the range 200-400 nm. Vaporization was carried out in a pyrocoated graphite tube and absorption was measured during the heating of the furnace from 500°C to 2000°C in 100 s. Alkali halides vaporize as molecular compounds which absorb radiation in the whole ultraviolet range. The complexity of the molecular bands as well as the extent of the absorption increases from fluorides to iodides. The limit of absorption at long wavelengths is 254 nm for NaF, 287 nm for NaCl, 320 nm for NaBr and 370 nm for NaI. The appearance of vapors was observed between 680°C (RbI) and 1220°C (LiF), while the maximum absorption was reached between 800°C (CsI) and 1440°C (LiF); the characteristic temperatures of the vaporization peak were shifted towards lower values going from fluorides to iodides.

Daminelli, G.; Katskov, D. A.; Mofolo, R. M.; Tittarelli, P.

1999-05-01

58

Soliton Atom Laser with Quantum State Transfer Property  

E-print Network

We propose a scheme to obtain soliton atom laser with nonclassical atoms based on quantum state transfer process from light to matter waves in nonlinear case, which may find novel applications in, e.g., an atom interferometer. The dynamics of the atomic gray solitons and the accompanied frequency chirp effect are discussed.

Xiong-Jun Liu; Hui Jing; Mo-Lin Ge

2005-10-11

59

Method validation for the determination of total mercury in fish muscle by cold vapour atomic absorption spectrometry.  

PubMed

A method was validated for the determination of total Hg in fish muscle using continuous flow cold vapour atomic absorption (CVAAS) after microwave digestion in closed vessels. The method was validated according to European Union Regulations 333/2007 and 657/2002, considering the maximum level for the metal in fish, established by European Union regulation 1881/2006. The procedure for determining linear range, selectivity, recovery, precision, trueness, decision limit (CC?), detection capability (CC?), measurement uncertainty and robustness of the method is reported. The results of the validation process demonstrate the method fulfils the provisions of the Commission Regulation. The selectivity study indicated that there was no matrix effect on the calibration curve between the concentration range of 1.0 and 30.0 µg Hg l(-1). The mean recovery calculated at six levels of fortification was in the range of 94-104%. The limit of detection (LOD) and limit of quantification (LOQ) values were 4.90 and 15.7 µg kg(-1), while the CC? and CC? values were 0.517 and 0.533 mg kg(-1), respectively, for the maximum contaminant level of 0.500 mg kg(-1). The relative expanded measurement uncertainty of the method was 0.055 mg kg(-1). The method was not affected by slight variations of some critical factors (ruggedness minor changes) as sample mass and volume of the HNO(3) and H(2)O(2) used in the digestion step. The method allowed accurate confirmation analyses of the CRM DORM 3. In fact, the Z-scores attained in a proficiency test round were well below the reference value of 2.0, proving the excellent performance of the laboratory. PMID:22250927

Nascimento Neto, A P; Costa, L C S Magalhães; Kikuchi, A N S; Furtado, D M S; Araujo, M Q; Melo, M C C

2012-01-01

60

Laser cooling and trapping of atomic ytterbium  

NASA Astrophysics Data System (ADS)

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 1S0- 1P1 atomic beam Zeeman slower, and a 1S0-1P 1 magneto-optical trap (MOT), are developed and described in detail. Overviews of the Yb internal level structure and theoretical principles underlying the employed laser cooling and trapping techniques are provided. Our studies begin with a new laser cooling based optical double-resonance technique for performing high-resolution measurements of isotope shifts and hyperfine splittings. This method is applied to the Yb 1 S0-1P1 transition, resulting in the most complete single- technique survey to date of the Yb 1S0-1 P1 isotope shifts and hyperfine splittings and the first spectral position measurement of the 173Yb 1 S0(F = 5/2)-1P 1(F = 7/2) transition. Cascade radiative decay from the 1P 1 excited- state to the (6s6p)3P 2,0 metastable states is predicted to fundamentally restrict 1S0-1P 1 Yb MOT storage times. Using power-dependent 174Yb trap loss, we verify this prediction and present the first measurement of the effective 1P1 --> 3P 2,0 radiative decay rate. Next we detail a new in situ technique for probing the static and dynamic properties of MOTs that utilizes probe-induced fluorescence from the 1S 0-3P1 transition and present measurements of trapping-beam- induced energy shifts of the 1S0 ground state. Finally, we demonstrate dual-isotope Yb MOTs of extreme experimental simplicity yet containing either Fermion- Boson or Boson-Boson isotope pairs, results that to date have not been obtained in any other single system. Along with providing an essential step toward future studies of quantum degenerate Yb mixtures, this experiment establishes a versatile pathway for studies of cross- isotope molecular formation in a system where the fundamental electronic structure of the interacting atoms can be directly manipulated. Lacking the requisite ground-state magnetic sub- structure, Yb and the alkaline earth atoms Magnesium (Mg), Calcium (Ca), and Strontium (Sr) cannot be held in the ground-state magnetic traps currently used for alkali-metal atoms. We theoretically analyze a solution to this problem that relies on magnetically trapping Yb, Mg, Ca, and Sr in the 3P 2(mJ = 2) metastable excited-state. Here, we demonstrate that 1S0- 1P1 MOT magnetic fields will confine Yb, Mg, Ca, and Sr 3P2(m J = 2) metastable state atoms that are pre-cooled only to the 1S0-1P 1 Doppler-limited temperature. Three potential loading schemes, one that utilizes the 1P1 --> 3P2,0 radiative decay channel studied earlier and is completely continuous, and a zero-background detection scheme are discussed. Preliminary experimental work necessary for magnetically trapping Yb, including the first measurement of the A((6s7s)3 S1-(6s6p)3P 1)/A((6s7s)3S1-(6s6p) 3P0) radiative branching ratio, is described.

Loftus, Thomas Howard

2001-12-01

61

Laser focusing of atoms: a particle-optics approach  

Microsoft Academic Search

The use of a TEMoi*-mode laser beam has been proposed as a means of focusing an atomic beam to nanometer- scale spot diameters. We have analyzed the classical trajectories of atoms through a TEM01*-mode laser beam, using methods developed for particle optics. The differential equation that describes the properties of the first- order paraxial lens has exactly the same form

J. J. McClelland; M. R. Scheinfein

1991-01-01

62

Lamb Shift of Laser-Dressed Atomic States  

E-print Network

We discuss radiative corrections to an atomic two-level system subject to an intense driving laser field. It is shown that the Lamb shift of the laser-dressed states, which are the natural state basis of the combined atom-laser system, cannot be explained in terms of the Lamb shift received by the atomic bare states which is usually observed in spectroscopic experiments. In the final part, we propose an experimental scheme to measure these corrections based on the incoherent resonance fluorescence spectrum of the driven atom.

U. D. Jentschura; J. Evers; M. Haas; C. H. Keitel

2003-07-07

63

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

64

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

65

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

66

Decoherence of Atomic Gases in Largely Detuned Laser Fields  

E-print Network

We study theoretically the decoherence of a gas of bosonic atoms induced by the interaction with a largely detuned laser beam. It is shown that for a standing laser beam decoherence coincides with the single-particle result. For a running laser beam many-particle effects lead to significant modifications.

Karl-Peter Marzlin

2001-02-02

67

Two-Photon Coherent Atomic Absorption of Multiple Laser Beams  

Microsoft Academic Search

Physical processes on two-photon coherent atomic absorption of multiple laser beams were discussed about thirty years ago [M. C. Li, Bull. Am. Phys. Soc. 20, 654 (1975)]. These processes can be divided into two distinct groups. In the first group, laser beams are from a single source, and in the second group laser beams are from two different sources [M.

Ming-Chiang Li

2006-01-01

68

Growth and Characterization of Electrodeposited Zinc Sulphide and Chemical Vapour Atomic Layer Deposited Zinc Oxide, Sulphide, and Oxysulphide Thin Films  

NASA Astrophysics Data System (ADS)

Thin films of ZnS and ZnO_{ rm 1-x}S_{rm x} were prepared by electrodeposition and chemical vapour atomic layer deposition (CVALD), respectively. This represents the first effort to apply the technique of electrodeposition to ZnS for the purposes of electroluminescence. This is also the first time thin films of ZnO_{ rm 1-x}S_{rm x} were grown by CVALD and represents the first analysis of how the films properties vary with a known stoichiometry. Characterization methods performed on the thin films include: Auger spectroscopy, Rutherford backscattering spectroscopy, scanning electron microscopy, x-ray powder diffraction, Hall measurements and uv/visible transmittance. The as electrodeposited films were nearly stoichiometric but conductive and oriented in a <200 > direction. After annealing the films became discontinuous and lost their crystallinity, but their absorption characteristics more closely resembled that of evaporated films. Ion implantation with Mn was successful and the films exhibited yellow-orange cathodoluminescence. The value of x in the formula ZnO_ {rm 1-x}S_{ rm x} could be varied from 0 to 0.95 by changing the amount of hydrogen sulphide admitted to the reaction chamber. Films with values of x near 0 grow in the <200> direction (of ZnO) and have a fine grained structure. As the value of x increases the films become more and more amorphous but split into a two phase structure close to x = 0.55. At this point the films exhibit a minimum bandgap. As x increases further the films become one phase again and become oriented into the <111 > direction of ZnS. The cathodoluminescent characteristics of these films also change with x. When x is zero the films appear to luminescence green or yellow depending on the deposition temperature. Even 5% S removes this luminescence however and the spectrum is dominated by a peak in the red. This peak steadily decreases then increases again as x increases.

Sanders, Brian Wayne

69

Collisional Redistribution Laser Cooling of a High Pressure Atomic Gas  

E-print Network

We describe measurements demonstrating laser cooling of an atomic gas by means of collisional redistribution of radiation. The experiment uses rubidium atoms in the presence of several hundred bar of argon buffer gas pressure. Frequent collisions in the dense gas transiently shift a far red detuned optical field into resonance, while spontaneous emission occurs close to the unperturbed atomic transition frequency. Evidence for the cooling is obtained both via thermographic imaging and via thermographic deflection spectroscopy. The cooled gas has a density above 10$^{21}$ atoms/cm$^3$, yielding evidence for the laser cooling of a macroscopic ensemble of gas atoms.

Ulrich Vogl; Anne Saß; Simon Haßelmann; Martin Weitz

2011-02-18

70

Cavity Assisted Nondestructive Laser Cooling of Atomic Qubits  

E-print Network

We analyze two configurations for laser cooling of neutral atoms whose internal states store qubits. The atoms are trapped in an optical lattice which is placed inside a cavity. We show that the coupling of the atoms to the damped cavity mode can provide a mechanism which leads to cooling of the motion without destroying the quantum information.

A. Griessner; D. Jaksch; P. Zoller

2004-02-18

71

Determination and speciation of mercury in a dental work-place by cold vapour atomic absorption spectrometry and gas-liquid chromatography.  

PubMed

Cold Vapour Atomic Absorption Spectrometry (CVAAS) and Gas-Liquid Chromatography (GLC) have been used for determination and speciation of mercury. Total mercury, methylmercury, ethylmercury and phenylmercury concentrations in urine samples taken from students and staff of a dental work-place were investigated. Air samples were also analyzed. Detection limits, as three times the standard deviation, and in units of ng analyte per ml urine were found to be 1.7, 12, 2.4 and 21 for total mercury, methylmercury chloride, ethylmercury chloride and phenylmercury chloride, respectively. PMID:3804555

Seçkin, M A; Aygün, S; Ataman, O Y

1986-01-01

72

Interaction of cold atoms with short laser pulses.  

NASA Astrophysics Data System (ADS)

We present a powerful diagnostic system to observe the interaction of ultrafast laser pulses with trapped ^87Rb atoms. The ionization of cold atoms and the formation of cold molecules in an intense laser field in the ?K temperature range open new branches of research in chemistry, metrology, and quantum physics. However, the interaction of cold atoms with short laser pulses and the subsequent ionization or molecule formation are processes which are not well understood and can be easily misinterpreted. In our proposed experimental setup, an existing ultrafast laser system at the University of Wisconsin-Stevens Point will be used in conjunction with Magneto Optical Trap Recoil Ion Momentum Spectroscopy (MOTRIMS) to directly measure the products formed by the interaction of ultrafast laser pulses with the cold trapped ^87Rb atoms.

Chamberlin, Karen; Lilla, Derek; Taylor, Kyle; Zick, Kevin; Taft, Greg; Nguyen, Hai

2006-05-01

73

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

74

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

75

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

76

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

77

Miniature, atomically referenced offset phase-locked laser for cold-atom sensors  

NASA Astrophysics Data System (ADS)

As ultracold atom sensors begin to see their way to the field, there is a growing need for small, accurate, and robust laser systems to cool and manipulate atoms for sensing applications such as magnetometers, gravimeters, atomic clocks and inertial sensing. In this poster we present an ultracompact, frequency agile laser source, referenced to a hyperfine transition of ^87Rb. The laser system is housed in a package roughly the size of a stack of business cards, is hermetically sealed, and contains no moving parts -- ideal for field deployment. The laser system includes two lasers with independent temperature control, a Rb-filled vapor cell, a high-speed photodetector for monitoring the offset frequency between the lasers, as well the necessary optical isolation. We will present designs of the ultracompact laser system, as well as quantitative results including size, weight, expected power consumption, frequency agility, and frequency stability.

Pino, Juan; Luey, Ben; Bickman, Sarah; Anderson, Mike

2012-06-01

78

Cooling of rubidium atoms in pulsed diffuse laser light  

NASA Astrophysics Data System (ADS)

This paper reports an experiment on laser cooling of 87Rb atoms in pulsed diffuse light, which is the key step towards a compact cold atom clock. It deduces an empirical formula to simulate the pulse cooling process based on the loading of cold atoms in cooling time and the loss in the dead time, which is in agreement with the experimental data. The formula gives a reference to select the parameters for the cold atom clock.

Cheng, Hua-Dong; Wang, Xu-Cheng; Xiao, Ling; Zhang, Wen-Zhuo; Liu, Liang; Wang, Yu-Zhu

2011-02-01

79

Laser system for secondary cooling of {sup 87}Sr atoms  

SciTech Connect

A laser system with a narrow generation line for secondary laser cooling of {sup 87}Sr atoms has been developed and investigated. It is planned to use ultracold {sup 87}Sr atoms loaded in an optical lattice in an optical frequency standard. To this end, a 689-nm semiconductor laser has been stabilised using an external reference ultrastable cavity with vibrational and temperature compensation near the critical point. The lasing spectral width was 80 Hz (averaging time 40 ms), and the frequency drift was at a level of 0.3 Hz s{sup -1}. Comparison of two independent laser systems yielded a minimum Allan deviation: 2 Multiplication-Sign 10{sup -14} for 300-s averaging. It is shown that this system satisfies all requirements necessary for secondary cooling of 87Sr atoms using the spectrally narrow {sup 1}S{sub 0} - {sup 3}P{sub 1} transition ({lambda} = 689 nm). (cooling of atoms)

Khabarova, K Yu; Slyusarev, S N; Strelkin, S A; Belotelov, G S; Kostin, A S; Pal'chikov, Vitaly G; Kolachevsky, Nikolai N

2012-11-30

80

Probing Molecules with Laser-Cooled Atomic Ions  

NASA Astrophysics Data System (ADS)

Trapped, laser-cooled atomic ions can be controlled with unprecedented precision and accuracy as demonstrated by both atomic ion clocks and prototype quantum computing devices. By trapping a mixture of laser-cooled atomic and molecular ions, the molecular ions will be sympathetically cooled to millikelvin temperatures. The reaction dynamics and spectroscopy of the molecular ion can then be observed without the thermal distribution of ion motion. Furthermore, the bright fluorescence of the atomic ion can be used as a signal for obtaining information about the molecular ion via the Coulombic interaction. In this talk, I will present our work towards performing single molecular ion spectroscopy on an atomic ion - molecular ion pair. I will discuss fundamental limits and applications of the technique for astrochemistry and the direct laser-cooling of molecular ions.

Brown, Kenneth R.

2012-06-01

81

The calibration of the spectroscopic diode laser sensor for the water vapour diagnostics at output of singlet oxygen generator for COIL  

NASA Astrophysics Data System (ADS)

A1GaAs/GaAs quantum-well diode laser (824 nm) with the short external cavity was used for water diagnostics in the pumped out gas cell. The laser provided the 63 GHz continuous tuning of the optical frequency by the scanning of a pump current and a spectral linewidth of oscillation was less than 0,2 GHz. The experimentally obtained dependence of a second derivative amplitude on the vapour pressure coincides well with the calculated curve in the range of 0,4-20 Torr. The change of output signal close to linear was recorded at a pressure in the sample gas cell less than 5 Ton. The minimum concentration of H20, which is still measured by the diode laser sensor is estimated at a level 1,5x1015 molecule/cm3.

Megenin, A. V.; Chernyshov, A. K.; Azyazov, V. N.

2005-06-01

82

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

83

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

84

Automated determination of inorganic mercury in blood after sulfuric acid treatment using cold vapour atomic absorption spectrometry and an inductively heated gold trap.  

PubMed

Inorganic mercury (InoHg) in whole blood and erythrocytes was determined by cold vapour atomic absorption spectrometry (CVAAS) after overnight treatment with sulfuric acid at 45 degrees C and reduction with SnII in the acidic mixture. Total mercury (TotHg) was determined after digestion with a mixture of nitric and perchloric acids. Mercury vapour was preconcentrated on an amalgamation trap made of gold wire. The mercury was rapidly released by inductive heating of the trap. InoHg could be determined specifically in the presence of methylmercury (MeHg). The concentration of MeHg could be calculated by subtracting the concentration of InoHg from that of TotHg. Calculated concentrations of MeHg in erythrocytes showed a strong correlation with the results of a gas chromatographic method, though a discrepancy in calibration was indicated. The detection limits (3 s) in blood (0.5 g) were 0.06 ng g-1 for TotHg and 0.04 ng g-1 for InoHg and S(r) for a 5 ng g-1 whole blood sample was 2% (n = 10) for both TotHg and InoHg. PMID:7771681

Bergdahl, I A; Schütz, A; Hansson, G A

1995-04-01

85

Development of a method for the determination of ultra-trace level mercury in adipose tissue by cold vapour atomic fluorescence spectrometry  

PubMed Central

A method for the determination of total mercury in rat adipose tissue by cold vapour atomic fluorescence spectrometry (CVAFS) has been developed. Adipose samples were initially subjected to a lyophilization procedure in order to facilitate the homogenization and accurate weighing of small tissue aliquots (~50 mg). A closed vessel microwave digestion procedure using a mixture of sulphuric and nitric acids was used to liberate mercury from the adipose matrix. All mercury species were quantitatively oxidized to Hg(II) by a potassium bromate/bromide oxidation, then reduced to Hg(0) vapour by stannous chloride prior to fluorescence detection. The CVAFS exhibited a linear range of 10 pg Hg/ml to 120 pg Hg/ml. The method detection limit in solution was 2 pg Hg/ml, or 1 ng Hg/g adipose tissue, based on a nominal 50 mg sample and a final volume of 25 ml. A reference material from the National Research Council of Canada (DOLT-2, trace metals in dogfish liver) was prepared in quadruplicate in order to assess the accuracy and precision of the method. Mercury in this material was recovered at 2.22 ± 0.08 ? g/g, which is 104% of the certified level (2.14 ± 0.10 ? g/g). PMID:18924864

Levine, Keith E.; Fernando, Reshan A.; Lang, M.; Essader, Amal; Handy, Robert W.; Collins, Bradley J.

2000-01-01

86

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

87

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

E-print Network

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 demon...

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

2014-01-01

88

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

89

Two-Photon Coherent Atomic Absorption of Multiple Laser Beams  

NASA Astrophysics Data System (ADS)

Physical processes on two-photon coherent atomic absorption of multiple laser beams were discussed about thirty years ago [M. C. Li, Bull. Am. Phys. Soc. 20, 654 (1975)]. These processes can be divided into two distinct groups. In the first group, laser beams are from a single source, and in the second group laser beams are from two different sources [M. C. Li, Phys. Rev. A 22 (1980) 1323]. Several experiments in the first group were carried out and have led to the 2005 Nobel Prize in physics. The second group is more interesting. Beside atoms are in random motion, two photons are from different sources. Classically, it is impossible for atoms to transit coherently in the absorption process, but quantum mechanically, such a transition is possible and that is one of the spooky phenomena in quantum mechanic. To assure the coherent transition, each photon as absorbed by the atom must have two possible paths of choices. If one photon has the choice and other one is not, then the atomic transitions cannot be coherent. Around1990, there were very active experimental pursuits on such a spooky phenomenon of two photons emitted from crystal parametric down conversion. The present talk will review various spooky phenomena associated with two-photon coherent atomic absorption. Hope that the talk will stimulate the interest on the long neglected experimental front on two-photon coherent atomic absorption from two different laser sources.

Li, Ming-Chiang

2006-05-01

90

A solar simulator-pumped atomic iodine laser  

NASA Technical Reports Server (NTRS)

An atomic iodine laser, a candidate for the direct solar-pumped gas laser, was excited with a 4-kW beam from a xenon arc solar simulator. Continuous lasing at 1.315 micron for over 10 ms was obtained for static filling of n-C3F7I vapor. By momentarily flowing the lasant, a 30-Hz pulsed output was obtained for about 200 ms. The peak laser power observed was 4 W for which the system efficiency reached 0.1%. These results indicate that direct solar pumping of a gas laser for power conversion in space is indeed feasible.

Lee, J. H.; Weaver, W. R.

1981-01-01

91

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

92

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

93

Preconcentration and separation of total mercury in environmental samples using chemically modified chloromethylated polystyrene-PAN (ion-exchanger) and its determination by cold vapour atomic absorption spectrometry.  

PubMed

The use of chemically modified chloromethylated polystyrene-PAN, CMPS-PAN (ion-exchanger) for the preconcentration and separation of total mercury after digestion in preparation for determination by cold vapour atomic absorption spectrometry (CVAAS) was described. The effects on the percentage of recovered mercury by mass change of ion-exchanger, stirring time, pH of the solution samples and eluent concentration were studied. The distribution coefficient K(d) is 10(6.6) ml g(-1). The interfering effects of some foreign ions were described. The metal complex formed between CMPS-PAN ion-exchanger and mercury was characterized by IR spectroscopy, pH-metric titration and thermal analysis. The method is simple and rapidly applicable for the determination of total mercury (ng ml(-1)) in natural water, milk and urine. PMID:18968164

Hafez, M A; Kenawy, I M; Akl, M A; Lashein, R R

2001-01-01

94

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

95

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

E-print Network

by Albert Einstein (Einstein, 1925b) using a method introduced by Satyen- dra Nath Bose to derive the blackNobel lecture: When atoms behave as waves: Bose-Einstein condensation and the atom laser* Wolfgang, such as Bose-Einstein con- densates first realized in 1995. Each of these achieve- ments in cooling has been

96

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

E-print Network

of Bose-Einstein condensation was predicted long ago, in a 1925 paper by Albert Einstein [1] usingWHEN ATOMS BEHAVE AS WAVES: BOSE-EINSTEIN CONDENSATION AND THE ATOM LASER Nobel Lecture, December 8, such as Bose-Einstein condensates first realized in 1995. Each of these achievements in cooling has been

97

Lithium atom interferometer using laser diffraction : description and experiments  

E-print Network

We have built and operated an atom interferometer of the Mach-Zehnder type. The atomic wave is a supersonic beam of lithium seeded in argon and the mirrors and beam-splitters for the atomic wave are based on elastic Bragg diffraction on laser standing waves at 671 nm. We give here a detailed description of our experimental setup and of the procedures used to align its components. We then present experimental signals, exhibiting atomic interference effects with a very high visibility, up to 84.5 %. We describe a series of experiments testing the sensitivity of the fringe visibility to the main alignment defects and to the magnetic field gradient.

Alain Miffre; Marion Jacquey; Matthias Büchner; Gérard Trenec; Jacques Vigue

2005-04-08

98

Scattering laser light on cold atoms: Toward multiple scattering signals from single-atom responses  

SciTech Connect

We deduce the coherent backscattering signal from two distant laser-driven atoms using single-atom equations. The background and interference components of the double scattering spectrum obtained by this alternative approach agree exactly with the results of the standard master equation treatment. In contrast to the master equation, however, the new approach is suitable for the generalization to a large number of atomic scatterers.

Wellens, Thomas; Geiger, Tobias; Shatokhin, Vyacheslav; Buchleitner, Andreas [Institut fuer Physik, Albert-Ludwigs-Universitaet Freiburg, Hermann-Herder-Str. 3, D-79104 Freiburg (Germany)

2010-07-15

99

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

100

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

101

X-ray refractive index of laser-dressed atoms  

NASA Astrophysics Data System (ADS)

We investigated the complex index of refraction in the x-ray regime of atoms in laser light. The laser (intensity up to 1013W/cm2 , wavelength 800nm ) modifies the atomic states but, by assumption, does not excite or ionize the atoms in their electronic ground state. Using quantum electrodynamics, we devise an ab initio theory to calculate the dynamic dipole polarizability and the photoabsorption cross section, which are subsequently used to determine the real and imaginary part, respectively, of the refractive index. The interaction with the laser is treated nonperturbatively; the x-ray interaction is described in terms of a one-photon process. We numerically solve the resolvents involved using a single-vector Lanczos algorithm. Finally, we formulate rate equations to copropagate a laser and an x-ray pulse through a gas cell. Our theory is applied to argon. We study the x-ray polarizability and absorption near the argon K edge over a large range of dressing-laser intensities. We find electromagnetically induced transparency (EIT) for x rays on the Ar 1s?4p pre-edge resonance. We demonstrate that EIT in Ar allows one to imprint the shape of an ultrafast laser pulse on a broader x-ray pulse (duration 100ps , photon energy 3.2keV ). Our work thus opens new opportunities for research with hard x-ray sources.

Buth, Christian; Santra, Robin

2008-10-01

102

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

103

Long Range Interactions With Laser Cooled Neutral Atoms  

SciTech Connect

Multiple scattering of light in a trap of laser cooled neutral atoms leads to repulsion forces between the atoms. The corresponding interactions have long range behavior in 1/r{sup 2} and are thus similar to Coulomb interaction in an one component confined plasma. Consequences of these interactions will be described in this paper, including the limitation of the spatial density one can obtain in such systems and self-sustained oscillations of the cloud.

Gattobigio, Giovanni Luca [Institut Non Lineaire de Nice, Universite de Nice-Sophia-Antipolis, CNRS UMR 661, 1361, route des Lucioles 06560 Valbonne France (France); Dipartimento di Fisica dell'Universita di Ferrara, 44100 Ferrara (Italy); Michaud, Franck; Labeyrie, Guillaume; Kaiser, Robin [Institut Non Lineaire de Nice, Universite de Nice-Sophia-Antipolis, CNRS UMR 661, 1361, route des Lucioles 06560 Valbonne (France); Loureiro, Jorge; Mendonca, Jose Tito; Tercas, Hugo [Instituto Superior Tecnico, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal); Pohl, Thomas [ITAMP, 60 Garden Street, Cambridge, MA 02138 (United States)

2008-09-07

104

Chemical oxygen-iodine laser with atomic iodine generated via Cl or F atoms  

NASA Astrophysics Data System (ADS)

Two alternative chemical methods of atomic iodine generation for a chemical oxygen-iodine laser (COIL) were studied. These methods are based on fast reactions of gaseous hydrogen iodide with chemically produced chlorine and fluorine atoms. Both processes were studied first in small-scale reactors. A yield of atomic iodine in the Cl system and nitrogen (non-reactive) atmosphere exceeded 80%, while in the F system it was only up to 27% related to F2 or 50% related to HI. The process of atomic iodine generation via Cl atoms was employed in operation of the supersonic COIL. A laser power of 430 W at 40 mmol Cl2/s, and the small signal gain up to 0.4%/cm were attained. The proposed methods promise an increase in laser power, easier control of laser operation, and simpler iodine management in comparison with the conventional source of atomic iodine using I2. The experimental results obtained so far with this experimental arrangement did not proved yet increasing COIL chemical efficiency because some process quenching a part of singlet oxygen was indicated. Therefore a modified experimental set-up has been designed and prepared for further investigation.

Spalek, Otomar; Jirasek, Vit; Censky, Miroslav; Kodymova, Jarmila; Jakubec, Ivo; Hager, Gordon D.

2005-03-01

105

Equilibrium temperature of laser cooled atoms in squeezed vacuum  

NASA Technical Reports Server (NTRS)

It is shown that by squeezing the vacuum fluctuations of the electromagnetic field the quantum fluctuations of the optical forces exerted on laser cooled two-level atoms, can be dramatically modified. Under certain conditions, this modification in concert with the enhanced average forces can lead to equilibrium temperatures below those attained under normal vacuum fluctuations.

Shevy, Y.

1992-01-01

106

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

107

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

108

Effect of laser power and specimen temperature on atom probe analyses of magnesium alloys.  

PubMed

The influence of laser power, wave length, and specimen temperature on laser assisted atom probe analyses for Mg alloys was investigated. Higher laser power and lower specimen temperature led to improved mass and spatial resolutions. Background noise and mass resolutions were degraded with lower laser power and higher specimen temperature. By adjusting the conditions for laser assisted atom probe analyses, atom probe results with atomic layer resolutions were obtained from all the Mg alloys so far investigated. Laser assisted atom probe investigations revealed detailed chemical information on Guinier-Preston zones in Mg alloys. PMID:21269771

Oh-ishi, K; Mendis, C L; Ohkubo, T; Hono, K

2011-05-01

109

Nonadiabatic tunneling ionization of atoms in elliptically polarized laser fields  

NASA Astrophysics Data System (ADS)

We theoretically investigate the nonadiabatic effects in strong field tunneling ionization of atoms in elliptically polarized laser fields by solving the 3D time-dependent Schrödinger equation (TDSE). Comparing our TDSE results with those of two semi-classical methods, i.e., the quantum-trajectory Monte Carlo simulation (QTMC) and the Coulomb-corrected strong field approximation (CCSFA), we confirm the existence of the nonadiabatic effects with its fingerprint in the nonzero initial lateral velocity at the tunneling exit in the laser polarization plane. Our study shows that these nonadiabatic initial lateral momentum effects become significant in high ellipticity or circularly polarized laser field. These results indicate that the calibration of the experimental laser intensity in this situation should be performed nonadiabatically, which may strongly affect the results of the real tunneling time delay measurements.

Geng, Ji-Wei; Qin, Liang; Li, Min; Xiong, Wei-Hao; Liu, Yunquan; Gong, Qihuang; Peng, Liang-You

2014-10-01

110

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

111

Atomic-signal-based zero field finding technique for unshielded laser-pumped atomic magnetometer  

E-print Network

We described a novel technique that can find the zero-field for unshielded laser-pumped atomic magnetometer using atomic signal itself. By comparing light density of pump beam after atomic vapor cell, it is decided which direction to move the compensation magnetic field and whether to increase or decrease the converging step length. The zero-field is found in less than 18s and the step length after converging is smaller than 10nT, 10nT and 40nT for x, y and z axes, respectively, limited by 50Hz noise in the lab environment.

Dong, Haifeng; Tang, Xinbin

2012-01-01

112

Atomic-signal-based zero field finding technique for unshielded laser-pumped atomic magnetometer  

E-print Network

We described a novel technique that can find the zero-field for unshielded laser-pumped atomic magnetometer using atomic signal itself. By comparing light density of pump beam after atomic vapor cell, it is decided which direction to move the compensation magnetic field and whether to increase or decrease the converging step length. The zero-field is found in less than 18s and the step length after converging is smaller than 10nT, 10nT and 40nT for x, y and z axes, respectively, limited by 50Hz noise in the lab environment.

Haifeng Dong; Hongbo Lin; Xinbin Tang

2012-03-05

113

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

114

Coherent inelastic backscattering of laser light from three isotropic atoms  

NASA Astrophysics Data System (ADS)

We study the impact of double- and triple-scattering contributions on coherent backscattering of laser light from saturated isotropic atoms in the helicity-preserving polarization channel. By using the recently proposed diagrammatic pump-probe approach, we analytically derive single-atom spectral responses to a classical polychromatic driving field, combine them self-consistently to double- and triple-scattering processes, and numerically deduce the corresponding elastic and inelastic spectra, as well as the total backscattered intensities. We find that accounting for the triple-scattering contribution leads to a faster decay of phase-coherence with increasing saturation of the atomic transition as compared with double scattering alone and to a better agreement with the experiment on strontium atoms.

Ketterer, Andreas; Buchleitner, Andreas; Shatokhin, Vyacheslav N.

2014-11-01

115

A cold atom pyramidal gravimeter with a single laser beam  

NASA Astrophysics Data System (ADS)

We demonstrate a scheme for realizing a compact cold atom gravimeter. The use of a hollow pyramidal configuration allows to achieve all functions: trapping, interferometer and detection with a unique laser beam leading to a drastic reduction in complexity and volume. In particular, we demonstrate a relative sensitivity to acceleration of gravity (g) of 1.7×10-7 at one second, with a moderate laser power of 50 mW. This simple geometry combined to such a high sensitivity opens wide perspectives for practical applications.

Bodart, Q.; Merlet, S.; Malossi, N.; Dos Santos, F. Pereira; Bouyer, P.; Landragin, A.

2010-03-01

116

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

117

Effects of injected atomic coherence in broad-area lasers  

SciTech Connect

We analyze the effect of injected atomic coherence on transverse patterns of a broad area laser by means of the semiclassical two-level Maxwell-Bloch equations. A single longitudinal mode is considered. The injected atomic coherence forces a spatially homogeneous profile to appear and locks the field phase to a single value. Above a pump threshold value a very rich scenario of patterns is developed. Near threshold we find stationary patterns such as rhombic and hexagonal lattices. Well above threshold nonstationary patterns such as complex highly ordered vortex lattices traveling along the cross section, and nearly traveling waves appear.

Calderon, Oscar G.; Cabrera, Eduardo; Carreno, F.; Anton, M.A.; Melle, Sonia; Guerra, J.M. [Departamento de Optica, Universidad Complutense de Madrid, Ciudad Universitaria s/n, 28040 Madrid (Spain)

2005-09-15

118

Differential atomic magnetometry based on a diverging laser beam  

SciTech Connect

The authors demonstrate a novel atomic magnetometer that uses differential detection of the spatially diverging components of a light field to monitor the Larmor precession frequency of atoms in a thermal vapor. The design is implemented in compact form with a micromachined alkali vapor cell and a naturally divergent light field emitted by a vertical-cavity surface-emitting laser. Operating the magnetometer in differential mode cancels common-mode noise and improves the sensitivity by a factor of 26 over single-channel operation. They also suggest ways in which the current sensitivity of 28 pT/{radical}Hz may be improved further without sacrificing size or simplicity.

Hodby, E.; Donley, E. A.; Kitching, J. [Time and Frequency Division, National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305 (United States)

2007-07-02

119

Laser-induced electron diffraction for probing rare gas atoms.  

PubMed

Recently, using midinfrared laser-induced electron diffraction (LIED), snapshots of a vibrating diatomic molecule on a femtosecond time scale have been captured [C.I. Blaga et al., Nature (London) 483, 194 (2012)]. In this Letter, a comprehensive treatment for the atomic LIED response is reported, a critical step in generalizing this imaging method. Electron-ion differential cross sections (DCSs) of rare gas atoms are extracted from measured angular-resolved, high-energy electron momentum distributions generated by intense midinfrared lasers. Following strong-field ionization, the high-energy electrons result from elastic rescattering of a field-driven wave packet with the parent ion. For recollision energies ?100 eV, the measured DCSs are indistinguishable for the neutral atoms and ions, illustrating the close collision nature of this interaction. The extracted DCSs are found to be independent of laser parameters, in agreement with theory. This study establishes the key ingredients for applying LIED to femtosecond molecular imaging. PMID:23368191

Xu, Junliang; Blaga, Cosmin I; DiChiara, Anthony D; Sistrunk, Emily; Zhang, Kaikai; Chen, Zhangjin; Le, Anh-Thu; Morishita, Toru; Lin, C D; Agostini, Pierre; DiMauro, Louis F

2012-12-01

120

Laser-cooled atomic ions as probes of molecular ions  

NASA Astrophysics Data System (ADS)

Trapped laser-cooled atomic ions are a new tool for understanding cold molecular ions. The atomic ions not only sympathetically cool the molecular ions to millikelvin temperatures, but the bright atomic ion fluorescence can also serve as a detector of both molecular reactions and molecular spectra. We are working towards the detection of single molecular ion spectra by sympathetic heating spectroscopy. Sympathetic heating spectroscopy uses the coupled motion of two trapped ions to measure the spectra of one ion by observing changes in the fluorescence of the other ion. Sympathetic heating spectroscopy is a generalization of quantum logic spectroscopy, but does not require ions in the motional ground state or coherent control of the ion internal states. We have recently demonstrated this technique using two isotopes of Ca+ [Phys. Rev. A, 81, 043428 (2010)]. Limits of the method and potential applications for molecular spectroscopy are discussed.

Brown, Kenneth R.; Viteri, C. Ricardo; Clark, Craig R.; Goeders, James E.; Khanyile, Ncamiso B.; Vittorini, Grahame D.

2015-01-01

121

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

122

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

123

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

E-print Network

with moderate laser power and with performances comparable to state of the art sensors. Pyramidal magneto single fiber and cools down 1.2 106 atoms to 2.5 µK. At each measurement cycle, these two laserA cold atom pyramidal gravimeter with a single laser beam Q. Bodart,1 S. Merlet,1 N. Malossi,1 F

Boyer, Edmond

124

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

125

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

126

From multimode to monomode guided atom lasers: an entropic analysis G. L. Gattobigio,1, 2  

E-print Network

From multimode to monomode guided atom lasers: an entropic analysis G. L. Gattobigio,1, 2 A 3 Australian Centre for Quantum Atom Optics, Physics Department, The Australian National University of the mode populations of guided atom lasers (GALs) by showing that the entropy per particle of an optically

Boyer, Edmond

127

Small-sized dichroic atomic vapor laser lock.  

PubMed

Two, lightweight diode laser frequency stabilization systems designed for experiments in the field are described. A significant reduction in size and weight in both models supports the further miniaturization of measurement devices in the field. Similar to a previous design, magnetic field lines are contained within a magnetic shield enclosing permanent magnets and a Rb cell, so that these dichroic atomic vapor laser lock (DAVLL) systems may be used for magnetically sensitive instruments. The mini-DAVLL system (49 mm long) uses a vapor cell (20 mm long) and does not require cell heaters. An even smaller micro-DAVLL system (9 mm long) uses a microfabricated cell (3 mm square) and requires heaters. These new systems show no degradation in performance with regard to previous designs while considerably reducing dimensions. PMID:21528995

Lee, Changmin; Iwata, G Z; Corsini, E; Higbie, J M; Knappe, S; Ledbetter, M P; Budker, D

2011-04-01

128

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

129

Mobility edge for cold atoms in laser speckle potentials.  

PubMed

Using the transfer-matrix method, we numerically compute the precise position of the mobility edge of atoms exposed to a laser speckle potential and study its dependence versus the disorder strength and correlation function. Our results deviate significantly from previous theoretical estimates using an approximate, self-consistent approach of localization. In particular, we find that the position of the mobility edge in blue-detuned speckles is much lower than in the red-detuned counterpart, pointing out the crucial role played by the asymmetric on-site distribution of speckle patterns. PMID:25148311

Delande, Dominique; Orso, Giuliano

2014-08-01

130

Mobility Edge for Cold Atoms in Laser Speckle Potentials  

NASA Astrophysics Data System (ADS)

Using the transfer-matrix method, we numerically compute the precise position of the mobility edge of atoms exposed to a laser speckle potential and study its dependence versus the disorder strength and correlation function. Our results deviate significantly from previous theoretical estimates using an approximate, self-consistent approach of localization. In particular, we find that the position of the mobility edge in blue-detuned speckles is much lower than in the red-detuned counterpart, pointing out the crucial role played by the asymmetric on-site distribution of speckle patterns.

Delande, Dominique; Orso, Giuliano

2014-08-01

131

Electron scattering by laser-excited barium atoms  

NASA Technical Reports Server (NTRS)

Inelastic and superelastic scattering of 30- and 100-eV electrons by laser-excited 6s 6p 1P and subsequent cascade-populated 6s 6p 3P, 6s 5d 1D, and 6s 5d 3D Ba atoms have been observed. Absolute differential cross sections for the singlet and relative scattering intensities for the triplet species have been determined in the 5 to 20 deg angular region. Under the present conditions excitations dominate over deexcitations.

Register, D. F.; Trajmar, S.; Jensen, S. W.; Poe, R. T.

1978-01-01

132

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

133

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

134

Ultra-narrow-linewidth combined CW Ti:Sapphire/Dye laser for atom cooling and high-precision spectroscopy  

E-print Network

Ultra-narrow-linewidth combined CW Ti:Sapphire/Dye laser for atom cooling and high.5 nm Ar laser 457.9 nm 514.5 nm Ar laser 457.9 nm CW Ti:Sapphire Laser Combined CW Ti:Sapphire/Dye Laser Introduction Dye laser and Ti:Sapphire laser are characterized by ability to tune over a wide

Kobtsev, Sergei M.

135

Selective reabsorption leading to multiple oscillations in the 8446-A atomic-oxygen laser.  

NASA Technical Reports Server (NTRS)

Laser oscillation of atomic oxygen at 8446 A occurs in four closely spaced lines with peculiar intensity ratios, all detuned from the atomic center frequencies of the three fine-structure transitions. These anomalies are caused by the selective reabsorption of resonance radiation from the lower laser level by ground-state oxygen atoms. The selectivity results from the fact that the velocity distribution of the laser levels is considerably wider than that of the ground state, because of the dissociative mode of production of excited oxygen atoms. Possible extension of this mechanism to the atomic-hydrogen system is discussed.

Feld, M. S.; Feldman, B. J.; Javan, A.; Domash, L. H.

1973-01-01

136

Confinement of ultracold atoms in a Laguerre-Gaussian laser beam created with diffractive optics  

E-print Network

We report 2D confinement of Rb 87 atoms in a Laguerre-Gaussian laser beam. Changing of the sign of the detuning from the atomic resonance dramatically alters the geometry of the confinement. With the laser detuned to the blue, the atoms are confined to the dark, central node of the Laguerre-Gaussian laser mode. This trapping method leads to low ac Stark shifts to the atomic levels. Alternatively, by detuning the laser to the red of the resonance, we confine atoms to the high intensity outer ring in a multiply-connected, toroidal configuration. We model the confined atoms to determine azimuthal intensity variations of the trapping laser, caused by slight misalignments of the Laguerre-Gaussian mode generating optics.

Kennedy, Sharon A; Farrar, J Tom; Akin, T G; Krzyzewski, S; Abraham, E R I

2013-01-01

137

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

138

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.

139

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

140

Atom number in magneto-optic traps with millimeter scale laser beams  

E-print Network

containing a low density atomic vapor [3]. Each beam has a flat-top intensity profile with a diameter dAtom number in magneto-optic traps with millimeter scale laser beams Gregory W. Hoth, Elizabeth A, N still scales as d3.6. OCIS codes: 020.3320, 020.7010, 130.3990. Instruments based on laser cooled

Bentz, Dale P.

141

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

142

Chemical generation of atomic iodine for chemical oxygen–iodine laser. I. Modelling of reaction systems  

Microsoft Academic Search

The mathematical modelling of reaction systems for chemical generation of atomic iodine is presented. This process is aimed to be applied in the chemical oxygen–iodine laser (COIL), where it can save a substantial part of energy of singlet oxygen and so increase the laser output power. In the suggested method, gaseous reactants for I atoms generation are admixed into the

V??t Jirásek; Otomar Špalek; Jarmila Kodymová; Miroslav ?enský

2001-01-01

143

Hydride generation atomic absorption spectrometry with different flow systems and in-atomizer trapping for determination of cadmium in water and urine-overview of existing data on cadmium vapour generation and evaluation of critical parameters.  

PubMed

An overview of literature data on vapour generation techniques for cadmium and comparison with own experiments by means of several different types of hydride generation-electrothermal atomic absorption spectrometric systems (HG-ETAAS) (batch, semi-batch (SB), continuous-flow (CF) and flow-injection (FI) as well as different gas-liquid separators (GLS) exhibits apparent variations and inconsistency. However, if data for optimal chemical conditions are re-plotted in another coordinates: C(HCl) (mol l(-1)) vs. the ratio of reductant-to-acid molar input rates (i.e. millimoles per minute), [BH(4)(-)]:[H(+)], much better consistency of data is revealed: more than half of data are clustered around 0.2-0.3 mol l(-1) HCl which appears an optimal acidity at moderate BH(4)(-) concentrations; the tetrahydroborate molar input rates should always be in excess versus the H(+) molar input rates (1.1 to tenfold); relatively high flow rates of argon purge gas are required (>/=120 ml min(-1)); special attention to the blank control at ng l(-1) levels as well as to the construction of gas-liquid separator and vapour transfer lines should be paid. 'Milder' conditions for HG could be provided with some of the examined systems and GLSs, thus minimizing reagent consumption, blanks, vigorous reactions, foaming, aerosol production and drift in measurements: e.g. 0.4 mol l(-1) HCl-3% m/v NaBH(4) with the semi-batch system and 0.25 mol l(-1) HCl-2% m/v NaBH(4) in continuous flow mode. Experimental system is based on the Transversely Heated Graphite Atomizer coupled with flow injection system FIAS 400. Integrated platforms are treated for permanent modification with Zr (110 mug) or W (240 mug) and then with Ir (8 mug). Temperatures of trapping, pyrolysis and atomization are 350, 500 and 1300 degrees C, respectively. The best overall efficiency of HG, transportation and trapping is 41%. The characteristic mass for peak area measurements is m(o)=2.8 pg and the limit of detection is 0.002 mug l(-1). The long-term stability of characteristic mass (within-day, 8 h) is m(o)=2.8+/-0.1 pg (R.S.D. 4.0%, n=8), whereas the corresponding between-day figures (1 mo) are m(o)=2.8+/-0.2 pg (R.S.D. 6.6%, n=6). The linear range is 0.002-0.12 mug l(-1) with a sample loop of 1.8 ml, being strongly impaired with smaller sample volumes in FI mode. The sample throughput rate is 10 h(-1) with the semi-batch system. Applications to real human and bovine urine samples and CRMs of sea water (CASS-3), river water (SLRS-1 and SLRS-3) and urine (SRM 2670) are presented. PMID:18969233

Lampugnani, Leonardo; Salvetti, Claudia; Tsalev, Dimiter L

2003-12-01

144

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

145

Modifying atomic collision dynamics with intense ultrashort laser pulses  

SciTech Connect

It has been suggested that ''short'' pulses of intense laser radiation can modify atomic collision dynamics in new and interesting ways. Recent experimental results in sodium-argon vapor with 1.6-psec pulses verify the existence of such an effect, although smaller in magnitude and at somewhat higher field intensities than had been predicted from theoretical arguments. Using quantum-mechanical wave-packet propagation on a realistic potential-energy curve under the parameters of the experiment, we determine that the time between curve crossings, the standard against which pulse durations should be measured, is on the order of 0.8 psec or less. The experimental results can then be understood in the context of having used too long a pulse to have clearly observed short-pulse effects.

DeVries, P.L.

1988-02-01

146

Z .Spectrochimica Acta Part B 56 2001 1565 1592 Laser excited atomic fluorescence spectrometry  

E-print Network

samples. The advent of diode lasers with their now somewhat improved range of wavelengths and power output of second and third harmonic crystals to pulsed diode lasers shows promise for compact and robustZ .Spectrochimica Acta Part B 56 2001 1565 1592 Review Laser excited atomic fluorescence

Michel, Robert G.

147

Characteristics of an all gas-phase iodine laser using molecular iodine as atomic iodine donor  

Microsoft Academic Search

The laser action of an all gas-phase iodine laser (AGIL), which uses molecular iodine as a source of iodine atoms, has been demonstrated. The laser is based on the energy transfer reaction between metastable NCl(a 1Delta) and ground state I(2P3\\/2) atoms, which are produced by the electric discharge of a mixture of I2 and He. At fixed flow rates of

Taizo Masuda; Tomonari Nakamura; Masamori Endo

2010-01-01

148

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

149

Guided-atom laser: Transverse mode quality and longitudinal momentum distribution  

SciTech Connect

We analyze the outcoupling of a matter wave into a guide by a time-dependent spilling of the atoms from an initially trapped Bose-Einstein condensate. This process yields intrinsically a breakdown of the adiabatic condition that triggers the outcoupling of the wave function. Our analysis of the time-dependent engineering and manipulation of condensates in momentum space in this context enables us to work out the limits due to interactions in the mode quality of a guided-atom laser. This study is consistent with recent experimental observations of low transverse excitations of guided-atom lasers and suggests (i) an optimal strategy to realize such quasimonomode guided-atom lasers with, in addition, the lowest possible longitudinal velocity dispersion or alternatively (ii) a strategy for engineering the atomic flux of the atom laser.

Vermersch, F.; Fabre, C. M.; Cheiney, P.; Gattobogio, G. L.; Mahevet, R.; Guery-Odelin, D. [Universite de Toulouse, UPS, Laboratoire Collisions Agregats Reactivite, IRSAMC, F-31062 Toulouse (France) and CNRS, UMR 5589, F-31062 Toulouse (France)

2011-10-15

150

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

151

Transient absorption spectra of the laser-dressed hydrogen atom  

NASA Astrophysics Data System (ADS)

We present a theoretical study of transient absorption spectra of laser-dressed hydrogen atoms, based on numerical solutions of the time-dependent Schrödinger equation. The timing of absorption is controlled by the delay between an extreme ultra violet (XUV) pulse and an infrared (IR) laser field. The XUV pulse is isolated and several hundred attoseconds in duration, which acts as a pump to drive the ground-state electron to excited p states. The subsequent interaction with the IR field produces dressed states, which manifest as sidebands between the 1s-np absorption spectra separated by one IR-photon energy. We demonstrate that the population of dressed states is maximized when the timing of the XUV pulse coincides with the zero crossing of the IR field, and that their energies can be manipulated in a subcycle time scale by adding a chirp to the IR field. An alternative perspective to the problem is to think of the XUV pulse as a probe to detect the dynamical ac Stark shifts. Our results indicate that the accidental degeneracy of the hydrogen excited states is removed while they are dressed by the IR field, leading to large ac Stark shifts. Furthermore, we observe the Autler-Townes doublets for the n=2 and 3 levels using the 656 nm dressing field, but their separation does not agree with the prediction by the conventional three-level model that neglects the dynamical ac Stark shifts.

Murakami, Mitsuko; Chu, Shih-I.

2013-10-01

152

Laser assisted electron-atom scattering in critical geometries  

NASA Astrophysics Data System (ADS)

We investigate the scattering of electrons off of neutral targets in the presence of a linearly polarized, low frequency laser field. The laser has large enough extent for the wavefunction to be treated in the Floquet expansion. The scattering geometries of interest are small angles where momentum transfer is nearly perpendicular to the field, and the Kroll Watson approximation breaks down. We use the eigenchannel R matrix method to solve the Schr"odinger equation, employing Hamiltonians in both the length and the velocity gauges in different regions. The target atom is represented by a model potential including a screened coulomb term near the origin and a longer range induced dipole interaction. The short range reaction matrix in the Kramers-Henneberger (acceleration) representation is found by matching the velocity gauge R matrix to spherical Gordon-Volkov states, and from this the cross section is derived. Experiments have shown emission and absorption cross sections at small angles to be much higher than the approximation predicts, and we hope to gain insight into the cause of this phenomenon.

Morrison, Nathan; Greene, Chris H.

2012-06-01

153

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

154

Polarization-gradient laser cooling as a way to create strongly localized structures for atom lithography  

SciTech Connect

Generally, conditions for deep sub-Doppler laser cooling do not match conditions for strong atomic localization, that takes place in a deeper optical potential and leads to higher temperature. Moreover, for a given detuning in a deep optical potential the secular approximation, which is frequently used for a quantum description of laser cooling, fails. Here we investigate the atomic localization in optical potential, using a full quantum approach for atomic density matrix beyond the secular approximation. It is shown that laser cooling in a deep optical potential, created by a light field with polarization gradients, can be used as an alternative method for the formation of high contrast spatially localized structures of atoms for the purposes of atom lithography and atomic nanofabrication. Finally, we analyze possible limits for the width and contrast of localized atomic structures that can be reached in this type of light mask.

Prudnikov, O. N.; Taichenachev, A. V.; Tumaikin, A. M.; Yudin, V. I. [Novosibirsk State University, Pirogova 2, Novosibirsk 630090 (Russian Federation); Institute of Laser Physics SB RAS, Lavrentyeva 13/3, Novosibirsk 630090 (Russian Federation)

2007-02-15

155

LASERS: Pulsed chemical oxygen---iodine laser with bulk formation of iodine atoms by an electric discharge  

Microsoft Academic Search

A preliminary investigation was made of a chemical oxygen---iodine laser with bulk formation of iodine atoms in an electric discharge. The output energy was comparable with that obtained for a photolysis variant of the laser, but the technical efficiency of the investigated discharge variant was much higher (91%). The pulse power (~100 kW) was approximately three orders of magnitude higher

Nikolai P. Vagin; V. S. Pazyuk; Nikolai N. Yuryshev

1995-01-01

156

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

Microsoft Academic Search

As the development of the electric discharge iodine laser continues, the role of oxygen atoms downstream of the discharge region was found to be very significant. One of the largest uncertainties is the rate of quenching of I* by O atoms. We have taken a series of measurements of O 2 ( 1 ?) emission, I* emission, O-atom titrations, gain\\/absorption,

D. L. Carroll; J. T. Verdeyen; D. M. King; J. W. Zimmerman; J. K. Laystrom

157

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

E-print Network

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...

Ariunbold, Gombojav O.; Kash, Michael M.; Sautenkov, Vladimir A.; Li, Hebin; Rostovtsev, Yuri V.; Welch, George R.; Scully, Marlan O.

2010-01-01

158

LASERS: Pulsed chemical oxygen—iodine laser with bulk formation of iodine atoms by an electric discharge  

NASA Astrophysics Data System (ADS)

A preliminary investigation was made of a chemical oxygen—iodine laser with bulk formation of iodine atoms in an electric discharge. The output energy was comparable with that obtained for a photolysis variant of the laser, but the technical efficiency of the investigated discharge variant was much higher (91%). The pulse power (~100 kW) was approximately three orders of magnitude higher than the power of a cw chemical oxygen—iodine laser with the same chlorine flow rate.

Vagin, Nikolai P.; Pazyuk, V. S.; Yuryshev, Nikolai N.

1995-08-01

159

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

160

Fast switching of alkali atom dispensers using laser-induced heating  

SciTech Connect

We show that by using an intense laser source to locally heat an alkali atom dispenser, one can generate a high flux of atoms followed by fast recovery (<100 ms) of the background pressure when the laser is extinguished. For repeated heating pulses a switch-on time for the atomic flux of 200 ms is readily attainable. This technique is suited to ultracold atom experiments using simple ultrahigh vacuum (UHV) chambers. Laser-induced heating provides a fast repetition of the experimental cycle, which, combined with low atom loss due to background gas collisions, is particularly useful for experiments involving far-off resonance optical traps, where sufficient laser power (0.5-4 W) is readily available.

Griffin, P.F.; Weatherill, K.J.; Adams, C.S. [Department of Physics, Rochester Building, University of Durham, South Road, Durham, DH1 3LE (United Kingdom)

2005-09-15

161

Time-resolved ionization of the hydrogen atom in strong laser fields  

NASA Astrophysics Data System (ADS)

We use the strong field approximation to study the single-photon ionization of the hydrogen atom in the time domain. During the interaction of the laser pulse and the atom, the electron is pumped to the Volkov state and has a widely energy distribution at the beginning of the laser pulse. With the time evolution, only the photon-electron with the energy hra - Ip is survived, where to is the laser angular frequency, and Ip is the ionization potential of the atom. Therefore we observed how the energy spectrum of the ionized electron builds in the time domain.

Cui, Sen; He, Feng

2014-04-01

162

Chemical generation of atomic iodine for chemical oxygen iodine laser. I. Modelling of reaction systems  

NASA Astrophysics Data System (ADS)

The mathematical modelling of reaction systems for chemical generation of atomic iodine is presented. This process is aimed to be applied in the chemical oxygen-iodine laser (COIL), where it can save a substantial part of energy of singlet oxygen and so increase the laser output power. In the suggested method, gaseous reactants for I atoms generation are admixed into the COIL primary gas flow containing singlet oxygen. Two reaction systems were proposed, based on the reaction of hydrogen iodide with chemically generated atomic fluorine or chlorine. It was found that the reaction path via Cl atoms better matches the experimental conditions of COIL with a yield of atomic iodine of up to 67%. As a result of modelling, a suitable reaction system and design of experimental arrangement for the effective production of atomic iodine in laser conditions were found.

Jirásek, Vít.; Špalek, Otomar; Kodymová, Jarmila; ?enský, Miroslav

2001-07-01

163

Methods and evaluation of frequency aging in distributed-feedback laser diodes for rubidium atomic clocks  

NASA Astrophysics Data System (ADS)

Distributed-feedback laser diodes emitting at 780nm have been evaluated, with respect to the aging of the injection current required for reaching the rubidium D2 resonance line. Results obtained for lasers operating in air and in vacuum for 9 months are reported. When operated at constant temperature, the laser current required for emission at the wavelength of the desired atomic resonance is found to decrease by 50 to 80?A per month. The impact of this result on the lifetime and long-term performances of laser-pumped rubidium atomic clocks is discussed.

Matthey, Renaud; Affolderbach, Christoph; Mileti, Gaetano

2011-09-01

164

Construction and Characterization of External Cavity Diode Lasers for Atomic Physics  

PubMed Central

Since their development in the late 1980s, cheap, reliable external cavity diode lasers (ECDLs) have replaced complex and expensive traditional dye and Titanium Sapphire lasers as the workhorse laser of atomic physics labs1,2. Their versatility and prolific use throughout atomic physics in applications such as absorption spectroscopy and laser cooling1,2 makes it imperative for incoming students to gain a firm practical understanding of these lasers. This publication builds upon the seminal work by Wieman3, updating components, and providing a video tutorial. The setup, frequency locking and performance characterization of an ECDL will be described. Discussion of component selection and proper mounting of both diodes and gratings, the factors affecting mode selection within the cavity, proper alignment for optimal external feedback, optics setup for coarse and fine frequency sensitive measurements, a brief overview of laser locking techniques, and laser linewidth measurements are included. PMID:24796259

Hardman, Kyle S.; Bennetts, Shayne; Debs, John E.; Kuhn, Carlos C. N.; McDonald, Gordon D.; Robins, Nick

2014-01-01

165

Modeling of the chemical generation of atomic iodine in a chemical oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

The mathematical modeling of reaction systems for chemical generation of atomic iodine is presented. This process can be applied in the chemical oxygen-iodine laser (COIL), where it can save a substantial part of energy of singlet oxygen and so increase the laser output power. The parametric study of the production of atomic fluorine and subsequently atomic iodine in dependence on the pressure and dilution with inert gas was made. The calculation of the interaction between produced atomic iodine and singlet oxygen was made with four different mixing/reacting schemes.

Jirasek, Vit; Spalek, Otomar; Kodymova, Jarmila; Censky, Miroslav

2002-05-01

166

Pulsed laser deposition of ZnSe:N epilayers assisted by active atomic nitrogen beams  

Microsoft Academic Search

Epilayers of ZnSe doped with nitrogen have been grown on polished GaAs(100) and Si(100) substrates by pulsed laser deposition (PLD) assisted by atomic nitrogen beams. An arc-heated beam source was used to dissociate N2 and produced neutral nitrogen atom beams with concentration of 1017–1019 at. sr?1s?1, which intersected with laser ablated plumes and substrate surfaces in the process of deposition.

N. Xu; Z. F. Ying; Y. C. Du; F. M. Li

2001-01-01

167

An all gas-phase iodine laser using molecular iodine as atomic iodine donor  

Microsoft Academic Search

The characteristics of an all gas-phase iodine laser (AGIL) that uses molecular iodine as a source of iodine atoms is studied. The laser is based on the energy transfer reaction between metastable NCl(a1Delta) and ground state I(2P3\\/2) atoms, which are produced by the electric discharge of a mixture of I2 and He. At fixed flow rates of the chemical species,

Taizo Masuda; Tomonari Nakamura; Masamori Endo

2010-01-01

168

Guiding of cold atoms by a red-detuned laser beam of moderate power  

E-print Network

Guiding of cold atoms by a red-detuned laser beam of moderate power B T Wolschrijn, R A Cornelussen the guided fraction as a function of laser power and detuning, and give an analytical expression that agrees well with our results. Although the guide is red detuned, the optical scattering rate at this detuning

Amsterdam, Universiteit van

169

Pulsed chemical oxygen—iodine laser with bulk formation of iodine atoms by an electric discharge  

Microsoft Academic Search

A preliminary investigation was made of a chemical oxygen—iodine laser with bulk formation of iodine atoms in an electric discharge. The output energy was comparable with that obtained for a photolysis variant of the laser, but the technical efficiency of the investigated discharge variant was much higher (91%). The pulse power (~100 kW) was approximately three orders of magnitude higher

Nikolai P Vagin; V S Pazyuk; Nikolai N Yuryshev

1995-01-01

170

Laser-Cooled Lithium Atoms: A New Source for Focused Ion Beams  

E-print Network

Laser-Cooled Lithium Atoms: A New Source for Focused Ion Beams P R O J E C T L E A D E R : Jabez Mc E N T S Designed and constructed a laser-cooled, magneto-optical trap-based lithium ion source mounted on a commercial focused ion beam system, creating the world's first lithium ion microscope

171

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

172

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.

173

Diode-laser atomic-absorption spectrometry by the double-beam—double-modulation technique  

Microsoft Academic Search

The limitations of absorption measurements in atomic-absorption spectrometry with tunable diode lasers are investigated. It is shown that the double modulation technique (diode-laser wavelength modulation and sample modulation) with detection at the sum or difference frequency suppresses spurious etalon effects, background absorption, residual diode-laser-amplitude modulation and the noise which accompanies these effects, and enables measurement of detection limits determined by

Vladimir Liger; Alexander Zybin; Yurii Kuritsyn; Kay Niemax

1997-01-01

174

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

175

A Review of Applications and Experimental Improvements Related to Diode Laser Atomic Spectroscopy  

Microsoft Academic Search

This article attempts to review the major advancements made in the past 12 years, since 1993, in the field of diode laser atomic spectroscopy. The discussion covers experimental improvements (e.g., wavelength stabilization, frequency upconversion, enhancement of tuning characteristics, spectral bandwidth using external cavities, etc.), diagnostic applications in various atomizers, as well as analytical applications (e.g., absorption, fluorescence, and ionization spectroscopy;

Gábor Galbács

2006-01-01

176

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

E-print Network

optical out fr 0 I(f) f Ca Oven fn = nfr #12;Optical Frequency Measurements Group Time and Frequency Perot cavity Feedback System Locks LO to atomic resonance Microwave Synthesizer Laser 456 986 240 494 Standard of U.S. S. Jefferts, L. Donley, T. Heavner #12;CSAC Design: All optical excitation of atomic

Van Stryland, Eric

177

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.

178

Interaction-induced phase fluctuations in a guided atom laser  

SciTech Connect

In this paper we determine the magnitude of phase fluctuations caused by atom-atom interaction in a one-dimensional beam of bosonic atoms. We imagine that the beam is created with a large coherence length, and that interactions only act in a specific section of the beam, where the atomic density is high enough to validate a Bogoliubov treatment. The magnitude and coherence length of the ensuing phase fluctuations in the beam after the interaction zone are determined.

Bouchoule, Isabelle [Institut d'Optique, 91 403 Orsay Cedex (France); Moelmer, Klaus [QUANTOP, Danish National Research Foundation Center for Quantum Optics, Department of Physics and Astronomy, University of Aarhus, DK 8000 Aarhus C (Denmark)

2003-01-01

179

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.

180

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

181

Experimental effects of atomic oxygen on the development of an electric discharge oxygen iodine laser  

Microsoft Academic Search

As the development of the electric discharge iodine laser continues, the role of oxygen atoms downstream of the discharge region was found to be very significant. One of the largest uncertainties is the rate of the quenching of I* by O atoms. We have taken a series of measurements of O2(1Delta) emission, I* emission, O-atom titrations, gain\\/absorption, and O2(1Delta) yield

David L. Carroll; Joseph T. Verdeyen; Darren M. King; J. W. Zimmerman; J. K. Laystrom; B. S. Woodard; G. F. Benavides; K. Kittell; Wayne C. Solomon

2005-01-01

182

Polarization response of interacting atomic systems in an intense resonance laser field  

SciTech Connect

The dynamics and quantum correlations are studied in a system of two interacting atoms in a resonance femtosecond laser field. The polarization response of a medium consisting of such pairs of interacting atoms is analyzed. Regimes are found in which the polarization response of the medium under study contains the intense component at a tunable low frequency. It is shown that the dipole response of the medium can be suppressed using the entanglement effect and symmetry properties of collective atomic states.

Gulyaev, A. V., E-mail: gulyaevav@gmail.com; Tikhonova, O. V. [Moscow State University (Russian Federation)

2012-05-15

183

Lasers as a Bridge between Atomic and Nuclear Physics  

E-print Network

This paper reviews the application of optical and UV laser radiation to several topics in low-energy nuclear physics. We consider the laser-induced nuclear anti-Stokes transitions, the laser-assisted and the laser-induced internal conversion, and the Electron Bridge and Inverse Electron Bridge mechanisms as tools for deexciting and exciting of low-lying nuclear isomeric states. A study of the anomalous, by low-lying, nuclear isomeric states (on an example of the $^{229}$Th nucleus) is presented in detail.

Sergei G. Matinyan

1997-06-02

184

Improved production of Br atoms near zero speed by photodissociating laser aligned Br2 molecules.  

PubMed

We theoretically investigated the improvement on the production rate of the decelerated bromine (Br) atoms near zero speed by photodissociating laser aligned Br2 precursors. Adiabatic alignment of Br2 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 Br2 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(2)???, the higher the production rate of the decelerated Br atoms near zero speed. For Br2 molecules with an initial rotational temperature of ~1 K, a ?cos(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(12) W/cm(2) for alignment. PMID:25362306

Deng, L Z; Yin, J P

2014-10-28

185

Background correction by wavelength modulation for pulsed-laser-excited atomic fluorescence spectrometry.  

PubMed

Instrumentation was constructed to modulate the dye laser wavelength for background correction in laser-excited atomic fluorescence spectrometry (LEAFS). To achieve wavelength modulation a piezoelectric pusher was used to drive the wavelength tuning mirror in a laboratory-constructed grazing incidence dye laser. The laser pulses were synchronized with the piezoelectric pusher movement so that alternate laser pulses measured the atomic fluorescence signal at the analytical atomic spectral line (on-line) and the background signal at a wavelength displaced to one side of the atomic line (off-line). The background-corrected signal was obtained by subtracting the off-line "background" from the on-line "signal plus background". The spectral line width (fwhm) of the dye laser was 0.003 nm, while the wavelength modulation interval was controllable over the range from 0 to 0.2 nm with a spectral resolution limited only by the spectral line width of the laser. This type of background correction could, in principle, be applied to other types of tunable lasers such as pulsed Ti: sapphire lasers. The performance of background correction by wavelength modulation (WM) was demonstrated by measurement of sodium resonance fluorescence in an air-acetylene flame and by thallium nonresonance fluorescence in a graphite furnace. The experimental data indicated that the wavelength modulation corrected, effectively and quantitatively, for flame background, blackbody emission from a graphite furnace, and scatter of laser radiation off aluminum chloride (1 mg/mL as AI) matrix particles in both the furnace and the flame. Analytical results were in good agreement with certified values for the determination of sodium in standard reference materials by the use of modulated LEAFS. PMID:1443620

Su, E G; Irwin, R L; Liang, Z; Michel, R G

1992-08-01

186

Watching the Real-time Evolution of a Laser Modified Atom Using Attosecond Pulses  

NASA Astrophysics Data System (ADS)

In the presence of even moderately strong laser fields, atomic states are heavily modified and develop rich structure. Such a laser dressed atom can be described using the Floquet theory in which the laser dressed states called Floquet states are composed of different Fourier components. In this work we use XUV attosecond pulses to excite a He atom from its ground state to near-infrared (NIR) laser dressed Floquet states, which are ionized by the dressing laser field. Quantum interferences between Fourier components of these Floquet states lead to oscillations in He ion yield as a function of time-delay between the XUV and NIR pulses. From the ion yield signal we measure the quantum phase difference between transition matrix elements to two different Fourier components as a function of both time-delay (instantaneous NIR intensity) and NIR pulse peak intensity. These measurements along with information from time-dependent Schrodinger equation simulations enable us to observe the real-time evolution of the laser modified atom as the dominant Floquet state mediating the ionization changes from the 5p Floquet state to the 2p Floquet state with increasing NIR intensity.

Shivaram, Niranjan; Timmers, Henry; Tong, Xiao-Min; Sandhu, Arvinder

2011-10-01

187

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

188

Determination of total urinary mercury by on-line sample microwave digestion followed by flow injection cold vapour inductively coupled plasma mass spectrometry or atomic absorption spectrometry.  

PubMed

The total mercury content in urine was determined by inductively coupled plasma mass spectrometry with the so-called cold vapour method after on-line oxidative treatment of the sample in a microwave oven (FI-MW-CV-ICPMS). Use of a KBr/KBrO(3) mixture, microwave digestion, and the final oxidation with KMnO(4), assure the complete recovery of the organic forms of Hg which would be difficult to determine otherwise if using only the CV-ICPMS apparatus. Quantitative recoveries were obtained for phenyl Hg chloride (PMC), dimethyl Hg (DMM), Hg acetate (MA) and methyl Hg chloride (MMC). Use of automatic flow injection microwave systems (FI-MW) for sample treatment reduces environmental contamination and allows detection limits suitable for the determination of reference values. Since no certified reference materials were commercially available in the concentration ranges of interest, the accuracy of the proposed procedure has been assessed by analysing a series of urine samples with two independent techniques, ICP-MS and AAS. When using the FI-MW-CV-ICP-MS technique, the detection limit was assessed at 0.03microg/L Hg, while with FI-MW-CV-AAS it was 0.2microg/L Hg. The precision of the method was less than 2-3% for FI-MW-CV-ICP-MS and about 3-5% for FI-MV-CV-AAS at concentrations below 1microg/L Hg. These results show that ICP-MS can be considered as a "reference technique" for the determination of total urinary Hg at very low concentrations, such as are present in non-exposed subjects. PMID:12125019

Bettinelli, M; Spezia, S; Ronchi, A; Minoia, C

2002-01-01

189

Chemical generation of atomic iodine for the chemical oxygen iodine laser. II. Experimental results  

NASA Astrophysics Data System (ADS)

A new method for the chemical generation of atomic iodine intended for use in a chemical oxygen-iodine laser (COIL) was investigated experimentally. The method is based on the fast reaction of hydrogen iodide with chemically produced chlorine atoms. Effects of the initial ratio of reactants and their mixing in a flow of nitrogen were investigated experimentally and interpreted by means of a computational model for the reaction system. The yield of iodine atoms in the nitrogen flow reached 70-100% under optimum experimental conditions. Gain was observed in preliminary experiments on the chemical generation of atomic iodine in a flow of singlet oxygen.

Špalek, Otomar; Jirásek, Vít.; ?enský, Miroslav; Kodymová, Jarmila; Jakubec, Ivo; Hager, Gordon D.

2002-08-01

190

Quantum interference effects in a ?-type atom interacting with two short laser pulse trains  

NASA Astrophysics Data System (ADS)

We study the quantum interference between the excitation pathways in a three-level ?-type atom interacting with two short laser pulse trains under the conditions of electromagnetically induced transparency. The probability amplitude equations which describe the interaction of a three-level ?-type atom with two laser pulse trains are numerically solved. We derive analytical expressions for the population of the upper excited state for resonant laser pulse trains with a rectangular temporal profile. By varying the parameters of the laser pulse trains such as area of a single pulse, detuning, repetition period, and number of individual pulses, we analyze the quantum interference between the excitation pathways in terms of the upper excited state population.

Buica, Gabriela

2014-10-01

191

Transverse laser cooling of a thermal atomic beam of dysprosium  

SciTech Connect

A thermal atomic beam of dysprosium atoms is cooled using the 4f{sup 10}6s{sup 2}(J=8){yields}4f{sup 10}6s6p(J=9) transition at 421 nm. The cooling is done via a standing light wave orthogonal to the atomic beam. Efficient transverse cooling to the Doppler limit is demonstrated for all observable isotopes of dysprosium. Branching ratios to metastable states are demonstrated to be <5x10{sup -4}. A scheme for enhancement of the nonzero-nuclear-spin-isotope cooling and a method for direct identification of possible trap states are proposed.

Leefer, N.; Cingoez, A. [Department of Physics, University of California at Berkeley, Berkeley, California 94720-7300 (United States); Gerber-Siff, B. [Swarthmore College, Swarthmore, Pennsylvania 19081 (United States); Sharma, Arijit [Raman Research Institute, Sadashivanagar, Bangalore 560080 (India); Torgerson, J. R. [Physics Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Budker, D. [Department of Physics, University of California at Berkeley, Berkeley, California 94720-7300 (United States); Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2010-04-15

192

Transverse laser cooling of a thermal atomic beam of dysprosium  

E-print Network

A thermal atomic beam of dysprosium (Dy) atoms is cooled using the $4f^{10}6s^2(J=8) \\to 4f^{10}6s6p (J=9)$ transition at 421 nm. The cooling is done via a standing light wave orthogonal to the atomic beam. Efficient transverse cooling to a temperature of $\\sim$ 22 mK is demonstrated for all stable isotopes of dysprosium. Branching ratios to metastable states are demonstrated to be $<2\\times10^{-4}$. A scheme for enhancement of the odd-isotope cooling is proposed as well as a method for direct identification of possible trap states.

Leefer, N; Gerber-Siff, B; Sharma, Arijit; Torgerson, J R; Budker, D

2009-01-01

193

Laser-induced desorption from silicon (111) surfaces with adsorbed chlorine atoms  

Microsoft Academic Search

We have studied the initial stage of the laser-induced reaction of silicon surfaces with adsorbed chlorine atoms in ultrahigh vacuum, by measuring the species desorbing from the surfaces. In particular, our studies have focused on photo-chemical etching without laser-induced thermal heating. We found that the primary species desorbing from Cl-saturated Si(111) surfaces is the molecule and that the desorption efficiency

K. Hattori; K. Shudo; T. Iimori; F. Komori; Y. Murata

1996-01-01

194

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

195

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

196

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

197

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

198

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

199

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

200

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

201

Influence of the wavelength on the spatial resolution of pulsed-laser atom probe  

SciTech Connect

Modern atom probes typically incorporate an ultrafast pulsed-laser source with wavelength ranging from infrared (IR) to ultraviolet (UV) depending on the specific instrument. In order to estimate the influence of the wavelength on the accuracy of the technique, the achievable in-depth spatial resolution has been measured for atom probe analyses of the same pure W specimen using three different wavelengths and across a range of laser pulse energies. UV illumination is shown to yield superior spatial resolution to both IR and visible (green) wavelengths. We propose that this improvement relates to a faster decay of temperature enabled by light absorption confined to the near apex region.

Gault, B. [Australian Centre for Microscopy and Microanalysis, Madsen Building F09, University of Sydney, NSW 2006 (Australia); Institute of Materials and Engineering Science, Australian Nuclear Science and Technology Organisation, Private Mail Bag 1, Menai, NSW 2234 (Australia); Chen, Y. M.; Hono, K. [Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-0047 (Japan); National Institute for Materials Science, Tsukuba 305-0047 (Japan); Moody, M. P.; Ringer, S. P. [Australian Centre for Microscopy and Microanalysis, Madsen Building F09, University of Sydney, NSW 2006 (Australia); Ohkubo, T. [National Institute for Materials Science, Tsukuba 305-0047 (Japan)

2011-11-01

202

Measurements of atomic carbon density in processing plasmas by vacuum ultraviolet laser absorption spectroscopy  

NASA Astrophysics Data System (ADS)

Measurements of the absolute C atom density in an inductively coupled plasma (ICP) source were carried out by using vacuum ultraviolet (VUV) laser absorption spectroscopy with the resonance lines of C atoms at wavelengths around 94.5 and 165.7 nm. A tunable VUV laser covering these wavelength ranges was generated by a two-photon resonance/four-wave mixing technique in Xe gas. No absorption at around 94.5 nm could be observed, but from the absorption spectra around 165.7 nm we successfully derived the absolute density of C atoms in the ICP source. The obtained values varied from 1×1010 to 1×1011 cm-3, depending on the source gas and operating conditions of the plasma source. The relatively small density values compared to other atomic species are attributed to the large loss rates, which mostly occur on the surface.

Tanaka, Norifusa; Tachibana, Kunihide

2002-11-01

203

Ejection of innershell electrons induced by recollision in a laser-driven carbon atom  

NASA Astrophysics Data System (ADS)

Ejection of core electrons as a result of recollision in a laser-driven carbon atom is theoretically investigated with a quasiclassical model. The model, called "fermionic molecular dynamics," gives rise to a ground-state carbon atom where the six electrons are paired in shells, with different binding energies. This feature renders possible, on a classical level, the discussion of the ejection of electrons from different shells. By analyzing a large number of trajectories of a carbon atom exposed to an intense, few-cycle laser pulse, we reveal a class of recollision trajectories where the recolliding electron is recaptured into the atomic core after ejecting a core electron. We also discuss the difference between quadruple ionization trajectories leading to a final C4 + ion where the two bound electrons have opposite spin, and the trajectories where the bound electrons have equal spin.

Lötstedt, Erik; Midorikawa, Katsumi

2014-10-01

204

A laser frequency and power control system in an atomic Talbot-Lau interferometer  

NASA Astrophysics Data System (ADS)

The importance of atom interferometers that have high sensitivity and super precision is well recognized in the fields of rotation sensing, inertial and gravitational forces sensing, relativity tests, and other precision measures. So many researchers are absorbed in atom interferometers. An atom interferometer consists of many parts, among of which optical part plays a significant role because of the need of laser beams in every parts. Based on this situation and some specific quantitive requirements to laser beams, this article presents a laser frequency and power control system for atom interferometer which can realize the functions of frequency shift and scan, power stabilization and modulation, and highspeed switch. The system lies on acousto-optical modulators (AOM) and a phase-locked loop frequency synthesizer is designed in the system as a very important part which has wide capture range of frequency and well stability. The experimental results show that the designed system is available and the performances of laser through AOM are as good as expected and the phase noise of the output is restrained. In addition, the system also could be used in other instruments and devices, such as atomic clock, gravimeter, gradiometer, and gyroscope.

Yang, Ting; Hu, Zhaohui; Qi, Lu

2013-12-01

205

INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Phase-sensitive electric modulation of photoluminescence upon bichromatic excitation of atoms  

NASA Astrophysics Data System (ADS)

A new type of modulation of the photoluminescence intensity of atoms excited by a bichromatic laser radiation with the frequency ratio 1:2 is proposed and analysed. The modulation is produced by alternating electric field acting on atoms and occurs due to the quantum interference of the amplitudes of two excitation channels of an atom, which proves to be possible because the applied electric field removes the parity selection rule for one of the excitation channels. An important feature of this process is the dependence of photoluminescence on the phase difference of monochromatic components of exciting radiation. The calculation was performed for an alkali metal atom excited at the s—s transition taking the saturation effect into account.

Astapenko, Valerii A.

2005-12-01

206

Entropy Driven Atomic Motion in Laser-Excited Bismuth  

SciTech Connect

We introduce a thermodynamical model based on the two-temperature approach in order to fully understand the dynamics of the coherent A{sub 1g} 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)] 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.; Gelle, A.; Arnaud, B. [Institut de Physique de Rennes (IPR), UMR UR1-CNRS 6251, Campus de Beaulieu-Bat 11 A, 35042 Rennes Cedex, France, EU (France)

2011-04-15

207

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

208

Stimulated emissions and quantum interference in potassium atom-laser interaction  

NASA Astrophysics Data System (ADS)

The interaction of a laser with potassium atoms is investigated by monitoring the radiation of the 5P-4S transition under the two-photon 4S1/2 -6S1/2 excitation. For low number density and laser intensity the observed radiation is parametric axial or conical, depending on the laser detuning from the two-photon resonance, the number density and the laser intensity. With increasing laser intensities and number densities, an additional delayed component is observed corresponding to a two-step four-wave mixing with the participation of internally generated photons. A two-photon quantum interference effect is observed for the total (axial and conical) parametric four-wave mixing emission. A deviation from the proposed model under certain experimental parameters is attributed to a two-step four-wave mixing and the phase mismatch of the parametric processes.

Merlemis, N.; Katharakis, M.; Koudoumas, E.; Efthimiopoulos, T.

2003-05-01

209

Compact solid-state laser source for 1S-2S spectroscopy in atomic hydrogen  

SciTech Connect

We demonstrate a compact solid-state laser source for high-resolution two-photon spectroscopy of the 1S-2S transition in atomic hydrogen. The source emits up to 20 mW at 243 nm and consists of a 972 nm diode laser, a tapered amplifier, and two doubling stages. The diode laser is actively stabilized to a high-finesse cavity. We compare the new source to the stable 486 nm dye laser used in previous experiments and record 1S-2S spectra using both systems. With the solid-state laser system, we demonstrate a resolution of the hydrogen spectrometer of 6x10{sup 11}, which is promising for a number of high-precision measurements in hydrogenlike systems.

Kolachevsky, N.; Alnis, J.; Bergeson, S. D.; Haensch, T. W. [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching (Germany)

2006-02-15

210

Rescattering and frustrated tunneling ionization of atoms in circularly polarized laser fields  

NASA Astrophysics Data System (ADS)

We investigate strong-field ionization dynamics of atoms in circularly polarized laser fields by a three-dimensional electron ensemble method which is validated by comparison with ab initio results of solving the time-dependent Schrödinger equation. We show that the Coulomb potential and the electron recollision play very crucial roles for single ionization of atoms with a lower ionization potential in circularly polarized laser fields. We find that the critical laser field strength for recollision scales as F0˜2ln10?2/?2Ip (Ip, ionization potential; ? , laser frequency), below which the rescattering is very crucial. As a consequence of recollision, a large amount of tunneled electrons will be ejected into the elliptical orbits of Rydberg states or strongly rescattered off the nucleus and eventually achieve large energy from laser fields. The characteristic feature is that both the relative frustrated tunneling rate and the hard rescattering rate decrease with increasing the laser intensity and the wavelength. This study sheds a light on those processes that are closely related with electron rescattering in circularly polarized laser fields, e.g., high-order harmonic generation and nonsequential double ionization.

Li, Min; Qin, Liang; Wu, Chengyin; Peng, Liangyou; Gong, Qihuang; Liu, Yunquan

2014-01-01

211

The interaction of 193-nm excimer laser irradiation with single-crystal zinc oxide: Neutral atomic zinc and oxygen emission  

SciTech Connect

We report mass-resolved time-of-flight measurements of neutral particles from the surface of single-crystal ZnO during pulsed 193-nm irradiation at laser fluences below the threshold for avalanche breakdown. The major species emitted are atomic Zn and O. We examine the emissions of atomic Zn as a function of laser fluence and laser exposure. Defects at the ZnO surface appear necessary for the detection of these emissions. Our results suggest that the production of defects is necessary to explain intense sustained emissions at higher fluence. Rapid, clean surface etching and high atomic zinc kinetic energies seen at higher laser fluences are also discussed.

Kahn, E. H. [Washington State University; Langford, S. C. [Washington State University; Dickinson, J. T. [Washington State University; Boatner, Lynn A [ORNL

2013-01-01

212

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

213

Atomistic modeling of femtosecond laser-induced melting and atomic mixing in Au film Cu substrate system  

E-print Network

, including laser surface alloying, cladding, annealing, and hardening, e.g. [1­6]. The improvement of surfaceAtomistic modeling of femtosecond laser-induced melting and atomic mixing in Au film ­ Cu substrate modification by laser irradiation is in the core of many modern processing and fabrication techniques

Zhigilei, Leonid V.

214

Ultra-narrow-linewidth combined CW Ti:Sapphire/Dye laser for atom cooling and high-precision spectroscopy  

E-print Network

Ultra-narrow-linewidth combined CW Ti:Sapphire/Dye laser for atom cooling and high 37, k. 141, Novosibirsk, 630058, Russia ABSTRACT Presented is a new combined CW Ti:Sapphire/Dye laser-term output line width does not exceed 10 kHz for the Ti:Sapphire laser and amounts to 50 kHz for the Dye

Kobtsev, Sergei M.

215

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.

Scheibner, Karl F. (Tracy, CA); Haynam, Christopher A. (Pleasanton, CA); Johnson, Michael A. (Pleasanton, CA); Worden, Earl F. (Diablo, CA)

1999-01-01

216

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

217

Time-resolved measurement of atomic emission enhancement by fs ns dual-pulsed laser-induced breakdown spectroscopy  

Microsoft Academic Search

Time-resolved measurement of atomic emission enhancement is performed by using a 500-fs KrF laser pulse incident upon a high density supersonic O2 gas jet, synchronized with an orthogonal ns frequency-doubled Nd:YAG laser pulse. The ultra-short pulse serves as an igniter of the gas jet, and the subsequent ns-laser pulse significantly enhances the atomic emission. Analysis shows that the contributions to

Li-Xin Yan; Yong-Sheng Zhang; Guo-Xin Zheng; Jing-Ru Liu; Jian-Ping Cheng; Min Lü

2006-01-01

218

Dynamic range improvement and background correction in diode laser atomic absorption spectrometry  

Microsoft Academic Search

The peculiarities of background correction and linearization of a calibration curve in atomic absorption spectrometry with semiconductor diode lasers have been investigated. The logarithmic conversion of a signal was shown to be a very efficient tool for signal processing. The linearity of the calibration curve up to a concentration nearly three orders of magnitude above the characteristic concentration (absorbance 1.7)

A. V. Zybin; V. V. Liger; Yu. A. Kuritsyn

1999-01-01

219

Theory of multiphoton ionization of atoms by strong, short pulsed lasers  

SciTech Connect

A numerical technique for investigating the behavior of many electron atoms in intense laser fields is presented. A description of the method is followed by results of an illustrative, application to helium for a number of wavelengths and intensities. A discussion of high order ionization dynamics for this system based on these calculations is provided. 10 refs.

Kulander, K.C.

1987-07-10

220

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

221

Characteristics of an all gas-phase iodine laser using molecular iodine as atomic iodine donor  

NASA Astrophysics Data System (ADS)

The laser action of an all gas-phase iodine laser (AGIL), which uses molecular iodine as a source of iodine atoms, has been demonstrated. The laser is based on the energy transfer reaction between metastable NCl(a 1?) and ground state I(2P3/2) atoms, which are produced by the electric discharge of a mixture of I2 and He. At fixed flow rates of the chemical species, the laser output powers are measured at three different positions in a flow reactor. The output power is characterized by a function of the optical axis position and is in reasonable agreement with the numerical simulation. A repetitive pulse of laser output at 50 Hz with a duty factor of 40% is observed. The highest output power is 40 mW at 210 mm downstream from the mixing point of I/H/He and NCl3. This is 80% of the output power generated from the conventional system using HI as an iodine donor. The measured results of the time-resolved laser output power suggest that the output power of the I2-AGIL is more sensitive to the electric discharge plasma intensity as compared with that of the HI-AGIL. An AGIL operated using I2 could potentially have the same output power as that of an AGIL operated using HI if a continuous-wave electric discharge generator is used.

Masuda, Taizo; Nakamura, Tomonari; Endo, Masamori

2010-10-01

222

Ultrafast laser-driven Rabi oscillations of a trapped atomic vapor.  

PubMed

We consider the Rabi oscillation of an atom ensemble of Gaussian spatial distribution interacting with ultrafast laser pulses. Based on an analytical model calculation, we show that its dephasing dynamics is solely governed by the size ratio between the atom ensemble and the laser beam, and that every oscillation peak of the inhomogeneously broadened Rabi flopping falls on the homogeneous Rabi oscillation curve. The results are verified experimentally with a cold rubidium vapor in a magneto-optical trap. As a robust means to achieve higher-fidelity population inversion of the atom ensemble, we demonstrate a spin-echo type Rx(?/2)Ry(?)Rx(?/2) composite interaction as well. PMID:25680137

Lee, Han-Gyeol; Kim, Hyosub; Ahn, Jaewook

2015-02-15

223

Four-level atomic interferometer driven by shaped ultrafast laser pulses  

SciTech Connect

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 5P{sub 1/2} and 5P{sub 3/2}). 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 [Department of Physics, Stony Brook University, Stony Brook, New York 11794 (United States)

2010-08-15

224

Analytic description of elastic electron-atom scattering in an elliptically polarized laser field  

NASA Astrophysics Data System (ADS)

An analytic description of laser-assisted electron-atom scattering (LAES) in an elliptically polarized field is presented using time-dependent effective range (TDER) theory to treat both electron-laser and electron-atom interactions nonperturbatively. Closed-form formulas describing plateau features in LAES spectra are derived quantum mechanically in the low-frequency limit. These formulas provide an analytic explanation for key features of the LAES differential cross section. For the low-energy region of the LAES spectrum, our result generalizes the Kroll-Watson formula to the case of elliptic polarization. For the high-energy (rescattering) plateau in the LAES spectrum, our result generalizes prior results for a linearly polarized field valid for the high-energy end of the rescattering plateau [Flegel , J. Phys. BJPAPEH0953-407510.1088/0953-4075/42/24/241002 42, 241002 (2009)] and confirms the factorization of the LAES cross section into three factors: two field-free elastic electron-atom scattering cross sections (with laser-modified momenta) and a laser field-dependent factor (insensitive to the scattering potential) describing the laser-driven motion of the electron in the elliptically polarized field. We present also approximate analytic expressions for the exact TDER LAES amplitude that are valid over the entire rescattering plateau and reduce to the three-factor form in the plateau cutoff region. The theory is illustrated for the cases of e-H scattering in a CO2-laser field and e-F scattering in a midinfrared laser field of wavelength ?=3.5?m, for which the analytic results are shown to be in good agreement with exact numerical TDER results.

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

2013-01-01

225

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

226

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

227

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

228

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.

229

Insecticidal vapours for aircraft disinsection.  

PubMed

A general discussion of the problem of aircraft disinsection is presented. The weaknesses of the present aerosol method, the limitations imposed by airline operators, government officials, passengers, and others, and the potential value of insecticidal vapours as a means of aircraft disinsection are discussed. An apparatus is described for screening insecticides for their vapour toxicity to houseflies and mosquitos. This apparatus led to the discovery of DDVP (O,O-dimethyl-2,2-dichlorovinyl phosphate) and its remarkable vapour toxicity to insects, and to the subsequent studies of its potential use in the vapour state for aircraft disinsection. PMID:13733751

PEARCE, G W; SCHOOF, H F; QUARTERMAN, K D

1961-01-01

230

Insecticidal Vapours for Aircraft Disinsection*  

PubMed Central

A general discussion of the problem of aircraft disinsection is presented. The weaknesses of the present aerosol method, the limitations imposed by airline operators, government officials, passengers, and others, and the potential value of insecticidal vapours as a means of aircraft disinsection are discussed. An apparatus is described for screening insecticides for their vapour toxicity to houseflies and mosquitos. This apparatus led to the discovery of DDVP (O,O-dimethyl-2,2-dichlorovinyl phosphate) and its remarkable vapour toxicity to insects, and to the subsequent studies of its potential use in the vapour state for aircraft disinsection. PMID:13733751

Pearce, G. W.; Schoof, H. F.; Quarterman, K. D.

1961-01-01

231

Time-dependent dynamics of an atom in an intense laser field  

SciTech Connect

A laser excited atom emits both electrons and photons. A method involving the explicit solution of the time-dependent Schroedinger equation is used to determine the ionization and photoemission rates for Kr in a 532 nm laser at intensities in the range from 10[sup 12]--10[sup 14] W/cm[sup 2]. The photon spectrum is dominated by strong peaks at odd multiples of the driving frequency. This is called harmonic generation. The results are compared to obtained experimental rates. Also electron angular distributions and spin-orbit branching ratios for the ion are given for the case of excitation by a 1064 nm laser and its second harmonic. The dependence of the final state distributions on the relative phase between the lasers is presented.

Kulander, K.C.; Krause, J.L.; Schafer, K.J.; Allendorf, S.W.; Crane, J.K.; Budil, K.S.; Perry, M.D.

1992-03-27

232

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

233

Spontaneuos and Parametric Processes in Warm Rubidium Vapours  

NASA Astrophysics Data System (ADS)

Warm rubidium vapours are known to be a versatile medium for a variety of experiments in atomic physics and quantum optics. Here we present experimental results on producing the frequency converted light for quantum applications based on spontaneous and stimulated processes in rubidium vapours. In particular, we study the efficiency of spontaneously initiated stimulated Raman scattering in the ?-level configuration and conditions of generating the coherent blue light assisted by multi-photon transitions in the diamond-level configuration. Our results will be helpful in search for new types of interfaces between light and atomic quantum memories.

D?browski, M.; Parniak, M.; P?cak, D.; Chrapkiewicz, R.; Wasilewski, W.

2014-12-01

234

VUV to UV laser spectroscopy of atomic species in processing plasmas  

NASA Astrophysics Data System (ADS)

Laser absorption spectroscopy in the vacuum ultraviolet range (VUV-LAS) has been applied for the quantitative measurement of light atomic species and halogen atoms, which are of importance in various plasma processing technologies. So far, measurements of F and C atoms have been made with this method. For the generation of a VUV laser, a two-photon resonance four-wave mixing method has been used in the sum frequency generation scheme or difference frequency generation scheme. Wavelength tunability is essential when the background absorption exists due to the parent molecules and other species produced in plasmas. The absolute density of target atoms can be derived from the integral over the line profile converted into the absorption coefficient. Since the VUV-LAS measurement can yield only the values averaged over the line-of-sight, some complementary methods such as two-photon absorption laser induced fluorescence (TALIF) and optical emission actinometry are used for the spatial resolution. Examples of experimental data are given for F and C (VUV-LAS) and for O, N and H (TALIF) with a brief discussion.

Tachibana, Kunihide

2002-08-01

235

Advances in the RF atomic iodine generator for oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

Recent advances in the RF atomic iodine generator for oxygen-iodine lasers are presented. The generator is based on the RF discharge dissociation of a suitable iodine donor immediately before its injection to the flow of singlet oxygen. The discharge is ignited directly in the iodine injector, and the configuration is ready for the laser operation. The dissociation fraction was derived from the atomic iodine number density measured at a presupposed position of laser resonator. The dissociation fraction and the fraction of RF power spent on the dissociation (discharge dissociation efficiency) were measured for the following donors: CH3I, CF3I and HI. A significant improvement of the discharge stability was achieved by increasing the cross-sectional area of the exit injection holes and employing a tangential inlet of working gas into the discharge chamber. The flow rates 0.15 mmol/s and 0.19 mmol/s of produced atomic iodine were achieved using the HI and CF3I, respectively. The atomic iodine number density in the supersonic flow attained 4.22 × 1014 cm-3. The dissociation efficiency was substantially better for HI than for studied organic iodides.

Jirásek, Vít; Schmiedberger, Josef; ?enský, Miroslav; Kodymová, Jarmila

2010-09-01

236

An all gas-phase iodine laser using molecular iodine as atomic iodine donor  

NASA Astrophysics Data System (ADS)

The characteristics of an all gas-phase iodine laser (AGIL) that uses molecular iodine as a source of iodine atoms is studied. The laser is based on the energy transfer reaction between metastable NCl(a1?) and ground state I(2P3/2) atoms, which are produced by the electric discharge of a mixture of I2 and He. At fixed flow rates of the chemical species, the laser output powers are measured at three different positions in a flow reactor. The output power is characterized by a function of the optical axis position and is reasonably reproduced by the numerical calculation. A repetitive pulse of laser output at 50 Hz with a duty factor of 40% is observed. The highest output power is 40 mW at 210 mm downstream from the mixing point of I/H/He and NCl3. This is 80% of the output power generated from the conventional system using HI as an iodine donor. The measured results of the time resolved laser output power suggest that the output power of the I2- AGIL is more sensitive to the electric discharge plasma intensity as compared to that of the HI-AGIL. An AGIL operated using I2 could potentially have the same output power as that of an AGIL operated using HI if a continuous-wave electric discharge generator is used.

Masuda, Taizo; Nakamura, Tomonari; Endo, Masamori

2010-09-01

237

Laser-assisted free-free transition in electron-atom collisions  

SciTech Connect

The free-free transition is studied for an electron-hydrogen atom system in the ground state at very low incident energies in the presence of an external homogeneous, monochromatic, and linearly polarized laser field. The incident electron is considered to be dressed by the laser field in a nonperturbative manner by choosing the Volkov solutions in both the initial and final channels. The space part of the scattering wave function for the electron is solved numerically by taking into account the effect of electron-exchange interactions, short-range interactions, as well as of long-range interactions. The laser-assisted differential as well as total elastic cross sections are calculated for single-photon absorption or 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. A significant difference is noted in the singlet and the triplet cross sections.

Sinha, C. [Theoretical Physics Department, Indian Association for the Cultivation of Science, Jadavpur, Kolkata-700032, West Bengal (India); Bhatia, A. K. [Solar Physics Laboratory, NASA/Goddard Space Flight Center, Greenbelt, Maryland 20771 (United States)

2011-06-15

238

Two photon laser spectroscopy of antiprotonic helium atoms at CERN's AD  

NASA Astrophysics Data System (ADS)

The ASACUSA collaboration of CERN has carried out two-photon laser spectroscopy of antiprotonic helium atoms using counter-propagating ultraviolet laser beams. This excited some non-linear transitions of the antiproton at the wavelengths ? = 139.8-197.0 nm, in a way that reduced the thermal Doppler broadening of the observed resonances. The resulting narrow spectral lines allowed the measurement of three transition frequencies with fractional precisions of 2.3-5 parts in 109. By comparing these values with three-body QED calculations, the antiproton-to-electron mass ratio was derived as 1836.1526736(23). We briefly review these results.

Hori, M.

2014-06-01

239

Photoionization of atomic hydrogen dressed by a circularly polarized CO2-laser field  

NASA Astrophysics Data System (ADS)

The two-color ionization profile of atomic hydrogen in the presence of both a weak tunable high-frequency laser field and a low-frequency laser field of moderate intensity is calculated. The high-frequency spectroscopic light is used to probe the structure of Rydberg states dressed by the low-frequency field. The photoionization spectrum from the sum of the resonance contributions is constructed by calculating the transition dipole moments between the initial state and the dressed Rydberg states, analogous to the study of photoionization in the presence of a dc field carried out by Alvarez and Silverstone.

Madajczyk, J. L.; Pont, Marcel; Potvliege, R. M.; Shakeshaft, Robin; Taylor, H. S.

1992-04-01

240

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

241

Bimodal velocity distribution of atoms released from nanosecond ultraviolet laser ablation  

SciTech Connect

We have investigated the velocity distributions of atoms released from a metallic gadolinium surface by UV laser ablation. The fluences of the nanosecond laser pulses were chosen for a pure release of neutrals and at a higher fluence level for the release of both neutrals and ions. In both cases a thermal Maxwell-Boltzmann slope has been observed for the low velocities, whereas for high velocities strong deviations from a thermal distribution have been seen. The observed velocity distribution has been explained by a bimodal structure including a thermal phase and a shockwave driven 'blow-off' phase.

Maul, J.; Karpuk, S.; Huber, G. [Institut fuer Physik, Johannes Gutenberg-Universitaet, D-55099 Mainz (Germany)

2005-01-15

242

Detection and discrimination of alcohol vapours using single-step anodised nanoporous alumina sensors  

Microsoft Academic Search

The electrical response of single-step anodised alumina sensors to alcohol vapours containing one to four carbon atoms has been studied. In this investigation, the real and imaginary impedance components have been measured in response to the equilibrium saturation vapour pressure of methanol, ethanol, butanol and two structural isomers of propanol. The response to each type of alcohol produces characteristic impedance

Martin Kocanda; Michael Haji-Sheikh; David S. Ballantine

2008-01-01

243

Proposed search for an electric-dipole moment using laser-cooled 171Yb atoms  

NASA Astrophysics Data System (ADS)

We propose an experiment to search for a permanent atomic electric-dipole moment (EDM) using laser-cooled 171Yb atoms launched in an atomic fountain. A uniform B field sets the quantization axis, and the Ramsey separated-oscillatory-fields method is used to measure the Zeeman precession frequency of the atoms. Laser beams of appropriate polarization are used for preparation and detection in a given magnetic sublevel. The signature of an EDM is a shift in the Ramsey resonance correlated with application of a large E field. The precision is expected to be at least 20 times better than current limits because the use of a cold atomic beam allows application of E field 10 times larger than in a vapor cell, and the interaction time with the E field is 200 times larger compared to a thermal beam. The leading source of systematic error in beam experiments, the {E} × {v}/c motional magnetic field, is reduced considerably because of the near-perfect reversal of velocity between up and down trajectories through the E-field region.

Natarajan, V.

2005-01-01

244

Small atomic displacements recorded in bismuth by the optical reflectivity of femtosecond laser-pulse excitations.  

PubMed

Subtle atomic motion in a Bi crystal excited by a 35 fs-laser pulse has been recovered from the transient reflectivity of an optical probe measured with an accuracy of 10(-5). Analysis shows that a novel effect reported here-an initial negative drop in reflectivity-relates to a delicate coherent displacement of atoms by the polarization force during the pulse. We also show that reflectivity oscillations with a frequency coinciding with that of cold Bi are related to optical phonons excited by the electron temperature gradient through electron-phonon coupling. PMID:18232923

Boschetto, D; Gamaly, E G; Rode, A V; Luther-Davies, B; Glijer, D; Garl, T; Albert, O; Rousse, A; Etchepare, J

2008-01-18

245

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

246

Tunable Diode Laser Absorption Spectroscopy of Metastable Atoms in Dusty Plasmas  

SciTech Connect

Spatial density profile of neon metastable produced in dusty plasma was investigated by means of tunable diode laser absorption spectroscopy. The line averaged measured density drops about 30% with the presence of dust particles. The observations provide evidence for a significant interaction between atoms and powder particles which are important for energy transfer from plasma to particles. The power per unit area absorbed by dust particles due to the collision of metastable atoms with dust particle surface is about some tens of mW/m{sup 2}.

Hoang Tung Do; Hippler, Rainer [Institut fuer Physik, Felix-Hausdorff-Str. 6, 17489 Greifswald (Germany)

2008-09-07

247

Generation of atomic iodine via fluorine for chemical oxygen iodine laser  

NASA Astrophysics Data System (ADS)

A method of the chemical generation of atomic iodine for a chemical oxygen-iodine laser (COIL) using atomic fluorine as a reaction intermediate was studied experimentally. This method is based on the reaction between F 2 and NO providing F atoms, and the reaction of F with HI resulting in iodine atoms generation. Atomic iodine was produced with efficiency exceeding 40% relative to initial F 2 flow rate. This efficiency was nearly independent on pressure and total gas flow rate. The F atoms were stable in the reactor up to 2 ms. An optimum ratio of the reactants flow rates was F 2:NO:HI = 1:1:1. A rate constant of the reaction of F 2 with HI was determined. The numerical modelling showed that remaining HI and IF were probably consumed in their mutual reaction. The reaction system was found suitable for employing in a generator of atomic iodine with its subsequent injection into a supersonic nozzle of a COIL.

Jirásek, Vít; Špalek, Otomar; ?enský, Miroslav; Picková, Irena; Kodymová, Jarmila; Jakubec, Ivo

2007-04-01

248

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

249

An electrothermal atomic absorption spectrometer using semiconductor diode lasers and a tungsten coil atomizer: design and first applications.  

PubMed

A new type of atomic absorption spectrometer using a laser diode as light source and a tungsten coil as atomizer is described. Compared to established atomic absorption spectrometers, it is much simpler in construction, smaller in size, and less expensive and it provides inherent background correction and high detection power. The performance of this concept is demonstrated by the determination of aluminum and chromium in water, blood serum and, using the slurry sampling technique, in powdered high-purity graphite and titanium dioxide samples. For calibration, the standard addition method was used. Possible interferences by impurities originating from the tungsten coils are discussed. Applying aqueous solutions of Al and Cr, detection limits of 0.9 and 0.03 ng/mL, respectively, were obtained, and for serum, they were 2.5 and 0.3 ng/mL, respectively. For these elements in graphite and titanium dioxide applied as slurry, the detection limits are between 0.02 (Cr in TiO2) and 0.6 micrograms/g (Al in graphite). The accuracy was checked by comparison of the results with those of other methods. The described system is especially suitable for on-site and on-line analysis. PMID:9737204

Krivan, V; Barth, P; Schnürer-Patschan, C

1998-09-01

250

Isolated attosecond pulse generation from atom radiated by a three-color laser pulse  

NASA Astrophysics Data System (ADS)

We theoretically investigate high-order harmonic and attosecond pulse generation from helium atom in a three-color laser field, which is synthesized by 10 fs/800 nm Ti-sapphire laser and a two-color field consisting of 30 fs/532 nm and 30 fs/1330 nm pulses. Compared with harmonic spectrum generated by a monochromatic field, the harmonics generated from the synthesized three-color field show a supercontinuum spectrum with a bandwidth of 235 eV, ranging from the 154th to the 306th order harmonic. This phenomenon can be attributed to the fact that the ionization of atoms as well as motion of ionized electron can be effectively controlled in the three-color field. Therefore, an isolated 46-as pulse can be generated by superposing supercontinuum from the 160th to the 210th order harmonics.

Qin, Yue-Fei; Guo, Fu-Ming; Li, Su-Yu; Yang, Yu-Jun; Chen, Gao

2014-09-01

251

Suppression of ionization and atomic electron localization by short intense laser pulses  

Microsoft Academic Search

Ionization suppression and electron localization have been observed in numerical modeling of two-photon ionization by very intense short-wavelength laser fields. In this paper we present similar results for one-photon ionization. We find that a one-dimensional atom follows one of three distinct routes to ionization depending whether the field is weak, strong, or superstrong. The first route can be described by

Q. Su; J. H. Eberly

1991-01-01

252

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

253

Atomic collisions in the presence of laser radiation: Time dependence and the asymptotic wave function  

SciTech Connect

A time-dependent, wave-packet description of atomic collisions in the presence of laser radiation is extracted from the more conventional time-independent, stationary-state description. This approach resolves certain difficulties of interpretation in the time-independent approach which arise in the case of asymptotic near resonance. In the two-state model investigated, the approach predicts the existence of three spherically scattered waves in this asymtotically near-resonant case.

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

1982-09-01

254

Atomic collisions in the presence of laser radiation - Time dependence and the asymptotic wave function  

NASA Technical Reports Server (NTRS)

A time-dependent, wave-packet description of atomic collisions in the presence of laser radiation is extracted from the more conventional time-independent, stationary-state description. This approach resolves certain difficulties of interpretation in the time-independent approach which arise in the case of asymptotic near resonance. In the two-state model investigated, the approach predicts the existence of three spherically scattered waves in this asymptotically near-resonant case.

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

1982-01-01

255

Vectorial atomic magnetometer based on coherent transients of laser absorption in Rb vapor  

E-print Network

We have designed and tested an atomic vectorial magnetometer based on the analysis of the coherent oscillatory transients in the transmission of resonant laser light through a Rb vapor cell. We show that the oscillation amplitudes at the Larmor frequency and its first harmonic are related through a simple formula to the angles determining the orientation of the magnetic field vector. The magnetometer was successfully applied to the measurement of the ambient magnetic field.

Lenci, L; Barreiro, S; Valente, P; Lezama, A; Failache, H

2014-01-01

256

An all-solid-state laser source at 671 nm for cold atom experiments with lithium  

E-print Network

We present an all solid-state narrow line-width laser source emitting $670\\,\\mathrm{mW}$ output power at $671\\,\\mathrm{nm}$ delivered in a diffraction-limited beam. The source is based on a frequency-doubled diode-end-pumped ring laser operating on the ${^4F}_{3/2} \\rightarrow {^4I}_{13/2}$ transition in Nd:YVO$_4$. By using periodically-poled potassium titanyl phosphate (ppKTP) in an external build-up cavity, doubling efficiencies of up to 86% are obtained. Tunability of the source over $100\\,\\rm GHz$ is accomplished. We demonstrate the suitability of this robust frequency-stabilized light source for laser cooling of lithium atoms. Finally a simplified design based on intra-cavity doubling is described and first results are presented.

Eismann, Ulrich; Canalias, Carlota; Zukauskas, Andrius; Trénec, Gérard; Vigué, Jacques; Chevy, Frédéric; Salomon, Christophe

2011-01-01

257

Laser-assisted multiphoton ionization of a hydrogen atom by electron impact  

E-print Network

The dynamics of the electron impact multiphoton ionization of a hydrogen atom in the presence of an intense laser field has been studied theoretically, with a view to comparing (qualitatively) the results with the recent kinematically complete experiments of Horr et al [ Phys. Rev. Lett., vol. 94, 153201, (2005) ] for the He target. Significant laser modifications are noted in the present doubly (DDCS) and the fully differential cross sections (TDCS). For most of the explored kinematics (chosen in accordance with the experiment), the present binary peak intensity of the laser-assisted TDCS is significantly enhanced with respect to the field free ones, in agreement with the experiment but in contradiction with the existing first order theories. Importance of the multiphoton effects are also studied.

Deb, S Ghosh; Sinha, C

2008-01-01

258

Dressed-atom approach to strong-field double-resonance fluorescence with laser phase fluctuations  

NASA Astrophysics Data System (ADS)

We discuss analytically the resonance fluorescence of a three-level ladder system whose two transitions are simultaneously saturated by the fields from two lasers. The laser fields have fluctuating phases, which may be correlated to some extent. We generalize the dressed-atom approach of Cohen-Tannoudji and Reynaud [J. Phys. B 10, 345 (1977)] to deal with phase fluctuations under conditions of overall two-photon resonance, but not single-photon resonance on the individual transitions. In this respect we also generalize the master-equation approach of Lawande, Puri, and D'Souza [Phys. Rev. A 33, 2504 (1986)]. The effect of spontaneous emission and laser fluctuations on the resonance fluorescence quintet is discussed in detail, and shown to marked effects. We also investigate the effect of these quantities on the steady-state dressed-atom occupation probabilities, and point out that the double-resonance experiment can be used to prepare the atom in a given dressed state with high probability.

Kennedy, T. A. B.; Swain, S.

1987-08-01

259

Atomic force microscopy and confocal laser scanning microscopy on the cytoskeleton of permeabilised and embedded cells.  

PubMed

We describe a technical method of cell permeabilisation and embedding to study the organisation and distribution of intracellular proteins with aid of atomic force microscopy and confocal laser scanning microscopy in identical areas. While confocal laser scanning microscopy is useful for the identification of certain proteins subsequent labelling with markers or antibodies, atomic force microscopy allows the observation of macromolecular structures in fixed and living cells. To demonstrate the field of application of this preparatory technique, cells were permeabilised, fixed, and the actin cytoskeleton was stained with phalloidin-rhodamine. Confocal laser scanning microscopy was used to show the organisation of these microfilaments, e.g. geodesic dome structures. Thereafter, cells were embedded in Durcupan water-soluble resin, followed by UV-polymerisation of resin at 4 degrees C. This procedure allowed intracellular visualisation of the cell nucleus or cytoskeletal elements by atomic force microscopy, for instance to analyse the globular organisation of actin filaments. Therefore, this method offers a great potential to combine both microscopy techniques in order to understand and interpret intracellular protein relations, for example, the biochemical and morphological interaction of the cytoskeleton. PMID:16360280

Meller, Karl; Theiss, Carsten

2006-03-01

260

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

261

Coherent excitation of the 5D5\\/2 level of ultra-cold rubidium atoms with short laser pulses  

Microsoft Academic Search

We demonstrate the use of stimulated Raman adiabatic passage (STIRAP) for population transfer from the ground state to the 5D5\\/2 level (5S1\\/2 ? 5P3\\/2 ? 5D5\\/2) in laser-cooled 87Rb atoms and examine the influence of the time delay between laser pulses, pulse height, pulse duration and frequency detuning from resonance on the efficiency of Rb atom excitation to the 5D5\\/2

S A Snigirev; A A Golovizin; G A Vishnyakova; A V Akimov; N N Kolachevskii

2012-01-01

262

Time-of-flight diode-laser velocimeter using a locally seeded atomic absorber: Application in a pulse detonation engine  

Microsoft Academic Search

A diode-laser velocimeter based on atomic absorption spectroscopy has been developed and applied to a pulse detonation engine (PDE). The velocimeter uses a salt-coated sting to seed an atomic absorber at any desired location and a single, fixed-wavelength diode laser to monitor the absorber's presence downstream of the sting. Salt particles stripped from the sting tend to form distinct \\

S. T. Sanders; D. W. Mattison; J. B. Jeffries; R. K. Hanson

2003-01-01

263

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

264

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

265

Development of the Chemical Oxygen-Iodine Laser (COIL) with chemical generation of atomic iodine  

NASA Astrophysics Data System (ADS)

This article addresses the development of a Chemical Oxygen-Iodine Laser (COIL) with alternative chemical ways of generating atomic iodine. Injection of atomic iodine as opposed to molecular iodine has the potential to improve the COIL efficiency. This paper describes two chemical methods for generating iodine atoms based on the gas phase reactions of hydrogen/deuterium iodide with fluorine or chlorine atoms, which are also produced chemically. Simplified one-dimensional gas dynamic modeling that describes the stream-wise profiles of species concentrations within both reaction systems is used to gain a theoretical understanding of both reaction systems under COIL conditions. The modeling results are used for the design of an experimental device and the interpretation of experimental data. The first experimental investigation studies the production of iodine atoms produced from reactions of Cl with HI. Atomic iodine yields of 70-100% in nitrogen are obtained, and the gain on the I(2P1/2)-I(2P3/2) transition in a flow of singlet oxygen is measured.

Kodymová, J.; Špalek, O.; Jirásek, V.; ?enský, M.; Hager, G. D.

266

Preparation of nanowire specimens for laser-assisted atom probe tomography.  

PubMed

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. PMID:25299058

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

2014-10-31

267

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

268

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

269

Non-neutral ion plasmas and crystals, laser cooling, and atomic clocks* J. J. Bollinger+ and D. J. Wineland  

E-print Network

Non-neutral ion plasmas and crystals, laser cooling, and atomic clocks* J. J. Bollinger+ and D. J. Wineland Time and Frequency Division, NIST, Boulder, Colorado 80303 Daniel H. E. Dubin Department correlations characteristic of a liquid or crystal. Laser beams also apply a torque which, by changing

270

Exact quantum-mechanical states of a model atom in a uniform magnetic field and in a laser field  

Microsoft Academic Search

The three-dimensional anisotropic charged harmonic oscillator in a uniform magnetic field and in a laser field in the dipole approximation is shown to be an exactly solvable quantum-mechanical problem. It can serve as a model for atoms or molecules interacting with magnetic and laser fields of arbitrary strength. The solution is derived in an entirely algebraic manner.

J. Bergou; F. Ehlotzky

1982-01-01

271

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

272

Observation of Atomic Emission Enhancement by fs-ns Dual-Pulse Laser-Induced Breakdown Spectroscopy  

Microsoft Academic Search

An experiment of a 500-fs KrF laser pulse incident upon a high density supersonic O2 gas jet synchronously with an ns frequency-doubled Nd:YAG laser pulse is performed in orthogonal configuration. Significant atomic emission enhancement of over forty-fold is observed with an optical multi-channel analyser. The enhancement effect is probably attributed to the different ionization mechanisms between fs and ns laser

Li-Xin Yan; Yong-Sheng Zhang; Li-Rong Zhang; Jing-Ru Liu; Jian-Ping Cheng; Min Lü

2006-01-01

273

Observation of Atomic Emission Enhancement by fs-ns Dual-Pulse Laser-Induced Breakdown Spectroscopy  

NASA Astrophysics Data System (ADS)

An experiment of a 500-fs KrF laser pulse incident upon a high density supersonic O2 gas jet synchronously with an ns frequency-doubled Nd:YAG laser pulse is performed in orthogonal configuration. Significant atomic emission enhancement of over forty-fold is observed with an optical multi-channel analyser. The enhancement effect is probably attributed to the different ionization mechanisms between fs and ns laser pulses.

Yan, Li-Xin; Zhang, Yong-Sheng; Zhang, Li-Rong; Liu, Jing-Ru; Cheng, Jian-Ping; Lü, Min

2006-01-01

274

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

275

Qualitative tissue differentiation by analysing the intensity ratios of atomic emission lines using laser induced breakdown spectroscopy (LIBS): prospects for a feedback mechanism for surgical laser systems.  

PubMed

The research work presented in this paper focuses on qualitative tissue differentiation by monitoring the intensity ratios of atomic emissions using 'Laser Induced Breakdown Spectroscopy' (LIBS) on the plasma plume created during laser tissue ablation. The background of this study is to establish a real time feedback control mechanism for clinical laser surgery systems during the laser ablation process. Ex-vivo domestic pig tissue samples (muscle, fat, nerve and skin) were used in this experiment. Atomic emission intensity ratios were analyzed to find a characteristic spectral line for each tissue. The results showed characteristic elemental emission intensity ratios for the respective tissues. The spectral lines and intensity ratios of these specific elements varied among the different tissue types. The main goal of this study is to qualitatively and precisely identify different tissue types for tissue specific laser surgery. (© 2013 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim). PMID:24376030

Kanawade, Rajesh; Mahari, Fanuel; Klämpfl, Florian; Rohde, Maximilian; Knipfer, Christian; Tangermann-Gerk, Katja; Adler, Werner; Schmidt, Michael; Stelzle, Florian

2015-01-01

276

CONTROL OF LASER RADIATION PARAMETERS: Effect of molecular additions on the radiation parameters of a laser on Xe atomic transitions  

NASA Astrophysics Data System (ADS)

An electron-beam-pumped laser on Xe atomic transitions is experimentally investigated at various pump durations and powers within wide ranges of pressures and working mixtures including additions of molecular gases. It is shown that the maximum specific lasing powers are achieved at high specific pump powers (above 200 kW cm-3 atm-1) and durations of the beam current pulse of tens of nanoseconds in high-pressure Ar — Xe mixtures with molecular gas additions (N2 and CO2). A specific output radiation power of ~ 4 kW cm-3 is obtained. For a pump pulse durations from hundreds of nanoseconds to 1 ?s, the highest lasing energies are reached without molecular additions at a comparatively low beam-current density (the specific pump power is ~ 10 kW cm-3 atm-1). However, in setups with specific pump powers above 40 kW cm-3 atm-1 and a working-mixture pressure limited by the strength of the laser chamber, molecular additions result in an increase in the radiation energy and efficiency. In wide-aperture facilities with high pump powers, molecular additions improve the distribution of the radiation power density over the laser-beam cross section.

Fedenev, A. V.; Tarasenko, Viktor F.; Skakun, V. S.

2002-05-01

277

On the applicability of the adiabatic theory for atomic systems in strong laser fields  

E-print Network

The photo-induced dynamics of atoms that interact with laser fields can be described by the Floquet solutions of the time dependent Schr\\"odinger equation when the duration of the laser pulse is sufficiently long. However, as the laser frequency $\\omega$ decreases, the calculation of the Floquet solutions (so called quasi-energy solutions) becomes more difficult due to the large number of the Floquet channels which are coupled one to another. Since in the limit of $\\omega\\to 0$ the ac field induced by the laser turns into a dc field, it is very appealing to use the adiabatic approximation where time is an instantaneous parameter (rather than a dynamical variable) as a zero-order approximation to describe the photo-induced dynamics. Indeed, the adiabatic approximation plays a key role in the derivation of the semiclassical three-step model (TSM). Here we show that in the low frequency regime the numerical effort which is needed to represent the Floquet operator is dramatically reduced when the time-periodic adiabatic solutions, and not the field-free solutions as usual, are used as a basis set. We derive a perturbation theory for the calculation of the Floquet solutions where the adiabatic Hamiltonian serves as the zero-order Hamiltonian and show how the radius of convergence can be calculated. A simple 1D illustrative numerical example is given. As one might expect, perturbation theory, where the adiabatic Hamiltonian is the zero-order hamiltonian, is applicable for high frequencies when the laser intensity is low. As the laser field intensity is increased the laser frequency, for which the perturbational approach is applicable, is reduced.

Hanna Martiskainen; Nimrod Moiseyev

2014-07-01

278

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

279

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

280

Time-of-flight spectroscopy of the energy distribution of laser-ablated atoms and ions.  

PubMed

The growth of ultrathin films, deposited by laser ablation, crucially depends on the energy of the ablated species. Therefore, a time-of-flight (TOF) spectrometer has been constructed and measurements have been carried out in order to determine the energy distribution of laser-ablated Fe and Pt atoms and ions in the plasma created by nanosecond pulses of a frequency-doubled neodymium doped yttrium aluminum garnet laser. The experiments have been performed in ultrahigh vacuum at relatively low laser power. For measuring the spectra of the neutrals, a cross-beam electron source for postionization and electric as well as magnetic fields for repelling the ions are employed. Nevertheless, measurements of neutral particles are restricted to low plasma densities due to electrostatic shielding within the plasma, leading to an inefficient deflection of charged particles by electrostatic and magnetic fields. Test measurements have been performed by utilizing the TOF spectrometer as a pressure gauge and also by chopping the electron beam, running the TOF spectrometer as a residual gas mass spectrometer. The spectra of the laser-ablated plasmas have shown plasma conditions with a Debye length of approximately 10(-4) m, densities of 10(15)-10(16) m(-3) and ion energies up to 150 eV. Neutral spectra have shown an unexpectedly low fraction of neutrals (10(-3)-10(-4)) and hyperthermal energies up to several 10 eV, possibly contributed by recombination of ions and electrons in the plasma. Even though gas spectra had demonstrated the expected sensitivity of the TOF spectrometer for low-energy neutrals, no thermally evaporated neutral atoms could be found. PMID:18447522

Buchsbaum, A; Rauchbauer, G; Varga, P; Schmid, M

2008-04-01

281

Time-of-flight spectroscopy of the energy distribution of laser-ablated atoms and ions  

NASA Astrophysics Data System (ADS)

The growth of ultrathin films, deposited by laser ablation, crucially depends on the energy of the ablated species. Therefore, a time-of-flight (TOF) spectrometer has been constructed and measurements have been carried out in order to determine the energy distribution of laser-ablated Fe and Pt atoms and ions in the plasma created by nanosecond pulses of a frequency-doubled neodymium doped yttrium aluminum garnet laser. The experiments have been performed in ultrahigh vacuum at relatively low laser power. For measuring the spectra of the neutrals, a cross-beam electron source for postionization and electric as well as magnetic fields for repelling the ions are employed. Nevertheless, measurements of neutral particles are restricted to low plasma densities due to electrostatic shielding within the plasma, leading to an inefficient deflection of charged particles by electrostatic and magnetic fields. Test measurements have been performed by utilizing the TOF spectrometer as a pressure gauge and also by chopping the electron beam, running the TOF spectrometer as a residual gas mass spectrometer. The spectra of the laser-ablated plasmas have shown plasma conditions with a Debye length of approximately 10-4m, densities of 1015-1016m-3 and ion energies up to 150eV. Neutral spectra have shown an unexpectedly low fraction of neutrals (10-3-10-4) and hyperthermal energies up to several 10eV, possibly contributed by recombination of ions and electrons in the plasma. Even though gas spectra had demonstrated the expected sensitivity of the TOF spectrometer for low-energy neutrals, no thermally evaporated neutral atoms could be found.

Buchsbaum, A.; Rauchbauer, G.; Varga, P.; Schmid, M.

2008-04-01

282

Time-resolved measurement of atomic emission enhancement by fs ns dual-pulsed laser-induced breakdown spectroscopy  

NASA Astrophysics Data System (ADS)

Time-resolved measurement of atomic emission enhancement is performed by using a 500-fs KrF laser pulse incident upon a high density supersonic O2 gas jet, synchronized with an orthogonal ns frequency-doubled Nd:YAG laser pulse. The ultra-short pulse serves as an igniter of the gas jet, and the subsequent ns-laser pulse significantly enhances the atomic emission. Analysis shows that the contributions to the enhancement effect are made mainly by the bremsstrahlung radiation and cascade ionization.

Yan, Li-Xin; Zhang, Yong-Sheng; Zheng, Guo-Xin; Liu, Jing-Ru; Cheng, Jian-Ping; Lü, Min

2006-10-01

283

[Dermatological laser treatment].  

PubMed

This article reviews the different lasers used in dermatology. Special emphasis is placed on the treatment of naevus flammeus ("portwine stain") where lasers are the treatment of choice. Argon laser and pulsed dye laser are the main lasers used in vascular skin diseases, and the article focuses on these two types. Copper vapour laser, neodymium-YAG-laser and CO2-laser are also presented. Information is provided about the availability of laser technology in the different health regions in Norway. PMID:1948901

Mørk, N J; Austad, J; Helland, S; Thune, P; Volden, G; Falk, E

1991-10-10

284

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

285

Hook spectroscopy as an atomic number density diagnostic applied to laser-ablated copper plasmas  

SciTech Connect

Hook spectroscopy has been used to determine the absolute number density of ground state copper atoms in laser-ablated plasma plumes. An ablation laser power flux of {approximately} 1.5 GW/cm{sup 2} is applied to a solid copper target in a background gas, producing a plasma plume suitable for studying homogeneous copper vapor condensation. Density is measured at post-ablation time delays ranging from 10 {mu}s to 3 ms with 25 torr of argon as the background gas. Planar laser-induced fluorescence (PLEF) images containing relative density information are used in conjunction with the hook spectra to resolve spatially the absolute density within the plume. Copper atom densities thus measured ranged from 1.9 {times} 10{sup 15} cm{sup {minus}3} at a delay of 10 {mu}s to 2.7 {times} 10{sup 13} cm{sup {minus}3} at 3 ms delay in 25 torr of argon The decrease in density is due to the condensation of copper vapor to form fine particulate. As a combustion diagnostic, the hook method may prove extremely useful for the determination of metal impurity density in coal fired flames as well as a single -- shot OH density and temperature diagnostic.

Zerkle, D.K.; Sappey, A.D.; Gamble, T.K.

1993-11-01

286

Theoretical Studies of Atomic and Molecular Multiphoton Processes in Intense and Superintense Laser Fields  

NASA Astrophysics Data System (ADS)

In this thesis work, several new nonperturbative theoretical formalisms and accurate and efficient computational methods are presented for ab initio comprehensive investigation of atomic and molecular multiphoton processes in intense and superintense laser fields. In the presence of strong fields, it is advantageous to treat the atoms/molecules quantum mechanically by using the time-dependent Schrodinger equation and treat the electromagnetic fields classically, leading to a set of coupled first-order time-dependent differential equations. The essence of the theoretical formalisms and computational methods developed can be summarized in the following several key elements: (1) For periodically or polychromatically time-dependent Hamiltonians, the time-dependent problems can be transformed into an equivalent time-independent infinite-dimensional Floquet Hamiltonians. (2) In the presence of external fields, all the bound states are coupled to the continuum and become quasi-bound states possessing complex quasi -energies. (3) To facilitate the calculation of the complex quasi-energies, a generalized pseudospectral technique is developed for the discretization of the non-Hermitian Floquet Hamiltonian and the construction of the Floquet matrix elements. (4) The Floquet matrices so generated are often very large scale, sparse, complex matrices. The formalisms and computational methods described above are applied to the studies of several high-intensity atomic and molecular multiphoton processes of current interests. The major accomplishments are summarized below: (1) The complex quasi-energies of excited states of atomic hydrogen in strong fields are determined for the first time. (2) Nonperturbative detailed calculations of the multiphoton detachment rates of H^- in one-color laser fields are performed for the first time. The intensity-averaged photodetachment rates calculated are in excellent agreement with those experimental data recently obtained in Los Alamos. (3) A generalized non-Hermitian two-mode Floquet theory is developed for the study of above-threshold multiphoton detachment of negative ions in intense two-color laser fields. (4) The two-color phase control of high-order harmonic generation (HHG) is investigated. It is shown that the HHG spectrum is sensitive to the relative phase of the two laser fields and a small admixture of a harmonic laser field to a fundamental laser field can lead to either increment or decrement of the HHG production rates. (5) The nature of chemical bond of D_2^+ molecules in intense one- and two-color laser fields is studied. An unexpected novel chemical bond hardening and molecular stabilization phenomenon is predicted: molecules initially prepared in highly excited vibrational states can become more stabilized and longer-lived with increasing laser intensity. Furthermore it is found that by tuning the relative phase between the fundamental and its third harmonic laser fields, the internuclear potential surface can be modified significantly, leading to a coherent control of the multiphoton dissociation dynamics. (Abstract shortened by UMI.).

Wang, Jingyan

287

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

288

Low-energy electron-impact laser-assisted ionization of atomic hydrogen  

NASA Astrophysics Data System (ADS)

We have studied the influence of a linearly polarized laser field on the dynamics of low (e ,2 e ) collisions in atomic hydrogen. The influence of the laser on the target states is treated using a first-order perturbation approach. The continuum states of the scattered and ejected electrons are described respectively by Volkov and Coulomb-Volkov wave functions. The second Born approximation is used to calculate triple differential cross sections for laser-assisted ionization by low-energy electron impact. The required scattering amplitudes are evaluated by using the Sturmian basis expansion. The influence of the laser parameters (photon energy, intensity, and direction of polarization) on the triple differential cross sections is analyzed, and several illustrative examples are discussed. Our second Born approximation results agree very well with those obtained in the first-order Born approximation at larger incident energies. The margins between the second and first Born approximation results are large at low incident energies in the vicinity of the recoil peaks.

Makhoute, A.; Ajana, I.; Khalil, D.

2014-11-01

289

Multiphoton effects in laser-assisted ionization of a helium atom by electron impact  

NASA Astrophysics Data System (ADS)

The dynamics of the electron impact multiphoton ionization of a He atom in the presence of an intense laser field ( n ? _e, 2 e) is studied theoretically for laser polarization (\\vert\\vert^l) and perpendicular (bot^r) to the incident momentum. The triple differential (TDCS) as well as the double differential (DDCS) cross sections are studied for the coplanar asymmetric geometry. The results are compared with the only available kinematically complete experiment at high incident energy (1000 eV). Significant laser modification (enhancement) is noted due to multiphoton effects in the present binary and recoil peak intensities of the TDCS for both the geometries, in qualitative agreement with the experiment. In the single photon case, the net effect of the laser field is to suppress the field free (FF) TDCS as well as the DDCS in the zeroth order approximation of the ejected electron wave function (CV), while in the first order (MCV), the cross sections are found to be enhanced. The CV multiphoton cross sections obey the famous Kroll Watson (KW) sum rule while the latter does not hold good in the corresponding MCV approximation.

Ghosh Deb, S.; Sinha, C.

2010-11-01

290

Multiphoton (e, 2e) process of hydrogen atom in strong laser field  

NASA Astrophysics Data System (ADS)

The dynamics of the electron impact multiphoton ionization of a hydrogen atom in the presence of an intense laser field (e, n ? e) has been studied theoretically for laser polarization parallel (\\vert \\vertl) and perpendicular (?r) to the incident momentum, with a view to comparing (qualitatively) the results with the recent kinematically complete experiments of Höhr et al. [Phys. Rev. Lett. 94, 153201 (2005)] for the He target. Significant laser modifications are noted in the present doubly (DDCS) and the fully differential multiphoton cross sections (TDCS) for both the geometries (\\vert \\vertl and ?r). For most of the explored kinematics (chosen in accordance with the experiment), the present binary peak intensity of the laser-assisted multiphoton TDCS is significantly enhanced with respect to the field free ones, in qualitative agreement with the experiment. Importance of the multiphoton effects is also studied. The multiphoton cross sections in the zeroth order approximation of the ejected electron wavefunction (CV) obeys the Kroll Watson sum rule while it does not hold good in the corresponding first order approximation (MCV).

Ghosh Deb, S.; Roy, S.; Sinha, C.

2009-12-01

291

Effects of Chirped Laser Pulses on Nonclassical Correlation and Entanglement of Photon Pairs from Single Atom  

E-print Network

We study the effects of arbitrary laser pulse excitations on quantum correlation, entanglement and the role of quantum noise. The transient quantities are computed exactly using a method that provides exact solutions of the Langevin field operators for photon pairs produced by a double Raman atom driven by laser pulses. Short pulses with appropriate chirping, delay and/or detuning can generate broadband photon pairs and yield results that provide insights on how to generate very large nonclassical correlation. We find that short pulses are not favorable for entanglement. The quantity was previously found to be phase-sensitive and this is used with the pulse area concept to explain the rapid variations of entanglement with pulse width and strength. Photon correlation and entanglement are favored by exclusively two different initial conditions. Analysis reinforces our understanding of the two nonclassical concepts.

C. H. Raymond Ooi

2008-03-15

292

MOTIS: A Focused Ion Beam Source Based On Laser-Cooled Atoms  

SciTech Connect

We have demonstrated high resolution focused ion beams based on a magneto-optical trap ion source (MOTIS), which takes advantage of the ultra cold temperatures of laser cooled atoms to produce high brightness, low emittance ion beams. We have created focused beams of both Cr{sup +} and Li{sup +} and present secondary electron micrographs obtained with these beams, demonstrating a focal spot size as low as 27 nm at a beam energy of 2 keV. This work shows that the MOTIS can be a useful source for focused ion beams that will open new opportunities for applications in materials characterization and metrology.

Knuffman, B.; Steele, A. V.; McClelland, J. J. [Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States); Orloff, J.; Maazouz, M. [FEI Company, Hillsboro, OR 97124 (United States)

2011-11-10

293

Electron's anomalous magnetic moment effects on laser assisted ionization of atomic hydrogen by electronic impact  

E-print Network

Electron-impact ionization of atomic hydrogen with the electron's anomalous mag- netic moment (AMM) effects are examined. The formulas for the laser-assisted relativis- tic triple differential cross section (TDCS) in the coplanar binary geometry developed earlier by Y. Attaourti and S. Taj [Phys. Rev. A 69, 063411 (2004)] are used to check the consistency of our computations when the anomaly $\\kappa$ is taken to be zero. We show that the contribution of the terms containing the AMM effects even in the first Born approximation has an important contribution, so it must be included in any reliable analysis. A full analytical calculation for the TDCS is presented.

Taj, S; Idrissi, M El; Attaourti, Y; Oufni, L

2012-01-01

294

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

295

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

296

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

297

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

298

Arcjet flow properties determined from laser-induced fluorescence of atomic nitrogen.  

PubMed

Flow property measurements that were recently acquired in the Ames Research Center Aerodynamic Heating Facility arcjet using two-photon laser-induced fluorescence (LIF) of atomic nitrogen (N) are reported. The flow properties, which include velocity, translational temperature, and N concentration, were measured simultaneously over a range of facility operating conditions for N(2)-argon test gas flows in the 30-cm-diameter nozzle. A recent measurement of the two-photon excitation cross section for the 3p(4)D degrees <-- 2p(4)S degrees transition of atomic nitrogen is used to convert the relative nitrogen concentration measurements to absolute values, and a nitrogen flow reactor is used to provide a room-temperature, reference-wavelength calibration of the translational temperature and velocity measurements. When combined with information from facility measurements, an analysis of the flow properties obtained using two-photon LIF of N yields the total free-stream flow enthalpy. PMID:18305816

Fletcher, D G

1999-03-20

299

Variation of the Fine-Structure Constant and Laser Cooling of Atomic Dysprosium  

E-print Network

Radio-frequency electric-dipole transitions between nearly degenerate, opposite parity levels of atomic dysprosium (Dy) were monitored over an eight-month period to search for a variation in the fine-structure constant, $\\alpha$. The data provide a rate of fractional temporal variation of $\\alpha$ of $(-2.7\\pm2.6)\\times 10^{-15}$ yr$^{-1}$ or a value of $(-8.7 \\pm 6.6) \\times 10^{-6}$ for $k_\\alpha$, the variation coefficient for $\\alpha$ in a changing gravitational potential. All results indicate the absence of significant variation at the present level of sensitivity. We also present initial results on laser cooling of an atomic beam of dysprosium.

Leefer, N A; Budker, D; Ferrell, S J; Yashchuk, V V; Lapierre, A; Nguyen, A -T; Lamoreaux, S K; Torgerson, J R

2008-01-01

300

Laser sustained discharge nozzle apparatus for the production of an intense beam of high kinetic energy atomic species  

DOEpatents

Laser sustained discharge apparatus for the production of intense beams of high kinetic energy atomic species. A portion of the plasma resulting from a laser sustained continuous optical discharge which generates energetic atomic species from a gaseous source thereof is expanded through a nozzle into a region of low pressure. The expanded plasma contains a significant concentration of the high kinetic energy atomic species which may be used to investigate the interaction of surfaces therewith. In particular, O-atoms having velocities in excess of 3.5 km/s can be generated for the purpose of studying their interaction with materials in order to develop protective materials for spacecraft which are exposed to such energetic O-atoms during operation in low earth orbit.

Cross, Jon B. (Santa Fe, NM); Cremers, David A. (Los Alamos, NM)

1988-01-01

301

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

302

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

303

Interaction de l'atome d'hydrogene avec un champ laser intense et bref a derive de frequence  

NASA Astrophysics Data System (ADS)

Nous presentons dans ce document une etude theorique de l'interaction entre l'atome d'hydrogene et un champ laser intense et bref a derive de frequence. Dans un premier temps, nous etablissons une methode basee sur les fonctions B-splines qui permet de decrire avec precision l'ensemble de la structure energetique du systeme atomique. Dans le second temps, nous developpons une approche non perturbative de type spectrale, basee sur la resolution exacte de l'equation de Schrodinger dependante du temps, pour decrire l'atome d'hydrogene en interaction avec un champ laser. Nous proposons particulierement une representation realiste d'une impulsion laser a derive de frequence. Finalement, nous etudions le processus d'ionisation au dessus du seuil de l'atome d'hydrogene soumis a une impulsion a derive de frequence. Nos resultats montrent que la derive de frequence laser permet de controler et d'optimiser le transfert de population de l'etat fondamental vers les etats electroniques intermediaires impliques dans le processus d'ionisation. Mots-cles : Atome d'hydrogene Fonctions B-splines Methode non perturbative spectrale Impulsion laser intense et breve Parametre de derive de frequence laser lonisation multiphotonique

Ba, Harouna Sileye

304

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

305

The interaction of 193-nm excimer laser radiation with single-crystal zinc oxide: The generation of atomic Zn line emission at laser fluences below breakdown  

SciTech Connect

The production of gas phase atomic and ionic line spectra accompanying the high laser fluence irradiation of solid surfaces is well known and is most often due to the production and interaction of high densities of atoms, ions, and electrons generated from laser-induced breakdown. The resulting plasma expands and moves rapidly away from the irradiated spot and is accompanied by intense emission of light. This type of “plume” is well studied and is frequently exploited in the technique of chemical analysis known as laser induced breakdown spectroscopy. Here, we describe a similar but weaker emission of light generated in vacuum by the laser irradiation of single crystal ZnO at fluences well below breakdown; this emission consists entirely of optical line emission from excited atomic Zn. We compare the properties of the resulting laser-generated gas-phase light emission (above and below breakdown) and describe a mechanism for the production of the low-fluence optical emission resulting from a fortuitous choice of material and laser wavelength.

Khan, Enamul H.; Langford, S. C.; Dickinson, J. T. [Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164–2814 (United States)] [Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164–2814 (United States); Boatner, L. A. [Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)] [Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)

2013-08-28

306

The interaction of 193-nm excimer laser radiation with single-crystal zinc oxide: The generation of atomic Zn line emission at laser fluences below breakdown  

SciTech Connect

The production of gas phase atomic and ionic line spectra accompanying the high laser fluence irradiation of solid surfaces is well known and is most often due to the production and interaction of high densities of atoms, ions, and electrons generated from laser-induced breakdown. The resulting plasma expands and moves rapidly away from the irradiated spot and is accompanied by intense emission of light. This type of plume is well studied and is frequently exploited in the technique of chemical analysis known as laser induced breakdown spectroscopy. Here, we describe a similar but weaker emission of light generated in vacuum by the laser irradiation of single crystal ZnO at fluences well below breakdown; this emission consists entirely of optical line emission from excited atomic Zn. We compare the properties of the resulting laser-generated gas-phase light emission (above and below breakdown) and describe a mechanism for the production of the low-fluence optical emission resulting from a fortuitous choice of material and laser wavelength.

Kahn, E. H. [Washington State University, Pullman; Langford, S. C. [Washington State University, Pullman; Dickinson, J. T. [Washington State University, Pullman; Boatner, Lynn A [ORNL

2013-01-01

307

ELEMENTS OF LASER SETUPS: Parameters of an electric-discharge generator of iodine atoms for a chemical oxygen---iodine laser  

Microsoft Academic Search

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 CH3I is used as the donor of atomic iodine. The fraction of iodine extracted from CH3I in the generator is ~50%. The optimal operation regimes are found in which 80%---90% of iodine contained in the output flow

V. N. Azyazov; M. V. Vorob'ev; A. I. Voronov; Nikolai V. Kupryaev; P. A. Mikheev; N. I. Ufimtsev

2009-01-01

308

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

309

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

310

Validity of the quantitative rescattering theory for high-order harmonic generation of atoms in two-color laser pulses  

NASA Astrophysics Data System (ADS)

The quantitative rescattering (QRS) theory has been recently developed to study the high-order harmonic generation (HHG) of atoms and molecules exposed to a linearly polarized single-color laser pulse. According to the QRS, the HHG spectra can be expressed as a product of the returning electron wave packet and the photorecombination differential cross section of the laser-free continuum electron back to the initial ground state. In this paper, we extend the QRS to the case of two-color laser fields. The validity of the QRS for two-color pulses is carefully examined by comparing the HHG spectra of several rare-gas atoms obtained from the QRS with those results from the solution of the time-dependent Schrödinger equation (TDSE) based on the single active electron approximation. Our results show that the QRS theory for the HHG of atoms works quite well in the case of two-color pulses.

Zhao, Song-Feng; Wang, Yunqin; Wang, Guoli; Zhou, Xiao-Xin

2014-10-01

311

Atomic force microscopy of hot spot reaction sites in impacted RDX and laser heated AP  

SciTech Connect

An atomic force microscope (AFM) has been used to reveal residual sub-micron sized decomposition sites in drop weight impacted RDX and laser irradiated AP crystals. In impacted RDX, the small and early reaction sites observed are hemispherical craters, ranging in size from 20--300 nm. The smallest reaction site encompassed about 10,000 molecules with an expected energy evolution of 2 {times} 10{sup {minus}14} J. On a somewhat larger scale hillocks of 200--800 nm were observed, their shape giving evidence of internal reaction and hot spot melting. Dislocation densities as high as 5 {times} 10{sup 12} per cm{sup 2} were observed in sub-ignited RDX. High resolution AFM images of the RDX lattice structure indicate molecular rotation as well as displacements at dislocation sites. In AP, after nanosecond pulsed laser irradiation, reaction sites were trumpet shaped with a smallest size of approximately 50 nm. Most sites contained a crystallographically oriented central square lid formed above the surrounding crystal surface, probably relating to the orthorhombic to cubic phase transition documented in micron scale cracking patterns observed at the laser heated sites.

Sharma, J.; Coffey, C.S. [Naval Surface Warfare Center, Silver Spring, MD (United States); Ramaswamy, A.L.; Armstrong, R.W. [Univ. of Maryland, College Park, MD (United States)

1996-07-01

312

Multiphoton and tunneling ionization probability of atoms and molecules in an intense laser field  

NASA Astrophysics Data System (ADS)

We theoretically studied ionization of atoms exposed to an intense laser field by using three different methods, i.e., the numerical solution of the single-active-electron approximation based time-dependent Schrödinger equation (SAE-TDSE), the Perelomov-Popov-Terent'ev (PPT) model, and the Ammosov-Delone-Krainov (ADK) model. The ionization of several linear molecules in a strong laser field is also investigated with the molecular ADK (MO-ADK) and the molecular PPT (MO-PPT) model. We show that the ionization probability from the PPT and the MO-PPT model agrees well with the corresponding SAE-TDSE result in both the multiphoton and tunneling ionization regimes. By considering the volume effect of the laser field, the ionization signal obtained from the PPT and the MO-PPT model fits well the experimental data in the whole range of the multiphoton and tunneling ionization regimes. However, both the ADK and MO-ADK models seriously underestimate the ionization probabilities (or signals) in the multiphoton regime.

Zhao, Song-Feng; Liu, Lu; Zhou, Xiao-Xin

2014-02-01

313

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

314

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

315

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

316

The effects of atomic rubidium vapor on the performance of optical windows in Diode Pumped Alkali Lasers (DPALs)  

NASA Astrophysics Data System (ADS)

Diode Pumped Alkali Lasers (DPALs) suffers from damage to its optical windows due to atomic alkali exposure. DPALs are of great interest since they can combine multiple lasers to achieve higher laser output power, scalable to megawatts, with very high quantum efficiency. However before scaling to higher laser output beam power, damage to the optical windows from atomic alkali exposure in the gain medium has to be addressed. A DPAL emulator chamber was constructed for the purpose of evaluating different optical windows in a representative hot alkali rich environment typical of a DPAL gain cell. Sample optical windows of fused silica, alumina, magnesium fluoride and calcium fluoride were exposed in the DPAL emulator in order to qualitatively and quantitatively demonstrate and assess the damaging effects of the atomic rubidium vapor on the optical windows. Methodologies to examine the damage were developed for comparing exposed and unexposed optical windows. We found that damage to the optical windows due to the atomic rubidium can be quantified by means of changes in laser energy transmission through the optical window after rubidium exposure.

Quarrie, Lindsay O.'Brien

2013-03-01

317

Femtosecond two-photon LIF imaging of atomic species using a frequency-quadrupled Ti:sapphire laser  

NASA Astrophysics Data System (ADS)

Femtosecond (fs)-duration laser pulses are well suited for two-photon laser-induced-fluorescence (TPLIF) imaging of key atomic species such as H, N, and O in gas-phase reacting flows. Ultrashort pulses enable efficient nonlinear excitation, while reducing interfering photochemical processes. Furthermore, amplified fs lasers enable high-repetition-rate imaging (typically 1-10 kHz) for capturing the dynamics of turbulent flow fields. However, two-dimensional (2D), single-laser-shot fs-TPLIF imaging of the above species is challenging in most practical flow fields because of the limited ultraviolet pulse energy available in commercial optical parametric amplifier (OPA)-based tunable laser sources. In this work, we report the development of an efficient, fs frequency-quadrupling unit [i.e., fourth-harmonic generator (FHG)] with overall conversion efficiency more than six times greater than that of commercial OPA-based systems. The development, characterization, and application of the fs-FHG system for 2D imaging of H atoms in flames are described in detail. The potential application of the same laser system for 2D imaging of N and O atoms is also discussed.

Kulatilaka, Waruna D.; Gord, James R.; Roy, Sukesh

2014-07-01

318

Parameters of an electric-discharge generator of iodine atoms for a chemical oxygen-iodine laser  

Microsoft Academic Search

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 CHI is used as the donor of atomic iodine. The fraction of iodine extracted from CHI in the generator is 50%. The optimal operation regimes are found in which 80%-90% of iodine contained in the output flow

V N Azyazov; M V Vorobev; A I Voronov; Nikolai V Kupryaev; P A Mikheev; N I Ufimtsev

2009-01-01

319

An electrostatic glass actuator for ultrahigh vacuum: A rotating light trap for continuous beams of laser-cooled atoms  

NASA Astrophysics Data System (ADS)

This article describes the design, characterization, and performance of an electrostatic glass actuator adapted to an ultrahigh vacuum environment (10-8mbar). 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.

Füzesi, F.; Jornod, A.; Thomann, P.; Plimmer, M. D.; Dudle, G.; Moser, R.; Sache, L.; Bleuler, H.

2007-10-01

320

An electrostatic glass actuator for ultrahigh vacuum: A rotating light trap for continuous beams of laser-cooled atoms  

SciTech Connect

This article describes the design, characterization, and performance of an electrostatic glass actuator adapted to an ultrahigh vacuum environment (10{sup -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.

Fuezesi, F.; Jornod, A.; Thomann, P.; Plimmer, M. D.; Dudle, G.; Moser, R.; Sache, L.; Bleuler, H. [Observatoire cantonal de Neuchatel (ON), rue de l'Observatoire 58, CH-2000 Neuchatel (Switzerland); Federal Office of Metrology (METAS), Lindenweg 50, CH-3003 Bern-Wabern (Switzerland); Laboratory of Robotic Systems (LSRO), EPFL Lausanne, CH-1015 Lausanne (Switzerland)

2007-10-15

321

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

322

Resolution enhancement of pHe+ atomic line profiles measured with a pulsed dye laser and a Fizeau wavelength meter.  

PubMed

A Fizeau wavelength meter was used to compensate for fluctuations in the longitudinal mode structure and wavelength of a pulsed dye laser. The average laser linewidth was effectively narrowed by selection of laser pulses with a single longitudinal mode. These techniques were recently employed to measure some atomic transition wavelengths in pHe+ to fractional precisions greater than 1 part in 10(7). The wavelengths were absolutely calibrated against iodine or tellurium lines by absorption spectroscopy or against neon or argon lines by optogalvanic spectroscopy. PMID:14690120

Hori, Masaki; Hayano, Ryugo S; Widmann, Eberhard; Torii, Hiroyuki A

2003-12-15

323

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...

324

A Photoionization Detector for Gases and Vapours  

Microsoft Academic Search

SENSITIVE ionization methods for the measurement of low gas and vapour concentration require the ionization of the test gas or vapour under conditions where an inert carrier gas is unionized. Such methods as the ionization of carbon compounds in a hydrogen flame1 and the reaction between gases and vapours and rare gas metastables2 are well established and successful for this

J. E. Lovelock

1960-01-01

325

Atomic force microscopy visualization of injuries in Enterococcus faecalis surface caused by Er,Cr:YSGG and diode lasers.  

PubMed

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. PMID:25475770

López-Jiménez, L; Arnabat-Domínguez, J; Viñas, M; Vinuesa, T

2014-12-01

326

LASERS: Self-initiating volume discharge in iodides used for producing atomic iodine in pulsed chemical oxygen — iodine lasers  

NASA Astrophysics Data System (ADS)

A volume self-sustained discharge (VSD) in iodides (C3H7I, C4H9I) and in their mixtures with SF6, N2, and O2 in the presence of small-scale inhomogeneities on the cathode surface is shown to develop in the form of a self-initiating volume discharge (SIVD), i.e., a volume discharge without any preionisation including discharge gaps with a strong edge enhancement of the electric field. Additions of SF6 or N2 to the iodides improves the stability and homogeneity of the SIVD, while adding up to 300 % (relative to the partial iodide pressure) of O2 to these mixtures has only an insignificant effect on the discharge stability. The possibility of SIVD initiation was modelled experimentally in a 1.5-L discharge volume. For the C4H9I:O2:SF6=0.083:0.25:0.67 mixture at a pressure of 72 Torr, the specific energy input into the discharge plasma ranged up to 130 J L-1 in this geometry. A conclusion was drawn that the SIVD is promising for the production of atomic iodine in the pulsed and repetitively pulsed operating regimes of a chemical oxygen — iodine laser.

Belevtsev, A. A.; Kazantsev, S. Yu; Saifulin, A. V.; Firsov, K. N.

2003-06-01

327

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

328

Secondary peaks in the atomic ionization by a resonant laser pulse  

NASA Astrophysics Data System (ADS)

The above-threshold ionization of atoms by XUV short laser pulses with frequencies resonant with a ground-excited state transition is investigated. A theory based on a variational expression with trial wave functions for the final and the initial states is presented. For the former we use a Coulomb-Volkov wave function, and for the latter a close-coupling solution of the time-dependent Schrödinger equation considering a few bound states and their depletion towards the continuum. We find that this discrete-continuum Coulomb-Volkov theory provides a very good description of the photoelectron spectrum. In particular it accounts for the splitting of the above-threshold ionization peaks by Rabi oscillations and the appearance of secondary-peaks observed in full numerical simulations.

Bustamante, M. G.; Rodríguez, V. D.; Barrachina, R. O.

2012-12-01

329

Parametrization of Electron-Impact Ionization Cross Sections from Laser-Excited and Aligned Atoms  

NASA Astrophysics Data System (ADS)

A set of parameters describing electron-impact ionization from laser-aligned atoms are reported, which define the "length", "width", and "direction" of the quadruple differential cross section (QDCS) as a function of target alignment kB for fixed ingoing electron momentum k0 and outgoing momenta k1, k2. Mg24 was used, with k0, k1, k2, and kB in the same plane. The parameters are derived for a range of k2 angles, with k1 set at 30° to k0. The QDCS is then determined for all kB. The parameters are very angle sensitive, the QDCS direction varying more than 90° as the length to width ratio varied more than an order of magnitude.

Nixon, Kate L.; Murray, Andrew James

2014-01-01

330

Parametrization of electron-impact ionization cross sections from laser-excited and aligned atoms.  

PubMed

A set of parameters describing electron-impact ionization from laser-aligned atoms are reported, which define the "length", "width", and "direction" of the quadruple differential cross section (QDCS) as a function of target alignment kB for fixed ingoing electron momentum k0 and outgoing momenta k1, k2. 24Mg was used, with k0, k1, k2, and kB in the same plane. The parameters are derived for a range of k2 angles, with k1 set at 30° to k0. The QDCS is then determined for all kB. The parameters are very angle sensitive, the QDCS direction varying more than 90° as the length to width ratio varied more than an order of magnitude. PMID:24484007

Nixon, Kate L; Murray, Andrew James

2014-01-17

331

Analysis of atomic and ion debris features of laser-produced Sn and Li plasmas  

SciTech Connect

Tin and lithium plasmas emit efficiently in the in-band region (13.5 nm with 2% bandwidth) necessary for extreme ultraviolet (EUV) lithography. We have made a detailed comparison of the atomic and ionic debris, as well as the emission features of Sn and Li plasmas under identical experimental conditions. Planar slabs of pure Sn and Li were irradiated with 1064 nm, 9 ns neodymium-doped yttrium aluminum garnet laser pulses for producing plasmas. A suite of diagnostics were used to analyze the emission and debris features, including optical emission spectroscopy (OES), a Faraday cup, an EUV pinhole camera, the absolute measurement of EUV conversion efficiency (CE), etc. Our results show that Sn plasmas provide a CE nearly twice that of Li. However, the kinetic energies of Sn ions are considerably higher, though with a lower flux. OES studies have showed that the kinetic energies of neutral species are substantially lower compared to that of the charged particle species.

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

2010-09-15

332

Optically Pumped Atomic Rubidium Lasers: Two-Photon and Exciplex Excitation Mechanisms  

NASA Astrophysics Data System (ADS)

The Doppler-broadened two-photon absorption (TPA) cross-section for the 52S1/2 ? 52 D5/2 transition in Rb is measured using direct absorption methods. The selection rule |DeltaF| ? 2 applied to both isotopes yields 17 transitions in 3 Doppler limited lines. A detailed model of the intensity profile was also developed to account for a focused Gaussian beam (with an M2 value of 1.09) propagating through a two-photon absorption medium. A peak absorbance of 24% was observed for an intensity of 6.28 kWcm2 at the focus, a Rb density of 4.6x1015 cm-3 , and a path length of 15 cm. Alkali concentrations from 1.61 - 8.52x1015 cm -3 were monitored in the far wing of the D 2 line. Extracting the hyperfine-broadened TPA cross-section from 87 test configurations, while varying the pump power, alkali concentration and focal length, yielded an error-weighted average of 6.75x10^-21 cm4W with a standard deviation of 3.61x10-21 cm4W. This cross-section is sufficient for a pulsed dye laser to bleach the pump transition in the Two-Photon Pumped Alkali Laser (TPAL) that lases at 420 nm and 5.2 microm. Optically pumped atomic rubidium lasers pumped in the blue satellite of the D2 line from the ground Rb-Ar or Rb-Kr collision pair to the dissociative B2S+1/2 state produce laser emission at 780.2 nm. Lasing is achieved for pump wavelengths of 752.3 to greater than 760 nm for the Rb-Ar system and 757.1 -- 760.4 nm for the Rb-Kr system. Slope efficiencies increase with both Rb and Ar concentrations and exceed 0.25% using a heat pipe configuration. The gain is very high with photon build-up times of 1--3.7 ns. Laser induced heating and subsequent condensation of alkali vapor in the heat pipe configuration currently limits operation to less than 2500 Torr.

Gallagher, Jeffrey E.

333

Gain and continuous-wave laser oscillation on the 1315 nm atomic iodine transition pumped by an air-helium electric discharge  

E-print Network

American Institute of Physics. DOI: 10.1063/1.2957678 The classical chemical oxygen iodine laser COIL re investigations into an electrically driven oxygen-iodine laser ElectricOIL that was demonstrated by Carroll et alGain and continuous-wave laser oscillation on the 1315 nm atomic iodine transition pumped by an air

Carroll, David L.

334

Mechanism of pulse discharge production of iodine atoms from CF3I molecules for a chemical oxygen–iodine laser  

Microsoft Academic Search

The pulsed chemical oxygen–iodine laser (COIL) development is aimed at many new applications. Pulsed electric discharge is most effective in turning COIL operation into the pulse mode by instant production of iodine atoms. A numerical model is developed for simulations of the pulsed COIL initiated by an electric discharge. The model comprises a system of kinetic equations for neutral and

I V Kochetov; A P Napartovich; N P Vagin; N N Yuryshev

2009-01-01

335

Mechanism of pulse discharge production of iodine atoms from CF3I molecules for a chemical oxygen-iodine laser  

Microsoft Academic Search

The pulsed chemical oxygen-iodine laser (COIL) development is aimed at many new applications. Pulsed electric discharge is most effective in turning COIL operation into the pulse mode by instant production of iodine atoms. A numerical model is developed for simulations of the pulsed COIL initiated by an electric discharge. The model comprises a system of kinetic equations for neutral and

I. V. Kochetov; A. P. Napartovich; N. P. Vagin; N. N. Yuryshev

2009-01-01

336

A general approach to few-cycle laser interactions with complex atoms  

NASA Astrophysics Data System (ADS)

We are developing a general method to solve the time-dependent Schr"odinger equation for the interaction of a strong laser pulse with a general atom, i.e., beyond the models of quasi-one or quasi-two-electron targets. The field-free hamiltonian matrices are generated in a B-spline R-matrix method [1], and the laser field is coupled in through dipole matrices generated with the same program. The major advantages of our approach are i) its generality and ii) the possibility of generating highly accurate target descriptions with small configuration interaction expansions. We propagate the solution of the TDSE by the Arnoldi method [2]. The generalized eigenvalue problem is transformed by diagonalizing the overlap matrix S of the non-orthogonal basis functions and generating new field-free hamiltonian and dipole matrix blocks through H' = S-1/2 H S-1/2 and D' = S-1/2 DS-1/2. Details of various numerical implementations will be discussed. 0.1truecm[1] O. Zatsarinny, Comp. Phys. Commun. 174, 273 (2006). [2] T.J. Park and J.C. Light, J. Chem. Phys. 85, 5870 (1986).

Guan, Xiaoxu; Zatsarinny, Oleg; Bartschat, Klaus; Feist, Johannes; Schneider, Barry; Noble, Cliff

2007-06-01

337

Development, analysis and control of a high-speed laser-free atomic force microscope.  

PubMed

This paper presents the development and control of a laser-free atomic force microscopy (AFM) system for high-speed imaging of micro- and nanostructured materials. The setup uses a self-sensing piezoresistive microcantilever with nanometer accuracy to abolish the need for a bulky and expensive laser measurement system. A basic model for the interaction dynamics of AFM tip and sample in the high-speed open-loop imaging mode is proposed, accounting for their possible separation. The effects of microcantilever and sample stiffness and damping coefficients on the accuracy of imaging are studied through a set of frequency-domain simulations. To improve the speed of operation, a Lyapunov-based robust adaptive control law is used for the AFM XY scanning stage. It is shown that the proposed controller overcomes the frequency limits of the PID (Proportional-Integral-Derivative) controllers typically used in AFM. Finally, the paper presents a set of experiments on a standard calibration sample with 200 nm stepped topography, indicating accurate imaging up to the scanning frequency of 30 Hz. PMID:20192502

Bashash, Saeid; Saeidpourazar, Reza; Jalili, Nader

2010-02-01

338

Atomic photoionization in combined intense XUV free-electron and infrared laser fields  

NASA Astrophysics Data System (ADS)

We present a systematic study of the photoionization of noble gas atoms exposed simultaneously to ultrashort (20 fs) monochromatic (1-2% spectral width) extreme ultraviolet (XUV) radiation from the Free-electron Laser in Hamburg (FLASH) and to intense synchronized near-infrared (NIR) laser pulses with intensities up to about 1013 W cm-2. Already at modest intensities of the NIR dressing field, the XUV-induced photoionization lines are split into a sequence of peaks due to the emission or absorption of several additional infrared photons. We observed a plateau-shaped envelope of the resulting sequence of sidebands that broadens with increasing intensity of the NIR dressing field. All individual lines of the nonlinear two-color ionization process are Stark-shifted, reflecting the effective intensity of the NIR field. The intensity-dependent cut-off energies of the sideband plateau are in good agreement with a classical model. The detailed structure of the two-color spectra, including the formation of individual sidebands, the Stark shifts and the contributions beyond the classical cut-off, however, requires a fully quantum mechanical description, as is demonstrated with time-dependent quantum calculations in single-active electron approximation.

Radcliffe, P.; Arbeiter, M.; Li, W. B.; Düsterer, S.; Redlin, H.; Hayden, P.; Hough, P.; Richardson, V.; Costello, J. T.; Fennel, T.; Meyer, M.

2012-04-01

339

Sub-Doppler absorption narrowing in atomic vapor at two intense laser fields.  

PubMed

We have experimentally studied electromagnetically induced transparency (EIT) and absorption (EIA) in hot 85Rb atomic vapor using probe and coupling light with comparable power levels. We have shown that strong-probe EIT has different linewidth and appears in fewer configurations than does usual, weak probe EIT. In V-scheme, where optical pumping and saturation are dominant mechanisms, narrow EIT is possible only when a probe is tuned to a closed transition. The width of the EIT resonance increases with laser intensity with non-linear dependence, similar to the weak-probe EIT in Lambda- scheme. The EIT in Lambda- scheme was observed when two transitions had balanced population losses. The EIA was modified for the case of a strong probe as well: in four-level N-scheme with Zeeman sublevels the EIA was observed only for a cycling transition when F'=F+1, where F and F' are the angular momenta of the 5 2S1/2 (ground) and 5 2P3/2 (excited) state hyper-fine levels, respectively. The combination of strong probe and strong coupling laser beam intensities allows observation of an absorption dip due to three-photon resonance in a four-level scheme that involves the Raman transitions via virtual level. PMID:19495020

Krmpot, Aleksandar; Mijailovi?, Marina; Pani?, Bratimir; Luki?, Dragan; Kovacevi?, Aleksander; Panteli?, Dejan; Jelenkovi?, Branislav

2005-03-01

340

Spectral analysis of irregular roughness artifacts measured by atomic force microscopy and laser scanning microscopy.  

PubMed

Atomic force microscopy (AFM) and laser scanning microscopy (LSM) measurements on a series of specially designed roughness artifacts were performed and the results characterized by spectral analysis. As demonstrated by comparisons, both AFM and LSM can image the complex structures with high resolution and fidelity. When the surface autocorrelation length increases from 200 to 500 nm, the cumulative power spectral density spectra of the design, AFM and LSM data reach a better agreement with each other. The critical wavelength of AFM characterization is smaller than that of LSM, and the gap between the measured and designed critical wavelengths is reduced with an increase in the surface autocorrelation length. Topography measurements of surfaces with a near zero or negatively skewed height distribution were determined to be accurate. However, obvious discrepancies were found for surfaces with a positive skewness owing to more severe dilations of either the solid tip of the AFM or the laser tip of the LSM. Further surface parameter evaluation and template matching analysis verified that the main distortions in AFM measurements are tip dilations while those in LSM are generally larger and more complex. PMID:25339140

Chen, Yuhang; Luo, Tingting; Ma, Chengfu; Huang, Wenhao; Gao, Sitian

2014-12-01

341

Pulsed erbium laser ablation of hard dental tissue: the effects of atomized water spray versus water surface film  

NASA Astrophysics Data System (ADS)

It has been established that the ability of erbium lasers to ablate hard dental tissue is due primarily to the laser- initiated subsurface expansion of the interstitial water trapped within the enamel and that by maintaining a thin film of water on the surface of the tooth, the efficiency of the laser ablation is enhanced. It has recently been suggested that a more aggressive ablative mechanism, designated as a hydrokinetic effect, occurs when atomized water droplets, introduced between the erbium laser and the surface of the tooth, are accelerated in the laser's field and impact the tooth's surface. It is the objective of this study to determine if the proposed hydrokinetic effect exists and to establish its contribution to the dental hard tissue ablation process. Two commercially available dental laser systems were employed in the hard tissue ablation studies. One system employed a water irrigation system in which the water was applied directly to the tooth, forming a thin film of water on the tooth's surface. The other system employed pressurized air and water to create an atomized mist of water droplets between the laser hand piece and the tooth. The ablative properties of the two lasers were studied upon hard inorganic materials, which were void of any water content, as well as dental enamel, which contained interstitial water within its crystalline structure. In each case the erbium laser beam was moved across the surface of the target material at a constant velocity. When exposing material void of any water content, no ablation of the surfaces was observed with either laser system. In contrast, when the irrigated dental enamel was exposed to the laser radiation, a linear groove was formed in the enamel surface. The volume of ablated dental tissue associated with each irrigation method was measured and plotted as a function of the energy within the laser pulse. Both dental laser systems exhibited similar enamel ablation rates and comparable ablated surface characteristics. The results of the study suggest that, although the manner in which the water irrigation was introduced differed, the mechanism by which the enamel was removed appeared basically the same for both dental laser systems, namely rapid subsurface expansion of the interstitially trapped water. It is the conclusion of this study that if the proposed hydrokinetic effect exists, it is not effective on hard materials, which are void of water, and it does not contribute in any significant degree in the ablation of dental enamel.

Freiberg, Robert J.; Cozean, Colette D.

2002-06-01

342

Two-photon absorption laser-induced fluorescence measurements of atomic nitrogen in a radio-frequency atmospheric-pressure plasma jet  

Microsoft Academic Search

The first direct measurements of atomic nitrogen species in a radio-frequency atmospheric-pressure plasma jet (APPJ) are presented. Atomic nitrogen radicals play a key role in new plasma medicine applications of APPJs. The measurements were performed with a two-photon absorption laser-induced fluorescence diagnostic, using 206.65 nm laser photons for the excitation of ground-state N atoms and observing fluorescence light around 744

E Wagenaars; T Gans; D O'Connell; K Niemi

2012-01-01

343

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

344

Electron-ion dynamics in laser-assisted desorption of hydrogen atoms from H-Si(111) surface  

SciTech Connect

In the framework of real time real space time-dependent density functional theory we have studied the electron-ion dynamics of a hydrogen-terminated silicon surface H-Si(111) subjected to intense laser irradiation. Two surface fragments of different sizes have been used in the simulations. When the intensity and duration of the laser exceed certain levels (which depend on the wavelength) we observe the desorption of the hydrogen atoms, while the underlying silicon layer remains essentially undamaged. Upon further increase of the laser intensity, the chemical bonds between silicon atoms break as well. The results of the simulations suggest that with an appropriate choice of laser parameters it should be possible to remove the hydrogen layer from the H-Si(111) surface in a matter of a few tens of femtoseconds. We have also observed that at high laser field intensities (2-4 V/A in this work) the desorption occurs even when the laser frequency is smaller than the optical gap of the silicon surface fragments. Therefore, nonlinear phenomena must play an essential role in such desorption processes.

Bubin, Sergiy; Varga, Kalman [Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235 (United States)

2011-09-15

345

Resonant-holographic-interferometry for absolute measurements of excimer laser-ablated neutral-atom plume line-density profiles  

NASA Astrophysics Data System (ADS)

Experiments have been performed to measure Al neutral atom absolute line-density profiles using resonant-holographic-interferometry. The ablation source is a KrF excimer laser with a per-pulse energy of about 0.8 J. Targets are either pure aluminum or Al2O3. Aluminum ground-state neutral atom line-densities are probed by a dye laser tuned near the 394.401 nm line. A double-pulse interferometry technique is employed in which one pulse includes the laser ablation plume and a second pulse generates reference fringes on a holographic plate by rotating a mirror. Holograms are reconstructed to give interference fringes on film by using a helium-neon laser. Interferograms of laser ablated Al metal give maximum Al neutral plume line-densities in the range of 4-10×104 cm-2. Aluminum neutral line-densities from Al2O3 targets are as much as 10-20 times larger than from Al metal targets. The sensitivity of this resonant diagnostic is 4 to 5 orders of magnitude higher than nonresonant neutral-particle interferometry and may be adjusted by tuning the dye laser wavelength shift away from the resonance line. This diagnostic has been demonstrated in vacuum, gas (14 mTorr - 35 Torr) and RF plasma (30 mTorr - 1 Torr) environments. At higher gas pressures, the nonresonant gas-dynamic fringe shift can be subtracted to give the resonant fringe shift and species density.

Gilgenbach, R. M.; Lindley, R. A.; Ching, C. H.; Lash, J. S.

1993-10-01

346

Lasers '81  

SciTech Connect

Progress in lasers is discussed. The subjects addressed include: excimer lasers, surface spectroscopy, modern laser spectroscopy, free electron lasers, cavities and propagation, lasers in medicine, X-ray and gamma ray lasers, laser spectroscopy of small molecules and clusters, optical bistability, excitons, nonlinear optics in the X-ray and gamma ray regions, collective atomic phenomena, tunable IR lasers, far IR/submillimeter lasers, and laser-assisted collisions. Also treated are: special applications, multiphoton processes in atoms and small molecules, nuclear pumped lasers, material processing and applications, polarization, high energy lasers, laser chemistry, IR molecular lasers, laser applications of collision and dissociation phenomena, solid state laser materials, phase conjugation, advances in laser technology for fusion, metal vapor lasers, picosecond phenomena, laser ranging and geodesy, and laser photochemistry of complex molecules.

Collins, C.B.

1982-01-01

347

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

348

Amplification of light and atoms in a Bose-Einstein condensate Bose-Einstein condensates illuminated by an off-resonant laser beam ("dressed  

E-print Network

-coherent amplification of matter waves [1, 2]. The amplification process involved the scattering of a condensate atom a threshold laser intensity, leading to matter wave gain. However, the symmetry between light and atoms) Matter wave grating Probe beam Amplification of light and atoms by off-resonant light scattering. (a

349

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

350

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

351

Study of a low power dissipation, miniature laser-pumped rubidium frequency standard  

NASA Astrophysics Data System (ADS)

This paper studies a miniature low power consumption laser-pumped atom vapour cell clock scheme. Pumping 87Rb with a vertical cavity surface emitting laser diode pump and locking the laser frequency on a Doppler-broadened spectral line, it records a 5 × 10-11?-1/2 (? < 500 s) frequency stability with a table-top system in a primary experiment. The study reveals that the evaluated scheme is at the level of 2.7 watts power consumption, 90 cm3 volume and 10-12?-1/2 short-term frequency stability.

Liu, Guo-Bin; Zhao, Feng; Gu, Si-Hong

2009-09-01

352

Radiative properties of Z-pinch and laser produced plasmas from mid-atomic-number materials  

NASA Astrophysics Data System (ADS)

The investigation of Z-pinches on university-scale pulsed power generators allows for the study of plasmas with a broad range of temperatures, densities, and sizes in cost effective experiments. In particular, X-pinches produce the hottest and densest plasma and are very suitable for x-ray radiation studies. The planar wire array has shown to be a powerful radiation source on the 1 MA Zebra generator at UNR. The radiative and implosion dynamics from such loads with mid-atomic-number materials were not studied previously in detail and are a topic of this dissertation. Specifically, the radiative and implosion characteristics of Z-pinch and X-pinch plasmas with mid-atomic-number materials (iron, nickel, copper, and zinc) will be discussed. The theoretical tool used to accomplish this is non-LTE kinetic modeling. This tool is not limited to Z-pinches, but can be applied to any plasma radiation source like laser produced plasmas which will be demonstrated. In addition, since the radiative characteristics of wire arrays are connected with the implosion characteristics, another theoretical tool, the Wire Ablation Dynamics Model was used in this dissertation to understand the ablation and implosion dynamics of wire arrays. The experiments were analyzed from two university-scale pulsed power machines: the 1 MA Zebra and COBRA generators. The research completed in this dissertation emphasizes the unique capabilities and usefulness of spectroscopy, particularly time-gated x-ray spectroscopy. For example, modeling of time-gated L-shell spectra captured from the precursor column of low-wire-number copper cylindrical wire arrays reveals electron temperatures ˜400 eV, which is significantly higher than any previous precursor measurements. From the analysis of experiments on COBRA, total energy was higher for the implosion of a compact cylindrical wire array made with alternating brass and aluminum wires than a uniform wire array made with just brass or aluminum. Comparison of L-shell radiation from mid-atomic-number wires placed in the inner or outer array from nested wire array implosions on COBRA shows that the material radiates more when placed on the outer array. Using different materials on the outer and inner arrays provides a unique opportunity to study the implosion dynamics of nested wire arrays, especially when using time-gated spectroscopy. Brass planar wire arrays represent a unique opportunity to study the performance of two L-shell radiators from mid-atomic-number materials (copper and zinc) at the same time in experiments on Zebra. The ablation and implosion dynamics of the single- and double-planar wire arrays was investigated and completed. Non-LTE kinetic modeling was used to describe the radiation from simultaneous measurements of K- and L-shell radiation from the interaction of a femtosecond laser system with an iron target. The K- and L-shell radiation originates from two distinct plasma regions. The L-shell radiation was emitted from a region of plasma created by the prepulse and modeling showed moderate electron temperatures and electron densities. The cold iron Kalpha line manifested from a region of plasma that was heated by hot electrons interacting with the solid dense iron target. K-shell modeling showed electron temperatures of tens of eV and less than 1% hot electrons. To study the time history of cold Kalpha lines for mid-atomic-number materials, experiments with planar wire arrays were performed on Zebra. Continuation of this study was accomplished using X-pinches to allow for the simultaneous measurements in time of hotter ionic and cold K-shell lines.

Ouart, Nicholas D.

353

Study of vertical Si/SiO2 interface using laser-assisted atom probe tomography and transmission electron microscopy.  

PubMed

Laser-assisted atom probe tomography has opened the way to three-dimensional visualization of nanostructures. However, many questions related to the laser-matter interaction remain unresolved. We demonstrate that the interface reaction can be activated by laser-assisted field evaporation and affects the quantification of the interfacial composition. At a vertical interface between Si and SiO2, a SiO2 molecule tends to combine with a Si atom and evaporate as a SiO molecule, reducing the evaporation field. The features of the reaction depend on the direction of the laser illumination and the inner structure of tip. A high concentration of SiO is observed at a vertical interface between Si and SiO2 when the Si column is positioned at the center of the tip, whereas no significant SiO is detected when the SiO2 layer is at the center. The difference in the interfacial compositions of two samples was due to preferential evaporation of the Si layer. This was explained using transmission electron microscopy observations before and after atom probe experiments. PMID:24411275

Lee, J H; Lee, B H; Kim, Y T; Kim, J J; Lee, S Y; Lee, K P; Park, C G

2014-03-01

354

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

355

LASERS: Electrode system for electric-discharge generation of atomic iodine in a repetitively pulsed oxygen --- iodine laser with a large active volume  

Microsoft Academic Search

Possibilities for increasing the active medium volume of a chemical oxygen --- iodine laser (CCOIL) with a pulsed electric-discharge generation of atomic iodine are studied. The reasons are analysed of the low stability of the transverse self-sustained volume discharge in electrode systems with metal cathodes under the conditions of the electric energy input into gas-discharge plasma that are typical for

S. Yu Kazantsev; I. G. Kononov; S. V. Podlesnykh; K. N. Firsov

2010-01-01

356

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

357

Thermal calcium atom interferometer with a phase resolution of a few milliradians based on a narrow-linewidth diode laser  

SciTech Connect

A symmetrical atom interferometer with a thermal calcium atom beam has been developed using a narrow linewidth diode laser stabilized to the resonance of a high-finesse cavity. The linewidth of the diode laser was estimated to be less than 1 Hz relative to the cavity resonance in noise measurement over the range of 100 Hz to 1 MHz, and the phase instability of the interference fringes obtained from the Allan deviation was improved to 2 mrad at an integration time of 300 s. Using this atom interferometer, the ac Stark phase shift between the {sup 1}S{sub 0} and {sup 3}P{sub 1} states of a Ca atom was measured as a function of a laser power near the resonance of the {sup 1}S{sub 0}-{sup 1} P{sub 1} transition at a wavelength of 423 nm. The decay rate of the {sup 1}P{sub 1} state was determined to be {gamma}=1.91(33)x10{sup 8} s{sup -1}.

Akatsuka, Tomoya; Mori, Yoshihiro; Sone, Nobuhiko; Ohtake, Yurie; Machiya, Mamoru; Morinaga, Atsuo [Faculty of Science and Technology, Tokyo University of Science, Noda-shi, Chiba 278-8510 (Japan)

2011-08-15

358

Laser spectroscopy with nanometric cells containing atomic vapor of metal: influence of buffer gas  

NASA Astrophysics Data System (ADS)

Comparison of absorption and fluorescence in a nano-cell containing Rb vapor with other Rb nano-cells with addition of neon gas is presented. It is shown that the effect of collapse and revival of Dicke-type narrowing occurs for Rb nanocells containing N2 as buffer gas under 6 and 20 Torr pressure for the thickness L = ? /2 and L = where ? is the resonant ?, laser wavelength 794 nm (D1 line). Particularly for 6 Torr the line-width of the transmission spectrum for the thickness L =?/2 is 2 times narrower than that for L = ?. For an ordinary Rb cell with L = 0.1 - 10 cm with addition of buffer gas, the velocity selective optical pumping/saturation (VSOP) resonances in saturated absorption spectra are fully suppressed when the buffer gas pressure > 0.5 Torr. A spectacular difference is that for L = ?, VSOP resonances located at the atomic transitions are still observable even when Ne pressure is >= 6 Torr. Narrowband fluorescence spectra of a nano-cell with L = ?/2 can be used as a convenient tool for online buffer gas pressure monitoring for the conditions when ordinary pressure gauges are unusable. Comparison of electromagnetically induced transparency (EIT) effect in a nano-cell filled with pure (without a buffer gas) Rb with another nano-cell, where buffer gas nitrogen is added, is presented. The use of N2 gas inside Rb nano-cells strongly extends the range of coupling laser detunings in which it is still possible to form EIT resonance.

Sarkisyan, D.; Hakhumyan, G.; Sargsyan, A.; Mirzoyan, R.; Leroy, C.; Pashayan-Leroy, Y.

2010-10-01

359

Noncontact estimation of intercellular breaking force using a femtosecond laser impulse quantified by atomic force microscopy  

PubMed Central

When a femtosecond laser pulse (fsLP) is focused through an objective lens into a culture medium, an impulsive force (fsLP-IF) is generated that propagates from the laser focal point (Of) in a micron-sized space. This force can detach individual adherent cells without causing considerable cell damage. In this study, an fsLP-IF was reflected in the vibratory movement of an atomic force microscopy (AFM) cantilever. Based on the magnitude of the vibration and the geometrical relationship between Of and the cantilever, the fsLP-IF generated at Of was calculated as a unit of impulse [N-s]. This impulsive force broke adhesion molecule-mediated intercellular interactions in a manner that depended on the adhesion strength that was estimated by the cell aggregation assay. The force also broke the interactions between streptavidin-coated microspheres and a biotin-coated substrate with a measurement error of approximately 7%. These results suggest that fsLP-IF can be used to break intermolecular and intercellular interactions and estimate the adhesion strength. The fsLP-IF was used to break intercellular contacts in two biologically relevant cultures: a coculture of leukocytes seeded over on an endothelial cell monolayer, and a polarized monolayer culture of epithelial cells. The impulses needed to break leukocyte–endothelial and interepithelial interactions, which were calculated based on the geometrical relationship between Of and the adhesive interface, were on the order of 10-13 and 10-12 N-s, respectively. When the total impulse at Of is well-defined, fsLP-IF can be used to estimate the force required to break intercellular adhesions in a noncontact manner under biologically relevant conditions. PMID:21245358

Hosokawa, Yoichiroh; Hagiyama, Man; Iino, Takanori; Murakami, Yoshinori; Ito, Akihiko

2011-01-01

360

Formation of atomic clusters through the laser ablation of refractory materials in a supersonic molecular beam source  

SciTech Connect

Concepts which guide the design of atomic cluster supersonic beam sources have been developed. These ideas are founded on the knowledge of laser ablation dynamics and are structured in order to take advantage of certain features of the ablation event. Some of the drawbacks of previous cluster source designs become apparent when the sequence of events following laser ablation are clarified. Key features of the new cluster source design include control of the cluster size distribution, uniform performance with a variety of solid materials and elements, high beam intensity, and significant removal of internal energy during the supersonic expansion.

Haufler, R.E.; Compton, R.N. [Oak Ridge National Lab., TN (United States); Puretzky, A.A. [Oak Ridge National Lab., TN (United States)]|[Russian Academy of Sciences, Troitsk, Moscow (Russian Federation). Inst. of Spectroscopy

1993-12-31

361

A practical uncertainty budget for ambient mercury vapour measurement  

NASA Astrophysics Data System (ADS)

Measurements of mercury in ambient air are assuming greater importance, because of increasing health concerns and European legislation. In order to have confidence in measured values and to assess compliance with target values, measurements must be made with validated methodologies which have traceable uncertainty statements associated with them. This paper presents a practical uncertainty budget for the measurement of vapour-phase mercury in ambient air, sampling onto a gold-coated silica adsorption tube and measuring with atomic fluorescence spectrometry. Moreover, this budget may be generalised for other related measurement methods for mercury vapour and other ambient air pollutants. All significant sources of uncertainty are discussed and estimated. Expanded relative uncertainties at the 95% confidence interval of approximately 17% are estimated for exemplar measurements made by the National Physical Laboratory (NPL) as part of the UK Heavy Metals Monitoring Network.

Brown, Richard J. C.; Brown, Andrew S.; Yardley, Rachel E.; Corns, Warren T.; Stockwell, Peter B.

362

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

363

Adapted vapour control for durable building enclosures  

Microsoft Academic Search

Well-insulated building envelope systems are subject to alternating vapour pressure gradients. Therefore the installation of traditional vapour barriers or retarders to avoid interstitial condensation may have undesirable side-effects. Numerous moisture damage cases can be attributed to the fact that a vapour barrier is nearly impermeable in both ways, i.e. it does not allow any dry-out either. Some wall and roof

H. M. Künzel

364

ELEMENTS OF LASER SETUPS: Parameters of an electric-discharge generator of iodine atoms for a chemical oxygen—iodine laser  

NASA Astrophysics Data System (ADS)

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 CH3I is used as the donor of atomic iodine. The fraction of iodine extracted from CH3I in the generator is ~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 ~3%.

Azyazov, V. N.; Vorob'ev, M. V.; Voronov, A. I.; Kupryaev, Nikolai V.; Mikheev, P. A.; Ufimtsev, N. I.

2009-01-01

365

ac Stark shift in double resonance and coherent population trapping in a wall-coated cell for compact Rb atomic clocks  

NASA Astrophysics Data System (ADS)

We present a comparative study of the light-shifts (ac Stark shift) in a Rb vapour cell using two possible schemes for Rb atomic clocks: double resonance (DR) and coherent population trapping (CPT). For both schemes, the same wall-coated cell in a compact atomic resonator was used. The light-shift resulting from a monochromatic (DR) or a non-monochromatic (CPT) optical excitation was measured as a function of the laser intensity and the laser frequency and compared with existing theoretical results.

Miletic, Danijela; Bandi, Thejesh; Affolderbach, Christoph; Mileti, Gaetano

2012-05-01

366

DICHLORVOS VAPOUR DISINSECTION OF AIRCRAFT.  

PubMed

The authors describe the testing of an automatic aircraft disinsection system permanently installed on a commercial DC-6B passenger aircraft. An air-compressor forces ambient cabin air, partially saturated with dichlorvos vapour at a set concentration, through the cabin, cockpit and baggage compartments of the aircraft for 30 minutes. Insecticide concentrations and insect mortality were observed in post-overhaul check flights, and insect mortality and passenger reactions were observed on scheduled flights between Miami, Florida, and Nassau, Bahamas.The results showed satisfactory biological efficiency. The passengers were unaware of the disinsection process and showed no signs of discomfort. PMID:14310904

JENSEN, J A; FLURY, V P; SCHOOF, H F

1965-01-01

367

Dichlorvos vapour disinsection of aircraft  

PubMed Central

The authors describe the testing of an automatic aircraft disinsection system permanently installed on a commercial DC-6B passenger aircraft. An air-compressor forces ambient cabin air, partially saturated with dichlorvos vapour at a set concentration, through the cabin, cockpit and baggage compartments of the aircraft for 30 minutes. Insecticide concentrations and insect mortality were observed in post-overhaul check flights, and insect mortality and passenger reactions were observed on scheduled flights between Miami, Florida, and Nassau, Bahamas. The results showed satisfactory biological efficiency. The passengers were unaware of the disinsection process and showed no signs of discomfort. ImagesFIG. 1FIG. 2FIG. 3 PMID:14310904

Jensen, Jens A.; Flury, Vincent P.; Schoof, Herbert F.

1965-01-01

368

Femtosecond quantum fluid dynamics of helium atom under an intense laser field  

SciTech Connect

A comprehensive, nonperturbative, time-dependent quantum mechanical (TDQM) approach is proposed for studying the dynamics of a helium atom under an intense, ultrashort (femtoseconds) laser pulse. The method combines quantum fluid dynamics (QFD) and density functional theory. It solves a single generalized nonlinear Schroedinger equation of motion (EOM), involving time and three space variables, which is obtained from two QFD equations, namely, a continuity equation and an Euler-type equation. A highly accurate finite difference scheme along with a stability analysis is presented for numerically solving the EOM. Starting from the ground-state Hartree-Fock density for He at t = 0, the EOM yields the time-dependent (TD) electron density, effective potential surface, difference density, difference effective potential, ground-state probability, {l_angle}r{r_angle}, magnetic susceptibility, polarizability, flux, etc. By a Fourier transformation of the TD dipole moment along the linearly polarized-field direction, the power and rate spectra for photoemission are calculated. eleven mechanistic routes for photoemission are identified, which include high harmonic generation as well as many other spectral transitions involving ionized, singly excited, doubly excited (autoionizing), and continuum He states, based on the evolution of the system up to a particular time. Intimate connections between photoionization and photoemission are clearly observed through computer visualizations. Apart from being consistent with current experimental and theoretical results, the present results offer certain predictions on spectral transitions which are open to experimental verification.

Dey, B.K. [Panjab Univ., Chandigarh (India). Dept. of Chemistry] [Panjab Univ., Chandigarh (India). Dept. of Chemistry; Deb, B.M. [Panjab Univ., Chandigarh (India). Dept. of Chemistry] [Panjab Univ., Chandigarh (India). Dept. of Chemistry; [Jawaharial Nehru Centre for advanced Scientific Research, Bangalore (India)

1998-10-05

369

Role of laser-driven electron-multirescattering in resonance-enhanced below-threshold harmonic generation in He atoms  

NASA Astrophysics Data System (ADS)

We present an ab initio investigation of the below-threshold harmonic generation of helium (He) atoms in few-cycle infrared laser fields by accurately solving the time-dependent Schrödinger equation and Maxwell's equation simultaneously. We find that the enhancement of the below-threshold harmonic generation only occurs to near the resonance structure of He, for which this mechanism is in agreement with the recent experimental study [M. Chini et al., Nat. Photonics 8, 437 (2014), 10.1038/nphoton.2014.83]. Moreover, we perform the quantum and semiclassical trajectories analysis, including both the atomic potential and the laser field, as well as the synchrosqueezed transform of the harmonic spectra. Our results reveal that several multirescattering trajectories contribute to the resonance-enhanced below-threshold harmonic generation.

Li, Peng-Cheng; Sheu, Yae-Lin; Laughlin, Cecil; Chu, Shih-I.

2014-10-01

370

Production efficiency of excited atoms in PDP cells with grooved dielectric structures studied by laser absorption spectroscopy  

Microsoft Academic Search

Performances of microplasmas in unit discharge cells with grooved structures in the dielectric layer covering the coplanar electrodes were investigated in alternating current (ac)-type plasma display panels filled with Ne-Xe(10%) mixture at 450 torr. The diagnostics are based on a microscopic laser-absorption spectroscopy technique for the spatiotemporally resolved measurements of absolute densities of Xe*(1s5,1s4) atoms, from which the production rate

Jun-Seok Oh; Kunihide Tachibana; Hidekazu Hatanaka; Young-Mo Kim; Seung-Hyun Son; Sang-Hun Jang

2006-01-01

371

Role of N2 molecules in pulse discharge production of I atoms for a pulsed chemical oxygen-iodine laser  

Microsoft Academic Search

A pulsed electric discharge is the most effective means to turn chemical oxygen-iodine laser (COIL) operation into the pulse mode by fast production of iodine atoms. Experimental studies and numerical simulations are performed on a pulsed COIL initiated by an electric discharge in a mixture CF3I : N2 : O2(3X) : O2(a 1Deltag) flowing out of a chemical singlet oxygen

I. V. Kochetov; A. P. Napartovich; N. P. Vagin; N. N. Yuryshev

2011-01-01

372

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 in hydrogen and metastable singly ionized helium 1312.6 nm . By using a twisted-mode cavity, we have obtained provide a precise measurement of the 2S Lamb shift.5­7 A measurement of the 2S­3S inter- val in hydrogen

Boyer, Edmond

373

Prospects for atomic magnetometers employing hollow core optical fibre  

NASA Astrophysics Data System (ADS)

Presently, among the most demanding applications for highly sensitive magnetometers are Magnetocardiography (MCG) and Magnetoencephalography (MEG), where sensitivities of around 1pT.Hz-1/2 and 1fT.Hz-1/2 are required. Cryogenic Superconducting Quantum Interference Devices (SQUIDs) are currently used as the magnetometers. However, there has been some recent work on replacing these devices with magnetometers based on atomic spectroscopy and operating at room temperature. There are demonstrations of MCG and MEG signals measured using atomic spectroscopy These atomic magnetometers are based on chip-scale microfabricated components. In this paper we discuss the prospects of using photonic crystal optical fibres or hollow core fibres (HCFs) loaded with Rb vapour in atomic magnetometer systems. We also consider new components for magnetometers based on mode-locked semiconductor lasers for measuring magnetic field via coherent population trapping (CPT) in Rb loaded HCFs.

Ironside, C. N.; Seunarine, K.; Tandoi, G.; Luiten, A. N.

2011-07-01

374

Attosecond XUV absorption spectroscopy of doubly excited states in helium atoms dressed by a time-delayed femtosecond infrared laser  

NASA Astrophysics Data System (ADS)

In the present paper, we investigate the time-resolved transient absorption spectroscopy of doubly excited states of helium atoms by solving the time-dependent two-electron Schrödinger equation numerically based on a one-dimensional model. The helium atoms are subjected to an extreme ultraviolet (XUV) attosecond pulse and a time-delayed infrared (IR) few-cycle laser pulse. A superposition of doubly excited states populated by the XUV pulse is identified, which interferes with the direct ionization pathway leading to Fano resonance profiles in the photoabsorption spectrum. In the presence of an IR laser, however, the Fano line profiles are strongly modified: A shifting, splitting, and broadening of the original absorption lines is observed when the XUV attosecond pulse and infrared few-cycle laser pulse overlap in time, which is in good agreement with recent experimental results. At certain time delays, we observe symmetric Lorentz, inverted Fano profiles, and even negative absorption cross sections indicating that the XUV light can be amplified during the interaction with atoms. We further prove that the above pictures are general for different doubly excited states by suitably varying the frequency of the IR field to coherently couple the corresponding states.

Yang, Z. Q.; Ye, D. F.; Ding, Thomas; Pfeifer, Thomas; Fu, L. B.

2015-01-01

375

Ultra-efficient ionization of heavy atoms by intense X-ray free-electron laser pulses  

NASA Astrophysics Data System (ADS)

X-ray free-electron lasers provide unique opportunities for exploring ultrafast dynamics and for imaging the structures of complex systems. Understanding the response of individual atoms to intense X-rays is essential for most free-electron laser applications. First experiments have shown that, for light atoms, the dominant interaction mechanism is ionization by sequential electron ejection, where the highest charge state produced is defined by the last ionic state that can be ionized with one photon. Here, we report an unprecedentedly high degree of ionization of xenon atoms by 1.5 keV free-electron laser pulses to charge states with ionization energies far exceeding the photon energy. Comparing ion charge-state distributions and fluorescence spectra with state-of-the-art calculations, we find that these surprisingly high charge states are created via excitation of transient resonances in highly charged ions, and predict resonance enhanced absorption to be a general phenomenon in the interaction of intense X-rays with systems containing high-Z constituents.

Rudek, Benedikt; Son, Sang-Kil; Foucar, Lutz; Epp, Sascha W.; Erk, Benjamin; Hartmann, Robert; Adolph, Marcus; Andritschke, Robert; Aquila, Andrew; Berrah, Nora; Bostedt, Christoph; Bozek, John; Coppola, Nicola; Filsinger, Frank; Gorke, Hubert; Gorkhover, Tais; Graafsma, Heinz; Gumprecht, Lars; Hartmann, Andreas; Hauser, Günter; Herrmann, Sven; Hirsemann, Helmut; Holl, Peter; Hömke, André; Journel, Loic; Kaiser, Christian; Kimmel, Nils; Krasniqi, Faton; Kühnel, Kai-Uwe; Matysek, Michael; Messerschmidt, Marc; Miesner, Danilo; Möller, Thomas; Moshammer, Robert; Nagaya, Kiyonobu; Nilsson, Björn; Potdevin, Guillaume; Pietschner, Daniel; Reich, Christian; Rupp, Daniela; Schaller, Gerhard; Schlichting, Ilme; Schmidt, Carlo; Schopper, Florian; Schorb, Sebastian; Schröter, Claus-Dieter; Schulz, Joachim; Simon, Marc; Soltau, Heike; Strüder, Lothar; Ueda, Kiyoshi; Weidenspointner, Georg; Santra, Robin; Ullrich, Joachim; Rudenko, Artem; Rolles, Daniel

2012-12-01

376

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

377

Temporal and spatial evolution of Si atoms in plasmas produced by a nanosecond laser ablating silicon carbide crystals.  

PubMed

Optical emission spectroscopy (OES) was used to study the evolution behavior of the neutral Si atoms in the plasma produced by nanosecond pulsed-laser beam irradiating on SiC crystal targets. The OES measurements indicated that the electron temperature and density in the plasma had maximum values around a region about 2mm from the target surface. Based on the temporal and spatial evolution of the spectral line at 633.19 nm originating from excited Si atoms, it was found that these Si atoms have short decay times and long range spatial distribution in vacuum. At the initial growth stage of SiC thin films using pulsed-laser deposition (PLD) technique, these Si atoms were found possibly to arrive at the Si substrate to form defects near the SiC/Si interface. By comparing the OES result measured in vacuum and that measured in ambient air, it was deduced that by properly adjusting the background gas species and pressure, the quality of the films prepared by PLD technique may be improved. PMID:19658821

Chen, Ming; Liu, Xiangdong; Zhao, Mingwen; Chen, Chuansong; Man, Baoyuan

2009-07-01

378

Water Vapour Isotopes in the Stratosphere  

Microsoft Academic Search

ABSTRACT Water vapour can be used as a tracer of the dynamics in the stratosphere, not only because of its long lifetime but also because ,the inflow through ,the tropical tropopause ,follows an annual cycle. An overview of areas where we can gain new knowledge,about the stratosphere and its dynamics ,using water vapour is given. A promising ,new ,tool for

M. Ridal

379

Optimal operation of simple vapour compression cycles  

E-print Network

W to above 100 MW. Most of these applications use the vapor compression cycle to "pump" energy from a lowChapter 1 Optimal operation of simple vapour compression cycles 1.1 Introduction Cyclic processes). This mixture is vaporized and heated through the evaporator giving a super-heated vapour (4) closing the cycle

Skogestad, Sigurd

380

Photothermal excitation and laser Doppler velocimetry of higher cantilever vibration modes for dynamic atomic force microscopy in liquid  

SciTech Connect

The authors present an optically based method combining photothermal excitation and laser Doppler velocimetry of higher cantilever vibration modes for dynamic atomic force microscopy in liquid. The frequency spectrum of a silicon cantilever measured in water over frequencies ranging up to 10 MHz shows that the method allows us to excite and detect higher modes, from fundamental to fifth flexural, without enhancing spurious resonances. By reducing the tip oscillation amplitude using higher modes, the average tip-sample force gradient due to chemical bonds is effectively increased to achieve high-spatial-resolution imaging in liquid. The method's performance is demonstrated by atomic resolution imaging of a mica surface in water obtained using the second flexural mode with a small tip amplitude of 99 pm; individual atoms on the surface with small height differences of up to 60 pm are clearly resolved.

Nishida, Shuhei; Kobayashi, Dai; Sakurada, Takeo; Nakazawa, Tomonori; Hoshi, Yasuo; Kawakatsu, Hideki [Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan)

2008-12-15

381

Zeeman effects in the hyperfine structure of atomic iodine photodissociation laser emission.  

NASA Technical Reports Server (NTRS)

Observation of hyperfine structure in laser emission from CF3I and C2F5I photodissociation lasers. Constant magnetic fields affect the time behavior of the emission by changing the relative gains of the hyperfine transitions. Time-varying fields usually present in photodissociation lasers further complicate the emission.

Hwang, W. C.; Kasper, J. V. V.

1972-01-01

382

Low phase noise diode laser oscillator for 1S2S spectroscopy in atomic hydrogen  

E-print Network

external cavity diode laser with an intracavity electro-optical modulator. The fractional power-stabilized diode lasers have become a power- ful tool for high-resolution spectroscopy and precise optical on a frequency- quadrupled master-oscillator power-amplifier diode laser system for high-resolution two-photon 1S

Hänsch, Theodor W.

383

LASERS AND PHYSICAL PROCESSES IN THEM: A more accurate method of measuring the cross section for the 52P1\\/2-->52P3\\/2 transition of atomic iodine in photodissociation lasers based on dynamic self-diffraction  

Microsoft Academic Search

We have developed a new method for measuring the cross section for the 52P1\\/2-->52P3\\/2 transition of atomic iodine in photodissociation lasers. The inverse recombination of iodine atoms is monitored via dynamic self-diffraction of the laser radiation in the active medium. We have measured the cross section in mixtures of H-C3F7I and CF3I with Xe. This new method substantially increases the

K. S. Korol'kov; A. Yu Krylov; O. Yu Nosach; E. P. Orlov

1992-01-01

384

Mesoscale modelling of water vapour in the tropical UTLS: two case studies from the HIBISCUS campaign  

NASA Astrophysics Data System (ADS)

In this study, we evaluate the ability of the BRAMS mesoscale model compared to ECMWF global analysis to simulate the observed vertical variations of water vapour in the tropical upper troposphere and lower stratosphere (UTLS). The observations are balloon-borne measurements of water vapour mixing ratio and temperature from micro-SDLA (Tunable Diode Laser Spectrometer) instrument. Data from two balloon flights performed during the 2004 HIBISCUS field campaign are used to compare with the mesoscale simulations and to ECMWF analysis. The mesoscale model performs significantly better than ECMWF analysis for water vapour in the upper troposphere and similarly or slightly worse for temperature. The improvement provided by the mesoscale model for water vapour comes mainly from (i) the enhanced vertical resolution in the UTLS (250 m for BRAMS and ~1 km for ECMWF model) and (ii) the more detailed microphysical parameterization providing ice supersaturations as in the observations. The ECMWF vertical resolution (~1 km) is too coarse to capture the observed fine scale vertical variations of water vapour in the UTLS. In near saturated or supersaturated layers, the mesoscale model relative humidity with respect to ice saturation is close to observations provided that the temperature profile is realistic. For temperature, ECMWF analysis gives good results partly thanks to data assimilation. The analysis of the mesoscale model results showed that in undersaturated layers, the water vapour profile depends mainly on the dynamics. In saturated/supersaturated layers, microphysical processes play an important role and have to be taken into account on top of the dynamical processes to understand the water vapour profiles. In the lower stratosphere, the ECMWF model and the BRAMS model give very similar water vapour profiles that are significantly dryer than micro-SDLA measurements. This similarity comes from the fact that BRAMS is initialised using ECMWF analysis and that no mesoscale process acts in the stratosphere leading to no modification of the BRAMS results with respect to ECMWF analysis.

Marécal, V.; Durry, G.; Longo, K.; Freitas, S.; Rivière, E. D.; Pirre, M.

2006-08-01

385

Physical properties of vapour grown indium monotelluride platelets  

NASA Astrophysics Data System (ADS)

Indium monotelluride (InTe) crystals were grown from vapour phase under different temperature gradients by employing physical vapour deposition (PVD) method. The morphology of these crystals such as whiskers, needles, platelets etc., strongly depends on the temperature distribution in the horizontal dual zone furnace. InTe platelets were deposited by setting the temperature of the charge (TC) and growth (TS) zones at 1073 K and 773 K (?T=300 K), respectively, for different growth periods (24 h, 48 h, 72 h and 96 h). The surface growth features have been analyzed by scanning electron microscopes, which indicate layer growth mechanism for all the crystals. Various crystals grown under ?T=200 K and 300 K (retaining TS invariant) were examined by X-ray diffraction and elemental analysis. InTe samples exhibited consistent lattice parameters, density and atomic percentage, establishing stoichiometry and chemical homogeneity. The results obtained for Seebeck coefficient, electrical conductivity, power factor, dislocation density and microhardness are found to be reproducible as well. The vapour deposited InTe platelets are mechanically stable and possess high value of TEP, which ensure their practical application in thermoelectric power generation.

Kunjomana, A. G.; Chandrasekharan, K. A.; Teena, M.

2015-02-01

386

Fluorescence spectroscopy of kerosene vapour at high temperatures and pressures: potential for gas turbines measurements  

NASA Astrophysics Data System (ADS)

Laser-induced fluorescence spectroscopy of kerosene vapour was performed in a heated test cell operating between 450 and 900 K, at pressure from 0.1 to 3.0 MPa, for oxygen molar fraction between 0 and 21 %, with different laser excitation wavelengths (248, 266, 282 and 308 nm). Results show that, depending on the laser excitation scheme, kerosene fluorescence spectrum exhibits one or two fluorescence bands in the UV-visible range (attributed to aromatics naturally present in kerosene fuel). Fluorescence intensity of these bands decreases with increasing temperature, pressure and oxygen molar fraction. Different imaging strategies were derived from spectroscopic findings to simultaneously measure temperature and equivalence ratio fields in kerosene/air sprays, or flame structure and fuel spatial distribution in kerosene/air aeronautical combustors, by means of planar laser-induced fluorescence on kerosene vapour (K-PLIF).

Orain, M.; Baranger, P.; Ledier, C.; Apeloig, J.; Grisch, F.

2014-09-01

387

Atomic force microscopy analysis of human cornea surface after UV (?=266 nm) laser irradiation  

NASA Astrophysics Data System (ADS)

Efficient cornea reshaping by laser irradiation for correcting refractive errors is still a major issue of interest and study. Although the excimer laser wavelength of 193 nm is generally recognized as successful in ablating corneal tissue for myopia correction, complications in excimer refractive surgery leads to alternative laser sources and methods for efficient cornea treatment. In this work, ablation experiments of human donor cornea flaps were conducted with the 4th harmonic of an Nd:YAG laser, with different laser pulses. AFM analysis was performed for examination of the ablated cornea flap morphology and surface roughness.

Spyratou, E.; Makropoulou, M.; Moutsouris, K.; Bacharis, C.; Serafetinides, A. A.

2009-07-01

388

Volumetric intensity dependence on the formation of molecular and atomic ions within a high intensity laser focus.  

PubMed

The mechanism of atomic and molecular ionization in intense, ultra-short laser fields is a subject which continues to receive considerable attention. An inherent difficulty with techniques involving the tight focus of a laser beam is the continuous distribution of intensities contained within the focus, which can vary over several orders of magnitude. The present study adopts time of flight mass spectrometry coupled with a high intensity (8 x 10(15) Wcm(-2)), ultra-short (20 fs) pulse laser in order to investigate the ionization and dissociation of the aromatic molecule benzene-d1 (C(6)H(5)D) as a function of intensity within a focused laser beam, by scanning the laser focus in the direction of propagation, while detecting ions produced only in a "thin" slice (400 and 800 microm) of the focus. The resultant TOF mass spectra varies significantly, highlighting the dependence on the range of specific intensities accessed and their volumetric weightings on the ionization/dissociation pathways accessed. PMID:15653366

Robson, Lynne; Ledingham, Kenneth W D; McKenna, Paul; McCanny, Thomas; Shimizu, Seiji; Yang, Jiamin M; Wahlström, Claes-Göran; Lopez-Martens, Rodrigo; Varju, Katalin; Johnsson, Per; Mauritsson, Johan

2005-01-01

389

Acquired acid resistance of human enamel treated with laser (Er:YAG laser and Co2 laser) and acidulated phosphate fluoride treatment: An in vitro atomic emission spectrometry analysis  

PubMed Central

Background: Dental caries is essentially a process of diffusion and dissolution. If the aspect of dissolution can be curtailed some degree of prevention can be achieved. Aims: The present study was carried out to evaluate and compare the effect of Er:YAG laser and Co2 laser irradiation combined with acidulated phosphate fluoride treatment on in vitro acid resistance of human enamel. Design: An in vitro study was carried out on 30 human premolars to evaluate the enamel's acid resistance using an atomic emission spectrometry analysis. Materials and Methods: A total of 60 enamel specimens were prepared from 30 human premolars and were randomly assigned to 6 groups: (1) Untreated (control); (2) 1.23% acidulated phosphate fluoride (APF) gel application alone for 4 min; (3) Er:YAG laser treatment alone; (4) Co2 laser treatment alone; (5) Er:YAG laser + APF gel application; (6) Co2 laser + APF gel application. The specimens were then individually immersed in 5 ml of acetate buffer solution (0.1 mol/L, pH 4.5) and incubated at 37°C for 24 h, and the acid resistance was evaluated by determining the calcium ion concentration using the atomic emission spectrometry. Statistical Analysis: An ANOVA model was constructed (P value of 0.05), followed by Tukey's test for multiple pair wise comparisons of mean values. Results: Significant differences were found between the control group and the test groups (P < 0.001). Conclusions: Combining acidulated phosphate fluoride with either Er:YAG or Co2 laser had a synergistic effect in decreasing the enamel demineralization more than either fluoride treatment or laser treatment alone. PMID:24015004

Mathew, Anju; Reddy, N. Venugopal; Sugumaran, D. K.; Peter, Joby; Shameer, M.; Dauravu, Liju Marcely

2013-01-01

390

Quantum cascade laser-based measurement of metal alkylamide density during atomic layer deposition.  

PubMed

An in situ gas-phase diagnostic for the metal alkylamide compound tetrakis(ethylmethylamido) hafnium (TEMAH), Hf[N(C(2)H(5))(CH(3))](4), was demonstrated. This diagnostic is based on direct absorption measurement of TEMAH vapor using an external cavity quantum cascade laser emitting at 979 cm(-1), coinciding with the most intense TEMAH absorption in the mid-infrared spectral region, and employing 50 kHz amplitude modulation with synchronous detection. Measurements were performed in a single-pass configuration in a research-grade atomic layer deposition (ALD) chamber. To examine the detection limit of this technique for use as a TEMAH delivery monitor, this technique was demonstrated in the absence of any other deposition reactants or products, and to examine the selectivity of this technique in the presence of deposition products that potentially interfere with detection of TEMAH vapor, it was demonstrated during ALD of hafnium oxide using TEMAH and water. This technique successfully detected TEMAH at molecular densities present during simulated industrial ALD conditions. During hafnium oxide ALD using TEMAH and water, absorbance from gas-phase reaction products did not interfere with TEMAH measurements while absorption by reaction products deposited on the optical windows did interfere, although interfering absorption by deposited reaction products corresponded to only ?4% of the total derived TEMAH density. With short measurement times and appropriate signal averaging, estimated TEMAH minimum detectable densities as low as ?2 × 10(12) molecules/cm(3) could be obtained. While this technique was demonstrated specifically for TEMAH delivery and hafnium oxide ALD using TEMAH and water, it should be readily applicable to other metal alkylamide compounds and associated metal oxide and nitride deposition chemistries, assuming similar metal alkylamide molar absorptivity and molecular density in the measurement chamber. PMID:22449311

Maslar, James E; Kimes, William A; Sperling, Brent A

2012-03-01

391

Atom probe tomography characterisation of a laser diode structure grown by molecular beam epitaxy  

SciTech Connect

Atom probe tomography (APT) has been used to achieve three-dimensional characterization of a III-nitride laser diode (LD) structure grown by molecular beam epitaxy (MBE). Four APT data sets have been obtained, with fields of view up to 400 nm in depth and 120 nm in diameter. These data sets contain material from the InGaN quantum well (QW) active region, as well as the surrounding p- and n-doped waveguide and cladding layers, enabling comprehensive study of the structure and composition of the LD structure. Two regions of the same sample, with different average indium contents (18% and 16%) in the QW region, were studied. The APT data are shown to provide easy access to the p-type dopant levels, and the composition of a thin AlGaN barrier layer. Next, the distribution of indium within the InGaN QW was analyzed, to assess any possible inhomogeneity of the distribution of indium (''indium clustering''). No evidence for a statistically significant deviation from a random distribution was found, indicating that these MBE-grown InGaN QWs do not require indium clusters for carrier localization. However, the APT data show steps in the QW interfaces, leading to well-width fluctuations, which may act to localize carriers. Additionally, the unexpected presence of a small amount (x = 0.005) of indium in a layer grown intentionally as GaN was revealed. Finally, the same statistical method applied to the QW was used to show that the indium distribution within a thick InGaN waveguide layer in the n-doped region did not show any deviation from randomness.

Bennett, Samantha E.; Humphreys, Colin J.; Oliver, Rachel A. [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge, CB2 3QZ (United Kingdom); Smeeton, Tim M.; Hooper, Stewart E.; Heffernan, Jonathan [Sharp Laboratories of Europe Limited, Edmund Halley Road, Oxford Science Park, Oxford, OX4 4GB (United Kingdom); Saxey, David W.; Smith, George D. W. [Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH (United Kingdom)

2012-03-01

392

One-dimensional Thomas-Fermi model of atoms, molecules, and small clusters exposed to an intense laser field  

NASA Astrophysics Data System (ADS)

We have developed a one-dimensional time-dependent Thomas-Fermi model of atoms, molecules, and small clusters exposed to an intense subpicosecond laser field. In this model, the dynamics of an electronic cloud is governed by the hydrodynamic equations of motion, whereas the nuclei move in accordance with the Newton equations. The quantum mechanics enters in this approach only through the constitutive relation between the pressure and the density, which is derived from the application of Fermi-Dirac statistics to a noninteracting T=0 temperature electron gas. The time-independent version of the model, formulated in terms of the integral equation for the electric potential, is also discussed. We present numerical results for diatomic molecules and small clusters irradiated by the strong laser pulses. In the case of molecules, we observe the multielectron ionization accompanied by dissociation. The kinetic energy defect, understood as a reduction of the energy of resulting ions in comparison with a simple Coulomb explosion picture, is explained in terms of a screening effect of escaping fragments by the ejected electrons. For small clusters we find that the explosion of the cluster has a stepwise character; the consecutive layers of atoms are stripped off one by one. We observe the highly energetic (as compared with diatomic systems) atomic fragments even for relatively low laser intensities and a few atoms clusters. Also, the model predicts the nonuniform energy distribution among the same charge state ions and supports the idea of hot electrons generated in the cluster via a mechanism of inverse bremsstrahlung.

Brewczyk, Miros?aw; Rza?ewski, Kazimierz

1999-09-01

393

Effect of electron correlation on high-order-harmonic generation of helium atoms in intense laser fields: Time-dependent generalized pseudospectral approach in hyperspherical coordinates  

E-print Network

Effect of electron correlation on high-order-harmonic generation of helium atoms in intense laser. The procedure is applied to the investigation of high-order-harmonic generation HHG of helium atoms states and the role of the individual spin orbital can- not be explicitly treated. The recent development

Chu, Shih-I

394

State-insensitive dichromatic optical-dipole trap for rubidium atoms: calculation and the dicromatic laser's realization  

NASA Astrophysics Data System (ADS)

Magic wavelength optical-dipole trap (ODT) allows confinement of neutral atoms and cancellation of the position-dependent spatially inhomogeneous differential light shift for a desired atomic transition. The light shift of the 87Rb 5P3/2 state can be expediently tailored to be equal to that of the 87Rb 5S1/2 state by employing dicromatic (?1 + ?2 (here ?2 = 2?1 ˜ 1.5 µm)) linearly polarized ODT lasers. In our calculation, two sets of state-insensitive dichromatic (784.3 + 1568.6 nm and 806.4 + 1612.8 nm) are obtained for the 87Rb 5S1/2 (F = 2) - 5P3/2 (F? = 3) transition. Further, 784.3 + 1568.6 nm dicromatic laser system with a moderate output power has been realized experimentally by marrying efficient second-harmonic generation using a PPMgO:LN bulk crystal with a fibre-amplified 1.5 µm telecom laser.

Wang, Junmin; Guo, Shanlong; Ge, Yulong; Cheng, Yongjie; Yang, Baodong; He, Jun

2014-05-01

395

Mechanism of pulse discharge production of iodine atoms from CF3I molecules for a chemical oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

The pulsed chemical oxygen-iodine laser (COIL) development is aimed at many new applications. Pulsed electric discharge is most effective in turning COIL operation into the pulse mode by instant production of iodine atoms. A numerical model is developed for simulations of the pulsed COIL initiated by an electric discharge. The model comprises a system of kinetic equations for neutral and charged species, electric circuit equation, gas thermal balance equation and the photon balance equation. Reaction rate coefficients for processes involving electrons are found by solving the electron Boltzmann equation, which is re-calculated in a course of computations when plasma parameters changed. The processes accounted for in the Boltzmann equation include excitation and ionization of atoms and molecules, dissociation of molecules, electron attachment processes, electron-ion recombination, electron-electron collisions, second-kind collisions and stepwise excitation of molecules. The last processes are particularly important because of a high singlet oxygen concentration in gas flow from the singlet oxygen chemical generator. Results of numerical simulations are compared with experimental laser pulse waveforms. It is concluded that there is satisfactory agreement between theory and the experiment. The prevailing mechanism of iodine atom formation from the CF3I donor in a very complex kinetic system of the COIL medium under pulse discharge conditions, based on their detailed numerical modelling and by comparing these results both with experimental results of other authors and their own experiments, is established. The dominant iodine atom production mechanism for conditions under study is the electron-impact dissociation of CF3I molecules. It was proved that in the conditions of the experiment the secondary chemical reactions with O atoms play an insignificant role.

Kochetov, I. V.; Napartovich, A. P.; Vagin, N. P.; Yuryshev, N. N.

2009-03-01

396

Laser-excited atomic fluorescence spectrometry in a graphite furnace with an  

E-print Network

, for the ® rst time, that solid-state lasers required for analysis (ml or mg) and the technique has direct based not dye lasers,5 the tunability of solid-state dye lasers is still as necessary owing to the long and by the development of dye-doped host materials for solid-state 460 ng ml� 1 for manganese. Di erent dilutions were

Michel, Robert G.

397

Photonic tunneling effect between two coupled single-atom laser cavities imbedded within a photonic-crystal platform  

SciTech Connect

In this paper we investigate the photonic tunneling effect between two coupled one-atom laser cavities. The physical system consists of two coupled photonic crystal microcavities and each cavity contains a coherently pumped two-level atom. The dynamics of the system can be described by the master equation in terms of the reduced density operator. It is shown that the photonic tunneling behavior depends on certain physical conditions of the system. In the absence of the pumping field and without dissipations, the coherent photon number imbalance between two cavities exhibits the alternating-current Josephson effect. However, when the pumping effect and losses of the system are taken into account, the mean photon number imbalance displays a damped oscillation. In addition, the influence of tunneling amplitude and photonic band-gap structure on the oscillations is also studied. The research gives a further insight into the correlated dynamics of two coupled one-atom laser systems and provides an idea for constructing novel photon tunnel devises.

Guo Xiaoyong [Department of Physics, Nanjing University, Nanjing 210093 (China); Ren Zhongzhou [Department of Physics, Nanjing University, Nanjing 210093 (China); Center of Theoretical Nuclear Physics, National Laboratory of Heavy-Ion Accelerator, Lanzhou 730000 (China)

2011-01-15

398

Effect of the electronic structure of target atoms on the emission continuum of laser plasma  

SciTech Connect

The low-temperature laser plasma at the surface of metal targets is experimentally investigated. Continuous spectra emitted from a laser plume are found to be similar for targets consisting of the elements of the same subgroup of the Mendeleev periodic table. The similarity manifests itself both in the dependence of the emission intensity on the external pressure and in the structure of absorption bands related to a fine-dispersed phase existing in the peripheral regions of the plume. (interaction of laser radiation with matter. laser plasma)

Kask, Nikolai E; Michurin, Sergei V; Fedorov, Gennadii M [D.V. Skobel'tsyn Institute of Nuclear Physics, M.V. Lomonosov Moscow State University, Moscow (Russian Federation)

2004-06-30

399

In-source laser spectroscopy of polonium isotopes: From atomic physics to nuclear structure  

E-print Network

The Resonance Ionization Laser Ion Source RILIS [1] at the CERN-ISOLDE on-line radioactive ion beam facility is essential for ion beam production for the majority of experiments, but it is also powerful tool for laser spectroscopy of rare isotopes. A series of experiments on in-source laser spectroscopy of polonium isotopes [2, 3] revealed the nuclear ground state properties of 191;211;216;218Po. However, limitations caused by the isobaric background of surface-ionized francium isotopes hindered the study of several neutron rich polonium isotopes. The development of the Laser Ion Source and Trap (LIST) [4] and finally its integration at ISOLDE has led to a dramatic suppression of surface ions. Meanwhile, the RILIS laser spectroscopy capabilities have advanced tremendously. Widely tunable titanium:sapphire (Ti:Sa) lasers were installed to complement the established dye laser system. Along with a new data acquisition system [5], this more versatile laser setup enabled rst ever laser spectroscopy of the radioact...

Rothe, S

2014-01-01

400

Two-Photon Laser-Induced Fluorescence O and N Atoms for the Study of Heterogeneous Catalysis in a Diffusion Reactor  

NASA Technical Reports Server (NTRS)

Advanced laser-based diagnostics have been developed to examine catalytic effects and atom/surface interactions on thermal protection materials. This study establishes the feasibility of using laser-induced fluorescence for detection of O and N atom loss in a diffusion tube to measure surface catalytic activity. The experimental apparatus is versatile in that it allows fluorescence detection to be used for measuring species selective recombination coefficients as well as diffusion tube and microwave discharge diagnostics. Many of the potential sources of error in measuring atom recombination coefficients by this method have been identified and taken into account. These include scattered light, detector saturation, sample surface cleanliness, reactor design, gas pressure and composition, and selectivity of the laser probe. Recombination coefficients and their associated errors are reported for N and O atoms on a quartz surface at room temperature.

Pallix, Joan B.; Copeland, Richard A.; Arnold, James O. (Technical Monitor)

1995-01-01

401

Spectral minimum and giant enhancement in photoelectron spectra from xenon atoms driven by intense midinfrared laser fields.  

PubMed

Our theoretical study shows that the spectral minimum and the giant enhancement structures observed in the high harmonic spectra also exist in the photoelectron spectra from driven Xe atoms. They are attributed to the inherent property of the radial part of the wave function of the Xe 5p subshell in momentum space. The spectral minimum is caused by the nodal point in the modulus of the radial wave function in momentum space, and the giant enhancement reflects the increase in magnitude of the modulus of the wave function. To observe these structures, midinfrared lasers of about 0.2 PW/cm(2) intensity are preferred. Employing circularly polarized laser light is suggested for exhibiting these structures in photoelectron spectra. PMID:23432239

Zhang, Jingtao; Guo, D-S

2013-02-01

402

Polarization-stable vertical-cavity surface-emitting lasers with inverted grating relief for use in microscale atomic clocks  

NASA Astrophysics Data System (ADS)

Vertical-cavity surface-emitting lasers (VCSELs) with single-mode, single-polarization emission at a wavelength of 894.6 nm have become attractive light sources for miniaturized Cs-based atomic clocks. So far, VCSELs used for these applications are single-mode because of small active diameters which has the drawbacks of increased ohmic resistance and reduced lifetime. By employing surface grating reliefs, enhanced fundamental-mode emission as well as polarization-stable laser oscillation are achieved. VCSELs with 5 ?m active diameter show side-mode suppression ratios of 20 dB even at currents close to thermal roll-over with orthogonal polarization suppression ratios better than 20 dB at elevated ambient temperatures up to 100 °C.

Al-Samaneh, A.; Bou Sanayeh, M.; Miah, M. J.; Schwarz, W.; Wahl, D.; Kern, A.; Michalzik, R.

2012-10-01

403

Theoretical and experimental (e ,2 e ) study of electron-impact ionization of laser-aligned Mg atoms  

NASA Astrophysics Data System (ADS)

We have performed calculations of the fully differential cross sections for electron-impact ionization of magnesium atoms. Three theoretical approximations, the time-dependent close coupling, the three-body distorted wave, and the distorted wave Born approximation, are compared with experiment in this article. Results will be shown for ionization of the 3 s ground state of Mg for both asymmetric and symmetric coplanar geometries. Results will also be shown for ionization of the 3 p state which has been excited by a linearly polarized laser which produces a charge cloud aligned perpendicular to the laser beam direction and parallel to the linear polarization. Theoretical and experimental results will be compared for several different alignment angles, both in the scattering plane as well as in the plane perpendicular to the incident beam direction.

Amami, Sadek; Murray, Andrew; Stauffer, Al; Nixon, Kate; Armstrong, Gregory; Colgan, James; Madison, Don

2014-12-01

404

Spectropolarimetric measurement of populations in degenerated atomic systems with metastable lower level during optical pumping in intense laser fields  

NASA Astrophysics Data System (ADS)

The prospects for application of a nonlinear laser polarization spectroscopy for measuring the steady-state population characteristics in the degenerated atomic systems with metastable lower state during optical pumping in intense laser fields are considered. It is shown that a combination of the polarization spectroscopy of a probe field and the Faraday effect allows to measure immediately the population differences for "enriched " and "depleted" Zeeman's sub-levels during the process of optical pumping as well as for optical coupled sub-levels of lower and upper states of the transition. The experimental results for the 1 s5?2 p2 (J=2?J=1) and 1 s5?2 p4 (J=2?J=2) Ne20 transitions and their comparison are given.

Dvoryanchikov, A. G.; Kartashov, I. A.; Shishaev, A. V.

2002-09-01

405

The Saga of Light-Matter Interaction and Magneto-optical Effects Applications to Atomic Magnetometry, Laser-cooled Atoms, Atomic Clocks, Geomagnetism, and Plant Bio-magnetism  

NASA Astrophysics Data System (ADS)

The quest to expand the limited sensorial domain, in particular to bridge the inability to gauge magnetic fields near and far, has driven the fabrication of remedial tools. The interaction of ferromagnetic material with a magnetic field had been the only available technique to gauge that field for several millennium. The advent of electricity and associated classical phenomena captured in the four Maxwell equations, were a step forward. In the early 1900s, the model of quantum mechanics provided a two-way leap forward. One came from the newly understood interaction of light and matter, and more specifically the three-way coupling of photons, atoms' angular momenta, and magnetic field, which are the foundations of atomic magnetometry. The other came from magnetically sensitive quantum effects in a fabricated energy-ladder form of matter cooled to a temperature below that of the energy steps; these quantum effects gave rise to the superconducting quantum interference device (SQUID). Research using atomic magnetometers and SQUIDs has resulted in thousands of publications, text books, and conferences. The current status in each field is well described in Refs. [48,49,38,42] and all references therein. In this work we develop and investigate techniques and applications pertaining to atomic magnetometry. [Full text: eric.corsini gmail.com].

Corsini, Eric P.

406

Phase-locked laser system for use in atomic coherence experiments Alberto M. Marinoa  

E-print Network

or an electro-optic modulator EOM . However, this is not possible when the frequency separation between operating around 795 nm. A low-power laser serves as a frequency reference for two high-power lasers which. Stroud, Jr. The Institute of Optics, University of Rochester, Rochester, New York 14627, USA Received 18

Stroud, Carlos R.

407

Two-mode single-atom laser as a source of entangled light RID A-5077-2009  

E-print Network

Two-mode single-atom laser as a source of entangled light M. Kiffner,1,* M. S. Zubairy,1,2,3,? J. Evers,1,? and C. H. Keitel1,? 1Max-Planck-Institut f?r Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany 2Institute for Quantum Studies... and Department of Physics, Texas A&M University, College Station, Texas 77843, USA 3Texas A&M University at Qatar, Education City, P.O. Box 23874, Doha, Qatar #1;Received 22 December 2006; revised manuscript received 25 January 2007; published 28 March 2007#2...

Kiffner, M.; Zubairy, M. Suhail; Evers, J.; Keitel, C. H.

2007-01-01

408

Nanoscale bending movement of biological micro-object induced by femtosecond laser impulse and its detection by atomic force microscopy  

NASA Astrophysics Data System (ADS)

A horizontal vibrational motion of biological tissue generated by a femtosecond laser-induced impulsive force was directly detected for the first time as angular shift of the cantilever of an atomic force microscope (AFM), which was directly in contact with the tissue. The motion of a small plant stem (diameter: 160 µm) on the force loading was detected by the torsional motion of the AFM cantilever. The sensitivity of the method was evaluated by a numerical simulation with the finite element method (FEM). The results conclusively demonstrated the efficacy of this method for nano-scale detection of the horizontal motion of biological micro-objects.

Takenaka, Masanobu; Iino, Takanori; Nagatani, Akira; Hosokawa, Yoichiroh

2014-08-01

409

Using Lasers and X-rays to Reveal the Motion of Atoms and Electrons (LBNL Summer Lecture Series)  

ScienceCinema

Summer Lecture Series 2009: 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.

Schoenlein, Robert [Deputy Director, Advanced Light Source

2011-04-28

410

Using Lasers and X-rays to Reveal the Motion of Atoms and Electrons (LBNL Summer Lecture Series)  

SciTech Connect

Summer Lecture Series 2009: 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.

Schoenlein, Robert (Deputy Director, Advanced Light Source) [Deputy Director, Advanced Light Source

2009-07-07

411

A new time-frequency method to reveal quantum dynamics of atomic hydrogen in intense laser pulses: Synchrosqueezing transform  

NASA Astrophysics Data System (ADS)

This study introduces a new adaptive time-frequency (TF) analysis technique, the synchrosqueezing transform (SST), to explore the dynamics of a laser-driven hydrogen atom at an ab initio level, upon which we have demonstrated its versatility as a new viable venue for further exploring quantum dynamics. For a signal composed of oscillatory components which can be characterized by instantaneous frequency, the SST enables rendering the decomposed signal based on the phase information inherited in the linear TF representation with mathematical support. Compared with the classical type of TF methods, the SST clearly depicts several intrinsic quantum dynamical processes such as selection rules, AC Stark effects, and high harmonic generation.

Sheu, Yae-lin; Hsu, Liang-Yan; Wu, Hau-tieng; Li, Peng-Cheng; Chu, Shih-I.

2014-11-01

412

A new time-frequency method to reveal quantum dynamics of atomic hydrogen in intense laser pulses: Synchrosqueezing Transform  

E-print Network

This study introduces a new adaptive time-frequency (TF) analysis technique, synchrosqueezing transform (SST), to explore the dynamics of a laser-driven hydrogen atom at an {\\it ab initio} level, upon which we have demonstrated its versatility as a new viable venue for further exploring quantum dynamics. For a signal composed of oscillatory components which can be characterized by instantaneous frequency, the SST enables rendering the decomposed signal based on the phase information inherited in the linear TF representation with mathematical support. Compared with the classical type TF methods, the SST clearly depicts several intrinsic quantum dynamical processes such as selection rules, AC Stark effects, and high harmonic generation.

Sheu, Yae-lin; Wu, Hau-tieng; Li, Peng-Cheng; Chu, Shih-I

2014-01-01

413

Long-distance channeling of cold atoms exiting a 2D magneto-optical trap by a Laguerre-Gaussian laser beam.  

PubMed

Using a blue-detuned laser, shaped into a nearly Laguerre-Gaussian (LG) donut mode, we channel atoms exiting a two-dimensional magneto-optical trap (2D-MOT) over a 30 cm distance. Compared to a freely propagating beam, the atomic flux (?10(10) at/s) is conserved whereas the divergence is reduced from 40 to 3 mrad. So, 30 cm far the 2D-MOT exit, the atomic beam has a 1 mm diameter and the atomic density is increased by a factor of ?200. The LG-channeled-2D-MOT has been studied versus the order of the LG mode (from 2 to 10) and versus the laser-atom frequency detuning (from 2 to 120 GHz). PMID:24487908

Carrat, Vincent; Cabrera-Gutiérrez, Citlali; Jacquey, Marion; Tabosa, José W; Viaris de Lesegno, Bruno; Pruvost, Laurence

2014-02-01

414

Optical force on two-level atoms by few-cycle-pulse Gaussian laser fields beyond the rotating-wave approximation  

SciTech Connect

We report a study on light force on a beam of neutral two-level atoms superimposed upon a few-cycle-pulse Gaussian laser field under both resonant and off-resonant conditions. The phenomena of focusing, defocusing, and steering of the neutral atoms in the laser field are analyzed by solving the optical Bloch equation beyond the rotating-wave approximation and the force equation self-consistently. We find that two-level atoms in an atomic beam can be focused and defocused for large, positively and negatively detuned interactions even in the regime of extreme nonlinear optics. The so-called optical potential may be used for stable trapping of the neutral two-level atoms for large positively detuned interaction. This work successfully reproduces some of the features reported in recent experimental and theoretical works.

Kumar, Parvendra; Sarma, Amarendra K. [Department of Physics, Indian Institute of Technology Guwahati, Guwahati-781039, Assam (India)

2011-10-15

415

Two-dimensional atom localization in a four-level tripod system in laser fields  

SciTech Connect

We propose a scheme for two-dimensional (2D) atom localization in a four-level tripod system under an influence of two orthogonal standing-wave fields. Position information of the atom is retained in the atomic internal states by an additional probe field either of a standing or of a running wave. It is shown that the localization factors depend crucially on the atom-field coupling that results in such spatial structures of populations as spikes, craters, and waves. We demonstrate a high-precision localization due to measurement of population in the upper state or in any ground state.

Ivanov, Vladimir [Turku Centre for Quantum Physics, Department of Physics and Astronomy, University of Turku, FIN-20014 Turku (Finland); Saint Petersburg State University of Information Technologies, Mechanics and Optics, 197101 St. Petersburg (Russian Federation); Rozhdestvensky, Yuri [Saint Petersburg State University of Information Technologies, Mechanics and Optics, 197101 St. Petersburg (Russian Federation)

2010-03-15

416

Three-dimensional atom localization by laser fields in a four-level tripod system  

NASA Astrophysics Data System (ADS)

We present a scheme for high-precision three-dimensional (3D) localization by the measurement of the atomic-level population. The scheme is applied to a four-level tripod-type atom coupled by three strong standing waves and a probe running wave. As a result, the atom can be localized in volumes that are substantially smaller than a cubic optical wavelength, which is achieved by the increase of standing-wave intensities. The upper-level distribution depends crucially on the atom-field coupling and it forms 3D periodic structures composed of spheres, hourglasses, bowls, donuts, or deformed barrels.

Ivanov, Vladimir S.; Rozhdestvensky, Yuri V.; Suominen, Kalle-Antti

2014-12-01

417

Pulse duration effects on laser-assisted electron transfer cross section for He2+ ions colliding with atomic hydrogen  

NASA Astrophysics Data System (ADS)

We study the effect of the pulse duration for an ultra-fast and intense laser on the fundamental process of electron capture by analyzing the excitation probability into the n = 2 and n = 3 states when He2+ collides with atomic hydrogen in the 0.05-10 keV/amu energy range, a region of interest for diagnostic processes on plasma and fusion power reactors. We solve the time-dependent Schrödinger equation to calculate the electron capture probability by means of a finite-differences, as well as by an electron-nuclear dynamics approach. In particular, we study the effects of 1, 3, 6, and 10 fs laser pulses at FWHM, wavelength of 780 nm and intensity of 3.5 × 1012 W/cm2. We report good agreement for the laser-free state and total electron transfer cross-sections when compared to available theoretical and experimental data. The effect of the laser pulse on the electron capture probability as a function of the impact parameter is such that the charge exchange probability increases considerably in the impact parameter radial region with an increase in the amplitude oscillations and a phase shift on the Stückelberg oscillations. We find an increase on the total electron exchange cross-section for low projectile collision energy when compared to the laser-free case with a minimal effect at high collision energies. We find that the 1 fs laser pulse has a minimal effect, except for very low collision energies. Although in general, the longer the laser pulse, the larger the electron capture probability, at very low collision energies all pulse widths have an effect. For processes in the atto-second region, our findings suggest that to enhance the laser-assisted charge exchange, the best region for short pulses is at very low collision energies. We also find that the s and p state charge exchange cross section are equally affected. We provide a qualitative discussion of these findings.

Domínguez-Gutiérrez, Francisco Javier; Cabrera-Trujillo, Remigio

2014-08-01

418

Creation and manipulation of bound states in the continuum with lasers: Applications to cold atoms and molecules  

NASA Astrophysics Data System (ADS)

We show theoretically that it is possible to create and manipulate a pair of bound states in the continuum in ultracold atoms by two lasers in the presence of a magnetically tunable Feshbach resonance. These bound states are formed due to coherent superposition of two electronically excited molecular bound states and a quasibound state in the ground-state potential. These superposition states are decoupled from the continuum of two-atom collisional states. Hence, in the absence of other damping processes they are nondecaying. We analyze in detail the physical conditions that can lead to the formation of such states in cold collisions between atoms and discuss the possible experimental signatures of such states. An extremely narrow and asymmetric shape with a distinct minimum of the photoassociative absorption spectrum or the scattering cross section as a function of collision energy will indicate the occurrence of a bound state in the continuum (BIC). We prove that the minimum will occur at the energy at which the BIC is formed. We discuss how a BIC will be useful for efficient the creation of Feshbach molecules and manipulation of cold collisions. Experimental realizations of BIC will pave the way for a new kind of bound-bound spectroscopy in ultracold atoms.

Deb, Bimalendu; Agarwal, G. S.

2014-12-01

419

Synergistic effect of EUV from the laser-sustained detonation plasma in a ground-based atomic oxygen simulation on fluorinated polymers  

SciTech Connect

The contribution of extreme ultraviolet (EUV) from a laser-sustained plasma on the mass loss phenomenon of fluorinated polymer in a ground-based laser-detonation atomic oxygen beam source was evaluated. The atomic oxygen beam and EUV from the oxygen plasma were separated by the high-speed chopper wheel installed in the beam source. The mass changes of the fluorinated polymer and polyimide were measured from the frequency shift of the quartz crystal microbalance during the beam exposures. It has been made clear that the fluorinated polymer erodes by EUV exposure alone. In contrast, no erosion was detected for polyimide by EUV alone. The atomic oxygen-induced erosion was measured for both materials even without EUV exposure. However, no strong synergistic effect was observed for a fluorinated polymer even under the simultaneous exposure condition of atomic oxygen and EUV. Similar results were observed even in simultaneous exposure of atomic oxygen (without EUV) and 172 nm vacuum ultraviolet (VUV) from an excimer lamp. These experiments suggest that the primary origin of the accelerated erosion of fluorinated polymer observed in a laser detonation atomic oxygen source is not the EUV from the laser-sustained plasma.

Tagawa, Masahito; Abe, Shingo; Kishida, Kazuhiro; Yokota, Kumiko; Okamoto, Akio [Graduate School of Engineering, Kobe University, Rokko-dai 1-1, Nada, Kobe 657-8501 (Japan); Technology Research Institute of Osaka Prefecture, Ayumino 2-7-1, Izumi, Osaka 594-1157 (Japan)

2009-01-05

420

A Laser System for the Spectroscopy of Highly-Charged Bismuth Ions  

E-print Network

We present and characterize a laser system for the spectroscopy on highly-charged ^209Bi^82+ ions at a wavelength of 243.87 nm. For absolute frequency stabilization, the laser system is locked to a near-infra-red laser stabilized to a rubidium transition line using a transfer cavity based locking scheme. Tuning of the output frequency with high precision is achieved via a tunable rf offset lock. A sample-and-hold technique gives an extended tuning range of several THz in the UV. This scheme is universally applicable to the stabilization of laser systems at wavelengths not directly accessible to atomic or molecular resonances. We determine the frequency accuracy of the laser system using Doppler-free absorption spectroscopy of Te_2 vapour at 488 nm. Scaled to the target wavelength of 244 nm, we achieve a frequency uncertainty of \\sigma_{244nm} = 6.14 MHz (one standard deviation) over six days of operation.

Albrecht, S; Siegel, C; Herschbach, N; Birkl, G

2011-01-01

421

A Laser System for the Spectroscopy of Highly-Charged Bismuth Ions  

E-print Network

We present and characterize a laser system for the spectroscopy on highly-charged ^209Bi^82+ ions at a wavelength of 243.87 nm. For absolute frequency stabilization, the laser system is locked to a near-infra-red laser stabilized to a rubidium transition line using a transfer cavity based locking scheme. Tuning of the output frequency with high precision is achieved via a tunable rf offset lock. A sample-and-hold technique gives an extended tuning range of several THz in the UV. This scheme is universally applicable to the stabilization of laser systems at wavelengths not directly accessible to atomic or molecular resonances. We determine the frequency accuracy of the laser system using Doppler-free absorption spectroscopy of Te_2 vapour at 488 nm. Scaled to the target wavelength of 244 nm, we achieve a frequency uncertainty of \\sigma_{244nm} = 6.14 MHz (one standard deviation) over six days of operation.

S. Albrecht; S. Altenburg; C. Siegel; N. Herschbach; G. Birkl

2011-08-25

422

Enhancement in the number of trapped atoms in a cesium magneto-optical trap by a near-resonant control laser  

SciTech Connect

We demonstrate enhancement in the number of trapped cesium atoms in a magneto-optical trap (MOT) using a control laser that illuminates only a small faction of the capture region of the trap without interacting with the cold cloud of atoms. The enhancement is maximized when the laser is slightly blue detuned with respect to the cooling transition. Trap loading curves point to approximately a twofold increase in the capture rate, which as a consequence results in the increase in the steady state number of trapped atoms. Enhanced loading is confirmed by MOT loading and decay curves taken under the modulation of the control laser beam. Optical pumping of the inaccessible Zeeman states into the stretched states is suggested as a possible mechanism.

Pradhan, S.; Gaur, S. J.; Manohar, K. G.; Jagatap, B. N. [Laser and Plasma Technology Division, Bhabha Atomic Research Center, Mumbai-400 085 (India)

2005-11-15

423

Electron collisions with cesium atoms—benchmark calculations and application to modeling an excimer-pumped alkali laser  

NASA Astrophysics Data System (ADS)

The B-spline R-matrix (BSR) with pseudostates method is employed to describe electron collisions with cesium atoms. Over 300 states are kept in the close-coupling expansion, including a large number of pseudostates to model the effect of the Rydberg spectrum and, most importantly, the ionization continuum on the results for transitions between the discrete physical states of interest. Predictions for elastic scattering, momentum transfer, excitation and ionization are presented for incident energies up to 200 eV and compared with results from previous calculations and available experimental data. In a second step, the results are used to model plasma formation in an excimer-pumped alkali laser operating on the Cs (62P3/2,1/2 ? 62S1/2) (852 nm and 894 nm) transitions. At sufficiently high operating temperature of a Cs-Ar containing quartz cell, pump power, and repetition rate, plasma formation in excess of 1014-1015 cm-3 occurs. This may reduce laser output power by electron collisional mixing of the upper and lower laser levels.

Zatsarinny, Oleg; Bartschat, Klaus; Babaeva, Natalia Yu; Kushner, Mark J.

2014-06-01

424

The in-gas-jet laser ion source: Resonance ionization spectroscopy of radioactive atoms in supersonic gas jets  

NASA Astrophysics Data System (ADS)

New approaches to perform efficient and selective step-wise resonance ionization spectroscopy (RIS) of radioactive atoms in different types of supersonic gas jets are proposed. This novel application results in a major expansion of the in-gas laser ionization and spectroscopy (IGLIS) method developed at KU Leuven. Implementation of resonance ionization in the supersonic gas jet allows to increase the spectral resolution by one order of magnitude in comparison with the currently performed in-gas-cell ionization spectroscopy. Properties of supersonic beams, obtained from the de Laval-, the spike-, and the free jet nozzles that are important for the reduction of the spectral line broadening mechanisms in cold and low density environments are discussed. Requirements for the laser radiation and for the vacuum pumping system are also examined. Finally, first results of high-resolution spectroscopy in the supersonic free jet are presented for the 327.4 nm 3d104s 2S1/2? 3d104p 2P1/2 transition in the stable 63Cu isotope using an amplified single mode laser radiation.

Kudryavtsev, Yu.; Ferrer, R.; Huyse, M.; Van den Bergh, P.; Van Duppen, P.

2013-02-01

425

LASERS: Electrode system for electric-discharge generation of atomic iodine in a repetitively pulsed oxygen — iodine laser with a large active volume  

NASA Astrophysics Data System (ADS)

Possibilities for increasing the active medium volume of a chemical oxygen — iodine laser (CCOIL) with a pulsed electric-discharge generation of atomic iodine are studied. The reasons are analysed of the low stability of the transverse self-sustained volume discharge in electrode systems with metal cathodes under the conditions of the electric energy input into gas-discharge plasma that are typical for CCOILs: low pressure of mixtures containing a strongly electronegative component, low voltage of discharge burning, low specific energy depositions, and long duration of the current pulse. An efficient electrode system is elaborated with the cathode based on an anisotropically-resistive material, which resulted in a stable discharge in the mixtures of iodide (CH3I, n-C3H7I, C2H5I) with oxygen and nitrogen at the specific energy depositions of ~5 J L-1, pressures of 10 — 25 Torr, and mixture volume of 2.5 L.

Kazantsev, S. Yu; Kononov, I. G.; Podlesnykh, S. V.; Firsov, K. N.

2010-08-01

426

Forbidden atomic transitions driven by an intensity-modulated laser trap  

NASA Astrophysics Data System (ADS)

Spectroscopy is an essential tool in understanding and manipulating quantum systems, such as atoms and molecules. The model describing spectroscopy includes the multipole-field interaction, which leads to established spectroscopic selection rules, and an interaction that is quadratic in the field, which is not often employed. However, spectroscopy using the quadratic (ponderomotive) interaction promises two significant advantages over spectroscopy using the multipole-field interaction: flexible transition rules and vastly improved spatial addressability of the quantum system. Here we demonstrate ponderomotive spectroscopy by using optical-lattice-trapped Rydberg atoms, pulsating the lattice light and driving a microwave atomic transition that would otherwise be forbidden by established spectroscopic selection rules. This ability to measure frequencies of previously inaccessible transitions makes possible improved determinations of atomic characteristics and constants underlying physics. The spatial resolution of ponderomotive spectroscopy is orders of magnitude better than the transition frequency would suggest, promising single-site addressability in dense particle arrays for quantum computing applications.

Moore, Kaitlin R.; Anderson, Sarah E.; Raithel, Georg

2015-01-01

427

Forbidden atomic transitions driven by an intensity-modulated laser trap.  

PubMed

Spectroscopy is an essential tool in understanding and manipulating quantum systems, such as atoms and molecules. The model describing spectroscopy includes the multipole-field interaction, which leads to established spectroscopic selection rules, and an interaction that is quadratic in the field, which is not often employed. However, spectroscopy using the quadratic (ponderomotive) interaction promises two significant advantages over spectroscopy using the multipole-field interaction: flexible transition rules and vastly improved spatial addressability of the quantum system. Here we demonstrate ponderomotive spectroscopy by using optical-lattice-trapped Rydberg atoms, pulsating the lattice light and driving a microwave atomic transition that would otherwise be forbidden by established spectroscopic selection rules. This ability to measure frequencies of previously inaccessible transitions makes possible improved determinations of atomic characteristics and constants underlying physics. The spatial resolution of ponderomotive spectroscopy is orders of magnitude better than the transition frequency would suggest, promising single-site addressability in dense particle arrays for quantum computing applications. PMID:25600089

Moore, Kaitlin R; Anderson, Sarah E; Raithel, Georg

2015-01-01

428

Transferring cold atoms in double magneto-optical trap by a continuous-wave transfer laser beam with large red detuning.  

PubMed

A novel scheme of transferring cold atoms in a double magneto-optical trap (MOT) system has been experimentally demonstrated. Cold cesium atoms trapped in a vapor-cell MOT are efficiently transferred to an ultrahigh-vacuum (UHV) MOT by a continuous-wave divergent Gaussian transfer laser beam. When large red detuning and moderate intensity are adopted for the transfer laser beam, enhancement of the recapturing of atoms in the UHV MOT is clearly observed. Using the divergent transfer laser beam (diameter of approximately 1.60 mm in the vapor-cell MOT region) with typical power of approximately 20.2 mW, up to approximately 85% of transfer efficiency is obtained when the frequency detuning is set to around -1.2 GHz, and it is not sensitive to small detuning variation. This transfer is much efficient compared with that in the case of continuous-wave near-resonance weak transfer laser beam (typical power of order of approximately 100 microW and typical frequency detuning of approximately-10 MHz) which is normally used in double-MOT experiment. The enhancement is ascribed to the guiding effect on cold atomic flux by transverse dipole potential of the large red-detuned transfer laser beam. PMID:19123554

Wang, Junmin; Wang, Jing; Yan, Shubin; Geng, Tao; Zhang, Tiancai

2008-12-01

429

Characterization of energetic and thermalized sputtered atoms in pulsed plasma using time-resolved tunable diode-laser induced fluorescence  

NASA Astrophysics Data System (ADS)

In this work, a time-resolved tunable diode-laser (DL) induced fluorescence (TR-TDLIF) method calibrated by absorption spectroscopy has been developed in order to determine atom and flux velocity distribution functions (AVDF and FVDF) of the energetic and the thermalized atoms in pulsed plasmas. The experimental set-up includes a low-frequency (˜3 Hz) and high spectral-resolution DL (˜0.005 pm), a fast rise-time pulse generator, and a high power impulse magnetron sputtering (HiPIMS) system. The induced TR-TDLIF signal is recorded every 0.5 ?s with a digital oscilloscope of a second-long trace. The technique is illustrated with determining the AVDF and the FVDF of a metastable state of the sputtered neutral tungsten atoms in the HiPIMS post-discharge. Gaussian functions describing the population of the four W isotopes were used to fit the measured TR-TDLIF signal. These distribution functions provide insight into transition from the energetic to thermalized regimes from the discharge onset. This technique may be extended with appropriate DLs to probe any species with rapidly changing AVDF and FVDF in pulsed and strongly oscillating plasmas.

Desecures, M.; de Poucques, L.; Easwarakhanthan, T.; Bougdira, J.

2014-11-01

430

Terracelike structure in the above-threshold-ionization spectrum of an atom in an IR+XUV two-color laser field  

NASA Astrophysics Data System (ADS)

Based on the frequency-domain theory, we investigate the above-threshold ionization (ATI) process of an atom in a two-color laser field with infrared (IR) and extreme ultraviolet (XUV) frequencies, where the photon energy of the XUV laser is close to or larger than the atomic ionization threshold. By using channel analysis, we find that the two laser fields play different roles in an ionization process, where the XUV laser determines the ionization probability by the photon number that the atom absorbs from it, while the IR laser accelerates the ionized electron and hence widens the electron kinetic energy spectrum. As a result, the ATI spectrum presents a terracelike structure. By using the saddle-point approximation, we obtain a classical formula which can predict the cutoff of each plateau in the terracelike ATI spectrum. Furthermore, we find that the difference of the heights between two neighboring plateaus in the terracelike structure of the ATI spectrum increases as the frequency of the XUV laser increases.

Zhang, Kui; Chen, Jing; Hao, Xiao-Lei; Fu, Panming; Yan, Zong-Chao; Wang, Bingbing

2013-10-01

431

The impact of several atomic and molecular laser spectroscopic techniques for chemical analysis  

NASA Astrophysics Data System (ADS)

Several laser-based methods, namely laser induced fluorescence, laser enhanced ionisation and thermal lensing spectrophotometry are discussed with respect to their capabilities of approaching the extremely high detection sensitivity which is nowadays required in many fields of application, notably in high purity materials, in biomedicine and in the nuclear industry. The discussion is restricted to atomisers operated at atmospheric pressure, i.e., combustion flames, plasmas and graphite furnaces. It is shown that the analytical limit of detection can be in the range of femtograms and that double-resonance excitation possesses significant advantages over single-resonance excitation, both in terms of signal-to-noise ratio and spectral selectivity. In addition, the combination of the fluorescence and ionisation techniques represents a remarkable diagnostic tool. In the nuclear field, the suitability of the technique of thermal lensing for the direct determination and chemical speciation of very low levels of uranium in water is discussed.

Omenetto, N.

1988-07-01

432

Effects of chemical kinetics of the performance of the atomic iodine laser system  

NASA Astrophysics Data System (ADS)

Model calculations show that chemical reactions which take place in the active medium of a photolytically pumped iodine laser limit the efficiency with which pump photons are utilized and convert significant amounts of the starting material RI to the unwanted by-products R2 and I2. Laser- and RF-discharge-based methods for regenerating starting materials from by-products are evaluated experimentally. For economical operation of large iodine laser systems, CF3I is presently the best starting material, and a pulsed RF-discharge technique is presently the best one for chemical regeneration. The absorbed energy required to regenerate one CF3I molecule using pulsed RF-discharge techniques is 5.8 eV.

Fisk, G. A.; Truby, F. K.

1980-01-01

433

Method using laser irradiation for the production of atomically clean crystalline silicon and germanium surfaces  

DOEpatents

This invention relates to a new method for removing surface impurities from crystalline silicon or germanium articles, such as off-the-shelf p- or n-type wafers to be doped for use as junction devices. The principal contaminants on such wafers are oxygen and carbon. The new method comprises laser-irradiating the contaminated surface in a non-reactive atmosphere, using one or more of Q-switched laser pulses whose parameters are selected to effect melting of the surface without substantial vaporization thereof. In a typical application, a plurality of pulses is used to convert a surface region of an off-the-shelf silicon wafer to an automatically clean region. This can be accomplished in a system at a pressure below 10.sup.-8 Torr, using Q-switched ruby-laser pulses having an energy density in the range of from about 60 to 190 MW/cm.sup.2.

Ownby, Gary W. (Knoxville, TN); White, Clark W. (Oak Ridge, TN); Zehner, David M. (Lenoir City, TN)

1981-01-01

434

Production mechanism of atomic nitrogen in atmospheric pressure pulsed corona discharge measured using two-photon absorption laser-induced fluorescence  

NASA Astrophysics Data System (ADS)

To study the production mechanism of atomic nitrogen, the temporal profile and spatial distribution of atomic nitrogen are measured in atmospheric pressure pulsed positive corona discharge using two-photon absorption laser-induced fluorescence. The absolute atomic nitrogen density in the streamer filaments is estimated from decay rate of atomic nitrogen in N2 discharge. The results indicate that the absolute atomic nitrogen density is approximately constant against discharge energy. When the discharge voltage is 21.5 kV, production yield of atomic nitrogen produced by an N2 discharge pulse is estimated to be 2.9 - 9.8 × 1013 atoms and the energy efficiency of atomic nitrogen production is estimated to be about 1.8 - 6.1 × 1016 atoms/J. The energy efficiency of atomic nitrogen production in N2 discharge is constant against the discharge energy, while that in N2/O2 discharge increases with discharge energy. In the N2/O2 discharge, two-step process of N2 dissociation plays significant role for atomic nitrogen production.

Teramoto, Yoshiyuki; Ono, Ryo; Oda, Tetsuji

2012-06-01

435

[Effect of cryotherapy and laser destruction on experimental model of human vascular tumor].  

PubMed

Macro- and microscopical changes in the biological model of hemangioma, hen's comb, were assessed to compare the effectiveness of cryotherapy, CO2-, YAG-Nd- and copper vapour (in the green part of the spectrum) laser radiation. The best results were obtained upon exposure to laser on copper vapour and SO2-laser of minor capacity. PMID:7785147

Soldatski?, Iu L; Shekhter, A B; Ponkratenko, A D; Malyshev, V N

1995-01-01

436

Title of Document: INTERACTION OF LASERS WITH ATOMIC CLUSTERS AND STRUCTURED PLASMAS  

E-print Network

of pulse propagation in a corrugated plasma channel and examine the laser-electron beam interaction. In particular, the corrugated plasma channel [Layer et al. Phys. Rev. Lett. (2007)] allows for the guiding the corrugated plasma channel ideal for the acceleration of electrons. We present a simple analytic model

Anlage, Steven

437

Ultrafast laser control of electron dynamics in atoms, molecules and solids  

E-print Network

and microscopy and extreme nonlinear optics including attosecond-science. As pointed out by the organizers issues.23­27 Suitable tools to achieve this goal are shaped femtosecond optical laser pulses in amplitude Discussions #12;Optimized light fields can be found for example by employing adaptive feedback learning loops

Kassel, Universität

438

Atom Interferometers  

E-print Network

Interference with atomic and molecular matter waves is a rich branch of atomic physics and quantum optics. It started with atom diffraction from crystal surfaces and the separated oscillatory fields technique used in atomic clocks. Atom interferometry is now reaching maturity as a powerful art with many applications in modern science. In this review we first describe the basic tools for coherent atom optics including diffraction by nanostructures and laser light, three-grating interferometers, and double wells on AtomChips. Then we review scientific advances in a broad range of fields that have resulted from the application of atom interferometers. These are grouped in three categories: (1) fundamental quantum science, (2) precision metrology and (3) atomic and molecular physics. Although some experiments with Bose Einstein condensates are included, the focus of the review is on linear matter wave optics, i.e. phenomena where each single atom interferes with itself.

Alexander D. Cronin; Joerg Schmiedmayer; David E. Pritchard

2007-12-21

439

A liquid crystalline chirality balance for vapours  

PubMed Central

Chiral discrimination of vapours plays an important role in olfactory perception of biological systems and its realization by artificial sensors has been an intriguing challenge. Here, we report a simple method that tangibly visualizes the chirality of a diverse variety of molecules dissolved from vapours with high sensitivity, by making use of a structural change in a periodic microstructure of a nematic liquid crystal confined in open microchannels. This microstructure is accompanied by a topological line defect of a zigzag form with equal lengths of ‘zig’ and ‘zag.’ We find that a tiny amount of vapour of chiral molecules injected onto the liquid crystal induces the imbalance of ‘zig’ and ‘zag’ depending on its enantiomeric excess within a few seconds. Our liquid-crystal-based ‘chirality balance’ offers a simple, quick and versatile chirality-sensing/-screening method for gas-phase analysis (for example, for odours, environmental chemicals or drugs). PMID:24781531

Ohzono, Takuya; Yamamoto, Takahiro; Fukuda, Jun-ichi

2014-01-01

440

A liquid crystalline chirality balance for vapours  

NASA Astrophysics Data System (ADS)

Chiral discrimination of vapours plays an important role in olfactory perception of biological systems and its realization by artificial sensors has been an intriguing challenge. Here, we report a simple method that tangibly visualizes the chirality of a diverse variety of molecules dissolved from vapours with high sensitivity, by making use of a structural change in a periodic microstructure of a nematic liquid crystal confined in open microchannels. This microstructure is accompanied by a topological line defect of a zigzag form with equal lengths of ‘zig’ and ‘zag.’ We find that a tiny amount of vapour of chiral molecules injected onto the liquid crystal induces the imbalance of ‘zig’ and ‘zag’ depending on its enantiomeric excess within a few seconds. Our liquid-crystal-based ‘chirality balance’ offers a simple, quick and versatile chirality-sensing/-screening method for gas-phase analysis (for example, for odours, environmental chemicals or drugs).

Ohzono, Takuya; Yamamoto, Takahiro; Fukuda, Jun-Ichi

2014-04-01

441

Atomic diffraction in counter-propagating Gaussian pulses of laser light  

E-print Network

We present an analysis of atomic diffraction due to the interaction of an atomic beam with a pair of Gaussian light pulses. We derive a simple analytical expression for the populations in different diffraction orders. The validity of the obtained solution extends beyond the Raman-Nath regime, where the kinetic energy associated with different diffraction peaks is neglected, into the so-called channeling regime where accurate analytical expressions have not previously been available for the diffraction. Comparison with experimental results and exact numerical solutions demonstrate the validity of our analytical formula.

Tapio P. Simula; Atom Muradyan; Klaus Molmer

2007-10-03

442

Comparative investigation of third- and fifth-harmonic generation in atomic and molecular gases driven by midinfrared ultrafast laser pulses  

SciTech Connect

We report on the comparative experimental investigation on third- and fifth-harmonic generation (THG and FHG) in atomic and molecular gases driven by midinfrared ultrafast laser pulses at a wavelength of {approx}1500 nm. We observe that the conversion efficiencies of both the THG and FHG processes saturate at similar peak intensities close to {approx}1.5 x 10{sup 14} W/cm{sup 2} for argon, nitrogen, and air, whose ionization potentials are close to each other. Near the saturation intensity, the ratio of yields of the FHG and THG reaches {approx}10{sup -1} for all the gases. Our results show that high-order Kerr effect seems to exist; however, contribution from the fourth-order Kerr refractive index coefficient alone is insufficient to balance the Kerr self-focusing without the assistance of plasma generation.

Ni Jielei; Yao Jinping; Zeng Bin; Chu Wei; Li Guihua; Zhang Haisu; Jing Chenrui [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, P.O. Box 800-211, Shanghai 201800 (China); Graduate School of the Chinese Academy of Sciences, Beijing 100039 (China); Chin, S. L. [Department of Physics, Engineering Physics and Optics, and Center for Optics, Photonics and Laser (COPL), Laval University, Laval, Quebec, G1K 7P4 (Canada); Cheng, Y.; Xu, Z. [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, P.O. Box 800-211, Shanghai 201800 (China)

2011-12-15

443

Effect of Surface Charge on Laser-induced Neutral Atom Desorption  

SciTech Connect

When an ionic metal oxide crystal is cleaved, inhomogeneous electrical charging of the surface can be a result. Such an effect has been well-documented in magnesium oxide (100). For example, recent rigorous AFM studies indicate that nanoscale charged clusters of MgO are created during cleavage, with high concentrations often located at terrace step edges.[1] In addition, ablation processes of freshly cleaved magnesium oxide crystals may be effected by remnant surface charging and microstructures.[2] We report here that such surface charging strongly impacts even neutral atom desorption, even under conditions of extremely mild excitation of surface terrace features. In our experiments, single crystal MgO (100) is cleaved in air and placed in an ultra-high vacuum chamber (UHV). We irradiate the crystal at 6.4 eV, photon energy resonant with five-coordinated (5-C) terrace sites and probe desorbing neutral oxygen atoms. It is found that a significant fraction of desorbed neutral oxygen atoms from the charged surface possess kinetic energies in excess of 0.7 eV. This is in contrast to uncharged samples (discharged in vacuo over 24 hours) that display a near-thermal oxygen atom distribution.

Beck, Kenneth M.; Joly, Alan G.; Hess, Wayne P.

2010-10-01

444

VOLUME 78, NUMBER 16 P H Y S I C A L R E V I E W L E T T E R S 21 APRIL 1997 High Intensity Laser Absorption by Gases of Atomic Clusters  

E-print Network

high .95% , indicating that substantial laser energy is deposited per particle in the plasma. IonVOLUME 78, NUMBER 16 P H Y S I C A L R E V I E W L E T T E R S 21 APRIL 1997 High Intensity Laser of high intensity, picosecond laser pulses in low density gases composed of large atomic clusters. We find

Ditmire, Todd

445

Application of atomic vapor laser isotope separation to the enrichment of mercury  

SciTech Connect

Workers at GTE/Sylvania have shown that the efficiency of fluorescent lighting may be markedly improved using mercury that has been enriched in the /sup 196/Hg isotope. A 5% improvement in the efficiency of fluorescent lighting in the United States could provide a savings of approx. 1 billion dollars in the corresponding reduction of electrical power consumption. We will discuss the results of recent work done at our laboratory to develop a process for enriching mercury. The discussion will center around the results of spectroscopic measurements of excited state lifetimes, photoionization cross sections and isotope shifts. In addition, we will discuss the mercury separator and supporting laser mesurements of the flow properties of mercury vapor. We will describe the laser system which will provide the photoionization and finally discuss the economic details of producing enriched mercury at a cost that would be attractive to the lighting industry.

Crane, J.K.; Erbert, G.V.; Paisner, J.A.; Chen, H.L.; Chiba, Z.; Beeler, R.G.; Combs, R.; Mostek, S.D.

1986-09-01

446

Unexpected temporal evolution of atomic spectral lines of aluminum in a laser induced breakdown spectroscopy experiment  

NASA Astrophysics Data System (ADS)

The temporal evolution of the laser induced breakdown (LIBS) signal of a pure aluminum sample was studied under nitrogen and air atmospheres. In addition to the usual decrease of signal due to plasma cooling, unexpected temporal evolutions were observed for a spectral lines of aluminum, which revealed the existence of collisional energy transfer effects. Furthermore, molecular bands of AlN and AlO were observed in the LIBS spectra, indicating recombination of aluminum with the ambient gas. Within the experimental conditions reported in this study, both collisional energy transfer and recombination processes occurred around 1.5 ?s after the laser shot. This highlights the possible influence of collisional and chemical effects inside the plasma that can play a role on LIBS signals.

Saad, Rawad; L'Hermite, Daniel; Bousquet, Bruno

2014-11-01

447

Spectroscopy of a narrow-line laser cooling transition in atomic dysprosium  

E-print Network

The laser cooling and trapping of ultracold neutral dysprosium has been recently demonstrated using the broad, open 421-nm cycling transition. Narrow-line magneto-optical trapping of Dy on longer wavelength transitions would enable the preparation of ultracold Dy samples suitable for loading optical dipole traps and subsequent evaporative cooling. We have identified the closed 741-nm cycling transition as a candidate for the narrow-line cooling of Dy. We present experimental data on the isotope shifts, the hyperfine constants A and B, and the decay rate of the 741-nm transition. In addition, we report a measurement of the 421-nm transition's linewidth, which agrees with previous measurements. We summarize the laser cooling characteristics of these transitions as well as other narrow cycling transitions that may prove useful for cooling Dy.

Lu, Mingwu; Lev, Benjamin L

2010-01-01

448

Spectroscopy of a narrow-line laser cooling transition in atomic dysprosium  

E-print Network

The laser cooling and trapping of ultracold neutral dysprosium has been recently demonstrated using the broad, open 421-nm cycling transition. Narrow-line magneto-optical trapping of Dy on longer wavelength transitions would enable the preparation of ultracold Dy samples suitable for loading optical dipole traps and subsequent evaporative cooling. We have identified the closed 741-nm cycling transition as a candidate for the narrow-line cooling of Dy. We present experimental data on the isotope shifts, the hyperfine constants A and B, and the decay rate of the 741-nm transition. In addition, we report a measurement of the 421-nm transition's linewidth, which agrees with previous measurements. We summarize the laser cooling characteristics of these transitions as well as other narrow cycling transitions that may prove useful for cooling Dy.

Mingwu Lu; Seo Ho Youn; Benjamin L. Lev

2010-09-15

449

Observation of Rydberg Series in Sodium Vapour by Two-Photon Resonant Nondegenerate Four-Wave Mixing  

NASA Astrophysics Data System (ADS)

We apply two-photon resonant nondegenerate four-wave mixing with a resonant intermediate state for the observation of Rydberg states in sodium vapour. The broadening and shift of the sodium 3S-11D transition perturbed by argon are investigated. This technique can achieve Doppler-free resolution of narrow spectral structures of Rydberg levels if lasers with narrow bandwidths are employed.

Wang, Yan-Bang; Jiang, Qian; Li, Long; Mi, Xin; Yu, Zu-He; Fu, Pan-Ming

2001-09-01

450

Bose-Einstein condensation of a system of two-level atoms in resonant interaction with a single-running-wave-mode laser field  

E-print Network

In this thesis, we study the influence of a single-running-wave-mode laser field to the critical temperature T[] of Bose-Einstein condensation(BEC) of a system of two-level bosonic atoms. Using a simple model, we obtain the dispersion relation...

Wang, Xinfeng

2001-01-01

451

Measuring molecular electric dipoles using trapped atomic ions and ultrafast laser pulses  

NASA Astrophysics Data System (ADS)

We study a hybrid quantum system composed of an ion and an electric dipole. We show how a trapped ion can be used to measure the small electric field generated by a classical dipole. We discuss the application of this scheme to measure the electric dipole moment of cold polar molecules, whose internal state can be controlled with ultrafast laser pulses, by trapping them in the vicinity of a trapped ion.

Mur-Petit, Jordi; García-Ripoll, Juan José