Note: This page contains sample records for the topic atomic vapour laser from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: August 15, 2014.
1

A eutectic gold vapour laser  

NASA Astrophysics Data System (ADS)

This paper presents a eutectic gold vapour laser (EGVL) which uses the eutectic alloy of gold and silicon, Au/3.15Si, as the lasant. It was observed that, at low input power operation, the presence of the silicon vapour could increase the output of the 627.8 nm laser line by (50-60)% when compared with a gold vapour laser (GVL) which uses pure gold as the lasant. The improved laser output for the EGVL may be explained by an increased electron density, as a result of Penning ionization of silicon atoms. However, for higher input power operation, the EGVL showed a slower rate of increase in its laser output power and was overtaken by GVLs at a tube operating temperature of around 1650°C. This may be explained by a lowering of the electron temperature owing to increasing inelastic collisions between the electrons and silicon atoms which, although excited, may not produce additional electrons.

Tou, T. Y.; Cheak, K. E.; Low, K. S.

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

Laser Ignited Glow Discharge in Lithium Vapour  

Microsoft Academic Search

The ignition of Li glow discharge is studied for three cases of laser excitation of lithium vapour: the first resonance at 670.8 nm (2s -> 2p transition), the quasiresonant line at 460.3 nm (2p -> 4d), or the two-photon resonant line at 639.1 nm (2s -> 3d transition) below self-breakdown voltage. The conditions for laser ignition of the discharge are

Hrvoje Skenderovic; Irena Labazan; Slobodan Milosevic; Goran Pichler

2000-01-01

4

Laser Keyhole Welding: The Vapour Phase  

NASA Astrophysics Data System (ADS)

Several aspects of the properties of the keyhole and its relationship to the weld pool in laser keyhole welding are considered. The aspect of most immediate importance is the exchange of energy between the laser beam itself and the molten material of the weld pool. Many mechanisms are involved, but the two considered here are the process of direct absorption at the keyhole wall (Fresnel absorption) and the two-stage process of absorption of energy by inverse bremsstrahlung into the ionised vapour that forms in the case of the longer-wavelength lasers such as the CO2, laser, followed by thermal conduction to the wall. Consideration is given to the role of the Knudsen layer at the boundary. The possibility that the exchange may be influenced by the vapour flow in the keyhole is considered. More generally, the dynamics of the flow is investigated and the balances necessary to keep the keyhole open are investigated. A simple model of the interaction of the vapour with the molten material in the weld pool is proposed which can be used to investigate their interaction. Order of magnitude estimates suggest that it is far from simple but that some simplifying approximations are possible.

Dowden, John

5

Laser Ignited Glow Discharge in Lithium Vapour  

NASA Astrophysics Data System (ADS)

The ignition of Li glow discharge is studied for three cases of laser excitation of lithium vapour: the first resonance at 670.8 nm (2s -> 2p transition), the quasiresonant line at 460.3 nm (2p -> 4d), or the two-photon resonant line at 639.1 nm (2s -> 3d transition) below self-breakdown voltage. The conditions for laser ignition of the discharge are described. The differences between the self-breakdown voltage and the breakdown voltage for laser initiation of the discharge are given for the different lithium number densities. We also found experimental conditions for the laser guided discharge in the dense lithium vapor. In addition we studied optogalvanic signal for the blue-green spectral region.

Skenderovic, Hrvoje; Labazan, Irena; Milosevic, Slobodan; Pichler, Goran

2000-06-01

6

Ultrafast vapourization dynamics of laser-activated polymeric microcapsules  

NASA Astrophysics Data System (ADS)

Precision control of vapourization, both in space and time, has many potential applications; however, the physical mechanisms underlying controlled boiling are not well understood. The reason is the combined microscopic length scales and ultrashort timescales associated with the initiation and subsequent dynamical behaviour of the vapour bubbles formed. Here we study the nanoseconds vapour bubble dynamics of laser-heated single oil-filled microcapsules using coupled optical and acoustic detection. Pulsed laser excitation leads to vapour formation and collapse, and a simple physical model captures the observed radial dynamics and resulting acoustic pressures. Continuous wave laser excitation leads to a sequence of vapourization/condensation cycles, the result of absorbing microcapsule fragments moving in and out of the laser beam. A model incorporating thermal diffusion from the capsule shell into the oil core and surrounding water reveals the mechanisms behind the onset of vapourization. Excellent agreement is observed between the modelled dynamics and experiment.

Lajoinie, Guillaume; Gelderblom, Erik; Chlon, Ceciel; Böhmer, Marcel; Steenbergen, Wiendelt; de Jong, Nico; Manohar, Srirang; Versluis, Michel

2014-04-01

7

Vapour phase dye lasers of the visible range  

NASA Astrophysics Data System (ADS)

Laser action is reported, in tmitrin 3(470 nm), imitrin 9(525 nm), coumarin 153 (C153(480 nm), C7(522 nm), C30 (526 nm), C6(520 nm) and 7 diethylamino-3(2'-benzoxazplyl)-eoumarin dyes in vapour phase with buffer gases (36 atm). Third harmonic of neodymium laser (355 nm, 100 mJ, 20 ns) was used for the excitation. Laser conversion efficiency for some coumarins exceeds 12%. POPOP vapour phase dye laser (395 am) efficiency exceeds 22%. Prospects of vapour phase dye laser development are discussed.

Basov, N. G.; Logunov, O. A.; Startsev, A. V.; Stoilov, Yu. Yu.; Zuev, V. S.

8

Mechanisms of vapour plume formation in laser deep penetration welding  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

9

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

SciTech Connect

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

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

2012-10-31

10

Control of the radiation parameters of a copper vapour laser  

SciTech Connect

The possibility of controlling the pulse shape and duration and the beam divergence of a copper vapour laser operating in the mode of double pump pulses, when the first pulse excites lasing in the active medium and the second amplifies it. It is shown that a change in the delay of the second pump pulse relative to the laser pulse initiated by the first pump pulse allows an efficient control of the laser-radiation characteristics. In this case, the coefficient of laser-radiation conversion into a beam with a diffraction-limited divergence may reach {approx}80 %. (control of laser radiation parameters)

Polunin, Yu P [Tomsk State University, Tomsk (Russian Federation); Yudin, Nikolai A [Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk (Russian Federation)

2003-09-30

11

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

SciTech Connect

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

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

2011-01-31

12

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

13

Manufacturing diamond films using copper vapour lasers  

SciTech Connect

Fifty nanosecond pulses of visible light have been used to produce hard, hydrogen-free diamond-like-carbon (DLC) films at irradiances between 5 x 10{sup 8} and 5 x 10{sup 10} W/cm{sup 2} The films were characterized by a number of techniques including: Raman spectroscopy, Electron Energy Loss Spectroscopy (EELS), atomic force microscopy, and spectroscopic ellipsometry. The cost for manufacturing DLC with high average power, high-pulse repetition frequency, visible light is low enough to compete with other diamond thin film production methods.

McLean, M., LLNL

1996-01-08

14

A Pumped Atom Laser  

Microsoft Academic Search

We have experimentally demonstrated simultaneous pumping and out-coupling of an atom laser via Bose enhanced (by the condensate) spontaneous photon emission. Source atoms in the |F = 2, MF = 0> hyperfine state of ^87Rb are coupled by a light field to the |F ' = 1, MF = 0> excited state and are then stimulated to emit a photon

John Close; Nick Robins; Cristina Figl; Matthew Jeppesen; Graham Dennis

2008-01-01

15

[Laser treatment in root canals. Effective by explosive vapour bubbles].  

PubMed

Since the late eighties pulsed infrared lasers like the Er:YAG and the Er,Cr:YSGG lasers are available for dentists. These lasers appear to have interesting applications in endodontics. It was demonstrated in vitro, with dyes, that a root canal can effectively be irrigated with them. Initially these lasers were recommended for preparation of enamel, dentin and bone and for surgery. The way that it worked in a root canal in combination with a liquid was, however, not clear. With a special high speed imaging technique the working mechanism of a pulsed infrared laser was studied, using a model of a root canal in a basin filled with either water or with a 5% NaOCl solution. The working mechanism can be attributed to the high stream of liquid, the turbulence and the cavity-effects, created by explosive vapour bubbles. These phenomena appear to make a major contribution to the cleansing and disinfecting of the root canal. PMID:19673234

Blanken, J W; Verdaasdonk, R M

2009-07-01

16

Collisional effects on metastable atom population in vapour generated by electron beam heating  

NASA Astrophysics Data System (ADS)

The metastable atom population distribution in a free expanding uranium vapour generated by electron beam (e-beam) heating is expected to depart from its original value near the source due to atom-atom collisions and interaction with electrons of the e-beam generated plasma co-expanding with the vapour. To investigate the dynamics of the electron-atom and atom-atom interactions at different e-beam powers (or source temperatures), probing of the atomic population in ground (0 cm-1) and 620 cm-1 metastable states of uranium was carried out by the absorption technique using a hollow cathode discharge lamp. The excitation temperature of vapour at a distance ~30 cm from the source was calculated on the basis of the measured ratio of populations in 620 to 0 cm-1 states and it was found to be much lower than both the source temperature and estimated translational temperature of the vapour that is cooled by adiabatic free expansion. This indicated relaxation of the metastable atoms by collisions with low energy plasma electrons was so significant that it brings the excitation temperature below the translational temperature of the vapour. So, with increase in e-beam power and hence atom density, frequent atom-atom collisions are expected to establish equilibrium between the excitation and translational temperatures, resulting in an increase in the excitation temperature (i.e. heating of vapour). This has been confirmed by analysing the experimentally observed growth pattern of the curve for excitation temperature with e-beam power. From the observed excitation temperature at low e-beam power when atom-atom collisions can be neglected, the total de-excitation cross section for relaxation of the 620 cm-1 state by interaction with low energy electrons was estimated and was found to be ~10-14 cm2. Finally using this value of cross section, the extent of excitational cooling and heating by electron-atom and atom-atom collisions are described at higher e-beam powers.

Dikshit, B.; Majumder, A.; Bhatia, M. S.; Mago, V. K.

2008-03-01

17

Co-laser photoacoustic spectroscopy of gases and vapours for trace gas analysis  

Microsoft Academic Search

This comprehensive study reviews the sensitive and selective detection of trace gases by laser photoacoustic spectroscopy. A computer controlled CO-laser photoacoustic system is presented. The wavelength range between 5.0 and 6.5 mum is of great interest because it coincides with specific absorption bands of various gases and vapours of environmental concern. However, since water-vapour, which is present in most samples,

S. Bernegger; M. W. Sigrist

1990-01-01

18

LASERS AND AMPLIFIERS: Copper vapour laser with an inductive energy storage and a semiconductor current interrupter  

NASA Astrophysics Data System (ADS)

A copper vapour laser is built in which a pump generator uses an inductive energy storage and a semiconductor current interrupter. Lasing was obtained in the stationary mode, using a self-heating active element 36 cm3 in volume, at a pulse repetition rate of 10 kHz and an average output power of 3.3 W. The use of the inductive energy storage in this laser resulted in a 20% increase in the average output power compared to that for a conventional pump circuit.

Kostyrya, I. D.; Evtushenko, Gennadii S.; Tarasenko, Viktor F.; Shiyanov, D. V.

2001-10-01

19

Atomic laser-beam finder.  

PubMed

We report on an experimental method to align a laser beam to a cloud of atoms trapped in a magneto-optical trap (MOT). We show how balanced lock-in detection leads to a very sensitive method to align the laser beam to the atoms in the plane perpendicular to the propagation direction. This provides a very reliable and fast way of aligning laser beams to atoms trapped in a MOT. PMID:23187377

Viering, Kirsten; Medellin, David; Mo, Jianyong; Raizen, Mark G

2012-11-01

20

Atoms, Light, and Lasers  

NASA Astrophysics Data System (ADS)

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

Bellac, Michel Le

2014-11-01

21

The Collective Atomic Recoil Laser  

NASA Astrophysics Data System (ADS)

An ensemble of periodically ordered atoms coherently scatters the light of an incident laser beam. The scattered and the incident light may interfere and give rise to a light intensity modulation and thus to optical dipole forces which, in turn, emphasize the atomic ordering. This positive feedback is at the origin of the collective atomic recoil laser (CARL). We demonstrate this dynamics using ultracold atoms confined by dipole forces in a unidirectionally pumped far red-detuned high-finesse optical ring cavity. Under the influence of an additional dissipative force exerted by an optical molasses the atoms, starting from an unordered distribution, spontaneously form a density grating moving at constant velocity. Additionally, steady state lasing is observed in the reverse direction if the pump laser power exceeds a certain threshold. We compare the dynamics of the atomic trajectories to the behavior of globally coupled oscillators, which exhibit phase transitions from incoherent to coherent states if the coupling strength exceeds a critical value.

Courteille, Ph. W.; von Cube, C.; Deh, B.; Kruse, D.; Ludewig, A.; Slama, S.; Zimmermann, C.

2005-05-01

22

Laser cooling of Iron atoms  

NASA Astrophysics Data System (ADS)

We report on the first laser cooling of Iron atoms. Our laser cooling setup makes use of 2 UV laser radiation sent colinearly in a 0.8 m Zeeman slower. One laser is meant for optical pumping of the Iron atoms from the ground state to the lowest energy metastable state. The second laser cools down the atoms using a quasi-perfect closed transition from the optical pumped metastable state. The velocity distribution at the exit of the Zeeman slower is obtained from a probe laser crossing the atom beam at an angle of 50 degrees. The fluorescence light is detected using a photomultiplier tube coupled with a boxcar analyzer. The Iron atom beam is produced with a commercial effusion cell working at around 1950 K. Our laser radiations are stabilized using standard saturated-absorption signals in both an Iron hollow cathode absorption cell and an Iodine cell. We will present our experimental setup, as well as the first evidences of cooled down Iron atoms at the exit of the Zeeman slower.

Bastin, Thierry; Huet, Nicolas; Krins, Stephanie

2013-03-01

23

A hollow cathode device for CW helium-metal vapour laser systems  

Microsoft Academic Search

Details of the design and operation of a simple, inexpensive, multiple anode-hollow cathode laser tube for CW helium-metal vapour laser systems are presented. The device is of metal construction and the component sections are connected by ordinary O ring couplings. To preserve the cleanliness of the system, helium from a high-pressure cylinder is slowly flushed through the tube. We have

J A Piper; C E Webb

1973-01-01

24

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

25

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

26

Influence of the switch parameters on the performance characteristics of a copper vapour laser  

SciTech Connect

Analysis of the circuits for exciting the active medium of a copper vapour laser (CVL) has shown that the main factors limiting the mean output power of the CVL are the cathode emissive power of an electron tube and the permissible current rise rate in a thyratron switch. The laser operation reliability and the thyratron service life are determined by the reverse voltage across the thyratron anode. The service life of a TGI1-1000/25 thyratron in a CVL corresponds to its certified value, if the reverse voltage at the thyratron anode is within 3 kV. (lasers)

Yudin, Nikolai A [Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk (Russian Federation)

2002-09-30

27

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

SciTech Connect

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

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

2011-11-30

28

Comparative laser performances of pyrromethene 567 and rhodamine 6G dyes in copper vapour laser pumped dye lasers  

NASA Astrophysics Data System (ADS)

Narrowband laser performances and photochemical stability of alcoholic solutions of pyrromethene 567 and rhodamine 6G dyes, under high-repetition rate copper vapour laser (at 510 nm), as well as, high-peak intensity Nd:YAG laser (at 532 nm) excitation have been investigated. We have observed that pyrromethene 567 dye solutions offer higher efficiency, wider tuning range, but lower photochemical stability and higher lasing threshold than that of rhodamine 6G dye solutions. An addition of about 100 mM DABCO, as a singlet oxygen quencher, in pyrromethene 567 dye solutions improved its photochemical stability close to that of rhodamine 6G. The observation of higher slope efficiency, in spite of higher threshold pump energy for pyrromethene 567 dye than that of rhodamine 6G dye solutions, was explained by a predictive model on gain characteristics of both dye solutions as a function of pump energy.

Ray, A. K.; Kundu, S.; Sasikumar, S.; Rao, C. S.; Mula, S.; Sinha, S.; Dasgupta, K.

2007-05-01

29

Laser-induced collisional energy-transfer process in a potassium-sodium vapour mixture  

Microsoft Academic Search

This paper reports the measurements of a new kind laser-induced collisional energy transfer ionization process in a K-Na vapour mixture. Theoretical analysis has been done by calculating the collision cross-sections of different transfer processes as a function of detuning. Bibtex entry for this abstract Preferred format for this abstract (see Preferences) Find Similar Abstracts: Use: Authors Title Abstract Text Return:

Qin Liu; Taoheng Sun

1989-01-01

30

Optics with an Atom Laser Beam  

Microsoft Academic Search

We report on the atom optical manipulation of an atom laser beam. Reflection, focusing, and its storage in a resonator are demonstrated. Precise and versatile mechanical control over an atom laser beam propagating in an inhomogeneous magnetic field is achieved by optically inducing spin flips between atomic ground states with different magnetic moment. The magnetic force acting on the atoms

Immanuel Bloch; Michael Koehl; Markus Greiner; Theodor W. Haensch; Tilman Esslinger

2001-01-01

31

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

32

Laser spectroscopy of sputtered atoms  

SciTech Connect

The use of laser radiation to study the sputtering process is of relatively recent origin. Much has been learned from this work about the basic physics of the sputtering process itself through measurements of velocity and excited state distributions of sputtered atoms and the effects of adsorbates on substrate sputtering yields. Furthermore, the identification, characterization, and sensitive detection of sputtered atoms by laser spectroscopy has led to the development of in situ diagnostics for impurity fluxes in the plasma edge regions of tokamaks and of ultrasensitive methods (ppB Fe in Si) for surface analysis with ultralow (picocoulomb) ion fluences. The techniques involved in this work, laser fluorescence and multiphoton resonance ionization spectroscopy, will be described and illustrations given of results achieved up to now. 55 refs., 5 figs., 1 tab.

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

1985-01-01

33

Vapour-liquid coexistence curves of the united-atomand anisotropic united-atom force fields for alkane mixtures  

Microsoft Academic Search

The performances of two categories of force field for mixtures of alkanes are compared. Configurational-bias Monte Carlo simulations in the Gibbs ensemble were carried out to compute the vapour-liquid coexistence curves (VLCC) for pure n-pentane and n-dodecane and for binary mixtures of these components with methane. The united-atom (UA) force field (Siepmann and coworkers) and the anisotropic united-atom (AUA) force

Jerome Delhommelle; Anne Boutin; Bernard Tavitian; Allan D. Mackie; Alain H. Fuchs

1999-01-01

34

Synthesis of single wall carbon nanotubes with invariant diameters using a modified laser assisted chemical vapour deposition route  

Microsoft Academic Search

We have developed a fast and facile CO2 laser assisted chemical vapour deposition LA-CVD synthesis route for carbon nanotubes, which requires no supplementary hydrocarbon feedstock. The technique yields a broad range of carbon nanostructures due to the sharp thermal gradient afforded by the laser. This in turn provides useful information on the changes in nanostructure formation with temperature. A distinct

M. H. Rümmeli; C. Kramberger; M. Löffler; M. Kalbác; H.-W. Hübers; A. Grüneis; A. Barreiro; D. Grimm; P. Ayala; T. Gemming; F. Schäffel; L. Dunsch; B. Büchner; T. Pichler

2006-01-01

35

Laser Trapping of Radioactive Atoms  

NASA Astrophysics Data System (ADS)

Stuart Freedman conceived the idea of laser trapping radioactive atoms for the purpose of studying beta correlation effects. ``This is really the theorist's view of a radioactive source,'' as he fondly claimed. It is ideal because the atoms form a point source, compressed in both position and momentum space, with no material walls nearby. The Berkeley group succeeded in trapping ^21Na (half-life = 22 s) atoms [Lu et al., PRL 72, 3791 (1994)], and determined its beta-neutrino correlation coefficient a=0.5502(60) to be in agreement with the Standard Model [Vetter et al., PRC 77, 035502 (2008)]. Other groups have joined this effort with searches for scalar or tensor couplings in the weak interaction. Moreover, the technique has been extended to trap very short lived ^8He (0.1 s) to study its halo structure or the very long lived ^81Kr (230,000 yr) to map the movement of groundwater.

Lu, Zheng-Tian

2013-04-01

36

DISCUSSION: On the simulation of a copper vapour laser with hydrogen admixtures  

NASA Astrophysics Data System (ADS)

The results of computer simulation of a pulsed copper vapour laser with hydrogen admixtures presented in [1-4] are discussed. It is pointed out that the simulation technique used in these papers has a number of serious drawbacks. In particular, it is shown that the prepulse electron temperature obtained with its help is much lower than the temperature of the wall of the gas-discharge tube, which is in direct contradiction with the thermodynamics. Possible reasons for the erroneous results obtained in these works are discussed.

Petrash, G. G.

2005-06-01

37

DISCUSSION: Critical prepulse densities of electrons and metastable states in copper vapour lasers  

NASA Astrophysics Data System (ADS)

Two mechanisms of population inversion quenching were considered based on a detailed model of the active medium of a copper vapour laser. One of them is due to a high prepulse density of metastable states and the other is due to a high prepulse electron density. For a given pumping system, lasing was shown to terminate when the initial densities of metastable states or electrons exceeded some critical values. The results of calculations of the critical initial electron density are consistent with our simple estimates proposed earlier.

Boichenko, Aleksandr M.; Yakovlenko, Sergei I.

2002-02-01

38

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

PubMed

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 Cd(2+)-complexed PCs) (i) by size exclusion chromatography coupled to UV diode array detector (SEC-DAD); (ii) by the derivatization of PC -SH groups in SEC fractions by p-hydroxymercurybenzoate (PHMB) and the indirect detection of PC-PHMB complexes by reversed phase liquid chromatography coupled to atomic fluorescence detector (RPLC-CVGAFS). MALDI-TOF/MS (matrix assisted laser desorption ionization time of flight mass spectrometry) analysis of underivatized synthetic PC samples was performed in order have a qualitative information of their composition. Quantitative analysis of synthetic PC solutions has been performed on the basis of peak area of PC-PHMB complexes of the mercury specific chromatogram and calibration curve of standard solution of glutathione (GSH) complexed to PHMB (GS-PHMB). The limit of quantitation (LOQ) in terms of GS-PHMB complex was 90 nM (CV 5%) with an injection volume of 35 microL, corresponding to 3.2 pmol (0.97 ng) of GSH. The method has been applied to analysis of extracts of cell cultures from Phaeodactylum tricornutum grown in Cd-containing nutrient solutions, analysed by SEC-DAD-CVGAFS and RPLC-DAD-CVGAFS. PMID:16963057

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

2006-11-10

39

Atom Skimmers and Atom Lasers Utilizing Them  

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

40

Asservissement de la frequence d'emission d'un laser a colorant sur le sommet d'une raie atomique du fer. (Frequency lock of a dye laser emission on iron atomic line top).  

National Technical Information Service (NTIS)

The aim of this thesis is to realize a frequency lock of a dye laser emission on iron atomic line top. To reach that goal, the author first presents the calculation of atomic vapour density by means of laser absorption ratio measure and studies the dye la...

P. Durand

1995-01-01

41

Laser Deceleration of an Atomic Beam  

Microsoft Academic Search

Deceleration and velocity bunching of Na atoms in an atomic beam have been observed. The deceleration, caused by absorption of counterpropagating resonant laser light, amounts to 40% of the initial thermal velocity, corresponding to about 15 000 absorptions. Atoms were kept in resonance with the laser by using a spatially varying magnetic field to provide a changing Zeeman shift to

William D. Phillips; Harold Metcalf

1982-01-01

42

Laser optics of neutral atomic beams  

Microsoft Academic Search

The use of laser light radiation pressure to manipulate neutral atoms is examined. The history of laser technology and the radiation forces on an atom from planes waves, Gaussian profile beams, and standing waves are reviewed. Consideration is given to processes used for the collimation, focusing, imaging, and reflection of an atomic beam. The prospects for future developments are discussed,

Victor I. Balykin; Vladilen S. Letokhov

1989-01-01

43

Mercury determination by cold vapour atomic absorption spectrometry in several biological indicators from Lake Maracaibo, Venezuela.  

PubMed

Two sampling sessions were carried out in Lake Maracaibo and eight sites selected in four pairs one in front of the other (El Moján-Ancón de iturre, Santa Cruz de Mara-Punta de Palmas, Maracaibo-Punta de Leiva and San Francisco-La Rita). Specimens of Cynosción acoupa Maracaiboencis (curvina, n = 5), Oligoplites palometa (palometa, n = 5), Penaeus schmitti (shrimp, n = 20), and Polymesoda arctata (mussels, n = 20) were collected. For the curvina and palometa, muscle, brain, kidney, gill, liver and heart were analysed. Shrimp and mussels were analysed whole, without the shells. Samples were lyophilized and cold digested in a mixture of sulfuric, nitric and perchloric acids, potassium permanganate and hydrogen peroxide. Spectrometric determination was carried out using cold vapour atomic absorption spectrometry and sodium borohydride as reducing agent. Accuracy was tested with a National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) RM50 Albacore Tuna, and against another method. The detection limit for Hg was 53 ng l-1. Good agreement was found between results for the analysis of SRM RM50 (Hg = 0.95 +/- 0.14 mg kg-1) and the assigned value furnished by NIST (Hg = 0.95 +/- 0.10 mg kg-1). Precision and the interference were also evaluated. Mercury concentrations in brain, kidney and heart tissues of the curvina and palometa were found to be higher than those in the muscle tissue. PMID:1580413

Colina de Vargas, M; Romero, R A

1992-03-01

44

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

45

Resonance enhanced multiphoton ionization probing of H atoms and CH 3 radicals in a hot filament chemical vapour deposition reactor  

Microsoft Academic Search

Resonance enhanced multiphoton ionization spectroscopy has been used to provide spatially resolved in situ measurements of H atom and CH3 radical relative number densities and the local gas temperature in a hot filament reactor used for diamond chemical vapour deposition (CVD). Parameters varied include the hydrocarbon (CH4 and C2H2), the hydrocarbon\\/H2 process gas mixing ratio, the total pressure and flow

James A. Smith; Moray A. Cook; Stephen R. Langford; Stephen A. Redman; Michael N. R. Ashfold

2000-01-01

46

Mercury speciation by coupling cold vapour atomic absorption spectrometry with flow injection on-line preconcentration and liquid chromatographic separation  

Microsoft Academic Search

A fully automated system for the direct determination of methylmercury (MeHg), ethylmercury (EtHg), phenylmercury (PhHg),\\u000a and inorganic mercury (Hg(II)) at the ng\\/L level is described. It is based on solid phase extraction preconcentration incorporated\\u000a in a flow injection (FI) system, high performance liquid chromatography (HPLC) separation, reduction combined with thermolysis\\u000a and determination by cold vapour atomic absorption spectrometry (CVAAS). For

Xuefeng Yin; Wolfgang Frech; Erwin Hoffmann; C. Lüdke; Jochen Skole

1998-01-01

47

Atom cooling by partially spatially coherent lasers  

NASA Astrophysics Data System (ADS)

Atom cooling and trapping by partially spatially coherent lasers is investigated both experimentally and theoretically. The degree of spatial coherence of the laser beams is controlled by the electro-optic crystal. The characteristics of the trapped atomic cloud are studied. The experimental results indicate that the atom number and atomic Gaussian density distribution stay unchanged due to the fact that the average photon scattering rate is independent of the spatial coherence of the laser beams. However, the measured temperature of the atomic cloud increases as the degree of spatial coherence of the laser beams decreases. The reason is that the scattering force of the partially spatially coherent lasers acting on the atoms fluctuates temporally and spatially, which broadens the velocity distribution of the atoms.

Zhang, Jing-Fang; Wang, Zhao-Ying; Cheng, Bing; Wang, Qi-Yu; Wu, Bin; Shen, Xiao-Xia; Zheng, Li-Ling; Xu, Yun-Fei; Lin, Qiang

2013-08-01

48

Quantum Theory of Atom Laser Cooling  

NASA Astrophysics Data System (ADS)

In this paper, we study the laser cooling mechanisms with extended Schrodinger quantum wave equation, which can describe a particle in conservative and non-conservative force field. We prove the atom in laser field can be cooled with the theory, and predict that the atom cooling temperature T is directly proportional to the atom vibration frequency ?, which are in accordance with experiment results (A.D. Oconnell, et al. in Nature 464:697, 2010).

Wu, Xiang-Yao; Zhang, Bai-Jun; Yang, Jing-Hai; Liu, Xiao-Jing; Wu, Yi-Heng; Wang, Qing-Cai; Wang, Yan; Ba, Nuo; Li, Jing-Wu

2011-09-01

49

Electron energy distribution function in laser-excited rubidium atoms  

NASA Astrophysics Data System (ADS)

The electron energy distribution function (EEDF) in laser-excited Rb vapour at the first resonance transition 5S-5P and 5p-nl transitions is calculated numerically from the Boltzmann equation under the experimental conditions of Barbier and Cheret (1987 J. Phys. B: At. Mol. Phys. 20 1229). The calculations included all the interactions between electrons and ground or excited states of atomic rubidium. We have also studied the time evolution and the laser power dependences of the EEDF and the electron density which is created during the interactions. The energy spectra of the electrons emerging from the interaction contain a number of peaks corresponding to the low-energy electrons produced by the associative and Hornbeck-Molnar ionization in addition to the electrons created from the various excited states by the ionizing collisions (Penning ionization). The low-energy electrons are then heated by one or more superelastic collisions leading to further ionization. However the calculations indicated that, under the conditions of low power laser intensity and relatively low atom density, the dominant processes are collisional ionization and collisional excitation.

Mahmoud, M. A.

2005-05-01

50

Effects of atomic diffraction on the collective atomic recoil laser  

NASA Astrophysics Data System (ADS)

We formulate a wave-atom-optics theory of the collective atomic recoil laser (CARL) where the atomic center-of-mass motion is treated quantum mechanically. By comparing the predictions of this theory with those of the ray-atom-optics theory, which treats the center-of-mass atomic motion classically, we show that for the case of a far off-resonant pump laser the ray-optics model fails to predict the linear response of the CARL when the temperature is of the order of the recoil temperature or less. This is due to the fact that in this temperature regime one can no longer ignore the effects of matter-wave diffraction on the atomic center-of-mass motion.

Moore, M. G.; Meystre, P.

1998-10-01

51

Waveguide atom beam splitter for laser-cooled neutral atoms  

Microsoft Academic Search

A laser-cooled neutral-atom beam from a low-velocity intense source is split into two beams while guided by a magnetic-field potential. We generate our multimode-beamsplitter potential with two current-carrying wires on a glass substrate combined with an external transverse bias field. The atoms bend around several curves over a $10$-cm distance. A maximum integrated flux of $1.5\\\\cdot10^{5} \\\\mathrm{atoms\\/s}$ is achieved with

Dirk Müller; Eric A. Cornell; Marco Prevedelli; Peter D. D. Schwindt; Alex Zozulya; Dana Z. Anderson

2000-01-01

52

Laser Technology in Commercial Atomic Clocks  

NASA Astrophysics Data System (ADS)

Commercial atomic frequency standards (AFS) are deployed in diverse civilian, military, and aerospace applications, ranging from high-precision measurement and calibration to navigation, communications and, of course, timekeeping. Currently, commercially available AFS include magnetically-selected cesium beam frequency standards and hydrogen masers and lamp-pumped rubidium oscillators. Despite the revolution in atomic physics and laboratory-scale AFS brought about by the advent of the tunable laser in the early 1970s, commercial AFS invariably rely on more conventional atomic physics technology developed in the 1950s. The reason for this lack of advancement of commercial AFS technology is the relatively poor reliability and environmental sensitivity of narrow-linewidth single-mode laser sources at atomic resonance wavelengths. Over the past 8 years, Symmetricom, in collaboration with laser manufacturers, has developed specialized laser sources for commercial AFS applications. These laser devices, optimized for high spectral purity and long-term reliability, will enable a new generation of commercial AFS. This talk will briefly describe two laser-based atomic frequency standard development programs at Symmetricom. The Chip-Scale Atomic Clock, two orders of magnitude smaller and lower power than any commercial AFS, will enable atomic timing accuracy in portable battery-powered applications. The Optically-Pumped Cesium Beam Frequency Standard, under development for deployment onboard the GPS-III satellite constellation, will provide enhanced short-term stability and longer lifetime compared to magnetically-selected cesium beam AFS.

Lutwak, R.

2006-05-01

53

Atomic absorption of ultra intense laser radiation  

Microsoft Academic Search

The authors derive an expression for the rate of absorption by an atomic system (bound or free) of radiation from an ultra intense laser beam. The absorption characteristics are radically different from those of conventional weak-field absorption theory.

S. Geltman; M. R. Teague

1974-01-01

54

Trapping cold atoms with ultrafast laser pulses  

NASA Astrophysics Data System (ADS)

The aim of this research is to pave the way for making a trap for cold neutral atoms based on the force generated by pulses of a mode-locked laser. As an onset towards such a trap we decided to use a far-off-resonance trap (FORT) loaded with cold rubidium atoms from a magneto-optical trap (MOT). Our FORT setup consists of a titanium-sapphire laser that can operate both in continuous wave mode and in mode-locked mode. Our MOT setup uses a magnetic field gradient, and two diode lasers whose frequency is locked very accurately to the atomic transition using polarisation spectroscopy. Since the measurements we do require very precise timing of the order of less than one millisecond between the various phases of the experiment, a time-sequencing program was developed. Using this sophisticated setup, several characteristics of FORTs made with continuous and pulsed lasers were analysed. For example, we have investigated the loading behaviour of the traps and found that under general circumstances there is no significant difference. However, under special conditions it is possible to load more atoms into a pulsed trap. The lifetime of the number of atoms in the trap shows no dependence on the power of the trap laser in the continuous case. For the pulsed trap, however, the increased scattering due to the high peak intensities of the pulses does limit the achievable lifetimes. Moreover, due to the presence of a large number of photoassociation lines, i.e. lines were loosely bound molecules are formed by the interaction of two atoms an a photon, the two-particle losses depend heavily on the wavelength of the trap laser. Furthermore we have done measurements of the temperature of the trapped atoms, which revealed that the temperature is a constant fraction of the trap depth. We also looked at the effects of parametric excitation of the atoms in the FORT. The anharmonicity of the trap formed by the titanium-sapphire laser results in interesting physics, including a change in the average temperature of the atoms, depending on the modulation frequency. We also investigated the trapping behaviour of the FORT at low pulse repetition rates by switching the laser intensity on and off on a kHz scale. We investigated the dependence of the number of atoms on the polarisation of the FORT laser light, both for continuous and pulsed traps. Atoms can be trapped at elliptical polarisations as well, although the number of trapped atoms is less. As the laser is detuned further to the red of the rubidium D line, this effect becomes less and less pronounced, as predicted by our model.

Karssen, L. C.

2008-10-01

55

Stochastic cooling of atoms using lasers  

NASA Astrophysics Data System (ADS)

We propose a method to laser-cool atoms based on stochastic cooling, first developed at CERN to cool antiprotons. Fluctuations in the momentum distribution will be detected in a pump-probe configuration with far-detuned lasers, and the appropriate correction kick will be accomplished with optical dipole potentials. Each stage of an iterative cooling process will involve measurement and feedback, with phase space remixing in between. We discuss possible applications of this method to magnetically trapped atoms and molecules.

Raizen, M. G.; Koga, , J.; Sundaram, B.; Kishimoto, Y.; Takuma, H.; Tajima, T.

1998-12-01

56

Cr 2O 3 thin films grown at room temperature by low pressure laser chemical vapour deposition  

Microsoft Academic Search

Chromia (Cr2O3) has been extensively explored for the purpose of developing widespread industrial applications, owing to the convergence of a variety of mechanical, physical and chemical properties in one single oxide material. Various methods have been used for large area synthesis of Cr2O3 films. However, for selective area growth and growth on thermally sensitive materials, laser-assisted chemical vapour deposition (LCVD)

P. M. Sousa; A. J. Silvestre; O. Conde

2011-01-01

57

Cr2O3 thin films grown at room temperature by low pressure laser chemical vapour deposition  

Microsoft Academic Search

Chromia (Cr2O3) has been extensively explored for the purpose of developing widespread industrial applications, owing to the convergence of a variety of mechanical, physical and chemical properties in one single oxide material. Various methods have been used for large area synthesis of Cr2O3 films. However, for selective area growth and growth on thermally sensitive materials, laser-assisted chemical vapour deposition (LCVD)

P. M. Sousa; A. J. Silvestre; O. Conde

2011-01-01

58

Laser modification of ultracold atomic collisions: Theory  

Microsoft Academic Search

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

Paul S. Julienne; Robert Heather

1991-01-01

59

Atomic-vapor-laser isotope separation  

SciTech Connect

This paper gives a brief history of the scientific considerations leading to the development of laser isotope separation (LIS) processes. The close relationship of LIS to the broader field of laser-induced chemical processes is evaluated in terms of physical criteria to achieve an efficient production process. Atomic-vapor LIS processes under development at Livermore are reviwed. 8 figures.

Davis, J.I.

1982-10-01

60

Ultrasensitive Laser Detection of Atoms and Molecules.  

National Technical Information Service (NTIS)

The technique of Resonance Ionization Spectroscopy (RIS) is being extended to develop a means for counting individual atoms of a selected isotope of a noble gas. In this method, lasers are used for RIS to obtain atomic species (Z) selectivity and a small ...

C. H. Chen

1984-01-01

61

Design for an optical cw atom laser  

PubMed Central

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.

Ashkin, Arthur

2004-01-01

62

High resolution laser spectroscopy of atomic hydrogen  

Microsoft Academic Search

It is speculated that in the near future very stringent tests of basic physics laws will become possible based on very high resolution laser spectroscopy of atomic hydrogen. By cooling hydrogen atoms below liquid helium temperature, two-photon optical Ramsey spectroscopy will be possible with a resolution of better than 1 part in 1015. (AIP)

R. G. Beausoleil; B. Couillaud; C. J. Foot; E. A. Hildum; D. H. McIntyre

1986-01-01

63

Atom-photon pair laser  

SciTech Connect

We study the quantum dynamics of an ultracold atomic gas trapped in an optical lattice within an optical high-Q resonator. The atoms are coherently illuminated with the cavity resonance tuned to a blue vibrational sideband so that stimulated gain of the resonator mode is accompanied by vibrational cooling of the atoms. This system exhibits a threshold above which pairwise stimulated generation of a cavity photon and an atom in the lowest vibrational band dominates spontaneous scattering and we find a combination of optical lasing with a buildup of a macroscopic population in the lowest lattice band. Including output coupling of ground-state atoms and replenishing of hot atoms into the cavity volume leads to a coherent, quantum correlated atom-photon pair source very analogous to twin light beam generation in a nondegenerate optical parametric oscillator.

Salzburger, Thomas; Ritsch, Helmut [Institute for Theoretical Physics, University of Innsbruck, Technikerstrasse 25/2, 6020 Innsbruck (Austria)

2007-06-15

64

Atom-photon pair laser  

NASA Astrophysics Data System (ADS)

We study the quantum dynamics of an ultracold atomic gas trapped in an optical lattice within an optical high- Q resonator. The atoms are coherently illuminated with the cavity resonance tuned to a blue vibrational sideband so that stimulated gain of the resonator mode is accompanied by vibrational cooling of the atoms. This system exhibits a threshold above which pairwise stimulated generation of a cavity photon and an atom in the lowest vibrational band dominates spontaneous scattering and we find a combination of optical lasing with a buildup of a macroscopic population in the lowest lattice band. Including output coupling of ground-state atoms and replenishing of hot atoms into the cavity volume leads to a coherent, quantum correlated atom-photon pair source very analogous to twin light beam generation in a nondegenerate optical parametric oscillator.

Salzburger, Thomas; Ritsch, Helmut

2007-06-01

65

Laser technology in atomic industry  

NASA Astrophysics Data System (ADS)

It is known that comparatively small beam divergence and sufficiently high beam intensity of CO2 lasers give possibility of their application in various technological processes, that demand distant interaction. The results of some technological applications of continuous wave (CW) and high repetition rate (HRR) CO2 lasers with average power up to 50 kW are presented. It is shown that these lasers can be used in the field of nuclear power.

Kosyrev, Feliks K.; Krasjukov, A. G.; Naumov, Valery G.; Rodin, Anatoly V.

2000-07-01

66

INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Laser-assisted etching of the surface of polycrystalline silicon carbide by copper-vapour laser radiation  

NASA Astrophysics Data System (ADS)

An investigation was made of laser-assisted (by radiation from a copper vapour laser) etching of polycrystalline silicon carbide in air and in liquid media (water, dimethyl sulfoxide). The maximum etching rate of ceramic SiC in air reached 0.24 ?m pulse-1 and in dimethyl sulfoxide it was 0.07 ?m pulse-1 when the energy density was 16 J cm-2 in both cases. Scanning electron microscopy and x-ray structure analysis were used to study changes in the morphology and chemical composition of the etched surface of SiC. Etching in air produced partly amorphised silicon carbide and microcrystals of free Si with a characteristic size of about 30 nm. The surface of silicon carbide subjected to laser-assisted etching was capable of chemical reduction of copper from a solution used for chemical metallisation. Copper coatings formed in this way adhered strongly to the surface (adhesion force up to 30 N mm-2).

Voronov, Valerii V.; Dolgaev, Sergei I.; Lyalin, A. A.; Shafeev, Georgii A.

1996-07-01

67

Determination of total mercury in biological tissues by flow injection cold vapour generation atomic absorption spectrometry following tetramethylammonium hydroxide digestion.  

PubMed

A simple, rapid and reliable method was developed for the determination of total mercury in biological samples. Samples were solubilized using tetramethylammonium hydroxide (TMAH). The organically bound mercury was cleaved and converted to inorganic mercury by on-line addition of KMnO4. The decomposed mercury together with inorganic mercury originally present in samples was determined by flow injection cold vapour atomic absorption spectrometry after reduction to elemental mercury vapour using NaBH4. A sample throughput of 100 measurements per hour was achieved after a 30 min dissolution with TMAH. The relative standard deviation for 20 micrograms l-1 Hg was 1.3% (n = 11) and the limit of detection was 0.1 microgram l-1 (3 sigma). The proposed method was validated by the analysis of a suite of certified marine biological reference materials, DORM-2 (dogfish muscle), DOLT-2 (dogfish liver) and TORT-2 (lobster hepatopancreas), with calibration against simple HgII standards. PMID:9764507

Tao, G; Willie, S N; Sturgeon, R E

1998-06-01

68

Ramsey interferometry with an atom laser.  

PubMed

We present results on a free-space atom interferometer operating on the first order magnetically insensitive |F = 1,mF = 0) --> |F = 2,mF = 0) ground state transition of Bose-condensed (87)Rb atoms. A pulsed atom laser is output-coupled from a Bose-Einstein condensate and propagates through a sequence of two internal state beam splitters, realized via coherent Raman transitions between the two interfering states. We observe Ramsey fringes with a visibility close to 100% and determine the current and the potentially achievable interferometric phase sensitivity. This system is well suited to testing recent proposals for generating and detecting squeezed atomic states. PMID:19997295

Döring, D; Debs, J E; Robins, N P; Figl, C; Altin, P A; Close, J D

2009-11-01

69

Determination and Speciation of Mercury in a Dental WorkPlace by Cold Vapour Atomic Absorption Spectrometry and Gas-Liquid Chromatography  

Microsoft Academic Search

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

M. Akif; Eçkin; Sezer Aygün; O. Yavuz Ataman

1986-01-01

70

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

71

Ultrasensitive laser detection of atoms and molecules  

SciTech Connect

The technique of Resonance Ionization Spectroscopy (RIS) is being extended to develop a means for counting individual atoms of a selected isotope of a noble gas. In this method, lasers are used for RIS to obtain atomic species (Z) selectivity and a small quadrupole mass spectrometer provides isotopic (A) selectivity. A few thousand small molecules can also possibly be counted by RIS and a mass spectrometer.

Chen, C.H.

1984-02-01

72

Apparatus For Laser Excitation of Lithium Atoms.  

NASA Astrophysics Data System (ADS)

We have constructed and tested a vacuum system and a simple lithium oven. Lithium atoms from this oven will be excited to high principal quantum number by a combination of three lasers. We have also built and tested the hardware needed to operate the first of these lasers. In the future we will study charge transfer collisions between excited lithium atoms and ions to gain a better understanding of the physical properties of fusion, astrophysical, and other types of plasmas. Our vacuum system is assembled from standard conflat vacuum parts and from parts designed and built at Holy Cross. The vacuum environment is maintained by a diffusion pump in conjunction with a cold water trap to prevent pump oil migrating into our vacuum system. Our lithium oven consists of a small steel tube filled with lithium and mounted inside our vacuum system. The oven is heated by high temperature heater tapes. We have reached oven temperatures of over 600C which provides a sufficiently intense Li beam for our needs. The laser used in the first excitation step of lithium is a diode laser operating at 671nm. We have assembled the mechanical structure used to mount the diode laser and collimate its light output. Commercial electronics control the laser diode current and its temperature. Initial tests of the properties of the laser have been made.

Daly, James; Flaherty, Suzy; Oxley, Paul

2006-10-01

73

Lattice interferometer for laser-cooled atoms.  

PubMed

We demonstrate an atom interferometer in which atoms are laser cooled into a 1D optical lattice, suddenly released, and later subjected to a pulsed optical lattice. For short pulses, a simple analytical theory predicts the signal. We investigate both short and longer pulses where the analytical theory fails. Longer pulses yield higher precision and larger signals, and we observe a coherent signal at times that can differ significantly from the expected echo time. The interferometer has potential for precision measurements of variant Planck's/m(A), and can probe the dynamics of atoms in an optical lattice. PMID:19792621

Andersen, Mikkel F; Sleator, Tycho

2009-08-14

74

Lattice Interferometer for Laser-Cooled Atoms  

SciTech Connect

We demonstrate an atom interferometer in which atoms are laser cooled into a 1D optical lattice, suddenly released, and later subjected to a pulsed optical lattice. For short pulses, a simple analytical theory predicts the signal. We investigate both short and longer pulses where the analytical theory fails. Longer pulses yield higher precision and larger signals, and we observe a coherent signal at times that can differ significantly from the expected echo time. The interferometer has potential for precision measurements of (Planck constant/2pi)/m{sub A}, and can probe the dynamics of atoms in an optical lattice.

Andersen, Mikkel F.; Sleator, Tycho [Atomic Physics Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8424 (United States) and Jack Dodd Center for Quantum Technology, Department of Physics, University of Otago (New Zealand); Department of Physics, New York University, 4 Washington Place, New York, New York 10003 (United States)

2009-08-14

75

Polarization spectroscopy of a closed atomic transition: applications to laser frequency locking  

NASA Astrophysics Data System (ADS)

We study polarization spectroscopy of Rb vapour. A weak probe beam analyses the birefringence induced in a room temperature vapour by a strong counterpropagating circularly polarized pump beam. In contrast to most other work on polarization spectroscopy, we use a polarization beam splitting cube and two detectors (rather than a polarizer and one detector) to analyse the probe beam. The signal is in the form of a derivative of a Lorentzian. For theoretical analysis we study the closed atomic transition 5 2S1/2 (F = 3) rightarrow 5 2P3/2 (F' = 4) in the D2 line of 85Rb. We study the time needed to redistribute population among the mF states, derive an expression for the expected lineshape and present experimental data in excellent agreement with theory. The polarization spectrum provides an ideal error signal for frequency stabilization of a laser. We describe the geometry and parameters for optimizing the error signal.

Pearman, C. P.; Adams, C. S.; Cox, S. G.; Griffin, P. F.; Smith, D. A.; Hughes, I. G.

2002-12-01

76

Reactions of Laser-Ablated Metal Atoms.  

National Technical Information Service (NTIS)

Laser-ablated boron atoms react with methyl fluoride in an argon stream to form two major products, CH2BF and CHBF. In similar reactions of boron with methyl chloride and methyl bromide, both CH2BX and CHBX are also observed, as well as the primary insert...

L. Andrews

2000-01-01

77

Collinear Laser Spectroscopy on Fast Atomic Beams  

Microsoft Academic Search

In collinear geometry we have observed laser-excited, narrow resonances in fast beams of Na and Cs atoms obtained from ion beams by charge transfer collisions. Being very sensitive, the method is suited for measuring isotope shifts and hyperfine structure of isotopes far from stability provided by on-line mass separators. It may be used furthermore to study inelastic charge transfer from

K.-R. Anton; S. L. Kaufman; W. Klempt; G. Moruzzi; R. Neugart; E.-W. Otten; B. Schinzler

1978-01-01

78

Laser manipulation of atomic and molecular flows  

NASA Astrophysics Data System (ADS)

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

Lilly, Taylor C.

79

Optogalvanic effect in a self-terminating copper atomic laser  

SciTech Connect

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

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

1999-09-30

80

Resonant laser ionization of radioactive atoms*1  

NASA Astrophysics Data System (ADS)

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

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

2003-06-01

81

Modification of MoO 3 surfaces by vapour-deposited cobalt atoms  

Microsoft Academic Search

The interaction of evaporated cobalt atoms with polycrystalline MoO3 surfaces was studied by means of X-ray photoelectron spectroscopy (XPS). In several steps cobalt was evaporated onto the clean MoO3 surface at 300K. With increasing cobalt layer thickness a shoulder in the Mo3d spectra indicated the formation of Mo4+ and Mo5+. From the very beginning of the evaporation the Co2p spectra

R. Kleyna; H. Mex; M. Voß; D. Borgmann; L. Viscido; J. M. Heras

1999-01-01

82

Theory of a collective atomic recoil laser  

NASA Astrophysics Data System (ADS)

We perform a study of a collective atomic recoil laser (CARL) that goes beyond the initial growth period. The study is based on a theory that treats both internal and external degrees of atomic freedom quantum mechanically but regards the laser light as a classical field obeying Maxwell's equations. We introduce the concepts of momentum families and diffraction groups and organize the matter wave equations in terms of diffraction groups. The steady-state lasing conditions are discussed in connection with the probe gain in the recoil-induced resonances. The nontrivial steady states and the linear stability analysis of the steady states are both carried out by the method of two-dimensional continued fractions. Both stable and unstable nontrivial steady states are calculated and discussed in the context of regarding the CARL as multiwave mixing involving many modes of matter waves and two optical fields.

Ling, H. Y.; Pu, H.; Baksmaty, L.; Bigelow, N. P.

2001-05-01

83

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

84

An automated on-line minicolumn preconcentration cold vapour atomic absorption spectrometer: application to determination of cadmium in water samples.  

PubMed

A method was developed for on-line solid phase preconcentration and cold vapour atomic absorption spectrometric determination of Cd(II) in aqueous samples. Lewatit Monoplus TP207 iminodiacetate chelating resin was used for the separation and preconcentration of Cd(II) ions at pH 4.0. The whole system was labmade. The influence of analytical parameters such as concentration of eluent and sodium tetrahydroborate solution, flow rate of eluent, sample, and Ar, and matrix ions were investigated. A preconcentration factor of 20 and a detection limit (3s(b)) of 2.1ngL(-1), along with a sampling frequency of 28h(-1) were achieved with 1.4min of sample loading time and with 2.8mL sample consumption. The relative standard deviation (R.S.D.) was 2.5% for 0.05?gL(-1) Cd(II) level. The developed method was used for Cd(II) analysis in water samples. The certified reference material (LGC6019) experimental results are in good agreement with the certified value. PMID:22265561

Sahan, Serkan; Sahin, U?ur

2012-01-15

85

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

Microsoft Academic Search

A method has been developed for mercury(II) and methyl mercury speciation on Staphylococcus aureus loaded Dowex Optipore V-493 micro-column in the presented work, by using cold vapour atomic absorption spectrometry. Selective and sequential elution with 0.1molL?1 HCl for methyl mercury and 2molL?1 HCl for mercury(II) were performed at the pH range of 2–6. Optimal analytical conditions including pH, amounts of

Mustafa Tuzen; Isa Karaman; Demirhan Citak; Mustafa Soylak

2009-01-01

86

Mercury speciation by liquid chromatography coupled with on-line chemical vapour generation and atomic fluorescence spectrometric detection (LC–CVGAFS)  

Microsoft Academic Search

Reverse phase chromatography (RPC) coupled on-line with UV–vis diode array detector (DAD) and cold vapour generation atomic fluorescence spectrometry (CVGAFS) is proposed for the speciation and determination of inorganic and organic mercury (methylmercury, ethylmercury and phenylmercury) in the form of cysteine, penicillamine and glutathione complexes. The mercury–thiol complexes are separated on a C18 Reverse Phase column and oxidized on-line with

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

2005-01-01

87

Design for a compact CW atom laser  

NASA Astrophysics Data System (ADS)

We present a design for a compact continuous-wave atom laser on a chip. A 2D spiral-shaped quadrupole guide is formed by two 0.5 mm x 0.5 mm wires carrying 5 A each embedded in a Si wafer; a 1.5 mm x 0.5 mm wire on the bottom layer carries -10 A, producing a horizontal B-field that pushes the guiding channel center above the chip surface. The center-to-center separation between the top wires is varied from 1.6 mm at the start of the guide to 1 mm at the end, decreasing the guide height from ˜500 ?m to ˜25 ?m above the surface as the atoms travel the 70 cm-long guide. The magnetic gradient of the guiding channel gradually increases from ˜100 G/cm to ˜930 G/cm. These features result in continuous surface adsorption evaporative cooling and progressive magnetic compression. Spin flip losses are mitigated by a solenoid sewn around the guide to produce a longitudinal B-field. ^87Rb atoms are gravitationally loaded into the guide. A far off-resonant light shift barrier at the end of the guide traps the atoms and allows formation of a BEC. Tuning the barrier height to create a non-zero tunneling rate equal to the loading rate completes the implementation of a CW atom laser. Two options for atom interferometry are implemented on the first-generation chip (matter-wave Fabry-Perot interferometer and guide-based Mach-Zehnder interferometer). Current construction status and challenges will be discussed, along with preliminary results.

Power, Erik; Raithel, Georg

2011-06-01

88

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

NASA Astrophysics Data System (ADS)

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

Boichenko, Aleksandr M.; Evtushenko, Gennadii S.; Zhdaneev, O. V.; Yakovlenko, Sergei I.

2005-06-01

89

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

90

DISCUSSION: Effect of the prepulse electron density and population of the lower laser level on the pulse repetition rate achievable in a copper vapour laser  

NASA Astrophysics Data System (ADS)

Factors are considered which restrict the limiting pulse repetition rate in a copper vapour laser. The existence of a critical prepulse electron density discussed in a paper of S.I.Yakovlenko [Quantum Electronics, 30, 501 (2000)] and new arguments in favour of the existence of the critical electron density reported in a paper of A.M. Boichenko and S.I.Yakovlenko [Quantum Electronics, 32, 172 (2002)] are analysed. The conclusion is made that the new arguments do not prove the existence of the critical electron density as well.

Petrash, G. G.

2002-02-01

91

Blast waves in atomic cluster media using intense laser pulses  

Microsoft Academic Search

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.

Roland Smith

2008-01-01

92

High-power atomic xenon laser  

NASA Astrophysics Data System (ADS)

The high pressure atomic xenon laser is becoming the most promising light source in the wavelength region of a few microns. The merits are high efficiency (so far up to 8 percent), high output energies (15 J/liter at 9 bar), high continuous output power (more than 200 W/liter), no gas dissociation and thermal heating of the lower laser level. Compared with the well-known low pressure xenon laser the power performance is now roughly a factor thousand higher. The operation of the system, based on three-body-collisions, uses the metastable state of the xenon atom as the ground state so that in the recirculation of energy a high quantum efficiency is obtained. Furthermore the homogeneous line broadening caused by the high collision frequency has also a strong beneficial effect on the efficiency. However, the required intense homogeneous excitation of the gas medium at high density is from a technical point of view a great challenge. From our experimental and theoretical work we found that at optimum performance the input power must be 1 to 2.5 [KW cm-3 atm-2]. We describe our results obtained with e-beam sustained and x-ray preionized systems delivering pulsed energies in the range of joules per liter. Furthermore we describe our recent results on continuous RF excited wave guide systems of about 37 cm length with output powers in the range of watts.

Witteman, Wilhelmus J.; Peters, Peter J.; Botma, Hako; Tskhai, S. N.; Udalov, Yu. B.; Mei, Qi-Chu; Ochkin, V. N.

1995-03-01

93

Measuring fast variations of ?^{18}O and ?^2H in atmospheric water vapour using laser spectroscopy: an instrument inter-comparison and characterisation study  

NASA Astrophysics Data System (ADS)

Fast variations of stable water isotopes in water vapour have become measurable lately using novel laser spectroscopic techniques. This allows us to perform process-based investigations of the atmospheric water cycle at the time scales of significant weather events. An important prerequisite for such studies implying automatic field measurements lasting for several weeks or even months is a detailed knowledge about sources of uncertainty and instrument properties. We present a comprehensive characterisation and comparison study of two commercial laser spectroscopic systems based on cavity ring-down spectroscopy (Picarro) and off-axis integrated cavity output spectroscopy (Los Gatos Resarch). The old versions (L1115-i, WVIA) and the new versions (L2130-i, WVIA-EP) of both systems were tested. The uncertainty components of the measurements were assessed in laboratory experiments, focussing on effects of (i) water vapour mixing ratio, (ii) measurement stability, (iii) uncertainties due to calibration and (iv) response times of the isotope measurements due to adsorption-desorption processes on the tubing and measurement cavity walls. Knowledge from our laboratory experiments was used to setup a one-week field campaign for comparing measurements of the ambient isotope signals from the L1115-i and WVIA systems. The optimal calibration strategy determined for both instruments was applied as well as the correction functions for water vapour mixing ratio effects. Using this field measurement data we address the question of how well the deuterium excess (d=?2H-8?18O) of atmospheric water vapour can be determined with laser spectroscopy. The deuterium excess is an interesting parameter for process-based atmospheric water cycle studies, which depends on humidity and temperature conditions at source location of water vapour. Up to now only very few high-time-resolution measurements of deuterium excess exist. Our concurrent measurements of atmospheric isotopes in water vapour using the two analysers allow us to evaluate the precision and accuracy of atmospheric deuterium-excess measurements.

Aemisegger, F.; Sturm, P.; Graf, P.; Sodemann, H.; Pfahl, S.; Knohl, A.; Wernli, H.

2012-04-01

94

Fabricating atom chips with femtosecond laser ablation  

NASA Astrophysics Data System (ADS)

We report on the microfabrication of atom chips using a femtosecond laser ablation technique to arbitrarily sculpture both thin conductive metal films and permanent magnetic materials. We have measured the threshold fluences for a variety of materials relevant to atom chip development (Au, Ag, Cu, Cr, Ni, TbGdFeCo, SmCo, CoCr). The quality of the ablation process is investigated by extracting the power spectral density of the edge roughness from composite scanning electron microscope images and through the use of a magnetoresistance microscope to measure the associated magnetic field noise. Finally, we present results from a sculptured wire which produces an array of tunable double wells designed for near-surface force sensing with Bose-Einstein condensates.

Wolff, C. H.; Whitlock, S.; Lowe, R. M.; Sidorov, A. I.; Hall, B. V.

2009-04-01

95

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

NASA Astrophysics Data System (ADS)

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

Traxler, Mallory A.

96

Long wavelength room temperature laser operation of a strained InGaAs\\/GaAs quantum well structure monolithically grown by metalorganic chemical vapour deposition on a low energy-plasma enhanced chemical vapour deposition graded misoriented Ge\\/Si virtual substrate  

Microsoft Academic Search

We report on the first room temperature (RT) laser operation at 1.04?m from strained InGaAs\\/GaAs quantum well structures grown by metalorganic chemical vapour deposition and monolithically integrated on Si using a 6° offcut Ge\\/GeSi\\/Si virtual substrate (VS) realised by low energy-plasma enhanced chemical vapour deposition. Similar threshold current density from identical control laser diodes grown on bulk germanium substrates demonstrates

Y. Chriqui; G. Saint-Girons; G. Isella; H. von Kaenel; S. Bouchoule; I. Sagnes

2005-01-01

97

Broadband laser cooling of trapped atoms with ultrafast pulses  

SciTech Connect

We demonstrate broadband laser cooling of atomic ions in an rf trap using ultrafast pulses from a mode-locked laser. The temperature of a single ion is measured by observing the size of a time-averaged image of the ion in the known harmonic trap potential. Although the lowest observed temperature was only about 1 K, this method efficiently cools very hot atoms and can sufficiently localize trapped atoms to produce near diffraction-limited atomic images.

Blinov, B.B.; Kohn, R.N. Jr.; Madsen, M.J.; Maunz, P.; Moehring, D.L.; Monroe, C. [FOCUS Center and Department of Physics, University of Michigan, Ann Arbor, Michigan 48109-1040 (United States)

2006-06-15

98

Energy characteristics of a copper vapour laser in the range of stable thyratron operation  

SciTech Connect

It is shown that selection of the pump parameters of lasers based on self-terminating transitions is governed by the range of stable operation of a thyratron used in the excitation circuit. The reverse voltage across a thyratron varies anomalously during the initial heating period of a gas-discharge tube. This reverse voltage should be controlled in selecting the pump parameters for the active medium of the laser. (control of laser radiation parameters)

Yudin, Nikolai A [Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk (Russian Federation)

1998-09-30

99

Dual-Beam Atom Laser Driven by Spinor Dynamics  

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

100

Laser manipulation of atomic beam velocities: Demonstration of stopped atoms and velocity reversal  

Microsoft Academic Search

Atomic-beam sodium atoms were slowed to zero or negative velocities by counterpropagating laser radiation which was frequency chirped with precise electro-optic modulation techniques. The resulting ``gas cloud'' had a temperature below 50 mK and a density above 106 atoms\\/cm3. We mention future possibilities in atom slowing, deflection, and storage.

W. Ertmer; R. Blatt; J. L. Hall; M. Zhu

1985-01-01

101

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

102

Laser-diode-tuned chromium atom trapping and fabrication with atom optics technology  

NASA Astrophysics Data System (ADS)

We developed a laser-beam-controlled atom-manipulation system to deposit nanometric structure of atoms on a substrate. Atom beam of chromium is thermally evaporated and collimated with Doppler cooling technique using frequency-tuned laser diode. The gradient force is exerted on atoms by a standing wave over the substrate, and atoms are trapped in a low potential region of the standing wave. Consequently, a series of lines are formed on the substrate with the same periodicity to the standing wave. We present the analysis of trajectories of atoms in the light force potential to find conditions of the laser power, the sign and the degree of the detuning of the laser frequency from the resonance frequency of the atom, to reduce the width of the structure.

Okamoto, Kenji; Inouye, Hironobu; Inouye, Yasushi; Kawata, Satoshi

1999-05-01

103

Nonlinearly-generated atomic signal for robust laser locking  

NASA Astrophysics Data System (ADS)

We have developed a very simple technique to stabilize a laser emission to an atomic or molecular transition, using only a single focused beam, photodetector and a simple electronic circuit to feed an error signal back to the frequency controller of the laser. We have demonstrated the performance of this technique in semiconductor lasers, resonant with the D2 lines of either Cs or Rb atoms.

Queiroga da Silva, F.; Soares Martins, W.; Vidal, I.; Passerat de Silans, T.; Oriá, M.

2012-11-01

104

Calculation of photoemission from atoms subject to intense laser fields  

Microsoft Academic Search

We use a nonperturbative method to solve the time-dependent Schroedinger equation for an electronic state of an atom subject to a very intense (<10¹³ W\\/cm²) laser. The oscillating, time-dependent dipole induced by the laser serves as a source for the photoemission. Calculations of single-atom photospectra reveal peaks at the odd harmonics of the incident laser field superimposed on a broad

Jeffrey L. Krause; Kenneth J. Schafer; Kenneth C. Kulander

1992-01-01

105

Some New Infrared Laser Transitions in Atomic Oxygen and Sulfur.  

National Technical Information Service (NTIS)

Laser action in the 2-5 micrometer range is reported for atomic oxygen and sulfur and the laser transitions identified. This new laser with a line at 4.5607 micrometers may have important application in monitoring carbon monoxide which has an absorption l...

C. Wittig, G. Hubner

1970-01-01

106

Analysis of Atomic Beams Produced by Laser-Induced Ablation  

Microsoft Academic Search

Pulsed atomic beams with flux densities above 1016 cm-2 s-1 have been produced in vacuum with high reproducibility by laser induced ablation from titanium and iron targets. The power of the TEA CO2 laser was kept at a level where plasma production at the target surface was avoided: no ions were detectable. The beams were analysed by laser fluorescence. The

K P Selter; H-J Kunze

1982-01-01

107

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

Microsoft Academic Search

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

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

108

Laser Methods in the Study of Nuclei, Atoms and Molecules  

NASA Astrophysics Data System (ADS)

The VIth International Workshop on Application of Lasers in Atomic Nuclei Research was held at Adam Mickiewicz University, Poznan in Poland from May 24 to 27, 2004. Its title this year was "Laser methods in the study of nuclei, atoms and molecules". Some topics are reviewed from a viewpoint of the atomic physics contribution to nuclear physics and its applications. It is suggested how this meeting should be organized in the future by taking the new geopolitics into account.

Inamura, Takashi T.

2005-01-01

109

Correlations and Counting Statistics of an Atom Laser  

SciTech Connect

We demonstrate time-resolved counting of single atoms extracted from a weakly interacting Bose-Einstein condensate of {sup 87}Rb atoms. The atoms are detected with a high-finesse optical cavity and single atom transits are identified. An atom laser beam is formed by continuously output coupling atoms from the Bose-Einstein condensate. We investigate the full counting statistics of this beam and measure its second order correlation function g{sup (2)}({tau}) in a Hanbury Brown-Twiss type experiment. For the monoenergetic atom laser we observe a constant correlation function g{sup (2)}({tau})=1.00{+-}0.01 and an atom number distribution close to a Poissonian statistics. A pseudothermal atomic beam shows a bunching behavior and a Bose distributed counting statistics.

Oettl, Anton; Ritter, Stephan; Koehl, Michael; Esslinger, Tilman [Institute of Quantum Electronics, ETH Zuerich, Hoenggerberg, CH-8093 Zurich (Switzerland)

2005-08-26

110

Lithium atom interferometer using laser diffraction: description and experiments  

Microsoft Academic Search

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

A. Miffre; M. Jacquey; M. Buchner; G. Trenec; J. Vigue

111

Experimental and theoretical study of the expansion of a metallic vapour plasma produced by laser  

Microsoft Academic Search

The interaction between a metallic plasma produced by laser ablation and an ambient gas (argon, air and nitrogen) at atmospheric pressure is studied. The experimental results are compared with theoretical ones given by numerical simulation. Aluminium and copper targets are used. The uniform repartition of iron impurities included in the target (1.6% for Al and 2% for Cu) is warranted

A. Gomes; A. Aubreton; J. J. Gonzalez; S. Vacquié

2004-01-01

112

An experimental study of a CW optically pumped far infrared formic acid vapour laser  

Microsoft Academic Search

This paper describes a comprehensive experimental study of the performance of an optically pumped formic acid waveguide laser operating at wavelengths of 394, 419, 433, and 513 microns. The variation of output power with Pyrex waveguide diameter, in the range 30-92 mm, and output coupling fraction, between 5 and 40 percent per double pass, is studied in detail. The results

L. B. Whitbourn; J. C. Macfarlane; P. A. Stimson; B. W. James; I. S. Falconer

1988-01-01

113

Laser reflectometry in situ monitoring of InGaAs grown by atmospheric pressure metalorganic vapour phase epitaxy  

NASA Astrophysics Data System (ADS)

InGaAs layers on undoped GaAs (0 0 1) substrates were grown by atmospheric pressure metalorganic vapour phase epitaxy (AP-MOVPE). In order to obtain films with different indium composition ( xIn), the growth temperature as a growth parameter, was varied from 420 to 680 °C. Furthermore, high-resolution X-ray diffraction (HRXRD) measurements were used to quantify the change of xIn. Crystal quality has been also studied as a function of growth conditions. On the other hand, laser reflectometry (LR) at 632.8 nm wavelength, was employed to in situ monitor epitaxy. Reflectivity-time signal was enabled to evaluate structural and optical properties of samples. We have fitted experimental data to determine optical constants and growth rate of InGaAs at 632.8 nm. In addition, the fitting provided InGaAs thickness as a function of growth time. Based on ex situ characterization by scanning electronic microscopy (SEM) and HRXRD, we propose a practical method, relating the contrast of first reflectivity maximum with the X-ray diffraction peak angular difference between the substrate and epitaxial layer, to determine in situ the In solid composition in InGaAs alloys.

Habchi, M. M.; Rebey, A.; Fouzri, A.; El Jani, B.

2006-10-01

114

Matter wave optics theory of the collective atomic recoil laser  

NASA Astrophysics Data System (ADS)

The collective atomic recoil laser, or CARL, is the atomic analog of the free electron laser. In the CARL system a gas of two-level atoms driven by a strong off-resonant pump laser undergoes an exponential instability characterized by the spontaneous formation of a density modulation at half the optical wavelength and the simultaneous generation of a second laser field counterpropogating with respect to the pump. The current CARL theory assumes that the atoms follow, at least approximately, classical trajectories, and is thus valid only at ``high'' temperatures where the thermal DeBroglie wavelength is much smaller than the optical wavelength. We present a matter wave optics model of the CARL valid in both the ultracold and BEC regimes, which demonstrates the tendency of atomic diffraction to counteract the bunching process and thus limit the operating range of the CARL.

Moore, Michael; Meystre, Pierre

1998-05-01

115

Gravitational wave detection with single-laser atom interferometers  

Microsoft Academic Search

We present a new general design approach of a broad-band detector of gravitational radiation that relies on two atom interferometers\\u000a separated by a distance L. In this scheme, only one arm and one laser will be used for operating the two atom interferometers. We consider atoms in\\u000a the atom interferometers not only as perfect inertial reference sensors, but also as

Nan Yu; Massimo Tinto

2011-01-01

116

Laser-enabled Auger decay in rare-gas atoms.  

PubMed

In rare-gas atoms, Auger decay in which an inner-valence shell ns hole is filled is not energetically allowed. However, in the presence of a strong laser field, a new laser-enabled Auger decay channel can open up to increase the double-ionization yield. This process is efficient at high laser intensities, where an ns hole can be filled within a few femtoseconds of its creation. This novel laser-enabled Auger decay process is of fundamental importance for controlling electron dynamics in atoms, molecules, and materials. PMID:21405392

Ranitovic, P; Tong, X M; Hogle, C W; Zhou, X; Liu, Y; Toshima, N; Murnane, M M; Kapteyn, H C

2011-02-01

117

Laser-Enabled Auger Decay in Rare-Gas Atoms  

SciTech Connect

In rare-gas atoms, Auger decay in which an inner-valence shell ns hole is filled is not energetically allowed. However, in the presence of a strong laser field, a new laser-enabled Auger decay channel can open up to increase the double-ionization yield. This process is efficient at high laser intensities, where an ns hole can be filled within a few femtoseconds of its creation. This novel laser-enabled Auger decay process is of fundamental importance for controlling electron dynamics in atoms, molecules, and materials.

Ranitovic, P.; Hogle, C. W.; Zhou, X.; Murnane, M. M.; Kapteyn, H. C. [JILA and Department of Physics, University of Colorado and NIST, Boulder, Colorado 80309-0440 (United States); Tong, X. M. [Institute of Materials Science, Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan); Center for Computational Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577 (Japan); Liu, Y. [College of Engineering, University of California at Berkeley, California 94720 (United States); Toshima, N. [Institute of Materials Science, Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan)

2011-02-04

118

Application of wavelength scanning for measuring water vapour concentration by distributed laser diode  

NASA Astrophysics Data System (ADS)

A technique which takes advantage of distributed feedback laser diode (DFB-LD) wavelength scanning to measure water vapor concentration is presented. Concentration is gotten by peak absorption rate according to Beer-Lambert law and absorption coefficient of water vapor in HITRAN database. Theoretical work on the pressure affection to light intensity absorption rate has been done, a scheme is presented to cope with the affection of overlap of two adjacent lines, it takes advantage of the peak absorption difference between 1368.597nm and 1367.862 nm, and the difference value is used to calculate the water-vapor concentration.

Chang, Jun; Guangping, Lv; Zhou, Guoqing; Chen, Kun; Zhang, Yan; Wang, Zhongliang; Zhang, Shicong; Wang, Qiang; Song, Fujun

2011-09-01

119

Laser-Guided Atoms in Hollow-Core Optical Fibers  

NASA Astrophysics Data System (ADS)

We have used optical forces to guide atoms through hollow-core optical fibers. Laser light is launched into the hollow region of a glass capillary fiber and guided by grazing-incidence reflection from the walls. When the laser is detuned 1-30 GHz red of the Rb D2 resonance lines, dipole forces attract atoms to the high-intensity region along the axis and guide them through the fiber. We show that atoms may be guided around bends in the fiber and that in initial experiments the atoms experience up to 18 reflections from the potential walls with minimal loss.

Renn, M. J.; Montgomery, D.; Vdovin, O.; Anderson, D. Z.; Wieman, C. E.; Cornell, E. A.

1995-10-01

120

A pulsed Sisyphus scheme for laser cooling of atomic hydrogen  

NASA Astrophysics Data System (ADS)

We discuss a 3-level laser cooling scheme and its application to cooling atomic Hydrogen. In this scheme, ground state atoms are repetitively excited to a meta-stable state that is shifted and quenched by a standing wave laser, and are subsequently cooled by a Sisyphus effect. We demonstrate numerically that this cooling scheme can have a large capture velocity and can have sub-Doppler equilibrium temperatures. The scheme may be particularly useful for cooling of atomic species that require deep-UV lasers for electronic excitations. In particular, we discuss the possibility of cooling magnetically trapped hydrogen atoms from a Kelvin down to 10's of milli-Kelvin temperatures with manageable photo-ionization and spin-flip losses, using high-power 2S-3P laser light (at 656 nm) and pulsed 1S-2S 2-photon excitation (at 243 nm).

Wu, Saijun; Brown, Roger C.; Phillips, William D.; Porto, J. V.

2010-03-01

121

Vacuum ultraviolet laser induced fluorescence on a Si atomic beam  

NASA Technical Reports Server (NTRS)

A broadly applicable vacuum ultraviolet experiment is described for measuring radiative lifetimes of neutral and singly-ionized atoms in a beam environment to 5-percent accuracy using laser induced fluorescence. First results for neutral Si are reported.

O'Brian, T. R.; Lawler, J. E.

1991-01-01

122

Output from an atom laser: theory vs. experiment  

Microsoft Academic Search

.   Atom lasers based on rf-outcoupling can be described by a set of coupled generalized Gross–Pitaevskii equations (GPE). We\\u000a compare the theoretical predictions obtained by numerically integrating the time-dependent GPE of an effective one-dimensional\\u000a model with recently measured experimental data for the F=2 and F=1 states of Rb-87. We conclude that the output of a rf atom-laser can be described

Jens Schneider; Axel Schenzle

1999-01-01

123

Confinement and manipulation of atoms using short laser pulses  

NASA Astrophysics Data System (ADS)

The force resulting from a position-dependent sequence of interactions with short counter-propagating ?-pulses of laser radiation can propel atoms towards the small region where the pulses overlap. The optical trap thus formed may be combined with Doppler-cooling laser beams.

Freegarde, T. G. M.; Walz, J.; Hänsch, T. W.

1995-02-01

124

Laser Induced Fluorescence Spectroscopy in Atomic Beams of Radioactive Nuclides.  

National Technical Information Service (NTIS)

Measurements of the resonant scattering of light from CW tunable dye lasers, by a well collimated atomic beam, enable hyperfine splittings and optical isotope shifts to be determined with high precision and high sensitivity. Recent off-line atomic beam ex...

H. Rebel G. Schatz

1982-01-01

125

Investigations of a two-mode atom-laser model  

Microsoft Academic Search

Atom lasers based on rf outcoupling from a trapped Bose-Einstein condensate can be described by a set of generalized, coupled Gross-Pitaevskii equations (GPEs). If not only one but two radio frequencies are used for outcoupling, the atoms emerging from the trap have two different energies and the total wave function of the untrapped spin state is a coherent superposition which

Jens Schneiderand; Axel Schenzle

2000-01-01

126

Energy transfer between laser beams propagating through an atomic vapor  

Microsoft Academic Search

It is shown that it is possible to transfer energy efficiently between two laser beams of comparable intensity by means of the near-resonant nonlinear response of an atomic vapor. The coupling is due to stimulated Rayleigh scattering and occurs when the frequency difference between the two beams is approximately the inverse of the lifetime of the excited atomic state. The

Mark T. Gruneisen; Kenneth R. MacDonald; Alexander L. Gaeta; Robert W. Boyd; Donald Harter

1989-01-01

127

Quantum statistical measurements of an atom laser beam  

NASA Astrophysics Data System (ADS)

We describe a scheme, operating in a manner analogous to a reversed Raman output coupler, for measuring the phase-sensitive quadrature statistics of an atom laser beam. This scheme allows for the transferral of the atomic field statistics to an optical field, for which the quantum statistics may then be measured using the well-developed technology of optical homodyne measurement.

Olsen, M. K.; Bradley, A. S.; Haine, S. A.; Hope, J. J.

2007-06-01

128

Laser Production of a Very Slow Monoenergetic Atomic Beam  

Microsoft Academic Search

With use of a resonant, counterpropagating laser beam the velocity of atoms in a neutral, thermal-sodium beam has been reduced to 40 m\\/s, or 4% of their initial velocity. These atoms have a kinetic energy comparable to the well depth of proposed optical traps. The \\

John V. Prodan; William D. Phillips; Harold Metcalf

1982-01-01

129

Reducing the linewidth of an atom laser by feedback.  

PubMed

A continuous atom laser will almost certainly have a linewidth dominated by the effect of the atomic interaction energy, which turns fluctuations in the condensate atom number into fluctuations in the condensate frequency. These correlated fluctuations mean that information about the atom number could be used to reduce the frequency fluctuations, by controlling a spatially uniform potential. We show that feedback based on a physically reasonable quantum nondemolition measurement of the atom number of the condensate in situ can reduce the linewidth enormously. PMID:11178030

Wiseman, H M; Thomsen, L K

2001-02-12

130

Strongly driven one-atom laser and decoherence monitoring  

SciTech Connect

We propose the implementation of a strongly driven one-atom laser, based on the off-resonant interaction of a three-level atom in {lambda} configuration with a single cavity mode and three laser fields. We show that the system can be described equivalently by a two-level atom resonantly coupled to the cavity and driven by a strong effective coherent field. The effective dynamics can be solved exactly, including a thermal field bath, allowing an analytical description of field statistics and entanglement properties. We also show the possible generation of quantum superposition (Schroedinger cat) states for the whole atom-field system and for the field alone after atomic measurement. We propose a way to monitor the system decoherence by measuring atomic populations. Finally, we confirm the validity of our model through numerical solutions.

Lougovski, P. [Hearne Institute for Theoretical Physics, Department of Physics and Astronomy, Louisiana State University, 202 Nicholson Hall, Baton Rouge, Louisiana 70803 (United States); Casagrande, F.; Lulli, A. [Dipartimento di Fisica, Universita di Milano, Via Celoria 16, 20133 Milan (Italy); Solano, E. [Physics Department, ASC, and CeNS, Ludwig-Maximilians-Universitaet, Theresienstrasse 37, 80333 Munich (Germany); Seccion Fisica, Departamento de Ciencias, Pontificia Universidad Catolica del Peru, Apartado 1761, Lima (Peru)

2007-09-15

131

Lithium atom interferometer using laser diffraction: description and experiments  

Microsoft Academic Search

.  We have built and operated an atom interferometer of the\\u000aMach-Zehnder type. The atomic wave is a supersonic beam of lithium\\u000aseeded in argon and the mirrors and beam-splitters for the atomic\\u000awave are based on elastic Bragg diffraction on laser standing\\u000awaves at =671 nm. We give here a detailed description of\\u000aour experimental set-up and of the procedures used

Alain Miffre; Marion Jacquey; M. Büchner; G. Trénec; J. Vigué

2005-01-01

132

Four-level atom interferometer with trichromatic laser fields  

SciTech Connect

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

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

2007-02-15

133

Atom dynamical dissipation in the laser cavity with quasimode  

NASA Astrophysics Data System (ADS)

In this paper we study the atom dissipation effect in a laser cavity. The cavity field mode is described by the Fox—Li quasimode due to the leakiness of the cavity. Our results show that the atom decay rate versus the decay rate of the quasimode is a Lorentz type. Effects of the atom—cavity detuning as well as cavity size are also discussed.

Jiang, Wen-Ying; Zhao, Zhi-Min; Tian, Tian; Zheng, Li; Zheng, Tai-Yu

2013-06-01

134

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

135

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

136

Design of a femtosecond laser assisted tomographic atom probe  

SciTech Connect

A tomographic atom probe (TAP) in which the atoms are field evaporated by means of femtosecond laser pulses has been designed. It is shown that the field evaporation is assisted by the laser field enhanced by the subwavelength dimensions of the specimen without any significant heating of the specimen. In addition, as compared with the conventional TAP, due to the very short duration of laser pulses, no spread in the energy of emitted ions is observed, leading to a very high mass resolution in a straight TAP in a wide angle configuration. At last, laser pulses can be used to bring the intense electric field required for the field evaporation on poor conductive materials such as intrinsic Si at low temperature. In this article, the performance of the laser TAP is described and illustrated through the investigation of metals, oxides, and silicon materials.

Gault, B.; Vurpillot, F.; Vella, A.; Gilbert, M.; Menand, A.; Blavette, D.; Deconihout, B. [GPM, UMR 6634 CNRS, Universite et INSA de Rouen, 76801 Saint-Etienne du Rouvray Cedex (France)

2006-04-15

137

Theory of a single-atom laser including light forces  

SciTech Connect

We study a single incoherently pumped atom moving within an optical high-Q resonator in the strong-coupling regime. Using a semiclassical description for the atom and field dynamics, we derive a closed system of differential equations to describe this coupled atom-field dynamics. For sufficiently strong pumping, the system starts lasing when the atom gets close to a field antinode, and the associated light forces provide for self-trapping of the atom. For a cavity mode blue detuned with respect to the atomic transition frequency, this is combined with cavity-induced motional cooling, allowing for long-term steady-state operation of such a laser. The analytical results for temperature and field statistics agree well with our earlier predictions based on quantum Monte Carlo simulations. We find sub-Doppler temperatures that decrease with gain and coupling strength, and can even go beyond the limit of passive cavity cooling. Besides demonstrating the importance of light forces in single-atom lasers, this result also gives strong evidence to enhance laser cooling through stimulated emission in resonators.

Salzburger, Thomas; Ritsch, Helmut [Institute for Theoretical Physics, University of Innsbruck, A-6020 Innsbruck, Technikerstrae 25/2 (Austria); Domokos, Peter [Research Institute for Solid State Physics and Optics, P.O. Box 49, H-1525 Budapest (Hungary)

2005-09-15

138

Laser enabled Auger decay in argon atoms and dimers  

NASA Astrophysics Data System (ADS)

In rare-gas atoms, Auger decay in which an inner-valence shell ns hole is filled is normally not energetically allowed. However, in the presence of a strong laser field, a new laser-enabled Auger decay channel can open up to increase the double-ionization yield. This process is efficient at high laser intensities, and an ns hole can be filled within a few femtoseconds of its creation. This novel laser-enabled Auger decay (LEAD) process is of fundamental importance for controlling electron dynamics in atoms, molecules, and materials. We then use LEAD to investigate charge transfer in a Coulomb exploding Ar dimer. We can selectively double-ionize either the Ar dimer (threshold ˜ 36 eV) or Ar atoms (threshold ˜ 43.5 eV) using combined laser (1.5 eV) and XUV photons (36 eV) in a time-resolved fashion, and then comparing the kinetic energy releases. The Ar dimer can be double ionized when the 3s hole is filled by a 3p electron from either one of the two Ar atoms through LEAD. Theoretical calculation will support data taken using COLTRIMS and HHG.

Ranitovic, Predrag; Tong, Xiao-Min; Hogle, Craig W.; Toshima, N.; Murnane, M. M.; Kapteyn, H. C.

2011-06-01

139

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

140

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

141

Recent Work with Laser Trapped Radioactive ^21Na Atoms  

NASA Astrophysics Data System (ADS)

^21Na(t_1/2=22 seconds) is produced on-line at the 88" Cyclotron at LBNL and is transferred to a magneto-optical trap where it is stored. Recent improvements to our apparatus, mainly in our oven and target, have resulted in 40,000 trapped ^21Na atoms. This number of atoms provides enough activity for ?-decay studies, our goal being precision measurements of fundamental weak interaction parameters (for example from the electron-neutrino correlations and the parity violating ?-asymmetry of spin-polarized nuclei). We have detected ?'s from our trapped sample and are currently investigating transferring our atoms to a second laser trap to provide a cleaner environment for ?-decay studies. We have also made a precise measurement of the atomic ground state hyperfine splitting of ^21Na using our trapped atoms. We induce transitions between the 3S_1/2(F=1) and the 3S_1/2(F=2) states with microwaves and probe the atoms with a laser pulse. The atomic fluorescence measures how many atoms make the transition as a function of microwave frequency. Our resolution improves the precision on the ground state hyperfine splitting by a factor of 100. This work is supported by DOE contract DE-AC03-76SF00098.

Rowe, Mary; Freedman, Stuart; Fujikawa, Brian; Gwinner, Gerald; Shang, Song-Quan; Vetter, Paul

1997-10-01

142

Bowls made of Laser Light to Corral Ultracold Atoms  

NASA Astrophysics Data System (ADS)

Using stable lasers, it is now possible to create nearly perfect bowls made of pure light, which are smaller than a piece of lint and store atoms for several minutes in an ultrahigh vacuum environment. These almost frictionless bowls are ideal for cooling atoms by evaporation, the same way that alcohol cools the skin. In just a few seconds, atoms trapped in the bowl are cooled to temperatures of ten of billionths of a degree above absolute zero, where the de Broglie wavelength is several microns. These ultracold atoms occupy the quantum energy levels of the bowl, producing a giant quantum system that can be directly observed using laser flash photography. I will describe our laser trapping methods and show how they can be use to study a unique quantum gas of spin-up and spin-down ^6Li atoms, which are fermions that obey the Pauli exclusion principle. I will describe how this ultracold atomic gas now tests predictions in nearly all fields of physics, from high temperature superconductors to neutron stars, the quark-gluon plasma of the Big Bang, and even string theory.

Thomas, John

2010-10-01

143

Sub-Doppler laser cooling of potassium atoms  

SciTech Connect

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

Landini, M. [LENS and Dipartimento di Fisica e Astronomia, Universita di Firenze, I-50019 Sesto Fiorentino (Italy); INFN, Sezione di Firenze, I-50019 Sesto Fiorentino (Italy); Dipartimento di fisica, Universita di Trento, I-38123 Povo (Trento) (Italy); Roy, S.; Carcagni, L.; Trypogeorgos, D. [LENS and Dipartimento di Fisica e Astronomia, Universita di Firenze, I-50019 Sesto Fiorentino (Italy); Fattori, M.; Inguscio, M.; Modugno, G. [LENS and Dipartimento di Fisica e Astronomia, Universita di Firenze, I-50019 Sesto Fiorentino (Italy); INFN, Sezione di Firenze, I-50019 Sesto Fiorentino (Italy)

2011-10-15

144

Control of atomic collisions by laser polarization.  

PubMed

Atomic collision pairs in a light field form a microscopic interferometer. The light acts as the beam splitter and controls at the same time the amplitudes and phases of the interfering waves. We demonstrate the complete tunability using linear and elliptic polarization. PMID:14753873

Schmidt, T; Figl, C; Grimpe, A; Grosser, J; Hoffmann, O; Rebentrost, F

2004-01-23

145

Calcium-atom interferometer comprised of four copropagating traveling laser beams  

Microsoft Academic Search

Four laser beams traveling in the same direction that split and reflect a thermal calcium atomic beam compose an atomic interferometer like the Mach-Zehnder optical interferometer. The interference performance of the atomic interferometer was examined by changing the phase of the induced dipole moment in the atomic wave due to the laser beams, or the phase of atomic ``wavepacket'' in

Atsuo Morinaga; Yasushi Ohuchi

1995-01-01

146

Three-level atom laser model with results and applications  

SciTech Connect

We present here a fully quantum-mechanical treatment of the laser using a three-level atom model. The phase-space method employed is identical to that in a previous publication of ours (Phys. Rev. A 38, 4073 (1988)) and again results in a Fokker-Planck description of the laser without any approximations. The third level only provides extra deterministic terms and, if it is regarded as a further reservoir to the lasing levels, then the resultant stochastic equations have much improved stability. These equations are suitable for extensive theoretical analysis of both the laser and optical bistability, although in this paper we have concentrated on the adiabatically eliminated limit and calculated the leading noise terms in various regimes. However, we do use the technique of direct numerical simulation to solve exactly the full system of laser equations. The results display clearly many of the known laser characteristics.

Smith, A.M.; Gardiner, C.W. (Department of Physics, University of Waikato, Hamilton, New Zealand (NZ))

1990-03-01

147

Numerical study of femtosecond laser-assisted atom probe tomography  

NASA Astrophysics Data System (ADS)

We investigate the mechanisms of a laser-assisted atom probe tomography technique. In this method, a sub-wavelength tip is subjected both to a very strong static electric field and to a femtosecond laser pulse. As a result, ions are ejected from the tip one by one. By using femtosecond lasers, one can analyze not only metals but also semiconductors and dielectric materials. To better understand the ejection process, a numerical model is developed based on the drift-diffusion approach. The model accounts for such effects as field penetration, hole and electron movement, and laser absorption. For the given value of the dc field, a substantial band bending and an increase in hole density at the surface of the silicon tip are observed. This bending effect changes silicon absorption coefficient at the surface and significantly increases recombination time of laser-induced carriers.

Silaeva, E. P.; Shcheblanov, N. S.; Itina, T. E.; Vella, A.; Houard, J.; Sévelin-Radiguet, N.; Vurpillot, F.; Deconihout, B.

2013-03-01

148

Laser-assisted positron-impact ionization of atomic hydrogen  

NASA Astrophysics Data System (ADS)

We study the ionization of atomic hydrogen by a fast positron in the presence of an external linearly polarized laser field. We concentrate on the limit of a small momentum transfer and describe the fast positron's continuum states by Volkov wave functions. The ejected electron is described by a Coulomb-Volkov wave function. We are limited to small laser intensities such that the dressed state of the target is treatable within the time-dependent perturbation theory, even though the laser intensity is still quite high by laboratory standards. Numerical results for the triply differential cross sections and their dependencies on laser-field parameters are discussed and compared with the results of laser-assisted ionization by electron impact.

Pan, Juan; Li, Shu-Min; Berakdar, Jamal

2007-03-01

149

Laser-assisted positron-impact ionization of atomic hydrogen.  

PubMed

We study the ionization of atomic hydrogen by a fast positron in the presence of an external linearly polarized laser field. We concentrate on the limit of a small momentum transfer and describe the fast positron's continuum states by Volkov wave functions. The ejected electron is described by a Coulomb-Volkov wave function. We are limited to small laser intensities such that the dressed state of the target is treatable within the time-dependent perturbation theory, even though the laser intensity is still quite high by laboratory standards. Numerical results for the triply differential cross sections and their dependencies on laser-field parameters are discussed and compared with the results of laser-assisted ionization by electron impact. PMID:17308568

Pan, Juan; Li, Shu-Min; Berakdar, Jamal

2007-03-15

150

Investigation of shadow effect in laser-focused atomic deposition  

NASA Astrophysics Data System (ADS)

The feature width broadening and height increasing of the Cr nanostructure have been experimentally observed in the gradual atom flux distribution divergent area on one sample along the standing wave direction in laser-focused atomic deposition. By applying an optimized ballistic deposition surface growth model to simulate this situation, it is demonstrated that the shadow effect of the forming nanostructure influences the deposition sites of the subsequent incident atoms, which leads to feature broadening and contrast decreasing of the nanostructures. The shadow effect theory provides a new understanding for the explanation of the discrepancy between the calculated results and the experimental observations.

Deng, Xiao; Ma, Yan; Zhang, Pingping; Zhang, Wanjing; Chen, Sheng; Xiao, Shengwei; Li, Tongbao

2012-11-01

151

Guiding cold atoms in a hollow laser beam  

NASA Astrophysics Data System (ADS)

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

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

1999-12-01

152

Cooperative atomic interactions in a single-mode laser  

SciTech Connect

An equation of motion for the reduced density matrix for the field in a single-mode laser is derived when the single- and two-atom interactions are included. An exact steady-state solution for the photon distribution function is presented and some aspects of the photon statistics are discussed.

Mahmood, S.; Zubairy, M.S.

1987-01-01

153

Rapidly solidified prealloyed powders by laser spin atomization  

Microsoft Academic Search

A new technique, termed laser spin atomization, for the production of rapidly solidified prealloyed powders is described. The results of experiments involving the production of powders of two alloys, one based on Ni, the other on Ti, are presented. The powders have been characterized using light optical metallography, scanning electron microscopy, energy dispersive X-ray spectroscopy, and Auger elec-tron spectroscopy, and

D. G. Konitzer; K. W. Walters; E. L. Heiser; H. L. Fraser

1984-01-01

154

Atomic and molecular emissions in laser-induced breakdown spectroscopy  

NASA Astrophysics Data System (ADS)

This article summarizes measurements and analysis of hydrogen Balmer series atomic lines following laser-induced optical breakdown. Electron number density on the order of 1 × 1025 m- 3 can be measured using H? Stark width and shift in the analysis of breakdown plasma in 1 to 1.3 × 105 Pa, gaseous hydrogen. The H? line can be utilized for electron number density up to 7 × 1023 m- 3. The historic significance is elaborated of accurate H? measurements. Electron excitation temperature is inferred utilizing Boltzmann plot techniques that include H? atomic lines and further members of the Balmer series. Laser ablation of aluminum is discussed in view of limits of application of the Balmer series. H? and H? lines show presence of molecular carbon in a 2.7 and 6.5 × 105 Pa, expanding methane flow. Diagnostic of such diatomic emission spectra is discussed as well. Laser-induced breakdown spectroscopy historically embraces elemental analysis, or atomic spectroscopy, and to a lesser extent molecular spectroscopy. Yet occurrence of superposition spectra in the plasma decay due to recombination or due to onset of chemical reactions necessitates consideration of both atomic and molecular emissions following laser-induced optical breakdown. Molecular excitation temperature is determined using so-called modified Boltzmann plots and fitting of spectra from selected molecular transitions. The primary interest is micro-plasma characterization during the first few micro-seconds following optical breakdown, including shadowgraph visualizations.

Parigger, Christian G.

2013-01-01

155

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

156

Laser atomic photoionization spectral analysis of element traces  

NASA Astrophysics Data System (ADS)

A new method for determining trace amounts of elements in a substance has been developed. It is based on thermal evaporation and atomization of a substance in vacuum and detection of the released trace atoms by the laser stepwise photoionization technique. A rather effective way of detecting atoms is their multistep excitation to Rydberg states by the radiation of tunable dye lasers with their subsequent ionization by electric field pulses. The analytical laser spectrometer consisting of several tunable, pulsed dye lasers, a vacuum chamber with an atomizer and a recording system is described. The microimpurities of elements have been detected in pure materials: the contents of Na impurities in CdS crystals (2×10-6%) and Al impurities in germanium (2×10-7%). The detection limit of about 10-9% was determined. A technique for direct determination of the content of elements in natural water and human blood is described. A high sensitivity, universality and other merits of the method enable it to be used in determining traces of many important elements at a level of 10-8 to 10-11% almost in any matrix.

Bekov, G. I.; Letokhov, V. S.

1983-04-01

157

Photoassociation of laser-cooled Potassium atoms  

Microsoft Academic Search

Photoassociation spectroscopy using ultra-cold alkali atoms is an important tool in understanding long-range vibrational motion of excited dimers. We present for the first time experimental data of the purely long-range 1u potential of ^39K and a quantitative theoretical model of the complex hyperfine structure of each vibrational level. In conventional spectroscopy these hyperfine effects are often negligible compared to rotational

Eite Tiesinga; Paul Julienne; Xiaotian Wang; He Wang; Phillip Gould; William Stwalley

1998-01-01

158

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

PubMed

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

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

2009-07-01

159

Rubidium isotope measurements in solid samples by laser ablation-laser atomic absorption spectroscopy  

Microsoft Academic Search

Laser atomic absorption was used to measure the rubidium isotopes in a laser-induced plasma. An 85Rb\\/87Rb isotope ratio of 2.7±0.2 was determined in solid calcium carbonate samples. A Nd:YAG laser was used to produce the plasma on the surface of solid samples placed inside a low pressure chamber with a controlled atmosphere of 150 mtorr to 10 torr. The plasma

L. A King; I. B Gornushkin; D Pappas; B. W Smith; J. D Winefordner

1999-01-01

160

Laser-driven atomic-probe-beam diagnostics  

NASA Astrophysics Data System (ADS)

A new laser-driven atomic-probe-beam diagnostic (LAD) is proposed for local, time-resolved measurements of electric field and ion dynamics in the accelerating gap of intense ion beam diodes. LAD adds new features to previous Stark-shift diagnostics which have been progressively developed in several laboratories, from passive observation of Stark effect on ion species or fast (charge-exchanged) neutrals present naturally in diodes, to active Stark atomic spectroscopy (ASAS) in which selected probe atoms were injected into the gap and excited to suitable states by resonant laser radiation. The LAD scheme is a further enhancement of ASAS in which the probe atoms are also used as a local (laser-ionized) ion source at an instant of time. Analysis of the ion energy and angular distribution after leaving the gap enables measurement, at the chosen ionization location in the gap, of both electrostatic potential and the development of ion divergence. Calculations show that all of these quantities can be measured with sub-mm and ns resolution. Using lithium or sodium probe atoms, fields from 0.1 to 10 MV/cm can be measured.

Knyazev, B. A.; Greenly, J. B.; Hammer, D. A.

2000-12-01

161

5p photoemission from laser-excited cesium atoms  

SciTech Connect

Fine-structure resolved 5p photoemission spectra of Cs in the ground state and after laser excitation into the [Xe]6p {sup 2}P{sub 1/2} and 6p{sup 2}P{sub 3/2} states have been studied. The 5p{sup 5}6p final states have been reached by the 5p{sup 6}6s{yields}5p{sup 5}6p conjugate shakeup process from ground-state atoms as well as by direct photoemission from laser-excited atoms. The laser-excited spectra can be well described with calculations based on the jK-coupling model. Calculations based on a multiconfiguration Dirac-Fock approach have been performed to investigate the deviations created by intermediate coupling from the pure jK-coupling scheme.

Schulz, J. [Department of Physical Sciences, University of Oulu, Box 3000, FIN-90014 (Finland); Department of Physics, Uppsala University, Box 530, SE-75121 Uppsala (Sweden); Maeaettae, M.; Heinaesmaeki, S.; Huttula, M.; Aksela, S.; Aksela, H. [Department of Physical Sciences, University of Oulu, Box 3000, FIN-90014 (Finland); Sankari, R. [Department of Physical Sciences, University of Oulu, Box 3000, FIN-90014 (Finland); Department of Physics, University of Turku, FIN-20014 Turku (Finland); Kukk, E. [Department of Physics, University of Turku, FIN-20014 Turku (Finland); Rander, T.; Svensson, S. [Department of Physics, Uppsala University, Box 530, SE-75121 Uppsala (Sweden)

2006-06-15

162

Chemical vapour deposition of coatings  

Microsoft Academic Search

Chemical Vapour Deposition (CVD) of films and coatings involve the chemical reactions of gaseous reactants on or near the vicinity of a heated substrate surface. This atomistic deposition method can provide highly pure materials with structural control at atomic or nanometer scale level. Moreover, it can produce single layer, multilayer, composite, nanostructured, and functionally graded coating materials with well controlled

K. L. Choy

2003-01-01

163

Hollow Atoms by Laser Plasma-Wall Interaction  

NASA Astrophysics Data System (ADS)

When a highly charged ion approaching a metal surface, it can capture a large amount of electrons. The ion, which is neutralized above the surface but highly excited forms a "hollow atom". The highly charged ion carries a lot of potential energy and could be used to create nanostructures. The relaxation of the transient hollow atom could act as a new intense x-ray source. One approach to create highly charged ions and hollow atoms is to use laser plasma-wall interaction (LPWI). A femtosecond laser beam (1mj/40fs/1kHz at 800nm) will be tightly focused on a rotating aluminum (or magnesium) target. The interaction between the created plasma shock wave and an aluminum wall will be studied by a pin diode and a Von Hamos spectrometer.

Wang, Quan; Knight, Larry; Shevelko, Alexander; Peatross, Justin

1998-10-01

164

Heteronuclear collisions between laser-cooled metastable neon atoms  

NASA Astrophysics Data System (ADS)

We investigate heteronuclear collisions in isotope mixtures of laser-cooled metastable (3P2) neon. Experiments are performed with spin-polarized atoms in a magnetic trap for all two-isotope combinations of the stable neon isotopes 20Ne, 21Ne, and 22Ne. We determine the rate coefficients for heteronuclear ionizing collisions to ?21,20=(3.9±2.7)×10-11 cm3/s, ?22,20=(2.6±0.7)×10-11 cm3/s, and ?21,22=(3.9±1.9)×10-11 cm3/s. We also study heteronuclear elastic collision processes and give upper bounds for heteronuclear thermal relaxation cross sections. This work significantly extends the limited available experimental data on heteronuclear ionizing collisions for laser-cooled atoms involving one or more rare gas atoms in a metastable state.

Schütz, Jan; Feldker, Thomas; John, Holger; Birkl, Gerhard

2012-08-01

165

Resonant electron-atom bremsstrahlung in an intense laser field  

NASA Astrophysics Data System (ADS)

We analyze a resonant mechanism for spontaneous laser-assisted electron bremsstrahlung (BrS) involving the resonant transition (via either laser-assisted electron-ion recombination or electron-atom attachment) into a laser-dressed intermediate quasibound state (corresponding, respectively, to either a field-free neutral atom or a negative-ion bound state) accompanied by ionization or detachment of this state by the laser field. This mechanism leads to resonant enhancement (by orders of magnitude) of the BrS spectral density for emitted photon energies corresponding to those for laser-assisted recombination or attachment. We present an accurate parametrization of the resonant BrS amplitude in terms of the amplitudes for nonresonant BrS, for recombination or attachment to the intermediate state, and for ionization or detachment of this state. The high accuracy of our general analytic parametrization of the resonant BrS cross section is shown by comparison with exact numerical results for laser-assisted BrS spectra obtained within time-dependent effective range theory. Numerical estimates of resonant BrS in electron scattering from a Coulomb potential are also presented.

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

2014-02-01

166

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

167

Modeling of the microwave and discharge excited atomic Xe laser  

SciTech Connect

The high pressure (> 0.5 atm) atomic Xe laser oscillates on at least 5 infrared transitions (1.73 {mu}m - 3.51 {mu}m), and operates at high intrinsic efficiencies (< 5%) using a variety of excitation sources. Recently pulsed electric discharge and microwave excitation has been experimentally investigated. The authors have developed computer models of those lasers to study scaling of the laser at high pump rates and energy deposition. A new modeling technique was developed which extends the use of the local field approximation for high pressure discharges to conditions where zero-crossings in the electric field occur. The authors find that microwave excitation is nearly equivalent to particle beam excitation when compared on the basis of power deposition, and exhibits similar high gas temperature effects. Pumping the Xe laser using a TEA discharge optimizes at lower Xe concentrations than using microwave or particle beam excitation.

Jong, W.; Kushner, S.; Kushner, M.J. [Univ. of Illinois, Urbana, IL (United States)

1992-12-01

168

Atomic electron correlations in intense laser fields  

SciTech Connect

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

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

1998-11-01

169

Cr2O3 thin films grown at room temperature by low pressure laser chemical vapour deposition  

Microsoft Academic Search

Chromia (Cr2O3) has been extensively explored for the purpose of developing\\u000awidespread industrial applications, owing to the convergence of a variety of\\u000amechanical, physical and chemical properties in one single oxide material.\\u000aVarious methods have been used for large area synthesis of Cr2O3 films.\\u000aHowever, for selective area growth and growth on thermally sensitive materials,\\u000alaser-assisted chemical vapour deposition (LCVD)

P. M. Sousa; A. J. Silvestre; O. Conde

2010-01-01

170

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

171

Modification of Atomic Collision Dynamics by Intense Ultrashort Laser Pulses.  

NASA Astrophysics Data System (ADS)

During the past decade there has been a great deal of effort put toward demonstrating that the dynamics of atomic collisions can be modified by the presence of intense laser fields. The term "modified collision dynamics" means here that the potential energy surfaces which govern the collision dynamics are actually distorted by the ac -Stark effect induced by the intense laser field. This results in altered probabilities for the scatterers to end up in certain outgoing channels. The attractiveness of the idea of modified collisions, of course, lies in the possibility of selectively controlling physical or chemical processes by judicious choice of laser frequency and intensity. If one uses laser pulses whose duration is less than an individual collision then the experimenter can actively change the shape of the potentials during the collision. In principle, if one can open and close reactive channels at appropriate times during the collision, one can strongly influence its outcome. In this thesis the first experimental observation of the modification of atomic collision dynamics by ultrashort laser pulses is reported. In order to more fully understand the interaction of the ultrashort laser field with the colliding atomic system, a theoretical model was developed using a solution to Schroedinger's equation in Bloch equation form. The numerical solution was then averaged over various uncontrollable parameters present in the experiment when using a thermally random distribution of atoms. Averaging over these parameters as well as using a realistic temporal pulse shape and spatial beam profile has proven to be extremely important in modeling the experimental outcome. The output of a dye oscillator-amplifier combination was used to study the collision process Na(3s) + Ar + (H/2PI)(omega) (--->) Na(3P(, 1/2)) + Ar. It has been found that at fixed laser intensity the efficiency of exciting the Na(3P(, 1/2)) state is higher for pulses shorter than a collision duration than for pulses with duration longer than the collision duration. This effect is caused by a time-dependent modification of the collision potentials by the intense laser field.

Sizer, Theodore, II

172

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

173

Advances in quantum dot lasers: From classical lasers to single artificial atom lasers with photonic crystal nanocavity  

Microsoft Academic Search

We overview recent advances in nanophotonics devices with emphasis on quantum dot lasers. The discussion includes high-performance quantum dot lasers and light-matter interaction in a single quantum dot with photonic crystal nanocavity. A single artificial atom lasers with two-dimensional photonic crystal nanocavity is demonstrated. Moreover, lasing oscillation in a quantum dot-three-dimensional photonic crystal nanocavity coupled system with the highest Q

Yasuhiko Arakawa; Mitsuru Sugawara; Satoshi Iwamoto; Masahiro Nomura; A. Tandaechanurat

2010-01-01

174

Optical gain and grating structure in the collective atomic recoil laser  

NASA Astrophysics Data System (ADS)

Considering atoms entering an interaction region with limited length, then continuously running away, we show the features of the optical gain and atomic grating structure in the collective atomic recoil laser (CARL).

Wang, Jun-Li; Qiao, Yao-Jun; Fan, Wen-Jun; Zhai, Peng-Wang; Gao, Jin-Yue

1999-04-01

175

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

176

Differential atomic magnetometry based on a diverging laser beam  

NASA Astrophysics Data System (ADS)

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/?Hz may be improved further without sacrificing size or simplicity.

Hodby, E.; Donley, E. A.; Kitching, J.

2007-07-01

177

Three-level atom interferometer with bichromatic laser fields  

SciTech Connect

We have developed a three-level atom interferometer using three-level atoms coupled with bichromatic fields in order to investigate the phase information between two excited states. First, we presented a theoretical description of the interaction of three-level atoms with bichromatic fields based on single-transition operators. Using the time evolution of a wave function, the equations of the interference fringes and the visibility were derived and calculated for several types of the three-level atom interferometers with bichromatic fields. Optimum excitation conditions were evaluated. Next, several types of three-level atom interferometers were demonstrated experimentally using a thermal calcium atomic beam with two Zeeman substates of m=1 and m=-1 in the long-lived excited state coupled with bichromatic resonant fields between the ground state and the excited states. The behaviors of the interference fringes were compared among them along with the calculated results. The three-level atom interferometer excited by two bichromatic laser beams separated in space was found to produce the largest visibility among them when the excitation power of each frequency component was the same.

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

2003-10-01

178

Strong Field Atomic Dynamics Driven by Shaped Ultrafast Laser Pulses  

NASA Astrophysics Data System (ADS)

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

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

2009-05-01

179

Rapidly solidified prealloyed powders by laser spin atomization  

Microsoft Academic Search

A new technique, termed laser spin atomization, for the production of rapidly solidified prealloyed powders is described.\\u000a The results of experiments involving the production of powders of two alloys, one based on Ni, the other on Ti, are presented.\\u000a The powders have been characterized using light optical metallography, scanning electron microscopy, energy dispersive X-ray\\u000a spectroscopy, and Auger elec-tron spectroscopy, and

D. G. Konitzer; K. W. Walters; E. L. Heiser; H. L. Fraser

1984-01-01

180

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

181

A heated vapor cell unit for dichroic atomic vapor laser lock in atomic rubidium.  

PubMed

The design and performance of a compact heated vapor cell unit for realizing a dichroic atomic vapor laser lock (DAVLL) for the D(2) transitions in atomic rubidium is described. A 5 cm long vapor cell is placed in a double-solenoid arrangement to produce the required magnetic field; the heat from the solenoid is used to increase the vapor pressure and correspondingly the DAVLL signal. We have characterized experimentally the dependence of important features of the DAVLL signal on magnetic field and cell temperature. For the weaker transitions both the amplitude and gradient of the signal are increased by an order of magnitude. PMID:17902946

McCarron, Daniel J; Hughes, Ifan G; Tierney, Patrick; Cornish, Simon L

2007-09-01

182

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

PubMed

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 × 7 mm(2) large and 20??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 (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(3)-10(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 ?EE ? 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. PMID:23635189

Cayzac, Witold; Frank, Alexander; Schumacher, Dennis; Roth, Markus; Blazevi?, Abel; Wamers, Felix; Träger, Michael; Berdermann, Elèni; Voss, Bernd; Hessling, Thomas

2013-04-01

183

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

NASA Astrophysics Data System (ADS)

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 × 7 mm2 large and 20 ?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 48Ca 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 103-104 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 ?EE ~ 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; Blaževi?, Abel; Wamers, Felix; Träger, Michael; Berdermann, Elèni; Voss, Bernd; Hessling, Thomas

2013-04-01

184

Search for a permanent EDM using laser cooled radioactive atom  

NASA Astrophysics Data System (ADS)

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

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

2011-07-01

185

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

186

Nuclear-driven flashlamp pumping of the atomic iodine laser  

NASA Astrophysics Data System (ADS)

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 B-10 and He-3, 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 percent. 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 percent) 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 C3F7I, 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

187

Near resonant absorption by atoms in intense fluctuating laser fields  

NASA Astrophysics Data System (ADS)

The objective of this program was to make quantitative measurements of the effects of higher-order phase/frequency correlations in a laser beam on nonlinear optical absorption processes in atoms. The success of this program was due in large part to a unique experimental capability for modulating the extracavity beam of a stabilized (approximately less than 200 kHz) continuous-wave laser with statistically-well-characterized stochastic phase (or frequency) fluctuations, in order to synthesize laser bandwidths to approximately 20 MHz (depending on noise amplitude), with profiles variable between Gaussian and Lorentzian (depending on noise bandwidth). Laser driven processes investigated included the following: (1) the optical Autler-Towns effect in the 3S(sub 1/2) (F = 2, M(sub F) = 2) yields 3P(sub 3/2) (F = 3, M(sub F) = 3) two-level Na resonance, using a weak probe to the 4D(sub 5/2) level; (2) the variance and spectra of fluorescence intensity fluctuations in the two-level Na resonance; (3) the Hanle effect in the (sup 1)S(sub 0) - (sup 3)P(sub 1), transition at lambda = 555.6 nm in Yb-174; (4) absorption (and gain) of a weak probe, when the probe is a time-delayed replica of the resonant (with the two-level Na transition) pump laser; and (5) four-wave-mixing in a phase-conjugate geometry, in a sodium cell, and, finally, in a diffuse atomic sodium beam. The experimental results from these several studies have provided important confirmation of advanced theoretical methods.

Smith, S. J.

1994-01-01

188

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

189

Linewidth of collimated wavelength-converted emission in Rb vapour  

NASA Astrophysics Data System (ADS)

We present a study of the spectral linewidth of collimated blue light (CBL) that results from wave mixing of low-power continuous-wave laser radiation at 780 and 776 nm and an internally generated mid-IR field at 5.23 ?m in Rb vapour. Using a high-finesse Fabry-Perot interferometer, the spectral width of the CBL is found to be <1.3 MHz for a wide range of experimental conditions. We demonstrate using frequency-modulated laser light that the CBL linewidth is mainly limited by the temporal coherence of the applied laser fields rather than the atom-light interaction itself. The obtained result allows the same 1.3 MHz upper limit to be set for the linewidth of the collimated mid-IR radiation at 5.23 ?m, which has not been directly detected.

Akulshin, Alexander; Perrella, Christopher; Truong, Gar-Wing; Luiten, Andre; Budker, Dmitry; McLean, Russell

2014-04-01

190

Modeling a semiconductor laser with an intracavity atomic absorber  

NASA Astrophysics Data System (ADS)

The dynamics of a semiconductor laser with an intracavity atomic absorber is studied numerically. The study is motivated by the experiments of Barbosa [Opt. Lett. 32, 1869 (2007)], using a semiconductor junction as an active medium, with its output face being antireflection coated, and a cell containing cesium vapor placed in a cavity that was closed by a diffraction grating (DG). The DG allowed scanning the lasing frequency across the D2 line in the Cs spectrum, and different regimes such as frequency bistability or dynamic instability were observed depending on the operating conditions. Here we propose a rate-equation model that takes into account the dispersive losses and the dispersive refractive index change in the laser cavity caused by the presence of the Cs vapor cell. These effects are described through a modification of the complex susceptibility. The numerical results are found to be in qualitative good agreement with some of the observations; however, some discrepancies are also noticed, which can be attributed to multi-longitudinal-mode emission in the experiments. The simulations clearly show the relevant role of the Lamb dips and crossover resonances, which arise on top of the Doppler-broadened D2 line in the Cs spectrum, and are due to the forward and backward intracavity fields interacting resonantly with the Cs atoms. When the laser frequency is locked in a dip, a reduction in the frequency noise and of the intensity noise is demonstrated.

Masoller, C.; Oria, M.; Vilaseca, R.

2009-07-01

191

The Effect of Intense Laser Radiation on Atomic Collisions  

NASA Astrophysics Data System (ADS)

Available from UMI in association with The British Library. Requires signed TDF. We have carried out theoretical and experimental studies into the effect of intense laser radiation on atomic collisions. The first experiment used neon. Excitation by electron impact in a gas discharge demanded a pressure of at least 0.075 Torr. Measurement of the intensity of 3^1S_0to 3^1P_1 fluorescence has been made for the case where high intensity ASE wings in the laser profile and background laser scatter are unimportant, with the laser tuned to resonance. The field intensity required to produce strong field fluorescence (exemplified by the Mollow triplet) was found to give rise to complications capable of screening the effects sought. Our theoretical model has suggested that at finite detunings, line-centre fluorescence will dominate Rayleigh scatter and omega_3 fluorescence. Our measurements provide information on the saturation of neon fluorescence but not of the variation of the intense field collision rate. Absorption of weak field 253.7 nm laser photons by ground state mercury atoms yielded a high 6 ^3P_1 population at a lower pressure of 0.02 Torr. The Mollow triplet has been observed in the self-broadened mercury system. Dressing of the upper transition (6^3P_1rightarrow 7^3S_1) by an intense laser close to 435.8 nm yielded the strong field signal. Polarisation studies were made possible by the 3-level mercury system (radiation trapping in a 2-level system would depolarise fluorescence) perturbed by argon. The studies yielded results that were explainable in terms of the selective population of Stark shifted dressed states by a detuned, weak probe field. Use has been made of the electric-dipole radiation selection rule m_{J}=0 rightarrow m_{J^' } = 0 unless J=J^' to devise a 'Stark shift collision switch'. The competition between collision and radiation induced transitions within the mercury atom has then been studied. The resonant, strong lambda 435.8 nm field was used in conjunction with the weak lambda 253.7 nm field detuned by 0 to 6 cm^ {-1}. Measurement of fluorescence intensity in two perpendicular planes of polarisation has revealed the dominant | e_1> to | e_2> excitation channel as a function of the Stark shift by way of the U.V. detuning. Competition between the channels was dependent on the generalised Rabi frequency. However, we could only monitor the relative strength of the channels and were thus unable to say that the Stark shift switched collisions off. (Abstract shortened by UMI.).

Young, Stephen Michael Radley

1991-02-01

192

Characterization of Vapour Plume Species and Deposition Residues Resulting from Pulsed Laser Ablation of a Graphite/Epoxy Composite.  

National Technical Information Service (NTIS)

A modified time-of-flight mass spectrometer fitted with a special collection stage for carbon-coated transmission electron microscope specimen grids is used to monitor laser-pulse ablation products from graphite/epoxy composite targets. Scanning electron ...

R. E. Roybal C. J. Miglionico C. Stein L. E. Murr K. A. Lincoln

1995-01-01

193

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

SciTech Connect

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

NONE

1994-02-01

194

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

SciTech Connect

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

Not Available

1994-12-01

195

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

SciTech Connect

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

Not Available

1992-04-01

196

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

PubMed

The aim of this study was to compare the effects of the Er,Cr:YSGG laser using chemical vapour deposition (CVD) bur cavity preparation with conventional preparation methods including a diamond bur and a carbide bur on the microleakage with two different adhesive systems. A total of 40 extracted human premolars were randomly assigned to four experimental groups according to the cavity preparation technique: group I diamond bur (Diatech); group II carbide bur (Diatech); group III Er,Cr:YSGG laser (Biolase Millennium II); and group IV CVD bur (CVDentUS). Using the different preparation techniques, Class V standardized preparations were performed on the buccal and lingual surfaces with gingival margins on the dentin and occlusal margins on the enamel. Each preparation group was randomly assigned to two subgroups (five teeth, ten preparations) according to the type of adhesive: an etch-and-rinse adhesive (Adper Single Bond), and a single-step self-etch adhesive (AdheSE One). All preparations were restored with a nanohybrid composite resin in a single increment. Following thermocycling (×500; 5-55°C), the teeth were immersed in basic fuchsin and sectioned in the orovestibular direction. Dye penetration was evaluated under a light microscope by two blinded examiners. Data were statistically analysed with the Kruskal-Wallis and Wilcoxon tests (p<0.05). There were no statistically significant differences between the preparation techniques with either of the two adhesive systems (p>0.05). Comparing the enamel and dentin leakage scores within each group, no statistically significant differences were found (p>0.05). The Er,Cr:YSGG laser cavity preparation did not differ from preparation with CVD, diamond or carbide bur in terms of microleakage with the different adhesive systems. PMID:20842517

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

2012-01-01

197

Core relaxation in atomic ultrastrong laser field ionization.  

PubMed

We have investigated atomic ionization dynamics in Kr in the transition regime from nonrelativistic to relativistic laser intensities (10(16) to 10(18) W/cm2) by measuring yields of highly charged ions stemming from an inner shell. Interpretation of the data is focused on the applicability of the single active electron description, which requires fully relaxed core states between successive ionization steps. In particular, we are concerned with transient core polarization or alignment effects originating from the strong dependence of the ionization rates on the magnetic quantum number. We found that for intense laser pulses with 40 fs pulse width internal m-mixing processes appear to be sufficiently fast to erase any transient core polarization. PMID:15783638

Gubbini, E; Eichmann, U; Kalashnikov, M; Sandner, W

2005-02-11

198

A stable 657nm laser for a Ca atom interferometer  

NASA Astrophysics Data System (ADS)

We will present an extremely stable laser to be used in an atom interferometer. A 657nm grating-stabilized diode laser is locked to a high-finesse cavity using the Pound-Drever-Hall method. Utilizing a feedback circuit with a bandwidth of 5 MHz we see a laser linewidth less than one kHz. In addition to a relatively high bandwidth, our circuit design allows for mode-hop-free scanning over a large range. We are also working on several improvements which should further reduce our linewidth; we are improving passive mechanical and thermal stability of the laser and the optical cavity and plan to change to a higher finesse cavity, we have designed and are testing a more stable current driver based on an updated Hall-Libbrecht design, and we calculating an optimized multiple-input feedback transfer function for our system. We will also present the measurement of the resonances of our optical cavity relative to the Ca intercombination line using a high-temperature vapor cell.

Neyenhuis, Brian; Erickson, Christopher; Tang, Rebecca; Doermann, Greg; van Zijll, Marshall; Durfee, Dallin

2006-05-01

199

Laser transition in atomic iodine for passive and active SETI  

NASA Astrophysics Data System (ADS)

It is proposed to use the wavelength 1.315 ?m of the laser transition 2P 1/2? 2P 3/2 in atomic iodine both for passive and active SETI. The search for an extraterrestrial signal at this wavelength is promising because an active quantum filter (AQF) with a quantum sensitivity limit and with strong fixing in the spectrum luminescence line of the width less than 0.01 cm -1, has been developed for the noted wavelength. Such AQF is capable of receiving the laser signals, consisting of only a few photons, against the background of emission from a star under study. In addition, the high-energy iodine lasers emitting diffraction-limited nanosecond pulses of energy of 2 kJ in a single beam at the wavelength 1.315 ?m have been created. The spectral tuning of radiation of these lasers allows one to compensate the frequency Doppler shift. A weak absorption of the 1.315 ?m radiation in the Earth atmosphere allows the search for extraterrestrial signals by using the ground optical telescopes equipped with adaptive optical systems.

Kutaev, Yu. F.; Mankevich, S. K.; Nosach, O. Yu.; Orlov, E. P.

2010-12-01

200

Search for permanent EDM using laser cooled Fr atoms  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

201

Comparison of chemical beam epitaxy and metalorganic chemical vapour deposition for highly strained multiple quantum well InGaAsP/InP 1.5 ?m lasers  

NASA Astrophysics Data System (ADS)

The performance and reliability of strained layer optoelectronic devices are in general limited by the integrity of metastable heterostructures. Misfit strain relaxation (and concomitant defects) can be avoided if the structural stability is optimised and elevated temperature exposure minimized. Chemical beam epitaxy (CBE) holds great promise in strained layer epitaxy, since by reducing growth temperature the overall thermal budget for epitaxy and processing can be significantly reduced. The design, epitaxial growth, fabrication and reliability issues related to strain and strain-compensated multi-quantum well lasers are first considered in order to determine the upper limits of compressive or tensile strain permissible in such structures. The benefits of strain (both tensile and compressive) on threshold current density are related to the amount of strain in the wells (via the reduction of the Auger recombination coefficient) and the well width (via the optical confinement factor). It is therefore the strain well-width product for the active region which is of key interest. In this survey the practical upper bound to stability is defined theoretically using an energy balance model, where the effect of strain compensation from oppositely strained barrier layers, balances the strain in the quantum wells and renders the multilayer stack "strain neutral". The susceptibility of strained multilayers to defect injection through epitaxial growth and subsequent device fabrication is determined by growth simulation. Using this model as a design tool we have investigated the structural stability of a compressively strained multiple quantum well (MQW) laser through the concept of "effective stress" for misfit dislocation injection. The upper limits for quantum well strain incorporation with and without strain compensation are quantitatively defined in light of recent laser reliability data. The evolution of the driving force for misfit strain relaxation is mapped out through a typical epitaxial growth sequence highlighting the points in the growth process of highest vulnerability to defect injection. These design concepts were used to optimize structures for highly strained quantum wells (QWs) in strain compensated InGaAs/InP MQW lasers. The stability of strain-compensated MQW laser structures is demonstrated for devices grown by conventional metalorganic chemical vapour deposition.

Houghton, D. C.; Davies, M.; Sudersena Rao, T.; Dion, M.

1994-03-01

202

A 650 J e-beam-pumped atomic xenon laser  

SciTech Connect

The atomic xenon laser has been scaled from the 80 J per pulse output energy level reported to 650 J, using a large two-sided {ital e}-beam-pumped device. The extraction volume dimensions were 0.5 m {center dot} 0.65 m {center dot} 3 m. The gas was pumped at a temporally and spatially averaged rate of 70 kW/cm{sup 3}, and the spatially averaged specific input energy was 115 J/L. An aluminum rear reflector and an uncoated, fused silica output coupler were aligned to form a plane-parallel optical resonator. Output energy measurements were made with a full-aperture calorimeter, and the temporal pulse shape of the 1.7 {mu}m laser radiation was recorded with a spectrally filtered germanium photodiode. The device was operated with argon-xenon gas mixtures at pressures ranging from 20 to 40 psia at a temperature of 23{degrees} C, and the xenon mole fraction was empirically optimized. The maximum output energy of 650 J was obtained at an intrinsic efficiency (output energy divided by energy deposited in gas) of 0.57%. A higher efficiency of 0.85% was achieved by using a shorter {ital e}-beam pulse, at a reduced laser output energy of 495 J. Laser output which began shortly after the start of the {ital e}-beam pulse continued well beyond the termination of that pulse, decaying at an exponential rate with an {ital e}-fold time of 1.8 {mu}s. A possible explanation for the observed laser pulse shape is discussed.

Litzenberger, L.N.; Trainor, D.W.; McGeoch, M.W. (Avco-Everett Research Lab., Everett, MA (USA))

1990-09-01

203

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

204

Laser Cooling of a Cesium Atomic Beam Using d1 Transitions and Stark Effect Frequency Compensation  

Microsoft Academic Search

In this dissertation, I present a new method of laser cooling that produces a continuous cold atomic beam. The changing Doppler shift of the slowing atoms is compensated with the Stark shift from a spatially varying static electric field. The atoms remain in resonance as they slow down. Cesium atoms emerging from an oven with an average velocity of 270

Jeng-Rong Yeh

1995-01-01

205

Laser radiation field control of the divergence of an atomic beam channeled in a polycapillary  

NASA Astrophysics Data System (ADS)

The condition of minimal divergence of an atomic beam in a polycapillary system under conditions of laser radiation input into the polycapillary wall is considered. The effect of errors in the microcapillary size on atomic beam divergence is studied. The microcapillary radius ensuring minimal divergence of the atomic beam is optimized with allowance for the quantum character of atomic motion.

Bavizhev, M. D.; Bavizhev, A. D.; Kot, N. V.

2012-09-01

206

Collective atomic recoil laser (CARL) optical gain without inversion by collective atomic recoil and self-bunching of two-level atoms  

NASA Astrophysics Data System (ADS)

We suggest a novel tunable laser concept, the Collective Atomic Recoil Laser (CARL) which unifies the physics of the FEL and of the atomic lasers. We demonstrate that a cold beam of two-level particles driven coherently by a counter-propagating resonant wave can amplify exponentially a co-propagating optical probe up to a saturation value through an instability very similar to that of a high gain FEL. In addition, the two level atoms undergo collective recoil and exponential self-bunching in space and form a longitudinal grating on the scale of the wavelength of the amplified optical signal.

Bonifacio, R.; De Salvo, L.

1994-03-01

207

Temperature measurement of laser-cooled atoms using vacuum Rabi splitting  

NASA Astrophysics Data System (ADS)

We laser cool rubidium atoms to form a magneto-optical trap, within a Fabry-Perot cavity, and demonstrate strong coupling of the cold atoms to the cavity. The coupling strength is measured using the vacuum Rabi frequency splitting (VRS) of transmitted, cavity-coupled light on atomic resonance. The VRS is measured for two- and three-level atomic systems and the atom-cavity-coupling strength for each system is determined. By allowing the laser-cooled atoms to expand for different times and measuring the corresponding VRS, we determine the number of atoms overlapped with the cavity mode as a function of time. This time-of-flight of atoms from the cavity permits the measurement of the temperature of the laser-cooled atoms. Finally, the need for this technique and its utility is discussed.

Ray, Tridib; Sharma, Arijit; Jyothi, S.; Rangwala, S. A.

2013-03-01

208

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

NASA Astrophysics Data System (ADS)

We report 2D confinement of 87Rb 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.; Biedermann, G. W.; Farrar, J. T.; Akin, T. G.; Krzyzewski, S. P.; Abraham, E. R. I.

2014-06-01

209

LASERS: Repetitively pulsed operating regime of a high-pressure atomic xenon transition laser  

NASA Astrophysics Data System (ADS)

The repetitively pulsed regime of an atomic xenon transition laser pumped by an electron beam with various pulse durations and an electron-beam-initiated discharge is studied experimentally. An average radiation power of 2.5 W has been achieved in a quasi-stationary regime for a pulse repetition rate of 5 Hz in a laser pumped by a radially convergent electron beam of duration 100 ?s without circulation of the Ar — Xe working mixture. The average output power for a laser pumped by a planar electron beam in quasi-stationary regime is 2 W. It is shown that for a specific energy contribution not exceeding 50 J L-1 and laser excitation by a train of electron-beam pulses at a repetition rate of 50 Hz, the amplitude and duration of the second lasing pulse virtually coincide with those of the first. For a laser pumped by a discharge initiated by a nanosecond electron beam, an average lasing power of 380 mW is achieved under steady-state conditions upon transverse circulation of the working mixture and a pump pulse repetition rate of 25 Hz. Pumping by an electron beam from two accelerators with a pulse duration of a few tens of microseconds under an Ar — Xe mixture pressure of about 1 atm and a specific pump power of 1 — 3 kW cm-3 per pulse is proposed for the development of 1.73-?m repetitively pulsed Xe lasers with a high average output power.

Alekseev, S. B.; Koval', N. N.; Orlovskii, Viktor M.; Skakun, V. S.; Tarasenko, Viktor F.; Tolkachev, Valerii S.; Fedenev, A. V.; Shulepov, M. A.; Shchanin, Pyotr M.

2004-06-01

210

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

211

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

212

The possibility of deep laser focusing of an atomic beam into the A-region  

Microsoft Academic Search

An atomic beam can be focused into an angstrom size spot by the action of the gradient force of a laser field having a special configuration. The main parameters and limitations of such laser objective for atomic beam microscopy are considered.

V. I. Balykin; V. S. Letokhov

1987-01-01

213

Interacting laser and Bose-Einstein-condensate atomic beams: Mutual guiding structures  

SciTech Connect

A basic set of equations describing the interaction of a Bose-Einstein condensate (BEC) with a laser field is derived based on a semiclassical model and applied to the problem of mutual guiding of laser and BEC atomic beams. Within this framework we have studied stationary spatially localized solutions of the nonlinear system which describe possible laser and BEC atomic beam guiding and have shown their stability as well. It is also shown that a self-guiding effect can be realized through both single- and multiple-scaled structures of a BEC atomic and a laser beam.

Cattani, F. [Department of Physics, Clarendon Laboratory, OX1 3PU, Oxford (United Kingdom); Geyko, V.; Kim, A. [Institute of Applied Physics, Russian Academy of Sciences, 603950 Nizhny Novgorod (Russian Federation); Anderson, D.; Lisak, M. [Department of Radio and Space Science, Chalmers University of Technology, SE-412 96 Goeteborg (Sweden)

2010-04-15

214

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

215

Very-High Resolution J-Resolved Photoelectron Spectroscoy of Laser-Excited Sodium Atoms  

Microsoft Academic Search

We have performed high-resolution photoionization experiments in laser-excited atoms by combining a cw dye laser and the photon beam available at the 10.0.1 station of the Advanced Light Source. Photoelectron ejected from laser-excited sodium atoms were analyzed using a high-resolution hemispherical Scienta analyzer. Ultimate resolution (FWHM) was 13 meV, while previous experiments were performed with 200 to 300 meV resolution

Francois Wuilleumier; Denis Cubaynes; Jean Marc Bizau; Michael Meyer; Sophie Canton; John Bozek; Bruce Rude; Eugene Kennedy; Nora Berrah

2003-01-01

216

Atomic photoionization with synchronized X-ray and optical lasers  

NASA Astrophysics Data System (ADS)

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

Meyer, Michael

2011-06-01

217

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

218

Fast-ion-beam laser probing of ion-source energy distributions and atomic structure  

NASA Astrophysics Data System (ADS)

Collinear fast-ion-beam laser spectroscopy is a very high resolution probe for measuring ion-beam energy distributions and atomic structure parameters of interest in nuclear physics, atomic physics, and astrophysics. We have used offline 10-keV beams of atomic ions and a CW laser system to study the behavior of a Penning ion source and to measure hyperfine structure, isotope shifts, atomic lifetimes, spontaneous-emission branching fractions, oscillator strengths, and absolute wavelengths of a variety of atomic species from the lanthanide and transition-metal groups.

Holt, Richard A.; Rosner, S. David

2013-04-01

219

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

220

Simple interface of high-performance liquid chromatography-atomic fluorescence spectrometry hyphenated system for speciation of mercury based on photo-induced chemical vapour generation with formic acid in mobile phase as reaction reagent.  

PubMed

Photo-induced chemical vapour generation (CVG) with formic acid in mobile phase as reaction reagent was developed as interface to on-line couple HPLC with atomic fluorescence spectrometry for the separation and determination of inorganic mercury, methylmercury (MeHg), ethylmercury (EtHg) and phenylmercury (PhHg). In the developed procedure, formic acid in mobile phase was used to decompose organomercuries and reduce Hg(2+) to mercury cold vapour under UV irradiation. Therefore, no post-column reagent was used and the flow injection system in traditional procedure is omitted. A number of operating parameters including pH of mobile phase, concentration of formate, flow rate of mobile phase, length of PTFE reaction coil, flow rate of carrier gas and Na(2)S(2)O(3) in sample matrix were optimized. The limits of detection at the optimized conditions were 0.085, 0.033, 0.029 and 0.038 microg L(-1) for inorganic mercury, MeHg, EtHg and PhHg, respectively. The developed method was validated by determination of certified reference material DORM-2 and was further applied in analyses of seafood samples from Yantai port, China. The UV-CVG with formic acid simplifies the instrumentation and reduces the analytical cost significantly. PMID:18184614

Yin, Yongguang; Liu, Jingfu; He, Bin; Shi, Jianbo; Jiang, Guibin

2008-02-15

221

Annealing study of H2O and O3 grown Al2O3 deposited by atomic layer chemical vapour deposition on n-type 4H-SiC  

NASA Astrophysics Data System (ADS)

Al2O3 has been grown by atomic layer chemical vapour deposition on HF cleaned n-type 4H-SiC using either H2O or O3 as an oxidant. After post-deposition annealing at high temperature (1000°C) in argon atmosphere for different durations (1, 2 and 3 h), bulk and interface properties of the films were studied by capacitance-voltage (CV), current-voltage (IV) and secondary ion mass spectrometry (SIMS) measurements. Electrical measurements show a decreasing shift of the flatband voltage indicating a diminution of the negative oxide charges with increasing annealing time. The SIMS measurements reveal accumulation of boron, sodium and potassium at the Al2O3/SiC interface but the accumulation decreases with annealing at 1000°C where also out diffusion of silicon into the Al2O3 film takes place.

Avice, Marc; Grossner, Ulrike; Nilsen, Ola; Christensen, Jens S.; Fjellvåg, Helmer; Svensson, Bengt G.

2006-09-01

222

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

223

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

224

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

225

Laser stabilization to an atomic transition using an optically generated dispersive line shape  

NASA Astrophysics Data System (ADS)

We report a simple and robust technique to generate a dispersive signal which serves as an error signal to electronically stabilize a monomode continuous-wave laser emitting around an atomic resonance. We explore nonlinear effects in the laser beam propagation through a resonant vapor by way of spatial filtering. The performance of this technique is validated by locking semiconductor lasers to the cesium and rubidium D2 lines and observing long-term reduction of the emission frequency drifts, making the lasers well adapted for many atomic physics applications.

Queiroga, F.; Soares Martins, W.; Mestre, V.; Vidal, I.; Passerat de Silans, T.; Oriá, M.; Chevrollier, M.

2012-05-01

226

Propagation effects in a collective atomic recoil laser  

NASA Astrophysics Data System (ADS)

We present a theoretical investigation of propagation effects in a collective atomic recoil laser (CARL) operating in the FEL limit. We consider the cases where the system evolves while in free space and while enclosed in a ring cavity. In the case where no cavity is present, we show that the scattered radiation consists of soliton-like superfluorescent pulses. In the case of a 'good' cavity we arrive analytically at a condition to neglect propagation effects. This condition implies that in order to use the so-called mean field approximation, the condition {(? L) }/{l {3}/{2}c}?0, T ? 0 must be satisfied with {(Tl c}/{(? L) {2}/{3}} finite where lc is the cooperation length of the system, T is the transmission coefficient of the mirrors, L and ? are the sample length and cavity length respectively. We confirm the validity of this condition using a numerical analysis and provide a simple physical interpretation. In the mean field limit, we show that if the cavity linewidth is greater than the spectral width of the pulse emitted by the sample, the emission remains superfluorescent and is not sensitive to the presence of the cavity. We also show that in the opposite case the emission is sensitive to the cavity parameters and no longer superfluorescent.

Bonifacio, R.; De Salvo, L.; Robb, G. R. M.

1997-02-01

227

Construction and characterization of external cavity diode lasers for atomic physics.  

PubMed

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 labs. Their versatility and prolific use throughout atomic physics in applications such as absorption spectroscopy and laser cooling makes it imperative for incoming students to gain a firm practical understanding of these lasers. This publication builds upon the seminal work by Wieman, 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

228

Novel laser atomic fluorescence spectrometer for environmental and biomedical analyses of heavy metals  

NASA Astrophysics Data System (ADS)

We report on the development of a novel experimental set-up using laser atomic fluorescence for detection and concentration measurements of heavy metal atoms for environmental and biomedical analyses. This spectrometer is based on the application of tunable LiF:F2+** and LiF:F2- color center and alexandrite lasers with nonlinear converters for narrowband excitation of atomic fluorescence and the use of gated multichannel CCD detectors for fluorescence measurements. A standard graphite furnace module was used for sample atomization. The laser sources used provide narrowband selective laser excitation continuously tunable in the 200 - 400 nm range and are therefore suitable for resonant excitation of atomic transitions in practically all known heavy metal atoms. In the first experiments, water samples containing Cu, Pb and Fe impurities were studied and detection levels of less than 1 ppb were observed. Comparison of the results of atomic laser fluorescence analysis and traditional atomic absorption spectrometry showed good qualitative agreement between these two methods. It is projected that full optimization of our experimental set up will allow for improved detection levels of several orders of magnitude. Possible optimization and simplification of the spectrometer are discussed in the context of developing a portable instrument for field use.

Dergachev, Alex Y.; Mirov, Sergey B.; Pitt, Robert E.; Parmer, Keith D.

1997-05-01

229

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

PubMed

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

Shahmoon, Ephraim; Mazets, Igor; Kurizki, Gershon

2014-06-15

230

Quantum control of qubits and atomic motion using ultrafast laser pulses  

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

231

Classical-trajectory simulation of accelerating neutral atoms with polarized intense laser pulses  

NASA Astrophysics Data System (ADS)

In the present paper, we perform the classical trajectory Monte Carlo simulation of the complex dynamics of accelerating neutral atoms with linearly or circularly polarized intense laser pulses. Our simulations involve the ion motion as well as the tunneling ionization and the scattering dynamics of valence electron in the combined Coulomb and electromagnetic fields, for both helium (He) and magnesium (Mg). We show that for He atoms, only linearly polarized lasers can effectively accelerate the atoms, while for Mg atoms, we find that both linearly and circularly polarized lasers can successively accelerate the atoms. The underlying mechanism is discussed and the subcycle dynamics of accelerating trajectories is investigated. We have compared our theoretical results with a recent experiment [Eichmann Nature (London)NATUAS0028-083610.1038/nature08481 461, 1261 (2009)].

Xia, Q. Z.; Fu, L. B.; Liu, J.

2013-03-01

232

Laser irradiated atomic clusters: resonant heating, high energy ions and fusion yield  

Microsoft Academic Search

Summary form only given. Clusters are van der Waals bound solid density atomic aggregates formed in cooled gas jets. When irradiated with laser pulses the clusters ionize and explode giving rise to interesting non-linear phenomenon such as generation of high-energy electrons and ions, higher harmonics, and fusion neutrons. Our simulations indicate that laser pulse duration and intensity as well as

A. Gupta; J. P. Palastro; T. Antonsen; H. Milchberg; T. Taguchi

2006-01-01

233

Error of finite basis expansions in time-dependent calculations of atom-laser interaction  

SciTech Connect

We propose a method to quantitatively estimate the error made with a finite basis expansion in time-dependent calculations. This method is applied to the hydrogen atom in intense laser fields and used to compare different basis sets with each other. We also show how to construct a Gaussian basis set suitable for the description of ionization dynamics in intense laser fields.

Uhlmann, Mathias; Kunert, Thomas; Schmidt, Ruediger [Institut fuer Theoretische Physik, Technische Universitaet Dresden, D-01062 Dresden (Germany)

2005-09-01

234

Laser scattering by density fluctuations of ultra-cold atoms in a magneto-optical trap  

Microsoft Academic Search

We study the spectrum of density fluctuations in the ultra-cold gas of neutral atoms, confined in a magneto-optical trap. We determine the corresponding amplitude and spectra of laser light scattered by this medium. We derive an expression for the dynamical structure function, by using a test particle method. We propose to use the collective laser scattering as a diagnostic method

J. T. Mendonça; H. Terças

2011-01-01

235

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

236

Charge transfer of 0.2-5.0 keV protons and hydrogen atoms in sodium-, potassium- and rubidium-vapour targets  

Microsoft Academic Search

Total cross sections sigma +0 and sigma +- for single- and double-electron capture by protons, and total cross sections sigma 0- and sigma 0+ for single-electron capture and single-electron loss by neutral hydrogen atoms in single collisions with atoms of sodium, potassium and rubidium have been measured in the energy range 0.2-5.0 keV. All electron capture cross sections show a

F. Ebel; E. Salzborn

1987-01-01

237

DOSSIER CONDENSATS DE BOSE-EINSTEIN ET LASERS À ATOMES  

Microsoft Academic Search

The development of high sensitivity and high accuracy atom interferometers requires new theoretical tools for their modelization: in this article we emphasize specifically a generalized Fresnel-Kirchhoff formula for atom optics in the form of ABCD matrices and covariant wave equations in the form of a Dirac equation for atom optics in the presence of gravito-inertial fields. As examples, we derive

BOSE-EINSTEIN CONDENSATES; ATOM LASERS

238

Na-atom beam deceleration by a mode-locked laser  

Microsoft Academic Search

We report the first observation of the deceleration of a Na-beam by a counterpropagating beam of a mode-locked laser. Very low, zero, and even negative velocities have been observed. The atomic velocity distribution, measured via fluorescence induced by a single-mode laser, clearly demonstrates the dependence of the deceleration on the intensity and on the mode spacing of the mode-locked laser.

P. Strohmeier; T. Kersebom; E. Krüger; H. Nölle; B. Steuter; J. Schmand; J. Andrä

1989-01-01

239

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

240

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

241

Spatial interference during the ionization of noble gas atoms by few-cycle XUV laser pulses  

NASA Astrophysics Data System (ADS)

We have investigated the spatial interference effects, which appear during the ionization of noble gas atoms by few-cycle XUV laser pulses. By using ab initio calculations, and single active electron model potentials, we have studied how the spatial interference pattern is influenced by the atomic species of the target.

Borbély, S.; Tóth, A.; Tökésit, K.; Nagy, L.

2014-04-01

242

Atomic-fluorescence method for determining the concentration of alkali metal vapor using a laser source  

Microsoft Academic Search

In this paper we examine the atomic-fluorescence method for determining the concentration of alkali metal vapors using a laser source for the example of cesium atoms. Alkali metal vapors of Rb and Cs are widely used as working substances in commercial quantum frequency standards [8], and the investigation of the dependence of their concentration on the temperature in the buffer-gas

L. A. Budkin; O. G. Okhotnikov; G. T. Pak; A. I. Pikhtelev; S. L. Puzanov

1984-01-01

243

NONLINEAR OPTICAL PHENOMENA: Resonances of coherent population trapping in samarium vapours  

Microsoft Academic Search

Resonances of coherent population trapping were detected in atomic vapours of the rare-earth element samarium. The coherent population trapping was produced by two external-cavity diode lasers (672 and 686 nm) in a Lambda-system formed by the three levels of 154Sm: the 4f66s2(7F0) ground state, the first fine-structure 4f66s2(7F1) sublevel of the ground state and the 4f6(7F)6s6p(3Po)9Fo1 upper level. The dependence

Nikolai N. Kolachevsky; A. V. Akimov; N. A. Kiselev; A. A. Papchenko; Vadim N. Sorokin; S. I. Kanorskii

2001-01-01

244

Ultraviolet-laser atom-probe tomographic three-dimensional atom-by-atom mapping of isotopically modulated Si nanoscopic layers  

Microsoft Academic Search

Using ultraviolet-laser assisted local-electrode atom-probe (UV-LEAP) tomography, we obtain three-dimensional (3D) atom-by-atom images of isotopically modulated 28Si and 30Si ultrathin layers having thicknesses in the range of 5-30 nm. The 3D images display interfaces between the different monoisotopic layers with an interfacial width of ~1.7 nm, thus demonstrating a significant improvement over isotope mapping achievable using secondary-ion mass-spectrometry or even

Oussama Moutanabbir; Dieter Isheim; David N. Seidman; Yoko Kawamura; Kohei M. Itoh

2011-01-01

245

Influence of laser radiation on charge transfer in proton--alkali-metal-atom collisions  

Microsoft Academic Search

The atomic-eigenfunction-expansion method is used to investigate the influence of laser radiation on charge-transfer processes in proton--alkali-metal-atom collisions. The radiation is treated classically. The cross sections for charge transfer into the ground state of hydrogen in collisions between a proton and any of the atoms sodium, potassium, rubidium, and cesium in the presence of radiation of wavelengths varying between 3000

Keka Choudhury; D. P. Sural

1986-01-01

246

Influence of laser radiation on charge transfer in proton-alkali-metal-atom collisions  

Microsoft Academic Search

The atomic-eigenfunction-expansion method is used to investigate the influence of laser radiation on charge-transfer processes in proton-alkali-metal-atom collisions. The radiation is treated classically. The cross sections for charge transfer into the ground state of hydrogen in collisions between a proton and any of the atoms sodium, potassium, rubidium, and cesium in the presence of radiation of wavelengths varying between 3000

Keka Basu Choudhury; D. P. Sural

1986-01-01

247

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

248

Ionization and entanglement of two interacting Rydberg atoms in a strong laser field  

NASA Astrophysics Data System (ADS)

Dynamics of ionization and entanglement of two Rydberg atoms interacting with each other and with external strong laser field is investigated. The phenomenon of interference stabilization of the bipartite atomic system is established in a strong field limit. The production of highly-entangled state of the studied atoms is shown to be realized. The possibility to control the evolution and time-dependent entanglement of the examined multilevel q-dit system is demonstrated.

Burenkov, Ivan A.; Tikhonova, Olga V.

2014-04-01

249

Doppler-Free Laser Spectroscopy of Atomic Hydrogen Using Pulsed Lasers.  

NASA Astrophysics Data System (ADS)

Available from UMI in association with The British Library. The 1S_{1/2} -2S_{1/2} transition frequency of atomic hydrogen has been measured by interferometric comparison with a reference line in ^{130 }Te_2, tellurium. A dye laser, at 486nm was pulse amplified using a three-stage amplifier chain, transversely pumped with a Nd:YAG laser. The amplified light was spectrally filtered using a confocal interferometer and frequency doubled in urea. The filter was frequency stabilized using an FM sideband technique to cw light acousto-optically upshifted in frequency to compensate for the 'amplifier shift'. Doppler-free two photon resonant, three photon ionization signals were detected. The value for the 1S_{1/2} -2S_{1/2} transition frequency of 2466061407(9)MHz is in good agreement with the theoretical value of 2466061414.12(68)MHz. The 1S Lamb shift can be inferred from this value and is 8180(9)MHz, agreeing within one standard deviation of other experiments and the theoretical value of 8172.94(9)MHz. Alternatively, a new value for the Rydberg constant of 109737.31542(40)cm^ {-1} can be deduced. This value also agrees with the currently accepted value within one standard deviation.

Tolchard, John Michael

1988-12-01

250

Pulsed lasers utilizing transitions in atoms and molecules  

NASA Astrophysics Data System (ADS)

An examination is made of processes occurring in the active media of lasers utilizing organic compounds, metal vapors, and dense gases. The laws are established which govern the relationships between the laser radiation characteristics and the parameters of the exciting electromagnetic field. The particular features of the conversion of high-power radiation of exciplex lasers by organic compounds are studied. Original active-element designs are created. The results of experimental and theoretical investigations of the physics of lasers utilizing self-terminating transitions in metal vapors are presented. Questions are considered which are related to the possibility of raising their physical efficiency, increasing the laser pulse-repetition frequency and the practical lasing efficiency, and of controlling the energy characteristics of a copper vapor laser. A description is given of the kinetics of the most important plasma-chemical processes which occur in pulsed lasers utilizing dense gases. Their dependence on the method of creating the population inversion and on the gas composition is indicated. A detailed description is given of lasers prototypes constructed using organic compounds, metal vapors, and dense gases, of laser systems based on them, and of applications in ecological monitoring systems, navigational systems, medicine, and other fields.

Maier, G. V.; Kopylova, T. N.; Soldatov, A. N.; Tarasenko, V. F.

1998-09-01

251

Multiphoton ionization of iodine atoms and CF 3I molecules by XeCl laser radiation  

NASA Astrophysics Data System (ADS)

We report about effective ionization of iodine atoms and CF3I molecules under the action of intense XeCl laser radiation (308 nm). The only ion fragment resulting from the irradiation of the CF3I molecules is the I+ ion. We have studied the influence of the intensity, spectral composition, and polarization of the laser radiation used on the intensity of the ion signal and the shape of its time-of-flight peak. Based on the analysis of the results obtained, we have suggested the mechanism of this effect. The conclusion drawn is that the ionization of the iodine atoms by the ordinary XeCl laser with a nonselective cavity results from a three- (2 + 1)-photon REMPI process. This process is in turn due to the presence of accidental two-photon resonances between various spectral components of the laser radiation and the corresponding intermediate excited states of the iodine atom. The probability of ionization of the atoms from their ground state I(2P3/2) by the radiation of the ordinary XeCl laser is more than two orders of magnitude higher than the probability of their ionization from the metastable state I*(2P1/2). The ionization of the CF3I molecules by the XeCl laser radiation occurs as a result of a four-photon process involving the preliminary one-photon dissociation of these molecules and the subsequent (2 + 1)-photon REMPI of the resultant neutral iodine atoms.

Lokhman, V. N.; Ogurok, D. D.; Ryabov, E. A.

2008-01-01

252

Non-additivity in laser-illuminated many-atom systems  

NASA Astrophysics Data System (ADS)

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

Shahmoon, Ephraim; Mazets, Igor; Kurizki, Gershon

2014-06-01

253

Three-level atom interferometer with bichromatic laser fields  

Microsoft Academic Search

We have developed a three-level atom interferometer using three-level atoms coupled with bichromatic fields in order to investigate the phase information between two excited states. First, we presented a theoretical description of the interaction of three-level atoms with bichromatic fields based on single-transition operators. Using the time evolution of a wave function, the equations of the interference fringes and the

Kazuhito Honda; Shinya Yanagimachi; Atsuo Morinaga

2003-01-01

254

Atomic Laser Action in Rare Gas-SF6 Mixtures.  

National Technical Information Service (NTIS)

Pulsed laser action was observed on a total of seven laser transitions in Ar, one of which has not been previously reported. In pure Ar, only one transition was observed; however, the other six transitions were observed to lase simultaneously upon the add...

D. G. Sutton L. Galvan P. R. Valenzuela S. N. Suchard

1975-01-01

255

An atom laser based on dark-state cooling: a detailed description  

NASA Astrophysics Data System (ADS)

It was proposed by two of us (Wiseman H M and Collett M J 1995 Phys. Lett. A 202 246) that a device producing a coherent atomic wave (that is, an atom laser) could be built using dark-state cooling of atoms in a trap. Here we present a more complete analysis of this system, including the effects of atomic interactions through dipole-dipole coupling and hard-core collisions. We show that for reasonable physical parameters the dipole interactions have little contribution to the atomic dynamics. In contrast, the hard-core collisions are likely to dominate the laser linewidth. In fact, it would appear necessary to select (or produce) a species with a hard-core scattering radius of much less than one nm in order for the output of the device to be phase coherent.

Wiseman, H. M.; Burnett, K.; Collett, M. J.

1999-08-01

256

Sub-parts-per-quadrillion-level graphite furnace atomic absorption spectrophotometry based on laser wave mixing.  

PubMed

Nonlinear laser wave mixing in a common graphite furnace atomizer is presented as a zeptomole-level, sub-Doppler, high-resolution atomic absorption spectrophotometric method. A nonplanar three-dimensional wave-mixing optical setup is used to generate the signal beam in its own space. Signal collection is efficient and convenient using a template-based optical alignment. The graphite furnace atomizer offers advantages including fast and convenient introduction of solid, liquid, or gas analytes, clean atomization environment, and minimum background noise. Taking advantage of the unique features of the wave-mixing optical method and those of the graphite furnace atomizer, one can obtain both excellent spectral resolution and detection sensitivity. A preliminary concentration detection limit of 0.07 parts-per-quadrillion and a preliminary mass detection limit of 0.7 ag or 8 zmol are determined for rubidium using a compact laser diode as the excitation source. PMID:15018584

Mickadeit, Fritz K; Berniolles, Sandrine; Kemp, Helen R; Tong, William G

2004-03-15

257

Transport of launched cold atoms with a laser guide and pulsed magnetic fields  

NASA Astrophysics Data System (ADS)

We propose the novel combination of a laser guide and magnetic lens to transport a cold atomic cloud. We have modelled the loading and guiding of a launched cloud of cold atoms with the optical dipole force. We discuss the optimum strategy for loading typically 30% of the atoms from a magneto-optical trap (MOT) and guiding them vertically through 22 cm. However, although the atoms are tightly confined transversely, thermal expansion in the propagation direction still results in a density loss of two orders of magnitude. By combining the laser guide with a single impulse from a magnetic lens we show one can actually increase the density of the guided atoms by a factor of 10.

Pritchard, Matthew J.; Arnold, Aidan S.; Cornish, Simon L.; Hallwood, David W.; Pleasant, Chris V. S.; Hughes, Ifan G.

2006-12-01

258

Activation of Silicon Implanted with Phosphorus Atoms by Infrared Semiconductor Laser Annealing  

NASA Astrophysics Data System (ADS)

We activated silicon implanted with phosphorus atoms by infrared semiconductor laser annealing with a diamond-like carbon (DLC) optical absorption layer. The silicon samples implanted with phosphorus atoms at 10 and 70 keV with concentrations of 5× 1014, 1× 1015, and 2× 1015 cm-2 were coated with 200-nm-thick DLC films. The samples were annealed by irradiation with a 940 nm continuous wave laser at 70 kW/cm2 with a beam diameter of 180 ?m. The laser beam was scanned using a moving stage at 3-20 cm/s, which gave an effective dwell time of 0.9-6.0 ms. The amorphized surface regions were recrystallized by laser annealing longer than 1.2 ms. The in-depth profile of phosphorus concentration hardly changed within 5 nm for laser annealing for 2.6 ms. The sheet resistance markedly decreased to 106 and 46 ?/sq for the samples implanted with phosphorus atoms at 10 and 70 keV by laser annealing at a dwell time of 2.6 ms, respectively. Phosphorus atoms were effectively activated with a carrier density near the phosphorus concentration for implantation at 70 keV. A low carrier generation rate was observed for implantation at 2× 1015 cm-2 and 10 keV. An intermediate SiO2 layer effectively blocked carbon incorporation to a level below 1017 cm-3.

Sameshima, Toshiyuki; Maki, Masato; Takiuchi, Megumu; Andoh, Nobuyuki; Sano, Naoki; Matsuda, Yasuhiro; Andoh, Yasunori

2007-10-01

259

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

SciTech Connect

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

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

2011-06-15

260

Laser Flash Heating Techniques for Atomic Absorption Spectroscopy.  

National Technical Information Service (NTIS)

This report comprises fundamental procedures and techniques employed to utilize a moderate power cw laser for vaporization of metallic alloys with subsequent spectrophotometric analysis. A substantial amount of data is presented for zinc, copper, lead, al...

N. H. Macoy F. Zweibaum

1967-01-01

261

Development of an electrothermal atomization laser-excited atomic fluorescence spectrometry procedure for direct measurements of arsenic in diluted serum.  

PubMed

A procedure for the direct determination of arsenic in diluted serum by electrothermal atomization laser-excited atomic fluorescence spectrometry (ETA-LEAFS) is reported. Laser radiation needed to excite As at 193.696 and 197.197 nm is generated as the second anti-Stokes stimulated Raman scattering output of a frequency-doubled dye laser operating near 230.5 and 235.5 nm, respectively. Two different LEAFS schemes have been utilized and provide limits of detection of 200-300 fg for As in aqueous standards. When measurements of serum samples diluted 1:10 with deionized water are performed, a stable background signal is observed that can be accounted for by taking measurements with the laser tuned off-wavelength. No As is detected in any of the bovine or human serum samples analyzed. Measurements of 100 pg/mL standard additions of As to a diluted bovine serum sample utilizing either inorganic or organic As species demonstrate a linear relationship of the fluorescence signal to As spike concentration, but exhibit a sensitivity of approximately half that observed in pure aqueous standards. The limit of detection for As in 1:10 diluted serum samples is 65 pg/mL or 650 fg absolute mass, which corresponds to 0.65 ng/mL As in undiluted serum. To our knowledge, the ETA-LEAFS procedure is currently the only one capable of directly measuring As in diluted serum at these levels. PMID:10565284

Swart, D J; Simeonsson, J B

1999-11-01

262

Atomic diffusion in laser surface modified AISI H13 steel  

NASA Astrophysics Data System (ADS)

This paper presents a laser surface modification process of AISI H13 steel using 0.09 and 0.4 mm of laser spot sizes with an aim to increase surface hardness and investigate elements diffusion in laser modified surface. A Rofin DC-015 diffusion-cooled CO2 slab laser was used to process AISI H13 steel samples. Samples of 10 mm diameter were sectioned to 100 mm length in order to process a predefined circumferential area. The parameters selected for examination were laser peak power, pulse repetition frequency (PRF), and overlap percentage. The hardness properties were tested at 981 mN force. Metallographic study and energy dispersive X-ray spectroscopy (EDXS) were performed to observe presence of elements and their distribution in the sample surface. Maximum hardness achieved in the modified surface was 1017 HV0.1. Change of elements composition in the modified layer region was detected in the laser modified samples. Diffusion possibly occurred for C, Cr, Cu, Ni, and S elements. The potential found for increase in surface hardness represents an important method to sustain tooling life. The EDXS findings signify understanding of processing parameters effect on the modified surface composition.

Aqida, S. N.; Brabazon, D.; Naher, S.

2013-07-01

263

Discharge-pumped cw gas lasers utilizing ``dressed-atom'' gain media  

NASA Astrophysics Data System (ADS)

The possibility of realizing an efficient gaseous laser-beam-generating medium that utilizes ? -type coherently phased (i.e., “dressed”) atoms for the active laser species, but that does not inherently require the use of external laser beams for pumping, is explored. Specifically, it is investigated if multiphoton stimulated hyper-Raman scattering (SHRS) processes driven by fluorescence radiation generated in a continuous electrical discharge present within the vapor-containing cell could produce continuous-wave (cw) optical gain at the ? -atom resonance frequencies ?o and ?o' . It is deduced that such gain could result from n -photon (n?4) SHRS processes only if absorption of fluorescence pump light occurs in the first three transitions of the n -photon sequence representing the process unit step. Estimates of the amount of optical gain that could be produced in such a system indicate that it should be sufficient to allow multiwatt cw laser operation to occur on one set of ? transitions connecting levels in a “double- ? ” structure, with the pump light being discharge-produced fluorescence centered about the transitions of the other ? pair. However, to initiate operation of such a device would require injection into the laser optical cavity of intense “starter” laser pulses at both lasing frequencies. What should be an optimal experimental configuration for determining feasibility of the proposed laser device is described. In the suggested configuration, Cs-atom 6S1/2-6P1/2 transitions form the double- ? structure.

Sorokin, P. P.; Glownia, J. H.; Hodgson, R. T.

2005-05-01

264

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

265

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

NASA Technical Reports Server (NTRS)

A pulsed high-flux source of nearly monoenergetic atomic oxygen was developed to perform accelerated erosion testing of spacecraft materials in a simulated low-earth orbit (LEO) environment. Molecular oxygen is introduced into an evacuated conical expansion nozzle at several atmospheres pressure through a pulsed molecular beam valve. A laser-induced breakdown is generated in the nozzle throat by a pulsed CO2 TEA laser. The resulting plasma is heated by the ensuing laser-supported detonation wave, and then it rapidly expands and cools. An atomic oxygen beam is generated with fluxes above 10 to the 18th atoms per pulse at 8 + or - 1.6 km/s with an ion content below 1 percent for LEO testing. Materials testing yielded the same surface oxygen enrichment in polyethylene samples as observed on the STS mission, and scanning electron micrographs of the irradiated polymer surfaces showed an erosion morphology similar to that obtained on low earth orbit.

Krech, Robert H.; Caledonia, George E.

1990-01-01

266

Kerr-free propagation of a near-resonant laser in an atomic vapor  

NASA Astrophysics Data System (ADS)

In this paper, we address the propagation of a near resonant laser inside an atomic vapor in the case when, due to the Kerr effect, the laser beam would either self-focus or self-defocus. We show, both theoretically and experimentally, how to get rid of such an alteration in the transverse beam profile without changing any of the characteristics of the laser light under consideration (wavelength, intensity, etc.), nor of the atomic vapor. Moreover, our proposed method offers a lot of control on the beam profile, whose transverse size after propagation may be chosen at will by making use of a second, copropagating laser, whose required wavelength and intensity may be derived analytically.

Bénisti, Didier; Gobert, Olivier; Comte, Michel

2014-01-01

267

Theoretical modeling of resonant laser excitation of atoms in a magnetic field  

NASA Astrophysics Data System (ADS)

The interaction of near-resonant laser radiation with atoms immersed in a magnetic B field is calculated using a quantum electrodynamic model. In this model, the magnetic field is assumed to produce a small perturbation such that the degeneracy of the magnetic substates is lifted while maintaining the usual quantum numbers that define the states (the Zeeman effect). The laser radiation is considered to have a narrow bandwidth and to be temporally and spatially coherent. The model produces three general coupled differential equations that describe the state populations and their relative coherences and the optical coherences between levels coupled by the laser radiation. The model can therefore be directly applied to different experiments ranging from atom trapping and cooling experiments through to collision experiments carried out in magnetic and laser fields.

Murray, Andrew James; MacGillivray, William; Hussey, Martyn

2008-01-01

268

NONLINEAR OPTICAL PHENOMENA: Interference of laser-induced resonances in the continuous structures of a helium atom  

NASA Astrophysics Data System (ADS)

Coherent effects in the interference of overlapping laser-induced resonances in helium atoms are considered. The simultaneous action of single-mode radiation of the 294-nm second harmonic of a cw dye laser and a 1064-nm Nd:YAG laser on helium atoms provides the overlap of two resonances induced by transitions from the 1s2s1S and 1s4s1S helium levels. The shape of the overlapping laser-induced resonances in the rotating-wave approximation is described by analytic expressions, which depend on the laser radiation intensities and the ratio of laser frequencies.

Magunov, A. I.; Strakhova, S. I.

2003-03-01

269

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

SciTech Connect

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

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

2007-10-31

270

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

SciTech Connect

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

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

2011-10-15

271

Diode-laser isotope enrichment of rubidium with a polarized atomic beam  

Microsoft Academic Search

Diode-laser isotope enrichment of rubidium by magnetic deflection of a polarized atomic beam has been experimentally studied with laser-induced fluorescence detection. The abundance of 85Rb was enhanced from the natural value of 72.8% to 97% and that of 87Rb, from 27.2% to 83%. The results were compared with those with hot-wire detection.

Gang-Hua Mei; Yuan Zhang; Gui-Long Huang; Xi-Wen Zhu; Yong-Fang Tan; Jin-Ting Liu

1993-01-01

272

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

SciTech Connect

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

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

2010-06-15

273

Atomic phase shifts in mixed-glass, multi-petawatt laser systems.  

PubMed

The influence of the active gain medium on the spectral amplitude and phase of amplified, femtosecond pulses in a laser system is studied. Results from a case study of a 15-petawatt laser based on Nd-doped mixed glasses show that gain-induced atomic phase shifts will distort the pulses, reducing their peak power. It is also shown that a phase compensation solution is possible and the corresponding coefficients are calculated. PMID:21997104

Filip, Catalin V

2011-10-10

274

Laser source of neutral atoms for collective-field particle accelerator  

Microsoft Academic Search

Laser sources for collective-field particle accelerators, of ions of almost all chemical elements, operate in deep vacuum and in a strong alternating magnetic field. A laser source is described that can deliver an atom flux of from 10 to the 11th to 10 to the 12th power in pulses of 10-100 ms duration from a target to electron rings. Variants

Y. A. Bykovskiy; V. Y. Mironov; V. P. Sarantsev; S. M. Silnov; Y. A. Sotnichenko; Z. A. Ter-Martirosyan; B. A. Shestakov

1984-01-01

275

Search for Laser-Induced Formation of Antihydrogen Atoms  

SciTech Connect

Antihydrogen can be synthesized by mixing antiprotons and positrons in a Penning trap environment. Here an experiment to stimulate the formation of antihydrogen in the n=11 quantum state by the introduction of light from a CO{sub 2} continuous wave laser is described. An overall upper limit of 0.8% with 90% C.L. on the laser-induced enhancement of the recombination has been found. This result strongly suggests that radiative recombination contributes negligibly to the antihydrogen formed in the experimental conditions used by the ATHENA Collaboration.

Amoretti, M.; Macri, M.; Testera, G.; Variola, A. [Istituto Nazionale di Fisica Nucleare, Sezione di Genova, 16146 Genova (Italy); Amsler, C.; Pruys, H.; Regenfus, C. [Physik-Institut, Zuerich University, 8057 Zuerich (Switzerland); Bonomi, G. [Dipartimento di Ingegneria Meccanica, Universita di Brescia, 25123 Brescia (Italy); Istituto Nazionale di Fisica Nucleare, Universita di Pavia, 27100 Pavia (Italy); Bowe, P. D.; Ejsing, A. M.; Hangst, J. S.; Madsen, N. [Department of Physics and Astronomy, University of Aarhus, 8000 Aarhus C (Denmark); Canali, C.; Carraro, C.; Lagomarsino, V.; Manuzio, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Genova, 16146 Genova (Italy); Dipartimento di Fisica, Universita di Genova, 16146 Genova (Italy); Cesar, C. L. [Instituto de Fisica, Univesidade Federal do Rio de Janeiro, Rio de Janeiro 21945-970 (Brazil); Charlton, M.; Joergensen, L. V.; Mitchard, D. [Department of Physics, University of Wales Swansea, Swansea SA2 8PP (United Kingdom)] (and others)

2006-11-24

276

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

277

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

278

Coherent control of atomic quantum states by single frequency-chirped laser pulses  

SciTech Connect

We present a scheme of population transfer between two metastable (ground) states of the {lambda} atom without considerable excitation of the atom using single frequency-chirped laser pulses. The physics of the process is generation of the 'trapped' superposition of the ground states by the laser pulse at sufficiently high laser peak intensity. The main conditions for realization of this regime are the following: The width of the transform-limited laser pulse envelope frequency spectrum (without chirp) must be smaller and the peak Rabi frequency of the pulse must be larger than the frequency interval between the two ground states of the {lambda} atom. During the frequency chirp, the laser pulse must first come into resonance with the transition from the initially occupied ground state to the excited state and after that with the transition between the excited and second initially empty ground states. In the case when the envelope frequency spectrum width (without chirp) of the pulse exceeds the frequency interval between the two ground states, we show a possibility of controllable generation of superposition of the ground states with a controllable excitation of the {lambda} atom.

Djotyan, G.P.; Bakos, J.S.; Soerlei, Zs.; Szigeti, J. [Research Institute for Particle and Nuclear Physics, XII. Konkoly Thege ut 29-33, P.O. Box 49, H-1525, Budapest (Hungary)

2004-12-01

279

Magnetic induced dichroism and frequency stabilization of violet-blue diode lasers on gallium atomic transitions  

SciTech Connect

We study the magnetic-field-induced dichroism on a sample of gallium neutral atoms created in a hollow cathode lamp and describe a method for robust stabilization of violet-blue diode lasers tuned on gallium atomic transitions for an atom nanofabrication experiment. We compare the experimental dichroic signals with theoretical simulations obtained by the solving of the exact atom-field interaction Hamiltonian. We find excellent agreement when considering the magnetic field shielding from the hollow cathode. This method allows for a wide range of frequency tuning, modulation-free locking, and long-term stability of external-cavity diode lasers. From analysis of a square root Allan variance we have achieved a stability of 1 MHz at 1-s average time.

Fazio, Barbara; Marago, Onofrio M.; Musso, Maurizio [Consiglio Nazionale delle Ricerche-Istituto per i Processi Chimico-Fisici sezione Messina, via La Farina 237, I-98123 Messina (Italy); Abteilung Physik unf Biophysik, Fachbereich Molekulare Biologie, Universitaet Salzburg, Hellbrunner Strasse 34, A-5020 Salzburg (Austria)

2005-06-01

280

Enhanced photon correlations due to strong laser-atom-cavity coupling  

NASA Astrophysics Data System (ADS)

We investigate the resonant quantum dynamics of a laser-pumped real or artificial two-level single-atom system embedded in a leaking microcavity. We found that for stronger laser-atom-cavity couplings the generated microcavity photons exhibit larger steady-state correlations. In particular, the second- and third-order photon correlation functions are greater than the corresponding ones obtained for an incoherent light source, respectively. Furthermore, the emitted microcavity photon flux is enhanced in comparison to weaker coupling cases.

Ciornea, Viorel; Bardetski, Profirie; Macovei, Mihai A.

2013-08-01

281

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

282

Laser assisted atom probe analysis of thin film on insulating substrate.  

PubMed

We demonstrate that the atom probe analyses of metallic thin films on insulating substrates are possible using laser assisted field evaporation. The tips with metallic thin film and insulating substrate (0.6-3 ?m in thickness) were prepared by the lift-out and annular ion beam milling techniques on tungsten supports. In spite of the existence of thick insulating layer between the metallic film and the tungsten support, atom probe tomography with practical mass resolution, signal-to-noise ratio and spatial resolution was found to be possible using laser assisted field evaporation. PMID:21172729

Kodzuka, M; Ohkubo, T; Hono, K

2011-05-01

283

First Measurements of Hollow Lithium States Produced by Triple Excitation of Laser-Excited Lithium Atoms  

Microsoft Academic Search

Hollow lithium atoms are usually formed(L. Kiernan et al., Phys. Rev. Lett. 72), 2359(1994). ^2Y. Azuma et al., Phys. Rev. Lett. 74, 3770(1995). ^3L. Journel et al., Phys. Rev. Lett. 76, 30(1996).-3 by simultaneous three electron excitations of lithium atoms in the ground state. Combining the use of a cw dye laser with the highly monochromatic beam of synchrotron radiation

Francois Wuilleumier; Denis Cubaynes; Segolene Diehl; Jean-Marc Bizau; Bruno Rouvellou; Loic Journel; Samir Al Moussalami; Nora Berrah; L. Voky; P. Faucher; A. Hibbert; T. J. Morgan; E. T. Kennedy; C. Blanchard; J. D. Bozek; A. S. Schlachter

1996-01-01

284

Site Specificity in Femtosecond Laser Desorption of Neutral H Atoms from Graphite(0001)  

NASA Astrophysics Data System (ADS)

Femtosecond laser excitation and density functional theory reveal site and vibrational state specificity in neutral atomic hydrogen desorption from graphite induced by multiple electronic transitions. Multimodal velocity distributions witness the participation of ortho and para pair states of chemisorbed hydrogen in the desorption process. Very slow velocities of 700 and 400ms-1 for H and D atoms are associated with the desorption out of the highest vibrational state of a barrierless potential.

Frigge, R.; Hoger, T.; Siemer, B.; Witte, H.; Silies, M.; Zacharias, H.; Olsen, T.; Schiøtz, J.

2010-06-01

285

Activation of Silicon Implanted with Phosphorus Atoms by Infrared Semiconductor Laser Annealing  

Microsoft Academic Search

We activated silicon implanted with phosphorus atoms by infrared semiconductor laser annealing with a diamond-like carbon (DLC) optical absorption layer. The silicon samples implanted with phosphorus atoms at 10 and 70 keV with concentrations of 5× 1014, 1× 1015, and 2× 1015 cm-2 were coated with 200-nm-thick DLC films. The samples were annealed by irradiation with a 940 nm continuous

Toshiyuki Sameshima; Masato Maki; Megumu Takiuchi; Nobuyuki Andoh; Naoki Sano; Yasuhiro Matsuda; Yasunori Andoh

2007-01-01

286

Laser-induced fluorescence measurement of a 50MeV hydrogen atom beam  

Microsoft Academic Search

Laser-induced fluorescence has been used to measure the velocity, direction, and divergence of a beam of neutral hydrogen atoms traveling at 50 MeV or one-third the speed of light. The beam was produced by neutralizing a negative hydrogen ion beam in a foil stripper, which generated a fraction of the atoms in the metastable 2s state. These metastables were measured

R. K. Sander; F. Archuleta; W. Harker; R. Martinez; C. R. Quick; R. Reeder; D. J. Taylor; F. Brumwell; C. Hummer

1991-01-01

287

Laser-induced reaction of Yb atoms with hydrogen chloride in the gas phase  

SciTech Connect

The results are presented of an investigation of the reaction of ytterbium atoms with hydrogen chloride initiated by laser radiation resonant with the /sup 1/S/sub O/-/sup 3/P/sub 1/ intercombination transition. The rate constant of extinction of the excited state of the ytterbium atom by a molecular reagent was measured: k/sub d/ = (6.4 +- 1.5) x 10/sup -10/ cm/sup 3/sec

Borisov, S.K.; Karpov, N.A.; Krynetskii, B.B.; Mishin, V.A.; Prokhorov, A.M.; Stel'makh, O.M.

1987-11-01

288

The History of Laser Trapping of Atoms and Particles  

Microsoft Academic Search

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

Arthur Ashkin

2003-01-01

289

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

290

Hyperfine structure measurement of rubidium atom and tunable diode laser stabilization by using Sagnac interferometer.  

PubMed

The Rubidium saturated absorption spectra for D2 transition lines are used to measure the Fabry-Perot interferometer free spectral range (FSR). The scale linearity of the laser frequency tuning is determined. The Sagnac interferometer has been used for the laser stabilization. The result shows that the laser frequency is stabilized upto sub-mega Herz level. Also the hyperfine structure [5(2)S(1/2) F = 3 --> F' = 2, 3, 4 5(2)P(3/2) 85Rb] of the rubidium atom has been measured by using the tilt locking method, which shows the same result as the conventional saturation spectroscopy. PMID:17252811

Kim, Jin-Tae; Zhen, Liu; Kapitanov, Venedikt; Kim, Hyun Su; Park, Jong Rak; Park, Si-Hyun

2006-11-01

291

Influence of lasers propagation delay on the sensitivity of atom interferometers  

Microsoft Academic Search

.  In atom interferometers based on two photon transitions,\\u000a the delay induced by the difference of the laser beams paths makes\\u000a the interferometer sensitive to the fluctuations of the frequency\\u000a of the lasers. We first study, in the general case, how the laser\\u000a frequency noise affects the performance of the interferometer\\u000a measurement. Our calculations are compared with the measurements\\u000a performed on

J. Le Gouët; P. Cheinet; J. Kim; D. Holleville; A. Clairon; A. Landragin; F. Pereira Dos Santos

2007-01-01

292

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

293

Imaging time-resolved electrothermal atomization laser-excited atomic fluorescence spectrometry for determination of mercury in seawater.  

PubMed

In this study, direct determination of mercury at the nanogram per liter level in the complex seawater matrix by imaging time-resolved electrothermal atomization laser-excited atomic fluorescence spectrometry (ITR-ETA-LEAFS) is described. In the case of mercury, the use of a nonresonant line for fluorescence detection with only one laser excitation is not possible. For measurements at the 253.652 nm resonant line, scattering phenomena have been minimized by eliminating the simultaneous vaporization of salts and by using temporal resolution and the imaging mode of the camera. Electrothermal conditions (0.1 M oxalic acid as matrix modifier, low atomization temperature) have been optimized in order to suppress chemical interferences and to obtain a good separation of specific signal and seawater background signal. For ETA-LEAFS, a specific response has been obtained for Hg with the use of time resolution. Moreover, an important improvement of the detection limit has been obtained by selecting, from the furnace image, pixels collecting the lowest number of scattered photons. Using optimal experimental conditions, a detection limit of 10 ng L(-1) for 10 ?L of sample, close to the lowest concentration level of total Hg in the open ocean, has been obtained. PMID:21524139

Le Bihan, Alain; Cabon, Jean-Yves; Deschamps, Laure; Giamarchi, Philippe

2011-06-15

294

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

295

1.8 watt cw atomic iodine photolysis laser at 1.315 micron  

NASA Astrophysics Data System (ADS)

A 1.8 watt cw photolytically excited atomic iodine laser at 1.315 micron is reported. This power is believed to be the highest level obtained via the cw photolysis of an alkyl-iodide gas like C3F7I. The enhanced laser performance was achieved using a cw microwave excited ultraviolet lamp for the laser's excitation and longitudinal flow for the removal of the quenching by-product I2. Over an excitation length of 25 cm, an average small signal gain coefficient of 2 percent/cm was produced and using a stable resonator, many higher order transverse modes were observed. Its easy operation and high power may make this iodine laser very useful for the experimental testing of peripheral iodine laser technologies.

Schlie, L. A.; Rathge, R. D.

1988-05-01

296

The effect of reusing laser gas on the fission-fragment pumped 1.73 {mu}m atomic xenon laser output  

SciTech Connect

Fission-fragment pumped 1.73 {mu}m atomic xenon laser output was measured without changing the laser gas mixture before each reactor pulse. For a Ar/Xe gas mixture at 260 Torr and 0.3 percent xenon, no degradation in laser output was noted for five reactor pulses.

Hebner, G.A.

1994-08-01

297

Entropy Driven Atomic Motion in Laser-Excited Bismuth  

NASA Astrophysics Data System (ADS)

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

Giret, Y.; Gellé, A.; Arnaud, B.

2011-04-01

298

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

299

The Hanbury Brown-Twiss effect in a pulsed atom laser.  

PubMed

We have used the Hanbury Brown-Twiss effect to directly compare the density correlations of a pulsed atom laser and a pulsed ultracold thermal source of metastable helium. It was found that the isotropic RF outcoupling of atoms from a Bose-Einstein condensate does not result in decoherence, while the 'bunching' typical of incoherent sources was observed for thermal atoms. This new method significantly increases data acquisition rates compared to previous measurements, and also permits future novel experiments which may allow us to probe processes such as the birth and death of a condensate by monitoring correlation effects. PMID:20940764

Manning, A G; Hodgman, S S; Dall, R G; Johnsson, M T; Truscott, A G

2010-08-30

300

Experimental evidence of excited multicharged atomic fragments coming from laser-induced coulomb explosion of molecules  

PubMed

Direct experimental evidence is presented for the production of excited multicharged atomic fragments in the laser-induced Coulomb explosion of molecules. The comparison of the fluorescence signals of several atomic and molecular species shows that the excited fragments come from transient excited multicharged molecules. The atomic fluorescence spectra recorded with NH3, N2, and N2O, in the 50-120 nm wavelength range, show that the excitation increases noticeably from NH3 to N2O. This effect is interpreted in terms of the initial electronic configuration, which favors a stronger excitation when the electronic density is more delocalized on the molecular nuclear structure. PMID:10990741

Quaglia; Cornaggia

2000-05-15

301

Trapping of laser-vaporized alkali metal atoms in rare-gas matrices  

NASA Astrophysics Data System (ADS)

Alkali metal atoms prepared by laser ablation of solid Li and Na are trapped in Ar, Kr, and Xe matrices and studied by electron paramagnetic resonance spectroscopy (EPR) at 15 K. Evidence for tight trapping sites, not observed for atoms generated by conventional Knudsen oven techniques, is presented. The novel tight trapping sites are characterized by a large increase in the isotropic hyperfine coupling constant and a simultaneous decrease in the isotropic g-value. Based on the EPR data, it is suggested that the observed tight trapping corresponds to single substitution of lattice atoms in Ar, Kr, and Xe matrices.

Vaskonen, Kari; Eloranta, Jussi; Kunttu, Henrik

1999-09-01

302

Atomic-absorption spectrometry of laser-nebulized samples.  

PubMed

Thermal nebulization of nickel-base alloys, corundum plates and residues of solutions was performed with a laser beam. The solid aerosol was aspirated into an acetylene-air flame by an ejector. Linear analytical curves in wide concentration ranges were established and an average relative standard deviation of 10% was found. The detection limit is in the ng range for iron and copper, and lower for zinc, cadmium and sodium. PMID:18961933

Kántor, T; Pólos, L; Fodor, P; Pungor, E

1976-08-01

303

Diode laser spectroscopy in a Ca atomic beam  

Microsoft Academic Search

The frequency of an extended cavity diode laser has been stabilized to a resonance of a high-Q optical resonator by using the rf phase modulation technique. A servo bandwidth of 200 kHz has been achieved using a two channel control loop with the fast corrections applied to the injection current and the slow ones to a piezo-driven external cavity mirror

A. Celikov; F. Riehle; V. L. Velichansky; J. Helmcke

1994-01-01

304

Surface diffusion limitation in laser focused atomic deposition  

NASA Astrophysics Data System (ADS)

We have previously demonstrated that an optical standing wave can be used to focus a neutral atomic beam into a structure which is deposited on a substrate, under conditions that are compatible with molecular beam epitaxy. We have made structures in sodium with linewidths of ? ? 45 nm and contrast better than 10:1. Here, we observe that the condition of the surface prior to deposition is critical in producing these features. With certain surface conditions, apparently the mobility of the atoms on the surface reduces the contrast of the grating to approximately 1:1. We discuss the condition necessary during deposition to insure that the resolution of the deposited features is retained.

Behringer, R. E.; Natarajan, Vasant; Timp, G.

1996-09-01

305

Line shapes and widths of CPT resonances: effect of laser beam profile in open atomic system  

Microsoft Academic Search

This work is concerned with the line profiles, amplitudes and widths of the coherent population trapping (CPT) resonances due to low frequency Zeeman coherences, in the Hanle configuration, applied to 87Rb atoms in the vacuum cell. Detailed calculations of the fluorescence were done with two different transverse intensity profiles of the excitation laser tuned to the open Fg = 2

M. Radonjic; D. Arsenovic; Z. Grujic; B. M. Jelenkovic

2008-01-01

306

Nonlinear optical diagnostics of gold nanoparticles by atomic-force microscopy and femtosecond laser pulses  

Microsoft Academic Search

This work is devoted to studying the possibilities of using a femtosecond laser facility and a scanning atomic- force microscope (AFM) for nonlinear optical diagnostics. The developed technique ensures an optical resolution of 30 nm for gold nanoparticles. It is shown that the presence of the AFM tip significantly affects the nonlinear optical response of separate gold nanoparticles. Gold nanoparticles

Alexander I. Smirnov; Andrey N. Stepanov; Dmitry A. Yashunin

2011-01-01

307

Classical and quantum regimes in the collective atomic recoil laser from a Bose-Einstein condensate  

NASA Astrophysics Data System (ADS)

A collective atomic recoil laser (CARL) realized with a Bose-Einstein condensate offers the possibility to investigate new effects in the coherent interaction between optical and matter waves. This paper discusses some aspects of the nonlinear evolution of scattered radiation and the matter-wave field in the high-Q cavity and superradiant CARL regimes.

Piovella, N.; Cola, M.; Bonifacio, R.

2004-06-01

308

Spontaneously generated coherence effects in a laser-driven four-level atomic system  

Microsoft Academic Search

In this paper we investigate the resonance fluorescence, the squeezing, and the absorption spectra of a laser-driven four-level atom consisting of three closely spaced upper levels decaying to a common lower level. The three upper levels are coupled by the same vacuum modes to the lower level leading to spontaneously generated coherence effects. High population inversion and extremely narrow emission

M. A. Anton; Oscar G. Calderon; F. Carreno

2005-01-01

309

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

310

The kinematic cooling of molecules with laser-cooled atoms  

NASA Astrophysics Data System (ADS)

We propose a new scheme for the production of milli-Kelvin molecules via kinematic cooling through collisions with atoms in a magneto-optical trap (MOT). We will discuss the kinematic conditions necessary for producing cold molecules, the limits of the final attainable temperatures and the experimental implementation of this technique. Finally, we will look at some specific physical systems and discuss the effectiveness of kinematic cooling inside a MOT.

Takase, Ken; Rahn, Larry A.; Chandler, David W.; Strecker, Kevin E.

2009-05-01

311

Coherently controlled emission from two atoms dressed via a standing wave laser field  

NASA Astrophysics Data System (ADS)

The influence of the standing wave amplitude on the resonance fluorescence of a three-level system of radiators is discussed. Great attention is devoted to the peculiarities of dressed states in the standing wave and the exchange integrals between two atoms situated in the anti-nodes or the nodes. The correlation functions of emitted photons at two dressed frequencies were obtained. It is shown that in the case when the distance between two atoms is smaller than the wavelength of the field, the emitted photons are strongly correlated. As was observed, for large values of laser field intensity, the control of spontaneous emission is possible at two frequencies as well as the atom-atom interaction process. The dependence of the fluorescent light spectrum as a function of the position of two atoms dressed in the standing wave is investigated.

Enaki, N. A.; Ciobanu, N.; Orszag, M.

2011-11-01

312

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

313

Multiphoton and tunneling ionization of atoms in an intense laser field  

NASA Astrophysics Data System (ADS)

We study the ionization probabilities of atoms by a short laser pulse with three different theoretical methods, i.e., the numerical solution of the time-dependent Schrödinger equation (TDSE), the Perelomov—Popov—Terent'ev (PPT) theory, and the Ammosov—Delone—Krainov (ADK) theory. Our results show that laser intensity dependent ionization probabilities of several atoms (i.e., H, He, and Ne) obtained from the PPT theory accord quite well with the TDSE results both in the multiphoton and tunneling ionization regimes, while the ADK results fit well to the TDSE data only in the tunneling ionization regime. Our calculations also show that laser intensity dependent ionization probabilities of a H atom at three different laser wavelengths of 600 nm, 800 nm, and 1200 nm obtained from the PPT theory are also in good agreement with those from the TDSE, while the ADK theory fails to give the wavelength dependence of ionization probability. Only when the laser wavelength is long enough, will the results of ADK be close to those of TDSE.

Fu, Yan-Zhuo; Zhao, Song-Feng; Zhou, Xiao-Xin

2012-11-01

314

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

NASA Astrophysics Data System (ADS)

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

Glushkov, Alexander

2011-11-01

315

Laser-assisted ion-atom collisions: Plateau, cutoff, and multiphoton peaks  

SciTech Connect

We study ionization in laser-assisted high-energy nonrelativistic ion-atom collisions and show that the low-energy angular differential electron spectrum may be enhanced by five orders of magnitude by an external field of strength less than 1/100 of the atomic field. With increasing strength of the assisting field, the energy spectrum develops a plateau with a characteristic cutoff. In the plateau region we predict distinct multiphoton peaks separated by the photon energy of the assisting field. In the present laser-assisted continuum-distorted-wave eikonal-initial-state theory, this effect may be related to the dynamics in the two-body electron-projectile subsystem. The laser-assisted distorted wave Born and first Born approximation do not account for the phase-distortion of the target electron by the incoming projectile and consequently the associated plateau, cutoff, and multiphoton features are not predicted by these latter theories.

Ciappina, Marcelo F.; Madsen, Lars Bojer [Max Planck Institute for the Physics of Complex Systems, Noethnitzer Strasse 38, D-01187 Dresden (Germany); Lundbeck Foundation Theoretical Center for Quantum System Research, Department of Physics and Astronomy, University of Aarhus, 8000 Aarhus C (Denmark)

2008-02-15

316

Exponential gain and self-bunching in a collective atomic recoil laser  

NASA Astrophysics Data System (ADS)

A source of tunable coherent radiation, the collective atomic recoil laser (CARL), a kind of hybrid between the free-electron laser (FEL) and the ordinary laser, with common physical features was described. The basic features and its operating principles were discussed in detail, making some specific predictions, and offering a preliminary analysis for an experimental proof of principle. By considering the translation degrees of freedom of the active medium, a mechanism was described that can lead to the exponential amplification of a weak probe. The role of the atomic coil was deemed significant to exponential amplification. There was no sign of collective self-bunching due to the self-consistent field generated by the bunching itself.

Bonifacio, R.; Desalvo, L.; Narducci, L. M.; D'Angelo, E. J.

1994-08-01

317

Optical control of an atomic inner-shell x-ray laser  

NASA Astrophysics Data System (ADS)

X-ray free-electron lasers have had an enormous impact on x-ray science by achieving femtosecond pulses with unprecedented intensities. However, present-day facilities operating by the self-amplified spontaneous emission principle have a number of shortcomings; namely, their radiation has a chaotic pulse profile and short coherence times. We put forward a scheme for a neon-based atomic inner-shell x-ray laser (XRL) which produces temporally and spatially coherent subfemtosecond pulses that are controlled by and synchronized to an optical laser with femtosecond precision. We envision that such an XRL will allow for numerous applications such as nuclear quantum optics and the study of ultrafast quantum dynamics of atoms, molecules, and condensed matter.

Darvasi, Gábor; Keitel, Christoph H.; Buth, Christian

2014-01-01

318

Circularly Polarized Laser Field-Induced Rescattering Plateaus in Electron-Atom Scattering  

NASA Astrophysics Data System (ADS)

Using effective range theory within a quasienergy state approach, we extend our recent analysis of the energy spectrum of electrons scattered from atoms in the presence of an intense, elliptically polarized laser field [1] to the case of atoms supporting negative ions having weakly bound p-electrons. Numerical results for e-H and e-F scattering are presented. In both cases there are two (i.e., low- and high-energy) plateau structures in the electron spectrum for any laser polarization, including for the case of circular polarization. The high-energy plateau is shown to originate from rescattering effects, thus providing the first example of the importance of recattering in the case of circular laser polarization. Basic equations of the rescattering scenario are deduced from our ab initio quantum results for the scattering amplitude in the quasiclassical limit. [1] A.V. Flegel et al., Phys. Lett. A 334, 197 (2005); J. Phys. B 38, L27 (2005).

Starace, Anthony F.; Flegel, A. V.

2005-05-01

319

INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Coherent phase control of excitation of atoms by bichromatic laser radiation in an electric field  

NASA Astrophysics Data System (ADS)

A new method for coherent phase control of excitation of atoms in a discrete spectrum under the action of bichromatic laser radiation with the frequency ratio 1:2 is analysed. An important feature of this control method is the presence of a electrostatic field, which removes the parity selection rule for one of the control channels. It is shown that for the phase difference between the monochromatic radiation components, corresponding to the destructive interference between channels, there exists the electrostatic field strength at which the excited atomic transition is 'bleached'. It is proposed to use luminescence at the adjacent atomic transition for detecting the phase dependence of optical excitation.

Astapenko, Valerii A.

2005-06-01

320

Magnetic coupling of laser-cooled atoms to a micro-resonator  

NASA Astrophysics Data System (ADS)

The direct coupling of the spin-degrees of freedom of an atomic vapor to the vibrational motion of a magnetic cantilever tip has recently been demonstrated [1], and prospects for coupling a BEC on an atom-chip to a nano- mechanical resonator have been recently discussed [2]. Possible applications include chip-scale atomic devices, in which localized interactions with magnetic cantilever tips selectively influence or probe atomic spins. As a next step towards the realization of a strongly coupled ultra-cold atom- resonator system, we have constructed an apparatus to study the direct coupling between the spins of trapped laser-cooled Rb atoms and a magnetic tip on a micro-cantilever. The atoms will be loaded into a magnetic trap formed by the cantilever tip and external magnetic fields. The cantilever will be driven capacitively at its resonance frequency, resulting in a coherent precession of the trapped atomic spins with a matching Larmor frequency. Prospects for measuring the back-action of the ensemble of atomic spins on a cantilever beam will also be discussed. [1] Y.-J. Wang,M. Eardley, S. Knappe, J. Moreland, L. Hollberg, and J. Kitching, PRL 97, 227602 (2006). [2] P. Treutlein,D. Hunger, S. Camerer, T. W. Hansch, and J. Reichel, PRL 99, 140403 (2007).

Geraci, Andrew; Wang, Ying-Ju; Eardley, Matthew; Moreland, John; Kitching, John

2009-05-01

321

Comparison of gain in group-III-nitride laser structures grown by metalorganic vapour phase epitaxy and plasma-assisted molecular beam epitaxy on bulk GaN substrates  

NASA Astrophysics Data System (ADS)

Light amplification features of similar group-III-nitride laser structures grown by metal organic vapour phase epitaxy (MOVPE) and plasma-assisted molecular beam epitaxy (PAMBE) as alternative techniques were investigated. The samples are characterized by very low dislocation density (105 cm-2) that results from the use of high-pressure-grown GaN substrates. Gain measurements were carried out by means of the variable stripe length method. A maximum excitation power of 464 kW cm-2 corresponds to a peak modal gain value of 180 cm-1 for the MOVPE-grown sample and 315 cm-1 for the PAMBE-grown one. Saturation lengths of 350 µm and 250 µm measured for MOVPE- and PAMBE-grown samples, respectively, indicate reduced nonradiative recombination compared to heteroepitaxy on foreign substrates. Activation energies associated with InGaN band profile fluctuations derived from temperature-dependent photoluminescence measurements yield values of 41 meV and 22 meV for MOVPE and PAMBE, respectively. Improved band profile smoothness is accompanied by a reduced threshold for stimulated emission in favour of the PAMBE-grown laser.

Swietlik, T.; Franssen, G.; Skierbiszewski, C.; Czernecki, R.; Wisniewski, P.; Krysko, M.; Leszczynski, M.; Grzegory, I.; Mensz, P.; Juršenas, S.; Suski, T.; Perlin, P.

2007-07-01

322

High-Coherence Electron and Ion Bunches from Laser-Cooled Atoms  

NASA Astrophysics Data System (ADS)

Cold atom electron and ion sources produce electron bunches and ion beams by photoionisation of laser cooled atoms. They offer high coherence and the potential for high brightness, with applications including ultrafast electron diffractive imaging of dynamic processes at the nanoscale. Here we present our cold atom electron/ion source, with an electron temperature of less than 10 K and a transverse coherence length of 10 nm. We also discuss experiments investigating space-charge effects with ions and the production of ultra-fast electron bunches using a femto-second laser. In the latter experiment we show that it is possible to produce both cold and fast electron bunches with our source.

McCulloch, A. J.; Sheludko, D. V.; Putkunz, C. T.; Saliba, S. D.; Thompson, D. J.; Speirs, R. W.; Murphy, D.; Torrance, J.; Sparkes, B. M.; Scholten, R. E.

2014-04-01

323

Four-level atomic interferometer driven by shaped ultrafast laser pulses  

NASA Astrophysics Data System (ADS)

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

Clow, Stephen; Weinacht, Thomas

2010-08-01

324

Comparison of atom interferometry with laser interferometry for gravitational wave observations in space  

NASA Astrophysics Data System (ADS)

Proposals were made earlier in 2008 to use atom interferometry based on Raman transitions for gravitational wave observations in space. Recently, Graham et al. have suggested a new atom interferometry method for such observations based on laser-induced single-photon transitions on highly forbidden optical transitions such as those used in recently developed optical clocks. However, a number of additional requirements that are not discussed by Graham et al. have to be considered if the sensitivity level they suggest is to be reached. When all of the requirements are considered, it appears that such an atom interferometry mission would be much more complex than a laser interferometry mission with better overall sensitivity.

Bender, Peter L.

2014-03-01

325

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

326

Phase shift induced from the dc Stark effect in an atom interferometer comprised of four copropagating laser beams  

Microsoft Academic Search

We observed the phase shift of the atomic wave function induced from the dc Stark effect using an atom interferometer comprised of four copropagating traveling laser beams. We calculated the interference signal for the interferometer in the case of a thermal atomic beam. By comparing the observed interference fringes with the calculated ones, the difference between the polarizabilities of the

A. Morinaga; M. Nakamura; T. Kurosu; N. Ito

1996-01-01

327

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

PubMed

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

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

2013-09-01

328

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

329

Quenching of 52P potassium atoms by collisions with H2, N2 and CH4  

Microsoft Academic Search

Potassium vapour, contained together with a buffer gas in a glass fluorescence cell at a controlled temperature, was irradiated with pulsed dye-laser radiation which excited the K atoms to the 52P1\\/2 or 52P3\\/2 state. The effective decay rate of the 52P atoms was determined in relation to the buffer gas densities by methods of fluorescence spectroscopy with time resolution. The

R W Berends; W Kedzierski; A G McConkey; J B Atkinson; L Krause

1989-01-01

330

Theory and experiment on laser-enabled inner-valence Auger decay of rare-gas atoms  

NASA Astrophysics Data System (ADS)

In rare-gas atoms, an inner-valence shell ns hole cannot be filled by Auger decay because of an energy deficiency. We show theoretically and experimentally that by adding a moderately intense infrared laser, Auger decay is possible with decay rates increasing dramatically for laser intensities ?1013 W/cm2. For Xe atoms, the simulated laser-enabled Auger decay yields are comparable with the experimental one, while for Ar atoms, the simulated ones are much smaller. We attribute the discrepancies to screening effects of the photoelectron. Laser-enabled Auger decay is of fundamental importance for understanding attosecond science, and is also important for experimental applications in ultrafast atomic, molecular, and materials dynamics using x rays. More importantly it may provide a way to control the Auger decay time and selectively break chemical bonds of molecules using a control infrared laser field.

Tong, X. M.; Ranitovic, P.; Hogle, C. W.; Murnane, M. M.; Kapteyn, H. C.; Toshima, N.

2011-07-01

331

High-stability compact atomic clock based on isotropic laser cooling  

SciTech Connect

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

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

2010-09-15

332

Laser cooling of quasi-free atoms in a nondissipative optical lattice  

SciTech Connect

A quasi-classical theory of laser cooling is applied to the analysis of cooling of unbound atoms with the angular momenta 1/2 in the ground and excited states in a one-dimensional nondissipative optical lattice. In the low-saturation limit with respect to the pumping field, the mechanisms of cooling can be interpreted within the framework of an effective two-level system of ground-state sublevels. In the limit of weak Raman transitions, the mechanism of cooling of unbound atoms is similar to the Doppler mechanism known in the theory of a two-level atom; in the limit of strong transitions, the mechanism of cooling is analogous to the well-known Sisyphys mechanism. In the slow-atom approximation, analytical expressions are obtained for the friction (drag) coefficient and the induced and spontaneous diffusion, and the kinetic temperature is estimated.

Matveeva, N. A.; Taichenachev, A. V.; Tumaikin, A. M.; Yudin, V. I. [Novosibirsk State Technical University (Russian Federation)], E-mail: llf@laser.nsc.ru

2007-08-15

333

A portable laser system for high-precision atom interferometry experiments  

NASA Astrophysics Data System (ADS)

We present a modular rack-mounted laser system for the cooling and manipulation of neutral rubidium atoms which has been developed for a portable gravimeter based on atom interferometry that will be capable of performing high-precision gravity measurements directly at sites of geophysical interest. This laser system is constructed in a compact and mobile design so that it can be transported to different locations, yet it still offers improvements over many conventional laboratory-based laser systems. Our system is contained in a standard 19? rack and emits light at five different frequencies simultaneously on up to 12 fibre ports at a total output power of 800 mW. These frequencies can be changed and switched between ports in less than a microsecond. The setup includes two phase-locked diode lasers with a phase noise spectral density of less than 1 ?rad/Hz1/2 in the frequency range in which our gravimeter is most sensitive to noise. We characterise this laser system and evaluate the performance limits it imposes on an interferometer.

Schmidt, M.; Prevedelli, M.; Giorgini, A.; Tino, G. M.; Peters, A.

2011-01-01

334

Optical studies of lithium vapour zones produced by thermal evaporation in noble gas  

Microsoft Academic Search

We have produced two vertically well separated zones of lithium vapour above the evaporation source in a confined noble gas atmosphere by setting an appropriate condition for the gas evaporation. Optical extinction spectra of lithium atoms, dimers and clusters were obtained by time-resolved and space-resolved measurements after the beginning of the evaporation. Also, vapour species in each zone were selectively

Shosuke Mochizuki; Mie Sasaki; Raphael Ruppin

1997-01-01

335

Atomic inner-shell X-ray laser at 1.46 nanometres pumped by an X-ray free-electron laser.  

PubMed

Since the invention of the laser more than 50 years ago, scientists have striven to achieve amplification on atomic transitions of increasingly shorter wavelength. The introduction of X-ray free-electron lasers makes it possible to pump new atomic X-ray lasers with ultrashort pulse duration, extreme spectral brightness and full temporal coherence. Here we describe the implementation of an X-ray laser in the kiloelectronvolt energy regime, based on atomic population inversion and driven by rapid K-shell photo-ionization using pulses from an X-ray free-electron laser. We established a population inversion of the K? transition in singly ionized neon at 1.46 nanometres (corresponding to a photon energy of 849 electronvolts) in an elongated plasma column created by irradiation of a gas medium. We observed strong amplified spontaneous emission from the end of the excited plasma. This resulted in femtosecond-duration, high-intensity X-ray pulses of much shorter wavelength and greater brilliance than achieved with previous atomic X-ray lasers. Moreover, this scheme provides greatly increased wavelength stability, monochromaticity and improved temporal coherence by comparison with present-day X-ray free-electron lasers. The atomic X-ray lasers realized here may be useful for high-resolution spectroscopy and nonlinear X-ray studies. PMID:22281598

Rohringer, Nina; Ryan, Duncan; London, Richard A; Purvis, Michael; Albert, Felicie; Dunn, James; Bozek, John D; Bostedt, Christoph; Graf, Alexander; Hill, Randal; Hau-Riege, Stefan P; Rocca, Jorge J

2012-01-26

336

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

337

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

338

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

NASA Astrophysics Data System (ADS)

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

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

339

Field phase dependence in the ionization of atoms by intense one-cycle laser pulses  

NASA Astrophysics Data System (ADS)

The phase sensitivity of the atomic ionization by intense one-cycle linearly polarized laser pulses has been discussed within the analytic Landau-Dykhne approximation. The generalized Keldysh parameter has been introduced for analysis of two regimes of ionization. In the case of super-intense laser field we found that ionization by cosine waveform pulse is much more effective than that by sine waveform pulse with the same energy in the pulse. This is pure quantum destructive interference effect. Electron energy spectra and effective electron temperatures are also derived analytically for both waveform pulses.

Rastunkov, V. S.; Krainov, V. P.

2007-07-01

340

Direct measurement of fine structure in the ground state of atomic carbon by laser magnetic resonance  

NASA Astrophysics Data System (ADS)

Laser magnetic resonance measurements of fine-structure intervals in the ground state of atomic carbon, which have made possible the detection of far infrared line emissions from C-12 in several interstellar sources, are reported. The 3P0 to 3P1 and 3P1 to 3P2 transitions in C-12 and C-13 atoms in a methane-fluorine atom flame were observed at 10 different optically pumped far infrared laser lines, and the C-12 fine structure intervals were determined from the combined data of all 10 lines and g-factors from the atomic beam experiments of Wolber et al. (1970). Interval spacings of 809.3446 (29) and 492.1623 (7) GHz are obtained for the 3P0-3P1 and 3P1-3P2 transitions, respectively. It is pointed out that the further detection of these transitions should lead to information regarding atomic abundances, isotope ratios, chemical fractionation effects, processes involving interstellar dust grains and the physical conditions of the interstellar medium

Saykally, R. J.; Evenson, K. M.

1980-06-01

341

A modification of the laser detonation-type hyperthermal oxygen atom beam source for a long-term operation  

SciTech Connect

It has been an impedimental problem, for the laser detonation-type atom beam generator, that a poppet in the pulsed supersonic valve is rapidly eroded by the irradiation of powerful laser light and high temperature plasma. In order to operate the atom beam source for a long duration, a modification was made to hide the poppet from direct irradiation of laser and plasma. The alteration of device configuration resulted in great improvement in endurance of poppet more than 300 000 repetitions. Morphology of a polyimide film exposed to approximately 200 000 pulses of hyperthermal oxygen atom beam showed a shaglike carpet structure, which is a characteristic to that exposed to energetic oxygen atoms. A flux of the oxygen atom beam was estimated to be 5x10{sup 14} atoms/cm{sup 2}/pulse at a location of 30 cm away from the nozzle throat.

Kinoshita, Hiroshi; Yamamoto, Shunsuke; Yatani, Hideaki; Ohmae, Nobuo [Department of Mechanical Engineering, Faculty of Engineering, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe 657-8501, Hyogo 565 (Japan)

2008-07-15

342

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

NASA Astrophysics Data System (ADS)

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, ?. The data provide a rate of fractional temporal variation of ? of (-2.4±2.3) × 10-15 yr-1 or a value of (-7.8 ± 5.9) × 10-6 for k?, the variation coefficient for ? 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.; Cingöz, A.; Budker, D.; Ferrell, S. J.; Yashchuk, V. V.; Lapierre, A.; Nguyen, A.-T.; Lamoreaux, S. K.; Torgerson, J. R.

2009-04-01

343

Magnetic Dichroism in K-Shell Photoemission from Laser Excited Li Atoms  

NASA Astrophysics Data System (ADS)

Magnetic dichroism in the angular distribution has been demonstrated for single-electron photoemission from inner ns2 subshells of gaseous atomic targets using the example of K-shell photoionization of polarized Li atoms laser prepared in the 1s22p P3/22 excited state. The effect is pronounced for the conjugate shakeup and conjugate shakedown photoelectron lines, and less important, though observable, for the main and direct shakeup lines. The phenomenon is caused by configuration interaction in the final continuum state and is quantitatively described by the close-coupling R-matrix calculations.

Meyer, M.; Grum-Grzhimailo, A. N.; Cubaynes, D.; Felfli, Z.; Heinecke, E.; Manson, S. T.; Zimmermann, P.

2011-11-01

344

A compact dual atom interferometer gyroscope based on laser-cooled rubidium  

Microsoft Academic Search

We present a compact and transportable inertial sensor for\\u000a precision sensing of rotations and accelerations. The sensor consists\\u000a of a dual atom interferometer operated with laser-cooled 87Rb.\\u000a Raman processes are employed to coherently manipulate the matter\\u000a waves. We describe and characterize the experimental apparatus. A\\u000a method for passing from a compact geometry to an extended\\u000a interferometer with three independent atom-light

T. Müller; M. Gilowski; M. Zaiser; P. Berg; Ch. Schubert; T. Wendrich; W. Ertmer; E. M. Rasel

2009-01-01

345

Analog Grover search by adiabatic passage in a cavity-laser-atom system  

NASA Astrophysics Data System (ADS)

A physical implementation of the adiabatic Grover search is theoretically investigated in a system of N identical three-level atoms trapped in a single-mode cavity. Some of the atoms are marked through the presence of an energy gap between their two ground states. The search is controlled by two partially delayed lasers which allow a deterministic adiabatic transfer from an initially entangled state to the marked states. Pulse schemes are proposed to satisfy the Grover speedup either exactly or approximately, and the success rate of the search is calculated.

Daems, D.; Guérin, S.

2008-08-01

346

Exterior complex scaling method in TDDFT: HHG of Ar atoms in intense laser fields  

NASA Astrophysics Data System (ADS)

Exterior complex scaling (ECS) method is applied in the framework of the time-dependent density functional theory to study high-order harmonic generation (HHG) of multielectron atoms in intense laser fields. ECS allows to impose correct (outgoing-wave) boundary conditions on the wave functions at large distances. In the present work, ECS is combined with the time-dependent generalized pseudospectral method for accurate and efficient solution of the time-dependent Kohn-Sham equations. Results for HHG of Ar atoms are presented.

Sosnova, Ksenia E.; Telnov, Dmitry A.; Rozenbaum, Efim; Chu, Shih-I.

2014-04-01

347

Measurements of atomic oscillator strengths using pulsed single-frequency dye lasers  

SciTech Connect

We have used two methods to measure the oscillator strength of the transition between the ground and 17992 cm/sup /minus/1/ level in XUYb. The first technique involves exciting the transition with a laser pulse that is nearly time-bandwidth limited, of uniform intensity, and has a reproducible shape from shot to shot. The population left in the excited state after the pulse varies sinusoidally with a period that depends on the integral over time of the electric field amplitude and the transition oscillator strength. These are the Rabi oscillations that are predicted by application of the Schrodinger equation to the two-level atom. The excited-state population is probed using a two-step photoionization to the continuum. The electric field amplitude is determined from the temporal profile and the intensity of the laser pulse. The second method involves observation of the polarization rotation of a set of degenerate sublevels brought about by a time-bandwidth limited light-shift laser. One sublevel (m/sub j/ = 0) of the J = 1 level at 17992 cm/sup /minus/1/ is populated by a linearly polarized laser. A second copropagating light-shift laser, which is linearly polarized at an angle to the first laser, is tuned between 7.5 and 30 GHz off-resonance with the transition. The light-shift laser causes population to be promoted into the m/sub j/ = +-1 levels by a virtual transition through the ground J = O, m/sub j/ = O level. Two linearly polarized photoionizing lasers photoionize the population only from the m/sub j/ = +-1 levels. The photoion signal oscillates sinusoidally with a period that depends only on the integrated pulse intensity, the laser detuning, and the transition oscillator strength. 5 refs., 15 figs.

Haynam, C.; Comaskey, B.; Johnson, M.; Paisner, J.; Worden, E.

1988-01-01

348

Ion beam generation by field ionization of laser-excited Rydberg atoms  

SciTech Connect

Sodium atoms (10/sup 8/--10/sup 11/ cm/sup -3/) effused from an oven where excited by two pulsed dye lasers (--8--15 ns, --100 ..mu..J) from the ground state 3s, via an intermediate state 3p, to a Rydberg state ns or nd (20less than or equal tonless than or equal to25). About 50 ns after the laser irradiation, a pulsed electric field (0.5--5.5 kV/cm) was applied to the Rydberg atoms to ionize them and accelerate the resulting ions. Thus, a pulsed ion beam was obtained with a maximum total electric charge of --5 pC, corresponding to a peak current of --25 ..mu..A with an output pulse of --200 ns full width at half-maximum.

Oomori, T.; Ono, K.; Fujita, S.; Murai, Y.

1987-01-12

349

Time-resolved ionization process of hydrogen atoms in strong laser fields  

NASA Astrophysics Data System (ADS)

Within the strong-field approximation, we study the time-resolved ionization process of a hydrogen atom in strong laser fields. At any time during the interaction between an atom and a laser field, the electron may instantaneously absorb all possible energies and build a wide momentum spectrum. As the interaction evolves in time, the coherent superposition of all previous instantaneous ionization events gradually filters out all other energy components except the part with an energy n? -Ip, where Ip is the ionization potential, ? is the photon energy, and n is a positive integer. The establishment of the electron energy spectra in above-threshold ionization, rescattering, and streaking can all be directly viewed by tracking the time-dependent momentum spectra.

Cui, Sen; He, Feng

2013-12-01

350

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

NASA Astrophysics Data System (ADS)

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.; Auyuanet, A.; Barreiro, S.; Valente, P.; Lezama, A.; Failache, H.

2014-04-01

351

Analysis of an atom laser based on the spatial control of the scattering length  

SciTech Connect

In this paper we analyze atom lasers based on the spatial modulation of the scattering length of a Bose-Einstein condensate. We demonstrate, through numerical simulations and approximate analytical methods, the controllable emission of matter-wave bursts and study the dependence of the process on the spatial shape of the scattering length along the axis of emission. We also study the role of an additional modulation of the scattering length in time.

Carpentier, Alicia V.; Michinel, Humberto; Rodas-Verde, Maria I.; Perez-Garcia, Victor M. [Area de Optica, Facultade de Ciencias de Ourense, Universidade de Vigo, As Lagoas s/n, Ourense, ES-32004 Spain (Spain); Departamento de Matematicas, ETSI Industriales, Universidad de Castilla-La Mancha, 13071 Ciudad Real (Spain)

2006-07-15

352

Fabrication of NiTi intermetallic compound by a reactive gas laser atomization process  

Microsoft Academic Search

We attempted to synthesize NiTi intermetallic compound from two types of stranded wires, pure Ti wire (with a diameter of 300 ?m) and pure Ni wire (with diameters of 300 and 250 ?m). The stranded wire was melted and reacted using a laser, and the melted metal was gas-atomized using high-pressure Ar gas or coated on an aluminum base material.

Hiroshi Tomochika; Hiroyuki Kikuchi; Takao Araki; Minoru Nishida

2003-01-01

353

Influence of low atomic number plasma component on the formation of laser-produced plasma jets  

SciTech Connect

The results of investigations are presented that are connected with a very simple method of plasma jet formation, which consists in irradiating a massive planar target made of material with relatively high atomic number by a partly defocused laser beam. This brief communication is aimed at investigations of interaction of axially symmetrical light (plastic-CH) plasma with heavy (copper) plasma. It demonstrates that a relatively thin plastic plasma envelope can compress the Cu plasma and control the Cu-jet formation.

Kasperczuk, A.; Pisarczyk, T.; Badziak, J.; Borodziuk, S.; Chodukowski, T. [Institute of Plasma Physics and Laser Microfusion, 23 Hery St., 00-908 Warsaw (Poland); Gus'kov, S. Yu.; Demchenko, N. N. [Institute of Plasma Physics AS CR, v.v.i., Za Slovankou 3, 182 00 Prague 8 (Czech Republic); Ullschmied, J.; Krousky, E.; Masek, K.; Pfeifer, M.; Rohlena, K.; Skala, J. [Institute of Physics AS CR, v.v.i., Na Slovance 2, 182 21 Prague 8 (Czech Republic); Pisarczyk, P. [Warsaw University of Technology, ICS, 15/19 Nowowiejska St., 00-665 Warsaw (Poland)

2010-11-15

354

Site-specific laser modification of MgO nanoclusters: Towards atomic-scale surface structuring  

Microsoft Academic Search

Direct neutral metal emission from MgO nanostructures is induced using laser light tuned to excite specific surface sites at energies well below the excitation threshold of the bulk material. We find that near UV excitation of MgO nanocrystalline films and nanocube samples desorbs neutral Mg atoms with hyperthermal kinetic energies in the range of 0.1-0.4eV . Our ab initio calculations

Kenneth M. Beck; Matthias Henyk; Chongmin Wang; Paolo E. Trevisanutto; Peter V. Sushko; Wayne P. Hess; Alexander L. Shluger

2006-01-01

355

Development of a helium cryostat for laser spectroscopy of atoms with unstable nuclei in superfluid helium  

NASA Astrophysics Data System (ADS)

We are developing a new nuclear laser spectroscopic technique for the study of nuclear structure that can be applied to short-lived low-yield atoms with unstable nuclei. The method utilizes superfluid helium (He II) as a trapping medium for high-energy ion beams. A liquid helium cryostat with optical windows is a key apparatus for this type of experiment. We describe the design and the performance of the cryostat which is developed for the present project.

Imamura, Kei; Furukawa, Takeshi; Wakui, Takashi; Yang, Xiaofei; Yamaguchi, Yasuhiro; Tetsuka, Hiroki; Mitsuya, Yosuke; Tsutsui, Yoshiki; Fujita, Tomomi; Ebara, Yuta; Hayasaka, Miki; Arai, Shino; Muramoto, Sosuke; Ichikawa, Yuichi; Ishibashi, Yoko; Yoshida, Naoki; Shirai, Hazuki; Hatakeyama, Atsushi; Wada, Michiharu; Sonoda, Tetsu; Ito, Yuta; Odashima, Hitoshi; Kobayashi, Tohru; Ueno, Hideki; Shimoda, Tadashi; Asahi, Koichiro; Matsuo, Yukari

2013-12-01

356

Kinetic study of nanofabrication on gold films by atomic force microscope tips under laser irradiation  

NASA Astrophysics Data System (ADS)

Recently, scanning probe microscope (SPM) has become a promising technique for nano-fabrication. In this paper, we present a novel method of nano-fabrication, namely, nano- fabrication by atomic force microscope (AFM) tips under laser irradiation. The SPM was operated as an AFM. During imaging and nano-fabrication, the AFM is in constant force mode. The tip is fixed with the sample moving via a tube scanner. Nano-lithography software controls the scanner motion in x and y directions. The SPM has an open architecture allowing an external laser beam incident on the tip at an incident angle between 0 to 45 degree(s). A vertical polarized Nd:YAG pulsed laser with a pulse duration of 7 ns was focused on the tip. An electrical shutter was introduced to switch the laser irradiation. Alignment between the laser beam and the tip was performed under a high-power charge coupled device (CCD) microscope. Nano- fabrication was carried out on gold films deposited on n- type Si substrates using the physical deposition method. The kinetics of the nanostructure fabrication has been studied. Craters were created in air ambient under different laser pulse numbers, pulse energies and tip force. The feature size of the craters, which are in the nanometer scale, increases with the pulse number, pulse energy and the tip force. This technique has potential applications in the high-density data storage.

Hu, B.; Lu, Yong F.; Mai, ZhiHong; Song, W. D.; Chim, W. K.

2000-11-01

357

Pumping iron: A KrF laser pumped atomic iron laser  

Microsoft Academic Search

A technique for producing stimulated emission in an optically pumped atomic iron system at room temperature is described. The required iron density (?1014 atoms\\/cm3) for single pass amplified spontaneous emission was produced at room temperature by two techniques: a low pressure (50 torr) discharge of iron pentacarbonyl and neon and by the flash photodecomposition of Fe(CO)5 in an argon buffer.

Daniel W. Trainor; Siva A. Mani

1978-01-01

358

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

359

Laser and isotope effects in charge transfer processes in atomic collisions  

NASA Astrophysics Data System (ADS)

Charge transfer processes are fundamental to the understanding of matter neutralization in atomic and molecular processes. Due to the polarizability of the material, charge transfer can be enhanced or suppressed during the interaction with electromagnetic radiation. Furthermore, charge transfer has different contributions arising from the radial and rotational regions of the potential interaction in the collision, which depend on the mass of the target and projectile. Since these effects appear in a very short time (femtoseconds), the dynamics must be carried out outside the Born-Oppenheimer approximation. In this work, we present charge transfer results for He2+ ions colliding with atomic hydrogen and tritium atoms for collision energies from 100 eV/amu up to 1.5 keV/amu, assisted by a fast, short laser pulses of intensity 3.5×1012 W/cm2 and wave length of 790 nm by means of an electron-nuclear dynamic treatment. We find large isotope effects in the low-energy region up to one order of magnitude in the charge transfer cross-section in the absence of the laser pulse. In the presence of the laser pulse, the isotope effect is negligible and the charge transfer cross-section is enhanced up to two orders of magnitude in the low-energy region.

Cabrera-Trujillo, R.

360

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

NASA Astrophysics Data System (ADS)

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

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

2007-04-01

361

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

PubMed

We report on a low-noise diode laser oscillator at 972?nm actively stabilized to an ultrastable vibrationally and thermally compensated reference cavity. To increase the fraction of laser power in the carrier we designed a 20?cm long external cavity diode laser with an intracavity electro-optical modulator. The fractional power in the carrier reaches 99.9%, which corresponds to an rms phase noise of ?(rms)2=1?mrad2 in 10?MHz bandwidth. Using this oscillator, we recorded 1S-2S spectra in atomic hydrogen and have not observed any significant loss of the excitation efficiency due to phase noise multiplication in the three consecutive two-photon processes. PMID:22048397

Kolachevsky, N; Alnis, J; Parthey, C G; Matveev, A; Landig, R; Hänsch, T W

2011-11-01

362

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

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

363

A Hertz-Linewidth Ultrastable Diode Laser System for Clock Transition Detection of Strontium Atoms  

NASA Astrophysics Data System (ADS)

The frequencies of two 698 nm external cavity diode lasers (ECDLs) are locked separately to two independently located ultrahigh finesse optical resonant cavities with the Pound—Drever—Hall technique. The linewidth of each ECDL is measured to be ~4.6 Hz by their beating and the fractional frequency stability below 5 × 10-15 between 1 s to 10 s averaging time. Another 698 nm laser diode is injection locked to one of the cavity-stabilized ECDLs with a fixed frequency offset for power amplification while maintaining its linewidth and frequency characteristics. The frequency drift is ~1 Hz/s measured by a femtosecond optical frequency comb based on erbium fiber. The output of the injection slave laser is delivered to the magneto-optical trap of a Sr optical clock through a 10-m-long single mode polarization maintaining fiber with an active fiber noise cancelation technique to detect the clock transition of Sr atoms.

Li, Ye; Lin, Yi-Ge; Wang, Qiang; Wang, Shao-Kai; Zhao, Yang; Meng, Fei; Lin, Bai-Ke; Cao, Jian-Ping; Li, Tian-Chu; Fang, Zhan-Jun; Zang, Er-Jun

2014-02-01

364

Measurement of the Zeeman effect in an atomic anion: Prospects for laser cooling of Os-  

NASA Astrophysics Data System (ADS)

The negative osmium ion Os- is one of very few atomic anions potentially suitable for laser cooling. We have made a measurement of the Zeeman splitting of a bound-bound transition in 192Os- by studying the laser excitation from the 5d76s2 4F9/2e ground to the 5d66s26p 6D9/2o excited state in a homogeneous external magnetic field. The experimental Landé factors gJ=1.31(7) and gJ=1.50(8), respectively, agree well with calculated values. Both levels are found to split into 10 Zeeman sublevels, resulting in 28 allowed transitions of different relative intensities, in agreement with calculations based on pure and composite LS states. In view of the experimental results, the prospects for laser cooling of Os- are discussed.

Kellerbauer, A.; Fischer, A.; Warring, U.

2014-04-01

365

Laser-Aided Diagnostics of Atoms and Particulates in Magnetron Sputtering Plasmas  

SciTech Connect

Laser-aided diagnostic technique is introduced as an advanced and valuable technique to evaluate the properties of plasma. This technique is an expensive and sophisticated technique which requires researchers to have a basic knowledge in optical spectroscopy. In the present paper, we will generally introduce the experimental work using laser-induced fluorescence (LIF) and laser light scattering (LLS) techniques. The LIF was used to evaluate the spatial distribution of Cu atoms in magnetron sputtering plasma. The change in the spatial distribution was studied as a function of discharge power. On the other hand, the LLS was used to evaluate the generation of Cu particulates in high-pressure magnetron sputtering plasma. The temporal evolution of Cu particulates in the gas phase of sputtering plasma was visualized successfully.

Nafarizal, N. [Microelectronics and Nanotechnology-Shamsuddin Research Centre (MiNT-SRC), Faculty of Electrical and Electronic Engineering, University Tun Hussein Onn Malaysia, 86400 Batu Pahat, Johor (Malaysia); Takada, N. [Department of Electrical Engineering and Computer Science, Nagoya University, 464-8603 Chikusa-ku Nagoya (Japan); Sasaki, K. [Plasma Nanotechnology Research Center, Nagoya University, 464-8603 Chikusa-ku Nagoya (Japan)

2009-07-07

366

Production of gallium atoms by excimer laser photolysis of trimethyl gallium  

SciTech Connect

The gas phase kinetics of group III elements such as gallium are important in possible chemically driven energy transfer lasers and in chemical vapor deposition processes in the electronics industry. Excimer laser photodissociation of volatile gallium compounds via multiple photon process provides, in principle, a convenient room temperature source of gallium atoms for study using laser photolysis-laser induced fluorescence techniques. In this paper, we report preliminary results of the multiple photon dissociation of trimethyl gallium at 193 nm. Prompt emission from a number of excited gallium states (5 /sup 2/S, 4 /sup 2/D, 6 /sup 2/S, 6 /sup 2/P/sup 0/, 5 /sup 2/D, and 4 /sup 4/P) has been observed. The time histories of the ground state (4/sup 2/P/sup 0//sub 1/2/) and the metastable (4 /sup 2/P/sup 0//sub 3/2/) have been measured using laser induced fluorescence. The resulting time profiles are complicated even in the absence of a reactant gas by the apparent production of ground state gallium at relatively long times (approx. 10 ..mu..s) after the excimer laser pulse. Possible mechanisms for this (i.e., radical reactions to produce gallium, energy transfer cascading from high lying metastable states, ionic processes, etc.) are being investigated. These results indicate that the photodissociation of trimethyl gallium at 193 nm is complex. Photolysis studies at other wavelengths and with other precursors are in progress to find a cleaner source of gas phase atomic gallium for kinetic studies. 20 refs., 7 figs.

Baughcum, S.L.; Oldenborg, R.C.; Winn, K.R.; Hof, D.E.

1985-03-01

367

Liquid\\/Vapour visualization of common rail diesel sprays in different ambient conditions with visible and UV laser light scattering and PLIF  

Microsoft Academic Search

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 =

L. Allocca; A. De Vita; S. S. Merola; B. M. Vaglieco

2005-01-01

368

Coherent transient effects in laser-cooled and room temperature atoms  

NASA Astrophysics Data System (ADS)

This thesis presents several coherent transient effects with laser cooled (100 ?K) and room temperature (298K) 85Rb atoms. The understanding of interaction of nearly resonant radiation and matter, which is a fundamental problem of physics can be obtained by investigation of such transient phenomena. With the help of laser cooling techniques, an ideal two-level system is achieved. Atomic properties such as transition probabilities, branching ratio, and atomic coherence decay time have been measured using optical free induction decay (FID) and nutation. The first attempt to get Rabi oscillations using one of the coherent radiation of atomic polarization (FID) have been performed. Dressed state free induction decay newly developed have been observed and investigated with simple dressed state picture. One of new echo techniques recently suggested creating coherences between ground state magnetic sublevels was used to study velocity changing collision. At high buffer gas pressure, the revival of the coherent transient have been observed due to a kind of Dicke narrowing effect. The temporal modulation of this signal in the presence of magnetic fields has also been investigated with linear and circular polarized excitations. The velocity-changing collision cross section, diffusion coefficient and spin-flip collision cross section between Rb and noble gas were measured.

Shim, Unyob

1997-11-01

369

Compilation of atomic and molecular data revelant to gas lasers. volume viii. Technical report  

SciTech Connect

The present volume serves to update most of the areas covered in the previous documents. Such areas include all nuclear processes, and atomic collisions occurring at high energies, i.e., above about 100 eV impact energy. However, even in those areas where new data are not presented here, references are given to past volumes in order to facilitate access to the previous data. Another function of the present volume is to expand somewhat the scope of our data coverage, both with respect to atomic nd molecular structural properties and with respect to atomic collisions (by the latter term, we mean two- and three- body collisions between electrons, ions, atoms, molecules, and photons at impact energies sufficiently low that nuclear forces are unimportant). New species and sets of collision partners that have recently assumed importance are treated here, and other systems that may become important in the gas laser context are given attention. A significant amount of new material is also added to the chapter on surface impact phenomena, partly because of current interest in hollow-cathode lasers.

McDaniel, E.W.; Flannery, M.R.; Thomas, E.W.; Manson, S.T.; Gallagher, J.W.

1980-12-01

370

Tunnel ionization of highly excited atoms in a noncoherent laser radiation field  

SciTech Connect

A theory is developed of the ionization of highly excited atomic states by a low-frequency field of noncoherent laser radiation with a large number of modes. Analytic formulas are obtained for the probability of the tunnel ionization in such a field. An analysis is made of the case of the hydrogen atom when the parabolic quantum numbers are sufficiently good in the low-frequency limit, as well as of the case of highly excited states of complex atoms when these states are characterized by a definite orbital momentum and parity. It is concluded that the statistical factor representing the ratio of the probability in a stochastic field to the probability in a monochromatic field decreases, compared with the case of a short-range potential, if the ''Coulomb tail'' is included. It is shown that at a given field intensity the statistical factor decreases on increase in the principal quantum number of the state being ionized.

Krainov, V.P.; Todirashku, S.S.

1982-10-01

371

A miniature differential atomic magnetometer based on a diverging laser beam  

NASA Astrophysics Data System (ADS)

We 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 [1]. 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, which serves to both optically pump the atoms and measure the transverse polarization. The size of the core physics assembly is < 1cm^3. The simplicity of the experimental design makes it ideally suited for highly miniaturized implementations and wafer-level mass production. Operating the magnetometer in differential mode cancels common-mode noise and improves the sensitivity by a factor of 26 over single-channel operation. Finally, we suggest ways in which the current sensitivity of 28 pT/Hz may be improved further without sacrificing size or simplicity. [1] E. Hodby et al. To be submitted.

Hodby, Eleanor; Donley, Elizabeth; Kitching, John

2007-06-01

372

Highly efficient and isotope selective photo-ionization of barium atoms using diode laser and LED light.  

PubMed

We demonstrated a simple method to photo-ionize barium atoms using 791 nm diode laser together with 310 nm UV LED. It solved the bottle-neck problem of previous method using 791 nm diode laser and 337 nm N(2) laser, whose ionization rate was limited by the repetition rate of N(2) laser. Compared with previous method, it has advantages of high efficiency together with simple and cheap setups. By tuning the frequency of 791 nm laser to be resonant with the desired isotope, isotope selective photo-ionization has been realized. PMID:21935008

Wang, B; Zhang, J W; Gao, C; Wang, L J

2011-08-15

373

Increase in the power of lasing on atomic and ion transitions in chemical elements  

SciTech Connect

A method for increasing the power of pulsed lasing on atomic and ion transitions in chemical elements obtained by the conversion of the UV radiation of excimer lasers in cells with metal vapours is studied. A part of UV radiation transmitted through a cell with metal vapour is used for pumping a dye solution in such a way that the cell converter with metal vapour represents a master oscillator, while the dye cell represents an amplifier. The study is performed by the example of amplification of weak spectral components of radiation from a XeCl* laser converted in mercury and barium vapours. In the amplifying stage the longitudinal pumping of the dye is used and a scheme for suppressing self-excitation is employed. It is found by selecting dyes that the alcohol solution of uranin is nearly optimal for amplification of the 546.1-nm laser line of mercury, while the best results in amplification of the 533-nm and 648.2-nm laser lines of barium were obtained by using alcohol solutions of rhodamine 6G and oxazine 17, respectively. The power of the 546.1-nm mercury line was increased by an order of magnitude, while the power of the 533-nm and 648.2-nm lines of barium - almost by a factor of twenty-five. (lasers)

Klimkin, V M; Sokovikov, V G [Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences, Tomsk (Russian Federation)

2007-02-28

374

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

375

Lasers Based on the O( Exp 1 S) Implies O( Exp 1 D) Transition in Atomic Oxygen.  

National Technical Information Service (NTIS)

Various concepts for realization of a laser based on the 0( exp 1 S) implies 0( exp 1 D) transition in atomic oxygen are discussed. The physics of the formation and destruction of 0( exp 1 S) is considered. The current progress related to laser mechanisms...

O. Judd

1975-01-01

376

Sub-Doppler Magnetic Field Resonances in the Resonant Stimulated Electronic Raman Scattering of Multimode Laser Light  

Microsoft Academic Search

Continuous wave lasing without the use of any feedback mirrors is observed when atomic Cesium and Rubidium vapours are optically pumped to their second excited resonance states. The stimulated emission in a number of infrared wavelengths is restricted to a very narrow angle in both the forward and the backward directions. With multimode pumping the gain of this laser shows

Anup Dayanand Sharma

1981-01-01

377

Arc Jet Flow Properties Determined from Laser- Induced Fluorescence of Atomic Species  

NASA Technical Reports Server (NTRS)

Flow property measurements that were recently acquired in the Ames Research Center Aerodynamic Heating Facility (AHF) arc jet using two-photon Laser-Induced Fluorescence (LIF) of atomic nitrogen and oxygen are reported. The measured properties, which include velocity, translational temperature, and species concentration, cover a wide range of facility operation for the 30 cm nozzle. During the tests, the arc jet pressure and input stream composition were maintained at fixed values and the arc current was varied to vary the flow enthalpy. As part of this ongoing effort, a measurement of the two-photon absorption coefficient for the 3p4D(left arrow)2p4S transition of atomic nitrogen was performed, and the measured value is used to convert the relative concentration measurements to absolute values. A flow reactor is used to provide a known temperature line shape profile to deconvolve the laser line width contribution to the translational temperature measurements. Results from the current experiments are compared with previous results obtained using NO-beta line profiles at room temperature and the problem of multimode laser oscillation and its impact on the two-photon excitation line shape are discussed. One figure is attached, and this figure show relative N atom concentration measurements as a function of the arc power. Other measurements have already been acquired and analyzed. The arc jet flow facilities are heavily used in thermal protection material development and evaluation. All hypersonic flight and planetary atmospheric entry vehicles will use materials tested in these arc jet facilities. This poster represents an application of laser-spectroscopic measurements in an important test facility.

Fletcher, Douglas G.

1997-01-01

378

Arcjet Flow Properties Determined from Laser-Induced Fluorescence of Atomic Species  

NASA Technical Reports Server (NTRS)

Flow property measurements that were recently acquired in the Ames Research Center Aerodynamic Heating Facility (AHF) arc jet using two-photon Laser-Induced Fluorescence (LIF) of atomic nitrogen and oxygen are reported. The measured properties, which include velocity, translational temperature, and species concentration, cover a wide range of facility operation for the 30 cm nozzle. During the tests, the arc jet pressure and input stream composition were maintained at fixed values and the arc current was varied to vary the flow enthalpy. As part of this ongoing effort, a measurement of the two-photon absorption coefficient for the 3p4D<-2p4S transition of atomic nitrogen was performed, and the measured value is used to convert the relative concentration measurements to absolute values. A flow reactor is used to provide a known temperature line shape profile to deconvolve the laser line width contribution to the translational temperature measurements. Results from the current experiments are compared with previous results obtained using NO-Beta line profiles at room temperature and the problem of multimode laser oscillation and its impact on the two-photon excitation line shape are discussed. One figure is attached, and this figure shows relative N atom concentration measurements as a function of the arc power. Other measurements have already been acquired and analyzed. This poster represents an application of laser-spectroscopic measurements in an important test facility. The arc jet flow facilities are heavily used in thermal protection material development and evaluation. All hypersonic flight and planetary atmospheric entry vehicles will use materials tested in these arc jet facilities.

Fletcher, Douglas G.

1997-01-01

379

Vapour pressure of diethyl phthalate  

Microsoft Academic Search

Measurements of vapour pressure in the liquid phase and of enthalpy of vaporisation and results of calculation of ideal-gas properties for diethyl phthalate are reported. The method of comparative ebulliometry, the static method, and the Knudsen mass-loss effusion method were employed to determine the vapour pressure. A Calvet-type differential microcalorimeter was used to measure the enthalpy of vaporisation. Simultaneous correlation

Vladislav Rohá?; Kv?toslav R?ži?ka; Vlastimil R?ži?ka; Dzmitry H. Zaitsau; Gennady J. Kabo; Vladimir Diky; Karel Aim

2004-01-01

380

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

381

Near resonant absorption by atoms in intense fluctuating laser fields. Final report  

SciTech Connect

The objective of this program was to make quantitative measurements of the effects of higher-order phase/frequency correlations in a laser beam on nonlinear optical absorption processes in atoms. The success of this program was due in large part to a unique experimental capability for modulating the extracavity beam of a stabilized ({approx_lt}200 kHz) continuous-wave laser with statistically-well-characterized stochastic phase (or frequency) fluctuations, in order to synthesize laser bandwidths to {approximately}20 MHz (depending on noise amplitude), with profiles variable between Gaussian and Lorentzian (depending on noise bandwidth). Laser driven processes investigated included the following: (1) the optical Autler-Towns effect in the 3S{sub 1/2} (F = 2, M{sub F} = 2) {yields} 3P{sub 3/2} (F = 3, M{sub F} = 3) two- level Na resonance, using a weak probe to the 4D{sub 5/2} level; (2) the variance and spectra of fluorescence intensity fluctuations in the two-level Na resonance; (3) the Hanle effect in the {sup 1}S{sub 0} {minus} {sup 3}P{sub 1}, transition at {lambda} = 555.6 nm in {sup 174} Yb; (4) absorption (and gain) of a weak probe, when the probe is a time-delayed replica of the resonant (with the two-level Na transition) pump laser; and (5) four-wave-mixing in a phase-conjugate geometry, in a sodium cell, and, finally, in a diffuse atomic sodium beam. The experimental results from these several studies have provided important confirmation of advanced theoretical methods.

Smith, S.J.

1994-01-01

382

Absorption spectroscopy characterization measurements of a laser-produced Na atomic beam  

SciTech Connect

This work describes a pulsed Na atomic beam source developed for spectroscopic diagnosis of a high-power ion diode on the Particle Beam Fusion Accelerator II. The goal is to produce a {approximately} 10{sup 12}-cm{sup {minus}3}-density Na atomic beam that can be injected into the diode acceleration gap to measure electric and magnetic fields from the Stark and Zeeman effects through laser-induced-fluorescence or absorption spectroscopy. A {approximately} 10 ns fwhm, 1.06 {micro}m, 0.6 J/cm{sup 2} laser incident through a glass slide heats a Na-bearing thin film, creating a plasma that generates a sodium vapor plume. A {approximately} 1 {micro}sec fwhm dye laser beam tuned to 5,890 {angstrom} is used for absorption measurement of the Na I resonant doublet by viewing parallel to the film surface. The dye laser light is coupled through a fiber to a spectrograph with a time-integrated CCD camera. A two-dimensional mapping of the Na vapor density is obtained through absorption measurements at different spatial locations. Time-of-flight and Doppler broadening of the absorption with {approximately} 0.1 {angstrom} spectral resolution indicate that the Na neutral vapor temperature is about 0.5 to 2 eV. Laser-induced-fluorescence from {approximately} 1 {times} 10{sup 12}-cm{sup {minus}3} Na I 3s-3p lines observed with a streaked spectrograph provides a signal level sufficient for {approximately} 0.06 {angstrom} wavelength shift measurements in a mock-up of an ion diode experiment.

Ching, C.H.; Bailey, J.E.; Lake, P.W.; Filuk, A.B.; Adams, R.G.; McKenney, J.

1996-06-01

383

Tunable frequency-stabilised laser for studying the cooling dynamics of Rb atoms in a magnetooptical trap  

SciTech Connect

A system is developed which allows one to stabilise the diode laser frequency at any point in the vicinity of the cyclic D{sub 2}-line transition in Rb in the interval from +40 to -150 MHz and to switch the laser frequency within this interval for {approx}1 ms. A method is proposed and realised for increasing the contrast of the reference sub-Doppler resonance observed in circularly polarised fields. The ultimate contrast of the resonance is estimated. This system can be used to study the anomalous light pressure force acting on atoms in an optical molasses. A magnetooptical trap for Rb atoms is described. (control of laser radiation parameters)

Yarovitsky, Alexander V; Vasil'ev, V V; Velichansky, Vladimir L; Razin, Oleg A; Sherstov, Ivan V [P.N. Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Prudnikov, O N [Novosibirsk State University, Novosibirsk (Russian Federation); Taichenachev, Aleksei V; Yudin, Valerii I [Institute of Laser Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk (Russian Federation)

2004-04-30

384

A review of normalization techniques in analytical atomic spectrometry with laser sampling: From single to multivariate correction  

NASA Astrophysics Data System (ADS)

Despite many advantages of laser sampling in analytical atomic spectrometry, the signal intensity of these hyphenated methods suffers from the specific influences resulting from the laser ablation process of a sample. The problems that arise affect the accuracy and precision of analytical results. Different techniques of analytical signal normalization which improve figures-of-merit for atomic spectrometry with laser sampling are considered in this review. The characteristics and application of these approaches including the use of internal standards, single or several reference signals and multivariate correction of analytical signal are discussed.

Zorov, Nikita B.; Gorbatenko, Alexander A.; Labutin, Timur A.; Popov, Andrey M.

2010-08-01

385

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

386

Compilation of atomic and molecular data relevant to gas lasers. volume VII. Technical report  

SciTech Connect

This volume and the succeeding volume are the seventh and the eighth in a series that presents data relevant to research and development in the field of gas lasers. The present volumes serve to update most of the areas covered in the previous documents. Those areas not treated here are considered to have been adequately dealt with earlier, as far as immediate data needs are concerned. However, even in those areas where new data are not presented here, references are given to past volumes in order to facilitate access to the previous data. Another function of the present work is to expand somewhat the scope of our data coverage, both with respect to atomic and molecular structural properties and with respect to atomic collisions. New species and sets of collision partners that have recently assumed importance are treated here, and other systems that may become important in the gas laser contex are given attention. A significant amount of new material is also added to the chapter on surface impact phenomena, partly because of current interest in hollow-cathode lasers.

McDaniel, E.W.; Flannery, M.R.; Thomas, E.W.; Manson, S.T.; Gallagher, J.W.

1980-12-01

387

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

388

Optogalvanic study of the atomic-oxygen laser lines at 844.5 nm  

NASA Astrophysics Data System (ADS)

The 3 3S1-3 3P0,1,2 laser lines at 844.5 nm of atomic oxygen are studied in a weak discharge cell with argon buffer gas, using the optogalvanic effect. Three Doppler-limited peaks are observed at the center frequencies of the three fine-structure transitions. The measurements of the spectral widths indicate that the atoms in the lower state (3 3S1) are at room temperature or ``cold.'' This excludes the previous assumption that all the triplet states are very ``hot'' and moreover is consistent with the long-range atom-ion interaction model [Kwon et al., Phys. Rev. A 42, 4408 (1990); Bjerre and Keiding, Phys. Rev. Lett. 56, 1459 (1986)]. Based on the results, one can understand the unexplained observations such as the anomalously broadened spectra associated with the 3 3P triplet state, the peculiar four-peak emission spectra of the laser lines, and the absence of the J=0-->J=1 transition.

Kwon, Namic; Yun, Young-Hwan; Jhe, Wonho

1995-08-01

389

Application of Coulomb wave function discrete variable representation to atomic systems in strong laser fields.  

PubMed

We present an efficient and accurate grid method for solving the time-dependent Schrodinger equation for an atomic system interacting with an intense laser pulse. Instead of the usual finite difference (FD) method, the radial coordinate is discretized using the discrete variable representation (DVR) constructed from Coulomb wave functions. For an accurate description of the ionization dynamics of atomic systems, the Coulomb wave function discrete variable representation (CWDVR) method needs three to ten times fewer grid points than the FD method. The resultant grid points of the CWDVR are distributed unevenly so that one has a finer grid near the origin and a coarser one at larger distances. The other important advantage of the CWDVR method is that it treats the Coulomb singularity accurately and gives a good representation of continuum wave functions. The time propagation of the wave function is implemented using the well-known Arnoldi method. As examples, the present method is applied to multiphoton ionization of both the H atom and the H(-) ion in intense laser fields. The short-time excitation and ionization dynamics of H by an abruptly introduced static electric field is also investigated. For a wide range of field parameters, ionization rates calculated using the present method are in excellent agreement with those from other accurate theoretical calculations. PMID:17059259

Peng, Liang-You; Starace, Anthony F

2006-10-21

390

Laser cooling and trapping of atomic particles. January 1970-September 1989 (Citations from the NTIS data base). Report for Jan 70-Sep 89  

SciTech Connect

This bibliography contains citations concerning theory and experiments on laser cooling and laser trapping of neutral atoms and atomic ions. Atoms and ions are cooled by laser radiation pressure to very low Kelvin temperatures and confined in electromagnetic traps with very high density. Atomic particles discussed include sodium atoms, mercury ions, beryllium ions, magnesium ions, and hydrogen. Applications include high performance spectroscopy, atomic clocks, microwave and optical frequency standards, relativistic neutral particle beam weapons, exotic fuels, cooling of electron beams, and space propulsion. (Contains 97 citations fully indexed and including a title list.)

Not Available

1989-11-01

391

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

NASA Astrophysics Data System (ADS)

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 1S0 and 3P1 states of a Ca atom was measured as a function of a laser power near the resonance of the 1S0-1P1 transition at a wavelength of 423 nm. The decay rate of the 1P1 state was determined to be ?=1.91(33)×108 s-1.

Akatsuka, Tomoya; Mori, Yoshihiro; Sone, Nobuhiko; Ohtake, Yurie; Machiya, Mamoru; Morinaga, Atsuo

2011-08-01

392

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

393

Time-resolved mapping of correlated electron emission from helium atom in an intense laser pulse  

NASA Astrophysics Data System (ADS)

We apply and analyze the concept of mapping ionization time on to the final momentum distribution to the correlated electron dynamics in the nonsequential double ionization of helium in a strong laser pulse (?=800 nm) and show how the mapping provides insight into the double ionization dynamics. To this end, we study, by means of numerical integration of the time-dependent Schrödinger equation of a fully correlated model atom, the temporal evolution of the center-of-mass momentum in a short laser pulse. Our results show that in the high intensity regime (I0=1.15×1015 W cm-2), the mapping is in good agreement with a classical model including binary and recoil rescattering mechanisms. In the medium intensity regime (I0=5×1014 W cm-2), we identify additional contributions from the recollision-induced excitation of the ion followed by subsequent field ionization (RESI).

Ruiz, C.; Becker, A.

2008-02-01

394

Laser-induced birefringence in a wavelength-mismatched cascade system of inhomogeneously broadened Yb atoms  

SciTech Connect

We report the observation of laser-induced birefringence (LIB) in a wavelength-mismatched cascade system (J=0{r_reversible}J=1{r_reversible}J=0 transitions) of inhomogeneously broadened ytterbium atoms with strong pump and probe fields. We investigate the transmission spectrum of two circular polarization ({sigma}{sub p}{sup +} and {sigma}{sub p}{sup -}) components of strong probe field at fixed frequency, depending on the detuning of a circularly polarized ({sigma}{sub c}{sup -}) coupling field from two-photon resonance. We find that the {sigma}{sub p}{sup +} ({sigma}{sub p}{sup -}) polarized component exhibits a narrow electromagnetically induced absorption (transparency) spectrum. Numerical solutions of density matrix equations show qualitative agreement with experimental results. A Doppler-free dispersive LIB signal is obtained by detecting the Stokes parameter of the probe field, enabling us to stabilize the frequency of the coupling laser without frequency modulation.

Yoon, Tai Hyun; Park, Chang Yong; Park, Sung Jong [Center for Optical Frequency Control, Korea Research Institute of Standards and Science, 1 Doryong, Yuseong, Daejeon 305-340 (Korea, Republic of)

2004-12-01

395

Effects of free-electron-laser field fluctuations on the frequency response of driven atomic resonances  

NASA Astrophysics Data System (ADS)

We study the effects of field fluctuations on the total yields of Auger electrons, obtained in the excitation of neutral atoms to a core-excited state by means of short-wavelength free-electron-laser pulses. Beginning with a self-contained analysis of the statistical properties of fluctuating free-electron-laser pulses, we analyze separately and in detail the cases of single and double Auger resonances, focusing on fundamental phenomena such as power broadening and ac Stark (Autler-Townes) splitting. In certain cases, field fluctuations are shown to influence dramatically the frequency response of the resonances, whereas in other cases the signal obtained may convey information about the bandwidth of the radiation as well as the dipole moment between Auger states.

Nikolopoulos, G. M.; Lambropoulos, P.

2012-09-01

396

Heating of an Atomic Force Microscope tip by femtosecond laser pulses  

NASA Astrophysics Data System (ADS)

For various applications of nanoscale surface modification by an Atomic Force Microscope, one would like to maintain the AFM tip near the surface and at an accurately controlled elevated temperature. We study the laser heating of an ordinary AFM silicon tip under ambient conditions, and show that a tightly focused laser beam can heat the tip apex to the desired temperature, while affecting the cantilever quite moderately. We demonstrate that the observation of the shift of the silicon Raman line scattered from the tip is an efficient and accurate way to determine the tip temperature, and we substantiate our observations by theoretically modeling the dynamics of heat accumulation in the tip-cantilever system. For situations where Raman measurements are not feasible, we introduce a new method for estimating the tip temperature by monitoring the mechanical resonance frequency shift of the probe.

Milner, Alexander A.; Zhang, Kaiyin; Garmider, Valery; Prior, Yehiam

2010-04-01

397

Atomic analysis and hardness measurement of the cavity prepared by laser.  

PubMed

The purpose of this study was to compare the compositional changes and microhardness of the cavity floor prepared by erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser irradiation with those of the conventional bur-prepared cavity. A total of 16 extracted human molar teeth (with no carious lesions or repairs) were selected for this study. On the buccal and lingual (palatal) surfaces of each tooth, cavities (diameter 3 mm, depth 2 mm) were prepared with an Er,Cr:YSGG laser system (Waterlase MD(TM), USA) and high-speed turbine. The cavities were cross-sectioned and subjected to atomic analysis by scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDX) and Vickers hardness test. Statistical analyses were performed with t-tests. Surface characteristics of the prepared cavities were also investigated by SEM. No significant differences were found between the calcium/phosphorus (Ca/P) ratio and Vickers hardness of laser- and bur-prepared cavities. The SEM observation revealed that the lased cavity surface was irregular, and there was also an absence of smear layer; the orifices of dentinal tubules were exposed. Microhardness measurement of the cavity floor confirmed that the Er,Cr:YSGG laser produced a clean-cut surface of the cavity. PMID:19575263

Shahabi, Sima; Zendedel, Somaeh

2010-05-01

398

Survey of atomic transitions for absolute frequency locking of lasers for lightwave systems  

NASA Astrophysics Data System (ADS)

The authors survey 26 excited-state transitions of Ar, Kr, and Ne around 1.3 and 1.5 microns. A 1200-lines/mm grating mounted on a piezoelectric translator forms the adjustable reflective element of an external cavity semiconductor laser, reducing the laser linewidth to below 100 kHz, and affording tens of nanometers of tunability. The laser may be tuned continuously over a range of approximately 2 GHz between mode hops by scanning the cavity length with the piezoelectric translator. Single-frequency oscillation is verified by the 750 MHz confocal Fabry-Perot, and the wavelength is measured by a wavemeter. Due to the limits of the tuning range defined by the gain curve of the 1.5 micron semiconductor laser, the experiment was constrained to the examination of lines at wavelengths shorter than 1.54 microns. The results of the survey of the atomic transitions are presented in tabular form. The optogalvanic signal per incident power exhibits variation of over two orders of magnitude. However, some of this arises from variation in the strength of the absorption.

Lucero, A. J.; Chung, Y. C.; Tkach, R. W.

1991-05-01

399

Oxygen atom density and thermal energy control in an electric-oxygen iodine laser  

NASA Astrophysics Data System (ADS)

Experiments[1] with Electric Oxygen-Iodine Laser (ElectricOIL) heat exchanger technology have demonstrated improved control of oxygen atom density and thermal energy, with minimal quenching of O2(a1?), and increasing small signal gain from 0.26% cm-1 to 0.30% cm-1. Heat exchanger technological improvements were achieved through both experimental and modeling studies, including estimation of O2(a1?) surface quenching coefficients for select ElectricOIL materials downstream of a radio-frequency discharge-driven singlet oxygen generator. Estimation of O2(a1?) quenching coefficients is differentiated from previous studies by inclusion of oxygen atoms, historically scrubbed using HgO[2-4] or AgO[5]. High-fidelity, time-dependent and steady-state simulations are presented using the new BLAZE-VI multi-physics simulation suite[6] and compared to data.

Benavides, G. F.; Palla, A. D.; Zimmerman, J. W.; Woodard, B. S.; Carroll, D. L.; Solomon, W. C.

2014-02-01

400

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

401

Atomic Oxygen Sensors Based on Nanograin ZnO Films Prepared by Pulse Laser Deposition  

NASA Astrophysics Data System (ADS)

High-quality nanograin ZnO thin films were deposited on c-plane sapphire (Al2O3) substrates by pulse laser deposition (PLD). Scanning electron microscopy (SEM) and x-ray diffraction (XRD) were used to characterize the samples. The structural and morphological properties of ZnO films under different deposition temperature have been investigated before and after atomic oxygen (AO) treatment. XRD has shown that the intensity of the (0 0 2) peak increases and its FWHM value decreases after AO treatment. The AO sensing characteristics of nano ZnO film also has been investigated in a ground-based atomic oxygen simulation facility. The results show that the electrical conductivity of nanograin ZnO films decreases with increasing AO fluence and that the conductivity of the films can be recovered by heating.

Wang, Yunfei; Chen, Xuekang; Li, Zhonghua; Zheng, Kuohai; Wang, Lanxi; Feng, Zhanzu; Yang, Shengsheng

2009-01-01

402

Isotropic vortex tangles in trapped atomic Bose-Einstein condensates via laser stirring  

NASA Astrophysics Data System (ADS)

The generation of isotropic vortex configurations in trapped atomic Bose-Einstein condensates offers a platform to elucidate quantum turbulence on mesoscopic scales. We demonstrate that a laser-induced obstacle moving in a figure-8 path within the condensate provides a simple and effective means to generate an isotropic three-dimensional vortex tangle due to its minimal net transfer of angular momentum to the condensate. Our characterization of vortex structures and their isotropy is based on projected vortex lengths and velocity statistics obtained numerically via the Gross-Pitaevskii equation. Our methodology provides a possible experimental route for generating and characterizing vortex tangles and quantum turbulence in atomic Bose-Einstein condensates.

Allen, A. J.; Parker, N. G.; Proukakis, N. P.; Barenghi, C. F.

2014-02-01

403

Hydrogen-Assisted Laser-Induced Resonant Transitions between Metastable States of Antiprotonic Helium Atoms  

SciTech Connect

Laser resonance transitions between normally metastable states of antiprotonic helium atoms were observed making use of state dependent quenching effects caused by small admixtures of H{sub 2} molecules. By selectively shortening the lifetimes of states with higher principal quantum number n as compared to those of lower n, this method for the first time provides access to all initially populated metastable states of {ital {bar p}}He{sup +} atoms. This was demonstrated by observing the transitions (n,l)=(38,l){r_arrow}(39,l+1), l=35,36,37 and (n,l)=(37,l){r_arrow}(38,l+1), l=34,35,36. {copyright} {ital 1997} {ital The American Physical Society}

Ketzer, B.; Hartmann, F.; von Egidy, T.; Maierl, C.; Pohl, R. [Physik-Department, Technische Universitaet Muenchen, D-85747 Garching (Germany)] [Physik-Department, Technische Universitaet Muenchen, D-85747 Garching (Germany); Eades, J.; Widmann, E.; Yamazaki, T. [CERN, CH-1211 Geneva 23 (Switzerland)] [CERN, CH-1211 Geneva 23 (Switzerland); Kumakura, M.; Morita, N. [Institute for Molecular Science, Myodaiji, Okazaki 444 (Japan)] [Institute for Molecular Science, Myodaiji, Okazaki 444 (Japan); Hayano, R.; Hori, M.; Ishikawa, T.; Torii, H. [Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113 (Japan)] [Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113 (Japan); Sugai, I. [Institute for Nuclear Study, University of Tokyo, 3-2-1 Midori-cho, Tanashi, Tokyo 188 (Japan)] [Institute for Nuclear Study, University of Tokyo, 3-2-1 Midori-cho, Tanashi, Tokyo 188 (Japan); Horvath, D. [Central Research Institute for Physics, Research Institute for Particle and Nuclear Physics, H-1525 Budapest (Hungary)] [Central Research Institute for Physics, Research Institute for Particle and Nuclear Physics, H-1525 Budapest (Hungary)

1997-03-01

404

Using Lasers and X-rays to Reveal the Motion of Atoms and Electrons  

SciTech Connect

July 7, 2009 Berkeley Lab summer lecture: The ultrafast motion of atoms and electrons lies at the heart of chemical reactions, advanced materials with exotic properties, and biological processes such as the first event in vision. Bob Schoenlein, Deputy Director for Science at the Advanced Light Source, will discuss how such processes are revealed by using laser pulses spanning a millionth of a billionth of a second, and how a new generation of light sources will bring the penetrating power of x-rays to the world of ultrafast science

Bob Schoenlein

2009-07-14

405

Using Lasers and X-rays to Reveal the Motion of Atoms and Electrons  

ScienceCinema

July 7, 2009 Berkeley Lab summer lecture: The ultrafast motion of atoms and electrons lies at the heart of chemical reactions, advanced materials with exotic properties, and biological processes such as the first event in vision. Bob Schoenlein, Deputy Director for Science at the Advanced Light Source, will discuss how such processes are revealed by using laser pulses spanning a millionth of a billionth of a second, and how a new generation of light sources will bring the penetrating power of x-rays to the world of ultrafast science

Bob Schoenlein

2010-01-08

406

REVIEWS OF TOPICAL PROBLEMS: Simple atomic systems in resonant laser fields  

NASA Astrophysics Data System (ADS)

The interaction of simple, two- and three-level atomic systems with monochromatic and nonmonochromatic laser radiation near resonance transitions is discussed based on the Schroedinger equation with radiation decay and no collisional relaxation, outside the framework of the usual perturbation theory. The mathematical schemes employed include the resonance approximation, exact methods, the quasi-energy method, the adiabatic approximation, etc. A large number of physical phenomena, such as oscillating and inverted populations, self-induced resonances, processes of first order in the weak field, Raman scattering, coherent population transfer, etc. are considered. The review is intended for a broad readership.

Ter-Mikhaelyan, Mikhail L.

1997-12-01

407

Collective Rayleigh scattering from dielectric particles: A classical theory of the Collective Atomic Recoil Laser  

NASA Astrophysics Data System (ADS)

A classical theory of Rayleigh scattering of electromagnetic radiation by dielectric particles is presented, in which the particles may interact cooperatively via common pump and probe radiation fields. The collective nature of the process is manifest both in the exponential growth of the bunching of the particles at the radiation wavelength to form a particle grating, and in the exponential growth of the counterpropagating probe radiation intensity. We call this `Collective Rayleigh Scattering'. This process arises from a fully classical description of the Collective Atomic Recoil Laser (CARL) with linear dielectric particles.

McNeil, B. W. J.; Robb, G. R. M.

1998-03-01

408

The RMT method for describing many-electron atoms in intense short laser pulses  

NASA Astrophysics Data System (ADS)

We describe how we have developed an ab initio R-Matrix incorporating Time (RMT) method to provide an accurate description of the single ionization of a general many-electron atom exposed to short intense laser pulses. The new method implements the "division-of-space" concept central to R-matrix theory and takes over the sophisticated time-propagation algorithms of the HELIUM code. We have tested the accuracy of the new method by calculating multiphoton ionization rates of He and Ne and have found excellent agreement with other highly accurate and well-established methods.

Lysaght, M. A.; Moore, L. R.; Nikolopoulos, L. A. A.; Parker, J. S.; van der Hart, H. W.; Taylor, K. T.

2012-11-01

409

Fabrication of atomically smooth SrRuO 3 thin films by laser molecular beam epitaxy  

Microsoft Academic Search

High-quality SrRuO3 (SRO) thin films and SrTiO3\\/SRO bilayer were grown epitaxially on SrTiO3 (STO)(001) substrates by laser molecular beam epitaxy. The results of in situ observation of reflection high-energy electron diffraction and ex situ X-ray diffraction ?-2? scan indicate that the SRO thin films have good crystallinity. The measurements of atomic force microscopy and scan tunneling\\u000a microscopy reveal that the

Guozhen Liu; Meng He; Kuijuan Jin; Guozhen Yang; Huibin Lü; Kun Zhao; Shijian Zheng; Xiuliang Ma

2008-01-01

410

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

411

High-fidelity modelling of an exciplex pumped alkali laser with radiative transport  

Microsoft Academic Search

The exciplex-pumped alkali laser (XPAL) system has been demonstrated in mixtures of Cs vapour, Ar, and ethane by pumping Cs-Ar atomic collision pairs and subsequent dissociation of diatomic, electronically excited CsAr molecules (exciplexes or excimers). Because of the addition of atomic collision pairs and exciplex states, modelling of the XPAL system is far more complicated than the modelling of the

Andrew D. Palla; David L. Carroll; Joseph T. Verdeyen; Michael C. Heaven

2011-01-01

412

Atom-probe tomography of nickel-based superalloys with green or ultraviolet lasers: a comparative study.  

PubMed

Recent developments in the technology of laser-pulsed local-electrode atom-probe (LEAP) tomography include a picosecond ultraviolet (UV) laser system having a 355 nm wavelength and both external and in-vacuum optics. This approach ensures focusing of the laser beam to a smaller spot diameter than has heretofore been obtained using a green (532 nm wavelength) picosecond laser. We compare the mass spectra acquired, using either green or UV laser pulsing, from nickel-based superalloy specimens prepared either electrochemically or by lifting-out from bulk material using ion-beam milling in a dual-beam focused ion beam microscope. The utilization of picosecond UV laser pulsing yields improved mass spectra, which manifests itself in higher signal-to-noise ratios and mass-resolving power (m/?m) in comparison to green laser pulsing. We employ LEAP tomography to investigate the formation of misoriented defects in nickel-based superalloys and demonstrate that UV laser pulsing yields better accuracy in compositional quantification than does green laser pulsing. Furthermore, we show that using a green laser the quality of mass spectra collected from specimens that were lifted-out by ion milling is usually poorer than for electrochemically-sharpened specimens. Employing UV laser pulsing yields, however, improved mass spectra in comparison to green laser pulsing even for ion-milled microtips. PMID:23046701

Amouyal, Yaron; Seidman, David N

2012-10-01

413

Sensitized and heavy atom induced production of acenaphthylene triplet: A laser flash photolysis study  

SciTech Connect

The triplet state of acenaphthylene has been examined by nanosecond laser flash photolysis using sensitization and heavy atom perturbation techniques. Although acenaphthylene does not form any observable triplet upon direct flash excitation, a transient with microsecond lifetime ({lambda}{sub max} = 315 nm) is observable when a solution of the sample is excited by sensitizers (benzophenone, thioxanthone, benzil). This transient is ascribed to the triplet of acenaphthylene on the basis of its quenching behavior toward oxygen, ferrocene, azulene, and {beta}-carotene. Quantitative data concerning the triplet-triplet absorption and quenching constants are presented. The triplet energy is estimated to lie between 46 and 47 kcal/mol. The triplet can also be produced by direct excitation in solvents containing heavy atoms (ethyl bromide, ethyl iodide). The triplet yield is found to increase with an increase of the amount of the heavy atom containing solvent. No saturation limit is obtained. These facts together with the effect of heavy atoms on the T{sub 1} {yields} S{sub 0} process allow the differing behavior of ethyl bromide and ethyl iodide on the photodimerization process of acenaphthylene to be explained. Triplet-state parameters (extinction coefficient and triplet yield) have been estimated in these solvents by the energy-transfer technique and actinometry.

Samanta, A.; Fessenden, R.W. (Univ. of Notre Dame, IN (USA))

1989-07-27

414

Progress towards an electron electric dipole moment measurement with laser-cooled atoms  

NASA Astrophysics Data System (ADS)

This dissertation recounts the progress made towards a measurement of the electron electric dipole moment. The existence of a permanent electric dipole moment of any fundamental particle would imply that both time reversal and parity invariance are violated. If an electric dipole moment were measured within current experimental limits it would be the first direct evidence for physics beyond the standard model. For our measurement we use laser-cooled alkali atoms trapped in a pair of 1D optical lattices. The lattices run through three electric field plates so that the two groups of atoms see opposing electric fields. The measurement chamber is surrounded by a four layer mu-metal magnetic shield. Under electric field quantization, the atoms are prepared in a superposition of magnetic sublevels that is sensitive to the electron electric dipole moment in Ramsey-like spectroscopy. The experiment requires very large electric fields and very small magnetic fields. Engineering a system compatible with both of these goals simultaneously is not trivial. Searches for electric dipole moments using neutral atoms in optical lattices have much longer possible interaction times and potentially give more precise information about the inherent symmetry breaking than other methods. This comes at the cost of a higher sensitivity to magnetic fields and possible sources of error associated with the trapping light. If noise and systematic errors can be controlled to our design specifications our experiment will significantly improve the current experimental limit of the electron electric dipole moment.

Solmeyer, Neal

415

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

416

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

417

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 is described. 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, J.B.; Cremers, D.A.

1986-01-10

418

Control and exploitation of a mode-locked ring laser's phase: Towards a better atomic clock  

NASA Astrophysics Data System (ADS)

The experiments performed use a mode-locked ring laser. The laser has two counter-propagating fields (pulses). When the pulses of the two counter-propagating fields are combined outside the cavity on a detector a beat note is observed which represents the 'average' phase difference or difference in longitudinal mode spacing between the two fields. This offset can be realized by non-reciprocal effects, such as rotation (1), insertion of a phase modulator pulsed at the cavity round trip time or placing an atomic beam in the cavity. This mode-locked ring laser can measure non-reciprocal phase differences as small as 10-6 for the unstabilized case and 10-8 for the stabilized case. Mechanical vibrations of the cavity account for the 100 Hz bandwidth of the observed beat note. The bandwidth can be reduced by stabilizing the laser to a reference. A comparison of two stabilization schemes is made. The first scheme involves locking to the side of a transmission fringe of a Fabry-Perot reference cavity. The second is the Pound-Drever-Hall (2,3) stabilization scheme which uses phase modulated side-band to lock to a Fabry-Perot reference cavity (1MHz bandwidth). The reference cavities are an Ultra-Low-Expansion block of quartz with mirrors optically contacted on the ends. With the longitudinal modes stabilized to the reference cavity the uncertainty of the bandwidth (4) can be as small as 0.001 Hz and is measured to be 0.33 Hz. This reduction by two orders of magnitude means that changes in rotation rates as small as 6 × 10-7 o/sec can be obtained or equivalently to change in the earth's rate of orbit about the sun. State-of-the-art technology in laser stability is 1 part in 1018, as compared with the current technology in cesium standards being 1 part in 1015. However, current technologies in converting the stabilized laser frequency to a useful radio frequency (RF) lose four to five orders of magnitude in precision (5). In stabilizing a mode-locked ring laser a useful RF, the pulse repetition rate is already present. This RF has the same stability as that of the laser at the optical frequencies. This stabilized mode-locked laser has improved the Allan variance of the pulse repetition rate by three to four orders of magnitude, down to 10-9 at one second. The placement of a three level atom in the cavity produces a sharp non-linear dispersion curve. This dispersion curve arises from inducing a non-zero off- diagonal matrix element between two levels that are not dipole coupled. This is accomplished by two counter- propagating fields interacting independently with two different transitions. These transitions share a common level. Population is transfered from the two dipole forbidden levels back and forth through the common level via the interacting laser fields. As the counter- propagating field are scanned across the transitions, the beat note changes frequency which is proportional to the non-linear dispersion curve. Looking the beat frequency, or the two counter-propagating fields to this non-linear dispersion curve will lead to a third standard at a 'low' frequency range. (Abstract shortened by UMI.)

Atherton, Briggs Walker

1997-09-01

419

Laser ablation inductively coupled plasma atomic emission spectrometry of a uranium-zirconium alloy : ablation properties and analytical behaviour.  

SciTech Connect

The ablation properties and analytical behavior of a uranium-zirconium alloy have been examined using tandem laser ablation/pneumatic nebulization sample introduction in conjunction with inductively coupled atomic emission spectrometry (LA-ICP-AES). An apparent change in composition of the laser ablation aerosol (1-15 GW cm{sup 2} Zr deficient, 40-250 GW cm{sup 2} Zr rich) is observed. This phenomenon is independent of laser wavelength. After collection and bulk chemical analysis of the ablation product, this phenomenon is attributed to an atomization interference in the ICP. Two distinct modes of laser ablation have been observed which depend upon the wavelength of the ablating laser (visible or near infrared). These two modes result in characteristic ablation crater types and analyte emission behavior. Ablation yields at 1064 nm are dependent upon laser power density only, whilst yields at 532 nm are dependent upon both laser power density and illumination area. The latter is considered to be symptomatic of direct interaction of the laser light with the surface, and the former, of indirect coupling of laser energy, via a micro-plasma, into the surface.

Goodall, P. S.; Wood, E. L.; Johnson, S. G.; Fuels and Engineering (Argonne-West)

1995-12-01

420

Laser ablation inductively coupled plasma atomic emission spectrometry of a uranium-zirconium alloy: ablation properties and analytical behavior  

NASA Astrophysics Data System (ADS)

The ablation properties and analytical behavior of a uranium-zirconium alloy have been examined using tandem laser ablation/pneumatic nebulization sample introduction in conjunction with inductively coupled atomic emission spectrometry (LA-ICP-AES). An apparent change in composition of the laser ablation aerosol (1-15 GW cm -2 Zr deficient, 40-250 GW cm -2 Zr rich) is observed. This phenomenon is independent of laser wavelength. After collection and bulk chemical analysis of the ablation product, this phenomenon is attributed to an atomization interference in the ICP. Two distinct modes of laser ablation have been observed which depend upon the wavelength of the ablating laser (visible or near infrared). These two modes result in characteristic ablation crater types and analyte emission behavior. Ablation yields at 1064 nm are dependent upon laser power density only, whilst yields at 532 nm are dependent upon both laser power density and illumination area. The latter is considered to be symptomatic of direct interaction of the laser light with the surface, and the former, of indirect coupling of laser energy, via a micro-plasma, into the surface.

Goodall, Phillip; Johnson, Stephen G.; Wood, Elon

1995-12-01

421

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

422

Controllable optical bistability in photonic-crystal one-atom laser  

NASA Astrophysics Data System (ADS)

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, Xiao-Yong; Lü, Shu-Chen

2009-10-01

423

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

424

CONTROL OF LASER RADIATION PARAMETERS: Tunable frequency-stabilised laser for studying the cooling dynamics of Rb atoms in a magnetooptical trap  

NASA Astrophysics Data System (ADS)

A system is developed which allows one to stabilise the diode laser frequency at any point in the vicinity of the cyclic D2-line transition in Rb in the interval from +40 to -150 MHz and to switch the laser frequency within this interval for ~1 ms. A method is proposed and realised for increasing the contrast of the reference sub-Doppler resonance observed in circularly polarised fields. The ultimate contrast of the resonance is estimated. This system can be used to study the anomalous light pressure force acting on atoms in an optical molasses. A magnetooptical trap for Rb atoms is described.

Yarovitsky, Alexander V.; Prudnikov, O. N.; Vasil'ev, V. V.; Velichansky, Vladimir L.; Razin, Oleg A.; Sherstov, Ivan V.; Taichenachev, Aleksei V.; Yudin, Valerii I.

2004-04-01

425

Comparison of recoil-induced resonances and the collective atomic recoil laser  

NASA Astrophysics Data System (ADS)

The theories of recoil-induced resonances (RIR) [J. Guo, P. R. Berman, B. Dubetsky, and G. Grynberg, Phys. Rev. A 46, 1426 (1992)] and the collective atomic recoil laser (CARL) [R. Bonifacio and L. De Salvo, Nucl. Instrum. Methods Phys. Res. A 341, 360 (1994)] are compared. Both theories can be used to derive expressions for the gain experienced by a probe field interacting with an ensemble of two-level atoms that are simultaneously driven by a pump field. It is shown that the underlying formalisms of the RIR and CARL are equivalent. Differences between the RIR and CARL arise because the theories are typically applied for different ranges of the parameters appearing in the theory. The RIR limit is one in which the time derivative of the probe field amplitude, dE2/dt, depends locally on E2(t) and the gain depends linearly on the atomic density, while the CARL limit is one in which dE2/dt=?t0f(t,t')E2(t')dt', where f is a kernel, and the gain has a nonlinear dependence on the atomic density. Validity conditions for the RIR or CARL limits are established in terms of the various parameters characterizing the atom-field interaction. The probe gain for a probe-pump detuning equal to zero is analyzed in some detail, in order to understand how gain arises in a system which, at first glance, appears to have a symmetry that would preclude the possibility for gain. Moreover, it is shown that these calculations, carried out in perturbation theory, have a range of applicability beyond the recoil problem. Experimental possibilities for observing CARL are discussed.

Berman, P. R.

1999-01-01

426

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

427

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

428

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

429

Spectroscopic measurement of the vapour pressure of ice.  

PubMed

We present a laser absorption technique to measure the saturation vapour pressure of hexagonal ice. This method is referenced to the triple-point state of water and uses frequency-stabilized cavity ring-down spectroscopy to probe four rotation-vibration transitions of at wavenumbers near 7180?cm(-1). Laser measurements are made at the output of a temperature-regulated standard humidity generator, which contains ice. The dynamic range of the technique is extended by measuring the relative intensities of three weak/strong transition pairs at fixed ice temperature and humidity concentration. Our results agree with a widely used thermodynamically derived ice vapour pressure correlation over the temperature range 0°C to -70°C to within 0.35 per cent. PMID:22547230

Bielska, K; Havey, D K; Scace, G E; Lisak, D; Hodges, J T

2012-06-13

430

Towards an Atomic Parity Violation Measurement with Laser Trapped Francium at ISAC  

NASA Astrophysics Data System (ADS)

The neutral atom trap for parity violation measurements at TRIUMF has recently accepted its first radioactive beam. The longest lived francium isotopes have half-lives of minutes, requiring us to produce them with the online mass separator of the ISAC facility. The ion beam is embedded into a catcher made of yttrium foil where it is neutralized. Subsequently, the foil is rotated and heated to release a pulse of atomic francium into the laser trap cell. Francium isotopes 207, 209 and 221 have successfully been cooled and confined in a magneto-optical trap, a crucial first step for later experiments. The next online measurements are planned for November 2012 where two physics goals will be pursued. Firstly, the hyperfine anomaly will be probed via high precision spectroscopy on the atomic D1 transition in order to investigate the nuclear magnetization distribution. This will be followed by ionization cross-section measurements from the 7p3/2 state to evaluate this as a potential problematic trap loss mechanism for future parity violation measurements.

Collister, R.; Tandecki, M.; Gwinner, G.; Zhang, J.; Orozco, L.; Behr, J. A.; Pearson, M. R.; Gomez-Garcia, E.; Aubin, S.

2012-10-01

431

Time-resolved laser-induced fluorescence of atomic nitrogen in a free-burning arc discharge  

Microsoft Academic Search

An experiment to detect ground-state atomic nitrogen in an atmospheric-pressure argon-nitrogen free-burning 200 A arc by time-resolved two-photon laser-induced fluorescence is described. The time decay of the fluorescence pulses showed that quenching of the laser-excited state is rapid. Upper bound estimates of the pulse-decay time were determined as a function of radius, and were found to be on the order

Stuart C. Snyder; Anna M. LeRoux

1997-01-01

432

Atomic hydrogen etching of silicon-incorporated diamond-like carbon films prepared by pulsed laser deposition  

Microsoft Academic Search

We have deposited Si-DLC films by pulsed laser deposition using KrF excimer laser, and have investigated etching of the Si-DLC films by atomic hydrogen. We have examined the structure and chemical bonding of the films by Raman spectroscopy, X-ray photoelectron spectroscopy and photoelectron spectroscopy using synchrotron radiation. Photoelectron spectra of Si 2p with 135 eV photons showed two distinguishing components. The

H. Nakazawa; H. Sugita; Y. Enta; M. Suemitsu; K. Yasui; T. Itoh; T. Endoh; Y. Narita; M. Mashita

2009-01-01

433

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

434

Activation of Implanted Boron Atoms in Silicon Wafers by Infrared Semiconductor Laser Annealing Using Carbon Films as Optical Absorption Layers  

NASA Astrophysics Data System (ADS)

We report continuous wave (CW) IR semiconductor laser annealing for the activation of boron atoms implanted into an n-type Si wafer with diamond-like carbon (DLC) films as optical absorption layers. Boron atoms were implanted at 10 keV at doses of 5× 1014, 1× 1015, and 1.5× 1015 cm-2. The depth at the boron concentration of 1018 cm-2 was 50 nm. Samples were annealed by irradiation at 66.5-80.5 kW/cm2 and 2.6 ms. The sheet resistance of the sample markedly decreased to 531 ?/sq for implantation at 1.5× 1015 cm-2 by laser annealing. Boron atoms were almost completely activated at a carrier density near the boron concentration for implantation at 10 keV. The largest diffusion length of boron atoms was 3 nm.

Sano, Naoki; Andoh, Nobuyuki; Sameshima, Toshiyuki; Matsuda, Yasuhiro; Andoh, Yasunori

2007-07-01

435

Generalized space-translated Dirac and Pauli equations for superintense laser-atom interactions  

NASA Astrophysics Data System (ADS)

We obtain a generalization of the nonrelativistic space-translation transformation to the Dirac equation in the case of a unidirectional laser pulse. This is achieved in a quantum-mechanical representation connected to the standard Dirac representation by a unitary operator T transforming the Foldy-Wouthuysen free-particle basis into the Volkov spinor basis. We show that a solution of the transformed Dirac equation containing initially low momenta p (p/mc?1) will maintain this property at all times, no matter how intense the field or how rapidly it varies (within present experimental capabilities). As a consequence, the transformed four-component equation propagates independently electron and positron wave packets, and in fact the latter are propagated via two two-component Pauli equations, one for the electron, the other for the positron. These we shall denote as the Pauli low-momentum regime (LMR) equations, equivalent to the Dirac equation for the laser field. Successive levels of dynamical accuracy appear depending on how accurately the operator T is approximated. At the level of accuracy considered in this paper, the Pauli LMR equations contain no spin matrices and are in fact two-component Schrödinger equations containing generalized time-dependent potentials. The effects of spin are nevertheless included in the theory because, in the calculation of observables which are formulated in the laboratory frame, use is made of the spin-dependent transformation operator T. In addition, the nonrelativistic limit of our results reproduces known results for the laboratory frame with spin included. We show that in intense laser pulses the generalized potentials can undergo extreme distortion from their unperturbed form. The Pauli LMR equation for the electron is applicable to one-electron atoms of small nuclear charge(?Z?1) interacting with lasers of all intensities and frequencies ??mc2.

Boca, Madalina; Florescu, Viorica; Gavrila, Mihai

2012-02-01

436

Polarization effects in ionizing thermal energy collisions of laser-excited Ne(3 p 3 D 3 ) atoms with Ar atoms  

Microsoft Academic Search

Using transverse and longitudinal excitation of a collimated metastable Ne(3s3P2.0) beam with average velocities of 500, 800, and 1,200 m\\/s by means of a single mode dye laser on the20Ne(3s3P2?3p3D3) transition, we have investigated ionizing collisions of polarized Ne(3s3P2) and Ne(3p3D3) atoms with Ar atoms. The product electrons were energy analyzed with high resolution (9–25 meV). The resulting Ne(3p3D3) electron

W. Bußert; T. Bregel; R. J. Allan; M.-W. Ruf; H. Hotop

1985-01-01

437

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

438

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

2014-04-01

439

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

440

Fluctuations in the process of resonant atomic absorption: laser phase-noise to amplitude-noise conversion  

Microsoft Academic Search

In the weak-field limit, resonant absorption is viewed as a passive process: an optical field impinges on an atom, and within some cross-sectional area the atom has a high probability for absorbing the radiant energy. Absorption, however, is a dynamic process. Consequently, though a singlemode laser is highly monochromatic, the field's phase noise (i.e., quantum noise) generates fluctuations in the

James Camparo

2003-01-01