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1

An externally heated copper vapour laser  

Microsoft Academic Search

A pulsed Copper Vapor Laser (CVL), with a nominal 6 kHz repetition rate, was designed, built, and commissioned at Chalk River Laboratories. The laser was required for Resonant Ionization Mass Spectroscopy (RIMS) experiments and for projects associated with Atomic Vapour Laser Isotope Separation (AVLIS) studies. For the laser to operate, copper coupons positioned along the length of a ceramic tube

P. A. Rochefort; F. C. Sopchyshyn; E. B. Selkirk; L. W. Green

1993-01-01

2

IV INTERNATIONAL CONFERENCE ON ATOM AND MOLECULAR PULSED LASERS (AMPL'99): Critical electron density in a self-contained copper vapour laser in the restricted pulse repetition rate  

NASA Astrophysics Data System (ADS)

One of the mechanisms of the inversion breaking in copper vapour lasers caused by a high prepulse electron density is considered. Inversion breaking occurs at a critical electron density Ne cr. If the prepulse electron density exceeds Ne cr, the electron temperature Te cr cannot reach, during a plasma heating pulse, the temperature of ~2eV required for lasing. A simple estimate of Ne cr is made.

Yakovlenko, Sergei I.

2000-06-01

3

Metal Vapour Lasers: Physics, Engineering and Applications  

NASA Astrophysics Data System (ADS)

Metal Vapour Lasers Christopher E. Little University of St Andrews, St Andrews, Scotland Since the first successful demonstration of a metal vapour laser (MVL) in 1962, this class of laser has become widely used in a broad range of fields including precision materials processing, isotope separation and medicine. The MVLs that are used today have a range of impressive characteristics that are not readily available using other technologies. In particular, the combination of high average output powers, pulse recurrence frequencies and beam quality available from green/yellow Cu vapour lasers (CVLs) and Cu bromide lasers, coupled with the high-quality, multiwatt ultraviolet (265-289 nm) radiation that can be produced using simple nonlinear optical techniques, means that Cu lasers will continue to be important for many years. Metal Vapour Lasers covers all the most commercially important and scientifically interesting pulsed and continuous wave (CW) gas-discharge MVLs, and includes device histories, operating characteristics, engineering, kinetics, commercial exploitation and applications. Short descriptions of gas discharges and excitation techniques make this volume self-consistent. A comprehensive bibliography is also provided. The greater part of this book is devoted to CVLs and their variants, including new sealed-off, high-power 'kinetically enhanced' CVLs and Cu bromide lasers. However, many other self-terminating MVLs are also discussed, including the red AuVL, green/infrared MnVL and infrared BaVL. Pulsed, high-gain, high average power lasers in the UV/violet (373.7, 430.5 nm) spectral regions are represented by Sr¯+ and Ca¯+ discharge-afterglow recombination lasers. The most commercially successful of the MVLs - the CW, UV/blue cataphoretic He-Cd¯+ ion laser - is described. Hollow cathode lasers are represented in two guises: 'white light' (blue/green/red) He-Cd¯+ ion lasers and UV/infrared Ne/He-Cu¯+ ion lasers. This unique volume is an essential reference source for all those working on metal vapour lasers, and all those who use them, from postgraduate students through to experienced scientists and engineers. It will also be extremely useful to all those working in other gas laser technologies, and in gas discharge physics.

Little, Christopher E.

1999-03-01

4

Ultrafast vapourization dynamics of laser-activated polymeric microcapsules.  

PubMed

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. PMID:24752357

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

2014-01-01

5

LASERS AND AMPLIFIERS: Peculiarities of pumping of copper vapour and copper bromide vapour lasers  

NASA Astrophysics Data System (ADS)

Lasing and peculiarities of pumping of a copper vapour laser with a commercially produced 'Crystal' LT-40Cu active element and of a CuBr laser with a large-volume experimental active element are studied experimentally. It is shown that the efficiency of lasers with an average radiation power up to 50 W relative to the energy supplied to the active medium during useful pumping achieves 4%. It is found that the stage of useful pumping of the central part of the laser tube is preceded by a partial breakdown of the discharge gap and the charging of parasitic capacitances. A distinguishing feature of the pumping of a CuBr laser as compared to the Cu laser is that the inductance of the leads from the pump oscillator to the active element and the inductance of the pump oscillator can be increased, while the average radiation power remains unchanged.

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

2001-08-01

6

Photonic metamaterials by direct laser writing and silver chemical vapour  

E-print Network

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

7

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

SciTech Connect

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

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

2012-01-31

8

The Development Of Gold And Copper Vapour Lasers For Medical Applications In Australia  

NASA Astrophysics Data System (ADS)

The first fully automated mobile copper and gold vapour lasers for medical applications were developed in Australia. The history of this development program is presented in this paper. These lasers have been tested in several clinical programs and success with the gold vapour laser in cancer phototherapy using HpD has been achieved in various types of tumours. Trials have commenced on the use of the 578 nm yellow line of the copper vapour laser for dermatology and plastic surgery.

Stanco, Alex

1987-04-01

9

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

10

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

Microsoft Academic Search

Ablation-using short-pulse lasers, e.g., excimer lasers and solid state lasers, is becoming an important technology for micro-machining, thin film formation and fine particle generation. Hence, there is a great interest to understand the interaction mechanisms between the radiation field and the evaporated material. Especially the laser-induced material vapour influences the efficiency and the quality of the ablation, as shown in

H. Schittenhelm; G. Callies; P. Berger; H. Hgel

1998-01-01

11

Tunable narrow-band UV laser system pumped by a copper vapour laser  

SciTech Connect

A narrow-band laser system is designed, which produces 10-ns pulses of tunable UV radiation with an average power of 3 W, pulse repetition rate of 12 kHz, and linewidth smaller than 45 MHz. The system uses a cw dye laser as a master oscillator. Its radiation is amplified by a three-stage dye system whose output signal is frequency doubled in a BBO crystal. The system is pumped by a copper vapour laser. (lasers)

Bokhan, P A; Zakrevskii, D E; Kochubei, S A; Stepanov, A Yu [Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk (Russian Federation); Fateev, N V [Institute of Laser Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk (Russian Federation)

2001-02-28

12

Guided quasicontinuous atom laser.  

PubMed

We report the first realization of a guided quasicontinuous atom laser by rf outcoupling a Bose-Einstein condensate from a hybrid optomagnetic trap into a horizontal atomic waveguide. This configuration allows us to cancel the acceleration due to gravity and keep the de Broglie wavelength constant at 0.5 microm during 0.1 s of propagation. We also show that our configuration, equivalent to pigtailing an optical fiber to a (photon) semiconductor laser, ensures an intrinsically good transverse mode matching. PMID:17155665

Guerin, W; Riou, J-F; Gaebler, J P; Josse, V; Bouyer, P; Aspect, A

2006-11-17

13

A cold-atom random laser  

NASA Astrophysics Data System (ADS)

In conventional lasers optical cavities are used to provide feedback to gain media. Mirrorless lasers can be built by using disordered structures to induce multiple scattering, which increases the path length in the medium, providing the necessary feedback. Interestingly, light or microwave amplification by stimulated emission also occurs naturally in stellar gases and planetary atmospheres. The possibility of additional scattering-induced feedback--random lasing--could explain the unusual properties of some space masers. Here, we report experimental evidence of random lasing in a controlled, cold atomic vapour, taking advantage of Raman gain. By tuning the gain frequency in the vicinity of a scattering resonance, we observe an enhancement of the light emission due to random lasing. The unique possibility to both control the experimental parameters and to model the microscopic response of our system provides an ideal test bench for better understanding natural lasing sources, in particular the role of resonant scattering feedback in astrophysical lasers.

Baudouin, Q.; Mercadier, N.; Guarrera, V.; Guerin, W.; Kaiser, R.

2013-06-01

14

Influence of the bath gas on the condensation of supersaturated iron atom vapour at room temperature  

Microsoft Academic Search

The influence of the kind of bath gas and its pressure on the iron nanoparticle formation and growth was investigated experimentally. Iron nanoparticles were synthesized from supersaturated iron vapour generated by ArF excimer laser pulse photolysis of gaseous Fe(CO)5 at room temperature. The particle size was determined by time-resolved laser-induced incandescence (TiRe-LII) as a function of time after photolysis at

A. Eremin; E. Gurentsov; C. Schulz

2008-01-01

15

Radiation trapping and Lvy flights in atomic vapours: an introductory review  

Microsoft Academic Search

Multiple scattering is a process in which a particle is repeatedly deflected by other particles. In an overwhelming majority of cases, the ensuing random walk can successfully be described through Gaussian, or normal, statistics. However, like a (growing) number of other apparently inoffensive systems, diffusion of light in dilute atomic vapours eludes this familiar interpretation, exhibiting a superdiffusive behaviour. As

Martine Chevrollier

2012-01-01

16

Collision lasers on atomic transitions  

SciTech Connect

This paper reviews the research of cw collision lasers on transitions of atoms and atomic ions and presents characteristics of systems that are considered to be collision lasers. Literature data on 'relaxation' and 'mixing' of levels by collisions with heavy particles are discussed, with particular attention to the relaxation of metastable levels. The major problems in the development of efficient cw collision lasers are analysed, including difficulties in realising discharges suitable for pumping collision lasers. The possibility of further advances in collision laser development is discussed. (review)

Petrash, G G [P.N. Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2009-02-28

17

An experimental study on iron thin films obtained by laser pyrolysis of iron pentacarbonyl vapour  

Microsoft Academic Search

The results of a study on laser-assisted CVD of iron thin films from Fe(CO)5 vapour using a CO2 laser are presented. The iron-based layers deposited onto quartz substrates were characterised by different analytical techniques, and the influence of the precursor pressure and laser incident energy on the physical and chemical properties of films was pointed out. It was deduced that

R. Cireasa; R. Alexandrescu; I. Voicu; I. Morjan; G. Pugna

1996-01-01

18

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

19

The Collective Atomic Recoil Laser  

SciTech Connect

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.; Cube, C. avon; Deh, B.; Kruse, D.; Ludewig, A.; Slama, S.; Zimmermann, C. [Physikalisches Institut, Eberhard-Karls-Universitaet Tuebingen, Auf der Morgenstelle 14, D-72076 Tuebingen (Germany)

2005-05-05

20

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

21

High-power copper vapour lasers and applications  

SciTech Connect

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

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

1995-08-01

22

Diffusion vapour transfer modelling for an end-capped atomizer. Part 1. Atomizer with closed injection port  

NASA Astrophysics Data System (ADS)

For end-cap equipped transverse-heated graphite atomizers (THGA) with integrated contacts used for analytical atomic spectrometry, a model equation describing the diffusional losses of analyte atomic vapour through the tube ends was constructed. The model assumes that the atomic density distribution is stepwise linear along the tube axis and the absence of a sample injection hole. With a quartz tube system, providing controlled experimental conditions at room temperature, the time constant of the diffusion removal function (T R) of mercury vapour was determined for various open and end-capped tube geometries. These results were also described by an empirical multiple regression equation with a residual standard deviation of 5%. The theoretically predicted T R values, corrected with an empirical factor of 1.33, agreed well (correlation coefficient = 0.996) with the experimentally obtained T R values for the endcapped quartz tubes. For the Perkin-Elmer THGA tubes, the diffusional transfer model was evaluated using the integrated atomic absorbance ratio between various end-capped and open tubes. This is meaningful because the signal ratio for graphite atomizers is closely equal to the corresponding T R ratio. For recommended atomization temperatures the average deviation between these experimental signal ratios and the theoretically predicted ratios for the elements Ag, In, Cd, Co, Hg and Cu was 1-5% for various end-capped tube geometries. The results for the individual elements deviated more from the theoretically predicted ratios mainly because of small differences in the mean gas-phase temperature between open and end-capped tubes. For elements which tend to form molecules in the gas phase at low temperatures and for which the atomization efficiency is increased with the atomization temperature, the experimental ratios tended to be higher than the theoretically predicted values (In, Al, Se, Sn, As), whereas experimental ratios were slightly lower for other elements (Cd, Co, Cu).

Hadgu, Negassi; Ohlsson, K. E. Anders; Frech, Wolfgang

1995-08-01

23

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

24

Dye laser pumped atomic iodine laser  

Microsoft Academic Search

Lasing has been demonstrated on the 2P1\\/2-2P3\\/2 transition in atomic iodine by optically pumping I2 vapor to dissociation with a flashlamp-pumped tunable dye laser. Lasing at 1.315 mu has been observed for pump wavelengths from 5010 to 4930 A˚. The device holds promise as a rapidly pulsed gain diagnostic for existing or future iodine systems.

S. J. Davis

1978-01-01

25

Dye laser pumped atomic iodine laser  

Microsoft Academic Search

Lasing has been demonstrated on the 2P1\\/22P3\\/2 transition in atomic iodine by optically pumping I2 vapor to dissociation with a flashlamp-pumped tunable dye laser. Lasing at 1.315 ? has been observed for pump wavelengths from 5010 to 4930 A?. The device holds promise as a rapidly pulsed gain diagnostic for existing or future iodine systems.

S. J. Davis

1978-01-01

26

Water Vapour Propulsion Powered by a High-Power Laser-Diode  

NASA Astrophysics Data System (ADS)

Most of the laser propulsion schemes now being proposed and developed assume neither power supplies nor on-board laser devices and therefore are bound to remote laser stations like a kite via a laser beam string. This is a fatal disadvantage for a space vehicle that flies freely though it is often said that no need of installing an energy source is an advantage of a laser propulsion scheme. The possibility of an independent laser propulsion space vehicle that carries a laser source and a power supply on board is discussed. This is mainly due to the latest development of high power laser diode (LD) technology. Both high specific impulse-low thrust mode and high thrust-low specific impulse mode can be selected by controlling the laser output by using vapour or water as a propellant. This mode change can be performed by switching between a high power continuous wave (cw), LD engine for high thrust with a low specific impulse mode and high power LD pumping Q-switched Nd:YAG laser engine for low thrust with the high specific impulse mode. This paper describes an Orbital Transfer Vehicle equipped with the above-mentioned laser engine system and fuel cell that flies to the Moon from a space platform or space hotel in Earth orbit, with cargo shipment from lunar orbit to the surface of the Moon, including the possibility of a sightseeing trip.

Minami, Y.; Uchida, S.

27

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

PubMed

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

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

2013-04-15

28

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

29

Atomic physics: An almost lightless laser  

E-print Network

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

Vuletic, Vladan

30

A simple laser system for atom interferometry  

NASA Astrophysics Data System (ADS)

We present here a simple laser system for a laser-cooled atom interferometer, where all functions (laser cooling, interferometry and detection) are realized using only two extended cavity laser diodes, amplified by a common tapered amplifier. One laser is locked by frequency modulation transfer spectroscopy, the other being phase locked with an offset frequency determined by an field-programmable gate array-controlled direct digital synthesizer, which allows for efficient and versatile tuning of the laser frequency. Raman lasers are obtained with a double pass acoustooptic modulator. We demonstrate a gravimeter using this laser system, with performances close to the state of the art.

Merlet, S.; Volodimer, L.; Lours, M.; Pereira Dos Santos, F.

2014-07-01

31

Atomic Laser Cooling and Laser Frequncy Stabilization  

NASA Astrophysics Data System (ADS)

Effective laser cooling of trapped ions requires the laser's frequency to be precise, with a frequency drift of no more than a few megahertz. Optical cavities can be used as frequency monitors and provide feedback to tunable lasers for correcting frequency drift. In the University of Washington Quantum Computing with Trapped Ions lab, Fabry-Perot resonator cavities were designed and built to stabilize the frequency of two lasers used for laser cooling trapped barium ions.

Davis, Anya

2010-03-01

32

Resonant Laser Manipulation of an Atomic Beam  

Microsoft Academic Search

Theories for laser-atom 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. A representative numerical investigation was conducted using a custom collisionless gas particle trajectory code, demonstrating this

T. C. Lilly; A. D. Ketsdever; S. F. Gimelshein

2011-01-01

33

Push-Pull Laser-Atomic Oscillator  

NASA Astrophysics Data System (ADS)

A vapor of alkali-metal atoms in the external cavity of a semiconductor laser, pumped with a time-independent injection current, can cause the laser to self-modulate at the field-independent 0-0 frequency of the atoms. Push-pull optical pumping by the modulated light drives most of the atoms into a coherent superposition of the two atomic sublevels with an azimuthal quantum number m=0. The atoms modulate the optical loss of the cavity at the sharply defined 0-0 hyperfine frequency. As in a maser, the system is not driven by an external source of microwaves, but a very stable microwave signal can be recovered from the modulated light or from the modulated voltage drop across the laser diode. Potential applications for this new phenomenon include atomic clocks, the production of long-lived coherent atomic states, and the generation of coherent optical combs.

Jau, Y.-Y.; Happer, W.

2007-11-01

34

The atomic iodine photodissociation laser  

SciTech Connect

After almost two decades of laboratory research and development, the iodine photodissociation laser is now a developed system with industrial and scientific applications. This article reviews the progress of the iodine laser, the basic configuration and performance of a flashlamp-pumped system, and several applications areas. The major impetus behind the development of the iodine photodissociation laser (IPL) has been the requirement for a high-power, short-pulse, terawatt laser for laser fusion studies.

Bannister, J.J.; King, T.A.

1984-08-01

35

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

36

Laser Spectroscopy of Atoms and Molecules.  

ERIC Educational Resources Information Center

Surveys new laser techniques and a variety of spectroscopic experiments that can be used to detect, measure and study very small numbers of atoms on molecules. The range of applicability of these techniques is also included. (HM)

Schawlow, Arthur L.

1978-01-01

37

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

38

Laser Cooled Atomic Clocks in Space  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

39

Atomic Spectroscopy with Laser Diodes and Undergraduates  

NASA Astrophysics Data System (ADS)

Laser spectroscopy provides powerful techniques for exploring numerous topics in atomic/molecular/optical physics and beyond. Investigations of atomic and molecular splittings, planetary atmospheres, nuclear shapes, ultrafast processes, exotic matter, plasma parameters, photoacoustic effects, and molecular dynamics via quantum control constitute a minuscule sampling of present day applications of laser spectroscopy. While diode lasers cannot fulfill many requirements regarding wavelength, power, and/or energy, their compactness, longevity, efficiency, reliability, quietude, ease of use, and low cost often make diodes the laser of choice for a given application of laser spectroscopy. In fact, the cost and spatial requirements of diode laser systems are so modest that an investigator, even when forced to operate on a tight budget, can maintain and usefully employ as many as a dozen independent diode laser systems. This talk will elaborate on several of these points and describe some unexpected results in recent measurements of fine-structures and Zeeman splittings in excited states of alkali and rare gas atoms via two- and three-step laser excitation spectroscopy.

Brandenberger, John R.

2004-03-01

40

Solar simulator-pumped atomic iodine laser  

SciTech Connect

An atomic iodine laser, a candidate for the direct solar-pumped gas laser, was excited with a 4-kW beam from a xenon arc solar simulator. Continuous lasing at 1.315 ..mu..m for over 10 ms was obtained for static filling of n-C/sub 3/F/sub 7/I vapor. By momentarily flowing the lasant, a 30-Hz pulsed output was obtained for about 200 ms. The peak laser power observed was 4 W for which the system efficiency reached 0.1%. These results indicate that direct solar pumping of a gas laser for power conversion in space is indeed feasible.

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

1981-07-15

41

Prospects of laser cooling in atomic thallium  

NASA Astrophysics Data System (ADS)

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

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

2011-10-01

42

Lasers: Harnessing the Atom's Light  

Microsoft Academic Search

Articles in Scientific American have for many years set a high standard of presentation alongside a carefully tuned technical level of presentation. To a first approximation, this book reads like a long Scientific American article. Here we have an ambitious attempt to take the reader through a large slice of the history, the physics and the technology of lasers. To

M J M Leask

1998-01-01

43

Steering neutral atoms in strong laser fields  

NASA Astrophysics Data System (ADS)

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

Eilzer, S.; Eichmann, U.

2014-10-01

44

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

PubMed

Monolayer molybdenum disulfide (MoS2) has attracted tremendous attention due to its promising applications in high-performance field-effect transistors, phototransistors, spintronic devices and nonlinear optics. The enhanced photoluminescence effect in monolayer MoS2 was discovered and, as a strong tool, was employed for strain and defect analysis in MoS2. Recently, large-size monolayer MoS2 has been produced by chemical vapour deposition, but has not yet been fully explored. Here we systematically characterize chemical vapour deposition-grown MoS2 by photoluminescence spectroscopy and mapping and demonstrate non-uniform strain in single-crystalline monolayer MoS2 and strain-induced bandgap engineering. We also evaluate the effective strain transferred from polymer substrates to MoS2 by three-dimensional finite element analysis. Furthermore, our work demonstrates that photoluminescence mapping can be used as a non-contact approach for quick identification of grain boundaries in MoS2. PMID:25404060

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

2014-01-01

45

Influence of the pre-pulse plasma electron density on the performance of elemental copper vapour lasers  

NASA Astrophysics Data System (ADS)

A detailed computer model for the kinetics in an elemental copper vapour laser (Cu-Ne-H 2) has been used to investigate the importance of the pre-pulse electron density on the performance and lasing characteristics of such a device. The results show that the laser output power and operating efficiency are increased by 65% and 100%, respectively, at a pulse repetition frequency of 17 kHz, if the pre-pulse electron density is reduced by a factor of 5-10. Modelling of the plasma kinetics during the afterglow period suggests that such a reduction is brought about when trace quantities (0.3%) of HCl are introduced into the plasma to increase the electron density decay rates via dissociative attachment reactions. The predicted improvements in laser performance which occur as a result of a reduced pre-pulse electron density are consistent with the observed operating characteristics of Kinetically Enhanced copper vapour lasers which use HCl-H 2-Ne buffer gas mixtures.

Carman, Robert J.; Withford, Michael J.; Brown, Daniel J. W.; Piper, James A.

1998-12-01

46

Measuring variations of ?18O and ?2H in atmospheric water vapour using laser spectroscopy: an instrument characterisation study  

NASA Astrophysics Data System (ADS)

Variations of stable water isotopes in water vapour have become measurable at a measurement frequency of about 1 Hz in recent years using novel laser spectroscopic techniques. This enables us to perform continuous measurements for process-based investigations of the atmospheric water cycle at the time scales relevant for synoptic meteorology. An important prerequisite for the interpretation of data from automated field measurements lasting for several weeks or months is a detailed knowledge about instrument properties and the sources of measurement uncertainty. We present here 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 Research). The uncertainty components of the measurements were first assessed in laboratory experiments, focussing on the 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. Based on the experience from our laboratory experiments we set up a one-week field campaign for comparing measurements of the ambient isotope signals of the two laser spectroscopic systems. The optimal calibration strategy determined for both instruments was applied as well as the correction functions for water vapour mixing ratio effects. The root mean square difference between the isotope signals from the two instruments during the field deployment was 2.3 for ?2H, 0.5 for ?18O and 3.1 for deuterium excess. These uncertainty estimates from field measurements compare well to those found in the laboratory experiments. The present quality of measurements from laser spectroscopic instruments combined with a calibration system opens new possibilities for investigating the atmospheric water cycle and the land-atmosphere moisture fluxes.

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

2012-02-01

47

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

E-print Network

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

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

2013-11-28

48

Free Fall of Atomic Laser Beam with Weak InterAtomic Interaction  

Microsoft Academic Search

Free falling atomic laser beams with sufficiently weak inter-atomic interaction are investigated. An approximate solution of one-dimensional Gross-Pitaevskii equation with gravitational potential is obtained by usingthe WKB analysis. This shows the effects of the inter-atomic interaction on the velocities of bosonic atoms. The analysis is extended to investigate the interference pattern of two atomic laser beams.

Takeya Tsurumi; Miki Wadati

2001-01-01

49

Atoms and Molecules in Strong Laser Fields  

NASA Astrophysics Data System (ADS)

The interactions of superstrong and ultrashort laser pulses with atoms and molecules have been a subject of great interest over the past two decades, as reflected in many books and review articles. The beginning of the twenty-first century is witnessing the development of several large- and medium-scale experimental facilities dedicated to the generation of laser light with unprecedented capabilities. The frequency spectrum covered by these new light sources ranges from the infrared up to the extreme ultraviolet and soft x-ray (produced in the FLASH free-electron laser facility at DESY). This calls for the development of new theoretical and computational tools to simulate laser-matter interactions at extreme conditions.

Ullrich, Carsten A.; Bandrauk, Andr D.

50

Continuous wave chemically pumped atomic iodine laser  

SciTech Connect

Cw laser action achieved on the 2p178-2p3/2 transition of the iodine atom by energy transfer from the 1 delta metastable state of O2 is discussed. The effluent from a conventional oxygen generator was mixed with molecular iodine at the entrance of a longitudinal flow laser cavity where the I2 was dissociated by a small amount of O2 (1 sigma ) that was present in the flow due to energy pooling processes. The measured output power was greater than 4MW

Benard, D.J.; Bousek, R.R.; Mcdermott, W.E.; Pchelkin, N.R.

1981-05-12

51

Entangling many atomic ensembles through laser manipulation  

E-print Network

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

L. -M. Duan

2002-01-28

52

Laser cooling and trapping of atomic mercury  

NASA Astrophysics Data System (ADS)

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

Paul, Justin; Lytle, Christian; Jones, Jason

2011-10-01

53

Efficient sum-frequency and second harmonic generation in a two-pass copper vapour laser amplifier  

SciTech Connect

New results are presented on the efficient generation of UV radiation by using nonlinear DKDP and BBO crystals and a two-pass copper vapour laser amplifier with the enhanced peak power. The average power (average optical efficiency) of laser radiation at the sum frequency ({lambda}=0.271 {mu}m) was 3.6 W (24%) for the BBO crystal and 2.1 W (14%) for the DKDP crystal. The maximum average second-harmonic power generated by using the BBO crystal was 3.4 W (44%) at 0.289 {mu}m and 2.1 W (27%) at 0.255 {mu}m. (nonlinear optical phenomena)

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

2005-09-30

54

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

NASA Astrophysics Data System (ADS)

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 and unusual aspect of this route is that, unlike other synthesis approaches, the obtained single wall carbon nanotube diameters show no dependence on the synthesis parameters and this is attributed to their nucleation via fullerenes and fullerene caps. The results suggest fullerene nucleation may also be active in other CVD synthesis routes.

Rmmeli, M. H.; Kramberger, C.; Lffler, M.; Kalbc, M.; Hbers, H.-W.; Grneis, A.; Barreiro, A.; Grimm, D.; Ayala, P.; Gemming, T.; Schffel, F.; Dunsch, L.; Bchner, B.; Pichler, T.

2006-11-01

55

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

56

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

PubMed

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

Lemos, Valfredo Azevedo; dos Santos, Liz Oliveira

2014-04-15

57

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

58

Atomic Absorption Spectrometry (flame, electrothermal, vapour generation) in Environmental, Biological and Food Analysis  

Microsoft Academic Search

\\u000a Atomic absorption spectrometry (AAS) is one of the most valuable and well established techniques in the vast application area\\u000a of biological and environmental analysis. Flame AAS is robust, selective and straightforward yet lacks sensitivity at analyte\\u000a concentrations below 0.110 g\\/g in analyses of liquid and solid samples, respectively. Two modern AAS techniques with better\\u000a detection power (101,000fold) as well as

Dimiter L. Tsalev

59

Laser-Excited Atomic Fluorescence in a Pulsed Glow Discharge.  

National Technical Information Service (NTIS)

A pulsed demountable glow discharge has been used as an atom cell for laser excited atomic fluorescence. Lead atoms are sputtered from the surface of copper and graphite cathodes and are excited by a pulsed frequency-doubled dye laser after the discharge ...

B. W. Smith, N. Omenetto, J. D. Winefordner

1984-01-01

60

Laser-Excited Atomic Fluorescence Spectrometry in a Pressure-Controlled Electrothermal Atomizer  

E-print Network

Laser-Excited Atomic Fluorescence Spectrometry in a Pressure-Controlled Electrothermal Atomizer was developed to describe the loss of analyte atoms in graphite furnaces during atomization. The model was based between these two processes. Optimal atomization efficiency was predicted to occur at a pressure where

Michel, Robert G.

61

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

SciTech Connect

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

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

2012-11-30

62

Solar-simulator-pumped atomic iodine laser kinetics  

Microsoft Academic Search

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

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

1983-01-01

63

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

64

Narrow linewidth single laser source system for onboard atom interferometry  

E-print Network

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

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

2014-01-01

65

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

66

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

E-print Network

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

Queensland, University of

67

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

E-print Network

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

Johannesson, Henrik

68

Miniature, compact laser system for ultracold atom sensors  

NASA Astrophysics Data System (ADS)

As ultracold atom sensors begin to see their way to the field, there is a growing need for small, accurate, and robust laser systems to cool and manipulate atoms for sensing applications such as magnetometers, gravimeters, atomic clocks and inertial sensing. In this paper we present a frequency-agile, butterfly packaged laser source, absolutely referenced to an atomic transition. We also present the entire laser system, including a fiber-coupled optical amplifier and liquid crystal shutters, replacing a laboratory table's worth of optics with a system the size of a paperback novel.

Pino, J. M.; Luey, B.; Bickman, S.; Anderson, M. H.

2013-05-01

69

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

SciTech Connect

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

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

2009-05-31

70

X-ray refractive index of laser-dressed atoms  

Microsoft Academic Search

We investigated the complex index of refraction in the x-ray regime of atoms in laser light. The laser (intensity up to 1013W\\/cm2 , wavelength 800nm ) modifies the atomic states but, by assumption, does not excite or ionize the atoms in their electronic ground state. Using quantum electrodynamics, we devise an ab initio theory to calculate the dynamic dipole polarizability

Christian Buth; Robin Santra

2008-01-01

71

Laser-excited atomic fluorescence in a pulsed glow discharge  

NASA Astrophysics Data System (ADS)

A pulsed demountable glow discharge has been used as an atom cell for laser excited atomic fluorescence. Lead atoms are sputtered from the surface of copper and graphite cathodes and are excited by a pulsed frequency-doubled dye laser after the discharge is switched off. The combination of a "dark" atom cell with non-resonance atomic fluorescence leads to a very low background signal. The detection limit for lead in copper is 0.1 ?g/g and for lead in aqueous solutions (5 ?l) deposited on graphite electrodes is 20 pg.

Smith, B. W.; Omenetto, N.; Winefordner, J. D.

72

A model for an atom laser XII INTERNATIONAL CONFERENCE  

E-print Network

; the prospects for this condensation in an atomic gas, first cooled with lasers, and further compressed, a most fascinating one is related to the manifestations of the statistical nature of the atoms, either emission of a bosonic atom in (b,gare induded in (2), leading to the factor 1+nb(p'). The last term of (2

Dalibard, Jean

73

Interaction of intense laser pulses with hydrogen atomic clusters  

NASA Astrophysics Data System (ADS)

The interaction between intense femtosecond laser pulses and hydrogen atomic clusters is studied by a simplified Coulomb explosion model. The dependences of average proton kinetic energy on cluster size, pulse duration, laser intensity and wavelength are studied respectively. The calculated results indicate that the irradiation of a femtosecond laser of longer wavelength on hydrogen atomic clusters may be a simple, economical way to produce highly kinetic hydrogen ions. The phenomenon suggests that the irradiation of femtosecond laser of longer wavelength on deuterium atomic clusters may be easier than that of shorter wavelength to drive nuclear fusion reactions. The product of the laser intensity and the squared laser wavelength needed to make proton energy saturated as a function of the squared cluster radius is also investigated. The proton energy distribution calculated is also shown and compared with the experimental data. Our results are in agreement with the experimental results fairly well.

Du, Hong-Chuan; Wang, Hui-Qiao; Liu, Zuo-Ye; Sun, Shao-Hua; Li, Lu; Ma, Ling-Ling; Hu, Bi-Tao

2010-03-01

74

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

75

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

2011-10-01

76

Laser manipulation of atomic and molecular flows  

Microsoft Academic Search

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

Taylor C. Lilly

2010-01-01

77

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 GrossPitaevskii 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

78

A solar simulator-pumped atomic iodine laser  

Microsoft Academic Search

An atomic iodine laser, a candidate for the direct solar-pumped gas laser, was excited with a 4-kW beam from a xenon arc solar simulator. Continuous lasing at 1.315 micron for over 10 ms was obtained for static filling of n-C3F7I vapor. By momentarily flowing the lasant, a 30-Hz pulsed output was obtained for about 200 ms. The peak laser power

J. H. Lee; W. R. Weaver

1981-01-01

79

A solar simulator-pumped atomic iodine laser  

Microsoft Academic Search

An atomic iodine laser, a candidate for the direct solar-pumped gas laser, was excited with a 4-kW beam from a xenon arc solar simulator. Continuous lasing at 1.315 ?m for over 10 ms was obtained for static filling of n-C3F7I vapor. By momentarily flowing the lasant, a 30-Hz pulsed output was obtained for about 200 ms. The peak laser power

Ja H. Lee; W. R. Weaver

1981-01-01

80

Glow discharge source atomization for the laser-excited atomic fluorescence spectrometric studies of indium  

NASA Astrophysics Data System (ADS)

A demountable glow discharge source has been used for the atomization of the analyte solutions deposited on graphite and copper rod cathodes. Indium atoms are sputtered-atomized from the cathode surface and are excited by a pulsed, frequency-doubled dye laser pumped by the nitrogen laser. Atomic fluorescence measurements were performed using the non-resonance fluorescence transition. The detection limits of indium in aqueous solutions (10?l) deposited on graphite and copper electrodes were 8 10 -9 and 11 10 -9g, respectively (8 ng and 11ng).

Patel, B. M.; Winefordner, J. D.

81

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 FoxLi 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 atomcavity 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

82

Measuring variations of ?18O and ?2H in atmospheric water vapour using two commercial laser-based spectrometers: an instrument characterisation study  

NASA Astrophysics Data System (ADS)

Variations of stable water isotopes in water vapour have become measurable at a measurement frequency of about 1 Hz in recent years using novel laser spectroscopic techniques. This enables us to perform continuous measurements for process-based investigations of the atmospheric water cycle at the time scales relevant for synoptic and mesoscale meteorology. An important prerequisite for the interpretation of data from automated field measurements lasting for several weeks or months is a detailed knowledge about instrument properties and the sources of measurement uncertainty. We present here 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 Research). The uncertainty components of the measurements were first assessed in laboratory experiments, focussing on the 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. Based on the experience from our laboratory experiments, we set up a one-week field campaign for comparing measurements of the ambient isotope signals from the two laser spectroscopic systems. The optimal calibration strategy determined for both instruments was applied as well as the correction functions for water vapour mixing ratio effects. The root mean square difference between the isotope signals from the two instruments during the field deployment was 2.3 for ?2H, 0.5 for ?18O and 3.1 for deuterium excess. These uncertainty estimates from field measurements compare well to those found in the laboratory experiments. The present quality of measurements from laser spectroscopic instruments combined with a calibration system opens new possibilities for investigating the atmospheric water cycle and the land-atmosphere moisture fluxes.

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

2012-07-01

83

Solar-simulator-pumped atomic iodine laser kinetics  

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

84

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

E-print Network

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

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

2014-01-01

85

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

86

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

E-print Network

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

Paris-Sud XI, Université de

87

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

E-print Network

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

88

A solar simulator-pumped atomic iodine laser  

NASA Technical Reports Server (NTRS)

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

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

1981-01-01

89

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

E-print Network

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

90

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

E-print Network

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

91

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

Microsoft Academic Search

Two alternative chemical methods of atomic iodine generation for a chemical oxygen-iodine laser (COIL) were studied. These methods are based on fast reactions of gaseous hydrogen iodide with chemically produced chlorine and fluorine atoms. Both processes were studied first in small-scale reactors. A yield of atomic iodine in the Cl system and nitrogen (non-reactive) atmosphere exceeded 80%, while in the

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

2005-01-01

92

Measurement of the absorption line profiles of water vapour isotopomers at 1.39 {mu}m using the methods of diode laser spectroscopy  

SciTech Connect

The issues related to high-precision measurement of the absorption line profiles of water vapour and its isotopomers using the methods of diode laser spectroscopy in the near IR range aimed at the analysis and detection of greenhouse gases are considered. The absorption line shape of H{sub 2}{sup 16}O is investigated as a function of pressure of different buffer gases. The influence of the instrument function of the diode laser (DL) on the precision of measuring the line profile is studied. From fitting the profile of Doppler-broadened H{sub 2}{sup 16}O absorption line to a model profile the lasing line width of the DL with a fibre pigtail is determined. The frequencies and intensities of absorption lines of water isotopomers H{sub 2}{sup 16}O, H{sub 2}{sup 17}O, H{sub 2}{sup 18}O, and HDO are measured in the range of DL oscillation. Analytical spectral regions are chosen for distant probing of water vapour using an airborne lab. (laser spectroscopy)

Kuz'michev, A S; Nadezhdinskii, Aleksandr I; Ponurovskii, Ya Ya

2011-07-31

93

Pulsed Raman output coupler for an atom laser  

SciTech Connect

We theoretically study a pulsed stimulated two-photon Raman outcoupler for an atom laser using a full three-dimensional description. A finite-temperature trapped Bose-condensed atomic gas is treated self-consistently by the Hartree-Fock-Bogoliubov equations. The model is closely related to a recent experiment on optical outcoupling [E. W. Hagley et al., Science 283, 1706 (1999)]. We analyze the momentum distribution of the output atoms and show how the output beam may be used as a probe of the quantum state for the trapped atomic gas and how it could be engineered and controlled in a nonlinear way.

Ruostekoski, J. [Department of Physical Sciences, University of Hertfordshire, Hatfield, Herts AL10 9AB, (United Kingdom); Gasenzer, T. [Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, (United Kingdom); Hutchinson, D. A. W. [Department of Physics, University of Otago, P.O. Box 56, Dunedin, (New Zealand)

2003-07-01

94

Theory of a single-atom laser including light forces  

E-print Network

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.

Thomas Salzburger; Peter Domokos; Helmut Ritsch

2005-04-12

95

Laser Technology in Commercial Atomic Clocks  

Microsoft Academic Search

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

R. Lutwak

2006-01-01

96

Laser-induced nonresonant nuclear excitation in muonic atoms  

E-print Network

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

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

2008-12-13

97

Microwave-pumped atomic gas laser  

Microsoft Academic Search

This patent describes a method of obtaining coherent optical or quasi-optical radiation from a chemical element whose first excited state is metastable. It includes: enclosing a solid compound containing the element in a gas-tight enclosure containing a buffer gas or mixture of gases; placing the enclosure in a microwave cavity and between laser mirrors; and pumping the compound with microwave

Bramley

1989-01-01

98

Experimental results on chemical generation of atomic iodine via Cl atoms for chemical oxygen-iodine laser  

Microsoft Academic Search

An alternative chemical way of atomic iodine generation for the chemical oxygen-iodine laser (COIL) was studied. This development was aimed at the laser power increase and simplification of the laser operation control. The method is based on the fast reaction of hydrogen iodide with chemically produced chlorine atoms. Kinetics of the process was studied in two types of the small-scale

Otomar Spalek; Vt Jirsek; Miroslav Censky; Jarmila Kodymov; Ivo Jakubec; Gordon D. Hager

2003-01-01

99

Controlling atomic structures and photoabsorption processes by an infrared laser  

SciTech Connect

We propose a theoretical method to calculate the infrared (IR) laser-assisted photoabsorption cross sections over a broad energy range by a single calculation. In this method we define an initial wave function as the product of the dipole operator and the atomic ground state, propagate the initial wave function in the IR laser field with different initial phases, then calculate the generalized autocorrelation function, which is defined as the averaged value of the autocorrelation function over the initial phase from 0 to 2{pi} (or one IR optical cycle). The IR laser-assisted photoabsorption cross sections are obtained by the Fourier transform of the generalized autocorrelation function. We apply this method to study the IR laser-assisted photoabsorption of He atoms. From the simulation results, we see that the IR laser field affects not only the resonant position but also the lifetime or the width of the bound states. This photoabsorption cross section is an important quantity to analyze the IR-laser-assisted dynamical processes by an attosecond pulse, a pulse train, or a free-electron laser.

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); 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)

2010-06-15

100

Ablation scaling in laser-produced plasmas with laser intensity, laser wavelength, and target atomic number  

NASA Astrophysics Data System (ADS)

Layered target experiments at 1.06 ?m have been performed in order to measure the mass-ablation rate ? and the ablation pressure Pa as a function of absorbed laser intensity Ia, laser wavelength ?L, and target atomic number Z in steady-state ablation dominated by nonlocalized inverse bremsstrahlung absorption. The results can be expressed as ?exp(kg/ sec cm2)?65 [Ia(W/cm2)/1013]5/9 ?-4/9L(?m)Z1/4 and Pa(Mbar)?2.5[Ia(W/ cm 2)/ 1013]7/9 ?-2/9L(?m)Z1/8. The measured results show good agreement with theory for nonlocalized absorption and with data of others.

Dahmani, Faiz

1992-06-01

101

Scalable Quantum Processor Technology Based on Laser Trapped Neutral Atoms.  

National Technical Information Service (NTIS)

This grant has supported an extensive effort aimed at using laser cooled Cs atoms trapped in optical lattices as qubits, and to demonstrate basic single- and two-qubit quantum gates. During the grant period we have made significant progress towards these ...

P. S. Jessen

2005-01-01

102

X-ray refractive index of laser-dressed atoms  

E-print Network

We investigated the complex index of refraction in the x-ray regime of atoms in laser light. The laser (intensity up to 10^13 W/cm^2, 800nm) modifies the atomic states but, by assumption, does not excite or ionize the atoms in their electronic ground state. Using quantum electrodynamics, we devise an ab initio theory to calculate the dynamic dipole polarizability and the photoabsorption cross section, which are subsequently used to determine the real and imaginary part, respectively, of the refractive index. The interaction with the laser is treated nonperturbatively; the x-ray interaction is described in terms of a one-photon process. We numerically solve the resolvents involved using a single-vector Lanczos algorithm. Finally, we formulate rate equations to copropagate a laser and an x-ray pulse through a gas cell. Our theory is applied to argon. We study the x-ray polarizability and absorption near the argon K edge over a large range of dressing-laser intensities. We find electromagnetically induced transp...

Buth, Christian

2008-01-01

103

Laser-focused nanofabrication: Beating of two atomic resonances  

NASA Astrophysics Data System (ADS)

We deposit a laser-collimated chromium beam onto a substrate through a laser standing-wave (SW) tuned above the atomic resonance at either of the two 52Cr transitions 7S3[right arrow]7P3o at 427.600 nm or 7S3[right arrow]7P4o at 425.553 nm. In both of these cases, the resulting pattern on the surface consists of nanolines with a period of that of the SW. We extend the range of periods accessible to laser-focused atom deposition by superimposing the structures grown at both these resonances. The resulting beating pattern exhibits a period of 44.46plus-or-minus0.04 mum as determined with a polarizing optical microscope. This structure provides a link between nanoscopic and macroscopic worlds and could potentially become a calibration standard for length metrology.

Jurdik, E.; Hohlfeld, J.; van Kempen, H.; Rasing, Th.; McClelland, J. J.

2002-06-01

104

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

E-print Network

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

Hart, Nathan Andrew

2012-10-19

105

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=(3.92.7)10-11 cm3/s, ?22,20=(2.60.7)10-11 cm3/s, and ?21,22=(3.91.9)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.

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

2012-08-01

106

Improved Sodium Lifetime and Hyperfine Structure Measurements Using Novel Precision Laser Spectroscopic Techniques with Laser Cooled\\/trapped Atoms  

Microsoft Academic Search

Laser cooling\\/trapping techniques can now produce cold atomic samples which offer new spectroscopic possibilities. This dissertation presents two atomic structure measurements which required development of precision laser spectroscopic techniques for use with laser-cooled atomic samples. This work also reports measurements on the first Na magneto -optic vapor cell trap and its corresponding cold ( ~40muK) atom velocity distribution. The first

Christopher Wallace Oates

1995-01-01

107

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

E-print Network

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

Dong, Haifeng; Tang, Xinbin

2012-01-01

108

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

E-print Network

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

Haifeng Dong; Hongbo Lin; Xinbin Tang

2012-03-05

109

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

E-print Network

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

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

2005-03-31

110

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

SciTech Connect

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

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

2009-11-30

111

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

112

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

113

The nuclear magnetic moment of ? by atomic beam laser spectroscopy  

Microsoft Academic Search

The magnetic dipole moment has been deduced for the 0954-3899\\/22\\/1\\/008\\/img2 nuclear ground state of the self-conjugate nucleus 0954-3899\\/22\\/1\\/008\\/img3 from the hyperfine splitting of the atomic 0954-3899\\/22\\/1\\/008\\/img4 ground state. The hyperfine structure of the 308.2 nm 0954-3899\\/22\\/1\\/008\\/img5 transition was measured by laser resonance fluorescence of an atomic beam. The tunable ultraviolet light was generated by frequency doubling using a lithium iodate

T. G. Cooper; J. Billowes; P. Campbell; M. R. Pearson

1996-01-01

114

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

115

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 28pT/?Hz may be improved further without sacrificing size or simplicity.

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

2007-07-01

116

Oscillator-free atomic clock using a multimode laser  

NASA Astrophysics Data System (ADS)

We developed an atomic clock using two modes from a single extended-cavity diode laser in multimode operation. The two modes are phase locked with reference to a dispersion signal from a coherent population trapping (CPT) resonance of R85b at 3.036 GHz. The design is in principle free from an oscillator and a modulator and it is a significant simplification over a conventional CPT-based atomic clock. Allan deviation of the beat frequency is 110-10 at 200 s integration time.

Yim, Sin Hyuk; Cho, D.

2010-05-01

117

Strong-field atomic ionization in elliptically polarized laser fields  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

118

Giant resonance and Rydberg series of laser excited chromium atoms  

SciTech Connect

Theoretical and experimental photoelectron spectra of ground state and laser excited Cr atoms in the region of the 3p-excitation are presented. The 3p{yields}4d,5d Rydberg excitations, which are very prominent in the 3d partial cross section of ground state Cr, and dramatically reduced by exciting the 4s electron into the 4p-shell. SPHF (spin polarized Hartree-Fock) calculations suggest that the well developed Rydberg series of ground state atoms are due to the delocalization of the 3d{down_arrow}, 4d{down_arrow} and 5d{down_arrow} wavefunctions, whereas, the corresponding wavefunctions of laser excited Cr do not undergo such an anticollapse.

Dohrmann, Th.; Arp, U.; Sonntag, B.; Wedowski, M.; Weisbarth, F.; Zimmermann, P.; Dolmatov, V. K. [II. Institut fuer Experimentalphysik, Universitaet Hamburg, Luruper Chaussee 149, D-22761 Hamburg (Germany); Institut fuer Strahlungs- und Kernphysik, TU Berlin, Hardenbergstrasse 36, D-10623 Berlin (Germany); S.V. Starodubtsev Physical-Technical Institute, G. Mavlyanova Str. 2, 700084 Tashkent (Uzbekistan)

1995-04-01

119

Four-level superradiant laser with full atomic cooperativity  

SciTech Connect

We investigate a four-level superradiant laser whose intensity is proportional to N{sup 2} and whose linewidth scales as 1/N{sup 2}. In the absence of spontaneous emissions, we derive the stationary solutions of the atomic full cooperativity, analyze their stabilities, and find the corresponding irreducible representation based on group U(4). We also investigate the spectra of the phase and amplitude fluctuations of the fields inside and outside the cavity and find that the amplitude fluctuations of the output fields cannot be squeezed in the low-frequency limit, which is completely different from the three-level superradiant laser system. Finally, we consider the stationary solutions corresponding to the partial cooperativity due to the symmetry breaking of U(4) induced by the atomic spontaneous emissions.

Yu Deshui [Department of Applied Physics, Graduate School of Engineering, University of Tokyo, Bunkyo-ku, Tokyo 113-8656 (Japan); Chen Jingbiao [Institute of Quantum Electronics and State Key Laboratory of Advanced Optical Communication System and Network, School of Electronics Engineering and Computer Science, Peking University, Beijing 100871 (China); State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai, 200062 (China)

2010-05-15

120

Vapour growth of II-VI single crystals doped by transition metals for mid-infrared lasers  

Microsoft Academic Search

A modified vapour phase contact-free method to grow homogeneous single crystals of II-VI compounds doped by transition metals is presented. Single crystals of ZnSe:Cr, ZnSe:Fe, ZnSe:Co, ZnSe:Ni, CdSe:Cr, ZnTe:Cr, ZnS:Fe and ZnS:Mn with doping level up to 1019 cm-3 have been grown. Efficient lasing at about 2.5 and 4 mum with ZnSe:Cr and ZnSe:Fe crystals respectively has been achieved. Dependence

V. A. Akimov; M. P. Frolov; Yu. V. Korostelin; V. I. Kozlovsky; A. I. Landman; Yu. P. Podmar'kov; A. A. Voronov

2006-01-01

121

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

122

Nuclear-driven flashlamp pumping of the atomic iodine laser  

SciTech Connect

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

Miley, G.H.

1992-03-01

123

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

124

A difference in using atomic layer deposition or physical vapour deposition TiN as electrode material in metal-insulator-metal and metal-insulator-silicon capacitors.  

PubMed

In this work, metal-insulator-metal (MIM) and metal-insulator-silicon (MIS) capacitors are studied using titanium nitride (TiN) as the electrode material. The effect of structural defects on the electrical properties on MIS and MIM capacitors is studied for various electrode configurations. In the MIM capacitors the bottom electrode is a patterned 100 nm TiN layer (called BE type 1), deposited via sputtering, while MIS capacitors have a flat bottom electrode (called BE type 2-silicon substrate). A high quality 50-100 nm thick SiO2 layer, made by inductively-coupled plasma CVD at 150 degrees C, is deposited as a dielectric on top of both types of bottom electrodes. BE type 1 (MIM) capacitors have a varying from low to high concentration of structural defects in the SiO2 layer. BE type 2 (MIS) capacitors have a low concentration of structural defects and are used as a reference. Two sets of each capacitor design are fabricated with the TiN top electrode deposited either via physical vapour deposition (PVD, i.e., sputtering) or atomic layer deposition (ALD). The MIM and MIS capacitors are electrically characterized in terms of the leakage current at an electric field of 0.1 MV/cm (I leak) and for different structural defect concentrations. It is shown that the structural defects only show up in the electrical characteristics of BE type 1 capacitors with an ALD TiN-based top electrode. This is due to the excellent step coverage of the ALD process. This work clearly demonstrates the sensitivity to process-induced structural defects, when ALD is used as a step in process integration of conductors on insulation materials. PMID:22097586

Groenland, A W; Wolters, R A M; Kovalgin, A Y; Schmitz, J

2011-09-01

125

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

E-print Network

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

126

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

E-print Network

Direct atomic flux measurement of electron-beam evaporated yttrium with a diode-laser-based atomic May 1997 A direct measurement of atomic flux in e-beam evaporated yttrium has been demonstrated with a diode-laser-based atomic absorption AA monitor at 668 nm. Atomic number density and velocity were

Fejer, Martin M.

127

Electron scattering by laser-excited barium atoms  

NASA Technical Reports Server (NTRS)

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

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

1978-01-01

128

Capture of laser-cooled atoms with a carbon nanotube  

NASA Astrophysics Data System (ADS)

We observe the capture and field ionization of individual atoms near the side-wall of a single, positively-charged, suspended carbon nanotube. The steep cylindrically-symmetric field gradient around the nanotube creates an attractive force that captures polarizable atoms, corresponding to a highly singular inverse-square potential. In this potential, atoms with angular momenta below a critical threshold value, determined by the charge on the nanotube, will be pulled towards the singularity at the origin of the potential-energy landscape. The strong fields near the nanotube will ionize the captured atoms, and these ions can be individually counted with a nearby ion detector operated in discrete pulse-counting mode. Extremely large cross-sections for ionization from a laser-cooled atomic beam are observed at modest voltages due to the nanotube's small radius and extended length. Efficient and sensitive neutral atom detectors can be based on the capture and field-ionization processes, as we have demonstrated. The effects of the field strength on both the atomic capture and the ionization process are clearly distinguished in the data. When atoms are captured, we expect that the capture cross-section will increase as a linear function of the voltage applied to the nanotube. We observe this behavior for charging voltages of 150--300 V, which demonstrates the proportionality between the capture cross-section and the strength of the electric field. The field affects the ionization process as well, and we report two pertinent observations: (1) the creation of ions is suppressed below 150 V, corresponding to the conditions where the field strength at the surface of the nanotube is no longer sufficient to rapidly ionize captured atoms; and (2) we observe prompt and delayed ionization events related to the locations at which these events occur, revealing that the strength of the field determines whether an ion generated very close to the surface will quickly escape from the attraction of its own image charge. Investigation of these effects reveals a rich variety of physical behaviors in the nanoscale regime.

Goodsell, Anne Laurel

129

Parametric studies on a short pulsed KrF pumped atomic iodine laser  

Microsoft Academic Search

This paper describes parametric studies performed on a short pulsed KrF excimer pumped atomic Iodine laser. Three different approaches were used to determine the gain in the laser cell. The first technique uses a tunable diode laser to directly measure the transient gain. The second method involves measuring the energy extracted from the laser for various outcoupling mirrors and applying

B. S. Hunt

1995-01-01

130

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

SciTech Connect

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

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

2009-06-30

131

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

2014-10-01

132

Atomic fountain of laser-cooled Yb atoms for precision measurements  

SciTech Connect

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

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

2010-10-15

133

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

Microsoft Academic Search

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

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

1991-01-01

134

J. Phys. B: Atom. Molec. Phys., Vol. 12, No. 20, 1979. Printed in Great Britain LETTER TO THE EDITOR  

E-print Network

the absorption spectrum of molecular iodine simultaneously with the atomic spectra;passing part of the laser. Using a single-mode dye laser to excite and a thermoionic diode to detect highly excited caesium vapour-'. The ability to scan the wavelength of a highly monochromatic cw dye laser allows selective excitation of long

Delande, Dominique

135

A review on laser diagnostics on atomization and evaporation of liquid fuel  

NASA Astrophysics Data System (ADS)

To evaluate the atomization and evaporation processes of liquid fuel, there are several laser diagnostics available in present. In this paper, the recent progress in laser diagnostics for atomization and evaporation will be introduced, as two categories: atomization and evaporation. The diagnostics for the former includes the primary breakup from liquid jet to ligaments or droplets and the secondary atomization from a bigger droplet to a smaller one, and the latter includes the droplet evaporation and the vapor distributions in a spray.

Zhang, Yuyin; Li, Shiyan; Lin, Baiyang; Liu, Yang; Wu, Jian; Xu, Bin

2014-08-01

136

Squeezed single-atom laser in a photonic crystal  

E-print Network

We study non-classical and spectral properties of a strongly driven single-atom laser engineered within a photonic crystal that facilitates a frequency-dependent reservoir. In these studies, we apply a dressed atom model approach to derive the master equation of the system and study the properties of the dressed laser under the frequency dependent transition rates. By going beyond the secular approximation in the dressed-atom cavity field interaction, we find that if, in addition, the non-secular terms are included into the dynamics of the system, then non-linear processes can occur that lead to interesting new aspects of cavity field behavior. We calculate variances of the quadrature phase amplitudes and the incoherent part of the spectrum of the cavity field and show that they differ qualitatively from those observed under the secular approximation. In particular, it is found that the non-linear processes lead to squeezing of the fluctuations of the cavity field below the quantum shot noise limit. The squeezing depends on the relative population of the dressed states of the system and is found only if there is no population inversion between the dressed states. Furthermore, we find a linewidth narrowing below the quantum limit in the spectrum of the cavity field that is achieved only when the secular approximation is not made. An interpretation of the linewidth narrowing is provided in terms of two phase dependent noise (squeezing) spectra that make up the incoherent spectrum. We establish that the linewidth narrowing is due squeezing of the fluctuations in one quadrature phase components of the cavity field.

Rong Tan; Gao-xiang Li; Zbigniew Ficek

2008-07-21

137

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

NASA Astrophysics Data System (ADS)

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

Lehmann, Bernhard E.

2001-08-01

138

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

139

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

E-print Network

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

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

2013-01-01

140

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

E-print Network

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

Stroud Jr., Carlos R.

141

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

142

IV INTERNATIONAL CONFERENCE ON ATOM AND MOLECULAR PULSED LASERS (AMPL'99): IV International Conference on Atomic and Molecular Pulsed Gas Lasers (AMPL'99)  

NASA Astrophysics Data System (ADS)

A brief review of the most interesting papers presented at the IV International Conference on Atomic and Molecular Pulsed Gas Lasers (AMPL'99), which was held in Tomsk, September 13-17, 1999, is provided.

Evtushenko, Gennadii S.; Kopylova, T. N.; Soldatov, A. N.; Tarasenko, Viktor F.; Yakovlenko, Sergei I.; Yancharina, A. M.

2000-06-01

143

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

Microsoft Academic Search

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

V??t Jirsek; Otomar palek; Jarmila Kodymov; Miroslav ?ensk

2001-01-01

144

Frequency-Stabilized Diode Laser with the Zeeman Shift in an Atomic Vapor  

Microsoft Academic Search

We demonstrate a robust method of stabilizing a diode laser frequency to an atomic transition. This technique employs the Zeeman shift to generate an antisymmetric signal about a Doppler-broadened atomic resonance, and therefore offers a large recapture range as well as high stability. The frequency of a 780-nm diode laser, stabilized to such a signal in Rb, drifted less than

Kristan L. Corwin; Zheng-Tian Lu; Carter F. Hand; Ryan J. Epstein; Carl E. Wieman

1998-01-01

145

Atoms and Molecules in Intense Laser Fields: Gauge Invariance of Theory and Models  

E-print Network

Atoms and Molecules in Intense Laser Fields: Gauge Invariance of Theory and Models A. D. Bandrauk1´eal, Canada, H3T 1J4 Abstract. Gauge invariance was discovered in the development of classical transformations is presented for atoms and molecules in interaction with intense short laser pulses, spanning

Lorin, Emmanuel

146

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

147

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

E-print Network

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

Qi-Ren Zhang

2006-08-06

148

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

E-print Network

of the electric discharge iodine laser continues, the role of oxygen atoms downstream of the discharge region temperature. Keywords: chemical oxygen-iodine laser, COIL, ElectriCOIL, RF excitation of oxygen, singlet-delta oxygen, DOIL 1.0 INTRODUCTION The classic chemical oxygen-iodine laser (COIL) system1 operates on the I(2

Carroll, David L.

149

Gain measurements on a short pulsed KrF pumped atomic iodine laser  

Microsoft Academic Search

This paper describes gain measurements on a short pulsed KrF excimer pumped atomic iodine laser. Three different approaches were used to determine the gain. The first technique uses a tunable diode laser to directly measure the transient gain. The second method involves measuring the energy extracted from the laser for various outcoupling mirrors and applying the threshold gain condition to

B. Scott Hunt; Jack McIver; Gordon D. Hager

1993-01-01

150

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

E-print Network

Laser-excited atomic fluorescence spectrometry in a graphite furnace with an optical parametric oscillator laser for sequential multi-element determination of cadmium, cobalt, lead, manganese and thallium, for the ® rst time, that solid-state lasers required for analysis (ml or mg) and the technique has direct based

Michel, Robert G.

151

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

152

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

153

Two-mode single-atom laser as a source of entangled light  

SciTech Connect

A two-mode single-atom laser is considered, with the aim of generating entanglement in macroscopic light. Two transitions in the four-level gain medium atom independently interact with the two cavity modes, while two other transitions are driven by control laser fields. Atomic relaxation as well as cavity losses are taken into account. We show that this system is a source of macroscopic entangled light over a wide range of control parameters and initial states of the cavity field.

Kiffner, M.; Evers, J.; Keitel, C. H. [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, 69117 Heidelberg (Germany); Zubairy, M. S. [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, 69117 Heidelberg (Germany); Institute for Quantum Studies and Department of Physics, Texas A and M University, College Station, Texas 77843 (United States); Texas A and M University at Qatar, Education City, P.O. Box 23874, Doha (Qatar)

2007-03-15

154

Chemical oxygen-iodine laser with a new method of atomic iodine generation  

Microsoft Academic Search

A study of recently proposed chemical method of atomic iodine production in the Chemical Oxygen-Iodine Laser (COIL) was performed. The process using gaseous reactants is based on the fast reaction of hydrogen iodide with chemically produced atomic chlorine. In the absence of singlet oxygen, the high yield of atomic iodine was attained (80 to 100 %). In the flow of

Otomar Spalek; Miroslav Censky; Vt Jirsek; Jarmila Kodymov; Ivo Jakubec; Gordon D. Hager

2003-01-01

155

New atomic and molecular laser transitions based on photodissociation of CdI2  

Microsoft Academic Search

Blue and red molecular laser action centered at 475 and 656 nm has been obtained in cadmium iodide (CdI) by dissociative pumping of CdI2 with a powerful ArF excimer laser. The laser emission corresponds to B(2 Sigma +)-X(2 Sigma) transitions. In addition, laser action at two Cd atomic lines at 508.6 nm and 643.8 nm corresponding to the transitions 6s

S. G. Dinev; H.-U. Daniel; H. Walther

1982-01-01

156

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

157

Electron Scattering From Laser Excited Ba and Yb Atoms  

NASA Astrophysics Data System (ADS)

Inelastic and elastic electron scattering out of the excited states of Ba and Yb has been studied at low collision energies. We present measurements (at 10 eV and 20 eV collision energies) of differential cross sections and orientation parameters for elastic scattering out of the 6 ^1P1 and 5 D levels of Ba and for inelastic scattering out of the 6 ^3P1 level of Yb to higher lying ^3D and ^3S levels. Collision studies are carried out using a momentum selected incident electron beam with momentum resolved scattered electron detection and excited atomic target populations generated by resonant laser radiation. To a good approximation, Ba and Yb are heavy two-electron systems comprising filled, approximately inert cores ([Xe] for Ba and [Xe]4f^14 for Yb) with two-electron 6s^2 valence configurations (in the ground state). Theoretical determinations of low-energy electron scattering parameters for these atoms, based on convergent close coupling and first order perturbative formalisms, have met with success in many cases. Such calculations have been applied to inelastic scattering from 6S, 5D and 6P target states in Ba and the 6S ground state in Yb (refs 1,2). Extension of previous experimental investigations to the new scattering processes described in this work will further test the efficacy of available theoretical methods. 1. I. Bray et al. J.Phys.B:At.Mol.Opt.Phys. 35 R117 (2002) 2. B Predojevic et al. J. Phys. B: At. Mol. Opt. Phys. 38 3489 (2005)

Zetner, Peter; Hein, Jeff

2007-06-01

158

Laser-Induced Continuum Structure and Third Harmonic Generation in - and Two-Valence Atoms.  

NASA Astrophysics Data System (ADS)

A model for calculating third harmonic generation (THG) in a near-resonantly coupled 4-level atomic system in the presence of laser-induced continuum structure (LICS) is formulated in terms of the time dependent density matrix elements which can be obtained by solving the time dependent density matrix equations for the atomic system interacting with laser pulses. The theory is applied to a single-valence -electron atom, sodium, as well as to a two-valence-electron atom, calcium. Analysis of the existing experimental data in sodium is given applying our theoretical model. It is found that the spatio-temporal overlap of the two laser pulses is a very sensitive factor for the experimental observation. Calculations of atomic parameters for a two -valence-electron atom (calcium) using multiconfiguration Hartree-Fock method with finite B spline basis is also presented. (Copies available exclusively from Micrographics Department, Doheny Library, USC, Los Angeles, CA 90089 -0182.).

Zhang, Jian

1991-05-01

159

Construction and Characterization of External Cavity Diode Lasers for Atomic Physics  

PubMed Central

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

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

2014-01-01

160

Resonance-enhanced multiphoton ionization spectroscopy of laser-ablated copper atoms  

NASA Astrophysics Data System (ADS)

Resonance-enhanced multiphoton ionization (REMPI) spectra of laser-ablated copper atoms entrained in a supersonic free jet expansion are reported. Depending on the ionization scheme employed, and the conditions under which the copper atoms are produced, very different spectra are produced, which are discussed. In some circumstances, high proportions of metastable atoms survive the ablation and expansion process and are clearly seen in the spectra. The spectroscopic transitions for the observed lines are identified, and it is noted that some caution is merited in the assumption that only ground state copper atoms are present following laser ablation.

Andrejeva, Anna; Harris, Joe P.; Wright, Timothy G.

2014-10-01

161

Survival window for atomic tunneling ionization with elliptically polarized laser fields  

NASA Astrophysics Data System (ADS)

We find a fraction of atoms remain unionized after the laser pulse when the tunneled electrons are released in a certain window of initial field phase and transverse velocity. The survival window shifts with laser polarization ellipticity and its width varies with respect to laser intensity and atomic ionization potential. Neutral atom yield can be calculated by summing up tunneling probabilities in the window. Our theory can quantitatively reproduce the distribution of the survival yields vs laser ellipticity observed for helium in experiment. For other atom species with smaller ionization potential such as magnesium, our theory predicts a wider distribution than the strong-field approximation model while closer to the three-dimensional semiclassical electron ensemble simulations, indicating the important role of the Coulomb effects.

Huang, Kai-yun; Xia, Qin-zhi; Fu, Li-Bin

2013-03-01

162

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

E-print Network

Ramond Ball Aero. ·$$ NIST, DARPA-MTO, ONR-CU-MURI, NASA-microgravity physics, LANL Mercury Standard Jim laser and length metrology Richard Fox #12;Types of Clocks Ruler Clock Decay Stable Oscillator Atomic

Van Stryland, Eric

163

Theory of x-ray absorption by laser-dressed atoms  

Microsoft Academic Search

An ab initio theory is devised for the x-ray photoabsorption cross section of atoms in the field of a moderately intense optical laser (800 nm, 10 W\\/cm). The laser dresses the core-excited atomic states, which introduces a dependence of the cross section on the angle between the polarization vectors of the two linearly polarized radiation sources. We use the Hartree-Fock-Slater

Christian Buth; Robin Santra

2007-01-01

164

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

165

Microstructural Evolution During Laser Resolidification of Fe-25 Atom Percent Ge Alloy  

E-print Network

selection is discussed using competitive growth kinetics. I. INTRODUCTION TECHNIQUES of rapidly melting the process of laser resolidification. Third, the inti- mate contact of the surface-melted layerMicrostructural Evolution During Laser Resolidification of Fe-25 Atom Percent Ge Alloy KRISHANU

Srivastava, Kumar Vaibhav

166

Diode-laser atomic-absorption spectrometry by the double-beamdouble-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

167

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

Microsoft Academic Search

A new method for the chemical generation of atomic iodine intended for use in a chemical oxygeniodine laser (COIL) was investigated experimentally. The method is based on the fast reaction of hydrogen iodide with chemically produced chlorine atoms. Effects of the initial ratio of reactants and their mixing in a flow of nitrogen were investigated experimentally and interpreted by means

Otomar palek; V??t Jirsek; Miroslav ?ensk; Jarmila Kodymov; Ivo Jakubec; Gordon D. Hager

2002-01-01

168

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

E-print Network

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

Bajcsy, M.

169

Scattering of light and acoustic disturbances in the atomic iodine laser  

SciTech Connect

An analysis is presented of the medium refractive index gradients and associated acoustic disturbances (ripples) observed in photolytically pumped atomic iodine laser oscillators. Coupled equations representing acoustic waves with a heating source, atomic iodine laser pumping and chemistry and the laser field are derived and used to evaluate the time-dependent growth rate of the instabilities in the oscillator. The theoretical, linearized model is found to be capable of accounting for growing instabilities, and the predicted scale size of the disturbance is in agreement with observations.

Riley, M.E.

1983-07-01

170

Velocity selection of ultra-cold atoms with Fabry-Perot laser devices: improvements and limits  

E-print Network

We discuss a method to select the velocities of ultra-cold atoms with a modified Fabry-Perot type of device made of two effective barriers and a well created, respectively, by blue and red detuned lasers. The laser parameters may be used to select the peak and width of the transmitted velocity window. In particular, lowering the central well provides a peak arbitrarily close to zero velocity having a minimum but finite width. The low-energy atomic scattering off this laser device is parameterized and approximate formulae are found to describe and explain its behaviour.

A. Ruschhaupt; F. Delgado; J. G. Muga

2005-02-28

171

Velocity distribution measurements in atomic beams generated using laser induced back-ablation  

E-print Network

We present measurements of the velocity distribution of calcium atoms in an atomic beam generated using a dual-stage laser back-ablation apparatus. Distributions are measured using a velocity selective Doppler time-of-flight technique. They are Boltzmann-like with rms velocities corresponding to temperatures above the melting point for calcium. Contrary to a recent report in the literature, this method does not generate a sub-thermal atomic beam.

Denning, A; Lee, S; Ammonson, M; Bergeson, S D

2008-01-01

172

Improving Raman velocimetry of laser-cooled cesium atoms by spin-polarization  

E-print Network

We study the peformances of Raman velocimetry applied to laser-cooled, spin-polarized, cesium atoms. Atoms are optically pumped into the F=4, m=0 ground-state Zeeman sublevel, which is insensitive to magnetic perturbations. High resolution Raman stimulated spectroscopy is shown to produce Fourier-limited lines, allowing, in realistic experimental conditions, atomic velocity selection to one-fiftieth of a recoil velocity.

Julien Chab; Hans Lignier; Pascal Szriftgiser; Jean Claude Garreau

2006-03-23

173

Strongly correlated growth of Rydberg aggregates in a vapour cell  

E-print Network

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

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

2014-01-01

174

Strongly correlated growth of Rydberg aggregates in a vapour cell  

E-print Network

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

A. Urvoy; F. Ripka; I. Lesanovsky; D. Booth; J. P. Shaffer; T. Pfau; R. Lw

2014-07-31

175

Lasers as a Bridge between Atomic and Nuclear Physics  

E-print Network

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

Sergei G. Matinyan

1997-06-02

176

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

177

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

E-print Network

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

Stroud Jr., Carlos R.

178

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

E-print Network

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

Loss, Daniel

179

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

NASA Astrophysics Data System (ADS)

We theoretically investigated the improvement on the production rate of the decelerated bromine (Br) atoms near zero speed by photodissociating laser aligned Br2 precursors. Adiabatic alignment of Br2 precursors exposed to long laser pulses with duration on the order of nanoseconds was investigated by solving the time-dependent Schrdinger equation. The dynamical fragmentation of adiabatically aligned Br2 precursors was simulated and velocity distribution of the Br atoms produced was analyzed. Our study shows that the larger the degree of the precursor alignment, ?cos2 ??, the higher the production rate of the decelerated Br atoms near zero speed. For Br2 molecules with an initial rotational temperature of 1 K, a ?cos2 ?? value of 0.88 can result in an improvement factor of over 20 on the production rate of the decelerated Br atoms near zero speed, requiring a laser intensity of only 1 1012 W/cm2 for alignment.

Deng, L. Z.; Yin, J. P.

2014-10-01

180

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

PubMed

We theoretically investigated the improvement on the production rate of the decelerated bromine (Br) atoms near zero speed by photodissociating laser aligned Br2 precursors. Adiabatic alignment of Br2 precursors exposed to long laser pulses with duration on the order of nanoseconds was investigated by solving the time-dependent Schrdinger equation. The dynamical fragmentation of adiabatically aligned Br2 precursors was simulated and velocity distribution of the Br atoms produced was analyzed. Our study shows that the larger the degree of the precursor alignment, ?cos(2)???, the higher the production rate of the decelerated Br atoms near zero speed. For Br2 molecules with an initial rotational temperature of ?1 K, a ?cos(2)??? value of ?0.88 can result in an improvement factor of over ?20 on the production rate of the decelerated Br atoms near zero speed, requiring a laser intensity of only ?1 10(12) W/cm(2) for alignment. PMID:25362306

Deng, L Z; Yin, J P

2014-10-28

181

Adiabatic quantum search scheme with atoms in a cavity driven by lasers.  

PubMed

We propose an implementation of the quantum search algorithm of a marked item in an unsorted list of N items by adiabatic passage in a cavity-laser-atom system. We use an ensemble of N identical three-level atoms trapped in a single-mode cavity and driven by two lasers. In each atom, the same level represents a database entry. One of the atoms is marked by having an energy gap between its two ground states. Appropriate time delays between the two laser pulses allow one to populate the marked state starting from an initial entangled state within a decoherence-free adiabatic subspace. The time to achieve such a process is shown to exhibit the square root N Grover speedup. PMID:17995312

Daems, D; Gurin, S

2007-10-26

182

Modern Laser-Atomic Physics and Stable Oscillators for Real World Applications  

NASA Astrophysics Data System (ADS)

This talk will consider how, when and where modern laser/atomic physics might play a significant role in real world applications. Advances in laser technology, control systems and precision laser spectroscopy are enabling many new capabilities for measurements and instrumentation, and can improve the performance of atomic clocks, magnetometers and inertial sensors by several orders of magnitude. Initial ideas of using lasers to enhance the performance of atom-based instruments dates back to the 1960s, and those early predictions were mostly well founded and have now been demonstrated, to varying degrees, in research laboratories and environments around the world. However, 40 years later, these promises have yet to be realized in industrial, governmental or commercial applications. As an example, the technology and performance (in terms of accuracy and stability) of commercially available atomic clocks has been rather stagnate since the 1970s, whereas those in research laboratories have continued to improve so that their performance is roughly 1000x better than the commercial frequency standards. We can, and should, ask why there is such a large gap between what is possible and what is commercially available? Reasons for the large disconnect in performance are multifold, and will be discussed. Atom-Optic Inertial sensors (gyros, accelerometers) are a more recent development and application that uses the same methods of laser atomic physics. Efforts are now underway to bring these atom interferometer inertial sensors to real world applications and commercial availability. Extremely stable microwave sources are another spinoff of precision laser technology and spectroscopy. It now appears that lasers may soon find their way into high performance commercial clocks and magnetometers and other instruments. However, our community has been making such promises and predictions for decades now...

Hollberg, Leo

2010-03-01

183

Glow Discharge Source Atomization for the Laser-Excited Atomic Fluorescence Spectrometric Studies of Indium.  

National Technical Information Service (NTIS)

A demountable glow discharge source has been used for the atomization of the analyte solutions deposited on graphite and copper rod cathodes. Indium atoms are sputtered-atomized from the cathode surface and are excited by a pulsed, frequency-doubled dye l...

B. M. Patel, J. D. Winefordner

1986-01-01

184

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

185

Toward an atom laser: Cold atoms in a long, high-gradient magnetic guide  

NASA Astrophysics Data System (ADS)

The propagation of an atomic beam through a 1.7 in long magnetic guide with magnetic field gradient of up to 2.7 kGauss-cm-1 has been demonstrated. The guide is side-loaded with an atomic beam from a Pyramidal MOT Low-velocity Intense Source. The atomic beam observed at the end of the guide has a flux of 3x107 atoms-s-1 with a velocity of 1.2mn/s, a transverse temperature of 420+/-40 muK and a longitudinal temperature of 1 mK. The guided atomic beam was mode-filtered by selective removal of high-energy atoms using radio-frequency coupling to magnetically un-trapped states. We found that the phase-space density of the atomic beam was very low for evaporative cooling to be functional. An imaging technique was developed to characterize the guided atomic flow in the presence of a high magnetic field gradient. This technique utilizes the open-channel transition to obtain nearly constant photon yield per atom independent of the location of the atone in the guide, providing a mapping of the fluorescence images to the atomic-density profiles. This technique was theoretically studied using Quantum Monte-Carlo Simulations and validated. A Zeeman slower was constructed and characterized to be used as the primary source of atoms to the magnetic guide. The Zeeman slower output atomic beam has a flux of 3x1011 atoms-s-1 at a velocity of 40 m/s. We have designed a new injection scheme to transfer atoms from the Zeeman slower to the magnetic guide efficiently. The details of a new method to evaporatively cool atoms in the magnetic guide using surface adsorption are described. Finally, a new guide geometry based on a spiral structure is discussed.

Mhaskar, Rahul Ramdas

186

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

NASA Astrophysics Data System (ADS)

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

Murray, Andrew

2012-06-01

187

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

188

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

189

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

190

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

NASA Astrophysics Data System (ADS)

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

Kaprlov-nsk, Petra Ruth; Moiseyev, Nimrod

2014-07-01

191

Atomic and molecular processes generated by linearly polarized few-cycle laser pulses  

NASA Astrophysics Data System (ADS)

S-matrix theory is used to analyze different atomic and molecular processes in a linearly polarized few-cycle laser field. The energy spectra of high-order above-threshold ionization (HATI) are presented. Electron-atom potential scattering assisted by a few-cycle laser pulse is also analyzed. It is shown that the plateau structures in the energy spectra of the electron-atom potential scattering are dependent on the carrier-envelope phase (CEP) of the laser pulse, so that the cutoff positions of the plateaus can be controlled by changing the CEP. Regarding our analysis of the molecular HATI process, the angle-resolved spectra, obtained by different theoretical approaches, are also presented.

Busuladi?, M.; ?erki?, A.; Odak, S.; Gazibegovi?-Busuladi?, A.; Hasovi?, E.; Habibovi?, D.; Miloevi?, D. B.

2014-09-01

192

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

193

Quantum theory of a laser with injected atomic coherence: Quantum noise quenching via nonlinear processes  

SciTech Connect

A quantum theory of a two-level single-mode laser with injected atomiccoherence is developed by generalizing the Scully-Lamb laser theory to a formappropriate for the analysis of a coherently pumped laser. We assume that theactive atoms are prepared initially in a coherent superposition of the upperand lower levels, and we derive the master equation for the field densityoperator by treating the interaction of the laser field with many active atomssimultaneously. It is shown that the photon-number distribution can be exactlyPoissonian. The laser operation is analyzed in terms of the Fokker-Planckequation for the laser field. Both the intensity and phase diffusioncoefficients are phase sensitive and, for stable laser operation, become muchsmaller than those of an ordinary laser. Consequently, the injected atomiccoherence reduces both the photon-number noise and phase noise simultaneously.The intensity diffusion coefficient can vanish exactly, and at the same timethe phase diffusion coefficient can become very small. This leads tospontaneous-emission noise quenching in the photon-number distribution, and thelaser field can become very close to a coherent state. A scheme to generate theproper form of the initial atomic coherence necessary for the quantum noisequenching is proposed and analyzed.

Lu, N.; Bergou, J. A.

1989-07-01

194

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

NASA Astrophysics Data System (ADS)

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

Buica, Gabriela

2014-10-01

195

Long operating time CW atomic iodine probe laser at 1. 315. mu. m  

Microsoft Academic Search

A photolytically pumped longitudinal flow CW atomic iodine laser at 1.315 ..mu..m with virtually an unlimited operating time and easy operation is reported. Several weeks of continual operation is easily attainable. The prolonged lasing is achieved by employing a passive closed cycle flow system of the CF-I laser fuel. A high pressure dc Hg arc lamp is used for the

L. A. Schlie; R. D. Rathge

1984-01-01

196

Z-pinch photo-pumped pulsed atomic iodine laser. Final report Oct 81-Sep 82  

SciTech Connect

A pulsed atomic iodine laser (CF3I) was designed and constructed using a coaxial xenon flash lamp as a pump source. The flash lamp was operated at low pressure to obtain pulse compression via xenon self-pinch. Electrical and optical diagnostics were performed for various xenon and CF3I pressures. Calorimeter data and burn patterns were obtained for the laser. Time-resolved spectroscopic data were taken throughout the CF3I pump band.

Stone, D.H.; Saunders, D.P.; Clark, M.C.

1984-03-01

197

Phase-locked laser system for use in atomic coherence experiments  

Microsoft Academic Search

We describe a phase-coherent laser system designed for use in experiments involving coherently prepared atomic media. We implement a simple technique based on a sample-and-hold circuit together with a reset of the integrating electronics that makes it possible to scan continuously the relative frequency between the lasers of over tens of gigahertz while keeping them phase locked. The system consists

Alberto M. Marino; C. R. Stroud

2008-01-01

198

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

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

199

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

200

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

201

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

202

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

203

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

NASA Astrophysics Data System (ADS)

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

Ltstedt, Erik; Midorikawa, Katsumi

2014-10-01

204

Bose-Einstein condensation transition studies for atoms confined in Laguerre-Gaussian laser modes  

E-print Network

Multiply-connected traps for cold, neutral atoms fix vortex cores of quantum gases. Laguerre-Gaussian laser modes are ideal for such traps due to their phase stability. We report theoretical calculations of the Bose-Einstein condensation transition properties and thermal characteristics of neutral atoms trapped in multiply connected geometries formed by Laguerre-Gaussian LG{p}{l} beams. Specifically, we consider atoms confined to the anti-node of a LG{0}{1} laser mode detuned to the red of an atomic resonance frequency, and those confined in the node of a blue-detuned LG{1}{1} beam. We compare the results of using the full potential to those approximating the potential minimum with a simple harmonic oscillator potential. We find that deviations between calculations of the full potential and the simple harmonic oscillator can be up to 3%-8% for trap parameters consistent with typical experiments.

Akin, T G; Dribus, Ben; Marzuola, Jeremy; Johnson, Lise; Alexander, Jason; Abraham, E R I

2011-01-01

205

Theory of x-ray absorption by laser-dressed atoms.  

SciTech Connect

An ab initio theory is devised for the x-ray photoabsorption cross section of atoms in the field of a moderately intense optical laser (800 nm, 10{sup 13} W/cm{sup 2}). The laser dresses the core-excited atomic states, which introduces a dependence of the cross section on the angle between the polarization vectors of the two linearly polarized radiation sources. We use the Hartree-Fock-Slater approximation to describe the atomic many-particle problem in conjunction with a nonrelativistic quantum-electrodynamic approach to treat the photon-electron interaction. The continuum wave functions of ejected electrons are treated with a complex absorbing potential that is derived from smooth exterior complex scaling. The solution to the two-color (x-ray plus laser) problem is discussed in terms of a direct diagonalization of the complex symmetric matrix representation of the Hamiltonian. Alternative treatments with time-independent and time-dependent non-Hermitian perturbation theories are presented that exploit the weak interaction strength between x rays and atoms. We apply the theory to study the photoabsorption cross section of krypton atoms near the K edge. A pronounced modification of the cross section is found in the presence of the optical laser.

Buth, C.; Santra, R.; Chemistry

2007-03-23

206

Theory of x-ray absorption by laser-dressed atoms  

SciTech Connect

An ab initio theory is devised for the x-ray photoabsorption cross section of atoms in the field of a moderately intense optical laser (800 nm, 10{sup 13} W/cm{sup 2}). The laser dresses the core-excited atomic states, which introduces a dependence of the cross section on the angle between the polarization vectors of the two linearly polarized radiation sources. We use the Hartree-Fock-Slater approximation to describe the atomic many-particle problem in conjunction with a nonrelativistic quantum-electrodynamic approach to treat the photon-electron interaction. The continuum wave functions of ejected electrons are treated with a complex absorbing potential that is derived from smooth exterior complex scaling. The solution to the two-color (x-ray plus laser) problem is discussed in terms of a direct diagonalization of the complex symmetric matrix representation of the Hamiltonian. Alternative treatments with time-independent and time-dependent non-Hermitian perturbation theories are presented that exploit the weak interaction strength between x rays and atoms. We apply the theory to study the photoabsorption cross section of krypton atoms near the K edge. A pronounced modification of the cross section is found in the presence of the optical laser.

Buth, Christian; Santra, Robin [Argonne National Laboratory, Argonne, Illinois 60439 (United States)

2007-03-15

207

Atomic processes in plasmas under ultra-intense laser irradiation  

SciTech Connect

Lasers delivering subpicosecond pulses with energies of a fraction of a Joule have made it possible to generate irradiance levels approaching 10{sup 20} W/cm{sup 2}. We presently operate two such systems, a KrF based excimer laser capable of producing a few 10{sup 17} W/cm{sup 2} at 248 nm with a repetition rate of 3--5 Hz and a XeCl based excimer laser capable of producing mid 10{sup 19} W/cm{sup 2} at 308 nm and 1 Hz. We will discuss some experimental results and the theory and modeling of the interaction of such intense laser pulses with aluminum. Because of a small ASE prepulse the high intensity interaction is not at the solid surface but rather at the n{sub e} = 2 {times} 10{sup 22} cm{sup {minus}3} critical density of the blowoff plasma generated by the ASE. The transient behavior of the plasma following the energy deposition by the intense subpicosecond pulse can be viewed as the energy-impulse response of the plasma. Experimental results and modeling of the x-ray emission from this plasma will be presented. 15 refs., 8 figs.

Schappert, G.T.; Casperson, D.E.; Cobble, J.A.; Comly, J.C.; Jones, L.A.; Kyrala, G.A.; LaGattuta, K.J.; Lee, P.H.Y.; Olson, G.L.; Taylor, A.J.

1989-11-01

208

6, 82418284, 2006 Water vapour  

E-print Network

ACPD 6, 8241­8284, 2006 Water vapour modelling in the tropical UTLS V. Mar´ecal et al. Title Page Chemistry and Physics Discussions Mesoscale modelling of water vapour in the tropical UTLS: two case studies Correspondence to: V. Mar´ecal (virginie.marecal@cnrs-orleans.fr) 8241 #12;ACPD 6, 8241­8284, 2006 Water vapour

209

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

E-print Network

1 Laser safety information for the Atomic, Molecular and Optical (AMO) Physics Labs at Lehigh University modified from the laser safety program developed by the office of Environmental Health and Safety using the following reference materials: I. American National Standards for Safe Use of Lasers - ANSI Z

Huennekens, John

210

TRINAT: measuring ?-decay correlations with laser-trapped atoms  

NASA Astrophysics Data System (ADS)

TRIUMF's neutral atom trap for ? decay (TRINAT) has been used to measure the most accurate ?- ? correlation. Plans include improving that measurement, and also carrying out a full program of spin-polarized ? decay correlation measurements complementary to the decay of the neutron

Behr, J. A.; Gorelov, A.; Jackson, K. P.; Pearson, M. R.; Anholm, M.; Kong, T.; Behling, R. S.; Fenker, B.; Melconian, D.; Ashery, D.; Gwinner, G.

2014-01-01

211

Photoionization by an ultraintense laser field: Response of atomic xenon  

SciTech Connect

We present energy- and angle-resolved photoionization from Xe in an ultrastrong laser field at 10{sup 19} W/cm{sup 2}. The observed yields are consistent with the tunneling ionization of Xe{sup 9+} to Xe{sup 24+}. However, energy and angle-resolved photoelectron spectra show differences for electrons whose final energies are above or below 0.5 MeV, which is approximately the ponderomotive energy at these intensities. Above 0.5 MeV, the observed photoelectron cutoff energy (between 1 and 1.35 MeV), photoelectron energy spectra, and the angle-resolved photoelectron azimuthal distributions agree with a model using tunneling ionization, multiple charge states, a classical relativistic continuum, and nonparaxial three-dimensional (3D) focused laser field. Below 0.5 MeV the yields and angular distributions observed indicate dynamics not included within a classical, single electron model of the interaction.

DiChiara, A. D.; Ghebregziabher, I.; Waesche, J. M.; Stanev, T.; Ekanayake, N.; Barclay, L. R.; Wells, S. J.; Watts, A.; Videtto, M.; Mancuso, C. A.; Walker, B. C. [Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716 (United States)

2010-04-15

212

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

E-print Network

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

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

2008-01-01

213

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

SciTech Connect

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

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

2013-01-01

214

Theoretical analysis of the performance of an atomic iodine laser amplifier chain  

Microsoft Academic Search

A numerical solution to the Maxwell-Bloch equations describing the pulse evolution in an amplifying or absorbing medium is used to analyze the performance of an atomic iodine laser amplifier chain with output powers close to 2 TW. Pulse compression occurring as a result of saturation, and related aspects such as damage to components, self-focusing, correlations between input and output pulse

T. Uchiyama; K. J. Witte

1982-01-01

215

Experimental and theoretical investigation of a coaxial pumped photolytic atomic bromine laser  

Microsoft Academic Search

Results of parametric studies on a high efficiency, 2.7 micrometers atomic bromine laser, produced by photolyzing IBr with 532 nm radiation, are presented. Concurrently, the results of a rate equation computer model show excellent agreement with experimental measurements. Bibtex entry for this abstract Preferred format for this abstract (see Preferences) Find Similar Abstracts: Use: Authors Title Abstract Text Return: Query

B. D. Rafferty; B. T. Anderson; J. Glassman; Harold C. Miller; A. I. Lampson; Gordon D. Hager

1997-01-01

216

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

217

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 Schrdinger equation (TDSE), the PerelomovPopovTerent'ev (PPT) theory, and the AmmosovDeloneKrainov (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

218

Velocity selective bipolarization spectroscopy for laser cooling of metastable krypton atoms  

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

219

Identification and Analysis of Atomic and Molecular Superposition Spectra Following Laser-Induced Optical Breakdown  

NASA Astrophysics Data System (ADS)

Molecular recombination and excitation of atoms following laser-induced optical breakdown provide means for simultaneous detection of atomic and molecular species. Atomic emission spectra may be analyzed to infer electron number and temperature. Careful analysis of select atomic spectra may reveal superposed diatomic molecular spectra. Nonlinear fitting of synthetic molecular spectra, calculated via diatomic quantum theory, provides tools for identification, temperature measurement, and further analyses of the diatomic molecules present. This presentation investigates the presence of C2 molecular Swan bands in Balmer Series atomic hydrogen spectra. Combustion plumes are also studied, including comparisons of temperatures obtained using a two-color pyrometer and from data reduction analysis of measured spectroscopic AlO data.

Woods, Alexander C.; Parigger, Christian G.

2011-10-01

220

Mechanical effect of retroreflected frequency-chirped laser pulses on two-level atoms  

SciTech Connect

We discuss the mechanical momentum transfer to two-level atoms by a pair of short, counterpropagating, frequency-chirped laser pulses, which partially overlap each other in the atomic medium. We show that such a pulse pair can induce a much greater change of momentum than pulses that do not overlap (interact separately with the atoms). The dispersive effect on the atomic velocity distribution is shown to be much smaller for the case of overlapping pulses. Furthermore, there are regimes where the method is not sensitive to the exact values of the pulse parameters or the initial velocity distribution. The interaction can be repeated for a cumulative effect, so a sequence of such pulse pairs can be used very effectively to manipulate the mechanical motion of atoms.

Demeter, G.; Djotyan, G. P.; Soerlei, Zs.; Bakos, J. S. [Institute for Particle and Nuclear Physics of the Hungarian Academy of Sciences, Konkoly-Thege Miklos ut 29-33, H-1121 Budapest (Hungary)

2006-07-15

221

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

NASA Technical Reports Server (NTRS)

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

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

1978-01-01

222

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

E-print Network

Continuous-wave laser oscillation on the 1315 nm transition of atomic iodine pumped by O2,,a1 of atomic iodine in favor of the I 2 P1/2 state. The laser output power was 220 mW in a stable cavity.1063/1.1883317 The classic chemical oxygen-iodine laser COIL system1 operates on the I 2 P1/2 I 2 P3/2 electronic transi

Carroll, David L.

223

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

224

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

E-print Network

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

Maryam Roghani; Heinz-Peter Breuer; Hanspeter Helm

2011-08-01

225

Propagation of frequency-chirped laser pulses in a medium of atoms with a {lambda}-level scheme  

SciTech Connect

We study the propagation of frequency-chirped laser pulses in optically thick media. We consider a medium of atoms with a {lambda} level-scheme (Lambda atoms) and also, for comparison, a medium of two-level atoms. Frequency-chirped laser pulses that induce adiabatic population transfer between the atomic levels are considered. They induce transitions between the two lower (metastable) levels of the {lambda}-atoms and between the ground and excited states of the two-level atoms. We show that associated with this adiabatic population transfer in {lambda}-atoms, there is a regime of enhanced transparency of the medium--the pulses are distorted much less than in the medium of two-level atoms and retain their ability to transfer the atomic population much longer during propagation.

Demeter, G.; Dzsotjan, D.; Djotyan, G. P. [Institute for Particle and Nuclear Physics of the Hungarian Academy of Sciences, Konkoly-Thege Miklos ut 29-33, H-1121 Budapest (Hungary)

2007-08-15

226

Vapour, or Meteoritic Particle  

Microsoft Academic Search

ABOUT 6.30 p.m. on Friday last, while out in the country, I observed a large meteor falling slowly and almost vertically in the north-north-east. After it had disappeared, half-way between the zenith and the horizon, I noticed, in the strong twilight, a faint phosphorescent trail, which did not disappear, but changed to a straw-colour, like a streak of vapour illuminated

F. B

1889-01-01

227

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

E-print Network

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

Boyer, Edmond

228

Nonlinear Effects in Optical Pumping of Atoms by a High-Intensity Multimode Gas Laser. General Theory  

Microsoft Academic Search

The optical pumping of atoms by a multimode gas laser, in the presence of a magnetic field, is studied theoretically. The atoms are described by their density matrix, which is expanded on an irreducible tensorial set. The atomic relaxation is assumed to be isotropic. In order to avoid the usual perturbation theory, we use the so-called \\

Martial Ducloy

1973-01-01

229

Single attosecond burst generation during ionization of excited atoms by intense ultrashort laser pulses  

SciTech Connect

We develop an analytical approach to describing the generation of a single attosecond burst during barrier-suppression ionization of a hydrogen atom by an intense laser pulse. We derive analytical expressions that describe the evolution of the electron wave packet in the time interval between the detachment from the atom and the collision with the parent ion for an arbitrary initial atomic state by assuming the atom to be fully ionized in one laser-field half-period. For various s-states, we derive expressions for the profile of the attosecond burst generated when the electron packet collides with the ion and analyze the dependence of its generation efficiency on the principal quantum number n of the initial atomic state. The results obtained are compared with the results of three-dimensional numerical calculations. We show that the attosecond pulse generation efficiency can be several orders of magnitude higher than that in the case of ionization from the ground state when pre-excited atomic states are used.

Emelin, M. Yu.; Ryabikin, M. Yu., E-mail: mike@ufp.appl.sci-nnov.ru; Sergeev, A. M. [Russian Academy of Sciences, Institute of Applied Physics (Russian Federation)

2008-02-15

230

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

NASA Astrophysics Data System (ADS)

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

Jirsek, Vt; Schmiedberger, Josef; ?ensk, Miroslav; Kodymov, Jarmila

2010-09-01

231

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

PubMed

Carbon quantification and the standardisation in a pure cementite were conducted using pulsed-laser atom probe tomography (APT). The results were analysed to investigate a dependence on three distinct experimental parameters; the laser pulse energy, the cryogenic specimen temperature and the laser pulse frequency. All the measurements returned an apparent carbon content of 25.01.0at%. Carbon content measurements showed no clear dependence on the cryogenic temperature or the laser pulse frequency. However, the results did demonstrate a strong correlation with the laser pulse energy. For lower laser pulse energies, the analysis returned carbon contents higher than the stoichiometric ratio. It was suggested that this effect is due to pile up of (56)Fe(++) at the detector and as a consequence there is a systematic preferential loss of these ions throughout the course of the experiment. Conversely, in experiments utilising higher laser pulse energies, it was found that the carbon contents were smaller than the stoichiometric ratio. In these experiments an increasing fraction of the larger carbon molecular ions (e.g., C5 ions) were detected as part of a multiple detection events, which could affect the quantification measurements. PMID:25048825

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

2014-12-01

232

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

SciTech Connect

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

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

2011-06-15

233

Stabilization of circular Rydberg atoms by circularly polarized infrared laser fields  

SciTech Connect

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

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

2011-09-15

234

Long operating time CW atomic iodine probe laser at 1. 315. mu. m  

SciTech Connect

A photolytically pumped longitudinal flow CW atomic iodine laser at 1.315 ..mu..m with virtually an unlimited operating time and easy operation is reported. Several weeks of continual operation is easily attainable. The prolonged lasing is achieved by employing a passive closed cycle flow system of the C/sub 3/F-I laser fuel. A high pressure dc Hg arc lamp is used for the photolytic pumping. Peak CW powers of 38 mW have been obtained along with good stability (about 1 percent amplitude fluctuations) in the fundamental TEM/sub 00/ mode via the use of an internal lens.

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

1984-10-01

235

Dipole Blockade at Foerster Resonances in High Resolution Laser Excitation of Rydberg States of Cesium Atoms  

SciTech Connect

High resolution laser excitation of np Rydberg states of cesium atoms shows a dipole blockade at Foerster resonances corresponding to the resonant dipole-dipole energy transfer of the np+np{yields}ns+(n+1)s reaction. The dipole-dipole interaction can be tuned on and off by the Stark effect, and such a process, observed for relatively low n(25-41), is promising for quantum gate devices. Both Penning ionization and saturation in the laser excitation can limit the range of observation of the dipole blockade.

Vogt, Thibault; Viteau, Matthieu; Zhao Jianming; Chotia, Amodsen; Comparat, Daniel; Pillet, Pierre [Laboratoire Aime Cotton, CNRS, Batiment 505, Campus d'Orsay, 91405 Orsay (France)

2006-08-25

236

Engineering steady-state entanglement for two atoms held in separate cavities through laser cooling  

NASA Astrophysics Data System (ADS)

We propose a scheme to prepare the steady-state entanglement for two atoms, which are held in separate cavities that are coupled through a short optical fiber or optical resonator. The entangled steady-state with a high fidelity can be achieved even with a low cooperativity parameter, by making use of the driving laser fields. Such a cooling mechanism is based on a resonant laser pump of the unwanted ground states to the excited states, which finally decay to the desired steady-state.

Shen, Li-Tuo; Chen, Rong-Xin; Wu, Huai-Zhi; Yang, Zhen-Biao

2014-04-01

237

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.

238

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

239

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

E-print Network

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

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

2014-01-01

240

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

PubMed

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

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

2014-01-01

241

Model for the Atomic Dielectric Response in Time Dependent Laser Fields  

E-print Network

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

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

2013-11-21

242

Collinear fast atomic-beam laser spectroscopy at riken garis/igisol  

NASA Astrophysics Data System (ADS)

We have constructed a fast atomic-beam collinear laser spectroscopy system connected to the on-line isotope separator facility GARIS/IGISOL at RIKEN. This system is potentially powerful in studying refractory elements. To test the system, an off-line collinear experiment was made on stable Hf isotopes produced by means of laser ablation technique. For production of radioactive Hf isotopes, the use of the inverse kinematics of a fusion reaction,9Be(166Er, xn)175- x Hf, was investigated. The radioactive isotope169Hf was successfully extracted from GARIS/IGISOL and accelerated up to 30 keV.

Koizumi, M.; Inamura, T. T.; Morita, K.; Takami, M.; Wakasugi, M.; Yoshida, A.; Azuma, M.; Katsuragawa, H.; Horiguchi, T.; Ishizuka, T.; Nakamura, I.; Nakaoka, M.; Iivonen, A.; Valli, K.; Matsuki, S.; Murayama, T.; Shimomura, K.; Shinozuka, T.; Sugai, I.; Tagishi, Y.

1992-10-01

243

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

E-print Network

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

Takaaki Nomura; Joe Sato; Takashi Shimomura

2006-05-03

244

Atomic plasma excitations in the field of a soft x-ray laser  

NASA Astrophysics Data System (ADS)

The interaction of atoms with short-wavelength radiation at ultra-high intensities is described by plasma excitation. In contrast to former works on optical radiation and ponderomotive motion of quasi-free electrons, the excitation of correlated and bound electrons is considered here. The ponderomotive motion of a free electron is included as a special case. Values for the energy transfer from the radiation field to an atom are obtained in fair agreement with the unexpectedly high charge states of xenon recently observed at the soft x-ray free-electron laser FLASH.

Richter, M.

2011-04-01

245

Relativistic and interchannel coupling effects in photoionization angular distributions by synchrotron spectrocopy of laser cooled atoms.  

PubMed

We investigate the angular distribution of photoionization fragments at low photon energies (12-40 eV) in an open shell atom, by synchrotron radiation recoil ion momentum spectroscopy in a laser cooled and trapped sample. For cesium atoms, for which relativistic effects play an important role and the ion recoil is relatively small, we could determine large and rapid changes of the asymmetry parameter beta from two, observed for s electrons outside resonances and far from the Cooper minimum. They can be explained by relativistic effects and interchannel coupling arising from final state configuration mixing. PMID:15525159

Coutinho, L H; Cavasso-Filho, R L; Rocha, T C R; Homem, M G P; Figueira, D S L; Fonseca, P T; Cruz, F C; Naves de Brito, A

2004-10-29

246

Ion-recoil momentum spectroscopy in a laser-cooled atomic sample  

NASA Astrophysics Data System (ADS)

We report an experiment on recoil-ion momentum spectroscopy of Rb+ ions formed by two-photon ionization of Rb2P3/2 at 790 nm. Laser-cooled atoms in a magneto-optic trap are used as the target in time-of-flight analysis of the recoil momentum. We demonstrate a resolution of 1 ?eV with a limiting momentum resolution below ?p=0.05 a.u. We also show the use of the photoionization technique for the characterization of cold atomic samples.

Wolf, Steffen; Helm, Hanspeter

2000-10-01

247

Production of iodine atoms for an oxygen-iodine laser from iodine-containing molecules with the help of atomic oxygen  

SciTech Connect

A new technique is proposed for the production of atomic iodine for a cw oxygen-iodine laser with the use of reactions between iodine donor molecules and oxygen atoms. The CH{sub 3}I, CF{sub 3}I, or I{sub 2} molecules can be used as donors. Oxygen atoms are injected into the reaction region by admixing the flow of partially dissociated oxygen produced in an electric discharge. The use of atomic iodine instead of molecular iodine excludes the consumption of singlet oxygen O{sub 2}({sup 1{Delta}}) for the dissociation of I{sub 2} and quenching of I* by the I{sub 2} molecules. The latter will supposedly allow raising the optimal density of I and accordingly the gain coefficient. Estimates were made of the required degree of dissociation of oxygen employed to obtain iodine atoms at which the above advantages can be realised. (lasers)

Shepelenko, A A; Mikheev, P A [Samara Branch of the P.N. Lebedev Physics Institute, Russian Academy of Sciences, Samara (Russian Federation)

2003-03-31

248

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

249

Optical Field Ionization of Atoms and Ions Using Ultrashort Laser Pulses  

NASA Astrophysics Data System (ADS)

This dissertation research is an investigation of the strong optical field ionization of atoms and ions by 120-fs, 614-nm 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^{+2}, Ne ^{+2} and Ar^ {+2}. The ion yields for He^ {+1}, Ne^{+1} and Ar^{+1} 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-nm 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 (number of ions produced versus irradiance) for three noble gases using linear, circular and elliptical polarizations of laser pulses.

Fittinghoff, David Neal

250

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

E-print Network

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

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

2014-01-01

251

Low-pressure mercury lamp pumped atomic iodine laser of high efficiency  

Microsoft Academic Search

For single pulse operation it was demonstrated that a low-pressure mercury lamp can successfully pump the atomic iodine laser using the active medium CF3I. For a 22 ms long pump pulse an output energy of 100 mJ emitted over the same time duration was obtained. Measured oscillator efficiency was 0.54%. With respect to stored optical energy an efficiency of 1.6%

K. J. Witte; P. Burkhard; H. R. Lthi

1979-01-01

252

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

SciTech Connect

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

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

2011-12-26

253

Overview of laser-radiofrequency double-resonance studies of atomic, molecular, and ionic beams  

Microsoft Academic Search

The molecular-beam laser-rf double-resonance method, first demonstrated about 15 years ago, has been used extensively in the years since to study properties of many electronic levels of both neutral and ionic atoms and molecules. The technique affords high precision (typically 1 ppm for hyperfine structure measurements), very high selectivity, and high sensitivity. In addition to revealing a wealth of details

W. J. Childs

1992-01-01

254

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

255

Measurement of fluorine atom concentrations and reaction rates in chemical laser systems  

Microsoft Academic Search

The line positions of all three components of the fluorine atom ground state fine structure transition have been measured by diode laser absorption spectroscopy, using a water vapor pure rotational line at 404.077\\/cm as a wavelength reference. These results imply a spin orbit splitting for fluorine of 404.142 + or - 0.005\\/cm. The results for the line positions are in

A. C. Stanton; J. C. Wormhoudt; J. W. Duff

1982-01-01

256

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

257

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

258

Theory of x-ray absorption by laser-dressed atoms  

E-print Network

An ab initio theory is devised for the x-ray photoabsorption cross section of atoms in the field of a moderately intense optical laser (10^13 W/cm^2). The laser dresses the core-excited atomic states, which introduces a dependence of the cross section on the angle between the polarization vectors of the two linearly polarized radiation sources. We use the Hartree-Fock-Slater approximation to describe the atomic many-body problem in conjunction with a non-relativistic quantum-electrodynamic approach to treat the photon-electron interaction. The continuum wave functions of ejected electrons are treated with a complex absorbing potential that is derived from smooth exterior complex scaling. The solution to the two-color (x-ray plus laser) problem is discussed in terms of a direct diagonalization of the complex symmetric matrix representation of the Hamiltonian. Alternative treatments with time-independent and time-dependent non-Hermitian perturbation theories are presented that exploit the weak interaction stren...

Buth, C; Buth, Christian; Santra, Robin

2006-01-01

259

Discharge formation systems for generating atomic iodine in a pulse-periodic oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

Generation characteristics of a pulse-periodic oxygen-iodine laser with the electro-discharge production of atomic iodine were compared with inductively stabilised edged or anisotropic- resistive cathodes used for ignition of the volume discharge. The discharge was initiated by the radiation of a barrier discharge from the side of a grid anode. It was found that at equal specific electrical energy depositions to the gas-discharge plasma, the system with the anisotropic-resistive cathode provides a more stable and uniform volume discharge with the possibility of varying the composition and pressure of working mixtures over a wide range and a greater specific extraction of laser energy is observed (up to 2.4 J L-1). At a high pulse repetition rate of laser pulses (50 - 100 Hz) and long duration of the pulse trains (longer than a minute) the surface of anisotropic-resistive cathode became eroded.

Aksinin, V. I.; Antsiferov, S. A.; Velikanov, S. D.; Gerasimov, A. Yu; Gostev, I. V.; Kazantsev, S. Yu; Kalinovskii, V. V.; Konovalov, V. V.; Kononov, I. G.; Mikhalkin, V. N.; Podlesnykh, S. V.; Sevryugin, I. V.; Firsov, K. N.

2014-01-01

260

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

261

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

E-print Network

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

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

2014-01-01

262

Drift of Electrons and Atoms in the Laser Radiation Field and Its Influence on the Optical Properties of Semiconductors  

NASA Astrophysics Data System (ADS)

We experimentally study the influence of the laser-induced drift (LID) of dopant electrons and atoms on the optical properties of semiconductors. It is shown that the LID of electrons results in a dramatic change in the refractive index in the region of laser-radiation output from semiconductor crystals, impairement of the total internal reflection in semiconductors, and the occurrence of astigmatism during self-defocusing of the laser radiation in anisotropic semiconductors. This effect influences the breaking of semiconductors by nanosecond and picosecond laser pulses. The LID of dopant atoms, caused by the electrostatic interaction between the ions of these atoms and the space charge of drifting electrons, changes differently the luminescence spectra on the input and output surfaces of crystals and also results in the appearance of a dark spot on the output surface of some ZnSe crystals after irradiation by a continuous-wave CO2 laser.

Krupa, N. N.; Korostil', A. M.; Skirta, Yu. B.

2005-08-01

263

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

NASA Astrophysics Data System (ADS)

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

Yang, Jing; Tian, Yuan; Tan, Bozhong; Yun, Peter; Gu, Sihong

2014-03-01

264

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

PubMed

The availability of reliable and well-engineered commercial instruments and data analysis software has led to development in recent years of robust and ergonomic atom-probe tomographs. Indeed, atom-probe tomography (APT) is now being applied to a broader range of materials classes that involve highly important scientific and technological problems in materials science and engineering. Dual-beam focused-ion beam microscopy and its application to the fabrication of APT microtip specimens have dramatically improved the ability to probe a variety of systems. However, the sample preparation is still challenging especially for emerging nanomaterials such as epitaxial nanowires which typically grow vertically on a substrate through metal-catalyzed vapor phase epitaxy. The size, morphology, density, and sensitivity to radiation damage are the most influential parameters in the preparation of nanowire specimens for APT. In this paper, we describe a step-by-step process methodology to allow a precisely controlled, damage-free transfer of individual, short silicon nanowires onto atom probe microposts. Starting with a dense array of tiny nanowires and using focused ion beam, we employed a sequence of protective layers and markers to identify the nanowire to be transferred and probed while protecting it against Ga ions during lift-off processing and tip sharpening. Based on this approach, high-quality three-dimensional atom-by-atom maps of single aluminum-catalyzed silicon nanowires are obtained using a highly focused ultraviolet laser-assisted local electrode atom probe tomograph. PMID:25299058

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

2014-10-31

265

Preparation of nanowire specimens for laser-assisted atom probe tomography  

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

266

Determination of airblast atomized spray structure using state-of-the-art laser diagnostics  

NASA Astrophysics Data System (ADS)

This paper presents the results of an integrated qualitative-quantitative investigation into the detailed structure of an airblast atomized gas turbine spray at near atmospheric pressure and temperature conditions. Pre-filming airblast atomizer was studied with aviation kerosine as the test fuel. Phase Doppler anemometry was utilized to interrogate droplet size, velocity and number density characteristics while high-energy, pulsed laser sheet illumination technique enabled the visualization of the condition of the liquid at atomizer exit as well as variations in droplet concentration. The spray is found to be generally inhomogeneous in structure and the extent of size, velocity, number density inhomogeneity increases as the axial distance of the measurement plane diminishes. This has implications for the attainment of a satisfactory combustion-emissions performance from modern combustors with compact reaction zones.

Jasuja, A. K.; Tam, C. K.

1992-07-01

267

Laser-induced continuum structure and third harmonic generation in one- and two-valence-electron atoms  

Microsoft Academic Search

A model for calculating third harmonic generation (THG) in a near-resonantly coupled 4-level atomic system in the presence of laser-induced continuum structure (LICS) is formulated in terms of the time dependent density matrix elements which can be obtained by solving the time dependent density matrix equations for the atomic system interacting with laser pulses. The theory is applied to a

Zhang Jian

1991-01-01

268

A semiclassical study of laser-induced atomic fluorescence from Na2, K2 and NaK  

NASA Technical Reports Server (NTRS)

A semiclassical treatment of laser-induced atomic fluorescence for the alkali-dimer systems Na2, K2 and NaK is presented. The variation of the fluorescence intensity with the frequency of the exciting laser photon is studied and a comparison of theoretical results with a set of experimental data is presented.

Yuan, J.-M.; Bhattacharyya, D. K.; George, T. F.

1982-01-01

269

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

E-print Network

Time-resolved diffraction profiles and atomic dynamics in short-pulse laser-induced structural transformations: Molecular dynamics study Zhibin Lin and Leonid V. Zhigilei* Department of Materials Science dynamics simulations of a 20 nm Au film irradiated with 200 fs laser pulses of different intensity

Zhigilei, Leonid V.

270

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

271

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

272

Output mode spectra, comparative parametric operation, quenching, photolytic reversibility, and short-pulse generation in atomic iodine photodissociation lasers  

Microsoft Academic Search

The advantages and disadvantages of the atomic iodine photodissociation laser for high-energy operation have been considered. Laser excitation by both slow and fast flashlamps has been investigated; in slow flash excitation, self-mode-locking occurs frequently and the output-mode characteristics of the laser operated in this way have been studied. The comparative performance of different parent materials for photodissociation has been investigated

C. C. Davis; R. J. Pirkle; R. A. McFarlane; G. J. Wolga

1976-01-01

273

Laser-induced excitation and ionization of a confined hydrogen atom in an exponential-cosine-screened Coulomb potential  

NASA Astrophysics Data System (ADS)

The energy spectra of spherically confined hydrogen atom embedded in an exponential-cosine-screened Coulomb potential is worked out by using the Bernstein-polynomial method. The interaction of short laser pulses in the femtosecond range with the system is studied in detail. The effect of shape of laser pulse, confinement radius, Debye screening length as well as different laser parameters on the dynamics of the system has been explored and analyzed.

Lumb, Shalini; Lumb, Sonia; Prasad, Vinod

2014-09-01

274

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

275

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

276

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

277

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

SciTech Connect

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

Buchsbaum, A.; Rauchbauer, G.; Varga, P.; Schmid, M. [Institut fuer Allgemeine Physik, TU Wien, Wiedner Hauptstrasse 8-10, A-1040 Wien (Austria)

2008-04-15

278

Direct measurements of fluorine atom concentration, gain length and small signal gain in an hydrogen fluoride overtone laser  

Microsoft Academic Search

Experimental techniques have been developed to directly measure the concentration of fluorine atoms, the gain length and the small signal gain in a hydrogen fluoride 5 cm slit nozzle laser. A gas phase titration technique was utilized to measure the fluorine atom concentration using HCl as the titrant. The gain length was measured using a pitot probe to locate the

Charles F Wisniewski; Kevin B Hewett; Gerald C Manke II; C Randall Truman; Gordon D Hager

2003-01-01

279

On-line characterisation of copper vapour evolution from linear vapour source generated using strip electron beam  

NASA Astrophysics Data System (ADS)

In electron beam assisted physical vapour deposition (EB-PVD) technique, the online characterization of the evaporator is essential for process optimisation and control. In applications such as decorative and corrosion resistance coating, the knowledge of time average distribution of vapour is essential, whereas in some real time applications such as isotope purification, surface hardening and alloying etc., real time knowledge of vapour distribution and vapour propagation is important. The online characterization of various parameters related to the evaporator and associated processes using least expensive techniques is necessary to know the process throughput. Measurement of atom flux using quartz crystal thickness monitor can be one such techniques. The experimental studies were carried out to characterize the evaporator using thickness monitor by measuring copper vapour propagation and distribution over the two dimensional source. The experimental data measured at two heights corresponding to aspect ratio 2 and 3 are presented and the behaviour of expanding vapour is discussed. This technique can also be used to estimate the source temperature from the deposition rate data, which is discussed in the paper with its validation using measured temperature using two-colour pyrometer.

Sahu, G. K.; Majumder, A.; Patankar, R. A.; Mago, V. K.; Thakur, K. B.

2008-05-01

280

Laser action on infrared chlorine and oxygen atomic transitions using uranium fission fragment pumping  

NASA Astrophysics Data System (ADS)

Quasi-cw laser action with pulse duration up to 10 ms on the 1.59-, 2.45-micrometers atomic Cl transitions and 2.65-, 2.76-micrometers atomic O transitions was observed under uranium fission fragment pumping of atmospheric-pressure gas media. The mixtures of He, Ne, Ar with CCl4, CHCl3, CF2Cl2, C2F3Cl3, O2, NO, or CO were used. Nuclear pumping of high-pressure gas media at the 2.45- and 2.65-micrometers lines has been achieved for the first time. To our knowledge, the 2.76-micrometers line is a new laser line. The maximum energy parameters (output power of 130 W, power efficiency of about 0.2%) were measured for the 1.59-micrometers chlorine line in He/Ne/CCl4 (25000/25000/1) mixture at 2 atm pressure. The minimum laser threshold was observed for this line at the thermal neutron flux of 2 X 1013 n/cm2s.

Melnikov, S. P.; Porkhaev, V. V.

1995-08-01

281

Comment on "Generation of cold low divergent atomic beam of indium by laser ablation" [Rev. Sci. Instrum. 76, 113302 (2005)].  

PubMed

We present measurements of the velocity distribution of calcium atoms in an atomic beam generated using a dual-stage laser back-ablation apparatus. Distributions are measured using a velocity selective Doppler time-of-flight technique. They are Boltzmann-like with rms velocities corresponding to temperatures above the melting point for calcium. Contrary to a recent report in the literature, this method does not generate a subthermal atomic beam. PMID:19405705

Denning, A; Booth, A; Lee, S; Amonson, M; Bergeson, S D

2009-04-01

282

Comment on ''Generation of cold low divergent atomic beam of indium by laser ablation'' [Rev. Sci. Instrum. 76, 113302 (2005)  

SciTech Connect

We present measurements of the velocity distribution of calcium atoms in an atomic beam generated using a dual-stage laser back-ablation apparatus. Distributions are measured using a velocity selective Doppler time-of-flight technique. They are Boltzmann-like with rms velocities corresponding to temperatures above the melting point for calcium. Contrary to a recent report in the literature, this method does not generate a subthermal atomic beam.

Denning, A.; Booth, A.; Lee, S.; Amonson, M.; Bergeson, S. D. [Department of Physics and Astronomy, Brigham Young University, Provo, Utah 84602 (United States)

2009-04-15

283

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

NASA Astrophysics Data System (ADS)

We report mass-resolved time-of-flight measurements of neutral particles from the (1010) surface of single-crystal ZnO during pulsed 193-nm irradiation at laser fluences below the threshold for avalanche breakdown. The major species emitted are atomic Zn and O. We examine the emissions of atomic Zn as a function of laser fluence and laser exposure. Defects at the ZnO surface appear necessary for the detection of these emissions. Our results suggest that the production of defects is necessary to explain intense sustained emissions at higher fluence. Rapid, clean surface etching and high atomic zinc kinetic energies seen at higher laser fluences are also discussed.

Khan, Enamul H.; Langford, S. C.; Dickinson, J. T.; Boatner, L. A.

2013-08-01

284

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

285

Photoelectron angular distributions from above threshold ionization of hydrogen atoms in strong laser fields.  

PubMed

We apply a scattering theory of nonperturbative quantum electrodynamics to study the photoelectron angular distributions (PADs) of a hydrogen atom irradiated by linearly polarized laser light. The calculated PADs show main lobes and jetlike structure. Previous experimental studies reveal that in a set of above-threshold-ionization peaks when the absorbed-photon number increases by one, the jet number also increases by one. Our study confirms this experimental observation. Our calculations further predict that in some cases three more jets may appear with just one-more-photon absorption. With consideration of laser-frequency change, one less jet may also appear with one-more-photon absorption. The jetlike structure of PADs is due to the maxima of generalized phased Bessel functions, not an indication of the quantum number of photoelectron angular momentum states. PMID:17155621

Bai, Lihua; Zhang, Jingtao; Xu, Zhizhan; Guo, Dong-Sheng

2006-11-10

286

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

NASA Astrophysics Data System (ADS)

We report the observation of laser-induced birefringence (LIB) in a wavelength-mismatched cascade system ( J=0?J=1?J=0 transitions) of inhomogeneously broadened ytterbium atoms with strong pump and probe fields. We investigate the transmission spectrum of two circular polarization ( ?p+ and ?p- ) components of strong probe field at fixed frequency, depending on the detuning of a circularly polarized (?c-) coupling field from two-photon resonance. We find that the ?p+ (?p-) 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

2004-12-01

287

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

NASA Technical Reports Server (NTRS)

An laser-spectroscopic investigation of the thermocheMical state of arcjet flows is currently being conducted in the Aerodynamic Heating Facility (AHF) Circlet at NASA Ames Research Center. Downstream of the nozzle exit, but upstream of the test article, Laser-Induced Fluorescence (LIF) of atomic nitrogen is used to assess the nonequilibriuM distribution of flow enthalpy in the free stream. The two-photon LIF technique provides simultaneous measurements of free stream velocity, translational temperature, and nitrogen number density on the flow centerline. Along with information from facility instrumentation, these measurements allow a determination of the free stream total enthalpy, and its apportionment in to thermal, kinetic, and chemical mode contributions. Experimental results are presented and discussed for two different niti-ogen/argon test gas flow runs during which the current is varied while the pressure remains constant .

Fletcher, Douglas; Wercinski, Paul F. (Technical Monitor)

1998-01-01

288

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

E-print Network

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 analyse 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

2012-01-01

289

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

290

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

SciTech Connect

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

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

2011-11-10

291

Opacity and atomic analysis of double pulse laser ablated Li plasma  

NASA Astrophysics Data System (ADS)

Opacity effects for neutral and ionic emission lines of lithium have been investigated by Atomic Data Analysis Structure (ADAS). Line ratios and opacity corrected photon emissivity coefficients are calculated over a wide range of electron temperatures and densities. The experimentally measured temporal evolution of the line profiles of the over dense Li plasma formed in the double pulse laser ablation experiment have been explained using the ADAS analysis and the plasma parameters of the plasma plume under consideration have been estimated. These results could be projected as a diagnostic tool to estimate plasma parameters of an over dense lithium plasma.

Sivakumaran, V.; Joshi, H. C.; Kumar, Ajai

2014-09-01

292

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

SciTech Connect

High-quality nanograin ZnO thin films were deposited on c-plane sapphire (Al{sub 2}O{sub 3}) substrates by pulse laser deposition (PLD). Scanning electron microscopy (SEM) and x-ray diffraction (XRD) were used to characterize the samples. The structural and morphological properties of ZnO films under different deposition temperature have been investigated before and after atomic oxygen (AO) treatment. XRD has shown that the intensity of the (0 0 2) peak increases and its FWHM value decreases after AO treatment. The AO sensing characteristics of nano ZnO film also has been investigated in a ground-based atomic oxygen simulation facility. The results show that the electrical conductivity of nanograin ZnO films decreases with increasing AO fluence and that the conductivity of the films can be recovered by heating.

Wang Yunfei; Chen Xuekang; Li Zhonghua; Zheng Kuohai; Wang Lanxi; Feng Zhanzu; Yang Shengsheng [National Key Laboratory of Vacuum and Cryogenics Technology and Physics, Lanzhou Institute of Physics, Lanzhou 730000 (China)

2009-01-05

293

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

294

Proposed method for laser spectroscopy of pionic helium atoms to determine the charged-pion mass  

E-print Network

Metastable pionic helium ($\\pi{\\rm He}^+$) is a three-body atom composed of a helium nucleus, an electron occupying the $1s$ ground state, and a negatively charged pion $\\pi^-$ in a Rydberg state with principal- and orbital angular momentum quantum numbers of $n\\sim \\ell+1\\sim 16$. We calculate the spin-independent energies of the $\\pi{\\rm ^3He}^+$ and $\\pi{\\rm ^4He}^+$ isotopes in the region $n=15$--19. These include relativistic and quantum electrodynamics corrections of orders $R_{\\infty}\\alpha^2$ and $R_{\\infty}\\alpha^3$ in atomic units, where $R_{\\infty}$ and $\\alpha$ denote the Rydberg and fine structure constants. The fine-structure splitting due to the coupling between the electron spin and the orbital angular momentum of the $\\pi^-$, and the radiative and Auger decay rates of the states are also calculated. Some states $(n,\\ell)=(16,15)$ and $(17,16)$ retain nanosecond-scale lifetimes against $\\pi^-$ absorption into the helium nucleus. We propose to use laser pulses to induce $\\pi^-$ transitions from these metastable states, to states with large ($\\sim 10^{11}$ s$^{-1}$) Auger rates. The $\\pi{\\rm He}^{2+}$ ion that remains after Auger emission of the $1s$ electron undergoes Stark mixing with the $s$, $p$, and $d$ states during collisions with the helium atoms in the experimental target. This leads to immediate nuclear absorption of the $\\pi^-$. The resonance condition between the laser beam and the atom is thus revealed as a sharp spike in the rates of neutrons, protons, deuterons, and tritons that emerge....(continued)

Masaki Hori; Anna Str; Vladimir I. Korobov

2014-04-30

295

Partial coherence of Bose-Einstein condensates and atom laser sources  

NASA Astrophysics Data System (ADS)

Finite-temperature quantum field theory is used to determine the second- and third-order coherence functions, g^(k)(r_1,dots,r_k) for k=2 and 3, for a trapped-atom Bose gas at temperatures below the critical temperature T0 for Bose-Einstein condensation. The condensate and non-condensate atoms are distributed differently within the trap, so e.g. g^(2)(r_1,r_2) does not depend on |r_1-r_2| alone, as would be the case for a homogeneous system. In the HFB-Popov approximation, the coherence functions are polynomials of the spatially resolved condensate fraction, f(r). Thus, experimental determinations of coherence functions reported (E. A. Burt et al.), Phys. Rev. Lett. 79, 337 (1997). ^, (W. Ketterle and H.-J. Miesner, Phys. Rev. A 57), 3291 (1997). for trapped-atom systems should be interpreted as yielding a spatial average of g^(k)(r). Such an average may underestimate the degree of coherence attainable in an atom laser by judicious engineering of the output coupler. (R. J. Dodd et al.), Optics Express 1, 284 (1997); M. Edwards et al., this meeting.

Dodd, R. J.; Clark, Charles W.; Edwards, Mark; Burnett, K.

1998-05-01

296

Characterizing the coherence of Bose-Einstein condensates and atom lasers  

NASA Astrophysics Data System (ADS)

For a dilute, interacting Bose gas of magnetically-trapped atoms at temperatures below the critical temperature T0 for Bose-Einstein condensation, we determine the second- and third-order coherence functions, g^(k)(r_1,r_2) for k=2 and 3, within the framework of a finite-temperature quantum field theory. We show that, because of the different spatial distributions of condensate and thermal atoms in the trap, g^(k)(r_1,r_2) does not depend on |r_1-r_2| alone, as would be the case for a homogeneous system. In the HFB-Popov approximation, the coherence functions are polynomials of the spatially--resolved condensate fraction, f(r). This means that experimental determinations of these functions reported for trapped--atom systems (E. A. Burt et al.), Phys. Rev. Lett. 79, 337 (1997). ^, (W. Ketterle and H.-J. Miesner, Phys. Rev. A 57), 3291 (1997). do not yield a unique value of g^(k)(0), such as would characterize a homogeneous system, but rather a spatial average of g^(k)(r,r). Such an average may underestimate the degree of coherence attainable in an atom laser by judicious engineering of the output coupler. (R. J. Dodd et al.), Optics Express 1, 284 (1997).

Dodd, R. J.; Clark, Charles W.; Edwards, Mark; Burnett, K.

1998-03-01

297

Quantum control of multilevel atoms with rotational degeneracy using short laser pulses  

SciTech Connect

We study the quantum control of multilevel atoms with rotationally degenerate levels using short laser pulses. Various control schemes are considered, ones using {pi} pulses, frequency-chirped pulses, two consecutive pulses, or two pulses that overlap each other partially. We study the possibilities of controlling the quantum state of an ensemble of atoms distributed randomly over one or more rotationally degenerate levels initially. For the sake of concreteness we use the hyperfine level scheme of the {sup 85}Rb D line, but the results can easily be generalized for any of the alkali-metal atoms used in cooling and trapping experiments. We find that even though a number of difficulties arise, such as unequal coupling constants between rotational sublevels or dephasing between different hyperfine levels during the interaction, control schemes using simple or multiphoton adiabatic passage can be used to control the internal states of the atoms effectively as well as the center-of-mass motion. Furthermore, it is shown that in some cases it is possible to exploit the inequality of the coupling constants to entangle the rotational substates with specific distinct translational quantum states and hence separate these substates in momentum space.

Demeter, G. [Institute for Particle and Nuclear Physics of the Hungarian Academy of Sciences, Konkoly-Thege Miklos ut 29-33, H-1121 Budapest (Hungary)

2010-10-15

298

Atomically Resolved Surface of Laser-MBE Grown SrRuO3 Thin Films  

NASA Astrophysics Data System (ADS)

Surface of SrRuO3 (SRO) thin films is of high interest since SRO layers are used as bottom electrodes in oxide heterostructures demanding sharp interfaces. Here we studied SRO films in-situ using STM with atomic resolution. Films were grown on undoped, SrTiO3 substrates by laser-MBE. Depending on preparation conditions, the film surfaces exhibited varying reconstructions. Films deposited at 650^oC and annealed at deposition conditions for 15 min. revealed surfaces with double-row 1D-structures along <110>pc of SRO. Atoms in the 1D-structures are packed in square or zigzag arrangements. The surface in-between the structures appeared poorly ordered. Similar patterns were observed on surfaces of films deposited at 700^oC without anneal. In turn, deposition at 700^oC with post-anneal resulted in well-ordered surfaces covered by double-rowed structures with square atomic arrangement. Ab initio DFT calculations show a high local DOS from oxygen adatoms with zigzag and square patterns contributing to STM images. Oxygen atoms have high adsorption energies and will be present at our growth conditions. Surface O-adatoms show AFM coupling to the film, with possible ramifications to understand interfacial bonding/magnetism between SRO and oxide-insulators.

Tselev, A.; Ganesh, P.; Baddorf, A. P.; Kalinin, S. V.

2013-03-01

299

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

300

Optical interface created by laser-cooled atoms trapped in the evanescent field surrounding an optical nanofiber  

E-print Network

Trapping and optically interfacing laser-cooled neutral atoms is an essential requirement for their use in advanced quantum technologies. Here we simultaneously realize both of these tasks with cesium atoms interacting with a multi-color evanescent field surrounding an optical nanofiber. The atoms are localized in a one-dimensional optical lattice about 200 nm above the nanofiber surface and can be efficiently interrogated with a resonant light field sent through the nanofiber. Our technique opens the route towards the direct integration of laser-cooled atomic ensembles within fiber networks, an important prerequisite for large scale quantum communication schemes. Moreover, it is ideally suited to the realization of hybrid quantum systems that combine atoms with, e.g., solid state quantum devices.

E. Vetsch; D. Reitz; G. Sagu; R. Schmidt; S. T. Dawkins; A. Rauschenbeutel

2009-12-07

301

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

302

Development of laser-plasma diagnostics using ultrafast atomic-scale dynamics. 96-ERD-046 final report  

SciTech Connect

Ultrashort laser pulse systems allow examination of intense, ultrafast laser-plasma interactions. More specifically, intense laser irradiation can induce short xuv/x-ray bursts from the surface of condensed phase targets. Ultrafast xuv/x-ray detection is needed to understand laser-plasma interactions in this dynamic regime. Support of the Stockpile Stewardship and Management Program requires this critical understanding. Our effort here has been to extend understanding of atomic-scale dynamics in such environments with the goal of developing next generation ultrafast xuv/x-ray diagnostics where the sensors will be the atoms and ions themselves and the time resolution will approach that of the induced atomic transitions ({approx} a few femtoseconds). Pivotal contributions to the rapidly developing field of highly nonperturbative interactions of ultrashort pulse lasers with atoms/ions have been made at this laboratory. In the visible/infrared wavelength regions the temporal and spectral content of ultrashort laser pulses are now reliably monitored within a single pulse using frequency resolved optical gating (FROG) which is based on rapid nonlinear optical processes such as the Kerr effect. New applications of this basic concept are still being developed. Corresponding detection for the xuv/x-ray wavelengths does not exist and is urgently needed in many laboratory programs. The FROG technique cannot be applied in the xuv/x-ray region. Current x-ray streak camera technology is limited to {approx}0.5 picosecond resolution.

Bolton, P.R.; Kulander, K.C. [Lawrence Livermore National Lab., CA (United States); Boreham, B.W. [Central Queensland Univ., Rockhampton, QLD (Australia). Dept. of Applied Physics

1997-03-01

303

Inverse bremsstrahlung heating rate in atomic clusters irradiated by femtosecond laser pulses  

NASA Astrophysics Data System (ADS)

In the interaction of atomic clusters with femtosecond laser pulses, nanoplasmas with high density and high temperature are created. The heating is mainly determined by inverse bremsstrahlung (IB) due to electron-ion collisions. In many approaches for the calculation of the IB heating rate such as the Born approximation, large-angle scattering events are underestimated. However, rescattering events of an electron on the same atomic ion play an important role because they increase the amount of energy exchanged between the electrons and the laser field. In noble gas plasmas, the electron-ion interaction is often considered to take place between point-like particles. For typical noble gas clusters studied in experiments, one is advised to take into account not only the screening by the surrounding plasma medium but also the inner structure of the ions what can be accomplished by the use of appropriate model potentials. In the present paper, the IB heating rate is calculated from the classical simulation of individual electron trajectories. Results are presented for xenon clusters and argon clusters with different degree of ionization. Especially for higher energies, the consideration of the ionic structure increases the heating rate compared with the scattering on point-like particles. The Born approximation, however, overestimates this effect.

Moll, M.; Bornath, Th.; Schlanges, M.; Krainov, V. P.

2012-03-01

304

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

305

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

306

Laser generated by the interaction of molecules containing the azide radical and a molecule containing a halogen atom  

SciTech Connect

This patent describes a method for generating a lasing effect in a chemically pumped laser using molecules containing the azide radical and a molecule containing an iodine atom. The method consists of: (a) providing a replenishable chemical source of N/sub 3/ and I; (b) introducing by mixing gas streams, the N/sub 3/ and I into a laser cavity; (c) reaching the N/sub 3/ and I in the laser cavity; (d) producing excited species within the laser cavity from the reaction of N/sub 3/ and I; (e) generating a lasing effect by the interaction of reactants contained within the laser cavity, the reactants selected from excited species and I; and (f) cooling the laser system to remove thermal energy.

Young, R.A.

1988-11-15

307

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

308

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 Schrdinger 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

309

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

E-print Network

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

Deb, Bimalendu

2014-01-01

310

Control of the atomic layer-by-layer growth process in laser molecular beam epitaxy with the emission monitoring method  

Microsoft Academic Search

In order to control the atomic layer-by-layer growth process in laser molecular beam epitaxy more strictly, the emission intensity accompanying the laser ablation of the target materials is monitored, and the thickness of each layer is estimated from the intensity. In some metal and oxide targets, such as Sr and CuO, the amount of the species generated by the ablation,

M. Kanai; T Kawai

1998-01-01

311

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

Microsoft Academic Search

The mechanism of atomic and molecular ionization in intense, ultra-short laser fields is a subject which continues to receive\\u000a considerable attention. An inherent difficulty with techniques involving the tight focus of a laser beam is the continuous\\u000a distribution of intensities contained within the focus, which can vary over several orders of magnitude. The present study\\u000a adopts time of flight mass

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

2005-01-01

312

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

313

Precision measurement of laser RF double resonance spectra with an effective compensation of residual magnetic field. For nuclear laser spectroscopy of RI atoms in superfluid helium  

NASA Astrophysics Data System (ADS)

We have been developing a novel laser spectroscopy method-"OROCHI" for radioisotopes trapped in superfluid helium. This new method is expected to determine nuclear spins and moments of exotic nuclei by precise measurement of Zeeman and hyperfine splitting of atoms using laser double resonance method. Its feasibility has been confirmed by means of a series of experiments with various stable atoms in superfluid helium, while the accuracy of experimental results is found strongly affected by external magnetic field. In order to obtain reliable and accurate results for atomic spectra with "OROCHI" method, based on laser RF double resonance spectroscopy of on-line experiment, we performed off-line test experiments for Rb in helium buffer gas. In this test experiment, we used three mutually orthogonal coils to effectively compensate for laboratory residual magnetic field and subsequently observed precise laser RF double resonance spectra of atoms which affords us accurate nuclear spin value. By comparison of those results, we could make clear the effect of residual magnetic field on experimental results. The details of "OROCHI" method and test experiments are presented.

Yang, X. F.; Furukawa, T.; Fujita, T.; Imamura, K.; Matsuo, Y.

2014-06-01

314

Direct measurement of laser-induced frequency shift rate of ultracold cesium molecules by analyzing losses of trapped atoms  

SciTech Connect

We report on a quantitative experimental determination of the laser-induced frequency shift rate of the ultracold cesium molecules formed via photoassociation (PA) by means of the trap loss measurement of the losses of trapped atoms in a standard magneto-optical trap. The experiment was directly performed by varying the photoassociation laser intensity without any additional frequency monitor technologies. Our experimental method utilized dependences of the losses on the laser-induced frequency shift rate based on the conditions of the identified photoassociation spectral shape. We demonstrated that the method is sensitive enough to determine small frequency shifts of rovibrational levels of ultracold cesium molecules.

Zhang Yichi; Ma Jie; Li Yuqing; Wu Jizhou; Zhang Linjie; Chen Gang; Wang Lirong; Zhao Yanting; Xiao Liantuan; Jia Suotang [State Key Laboratory of Quantum Optics and Quantum Optics Devices, Laser Spectroscopy Laboratory, Shanxi University, Taiyuan 030006 (China)

2012-09-24

315

Generalized ramsey scheme for precision spectroscopy of ultracold atoms and ions: Inclusion of a finite laser line width and spontaneous relaxation of the atomic levels  

NASA Astrophysics Data System (ADS)

Ramsey schemes with pulses of different lengths and with a composite pulse have been analyzed taking into account a finite width of the laser line and spontaneous relaxation of atomic levels. The optimal parameters of pulses corresponding to the maximum suppression of the excitation-related shift and the maximum resonance amplitude have been found for both schemes. According to the numerical results, spontaneous relaxation of the atomic levels and a finite width of the laser line must be taken into account in the calculation of the optimal parameters of the excitation pulses. The Ramsey scheme with a composite pulse is less sensitive to fluctuations of the Rabi frequency than the scheme with pulses of different lengths.

Tabatchikova, K. S.; Taichenachev, A. V.; Yudin, V. I.

2013-05-01

316

Controlling double ionization of atoms in an intense bichromatic laser pulse  

SciTech Connect

We consider the classical dynamics of a two-electron system subjected to an intense bichromatic linearly polarized laser pulse. By varying the parameters of the field, such as the phase lag and the relative amplitude between the two colors of the field, we observe several trends from the statistical analysis of a large ensemble of trajectories initially in the ground-state energy of the helium atom: high sensitivity of the sequential double-ionization component, low sensitivity of the intensities where nonsequential double ionization occurs, while the corresponding yields can vary drastically. All these trends hold irrespective of which parameter is varied: the phase lag or the relative amplitude. We rationalize these observations by an analysis of the phase-space structures that drive the dynamics of this system and determine the extent of double ionization. These trends turn out to be mainly regulated by the dynamics of the inner electron.

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

2011-03-15

317

Self-consistent finite-temperature model of atom-laser coherence properties  

SciTech Connect

We present a mean-field model of a continuous-wave atom laser with Raman output coupling. The noncondensate is pumped at a fixed input rate which, in turn, pumps the condensate through a two-body scattering process obeying the Fermi golden rule. The gas is then coupled out by a Gaussian beam from the system, and the temperature and particle number are self-consistently evaluated against equilibrium constraints. We observe the dependence of the second-order coherence of the output upon the width of the output-coupling beam, and note that even in the presence of a highly coherent trapped gas, perfect coherence of the output matter wave is not guaranteed.

Fergusson, J.R.; Geddes, A.J.; Hutchinson, D.A.W. [Department of Physics, Otago University, Dunedin (New Zealand)

2005-03-01

318

Breakthrough: X-ray Laser Captures Atoms and Molecules in Action  

ScienceCinema

The Linac Coherent Light Source at SLAC is the world's most powerful X-ray laser. Just two years after turning on in 2009, breakthrough science is emerging from the LCLS at a rapid pace. A recent experiment used the X-rays to create and probe a 2-million-degree piece of matter in a controlled way for the first time-a significant leap toward understanding the extreme conditions found in the hearts of stars and giant planets, and a finding which could further guide research into nuclear fusion, the mechanism that powers the sun. Upcoming experiments will investigate the fundamental, atomic-scale processes behind such phenomena as superconductivity and magnetism, as well as peering into the molecular workings of photosynthesis in plants.

Bergmann, Uwe

2014-05-21

319

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 0C to -70C to within 0.35 per cent. PMID:22547230

Bielska, K; Havey, D K; Scace, G E; Lisak, D; Hodges, J T

2012-06-13

320

Cluster calibration in mass spectrometry: laser desorption/ionization studies of atomic clusters and an application in precision mass spectrometry.  

PubMed

For accurate mass measurements and identification of atomic and molecular species precise mass calibration is mandatory. Recent studies with laser desorption/ionization and time-of-flight analysis of cluster ion production by use of fullerene and gold targets demonstrate the generation of atomic clusters for calibration purposes. Atomic ion results from the Penning trap mass spectrometer ISOLTRAP, in which a carbon cluster ion source has recently been installed, are presented as an application in the field of precision mass spectrometry. PMID:14647934

Blaum, K; Herlert, A; Huber, G; Kluge, H-J; Maul, J; Schweikhard, L

2003-12-01

321

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

NASA Astrophysics Data System (ADS)

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

Gallagher, Jeffrey E.

322

Atomic-Scale Monitoring of Step-Flow Growth During Perovskite Pulsed Laser Deposition  

NASA Astrophysics Data System (ADS)

The nearly perfect lattice match between EuTiO3 and SrTiO3 allows two-dimensional growth of strain-free films during pulsed laser deposition. We have observed 50 ``anti-Bragg'' x-ray intensity oscillations during film growth, indicating that this system enters a steady state regime where two-dimensional growth can persist indefinitely, under optimal conditions. While we monitored the anti-Bragg oscillations to index monolayer completion, we simultaneously integrated the Eu L?1 x-ray fluorescence intensity to measure the total quantity of deposited material. Two-dimensional film growth occurs from 100^oC to 700^oC, at 0.1Hz laser repetition rate, and from 0.1Hz to 4Hz at 650^oC, in a 7x10-6Torr O2 background. As a film grows, the specular crystal truncation rod exhibits an increasing number of interference (Kiessig) fringes, due to electronic density contrast between substrate and film. In this talk, I will discuss how the modulation of anti-Bragg intensity by interference fringes may enable precise monitoring of film thickness in the step-flow regime, enabling growth of atomically perfect structures. This work was supported by the Cornell Center for Materials Research, under National Science Foundation Grant No. DMR-9632275, and made use of facilities at the Cornell High Energy Synchrotron Source, NSF Grant No. DMR-9311772.

Fleet, Aaron; Wang, H. H.; Brock, J. D.; Dale, Darren; Suzuki, Y.

2003-03-01

323

Controlling desorption of H, O, atoms and OH group from graphene by pulse laser  

NASA Astrophysics Data System (ADS)

Possibilities of reduction of graphene oxide and one-side dehydrogenation of graphane (H-terminated graphene) with using ultra-short pulse (2 fs) laser are discussed. We have performed molecular dynamics (MD) simulation of O-, H-, and OH-adsorbed graphene sheets induced by electronic excitation upon irradiation with laser pulse. The time-dependent density functional theory treating real-time propagation of electron wave functions combined with the Ehrenfest approximation for the MD was employed and FPSEID [1] code was used to check the energy conservation rule under dynamical external field [2]. We found asymmetric pulse shape as a function of time causes an efficient desorption of O atoms and OH groups from graphene which can be applicable for reduction of graphene oxide alternative to chemical and thermal treatment. Meanwhile, such asymmetric pulse shape is beneficial for one-side H-desorption from graphane that will trigger further structural changes such as spontaneous shrink/rippling or heterogeneous termination on side-by-side.[4pt] [1]O. Sugino, Y. Miyamoto, PRB59, 2579, (1999);B66, 089901(E) (2002)[0pt] [2]Y. Miyamoto, H. Zhang, PRB77, 165123 (2008)

Miyamoto, Yoshiyuki; Zhang, Hong

2012-02-01

324

On a new method for chemical production of iodine atoms in a chemical oxygen-iodine laser  

SciTech Connect

A new method is proposed for generating iodine atoms in a chemical oxygen-iodine laser. The method is based on a branched chain reaction of dissociation of the alkyl iodide CH{sub 3}I in a medium of singlet oxygen and chlorine. (active media)

Andreeva, Tamara L; Kuznetsova, S V; Maslov, A I; Sorokin, Vadim N [P.N. Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2004-11-30

325

Diagnostics of Carbon Nanotube Formation in a Laser Produced Plume: An Investigation of the Metal Catalyst by Laser Ablation Atomic Fluorescence Spectroscopy  

NASA Technical Reports Server (NTRS)

Carbon nanotubes, elongated molecular tubes with diameters of nanometers and lengths in microns, hold great promise for material science. Hopes for super strong light-weight material to be used in spacecraft design is the driving force behind nanotube work at JSC. The molecular nature of these materials requires the appropriate tools for investigation of their structure, properties, and formation. The mechanism of nanotube formation is of particular interest because it may hold keys to controlling the formation of different types of nanotubes and allow them to be produced in much greater quantities at less cost than is currently available. This summer's work involved the interpretation of data taken last summer and analyzed over the academic year. The work involved diagnostic studies of carbon nanotube formation processes occurring in a laser-produced plume. Laser ablation of metal doped graphite to produce a plasma plume in which carbon nanotubes self assemble is one method of making carbon nanotube. The laser ablation method is amenable to applying the techniques of laser spectroscopy, a powerful tool for probing the energies and dynamics of atomic and molecular species. The experimental work performed last summer involved probing one of the metal catalysts, nickel, by laser induced fluorescence. The nickel atom was studied as a function of oven temperature, probe laser wavelength, time after ablation, and position in the laser produced plume. This data along with previously obtained data on carbon was analyzed over the academic year. Interpretations of the data were developed this summer along with discussions of future work. The temperature of the oven in which the target is ablated greatly influences the amount of material ablated and the propagation of the plume. The ablation conditions and the time scale of atomic and molecular lifetimes suggest that initial ablation of the metal doped carbon target results in atomic and small molecular species. The metal atoms survive for several milliseconds while the gaseous carbon atoms and small molecules nucleate more rapidly. Additional experiments and the development of in situ methods for carbon nanotube detection would allow these results to be interpreted from the perspective of carbon nanotube formation.

deBoer, Gary; Scott, Carl

2003-01-01

326

Proposed method for laser spectroscopy of pionic helium atoms to determine the charged-pion mass  

E-print Network

Metastable pionic helium ($\\pi{\\rm He}^+$) is a three-body atom composed of a helium nucleus, an electron occupying the $1s$ ground state, and a negatively charged pion $\\pi^-$ in a Rydberg state with principal- and orbital angular momentum quantum numbers of $n\\sim \\ell+1\\sim 16$. We calculate the spin-independent energies of the $\\pi{\\rm ^3He}^+$ and $\\pi{\\rm ^4He}^+$ isotopes in the region $n=15$--19. These include relativistic and quantum electrodynamics corrections of orders $R_{\\infty}\\alpha^2$ and $R_{\\infty}\\alpha^3$ in atomic units, where $R_{\\infty}$ and $\\alpha$ denote the Rydberg and fine structure constants. The fine-structure splitting due to the coupling between the electron spin and the orbital angular momentum of the $\\pi^-$, and the radiative and Auger decay rates of the states are also calculated. Some states $(n,\\ell)=(16,15)$ and $(17,16)$ retain nanosecond-scale lifetimes against $\\pi^-$ absorption into the helium nucleus. We propose to use laser pulses to induce $\\pi^-$ transitions from...

Hori, Masaki; Korobov, Vladimir I

2014-01-01

327

Strong influence of configuration interactions on the orientation and alignment dichroism in the 3p photoelectron spectra of free laser-polarized Fe atoms  

Microsoft Academic Search

The 3p photoelectron spectra of oriented and aligned free Fe atoms are presented. The atomic polarization was achieved by optical pumping. For this purpose single-mode ultraviolet continuous wave laser radiation was produced by second harmonic generation in an external ring resonator. The ground state Fe 3d64s2 D45 was oriented by circularly polarized laser radiation and aligned by linearly polarized laser

R. Mller; J. Schulz; Ph. Wernet; K. Godehusen; M. Martins; B. Sonntag; P. Zimmermann

2007-01-01

328

Local structure of Liquid-Vapour Interfaces  

E-print Network

The structure of a simple liquid may be characterised in terms of ground state clusters of small numbers of atoms of that same liquid. Here we use this sensitive structural probe to consider the effect of a liquid-vapour interface upon the liquid structure. At higher temperatures (above around half the critical temperature) we find that the predominant effect of the interface is to reduce the local density, which significantly suppresses the local cluster populations. At lower temperatures, however, pronounced interfacial layering is found. This appears to be connected with significant orientational ordering of clusters based on 3- and 5-membered rings, with the rings aligning perpendicular and parallel to the interface respectively. At all temperatures, we find that the population of five-fold symmetric structures is suppressed, rather than enhanced, close to the interface.

Maia Godonoga; Alex Malins; Jens Eggers; C. Patrick Royall

2011-02-15

329

Continuous-wave laser oscillation in subsonic flow on the 1315 nm atomic iodine transition pumped by electric discharge produced O2,,a 1  

E-print Network

Continuous-wave laser oscillation in subsonic flow on the 1315 nm atomic iodine transition pumped.993% reflective mirrors. © 2006 American Institute of Physics. DOI: 10.1063/1.2346134 Oxygen-iodine laser systems1 into the possibility of a continu- ous flow hybrid electrically powered oxygen-iodine laser ElectricOIL with electric

Carroll, David L.

330

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

E-print Network

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

Carroll, David L.

331

Analysis of geological samples by atomic emission spectroscopy of plasmas induced by laser ablation at low pressures  

NASA Astrophysics Data System (ADS)

Elemental analysis of geologic samples based on atomic emission spectroscopy is currently considered for several future space lander missions to planets, moons and asteroids in solar system. The spectroscopic techniques, called laser-induced plasma (breakdown) spectroscopy (LIBS), provides quantitatively the microscopic in-situ abundances of all major and many trace elements of surfaces of solar system bodies. Excitation and evolution of the plasmas induced by lasers depend on the properties of the investigated material and on environmental conditions. This study focuses on the feasibility of spectroscopy of plasmas induced by low-energy laser (below 1 mJ per pulse) for the exploration of solar system bodies with thin atmospheres (pressures below 1 mPa). At such low pressures the excited plasmas have small plumes and expand very rapidly, which limits both the LIBS signal intensity and the available acquisition time. This, in turn, requires usually relatively powerful laser sources to create a detectable LIBS plasma. The low pressure conditions are simulated in a dedicated chamber at the DLR-Berlin Institute of Planetary Research, that can hold the Martian-like atmosphere or high vacuum conditions. Two infrared Q-switched lasers are used for comparative investigation of atomic emission spectra: Firstly, a Nd:YAG laser (Inlite, Continuum) operating at 1064 nm and at 10 Hz, pulse energy up to 230 mJ at 8-10 ns pulse duration and, secondly, developed for future planetary missions Nd:YLF laser (NeoLASE) operating at 1053 nm and at 10-50 Hz, pulse energy up to 3 mJ at 3-5 ns pulse duration. The emitted light of the laser-induced plasma is analysed by an echelle spectrometer (LTB Aryelle Butterfly) covering the wavelength range of 280-900 nm with a spectral resolution of around 104. Identification of atomic transitions is performed using the LTB built-in spectrometer software by comparison with the NIST spectral database. Several basaltic rock and sediment standards were crushed to powder and pressed into pellets. Reduction of both pressure and laser excitation energy results in a significant decrease of the signal-to-noise ratio for most atomic lines (an exception are the widely broadened lines of H). However, the detection of atomic emission lines of elements with relative abundances above 10-3 (0.1 wt%) - Al, Ca, Cr, H, K, Mg, Mn, Na, Ni, O, Si, Ti, - is possible down to a laser excitation energy of 0.9 mJ (laser irradiance on the sample surface 46 MW/mm2). Additionally, the detection of carbon and sulphur, having strong atomic transitions in ultraviolet range, can be expected by extension of the spectral range of the LIBS spectrometer to 190 nm. Atomic doublet and triplet transitions, broadened by atomic collisions at ambient pressures (100 kPa), become spectrally resolved and are identified below 1 mPa. This demonstrates the feasibility of miniaturized laser-induced breakdown spectrometry for space missions to solar bodies with absent or thin atmospheres.

Pavlov, S.; Schrder, S.; Jessberger, E.; Hbers, H.

2011-12-01

332

Vapour Intrusion into Buildings - A Literature Review  

EPA Science Inventory

This chapter provides a review of recent research on vapour intrusion of volatile organic compounds (VOCs) into buildings. The chapter builds on a report from Tillman and Weaver (2005) which reviewed the literature on vapour intrusion through 2005. Firstly, the term ?vapour intru...

333

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

SciTech Connect

Laser-induced fluorescence is used for measuring the concentration of iodine molecules at the output of an electric-discharge generator of atomic iodine. Methyl iodide CH{sub 3}I is used as the donor of atomic iodine. The fraction of iodine extracted from CH{sub 3}I in the generator is {approx}50%. The optimal operation regimes are found in which 80%-90% of iodine contained in the output flow of the generator was in the atomic state. This fraction decreased during the iodine transport due to recombination and was 20%-30% at the place where iodine was injected into the oxygen flow. The fraction of the discharge power spent for dissociation was {approx}3%. (elements of laser setups)

Azyazov, V N; Vorob'ev, M V; Voronov, A I; Kupryaev, Nikolai V; Mikheev, P A; Ufimtsev, N I [Samara Branch of the P.N. Lebedev Physics Institute, Russian Academy of Sciences, Samara (Russian Federation)

2009-01-31

334

The vapour - liquid equilibrium of n-alkanes  

NASA Astrophysics Data System (ADS)

The vapour - liquid equilibrium of short n-alkanes is considered by using perturbation theory. This requires as a previous step obtaining an equation of state (EOS) for hard flexible models. An EOS for hard-n-alkane models which shows excellent agreement with computer simulation of hard-n-alkane models with up to 100 carbon atoms is proposed. This EOS is combined with a mean-field term and the vapour - liquid equilibrium of n-alkanes is computed. When theoretical critical densities and pressures are plotted as a function of the number of carbon atoms, a maximum is found. This is in agreement with experiment. The conditions for the appearance of such a maximum in general chain models are established. Some ways of improving the mean-field theory are suggested.

Vega, C.; Garzon, B.; MacDowell, L. G.; Padilla, P.; Calero, S.; Lago, S.

1996-11-01

335

Amorphous vapour-quenched gadolinium-silver alloys  

Microsoft Academic Search

The structure of vapour-quenched thin films of gadolinium-silver alloys has been examined by X-ray diffraction techniques. The films approximately 6000 AA thick were prepared on copper, sapphire and glass substrates held at 77K. Alloys containing between 88 and 86 atomic per cent gadolinium are found to have an amorphous structure consistent with a theoretical model suggested by Sadoc (1973) for

J. Popplewell; S. W. Charles; D. D. Jenkins

1975-01-01

336

Laser driven self-assembly of shape-controlled potassium nanoparticles in porous glass  

E-print Network

We observe growth of shape-controlled potassium nanoparticles inside a random network of glass nanopores, exposed to low-power laser radiation. Visible laser light plays a dual role: it increases the desorption probability of potassium atoms from the inner glass walls and induces the self-assembly of metastable metallic nanoparticles along the nanopores. By probing the sample transparency and the atomic light-induced desorption flux into the vapour phase, the dynamics of both cluster formation/evaporation and atomic photo-desorption processes are characterized. Results indicate that laser light not only increases the number of nanoparticles embedded in the glass matrix but also influences their structural properties. By properly choosing the laser frequency and the illumination time, we demonstrate that it is possible to tailor the nanoparticles'shape distribution. Furthermore, a deep connection between the macroscopic behaviour of atomic desorption and light-assisted cluster formation is observed. Our result...

Marmugi, L; Burchianti, A; Veronesi, S; Moi, L; Marinelli, C

2014-01-01

337

Self-injection and acceleration of electrons during ionization of gas atoms by a short laser pulse  

SciTech Connect

Using a relativistic three-dimensional single-particle code, acceleration of electrons created during the ionization of nitrogen and oxygen gas atoms by a laser pulse has been studied. Barrier suppression ionization model has been used to calculate ionization time of the bound electrons. The energy gained by the electrons peaks for an optimum value of laser spot size. The electrons created near the tail do not gain sufficient energy for a long duration laser pulse. The electrons created at the tail of pulse escape before fully interacting with the trailing part of the pulse for a short duration laser pulse, which causes electrons to retain sufficient energy. If a suitable frequency chirp is introduced then energy of the electrons created at the tail of the pulse further increases.

Singh, K.P. [Computational Plasma Dynamics Laboratory, Kettering University, Flint, Michigan 48504 (United States)

2006-04-15

338

Non-contact quantification of laser micro-impulse in water by atomic force microscopy and its application for biomechanics  

NASA Astrophysics Data System (ADS)

We developed a local force measurement system of a femtosecond laser-induced impulsive force, which is due to shock and stress waves generated by focusing an intense femtosecond laser into water with a highly numerical aperture objective lens. In this system, the force localized in micron-sized region was detected by bending movement of a cantilever of atomic force microscope (AFM). Here we calculated the bending movement of the AFM cantilever when the femtosecond laser is focused in water at the vicinity of the cantilever and the impulsive force is loaded on the cantilever. From the result, a method to estimate the total of the impulsive force at the laser focal point was suggested and applied to estimate intercellular adhesion strength.

Hosokawa, Yoichiroh

2011-12-01

339

JOURNAL DE PHYSIQUE ColZoque C9, suppZe'ment au nO1l, Tome 41, novembre 1980, page C9-449 A POTENTIAL ATOMIC IODINE LASER PUMPED BY ELECTRICALLY GENERATED 'A OXYGEN  

E-print Network

-449 A POTENTIAL ATOMIC IODINE LASER PUMPED BY ELECTRICALLY GENERATED 'A OXYGEN G. Fournier, J. Bonnet and D temperature. The usual atomic iodine laser However, that efficiency in ordinary dis- I 2 ~ 1 2+ I 2 ~ 3 / 2at that an atomic iodine laser than the value for self-sustained oper- can be continuously pumped with a chemical

Paris-Sud XI, Université de

340

Role of Photoexcitation and Field Ionization in the Measurement of Accurate Oxide Stoichiometry by Laser-Assisted Atom Probe Tomography  

SciTech Connect

Pulsed lasers extend the high spatial and mass resolution of atom probe tomography (APT) to non-conducting materials, such as oxides. For prototypical metal oxide MgO, measured stoichiometry depends strongly upon pulse energy and applied voltage. Very low laser energies (0.02 pJ) and high electric fields yield optimal stoichiometric accuracy, attributed to the field-dependent ionization of photo-desorbed O or O2 neutrals. This emphasizes the importance of considering electronic excitations in APT analysis of oxides ionic materials.

Devaraj, Arun; Colby, Robert J.; Hess, Wayne P.; Perea, Daniel E.; Thevuthasan, Suntharampillai

2013-03-06

341

IV INTERNATIONAL CONFERENCE ON ATOM AND MOLECULAR PULSED LASERS (AMPL'99): Efficiency of an H2SF6 laser with electron-beam initiation of chemical reactions  

NASA Astrophysics Data System (ADS)

The spectral and amplitudetime characteristics of HF lasers pumped by a nonchain chemical reaction and initiated by radially convergent and planar electron beams were investigated. The principal channels leading to the formation of vibrationally excited HF molecules were analysed. It was confirmed that high efficiencies (~10%) of a nonchain HF laser may be attained only as a result of the simultaneous formation of atomic and molecular fluorine when the active mixture is acted upon by an electron beam and of the participation of molecular fluorine in population inversion. It was shown that a laser pulse has a complex spectraltemporal profile caused by the successive generation of P-lines and the overlap during the radiation pulse of both the rotational lines of the same vibrational band and of individual vibrational bands.

Erofeev, M. V.; Orlovskii, Viktor M.; Skakun, V. S.; Sosnin, E. A.; Tarasenko, Viktor F.

2000-06-01

342

Interference-induced enhancement of field entanglement in a microwave-driven V-type single-atom laser  

E-print Network

We investigate the generation and the evolution of two-mode continuous-variable (CV) entanglement from system of a microwave-driven V-type atom in a quantum beat laser. By taking into account the effects of spontaneously generated quantum interference between two atomic decay channels, we show that the CV entanglement with large mean number of photons can be generated in our scheme, and the property of the filed entanglement can be adjusted by properly modulating the frequency detuning of the fields. More interesting, it is found that the entanglement can be significantly enhanced by the spontaneously generated interference.

Wen-Xing Yang; Ai-Xi Chen; Ting-Ting Zha; Yanfeng Bai; Ray-Kuang Lee

2014-04-04

343

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

PubMed

This article describes the design, characterization, and performance of an electrostatic glass actuator adapted to an ultrahigh vacuum environment (10(-8) mbar). The three-phase rotary motor is used to drive a turbine that acts as a velocity-selective light trap for a slow continuous beam of laser-cooled atoms. This simple, compact, and nonmagnetic device should find applications in the realm of time and frequency metrology, as well as in other areas of atomic, molecular physics and elsewhere. PMID:17979408

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

2007-10-01

344

A double-interferometer laser system for cold 87Rb atom gyroscopes based on stimulated Raman transitions  

E-print Network

We proposed and implemented a double-interferometer laser system to manipulate cold 87Rb atoms to interfere. A frequency-modulated continuous-wave technique was applied to determine and compensate the optical path difference between the two Raman beams. With a coherent self-heterodyne method, the beat signal's FWHM linewidth was measured and the obtained linewidth of ~1Hz mainly limited by the resolution bandwidth of the spectrum analyzer indicates a good coherence degree of the two Raman beams, paving the way to realize a highly sensitive atom gyroscope.

Song, Ningfang; Li, Wei; Li, Yang; Liu, Jixun; Xu, Xiaobin; Pan, Xiong

2014-01-01

345

[Atomic Vapor Laser Isotope Separation (AVLIS) program]. Final report, [January--July 1992  

SciTech Connect

This report summarizes work performed for the Atomic Vapor Laser Isotope Separation (AVLIS) program from January through July, 1992. Each of the tasks assigned during this period is described, and results are presented. Section I details work on sensitivity matrices for the UDS relay telescope. These matrices show which combination of mirror motions may be performed in order to effect certain changes in beam parameters. In Section II, an analysis is given of transmission through a clipping aperture on the launch telescope deformable mirror. Observed large transmission losses could not be simulated in the analysis. An EXCEL spreadsheet program designed for in situ analysis of UDS optical systems is described in Section III. This spreadsheet permits analysis of changes in beam first-order characteristics due to changes in any optical system parameter, simple optimization to predict mirror motions needed to effect a combination of changes in beam parameters, and plotting of a variety of first-order data. Optical systems may be assembled directly from OSSD data. A CODE V nonsequential model of the UDS optical system is described in Section IV. This uses OSSD data to build the UDS model; mirror coordinates may thus be verified. Section V summarizes observations of relay telescope performance. Possible procedures which allow more accurate assessment of relay telescope performance are given.

Not Available

1992-12-04

346

Adaptive numerical methods for time-dependent Schrodinger equation in atomic and laser physics  

NASA Astrophysics Data System (ADS)

Stable adaptive methods for solving the time-dependent Schrodinger equation (TDSE)) are considered in the framework of conventional finite-element representation of smooth solutions over coordinate spaces of a projective type with long derivatives. Generalization of Cranck-Nicholson scheme of forth order in time step is implemented. Projective "hidden variable" representation of strongly oscillating solutions is realized to extract explicitly the strongly variable gauge phase factor and to evaluate only the "pilot solution" which is reduced to a smooth envelope of the solution under consideration. Such an approach corresponds to the known transformation from Euler space variables to Lagrangian ones and the inducing characteristic representation of self-similar solutions widely used in the flow propagation problems. We study both smooth and strongly oscillating solutions of TDSE describing conventional atomic models in the laser pulse field. It is shown that for short-range potentials the "pilot solution" can be naturally interpreted as the spectrum of the outgoing wave. The examples considered show the efficiency and stability of the elaborated methods.

Derbov, Vladimir L.; Kaschiev, M. S.; Serov, V. V.; Gusev, A. A.; Vinitsky, S. I.

2003-09-01

347

Experiment to measure the electric dipole moment (edm) of the electron using laser-cooled Cs atoms  

NASA Astrophysics Data System (ADS)

The electron edm de is known to be smaller in magnitude than 1.6x10-27e.cm [1]. We will describe progress on an ongoing experiment designed to be sensitive to an electron EDM de as small as 10-29e.cm. The experiment will search for the resulting edm of the Cs atom, proportional to de, using laser-cooled Cs atoms held in an optical dipole force trap. Important features of the experiment include resonant optical cavities to accurately define the trapping laser field, in-vacuum high voltage electrodes, and methods to reduce magnetic noise to low levels, including the use of a novel titanium vacuum chamber [4pt] [1] B. C. Regan et al. Phys. Rev. Lett. 88, 071805 (2002)

Ihn, Yong-Sup; Heinzen, Daniel

2010-03-01

348

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

349

Nd:YLF laser at 1.3 m for calcium atom optical clocks and precision spectroscopy of hydrogenic systems  

E-print Network

Nd:YLF laser at 1.3 m for calcium atom optical clocks and precision spectroscopy of hydrogenic in hydrogen and metastable singly ionized helium 1312.6 nm . By using a twisted-mode cavity, we have obtained provide a precise measurement of the 2S Lamb shift.5­7 A measurement of the 2S­3S inter- val in hydrogen

Boyer, Edmond

350

Doubly resonant three-photon double ionization of Ar atoms induced by an EUV free-electron laser  

SciTech Connect

A mechanism for three-photon double ionization of atoms by extreme-ultraviolet free-electron laser pulses is revealed, where in a sequential process the second ionization step, proceeding via resonant two-photon ionization of ions, is strongly enhanced by the excitation of ionic autoionizing states. In contrast to the conventional model, the mechanism explains the observed relative intensities of photoelectron peaks and their angular dependence in three-photon double ionization of argon.

Gryzlova, E. V. [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577 (Japan); Institute of Nuclear Physics, Moscow State University, Moscow 119991 (Russian Federation); Ma, Ri [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577 (Japan); RIKEN, XFEL Project Head Office, Sayo, Hyogo 679-5148 (Japan); Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012 (China); Fukuzawa, H.; Motomura, K.; Yamada, A.; Ueda, K. [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577 (Japan); RIKEN, XFEL Project Head Office, Sayo, Hyogo 679-5148 (Japan); Grum-Grzhimailo, A. N.; Strakhova, S. I. [Institute of Nuclear Physics, Moscow State University, Moscow 119991 (Russian Federation); Kabachnik, N. M. [Institute of Nuclear Physics, Moscow State University, Moscow 119991 (Russian Federation); European XFEL GmbH, D-22761 Hamburg (Germany); Rouzee, A.; Hundermark, A. [RIKEN, XFEL Project Head Office, Sayo, Hyogo 679-5148 (Japan); Max-Born-Institut, Max-Born Strasse 2A, D-12489 Berlin (Germany); FOM Institute AMOLF, NL-1098 XG Amsterdam (Netherlands); Vrakking, M. J. J. [Max-Born-Institut, Max-Born Strasse 2A, D-12489 Berlin (Germany); FOM Institute AMOLF, NL-1098 XG Amsterdam (Netherlands); Johnsson, P. [RIKEN, XFEL Project Head Office, Sayo, Hyogo 679-5148 (Japan); Department of Physics, Lund University, Post Office Box 118, SE-22100 Lund (Sweden); Nagaya, K.; Yase, S.; Mizoguchi, Y.; Yao, M. [RIKEN, XFEL Project Head Office, Sayo, Hyogo 679-5148 (Japan); Department of Physics, Kyoto University, Kyoto 606-8502 (Japan); Nagasono, M.; Tono, K.; Yabashi, M. [RIKEN, XFEL Project Head Office, Sayo, Hyogo 679-5148 (Japan); and others

2011-12-15

351

Quantum theory of two-photon correlated-spontaneous-emission lasers: Exact atom-field interaction Hamiltonian approach  

SciTech Connect

A quantum theory of two-photon correlated-spontaneous-emission lasers (CEL's) is developed, starting from the exact atom-field interaction Hamiltonian for cascade three-level atoms interacting with a single-mode radiation field. We consider the situation where the active atoms are prepared initially in a coherent superposition of three atomic levels and derive a master equation for the field-density operator by using a quantum theory for coherently pumped lasers. The master equation is transformed into a Fokker-Planck equation for the antinormal-ordering {ital Q} function. The drift coefficients of the Fokker-Planck equation enable us to study the steady-state operation of the two-photon CEL's analytically. We have studied both resonant two-photon CEL for which there is no threshold, and off-resonant two-photon CEL for which there exists a threshold. In both cases the initial atomic coherences provide phase locking, and squeezing in the phase quadrature of the field is found. The off-resonant two-photon CEL can build up from a vacuum when its linear gain is larger than the cavity loss (even without population inversion). Maximum squeezing is found in the no-population-inversion region with the laser intensities far below saturation in both cases, which are more than 90% for the resonant two-photon CEL and nearly 50% for the off-resonant one. Approximate steady-state {ital Q} functions are obtained for the resonant two-photon CEL and, in certain circumstances, for the off-resonant one.

Lu, N.; Zhu, S. (Center for Advanced Studies and Department of Physics and Astronomy, University of New Mexico, Albuquerque, New Mexico 87131 (US))

1989-11-15

352

Two-dimensional imaging of atomic and nanoparticle components in copper plasma plume produced by ultrafast laser ablation  

NASA Astrophysics Data System (ADS)

We report on the spatial and temporal evolution of the plume generated during ultrafast laser ablation of a pure copper target with 800 nm, ?50 fs, Ti: Sapphire laser pulses. Time-gated imaging was used to record 2-dimensional images of plume populations. The temporal evolution of neutral (Cu*), and ionic (Cu+) components of the plume are separately imaged by exploiting bandpass interference filters, while nanoparticles are investigated by collecting their characteristic broadband emission. The ionic component of the plume moves two to three times faster than the neutral component, with a velocity which is almost independent of laser fluence. Plume emission intensity variations at different fluences and delay times are studied for both atomic and nanoparticle components.

Anoop, K. K.; Ni, Xiaochang; Bianco, M.; Paparo, D.; Wang, X.; Bruzzese, R.; Amoruso, S.

2014-10-01

353

High-resolution optical spectroscopy of Os-with a view to laser cooling of atomic anions  

NASA Astrophysics Data System (ADS)

Atomic anions are generally not amenable to optical spectroscopy because they are loosely bound systems and rarely have bound excited states. Until recently, there was only one known negative ion with a strong bound-bound electronic transition, the osmium anion Os-. The electric-dipole transition between the 4Fe9/2 ground and 6DoJ excited state of this ion provides unique insight into the structure of atomic anions. In addition, it may enable the preparation of ultracold ensembles of negative ions. Laser excitation of the electric-dipole transition in Os- ions could be used to laser-cool them to microkelvin temperatures. If demonstrated to be successful, the technique would allow the cooling of any species of negatively charged ions - from subatomic particles to molecular anions - to ultracold temperatures by sympathetic cooling. We have been investigating the bound-bound electric-dipole transition in Os- by high-resolution laser spectroscopy with a view to using it for the first laser cooling of negative ions. The principle of the method, its potential applications, as well as experimental results are presented.

Kellerbauer, Alban; Fritzsche, Stephan

2012-11-01

354

High efficiency coherent optical memory with warm rubidium vapour  

PubMed Central

By harnessing aspects of quantum mechanics, communication and information processing could be radically transformed. Promising forms of quantum information technology include optical quantum cryptographic systems and computing using photons for quantum logic operations. As with current information processing systems, some form of memory will be required. Quantum repeaters, which are required for long distance quantum key distribution, require quantum optical memory as do deterministic logic gates for optical quantum computing. Here, we present results from a coherent optical memory based on warm rubidium vapour and show 87% efficient recall of light pulses, the highest efficiency measured to date for any coherent optical memory suitable for quantum information applications. We also show storage and recall of up to 20 pulses from our system. These results show that simple warm atomic vapour systems have clear potential as a platform for quantum memory. PMID:21285952

Hosseini, M.; Sparkes, B.M.; Campbell, G.; Lam, P.K.; Buchler, B.C.

2011-01-01

355

High efficiency coherent optical memory with warm rubidium vapour.  

PubMed

By harnessing aspects of quantum mechanics, communication and information processing could be radically transformed. Promising forms of quantum information technology include optical quantum cryptographic systems and computing using photons for quantum logic operations. As with current information processing systems, some form of memory will be required. Quantum repeaters, which are required for long distance quantum key distribution, require quantum optical memory as do deterministic logic gates for optical quantum computing. Here, we present results from a coherent optical memory based on warm rubidium vapour and show 87% efficient recall of light pulses, the highest efficiency measured to date for any coherent optical memory suitable for quantum information applications. We also show storage and recall of up to 20 pulses from our system. These results show that simple warm atomic vapour systems have clear potential as a platform for quantum memory. PMID:21285952

Hosseini, M; Sparkes, B M; Campbell, G; Lam, P K; Buchler, B C

2011-01-01

356

High efficiency coherent optical memory with warm rubidium vapour  

E-print Network

By harnessing aspects of quantum mechanics, communication and information processing could be radically transformed. Promising forms of quantum information technology include optical quantum cryptographic systems and computing using photons for quantum logic operations. As with current information processing systems, some form of memory will be required. Quantum repeaters, which are required for long distance quantum key distribution, require optical memory as do deterministic logic gates for optical quantum computing. In this paper we present results from a coherent optical memory based on warm rubidium vapour and show 87% efficient recall of light pulses, the highest efficiency measured to date for any coherent optical memory. We also show storage recall of up to 20 pulses from our system. These results show that simple warm atomic vapour systems have clear potential as a platform for quantum memory.

Hosseini, M; Lam, P K; Buchler, B C

2010-01-01

357

Lasers.  

ERIC Educational Resources Information Center

Examines the nature of laser light. Topics include: (1) production and characteristics of laser light; (2) nine types of lasers; (3) five laser techniques including holography; (4) laser spectroscopy; and (5) laser fusion and other applications. (SK)

Schewe, Phillip F.

1981-01-01

358

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

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

359

Two-color, two-photon laser-induced polarization spectroscopy (LIPS) measurements of atomic hydrogen in near-adiabatic, atmospheric pressure hydrogen\\/air flames  

Microsoft Academic Search

Two-color, two-photon laser-induced polarization spectroscopy (LIPS) of atomic hydrogen has been demonstrated and applied in atmospheric pressure hydrogen\\/air flames. Fundamental and frequency-doubled beams from a single 486-nm dye laser were used in the experiments. The 243-nm pump beam in the measurements was tuned to the two-photon n=1?n=2 resonance of the hydrogen atom. The 486-nm probe beam was tuned to the

Waruna D. Kulatilaka; Robert P. Lucht; Sherif F. Hanna; Viswanath R. Katta

2004-01-01

360

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

PubMed

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

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

2012-03-01

361

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

SciTech Connect

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

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

2012-03-01

362

Atomic physics of relativistic high contrast laser-produced plasmas in experiments on Leopard laser facility at UNR  

NASA Astrophysics Data System (ADS)

The results of the recent experiments focused on study of x-ray radiation from multicharged plasmas irradiated by relativistic (I > 1019 W/cm2) sub-ps laser pulses on Leopard laser facility at NTF/UNR are presented. These shots were done under different experimental conditions related to laser pulse and contrast. In particular, the duration of the laser pulse was 350 fs or 0.8 ns and the contrast was varied from high (10-7) to moderate (10-5). The thin laser targets (from 4 to 750 ?m) made of a broad range of materials (from Teflon to iron and molybden to tungsten and gold) were utilized. Using the x-ray diagnostics including the high-precision spectrometer with resolution R 3000 and a survey spectrometer, we have observed unique spectral features that are illustrated in this paper. Specifically, the observed L-shell spectra for Fe targets subject to high intensity lasers (1019 W/cm2) indicate electron beams, while at lower intensities (1016 W/cm2) or for Cu targets there is much less evidence for an electron beam. In addition, K-shell Mg features with dielectronic satellites from high-Rydberg states, and the new K-shell F features with dielectronic satellites including exotic transitions from hollow ions are highlighted.

Safronova, A. S.; Kantsyrev, V. L.; Faenov, A. Y.; Safronova, U. I.; Wiewior, P.; Renard-Le Galloudec, N.; Esaulov, A. A.; Weller, M. E.; Stafford, A.; Wilcox, P.; Shrestha, I.; Ouart, N. D.; Shlyaptseva, V.; Osborne, G. C.; Chalyy, O.; Paudel, Y.

2012-06-01

363

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

E-print Network

2009) We demonstrate a scheme for realizing a compact cold atom gravimeter. The use of a hollow.1063/1.3373917 #12;2 Gravimeters, based on atoms interferometry, measure the Earth's gravity as a phase shift between that an atom interferometer based on Raman transitions [7] can be realized exploiting an hollow pyramid

Boyer, Edmond

364

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

PubMed Central

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

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

2013-01-01

365

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

NASA Astrophysics Data System (ADS)

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

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

2009-03-01

366

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

367

High-order LaguerreGaussian laser modes for studies of cold atoms  

Microsoft Academic Search

The generation of high-order LaguerreGaussian (LG) laser modes at 780 nm from a simple external-cavity diode laser is demonstrated. The beams are derived from computer-generated holograms and a high conversion efficiency of 40% is achieved for LG beams with mode indices from l=1 to l=6. The line width of the external cavity diode laser is below 1 MHz. This system

M. A Clifford; J. Arlt; J. Courtial; K. Dholakia

1998-01-01

368

Explosives: A microsensor for trinitrotoluene vapour  

Microsoft Academic Search

Sensing devices designed to detect explosive vapours are bulky, expensive and in need of technological improvement - dogs remain the most effective detectors in the fight against terrorism and in the removal of land-mines. Here we demonstrate the deflagration of trinitrotoluene (TNT) in a small localized explosion on an uncoated piezoresistive microcantilever. This explosive-vapour sensor, which has a detection capability

L. A. Pinnaduwage; A. Gehl; D. L. Hedden; G. Muralidharan; T. Thundat; R. T. Lareau; T. Sulchek; L. Manning; B. Rogers; M. Jones; J. D. Adams

2003-01-01

369

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

SciTech Connect

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

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

2011-01-15

370

films deposited by chemical vapour deposition  

NASA Astrophysics Data System (ADS)

A few properties of polycrystalline silicon germanium (poly-Si1- x Ge x ) films can be tailored by modulating the germanium incorporation. In this paper, the structural, mechanical and electrical properties of heavily doped ultrathin (~100 nm) poly-Si1- x Ge x films (0.84 ? x ? 0.88) fabricated by low-pressure chemical vapour deposition were investigated. For a boron concentration of ~2.2 1021 atoms/cm3, a slight increase of germanium fraction significantly enhances the deposition rate, crystallinity and Hall mobility while having negligible influence on the Young's modulus and hardness. The grain size increases from ~6 to ~12 nm while the grain structure becomes more columnar. In addition, the resistivity decreases from 7.4 to 1.1 m ? cm with a corresponding increase in the Hall mobility from ~0.9 to ~4.2 cm2 V-1 s-1. However, the Young's modulus (~101 GPa) and hardness (~8.8 GPa) are virtually unaffected within the range of germanium fraction explored. In practice, poly-SiGe layer having low resistivity, high modulus, high mobility and low surface roughness can be successfully applied for resonators, biosensors and nanoswitches among others.

Asafa, T. B.; Witvrouw, A.; Morcos, B. S.; Vanstreels, K.; Said, S. A. M.

2014-08-01

371

Chemical reactions of excited nitrogen atoms for short wavelength chemical lasers. Final technical report  

SciTech Connect

Accomplishments of this program include the following: (1) Scalable, chemical generation of oxygen atoms by reaction of fluorine atoms and water vapor. (2) Production of nitrogen atom densities of 1 {times} 10{sup 1}5 cm{sup {minus}3} with 5% electrical efficiency by injecting trace amounts of fluorine into microwave discharged nitrogen. (3) Production of cyanide radicals by reaction of high densities of N atoms with cyanogen. (4) Production of carbon atoms by reaction of nitrogen atoms with cyanogen or with fluorine atoms and hydrogen cyanide. (5) Confirmation that the reaction of carbon atoms and carbonyl sulfide produces CS(a{sup 3} {Pi}{sub r}), as predicted by conservation of electron spin and orbital angular momenta and as proposed by others under another SWCL program. (6) Production of cyanide radicals by injection of cyanogen halides into active nitrogen and use as spectroscopic calibration source. (7) Demonstration that sodium atoms react with cyanogen chloride, bromide and iodide and with cyanuric trifluoride to produce cyanide radicals. (8) Demonstration of the potential utility of the fluorine atom plus ammonia reaction system in the production of NF(b{sup l}{Sigma}{sup +}) via N({sup 2}D) + F{sub 2}.

Not Available

1989-12-15

372

Densification behavior of gas and water atomized 316L stainless steel powder during selective laser melting  

Microsoft Academic Search

The densification during selective laser melting (SLM) process is an important factor determining the final application of SLM-part. In the present work, the densifications under different processing conditions were investigated and the densification mechanisms were elucidated. It was found that the higher laser power, lower scan speed, narrower hatch spacing and thinner layer thickness could enable a much smoother melting

Ruidi Li; Yusheng Shi; Zhigang Wang; Li Wang; Jinhui Liu; Wei Jiang

2010-01-01

373

Multiple-composition hyperthermal atomic beams formed by a laser-induced plasma for planetary environmental studies  

NASA Astrophysics Data System (ADS)

A multiple-composition beam with a velocity of 8 km s-1 was formed using a laser detonation source in order to simulate the physical and chemical effects of neutral gas collisions on a material in the sub-low earth orbit (LEO). A premixed target gas was applied in the laser detonation beam technique. It was found that atoms of different masses, O and Ar for Ar + O2 target gas, are accelerated to similar velocities, i.e. different translational energies. Promotion of O2 decomposition is confirmed by using a mixed gas target. It is concluded that the multiple-composition beam obtained using a mixed target gas is suitable for simulating a neutral gas environment in the sub-LEO region.

Yokota, Kumiko; Watanabe, Daiki; Ohira, Junki; Tagawa, Masahito

2014-05-01

374

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

375

Simulating the vapourliquid equilibria of large cyclic alkanes  

E-print Network

Self-adapting fixed endpoint configurational-bias Monte Carlo simulations in the Gibbs ensemble were carried out to determine the vapourliquid coexistence curves of cyclic alkanes from c-pentane to c-octadecane. In general, the critical temperatures and densities of the cyclic alkanes are substantially higher than those of their linear counterparts. Furthermore, the simulation data point to a maximum in the critical density for cyclic alkanes with about eight carbon atoms as also observed for the linear alkanes. 1.

Jun-seok Lee; Collin D. Wick; John M. Stubbs; J. Ilja Siepmann

2004-01-01

376

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

ScienceCinema

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

Schoenlein, Robert [Deputy Director, Advanced Light Source

2011-04-28

377

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

E-print Network

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

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

2014-01-01

378

Atomic vapor filter for two-dimensional Rayleigh imaging experiments with a narrow-band KrF excimer laser.  

PubMed

An optical transition of atomic iron can be used to build a two-dimensional absorption filter that operates in the tuning range of a narrow-band KrF excimer laser (0.05-cm(-1) bandwidth). Iron atoms with a number density of 2 10(13) cm(-3) are produced by thermal dissociation of iron pentacarbonyl [Fe(CO)(5)]. With this filter it is possible to discriminate Mie and surface-scattered light against Rayleigh scattering. For Rayleigh scattering from the exhaust gas of a methane-air flame at a measured temperature of 1970 K, the ratio of transmission for Rayleigh scattering to transmission for Mie scattering is 16.8. Single-shot scattering from the exhaust gas of a high-pressure burner is presented as an application. PMID:21127620

Glz, P; Andresen, P

1996-10-20

379

Amorphous germanium layers prepared by UV-photo-induced chemical vapour deposition  

Microsoft Academic Search

Hydrogenated amorphous germanium (a-Ge:H) films have been deposited via laser induced chemical vapour deposition (LCVD) by irradiating germane\\/helium mixtures with an ArF excimer laser beam passing parallel above Si(100) wafers, metal plates and glass substrates. The analysis of the film thicknesses by profilometry and the characterisation of the material properties by scratch testing, FTIR spectroscopy, Raman spectroscopy, and hydrogen effusion

S. Chiussi; P. Gonzlez; J. Serra; B. Len; M. Prez-Amor

1996-01-01

380

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

PubMed

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

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

2014-02-01

381

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

SciTech Connect

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

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

2011-10-15

382

A validated cold vapour-AAS method for determining mercury in human red blood cells  

Microsoft Academic Search

A cold vapour-atomic absorption spectrometry (CV-AAS) method for determining mercury in dental students and clinical teaching staff red blood cells at a dental school using amalgam as a restorative material has been validated. A number of blood samples (n = 122) from dental students in years I to V, clinical teachers in restorative dentistry and controls were collected and analysed.

O. S. Ertas; H. Tezel

2004-01-01

383

Toward an In Situ Organic and Atomic Microprobe with Laser TOF-MS  

NASA Technical Reports Server (NTRS)

We present details of a new miniature laser time-of-flight mass spectrometer (TOF-MS) with improved resolution and sensitivity, for in situ analysis of elemental, isotopic, and organic/molecular composition.

Brinckerhoff, W. B.; Cornish, T. J.; McEntire, R. W.; Cheng, A. F.; Benson, R. C.

2000-01-01

384

The ESA DUE GlobVapour Project  

NASA Astrophysics Data System (ADS)

The European Space Agency (ESA) Data User Element (DUE) project series aims at bridging the gap between research projects and the sustainable provision of Earth Observation (EO) climate data products at an information level that fully responds to the operational needs of user communities. The ultimate objective of GlobVapour is to provide long-term coherent water vapour data sets exploiting the synergistic capabilities of different EO missions aiming at improved accuracies and enhanced temporal and spatial sampling better than those provided by the single sources. The project seeks to utilize the increasing potential of the synergistic capabilities of past, existing and upcoming satellite missions (ERS-1 and -2, ENVISAT, METOP, MSG as well as relevant non-European missions and in-situ data) in order to meet the increasing needs for coherent long-term water vapour datasets required by the scientific community. GlobVapour develops, validates and applies novel water vapour climate data sets derived from various sensors. More specifically, the primary objectives of the GlobVapour project are: 1)The development of multi-annual global water vapour data sets inclusive of error estimates based on carefully calibrated and inter-calibrated radiances. 2)The validation of the water vapour products against ground based, airborne and other satellite based measurements. 3) The provision of an assessment of the quality of different IASI water vapour profile algorithms developed by the project partners and other groups. 4) The provision of a complete processing system that can further strengthen operational production of the developed products. 5) A demonstration of the use of the products in the field of climate modelling, including applying alternative ways of climate model validation using forward radiation operators. 6) The promotion of the strategy of data set construction and the data sets themselves to the global research and operational community. The ultimate goal of the DUE GlobVapour project is the preparation of recognised data sets and successful concepts that can be used to ensure a sustainable provision of such data from operational entities such as the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) Satellite Application Facility (SAF) network. Key scientific questions which GlobVapour data can contribute to are climate monitoring and attribution, assimilation of different water vapour datasets to form a consistent analysis, model process studies, evaluation of in-situ water vapour measurements, validation of climate models and reanalyses, assessing the relationship between water vapour and dynamics, research and development for operational applications and input to atmospheric reanalyses. This presentation will introduce the GlobVapour project and concept as well as the products which are the global total column water vapour (TCWV) time series from a combination of MERIS and SSM/I as well as TCWV data sets derived from the GOME/SCIAMACHY/GOME-2 and the (A)ATSR instruments. A shorter time series of water vapour profiles will be derived from a combination of IASI and SEVIRI. The retrieval and combination methods as well as first validation results will also be discussed.

Schrder, M.; ESA Due Globvapour Project Team

2010-12-01

385

Epitaxial Growth of Atomically Flat Yttrium Iron Garnet Thin Films on Gadolinium Gallium Garnet by Pulse Laser Deposition  

NASA Astrophysics Data System (ADS)

Yttrium iron garnet (YIG) is a ferrimagnetic insulator which is useful for magneto-optical, microwave, and more recently spintronic devices. Pulsed laser deposition (PLD) has emerged as a preferred technique to deposit complex oxide thin films, heterostructures, and superlattices with high quality. Deposition of YIG films using PLD has been reported by several groups. The layer-by-layer growth mode has been achieved with a high laser repetition rate. No details about surface morphology were discussed. Here we report our approach to grow YIG films with thickness ranging from 10 to 100 nm on (110)- and (111)-oriented gadolinium gallium garnet (GGG) substrates. In both orientations, we have successfully grown epitaxial YIG thin films confirmed by the patterns of the reflection high-energy electron diffraction. The magnetic properties are measured by a vibrating sample magnetometer. The in-plane easy-axis coercivity is less than 1 Oe, while the perpendicular saturation field is 2000 Oe. For both orientations, the atomic force microscopy images show that the YIG surface is extremely flat with roughness 0.6. Flat terraces are found with the atomic step height in films with both orientations. This work paves the way to engineering anisotropy of the thin films for YIG-based magnetic devices.

Lin, Tao; Tang, Chi; Shi, Jing

2013-03-01

386

Atom Interferometers  

E-print Network

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

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

2007-12-21

387

IV INTERNATIONAL CONFERENCE ON ATOM AND MOLECULAR PULSED LASERS (AMPL'99): Discharge characteristics in a nonchain HF(DF) laser  

NASA Astrophysics Data System (ADS)

It is found that for SF6hydrocarbon (deuterocarbon) mixtures having a composition typical for nonchain HF(DF) lasers, the electric field strength reduced to the partial pressure of SF6 (pSF6) in the quasistationary phase of a volume self-sustained discharge (E/pSF6)st=92 V m-1 Pa-1 is close to the known critical value (E/p)cr=89 V m-1 Pa-1, which is specified by the condition that the electron-impact ionisation rate of SF6 is equal to the rate of electron attachment to SF6 molecules. This testifies to the decisive role of these two processes and allows the use of the known approximations of the effective ionisation coefficient and the electron drift velocity for pure SF6 when calculating the discharge characteristics. The oscilloscope traces of voltage and current calculated in this approximation for lasers with apertures ranging from 4 to 27 cm deviated from the experimental data by no more than 10%.

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

2000-06-01

388

Discerning and selectively manipulating laser-trapped atoms using non-paraxial light  

E-print Network

We demonstrate that the non-paraxial character of a strongly confined light field can be used to spectrally discern and selectively manipulate two initially equivalent atomic ensembles of the same species. The technique is implemented with two symmetric linear arrays of cesium atoms, trapped on opposite sides of an optical nanofiber and separated by less than a micron. The nanofiber provides an evanescent field interface between the atoms and the guided light, where the latter exhibits a strongly position-dependent polarization. In the case of resonant interaction, this allows us to optically pump the ensembles into two distinct Zeeman states. In the case of dispersive interaction, the strong gradient of the light-induced fictitious magnetic field permits us to selectively address the ensembles with microwave radiation, thereby preparing them in distinct hyperfine states. This results in a composite fiber-coupled atomic medium with high potential for nonlinear optics at ultra-low light levels.

Mitsch, R; Albrecht, B; Schneeweiss, P; Rauschenbeutel, A

2014-01-01

389

In situ detection of potassium atoms in high-temperature coal-combustion systems using near-infrared-diode lasers  

NASA Astrophysics Data System (ADS)

Direct tunable diode laser absorption spectroscopy at 769.9 and 767.5 nm was used to measure potassium (K) atom concentrations in situ in the high temperature (up to 1650 K) flue gas of two different pulverized coal dust combustion systems (atmospheric or pressurized (12 bar)). Two laser types (Fabry-Prot (FP) and vertical-cavity surface-emitting lasers (VCSEL)) were used for the spectrometer and characterized with respect to the magnitude and linearity of their static and dynamic wavelength tuning properties. The wide continuous current-induced tuning range of the VCSEL of 20 cm -1 (compared to 1 cm -1 for the FP) make this laser ideal for species monitoring in high pressure processes. Two VCSELs were time-multiplexed to realize the simultaneous detection of the potassium D1 and D2 lines. Several oxygen absorption lines in the A-band, which are in close spectral vicinity of the K lines, were detected simultaneously, showing the possibility of multi-species detection with one laser. Using the FP-DL for the atmospheric process and the VCSEL for the high pressure process, the pressure-dependent coefficients for spectral broadening as well as a shift of the K line in the flue gas were determined to be (0.180.01) and (-0.0600.003) cm -1 per atm (at 1540 K and 11.2 bar). The total width and shift of the D1 line (11.2 bar/1540 K) were 60 and -20 GHz, respectively. The K atom concentration was determined continuously for several days in both plants under various operation conditions. Typical concentrations in the atmospheric plant were around 2 ?g m -3 with a range of 50 ng m -3-30 ?g m -3. Averaging 100 scans for each concentration value, we achieved a time resolution of 1.7 s and a detection limit of 10 ng m -3, which corresponds to a fractional absorption in the 10 -3-10 -4 range. A strong anti-correlation with the oxygen concentration could be verified. At the 12 bar plant, the concentration was again typically around 2 ?g m -3 but K levels up to 60 ?g m -3 were observed. Here, a strong dependence of the K-signal on the type of fuel could be verified.

Schlosser, E.; Fernholz, T.; Teichert, H.; Ebert, V.

2002-09-01

390

Anomalous signal from S atoms in protein crystallographic data from an X-ray free-electron laser.  

PubMed

X-ray free-electron lasers (FELs) enable crystallographic data collection using extremely bright femtosecond pulses from microscopic crystals beyond the limitations of conventional radiation damage. This diffraction-before-destruction approach requires a new crystal for each FEL shot and, since the crystals cannot be rotated during the X-ray pulse, data collection requires averaging over many different crystals and a Monte Carlo integration of the diffraction intensities, making the accurate determination of structure factors challenging. To investigate whether sufficient accuracy can be attained for the measurement of anomalous signal, a large data set was collected from lysozyme microcrystals at the newly established `multi-purpose spectroscopy/imaging instrument' of the SPring-8 ngstrom Compact Free-Electron Laser (SACLA) at RIKEN Harima. Anomalous difference density maps calculated from these data demonstrate that serial femtosecond crystallography using a free-electron laser is sufficiently accurate to measure even the very weak anomalous signal of naturally occurring S atoms in a protein at a photon energy of 7.3?keV. PMID:23633593

Barends, Thomas R M; Foucar, Lutz; Shoeman, Robert L; Bari, Sadia; Epp, Sascha W; Hartmann, Robert; Hauser, Gunter; Huth, Martin; Kieser, Christian; Lomb, Lukas; Motomura, Koji; Nagaya, Kiyonobu; Schmidt, Carlo; Strecker, Rafael; Anielski, Denis; Boll, Rebecca; Erk, Benjamin; Fukuzawa, Hironobu; Hartmann, Elisabeth; Hatsui, Takaki; Holl, Peter; Inubushi, Yuichi; Ishikawa, Tetsuya; Kassemeyer, Stephan; Kaiser, Christian; Koeck, Frank; Kunishima, Naoki; Kurka, Moritz; Rolles, Daniel; Rudek, Benedikt; Rudenko, Artem; Sato, Takahiro; Schroeter, Claus Dieter; Soltau, Heike; Strueder, Lothar; Tanaka, Tomoyuki; Togashi, Tadashi; Tono, Kensuke; Ullrich, Joachim; Yase, Satoshi; Wada, Shin Ichi; Yao, Makoto; Yabashi, Makina; Ueda, Kiyoshi; Schlichting, Ilme

2013-05-01

391

WATER VAPOUR ABSORPTION IN TERRESTRIAL ISOPODS  

Microsoft Academic Search

Summary Continuous and intermittent gravimetric measurements have identified active water vapour absorption (WVA) in three species of terrestrial Isopoda. Water activity thresholds for uptake lie in the range 0.92-0.95. Above the threshold, WVA shows non-saturated kinetics; the rectum apparently serves as a supplemen- tary avenue for fluid resorption during rapid uptake. Standardized uptake fluxes, corrected for vapour pressure deficit, can

JONATHAN C. WRIGHT; JOHN MACHIN

1990-01-01

392

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

SciTech Connect

Model calculations show that chemical reactions which take place in the active medium of a photolytically pumped iodine laser limit the efficiency with which pump photons are utilized and convert significant amounts of the starting material RI to the unwanted by-products R/sub 2/ and I/sub 2/. Laser- and rf-discharge-based methods for regenerating starting materials from by-products are evaluated experimentally. For economical operation of large iodine laser systems, CF/sub 3/I is presently the best starting material, and a pulsed rf-discharge technique is presently the best one for chemical regeneration. The absorbed energy required to regenerate one CF/sub 3/I molecule using pulsed rf-discharge techniques is 5.8 eV.

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

1980-01-01

393

Experimental and theoretical investigation of a coaxial pumped photolytic atomic bromine laser  

SciTech Connect

This paper describes the results from a combined experimental/theoretical investigation of a coaxial pumped photolytic bromine laser. A 532-nm pump was used to photodissociate IBr and produce Br*({sup 2}P{sub 1/2}) with subsequent lasing on the ({sup 2}P{sub 1/2}) {yields} ({sup 2}P{sub 3/2}) transition. Experimental results are presented for output energy, mode buildup time and small-signal gain as a function of pump energy and mirror outcoupling fraction. A simplified rate equation model was developed to predict the laser performance parameters and shows goods agreement with the laser output energy and small-signal gain.

Rafferty, B.D.; Anderson, B.T.; Glassman, J.; Miller, H.C.; Hager, G.D. [Phillips Lab., Kirtland AFB, NM (United States)] [Phillips Lab., Kirtland AFB, NM (United States); Lampson, A.I. [Logicon RDA, Albuquerque, NM (United States)] [Logicon RDA, Albuquerque, NM (United States)

1997-05-01

394

Local Atomic Configuration in Laser Synthesized Si/C/N Powders Studied by X-Ray Photoelectron Spectroscopy  

NASA Astrophysics Data System (ADS)

Nanometric Si/C/N powders have been obtained from the laser synthesis of a liquid precursor: hexamethydisilazane. The chemical composition of the products is a function of the experimental parameters: the C/N ratio in the powders is controlled in the range 0.34 to 1.34 by varying the ammonia content in the flowing gas (argon). This paper presents some results obtained by X-ray Photoelectron Spectroscopy (XPS) about the local atomic structure of these powders. The evolution of the powders after annealing treatments at 1500 and 1600 C under nitrogen atmosphere has been studied. The chemical composition deduced from XPS wide spectra axe compared with chemical analysis. From the analysis of the Si-2p core level, information about the local atomic bonding around silicon atoms are obtained. The different environments present in the system and their evolution with temperature have been deduced from the comparison with data obtained for stoichiometric compounds (SiC, Si3N4 and SiO2). The existence of local chemical disorder is shown in the as-formed powders. For powders with C/N : ? 0.6, the samples remains amorphous until 1500 C; crystallization which starts around 1500 C is total at 1600 C. The existence of C N bonds at 1500 and 1600 C is evidenced. This result is in good agreement with results obtained by neutron diffraction and X-ray absorption (XAS).

Gheorghiu, A.; Dufour, G.; Snmaud, C.; Herlin, N.; Musset, E.; Cauchetier, M.; Armand, X.

1997-03-01

395

Sensitive Doppler-Free Laser Spectroscopy Based on Degenerate Four-Wave Mixing for Isotope Analysis Using Flame Atomizers.  

NASA Astrophysics Data System (ADS)

Doppler-free flame spectrometry based on resonant degenerate four-wave mixing (DFWM) is shown to be an effective analytical tool for the determination of analytes at high spectral resolution. Optical phase conjugation is produced in flame atomizers resulting in an optical signal that is a coherent time-reversed replica of the probe beam. DFWM is a nonlinear laser spectroscopic technique that combines three beams in a nonlinear medium to produce a signal beam. Since two beams in the experimental arrangement are counterpropagating, the detected signal is Doppler free. Computer simulations of the DFWM spectral profiles show that the DFWM signal is also sub-Lorentzian even with the use of a room pressure flame atomizer. This high resolution technique is suitable for the determination of isotope ratios and hyperfine structure analysis. The degenerate four-wave mixing spectrum of barium for the transition at 18060.19 cm^ {-1} is collected with a linewidth of 0.08 cm^{-1} (FWHM) using a convenient continuously-flowing atmospheric-pressure flame atomizer. An excellent detection limit of 0.05 ng/ml for rubidium is achieved in an air/acetylene flame, while maintaining the ability to resolve the isotope structure of the transition at 780.0 nm.

Weed, Kenneth Merle

396

An assessment of vapour pressure estimation methods.  

PubMed

Laboratory measurements of vapour pressures for atmospherically relevant compounds were collated and used to assess the accuracy of vapour pressure estimates generated by seven estimation methods and impacts on predicted secondary organic aerosol. Of the vapour pressure estimation methods that were applicable to all the test set compounds, the Lee-Kesler [Reid et al., The Properties of Gases and Liquids, 1987] method showed the lowest mean absolute error and the Nannoolal et al. [Nannoonal et al., Fluid Phase Equilib., 2008, 269, 117-133] method showed the lowest mean bias error (when both used normal boiling points estimated using the Nannoolal et al. [Nannoolal et al., Fluid Phase Equilib., 2004, 226, 45-63] method). The effect of varying vapour pressure estimation methods on secondary organic aerosol (SOA) mass loading and composition was investigated using an absorptive partitioning equilibrium model. The Myrdal and Yalkowsky [Myrdal and Yalkowsky, Ind. Eng. Chem. Res., 1997, 36, 2494-2499] vapour pressure estimation method using the Nannoolal et al. [Nannoolal et al., Fluid Phase Equilib., 2004, 226, 45-63] normal boiling point gave the most accurate estimation of SOA loading despite not being the most accurate for vapour pressures alone. PMID:25105180

O'Meara, Simon; Booth, Alastair Murray; Barley, Mark Howard; Topping, David; McFiggans, Gordon

2014-09-28

397

Breakdown voltage of zinc and magnesium vapours  

NASA Astrophysics Data System (ADS)

In this paper the findings of a study into the electrical breakdown of zinc and magnesium metal vapours are reported. The interest in the breakdown of these vapours lies in the fact that there is a growing interest in producing zinc-magnesium coated articles using physical vapour deposition. For commercial scale operations which require a high power input, a disturbance by electrical breakdown of the metal vapour is unacceptable. Hence, knowledge of the breakdown voltage and pressure relation of these elements is essential in the engineering of a set-up. To determine the breakdown of these metal vapours, a Knudsen effusion cell is built. It is proven that the flow through the Knudsen cell does not change the minimum breakdown voltage or location of this minimum, and is a reliable apparatus for determining the zinc and magnesium vapour data. The outcome of the experiments show that the minimum breakdown for zinc is in agreement with the reported data in the literature, around 350 V. Magnesium has a much lower minimum breakdown voltage than that found for zinc, around 110 V. Furthermore, the locations of the minimum breakdown voltages of both zinc and magnesium are found at around 4-7 Pa m and 1.5 Pa m respectively.

Zoestbergen, E.; Commandeur, C.; Maalman, T.

2014-06-01

398

Mechanisms on the Photoelectron Angular Distributions of Atoms Ionized in Mid-Infrared Laser Fields  

NASA Astrophysics Data System (ADS)

By solving the time-dependent Schrodinger equation, we show conclusively that low energy/momenta structure in the photoelectron angular distribution originates from multiple scatterings of the tunnel-ionized electron with the ion. We also show that two conditions must be satisfied simultaneously in order to observe prominent low-energy features. First, multiple scattering of the tunnel-ionized electron wave packet is necessary. Second, tunnel ionization must dominate over multiphoton ionization. While the first condition is generally satisfied for all laser wavelengths, the second condition is satisfied only for longer laser wavelengths.

Tong, X. M.; Ranitovic, P.; Hickstein, D. D.; Murnane, M. M.; Kapteyn, H. C.; Toshima, N.

2014-04-01

399

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

E-print Network

for mode matching due to the lack of mode structure in the laser beam. Lenses were avoided as much as possible because of absorption of UV light, and chromatic abberation. All of the mirrors used were aluminum front surfaced. All lenses and vacuum... for mode matching due to the lack of mode structure in the laser beam. Lenses were avoided as much as possible because of absorption of UV light, and chromatic abberation. All of the mirrors used were aluminum front surfaced. All lenses and vacuum...

Ashe, William Monroe

2012-06-07

400

The behavior of interstitial oxygen atoms induced by F 2 laser irradiation of oxygen-rich glassy SiO 2  

Microsoft Academic Search

Interstitial oxygen atoms in glassy silicon dioxide were created by photolysis of pre-existing interstitial oxygen molecules O2 with a fluorine excimer laser (7.9 eV). The concentration of atomic oxygen interstitials was indirectly monitored by the disappearance and subsequent recovery of interstitial molecules which were monitored by their 1272 nm photoluminescence band. Most of the oxygen interstitials (>95%) are immobile at

L. Skuja; K. Kajihara; T. Kinoshita; M. Hirano; H. Hosono

2002-01-01

401

Combining high-resolution photoelectron spectroscopy and laser polarization for a study of the 4f and 5p photoionization of atomic thulium  

Microsoft Academic Search

The 4f and 5p subvalence photoionization of atomic Tm has been investigated by combining high-resolution photoelectron spectroscopy and dichroism measurements of the laser-polarized atoms. The experimental results are compared to Hartree-Fock calculations. The Tm 5p photoelectron spectrum is dominated by spin-orbit splitting whereas mixing of the final ionic states strongly influences the Tm 4f photoionization. Intermediate coupling is appropriate for

Ph Wernet; A. Verweyen; J. Schulz; B. Sonntag; K. Godehusen; R. Mller; P. Zimmermann; M. Martins

2002-01-01

402

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

E-print Network

. Demonstrated that the light mass and low surface sputtering rate of laser-cooled lithium allows for non) to provide ions for a focused ion beam (FIB) capable of non-destructive imaging. K E Y A C C O M P L I S H M-destructive imaging with a characteristic focal spot size of

403

Frequency response of an atomic resonance driven by weak free-electron-laser fluctuating pulses  

E-print Network

Motivated by recent experiments pertaining to the interaction of weak SASE-FEL pulses with atoms and molecules, we investigate the conditions under which such interactions can be described in the framework of a simple phase-diffusion model with decorrelated atom-field dynamics. The nature of the fluctuations that are inevitably present in SASE-FEL pulses is shown to play a pivotal role in the success of the decorrelation. Our analysis is performed in connection with specific recent experimental results from FLASH in the soft X-ray regime.

G M Nikolopoulos; P Lambropoulos

2014-01-20

404

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

E-print Network

mode from the #5;b#6;? #5;d#6; transition, #3;1 = #1;1 ? #4;ac, #3;2 = #1;2 ? #4;bd. #1;2#2; The resonance frequencies on the #5;a#6;? #5;c#6; and #5;b#6;? #5;d#6; tran- sitions have been labeled by #4;ac and #4;bd, respectively. In addition...;? #5;c#6; transition. In the rotating-wave approximation, the atom-laser interaction reads HL = ? #2;#5;3#5;a#6;#7;d#5;e?i#4;3t ? #2;#5;4#5;b#6;#7;c#5;e?i#4;4t + H.c. #1;3#2; Note that the Rabi frequencies #5;3= #5; 3 #5;exp#1;i#6;3#2; and #5;4 = #5...

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

2007-01-01

405

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

SciTech Connect

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

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

2011-12-15

406

INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Imaging of the spatial distribution of atoms in an optical-breakdown plasma with one-dimensional coherent hyper-Raman scattering  

Microsoft Academic Search

A technique based on coherent four-wave mixing with a hyper-Raman resonance in wide beams was developed for line-by-line reconstruction of the spatial distribution of excited atoms in a laser-produced plasma. This method was used to study the spatial distribution of excited lead atoms in an optical-breakdown plasma formed on a metal target. A comparison was made of the technique of

Denis A. Akimov; Aleksei M. Zheltikov; Nikolai I. Koroteev; R. B. Miles; A. N. Naumov; D. A. Sidorov-Biryukov; Andrei B. Fedotov

1998-01-01

407

Candidates for laser cooling of atomic anions: La{sup -} versus Os{sup -}  

SciTech Connect

This brief report is a follow-up to the recent proposal to use La{sup -} as another candidate, in addition to Os{sup -}, in laser cooling of anions, which can then be used to cool antiprotons sympathetically. Using the relativistic configuration interaction formalism, we calculate the photodetachment cross sections of the upper laser cooling state La{sup -} 5d6s{sup 2}6p {sup 3}D{sub 1} and Os{sup -} 5d{sup 6}6s{sup 2}6p {sup 6}D{sub 9/2}. Our results show that La{sup -} has a very similar two-photon detachment loss as Os{sup -}, retaining it as another promising candidate for cooling antiprotons sympathetically.

Pan, Lin; Beck, Donald R. [Physics Department, Michigan Technological University, Houghton, Michigan 49931 (United States)

2010-07-15

408

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

409

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

E-print Network

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

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

2011-08-25

410

Experimental and theoretical investigation of a coaxial pumped photolytic atomic bromine laser  

Microsoft Academic Search

This paper describes the results from a combined experimental theoretical investigation of a coaxial pumped photolytic bromine laser. A 532-nm pump was used to photodissociate IBr and produce Br*(2 P1\\/2) with subsequent lasing on the (2P1\\/2)?(2P3\\/2) transition. Experimental results are presented for output energy, mode buildup time and small-signal gain as a function of pump energy and mirror outcoupling fraction.

Brent D. Rafferty; Brian T. Anderson; Jack Glassman; Harold C. Miller; Alan I. Lampson; Gordon D. Hager

1997-01-01

411

Krypton atom and testing the limits of extreme-ultraviolet tunable-laser spectroscopy  

SciTech Connect

Measurements of several transitions in krypton carried out with a high-resolution extreme ultraviolet (xuv) laser source in 1987 were recently reanalyzed. This analysis, based on simulating the Doppler-broadened line shape of the iodine reference lines with new, greatly improved iodine reference data, yielded an order-of-magnitude improvement in the agreement between several {sup 86}Kr transition frequencies between 94.5 nm and 116.5 nm to {+-}5x10{sup -9}. The overall relative uncertainty is estimated to be {+-}6x10{sup -9}, which matches the best accuracies achieved in nanosecond short-wavelength experiments. The influence of frequency chirping in the pulsed dye amplifier chain was estimated to be rather low and to vary approximately between -7.1 MHz and +5.0 MHz for the three laser dyes used in this experiment. It is concluded that with an even more careful laser design the chirp-induced frequency shifts could be reduced to less than 1 MHz. Based on the analysis of the presumable chirp effects a correction for the {sup 86}Kr atlas by Kaufman and Humphries -0.055 53 cm{sup -1} is determined, which agrees with the result of a very recent two-photon experiment with frequency combs within just 0.000 46 cm{sup -1} (14 MHz), i.e., well within the combined errors of the three data sources involved in the intercomparison.

Trickl, T. [Forschungszentrum Karlsruhe, Institut fuer Meteorologie und Klimaforschung (IMK-IFU), Kreuzeckbahnstrasse 19, D-82467 Garmisch-Partenkirchen (Germany); Kung, A. H. [Institute of Atomic and Molecular Sciences, Academia Sinica, P.O. Box 23-166, Taipei, Taiwan 10617 (China); Lee, Y. T. [Office of the President, Academia Sinica, Nankang, Taipei (China)

2007-02-15

412

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

SciTech Connect

A volume self-sustained discharge (VSD) in iodides (C{sub 3}H{sub 7}I, C{sub 4}H{sub 9}I) and in their mixtures with SF{sub 6}, N{sub 2}, and O{sub 2} in the presence of small-scale inhomogeneities on the cathode surface is shown to develop in the form of a self-initiating volume discharge (SIVD), i.e., a volume discharge without any preionisation including discharge gaps with a strong edge enhancement of the electric field. Additions of SF{sub 6} or N{sub 2} to the iodides improves the stability and homogeneity of the SIVD, while adding up to 300 % (relative to the partial iodide pressure) of O{sub 2} to these mixtures has only an insignificant effect on the discharge stability. The possibility of SIVD initiation was modelled experimentally in a 1.5-L discharge volume. For the C{sub 4}H{sub 9}I:O{sub 2}:SF{sub 6}=0.083:0.25:0.67 mixture at a pressure of 72 Torr, the specific energy input into the discharge plasma ranged up to 130 J L{sup -1} in this geometry. A conclusion was drawn that the SIVD is promising for the production of atomic iodine in the pulsed and repetitively pulsed operating regimes of a chemical oxygen - iodine laser. (lasers)

Belevtsev, A A [Institute for High Energy Densities, Associated Institute for High Temperatures, Russian Academy of Sciences, Moscow (Russian Federation); Kazantsev, S Yu; Saifulin, A V; Firsov, K N [A.M. Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2003-06-30

413

Coupled, time-dependent treatment of the electron transfer and ionization dynamics in field-free and laser-assisted ion-atom collisions  

Microsoft Academic Search

Electron transfer and excitation processes in ion-atom collisions can be understood in terms of dynamical couplings of quasimolecular states if the collision velocity is well below the average revolution velocity of the active electrons. In this contribution, I will address the question to which extent such sub-femotsecond electronic processes can be modified by embedding the collision in a laser field.

Tom Kirchner

2003-01-01

414

Bose-Einstein condensation of a system of two-level atoms in resonant interaction with a single-running-wave-mode laser field  

E-print Network

In this thesis, we study the influence of a single-running-wave-mode laser field to the critical temperature T[] of Bose-Einstein condensation(BEC) of a system of two-level bosonic atoms. Using a simple model, we obtain the dispersion relation...

Wang, Xinfeng

2012-06-07

415

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

NASA Astrophysics Data System (ADS)

A pulsed electric discharge is the most effective means to turn chemical oxygen-iodine laser (COIL) operation into the pulse mode by fast production of iodine atoms. Experimental studies and numerical simulations are performed on a pulsed COIL initiated by an electric discharge in a mixture CF3I : N2 : O2(3X) : O2(a 1?g) flowing out of a chemical singlet oxygen generator. A transverse pulsed discharge is realized at various iodide pressures. The model comprises a system of kinetic equations for neutral and charged species, the electric circuit equation, the gas thermal balance equation and the photon balance equation. Reaction rate coefficients for processes involving electrons are repeatedly re-calculated by the electron Boltzmann equation solver when the plasma parameters are changed. The processes accounted for in the Boltzmann equation include direct and stepwise excitation and ionization of atoms and molecules, dissociation of molecules, electron attachment processes, electron-ion recombination, electron-electron collisions and second-kind collisions. The last processes are particularly important because of a high singlet oxygen concentration in gas flow from the singlet oxygen chemical generator. A conclusion is drawn about satisfactory agreement between the theory and the experiment.

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

2011-09-01

416

Four level, atomic Cs laser at 852.1 nm with a quantum efficiency above 98%: Observation of three body photoassociation  

SciTech Connect

Lasing on the D{sub 2} (6p {sup 2}P{sub 3/2}->6s {sup 2}S{sub 1/2}) transition of atomic Cs at 852.1 nm has been observed with a four level system in which the Cs 6p {sup 2}P{sub 3/2} state is pumped by the photoassociation and subsequent dissociation of Cs-rare gas collision pairs. Characterized by a quantum efficiency >98%, this laser requires no atomic precursor to the upper laser level and provides oscillation on an alkali transition inaccessible to three level, photopumped alkali laser systems. Measurements of photoabsorption and pump energy threshold in Cs-Ar-Kr mixtures reveal the influence of three body photoassociation.

Readle, J. D.; Eden, J. G. [Laboratory for Optical Physics and Engineering, Department of Electrical and Computer Engineering, University of Illinois, Urbana, Illinois 61801 (United States); Verdeyen, J. T.; Carroll, D. L. [CU Aerospace, 2100 South Oak Street, Suite 206, Champaign, Illinois 61820 (United States)

2010-07-12

417

Control of atomic single and double ionization dynamics using orthogonally polarized two-color laser pulses  

NASA Astrophysics Data System (ADS)

Single- and double-ionization of neon with orthogonally polarized two-color (OTC) laser fields is investigated using the COLTRIMS method. We study the influence of the long range Coulomb potential of the parent ion on the final momentum distribution of electrons emitted during single ionization. Furthermore, we investigate nonsequential double ionization in OTC fields and demonstrate that the electron-electron correlation is highly sensitive to the sub-cycle field shape of the OTC pulses, in agreement with recent theoretical predictions.

Zhang, L.; Xie, X.; Roither, S.; Kartashov, D.; Schffler, M.; Shafir, D.; Corkum, P. B.; Baltuka, A.; Staudte, A.; Kitzler, M.

2014-04-01

418

Determination of transient atomic structure of laser-excited materials from time-resolved diffraction data  

NASA Astrophysics Data System (ADS)

The time evolution of the Bragg peaks of photo-excited gold nanofilms is measured using transmission ultrafast electron diffraction (UED) with 3.0 MeV electron pulses and the corresponding structure evolution is calculated using two-temperature molecular dynamics (2T-MD). The good agreement obtained between the measured and calculated Bragg peaks, over the full experimental timescale, enables the lattice temperature effects and the structural changes to be disentangled for the first time. The agreement demonstrates that 2T-MD is a reliable method for solving the inverse problem of structure determination of laser irradiated metals in UED measurements.

Giret, Yvelin; Naruse, Nobuyasu; Daraszewicz, Szymon L.; Murooka, Yoshie; Yang, Jinfeng; Duffy, Dorothy M.; Shluger, Alexander L.; Tanimura, Katsumi

2013-12-01

419

Fraunhofer diffraction of atomic matter waves: electron transfer studies with a laser cooled target.  

PubMed

We have constructed an apparatus combining the experimental techniques of cold target recoil ion momentum spectroscopy and a laser cooled target. We measure angle differential cross sections in Li(+)+Na-->Li+Na(+) electron transfer collisions in the keV energy regime with a momentum resolution of 0.12 a.u. yielding an order of magnitude better angular resolution than previous measurements. We resolve Fraunhofer-type diffraction patterns in the differential cross sections. Good agreement with predictions of the semiclassical impact parameter method is obtained. PMID:11580506

van der Poel, M; Nielsen, C V; Gearba, M A; Andersen, N

2001-09-17

420

A liquid crystalline chirality balance for vapours  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

421

A liquid crystalline chirality balance for vapours  

PubMed Central

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

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

2014-01-01

422

Pulsed hollow-cathode ion lasers: pumping and lasing parameters  

SciTech Connect

Optimal discharge conditions have been experimentally found for ion lasers excited in the hollow-cathode discharge plasma by microsecond current pulses by pumping working atoms in secondkind collisions with ions and metastable buffer-gas atoms. Measurements of the output power of krypton ion and zinc-, cadmium-, mercury-, thallium-, copper-, and gallium-vapour lasers in tubes with cathodes of different diameters showed that the pulse power reaches several tens of watts, and the average power obtained with cathodes 2 cm in diameter and a length of 40 cm or more approaches 1 W. Lasing in most media is observed simultaneously at several lines (the multi-wavelength regime). Lasing on a three-component (He - Kr - Hg) mixture is realised in the multi-wavelength regime at blue, red, and IR lines.

Zinchenko, S P; Ivanov, I G

2012-06-30

423

Pulsed hollow-cathode ion lasers: pumping and lasing parameters  

NASA Astrophysics Data System (ADS)

Optimal discharge conditions have been experimentally found for ion lasers excited in the hollow-cathode discharge plasma by microsecond current pulses by pumping working atoms in secondkind collisions with ions and metastable buffer-gas atoms. Measurements of the output power of krypton ion and zinc-, cadmium-, mercury-, thallium-, copper-, and gallium-vapour lasers in tubes with cathodes of different diameters showed that the pulse power reaches several tens of watts, and the average power obtained with cathodes 2 cm in diameter and a length of 40 cm or more approaches 1 W. Lasing in most media is observed simultaneously at several lines (the multi-wavelength regime). Lasing on a three-component (He Kr Hg) mixture is realised in the multi-wavelength regime at blue, red, and IR lines.

Zinchenko, S. P.; Ivanov, I. G.

2012-06-01

424

Atomic Emission, Absorption and Fluorescence in the Laser-induced Plasma  

SciTech Connect

The main result of our efforts is the development and successful application of the theoretical model of laser induced plasma (LIP) that allows a back-calculation of the composition of the plasma (and the condensed phase) based on the observable plasma spectrum. The model has an immediate experimental input in the form of LIP spectra and a few other experimentally determined parameters. The model is also sufficiently simple and, therefore, practical. It is conveniently interfaced in a graphical user-friendly form for using by students and any laboratory personnel with only minimal training. In our view, the model opens up the possibility for absolute analysis, i.e. the analysis which requires no standards and tedious calibration. The other parts of this proposal (including plasma diagnostics) were somewhat subordinate to this main goal. Plasma diagnostics provided the model with the necessary experimental input and led to better understanding of plasma processes. Another fruitful direction we pursued was the use of the correlation analysis for material identification and plasma diagnostics. Through a number of computer simulations we achieved a clear understanding of how, where and why this approach works being applied to emission spectra from a laser plasma. This understanding will certainly improve the quality of forensic and industrial analyses where fast and reliable material identification and sorting are required.

Winefordner, J. D.

2009-01-22

425

Explosives: A microsensor for trinitrotoluene vapour  

NASA Astrophysics Data System (ADS)

Sensing devices designed to detect explosive vapours are bulky, expensive and in need of technological improvement - dogs remain the most effective detectors in the fight against terrorism and in the removal of land-mines. Here we demonstrate the deflagration of trinitrotoluene (TNT) in a small localized explosion on an uncoated piezoresistive microcantilever. This explosive-vapour sensor, which has a detection capability that is comparable to that of a dog, should enable extremely sensitive, miniature detection devices to be used on a large scale.

Pinnaduwage, L. A.; Gehl, A.; Hedden, D. L.; Muralidharan, G.; Thundat, T.; Lareau, R. T.; Sulchek, T.; Manning, L.; Rogers, B.; Jones, M.; Adams, J. D.

2003-10-01

426

Effects of ultrashort laser-pulse durations on Fano resonances in atomic spectra  

NASA Astrophysics Data System (ADS)

The Fano resonance theory is modified to account for photoionization by ultrashort laser pulses where the probability definition due to the nonlinear dependence on time is no longer valid. We employ the exact integrals over the Fourier transform of the photoionization cross section including the Fano resonances and a corrected Gaussian pulse shape that has vanishing electric field for zero frequency. Numerical results are presented for neutral helium that allow us to deduce the spectral distribution of the Fano resonance for different parameters and to identify the cases where the linear regime is invalid. Analytical approximations are given that provide a clear understanding of the linear and nonlinear regime related to the Fano parameter q , the detuned carrier frequencies, and pulse durations.

Rosmej, F. B.; Astapenko, V. A.; Lisitsa, V. S.

2014-10-01

427

Laser Safety Introduction  

E-print Network

Laser Safety #12;Introduction · A Laser is a device that controls the way energized atoms release photons. · LASER is an acronym for "Light Amplification by Stimulated Emission of Radiation" · The light emitted by a laser is non

McQuade, D. Tyler

428

Interaction of vacuum ultraviolet excimer laser radiation with fused silica: II. Neutral atom and molecule emission  

NASA Astrophysics Data System (ADS)

We report mass-resolved time-of-flight measurements of neutral Si, O, and SiO from ultraviolet-grade fused silica during pulsed 157-nm irradiation at fluences well below the threshold for optical breakdown. Although the emission intensities are strongly affected by thermal treatments that affect the density of strained bonds in the lattice, they are not consistently affected by mechanical treatments that alter the density of point defects, such as polishing and abrasion. We propose that the absorption of single 157 nm photons cleave strained bonds to produce defects that subsequently diffuse to the surface. There they react with dangling bonds to release neutral atoms and molecules. Hartree-Fock calculations on clusters containing these defects support the contention that defect interactions can yield emission. More direct emission by the photoelectronic excitation of antibonding chemical states is also supported.

George, Sharon R.; Langford, S. C.; Dickinson, J. T.

2010-02-01

429

Interaction of vacuum ultraviolet excimer laser radiation with fused silica: II. Neutral atom and molecule emission  

SciTech Connect

We report mass-resolved time-of-flight measurements of neutral Si, O, and SiO from ultraviolet-grade fused silica during pulsed 157-nm irradiation at fluences well below the threshold for optical breakdown. Although the emission intensities are strongly affected by thermal treatments that affect the density of strained bonds in the lattice, they are not consistently affected by mechanical treatments that alter the density of point defects, such as polishing and abrasion. We propose that the absorption of single 157 nm photons cleave strained bonds to produce defects that subsequently diffuse to the surface. There they react with dangling bonds to release neutral atoms and molecules. Hartree-Fock calculations on clusters containing these defects support the contention that defect interactions can yield emission. More direct emission by the photoelectronic excitation of antibonding chemical states is also supported.

George, Sharon R.; Langford, S. C.; Dickinson, J. T. [Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164-2814 (United States)

2010-02-15

430

Saturated Vapour Pressure and Refrigeration - Part I  

ERIC Educational Resources Information Center

The first part of a two-part article describes an experimental approach that can be used in teaching the concept of saturated vapour pressure. This leads to a discussion of refrigeration cycles in the second part of the article. (JR)

Bunker, C. A.

1973-01-01

431

Modelling of chemical vapour deposition for optical fibre manufacture  

Microsoft Academic Search

A study of numerical modelling has been carried out for chemical vapour deposition processes with applications to manufacture of optical fibres. Temperature distributions and thermophoretic particle deposition have been calculated for the modified chemical vapour deposition (MCVD) and the outside vapour deposition (OVD) processes. A two torch formulation and a heat flux boundary condition are used for MCVD and the

M. Choi; K. S. Park; J. Cho

1995-01-01

432

Laser induced fluorescence and vacuum ultraviolet spectroscopic studies of H-atom production in the dissociative recombination of some protonated ions  

NASA Astrophysics Data System (ADS)

Measurements were made at 300 K in two laboratories by two different methods to determine the fractional H-atom contributions (fH) to the product distributions for the dissociative recombination with electrons of protonated N2H(+), HCO(+), HCO2(+), N2OH(+), OCSH(+), H2CN(+), H3O(+), H3S(+), NH4(+), and CH5(+). The two techniques were: (1) a direct determination of the H-atom density, using vacuum UV absorption spectroscopy at 121.6 nm wavelength and (2) conversion of the H atoms to OH radicals using the reaction between H and NO2 yielding OH + NO, followed by laser-induced fluorescence to determine the OH number density. Excellent agreement was obtained between the two techniques. Values of fH varying from about 0.2 (for OCSH/+/) to 1.2 (for CH/+/) were obtained, indicating that, in some cases, recombination can lead to the ejection of two separate H atoms.

Adams, N. G.; Herd, C. R.; Geoghegan, M.; Smith, D.; Canosa, A.

1991-04-01

433

Modelling the budget of middle atmospheric water vapour isotopes  

NASA Astrophysics Data System (ADS)

A one-dimensional chemistry model is applied to study the stable hydrogen (D) and stable oxygen isotope (17O, 18O) composition of water vapour in stratosphere and mesosphere. In the troposphere, this isotope composition is determined by "physical'' fractionation effects, that are phase changes (e.g. during cloud formation), diffusion processes (e.g. during evaporation from the ocean), and mixing of air masses. Due to these processes water vapour entering the stratosphere first shows isotope depletions in D/H relative to ocean water, which are ~5 times of those in 18O/16O, and secondly is mass-dependently fractionated (MDF), i.e. changes in the isotope ratio 17O/16O are ~0.52 times of those of 18O/16O. In contrast, in the stratosphere and mesosphere "chemical'' fractionation mechanisms, that are the production of HO due to the oxidation of methane, re-cycling of H2O via the HOx family, and isotope exchange reactions considerably enhance the isotope ratios in the water vapour imported from the troposphere. The model reasonably predicts overall enhancements of the stable isotope ratios in H2O by up to ~25% for D/H, ~8.5% for 17O/16O, and ~14% for 18O/16O in the mesosphere relative to the tropopause values. The 17O/16O and 18O/16O ratios in H2O are shown to be a measure of the relative fractions of HOx that receive the O atom either from the reservoirs O2 or O3. Throughout the middle atmosphere, MDF O2 is the major donator of oxygen atoms incorporated in OH and HO2 and thus in H2O. In the stratosphere the known mass-independent fractionation (MIF) signal in O3 is in a first step transferred to the NOx family and only in a second step to HOx and H2O. In contrast to CO2, O(1D) only plays a minor role in this MIF transfer. The major uncertainty in our calculation arises from poorly quantified isotope exchange reaction rate coefficients and kinetic isotope fractionation factors.

Zahn, A.; Franz, P.; Bechtel, C.; Groo, J.-U.; Rckmann, T.

2006-06-01

434

Laser optogalvanic spectroscopy of the even-parity Rydberg states of atomic mercury  

SciTech Connect

We present new experimental data on the highly excited levels in mercury using the optogalvanic detection technique in conjunction with a dc discharge cell. The collisionally populated 6s6p {sup 3}P{sub 2} metastable level has been used as an intermediate level to access the Rydberg states using a frequency-doubled dye laser covering the wavelength region between 370 and 249 nm. The optogalvanic data reveal 6sns {sup 3}S{sub 1}(13{<=}n{<=}50), 6snd {sup 1}D{sub 2}(6{<=}n{<=}18), 6snp {sup 3}D{sub 1}(6{<=}n{<=}14), 6snd {sup 3}D{sub 2}(6{<=}n{<=}15), and 6snd {sup 3}D{sub 3}(6{<=}n{<=}59) Rydberg series. The 6sns {sup 3}S{sub 1} and 6snd {sup 3}D{sub 3} Rydberg series to such a high n value have been reported for the first time. In addition, collisionally induced parity-forbidden transitions 6snp {sup 3}P{sub 1}(44{<=}n{<=}50) have been detected.

Zia, M.A.; Baig, M.A. [Atomic and Molecular Physics Laboratory, Quaid-i-Azam University 54320 Islamabad (Pakistan)

2005-12-01

435

Numerical study of He/CF3I pulsed discharge used to produce iodine atom in chemical oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

The pulsed discharge for producing iodine atoms from the alkyl and perfluoroalky iodides (CH3I, CF3I, etc.) is the most efficient method for achieving the pulse operating mode of a chemical oxygen-iodine laser. In this paper, a one-dimensional fluid model is developed to study the characteristics of pulsed discharge in CF3I-He mixture. By solving continuity equation, momentum equation, Poisson equation, Boltzmann equation, and an electric circuit equation, the temporal evolution of discharge current density and various discharge products, especially the atomic iodine, are investigated. The dependence of iodine atom density on discharge parameters is also studied. The results show that iodine atom density increases with the pulsed width and pulsed voltage amplitude. The mixture ratio of CF3I and helium plays a more significant role in iodine atom production. For a constant voltage amplitude, there exists an optimal mixture ratio under which the maximum iodine atom concentration is achieved. The bigger the applied voltage amplitude is, the higher partial pressure of CF3I is needed to obtain the maximum iodine atom concentration.

Zhang, Jiao; Wang, Yanhui; Duo, Liping; Li, Guofu; Wang, Dezhen

2013-04-01

436

Laser cooling of dense atomic gases by collisional redistribution of radiation and spectroscopy of molecular dimers in a dense buffer gas environment  

E-print Network

We study laser cooling of atomic gases by collisional redistribution of fluorescence. In a high pressure buffer gas regime, frequent collisions perturb the energy levels of alkali atoms, which allows for the absorption of a far red detuned irradiated laser beam. Subsequent spontaneous decay occurs close to the unperturbed resonance frequency, leading to a cooling of the dense gas mixture by redistribution of fluorescence. Thermal deflection spectroscopy indicates large relative temperature changes down to and even below room temperature starting from an initial cell temperature near 700 K. We are currently performing a detailed analysis of the temperature distribution in the cell. As we expect this cooling technique to work also for molecular-noble gas mixtures, we also present initial spectroscopic experiments on alkali-dimers in a dense buffer gas surrounding.

Sa, Anne; Christopoulos, Stavros; Knicker, Katharina; Moroshkin, Peter; Weitz, Martin

2014-01-01

437

Nano-porous indium oxide transistor sensor for the detection of ethanol vapours at room temperature  

NASA Astrophysics Data System (ADS)

Porous indium oxide thin film prepared by the dip coating technique has been used in the construction of a field effect transistor. The coating solution was prepared from indium chloride precursor. The average particle size of the dip coated thin film was found to be 25 nm. Scanning electron microscopic images show the porous nature of the film, and the root mean square roughness of the film calculated using atomic force microscope was 24 nm. A transistor has been constructed by evaporating metal Aluminium as source and drain electrodes on the indium oxide active layer and employing the silicon substrate itself as a gate. The sensor response of the constructed transistor was tested with ethanol, ammonia and acetone vapours. The sensor showed good response to ethanol vapours even at 5-ppm level, and the time for response and recovery of the gas was nearly 1 min. Response to ammonia and acetone was comparatively poor. When the gate voltage was increased from 0 to 300 mV, a considerable increase in the source-drain current was observed. As the temperature of the sensing element increased, response to ethanol vapours also increased. There was nearly a linear variation in the transistor response for 100 ppm of ethanol vapours when the gate voltage was swept from 0 to 300 mV. The sensor response of the transistor increases with the gas concentration. The constructed transistor was found to be selectively sensitive to ethanol; therefore it can be implemented to work as a breath alcohol checker.

Seetha, M.; Mangalaraj, D.

2012-01-01

438

Measurement of fluorine atom concentrations and reaction rates in chemical laser systems. Final report 23 Jul 80-30 Jun 82  

Microsoft Academic Search

The line positions of all three components of the fluorine atom ground state fine structure transition have been measured by diode laser absorption spectroscopy, using a water vapor pure rotational line at 404.077\\/cm as a wavelength reference. These results imply a spin orbit splitting for fluorine of 404.142 + or - 0.005\\/cm. The results for the line positions are in

A. C. Stanton; J. C. Wormhoudt; J. W. Duff

1982-01-01

439

Atmospheric water vapour from CONT-campaigns  

NASA Astrophysics Data System (ADS)

During the last ten years, four continuous observation campaigns were performed that involved a number of international geodetic stations with co-located equipment for several space geodetic techniques. These so-called CONT-campaigns concentrated primarily on Very Long Baseline Interferometry (VLBI) measurements and observations of Global Navigation Satellite System (GNSS) signals. The analysis of these data sets allows deriving information on the amount of atmospheric water vapour, usually parameterized as so-called zenith wet delay and horizontal delay gradients. Furthermore, did several of the participating stations additionally operate ground-based microwave radiometers during these CONT-campaigns, and for some of the stations also observations from relatively nearby radiosonde launch sites are available. Time series of atmospheric water vapour can be derived also from these two techniques, too. Additionally, atmospheric water vapour information is also available from Numerical Weather Models (NWP). The different techniques are based on different measurement principles and provide results with different temporal and spatial resolution. The individual data sets are used to perform inter-technique comparisons and to assess the agreement of the results derived from the various techniques. The data are also used to derive parameters of a model describing atmospheric turbulence and approaches to handle atmospheric corrections for the space geodetic techniques are tested.

Haas, R.

2012-04-01

440

Multiple ionization of atom clusters by intense soft X-rays from a free-electron laser  

Microsoft Academic Search

Intense radiation from lasers has opened up many new areas of research in physics and chemistry, and has revolutionized optical technology. So far, most work in the field of nonlinear processes has been restricted to infrared, visible and ultraviolet light, although progress in the development of X-ray lasers has been made recently. With the advent of a free-electron laser in

H. Wabnitz; L. Bittner; A. R. B. de Castro; R. Dhrmann; P. Grtler; T. Laarmann; W. Laasch; J. Schulz; A. Swiderski; K. von Haeften; T. Mller; B. Faatz; A. Fateev; J. Feldhaus; C. Gerth; U. Hahn; E. Schneidmiller; K. Sytchev; K. Tiedtke; R. Treusch; M. Yurkov

2002-01-01

441

Two-dimensional laser-induced fluorescence-detection system for measurements of number density profiles of seed alkali atoms in MHD combustion gas plasmas  

NASA Astrophysics Data System (ADS)

A thermally assisted laser-induced fluorescence (LIF) detection system is developed to measure two-dimensional spatial profiles of number density of alkali atoms seeded in an open-cycle MHD generator, especially in the boundary layer on channel electrodes. The spatial resolution of this system is evaluated to be 1.3 mm. To assess the system, the LIF intensity from Na atoms used as a seed tracer is measured in a laminar air-acetylene flame. The detected spatial profiles of the intensity show good agreement with those of the number density of sodium atoms measured by the spectral line absorption method. The LIF intensity near the surface of a cooled metal piece placed in the acetylene flame is also measured with this system as a preliminary experiment for applying it to the boundary layer on MHD channel electrodes.

Watanabe, Y.; Ikegami, T.; Ueno, T.; Masuda, M.; Akazaki, M.

1987-09-01

442

Development of a hybrid quantum system employing a tunable high-Q superconducting microwave resonator and trapped laser-cooled atoms  

NASA Astrophysics Data System (ADS)

We present progress toward a hybrid quantum system in which microwave quanta stored in a superconducting flux qubit are coupled through a magnetic dipole interaction to laser-trapped atoms. In initial experiments, our goal will be to couple a microfabricated superconducting LC resonator to the 6.835 GHz hyperfine splitting in an ensemble of ^87Rb atoms. By trapping the atoms in the evanescent field of a 500-nm-wide optical fiber, we will seek to place them within 10 micrometers of the chip surface, where they will interact with the near-field of the microwave mode. In previous work we have demonstrated a frequency-tunable superconducting resonator having Q 100,000. [1] Here we will describe improvements in the resonator's design to reduce its sensitivity to absorbed photons, as well as the design of components to position the resonator relative to the optical fiber within a dilution refrigerator.

Hertzberg, Jared; Voigt, K.; Kim, Z.; Hoffman, J.; Grover, J.; Lee, J.; Ravets, S.; Hafezi, M.; Taylor, J.; Choudhary, A.; Anderson, J.; Lobb, C.; Orozco, L.; Rolston, S.; Wellstood, F.

2013-03-01