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1

Scalable chemical oxygen - iodine laser  

SciTech Connect

The problem of scaling chemical oxygen - iodine lasers (COILs) is discussed. The results of experimental study of a twisted-aerosol singlet oxygen generator meeting the COIL scalability requirements are presented. The energy characteristics of a supersonic COIL with singlet oxygen and iodine mixing in parallel flows are also experimentally studied. The output power of {approx}7.5 kW, corresponding to a specific power of 230 W cm{sup -2}, is achieved. The maximum chemical efficiency of the COIL is {approx}30%.

Adamenkov, A A; Bakshin, V V; Vyskubenko, B A; Efremov, V I; Il'in, S P; Ilyushin, Yurii N; Kolobyanin, Yu V; Kudryashov, E A; Troshkin, M V [Russian Federal Nuclear Center 'All-Russian Research Institute of Experimental Physics', Sarov, Nizhnii Novgorod region (Russian Federation)

2011-12-31

2

Micro Chemical Oxygen-Iodine Laser (COIL).  

National Technical Information Service (NTIS)

It has been previously proposed to improve the performance and compactness of chemical oxygen-iodine lasers (COIL) through the replacement of some of their macroscale components with arrays of higher-performing microscale (MEMS) components. In this progra...

C. Livermore-Clifford

2007-01-01

3

Supersonic cw chemical oxygen-iodine laser  

Microsoft Academic Search

Summary form only given. Supersonic continuous wave (cw) chemical oxygen-iodine lasers (COIL) have been studied for many years. By using the rotating disk O\\/sub 2\\/ generator and using supersonic gas flow instead of subsonic gas flow in the laser cavity, the laser output power has been improved. We got 5-kW laser output power with Cl flow rate at 0.3 moles\\/second.

Li Bin; Cheng Fang; Sang Feng Ting; Zhou Da Zheng; Zhuang Qi; Yang Bo Ling

1996-01-01

4

Chemical kinetics of discharge-driven oxygen-iodine lasers  

Microsoft Academic Search

Oxygen-iodine lasers that utilize electrical discharges to produce O2(a1Delta) are currently being developed. The discharge generators differ from those used in chemical oxygen-iodine lasers in that they produce significant amounts of atomic oxygen and traces of ozone. As a consequence of these differences, the chemical kinetics of the discharge laser are markedly different from those of a conventional chemical oxygen-iodine

Valeriy N. Azyazov; Ivan O. Antonov; Michael C. Heaven

2007-01-01

5

Cutting performance of a chemical oxygen-iodine laser  

Microsoft Academic Search

Chemical Oxygen-Iodine Laser (COIL) is a member of the class of high power lasers for industrial applications, including the materials processing tasks of high speed cutting and drilling. COIL technology has received considerable interest over the last several years due to its short, fiber- deliverable wavelength (1.315 microns), scalability to very high powers (tens of kilowatts, cw), and demonstrated nearly

William P. Latham; James A. Rothenflue; Charles A. Helms; Aravinda Kar; David L. Carroll

1998-01-01

6

Phillips Laboratory COIL technology overview. [Chemical oxygen-iodine laser  

Microsoft Academic Search

The basic technology and performance of the chemically dumped oxygen-iodine laser is reviewed. The performance is discussed in terms of the operation of the chemical oxygen generator, the kinetics of energy transfer from oxygen to iodine, and the extraction of power by the optical resonator. Techniques for generation of excited oxygen and iodine are reviewed. In addition advanced concepts for

K. A. Truesdell; S. E. Lamberson; G. D. Hager

1992-01-01

7

Experimental Study of Supersonic Chemical Oxygen-Iodine Laser (COIL).  

National Technical Information Service (NTIS)

A 5kW supersonic chemical oxygen-iodine laser (COIL) was constructed. A rotating mesh-type singlet-delta oxygen generator (SOG) was used that appears to be simpler, lighter in weight, and more efficient than the rotating disk SOG. An output power of 1kw f...

S. Fengting C. Fang Y. Bailing S. Yizhu J. Yuqi

1996-01-01

8

Experimental study of a CW chemical oxygen-iodine laser  

SciTech Connect

Through experimentation, a continuous wave oxygen-iodine chemical laser was achieved. When the amount of chlorine flow was 50mmol/s, the output power reached 1kW. In conjunction with this, measurements were made of beam divergence angles, investigating the relationships between beam divergence angles and power as well as cavity reflector curvature radii.

Sang, F.; Gu, C.

1995-11-21

9

Novel mixing nozzles for supersonic chemical oxygen iodine laser  

NASA Astrophysics Data System (ADS)

Mixing enhancement technique of supersonic chemical oxygen-iodine laser (COIL) is studied. The difficulty of supersonic mixing due to the compressibility of the fluid has been overcome by the introduction of streamwise vortex into the flow. The developed nozzle is a staggered array of wedges, looks like "X" letter from the side of the flow duct. Computational fluid dynamics (CFD) is employed for the design optimization of the proposed mixing nozzle. A remarkable mixing condition is found when iodine injector is located at the exit plane of the mixing nozzle. Experiments are conducted and good agreement with calculation is obtained in terms of iodine molecule distribution. A 266W of output power with chemical efficiency of 14.6% is obtained and good mixing capability of the proposed nozzle design is confirmed.

Hirata, Takayuki; Endo, Masamori; Shinoda, Kazuhiko; Osaka, Tatsuo; Nanri, Kenzo; Takeda, Shuzaburo; Fujioka, Tomoo

2003-12-01

10

Research on advanced chemical and discharge oxygen-iodine lasers  

NASA Astrophysics Data System (ADS)

Generation of singlet oxygen and atomic iodine for operation of the chemical or discharge oxygen-iodine laser (COIL/DOIL) is described, employing novel methods and device configurations proposed in our laboratory. A centrifugal spray generator of singlet oxygen was developed, based on the conventional reaction between chlorine and basic hydrogen peroxide. Recent results of theoretical and experimental investigation of the generator parameters are presented. A new conception of the discharge generator of singlet oxygen was initiated, based on a combined DC arc jet and RF discharge techniques. Principle of the generator currently developed and constructed is described. A new device configuration was designed for the alternative method of atomic iodine generation using a radiofrequency discharge decomposition of iodine compounds like CH3I or CF3I. Some recent experimental results of this research are also presented.

Kodymov, Jarmila; Jirsek, Vt; Schmiedberger, Josef; Spalek, Otomar; Censk, Miroslav

2009-02-01

11

Feasibility of high pressure operation and determination of the optimum gain zone in chemical oxygen-iodine lasers  

SciTech Connect

Use is made of a simple model to theoretically prove that there exist optimum values for small signal gains in chemical Oxygen-Iodine lasers dependent on overall system oxygen pressures. At the same time, the feasibility of chemical oxygen-iodine laser operations under high pressure is discussed. Finally, methods for determining optimum gain zones for chemical oxygen-iodine lasers are given.

Li, F.

1995-11-29

12

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

13

LASERS, ACTIVE MEDIA: Calculation of the mixing chamber of an ejector chemical oxygen --- iodine laser  

Microsoft Academic Search

Gas parameters are calculated at the outlet of the mixing chamber of an ejector chemical oxygen---iodine laser with a nozzle unit consisting of nozzles of three types, which provides a total pressure of the active medium that substantially exceeds a pressure in the generator of singlet oxygen. This technique of forming the laser active medium substantially facilitates the ejection of

M. V. Zagidullin; V. D. Nikolaev

2001-01-01

14

COIL--Chemical Oxygen Iodine Laser: advances in development and applications  

Microsoft Academic Search

Advantageous features of Chemical Oxygen-Iodine Laser (COIL) for laser technologies have increased considerably activities of international COIL communities during past ten years. They have been focused on the advanced concepts of hardware designs of the COIL subsystems, and testing and scaling-up of existing laser facilities. Prospective special applications of COIL technology, both civil and military, have received a significant attention

Jarmila Kodymova

2005-01-01

15

Calculation of the mixing chamber of an ejector chemical oxygen - iodine laser  

Microsoft Academic Search

Gas parameters are calculated at the outlet of the mixing chamber of an ejector chemical oxygen-iodine laser with a nozzle unit consisting of nozzles of three types, which provides a total pressure of the active medium that substantially exceeds a pressure in the generator of singlet oxygen. This technique of forming the laser active medium substantially facilitates the ejection of

M V Zagidullin; V D Nikolaev

2001-01-01

16

Cutting performance of a chemical oxygen-iodine laser on aerospace and industrial materials  

Microsoft Academic Search

A chemical oxygen-iodine laser (COIL) was used for cutting aluminum, titanium, inconel and copper plates. The laser was operated with a stable resonator having an intracavity aperture to produce a circular COIL beam with very few transverse modes. The multimode focal spot diameter was calculated to be 0.24 mm. The new aluminum cut was of particularly high kerf edge quality.

William P. Latham; Kip R. Kendrick; James A. Rothenflue; Aravinda Kar; David L. Carroll

2000-01-01

17

Efficient generation in a chemical oxygen iodine laser with a low buffer-gas flow rate  

Microsoft Academic Search

The efficient generation in a chemical oxygen iodine laser (COIL) with a low buffer-gas flow rate for Mach numbers M ? 1 is demonstrated. The maximum output power of the COIL was 415 W for a molecular chlorine flow rate of 20 mmol s-1, which corresponds to a chemical efficiency ?ch =23%. It is shown that the substitution of

V N Azyazov; V S Safonov; N I Ufimtsev

2002-01-01

18

Efficient generation in a chemical oxygen - iodine laser with a low buffer-gas flow rate  

Microsoft Academic Search

The efficient generation in a chemical oxygen - iodine laser (COIL) with a low buffer-gas flow rate for Mach numbers M {<=} 1 is demonstrated. The maximum output power of the COIL was 415 W for a molecular chlorine flow rate of 20 mmol s⁻¹, which corresponds to a chemical efficiency η{sub ch} =23%. It is shown that the substitution

V N Azyazov; V S Safonov; N I Ufimtsev

2002-01-01

19

Chemical oxygen-iodine laser for high-speed cutting of thick stainless steel  

Microsoft Academic Search

A high power chemical oxygen-iodine laser (COIL) at the Air Force's Phillips Laboratory was evaluated to determine its cutting capability in thick section stainless steel. The results of this experiment were used to validate a new model that describes the effects of using rectangular- shaped beams for thick section materials processing. That model, while derived in a way similar to

Joseph E. Scott; James A. Rothenflue; William P. Latham; Aravinda Kar

1996-01-01

20

Measuring the Yield of Singlet Oxygen in a Chemical Oxygen Iodine Laser (Postprint).  

National Technical Information Service (NTIS)

A critical parameter for understanding the performance of Chemical Oxygen Iodine Lasers is the yield of singlet oxygen produced by the generator. Off-Axis Integrated Cavity Output Spectroscopy (Off-Axis ICOS) has been utilized to measure the absolute dens...

J. E. McCord K. B. Hewett M. Gupta T. Owano

2006-01-01

21

Computational fluid dynamics methodologies for simulation of chemical oxygen-iodine laser flowfields  

Microsoft Academic Search

Simulation of chemical lasers such as the chemical oxygen-iodine laser (COIL) is of timely interest due to the recent acceleration of the airborne laser military research program and ongoing commercial development programs. As a part of these efforts, a 3-D COIL simulation model was developed based on the Computational Fluid Dynamics (CFD) code GASP which solves the conservative, finite-volume formulation

Timothy John Madden

1997-01-01

22

Modeling of high-pressure O2(1^) generators for chemical oxygen-iodine lasers  

Microsoft Academic Search

A theoretical model is developed for chemical generators producing O2(1(Delta) ) at high pressure. Such generators are especially important for supersonic chemical oxygen-iodine lasers. The model treats different types of generators, e.g., bubble column, film, aerosol, and jet generators. The main factor affecting the O2(1(Delta) ) yield under high pressure is liquid-phase quenching enhanced by depletion of HO2- ions near

B. D. Barmashenko; Salman Rosenwaks

1993-01-01

23

GENETIC ALGORITHMS AND OPTIMIZING CHEMICAL OXYGEN-IODINE LASERS  

Microsoft Academic Search

This paper presents results from the first known application of the genetic algorithm (GA) technique for optimizing the performance of a laser system (chemical, solid-state, or gaseous). The effects of elitism, single point and uniform crossover, creep mutation, different random number seeds, population size, niching and the number of children per pair of parents on the performance of the GA

David L. Carroll

1996-01-01

24

A pared-down gas-phase kinetics for the chemical oxygen-iodine laser medium  

NASA Astrophysics Data System (ADS)

Kinetic data obtained in the last decade has resulted in revisions of some mechanisms of excitation and deactivation of excited states in the chemical oxygen-iodine laser (COIL) medium. This review considers new kinetic data and presents analyses of the mechanisms of pumping and quenching of electronically and vibrationally excited states in the oxygen-iodine laser media. An effective three-level model of I2 molecule excitation and relaxation has been developed. The calculated effective rate constants for deactivation of I2(X,11 ? ? ? 24) by O2, N2, He and CO2 are presented. A simplified kinetic package for the COIL active medium is recommended. This model consists of a 30-reaction set with 14 species. The results of calculations utilizing simplified model are in good agreement with the experimental data.

Pichugin, S. Yu.; Heaven, M. C.

2013-11-01

25

Calculation of the mixing chamber of an ejector chemical oxygen - iodine laser  

SciTech Connect

Gas parameters are calculated at the outlet of the mixing chamber of an ejector chemical oxygen-iodine laser with a nozzle unit consisting of nozzles of three types, which provides a total pressure of the active medium that substantially exceeds a pressure in the generator of singlet oxygen. This technique of forming the laser active medium substantially facilitates the ejection of the exhaust gas to the atmosphere by using a diffuser and single-stage vacuum systems based on water circulating pumps. (lasers, active media)

Zagidullin, M V; Nikolaev, V D [Samara Branch of the P.N. Lebedev Physics Institute, Russian Academy of Sciences, Samara (Russian Federation)

2001-06-30

26

LASERS: Efficient generation in a chemical oxygen --- iodine laser with a low buffer-gas flow rate  

Microsoft Academic Search

The efficient generation in a chemical oxygen --- iodine laser (COIL) with a low buffer-gas flow rate for Mach numbers M <= 1 is demonstrated. The maximum output power of the COIL was 415 W for a molecular chlorine flow rate of 20 mmol s-1, which corresponds to a chemical efficiency etach =23%. It is shown that the substitution of

V. N. Azyazov; V. S. Safonov; N. I. Ufimtsev

2002-01-01

27

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

28

Test bed for a high throughput supersonic chemical oxygen - iodine laser  

SciTech Connect

The paper reports the development of a test bed for a chemical oxygen - iodine laser based on a high throughput jet flow singlet oxygen generator (JSOG). The system provides vertical singlet oxygen extraction followed by horizontal orientation of subsequent subsystems. This design enables the study of flow complexities and engineering aspects of a distributed weight system as an input for mobile and other platform-mounted systems developed for large scale power levels. The system under consideration is modular and consists of twin SOGs, plenum and supersonic nozzle modules, with the active medium produced in the laser cavity. The maximal chlorine flow rate for the laser is {approx}1.5 mole s{sup -1} achieving a typical chemical efficiency of about 18%. (lasers)

Singhal, Gaurav; Mainuddin; Rajesh, R; Varshney, A K; Dohare, R K; Kumar, Sanjeev; Singh, V K; Kumar, Ashwani; Verma, Avinash C; Arora, B S; Chaturvedi, M K; Tyagi, R K; Dawar, A L

2011-05-31

29

Chemical oxygen-iodine laser with atomic iodine generated in a separate reactor  

NASA Astrophysics Data System (ADS)

The chemical oxygen-iodine laser (COIL) with a chemical method of atomic iodine generation was studied. Two methods of atomic iodine generation were proposed and developed. They are based on fast reactions of gaseous hydrogen iodide with chemically produced chlorine or fluorine atoms. Atomic iodine formation via Cl atoms we studied earlier by mixing of reaction gases directly in the primary O2(1?g) flow in COIL. A revealed oxidation of HI by singlet oxygen and the O2(1?g) quenching by some reaction product, however, reduced the attainable laser gain. This problem could be avoided by atomic iodine generation in separate reactors with following injection of atomic iodine into the primary O2(1?g) flow. Gain measurements using this arrangement are presented in this paper. New experimental results on atomic iodine production via F atoms are also summarized. Using of reactive gases commercially available in pressure cylinders is the main advantage of this method.

palek, Otomar; Jirsek, Vt; ?ensk, Miroslav; Kodymova, Jarmila; Pickova, Irena; Jakubec, Ivo

2006-05-01

30

Cutting performance of a chemical oxygen-iodine laser on aerospace and industrial materials  

NASA Astrophysics Data System (ADS)

A chemical oxygen-iodine laser (COIL) was used for cutting aluminum, titanium, inconel and copper plates. The laser was operated with a stable resonator having an intracavity aperture to produce a circular COIL beam with very few transverse modes. The multimode focal spot diameter was calculated to be 0.24 mm. The new aluminum cut was of particularly high kerf edge quality. These COIL cutting data are compared with an existing theoretical laser cutting model. Using thermophysical data for aluminum, titanium,l inconel and copper, this theory agrees very well with the data. To test the versatility of the model, the effects of different assumptions are examined; different assumptions produced very little effect on model predictions at high cutting speeds and a small difference at very slow cutting speeds. Overall, the theoretical model provides good agreement with experiments for a wide variety of metals.

Latham, William P.; Kendrick, Kip R.; Rothenflue, James A.; Kar, Aravinda; Carroll, David L.

2000-01-01

31

Pulse-periodic chemical oxygen-iodine laser with active medium formation by volumetric electric discharge  

NASA Astrophysics Data System (ADS)

The paper describes a study of pulse-periodic operation of a chemical oxygen-iodine laser. The generator in use was of the jet type with high chlorine utilization degree (>=97%). Atomic iodine was released by dissociating methyl-iodide (CH3I) in volumetric electric discharge. Steady lasing was achieved at a repetition rate up to 30 Hz. The emission energy attained per individual pulse in a train was 1.1 J at a pulse energy repeatability of (35) % and a specific energy extraction from the active medium of 1.7 J/L. The lasing pulse duration depended on the concentration of methyl-iodide and the energy deposited into discharge. The minimal half-height duration of pulses was achieved as 10 ?m at a concentration of atomic iodine in the laser cavity ~1*1015 cm-3.

Velikanov, S. D.; Gorelov, V. G.; Gostev, I. V.; Ireshev, Ye. V.; Kalinovsky, V. V.; Komissarov, I. A.; Konovalov, V. V.; Konovalov, I. V.; Mikhalkin, V. N.; Nikolaev, V. D.; Sevryugin, I. V.; Smirnov, A. V.; Sobolev, R. E.; Shornikov, L. N.

2007-05-01

32

Use of basic deuterium peroxide in the chemical oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

The chemical oxygen-iodine laser (COIL) uses a reaction of gaseous chorine and aqueous solution of basic oxygen peroxide (BHP) to produce oxygen singlet delta molecules, O2(1(Delta) ). Quenching of O2(1(Delta) ) during its extraction from the BHP solution and quenching of excited atomic iodine I* by water vapor from the O2(1(Delta) ) production process are well-known parasitic effects in COIL. This paper shows that both of these effects can be significantly reduced by replacing the hydrogen 1H1 isotope atoms in BHP by the 1H2 isotope atoms. In addition to restoring laser power lost to parasitic quenching, use of basic deuterium peroxide (BDP) rather than BHP is expected to allow generation of O2(1(Delta) ) at elevated temperature. This approach promises to save refrigerant, reduce the risk of BDP freezing, and delay precipitation of salt form BDP solution. Methods for producing BDP are outlined.

Vetrovec, John; Yang, Tien T.; Copeland, Drew A.

2000-05-01

33

Chemical oxygen-iodine laser (COIL) for the dismantlement of nuclear facilities  

NASA Astrophysics Data System (ADS)

The dismantlement of obsolete nuclear facilities is a major challenge for both the US Department of Energy and nuclear power utilities. Recent demonstrations have shown that lasers can be highly effective for size reduction cutting, especially for the efficient storage and recycling of materials. However, the full benefits of lasers can only be realized with high average power beams that can be conveniently delivered, via fiber optics, to remote and/or confined areas. Industrial lasers that can meet these requirements are not available now or for the foreseeable future. However, a military weapon laser, a Chemical Oxygen Iodine Laser (COIL), which has been demonstrated at over a hundred kilo Watts, could be adapted to meet these needs and enable entirely new industrial applications. An 'industrialized' COIL would enable rapid sectioning of thick and complex structures, such as glove boxes, reactor vessels, and steam generators, accelerating dismantlement schedules and reducing worker hazards. The full advantages of lasers in dismantlement could finally be realized with a portable COIL which is integrated with sophisticated robotics. It could be built and deployed in less than two years, breaking the paradigm of labor-intensive dismantlement operations and cutting processing times and costs dramatically.

Hallada, Marc R.; Seiffert, Stephan L.; Walter, Robert F.; Vetrovec, John

2000-05-01

34

Parametric study of an efficient supersonic chemical oxygen-iodine laser\\/jet generator system operating without buffer gas  

Microsoft Academic Search

A detailed experimental study of an efficient supersonic chemical oxygen-iodine laser is presented. The laser is energized by a jet-type singlet oxygen generator, operated without primary buffer gas and applies simple nozzle geometry and transonic mixing of iodine and oxygen. Output power of 190 W with chemical efficiency of 18% was obtained in a 5-cm gain length for Cl2 flow

D. Furman; B. D. Barmashenko; S. Rosenwaks

1998-01-01

35

Quantitative determination of oxygen yield in a chemical oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

With the advent of the Airborne Laser program, the emphasis of chemical oxygen-iodine laser (COIL) research has shifted toward improving the overall efficiency. A key component of COIL is the singlet-oxygen generator (SOG). To asses the efficiency of the SOG an accurate method of determining the yield of O2((alpha) 1(Delta) g),[O2((alpha) 1(Delta) g)]/[O2(total)] where [O2(total)]equals[O2((alpha) 1(Delta) g)]+[O2(X3(Sigma) g-)], has been developed. Absorption measurements of ground-state oxygen utilizing the magnetic-dipole transition, O2(X3(Sigma) g-) at 763 nm, have been obtained using a diode laser in conjunction with a multiple-pass Herriot-cell on a 10 kW class supersonic SOIL (RADICL). When RADICL is configured with a 0.35' throat, 15' diskpack, and a medium volume transition duct, with a diluent ratio (He:O2) of 3:1, the yield of O2((alpha) 1(Delta) g) in the diagnostic duct is 0.41 +/- 0.02.

Kendrick, K. R.; Helms, Charles A.; Quillen, B.; Copland, R. J.

1998-05-01

36

Two-dimensional source flow gain model for the chemical oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

A source flow gain model for optical extraction from the chemical oxygen-iodine laser medium is presented. In this model the gas dynamics of the reactive flow through the optical cavity, transverse to the optical axis, is described by the two-dimensional boundary-layer approximation to the full Navier-Stokes equations. The appropriate mass continuity, species, momentum, and energy conservation equations in cylindrical polar coordinates are presented and discussed. The gas kinetics are described by a reduced set of fourteen reactions among nine chemical species and includes pumping of the upper laser level by O2(1(Delta) ), deactivation by water and energy pooling with O2(1(Delta) ), and the Heidner molecular I2 dissociation mechanism. Stimulated emission on the 3 YLD 4 hyperfine transition of atomic iodine is described by a generalized version of the Zagidullian gain model which includes finite hyperfine relaxation of the 2P1/2 and 2P3/2 iodine sublevels, velocity cross-relaxation of the iodine atoms, and allows for incomplete I2 dissociation. The model is illustrated by application to a laboratory-sized device and the effects of the boundary layer upon the gas flow, I2 dissociation, O2(1(Delta) ) fraction, small signal gain, optical extraction, and the medium homogeneity are examined.

Copeland, Drew A.; Yang, Tien T.

1997-05-01

37

Theoretical and experimental studies of thick-section cutting with a chemical oxygen-iodine laser (COIL)  

Microsoft Academic Search

A simple mathematical model of thick-section stainless steel cutting with a high power chemical oxygen-iodine laser (COIL) is presented and compared with experimental results obtained with a 10-kilowatt COIL at the US Air Force`s Phillips Laboratory. This model uses a lumped-parameter technique to relate the cutting kerf depth with various process parameters and can be used to predict scaled laser

A. Kar; J. E. Scott; W. P. Latham

1996-01-01

38

Ejector Chemical Oxygen-Iodine Laser with Supersonic Nozzle Bank Based on a Trip-Jet Mixing System  

Microsoft Academic Search

Nozzle banks for an ejector chemical oxygen-iodine laser consisting of two-dimensional slit nozzles with a trip-jet mixing system were tested in the cold- and hot-flow operation regimes. Horizontal Pitot scan experiments demonstrated that the mixing ability of the trips is excellent. The Mach number of the mixed flow was approximately 3. Gain measurements were conducted, and the results of these

Kazuyoku Tei; Kazuhiko Horioka; Mitsuo Nakajima; Daichi Sugimoto; Goro Watanabe; Shigeki Muto; Tomoo Fujioka

2008-01-01

39

The I2 dissociation mechanisms in the chemical oxygen-iodine laser revisited  

NASA Astrophysics Data System (ADS)

The recently suggested mechanism of I2 dissociation in the chemical oxygen-iodine laser (COIL) [K. Waichman, B. D. Barmashenko, and S. Rosenwaks, J. Appl. Phys. 106, 063108 (2009); and J. Chem. Phys. 133, 084301 (2010)] was largely based on the suggestion of V. N. Azyazov, S. Yu. Pichugin, and M. C. Heaven [J. Chem. Phys. 130, 104306 (2009)] that the vibrational population of O2(a) produced in the chemical generator is high enough to play an essential role in the dissociation. The results of model calculations based on this mechanism agreed very well with measurements of the small signal gain g, I2 dissociation fraction F, and temperature T in the COIL. This mechanism is here revisited, following the recent experiments of M. V. Zagidullin [Quantum Electron. 40, 794 (2010)] where the observed low population of O2(b, v = 1) led to the conclusion that the vibrational population of O2(a) at the outlet of the generator is close to thermal equilibrium value. This value corresponds to a very small probability, ~0.05, of O2(a) energy pooling to the states O2(X,a,b, v > 0). We show that the dissociation mechanism can reproduce the experimentally observed values of g, F, and T in the COIL only if most of the energy released in the processes of O2(a) energy pooling and O2(b) quenching by H2O ends up as vibrational energy of the products, O2(X,a,b), where the vibrational states v = 2 and 3 are significantly populated. We discuss possible reasons for the differences in the suggested vibrational population and explain how these differences can be reconciled.

Waichman, K.; Barmashenko, B. D.; Rosenwaks, S.

2012-06-01

40

Analysis of lasing in chemical oxygen-iodine lasers with unstable resonators using a geometric-optics model.  

PubMed

A simple geometric-optics model is developed that describes the power extraction in chemical oxygen-iodine lasers (COILs) with unstable resonators. The positive and negative branch unstable resonators with cylindrical mirrors that were recently used in COILs are studied theoretically. The optical extraction efficiency, spatial distributions of the intracavity radiation intensity in the flow direction, and the intensity in the far field are calculated for both kinds of resonator as a function of both the resonator and the COIL parameters. The optimal resonator magnifications that correspond to the maximum intensity in the far field are found. PMID:19412214

Barmashenko, Boris D

2009-05-01

41

Chemical Oxygen-Iodine Laser Diluted by CO2/N2 Buffer Gases with a Cryosorption Vacuum Pump  

NASA Astrophysics Data System (ADS)

Experiments were carried out on a verti-chemical oxygen-iodine laser (COIL), which was designed for N2 and energized by a square-pipe jet singlet oxygen generator (JSOG). A cryosorption vacuum pump was used as the pressure recovery system for CO2 and N2 buffer gases. The output power with CO2 was 27.3% lower than that with N2, but the zeolite bed showed an adsorption capacity threefold higher for CO2 than for N2 in the continuous operation with a Cl2 flow rate of 155 mmol/s and a total flow rate of 430 3 mmol/s.

Xu, Mingxiu; Sang, Fengting; Jin, Yuqi; Fang, Benjie; Chen, Fang; Geng, Zicai; Li, Yongzhao

2008-11-01

42

A simplified analytic model for gain saturation and power extraction in the flowing chemical oxygen-iodine laser  

SciTech Connect

This paper describes the development of a simplified saturation model (SSM) for predicting power extraction from a chemical oxygen-iodine laser (COIL). Using the Fabry-Perot gain saturation assumption, analytic expressions for COIL extraction efficiency are presented for both constant-density and variable-density cavity conditions. The model treats mirror scattering, nonsaturable distributed losses, and diffractive losses from the mode-limiting aperture and is shown to be in excellent agreement with experimental COIL power extraction data. A comparison of the model with the Rigrod power extraction model is presented showing that the Rigrod model accurately predicts COIL extraction efficiency only in the limit that the COIL device no longer behaves as a transfer laser.

Hager, G.D.; Helms, C.A.; Truesdell, K.A. [Phillips Lab., Kirtland AFB, NM (United States); Plummer, D.; Erkkila, J.; Crowell, P. [Logicon RDA, Albuquerque, NM (United States)

1996-09-01

43

CONTROL OF LASER RADIATION PARAMETERS: Enhancement of the efficiency and control of emission parameters of an unstable-resonator chemical oxygeniodine laser  

NASA Astrophysics Data System (ADS)

The outlook is considered for the development of a high-power supersonic flowing chemical oxygeniodine laser operating as an amplifier and controlled by radiation from a master oscillator by using an unstable resonator with a hole-coupled mirror. The influence of the seed radiation intensity, the coupling-hole diameter, the active-medium length, and the magnification factor on the parameters of laser radiation is analysed. It is shown that the use of such resonators is most advisable in medium-power oxygeniodine lasers for which classical unstable resonators are inefficient because of their low magnification factors. The use of unstable resonators with a hole-coupled mirror and injection provides the control of radiation parameters and a considerable increase in the output power and brightness of laser radiation.

Boreisho, A. S.; Lobachev, V. V.; Savin, A. V.; Strakhov, S. Yu; Trilis, A. V.

2007-07-01

44

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

NASA Astrophysics Data System (ADS)

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

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

2003-06-01

45

PHYSICAL PROCESSES IN LASERS AND CONTROL OF LASER RADIATION PARAMETERS: Control of the duration of optical pulses from an oxygen-iodine chemical laser  

NASA Astrophysics Data System (ADS)

It is shown that long radiation pulses needed in applications of lasers in technology may be emitted efficiently by an oxygen-iodine chemical laser. Slow photolysis can increase the output pulse duration to approximately 1 ms while retaining a high efficiency. Calculations yield the dependence of the lasing characteristics on all the parameters of interest. It is demonstrated that at high active medium pressures (up to 100 Torr) and low iodine concentrations, the pulse duration may be regulated with a high specific output energy and a high photolysis efficiency.

Zagidullin, M. V.; Zaikin, A. P.; Igoshin, Valerii I.

1989-04-01

46

Review of the simple model for metal cutting with the chemical oxygen-iodine laser  

Microsoft Academic Search

The COIL has drawn considerable attention owing to its short, fiber-deliverable wavelength, scalability to very high powers, and nearly diffraction-limited optical quality. These unique abilities make it an ideal candidate for rapid cutting of thick metals and other laser materials processing applications. Cutting experiments have been conducted at the Air Force Research Laboratory Chemical Laser Facility for a number of

William P. Latham; Aravinda Kar

2000-01-01

47

Review of the simple model for metal cutting with the chemical oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

The COIL has drawn considerable attention owing to its short, fiber-deliverable wavelength, scalability to very high powers, and nearly diffraction-limited optical quality. These unique abilities make it an ideal candidate for rapid cutting of thick metals and other laser materials processing applications. Cutting experiments have been conducted at the Air Force Research Laboratory Chemical Laser Facility for a number of metals including stainless steel, nickel, copper, titanium and aluminum. A simple model for the cutting performance has been very successful in predicting the cutting sped and depth for most of these materials. Different assumptions of this model produce very little effect on the model predictions at high cutting speeds an a small difference at very slow cutting speeds. Additional physical effects such as the effects of vaporization, which can be significant at slow cutting speeds when cutting very thick sections, is incorporated into the model. This paper demonstrates how various assumptions within the derivation of the model can lead to different forms of the scaling law.

Latham, William P.; Kar, Aravinda

2000-01-01

48

Kinetic-fluid dynamics modeling of I{sub 2} dissociation in supersonic chemical oxygen-iodine lasers  

SciTech Connect

The mechanism of I{sub 2} dissociation in supersonic chemical oxygen-iodine lasers (COILs) is studied applying kinetic-fluid dynamics modeling, where pathways involving the excited species I{sub 2}(X {sup 1}SIGMA{sub g}{sup +},10<=v<25), I{sub 2}(X {sup 1}SIGMA{sub g}{sup +},25<=v<=47), I{sub 2}(A{sup '} {sup 3}PI{sub 2u}), I{sub 2}(A {sup 3}PI{sub 1u}), O{sub 2}(X {sup 3}SIGMA{sub g}{sup -},v), O{sub 2}(a {sup 1}DELTA{sub g},v), O{sub 2}(b {sup 1}SIGMA{sub g}{sup +},v), and I({sup 2}P{sub 1/2}) as intermediate reactants are included. The gist of the model is adding the first reactant and reducing the contribution of the second as compared to previous models. These changes, recently suggested by Azyazov, et al. [J. Chem. Phys. 130, 104306 (2009)], significantly improve the agreement with the measurements of the gain in a low pressure supersonic COIL for all I{sub 2} flow rates that have been tested in the experiments. In particular, the lack of agreement for high I{sub 2} flow rates, which was encountered in previous models, has been eliminated in the present model. It is suggested that future modeling of the COIL operation should take into account the proposed contribution of the above mentioned reactants.

Waichman, K. [Department of Physics, NRCN, P.O. Box 9001, Beer Sheva 89140 (Israel); Barmashenko, B. D.; Rosenwaks, S. [Department of Physics, Ben-Gurion University of the Negev, Beer Sheva 84105 (Israel)

2009-09-15

49

Deactivation rate of I{sub 2} molecules (X, v {>=} 30) in the medium of a chemical oxygen-iodine laser  

SciTech Connect

The effective deactivation rate constants are calculated for I{sub 2}(X) molecules at vibrational levels with v {>=} 30 colliding with N{sub 2} and O{sub 2} molecules in the medium of a chemical oxygen-iodine laser. The calculated constants (4x10{sup -12} cm{sup 3} s{sup -1} and 3x10{sup -12} cm{sup 3} s{sup -1}) are less by half plus than the corresponding constants found earlier in the paper of Lawrence et al., where the dissociation of I{sub 2} was neglected in calculations. (lasers, active media)

Pichugin, S Yu [Samara Branch of the P. N. Lebedev Physics Institute, Russian Academy of Sciences, Samara (Russian Federation)

2008-08-31

50

FUNDAMENTAL AREAS OF PHENOMENOLOGY (INCLUDING APPLICATIONS): Pulse Operation of Chemical Oxygen-Iodine Laser by Pulsed Gas Discharge with the Assistance of Spark Pre-ionization  

NASA Astrophysics Data System (ADS)

The continuous wavelength chemical oxygen-iodine laser can be turned into pulse operation mode in order to obtain high energy and high pulse power. We propose an approach to produce iodine atoms instantaneously by pulsed gas discharge with the assistance of spark pre-ionization to achieve the pulsed goal. The influence of spark pre-ionization on discharge homogeneity is discussed. Voltage-current characteristics are shown and discussed in existence of the pre-ionization capacitor and peaking capacitor. The spark pre-ionization and peaking capacitor are very helpful in obtaining a stable and homogeneous discharge. The lasing is achieved at the total pressure of 2.2-2.9kPa and single pulse energy is up to 180 mJ, the corresponding specific output energy is 1.0 J/L.

Li, Guo-Fu; Yu, Hai-Jun; Duo, Li-Ping; Jin, Yu-Qi; Wang, Jian; Sang, Feng-Ting; Fang, Ben-Jie; Wang, De-Zhen

2009-11-01

51

The electric oxygen-iodine laser: Chemical kinetics of O2(a 1 ?) production and I(2P1\\/2) excitation in microwave discharge systems  

Microsoft Academic Search

Generation of singlet oxygen metastables, O2(a 1 ?), in an electric discharge plasma offers the potential for development of compact electric oxygen-iodine laser (EOIL) systems using a recyclable, all-gas-phase medium. The primary technical challenge for this concept is to develop a high-power, scalable electric discharge configuration that can produce high yields and flow rates of O2(a) to support I( 2

W. T. Rawlins; S. Lee; W. J. Kessler; D. B. Oakes; L. G. Piper; S. J. Davis

52

The electric oxygen-iodine laser: chemical kinetics of O2(a1Delta) production and I(2 P1\\/2) excitation in microwave discharge systems  

Microsoft Academic Search

Generation of singlet oxygen metastables, O2(a1Delta), in an electric discharge plasma offers the potential for development of compact electric oxygen-iodine laser (EOIL) systems using a recyclable, all-gas-phase medium. The primary technical challenge for this concept is to develop a high-power, scalable electric discharge configuration that can produce high yields and flow rates of O2(a) to support I(2P1\\/2->2P3\\/2) lasing at high

W. T. Rawlins; S. Lee; W. J. Kessler; D. B. Oakes; L. G. Piper; S. J. Davis

2006-01-01

53

Excited states in the active media of oxygen - iodine lasers  

SciTech Connect

A review of investigations of kinetic processes in active media oxygen - iodine lasers (OILs) performed in the last decade is presented. The mechanisms of pumping and quenching of electronically and vibrationally excited O{sub 2} and I{sub 2} molecules are considered, and dissociation mechanisms of I{sub 2} in the active medium of the OIL are analysed. The values of kinetic constants of processes proceeding in the active media of OILs are recommended. (review)

Azyazov, V N [Samara Branch of the P.N. Lebedev Physical Institute, Russian Academy of Sciences, Samara (Russian Federation)

2009-11-30

54

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

55

Test bench for studying the outlook for industrial applications of an oxygen-iodine laser  

SciTech Connect

We report the development and tests of a chemical oxygen-iodine laser test bench based on a twisted-aerosol-flow singlet-oxygen generator and a supersonic laser model for studying the outlook for industrial applications of this laser. The maximal output power of the laser is {approx}65 kW (the average power is {approx}50 kW), corresponding to a specific output power of {approx}110 W cm{sup -2}. The maximal chemical efficiency is {approx}34%. (letters)

Adamenkov, A A; Bakshin, V V; Bogachev, A V; Buryak, E V; Vdovkin, L A; Velikanov, S D; Vyskubenko, B A; Garanin, Sergey G; Gorbacheva, E V; Grigorovich, Sergei V; Il'in, S P; Il'kaev, R I; Ilyushin, Yurii N; Kalashnik, A M; Kolobyanin, Yu V; Leonov, M L; Svischev, V V; Troshkin, M V [Russian Federal Nuclear Center 'All-Russian Scientific Research Institute of Experimental Physics', Sarov, Nizhnii Novgorod Region (Russian Federation)

2007-07-31

56

Analytic study of the chain dark decomposition reaction of iodides - atomic iodine donors - in the active medium of a pulsed chemical oxygen-iodine laser: 2. Limiting parameters of the branching chain dark decomposition reaction of iodides  

SciTech Connect

The final stages in the development of a branching chain decomposition reaction of iodide in the active medium of a pulsed chemical oxygen-iodine laser (COIL) are analysed. Approximate expressions are derived to calculate the limiting parameters of the chain reaction: the final degree of iodide decomposition, the maximum concentration of excited iodine atoms, the time of its achievement, and concentrations of singlet oxygen and iodide at that moment. The limiting parameters, calculated by using these expressions for a typical composition of the active medium of a pulsed COIL, well coincide with the results of numerical calculations. (active media)

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

2009-08-31

57

Oxygen-iodine ejector laser with a centrifugal bubbling singlet-oxygen generator  

SciTech Connect

It is shown that if a supersonic oxygen-iodine ejector laser is fed by singlet oxygen from a centrifugal bubbling generator operating at a centrifugal acceleration of {approx}400g, the laser output power achieves a value 1264 W at a chemical efficiency of 24.6% for an alkaline hydrogen peroxide flow rate of 208 cm{sup 3}s{sup -1} and a specific chlorine load of 1.34 mmol s{sup -1} per square centimetre of the bubble layer. (lasers)

Zagidullin, M V; Nikolaev, V D; Svistun, M I; Khvatov, N A [Samara Branch of the P.N. Lebedev Physics Institute, Russian Academy of Sciences, Samara (Russian Federation)

2005-10-31

58

Analytic study of the chain dark decomposition reaction of iodides - atomic iodine donors - in the active medium of a pulsed chemical oxygen-iodine laser: 1. Criteria for the development of the branching chain dark decomposition reaction of iodides  

SciTech Connect

The scheme of chemical processes proceeding in the active medium of a pulsed chemical oxygen-iodine laser (COIL) is analysed. Based on the analysis performed, the complete system of differential equations corresponding to this scheme is replaced by a simplified system of equations describing in dimensionless variables the chain dark decomposition of iodides - atomic iodine donors, in the COIL active medium. The procedure solving this system is described, the basic parameters determining the development of the chain reaction are found and its specific time intervals are determined. The initial stage of the reaction is analysed and criteria for the development of the branching chain decomposition reaction of iodide in the COIL active medium are determined. (active media)

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

2009-02-28

59

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

NASA Astrophysics Data System (ADS)

Laser-induced fluorescence is used for measuring the concentration of iodine molecules at the output of an electric-discharge generator of atomic iodine. Methyl iodide CH3I is used as the donor of atomic iodine. The fraction of iodine extracted from CH3I in the generator is ~50%. The optimal operation regimes are found in which 80%90% of iodine contained in the output flow of the generator was in the atomic state. This fraction decreased during the iodine transport due to recombination and was 20%30% at the place where iodine was injected into the oxygen flow. The fraction of the discharge power spent for dissociation was ~3%.

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

2009-01-01

60

Theoretical research of alpha-RF discharge in slab oxygen iodine lasers  

Microsoft Academic Search

A theoretical model is established to describe the alpha-RF discharge in slab Oxygen Iodine lasers, according to the continuity equation of electron density, the electron energy equilibrium equation and the continuity equation of current density. Assuming a Maxwellian energy distribution, the spatial distributions of electron density and electric field in RF plasma are obtained by numerical method. The effects of

Xueling Zhang; Xinbing Wang; Guofu Li; Fan He; Junke Jiao; Yanzhao Lu

2008-01-01

61

Chemical oxygen-iodine laser (COIL) beam quality predictions using 3D Navier-Stokes (MINT) and wave optics (OCELOT) codes  

Microsoft Academic Search

This paper describes a series of analyses using the 3-d MINT Navier-Stokes and OCELOT wave optics codes to calculate beam quality in a COIL laser cavity. To make this analysis tractable, the problem was broken into two contributions to the medium quality; that associated with microscale disturbances primarily from the transverse iodine injectors, and that associated with the macroscale including

Alan I. Lampson; David N. Plummer; John H. Erkkila; Peter G. Crowell; Charles A. Helms

1998-01-01

62

Discharge-driven electric oxygen-iodine laser superlinear enhancement via increasing g0L.  

PubMed

The authors report the development of an electric oxygen-iodine laser with higher output using a larger product of gain and gain length, g0L. A factor of 4.4 increase in laser power output on the 1315 nm atomic iodine transition was achieved with a factor of 3 increase in gain length. I(2P1/2) is pumped using energy transferred from O2(a1?) produced by flowing a gas mixture of O2-He-NO through three coaxial geometry radio-frequency discharges. Continuous wave (CW) average total laser power of 481 W was extracted with g0L=0.042. PMID:22555687

Benavides, G F; Zimmerman, J W; Woodard, B S; Day, M T; King, D M; Carroll, D L; Palla, A D; Verdeyen, J T; Solomon, W C

2012-05-01

63

Similarity criteria in calculations of the energy characteristics of a cw oxygen - iodine laser  

NASA Astrophysics Data System (ADS)

The calculated and experimental data on the energy efficiency of a cw oxygen - iodine laser (OIL) are analysed based on two similarity criteria, namely, on the ratio of the residence time of the gas mixture in the resonator to the characteristic time of extraction of the energy stored in singlet oxygen td and on the gain-to-loss ratio ?. It is shown that the simplified two-level laser model satisfactorily predicts the output characteristics of OILs with a stable resonator at ?d <= 7. Efficient energy extraction from the OIL active medium is achieved in the case of ?d = 5 - 7, ? = 4 - 8.

Mezhenin, A. V.; Azyazov, V. N.

2012-12-01

64

An oxygen-iodine laser utilizing an oscillator of high-pressure O2(1Delta)  

NASA Astrophysics Data System (ADS)

An oxygen-iodine laser developed on the basis of a fluid singlet-oxygen oscillator (SOO) is presented. The stimulated emission of the laser was observed up to oxygen pressures at the SOO output as high as 300 mm Hg. A diagram of the experimental setup is presented.

Zagidullin, M. V.; Erasov, N. V.; Kurov, A. Iu.; Nikolaev, V. D.; Svistun, M. I.; Khvatov, N. A.

1991-12-01

65

Studies of oxygen-helium discharges for use in electric oxygen-iodine lasers  

NASA Astrophysics Data System (ADS)

In recent work, the performance of the Electric Oxygen-Iodine Laser (ElectricOIL), developed in partnership by researchers at the University of Illinois and CU Aerospace, has been greatly improved through systematic study of various components of this new laser technology. One major contribution to the advancement of ElectricOIL technology has been the development of electric discharges capable of producing significant flow rates of the precursor electronically-excited molecular oxygen, O2(a1Delta). O2(a 1Delta) serves as an energy reservoir in the laser system, pumping atomic iodine by near-resonant energy transfer producing gain and laser on the I(2P1/2) ? I(2P3/2 ) transition at 1315 nm. Initial experimental work with radio-frequency discharges showed the importance of controlling O-atom flow rates to reduce quenching losses of energy stored in O2(a1Delta), and determined proper selection of the helium diluent ratio and specific power deposition (power per O2 flow rate). Further experimental investigations with transverse capacitive radio-frequency discharges in O2/He/NO mixtures in the pressure range of 1-100 Torr and power range of 0.1-1.2 kW have indicated that O2(a1Delta) production is a strong function of geometry (transverse gap), excitation frequency, and pressure. These parameters along with gas flow mixture dictate the current density at which the discharge operates, and its modal characteristics (normal vs. abnormal, homogeneous vs. inhomogeneous). A key result is that to encourage efficient O2(a1Delta) production these parameters should be selected in order to promote a homogeneous (low current density) discharge. The discharge behavior is characterized using terminal current-voltage-characteristics, microwave interferometer measurements, and plasma emission intensity measurements. Numerous spectroscopic measurements of O2(a1Delta), oxygen atoms, and discharge excited states are made in order to describe the discharge performance dependent on various parameters. The influence of NO on O-atom flow rates and O2(a1Delta) production is investigated. Progress of laser power extraction since initial reports in 2005 is overviewed.

Zimmerman, Joseph William

66

Three-block model of the kinetics of vibrationally excited I{sub 2}(X) molecules in the active media of oxygen - iodine lasers  

SciTech Connect

A three-block model of the kinetics of vibrationally excited I{sub 2}(X) molecules in the active media of chemical oxygen - iodine lasers is developed. Instead of the system of equations describing a change in the concentrations of I{sub 2}(X, u) (u=0 - 47) molecules, this model uses equations for the total concentrations of iodine molecules belonging to the blocks of vibrational levels with u {<=} 10, u = 11 - 24, and u {>=} 25. Effective deactivation rate constants of I{sub 2}(X, 11 {<=} u {<=} 24) molecules are found for laser media of different compositions. The results of calculations performed using the proposed model agree with experimental data and are close to the parameters calculated previously by using the total system of equations for populations of individual vibrational levels of I{sub 2}(X, u). (laser applications and other topics in quantum electronics)

Pichugin, S Yu [Samara Branch of the P.N. Lebedev Physical Institute, Russian Academy of Sciences, Samara (Russian Federation)

2012-09-30

67

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

SciTech Connect

Possibilities for increasing the active medium volume of a chemical oxygen - iodine laser (CCOIL) with a pulsed electric-discharge generation of atomic iodine are studied. The reasons are analysed of the low stability of the transverse self-sustained volume discharge in electrode systems with metal cathodes under the conditions of the electric energy input into gas-discharge plasma that are typical for CCOILs: low pressure of mixtures containing a strongly electronegative component, low voltage of discharge burning, low specific energy depositions, and long duration of the current pulse. An efficient electrode system is elaborated with the cathode based on an anisotropically-resistive material, which resulted in a stable discharge in the mixtures of iodide (CH{sub 3}I, n-C{sub 3}H{sub 7}I, C{sub 2}H{sub 5}I) with oxygen and nitrogen at the specific energy depositions of {approx}5 J L{sup -1}, pressures of 10 - 25 Torr, and mixture volume of 2.5 L. (lasers)

Kazantsev, S Yu; Kononov, I G; Podlesnykh, S V; Firsov, K N [A M Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2010-08-03

68

2D gasdynamic simulation of the kinetics of an oxygen-iodine laser with electric-discharge generation of singlet oxygen  

SciTech Connect

The kinetic processes occurring in an electric-discharge oxygen-iodine laser are analyzed with the help of a 2D (r, z) gasdynamic model taking into account transport of excited oxygen, singlet oxygen, and radicals from the electric discharge and their mixing with the iodine-containing gas. The main processes affecting the dynamics of the gas temperature and gain are revealed. The simulation results obtained using the 2D model agree well with the experimental data on the mixture gain. A subsonic oxygen-iodine laser in which singlet oxygen is generated by a 350 W transverse RF discharge excited in an oxygen flow at a pressure P = 10 Torr and the discharge tube wall is covered with mercury oxide is simulated. The simulated mixing system is optimized in terms of the flow rate and the degree of preliminary dissociation of the iodine flow. The optimal regime of continuous operation of a subsonic electric-discharge oxygen-iodine laser is found.

Chukalovsky, A. A.; Rakhimova, T. V.; Klopovsky, K. S.; Mankelevich, Yu. A.; Proshina, O. V. [Moscow State University, Skobeltsyn Institute of Nuclear Physics (Russian Federation)

2011-03-15

69

Prospects of a visible (green) chemical laser  

SciTech Connect

The experimental conditions for a 1.25-kW visible (green) chemical laser are detailed. In this system, a supersonic oxygen--iodine laser is optically coupled straightforwardly to a nitrogen flouride DFlike supersonic flow. The design conditions presented here are based on previously unpublished experimental and theoretical results that are shown to be in good agreement.

Herbelin, J.M.

1986-07-01

70

Effect of the solution temperature in a singlet-oxygen generator on the formation of active medium in an ejector oxygen - iodine laser  

SciTech Connect

The influence of the solution temperature in a singlet-oxygen generator on the formation of the active medium in the ejector oxygen - iodine laser is investigated. The following parameters of the active medium at the solution temperature -20{sup 0}C are obtained: the gain is 7.2 x 10{sup -3} cm{sup -1}, the Mach number is M=2, the temperature is 205 K, and the static pressure is 9.3 mmHg. As the solution temperature is increased to -4{sup 0}C, the gain decreases to 5 x 10{sup 3} cm{sup -1}, the Mach number decreases to 1.78, while the temperature and the static pressure increase to 241 K and 10.7 mmHg, respectively. As the solution temperature increases from -20 to -4{sup 0}C, the losses in O{sub 2}({sup 1}{Delta}) increase by less than 20%, while the dissociation efficiency of molecular iodine decreases by less than 21%. (lasers, active media)

Zagidullin, M V; Nikolaev, V D; Svistun, M I; Khvatov, N A [Samara Branch of the P.N. Lebedev Physics Institute, Russian Academy of Sciences, Samara (Russian Federation); Palina, N Yu [Samara State University, Samara (Russian Federation)

2002-02-28

71

Chemical generator and epr studies of the chemical-oxygen-iodine-laser system. Technical report  

SciTech Connect

Formation of 02(1 delta) by reaction of Cl2 gas with basic H202 liquid was studied using a small scale batch reactor. Effect on 02(1 delta) yield of certain reaction/reactor parameters were evaluated. Parameters included molarity of base and presence of Cl(-) in initial reaction solution, use of Br2 as reactant, depth of Cl2 injector in solution, area of colled trap surface, and use of halocarbon coating on flow tube walls. Use of Cl2, base molarity, and trap condition were areas in which greatest effects were observed. Mixtures of argon and I2 were added to the flowing output from the generator and the high-field (1.7-2.4 T) EPR spectrum was scanned. No I2 or I species were observed. Values of g exp for two previously unreported EPR lines in the J=3 level of 02(1 delta) were obtained.

Cummings, M.E.; Davis, L.P.; Dymek, C.J. Jr; Fox, J.W.; Stoner, D.W.

1983-03-01

72

Short Wavelength Chemical Laser (SWCL) Workshop  

NASA Astrophysics Data System (ADS)

The workshop was held for the purpose of identifying the government's interest in SWCL technology, reviewing past and present efforts in this area and presenting the government's plans for a new thrust in SWCL source development. In addition, the workshop was to provide a forum for interaction between members of the Strategic Defense Initiation Organization (SDIO) and the 6.1 agencies with the technical community in order to create an enthusiastic response to the SWCL thrust and to generate new concepts as well as to involve new participants in this technically challenging area. This document contains abstracts of papers presented at the workshops. Some of the topics discussed in the sessions include: HF Lasers - What have we learned?; Chemical Oxygen Iodine Laser Review; Why So FEw Chemical Lasers?; Approach to Efficient Short-Wavelength Chemical Lasers; Metal/Oxidizer Systems; Pyrotechnic Systems; Metastable State Production; Metastable Transfer Systems; Energy Exchange Mechanisms.

Watt, W.

1984-12-01

73

Chemical lasers  

NASA Astrophysics Data System (ADS)

The application and the advances of quantum electronics, specifically, of optical quantum generators lasers is reviewed. Materials are cut, their surfaces are machined, chemical transformations of substances are carried out, surgical operations are performed, data are transmitted, three dimensional images are produced and the content of microimpurities, in the atmosphere, are analyzed by use of a beam. Laser technology is used in conducting investigations in the most diverse fields of the natural and technical sciences from controlled thermonuclear fusion to genetics. Many demands are placed on lasers as sources of light energy. The importance of low weight, compactness of the optical generator and the efficiency of energy conversion processes is emphasized.

Khariton, Y.

1984-08-01

74

Kinetics of the electrical discharge pumped oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

A systematic study of microwave discharges at 2.45 GHz has been performed through the pressure range of sustainable electric discharges in pure oxygen flows of 2 to 10 Torr. A corresponding study of 13.56 MHz has also been performed at pressures of 2, 4, and 7 Torr. Optical emissions from O2( a),O2(b), and O-atoms have been measured from the center of a microwave discharge. Discharge residence times from 0.1 to 5 ms have been reported, establishing that gas temperatures arrive at stationary values within the first 0.3 ms upon entering the discharge region. The O2(b) emissions, with a spectral resolution of 0.01 nm, have been used to measure the temperature of the gas, which typically reaches a steady-state of 1,200 K. A theoretical description of the gas heating is fit to measured temperatures, which determines that the fraction of discharge energy coupled into gas heating is 17 +/- 2%. The yield of O2( a) comes to steady-state at all pressures within 1 ms of entering the discharge region. The interpretation of the measured yield, using a streamlined, nearly analytic model, cast new light on the kinetics within the electric discharge. The pseudo-first order quenching rate of O2 (a) ranges from 6,000 1/s for microwave discharges to 600 1/s for radio frequency (RF) discharges, independent of gas pressure and flow rate. The slower decay rate for the RF discharge corresponds with a considerably lower ionization rate. The observations are consistent with a second order reaction channel that is dependent on both the electron and molecular oxygen ground state concentrations. Destruction of the O2 (b) state by direct impact with electrons or atomic oxygen does not adequately describe the observed behavior of O2( a). The role of vibrationally excited ground state oxygen is explored and provides a plausible destruction mechanism.

Lange, Matthew A.

75

High-power iodine laser application for remote D&D cutting  

NASA Astrophysics Data System (ADS)

This paper discusses the use of high-power lasers to remotely process material for decommissioning and dismantlement of nuclear facilities. Process requirements are established and suitable laser systems are compared. The chemical oxygen- iodine laser was identified as the leading candidate for long term dismantlement activities because it offers a high-power, high-brightness beam that can be remotely delivered into radiation containment by optical fibers.

Vetrovec, John; Hindy, Robert N.; Subbaraman, Ganesan; Spiegel, Lyle P.

1997-04-01

76

Mixing in a supersonic COIL laser: influence of trip jets  

Microsoft Academic Search

We present an experimental study of a supersonic nozzle with supersonic iodine injection. This nozzle simulates Chemical Oxygen Iodine Laser (COIL) flow conditions with non-reacting, cold flows. During the experiments, we used a laser sheet near 565 nm to excite fluorescence in iodine, which we imaged with an intensified and gated CCD camera. We captured streamwise and semi-spanwise (oblique-view) images,

Carrie Noren; Peter Vorobieff; C. Randall Truman; Timothy J. Madden

2011-01-01

77

Aspects of chemical laser simulation  

Microsoft Academic Search

Theoretical models for chemical lasers depend on a variety of assumptions and empirical data to provide closure and simplify solution of the governing equations. Among the various assumptions and empirical data built into models for chemical lasers are assumptions regarding steadiness in the time domain and geometric similarity of the computational domain. The objective of our work is to generate

Timothy J. Madden; James H. Miller

2003-01-01

78

Development of safe infrared gas lasers  

NASA Astrophysics Data System (ADS)

Infrared gas lasers find application in numerous civil and military areas. Such lasers are therefore being developed at different institutions around the world. However, the development of chemical infrared gas lasers such as chemical oxygen iodine lasers (COIL) involves the use of several hazardous chemicals. In order to exploit full potential of these lasers, one must take diligent care of the safety issues associated with the handling of these chemicals and the involved processes. The present paper discusses the safety aspects to be taken into account in the development of these infrared gas lasers including various detection sensors working in conjunction with a customized data acquisition system loaded with safety interlocks for safe operation. The developed safety schemes may also be implemented for CO2 gas dynamic laser (GDL) and hydrogen fluoride-deuterium fluoride (HF-DF) Laser.

Mainuddin; Singhal, Gaurav; Tyagi, R. K.; Maini, A. K.

2013-04-01

79

High Repetition Rate Chemical Laser.  

National Technical Information Service (NTIS)

A hydrogen fluoride (HF) chemical laser with an active medium 10 cm in length was constructed for operation at high pulse repetition rates using transverse excitation. The device employed 29 resistively loaded electrodes; open-cycle operation was achieved...

T. V. Jacobson G. H. Kimbell A. R. Lambert D. R. Snelling

1973-01-01

80

Infrared Laser Catalyzed Chemical Reactions  

Microsoft Academic Search

The development of the laser some twelve years ago has resulted in the creation and\\/or the resuscitation of a number of experimental disciplines involving measurements of energy transfer, chemical reaction rates, high resolution spectroscopy as well as nonlinear effects. In the last three years more and more work involving the use of lasers has been reported on in the literature

A. M. Ronn

1975-01-01

81

Continuous Wave Chemical Laser for Laser-Induced Fluorescence Studies.  

National Technical Information Service (NTIS)

Laser-induced fluorescence experiments have been accomplished with a newly developed cw chemical laser. The design and operating characteristics of this small-scale transverse flow chemical laser source are presented. The fluorescence measurement techniqu...

R. R. Stephens T. A. Cool

1971-01-01

82

Laser Chemical Analysis.  

ERIC Educational Resources Information Center

Reviews applications of laser methods to analytical problems, selecting examples from multiphoton ionization and fluorescence analysis. Indicates that laser methodologies promise to improve dramatically the detection of trace substances embedded in "real" matrices, giving the analyst a most powerful means for determining the composition of

Zare, Richard N.

1984-01-01

83

Amplification and gas-dynamic parameters of the active oxygen-iodine medium produced by an ejector nozzle unit  

SciTech Connect

The gain, the temperature, and the absolute velocity of the supersonic active oxygen-iodine medium produced by an ejector nozzle unit were determined by the technique of high-resolution diode laser spectroscopy. The gain in the active medium is formed at less than 44 mm from the nozzle unit for an absolute flow velocity {nu} {approx} 600 m s{sup -1}. Upon dilution of oxygen by primary nitrogen in the ratio of 1 : 6.9, the gain of the active medium amounts to 7x10{sup -3} cm{sup -1}, the temperature of the active medium to 200 K, the absolute flow velocity to 580 m s{sup -1}, and the pressure to 58 Torr. As the dilution is increased to 1 : 13.5, the gain reduces to 4.5x10{sup -3} cm{sup -1}, the temperature lowers to 180 K, the velocity of the active medium increases to 615 m s{sup -1}, and the pressure increases to 88 Torr. The increase in the initial content of water vapour in the oxygen flow results in an increase in the temperature and a decrease in the gain of the active medium. (active media)

Zagidullin, M V; Nikolaev, V D; Svistun, M I; Khvatov, N A [Samara Branch of the P.N. Lebedev Physics Institute, Russian Academy of Sciences, Samara (Russian Federation); Anderson, B T; Tate, R F; Hager, G D [US Air Force Research Laboratories, Kirtland, New Mexico (United States)

2001-08-31

84

Chemical Laser Pump.  

National Technical Information Service (NTIS)

The sharply defined bright zone produced by the detonation of a cyanogen-oxygen mixture in small test vehicles looks promising as a pump for solid-state lasers such as neodymium-doped glass and ruby. Brightness temperatures between 6000 to 7000 K are rout...

J. L. Wright

1966-01-01

85

Prediction of Chemical Laser Flow.  

National Technical Information Service (NTIS)

Numerical simulations of high-speed mixing flows were carried out using GASP, a computational fluid dynamics (CFD) code. The ultimate goal is to use GASP for prediction and optimization of chemical laser flows. Numerical simulations were used for code val...

P. Vorobieff C. R. Truman

2006-01-01

86

Laser induced chemical vapor deposition of carbon  

Microsoft Academic Search

Initial results on laser-induced chemical vapor deposition using the visible radiation of an Ar+ laser are presented. Due to the smaller wavelength of Ar+ laser radiation in comparison to the infrared radiation of a CO2 laser used in earlier experiments, much finer patterns could be produced. The influence of laser irradiance on the deposition rate and widths of patterns was

G. Leyendecker; D. Buerle; P. Geittner; H. Lydtin

1981-01-01

87

Quantum cascade lasers in chemical physics  

Microsoft Academic Search

In the short space of 15years since their first demonstration, quantum cascade lasers have become the most useful sources of tunable mid-infrared laser radiation. This Letter describes these developments in laser technology and the burgeoning applications of quantum cascade lasers to infrared spectroscopy. We foresee the potential application of quantum cascade lasers in other areas of chemical physics such as

Robert F. Curl; Federico Capasso; Claire Gmachl; Anatoliy A. Kosterev; Barry McManus; Rafal Lewicki; Michael Pusharsky; Gerard Wysocki; Frank K. Tittel

2010-01-01

88

Chemical laser systems: An engineering approach. Volume 1: Chemical laser analysis program  

Microsoft Academic Search

The Chemical Laser Analysis Program presented in this report is a computer program for the rapid, parametric evaluation of high energy, chemical laser systems, including the combustion chemistry, laser devices gas dynamics, various diffuser-ejector pressure recovery subsystems, and system volume\\/mass estimates. The program does not calculate specific laser power but relies on experimental data for scaling information. The FORTRAN EXTENDED

C. D. Mikkelsen; B. J. Walker

1979-01-01

89

A multilevel pulsed chemical laser model  

Microsoft Academic Search

Short-pulsed chemical lasers are analyzed with regard to establishing diagnostic relations and determining limits on laser performance. Time-dependent population inversions incorporating the effects of collisional deactivation, stimulated emission, and chemical source variation are determined using a rigorous matrix procedure. These inversions are combined with a radiative rate equation, and the resulting output intensity profiles and total energy density are evaluated

B. Curry; R. Kidder

1973-01-01

90

Chemically-Assisted Pulsed Laser-Ramjet  

NASA Astrophysics Data System (ADS)

A preliminary study of a chemically-assisted pulsed laser-ramjet was conducted, in which chemical propellant such as a gaseous hydrogen/air mixture was utilized and detonated with a focused laser beam in order to obtain a higher impulse compared to the case only using lasers. CFD analysis of internal conical-nozzle flows and experimental measurements including impulse measurement were conducted to evaluate effects of chemical reaction on thrust performance improvement. From the results, a significant improvement in the thrust performances was confirmed with addition of a small amount of hydrogen to propellant air, or in chemically-augmented operation.

Horisawa, Hideyuki; Kaneko, Tomoki; Tamada, Kazunobu

2010-10-01

91

Chemically-Assisted Pulsed Laser-Ramjet  

SciTech Connect

A preliminary study of a chemically-assisted pulsed laser-ramjet was conducted, in which chemical propellant such as a gaseous hydrogen/air mixture was utilized and detonated with a focused laser beam in order to obtain a higher impulse compared to the case only using lasers. CFD analysis of internal conical-nozzle flows and experimental measurements including impulse measurement were conducted to evaluate effects of chemical reaction on thrust performance improvement. From the results, a significant improvement in the thrust performances was confirmed with addition of a small amount of hydrogen to propellant air, or in chemically-augmented operation.

Horisawa, Hideyuki; Kaneko, Tomoki; Tamada, Kazunobu [Department of Aeronautics and Astronautics, Tokai University, Hiratsuka, Kanagawa, 259-1292 (Japan)

2010-10-13

92

Mixing enhancement in chemical lasers. II. Theory  

SciTech Connect

A phenomenological model for reactant mixing in trip nozzle chemical lasers by means of a surface-stretching mechanism is used in conjunction with a two-level laser model to derive scaling laws for numerous features noted in the trip nozzle data. This mixing model is then employed with an aerokinetics code in order to obtain quantitative laser gain predictions. The results yielded by the code are in good agreement with small-signal data. It is determined that trip jet mixing will not increase laser efficiency at low cavity pressures, but will at high cavity pressures result in a doubling of laser power output. 12 references.

Driscoll, R.J.

1987-07-01

93

Laser spectroscopy for studying chemical processes  

NASA Astrophysics Data System (ADS)

In recent years, various methods have been developed to observe and to influence the course of chemical reactions using laser radiation. By selectively increasing the translational, rotational, and vibrational energies and by controlling the relative orientation of the reaction partners with tunable infrared and UV lasers, direct insight can be gained into the molecular course of the breaking and re-forming of chemical bonds. As exmaples for the application of lasers in chemical synthesis the production of monomers and catalysts is discussed. The application of linear and nonlinear laser spectroscopic methods, such as laser-induced fluorescence (LIF), Coherent anti-Stokes Raman Scattering (CARS), infrared-absorption measurements with tunable diode and molecular lasers is described for non-intrusive observation of the interaction of transport processes with chemical reactions used in industrial processes with high temporal, spectral and spatial resolution. Finally the application of a UV laser microbeam apparatus in genetic engineering for laser-induced cell fusion, genetic transformation of plant cells as well as diagnosis of human diseases by laser-microdissection of chromosomes is described.

Wolfrum, J.

1988-07-01

94

Alpha high-power chemical laser program  

Microsoft Academic Search

Alpha is a megawatt-class ground demonstration of a hydrogen fluoride, continuous wave, space-based chemical laser. The laser operates in the infrared at 2.8 microns. The basic device consists of a cylindrical combustion chamber that exhausts radially outward through circumferential nozzles into an annular lasing area. An annular ring resonator is used to extract the laser energy from this area. Technical

Anthony J. Cordi; Henry Lurie; David W. Callahan; Matthew Thomson

1993-01-01

95

Alpha high-power chemical laser program  

Microsoft Academic Search

Alpha is a megawatt-class hydrogen fluoride, continuous wave, space based chemical laser brassboard which demonstrates and validates technology for space-based applications. It consists of a cylindrical gain generator that exhausts radially outward through circumferential nozzles forming an annular lasing media and an annular ring resonator, which extracts the laser energy. Technical innovations first demonstrated on Alpha include: (1) use of

Richard Ackerman; David Callahan; Anthony J. Cordi; Henry Lurie; Matthew Thomson

1995-01-01

96

Laser-based detection of chemical contraband  

Microsoft Academic Search

The goal of our work is tow fold; 1) develop a portable and rapid laser based air sampler for detection of specific chemical contraband and 2) compile a spectral data base in both the near- and mid-IR of sufficiently high quality to be useful for gas phase spectroscopic identification of chemical contraband. During the synthesis or 'cooking' of many illicit

Robert G. Clemmer; James F. Kelly; Steven W. Martin; Gary M. Mong; Steven W. Sharpe

1997-01-01

97

Hydrogen peroxide sensor using laser grade dye Rhodamine B  

NASA Astrophysics Data System (ADS)

Many chemical sensors based on fluorescence spectroscopy have been reported in applications, ranging from biomedical and environmental monitoring to industrial process control. In these diverse applications, the analyte can be probed directly, by measuring its intrinsic absorption, or by incorporating some transduction mechanism such as reagent chemistry to enhance sensitivity and selectivity. Hydrogen Peroxide is a colorless liquid. It is a common oxidizing and bleaching agent. It plays an important role in High Power Laser such as Chemical Oxygen Iodine Laser (COIL). As it is on the Hazardous substance list and on the special health hazard substance list, detection of Hydrogen Peroxide is of great importance. In the present study the detection of hydrogen Peroxide is by fluorescence quenching of laser grade dye Rhodamine B. Estimation of rate constant of the bimolecular quenching reaction is made.

Pattanaik, Amitansu; Sahare, P. D.; Nanda, Maitreyee

2007-11-01

98

HCL or DCL chemical laser using laser induced chemistry  

SciTech Connect

A chemical HCL or DCL laser is obtained by irradiating CoCl2+H2/D2 in admixture with the P54 line of a CO2 laser. The irradiation is accomplished in a laser cavity provided with appropriate brewster windows, mirrors, and coupling means. The CoCl2 is mixed with H2 or D2 in a properly conditioned system without reacting. The irradiating by the P54 line of a CO2 laser dissociates the CoCl2 to form CO+2Cl* (Cl*-atom in an excited state). The Cl* atom then reacts with H2/D2 present to produce HCL or DCL in an excited vibrational state. The halogen containing molecule then lases.

Merritt, J.A.

1980-05-13

99

Laser-based detection of chemical contraband  

NASA Astrophysics Data System (ADS)

The goal of our work is tow fold; 1) develop a portable and rapid laser based air sampler for detection of specific chemical contraband and 2) compile a spectral data base in both the near- and mid-IR of sufficiently high quality to be useful for gas phase spectroscopic identification of chemical contraband. During the synthesis or 'cooking' of many illicit chemical substances, relatively high concentrations of volatile solvents, chemical precursors and byproducts are unavoidably released to the atmosphere. In some instances, the final product may have sufficient vapor pressure to be detectable in the surrounding air. The detection of a single high-value effluent or the simultaneous detection of two or more low-value effluents can be used as reliable indicators of a nearby clandestine cooking operation. The designation of high- versus low-value effluent reflects both the commercial availability and legitimate usage of a specific chemical. This paper will describe PNNL's progress and efforts towards the development of a portable laser based air sampling system for the detection of clandestine manufacturing of methamphetamine. Although our current efforts ar focused on methamphetamine, we see no fundamental limitations on detection of other forms of chemical contraband manufacturing. This also includes the synthesis of certain classes of chemical weapons that have recently been deployed by terrorist groups.

Clemmer, Robert G.; Kelly, James F.; Martin, Steven W.; Mong, Gary M.; Sharpe, Steven W.

1997-02-01

100

Laser-controlled chemical etching of aluminum  

NASA Astrophysics Data System (ADS)

A new technique is described for high-spatial-resolution (less than 2-micron linewidth) etching of Al thin films. The process is based upon moderate local heating by a tightly focused Ar(+) laser beam to activate an etching reaction in mixtures of phosphoric acid, nitric acid, and potassium dichromate. By chemically biasing the reaction near its passive/active transition, the laser can enhance the reaction rate by more than six orders of magnitude. The etching mechanism has been studied by etch-rate measurements, ellipsometry, and Auger spectroscopy, and is ascribed to a competition between the formation of soluble aluminum phosphates and insoluble aluminum oxides.

Tsao, J. Y.; Ehrlich, D. J.

1983-07-01

101

Chemically assisted laser ablation ICP mass spectrometry.  

PubMed

A new laser ablation technique combined with a chemical evaporation reaction has been developed for elemental ratio analysis of solid samples using an inductively coupled plasma mass spectrometer (ICPMS). Using a chemically assisted laser ablation (CIA) technique developed in this study, analytical repeatability of the elemental ratio measurement was successively improved. To evaluate the reliability of the CLA-ICPMS technique, Pb/U isotopic ratios were determined for zircon samples that have previously been analyzed by other techniques. Conventional laser ablation for Pb/U shows a serious elemental fractionation during ablation mainly due to the large difference in elemental volatility between Pb and U. In the case of Pb/U ratio measurement, a Freon R-134a gas (1,1,1,2-tetrafluoroethane) was introduced into the laser cell as a fluorination reactant. The Freon gas introduced into the laser cell reacts with the ablated sample U, and refractory U compounds are converted to a volatile U fluoride compound (UF6) under the high-temperature condition at the ablation site. This avoids the redeposition of U around the ablation pits. Although not all the U is reacted with Freon, formation of volatile UF compounds improves the transmission efficiency of U. Typical precision of the 206Pb/238U ratio measurement is 3-5% (2sigma) for NIST SRM 610 and Nancy 91500 zircon standard, and the U-Pb age data obtained here show good agreement within analytical uncertainties with the previously reported values. Since the observed Pb/U ratio for solid samples is relatively insensitive to laser power and ablation time, optimization of ablation conditions or acquisition parameters no longer needs to be performed on a sample-to-sample basis. PMID:12553756

Hirata, Takafumi

2003-01-15

102

Laser remote chemical sensors at Raytheon  

NASA Astrophysics Data System (ADS)

Raytheon and the U.S. Army have been developing laser remote chemical sensors for the last decade. This has included advanced transmitter and sensor development, field testing, and concepts for spacecraft, aircraft, unmanned aerial vehicles, ground-mobile transports, and fixed sites. The WILDCAT sensor utilizes a wavelength agile CO2 laser with output energy of 1 J/pulse at a repetition rate of 100 Hz for ranges of 40 km. The receiver is composed of a 60 cm dia. telescope and HgCdTe detector, integrated into a gimbal system with full hemispherical scan. Algorithms allow for real-time data processing and concentration map display. An all solid state sensor breadboard has also been developed that is capable of 300 (mu) J output at 8-12 micrometers and 300 Hz repetition rate. The system is based on a Nd:YAG pump slab laser and two-stage, angle-tuned, optical parametric oscillator wavelength shifter. The system provides for power efficiency, compactness, and light weight that are consistent with manportability. Anticipated horizontal range is 3 km on the ground and 5 km vertically. Analysis of a space-based, low earth orbit system shows that chemical and biological species detection can be performed effectively by sensors derived from the laser components developed under these programs.

Cohn, David B.; Fukumoto, Joseph M.; Shepard, James G.; Swim, Cynthia R.

2002-02-01

103

Liquid and Gaseous Reactants for Advanced Chemical Lasers.  

National Technical Information Service (NTIS)

This report presents the results of a program conducted to study and demonstrate liquid and gaseous reactants for use in advanced DF chemical lasers. Included within this program was the careful screening of numerous potential laser reactants with ranking...

J. F. Hon L. S. Forman

1975-01-01

104

Long pulse chemical laser. Final technical report  

SciTech Connect

This report covers the technical effort through February, 1989. This effort was directed towards the technology associated with the development of a large scale, long pulse DF-CO{sub 2} chemical laser. Optics damage studies performed under Task 1 assessed damage thresholds for diamond-turned salt windows. Task 2 is a multi-faceted task involving the use of PHOCL-50 for laser gain measurements, LTI experiments, and detector testing by LANL personnel. To support these latter tests, PHOCL-50 was upgraded with Boeing funding to incorporate a full aperture outcoupler that increased its energy output by over a factor of 3, to a full kilojoule. The PHOCL-50 carbon block calorimeter was also recalibrated and compared with the LANL Scientech meter. Cloud clearing studies under Task 3 initially concentrated on delivering a Boeing built Cloud Simulation Facility to LANL, and currently involves design of a Cold Cloud Simulation Facility. A Boeing IRAD funded theoretical study on cold cloud clearing revealed that ice clouds may be easier to clear then warm clouds. Task 4 involves the theoretical and experimental study of flow system design as related to laser beam quality. Present efforts on this task are concentrating on temperature gradients induced by the gas filling process. General support for the LPCL field effort is listed under Task 5, with heavy emphasis on assuring reliable operation of the Boeing built Large Slide Valve and other device related tests. The modification of the PHOCL-50 system for testing long pulse DF (4{mu}m only) chemical laser operation is being done under Task 6.

Bardon, R.L.; Breidenthal, R.E.; Buonadonna, V.R. [and others] [Boeing Aerospace Co., Seattle, WA (United States)

1989-02-01

105

PHYSICAL EFFECTS OCCURRING DURING GENERATION AND AMPLIFICATION OF LASER RADIATION: Efficient solutions for low-temperature singlet-oxygen generators  

NASA Astrophysics Data System (ADS)

Experimental investigations were made of the physicochemical characteristics of the active solutions for a chemical generator in an oxygen-iodine laser. A strong temperature dependence of the viscosity of the solution was observed. The influence of this factor on the operation of the singlet-oxygen generator and the laser is discussed. The cyclic operation of a laser with efficient neutralization of the reagents and the addition of an alkali is simulated. It is shown that hydrogen peroxide may be 50% utilized when the temperature of the solution is no higher than - 30 C. A method of preparing a solution for an iodine laser with a low freezing point (between - 30 C and - 40 C) is developed. It is shown that an aqueous solution of hydrogen peroxide with a concentration of 25-40% is suitable.

Igoshin, Valerii I.; Karyshev, V. D.; Katulin, V. A.; Kirilin, A. V.; Kisletsov, A. V.; Konnov, S. A.; Kupriyanov, N. L.; Medvedev, A. M.; Nadezhina, T. N.

1989-02-01

106

Advanced CW hydrogen fluoride chemical laser performance  

NASA Astrophysics Data System (ADS)

The performance of combustion driven CW HF chemical lasers using the hypersonic low-temperature (HYLTE) nozzle at the fundamental and overtone wavelengths was investigated. A pseudo-2D, rotational equilibrium, finite rate, chemical kinetic, mixing laser simulation code, Blaze II, was used to model the HYLTE nozzle. The fluid dynamic profiles from Blaze II were used as an input to a computationally efficient, rotational nonequilibrium model, ORNECL, which was used for power and small signal gain (SSG) calculations. The ORNECL model was used to predict the performance of the HYLTE nozzle in an advanced gain generator configuration. Calculated powers, SSG's and power spectral distributions are reported. Results indicate that overtone efficiencies of only 40-50 percent may be observed with the ORACL module due to a relatively short gain length and 99.77 percent reflective mirrors. It was found that at a fundamental power flux of 40 W/sq cm, an 81 percent increase in cavity mass efficiency may be achievable by minimizing heat loss and by using alternate reactants.

Waldo, Robert E.

1993-07-01

107

Precision Carbon Deposition Using Pyrolytic Laser Chemical Vapor Deposition (LCVD)  

Microsoft Academic Search

Laser Chemical Vapor Deposition (LCVD) can be used to rapid prototype many different metals and ceramics. The spatial resolution is potentially very fine, depending on the accuracy of stage or laser movement, and the size of the laser spot used for the localized heating. This paper describes a set of experiments performed using an LCVD system powered with a 100

Daniel L. Jean; Chad E. Duty; Brian T. Fuhrman; W. Jack

108

Chemically amplified laser direct-writing of aluminum  

NASA Astrophysics Data System (ADS)

Laser microchemical direct writing has important advantages over other techniques for the deposition of thin-film patterns. Disadvantages, however, are lower throughput and the need to suppress competing processes such as gas phase nucleation of particles or substrate damage. Methods for increasing the overall speed of laser direct writing by microchemistry were investigated. A class of laser deposition techniques has emerged in which laser radiation is used only to enhance or to impede the initial nucleation of a thin film. In general, it is convenient to draw a distinction between nucleation barriers due to physical effects and those due to chemical effects. The first type of barrier is derived from surface tension. The laser deposits a pattern of heterogeneous catalyst to initiate a subsequent transformation that is chemically self-sustaining or autocatalytic. Experiments, in which the laser direct writing of patterned thin films of Al is chemically amplified by subsequent selective pyrolytic chemical vapor deposition are summarized.

Tsao, J. Y.; Ehrlich, D. J.

109

Remote chemical sensing with quantum cascade lasers  

NASA Astrophysics Data System (ADS)

A trailer based sensor system has been developed for remote chemical sensing applications. The sensor uses quantum cascade lasers (QCL) that operate in the long wave infrared. The QCL is operated continuous wave, and its wavelength is both ramped over a molecular absorption feature and frequency modulated. Lock-in techniques are used to recover weak laser return signals. Field experiments have monitored ambient water vapor and small quantities of nitrous oxide, tetrafluoroethane (R134a), and hydrogen sulfide released as atmospheric plumes. Round trip path lengths up to 10 km were obtained using a retroreflector. Atmospheric turbulence was found to be the dominating noise source. It causes intensity fluctuations in the received power, which can significantly degrade the sensor performance. Unique properties associated with QCLs enabled single beam normalization techniques to be implemented thus reducing the impact that turbulence has on experimental signal to noise. Weighted data averaging was additionally used to increase the signal to noise of data traces. Absorbance sensitivities as low as ~1x10-4 could be achieved with 5 seconds of data averaging, even under high turbulence conditions.

Harper, Warren W.; Strasburg, Jana D.

2004-09-01

110

Mixing enhancement in chemical lasers. I. Experiments  

SciTech Connect

Nonreacting and reacting flow visualization experiments were used to demonstrate the ability of a new supersonic nozzle design (called the ramp nozzle) to accelerate mixing in a deuterium floride chemical laser via the reactant surface stretching mechanism. Unlike trip nozzles, which use inert gas injection to cause reactant surface stretching, the ramp nozzle causes a similar effect through its geometry without gas injection. The results from laser-induced fluorescence experiments indicate the ramp nozzle design produces a factor of two increase in the reactant interface length within about a centimeter of the nozzle exit. A side-by-side comparison in reacting flow of the ramp and gas trip nozzles suggest that both designs produce similar levels of mixing enhancement. These data are used to develop a phenomenological model for mixing enhancement in gas trip and ramp nozzles. This model describes a possible mechanism by which trip jets cause reactant surface stretching, indicates how the surface stretching rates can be calculated from the reactant nozzle geometry and flow conditions, and permits performance scaling laws consistent with the trip nozzle data to be derived. 13 references.

Driscoll, R.J.

1986-07-01

111

Remote chemical sensing with quantum cascade lasers  

SciTech Connect

A trailer based sensor system has been developed for remote chemical sensing applications. The sensor uses quantum cascade lasers (QCL) that operate in the long wave infrared. The QCL is operated continuous wave, and its wavelength is both ramped over a molecular absorption feature and frequency modulated. Lock-in techniques are used to recover weak laser return signals. Field experiments have monitored ambient water vapor and small quantities of nitrous oxide, tetrafluoroethane (R134a), and hydrogen sulfide released as atmospheric plumes. Round trip path lengths up to 10 km were obtained using a retro-reflector. Atmospheric turbulence was found to be the dominating noise source. It causes intensity fluctuations in the received power, which can significantly degrade the sensor performance. Unique properties associated with QCLs enabled single beam normalization techniques to be implemented thus reducing the impact that turbulence has on experimental signal to noise. Weighted data averaging was additionally used to increase the signal to noise of data traces. Absorbance sensitivities as low as {approx}1 x 10{sup -4} could be achieved with 5 seconds of data averaging, even under high turbulence conditions.

Harper, Warren W.; Strasburg, Jana D.

2004-10-15

112

Laser machining of CVD diamond: chemical and structural alteration effects  

Microsoft Academic Search

Nd:YAG laser (1064 nm) and ArF laser (193 nm) surface machining of 400 ?m thick, free-standing CVD diamond plates produced photon interaction zones which were chemically and structurally altered. A significant H loss and change in C?C bonding environment were observed in the Nd:YAG laser-processed specimens, while ArF laser processing exhibited less H depletion and structural alteration on a less

Philip M. Fabis

1996-01-01

113

Chemical imaging sensor and laser beacon.  

PubMed

Design and functional aspects of PANSPEC, a panoramic-imaging chemical vapor sensor (PANSPEC is an abbreviation for infrared panoramic-viewing spectroradiometer), were advanced and its optical system reoptimized accordingly. The PANSPEC model unites camera and fused solid-state interferometer and photopolarimeter subsystems. The camera is an eye of the open atmosphere that collects, collimates, and images ambient infrared radiance from a panoramic field of view (FOV). The passive interferometer rapidly measures an infrared-absorbing (or infrared-emitting) chemical cloud traversing the FOV by means of molecular vibrational spectroscopy. The active photopolarimeter system provides a laser beam beacon. This beam carries identification (feature spectra measured by the interferometer) and heading (detector pixels disclosing these feature spectra) information on the hazardous cloud through a binary encryption of Mueller matrix elements. Interferometer and photopolarimeter share a common configuration of photoelastic modulation optics. PANSPEC was optimized for minimum aberrations and maximum resolution of image. The optimized design was evaluated for tolerances in the shaping and mounting of the optical system, stray light, and ghost images at the focal plane given a modulation transfer function metric. PMID:12777015

Carrieri, Arthur H

2003-05-20

114

Laser-based instrumentation for the detection of chemical agents  

SciTech Connect

Several laser-based techniques are being evaluated for the remote, point, and surface detection of chemical agents. Among the methods under investigation are optoacoustic spectroscopy, laser-induced breakdown spectroscopy (LIBS), and synchronous detection of laser-induced fluorescence (SDLIF). Optoacoustic detection has already been shown to be capable of extremely sensitive point detection. Its application to remote sensing of chemical agents is currently being evaluated. Atomic emission from the region of a laser-generated plasma has been used to identify the characteristic elements contained in nerve (P and F) and blister (S and Cl) agents. Employing this LIBS approach, detection of chemical agent simulants dispersed in air and adsorbed on a variety of surfaces has been achieved. Synchronous detection of laser-induced fluorescence provides an attractive alternative to conventional LIF, in that an artificial narrowing of the fluorescence emission is obtained. The application of this technique to chemical agent simulants has been successfully demonstrated. 19 figures.

Hartford, A. Jr.; Sander, R.K.; Quigley, G.P.; Radziemski, L.J.; Cremers, D.A.

1982-01-01

115

Remote Chemical Sensing Using Quantum Cascade Lasers  

SciTech Connect

Research done by the IR sensors team at PNNL is focused on developing advanced spectroscopic methods for detecting signatures of nuclear, chemical, biological and explosives weapons or weapons production. The sensors we develop fall into two categories: remote sensors that can be operated at distances ranging from 150 m to 10 km, and point sensors that are used for in-situ inspection and detection. FY03 has seen an explosion in FM DIAL progress with the net result being solid confirmation that FM DIAL is a technique capable of remote chemical monitoring in a wide variety of venues. For example, FM DIAL was used to detect a small plume of hydrogen sulfide, a candidate CW agent, released in the desert environment of the Hanford 200 Area site. These experiments were conducted over a range of physical conditions including outside temperatures ranging from 70 F to 105 F and turbulence conditions ranging from quiescent to chaotic. We are now rapidly developing the information needed to design prototype FM DIAL systems that are optimized for specific applications that include scenarios such as fixed position stand-off detection and mobile UAV mounted remote monitoring. Just as an example, in FY04 we will use FM DIAL to detect both in-facility and outdoor release of enriched UF6. The rapid progress in FM DIAL research made in FY03 is attributed to several advances. First, final construction of a custom-designed trailer allowed the instrument to be housed in a mobile temperature-controlled environment. This allowed the experiment to be transported to several locations so that data could be collected under a range of physical conditions. This has led to a better understanding of a variety of experimental noise sources. With this knowledge, we have been able to implement several changes in the way the FM DIAL data is collected and processed, with the net result being a drastic improvement in our confidence of analyte concentration measurement and an improvement i n the instrument detection limit. The range of chemicals detectable by FM DIAL has also been extended. Prior to FY03 only water and nitrous oxide (N2O) had been seen. Experiments on extending the tuning range of the quantum cascade laser (QCL) currently used in the experiments demonstrate that many more species are now accessible including H2S, C2F4H2, and CH4. We additionally demonstrated that FM DIAL measurements can be made using short wave infrared (SWIR) telecommunications lasers. While measurements made using these components are noisier because turbulence and particulate matter cause more interference in this spectral region, monitoring in this region enables larger species to be detected simply because these lasers have a greater tuning range. In addition, SWIR monitoring also allows for the detection of second-row hydride species such as HF and HCl, which are important nuclear and CWA proliferation signatures.

Harper, Warren W.; Strasburg, Jana D.; Aker, Pam M.; Schultz, John F.

2004-01-20

116

Laser cutting with chemical reaction assist.  

National Technical Information Service (NTIS)

This invention is comprised of a method for cutting with a laser beam where an oxygen-hydrocarbon reaction is used to provide auxiliary energy to a metal workpiece to supplement the energy supplied by the laser. oxygen is supplied to the laser focus point...

D. J. Gettemy

1991-01-01

117

Maskless Fabrication of High Quality DFB Laser Gratings by Laser Induced Chemical Etching  

Microsoft Academic Search

High quality submicron DFB laser gratings with 130 nm groove depth are fabricated without roughness on a grating surface by laser induced chemical etching. It is found that rigid configuration of an irradiation cell and directional etching performance of laser etching is very important to obtain high quality gratings.

Yoshinobu Aoyagi; Satoshi Masuda; Atsutoshi Doi; Susumu Namba

1985-01-01

118

Remote chemical sensing by laser optical pumping  

SciTech Connect

We are exploring a new approach to remote chemical identification that promises higher precision than can be achieved by conventional DIAL approaches. This technique also addresses and potentially solves the problem of detecting a target gas in the presence of an interfering gas or gases. This new approach utilizes an eye-safe infrared optical pumping pulse to deplete the population of a specific rotational level(s) and then sends probe pulses at the same or different wavelengths to interrogate the bleaching of the absorption. We have experimentally measured optical saturation fluence level at atmospheric pressure for HCl, and find this level to be {approximately}1 mJ/cm{sup 2}, significantly below eye-safe limits in agreement with calculations. Calculations have been performed on other molecules of interest with similar results. In the laboratory, using time-delay-replicated pulses at a single frequency we have made absorption measurements with precision levels routinely approaching 0.1% after averaging 200 laser pulses. These results as well as those of two other pulse experiments will be presented. 5 refs., 9 figs., 1 tab.

Stevens, C.G.; Magnotta, F.

1996-08-01

119

Chemical-free cleaning using excimer lasers  

NASA Astrophysics Data System (ADS)

A critical requirement in many industrial processes is the cleaning of oils and grease, oxides, solvent residues, particles, thin films and other contaminants from surfaces. There is a particularly acute need in the electronics industry for cleaning semiconductor wafers and computer chips and in the metals industry for removing oxides and other contaminants. Cleaning traditionally is done by various wet chemical processes, almost all consuming large amounts of water and producing large amounts of hazardous wastes. To further complicate this, some of these cleaning agents and vast water consumption are undergoing stringent restrictions. The Radiance ProcessSM is a novel, patented Excimer Laser approach to dry surface cleaning. The process has removed particles from 80 microns to submicron sizes, paints, inks, oxides, fingerprints, hazes, parts of molecules and metallic ions in fingerprints. The process does not ablate, melt or damage the underlying surface. Micro-roughening on some Silicon and Gallium Arsenide is on the order of 1A or less. This paper will discuss the various applications with this process and the latest results from a beta wafer cleaning prototype test bed system that is being built under an EPA grant and joint partnership between Radiance Services Company, Neuman Micro Technologies, Inc. and the Microelectronics Research Laboratory.

Lizotte, Todd E.; O'Keeffe, Terence R.

1996-04-01

120

Laser Based Chemical Sensor Technology: Recent Advances and Applications  

Microsoft Academic Search

There is an increasing need in many chemical sensing applications ranging from environmental science to industrial process\\u000a control as well as medical diagnostics for fast, sensitive, and selective trace gas detection based on laser spectroscopy.\\u000a The recent availability of continuous wave near infrared diode lasers-, mid-infrared quantum cascade and interband cascade\\u000a distributed feedback (QC and IC DFB) lasers as mid-infrared

Frank K. Tittel; Yury A. Bakhirkin; Robert F. Curl; Anatoliy A. Kosterev; Matthew R. McCurdy; Stephen G. So; Gerard Wysocki

121

Experimental Investigation of a Chemical Laser Cavity Flowfield.  

National Technical Information Service (NTIS)

Chemical lasers require a cavity that establishes and maintains the proper gas dynamic properties during lasing. The design and performance of a flow system capable of supporting the hypersonic flow conditions in a lasing cavity are described. Using cold ...

S. W. Stiglich

1989-01-01

122

Chemical processes in active volume of photodissociative iodine laser  

NASA Astrophysics Data System (ADS)

The effective rate constants for chemical reactions in a gaseous active mixture have been calculated using kinetic models for a photodissociation iodine laser. The analysis was based on a detailed reaction scheme and Lindemann's collisional mechanism. Rate constants for all reactions occurring in the laser active volume are presented for the most important perfluorocarbon radials.

Skorobogatov, G. A.

1991-12-01

123

More exact modeling of COIL laser performance  

NASA Astrophysics Data System (ADS)

The chemical oxygen-iodine laser (COIL) is the shortest wavelength and high-power chemical laser demonstrated. To model the complete COIL lasing interaction, a three-dimensional formulation of the fluid dynamics, species continuity and radiation transport equations is necessary. The computational effort to calculate the flow field over the entire nozzle bank with a grid fine enough to resolve the injection holes is so large as to preclude doing the calculation. The approach to modeling chemical lasers then has been to reduce the complexity of the model to correspond to the available computational capability, adding details as computing power increased. The modeling of lasing in COIL is proposed, which is coupling with the effects induced by transverse injection of secondary gases, non-equilibrium chemical reactions, nozzle tail flow and boundary layer. The coupled steady solutions of the fluid dynamics and optics in a COIL complex three dimensional cavity flow field are obtained following the proposal. The modeling results show that these effects have some influence on the lasing properties. A feasible methodology and a theoretical tool are offered to predict the beam quality for the large scale COIL devices.

Li, Shouxian; Shu, Xiaojian; Du, Yanyi; Su, Hua; Li, Yan; Yu, Zhen

2012-05-01

124

Laser micromachining of chemically altered polymers  

SciTech Connect

During the last decade laser processing of polymers has become an important field of applied and fundamental research. One of the most promising proposals, to use laser ablation as dry etching technique in photolithography, has not yet become an industrial application. Many disadvantages of laser ablation, compared to conventional photolithography, are the result of the use of standard polymers. These polymers are designed for totally different applications, but are compared to the highly specialized photoresist. A new approach to laser polymer ablation will be described; the development of polymers, specially designed for high resolution laser ablation. These polymers have photolabile groups in the polymer backbone, which decompose upon laser irradiation or standard polymers are modified for ablation at a specific irradiation wavelength. The absorption maximum can be tailored for specific laser emissino lines, e.g. 351, 308 and 248 nm lines of excimer lasers. The authors show that with this approach many problems associated with the application of laser ablation for photolithography can be solved. The mechanism of ablation for these photopolymers is photochemical, whereas for most of the standard polymers this mechanism is photothermal. The photochemical decomposition mechanism results in high resolution ablation with no thermal damage at the edges of the etched structures. In addition there are no redeposited ablation products or surface modifications of the polymer after ablation.

Lippert, T.

1998-08-01

125

Standoff chemical detection using quantum cascade lasers and photoacoustic sensing  

NASA Astrophysics Data System (ADS)

We report in this paper the feasibility of standoff chemical detection using quantum cascade lasers (QCLs) and photoacoustic technique. In the experiment, we use a QCL with an emission wavelength near 7.9 ?m, an electret condenser microphone, and isopropanol (IPA) vapor as a safer experimental substitute of the explosive, RDX. The QCL is operated at pulsed mode and the laser beam focused on the IPA vapor sample. The photoacoustic sound wave is generated and detected by the microphone at a remote distance. With less than 40 mW laser power, standoff photoacoustic chemical detection distance over 35 cm is achieved.

Chen, Xing; Janssen, Douglas; Choa, Fow-Sen

2011-05-01

126

Remote Chemical Sensing Using Quantum Cascade Lasers  

Microsoft Academic Search

Spectroscopic chemical sensing research at Pacific Northwest National Laboratory (PNNL) is focused on developing advanced sensors for detecting the production of nuclear, chemical, or biological weapons; use of chemical weapons; or the presence of explosives, firearms, narcotics, or other contraband of significance to homeland security in airports, cargo terminals, public buildings, or other sensitive locations. For most of these missions,

Warren W. Harper; John F. Schultz

2003-01-01

127

A simple model of the transverse injection chemical laser nozzle  

NASA Astrophysics Data System (ADS)

In the design of chemical laser configurations, certain difficulties have been experienced with the nozzle. One of a number of novel approaches investigated was related to the transverse injection of the fuel into the oxidizer stream. During the initial performance projections for a transverse injection chemical laser, it became apparent that the viscous nozzle analysis, used to determine the initial conditions for the lasing cavity efficiency calculation, was not flexible enough to determine the losses due to the injection of the fuel jet. A simple model of the fluid dynamics of the transverse injection was developed with the aim to alleviate this situation. In the present paper, a model for the transverse injection chemical laser is presented. This model provides an analytic tool for determining the effect of geometry and flow composition on the lasing cavity entrance conditions.

Smith, W.

1985-07-01

128

Chemical sensors based on quantum cascade lasers  

Microsoft Academic Search

Quantum cascade lasers operating in the 3.5 to 24 micron spectral range can be used for trace gas detection in ambient air based on absorption spectroscopy. Recent advances in spectroscopic detection techniques have been employed to achieve minimum detectable absorption coefficients of 10-9 cm-1 in several real world applications.

Frank K. Tittel; Anatoliy A. Kosterev; Yury A. Bakhirkin; Chad B. Roller; Damien Weidmann; Robert F. Curl

2003-01-01

129

Fluid dynamic issues in continuous wave short wavelength chemical lasers  

SciTech Connect

This paper addresses fluid dynamic issues of concern in the design and development of Continuous Wave (CW) Short Wavelength Chemical Lasers (SWCLs). Short Wavelength Chemical Laser technology is in its research stage and SWCL concepts are in their evolving mode. Researchers are presently addressing candidate chemical systems and activation concepts. Since these lasers will be flowing systems, it is necessary to discuss both the probable fluid dynamics issues, because of the inherent complexities fluid dynamicist can support this activity. In addition to addressing the SWCL fluid dynamic issues, this paper will review past fluid dynamic activities in high energy lasers and discuss additional research still required. This paper will also address the various levels of fluid dynamic modeling and how these models can be applied in studying the fluid dynamics of Short Wavelength Chemical Lasers. Where it is felt that specific fluid methodologies are not available, but are required in order to conduct specific analyses, they will be defined. 34 refs., 6 figs., 1 tab.

Mikatarian, R.R.; Jumper, E.J.; Woolhiser, C.

1988-01-01

130

Laser-chemical finishing of micro forming tools  

NASA Astrophysics Data System (ADS)

In this contribution, we report on a laser-chemical removal method for precise machining of micro forming tools. Thereby, a focused machining laser beam is guided coaxially to an etchant jet stream. Since the material removal is caused by laser-induced chemical reactions using this method, machining is achieved at low laser powers. Hence, material stressing involving micro cracks and further parasitic effects can be avoided. Due to these advantages, this method offers a suitable technique for the finishing of precision micro tools. Several experiments have been performed at rotary swaging jaws made of Stellite 21 in order to chamfer the edged transition section between the operating sphere and the tool flank. The influence of both different laser powers and work piece traverse speeds has been investigated. For this purpose, several parallel laser paths were applied along the edged transition section when varying the process parameters. Here, the incident laser beam is subjected to different angles of incidence. Due to reflection effects, the process parameters have to be matched with respect to the particular angle of incidence during the machining. In this vein, the edged transition section of rotary swaging jaws was chamfered at radii in the range of 120 ?m.

Stephen, Andreas; Gerhard, Christoph; Vollertsen, Frank

2011-02-01

131

Effect of reactant-surface stretching on chemical laser performance  

SciTech Connect

It is noted that the laser cavity reactant mixing rate in high-pressure DF chemical lasers is increased with the aid of gas trip jets. In comparison with the laminar mixing value, the trip jets can improve the laser efficiency by about 100 percent. It is postulated that the trip jets give rise to a secondary flow that increases the mixing rate by stretching the contact surface between the reactant streams. A strain rate can be used to describe the surface stretching rate. The performance characteristics of trip-nozzle lasers are explained qualitatively by developing flow and laser models that can define the effect of strain on the reactant burning rate and laser efficiency. Strain affects the performance of the laser through a single parameter gamma, equal to twice the characteristic constant linear strain rate divided by the characteristic collisional deactivation rate for the lasing specie. Strain levels where gamma 2-3 are seen as consistent with trip nozzle data. The model also reveals that the efficiency of low-pressure laminar mixing (gamma 0) lasers could be increased significantly for strain rate levels where gamma is 3-5. 13 references.

Driscoll, R.J.

1984-01-01

132

Experimental investigation of a chemical laser cavity flowfield  

Microsoft Academic Search

Chemical lasers require a cavity that establishes and maintains the proper gas dynamic properties during lasing. The design and performance of a flow system capable of supporting the hypersonic flow conditions in a lasing cavity are described. Using cold air as the working medium, the flow control system configuration and nozzle-cavity-supersonic diffuser assembly configuration were developed to establish acceptable flow

Stephen Walter Stiglich Jr.

1989-01-01

133

Evaluation of frequency agile laser (FAL) for chemical detection  

Microsoft Academic Search

The Night Vision and Electronic Sensors Directorate's (NVESD's) Signatures and Sensors Branch performed a series of experiments to evaluate the feasibility of developing a man portable LIDAR system to perform column content and\\/or range resolved chemical detection. In order to perform these experiments in an expedient and low cost manner an existing Frequency Agile Laser system was utilized. These experiments

Gerry Klauber; Christopher Simi; Paul M. Brinegar; Mary M. Williams

1997-01-01

134

A UV laser source for biological and chemical sensing  

NASA Astrophysics Data System (ADS)

Optical parametric oscillator (OPO) and sum-frequency mixing (SFM) devices are useful tools for constructing ultraviolet (UV) laser sources for fluorescence spectroscopy. Here, a compact UV-laser sources based on frequency conversion of an actively Q-switched Nd:YAG laser is presented. The second harmonic generation from a Nd:YAG laser was utilized as pump radiation for a periodically poled KTiOPO4 nanosecond optical parametric oscillator. The OPO-signal and the remaining pump were spatially mode-matched for Type I SFM in a ?-barium borate (BBO) crystal and UV radiation at 293 nm could be generated. This corresponds to a conversion efficiency of 2% with respect to the 532 nm harmonic radiation. The wavelength region accessible with this UV source is useful for chemical and biological sensing. Excitation of tryptophan at 293 nm for detection of fluorescence emission in ovalbumin and transthyretin was demonstrated.

Tiihonen, Mikael; Pasiskevicius, Valdas; Laurell, Fredrik; Hammarstrom, Per; Lindgren, Mikael

2004-01-01

135

Laser welding of sheet metals  

NASA Astrophysics Data System (ADS)

Laser welding of sheet metals is an important application of high power lasers, and has many advantages over conventional welding techniques. Laser welding has a great potential to replace other welding technique in the car-body manufacturing because of high laser weld quality and relatively low manufacturing cost associated with the laser technique. However, a few problems related to the laser welding of sheet metals limit its applications in industries. To have a better understanding of the welding process, laser welding experimental studies and theoretical analysis are necessary. Temperature-dependent absorptivities of various metals are obtained theoretically for COsb2, COIL (Chemical Oxygen-Iodine Laser) and Nd:YAG lasers. It is found that the absorptivities for COIL and Nd:YAG lasers are 2.84 and 3.16 times higher than for the COsb2 laser, and the absorptivity increases with increasing temperature of the metals. Surface roughness and oxide films can enhance the absorption significantly. The reflectivity of as-received steel sheets decreases from 65-80% to 30-40% with surface oxide films for COsb2 lasers. Laser welding experiments show that the tensile strengths of the weld metals are higher than the base metals. For samples with surface oxide films, the oxygen concentration in the weld metals is found to be higher than in the specimens without oxidation, and the toughness of the weld metals is degraded. When steel powders are added to bridge the gap between two sheets, the oxygen content in the weld metals decreases and the toughness increases. A mathematical model is developed for the melt depth due to a stationary laser beam. The model results show that the melt depth increases rapidly with time at the beginning of laser irradiation and then increases slowly. Also, the melt depth is found to increase rapidly with laser intensities and then increases slowly for higher intensity. The average rate of melting and the times to reach the melting and boiling temperatures at the substrate surface are obtained by using the model. Another mathematical model is developed for the weld width weld pool shape due to a moving Gaussian laser beam. The model prediction compare well with experimental results.

Xie, Jian

136

A Q-switch CW chemical HF laser  

NASA Astrophysics Data System (ADS)

An experimental study was carried out of pulse-periodic (rap-rate) operation of a CW chemical HF laser with optomechanical up to 103 Hz Q-switched cavity. Output pulse power shown increases at the experimental conditions no less than five-fold through the frequency region of 17-250 Hz. Average power of the rap-rate output reduced considerably comparatively to the same of CW mode operation, but shoot up with growing of the modulation frequency (in the same frequency region) faster than peak pulse power. It were discussed the possible causes of experimental and calculation characteristics differences of laser.

Azarov, Michail A.; Mashendzhinov, V. I.; Maksimov, Ju. P.; Revitch, V. E.; Rotinian, M. A.; Sudarikov, V. V.; Tret'jakov, N. E.; Fedorov, I. A.; Eller, V. A.; Etzina, A. L.

2005-03-01

137

Femtosecond laser-induced breakdown spectroscopy of surface nitrate chemicals.  

PubMed

Ultrashort laser-induced breakdown spectroscopy was used to detect the emission radiation from the breakdown of surface contaminants by a femtosecond laser pulse. This study focused on the detection of visible to near-infrared radiation signatures from molecular fragments of the nitro (NO(x)) group present in the breakdown plasma, where target chemicals of potassium nitrate (KNO(3)) and sodium nitrate (NaNO(3)) were used. Spectral signatures at a wavelength region around 410 nm were observed for both KNO(3) and NaNO(3), and were identified as the fluorescence transitions of the NO(x)-molecular structures. The signatures obtained were systematically analyzed and studied as functions of laser parameters. It is shown that for laser parameters used in this study, laser pulse durations ?1 ps were not as effective as shorter pulses in generating these signatures. A visible wavelength NO(x) signature and the extended high-intensity propagation of a femtosecond laser could be advantageous to detecting nitro-group energetic materials at standoff distances. PMID:23669773

Ahmido, Tariq; Ting, Antonio; Misra, Prabhakar

2013-05-01

138

Conformal window for the airborne laser aircraft  

NASA Astrophysics Data System (ADS)

The Airborne Laser (ABL) program requires a large aperture, highly transparent window to allow the high energy laser beam to be focused on targets. This window presents many challenges as it is thin, large in diameter and very highly curved. Additionally, the window must be made from a material highly transparent at 1.315 micrometers, the chemical oxygen-iodine laser wavelength, have good transmission from the visible through 3 micrometers and be able to withstand the rigors of operations on a tactical aircraft. To manufacture this window, a unique partnership between two companies, Heraeus and Corning, was forged to demonstrate the process and manufacture the window blanks. Infrasil 302, a Heraeus product, is the only material with low absorption at 1.31 micrometers that can be produced in large enough quantities to make a window blank of the required size. Corning has developed the technology to flow- out and sag glass products to make highly curved optics without the need to machine them out of a cylindrical block. Using their experience and a common desire to support the ABL program, the two companies worked together to develop the processes that produce the window blanks. Contraves Brashear Systems of Pittsburgh will polish the blank in to its final form, with coatings applied by Optical Coating Laboratories, Inc. of Santa Rosa to maximize transmission.

Gritz, David N.; Mazzuca, Ronald R.; Edwards, Mary J.; Fagan, James G.; Peters, Gene; Decker, William M.; Kelchner, Bryan L.; Mayo, James W.; McCarthy-Brow, Theresa

1999-08-01

139

Molecular dispersion spectroscopy--new capabilities in laser chemical sensing.  

PubMed

Laser spectroscopic techniques suitable for molecular dispersion sensing enable new applications and strategies in chemical detection. This paper discusses the current state of the art and provides an overview of recently developed chirped laser dispersion spectroscopy (CLaDS)-based techniques. CLaDS and its derivatives allow for quantitative spectroscopy of trace gases and enable new capabilities, such as extended dynamic range of concentration measurements, high immunity to photodetected intensity fluctuations, or capability of direct processing of spectroscopic signals in optical domain. Several experimental configurations based on quantum cascade lasers and examples of molecular spectroscopic data are presented to demonstrate capabilities of molecular dispersion spectroscopy in the mid-infrared spectral region. PMID:22809459

Nikodem, Michal; Wysocki, Gerard

2012-07-01

140

Stabilized Quantum Cascade Lasers and Ultrasensitive Chemical Sensing  

NASA Astrophysics Data System (ADS)

Quantum Cascade Lasers (QCLs) are a relatively new type of semiconductor laser operating in the mid- to long-wave infrared. Being monopolar multilayered quantum well structures, they can be fabricated to operate anywhere in a 3 to 20 micron region. This makes them an ideal choice for infrared chemical sensing, a topic of great interest at present. The broad range of applications of this technology includes everything from environmental sensing to homeland security and the non-proliferation of weapons of mass destruction. In addition to a discussion of these new laser devices, we will show results of resent experiments, including frequency stabilization of QCLs down to a relative frequency of 5.6Hz. In this experiment we use two QCLs locked to two separate optical cavities, and we observe the heterodyne beat. A third control loop (in addition to the two for locking the lasers) is used to remove low frequency noise between the two cavity systems. We also present data from several different cavity-enhanced QCL chemical sensors demonstrating sensitivities down to the mid 10-11/cm/root(Hz).

Taubman, Matthew S.

2003-03-01

141

Free-standing silicon microstructures fabricated by laser chemical processing  

Microsoft Academic Search

Laser-assisted chemical-vapor deposition (LCVD) is used for growth in free space of microscale fibers and helical structures of silicon. The LCVD technique is also used for fabrication of a tungsten coil on a cylindrical silicon substrate, i.e., a microsolenoid is realized. The microstructure of the silicon deposits is investigated by transmission electron microscopy, and their mechanical strength is evaluated by

Helena Westberg; Mats Boman; Stefan Johansson; Jan-ke Schweitz

1993-01-01

142

Inhomogeneous broadening effects in multimode CW chemical lasers  

NASA Astrophysics Data System (ADS)

The performance of a multiple longitudinal mode CW chemical laser is investigated with reference to the effects of inhomogeneous broadening for the case where the longitudinal mode spacing is small compared with the characteristic Doppler and homogeneous widths of the lasing medium. Both a Fabry-Perot resonator and a saturated amplifier are considered, using a two-vibrational-level model. Closed form solutions are obtained which are shown to be in good agreement with the numerical results of Bullock and Lipkis (1979).

Mirels, H.

1981-01-01

143

CN x thin films prepared by laser chemical vapor deposition  

Microsoft Academic Search

Amorphous CNx thin films with 0.7 ?x ? 1.1 were obtained by ArF excimer laser chemical vapor deposition from NH3 and CCl4 as precursors in the substrate temperature range of 200 to 400 C. The slightly brownish films are optically transparent and electrically insulating. They are mechanically stable (several mm free standing at about 100 nm thickness) and very smooth

F. Falk; J. Meinschien; G. Mollekopf; K. Schuster; H. Stafast

1997-01-01

144

Oscillations in a laser-induced chemical reaction: coupling of chemical reactions with an acoustic effect  

Microsoft Academic Search

An oscillatory phenomenon has been observed in a laser-induced photochemical reaction occurring in a degassed acetone or benzene solution of the complex [}Au[P(C6H4OMe-p)3{]2-(?-C?C)] after flash photolysis. It been confirmed that the observed oscillation is due to the chemical reactions coupling with the photoacoustic effect.

Yu-Xiang Weng; Hong Xiao; Kwok-Chu Chan; Chi-Ming Che

1997-01-01

145

Laser physico-chemical vapour deposition of cubic boron nitride thin films  

Microsoft Academic Search

A laser physico-chemical vapour deposition (LPCVD) technique was developed based on the interaction of an ultraviolet laser beam with a boron nitride target and borazine gas to synthesize cubic boron nitride (CBN) thin films on silicon substrates. The process involved a hybrid of pulsed laser ablation (PLA) of a solid HBN target and chemical vapour deposition (CVD) using borazine as

P. A. Molian

1994-01-01

146

Laser interrogation of surface agents (LISA) for chemical agent reconnaissance  

NASA Astrophysics Data System (ADS)

Laser Interrogation of Surface Agents (LISA) is a new technique which exploits Raman scattering to provide standoff detection and identification of surface-deposited chemical agents. ITT Industries, Advanced Engineering and Sciences Division is developing the LISA technology under a cost-sharing arrangement with the US Army Soldier and Biological Chemical Command for incorporation on the Army's future reconnaissance vehicles. A field-engineered prototype LISA-Recon system is being designed to demonstrate on-the- move measurements of chemical contaminants. In this article, we will describe the LISA technique, data form proof-of- concept measurements, the LISA-Recon design, and some of the future realizations envisioned for military sensing applications.

Higdon, N. S.; Chyba, Thomas H.; Richter, Dale A.; Ponsardin, Patrick L.; Armstrong, Wayne T.; Lobb, C. T.; Kelly, Brian T.; Babnick, Robert D.; Sedlacek, Arthur J.

2002-06-01

147

Laser-assisted chemical vapor deposition of nickel and laser cutting in integrated circuit restructuring  

NASA Astrophysics Data System (ADS)

Laser-assisted chemical vapor deposition (LCVD) of nickel from Ni(CO)4 has been utilised for the restructuring of integrated circuit (IC) interconnections. Nickel lines were deposited on a SiO2 passivated IC to achieve new local interconnections between integrated circuit structures. Depositions were carried out over the pressure range of 0.2 to 2.2 mbar of pure Ni(CO)4 buffered in 0 to 800 mbar He. Argon ion laser wavelengths of 488 and 514.5 nm, laser power of 50-150 mW and a laser scan speed of 80 ?m/s were utilised for the deposition. The morphology and chemical contents of the deposited interconnection microstructures was examined by AFM, optical microscopy and LIMA. The resistivity of the deposited lines was found to be close to the nickel bulk resistivity. The utilisation of Nd: YAG and XeCl excimer lasers in the cutting of Al and Mo conductor lines for integrated circuit modification is also described.

Remes, J.; Moilanen, H.; Leppvuori, S.

1997-01-01

148

Production of radioactive Ag ion beams with a chemically selective laser ion source  

NASA Astrophysics Data System (ADS)

We have developed a chemically selective laser ion source at the CERN-ISOLDE facility in order to study neutron-rich Ag nuclides. A pulsed laser system with high repetition rate has been used based on high-power copper-vapour pump lasers and dye lasers. With this source significant reductions of the isobaric background has been achieved.

Jading, Y.; Catherall, R.; Jokinen, A.; Jonsson, O. C.; Kugler, E.; Lettry, J.; Ravn, H. L.; Tengblad, O.; Kautzsch, T.; Klckl, I.; Kratz, K.-L.; Scheerer, F.; Fedoseyev, V. N.; Mishin, V. I.; van Duppen, P.; Whr, A.; Walters, W. B.

1996-04-01

149

Physical and Chemical Changes of Polystyrene Nanospheres Irradiated with Laser  

NASA Astrophysics Data System (ADS)

It has been reported that polymer resist such as PMMA (Poly(methyl methacrylate) which is a well known and commonly used polymer resist for fabrication of electronic devices can show zwitter characteristic due to over exposure to electron beam radiation[1]. Overexposed PMMA tend to changes their molecular structure to either become negative or positive resist corresponded to electron beam irradiation doses. These characteristic was due to crosslinking and scissors of the PMMA molecular structures, but till now the understanding of crosslinking and scissors of the polymer resist molecular structure due to electron beam exposure were still unknown to researchers [2-5].Previously we have over exposed polystyrene nanospheres to various radiation sources, such as electron beam, solar radiation and laser, which is another compound that can act as polymer resist. We investigated the physical and chemical structures of the irradiated polystyrene nanospheres with FTIR analysis. It is found that the physical and chemical changes of the irradiated polystyrene were found to be corresponded with the radiation dosages. Later, combining Laser irradiation and Reactive Ion Etching manipulation, created a facile technique that we called as LARIEA NSL (Laser and Reactive Ion Etching Assisted Nanosphere Lithography) which can be a facile technique to fabricate controllable carbonaceous nanoparticles for applications such as lithographic mask, catalysts and heavy metal absorbers.

Mustafa, Mohd Ubaidillah; Agam, Mohd Arif; Juremi, Nor Rashidah Md.; Mohamad, Farizan; Wibawa, Pratama Jujur; Ali, Ahmad Hadi

2011-05-01

150

Physical and Chemical Changes of Polystyrene Nanospheres Irradiated with Laser  

SciTech Connect

It has been reported that polymer resist such as PMMA (Poly(methyl methacrylate) which is a well known and commonly used polymer resist for fabrication of electronic devices can show zwitter characteristic due to over exposure to electron beam radiation. Overexposed PMMA tend to changes their molecular structure to either become negative or positive resist corresponded to electron beam irradiation doses. These characteristic was due to crosslinking and scissors of the PMMA molecular structures, but till now the understanding of crosslinking and scissors of the polymer resist molecular structure due to electron beam exposure were still unknown to researchers. Previously we have over exposed polystyrene nanospheres to various radiation sources, such as electron beam, solar radiation and laser, which is another compound that can act as polymer resist. We investigated the physical and chemical structures of the irradiated polystyrene nanospheres with FTIR analysis. It is found that the physical and chemical changes of the irradiated polystyrene were found to be corresponded with the radiation dosages. Later, combining Laser irradiation and Reactive Ion Etching manipulation, created a facile technique that we called as LARIEA NSL (Laser and Reactive Ion Etching Assisted Nanosphere Lithography) which can be a facile technique to fabricate controllable carbonaceous nanoparticles for applications such as lithographic mask, catalysts and heavy metal absorbers.

Mustafa, Mohd Ubaidillah; Juremi, Nor Rashidah Md.; Mohamad, Farizan; Wibawa, Pratama Jujur [Microelectronic and Nanotechnology-Shamsudin Research Centre, Faculty of Electrical and Electronic Engineering, University Tun Hussein Onn Malaysia (Malaysia); Agam, Mohd Arif; Ali, Ahmad Hadi [Faculty of Science, Art and Heritage, University Tun Hussein Onn Malaysia (Malaysia)

2011-05-25

151

Laser-chemical precision machining of micro forming tools at low laser powers  

NASA Astrophysics Data System (ADS)

Micro forming tools require high surface quality as well as contour accuracy, i.e. close tolerances at small dimensions. However, their structuring with necessary accuracy is limited to a small number of applicable technologies due to the mechanical properties of the tool material on micro scale. This contribution reports on an approach for machining techniques for precise tool finishing, developed at Bremer Institut fr angewandte Strahltechnik GmbH (BIAS) called Laser-Jet-Process (LJP). This approach is based on a laser-chemical etching method where a focused laser beam is guided coaxially to an etchant jet-stream onto the material surface. The material removal is a result of laser-induced chemical reactions between etchant and surface at low laser powers. The evaluation of data shows a strong correlation of material removal and several process variables. In particular, high laser powers combined with high feed rates of the work piece and low flow rates of the etchant result in a break-off in material removal. In order to overcome this issue, the process boundaries have been experimentally determined and implemented in a quality control system. The quality control system consists of an automated path planning model and an inverse process model. The automated path planning model computes position and Gaussian intensity profile for a sequence of overlapping laser removal paths to achieve the desired tool shape. The inverse process model renders specific process variables for every single removal path from a pre-assembled data pool within experimentally defined boundary conditions.

Mehrafsun, Salar; Zhang, Peiran; Vollertsen, Frank; Goch, Gert

2012-02-01

152

Chemical analysis of surgical smoke by infrared laser spectroscopy  

NASA Astrophysics Data System (ADS)

The chemical composition of surgical smoke, a gaseous by-product of some surgical deviceslasers, drills, vessel sealing devicesis of great interest due to the many toxic components that have been found to date. For the first time, surgical smoke samples collected during routine keyhole surgery were analyzed with infrared laser spectroscopy. Traces (ppm range) of methane, ethane, ethylene, carbon monoxide and sevoflurane were detected in the samples which consisted mostly of carbon dioxide and water vapor. Except for the anaesthetic sevoflurane, none of the compounds were present at dangerous concentrations. Negative effects on the health of operation room personnel can be excluded for many toxic compounds found in earlier studies, since their concentrations are below recommended exposure limits.

Gianella, Michele; Sigrist, Markus W.

2012-11-01

153

Laser-based instrumentation for the detection of chemical agents  

NASA Astrophysics Data System (ADS)

Evaluation of the detection of chemical agents and their simulants by synchronous detection of laser-induced flurescence (SDLIF) and laser-induced breakdown spectroscopy (LIBS) continued. The recently completed SDLIF apparatus was tested with a solution of tetracene in benzene. The conventional fluorescence spectrum of tetracene exhibits a bandwidth of approximately 90 nm, whereas the synchronously detected spectrum has a spectral width of only 7 nm. The potential impact of both spontaneous and stimulated Raman scattering on agent detection by SDLIF was investigated. Neither Raman process seemed to impose detection limitations. Extension of the spectral tuning range of the SDLIF system to wavelengths as short as 210 nm was begun. This capability is vital, because the absorption bands of most agents and their simulants are in this portion of the ultraviolet range. Further attempts to use LIBS to detect nascent CN radicals arising from molecules containing this species were unsuccessful.

1982-03-01

154

Laser-assisted chemical vapor deposition of diamond films  

NASA Astrophysics Data System (ADS)

In this paper, it is reported that diamond films have been synthesized by the Laser Assisted Chemical Vapor Deposition (LACVD) method using the mixture of acetone and hydrogen. The XeCl excimer laser with a wavelength of 308 nm has been utilized as photo-dissociation energy source for carbohydrate, and H2 has been predissociated by hot filament at the temperature of 2000 degrees Celsius. P-type silicone was employed as substrate, which temperature was controlled at about 800 degrees Celsius. The specimens deposited by the method of LACVD were analyzed and evaluated by Raman spectroscopy and scanning electronics microscopy (SEM) accordingly. A character peak of diamond films at 1332 cm-1 can be observed from Raman spectrum. The experimental result have shown that a high-quality diamond film can be obtained.

Ren, Deming; Hu, Xiaoyong Y.; Liu, Fengmei M.; Qu, Yanchen C.; Zhao, Jingshan

1998-08-01

155

Numerical modeling of pyrolytic laser-induced chemical vapor deposition  

NASA Astrophysics Data System (ADS)

Laser chemical vapor deposition (LCVD) is a technique to deposit thin films of oxidation, corrosion, and wear resistant as well as electronic, optoelectronic, and superconductor materials. In order to understand the underlying mechanisms of such a process we have developed a numerical model using computational fluid dynamics (CFD). The Navier-Stokes equations governing the flow, heat transfer, and chemical reactions of the gases are solved numerically while the temperature distribution in the substrate is determined by solving the corresponding heat conduction equation. The present CFD model provides an opportunity to assess the important parameters concerning the LCVD process, such as the gas flow field, temperature distribution, concentration of reactants/products, and deposition height. Indicative results are presented for the deposition of titanium carbide upon AISI 1060 carbon. These results provide understanding of the LCVD process and enable its optimization.

Koutlas, G. N.; Vlachos, N. S.

2003-03-01

156

Performance characteristics of a wave attenuation for pulsed chemical lasers  

NASA Astrophysics Data System (ADS)

Parametric performance measurements are reported for a pulsed chemical laser wave attenuator. The attenuator utilizes the combined effects of flow channel area expansion, caustic water spray, and flow-through damping screens to suppress and control the pressure disturbances produced by the chemical heat release of the F2 + D2 chain reaction. Experimental results that illustrate the effects of different area expansion geometries, water spray configurations, and damping screen arrangements are presented. Capability to tune the attenuator system to provide short pressure wave clearing times is emphasized. An attenuator configuration is reported which gives a wave clearing time of 2 msec with a corresponding entropy-wave density nonuniformity of 0.001 for a 18.5/6/76.5 F2/O2/diluent gas mixture at a pulse repetition frequency of 100 Hz.

Buonadonna, V.; Weisbach, M. F.; Tong, K.-O.; McClure, J. D.

1981-06-01

157

Combustion Research Program: Flame studies, laser diagnostics, and chemical kinetics  

SciTech Connect

This project has comprised laser flame diagnostic experiments, chemical kinetics measurements, and low pressure flame studies. Collisional quenching has been investigated for several systems: the OH radical, by H{sub 2}0 in low pressure flames; the rotational level dependence for NH, including measurements to J=24; and of NH{sub 2} at room temperature. Transition probability measurements for bands involving v{prime} = 2 and 3 of the A-X system of OH were measured in a flame. Laser-induced fluorescence of vinyl radicals was unsuccessfully attempted. RRKM and transition state theory calculations were performed on the OH + C{sub 2}H{sub 4} reaction, on the t-butyl radical + HX; and transition state theory has been applied to a series of bond scission reactions. OH concentrations were measured quantitatively in low pressure H{sub 2}/N{sub 2}O and H{sub 2}/O{sub 2} flames, and the ability to determine spatially precise flame temperatures accurately using OH laser-induced fluorescence was studied.

Crosley, D.R.

1992-09-01

158

DESALE-5: A Comprehensive Scheduled Mixing Model for CW Chemical Lasers.  

National Technical Information Service (NTIS)

The development and application of a comprehensive model for calculating cw chemical laser performance are described. The effects of mixing through the use of a scheduled mass addition algorithm, extensive modeling of the pertinent chemical reactions, Fab...

M. Epstein

1979-01-01

159

Free-Electron Lasers, Thermal Diffusion, Chemical Kinetics, and Surgery  

NASA Astrophysics Data System (ADS)

Experiments demonstrate that the Mark-III FEL is a particularly effective tool for etching soft matter with remarkably little damage surrounding the site when tuned to wavelengths near 6.45 microns. Based on these observatons, human neuorsurgical and ophthalmic procedures were developed and have been performed successfully. A thermodynamic model was proposed to account for the wavelength dependence; however, the dynamics have not been well understood. We have theoretically investigated thermal diffusion and chemical kinetics in a system of alternating layers of protein and water as heated by a Mark-III FEL. The model is representative of cornea and the exposure conditions are comparable to previous experimental FEL investigations. A substantial temperature enhancement develops in the surface layer on the ten-nanosecond time scale. We consider the onset of both the helix-coil transition and chemical bond breaking of collagen in terms of the thermal, chemical, and structural properties of the system as well as laser wavelength and pulse structure.

Edwards, Glenn; Hutson, M. Shane

2001-11-01

160

Low-temperature silicon amorphous and crystalline film formation by laser chemical vapor deposition  

NASA Astrophysics Data System (ADS)

Laser chemical vapor deposition (LCVD) method was used for silicon films formation. Results on Raman scattering and x-ray induced photoelectron spectroscopy (XPS) of these polycrystalline and amorphous films are presented. The same LCVD methods for the case of quasi-resonant molecules were studied too. Theoretical criteria for nonthermal and thermal reactions in laser fields are given. The frequency dependence of laser chemical reaction ignition threshold was experimentally registered for the silicon tetrafluoride decomposition reaction in carbon-dioxide-laser field. It was proved that the laser radiation intensity needed for maintaining the reaction is substantially lower than the threshold ignition intensity.

Dar'jushkin, A. U.; Kondratiev, N. L.; Korovin, S. B.; Orlov, A. N.; Prokhorov, Alexander M.; Pustovoy, Vladimir I.; Ulitina, J. I.

1996-03-01

161

Laser mass spectrometry of chemical warfare agents using ultrashort laser pulses  

SciTech Connect

Fast relaxation processes in excited molecules such as IC, ISC, and fragmentation are observed in many environmentally and technically relevant substances. They cause severe problems to resonance ionization mass spectrometry because they reduce the ionization yield and lead to mass spectra which do not allow the identification of the compound. By the use of ultrashort laser pulses these problems can be overcome and the advantages of REMPI over conventional ionization techniques in mass spectrometry can be regained. This is demonstrated using soil samples contaminated with a chemical warfare agent.

Weickhardt, C.; Grun, C.; Grotemeyer, J. [Lehrstuhl Fuer Physikalische Chemie und Analytik, BTU Cottbus, Am Technologiepark 1, D-03099 Kolkwitz (Germany)

1998-12-16

162

Applications of computational fluid dynamics to HF chemical laser nozzle design  

Microsoft Academic Search

The development of a specialized predictive tool employing CFD techniques for the analysis of chemical laser nozzle and cavity flow fields is traced. A brief background of the general-purpose PARCH Navier-Stokes field solver is provided, as well as some details of the steps taken to specialize PARCH for chemical laser applications, and flow field predictions of the hypersonic-low-temperature (HYLTE) chemical

J. Long; W. Smith; R. Acebal; N. Sinha; W. A. Duncan

1991-01-01

163

Metal film deposition by laser breakdown chemical vapor deposition  

SciTech Connect

Dielectric breakdown of gas mixtures can be used to deposit homogeneous thin films by chemical vapor deposition with appropriate control of flow and pressure conditions to suppress gas phase nucleation and particle formation. Using a pulsed CO/sub 2/ laser operating at 10.6 microns where there is no significant resonant absorption in any of the source gases, we have succeeded in depositing homogeneous films from several gas phase precursors by gas phase laser pyrolysis. Nickel and molybdenum from the respective carbonyls and tungsten from the hexafluoride have been examined to date. In each case the gas precursor is buffered to reduce the partial pressure of the reactants and to induce breakdown. The films are spectrally reflective and uniform over a large area. Films have been characterized by Auger electron spectroscopy, x-ray diffraction, pull tests, and resistivity measurements. The highest quality films have resulted from the nickel depositions. Detailed x-ray diffraction analysis of these films yields a very small domain size (approx. 50 A) consistent with rapid quenching from the gas phase reaction zone. This analysis also shows nickel carbide formation consistent with the temperature of the reaction zone and the Auger electron spectroscopy results which show some carbon and oxygen incorporation (8% and 1% respectively). Gas phase transport and condensation of the molybdenum carbonyl results in substantial carbon and oxygen contamination of the molybdenum films requiring heated substrates, a requirement not consistent with the goals of the program to maximize the quench rate of the deposition. Results from tungsten deposition experiments representing a reduction chemistry instead of the decomposition chemistry involved in the carbonyl experiments are also reported.

Jervis, T.R.

1985-01-01

164

Studies of Elementary Processes and Coupling Involved in the D2/F2 Chemical Laser.  

National Technical Information Service (NTIS)

The performance of a H2/D2 chemical laser is a function of the nascent energy disposal parameters for the F + H2 (D2) and H (D) + F2 chemical reactions and the vibrational relaxation of HF (DF). Chemiluminescence Mapping (CM) in which chemical components ...

D. C. Tardy

1986-01-01

165

Laser-induced fluorescence: quantitative analysis of atherosclerotic plaque chemical content in human aorta  

Microsoft Academic Search

We have been studying laser-induced fluorescence as a technique for identification of selected changes in the chemical composition of atherosclerotic plaque. Formulae for quantification of chemical changes have been developed based upon analysis of fluorescence emission spectra using multiple regression analysis and the principal of least squares. The intima of human aortic necropsy specimens was injected with chemical compounds present

Erbin Dai; David Wishart; Samir Khoury; Cyril M. Kay; Bodh I. Jugdutt; John Tulip; Alexandra Lucas

1996-01-01

166

About possibilities of clearing near-Earth space from dangerous debris by a spaceborne laser system with an autonomous cw chemical HF laser  

Microsoft Academic Search

The possibility of clearing hazardous near-Earth space debris using a spaceborne laser station with a large autonomous cw chemical HF laser is substantiated and the requirements to its characteristics (i.e., power and divergence of laser radiation, pulse duration in the repetitively pulsed regime, repetition rate and total time of laser action on space debris, necessary to remove them from the

A V Avdeev; A S Bashkin; Boris I Katorgin; M V Parfenev

2011-01-01

167

Experimental investigation of a chemical laser cavity flowfield  

NASA Astrophysics Data System (ADS)

Chemical lasers require a cavity that establishes and maintains the proper gas dynamic properties during lasing. The design and performance of a flow system capable of supporting the hypersonic flow conditions in a lasing cavity are described. Using cold air as the working medium, the flow control system configuration and nozzle-cavity-supersonic diffuser assembly configuration were developed to establish acceptable flow conditions in the test section. Performance evaluation was based on pressure measurements in the nozzle-cavity-diffuser assembly and schlieren photographs of the flowfield in the cavity. Flow conditions in the test section were broken up into three different regions: flow in the hypersonic nozzles, flow in the base region and flow in the cavity region. Flow in the nozzles was analyzed using one-dimensional, steady, isentropic flow theory. Test results indicated that the hypersonic nozzles performed to design specifications. The Korst two-dimensional base-pressure flow model was used to describe the flow in the nozzle exit plane and base region. Experimentally calculated Mach numbers and static pressures corresponded very closely to theoretical values. Static pressure ports and schlieren photographs were used to describe the flow-field conditions in the cavity region.

Stiglich, Stephen Walter, Jr.

1989-12-01

168

CONTROL OF LASER RADIATION PARAMETERS: Computational and experimental study of a Q-switched cw chemical HF/DF laser  

NASA Astrophysics Data System (ADS)

The energy and temporal parameters of radiation from a cw chemical medium-size HF/DF laser mechanically Q-switched by a mirror rotating at a frequency of up to 1 kHz are calculated and studied experimentally. The peak power of laser pulses in the repetitively pulsed regime exceeds the cw output power of the HF laser at least by a factor of four. The average power in the repetitively pulses regime is lower than that in the cw regime, but it increases (approximately doubles) with increasing modulation frequency. The time of the complete recovery of the gain profile in the active medium is measured to be 6-7 ?s. Two numerical models are developed which describe the dynamics of Q-switched HF and DF lasers. Some specific features of the operation of these lasers are analysed with the help of these models.

Aleksandrov, Boris S.; Kuprenyuk, V. I.; Maksimov, Yurii P.; Mashendzhinov, Viktor I.; Rodionov, A. Yu; Rotinyan, Mikhail A.; Sudarikov, V. V.; Tret'yakov, Nikolai E.; Fedorov, Igor'A.; Etsina, Alla L.

2007-06-01

169

Calcium fluoride windows for high-energy chemical lasers  

NASA Astrophysics Data System (ADS)

The development of high-energy lasers requires optical windows capable of handling megajoule beam energies without compromising the system's performance. Calcium fluoride (CaF2) has been identified as a prime candidate for windows operating at chemical laser wavelengths due to very low bulk absorption and exceptionally small thermal lensing coefficients; it is, however, vulnerable to structural failure owing to poor mechanical strength characteristics and a large thermal stress factor. It is, therefore, essential to properly assess the ultimate potential of this material, which we attempt to do here in the following manner: (a) We assemble reliable numbers for all pertinent properties of (111)-oriented CaF2 single crystals and polycrystalline isotropic aggregates (PIAs), such as fusion-cast CaF2, which requires addressing issues relating to the elastic properties, the stress-optic coefficients, and the flexural strength. (b) We provide correct analytical expressions for evaluating the impact of pressure- and beam-induced effects on wave-front phase distortions and mechanical failure modes, taking advantage of a previous investigation [J. Appl. Phys. 98, 043103 (2005)]. (c) We perform detailed calculations on ``model'' windows made of either (111)CaF2 or (PIA)CaF2 that transmit optimally truncated Gaussian beams at wavelengths of 1.15 and 3.39 ?m, for run times such that lateral heat conduction and surface cooling can be ignored. Our main conlusions are as follows: (a) With CaF2 windows thermal lensing, as measured in terms of the Strehl ratio and on assuming coating absorptances of no more than 310-5, is of no consequence in the sense that catastrophic failure may occur at fluence levels way below the threshold for optical distortion. (b) Evidence of a poor Weibull shape factor (m~=3.5) degrades the design safety margins, which requires operating at peak intensities of no more than 100 kW/cm2 to achieve optimum on-target fluences. (c) Regarding the issue of (111)CaF2 vs (PIA)CaF2, we note that fusion-cast material outperforms single crystals based on the figure of merit for distortion, as well as fracture and yield strengths, but contrary to (111)-oriented material, it exhibits birefringence that may rule out its use if depolarization is of concern.

Klein, Claude A.

2006-10-01

170

Optical far- and near-field femtosecond laser ablation of Si for nanoscale chemical analysis  

Microsoft Academic Search

Extending spatial resolution in laser-based chemical analysis to the nanoscale becomes increasingly important as nanoscience\\u000a and nanotechnology develop. Implementation of femtosecond laser pulses arises as a basic strategy for increasing resolution\\u000a since it is associated with spatially localized material damage. In this work we study femtosecond laser far- and near-field\\u000a processing of silicon (Si) at two distinct wavelengths (400 and

Vassilia Zorba; Xianglei Mao; Richard E. Russo

2010-01-01

171

Mushroom'' double-channel double-heterostructure lead chalcogenide lasers made by chemical etching  

SciTech Connect

Double-channel double-heterostructure (DCDH) lead chalcogenide lasers were made using a chemical etchant. The etching rate depends strongly on the europium content of the ternary compound Pb{sub {ital x}}Eu{sub 1{minus}{ital x}}Se. This technique allows the development of selective etching processes for advanced laser design. The DCDH lasers show low-threshold current densities of 60 A/cm{sup 2} at 20 K and suppression of lateral modes.

Schlereth, K.; Boettner, H.; Tacke, M. (Fraunhofer-Institut fuer Physikalische Messtechnik, Heidenhofstrasse 8, D-7800 Freiburg (Federal Republic of Germany))

1990-05-28

172

Concepts of risk assesment of complex chemical mixtures in laser pyrolysis fumes  

Microsoft Academic Search

Laser-tissue interaction may generate by energy absorption a complex mixture of gaseous, volatile, semi-volatile and particular substances. At the time about 150 different components are known from IR-laser interaction with different organ tissues like liver, fat, muscle and skin. The laser-tissue interaction process thereby is dominated by heating processes, which is confirmed by the similarity of formed chemical products in

Lothar Weber; Thomas H. Meier

1996-01-01

173

The Creation and Characterization of Chemically Created Atomic Population Inversions for the Development of a Visible Chemical Laser  

NASA Astrophysics Data System (ADS)

The possibility of developing a chemically pumped laser in the visible region has been investigated. First, the history and the recent developments of short wavelength chemical lasers (SWCL) were reviewed. The energy transfer pumped thallium self-terminating visible chemical laser and the chemically pumped sodium dimer laser amplifier developed previously in the Georgia Tech chemical physics laboratory were discussed in detail. Combining the basic knowledge of laser physics, gas dynamics, reaction chemistry and the experience accumulated by other researchers in the past quarter century, a mode of energy transfer pumping of an atomic laser medium is adopted. Efficient near-resonant energy transfer involving metastable excited states of SiO* (or GeO*) and ground state alkali (Na and K) or copper atoms have been realized. The energy donors, SiO* (or GeO*) in rm a^3 Sigma^+ and rm b^3 {bfPi} states, were generated in high yield from rm Si+N_2O (or rm Ge+O_3) reactions. The energy stored in these triplet states is transferred in a near resonant process to excite sodium to its rm 3d^2D, 4d^2D and rm 5s^2S states. rm(5d ^2D, 6s^2S.. in potassium and rm 4p^2p^0 in copper.). An electronically inverted atomic configuration in sodium atoms is formed from highly efficient near resonant intermolecular energy transfer using a newly developed chemical laser apparatus. Evidence was shown that the Si-N_2O-Na system satisfies the basic requirements for a visible chemical laser and has the potential to lase at a few hundred milliwatts at 569nm in the current laboratory scale apparatus. Gains were measured in the Si-N_2 O-Na system using three different methods. With an amplified spontaneous emission (ASE) method, gains at lambda = 569,616 and 819nm, corresponding to the rm 4d^2D, 5s^2S and rm 3d^2D to rm 3p^2P transitions, were detected. Gain at 569nm was also measured with a sodium discharge lamp and with a single mode dye laser. Efforts are also made to oscillate the sodium rm 4d^2D -rm 3p^2P transition at 569nm. Evidence from full optical cavity experiments demonstrated that the output intensity has exceeded the chemiluminescent intensity, indicating light amplification and initial oscillation.

Shen, Kang-Kang

174

Laser Applications to Chemical, Security, and Environmental Analysis: introduction to the feature issue  

SciTech Connect

This Applied Optics feature issue on Laser Applications to Chemical, Security,and Environmental Analysis (LACSEA) highlights papers presented at theLACSEA 2006 Tenth Topical Meeting sponsored by the Optical Society ofAmerica.

Dreizler, Andreas; Fried, Alan; Gord, James R

2007-07-01

175

Nucleation and Growth of Silicon Thin Film Microstructures by Localized Laser Chemical Vapor Deposition.  

National Technical Information Service (NTIS)

Localized laser chemical vapor deposition (LLCVD) has become an important process for the direct generation of thin film microstructures, and is finding novel applications in microelectronics processing. Understanding the fundamental dynamics associated w...

D. E. Kotecki

1988-01-01

176

ARTICLES: Chemical laser emitting visible radiation as a result of oxidation reactions  

Microsoft Academic Search

It is demonstrated that, in principle, oxidation of germanium and tin, resulting in a population inversion of electronic levels of the GeO SnO molecules, can be used in chemical lasers emitting visible radiation. Initiation by infrared radiation emitted by CO2 or CO lasers or by a thermal method is considered.

A. S. Bashkin; N. L. Kupriyanov; A. N. Oraevskii

1977-01-01

177

Laser assisted chemical vapor deposition synthesis of carbon nanotubes and their characterization  

Microsoft Academic Search

The deposition of carbon nanotubes using the laser assisted chemical vapor deposition process was studied to determine the effects of processing conditions on the quantity and quality of the tubes. A structured experimental design was utilized to test the effects of laser power, and concentration of the two precursors, acetylene and iron pentacarbonyl. Processing conditions were optimized with the assistance

S. N. Bondi; W. J. Lackey; R. W. Johnson; X. Wang; Z. L. Wang

2006-01-01

178

High-efficiency multikilojoule deuterium fluoride (DF) chemical lasers initiated by intense electron beams  

Microsoft Academic Search

A multikilojoule deuterium fluoride (DF) chemical laser with a low-pressure mixture of F2\\/D2\\/O2\\/SF6 was developed in which a Lambda-type electron beam initiation scheme was used. The DF laser output obtained from a 27-liter active volume was 2.5 kJ with a pulsewidth of about 500 ns. The corresponding electrical efficiency and chemical efficiency are 128 percent and 10.5 percent, respectively.

Hirohito Inagaki; Fumihiko Kannari; Akira Suda; Minoru Obara

1986-01-01

179

Boron nitride microfibers grown by plasma-assisted laser chemical vapor deposition without a metal catalyst  

SciTech Connect

Boron nitride fibers were found to grow on polycrystalline nickel and Si(100) substrates by plasma-assisted laser chemical vapor deposition from B{sub 2}H{sub 6}+NH{sub 3} using an excimer laser at 193 nm. Their diameter was typically a few hundreds of nanometers, while the length was a few tens of micrometers. They were stoichiometric or boron-rich BN in chemical composition. When the substrate was rotated during deposition, spiral fibers were found to grow. We conclude that they grew with the help of laser light by other than the vapor-liquid-solid mechanism.

Komatsu, Shojiro; Kazami, Daisuke; Tanaka, Hironori; Shimizu, Yoshiki; Moriyoshi, Yusuke; Shiratani, Masaharu; Okada, Katsuyuki [Advanced Materials Laboratory, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Department of Materials Science, College of Engineering, Hosei University, 3-7-2 Kajino-machi, Koganei, Tokyo 184-8584 (Japan); National Institute for Advanced Industrial Science and Technology, Tsukuba Central 1, Tsukuba, Ibaraki 305-8561 (Japan); Department of Materials Science, College of Engineering, Hosei University, 3-7-2 Kajino-machi, Koganei, Tokyo 184-8584 (Japan); Department of Electronics, Graduate School of Information Science and Electrical Engineering, Kyushu University, Hakozaki, Fukuoka 812-8581 (Japan); Advanced Materials Laboratory, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)

2006-04-10

180

Chemical and Structural Changes in Blood Undergoing Laser Photocoagulation  

Microsoft Academic Search

The treatment of cutaneous vascular lesions (port wine stains etc.) using lasers has been guided by theories based on the ''cold'' or room-temperature optical properties of the hemo- globin target chromophore. We have recently presented evidence showing that under the influence of laser irradiation, the optical properties of blood in vitro are time and temperature dependent. Such complications are not

John F. Blacky; Jennifer Kehlet Barton

2004-01-01

181

Surface chemical reaction of laser ablated aluminum sample for detonation initiation  

SciTech Connect

We explore the evolution of metal plasma generated by high laser irradiances and its effect on the surrounding air by using shadowgraph images after laser pulse termination; hence the formation of laser supported detonation and combustion processes has been investigated. The essence of the paper is in observing initiation of chemical reaction between ablated aluminum plasma and oxygen from air by inducing high power laser pulse (>1000 mJ/pulse) and conduct a quantitative comparison of chemically reactive laser initiated waves with the classical detonation of exploding aluminum (dust) cloud in air. Findings in this work may lead to a new method of initiating detonation from metal sample in its bulk form without the need of mixing nano-particles with oxygen for initiation.

Kim, Chang-hwan; Yoh, Jack J. [School of Mechanical and Aerospace Engineering, Seoul National University, 599 Kwanakro, Kwanakgu, Seoul, Korea 151-742 (Korea, Republic of)

2011-05-01

182

Study of the chemical hf laser pumped by phototriggered discharge  

NASA Astrophysics Data System (ADS)

The non-chain reaction HF laser energized by an x-ray photo- triggered discharge has been studied for Ne/SF6/C2H6 and Ne/SF6H2 gas mixtures. For an active volume of 312 cm3, a high specific output laser energy of 10 J/l has been reached with an electric efficiency of 4.7% for the mixture with ethane, whereas only 6 J/l is obtained with an efficiency of 3.1% for the mixture with hydrogen. The study of the discharge development shows that the total production of HF molecules weakly depends on the gas mixture type, so that the plasma kinetic is not responsible for the difference observed between the laser performances obtained with the two mixtures. Time and spatially resolved measurements of the plasma fluorescence shows that discharge instabilities occur in the Ne/SF6 discharge, which are responsible for the HF laser emission disruption when hydrogen is added. But addition of ethane at about 3% of the total pressure induces the discharge stabilization, and allows the laser emission to occur in an homogeneous medium. As a result, this work clearly establishes the physical reason of the observed laser performance improvement when hydrogen is replaced by some hydrocarbons in discharge pumped HF laser.

Richeboeuf, L.; Doussiet, F.; Legentil, M.; Pasquiers, S.; Postel, C.; Puech, Vincent

1996-08-01

183

Tooth bleaching using three laser systems, halogen-light unit, and chemical action agents  

NASA Astrophysics Data System (ADS)

?The study describes the preclinical experience with laser-activated bleaching agent for discolored teeth. Extracted human upper central incisors were selected, and in the bleaching experiment 35% hydrogen peroxide was used. Three various laser systems and halogen-light unit for activation of the bleaching agent were applied. They were Alexandrite laser (wavelength 750 nm and 375 nm - SHG), Nd:YAG laser (wavelength 1.064 m), and Er:YAG laser (wavelength 2.94 ?m). The halogen-light unit was used in a standard regime. The enamel surface was analyzed in the scanning electron microscope. The method of chemical oxidation results in a 2-3 shade change in one treatment. The halogen-light units produced the same effect with shorter time of bleaching process (from 630 s to 300 s). The Alexandrite laser (750 nm) and bleaching agent helped to reach the desired color shade after a shorter time (400 s). Alexandrite laser (375 nm) and Nd:YAG laser had no effect on the longevity of the process of bleaching. Overheating of the chemical bleaching agent was visible after Er:YAG laser activation (195 s). Slight surface modification after bleaching process was detected in SEM.

Dostalova, Tatjana; Jelinkova, Helena; Housova, Devana; Sulc, Jan; Nemec, Michal; Koranda, Petr; Miyagi, Mitsunobu; Shi, Yi-Wei; Matsuura, Yuji

2004-09-01

184

DESALE-5: A comprehensive scheduled mixing model for CW chemical lasers  

Microsoft Academic Search

The development and application of a comprehensive model for calculating cw chemical laser performance are described. The effects of mixing through the use of a scheduled mass addition algorithm, extensive modeling of the pertinent chemical reactions, Fabry-Perot optics, nozzle blockage, and nonuniform initial profiles resulting from nozzle boundary layers are given. Illustrative examples are provided to demonstrate the capability of

M. Epstein

1979-01-01

185

Desale-5: a comprehensive scheduled mixing model for cw chemical lasers. Interim report  

Microsoft Academic Search

The development and application of a comprehensive model for calculating cw chemical laser performance are described. The effects of mixing through the use of a scheduled mass addition algorithm, extensive modeling of the pertinent chemical reactions, Fabry-Perot optics, nozzle blockage, and nonuniform initial profiles resulting from nozzle boundary layers are given. Illustrative examples are provided to demonstrate the capability of

Epstein

1979-01-01

186

Chemical reactions in the plasma active medium of a cw electron-beam-ionization CO/sub 2/ laser  

SciTech Connect

A study of the chemical changes in the composition of the plasma laser mixture which occurs during prolonged operation of a technological cue electron-beam-ionization CO/sub 2/ laser is reported. (AIP)

Averin, A.; Basov, N.; Glotov, E.; Danilychev, V.; Leonov, Y.; Sazhina, N.; Soroka, A.; Yugov, V.

1981-07-01

187

Study of the chemical hf laser pumped by phototriggered discharge  

Microsoft Academic Search

The non-chain reaction HF laser energized by an x-ray photo- triggered discharge has been studied for Ne\\/SF6\\/C2H6 and Ne\\/SF6H2 gas mixtures. For an active volume of 312 cm3, a high specific output laser energy of 10 J\\/l has been reached with an electric efficiency of 4.7% for the mixture with ethane, whereas only 6 J\\/l is obtained with an efficiency

L. Richeboeuf; F. Doussiet; M. Legentil; S. Pasquiers; C. Postel; Vincent Puech

1996-01-01

188

Laser-machined components for microanalytical and chemical separation devices  

NASA Astrophysics Data System (ADS)

Excimer lasers have proven to be powerful tools for machining polymeric components used in microanalytical and microchemical separation devices. We report the use of laser machining methods to produce microfluidic channels and liquid/liquid contact membranes for a number of devices fabricated at our laboratory. Microchannels 50- to 100- micrometers -wide have been produced directly in bulk polycarbonate chips using a direct-write laser micromachining system. Wider microchannels have been produced by laser machining paths through sheets of polyimide film, then sandwiching the patterned piece between solid chips of polycarbonate stock. A comparison of direct-write and mask machining processes used to produce some of the microfluidic features is made. Examples of microanalytical devices produced using these methods are presented. Included are microdialysis units used to remove electrolytes from liquid samples and electrophoretic separation devices, both used for extremely low volume samples intended for mass spectrometric analysis. A multilayered microfluidic device designed to analyze low volume groundwater samples for hazardous metals and a fluidics motherboard are also described. Laser machining processes have also been explored for producing polymeric membranes suitable for use in liquid/liquid contactors used for removal of soluble hazardous components from waste streams. A step-and-repeat mask machining process was used to produce 0.5 X 8 cm membranes in 25- and 50-micrometers -thick polyimide. Pore diameters produced using this method were five and ten micrometers. The laser machined membranes were sputter coated with PTFE prior to use to improve fluid breakthrough characteristics.

Matson, Dean W.; Martin, Peter M.; Bennett, Wendy D.

1998-10-01

189

Effects of pressure ratio on population inversion in a DF chemical laser with concurrent lasing  

NASA Astrophysics Data System (ADS)

A numerical simulation is presented for investigating the effects of pressure ratio of D2 injector to supersonic nozzle on the population inversion in the DF chemical laser cavity, while a lasing concurrently takes place. The chemical laser is generally used for the industrial process and manufacturing as well as the military weapon system, which requires high power characteristic of laser system rather than the others. The population inversion is absolutely needed to generate the laser beam and is non-equilibrium process. The laser beam is generated between the mirrors in the cavity and it is important to obtain stronger population inversion and more uniform distribution of the excited molecules in the laser cavity in order to produce high-power laser beam with good quality. In this study, these phenomena are investigated by means of analyzing the distributions of the DF excited molecules and the F atom used as an oxidant, while simultaneously estimating the maximum small signal and saturated gains and power in the DF chemical laser cavity. For the numerical solution, a fully conservative implicit method and a second order total variation diminishing (TVD) scheme are used with the finite-volume method (FVM). An 11-species (including DF molecules in various excited states of energies), 32-step chemistry model is adopted for the chemical reaction of the DF chemical laser system. The results are discussed by comparison with two D2 injector pressure cases; 192 and 388.64 torr. Major results reveal that in the resonator, stronger population inversions occur in the all transitions except DF(1)-DF(0), when the D2 injection pressure is lower. But, the higher D2 injection pressure provides a favorable condition for DF(1)-DF(0) transition to generate the higher power laser beam. In other words, as the pressure of D2 injector increases, the maximum small signal gain in the v transition, which is in charge of generating most of laser power, becomes higher. Therefore, the total laser beam power becomes higher.

Park, Jun Sung; Baek, Seung Wook

2005-04-01

190

Use of unstable resonators in CW chemical lasers with radial flow of a gas mixture  

NASA Astrophysics Data System (ADS)

Theoretical studies have shown that the ring variant of a CW chemical laser has possibly a great potential in connection with applications involving the use of gasdynamic lasers. However, as a consequence of the employed geometrical design, it is difficult to construct an optical resonator which would ensure an effective utilization of the available energy and produce a laser beam of small divergence. The present investigation is concerned with an unstable telescopic resonator formed by toroidal ring mirrors. In principle, such a resonator can be regarded as a cylindrical telescopic resonator with the two ends jointed to form a toroidal ring. It is found that the use of the considered device in a ring model of a CW chemical laser makes it possible to ensure a high directionality of the output radiation and single-mode emission. Resonators of the type studied present certain problems with respect to construction and alignment. However, it appears that the difficulties can be overcome.

Stepanov, A. A.; Shcheglov, V. A.

1982-09-01

191

Zeeman laser interferometry for detection and chemical analysis  

SciTech Connect

Zeeman interferometry has a number of applications for ultrasensitive detection and chemical analysis, including refractive index detection, micro-thermometry, thermooptic spectroscopy, and light scattering.

Johnston, R.G.

1993-12-01

192

Chemical modification of titanium immersed in hydrogen peroxide using nanosecond pulsed fiber laser irradiation  

Microsoft Academic Search

This paper addresses chemical alteration of titanium using pulsed Ytterbium fiber laser irradiation. For this study, Hydrogen Peroxide (HP) is used as the medium to study its effect on increasing anatase-titania composition in titanium substrates for samples irradiated by the laser. The variation of anatasei-rutile transformation generated in HP is compared with those generated in air. X-Ray diffraction (XRD) analysis

Negar Rasti; Ehsan Toyserkani; Fathy Ismail

2011-01-01

193

Windows for HF\\/DF chemical lasers - CaF2 or ZnSe  

Microsoft Academic Search

An investigation of laser-driven phenomena occurring in CaF2 and ZnSe window materials which affect the performance of high energy laser systems at chemical wavelengths is reported. The systems studied comprised an optical cavity, relay tube, beam expander, and output window to the focus. An analysis of the cumulative phaseshifts due to beam defocusing and distortion caused by thermally generated aberrations

C. A. Klein

1981-01-01

194

Kinetics of laser chemical vapor deposition of carbon and refractory metals  

Microsoft Academic Search

Three-dimensional laser chemical vapor deposition (3D-LCVD) has been used to grow rods of carbon, tungsten, titanium, and hafnium from a variety of hydrocarbons and metal halide-based precursors. A novel computerized 3D-LCVD system was designed and successfully used in the experiments. A focused Nd:Yag laser beam (lambda = 1.06 mum) was utilized to locally heat up a substrate to deposition temperature.

Feng Gao

2000-01-01

195

Ar ion laser-assisted chemical etching of molybdenum foils in air  

Microsoft Academic Search

Ar ion laser-assisted chemical etching of Mo foils in air is reported. Etching occurred due to local heating by the focused laser beam which induced the Mo oxidation to form the volatile MoO3 at the elevated sample temperature. Holes and slots with slightly tapered walls and a minimum hole diameter of less than 10 ?m could be etched in 25-,

G. Koren

1986-01-01

196

Applications of computational fluid dynamics to HF chemical laser nozzle design  

NASA Astrophysics Data System (ADS)

The development of a specialized predictive tool employing CFD techniques for the analysis of chemical laser nozzle and cavity flow fields is traced. A brief background of the general-purpose PARCH Navier-Stokes field solver is provided, as well as some details of the steps taken to specialize PARCH for chemical laser applications, and flow field predictions of the hypersonic-low-temperature (HYLTE) chemical laser nozzle and cavity. The convergence of the solution of the complete problem is facilitated by an overlapping zonal approach, which was very effective in obtaining separate converged solutions in each of the four zones (transonic-nozzle-throat, supersonic-nozzle, injector, and cavity) employed. Results from the four zones are presented as selected line plots and color-filled contour plots for temperature, velocity, concentration, and other flow properties.

Long, J.; Smith, W.; Acebal, R.; Sinha, N.; Duncan, W. A.

1991-06-01

197

On chemical reactions in the laser-induced breakdown of a liquid  

NASA Astrophysics Data System (ADS)

It is shown experimentally that a laser-induced breakdown of a liquid is accompanied by chemical reactions initiated by radicals and excited species formed in the spark. It is found that, in water, the laser-induced breakdown is accompanied by the dissociation of water and dissolved nitrogen molecules with the formation of HNO2 and HNO3, while, in a FeSO4 aqueous solution, by the Fe2+ ? Fe3+ oxidation reaction. It is assumed that the mechanism of the process is analogous to that of the action of ionizing radiations and the chemical action of ultrasonically induced cavitation (it is proposed that this mechanism of chemical action of a laser-induced spark proposed be termed indirect). Energy yields of these reactions are found to be of the same order of magnitude as for sonochemical redox reactions. It is shown that the laser-induced breakdown of an aqueous solution of maleic acid is accompanied by its stereoisomerization into fumaric acid, a process catalyzed by small amounts of an alkyl bromide. It is established that, for the formation of fumaric acid in a laser-induced spark, the energy yield is about five orders of magnitude higher than that typical of the above-mentioned redox reactions in the laser-induced spark.

Margulis, M. A.; Ovchinnikov, O. B.; Margulis, I. M.

2006-06-01

198

Facial skin rejuvenation: Ablative laser resurfacing, chemical peels, or photodynamic therapy? Facts and controversies.  

PubMed

Patients and cosmetic surgeons continue to develop innovative devices and techniques in search of the elusive fountain of youth. Our efforts in the past decade can be distilled to three primary approaches: refinement of existing technologies (ablative lasers); refinement of tried-and-true techniques (chemical peeling); and innovative use of new technologies (photorejuvenation). In this contribution, the authors discuss how these three approaches are used to achieve facial skin rejuvenation. Specifically, the authors compare and contrast the clinical benefits and disadvantages of the ablative fractionated and unfractionated carbon dioxide resurfacing lasers, medium-depth and deep chemical peeling, and the combination of photodynamic therapy with intense-pulsed light. PMID:24160279

Hassan, Khaled M; Benedetto, Anthony V

199

Recombination lasers utilizing vapors of chemical elements. II. Laser action due to transitions in metal ions  

Microsoft Academic Search

General requirements specifying the distribution of energy levels and discharge conditions are used as the basis of a discussion of the stimulated emission mechanisms in ionic recombination lasers utilizing strontium, calcium, beryllium, aluminum, tin, and lead vapors. The attention is concentrated on the strontium vapor laser. The population inversion which results in the emission of ?=430.5 nm radiation from Sr

V V Zhukov; V S Kucherov; Evgeny L Latush; M F Sm

1977-01-01

200

Laser-Induced Destruction of Hazardous Chemicals: A Preliminary Analysis.  

National Technical Information Service (NTIS)

Society's increasing dependence on chemicals in recent years had led to the production of vast amounts of solid, liquid, and gaseous wastes. The Resource Conservation and Recovery Act was designed to control solid and liquid hazardous waste products once ...

K. A. Wolf P. F. Morrison

1982-01-01

201

Selective wet chemical etching of metallic thin films designed by laser interference metallurgy (LIMET)  

NASA Astrophysics Data System (ADS)

The physical and chemical behaviour of materials is strongly correlated with their microstructure. Therefore, much effort is invested in the advanced microstructural design of metallic thin films. Laser Interference Metallurgy (LIMET) is used to locally tune the grain architecture of metallic thin films from the nanoto the microscale. This means a defined size and orientation of the grains with lateral periodicity, by interfering on the sample surface two or more laser beams of a high power nanosecond pulsed Nd:YAG laser. This technique enables the local nucleation and crystallization of amorphous or nanocrystalline metallic thin films, thus combining nano- and microcrystalline regions ordered in periodic line- or lattice-like arrangements in a composite architecture. After having locally modified the microstructure of e-beam evaporated Pt and Au thin films by laser irradiation a wet chemical etching procedure was induced in hot aqua regia. Doing so, a selective etching is achieved without using conventional lithography. Due to the laser-induced recrystallization in periodic structures, these microcrystalline zones of specific oriented grains show a higher resistance against the wet chemical etchant than the as-deposited, nanocrystalline areas, which are completely removed down to the substrate. Therefore, this procedure may have the potential to be an alternative, low cost approach to conventional lithographic techniques and provides a novel method for a straight-forward patterning of metallic thin films.

Catrin, Rodolphe; Gachot, Carsten; Marchand, Gnter; Schmid, Ulrich; Mcklich, Frank

2009-05-01

202

Laser chemical vapor deposition of Cu and Ni in integrated circuit repair  

NASA Astrophysics Data System (ADS)

Laser-assisted chemical vapor deposition (LCVD) of nickel from Ni(CO)4 and copper from Cu(hfac)tmvs was utilized in the restructuring of an integrated circuit (IC) interconnection. Nickel and copper lines were deposited on passivated ICs by using a focused Ar+ laser beam to achieve new local rewirings on the chip. Nickel line depositions were carried out over the pressure range of 0.2 to 2.2 mbar of Ni(CO)4 buffered in 200 - 800 mbar He. The typical laser beam scan speed was 24 micrometers per second for both metals. The Cu(hfac)tmvs precursor gas partial pressure was 0.3 mbar buffered in 10 mbar He or H2 and typical laser scan speed was 24 micrometers per second. The morphology and chemical contents of the deposited interconnection microstructures was examined by atomic force microscopy (AFM), optical microscopy and laser ionization mass analysis (LIMA). The LIMA analysis indicated that the deposited copper surface was contaminated but the contamination level decreased when the layer was depth profiled. The deposited Ni lines were found to be pure Ni with only traces of carbon contamination. The utilization of XeCl excimer laser in the cutting of Al and Mo conductor lines and passivation contact via opening for IC modification is also described. LCVD method was successful in numerous different IC failure inspection and circuit modification cases.

Leppaevuori, Seppo; Remes, Janne; Moilanen, Hannu

1996-09-01

203

Lifetime of a two-phase active medium of a pulsed chemical HF laser  

SciTech Connect

An analysis of the response of an aerosol and of the laser-chemical kinetics of a photon-branched chain reaction is used to determine the range of the maximum permissible parameters of the disperse component capable of supporting the operation of a pulsed chemical HF laser with a two-phase active medium (particle radius 0.09 - 0.4 {mu}m, particle concentration 10{sup 9} - 10{sup 7} cm{sup -3} ). It is shown that, in this range of parameters, the lifetime of the active medium of an HF laser with disperse Al particles is governed by coagulation, precipitation, and electrostatic scattering of particles, and that it amounts to 250 s. The main contribution to the degradation of the disperse component of the active medium comes from Brownian coagulation. (active media)

Letfullin, R R; Melikhov, K G; Igoshin, Valerii I [Samara Branch of the P.N. Lebedev Physics Institute, Russian Academy of Sciences, Samara (Russian Federation); Mitlina, L A [Samara State Technical University, Samara (Russian Federation)

1998-10-31

204

The influence of inhomogeneous gain on high-frequency phase of chemical laser beam  

NASA Astrophysics Data System (ADS)

By establishing the model of chemical laser cavity, the eigen mode of laser and the phase distribution of output beam have been simulated numerically, and the influence of inhomogeneous gain on phase characteristics of output beam has been discussed detailedly by analyzing the power spectral density of wavefront phase. The results show that the inhomogeneous gain of chemical laser gives rise to the phase distortion of output wavefront and the obvious increase of high-frequency phase in distortion wavefront; in addition, the degree of high-frequency phase distortion is influenced by the ratio of each component in gain mediums. Therefor, the key factor that resulting in the distortion of high-frequency phase is the inhomogeneous gain.

Fu, Fu-xing; Zhang, Bin

2013-08-01

205

Some effects of unstable resonators on performance of CW chemical lasers  

Microsoft Academic Search

A description is presented of some computed results which show the effect of various cylindrical confocal unstable resonator configurations on the performance of a CW chemical laser. These results have been obtained using the non-time-dependent LAMPPOST code reported by Glowacki et al. (1976) and Chien and Glowacki (1976) together with the technique described by Chien and Glowacki (1978) for accelerating

W. J. Glowacki; K.-Y. Chien; W. P. Altman

1978-01-01

206

Experimental investigation of a chemical-laser-cavity flowfield. Master's thesis  

Microsoft Academic Search

Chemical lasers require a cavity that establishes and maintains the proper gas dynamic properties during lasing. The design and performance of a flow system capable of supporting the hypersonic flow conditions in a lasing cavity are described. Using cold air as the working medium, the flow control system configuration and nozzle-cavity-supersonic diffuser assembly configuration were developed to establish acceptable flow

Stiglich

1989-01-01

207

Laser photoacoustic spectroscopy helps fight terrorism: High sensitivity detection of chemical Warfare Agent and explosives  

Microsoft Academic Search

Tunable laser photoacoustic spectroscopy is maturing rapidly in its applications to real world problems. One of the burning problems of the current turbulent times is the threat of terrorist acts against civilian population. This threat appears in two distinct forms. The first is the potential release of chemical warfare agents (CWA), such as the nerve agents, in a crowded environment.

C. K. N. Patel

2008-01-01

208

Laser-induced fluorescence: quantitative analysis of atherosclerotic plaque chemical content in human aorta  

NASA Astrophysics Data System (ADS)

We have been studying laser-induced fluorescence as a technique for identification of selected changes in the chemical composition of atherosclerotic plaque. Formulae for quantification of chemical changes have been developed based upon analysis of fluorescence emission spectra using multiple regression analysis and the principal of least squares. The intima of human aortic necropsy specimens was injected with chemical compounds present in atherosclerotic plaque. Spectra recorded after injection of selected chemical components found in plaque (collagen I, III, IV, elastin and cholesterol) at varying concentrations (0.01 - 1.0 mg) were compared with saline injection. A single fiber system was used for both fluorescence excitation (XeCl excimer laser, 308 nm, 1.5 - 2.0 mJ/ pulse, 5 Hz) and fluorescence emission detection. Average spectra for each chemical have been developed and the wavelengths of peak emission intensity identified. Curve fitting analysis as well as multiple regression analysis were used to develop formulae for assessment of chemical content. Distinctive identifying average curves were established for each chemical. Excellent correlations were identified for collagen I, III, and IV, elastin, and cholesterol (R2 equals 0.92 6- 0.997). Conclusions: (1) Fluorescence spectra of human aortas were significantly altered by collagen I, collagen III, elastin and cholesterol. (2) Fluorescence spectroscopic analysis may allow quantitative assessment of atherosclerotic plaque chemical content in situ.

Dai, Erbin; Wishart, David; Khoury, Samir; Kay, Cyril M.; Jugdutt, Bodh I.; Tulip, John; Lucas, Alexandra

1996-05-01

209

PPLN laser-based system for chemical imaging  

NASA Astrophysics Data System (ADS)

An infrared-imaging instrument is being developed to provide in situ qualitative and quantitative assessment of hydrocarbon contaminants on metallic surfaces for cleaning verification. A continuous-wave infrared optical parametric oscillator (OPO), based on the quasi-phasematched material periodically poled lithium niobate (PPLN), is interfaced with an InSb focal plane array camera to perform fast, non-invasive analysis by reflectance spectroscopy. The period range of the designed fan-out PPLN crystal determines the range of the output wavelength of the light source. It is able to scan hundreds of wavenumbers positioned in the range of 2820 - 3250 cm-1, which is sufficient to detect functional groups of common organic compounds (-CH, -OH, and -NH). The capability of the instrument has been demonstrated in a preliminary investigation of reflectance measurements for hydrocarbon solvents (methanol and d-limonene) on an aluminum surface. A substantial difference in absorption is obtained for the two solvents at two different laser-illumination wavelengths, thus permitting hydrocarbon detection and molecular species differentiation. Preliminary reflectance spectra of a mixture of aliphatic hydrocarbon lubricants and drawing agents on an aluminum panel are also presented. The relative thickness of the hydrocarbon thin film is determined by the intensity ratio of images acquired at two different laser illumination frequencies.

Ludowise, Peter D.; Ottesen, David K.; Kulp, Thomas J.; Goers, Uta-Barbara; Celina, M.; Armstrong, K.; Allendorf, Sarah W.

1999-10-01

210

Generation of cavitation luminescence by laser-induced exothermic chemical reaction  

NASA Astrophysics Data System (ADS)

Absorption of high power laser radiation by aqueous carbon suspensions is known to result in the formation of highly compressed bubbles of hydrogen and carbon monoxide through the endothermic carbon-steam reaction. The bubbles expand rapidly, overreaching their equilibrium diameter, and then collapse tens to hundreds of microseconds after formation to give a flash of radiation. Here we report on the effects of laser-initiated exothermic chemical reaction on cavitation luminescence. Experiments with hydrogen peroxide added to colloidal carbon suspensions show that both the time of the light flash following the laser pulse and the intensity of luminescence increase with hydrogen peroxide concentration, indicating that large, highly energetic gas bubbles are produced. Additional experiments with colloidal carbon suspensions show the effects of high pressure on the luminescent intensity and its time of appearance following firing of the laser.

Jung Park, Han; Diebold, Gerald J.

2013-08-01

211

Chemical Laser Action in Low Pressure Metal Vapor Flames  

Microsoft Academic Search

Chemiluminescence in the visible has indicated the production of electronically excited products in the low pressure reactions of alkaline earlh metals with oxygen, halogens, halogen compounds and other oxidants. Thermochemical calculations on many such systems have indicated energy release more than adequate for electronic excitation of the product molecules. Comparisons of radiative lifetimes, rates of chemical reaction and col-lisional de-excitation

M. L. ZWILLENBERG; D. W. NAEGELI; I. GLASSMAN

1973-01-01

212

Synchronization: from pendulum clocks to chaotic lasers and chemical oscillators  

NASA Astrophysics Data System (ADS)

Many natural and human-made nonlinear oscillators exhibit the ability to adjust their rhythms due to weak interaction: two lasers, being coupled, start to generate with a common frequency; cardiac pacemaker cells fire simultaneously; violinists in an orchestra play in unison. Such coordination of rhythms is a manifestation of a fundamental nonlinear phenomenon--synchronization. Discovered in the 17th century by Christiaan Huygens, it was observed in physics, chemistry, biology and even social behaviour, and found practical applications in engineering and medicine. The notion of synchronization has been recently extended to cover the adjustment of rhythms in chaotic systems, large ensembles of oscillating units, rotating objects, continuous media, etc. In spite of essential progress in theoretical and experimental studies, synchronization remains a challenging problem of nonlinear sciences.

Rosenblum, Michael; Pikovsky, Arkady

2003-05-01

213

ACTIVE MEDIA: Optical quality of the active media of high-power cw chemical lasers  

NASA Astrophysics Data System (ADS)

The influence of inhomogeneities of the refractive indices of the active media of high-power cw chemical (CWC) hydrogen fluoride lasers on the quality of the output beam is discussed. The spatial compensation of the small-scale periodic inhomogeneities of the active media of CWC lasers for a certain geometry of the nozzle array is examined and the conditions for manifestation of this effect are indicated. Specific CWC-laser nozzle array schemes, designed taking into account such compensation, are presented. The large-scale inhomogeneities, associated with the chemical processes in the active medium and with the downstream pressure rise and having in the main the form of an optical wedge, are estimated. The contributions of the resonant and nonresonant components to the refractive index of the active medium are examined. It is shown that, in the operation of a laser in the amplification regime, the resonant component of the refractive index exceeds appreciably the nonresonant component and this actually makes the main contribution to the distortions of the wavefront of the CWC laser output radiation.

Aleksandrov, B. P.; Stepanov, A. A.; Troshchenkov, S. V.; Shcheglov, V. A.

1999-06-01

214

Change in the surface morphology and chemical composition of some oxide crystals under UV laser irradiation  

SciTech Connect

The effect of the 248-nm KrF and 355-nm YAG:Nd{sup 3+} laser radiation on the surface morphology and chemical composition of SrTiO{sub 3}, Sr{sub 2}RuO{sub 4}, PbMoO{sub 4}, LiNbO{sub 3}, Y{sub 3}Al{sub 5}O{sub 12}, and Al{sub 2}O{sub 3} crystals has been studied. A relationship between the laser energy density on the sample surface and the surface roughness caused by the irradiation is determined. A technique for determining exactly the geometric surface characteristics is proposed. The effect of the surface roughness on the results of energy-dispersive X-ray (EDX) microanalysis has been investigated. A method for correcting the EDX data for samples with a rough surface has been developed. It is shown that the small variation in the composition of PbMoO{sub 4}, LiNbO{sub 3}, Y{sub 3}Al{sub 5}O{sub 12}, and Al{sub 2}O{sub 3} samples after laser irradiation can be explained by the measurement error, related to the change in the surface roughness. At the same time, the irradiation of SrTiO{sub 3} and Sr{sub 2}RuO{sub 4} crystals by a YAG:Nd laser changes the chemical composition of their surface layers. (interaction of laser radiation with matter)

Kuzanyan, A S; Badalyan, G R; Kuzanyan, V S; Nikogosyan, V R; Pilosyan, S Kh; Nesterov, V M

2011-07-31

215

Red SOX (Singlet Oxygen) Laser: A Chemically-Pumped, 0.76 Micrometer Singlet Oxygen Laser.  

National Technical Information Service (NTIS)

The feasibility of a red singlet oxygen laser based on production of (b) state singlet oxygen by the electronic energy pooling reaction of (a) state singlet oxygen was investigated. A microwave discharge-flow system for studying the quenching kinetics of ...

G. E. Busch M. B. Knickelbein

1986-01-01

216

Physics of a ballistic missile defense: The chemical laser boost-phase defense  

SciTech Connect

The basic physics involved in proposals to use a chemical laser based on satellites for a boost-phase defense are investigated. After a brief consideration of simple physical conditions for the defense, a calculation of an equation for the number of satellites needed for the defense is made along with some typical values of this for possible future conditions for the defense. Basic energy and power requirements for the defense are determined. A summary is made of probable minimum conditions that must be achieved for laser power, targeting accuracy, numbers of satellites, and total sources of power needed.

Grabbe, C.L.

1988-01-01

217

Change in the surface morphology and chemical composition of some oxide crystals under UV laser irradiation  

Microsoft Academic Search

The effect of the 248-nm KrF and 355-nm YAG:Nd3+ laser radiation on the surface morphology and chemical composition of SrTiO3, Sr2RuO4, PbMoO4, LiNbO3, Y3Al5O12, and Al2O3 crystals has been studied. A relationship between the laser energy density on the sample surface and the surface roughness caused by the irradiation is determined. A technique for determining exactly the geometric surface characteristics

A. S. Kuzanyan; G. R. Badalyan; V. S. Kuzanyan; V. R. Nikogosyan; S. Kh Pilosyan; V. M. Nesterov

2011-01-01

218

Change in the surface morphology and chemical composition of some oxide crystals under UV laser irradiation  

Microsoft Academic Search

The effect of the 248-nm KrF and 355-nm YAG:Nd{sup 3+} laser radiation on the surface morphology and chemical composition of SrTiO, SrRuO, PbMoO, LiNbO, YAlO, and AlO crystals has been studied. A relationship between the laser energy density on the sample surface and the surface roughness caused by the irradiation is determined. A technique for determining exactly the geometric surface

A S Kuzanyan; G R Badalyan; V S Kuzanyan; V R Nikogosyan; S Kh Pilosyan; V M Nesterov

2011-01-01

219

Chemical characterization of aerosol particles by laser Raman spectroscopy. Revision  

SciTech Connect

The importance of aerosol particles in many branches of science, such as atmospheric chemistry, combustion, interfacial science, and material processing, has been steadily growing during the past decades. One of the unique properties of these particles is the very high surface-to-volume ratios, thus making them readily serve as centers for gas-phase condensation and heterogeneous reactions. These particles must be characterized by size, shape, physical state, and chemical composition. Traditionally, optical elastic scattering has been applied to obtain the physical properties of these particle (e.g., particle size, size distribution, and particle density). These physical properties are particularly important in atmospheric science as they govern the distribution and transport of atmospheric aerosols.

Fung, K.H.

1999-12-01

220

Effect of absolute laser phase on reaction paths in laser-induced chemical reactions  

SciTech Connect

Potential surfaces, dipole moments, and polarizabilities are calculated by ab initio methods [unrestricted MP2(full)/6-311++G(2d,2p)] along the reaction paths of the F+CH{sub 4} and Cl+CH{sub 4} reaction systems. It is found that in general dipole moments and polarizabilities exhibit peaks near the transition state. In the case of X=F these peaks are on the products side and in the case of X=Cl they are on the reactants side indicating an early transition state in the case of fluorine and a late transition state in the case of chlorine. An analysis of the geometric changes along the reaction paths reveals a one-to-one correspondence between the peaks in the electric properties and peaks in the rate of change of certain internal geometric coordinates along the reaction path. Interaction with short infrared intense laser fields pulses leads to the possibility of interferences between the dipole and polarizability laser-molecule interactions as a function of laser phase. The larger dipole moment in the Cl+CH{sub 4} reaction can lead to the creation of deep wells (instead of energy barriers) and new strongly bound states in the transition state region. This suggests possible coherent control of the reaction path as a function of the absolute phase of the incident field, by significant modification of the potential surfaces along the reaction path and, in particular, in the transition state region.

Bandrauk, Andre D.; Sedik, El-Wallid S.; Matta, Cherif F. [Laboratoire de Chimie Theorique, Faculte des Sciences, Universite de Sherbrooke, Sherbrooke, Quebec J1K 2R1 (Canada); Lash Miller Chemical Laboratories, Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6 (Canada)

2004-10-22

221

Closed-loop control of laser assisted chemical vapor deposition growth of carbon nanotubes  

NASA Astrophysics Data System (ADS)

Laser-assisted chemical vapor deposition growth is an attractive mask-less process for growing locally aligned nanotubes in selected places on temperature sensitive substrates. An essential parameter for a successful and reproducible synthesis of nanotubes is the temperature during growth. Here, we demonstrate a temperature feedback control mechanism based on the dynamic, in situ monitoring of the infrared radiation coupled with reflectivity information. With the information provided by these sensors, an infrared laser, focused on a silicon substrate covered with aluminum-oxide and iron catalyst layers, can be controlled. The growth takes place in a gaseous mixture of argon (carrier gas), hydrogen (process gas), and ethylene (carbon-containing gas). Scanning electron microscopy and Raman spectroscopy analysis demonstrate the excellent reproducibility of the closed-loop control process over multiple experiments. Furthermore, we developed a unique method to identify the onset for catalyst formation and activation by monitoring the fluctuation of the reflected laser beam.

van de Burgt, Yoeri; Bellouard, Yves; Mandamparambil, Rajesh; Haluska, Miro; Dietzel, Andreas

2012-08-01

222

Middle infrared active coherent laser spectrometer for standoff detection of chemicals.  

PubMed

Using a quantum cascade laser emitting at 7.85?m, a middle infrared active coherent laser spectrometer has been developed for the standoff detection of vapor phase chemicals. The first prototype has been tested using diffuse target backscattering at ranges up to ?30??m. Exploiting the continuous frequency tuning of the laser source, spectra of water vapor, methane, nitrous oxide, and hydrogen peroxide were recorded. A forward model of the instrument was used to perform spectral unmixing and retrieve line-of-sight integrated concentrations and their one-sigma uncertainties. Performance was found to be limited by speckle noise originating from topographic targets. For absorbers with large absorption cross sections such as nitrous oxide (>10-19??cm2molecule-1), normalized detection sensitivities range between 14 and 0.3??ppmmHz-1/2, depending on the efficiency of the speckle reduction scheme implemented. PMID:24081032

Macleod, Neil A; Rose, Rebecca; Weidmann, Damien

2013-10-01

223

Direct Laser Ablation and Ionization of Solids for Chemical Analysis by Mass Spectrometry  

SciTech Connect

A laser ablation/ionization mass spectrometer system is described for the direct chemical analysis of solids. An Nd:YAG laser is used for ablation and ionization of the sample in a quadrupole ion trap operated in an ion-storage (IS) mode that is coupled with a reflectron time-of-flight mass spectrometer (TOF-MS). Single pulse experiments have demonstrated simultaneous detection of up to 14 elements present in glasses in the ppm range. However, detection of the components has produced non-stoichiometric results due to difference in ionization potentials and fractionation effects. Time-of-flight secondary ionization mass spectrometry (TOF-SIMS) was used to spatially map elemental species on the surface and provide further evidence of fractionation effects. Resolution (m/Dm) of 1500 and detection limits of approximately 10 pg have been achieved with a single laser pulse. The system configuration and related operating principles for accurately measuring low concentrations of isotopes are described.

Holt, J K; Nelson, E J; Klunder, G L

2005-09-02

224

Chemical taggant detection and analysis by laser-induced breakdown spectroscopy  

SciTech Connect

A commercially available chemical identification taggant that imparts a unique elemental fingerprint to any object and can be analytically distinguished from billions of possible combinations has been developed. The liquid tag is easily applied and, once dry, can be removed and analyzed by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to determine the combination of elements present in the sample. The current study investigates the use of laser-induced breakdown spectroscopy (LIBS) as an alternative, and perhaps more practical, analysis scheme to LA-ICP-MS for this taggant. LIBS provides excellent discrimination potential, sensitivity, and repeatability of analysis for up to 17 rare-earth elements using a Nd:YAG 266 nm or 1064 nm laser and an intensified CCD detector.

Wise, Steven H.; Almirall, Jose R

2008-11-01

225

Comparison of laser-ablation and hot-wall chemical vapour deposition techniques for nanowire fabrication  

NASA Astrophysics Data System (ADS)

A comparison of the transport properties of populations of single-crystal, In2O3 nanowires (NWs) grown by unassisted hot-wall chemical vapour deposition (CVD) versus NWs grown by laser-ablation-assisted chemical vapour deposition (LA-CVD) is presented. For nominally identical growth conditions across the two systems, NWs fabricated at 850 C with laser-ablation had significantly higher average mobilities at the 99.9% confidence level, 53.3 5.8 cm2 V-1 s-1 versus 10.2 1.9 cm2 V-1 s-1. It is also observed that increasing growth temperature decreases mobility for LA-CVD NWs. Transmission electron microscopy studies of CVD-fabricated samples indicate the presence of an amorphous In2O3 region surrounding the single-crystal core. Further, low-temperature measurements verify the presence of ionized impurity scattering in low-mobility CVD-grown NWs.

Stern, E.; Cheng, G.; Guthrie, S.; Turner-Evans, D.; Broomfield, E.; Lei, B.; Li, C.; Zhang, D.; Zhou, C.; Reed, M. A.

2006-06-01

226

Chemical vapor synthesis of nanocrystalline perovskites using laser flash evaporation of low volatility solid precursors  

NASA Astrophysics Data System (ADS)

One key requirement for the production of multinary oxide films by chemical vapor deposition (CVD) or nanocrystalline multinary oxides particles by chemical vapor synthesis (CVS) is the availability of precursors with high vapor pressure. This is especially the case for CVS where much higher production rates are required compared to thin films prepared by CVD. However, elements, which form low valent cations such as alkaline earth metals, are typically only available as solid precursors of low volatility, e.g., in form of ?-diketonates. This study describes laser flash evaporation as precursor delivery method for CVS of nanocrystalline perovskites. Laser flash evaporation exploits the nonequilibrium evaporation of solid metal organic precursors of low vapor pressure by absorption of the infrared radiation of a CO2 laser. It is shown that stoichiometric, nanocrystalline particles consisting of SrZrO3 and SrTiO3 can be formed from corresponding mixtures of ?-diketonates which are evaporated nonselectively and with high rates by laser flash evaporation.

Winterer, Markus; Srdic, Vladimir V.; Djenadic, Ruzica; Kompch, Alexander; Weirich, Thomas E.

2007-12-01

227

Mid-infrared vertical-cavity surface-emitting lasers for chemical sensing.  

PubMed

The first (to our knowledge) III-V mid-IR vertical-cavity surface-emitting lasers (lambda = 2.9 microm) are demonstrated and show promising characteristics for chemical detection applications. The cw optical-pumping threshold is low (4 mW at 80 K) and efficiency is high (5.6% W/W). Pulsed operation is obtained up to 280 K and cw up to 160 K. Lateral-mode confinement will lead to spectrally pure, single-mode output for chemical identification. PMID:18305773

Bewley, W W; Felix, C L; Vurgaftman, I; Aifer, E H; Olafsen, L J; Meyer, J R; Goldberg, L; Chow, D H

1999-03-20

228

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

229

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

230

Modeling of a pump discharge for chemical non-chain-reaction HF lasers  

Microsoft Academic Search

A model of a pump discharge for a chemicalHF laser in aNe\\/SF\\u000a 6\\/C2H6 gaseous mixture excited with a self-maintained discharge is described. The results of numerical modeling are presented. It\\u000a is shown that the density of positive and negative ions in the current maximum of such discharges exceeds the electron density\\u000a by two orders of magnitude.

A. G. Yastremskii; S. A. Yampol'skaya

1999-01-01

231

Laser skin resurfacing, chemical peels, and other cutaneous treatments of the brow and upper lid.  

PubMed

The focus of this article is treatments of the brow and upper lid, in the context of appreciating their relationship to the forehead and periorbital complex to best evaluate and treat. This material is focused on treatments designed to stimulate collagen synthesis, as well as improve fine lines, wrinkles, and overall appearance of the skin, by mechanical dermabrasion, application of chemical peels, laser surgery, and treatment with energy devices including radiofrequency and focused ultrasound. PMID:23186758

Brauer, Jeremy A; Patel, Utpal; Hale, Elizabeth K

2013-01-01

232

Laser photoacoustic spectroscopy helps fight terrorism: High sensitivity detection of chemical Warfare Agent and explosives  

Microsoft Academic Search

.\\u000a Tunable laser photoacoustic spectroscopy is maturing \\u000a rapidly in its applications to real world problems. One of the burning \\u000a problems of the current turbulent times is the threat of terrorist acts \\u000a against civilian population. This threat appears in two distinct forms. The \\u000a first is the potential release of chemical warfare agents (CWA), such as the \\u000a nerve agents, in a crowded

C. K. N. Patel

2008-01-01

233

The development of chemically pumped visible lasers from efficient electronic energy transfer  

NASA Astrophysics Data System (ADS)

Visible chemical laser amplifiers have been generated in select wavelength regions near 527, 492, and 460 nm employing the highly efficient and selective formation of sodium dimer electronically excited states from the sodium trimer-halogen atom, Na3-X, (x = Cl, Br, I) reactions. Witha focus to increasing amplifier gain length and amplifying medium concentration, an extended path length slit source device has been constructed which created intersecting alkali ahd halogen sheaths forming the basis for the development of a visible chemical laser oscillator. This device has now revealed the first Raman pumping resulting entirely from a chemical reaction, the process being observed in the absence of an external light source. Extrapolations on the Na3-X amplifier concept involving Group IIA metal - F, CI reactions are considered. Very near resonant energy transfers from selectively formed metastable states of SiO to receptor alkali atoms form sodium or potassium atom laser amplifiers, resulting in a gain condition at lambda = 569, 616, 819, and 581 mm.

Gole, James L.

1995-06-01

234

Active coherent laser spectrometer for remote detection and identification of chemicals  

NASA Astrophysics Data System (ADS)

Currently, there exists a capability gap for the remote detection and identification of threat chemicals. We report here on the development of an Active Coherent Laser Spectrometer (ACLaS) operating in the thermal infrared and capable of multi-species stand-off detection of chemicals at sub ppm.m levels. A bench top prototype of the instrument has been developed using distributed feedback mid-infrared quantum cascade lasers as spectroscopic sources. The instrument provides active eye-safe illumination of a topographic target and subsequent spectroscopic analysis through optical heterodyne detection of the diffuse backscattered field. Chemical selectivity is provided by the combination of the narrow laser spectral bandwidth (typically < 2 MHz) and frequency tunability that allows the recording of the full absorption spectrum of any species within the instrument line of sight. Stand-off detection at distances up to 12 m has been demonstrated on light molecules such as H2O, CH4 and N2O. A physical model of the stand-off detection scenario including ro-vibrational molecular absorption parameters was used in conjunction with a fitting algorithm to retrieve quantitative mixing ratio information on multiple absorbers.

MacLeod, Neil A.; Weidmann, Damien

2012-10-01

235

Simulations of erosion/corrosion surface chemical reactions with a laser beam  

SciTech Connect

Surface chemical reactions in highly transient reactive environments frequently contribute to material degradation and subsequent loss by erosion/corrosion mechanisms. An attempt was made to simulate these reactions with a pulsed laser system in a pressure chamber. Gaseous carburizing and nitriding reactions were studied because of their frequent occurrence in erosion/corrosion environments. Reactions in pure iron and AISI 4340 steel were characterized by secondary ion mass spectroscopy (SIMS), optical metallography, and scanning electron microscopy (SEM). Gases used for laser-pulsing included argon, methane, carbon monoxide, ammonia, and nitrogen. The effect of gas pressure also was investigated. The results demonstrate that significant amounts of the reactive species can be driven into metal surfaces if the energy of the laser pulse exceeds the threshold for surface melting to occur. Specimen response appears to be reproducibly sensitive to the environment even in the relatively short time frame of the 600-..mu..s laser pulse. Tests also were performed on AISI 4340 steel specimens coated with tungsten to demonstrate the capability of the laser system to test candidate coating materials.

Price, C.W.

1983-11-01

236

Highly (100)-oriented CeO 2 films prepared on amorphous substrates by laser chemical vapor deposition  

Microsoft Academic Search

CeO2 films were prepared on amorphous silica substrates by laser chemical vapor deposition using cerium dipivaloylmethanate precursor and a semiconductor InGaAlAs (808nm in wavelength) laser system. The laser spot size was about 20mm, which was sufficient to cover the whole substrate. Highly (100)-oriented CeO2 films were obtained at extraordinary high deposition rates ranging from 60 to 132?m\\/h. Films exhibited a

J. R. Vargas-Garcia; L. Beltran-Romero; R. Tu; T. Goto

2010-01-01

237

Comparing the bioremoval of black crusts on colored artistic lithotypes of the Cathedral of Florence with chemical and laser treatment  

Microsoft Academic Search

The external walls of the Cathedral of Florence are made of green serpentine, red marlstone and Carrara white marble, and intensive air pollution attack has led to their weathering, which caused black crust formation. A study was performed to evaluate the most appropriate cleaning treatment for black crust removal, adopting chemical (ammonium carbonate poultice), laser (1064nm, Nd:YAG laser), and microbial

Eleonora Giovent; Paola Franca Lorenzi; Federica Villa; Claudia Sorlini; Maria Rizzi; Andrea Cagnini; Alessandra Griffo; Francesca Cappitelli

2011-01-01

238

ACTIVE MEDIA Nonequilibrium population of the first vibrational level of O2(1?) molecules in O2 O2(1?) H2O gas flow at the output of chemical singlet-oxygen generator  

NASA Astrophysics Data System (ADS)

The concentrations of electron-excited particles have been determined by measuring the absolute spectral irradiance in the range of 600 800 nm of O2 O2(1?) H2O gas mixture at the output of a chemical singlet-oxygen generator (SOG). A nonequilibrium population of the first vibrational level of O2(1?) molecules has been clearly observed and found to depend on the water vapour content. In correspondence with the results of these measurements and according to the analysis of kinetics processes in the O2 O2(1?) H2O mixture, the maximum number of vibrational quanta generated in the O2(1?) + O2(1?) ? O2(1?) + O2(3?) reaction is 0.05 0.03. It is concluded that the vibrational population of O2(1?) at the output of the SOG used in a chemical oxygeniodine laser is close to thermal equilibrium value.

Zagidullin, M. V.

2010-11-01

239

Effect of surface topography in the generation of chemical maps by laser-induced plasma spectroscopy  

NASA Astrophysics Data System (ADS)

The development of technologically advanced materials is propelling the improvement of surface analytical techniques. In particular, the composition and hence the properties of most of these new materials are spatial dependent. Between the techniques able to provide chemical spatial information, laser-induced plasma spectroscopy known also as laser-induced breakdown spectroscopy (LIBS) is a very promising analytical technique. During the last decade, LIBS was successfully applied to the analysis of surfaces and the generation of chemical maps of heterogeneous materials. In the LIBS analysis, several experimental factors including surface topography must be taken into account. In this work, the influence of surface roughness in LIBS signal during the point analysis and acquisition of chemical maps was studied. For this purpose, samples of stainless steel with different surface finishes were prepared and analyzed by LIBS. In order to characterize the different surfaces, confocal microscopy images were obtained. Afterwards, both topographic and spectroscopic information were combined to show the relationship between them. Additionally, in order to reveal the effect of surface topography in the acquisition of chemical maps, a three dimensional analysis of a sample exhibiting two different finishes was carried out.

Lopez-Quintas, I.; Pion, V.; Mateo, M. P.; Nicolas, G.

2012-09-01

240

Nondestructive detection of hidden chemical compounds with laser Compton-scattering gamma rays  

NASA Astrophysics Data System (ADS)

A nondestructive assay method for measuring a shielded chemical compound has been proposed. The chemical compound is measured by using a nuclear resonance fluorescence (NRF) measurement technique with an energy tunable laser Compton-scattering (LCS) ?-ray source. This method has an advantage that hidden materials can be detected through heavy shields such as iron plates of a thickness of several centimeters. A detection of a chemical compound of melamine, C3H6N6, shielded by 15-mm-thick iron and 4-mm-thick lead plates is demonstrated. The NRF ?-rays of 12C and 14N of the melamine are measured by using the LCS ?-rays of the energies of up to 5.0 MeV. The observed ratio (12C/14N)exp=0.39+/-0.12 is consistent with (C/N)melamine=0.5.

Hayakawa, Takehito; Ohgaki, Hideaki; Shizuma, Toshiyuki; Hajima, Ryoichi; Kikuzawa, Nobuhiro; Minehara, Eisuke; Kii, Toshiteru; Toyokawa, Hiroyuki

2009-04-01

241

Modeling of a photolytically excited HF chemical laser based on a NF3/H2 gas mixture  

NASA Astrophysics Data System (ADS)

A numerical code has been developed to simulate the characteristics of HF chemical laser based on non-chain reaction pumped by a planar sliding discharge radiation. The model considers transport of VUV pump radiation through the nonlinear absorptive active medium containing NF3/H2/N2/Ar gas mixture coupled with chemical and lasing kinetics describing the temporal and spatial evolution of particle species concentration and intracavity lasing photons density. The relative importance of various kinetic processes is evaluated and a 3.2 J/l laser output specific energy is calculated along the laser axis.

Sabonnadiere, M. P.; Tcheremiskine, V. I.; Sentis, Marc L.; Mikheev, L. D.; Delaporte, Philippe C.

1998-12-01

242

Formation of the chemical composition of transition metal dichalcogenide thin films at pulsed laser deposition  

NASA Astrophysics Data System (ADS)

The formation of the chemical composition of dichalcogenide films at pulsed laser deposition in vacuum and in rarefied gases (Ar, H2) is investigated with MoSe x thin-film coatings. It is found that deposition in gases increases the selenium concentration and somewhat flattens the composition over the substrate surface. To elucidate the mechanisms underlying the MoSe x film formation, a computer model is used that simulates the motion of a pulsed laser-initiated atomic flux through a rarefied gaseous medium. Using this model, the energy and angular parameters of atomic Mo and Se fluxes toward the substrate are calculated. It is shown that the expansion dynamics of laser plume components (Mo and Se) and the selective sputtering of selenium are the main factors governing the formation of the chemical composition and its distribution over the substrate. The influence of the sort of gas on the efficiency of atomic flux slowdown and scattering and on material losses during deposition is considered.

Fominski, V. Yu.; Romanov, R. I.; Gnedovets, A. G.; Nevolin, V. N.

2010-10-01

243

Estimation of risks by chemicals produced during laser pyrolysis of tissues  

NASA Astrophysics Data System (ADS)

Use of laser systems in minimal invasive surgery results in formation of laser aerosol with volatile organic compounds of possible health risk. By use of currently identified chemical substances an overview on possibly associated risks to human health is given. The class of the different identified alkylnitriles seem to be a laser specific toxicological problem. Other groups of chemicals belong to the Maillard reaction type, the fatty acid pyrolysis type, or even the thermally activated chemolysis. In relation to the available different threshold limit values the possible exposure ranges of identified substances are discussed. A rough estimation results in an exposure range of less than 1/100 for almost all substances with given human threshold limit values without regard of possible interactions. For most identified alkylnitriles, alkenes, and heterocycles no threshold limit values are given for lack of, until now, practical purposes. Pyrolysis of anaesthetized organs with isoflurane gave no hints for additional pyrolysis products by fragment interactions with resulting VOCs. Measurements of pyrolysis gases resulted in detection of small amounts of NO additionally with NO2 formation at plasma status.

Weber, Lothar; Spleiss, Martin

1995-01-01

244

Direct synthesis of single-walled carbon nanotubes bridging metal electrodes by laser-assisted chemical vapor deposition  

NASA Astrophysics Data System (ADS)

Direct synthesis of single-walled carbon nanotubes (SWNTs) bridging prepatterned Mo electrodes has been achieved using laser-assisted chemical vapor deposition (LCVD). The synthesized SWNTs are found predominantly semiconducting. By controlling the spot size of the focused laser beam, synthesis of SWNTs can be achieved in a localized manner, which is governed by the thermal and optical properties of materials as well as the laser parameters. The synthesis process is fast and can be achieved in both far- and near-infrared laser wavelength regions. LCVD method provides a potential approach to in situ remove SWNTs with specific chiralities during the growth.

Shi, J.; Lu, Y. F.; Yi, K. J.; Lin, Y. S.; Liou, S. H.; Hou, J. B.; Wang, X. W.

2006-08-01

245

Mid-IR interband cascade lasers for remote chemical sensing applications  

NASA Astrophysics Data System (ADS)

The realization of efficient, compact and easy to operate mid-IR (2-25 ?m) diode lasers could enable the development of a new generation of low cost, light weight and compact remote chemical sensing systems for trace gas detection applications. Recently, we proposed and demonstrated an interband cascade laser based on InAs/Ga(In)Sb type-II quantum wells which operates in the 3-5 ?m atmospheric transmission window and promises significant performance improvement. High power and high efficiency operation has already been achieved at wavelengths around ~4 ?m with the potential to be extended to much longer wavelengths. The threshold current density at 80 K was 290 A/cm2, which is substantially lower than those reported for the quantum cascade lasers, and the characteristic temperature was 81 K at operating temperatures up to 165 K. At 80 K, the maximum output power was ~0.5 W/facet with a slop efficiency of 211 mW/A per facet, corresponding to a differential external quantum efficiency of 1.3 emitted photons per injected electron, which exceeds all previously published mid-IR laser results at this wavelength. However, cross-sectional scanning tunneling microscopy shows the crystalline and interface quality in these structures is far from ideal, suggesting that significant improvement in device performance can be expected with better materials.

Zhang, D.; Lin, C.-H.; Yang, R. Q.; Yang, B. H.; Pei, S. S.; Harper, J.; Weimer, M.

1998-01-01

246

Sub-millisecond post exposure bake of chemically amplified resists by CO2 laser heat treatment  

NASA Astrophysics Data System (ADS)

Chemically amplified photoresists require a post exposure bake (PEB), typically on a hot plate at 90-150C for 30-120 seconds, to catalytically deprotect the polymer backbone. During PEB, excessive diffusion of the photo-generated acid results in loss of line edge definition, blurring of latent images and changes in the line edge roughness. Both acid diffusion and deprotection are thermally activated processes, with the relative rates affected by the time/temperature profile of the PEB. In this work, we introduce an alternate PEB method involving 500 ?s time scale heating over a temperature range of 130C to 450C using a continuous wave CO2 laser. A methodology is developed for characterizing this laser PEB and comparing the behavior with conventional hot plate PEB. The thermal stability of several polymer and photoacid generator (PAG) resist systems were studied and shown to be stable at these high temperatures due to the short heating duration. Sensitivity of resists under hot plate and laser PEB were measured. Under moderate temperatures, the laser PEB sensitivity can exceed that of hot plate PEB by an order of magnitude. Quantitative determination of the acid diffusion was obtained using resist bilayers (PAG loaded / PAG free). Despite the five orders of magnitude difference in PEB time, systems with l-PEB and hot-plate PEB exhibit comparable imaging quality under deep ultraviolet exposure.

Jung, Byungki; Sha, Jing; Paredes, Florencia; Ober, Christopher K.; Thompson, Michael O.; Chandhok, Manish; Younkin, Todd R.

2010-03-01

247

Laser induced and controlled chemical reaction of carbon monoxide and hydrogen  

NASA Astrophysics Data System (ADS)

Bimolecular chemical reaction control of gaseous CO and H2 at room temperature and atmospheric pressure, without any catalyst, using shaped femtosecond laser pulses is presented. High intensity laser radiation applied to a reaction cell facilitates non-resonant bond breakage and the formation of a range of ions, which can then react to form new products. Stable reaction products are measured after irradiation of a reaction cell, using time of flight mass spectroscopy. Bond formation of C-O, C-C, and C-H bonds is demonstrated as CO2+, C2H2+, CH+, and CH3+ were observed in the time of flight mass spectrum of the product gas, analyzed after irradiation. The formation of CO2 is shown to be dependent on laser intensity, irradiation time, and on the presence of H2 in the reaction cell. Using negatively chirped laser pulses more C-O bond formation takes place as compared to more C-C bond formation for unchirped pulses.

Du Plessis, Anton; Strydom, Christien A.; Uys, Hermann; Botha, Lourens R.

2011-11-01

248

The combined effect of laser fluence and target deterioration in determining the chemical composition of pulsed laser deposited boron carbide films  

Microsoft Academic Search

A series of boron carbide films of 18030 nm thickness has been deposited by KrF excimer laser ablation of a sintered B4C target in high vacuum. Rutherford backscattering spectroscopy revealed that the chemical composition of the films grown on Si substrates, at room temperature, at laser fluences tuned between 2 and 14.3 Jcm?2 varied depending not only on the actual

T. Szrnyi; J.-P. Stoquert; F. Antoni; E. Fogarassy

2004-01-01

249

Remote Continuous Wave and Pulsed Laser Raman Detection of Chemical Warfare Agents Simulants and Toxic Industrial Compounds  

Microsoft Academic Search

This study describes the design, assembly, testing and comparison of two Remote Raman Spectroscopy (RRS) systems intended for standoff detection of hazardous chemical liquids. Raman spectra of Chemical Warfare Agents Simulants (CWAS) and Toxic Industrial Compounds (TIC) were measured in the laboratory at a 6.6 m source-target distance using continuous wave (CW) laser detection. Standoff distances for pulsed measurements were

William Ortiz-Rivera; Leonardo C. Pacheco-Londoo; Samuel P. Hernndez-Rivera

2010-01-01

250

Electric-discharge chemical laser utilizing a mixture of chlorine monofluoride with hydrogen  

SciTech Connect

A determination was made of the energy, spectrum, and duration of emission of radiation generated as a result of vibrational--rotational transitions in HF and HCl molecules in a chemical laser utilizing ClF--H/sub 2/--He mixtures and subjected to short-pulse initiation of the pump reactions by a transverse electric discharge preceded by photopreionization. When the total energy of the output radiation pulses due to both HF and HCl molecules was 0.16 J, the efficiency of the laser measured relative to the energy deposited in the active medium was 60%, the specific output energy was 4 J/liter, and the power per pulse was 0.4 MW.

Kolovskii, V.B.; Drobakha, S.A.; Zhitneva, G.P.; Abakumov, G.A.; Simonov, A.P.

1984-12-01

251

Frequency-tunable UV laser system for biological and chemical detection  

NASA Astrophysics Data System (ADS)

An efficient, compact, tunable ultraviolet laser system has been constructed by frequency tripling a Q-switched, tunable near-infrared Cr:LiSAF laser source. The nonlinear conversion from the fundamental to the third harmonic was accomplished through second harmonic generation in lithium triborate (LBO) followed by sum frequency mixing of the fundamental and the second harmonic in beta-barium borate (BBO). Third harmonic output with this combination of nonlinear crystals has yielded 5 mJ of energy at 280 nm with an overall conversion efficiency of 7%. The Cr:LiSAF master oscillator has been modeled in detail to optimize performance. System specifications of tuning range, linewidth, output energy, temporal behavior, and repetition rate were determined by the end use application as a UV excitation source for a chemical and biological stand-off detection system.

Gorda, James E.; Park, Eric D.; Richardson, Martin C.; Fox, Jay A.; Swim, Cynthia R.

1996-06-01

252

Selective reactivity, ultrafast energy transfer and the development of chemically pumped visible lasers  

NASA Astrophysics Data System (ADS)

Two successful approaches to the formation of electronically inverted atomic diatomic configurations based on (1) highly efficient near resonant intermolecular energy transfer, and (2) highly efficient and selective fast direct chemical reaction are outlined. Near resonant energy transfer pumping from selectively formed metastable states of SiO and GeO is used to form thallium, gallium, sodium, and potassium atom laser amplifiers at lambda = 535, 417, 569, 616, 819, and 581 nm. The gain condition in the Tl, Ga, Na, and K systems forms the basis for full cavity oscillation on the Tl 7(sup 2)S(sub 1/2)- 6(sup 2)P(sub 3/2) transition at 535 nm and the Na 4d(sup 2)D - 3p(sup 2)P transition at 569 m. The extremely high cross section Na(sub n) (n=2,3) - X(Cl,Br,I) reactions are employed to create a continuous electronic population inversion based on the chemical pumping of sodium dimer (Na2). Optical gain through stimulated emission was demonstrated in select regions close to 527, 492, and 460 nm. The considered amplifiers are being optimized and modeled with a focus to increasing amplifier gain length and amplifying medium concentration so as to facilitate their conversion to visible chemical laser oscillators. The study of addition analog systems suggests that the two concepts considered wil be generic.

Gole, James L.

1992-11-01

253

'Laser chemistry' synthesis, physicochemical properties, and chemical processing of nanostructured carbon foams.  

PubMed

Laser ablation of selected coordination complexes can lead to the production of metal-carbon hybrid materials, whose composition and structure can be tailored by suitably choosing the chemical composition of the irradiated targets. This 'laser chemistry' approach, initially applied by our group to the synthesis of P-containing nanostructured carbon foams (NCFs) from triphenylphosphine-based Au and Cu compounds, is broadened in this study to the production of other metal-NCFs and P-free NCFs. Thus, our results show that P-free coordination compounds and commercial organic precursors can act as efficient carbon source for the growth of NCFs. Physicochemical characterization reveals that NCFs are low-density mesoporous materials with relatively low specific surface areas and thermally stable in air up to around 600C. Moreover, NCFs disperse well in a variety of solvents and can be successfully chemically processed to enable their handling and provide NCF-containing biocomposite fibers by a wet-chemical spinning process. These promising results may open new and interesting avenues toward the use of NCFs for technological applications. PMID:23679938

Seral-Ascaso, Andrs; Garriga, Rosa; Sanjun, Mara Luisa; Razal, Joselito M; Lahoz, Ruth; Laguna, Mariano; de la Fuente, Germn F; Muoz, Edgar

2013-05-16

254

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

255

Laser-Micromachined and Laminated Microfluidic Components for Miniaturized Thermal, Chemical and Biological Systems  

SciTech Connect

Microchannel microfluidic components are being developed for heat transfer, chemical reactor, chemical analysis, and biological analytical applications. Specific applications include chemical sensing, DNA replication, blodd analysis, capillary electrophoresis, fuel cell reactors, high temperature chemical reactors, heat pumps, combustors, and fuel processors. Two general types of component architectures have been developed and the fabrication processes defined. All involve a lamination scheme using plastic, ceramic, or metal laminates, as opposed to planar components. The first type is a stacked architecture that utilizes functionality built in each layer, with fluid flow interconnects between layers. Each layer of the laminate has specific microchannel geometry, and performs a specific function (such as mixing, heat exchange, or chemical reaction). Polymeric materials are used primarily. Fabrication processes used are laser micromaching, wet and dry etching, and coating deposition. T he laminates can also be micromolded plastics. The second architecture employs laminates to form internal microchannels and interconnects. Materials include ceramic tapes and high temperature metals. Catalysts can be placed in the microchannels. Fabrication processes used are diffusion bonding, ceramic bonding and firing, photochemical etching, and electrochemical micromaching. Bonding, thus sealing, the laminates is an important issue. Process conditions have been developed to reduce distortion of the laminates and to hermetically seal the components.

Martin, Peter M. (BATTELLE (PACIFIC NW LAB)); Matson, Dean W. (BATTELLE (PACIFIC NW LAB)); Bennett, Wendy D. (BATTELLE (PACIFIC NW LAB)); Stewart, Donald C. (BATTELLE (PACIFIC NW LAB)); Lin, Yuehe (BATTELLE (PACIFIC NW LAB))

1999-01-01

256

Pulsed high-pressure chemical HF laser with electric-discharge initiation  

SciTech Connect

Measurements were made of the energy and time characteristics of the radiation emitted by a chemical HF laser subjected to short-pulse (approx.100 nsec) electric-discharge initiation. A mixture of the composition F/sub 2/:O/sub 2/:SF/sub 6/:H/sub 2/ = 6.5:0.7:15.0:2.0 with a total pressure of 180 Torr had a specific output energy of 17.5 J/liter. The efficiency of conversion of the energy deposited in the discharge was approx.65% and the active volume was approx.0.3 liter.

Bosamykin, V.S.; Gordon, E.B.; Gorokhov, V.V.; Karelin, V.I.; Matyushenko, V.I.; Repin, P.B.; Sizov, V.D.

1982-07-01

257

Nucleation and Growth of Silicon Thin Film Microstructures by Localized Laser Chemical Vapor Deposition.  

NASA Astrophysics Data System (ADS)

Localized laser chemical vapor deposition (LLCVD) has become an important process for the direct generation of thin film microstructures, and is finding novel applications in microelectronics processing. Understanding the fundamental dynamics associated with thin film growth by LLCVD is necessary to control interface and thin film properties, and maintain reproducibility of deposit formation. In this dissertation, the nucleation and initial stages of silicon thin film growth by LLCVD from low pressure (<10 Torr) silane (SiH_4) on surfaces of c-Si and amorphous Si_{rm x}N_{rm y} are investigated. The nucleation stage of thin film growth is modeled via a real time Monte Carlo simulation. This model includes the effects of laser-substrate heating, transport of parent molecules to the surface and reaction products away from the surface, heterogeneous pyrolytic decomposition of the parent molecule on the laser-heated region of the surface, and adatom migration and desorption dynamics. The first predictions of the initial thin film morphology and its temporal evolution during static laser-heating of micron -dimensional regions of the surface are obtained. The nucleation phase of thin film growth is shown to influence the initial thin film morphology strongly. Silicon thin films are grown by LLCVD from silane on well prepared surfaces of c-Si and Si_ {rm x}N_{rm y} using a focused (2.3 ?m diameter FWHM), visible (2.4 eV) laser. The thin film growth characteristics are subsequently determined by scanning electron microscopy and stylus profilometry, and compared to model predictions. For silicon thin films grown on the Si(100) surface, the experimentally measured overall growth rate, incubation period prior to nucleation, and the deposit morphology deviate sharply vis a vis model predictions. The first experiments of silicon thin film growth by hybrid-heating deposition, in which both thermal conduction heating and laser-heating are used simultaneously, are conducted to resolve these discrepancies. In summary, for deposition on Si surfaces, suppressed silicon growth and an altered morphology are observed within the laser -irradiated region, strongly indicating that a nonthermal, nonCVD growth mechanism is important in silicon thin film growth by LLCVD. This nonthermal effect is attributed to an interaction between silicon adatoms and the large concentration of photon-induced electron-hole pairs at the silicon surface. This is the first reported observation of a nonthermal growth mechanism in LLCVD under these conditions, and this effect is shown to be responsible for the deviations between the LLCVD experimental results and model predictions.

Kotecki, David Edward

258

Chemical applications of laser- and sympathetically-cooled ions in ion traps.  

PubMed

Ensembles of cold atomic and molecular ions in ion traps prepared at millikelvin temperatures by laser and sympathetic cooling have recently found considerable interest in both physics and chemistry. At very low temperatures the ions form ordered structures in the trap also known as "Coulomb crystals". Ion Coulomb crystals exhibit a range of intriguing properties which render them attractive systems for novel experiments in chemical dynamics, ultrahigh-resolution spectroscopy and quantum-information processing. In this article we review the methods used to prepare atomic and molecular ion Coulomb crystals and discuss some recent studies in mass spectrometry, low-temperature chemistry and precision spectroscopy to illustrate their scientific potential for chemical applications. Finally, we conclude with an outlook on outstanding challenges and prospective further developments in the field. PMID:19060963

Willitsch, Stefan; Bell, Martin T; Gingell, Alexander D; Softley, Timothy P

2008-10-22

259

A 2D CFD comparison of straight versus contoured wall HF chemical laser nozzle designs  

NASA Astrophysics Data System (ADS)

This paper presents the results of a comparison of the flowfields produced by Two Dimensional Computational Fluid Dynamics (2D CFD) analysis of the current Hypersonic Low Temperature (HYLTE) HF chemical laser straight wall design with that of an optimized contour design. The 2D CFD model used for the comparison is the PARCH/LF code that solves the full Navier Stokes equations, including detailed finite-rate chemical kinetics, using state-of-art implicit procedures based in block-matrix inversion within a time-asymptotic framework to arrive at the steady state solution. Results from the analysis are presented as comparisons of selected line plots and color filled contour plats for the temperature, velocity, specie concentrations and other flow properties in the nozzle base/cavity region.

Long, Jerry E.; Smith, Wilford

1992-07-01

260

A 2D CFD comparison of straight versus contoured wall HF chemical laser nozzle designs  

SciTech Connect

This paper presents the results of a comparison of the flowfields produced by Two Dimensional Computational Fluid Dynamics (2D CFD) analysis of the current Hypersonic Low Temperature (HYLTE) HF chemical laser straight wall design with that of an optimized contour design. The 2D CFD model used for the comparison is the PARCH/LF code that solves the full Navier Stokes equations, including detailed finite-rate chemical kinetics, using state-of-art implicit procedures based in block-matrix inversion within a time-asymptotic framework to arrive at the steady state solution. Results from the analysis are presented as comparisons of selected line plots and color filled contour plats for the temperature, velocity, specie concentrations and other flow properties in the nozzle base/cavity region. 3 refs.

Long, J.E.; Smith, W. (Science Applications International Corp., Marietta, GA (United States))

1992-07-01

261

InGaAsP-InP planar-stripe lasers fabricated by wet chemical etching  

NASA Astrophysics Data System (ADS)

It is pointed out that the 1.4-1.7 micrometers spectral region is currently of great interest because of the recent development of low-loss optical fibers for this region. InGaAsP-InP double-heterostructure (DH) lasers emitting in the 1.4-1.7 micrometers wavelength range become therefore prospective light sources for an optical fiber communication system. An investigation is reported concerning the monolithic fabrication of planar-stripe InGaAsP-InP DH lasers by wet chemical etching. The InGaAsP-InP wafers used in the experiments were grown in a specially designed carbon boat by low-temperature liquid phase epitaxy. The four-layer double heterostructure, nI-InP, InGaAsP, p-InP and n-InGaAsP was grown on a (001) n-InP substrate. To prepare the planar-stripe laser, a SiO2 film was sputtered onto the n-InGaAsP cap layer and 10-micrometers wide stripe windows were opened by standard photolithography techniques. A 0.3 vol. % Br2 in methanol solution was used in the experiments.

Adachi, S.; Kawaguchi, H.

1981-05-01

262

Laser-micromachined and laminated microfluidic components for miniaturized thermal, chemical, and biological systems  

NASA Astrophysics Data System (ADS)

Microchannel microfluidic components are being developed for heat transfer, chemical reactor, chemical analysis, and biological analytical applications. Specific applications include chemical sensing, DNA replication, blood analysis, capillary electrophoresis, fuel cell reactors, high temperature chemical reactors, heat pumps, combustors, and fuel processors. Two general types of component architectures have been developed and the fabrication processes defined. All involve a lamination scheme using plastic, ceramic, or metal laminates, as opposed to planar components. The first type is a stacked architecture that utilizes functionality built in each layer, with fluid flow interconnects between layers. Each layer of the laminate has specific microchannel geometry, and performs a specific function. Polymeric materials are used primarily. Fabrication processes used are laser micromachining, wet and dry etching, and coating deposition. the laminates can also be micromolded plastics. The second architecture employs laminates to form internal microchannels and interconnects. Materials include ceramic tapes and high temperature metals. Catalysts can be placed in the microchannels. Fabrication processes used are diffusion bonding, ceramic bonding and firing, photochemical etching, and electrochemical micromachining. Bonding, thus sealing, the laminates is an important issue. Process conditions have been develop to reduce distortion of the laminates and to hermetically seal the components.

Martin, Peter M.; Matson, Dean W.; Bennett, Wendy D.; Stewart, Donald C.; Lin, Yuehe

1999-03-01

263

Strong chemical bond of stable He2 in strong linearly polarized laser fields  

NASA Astrophysics Data System (ADS)

The van der Waals complex of the helium dimer has a binding energy of 10-7 eV and a bond distance of 52 . Our ab initio electronic structure calculations show that in an ac electric field of ?5.6141019 W/cm2 with a high photon energy (?108 eV), stable He2 molecules with a binding energy of 12.5 eV, which are much stronger than conventional molecular hydrogen bonds, are produced. The chemical bond distance of He2 produced by the strong laser field is equal to 2.01 . The strength of the chemical bond of He2 is reflected in more than 4500 rovibrational bound states. The strongly bound He2 is aligned by the linear polarized field, like in other diatomic molecules. However, it is shown that the mechanism of the alignment of the He2 molecule produced by light differs from the usual alignment mechanism of real molecules. Our results indicate the possibility of producing unusual chemical species, and perhaps chemical reactions that differ from what we know today, in the presence of strong electromagnetic radiation.

Balanarayan, P.; Moiseyev, Nimrod

2012-03-01

264

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

Microsoft Academic Search

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

R. WINDHOLZ; P. A. MOLIAN

1997-01-01

265

HF repetitively pulsed chemical laser with a large discharge gap operating on the mixture F2 + H2  

Microsoft Academic Search

The efficient repetitively pulsed (10 Hz) HF chemical laser initiated by barrier electric discharge with electrode gap 10 cm was realised. In mono-pulse mode specific output energy 3 and 23 J\\/l, technical efficiency (eta) 3.4 and 26%, for non-chain and chain process, correspondingly, were obtained. In the repetitively pulsed (RP) mode of the laser operation at 10 Hz on the

Boris S. Alexandrov; Evgueni A. Klimuk; Constantin A. Kutumov; Bernard Lacour; Vincent Puech; Georgiy A. Troshchinenko

2005-01-01

266

Efficiency of an electron-beam-pumped chemical laser with an SF 6 -H 2 working mixture  

Microsoft Academic Search

Results are presented from a study of HF lasers pumped by non-chain chemical reactions initiated by a radially convergent\\u000a and by a planar electron beam. The main channels of formation of vibrationally excited HF molecules are analyzed. The distribution\\u000a of the energy density of the radiation in the output beam of a wide-aperture laser is measured. In 30 liters of

V. M. Orlovskii; . A. Sosnin; V. F. Tarasenko; A. G. Ponomarenko; Yu. I. Khapov

1999-01-01

267

Continuous deposition of carbon nanotubes on a moving substrate by open-air laser-induced chemical vapor deposition  

Microsoft Academic Search

Continuous deposition of carbon nanotubes under open-air conditions on a moving fused quartz substrate is achieved by pyrolytic laser-induced chemical vapor deposition. A CO2 laser is used to heat a traversing fused quartz rod covered with bimetallic nanoparticles. Pyrolysis of hydrocarbon precursor gas occurs and subsequently gives rise to rapid growth of a multi-wall carbon nanotube forest on the substrate

Kinghong Kwok; Wilson K. S. Chiu

2005-01-01

268

Comparisons between a gas-phase model of silane chemical vapor deposition and laser-diagnostic measurements  

Microsoft Academic Search

Theoretical modeling and experimental measurements have been used to study gas-phase chemistry in the chemical vapor deposition (CVD) of silicon from silane. Pulsed laser Raman spectroscopy was used to obtain temperature profiles and to obtain absolute density profiles of silane during deposition at atmospheric and 6-Torr total pressures for temperatures ranging from 500 to 800°C. Laser-excited fluorescence was used to

William G. Breiland; Michael E. Coltrin; Pauline Ho

1986-01-01

269

Comparisons between a gas-phase model of silane chemical vapor deposition and laser-diagnostic measurements  

Microsoft Academic Search

Theoretical modeling and experimental measurements have been used to study gas-phase chemistry in the chemical vapor deposition (CVD) of silicon from silane. Pulsed laser Raman spectroscopy was used to obtain temperature profiles and to obtain absolute density profiles of silane during deposition at atmospheric and 6-Torr total pressures for temperatures ranging from 500 to 800 C. Laser-excited fluorescence was used

William G. Breiland; Michael E. Coltrin; Pauline Ho

1986-01-01

270

A review of laser machining of composites and the chemical by-product formed by such processes  

NASA Astrophysics Data System (ADS)

The laser-cutting of polymers and polymer-based composites is reviewed with emphasis placed on the chemical by-products formed by such processes. It has been reported that toxic and potentially carcinogenic materials are formed; therefore, appropriate control measures need to be incorporated into the engineering design of laser-cutting facilities to maintain air quality of the workplace within the guidelines established by governmental regulatory agencies.

Doyle, Daryl J.

271

Chemical characterization of microparticles by laser ablation in an ion trap mass spectrometer  

SciTech Connect

We are developing a new technique for the chemical characterization of microparticles based upon the use of electrodynamic traps. The electrodynamic trap has achieved widespread use in the mass spectrometry community in the form of the ion trap mass spectrometer or quadrupole ion trap. Small macroscopic particles can be confined or leviated within the electrode structure of a three-dimensional quadrupole electrodynamic trap in the same way as fundamental charges or molecular ions by using a combination of ac and dc potentials. Our concept is to use the same electrode structure to perform both microparticle levitation and ion trapping/mass analysis. The microparticle will first be trapped and spatially stabilized within the trap for characterization by optical probes, i.e., absorption, fluorescence, or Raman spectroscopy. After the particle has been optically characterized, it is further characterized using mass spectrometry. Ions are generated from the particle surface using laser ablation or desorption. The characteristics of the applied voltages are changed to trap the ions formed by the laser with the ions subsequently mass analyzed. The work described in this paper focuses on the ability to perform laser desorption experiments on microparticles contained within the ion trap. Laser desorption has previously been demonstrated in ion trap devices by applying the sample to a probe which is inserted so as to place the sample at the surface of the ring electrode. Our technique requires the placement of a microparticle in the center of the trap. Our initial experiments have been performed on falling microparticles rather than levitated particles to eliminate voltage switching requirements when changing from particle to ion trapping modes.

Dale, J.M.; Whitten, W.B.; Ramsey, J.M.

1991-01-01

272

Bioactive Ti metal analogous to human cancellous bone: Fabrication by selective laser melting and chemical treatments.  

PubMed

Selective laser melting (SLM) is a useful technique for preparing three-dimensional porous bodies with complicated internal structures directly from titanium (Ti) powders without any intermediate processing steps, with the products being expected to be useful as a bone substitute. In this study the necessary SLM processing conditions to obtain a dense product, such as the laser power, scanning speed, and hatching pattern, were investigated using a Ti powder of less than 45 ?m particle size. The results show that a fully dense plate thinner than 1.8 mm was obtained when the laser power to scanning speed ratio was greater than 0.5 and the hatch spacing was less than the laser diameter, with a 30 ?m thick powder layer. Porous Ti metals with structures analogous to human cancellous bone were fabricated and the compressive strength measured. The compressive strength was in the range 35-120 MPa when the porosity was in the range 75-55%. Porous Ti metals fabricated by SLM were heat-treated at 1300 C for 1h in an argon gas atmosphere to smooth the surface. Such prepared specimens were subjected to NaOH, HCl, and heat treatment to provide bioactivity. Field emission scanning electron micrographs showed that fine networks of titanium oxide were formed over the whole surface of the porous body. These treated porous bodies formed bone-like apatite on their surfaces in a simulated body fluid within 3 days. In vivo studies showed that new bone penetrated into the pores and directly bonded to the walls within 12 weeks after implantation into the femur of Japanese white rabbits. The percentage bone affinity indices of the chemical- and heat-treated porous bodies were significantly higher than that of untreated implants. PMID:20883832

Pattanayak, Deepak K; Fukuda, A; Matsushita, T; Takemoto, M; Fujibayashi, S; Sasaki, K; Nishida, N; Nakamura, T; Kokubo, T

2010-09-29

273

In Situ Chemical Composition Measurements of Planetary Surfaces with a Laser Ablation Mass Spectrometer  

NASA Astrophysics Data System (ADS)

The knowledge of the chemical composition of moons, comets, asteroids or other planetary bodies is of particular importance for the investigation of the origin and evolution of the Solar System. For cosmochemistry, the elemental and isotopic composition of the surface material is essential information to investigate origin, differentiation and evolution processes of the body and therefore the history of our Solar System [1]. We show that the use of laser-based mass spectrometers is essential in such research because of their high sensitivity in the ppm range and their capability for quantitative elemental and isotopic analysis. A miniaturised Laser Ablation Time-of-Flight Mass Spectrometer (LMS) was developed in our group to study the elemental composition of solid samples [2]. The instrument's small size and light weight make it suitable for an application on a space mission to determine the elemental composition of a planetary surface for example [3]. Meteorites offer the excellent possibility to study extraterrestrial material in the laboratory. To demonstrate the sensitivity and functionality of the LMS instrument, a sample of the Allende meteorite has been investigated with a high spatial resolution. The LMS measurements allowed investigations of the elemental abundances in the Allende meteorite and detailed studies of the mineralogy and volatility [4]. These approaches can be of considerable interest for in situ investigation of grains and inhomogeneous materials with high sensitivity on a planetary surface. [1] Wurz, P., Whitby, J., Managadze, G., 2009, Laser Mass Spectrometry in Planetary Science, AIP Conf. Proc. CP1144, 70-75. [2] Tulej, M., Riedo, A., Iakovleva, M., Wurz, P., 2012, Int. J. Spec., On Applicability of a Miniaturized Laser Ablation Time of Flight Mass Spectrometer for Trace Element Measurements, article ID 234949. [3] Riedo, A., Bieler, A., Neuland, M., Tulej, M., Wurz, P., 2012, Performance evaluation of a miniature laser ablation time-of-flight mass spectrometer designed for in-situ investigations in planetary space research, J. Mass Spectrom., in press. [4] Neuland, M.B., Meyer, S., Mezger, K., Riedo, A., Tulej, M., Wurz, P., Probing the Allende meteorite with a miniature Laser-Ablation Mass Analyser for space application, Planetary and Space Science, Special Issue: Terrestrial Planets II, submitted

Brigitte Neuland, Maike; Riedo, Andreas; Meyer, Stefan; Mezger, Klaus; Tulej, Marek; Wurz, Peter

2013-04-01

274

Static diode pumped alkali lasers: Model calculations of the effects of heating, ionization, high electronic excitation and chemical reactions  

NASA Astrophysics Data System (ADS)

The effects of heating, ionization, high electronic excitation and chemical reactions on the operation of diode pumped alkali lasers (DPALs) with a static, non-flowing gain medium are calculated using a semi-analytical model. Unlike other models, assuming a three-level scheme of the laser and neglecting influence of the temperature on the lasing power, it takes into account the temperature rise and losses of neutral alkali atoms due to ionization and chemical reactions, resulting in decrease of the pump absorption and slope efficiency. Good agreement with measurements in a static DPAL [B.V. Zhdanov, J. Sell, R.J. Knize, Electron. Lett. 44 (2008) 582] is obtained. It is found that the ionization processes have a small effect on the laser operation, whereas the chemical reactions of alkali atoms with hydrocarbons strongly affect the lasing power.

Barmashenko, B. D.; Rosenwaks, S.; Heaven, M. C.

2013-04-01

275

Morphology and chemical composition analysis on multi-pulsed CO2 laser ablation of HgCdTe crystals  

NASA Astrophysics Data System (ADS)

In order to study deeply damage mechanism of HgCdTe crystal irradiated by multi-pulsed CO2 laser and obtain the characteristics of surface morphological and chemical composition changes. Firstly, Irradiation effect experiment is conducted on the Hg0.826Cd0.174Te crystal by pulsed CO2 laser, which has a pulse width of 200ns and repetition frequency ranges from 1 Hz to 100 kHz. Then morphological and chemical composition changes of Hg0.826Cd0.174Te crystal is measured by field emission scanning electron microscope (FESEM) and damage threshold is obtained by morphology method. Finally, the impact of laser power density on morphological and chemical composition changes is analyzed. The research results show that: damage threshold of Hg0.826Cd0.174Te crystal which is irradiated by multi-pulsed CO2 laser is 950 W/cm2. The crystal surface melting phenomenon is very obvious, the obvious crack which is caused by thermal stress is not found in the surface, and a large number of bulges and pits are taken shape in the laser ablation zone. Chemical composition changes of the crystal are obvious, and a lot of O element is found in the laser ablation zone. With the increase of laser irradiation power, the content of Hg element decrease rapidly, the content of Cd, Te and O element raise by degrees, and chemical composition changes of the crystal are more and more obvious. When the irradiation power density is 1.8kW/cm2, the surface becomes smooth in the ablation zone due to the impact of laser impulse force, and the content of the chemical compositions is that Hg accounts for 0.23%, Cd accounts for 21.38%, Te accounts for 26.27%, and O accounts for 52.12%. The conclusions of the study have a reference value for the Hg0.826Cd0.174Tecrystal in the application of making infrared detector and pulsed CO2 laser in the aspect of laser processing.

Tang, Wei; Guo, Jin; Shao, Jun-feng; Wang, Ting-feng

2013-09-01

276

An infrared free-electron laser for the Chemical Dynamics Research Laboratory  

NASA Astrophysics Data System (ADS)

This document describes a free-electron laser (FEL) proposed as part of the Chemical Dynamics Research Laboratory (CDRL), a user facility that also incorporates several advanced lasers of conventional design and two beamlines for the ALS. The FEL itself addresses the needs of the chemical sciences community for a high-brightness, tunable source covering a broad region of the infrared spectrum--from 3 to 50 microns. All of these sources, together with a variety of sophisticated experimental stations, will be housed in a new building to be located adjacent to the ALS. The radiation sources can be synchronized to permit powerful two-color, pump-probe experiments that will further our fundamental understanding of chemical dynamics at the molecular level, especially those aspects relevant to practical issues in combustion chemistry. The technical approach adopted in this design makes use of superconducting radiofrequency (SCRF) accelerating structures. The primary motivation for adopting this approach was to meet the user requirement for wavelength stability equal to one part in 10(exp 4). Previous studies concluded that a wavelength stability of only one part in 10(exp 3) could be achieved with currently available room-temperature technology. In addition, the superconducting design operates in a continuous-wave (CW) mode and hence offers considerably higher average optical output power. It also allows for various pulse-gating configurations that will permit simultaneous multiuser operations. A summary of the comparative performance attainable with room-temperature and superconducting designs is given. The FEL described in this report provides a continuous train of 30-ps micropulses, with 100 micro-J of optical energy per micropulse, at a repetition rate of 6.1 MHz. The device can also deliver pulses at a cw repetition rate of 12.2 MHz, with a peak power of 50 micro-J per micropulse.

Vaughan, D.

1992-04-01

277

An infrared free-electron laser for the Chemical Dynamics Research Laboratory. Design report  

SciTech Connect

This document describes a free-electron laser (FEL) proposed as part of the Chemical Dynamics Research Laboratory (CDRL), a user facility that also incorporates several advanced lasers of conventional design and two beamlines for the ALS. The FEL itself addresses the needs of the chemical sciences community for a high-brightness, tunable source covering a broad region of the infrared spectrum -- from 3 to 50 {mu}m. All of these sources, together with a variety of sophisticated experimental stations, will be housed in a new building to be located adjacent to the ALS. The radiation sources can be synchronized to permit powerful two-color, pump-probe experiments that will further our fundamental understanding of chemical dynamics at the molecular level, especially those aspects relevant to practical issues in combustion chemistry. The technical approach adopted in this design makes use of superconducting radiofrequency (SCRF) accelerating structures. The primary motivation for adopting this approach was to meet the user requirement for wavelength stability equal to one part in 10{sup 4}. Previous studies concluded that a wavelength stability of only one part in 10{sup 3} could be achieved with currently available room-temperature technology. In addition, the superconducting design operates in a continuous-wave (cw) mode and hence offers considerably higher average optical output power. It also allows for various pulse-gating configurations that will permit simultaneous multiuser operations. A summary of the comparative performance attainable with room-temperature and superconducting designs is given. The FEL described in this report provides a continuous train of 30-ps micropulses, with 100{mu}J of optical energy per micropulse, at a repetition rate of 6.1 MHz. The device can also deliver pulses at a cw repetition rate of 12.2 MHz, with a peak power of 50 {mu}J per micropulse. 70 ref.

Vaughan, D. [comp.

1992-04-01

278

An infrared free-electron laser for the Chemical Dynamics Research Laboratory  

SciTech Connect

This document describes a free-electron laser (FEL) proposed as part of the Chemical Dynamics Research Laboratory (CDRL), a user facility that also incorporates several advanced lasers of conventional design and two beamlines for the ALS. The FEL itself addresses the needs of the chemical sciences community for a high-brightness, tunable source covering a broad region of the infrared spectrum -- from 3 to 50 {mu}m. All of these sources, together with a variety of sophisticated experimental stations, will be housed in a new building to be located adjacent to the ALS. The radiation sources can be synchronized to permit powerful two-color, pump-probe experiments that will further our fundamental understanding of chemical dynamics at the molecular level, especially those aspects relevant to practical issues in combustion chemistry. The technical approach adopted in this design makes use of superconducting radiofrequency (SCRF) accelerating structures. The primary motivation for adopting this approach was to meet the user requirement for wavelength stability equal to one part in 10{sup 4}. Previous studies concluded that a wavelength stability of only one part in 10{sup 3} could be achieved with currently available room-temperature technology. In addition, the superconducting design operates in a continuous-wave (cw) mode and hence offers considerably higher average optical output power. It also allows for various pulse-gating configurations that will permit simultaneous multiuser operations. A summary of the comparative performance attainable with room-temperature and superconducting designs is given. The FEL described in this report provides a continuous train of 30-ps micropulses, with 100{mu}J of optical energy per micropulse, at a repetition rate of 6.1 MHz. The device can also deliver pulses at a cw repetition rate of 12.2 MHz, with a peak power of 50 {mu}J per micropulse. 70 ref.

Vaughan, D. (comp.)

1992-04-01

279

C-w (continuous-wave) stimulated brillouin scattering of long-pulse chemical laser beams. Technical report  

SciTech Connect

Backward Stimulated Brillouin Scattering (SBS) is currently under consideration as a nonlinear optical process for passive phase conjugation (beam clean up) phase matching (beam combination), and pointing and tracking of continuous-wave (CW) HF chemical lasers for high power applications. Theoretical considerations indicate, however, that forward SBS processes dominate over backward SBS phenomena in the steady-state limit, so that SBS exhibits the desired properties (phase conjugation) only for short time periods. Since backward SBS thresholds for CW HF lasers are about 0.20 MW per spectral line, long-pulse laboratory chemical laser sources (PCLs) are needed to investigate small-angle forward scattering phenomena and the development of techniques for their suppression. The laser data presented herein suggest that a moderate-volume, photolysis-pumped PCL is a suitable source for the study of steady-state forward SBS processes and their suppression. In particular, low pressure PCLs can simulate CW HF-laser SBS behavior under conditions of the proper bandwidth, laser spectrum, SBS media effects, longitudinal mode structure, and other high-power HF laser characteristics.

Amimoto, S.T.; Hofland, R.

1989-11-15

280

Studies of elementary processes and coupling involved in the D2/F2 chemical laser  

NASA Astrophysics Data System (ADS)

The performance of a H2/D2 chemical laser is a function of the nascent energy disposal parameters for the F + H2 (D2) and H (D) + F2 chemical reactions and the vibrational relaxation of HF (DF). Chemiluminescence Mapping (CM) in which chemical components are observed by their spectral and time resolution is a technique which is capable of providing fundamental information on both nascent energy distributions for bimolecular exchange reactions and vibrational relaxation. Knowledge of the reactants (atoms or ions) and residence times must be known in order to interpret the data. Using a double floating probe the ion content flowing from a microwave discharge of hydrogen was found to be less than .0000018 of the total flow, thus ion molecule reactions are unimportant. The interpretation of CM experiments requires realistic modeling to deconvolute the experimental data. Both types of CM experiments provide nascent vibrational energy distributions. CM-LP experiments also provide total reaction rate constants and microscopic relaxation rate constants. In addition to the F + H2(D2) benchmark reactions, experimental results for H(D)+F2, F+ HBr, and F+CH2Cls are discussed and compared to other studies when available.

Tardy, D. C.

1986-12-01

281

Examination of the laser-induced variations in the chemical etch rate of a photosensitive glass ceramic  

NASA Astrophysics Data System (ADS)

Previous studies in our laboratory have reported that the chemical etch rate of a commercial photosensitive glass ceramic (FoturanTM, Schott Corp., Germany) in dilute hydrofluoric acid is strongly dependent on the incident laser irradiance during patterning at ?=266 nm and ?=355 nm. To help elucidate the underlying chemical and physical processes associated with the laser-induced variations in the chemical etch rate, several complimentary techniques were employed at various stages of the UV laser exposure and thermal treatment. X-ray diffraction (XRD) was used to identify the crystalline phases that are formed in Foturan following laser irradiation and annealing, and monitor the crystalline content as a function of laser irradiance at ?=266 nm and ?=355 nm. The XRD results indicate the nucleation of lithium metasilicate (Li2SiO3) crystals as the exclusive phase following laser irradiation and thermal treatment at temperatures not exceeding 605 C. The XRD studies also show that the Li2SiO3 density increases with increasing laser irradiance and saturates at high laser irradiance. For our thermal treatment protocol, the average Li2SiO3 crystal diameters are 117.010.0 nm and 91.25.8 nm for ?=266 nm and ?=355 nm, respectively. Transmission electron microscopy (TEM) was utilized to examine the microscopic structural features of the lithium metasilicate crystals. The TEM results reveal that the growth of lithium metasilicate crystals proceeds dendritically, and produces Li2SiO3 crystals that are 700 1000 nm in length for saturation exposures. Optical transmission spectroscopy (OTS) was used to study the growth of metallic silver clusters that act as nucleation sites for the Li2SiO3 crystalline phase. The OTS results show that the (Ag0)x cluster concentration has a dependence on incident laser irradiance that is similar to the etch rate ratios and Li2SiO3 concentration. A comparison between the XRD and optical transmission results and our prior etch rate results show that the etch rate contrast and absolute etch rates are dictated by the Li2SiO3 concentration, which is in turn governed by the (Ag0)x cluster concentration. These results characterize the relationship between the laser exposure and chemical etch rate for Foturan, and permit a more detailed understanding of the photophysical processes that occur in the general class of photostructurable glass ceramic materials. Consequently, these results may also influence the laser processing of other photoactive materials.

Voges, Melanie; Beversdorff, Manfred; Willert, Chris; Krain, Hartmut

2007-10-01

282

Thermo-Chemical Approach to Laser Cutting of Thick Metallic Solids.  

National Technical Information Service (NTIS)

Laser cutting of metallic solids offers numerous benefits in metal-working industries. One of the major limitations of laser cutting is the thickness of the part. Experimental and theoretical investigations of laser cutting using organic gases, gas-nozzle...

P. A. Molian I. Pogorelsky M. R. Beltran

1990-01-01

283

Modeling of a photolytically excited HF chemical laser based on a NF3\\/H2 gas mixture  

Microsoft Academic Search

A numerical code has been developed to simulate the characteristics of HF chemical laser based on non-chain reaction pumped by a planar sliding discharge radiation. The model considers transport of VUV pump radiation through the nonlinear absorptive active medium containing NF3\\/H2\\/N2\\/Ar gas mixture coupled with chemical and lasing kinetics describing the temporal and spatial evolution of particle species concentration and

M. P. Sabonnadiere; V. I. Tcheremiskine; Marc L. Sentis; L. D. Mikheev; Philippe C. Delaporte

1998-01-01

284

Characterization of electron-deficient chemical bonding of diborane with attosecond electron wavepacket dynamics and laser response  

Microsoft Academic Search

We report a theoretical study of non-adiabatic electronsnuclei coupled dynamics of diborane H2BH2BH2 under several types of short pulse lasers. This molecule is known to have particularly interesting geometrical and electronic structures, which originate from the electron-deficient chemical bondings. We revisit the chemical bonding of diborane from the view point of electron wavepacket dynamics coupled with nuclear motions, and attempt

Takehiro Yonehara; Kazuo Takatsuka

2009-01-01

285

Remote Continuous Wave and Pulsed Laser Raman Detection of Chemical Warfare Agents Simulants and Toxic Industrial Compounds  

Microsoft Academic Search

This study describes the design, assembly, testing and comparison of two Remote Raman Spectroscopy (RRS) systems intended\\u000a for standoff detection of hazardous chemical liquids. Raman spectra of Chemical Warfare Agents Simulants (CWAS) and Toxic\\u000a Industrial Compounds (TIC) were measured in the laboratory at a 6.6m source-target distance using continuous wave (CW) laser\\u000a detection. Standoff distances for pulsed measurements were 35m

William Ortiz-Rivera; Leonardo C. Pacheco-Londoo; Samuel P. Hernndez-Rivera

2010-01-01

286

Luminescence properties of SiO{sub x}N{sub y} irradiated by IR laser 808 nm: The role of Si quantum dots and Si chemical environment  

SciTech Connect

We investigated optical, structural, and chemical properties of SiO{sub x}N{sub y} layers irradiated by CW IR laser during a time lapse of few milliseconds. We observed tunable photoluminescence signal at room temperature in the range 750-950 nm, without Si/SiO{sub 2} phase separation, depending on the IR laser power irradiation. Furthermore, no photoluminescence signal was recorded when the IR laser power density was high enough to promote phase separation forming Si quantum dots. By chemical analysis the source of the luminescence signal has been identified in a change of silicon chemical environment induced by IR laser annealing inside the amorphous matrix.

Ruggeri, Rosa; Neri, Fortunato [Dipartimento di Fisica della Materia e Ingegneria Elettronica, Universita di Messina, Salita, Sperone 31, 98166 Messina (Italy); Sciuto, Antonella; Privitera, Vittorio; Spinella, Corrado; Mannino, Giovanni [CNR-IMM, Strada VIII no 5, Zona Industriale, 95121 Catania (Italy)

2012-01-23

287

Metastable phase formation in thin films formed by laser breakdown chemical vapor deposition  

NASA Astrophysics Data System (ADS)

Thin films produced by laser breakdown chemical vapor deposition (LBCVD) from Ni and Fe carbonyls were examined and their structure characterized, with emphasis on identifying the phases present. A brightfield micrograph observed in the Ni samples and the corresponding selected area diffraction (SAD) pattern are shown along with two darkfield micrographs of Ni-C film obtained from two positions on the same diffraction ring. It is seen that the decomposition of both carbonyls results in the formation of a supersaturated fcc phase and the carbide phase. The study shows that even a severe quench from the gas phase fails to completely stop the system from approaching its equilibrium structure. This indicates that the carbides Ni3C and Fe3C are associated with a very high thermodynamic driving force for their formation even though both of these phases are metastable.

Menon, S. K.; Jervis, T. R.

1986-11-01

288

Theoretical analysis of dynamic chemical imaging with lasers using high-order harmonic generation  

SciTech Connect

We report theoretical investigations of the tomographic procedure suggested by Itatani et al. [Nature (London) 432, 867 (2004)] for reconstructing highest occupied molecular orbitals (HOMOs) using high-order harmonic generation (HHG). Due to the limited range of harmonics from the plateau region, we found that even under the most favorable assumptions, it is still very difficult to obtain accurate HOMO wave functions using the tomographic procedure, but the symmetry of the HOMOs and the internuclear separation between the atoms can be accurately extracted, especially when lasers of longer wavelengths are used to generate the HHG. Since the tomographic procedure relies on approximating the continuum wave functions in the recombination process by plane waves, the method can no longer be applied upon the improvement of the theory. For future chemical imaging with lasers, we suggest that one may want to focus on how to extract the positions of atoms in molecules instead, by developing an iterative method such that the theoretically calculated macroscopic HHG spectra can best fit the experimental HHG data.

Van-Hoang Le [J. R. Macdonald Laboratory, Department of Physics, Cardwell Hall, Kansas State University, Manhattan, Kansas 66506 (United States); Department of Physics, University of Pedagogy, 280 An Duong Vuong, Ward 5, Ho Chi Minh City (Viet Nam); Anh-Thu Le; Xie Ruihua; Lin, C. D. [J. R. Macdonald Laboratory, Department of Physics, Cardwell Hall, Kansas State University, Manhattan, Kansas 66506 (United States)

2007-07-15

289

Theoretical study of a pulsed HF chemical laser - Comparison of performance between F2\\/H2 and F\\/H2 systems  

Microsoft Academic Search

The performance of a pulsed HF chemical laser with an F2\\/H2 chain reaction system is widely compared to that of an F\\/H2 non-chain reaction system by using a chemical laser simulation code based on the constant gain method. According to the simulation results, peak power differs little between both systems; laser pulse duration is more than an order of magnitude

M. Udagawa; M. Obara; T. Fujioka

1981-01-01

290

Microchanneled Chirped Fiber Bragg Grating Formed by Femtosecond Laser-Aided Chemical Etching for Refractive Index and Temperature Measurements  

Microsoft Academic Search

In this work, a microchanneled chirped fiber Bragg grating (MCFBG) is proposed and fabricated through the femtosecond laser-assisted chemical etching. The microchannel ( $sim$550 $mu$ m) gives access to the external index liquid, thus inducing refractive index (RI) sensitivity to the structure. In the experiment, the transmission bands induced by the reduced effective index in the microchannel region were used

Hongyan Fu; Kaiming Zhou; Pouneh Saffari; Chengbo Mou; Lin Zhang; Sailing He; Ian Bennion

2008-01-01

291

A study of the chemical and morphological alterations of PS and PC surfaces induced by excimer laser treatments  

Microsoft Academic Search

The effect of laser irradiation on polystyrene (PS) and bisphenol-A polycarbonate (PC) has been studied by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), optical microscopy and surface profilometry. The dependence of the surface chemical and morphological properties on wavelength and fluence has been investigated.

E. Occhiello; F. Garbassi; V. Malatesta

1989-01-01

292

Progression of subcellular changes during chemical hypoxia to cultured rat hepatocytes: A laser scanning confocal microscopic study  

Microsoft Academic Search

The aim of this study was to evaluate changes in the subcellular organelles of cultured hepatocytes by laser scanning confocal microscopy during chemical hypoxia with cyanide and iodoacetate, inhibitors of mitochondrial respiration and glycolysis, respectively. Parameter-specific fluorophores used were calcein for cell topography and membrane permeability, rhodaminedextran for lysosomes, rhodamine 123 and tetramethylrhodamine methylester (TMRM) for mitochondrial membrane potential (??)

George Zahrebelski; Anna-Liisa Nieminen; Kristin Al-Ghoul; Ting Qian; Brian Herman; John J. Lemasters

1995-01-01

293

Chemical vapor deposition of highly adherent diamond coatings onto co-cemented tungsten carbides irradiated by high power diode laser.  

PubMed

The present investigation deals with the definition of a new eco-friendly alternative to pretreat Co-cemented tungsten carbide (WC-Co) substrates before diamond deposition by hot filament chemical vapor deposition (HFCVD). In particular, WC-5.8 wt %Co substrates were submitted to a thermal treatment by a continuous wave-high power diode laser to reduce surface Co concentration and promote the reconstruction of the WC grains. Laser pretreatments were performed both in N(2) and Ar atmosphere to prevent substrate oxidation. Diamond coatings were deposited onto the laser pretreated substrates by HFCVD. For comparative purpose, diamond coatings were also deposited on WC-5.8 wt %Co substrates chemically etched by the well-known two-step pretreatment employing Murakami's reagent and Caro's acid. Surface morphology, microstructure, and chemical composition of the WC-5.8 wt %Co substrates after the different pretreatments and the deposition of diamond coatings were assessed by surface profiler, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction analyses. Wear performance of the diamond coatings was checked by dry sliding linear reciprocating tribological tests. The worn volume of the diamond coatings deposited on the laser pretreated substrates was always found lower than the one measured on the chemically etched substrates, with the N(2) atmosphere being particularly promising. PMID:22206356

Barletta, M; Rubino, G; Valle, R; Polini, R

2012-01-20

294

Thermal diffusion and chemical kinetics in laminar biomaterial due to heating by a free-electron laser  

Microsoft Academic Search

We have theoretically investigated the role of thermal diffusion and chemical kinetics as a possible dynamic explanation for the preferential ablative properties of infrared radiation from a free-electron laser ~FEL!. The model is based on a laminar system composed of alternating layers of protein and saline. We have compared exposure to 3 mm where water is the main absorber and

M. Shane Hutson; Susanne A. Hauger; Glenn Edwards

2002-01-01

295

Gas laser technology  

SciTech Connect

These proceedings collect papers on lasers. Topics include: industrial excimer lasers, broadband UV diatomic sulfur lasers, copper vapor lasers, laser processing, recombination lasers, CO/sub 2/ lasers, laser photo-chemical vapor deposition, and x-ray preionized, discharge-pumped xenon chloride discharge lasers.

Sauerbrey, R.A.; Tillotson, J.H.; Chenausky, P.P.

1988-01-01

296

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

297

ARTICLES: Recombination lasers utilizing vapors of chemical elements. II. Laser action due to transitions in metal ions  

Microsoft Academic Search

General requirements specifying the distribution of energy levels and discharge conditions are used as the basis of a discussion of the stimulated emission mechanisms in ionic recombination lasers utilizing strontium, calcium, beryllium, aluminum, tin, and lead vapors. The attention is concentrated on the strontium vapor laser. The population inversion which results in the emission of lambda=430.5 nm radiation from Sr

V. V. Zhukov; V. S. Kucherov; Evgeny L. Latush; M. F. Sm

1977-01-01

298

Synthesis of nanostructured carbon materials by open-air laser-induced chemical vapor deposition  

NASA Astrophysics Data System (ADS)

Elemental carbon in the sp2 hybridization state can form a great variety of graphitic and amorphous structures. Carbon nanotube is a well-known form of graphitic carbon that has remarkable mechanical, electronic and electrochemical properties with applications ranging from reinforced composite materials to micro-scale electronic devices. Pyrolytic carbon film with turbostratic structure is a form of amorphous carbon that possesses excellent barrier properties against diffusion of moisture and hydrogen, and is used as hermetic coating for optical fibers operating under harsh environments. Current deposition techniques for these novel carbon materials are limited in production rate, quality and reproducibility, thereby restricting their usage for advanced applications. In this dissertation, an open-air laser-induced chemical vapor deposition technique is proposed and investigated for the rapid growth of high quality carbon nanotubes and nanometer thick pyrolytic carbon films. The first part of the thesis focuses on the open-air synthesis of carbon nanotubes on stationary and moving fused quartz substrates. The second part will study the deposition of pyrolytic carbon film on various optical components including optical fibers. Optical microscopy, high-resolution transmission and scanning electron microscopy, Raman and Auger electron spectroscopy, as well as x-ray energy-dispersive spectrometry, scanning white-light interferometry and thermal pyrometry are used to investigate the deposition rate, morphology, microstructure and chemical composition of the deposited carbon materials.

Kwok, Kinghong

299

Atomic Force Microscopy Study on the Dissolution Processes of Chemically Amplified Resists for KrF Excimer Laser Lithography  

NASA Astrophysics Data System (ADS)

The surface images of chemically amplified KrF excimer laser resists after development were measured by atomic force microscopy (AFM). From the AFM images at various exposure doses, the dissolution behavior of the polyvinylphenol-based KrF resists differed from that of novolak-diazonaphthoquinone (DNQ) resists. An explanation for the different dissolution behavior has been proposed by considering the difference in the mechanisms of formation of soluble sites between chemically amplified resists and novolak-DNQ resists (non-chemically amplified resists). In addition, AFM topographic images of the resists dissolving layer by layer were observed clearly in the resist spin-coated on a Si wafer. The step heights of the layered structure observed by AFM are in good agreement with the computed value of the distance between two adjacent nodes of standing waves formed by KrF excimer laser exposure. The layered dissolution may be applied to the processing of thin polymer films.

Kanzaki, Kenichi; Ohfuji, Takeshi; Sasago, Masaru; Tagawa, Seiichi

1999-05-01

300

Lasers.  

National Technical Information Service (NTIS)

The optical laser was first developed in 1960. Among the first medical applications for lasers was the dermatologic application of this Ruby laser in 1964. Since that time, the application of lasers in medical and surgical uses has grown quite extensively...

J. A. Werkhaven R. H. Ossoff D. Harris

1991-01-01

301

Chemical Beam Epitaxy (cbe) and Laser-Enhanced CBE of Gallium Arsenide and Indium Gallium Arsenide Using Novel Gas Sources.  

NASA Astrophysics Data System (ADS)

In recent years, chemical beam epitaxy (CBE), or metalorganic molecular beam epitaxy (MOMBE), has been under active development to exploit the advantages of conventional solid-source molecular beam epitaxy (MBE) and metal-organic vapor phase epitaxy (MOVPE). One of the important issues in CBE/MOMBE is the selective-area growth by direct writing with an external energy source, e.g., an argon ion laser. The objectives of this dissertation are to investigate the use of a safer alternative source, tris-dimethylaminoarsenic (TDMAAs), to the highly toxic arsine as the group V source and the effects of argon ion laser irradiation on MOMBE/CBE growth of GaAs and InGaAs/GaAs quantum-well structures. Different carbon incorporation efficiencies in undoped and carbon-doped GaAs films (by CI_2 H_2) were obtained for cracked and uncracked TDMAAs. The presence of beta -hydride elimination reaction on the GaAs surface using uncracked TDMAAs and the absence of such an effect using cracked TDMAAs may have caused the above difference. The in situ GaAs etching effect was observed when the substrate was exposed to only uncracked TDMAAs, but not cracked TDMAAs. The laser-assisted growth with TDMAAs, compared to As_4 or AsH_3, provides a much wider temperature range of selective -area growth at low substrate temperatures. The enhanced growth rate increases as the laser power density increases and saturates at high laser power densities. The laser -modified carbon-doped GaAs films by CI_2 H_2 show a much higher hole concentration (as high as two orders of magnitude) than the films grown simultaneously without laser irradiation. Laser irradiation was also found to enhance GaAs etching rate. Photothermal effect is responsible for laser-enhanced growth and etching, but the wider temperature window in laser-enhanced growth and laser-enhanced carbon incorporation are caused by additional photochemical effects. Moreover, laser irradiation of the InGaAs quantum wells in InGaAs/GaAs multiple quantum well structures produces blue shift in photoluminescence emission due to an increased GaAs partial growth rate and/or a reduced In concentration. The much wider temperature window for selective -area growth using TDMAAs, the selective-area doping and composition modification, and the enhanced GaAs etching by laser irradiation may provide novel applications for electronic and optoelectronic devices.

Dong, Haike

1995-01-01

302

Femtosecond laser pulses for chemical-free embryonic and mesenchymal stem cell differentiation  

NASA Astrophysics Data System (ADS)

Owing to their self renewal and pluripotency properties, stem cells can efficiently advance current therapies in tissue regeneration and/or engineering. Under appropriate culture conditions in vitro, pluripotent stem cells can be primed to differentiate into any cell type some examples including neural, cardiac and blood cells. However, there still remains a pressing necessity to answer the biological questions concerning how stem cell renewal and how differentiation programs are operated and regulated at the genetic level. In stem cell research, an urgent requirement on experimental procedures allowing non-invasive, marker-free observation of growth, proliferation and stability of living stem cells under physiological conditions exists. Femtosecond (fs) laser pulses have been reported to non-invasively deliver exogenous materials, including foreign genetic species into both multipotent and pluripotent stem cells successfully. Through this multi-photon facilitated technique, directly administering fs laser pulses onto the cell plasma membrane induces transient submicrometer holes, thereby promoting cytosolic uptake of the surrounding extracellular matter. To display a chemical-free cell transfection procedure that utilises micro-litre scale volumes of reagents, we report for the first time on 70 % transfection efficiency in ES-E14TG2a cells using the enhanced green fluorescing protein (EGFP) DNA plasmid. We also show how varying the average power output during optical transfection influences cell viability, proliferation and cytotoxicity in embryonic stem cells. The impact of utilizing objective lenses of different numerical aperture (NA) on the optical transfection efficiency in ES-E14TG2a cells is presented. Finally, we report on embryonic and mesenchymal stem cell differentiation. The produced specialized cell types could thereafter be characterized and used for cell based therapies.

Mthunzi, Patience; Dholakia, Kishan; Gunn-Moore, Frank

2011-09-01

303

Laser photoacoustic spectroscopy helps fight terrorism: High sensitivity detection of chemical Warfare Agent and explosives  

NASA Astrophysics Data System (ADS)

Tunable laser photoacoustic spectroscopy is maturing rapidly in its applications to real world problems. One of the burning problems of the current turbulent times is the threat of terrorist acts against civilian population. This threat appears in two distinct forms. The first is the potential release of chemical warfare agents (CWA), such as the nerve agents, in a crowded environment. An example of this is the release of Sarin by Aum Shinrikyo sect in a crowded Tokyo subway in 1995. An example of the second terrorist threat is the ever-present possible suicide bomber in crowded environment such as airports, markets and large buildings. Minimizing the impact of both of these threats requires early detection of the presence of the CWAs and explosives. Photoacoustic spectroscopy is an exquisitely sensitive technique for the detection of trace gaseous species, a property that Pranalytica has extensively exploited in its CO2 laser based commercial instrumentation for the sub-ppb level detection of a number of industrially important gases including ammonia, ethylene, acrolein, sulfur hexafluoride, phosphine, arsine, boron trichloride and boron trifluoride. In this presentation, I will focus, however, on our recent use of broadly tunable single frequency high power room temperature quantum cascade lasers (QCL) for the detection of the CWAs and explosives. Using external grating cavity geometry, we have developed room temperature QCLs that produce continuously tunable single frequency CW power output in excess of 300 mW at wavelengths covering 5 ?m to 12 ?m. I will present data that show a CWA detection capability at ppb levels with false alarm rates below 1:108. I will also show the capability of detecting a variety of explosives at a ppb level, again with very low false alarm rates. Among the explosives, we have demonstrated the capability of detecting homemade explosives such as triacetone triperoxide and its liquid precursor, acetone which is a common household liquid. This capability, deployed at airports and other public places, will go a long way towards increasing public safety and minimizing inconveniences faced in airline travel.

Patel, C. K. N.

2008-01-01

304

HF repetitively pulsed chemical laser with a large discharge gap operating on the mixture F2 + H2  

NASA Astrophysics Data System (ADS)

The efficient repetitively pulsed (10 Hz) HF chemical laser initiated by barrier electric discharge with electrode gap 10 cm was realised. In mono-pulse mode specific output energy 3 and 23 J/l, technical efficiency (?) 3.4 and 26%, for non-chain and chain process, correspondingly, were obtained. In the repetitively pulsed (RP) mode of the laser operation at 10 Hz on the depleted fluorine-hydrogen mixture (20% F2, 5% H2) the mean laser power of 43 W was obtained (specific output energy E/V ~ 10 J/l, ?=11.3%). The computational prediction for laser operation in repetitively pulsed mode at active length of about 0.5 m has shown the possibility of achievement of the specific laser energy about 15 J/l and technical efficiency up to 20%. Output laser specific energy ~ 14 J/l under RPCL conditions at length of active medium 0.37 m in mono-pulse mode was obtained in a good agreement with numerical prediction.

Alexandrov, Boris S.; Klimuk, Evgueni A.; Kutumov, Constantin A.; Lacour, Bernard; Puech, Vincent; Troshchinenko, Georgiy A.

2005-03-01

305

Start features of supersonic chemical laser (SCL) channel operating with pressure recovery system (PRS)  

NASA Astrophysics Data System (ADS)

The particularity of start process of rectangular laser channel in comparison with star of wind tunnel - the state of understart - is discovered. The higher pressure level is realized in laser cavity as result of this phenomena and it brings to laser power decrease.

Boreysho, A. S.; Malkov, V. M.

2007-05-01

306

Particle Generation by Laser Ablation in Support of Chemical Analysis of High Level Mixed Waste from Plutonium Production Operations  

SciTech Connect

Investigate particles produced by laser irradiation and their analysis by Laser Ablation Inductively Coupled Plasma Mass Spectroscopy (LA/ICP-MS), with a view towards optimizing particle production for analysis of high level waste materials and waste glass. LA/ICP-MS has considerable potential to increase the safety and speed of analysis required for the remediation of high level wastes from cold war plutonium production operations. In some sample types, notably the sodium nitrate-based wastes at Hanford and elsewhere, chemical analysis using typical laser conditions depends strongly on the details of sample history composition in a complex fashion, rendering the results of analysis uncertain. Conversely, waste glass materials appear to be better behaved and require different strategies to optimize analysis.

J. Thomas Dickinson; Michael L. Alexander

2001-11-30

307

650-nm AlGaInP multiple-quantum-well lasers grown by metalorganic chemical vapor deposition using tertiarybutylphosphine  

NASA Astrophysics Data System (ADS)

Using tertiarybutylphosphine (TBP) as phosphorus precursor, high-quality AlGaInP epilayers and AlGaInP/GaInP multiple-quantum-well (MQW) structures have been grown by metalorganic chemical vapor deposition. The photoluminescence results indicate that the AlGaInP materials are as good as those grown using PH3 in terms of optical quality. Finally, AlGaInP MQW red laser structures have been grown, and the electrically pumped AlGaInP red lasers grown by TBP have been demonstrated with the emission wavelength of 647 nm, indicating that TBP can be used to grow high-quality AlGaInP epilayers and AlGaInP-based red lasers, which presently is dominated by the highly toxic gas source PH3.

Dong, Jian-Rong; Teng, Jing-Hua; Chua, Soo-Jin; Foo, Boon-Chin; Wang, Yan-Jun; Yuan, Hai-Rong; Yuan, Shu

2003-07-01

308

Combined Chemical and Topographic Imaging at Atmospheric Pressure via Microprobe Laser Desorption/Ionization Mass Spectrometry-Atomic Force Microscopy  

SciTech Connect

The operational characteristics and imaging performance are described for a new instrument comprising an atomic force microscope (AFM) coupled with a pulsed laser and a linear ion trap mass spectrometer. The AFM operating mode is used to produce topographic surface images having nanometer-scale spatial and height resolution. Spatially resolved mass spectra of ions, produced from the same surface via microprobe-mode laser desorption/ionization at atmospheric pressure, are then used to create a 100 x 100 m chemical image. The effective spatial resolution of the image (~2 m) was constrained by the limit of detection (estimated to be 109 1010 ions) rather than by the diameter of the focused laser spot or the step size of the AFM sample stage. Thus, it is expected that improvements in imaging performance can be realized by implementation of post-ionization methods.

Bradshaw, James A [ORNL; Ovchinnikova, Olga S [ORNL; Meyer, Kent A [ORNL; Goeringer, Doug [ORNL

2009-01-01

309

Laser-Induced Acoustic Desorption/Atmospheric Pressure Chemical Ionization Mass Spectrometry  

PubMed Central

Laser-induced acoustic desorption (LIAD) was successfully coupled to a conventional atmospheric pressure chemical ionization (APCI) source in a linear quadrupole ion trap mass spectrometer (LQIT). Model compounds representing a wide variety of different types, including basic nitrogen and oxygen compounds, aromatic and aliphatic compounds, as well as unsaturated and saturated hydrocarbons, were tested separately and as a mixture. These model compounds were successfully evaporated into the gas phase by using LIAD and then ionized by using APCI with different reagents. Four APCI reagent systems were tested: the traditionally used mixture of methanol and water, neat benzene, neat carbon disulfide, and nitrogen gas (no liquid reagent). The mixture of methanol and water produced primarily protonated molecules, as expected. However, only the most basic compounds yielded ions under these conditions. In sharp contrast, using APCI with either neat benzene or neat carbon disulfide as the reagent resulted in the ionization of all the analytes studied to predominantly yield stable molecular ions. Benzene yielded a larger fraction of protonated molecules than carbon disulfide, which is a disadvantage. A similar amount of fragmentation was observed for these reagents. When the experiment was performed without a liquid reagent(nitrogen gas was the reagent), more fragmentation was observed. Analysis of a known mixture as well as a petroleum cut was also carried out. In summary, the new experiment presented here allows the evaporation of thermally labile compounds, both polar and nonpolar, without dissociation or aggregation, and their ionization to form stable molecular ions.

Gao, Jinshan; Borton, David J.; Owen, Benjamin C.; Jin, Zhicheng; Hurt, Matt; Amundson, Lucas M.; Madden, Jeremy T.; Qian, Kuangnan; Kenttamaa, Hilkka I.

2010-01-01

310

Experimental investigation of a chemical-laser-cavity flowfield. Master's thesis  

SciTech Connect

Chemical lasers require a cavity that establishes and maintains the proper gas dynamic properties during lasing. The design and performance of a flow system capable of supporting the hypersonic flow conditions in a lasing cavity are described. Using cold air as the working medium, the flow control system configuration and nozzle-cavity-supersonic diffuser assembly configuration were developed to establish acceptable flow conditions in the test section. Performance evaluation was based on pressure measurements in the nozzle-cavity-diffuser assembly and schlieren photographs of the flowfield in the cavity. Flow conditions in the test section were broken up into three different regions: flow in the hypersonic nozzles, flow in the base region and flow in the cavity region. Flow in the nozzles was analyzed using one-dimensional, steady, isentropic flow theory. Test results indicated that the hypersonic nozzles performed to design specifications. The Korst two-dimensional base-pressure flow model was used to describe the flow in the nozzle exit plane and base region. Experimentally calculated Mach numbers and static pressures corresponded very closely to theoretical values. Static pressure ports and schlieren photographs were used to describe the flow-field conditions in the cavity region. Pressure measurements indicated that supersonic conditions were reached in the cavity for specific supersonic diffuser throat areas settings, but conditions were short lived. Boundary layer, frictional, and three-dimensional effects were suspected as the main contributors to the flowfield degradation.

Stiglich, S.W.

1989-12-01

311

Data analysis of multi-laser standoff spectral identification of chemical and biological compounds  

NASA Astrophysics Data System (ADS)

With the availability of tunable broadband coherent sources that emit mid-infrared radiation with well-defined beam characteristics, spectroscopies that were traditionally not practical for standoff detection1 or for development of miniaturized infrared detectors2, 3 have renewed interest. While obtaining compositional information for objects from a distance remains a major challenge in chemical and biological sensing, recently we demonstrated that capitalizing on mid-infrared excitation of target molecules by using quantum cascade lasers and invoking a pump probe scheme can provide spectral fingerprints of substances from a variable standoff distance.3 However, the standoff data is typically associated with random fluctuations that can corrupt the fine spectral features and useful data. To process the data from standoff experiments toward better recognition we consider and apply two types of denoising techniques, namely, spectral analysis and Karhunen-Loeve Transform (KLT). Using these techniques, infrared spectral data have been effectively improved. The result of the analysis illustrates that KLT can be adapted as a powerful data denoising tool for the presented pump-probe infrared standoff spectroscopy.

Farahi, R.; Zaharov, V.; Tetard, L.; Thundat, T.; Passian, A.

2013-06-01

312

Examination of quantum cascade laser source for a MEMS-scale photoacoustic chemical sensor  

NASA Astrophysics Data System (ADS)

Photoacoustic spectroscopy is a useful monitoring technique that is well suited for trace gas detection. The technique also possesses favorable detection characteristics when the system dimensions are scaled to a micro-system design. The objective of present work is to incorporate two strengths of the Army Research Laboratory (ARL), Quantum Cascade Laser (QCL) source development and chemical and biological sensing into a monolithic micro-electromechanical systems (MEMS) photoacoutic trace gas sensor. Past examination of a one quarter scale photoacoustic (PA) macro-cell has indicated a pathway to incorporate a photoacoustic resonance structure in a micro-mechanical platform. Initial studies involve the incorporation of a QCL source operating @ ~3.45 ?m into the PA macro-cell system as a means to discern proper operational characteristics in relation to the photoacoustic cell design. Results will be presented describing beam conditioning, modulation control and wavelength selection associated with the QCL source. Some preliminary information regarding MEMS-scale designs based off of hybrid concept, involving commercially available microphone and fully fabricated MEMS photoacoustic resonator will be described.

Heaps, David A.; Pellegrino, Paul M.

2006-06-01

313

Data Analysis of Multi-Laser Standoff Spectral identification of chemical and biological compounds  

SciTech Connect

With the availability of tunable broadband coherent sources that emit mid-infrared radiation with well-defined beam characteristics, spectroscopies that were traditionally not practical for standoff detection1 or for develop- ment of miniaturized infrared detectors2, 3 have renewed interest. While obtaining compositional information for objects from a distance remains a major challenge in chemical and biological sensing, recently we demonstrated that capitalizing on mid-infrared excitation of target molecules by using quantum cascade lasers and invoking a pump probe scheme can provide spectral fingerprints of substances from a variable standoff distance.3 However, the standoff data is typically associated with random fluctuations that can corrupt the fine spectral features and useful data. To process the data from standoff experiments toward better recognition we consider and apply two types of denoising techniques, namely, spectral analysis and Karhunen-Loeve Transform (KLT). Using these techniques, infrared spectral data have been effectively improved. The result of the analysis illustrates that KLT can be adapted as a powerful data denoising tool for the presented pump-probe infrared standoff spectroscopy.

Farahi, R H [ORNL; Zaharov, Viktor [ORNL; Tetard, Laurene [ORNL; Thundat, Thomas George [ORNL; Passian, Ali [ORNL

2013-01-01

314

A Study on Fractional Erbium Glass Laser Therapy Versus Chemical Peeling for the Treatment of Melasma in Female Patients  

PubMed Central

Introduction: Melasma is a commonly acquired hypermelanosis and a common dermatologic skin disease that occurs on sun-exposed areas of face. Aims: To assess the efficacy and safety of non-ablative 1,550 nm Erbium glass fractional laser therapy and compare results with those obtained with chemical peeling. Materials and Methods: We selected 30 patients of melasma aged between 20 years and 50 years for the study. The patients were divided into two groups of 15 patients each. Group I patients were subjected to four sessions of 1,550 nm Erbium glass non-ablative fractional laser at 3 weeks interval. In group II patients, four sessions of chemical peeling with 70% glycolic acid was performed. Results: After 12 weeks of treatment, percentage reduction in Melasma Area and Severity Index (MASI) score was seen in 62.9% in the laser group and 58.7% in the peels group. Conclusion: It was observed that 1,550 nm fractional laser is as effective as 70% glycolic acid peel in reducing MASI score in patients with melasma.

Puri, Neerja

2013-01-01

315

Application of confocal laser scanning microscopy in characterization of chemical enhancers in drug-in-adhesive transdermal patches  

Microsoft Academic Search

The purpose of this study was to evaluate the application of confocal laser scanning microscopy (CLSM) in the examination\\u000a of the embedment and the release characteristics of chemical permeation enhancers from transdermal drug delivery systems (TDDSs)\\u000a of the drug-in-adhesive type. The enhancer lauric acid and a lauric acid fluorescing probe of the Bodipy type were incorporated\\u000a into TDDSs consisting of

Michael H. Qvist; Ulla Hoeck; Bo Kreilgaard; Flemming Madsen; Lars Hovgaard; Sven Frokjaer

2002-01-01

316

Epitaxially deposited SrVO3 conducting films by laser ablation and metal organic chemical vapor deposition  

Microsoft Academic Search

We have grown epitaxial thin films (100-200 nm) of SrVO3 with pulsed laser deposition and metal organic chemical vapor deposition on Si, YSZ, MgO, LaAlO3, and and SrTiO3 . These films range from insulating to semiconducting to metallic, depending on growth conditions. Resistivity has been measured with the standard four point method, and has been found to be as low

D. L. Ritums; N. J. Wu; D. Liu; Q. Zhong; Y. M. Chen; X. Zhang; P. C. Chou; A. Ignatiev

1996-01-01

317

Influence of sample surface condition on chemical analysis using laser ablation inductively coupled plasma atomic emission spectroscopy  

Microsoft Academic Search

The influence of sample surface condition on chemical analysis was investigated when using laser ablation sampling with inductively coupled plasma atomic emission spectroscopy (ICP-AES). The ablated mass quantity and composition were found to be significantly different from original vs. pre-ablated surfaces. The ablated mass quantity from original surfaces was much greater than that from pre-ablated surfaces, and the ablation rate

Xianglei Mao; Richard E. Russo; Wing-Tat Chan

1997-01-01

318

Improved AMOLED with aligned poly-Si thin-film transistors by laser annealing and chemical solution treatments  

Microsoft Academic Search

Low-temperature polycrystalline silicon (LTPS) thin-film transistors (TFT) were prepared for the active-matrix organic light-emitting displays (AMOLED). The excimer laser annealing (ELA) recrystallization technique was employed with a chemical solution treatment process to improve the TFT characteristic uniformity and the AMOLED display image quality. The characteristics of the poly-Si array thin films were influenced by XeCl ELA optic module design, TFT

G. M. Wu; C. N. Chen; W. S. Feng; H. C. Lu

2009-01-01

319

TA5--H2\\/F2flame propagation and repetitively pulsed hydrogen flouride (HF) chain-reaction chemical laser  

Microsoft Academic Search

The burning velocity and the nature of the H2\\/F2flame at various gas compositions gas compositions have been experimentally determined. It was found that reactions induced by a diffusion-type flame proceed rather slowly, but reactions triggered by a compression wave proceed with supersonic speed. Based on the measurements of gas stability, repetetive pulse operation of H2\\/F2chemical lasers at atmospheric pressure has

Hao-Lin Chen; JACK D. DAUGHERTY; WALTER FYFE

1975-01-01

320

Topographical and surface chemical characterization of nanosecond pulsed-laser micromachining of titanium at 532-nm wavelength  

Microsoft Academic Search

Electropolished titanium was micromachined by single, 5-ns pulses from a frequency-doubled (532nm) Nd:YAG laser. The focal spot size was varied from 10 to 100m and the applied fluences varied from the melting threshold (~1J\\/cm 2) to more than 100J\\/cm 2. The resulting craters were imaged by optical microscopy, topographically characterized by interferometry and chemically characterized on the surface by small-spot

H. Reimers; J. Gold; B. Kasemo; D. Chakarov

2003-01-01

321

Synthesis and alignment of Zn and ZnO nanoparticles by laser-assisted chemical vapor deposition  

Microsoft Academic Search

A simple, versatile, and fast laser-assisted chemical vapor deposition (LCVD) technique that produces linear arrays of Zn and ZnO nanoparticles on a silicon substrate, covering an extended region, is described. A series of consecutive steps is involved in the synthesis and alignment of Zn\\/ZnO nanoparticles. First, a Lloyds mirror arrangement is employed to produce two types of periodic nanostructure, i.e.,

Y F Guan; A J Pedraza

2008-01-01

322

Influence of laser power on the orientation and microstructure of CeO 2 films deposited on Hastelloy C276 tapes by laser chemical vapor deposition  

Microsoft Academic Search

CeO2 films were prepared on LaMnO3\\/MgO\\/Gd2Zr2O7 multi-coated Hastelloy C276 tapes by laser chemical vapor deposition at different laser power (PL) from 46 to 101W. Epitaxial (100) CeO2 films were prepared at PL=4693W (deposition temperature, Tdep=705792K). Epitaxial CeO2 films had rectangular-shaped grains at PL=4677W (Tdep=705754K), while square-shaped grains were obtained at PL=8593W (Tdep=769792K). CeO2 films showed a columnar microstructure. Epitaxial (100)

Pei Zhao; Akihiko Ito; Rong Tu; Takashi Goto

2010-01-01

323

Laser-assisted chemical vapor deposition of carbon for the growth of high-aspect ratio microrods and direct writing of surface patterns  

Microsoft Academic Search

Laser-assisted chemical vapor deposition is investigated as a useful method to fabricate micrometer size carbon rods and to directly write an arbitrary deposit pattern. The deposits were produced on graphite substrates from pyrolytic decomposition of ethylene by irradiating focused argon ion laser beam at a wavelength of 514.5nm. Depending on whether the laser beam is stationary on a fixed location

Sung Ho Jeong; Jinbun Kim; Sunghoon Kim; Dongjun Lee

2003-01-01

324

Field Tests of the Laser Interrogation of Surface Agents (Lisa) System for On-the-Move Standoff Sensing of Chemical Agents.  

National Technical Information Service (NTIS)

Laser Interrogation of Surface Agents (LISA) is a new technique based on short-range Raman sensing that provides standoff detection and identification of surface-deposited chemical agents. ITT Industries, Advanced Engineering and Sciences Division is curr...

C. T. Lobb N. S. Higdon P. L. Ponsardin T. H. Chyba W. T. Armstrong

2003-01-01

325

Two-coordinate control of the radiation pattern of a chemical non-chain electric-discharge DF laser by using space-time light modulators  

Microsoft Academic Search

The results of studies of radiation parameters of a chemical non-chain DF laser (emitting in the range from 3.5 to 4.1 m) with an intracavity control of the radiation pattern with the help of spatiotemporal modulators based on PLZT electrooptic ceramics are presented. (control of laser radiation parameters)

V N Alekseev; V N Kotylev; V I Liber

2008-01-01

326

Two-coordinate control of the radiation pattern of a chemical non-chain electric-discharge DF laser by using space-time light modulators  

SciTech Connect

The results of studies of radiation parameters of a chemical non-chain DF laser (emitting in the range from 3.5 to 4.1 {mu}m) with an intracavity control of the radiation pattern with the help of spatiotemporal modulators based on PLZT electrooptic ceramics are presented. (control of laser radiation parameters)

Alekseev, V N; Kotylev, V N; Liber, V I [Research Institute for Complex Testing of Optoelectronic Devices and Systems, Leningrad region (Russian Federation)

2008-07-31

327

A Miniaturized Laser Instrument for Chemical and Mineralogical In-Situ Analysis on Planetary Surfaces  

NASA Astrophysics Data System (ADS)

Planetary in-situ analysis is going to become one of the most important tools for exploring the accessible celestial bodies. Chemical, mineralogical, structural, isotopic, and molecular information will provide stringent boundary conditions for the origin and evolution of these bodies and hence of the solar system. The past showed some unprecedented examples of operating in-situ analysis instruments and even rather complex instrument facilities are at present underway. Although their capabilities are remarkable, these "first generation" instruments still suffer from constraints in terms of size, mass, and operations for the accommodating systems. They pose restrictions in particular on the most recently projected explorative missions such as ESA's EXOMARS mission that aims at large operating radii of some kilometers or some tens of kilometers. Whereas the classical operational scenario was more or less stationary, the high degree of mobility calls for a new type of instrumentation, which can be characterized as follows: begin{itemize} Short measurement duration: seconds instead of hours High sensitivity, high repetition rate, high reproducibility Low mass, size, and resource needs High flexibility with respect to type, shape, and size of sample material Robustness towards surface contamination Laser-Induced-Plasma-Spectrometry (LIPS) in combination with Raman-spectroscopy has the potential to meet these requirements and to enable in-situ elemental and mineralogical analyses with a new level of accuracy, performance and operational flexibility. This contribution describes the preliminary results in the definition process of such a new instrument for planetary in-situ exploration. It is based on the work carried out at institutes and research establishments in Germany and Austria. It relates furthermore to a definition study on a combined LIPS/Raman instrument carried out for the European Space Agency.

Bertrand, R.; del Bianco, A.; Harnisch, B.; Jessberger, E. K.; Peuser, P.; Romstedt, J.; Rost, D.; Schneider, K.; Weber, I.

2003-04-01

328

A chemically driven visible laser transition using fast near-resonant energy transfer  

NASA Astrophysics Data System (ADS)

Evidence is obtained which demonstrates the potential for developing purely chemical visible lasers based on rapid near-resonant energy transfer from metastable excited triplet states of germanium and silicon monoxide (a 3Sigma+, b 3Pi) to select metal atoms. In this study, the Group IIIA metal atoms were chosen as the energy receptors for the energy transfer-pump sequence. Excited triplet states were generated from the Ge-O3, Ge-N2, Si-N2O, and Si-NO2 reactions; the bulk of the experimental results was obtained with a germanium-based system. The energy stored in the long-lived triplet states is transferred to pump X2P1/2 thallium, indium, and gallium atoms to their lowest lying 2S1/2 states; the process with thallium and gallium atoms appears particularly efficient. Adopting a pumping sequence in which a premixed Ge-Tl atom combination is oxidized, the authors observe a system temporal behavior which suggests the creation of a population inversion producing a gain condition and forming the basis for full cavity oscillation on the Tl 72S1/2 -6P3/2 transition at 535 nm. In an extremely efficient energy transfer, GeO metastables formed in the Ge-O3 reaction rapidly pump those Tl atoms with which they are intimately mixed to populate the 2S1/2 excited state, creating a temporary population inversion with respect to the upper X2P3/2 component of the ground 2P thallium atom configuration.

Woodward, James R.; Cobb, Stephen H.; Shen, Kangkang; Gole, James L.

1990-09-01

329

Investigation of lamp chemical composition by laser-induced breakdown spectroscopy  

Microsoft Academic Search

Summary form only given, as follows. The utilization of laser-induced breakdown spectroscopy (LIBS) as a non-destructive experimental diagnostic for studying lighting devices is discussed. LIBS involves the creation of a small plasma localized at the focus of a pulsed laser beam, and corresponding analysis of the spectrally dispersed radiation from the plasma. LIBS has been used as a method for

N. H. Chen; H. G. Adler; W. P. Lapatovich

1998-01-01

330

Chemical Assisted Laser Machining for The Minimisation of Recast and Heat Affected Zone  

Microsoft Academic Search

Laser processing techniques have been widely used for high speed, high accuracy subtractive manufacturing such as cutting, drilling, milling and micro-machining. Most of these processes are based on thermal mechanisms. For the machining of metallic materials, a layer of recast and heat affected zone is normally present on the laser-machined components. This paper reports a novel technique that aims to

L. Li; C. Achara

2004-01-01

331

Stabilization, Injection and Control of Quantum Cascade Lasers, and Their Appli-cation to Chemical Sensing in the Infrared  

SciTech Connect

Quantum cascade lasers (QCLs) are a relatively new type of semiconductor laser operating in the mid- to long-wave infrared. These monopolar multilayered quantum well structures can be fabricated to operate anywhere between 3.5 microns and 20 microns, which includes the molecular fingerprint region of the in-frared. This makes them an ideal choice for infrared chemical sensing, a topic of great interest at present. Frequency stabilization and injection locking increase the utility of QCLs. We present results of locking quantum cascade lasers to optical cavities, achieving relative linewidths down to 5.6 Hz. We report injec-tion locking of one distributed feedback grating QCL with light from a similar QCL, demonstrating capture ranges of up to 500 MHz, and suppression of amplitude modulation by up to 49 dB. We also present various cavity-enhanced chemical sensors employing the frequency stabilization techniques developed, in-cluding the resonant sideband technique known as Nice-Ohms. Sensitivities of 9.7 x 10-11 cm-1 Hz-1/2 have been achieved in nitrous oxide.

Taubman, Matthew S.; Myers, Tanya L.; Cannon, Bret D.; Williams, Richard M.

2004-12-01

332

Efficient nonchain chemical HF lasers initiated by e-beam and self-sustained discharge  

NASA Astrophysics Data System (ADS)

Non-chain HF lasers initiated by electric discharge and e- beam are described. A generator with an inductive energy storage and semiconducting opening switch was used for discharge formation. The generator was shown to be very promising for development of efficient discharge HF lasers with high output energy. It produces very uniform discharge in SF6-H2(C3H8) gas mixtures at elevated pressure and increases its stability. Discharge HF laser efficiency up to 5.5% was demonstrated. Radially convergent e-beam was used to pump 30 1 HF laser. Optimal gas mixture SF6:H2 equals 8:1 under pressure of 0.45 atm was chosen to provide no more than two-fold specific output power variations across the laser beam area. Output energy as high as 115 J and efficiency with respect to e-beam energy deposited into gas mixture up to 7-8% were demonstrated. Total laser energy and efficiency with respect to deposited energy at pressure of 1.1 atm when the output distribution was non-uniform were found to be up to 200 J and 11%, respectively. The `jump' of pressure in SF6-H2 mixture at the instance of e-beam injection was found to be lower than that in excimer laser mixtures due to SF6 high density. This simplifies creation of wide-aperture e- beam HF-lasers. We expect that the use of pulse generators and wide-aperture laser setup available at HCEI enable us to develop 1 kJ non-chain HF laser initiated either by self- sustained discharge or e-beam.

Tarasenko, Victor F.; Baksht, Evgenii H.; Lomaev, Mikhail I.; Orlovskii, Victor M.; Panchenko, Alexei N.; Sosnin, Eduard A.

1998-05-01

333

Continuous-wave operation of AlGaInP/GaInP quantum-well lasers grown by metalorganic chemical vapor deposition using tertiarybutylphosphine  

NASA Astrophysics Data System (ADS)

Strained AlGaInP/GaInP multiple-quantum-well laser structures have been grown by metalorganic chemical vapor deposition using teriarybutylphosphine as the phosphorus precursor and ridge waveguide lasers of 4 ?m wide have been fabricated. Room temperature continuous-wave lasing has been obtained with an emission wavelength of about 670 nm. A single-facet output power of more than 18 mW has been achieved for an as-cleaved laser chip. It can be concluded that it is feasible to fabricate AlGaInP red lasers using less toxic metalorganic source tertiarybutylphosphine in parallel with conventionally used highly toxic PH3.

Dong, Jian-Rong; Teng, Jing-Hua; Chua, Soo-Jin; Foo, Boon-Chin; Wang, Yan-Jun; Zhang, Lian-Wen; Yuan, Hai-Rong; Yuan, Shu

2004-05-01

334

PLIF Visualization and Quantitative Mixing Measurements of a Supersonic Injection Nozzle.  

National Technical Information Service (NTIS)

Planar Laser-Induced Fluorescence (PLIF) was used to visualize the flow of a supersonic nozzle with a single supersonic injector. The nozzle simulates Chemical Oxygen Iodine Laser (COIL) flow conditions with non-reacting, cold flows, where the injected fl...

C. A. Noren C. R. Truman G. D. Hager P. V. Vorobieff T. J. Madden

2006-01-01

335

Mapping chemical bonding of reaction intermediates with femtosecond X-ray laser spectroscopy  

NASA Astrophysics Data System (ADS)

We determine the pathways in the photo-dissociation reactions of Fe(CO)5 both in the gas phase and in solution by mapping the valence electronic structure of the reaction intermediates with femtosecond X-ray laser spectroscopy.

Wernet, Ph.; Beye, M.; de Groot, F.; Dsterer, S.; Gaffney, K.; Grbel, S.; Hartsock, R.; Hennies, F.; Josefsson, I.; Kennedy, B.; Kunnus, K.; Leitner, T.; Mazza, T.; Meyer, M.; Nordlund, D.; Odelius, M.; Quevedo, W.; Radcliffe, P.; Rajkovic, I.; Schlotter, B.; Scholz, M.; Schreck, S.; Suljoti, E.; Techert, S.; Turner, J.; Weniger, C.; Zhang, W.; Fhlisch, A.

2013-03-01

336

Diode Laser-Based Measurements of Hydrogen Fluoride Gas During Chemical Suppression of Fires.  

National Technical Information Service (NTIS)

Near-infrared tunable diode laser (NIR-TDL) spectroscopy is used to quantify hydrogen fluoride (HF) gas produced during fire-suppressant testing of Halon alternatives. Results of comparisons with other techniques for measuring HF gas concentrations are di...

K. L. McNesby R. R. Skaggs A. W. Miziolek M. Clay S. H. Hoke

1998-01-01

337

Chemical Kinetics and Molecular Physics Pertinent to Proposed Mercury Dimer Lasers.  

National Technical Information Service (NTIS)

Since the dimeric mercury molecule has several bound-excited electronic states, but a largely dissociative molecular ground state, It has been proposed as a molecular system for laser development. This note reviews much of the literature pertinent to the ...

C. E. Kolb

1973-01-01

338

High-performance dichroic beam splitters for deuterium fluoride chemical lasers  

SciTech Connect

The optical performance of dichroic beam splitters developed for deuterium fluoride (DF) laser applications as shared-aperture components is presented. These components simultaneously provide high reflectance/transmittance in the 3.8-..mu..m DF laser output band and high transmittance/reflectance in the long-wavelength 8--14-..mu..m band. Optical evaluation of the reflecting dichroic yields absorption and transmission losses of <0.2 and 0.1%, respectively, at DF laser wavelengths and average transmittance 80% in the 8--14-..mu..m band. The 3.8-..mu..m transmitting dichroic yields absorptance losses of <0.4% in the DF laser band and average reflectance of >50% in the 8--14-..mu..m region.

Rudisill, J.E.; Garcia, B.; Bobbs, B.L.; Braunstein, M.

1980-07-01

339

Efficient nonchain chemical HF lasers initiated by e-beam and self-sustained discharge  

Microsoft Academic Search

Non-chain HF lasers initiated by electric discharge and e- beam are described. A generator with an inductive energy storage and semiconducting opening switch was used for discharge formation. The generator was shown to be very promising for development of efficient discharge HF lasers with high output energy. It produces very uniform discharge in SF6-H2(C3H8) gas mixtures at elevated pressure and

Victor F. Tarasenko; Evgenii H. Baksht; Mikhail I. Lomaev; Victor M. Orlovskii; Alexei N. Panchenko; Eduard A. Sosnin

1998-01-01

340

Chemical composition of ZrC thin films grown by pulsed laser deposition  

Microsoft Academic Search

ZrC films were grown on (100) Si substrates by the pulsed laser deposition (PLD) technique using a KrF excimer laser working at 40Hz. The nominal substrate temperature during depositions was set at 300C and the cooling rate was 5C\\/min. X-ray diffraction investigations showed that films deposited under residual vacuum or under 210?3Pa of CH4 atmosphere were crystalline, exhibiting a (200)-axis

D. Craciun; G. Socol; N. Stefan; G. Bourne; V. Craciun

2009-01-01

341

Structure and chemical composition of BN thin films grown by pulsed-laser deposition (PLD)  

Microsoft Academic Search

BN thin films are grown on Si(100) substrates in a pulsed-laser deposition (PLD) process using a pulsed CO2 laser, a hexagonal-phase BN (h-BN) target, and N2 as processing gas. The effect of RF power coupled to the substrate during PLD is investigated. Films are analysed using optical microscopy and micro-Raman and X-ray photoemission spectroscopies. They are generally composed of a

T. Klotzbcher; W. Pfleging; M. Mertin; D. A. Wesner; E. W. Kreutz

1995-01-01

342

Quantum cascade laser-based photoacoustic spectroscopy of volatile chemicals: Application to hexamethyldisilazane  

NASA Astrophysics Data System (ADS)

The use of photoacoustic spectroscopy and mid-infrared quantum-cascade lasers (QCLs) for the detection of hexamethyldisilazane (HMDS) is reported. A detection limit of 200 parts in 10 9 is found using a Fabry-Perot QCL operated at 8.4 ?m in pulsed mode and a photoacoustic cell equipped with four electret microphones. The laser multimode spectrum matches the range of the N-H bending absorption band of HMDS. Further improvements to reach lower detection limits are discussed.

Elia, A.; Rizzi, F.; Di Franco, C.; Lugar, P. M.; Scamarcio, G.

2006-05-01

343

Development of multihundredjoule HF (H2\\/SF6) chemical lasers initiated by intense electron beams  

Microsoft Academic Search

The development of an electron-beam initiated HF(H2\\/SF6) laser is described. Typical parameters of the circular electron beam used in the experiment are 2 MeV, 80 kA, 65 ns (FWHM), and 9 cm in diameter. The maximum laser energy of 250 J in a 70 ns FWHM pulse is obtained with an electrical efficiency of 8.3 percent at SF6\\/H2 = 200\\/2

Fumihiko Kannari; Tadashi Suzuki; Minoru Obara; Tomoo Fujioka

1983-01-01

344

A Model for Incorporating Chemical Reactions in Mesoscale Modeling of Laser Ablation of Polymers  

Microsoft Academic Search

We have developed a methodology for including effects of chemical reactions in coarse-grained computer simulations such as those that use the united atom or bead and spring approximations. The new coarse-grained chemical reaction model (CGCRM) adopts the philosophy of kinetic Monte Carlo approaches and includes a probabilistic element to predicting when reactions occur, thus obviating the need for a chemically

Barbara J. Garrison; Yaroslava G. Yingling

2004-01-01

345

High-power supersonic chemical lasers: gas-dynamic problems of operation of mobile systems with PRS  

NASA Astrophysics Data System (ADS)

Supersonic chemical lasers, such as HF /DF and COIL, have always been in the focus of special interest as the most powerful sources of continuous wave generation. Presently, autonomous mobile laser complexes (both air- and landbased) are being developed on the basis of SCL [1-3]. It is commonly accepted that SCL appeared, conditionally speaking, at the crossroads of a number of sciences: of physics - quantum electronics and physical kinetics; chemistry - combustion theory and chemical kinetics; classic optics - theory of resonators, aero-optics, and gas dynamics (there is a supersonic flow in the SCL channel). Due to this fact, all tasks and problems which could be resolved in the course of SCL development have complex character and could be considered as the next stage of complexity in comparison with the well known similar tasks which had been considered earlier. This is why they should be resolved anew with consideration of the specific aspects of the SCL processes. This is true for the gas-dynamic problems: new parameter areas, non-traditional channel geometry, consideration of new phenomena, etc.Supersonic chemical lasers, such as HF /DF and COIL, have always been in the focus of special interest as the most powerful sources of continuous wave generation. Presently, autonomous mobile laser complexes (both air- and landbased) are being developed on the basis of SCL [1-3]. It is commonly accepted that SCL appeared, conditionally speaking, at the crossroads of a number of sciences: of physics - quantum electronics and physical kinetics; chemistry - combustion theory and chemical kinetics; classic optics - theory of resonators, aero-optics, and gas dynamics (there is a supersonic flow in the SCL channel). Due to this fact, all tasks and problems which could be resolved in the course of SCL development have complex character and could be considered as the next stage of complexity in comparison with the well known similar tasks which had been considered earlier. This is why they should be resolved anew with consideration of the specific aspects of the SCL processes. This is true for the gas-dynamic problems: new parameter areas, non-traditional channel geometry, consideration of new phenomena, etc.

Boreysho, A. S.; Malkov, V. M.; Savin, A. V.

2008-10-01

346

Phillips Laboratory COIL technology overview  

Microsoft Academic Search

The basic technology and performance of the chemically dumped oxygen-iodine laser is reviewed. The performance is discussed in terms of the operation of the chemical oxygen generator, the kinetics of energy transfer from oxygen to iodine, and the extraction of power by the optical resonator. Techniques for generation of excited oxygen and iodine are reviewed. In addition advanced concepts for

K. A. Truesdell; S. E. Lamberson; G. D. Hager

1992-01-01

347

Research on a new type eject singlet oxygen generator  

Microsoft Academic Search

Singlet oxygen generator is the key of chemical oxygen-iodine laser (COIL) which supplies energy for the system. However, the traditional generators have some drawbacks just as the bigger volume and the lower chemical efficiency. Specific surface area is the important factor restricting the development of singlet oxygen generator. Many researches on increasing specific surface area have been done to improve

Zhendong Liu; Wenwu Chen; Xiaobo Xu; Jinglong Wang; Yushi Liu; Yueren Ma; Guosheng Lv; Yuqi Jin; Fengting Sang; Rongshan Bi; Yun Yao; Fangfei Guo

2010-01-01

348

[Lasers].  

PubMed

Lasers are a very effective approach for treating many hyperpigmented lesions. They are the gold standard treatment for actinic lentigos and dermal hypermelanocytosis, such as Ota nevus. Becker nevus, hyperpigmented mosaicisms, and lentigines can also be successfully treated with lasers, but they could be less effective and relapses can be observed. However, lasers cannot be proposed for all types of hyperpigmentation. Thus, freckles and caf-au-lait macules should not be treated as the relapses are nearly constant. Due to its complex pathophysiology, melasma has a special place in hyperpigmented dermatoses. Q-switched lasers (using standard parameters or low fluency) should not be used because of consistent relapses and the high risk of post-inflammatory hyperpigmentation. Paradoxically, targeting the vascular component of the melasma lesion with lasers could have a beneficial effect. However, these results have yet to be confirmed. In all cases, a precise diagnosis of the type of hyperpigmentation is mandatory before any laser treatment, and the limits and the potential side effects of the treatment must be clearly explained to patients. PMID:23260518

Passeron, T

2012-11-01

349

Lasers.  

PubMed

Lasers are a very effective approach for treating many hyperpigmented lesions. They are the gold standard treatment for actinic lentigos and dermal hypermelanocytosis, such as Ota nevus. Becker nevus, hyperpigmented mosaicisms, and lentigines can also be successfully treated with lasers, but they could be less effective and relapses can be observed. However, lasers cannot be proposed for all types of hyperpigmentation. Thus, freckles and caf-au-lait macules should not be treated as the relapses are nearly constant. Due to its complex pathophysiology, melasma has a special place in hyperpigmented dermatoses. Q-switched lasers (using standard parameters or low fluency) should not be used because of consistent relapses and the high risk of post-inflammatory hyperpigmentation. Paradoxically, targeting the vascular component of the melasma lesion with lasers could have a beneficial effect. However, these results have yet to be confirmed. In all cases, a precise diagnosis of the type of hyperpigmentation is mandatory before any laser treatment, and the limits and the potential side effects of the treatment must be clearly explained to patients. PMID:23522632

Passeron, T

2012-12-01

350

Combustion Research Program: Flame studies, laser diagnostics, and chemical kinetics. Final report, 15 July 1987--15 June 1992  

SciTech Connect

This project has comprised laser flame diagnostic experiments, chemical kinetics measurements, and low pressure flame studies. Collisional quenching has been investigated for several systems: the OH radical, by H{sub 2}0 in low pressure flames; the rotational level dependence for NH, including measurements to J=24; and of NH{sub 2} at room temperature. Transition probability measurements for bands involving v{prime} = 2 and 3 of the A-X system of OH were measured in a flame. Laser-induced fluorescence of vinyl radicals was unsuccessfully attempted. RRKM and transition state theory calculations were performed on the OH + C{sub 2}H{sub 4} reaction, on the t-butyl radical + HX; and transition state theory has been applied to a series of bond scission reactions. OH concentrations were measured quantitatively in low pressure H{sub 2}/N{sub 2}O and H{sub 2}/O{sub 2} flames, and the ability to determine spatially precise flame temperatures accurately using OH laser-induced fluorescence was studied.

Crosley, D.R.

1992-09-01

351

Method Research for Flow and Mixing Process of HYLTE Nozzle of DF Chemical Laser  

NASA Astrophysics Data System (ADS)

The feasibility of High-speed imaging and Nano-based Planar Laser Scattering (NPLS) which are used to evaluate the mixing performance of a designed HYLTE (HYpersonic Low TEmperature) nozzle has been studied. In order to visualize the expanding part that includes transverse injecting and mixing process, a single throat nozzle laser with windows has been designed and manufactured. Two simulation methods have been studied to get the flowfield of HYLTE nozzle and cavity. In order to visualize the real mixing flowfield in laser, one 3D procedure concerning 15 species and 102 one-way primary reactions expressed by finite rate equations are built. Also, the LES method has been put forward to research vortex structure and mixing mechanism.

Lei, J.; Lai, L.; Wang, Z. G.

352

Time-Resolved Quantum Cascade Laser Absorption Spectroscopy of Pulsed Plasma Assisted Chemical Vapor Deposition Processes Containing BCl3  

NASA Astrophysics Data System (ADS)

In situ measurements are reported giving insight into the plasma chemical conversion of the precursor BCl3 in industrial applications of boriding plasmas. For the online monitoring of its ground state concentration, quantum cascade laser absorption spectroscopy (QCLAS) in the mid-infrared spectral range was applied in a plasma assisted chemical vapor deposition (PACVD) reactor. A compact quantum cascade laser measurement and control system (Q-MACS) was developed to allow a flexible and completely dust-sealed optical coupling to the reactor chamber of an industrial plasma surface modification system. The process under the study was a pulsed DC plasma with periodically injected BCl3 at 200 Pa. A synchronization of the Q-MACS with the process control unit enabled an insight into individual process cycles with a sensitivity of 10-6 cm-1\\cdotHz-1/2. Different fragmentation rates of the precursor were found during an individual process cycle. The detected BCl3 concentrations were in the order of 1014 molecules\\cdotcm-3. The reported results of in situ monitoring with QCLAS demonstrate the potential for effective optimization procedures in industrial PACVD processes.

Lang, Norbert; Hempel, Frank; Strmke, Siegfried; Rpcke, Jrgen

2011-08-01

353

Systems and methods for laser assisted sample transfer to solution for chemical analysis  

DOEpatents

Systems and methods are described for laser ablation of an analyte from a specimen and capturing of the analyte in a dispensed solvent to form a testing solution. A solvent dispensing and extraction system can form a liquid microjunction with the specimen. The solvent dispensing and extraction system can include a surface sampling probe. The laser beam can be directed through the surface sampling probe. The surface sampling probe can also serve as an atomic force microscopy probe. The surface sampling probe can form a seal with the specimen. The testing solution including the analyte can then be analyzed using an analytical instrument or undergo further processing.

Van Berkel, Gary J; Kertesz, Vilmos; Ovchinnikova, Olga S

2013-08-27

354

Chemical, morphological and chromatic behavior of mural paintings under Er:YAG laser irradiation  

Microsoft Academic Search

Several pigments (malachite CuCO3?Cu(OH)2, azurite 2CuCO3?Cu(OH)2, yellow ochre (goethite ?-FeOOH, gypsum CaSO4?2H2O), St. Johns white CaCO3 formed from slaked lime) and respective mural paintings specimens were subjected to the free-running Er:YAG laser radiation\\u000a in order to study their damage thresholds, in a broad range of laser fluences, both in dry and wet conditions. The specimens\\u000a damage thresholds were evaluated by

J. Striova; M. Camaiti; E. M. Castellucci; A. Sansonetti

2011-01-01

355

Laser Control of Chemical Dynamics. I. Control of Electronic Transitions by Quadratic Chirping  

NASA Astrophysics Data System (ADS)

An effective scheme for the laser control of wavepacket dynamics applicable to systems with many degrees of freedom is discussed. It is demonstrated that specially designed quadratically chirped pulses can be used to achieve fast and near-complete excitation of the wavepacket without significantly distorting its shape. The parameters of the laser pulse can be estimated analytically from the Zhu-Nakamura (ZN) theory of nonadiabatic transitions. The scheme is applicable to various processes, such as simple electronic excitations, pump-dumps, and selective bond-breaking, and, taking diatomic and triatomic molecules as examples, it is actually shown to work well.

Zou, S.; Kondorskiy, A.; Mil'nikov, G.; Nakamura, H.

356

Quantum cascade laser-based photoacoustic spectroscopy of volatile chemicals: application to hexamethyldisilazane.  

PubMed

The use of photoacoustic spectroscopy and mid-infrared quantum-cascade lasers (QCLs) for the detection of hexamethyldisilazane (HMDS) is reported. A detection limit of 200 parts in 10(9) is found using a Fabry-Perot QCL operated at 8.4 microm in pulsed mode and a photoacoustic cell equipped with four electret microphones. The laser multimode spectrum matches the range of the N-H bending absorption band of HMDS. Further improvements to reach lower detection limits are discussed. PMID:16420984

Elia, A; Rizzi, F; Di Franco, C; Lugar, P M; Scamarcio, G

2006-01-18

357

DIODE LASER-BASED MEASUREMENTS OF HYDROGEN FLUORIDE GAS DURING CHEMICAL SUPPRESSION OF FIRES  

EPA Science Inventory

Near-infrared tunable diode laser (NIR-TDL) spectroscopy is used to quantify hydrogen fluoride (HF) gas produced during fire-suppressant testing of Halon alternatives. Results of comparisons with other techniques for measuring HF gas concentrations are discussed. Measurements of ...

358

DIODE-LASER-BASED MEASUREMENTS OF HYDROGEN FLUORIDE GAS DURING CHEMICAL SUPPRESSION OF FIRES  

EPA Science Inventory

Near-infrared tunable diode laser (NIR-TDL) spectroscopy is used to quantify HF gas produced during fire suppressant testing of Halon alternatives. Results of comparisons with other techniques for measuring HF gas concentrations are discussed. Measurements of HF gas produced in l...

359

Reliability of AlGaAs/GaAs laser diodes grown by metalorganic chemical vapor deposition  

NASA Astrophysics Data System (ADS)

The results from an extensive life test of wide stripe laser diodes operating in the 808 nm wavelength region and at a heatsink temperature of -20 C are reported. Devices were mounted p-side down on BeO heatsinks with indium solder. Stringent screening and burn-in criteria were applied to the device population prior to selection for long term test.

Dreisewerd, D.; Fritz, W.; Begley, D.; Schwedt, S.; Elliott, G.

1988-01-01

360

ARTICLES: Nonlinear scattering of laser radiation and kinetics of chemical reactions in microvolumes of material  

Microsoft Academic Search

An experimental investigation was made of nonlinear scattering of laser radiation during repeated irradiation of an absorbing microinhomogeneity in BK-8 glass. Theoretical calculations of the experimental data were carried out and dependences of the change in the absorption coefficient and size of the inhomogeneity as a function of the number of radiation pulses were obtained. On the basis of these

A. A. Kovalev; B. I. Makshantsev; N. F. Pilipetskii; S. Yu Savanin; V. M. Finkel'berg

1984-01-01

361

Chemical kinetic studies of atmospheric reactions using tunable diode laser spectroscopy  

Microsoft Academic Search

IR absorption using tunable diode laser spectroscopy provides a sensitive and quantitative detection method for laboratory kinetic studies of atmospheric trace gases. Improvements in multipass cell design, real time signal processing, and computer controlled data acquisition and analysis have extended the applicability of the technique. We have developed several optical systems using off-axis resonator mirror designs which maximize path length

Douglas R. Worsnop; David D. Nelson; Mark S. Zahniser

1993-01-01

362

Chemical Processing of Novel Multifunctional Materials for Sensor Protection Against Laser Threats.  

National Technical Information Service (NTIS)

There is an immediate need for the development of materials that could function to protect human vision and light sensitive equipment from laser based weapons. The goal of the just concluded research was to synthesize a compound that would incorporate a n...

M. K. Casstevens R. Burzynski

1991-01-01

363

Droplet shattering, vaporization, and recondensation in cloud clearing with long pulse infrared chemical lasers  

Microsoft Academic Search

Results of experimental attempts to produce an optically clear channel in a water cloud by evaporating the cloud droplets with a CO2 laser are presented. The use of scattered light makes it possible to visualize the clear channel produced. Measurements of the fraction of power transmitted through the channel at visible wavelengths give insight into the clearing mechanisms. The present

E. J. Caramana; J. L. Kindel; R. L. Morse; G. P. Quigley; R. B. Webster; G. W. York

1990-01-01

364

Laser structuring and modification of surfaces for chemical and medical micro components  

NASA Astrophysics Data System (ADS)

In the production of micro devices for applications in chemistry, biotechnology and medical technologies surface properties become more and more important. The microscale topography and surface chemistry have influence on wetting properties and cell behavior. Therefore the design of material surface determines the success of artificial devices in contact with biological systems. For applications in the field of medical implants laser technologies have been developed for micro structuring of polymers to modify the surface properties with respect to wettability and controlled cell growth. The technology is based on excimer laser treatment of polymer surfaces using laser wavelength 193 nm (ArF) with different fluences and cumulated energies. Depending on the processing parameters and examined polymers either hydrophobic or hydrophilic surfaces can be increased. The water contact angle of polydimethylsiloxane (PDMS) for example can be increased from 113 to approx. 150 so that the surface exhibits the so called lotus effect. The laser generated micro patterns reveal influence on cell density and cell distribution which can be used for cell guidance. Results for cell growing experiments are shown for different polymers.

Bremus-Kbberling, Elke A.; Gillner, Arnold

2003-11-01

365

Relationship between the chemical and morphological characteristics of human dentin after Er:YAG laser irradiation  

NASA Astrophysics Data System (ADS)

The effects of laser etching on dentin are studied by microenergy-dispersive x-ray fluorescence spectrometry (?-EDXRF) and scanning electron microscopy (SEM) to establish the correlation of data obtained. Fifteen human third molars are prepared, baseline ?-EDXRF mappings are performed, and ten specimens are selected. Each specimen received four treatments: acid etching (control-CG) or erbium:yttrium-aluminum-garnet (Er:YAG) laser irradiation (I-100 mJ, II-160 mJ, and III-220 mJ), and maps are done again. The Ca and P content are significantly reduced after acid etching (p<0.0001) and increased after laser irradiation with 220 mJ (Ca: p<0.0153 and P: p=0.0005). The Ca/P ratio increased and decreased after CG (p=0.0052) and GI (p=0.0003) treatments, respectively. CG treatment resulted in lower inorganic content (GI: p<0.05, GII: p<0.01, and GIII: p<0.01) and higher Ca/P ratios than laser etching (GI: p<0.001, GII: p<0.01, and GIII: p<0.01). The SEM photomicrographies revealed open (CG) and partially open dentin tubules (GI, GII, and GIII). ?-EDXRF mappings illustrated that acid etching created homogeneous distribution of inorganic content over dentin. Er:YAG laser etching (220 mJ) produced irregular elemental distribution and changed the stoichiometric proportions of hydroxyapatite, as showed by an increase of mineral content. Decreases and increases of mineral content in the ?-EDXRF images are correlated to holes and mounds, respectively, as found in SEM images.

Silva Soares, Lus Eduardo; Lavesa Martin, Ovdio Csar; Moriyama, Lilian Tan; Kurachi, Cristina; Martin, Airton Abraho

2013-06-01

366

Laser directed growth of carbon-based nanostructures by plasmon resonant chemical vapor deposition.  

PubMed

We exploit the strong plasmon resonance of gold nanoparticles in the catalytic decomposition of CO to grow various forms of carbonaceous materials. Irradiating gold nanoparticles in a CO environment at their plasmon resonant frequency generates high temperatures and strong electric fields required to break the CO bond. By varying the laser power, exposure time, and gas flow rate, we deposit amorphous carbon, graphitic carbon, and carbon nanotubes. The formation of iron oxide nanocrystals catalyzes the growth of carbon nanotubes. Predefined microstructure geometries are patterned by moving the focused laser spot during the growth process, forming suspended single-walled carbon nanotube structures. Raman spectroscopy, energy dispersive X-ray spectroscopy, and transmission electron microscopy are used to characterize the resulting material. The localized nature of the plasmonic heating enables growth of these materials, while the underlying substrate remains at room temperature. PMID:18771333

Hung, Wei Hsuan; Hsu, I-Kai; Bushmaker, Adam; Kumar, Rajay; Theiss, Jesse; Cronin, Stephen B

2008-09-05

367

Scanning Diode Laser Desorption Thin-Layer Chromatography Coupled with Atmospheric Pressure Chemical Ionization Mass Spectrometry  

NASA Astrophysics Data System (ADS)

Continuous wave diode laser is applied for desorption of an analyte from a porous surface of a thin-layer plate covered with a graphite suspension. The thermally desorbed analyte molecules are ionized in the gas phase by a corona discharge at atmospheric pressure. Therefore, both essential processes - the desorption and the ionization of analyte molecules, which are often performed in one step - are separated. Reserpine was chosen as model analyte, which is often used for specification of mass spectrometers. No fragmentation was observed because of efficient collisional cooling under atmospheric pressure. The influence of diode laser power and the composition of the graphite suspension were investigated, and a primary optimization was performed. An interface to allow online qualitative and quantitative full plate detection and analysis of compounds separated by thin-layer chromatography is presented.

Peng, Song; Ahlmann, Norman; Edler, Michael; Franzke, Joachim

368

Pulsed chemical laser technology development test plan single pulse diagnostic testing  

NASA Astrophysics Data System (ADS)

Single pulse DF and DF/CO2 transfer laser testing will be conducted to expand the data base for verification and extension of performance scaling relations. Scaling relations are currently based on the analytical effort completion under Task I and the comparison of this analysis with the available data. Tests will explore the effects on performance of gas composition with constituents included F2, D2, O2, HF, NF3, He, N2, and CO2 at both DF and CO2 wavelengths. Tests will explore the nature of the medium in terms of F atom initiation level and gain, the nature of the initiating electron beam source in terms of energy deposition level and uniformity and pulse length, and laser yield in terms of total energy, pulse shape and time resolved spectra. The system will operate at pressures ranging from 200 to 760 torr.

Moran, J. P.

1986-04-01

369

Diode-laser-based measurements of hydrogen fluoride gas during chemical suppression of fires  

NASA Astrophysics Data System (ADS)

Near-infrared tunable diode laser (NIR-TDL) spectroscopy is used to quantify HF gas produced during fire suppressant testing of Halon alternatives. Results of comparisons with other techniques for measuring HF gas concentrations are discussed. Measurements of HF gas produced in laboratory and real-scale fire suppression testing are presented. The necessity for time-resolved measurements during testing of suppression systems designed to scavenge HF gas is demonstrated.

McNesby, K. L.; Reed Skaggs, R.; Miziolek, A. W.; Clay, M.; Hoke, S. H.; Miser, C. S.

1998-10-01

370

Line-shape flattening resulting from hypersonic nozzle wedge flow in low-pressure chemical lasers  

Microsoft Academic Search

The new hypersonic wedge nozzle (HYWN) supersonic wedge nozzle design produces a significant component of directed gas flow along the optical axis of a laser cavity comparable to thermal speeds. The gain-line-shape function is broadened and the refractive-index line shape is also spread as a function of wedge-flow half-angle. An analytical treatment as well as a numerical study is presented

P. M. Livingston; D. L. Bullock

1980-01-01

371

Composition and chemical reactions of titanium oxide films deposited by laser evaporation  

Microsoft Academic Search

Thin films were deposited on Pyrex glass substrates from Ti and TiO2 targets at room temperature by laser evaporation technique. These films were characterized by scanning electron microscopy, Auger electron spectroscopy, and depth profile analysis. The films deposited from Ti target are TiCx and TiOy matrix, while films from TiO2 target are almost stoichiometric in oxygen. The films have a

C. M. Dai; C. S. Su; D. S. Chuu

1991-01-01

372

Laser based in-situ and standoff detection of chemical warfare agents and explosives  

NASA Astrophysics Data System (ADS)

Laser based detection of gaseous, liquid and solid residues and trace amounts has been developed ever since lasers were invented. However, the lack of availability of reasonably high power tunable lasers in the spectral regions where the relevant targets can be interrogated as well as appropriate techniques for high sensitivity, high selectivity detection has hampered the practical exploitation of techniques for the detection of targets important for homeland security and defense applications. Furthermore, emphasis has been on selectivity without particular attention being paid to the impact of interfering species on the quality of detection. Having high sensitivity is necessary but not a sufficient condition. High sensitivity assures a high probability of detection of the target species. However, it is only recently that the sensor community has come to recognize that any measure of probability of detection must be associated with a probability of false alarm, if it is to have any value as a measure of performance. This is especially true when one attempts to compare performance characteristics of different sensors based on different physical principles. In this paper, I will provide a methodology for characterizing the performance of sensors utilizing optical absorption measurement techniques. However, the underlying principles are equally application to all other sensors. While most of the current progress in high sensitivity, high selectivity detection of CWAs, TICs and explosives involve identifying and quantifying the target species in-situ, there is an urgent need for standoff detection of explosives from safe distances. I will describe our results on CO2 and quantum cascade laser (QCL) based photoacoustic sensors for the detection of CWAs, TICs and explosives as well the very new results on stand-off detection of explosives at distances up to 150 meters. The latter results are critically important for assuring safety of military personnel in battlefield environment, especially from improvised explosive devices (IEDs), and of civilian personnel from terrorist attacks in metropolitan areas.

Patel, C. Kumar N.

2009-09-01

373

Chemical Kinetics of Triplet Methylene from Infrared Diode Laser Flash Kinetic Spectroscopy  

Microsoft Academic Search

A flash kinetic spectrometer based on a tunable infrared diode laser has been constructed. This spectrometer can measure Doppler limited spectra in the frequency region from 300-3000 cm^{-1}, allowing for the detection of nearly any molecular species. The spectrometer can be used in a spectroscopy mode to obtain the high resolution (<=q10^ {-3} cm^{-1})^ectrum of the species, or in a

David Charles Darwin

1989-01-01

374

Laser-assisted chemical vapor deposition of carbon for the growth of high-aspect ratio microrods and direct writing of surface patterns  

NASA Astrophysics Data System (ADS)

Laser-assisted chemical vapor deposition is investigated as a useful method to fabricate micrometer size carbon rods and to directly write an arbitrary deposit pattern. The deposits were produced on graphite substrates from pyrolytic decomposition of ethylene by irradiating focused argon ion laser beam at a wavelength of 514.5nm. Depending on whether the laser beam is stationary on a fixed location or scanning over the substrate, a growth of micro carbon rod or a direct writing can be achieved, respectively. Micro rods with various diameters, ranging from about 30 to 400 micrometers, with an aspect ratio of as large as 100 are fabricated using this method. Generally, a larger diameter rod is obtained as the laser power increases. Averaged growth rate of the rod varies from approximately 4 to 35 micrometer per second and increases with both gas pressure and laser power. Laser direct writing of carbon film is achieved by controlling scanning speed of the laser beam. When the scanning speed is too small, the film transforms into a rod growing toward the laser beam while a continuous film is obtained as the scanning speed and the deposition rate is balanced.

Jeong, Sung Ho; Kim, Jinbun; Kim, Sunghoon; Lee, Dongjun

2003-02-01

375

Comparison of the structural and chemical composition of two unique micro/nanostructures produced by femtosecond laser interactions on nickel  

NASA Astrophysics Data System (ADS)

The structural and chemical composition of two unique microstructures formed on nickel, with nanoscale features, produced using femtosecond laser surface processing (FLSP) techniques is reported in this paper. These two surface morphologies, termed mounds and nanoparticle-covered pyramids, are part of a larger class of self-organized micro/nanostructured surfaces formed using FLSP. Cross-sections of the structures produced using focused ion beam milling techniques were analyzed with a transmission electron microscope. Both morphologies have a solid core with a layer of nanoparticles on the surface. Energy dispersive X-ray spectroscopy by scanning transmission electron microscopy studies reveal that the nanoparticles are a nickel oxide, while the core material is pure nickel.

Zuhlke, Craig A.; Anderson, Troy P.; Alexander, Dennis R.

2013-09-01

376

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

377

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

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

378

Investigation of silicon-based nanostructure morphology and chemical termination on laser desorption ionization mass spectrometry performance.  

PubMed

We have evaluated the laser desorption ionization mass spectrometry (LDI-MS) performance of six nanostructured silicon surfaces of different morphologies and chemical functionalizations. The substrates have been synthesized either by metal-assisted etching method or by vapor-liquid-solid (VLS) growth technique. In addition to the commercial nanostructured silicon-based surface (NALDI) target plates, serving as reference, the homemade surfaces have been evaluated in mass spectrometry experiments conducted with peptide solutions mimicking tryptic digests. LDI surfaces synthesized by metal-assisted etching method were the most efficient in terms of signal intensities and number of detected peptides. The surface providing the best LDI-MS performance was composed of two nanostructured layers. Interestingly, we also observed a significant influence of the type of organic coating (hydrocarbon vs fluorocarbon) on peptide ionization discrimination. PMID:23163782

Dupr, Mathieu; Enjalbal, Christine; Cantel, Sonia; Martinez, Jean; Megouda, Nacra; Hadjersi, Toufik; Boukherroub, Rabah; Coffinier, Yannick

2012-11-30

379

Comparative optical and structural studies of CdSe films grown by chemical bath deposition and pulsed laser deposition  

NASA Astrophysics Data System (ADS)

Cadmium selenide thin films were prepared by chemical bath deposition (CBD) and pulsed laser deposition (PLD) methods. For CBD films, cadmium chloride (CdCl2) and cadmium acetate (Cd(CH3COO)2) solutions were employed as Cd2+ source while a freshly prepared sodium selenosulfite (Na2SeSO3) solution provided the Se2- ions. The pH of the bath was adjusted by adding ammonium hydroxide. The effects of the bath temperatures (30 90 C) and the Cd/Se ratio on film properties were investigated. On the other hand, PLD films were grown by the ablation of a sintered pure CdSe target using a Nd:YAG laser beam (355 nm) with 1 J/cm2 fluence. The deposition chamber was maintained under vacuum pressure (10-6 mbar) and at room temperature. The CBD films are constituted by crystallites of metastable cubic phase (7 nm) with some amorphous phase present, whereas the PLD films showed better crystalline quality and higher crystalline size. Optical absorption analysis shows that the band gap value of the CBD films is higher than that of the bulk material and decreases with the bath temperature. Annealing transforms the metastable cubic phase into the hexagonal phase and causes a redshift in the band gap of the CBD and PLD films due to the crystal size increase.

Hernandez-Perez, M. A.; Aguilar-Hernandez, J.; Contreras-Puente, G.; Vargas-Garca, J. R.; Rangel-Salinas, E.

2008-05-01

380

CONTROL OF LASER RADIATION PARAMETERS: Two-coordinate control of the radiation pattern of a chemical non-chain electric-discharge DF laser by using spacetime light modulators  

NASA Astrophysics Data System (ADS)

The results of studies of radiation parameters of a chemical non-chain DF laser (emitting in the range from 3.5 to 4.1 ?m) with an intracavity control of the radiation pattern with the help of spatiotemporal modulators based on PLZT electrooptic ceramics are presented.

Alekseev, V. N.; Kotylev, V. N.; Liber, V. I.

2008-07-01

381

CONTROL OF LASER RADIATION PARAMETERS: Two-coordinate control of the radiation pattern of a chemical non-chain electric-discharge DF laser by using spacetime light modulators  

Microsoft Academic Search

The results of studies of radiation parameters of a chemical non-chain DF laser (emitting in the range from 3.5 to 4.1 mum) with an intracavity control of the radiation pattern with the help of spatiotemporal modulators based on PLZT electrooptic ceramics are presented.

V. N. Alekseev; V. N. Kotylev; V. I. Liber

2008-01-01

382

Solution-based synthesis of crystalline silicon from liquid silane through laser and chemical annealing.  

PubMed

We report a solution process for the synthesis of crystalline silicon from the liquid silane precursor cyclohexasilane (Si(6)H(12)). Polysilane films were crystallized through thermal and laser annealing, with plasma hydrogenation at atmospheric pressure generating further structural changes in the films. The evolution from amorphous to microcrystalline is characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy and impedance spectroscopy. A four-decade enhancement in the electrical conductivity is attributed to a disorder-order transition in a bonded Si network. Our results demonstrate a potentially attractive approach that employs a solution process coupled with ambient postprocessing to produce crystalline silicon thin films. PMID:22545711

Iyer, Ganjigunte R S; Hobbie, Erik K; Guruvenket, Srinivasan; Hoey, Justin M; Anderson, Kenneth J; Lovaasen, John; Gette, Cody; Schulz, Douglas L; Swenson, Orven F; Elangovan, Arumugasamy; Boudjouk, P

2012-05-08

383

Line-shape flattening resulting from hypersonic nozzle wedge flow in low-pressure chemical lasers.  

PubMed

The new hypersonic wedge nozzle (HYWN) supersonic wedge nozzle design produces a significant component of directed gas flow along the optical axis of a laser cavity comparable to thermal speeds. The gain-line-shape function is broadened and the refractive-index line shape is also spread as a function of wedge-flow half-angle. An analytical treatment as well as a numerical study is presented that evaluates the Doppler-directed-flow impact on the number of longitudinal modes and their frequencies as well as on gain and refractive-index saturation of those that lase in a Fabry-Perot cavity. PMID:19693204

Livingston, P M; Bullock, D L

1980-07-01

384

Line-shape flattening resulting from hypersonic nozzle wedge flow in low-pressure chemical lasers  

SciTech Connect

The new hypersonic wedge nozzle (HYWN) supersonic wedge nozzle design produces a significant component of directed gas flow along the optical axis of a laser cavity comparable to thermal speeds. The gain-line-shape function is broadened and the refractive-index line shape is also spread as a function of wedge-flow half-angle. An analytical treatment as well as a numerical study is presented that evaluates the Doppler-directed-flow impact on the number of longitudinal modes and their frequencies as well as on gain and refractive-index saturation of those that lase in a Fabry--Perot cavity.

Livingston, P.M.; Bullock, D.L.

1980-07-01

385

Stability and performance of CDRL-FEL (Chemical Dynamics Research Laboratory-Free Electron Laser)  

SciTech Connect

We study the performance of a proposed infrared free electron laser at Lawrence Berkeley Laboratory, which would be a user facility and therefore has a unique set of requirements in intensity, spectrum and stability. The output performance in intensity and spectrum, and methods to optimize the performance, are studied in detail. The effect of the electron beam fluctuation on FEL stability is carefully evaluated to set a tolerance for the accelerator design. Use of intracavity gratings is studied as a means of further improving the spectral purity and stability. 19 refs., 12 figs., 2 tabs.

Kim, K.J.; Xie, M.

1990-11-01

386

Combining Transmission Geometry Laser Ablation and a Non Contact Continuous Flow Surface Sampling Probe/Electrospray Emitter for Mass Spectrometry-Based Chemical Imaging  

SciTech Connect

This paper describes the coupling of ambient pressure transmission geometry laser ablation with a liquid phase sample collection into a continuous flow surface sampling probe/electrospray emitter for mass spectrometry based chemical imaging. The flow probe/emitter device was placed in close proximity to the surface to collect the sample plume produced by laser ablation. The sample collected was immediately aspirated into the probe and on to the electrospray emitter, ionized and detected with the mass spectrometer. Freehand drawn ink lines and letters and an inked fingerprint on microscope slides were analyzed. The circular laser ablation area was about 210 m in diameter and under the conditions used in these experiments the spatial resolution, as determined by the size of the surface features distinguished in the chemical images, was about 100 m.

Ovchinnikova, Olga S [ORNL; Kertesz, Vilmos [ORNL; Van Berkel, Gary J [ORNL

2011-01-01

387

Advanced COIL--physics, chemistry and uses  

Microsoft Academic Search

A review of Chemical Oxygen Iodine Laser (COIL) chemistry, physics, and technology is presented. Individual COIL components are discussed in relation to the COIL heuristic equation, which predicts COIL performance based on well-known, measurable, device performance parameters. Topics include singlet oxygen generators (SOGs), supersonic nozzle designs, I 2 mixing, and I 2 dissociation. In addition, a brief summary of the

GERALD MANKE II; GORDON HAGER

2002-01-01

388

Supercritical explosion of a liquid drop in a laser emission field and effect of plasma-chemical reactions on optical breakdown initiation in air  

NASA Astrophysics Data System (ADS)

The explosion of a water drop in air in the emission field of a CO2 laser is investigated using mathematical modeling. Processes associated with optical breakdown initiation in air in the presence of a shock wave are identified. It is shown that initially air ionization results from plasma-chemical reactions and then from an electron avalanche.

Budnik, A. P.; Popov, A. G.

1991-07-01

389

Two-coordinate control of the radiation pattern of a chemical non-chain electric-discharge DF laser by using spacetime light modulators  

Microsoft Academic Search

The results of studies of radiation parameters of a chemical non-chain DF laser (emitting in the range from 3.5 to 4.1 ?m) with an intracavity control of the radiation pattern with the help of spatiotemporal modulators based on PLZT electrooptic ceramics are presented.

V N Alekseev; V N Kotylev; V I Liber

2008-01-01

390

Design and chemical synthesis of iodine-containing molecules for application to solar-pumped I* lasers. Semiannual progress report, 1 January30 June 1986  

Microsoft Academic Search

The design and chemical synthesis of new media for solar pumped iodine molecule lasers are explored. In an effort to prepare an iodo fluorocarbon compound absorbing strongly at 300 nm or above, the synthesis of perfluoro allylic iodides was investigated. These compounds furnish especially stable allylic radicals upon photodissociation. The desired red shift is anticipated in the absorption maximum could

Shiner

1986-01-01

391

Laboratory feasibility study of fusion vessel inner wall chemical analysis by Laser Induced Breakdown Spectroscopy  

NASA Astrophysics Data System (ADS)

Laser Induced Breakdown Spectroscopy (LIBS) is nowadays a well established tool for qualitative, semi-quantitative and quantitative analyses of surfaces, with micro-destructive characteristics and capabilities for stratigraphy. LIBS is an appealing technique compared with many other types of elemental analysis thanks to the set up versatility facilitating non-invasive and remote analyses, as well as suitability to diagnostics in harsh environments. In this work, LIBS capabilities were used for the determination of the atomic composition of multilayered samples simulating the tiles of plasma facing components in the next generation fusion machines such as ITER. A new experimental setup was designed and realized in order to optimize the characteristics of an LIBS system working at low pressure and remotely, as it should be for an in situ system to be applied in monitoring the erosion and redeposition phenomena occurring on the inner walls of a fusion device. The effects of time delay and laser fluence on LIBS sensitivity at reduced pressure were examined, looking for operational conditions suitable to analytical applications. The quantitative analysis of some atomic species in the superficial layer has been carried out using a Calibration Free (CF) approach in the time window where Local Thermal Equilibrium (LTE) was assumed for an LIBS analysis.

Almaviva, Salvatore; Caneve, Luisa; Colao, Francesco; Fantoni, Roberta; Maddaluno, Giorgio

2012-04-01

392

Tailoring the chemical reactivity and optical properties of clusters by size, structures and lasers  

NASA Astrophysics Data System (ADS)

We present results of theoretical investigations in three areas. I. Reactivity of anionic noble metal oxide clusters (Ag, Au) relevant for catalyst design: It will be shown that the cooperative effects are needed to activate clusters in order to invoke strongly size selective reactions with O2 and CO. These results obtained with DFT method elucidated fully experimental findings. II. Stationary optical properties of silver clusters: ab initio results on absorption spectra of small silver clusters and on geometric relaxation of their excited states leading to the observed fluorescence are presented and compared with experimental data. III. Real-time investigation of ultrafast processes and their control by tailored laser fields: nonstoichiometric NanF{n-1} clusters are suitable prototypes to study dynamics in excited electronic states. For this purpose we use our combination of the Wigner distribution method and MD on the fly allowing to treat all degrees of freedom. Analysis of simulated pump-probe signals will be shown for Na2F for which experimental data are available. Pump-dump control of the photoisomerization in Na3F2 avoiding conical intersection will be presented using our new strategy for obtaining tailored laser fields based on the intermediate target in excited state which (if available) guarantees the controllability in the complex systems.

Bona?i?-Kouteck, V.; Mitri?, R.; Brgel, C.; Noack, H.; Hartmann, M.; Pittner, J.

2005-07-01

393

Possibilities of improving the performance of an autonomous cw chemical DF laser by replacing the slot nozzles by the ramp ones in the nozzle array  

NASA Astrophysics Data System (ADS)

The results of a comparative numerical study of the performance of an autonomous cw chemical DF laser are obtained by simulating the processes in the nozzles and laser cavity where several configurations of slot and ramp nozzle arrays are employed. Three-dimensional NavierStokes equations solved with the Ansys CFX software are used to describe the reacting multicomponent flow in the nozzles and laser cavity. To investigate lasing characteristics, a supplementary code is developed and is used to calculate the radiation intensity in the FabryPerot resonator, taking into account its nonuniform distribution along the aperture width and height. It is shown that the use of the nozzle array consisting of ramp nozzles, which, in contrast to the slot nozzles, provide enhanced mixing of the reactants makes it possible to improve the laser performance in the case of a high-pressure (more than 15 Torr) active medium.

Bashkin, A. S.; Gurov, L. V.; Kurdyukov, M. V.

2011-08-01

394

Possibilities of improving the performance of an autonomous cw chemical DF laser by replacing the slot nozzles by the ramp ones in the nozzle array  

SciTech Connect

The results of a comparative numerical study of the performance of an autonomous cw chemical DF laser are obtained by simulating the processes in the nozzles and laser cavity where several configurations of slot and ramp nozzle arrays are employed. Three-dimensional Navier-Stokes equations solved with the Ansys CFX software are used to describe the reacting multicomponent flow in the nozzles and laser cavity. To investigate lasing characteristics, a supplementary code is developed and is used to calculate the radiation intensity in the Fabry-Perot resonator, taking into account its nonuniform distribution along the aperture width and height. It is shown that the use of the nozzle array consisting of ramp nozzles, which, in contrast to the slot nozzles, provide enhanced mixing of the reactants makes it possible to improve the laser performance in the case of a high-pressure (more than 15 Torr) active medium. (control of radiation parameters)

Bashkin, A S; Gurov, L V; Kurdyukov, M V

2011-08-31

395

Improving the performance of high-laser-damage-threshold, multilayer dielectric pulse-compression gratings through low-temperature chemical cleaning.  

PubMed

A low-temperature chemical cleaning approach has been developed to improve the performance of multilayer dielectric pulse-compressor gratings for use in the OMEGA EP laser system. X-ray photoelectron spectroscopy results guided the selection of targeted cleaning steps to strip specific families of manufacturing residues without damaging the grating's fragile 3D profile. Grating coupons that were cleaned using the optimized method consistently met OMEGA EP requirements on diffraction efficiency and 1054 nm laser-damage resistance at 10 ps. The disappearance of laser-conditioning effects for the highest-damage-threshold samples suggests a transition from a contamination-driven laser-damage mechanism to defect-driven damage for well-cleaned components. PMID:23478773

Howard, Heather P; Aiello, Anthony F; Dressler, Justin G; Edwards, Nicholas R; Kessler, Terrance J; Kozlov, Alexei A; Manwaring, Ian R T; Marshall, Kenneth L; Oliver, James B; Papernov, Semyon; Rigatti, Amy L; Roux, Alycia N; Schmid, Ansgar W; Slaney, Nicholas P; Smith, Christopher C; Taylor, Brittany N; Jacobs, Stephen D

2013-03-10

396

Particle generation by laser ablation in support of chemical analysis of high level mixed waste from plutonium production operations. 1998 annual progress report  

SciTech Connect

'The authors goal is to provide fundamental mechanistic studies of laser produced particulate formation in support of the use of Laser Assisted-Inductively Coupled Plasma-Mass Spectroscopy (LA-ICP-MS) to be used for analysis of radioactive/toxic materials. The work reported here represents the first nine months of this 3-year project. The major focus of these studies is determining the detailed mechanisms and character of the particulates generated by laser ablation of solid targets relevant to sampling materials for chemical analysis using inductively coupled mass spectroscopy, ICP-MS. In this application, particles generated by laser ablation must be transported to the plasma torch of the ICP-MS, often through a hollow tube with an interior diameter of a few mm. Proper digestion and ionization of particles in the plasma limits particle sizes to under a micron. Thus the production of submicron particles which truly represent the stoichiometry of the specimen is of critical importance.'

Dickinson, J.T. [Washington State Univ., Pullman, WA (US); Alexander, M.L. [Pacific Northwest National Lab., Richland, WA (US)

1998-06-01

397

Chemical processing of novel multifunctional materials for sensor protection against laser threats  

NASA Astrophysics Data System (ADS)

There is an immediate need for the development of materials that could function to protect human vision and light sensitive equipment from laser based weapons. The goal of the just concluded research was to synthesize a compound that would incorporate a nonlinear two photon absorbing functional group adjacent to a photoreactive moiety. This innovative approach would lead to broad band high optical transparency at lower power levels and efficient and fast attenuation at higher power levels. The use of organic compounds in this application ensures that the molecular structure could be further optimized by careful adjustment of the molecular structure. The synthesized compound, anthracene leuconitrile, was found to be photochemically unstable and took an inappropriately long time for the reconversion from the absorbing to the transmitting form.

Burzynski, Ryszard; Casstevens, Martin K.

1991-05-01

398

Forced convection and transport effects during hyperbaric laser chemical vapor deposition  

SciTech Connect

This work explores mass transport processes during HP-LCYD, including the transverse forced-flow of precursor gases through a nozzle to enhance fiber growth rates. The use of laser trapping and suspension of nano-scale particles in the precursor flow is also described, providing insights into the nature of the gas flow, including jetting from the fiber tip and thermodiffusion processes near the reaction zone. The effects of differing molecular-weight buffer gases is also explored in conjunction with the Soret effect, and it is found that nucleation at the deposit surface (and homogeneous nucleation in the gas phase) can be enhanced/ retarded, depending on the buffer gas molecular weight. To demonstrate that extensive microstructures can be grown simultaneously, three-dimensional fiber arrays are also grown in-parallel using diffractive optics--without delatory effects from neighboring reaction sites.

Maxwell, James L [Los Alamos National Laboratory; Chavez, Craig A [Los Alamos National Laboratory; Espinoza, Miguel [Los Alamos National Laboratory; Black, Marcie [Los Alamos National Laboratory; Maskaly, Karlene [Los Alamos National Laboratory; Boman, Mats [UPPSALA UNIV

2009-01-01

399

Physical and chemical modifications of PET surface usingalaser-plasma EUV source  

Microsoft Academic Search

Extreme ultraviolet (EUV) radiation is the electromagnetic radiation ranging from vacuum ultraviolet to soft X-rays. Asingle\\u000a EUV photon carries enough energy to ionize any atom or molecule. The penetration depth of the radiation in any material is\\u000a very short, ranging from tens to hundreds nanometers. Intense EUV pulses can remove material from the surface or modify its\\u000a morphology or\\/and chemical

A. Bartnik; H. Fiedorowicz; R. Jarocki; J. Kostecki; M. Szczurek; A. Bilinski; O. Chernyayeva; J. W. Sobczak

2010-01-01

400

Theoretical study of a pulsed HF chemical laser - Comparison of performance between F2/H2 and F/H2 systems  

NASA Astrophysics Data System (ADS)

The performance of a pulsed HF chemical laser with an F2/H2 chain reaction system is widely compared to that of an F/H2 non-chain reaction system by using a chemical laser simulation code based on the constant gain method. According to the simulation results, peak power differs little between both systems; laser pulse duration is more than an order of magnitude shorter in the F/H2 system than that in the F2/H2 system; laser pulse energy in the F2/H2 system is greater than that in the F/H2 system; difference in these energies is exponentially proportional to the inverse of the initial fluorine atom concentration; laser pulse energy per mol of HF/v/ produced prior to termination of the lasing differs little between both systems; the thermodynamical efficiency is a decreasing function of the initial fluorine atom concentration in the F2/H2 system while in the F/H2 system it has a maximum value at the certain concentration.

Udagawa, M.; Obara, M.; Fujioka, T.

1981-03-01

401

Applications of a laser assisted defect detection system for chemical mechanical planarization (CMP) slurry development in rigid disk polishing  

NASA Astrophysics Data System (ADS)

A laser assisted optical surface analyser (OSA) was applied for inspecting scratch defects on rigid disks used for hard disk drives (HDDs). The disk samples were polished with a chemical mechanical planarization (CMP) technique beforehand. Since it has been recognized that the CMP slurry formulation highly affects the scratch performance of rigid disks, a reliable defect evaluation system is required for efficient slurry development. In this paper, the capability of the OSA tool (Candela C10, KLA-Tencor Corp.) for scratch evaluation is discussed with reference to the scratch data acquired with a conventional dark field microscope (DFM) technique. A gauge repeatability and reproducibility (R&R) study revealed that the Candela had more than three times better R&R performance than the DFM. Scratch counts measured using the two tools were correlated, but not matched, due to the differences in the detection systems. The linear regression correlation coefficient (R2) was found to be 71% for the relatively larger size (>1 mm) of scratch categories. Another study was conducted using a scratch control additive in CMP slurry. The results showed that the effect of the additive was readily detected by the Candela, but was not obvious for the DFM detection. Based on the findings, the similarities and differences of the Candela and the DFM techniques are discussed. It was also found that the tuning capability of the Candela analysis recipe allowed consistent scratch counts with another type of laser assisted defect evaluation tool. This flexibility of the Candela system is a main characteristic which can be effectively used for CMP slurry development. An approach to targeted slurry designs is suggested in conjunction with the advantages and opportunities of the Candela method.

Kasai, Toshi; Dowell, Charles; Somanchi, Anoop

2007-05-01

402

Development of a measurement system of peroxy radicals using a chemical amplification/laser-induced fluorescence technique  

NASA Astrophysics Data System (ADS)

An instrument for measuring atmospheric peroxy radicals has been developed by chemical amplification/laser-induced fluorescence (PERCA/LIF) technique. The small concentration of peroxy radicals is converted to the large amount of NO2, which is measured by laser-induced fluorescence instead of luminol chemiluminescence. Several advantages, that is, high sensitivity, high selectively, and fast time response, are expected by use of LIF for the NO2 measurement, in comparison with luminol chemiluminescence. When using this system, simultaneous measurements of NO2 and peroxy radicals are available. The present optimum condition for the reaction tube (1/4 in. Teflon) was determined to be the reaction tube length of 3 m, the NO and CO concentrations of 3 ppmv and 10%, respectively. The calibration, including humidity dependence of the detection sensitivity of peroxy radicals, was conducted and the present detection limit of peroxy radicals was determined to be 2.7 and 3.6 pptv at the ambient relative humidity of 50 and 80%, respectively, for the integration time of 1 min (S/N=2). This detection limit was calculated assuming the ambient O3 and NO2 mixing ratios of 30 and 20 ppbv, respectively. The influence of the NO2 detection sensitivity by adding high concentrations of CO was investigated and the quenching of excited NO2 by CO can affect the ambient measurement significantly under the high NO2 and low peroxy radical concentrations. Exploratory ambient air measurements were made in suburban area of Osaka, Japan. These results demonstrated the performance of PERCA/LIF for ambient measurements.

Sadanaga, Yasuhiro; Matsumoto, Jun; Sakurai, Ken-Ichi; Isozaki, Ryoko; Kato, Shungo; Nomaguchi, Tomoki; Bandow, Hiroshi; Kajii, Yoshizumi

2004-04-01

403

Short-wavelength chemical lasers driven by intense light source. Final report, 15 August 1985--15 August 1987  

SciTech Connect

The goal of this research effort has been to assess the possibility of producing a short-wavelength chemical laser system pumped by an intense light source. The lasing systems that we have concentrated on are XeCl, which emits at 308 mn, and Xe{sub 2}Cl, with a peak emission at 480 nm. The latter is favored in systems with high Xe concentrations. Both systems have been demonstrated to be efficient lasers when discharge or electron-beam pumping is utilized. We have considered pumping by an intense, blackbody (Planckian) light source. Thus, we have studied the excimer fluorescence yield over a wide range of excitation energies accessible with a 40,000 K blackbody (6.4 to > 12.8 eV) source. Several photochemical reaction channels have been identified in Xe/Cl{sub 2} mixtures that produce the desired excimers. The scaling of the fluorescence yield with reactant pressure has been studied for each reaction mechanism. The reaction channels scale differently with reactant pressure, causing the scaling behavior of the total fluorescence output to be interrelated and complex. Quenching processes in the excimer systems have been studied and a rate constant for quenching of Xe{sub 2}Cl by CCl{sub 4}, an alternative chlorine source, has been measured. The efficiency of coupling radiant energy into the excimer system via absorption by Cl{sub 2} or collision-induced absorption by Xe-Cl{sub 2} collision pairs in the vacuum-UV (VUV) region of the spectrum remain two major unknown factors in assessing the system performance.

Berman, M.R.; Bragg, S.L. [McDonnell Douglas Research Labs., St. Louis, MO (United States)

1987-12-31

404

Liquid droplet supercritical explosion in the field of CO2 laser radiation and influence of plasma chemical reactions on initiation of optical breakdown in air  

NASA Astrophysics Data System (ADS)

Mathematical modeling of water droplet explosion in air in the field of CO2-laser radiation (LR) was carried out. Some processes leading to air optical breakdown (OB) initiation in shock wave (SW) were investigated. OB of shock-heated air has been shown to develop in two stages. At the first stage, initial electrons are caused by plasma chemical reactions in heated and compressed air. At the second stage, these electrons, under influence of laser radiation, give rise to an electron avalanche, which leads to air OB.

Budnik, A. P.; Popov, A. G.

1991-12-01

405

Chemically driven visible laser amplifiers and oscillators based on fast intermolecular electronic energy transfer  

NASA Astrophysics Data System (ADS)

Near-resonant intermolecular energy transfer from selectively formed metastable states of SiO and GeO is used to form continuous sodium and potassium based laser amplifiers. These materials are brought into contact with the appropriate atomic receptors to energy transfer pump X 2S1/2 Na atoms (SiO) to excited 4d2D and 5s2S states and 2S1/2 K atoms (GeO) to the excited 5d2D state. Population inversion and corresponding gain conditions on the Na 4d2D to 3p2P and 5s2S to 3p2P transitions at 569 and 616 nm, and the K 5d2D to 4p2P transition at 581 nm, are observed, forming the basis for full cavity oscillation on the Na transitions. Continuous light output at 569 nm exceeding 1000 times that observed with a blocked (single pass) high reflector is achieved with 0.2 percent output coupling from a full cavity configuration surrounding a 5 cm reaction-energy transfer-amplification zone formed by the 90 deg intersection of entrained metastable SiO and Na atom flows. Improved cavity output based on the use of concentric flow configurations, optimization of output coupling, and operation in windowless configuration, is discussed.

Gole, J. L.; Shen, K. K.; Wang, H.; Winstead, C. B.; Stephens, J.

1993-07-01

406

Temperature dependences of optical properties, chemical composition, structure, and laser damage in Ta2O5 films  

NASA Astrophysics Data System (ADS)

Ta2O5 films are prepared by e-beam evaporation with varied deposition temperatures, annealing temperatures, and annealing times. The effects of temperature on the optical properties, chemical composition, structure, and laser-induced damage threshold (LIDT) are systematically investigated. The results show that the increase of deposition temperature decreases the film transmittance slightly, yet annealing below 923 K is beneficial for the transmittance. The XRD analysis reveals that the film is in the amorphous phase when annealed below 873 K and in the hexagonal phase when annealed at 1073 K. While an interesting near-crystalline phase is found when annealed at 923 K. The LIDT increases with the deposition temperature increasing, whereas it increases firstly and then decreases as the annealing temperature increases. In addition, the increase of the annealing time from 4 h to 12 h is favourable to improving the LIDT, which is mainly due to the improvement of the O/Ta ratio. The highest LIDT film is obtained when annealed at 923 K, owing to the lowest density of defect.

Xu, Cheng; Yang, Shuai; Zhang, Sheng-Hui; Niu, Ji-Nan; Qiang, Ying-Huai; Liu, Jiong-Tian; Li, Da-Wei

2012-11-01

407

CO2 laser-based differential absorption lidar system for range-resolved and long-range detection of chemical vapor plumes  

NASA Astrophysics Data System (ADS)

A dual CO2 laser-based differential absorption lidar (DIAL) system has been constructed and demonstrated for range-resolved mapping of chemical vapor plumes. The system acquires high range resolution through the use of plasma-shutter pulse clippers that extinguish the nitrogen tail of the CO2-laser output. A programmable servomotor-driven scanner allows full hemispherical coverage of the interrogated field. A high-speed direct-detection receiver subsystem is used to gather, process, and display vapor-concentration data in near real time. Data demonstrating range-resolved detection of low concentrations of chemical plumes from ranges of 1 to 2 km are presented. In the column-content detection mode, trace levels of secondary vapors from various organophosphate liquids were monitored. Detection of an SF6 vapor plume released 16 km from the DIAL system is also adduced.

Carlisle, Clinton B.; van der Laan, Jan E.; Carr, Lewis W.; Adam, Philippe; Chiaroni, Jean-Pierre

1995-09-01

408

Involvement of laser photo-CIDNP (chemically induced dynamic nuclear polarization)-reactive amino acid side chains in ligand binding by galactoside-specific lectins in solution  

Microsoft Academic Search

For proteins in solution the validity of certain crystallographic parameters can be ascertained by a combination of molecular-dynamics (MD) simulations and NMR spectroscopy. Using the laser photoCIDNP (chemically induced dynamic nuclear polarization) technique as a measure for surface accessibility of histidine, tyrosine and tryptophan, the spectra of bovine galectin-1 and Erythrina corallodendron lectin (EcorL) are readily reconcilable with the crystallographic

J. F. G. Vliegenthart; H.-C Siebert; R. Adar; R. Arango; M. Burchert; H. Kaltner; G. Kayser; C.-W. Tajkhorshid; Robert Kaptein; Nathan Sharon; Hans-Joachim Gabius

1997-01-01

409

Chemical Structure and Micro-Mechanical Properties of Ultra-Thin Films of Boron Carbide Prepared by Pulsed-Laser Deposition  

Microsoft Academic Search

Ultra-thin boron carbide films with a thickness of about 40 nm were deposited on silicon substrates by means of pulsed-laser ablation of a sintered B4C target in vacuum. Together with the determination of the film composition by X-ray photoelectron spectroscopy (XPS) and the observation of the surface topography by atomic force microscopy (AFM), the chemical structure of the films was

J. Sun; H. Ling; W. J. Pan; N. Xu; Z. F. Ying; W. D. Shen; J. D. Wu

2004-01-01

410

Atomic mixing and chemical bond formation in MoS x \\/Fe thin-film system deposited from a laser plume in a high-intensity electrostatic field  

Microsoft Academic Search

The potential of pulsed laser deposition in an applied uniform electrostatic field was investigated. A flat, positively charged, fine-celled-grid counter electrode was used to provide bias voltage of up to +50 kV with respect to the substrate. This enabled control of the atomic mixing and made it possible to initiate chemical bond formation at the interfaces of the films formed

V. Fominski; V Nevolin; R Romanov; A Smirnov; V Titov; W Scharff

2002-01-01

411

The influence of multivariate analysis methods and target grain size on the accuracy of remote quantitative chemical analysis of rocks using laser induced breakdown spectroscopy  

Microsoft Academic Search

Laser-induced breakdown spectroscopy (LIBS) was used to quantitatively analyze 195 rock slab samples with known bulk chemical compositions, 90 pressed-powder samples derived from a subset of those rocks, and 31 pressed-powder geostandards under conditions that simulate the ChemCam instrument on the Mars Science Laboratory Rover (MSL), Curiosity. The low-volatile (<2 wt.%) silicate samples (90 rock slabs, corresponding powders, and 22

Ryan B. Anderson; Richard V. Morris; Samuel M. Clegg; James F. Bell; Roger C. Wiens; Seth D. Humphries; Trevor G. Graff; Rhonda McInroy

2011-01-01

412

The influence of multivariate analysis methods and target grain size on the accuracy of remote quantitative chemical analysis of rocks using laser induced breakdown spectroscopy  

Microsoft Academic Search

Laser-induced breakdown spectroscopy (LIBS) was used to quantitatively analyze 195 rock slab samples with known bulk chemical compositions, 90 pressed-powder samples derived from a subset of those rocks, and 31 pressed-powder geostandards under conditions that simulate the ChemCam instrument on the Mars Science Laboratory Rover (MSL), Curiosity. The low-volatile (<2wt.%) silicate samples (90 rock slabs, corresponding powders, and 22 geostandards)

Ryan B. Anderson; Richard V. Morris; Samuel M. Clegg; James F. Bell; Roger C. Wiens; Seth D. Humphries; Trevor G. Graff; Rhonda McInroy

2011-01-01

413

Growth kinetics and microstructure of carbon deposited on quartz plates and optical fibers by open-air laser-induced chemical vapor deposition  

Microsoft Academic Search

Pyrolytic carbon has been successfully deposited on fused silica optical fibers and fused quartz plates by open-air laser-induced chemical vapor deposition. Raman spectroscopy, scanning electron microscopy, ion-beam sputtering and scanning white-light interferometry were used to investigate the microstructure, composition and uniformity of the carbon film. The pyrolytic carbon was derived from methane, acetylene, propane and butane precursors. Both the axial

Kinghong Kwok; Wilson K. S. Chiu

2005-01-01

414

Thermal and chemical modification of dentin by pulsed CO2 laser irradiation at 9 to 11 um  

Microsoft Academic Search

Previous studies have shown that dentin can be thermally modified by pulsed CO2 laser irradiation to form a more highly mineralized tissue. The implications are important for the potential laser modification or removal of dentinal and root caries. Temperature excursions were followed after (lambda) equals 9.3, 9.6, 10.3, and 10.6 micrometers laser irradiation with pulses of 100 (Mu) s duration

Daniel S. Fried; Michael J. Zuerlein; John D. Featherstone; Darren Machule

1997-01-01

415

The laser guidebook  

SciTech Connect

In introductory chapters, the author discusses such topics as the evolution of the laser concept, laser theory and principles, methods to enhance laser operation, and accessories that improve laser performance. The heart of the book, however, is devoted to individual laser types. In these chapters, Hecht examines the major and minor kinds of lasers that are commercially available, such as helium-neon, ion, carbon dioxide, chemical, copper vapor, excimer, far-infrared, dye, nitrogen, gallium arsenide, semiconductor diode, and neodymium.

Hecht, J.

1986-01-01

416

First steps towards probing chemical systems and dynamics with free-electron laser radiation--case studies at the FLASH facility  

NASA Astrophysics Data System (ADS)

It is expected that free-electron laser (FEL) radiation with its unique properties will allow real-time tracking of structural changes during chemical reactions. The methods suggested being applied range from x-ray spectroscopy to diffraction. In order to reach this goal, in this work we will present our studies utilizing soft x-ray FEL radiation generated at the FLASH facility. We will present case studies of ultrafast x-ray diffraction on nanocrystalline lamellar assemblies of chemical relevance and heat dissipation studies on polymer foils (upon FLASH excitation) as revealed by ultrafast optical reflectivity. The extension of these studies to characterize in vacuum water jets during their interaction with FEL radiation will be given at the end if this overview. In conclusion, it can be stated that FLASH-FEL radiation can be used for studying chemical processes as long as the pulse duration is smaller than the characteristic time scales of destruction (ionization) and heat dissipation processes.

Hallmann, J.; Grbel, S.; Rajkovic, I.; Quevedo, W.; Busse, G.; Scholz, M.; More, R.; Petri, M.; Techert, S.

2010-10-01

417

Investigation by laser induced breakdown spectroscopy, X-ray fluorescence and X-ray powder diffraction of the chemical composition of white clay ceramic tiles from Veliki Preslav  

NASA Astrophysics Data System (ADS)

The paper presents the results of the application of laser induced breakdown spectroscopy, X-ray fluorescence spectrometry, and X-ray powder diffraction in assessing the chemical and phase composition of white clay decorative ceramic tiles from the medieval archaeological site of Veliki Preslav, a Bulgarian capital in the period 893-972 AC, well-known for its original ceramic production. Numerous white clay ceramic tiles with highly varied decoration, produced for wall decoration of city's churches and palaces, were found during the archaeological excavations in the old capital. The examination of fourteen ceramic tiles discovered in one of the city's monasteries is aimed at characterization of the chemical profile of the white-clay decorative ceramics produced in Veliki Preslav. Combining different methods and comparing the obtained results provides complementary information regarding the white-clay ceramic production in Veliki Preslav and complete chemical characterization of the examined artefacts.

Blagoev, K.; Grozeva, M.; Malcheva, G.; Neykova, S.

2013-01-01

418

PhotoChemical Synthesis of Iron Oxide Nanowires Induced by Pulsed Laser Ablation of Iron Powder in Liquid Media  

Microsoft Academic Search

Iron oxide nanowires are synthesized by photochemical method through nanosecond pulsed laser ablation of iron powder in liquid media. The synthesis is tried using various wavelengths (248 and 532 nm) of pulsed laser at different liquids (water, ethanol, methanol, isopropanol and glycol). The solution of iron oxide nanowires is obtained only in methanol when the iron powder (size 60 mu

S. Mollah; S. J. Henley; C. E. Giusca; S. R. P. Silva

2010-01-01

419

Laser Femtochemistry,  

National Technical Information Service (NTIS)

Femtochemistry is concerned with the very act of the molecular motion that brings about chemistry, chemical bond breaking, or bond formation on the femtosecond 10 to the -15th time scale. With lasers it is now possible to record snapshots of chemical reac...

A. H. Zewail

1988-01-01

420

Structural and chemical surface analysis with EUV\\/XUV radiation using a broadband laser plasma source and optics system  

Microsoft Academic Search

This paper presents the development of a laser-driven plasma source for soft X-ray production in the 2-20 nm spectral range. In the experiment, a Nd:YAG laser (1064 nm, 800 mJ, 6 ns) is focused into a gas-target, that leads to the formation of a plasma, which in turn emits characteristic soft X-ray radiation. A flexible Kirkpatrick-Baez optics is developed for

A. Bayer; F. Barkusky; S. Doring; B. Floter; C. Peth; K. Mann

2009-01-01

421

Excimer laser ablation mass spectrometry of inorganic solids: Chemical, matrix, and sampling effects on polyatomic ion yields  

Microsoft Academic Search

Positive ions formed directly by excimer laser ablation in vacuum of several lanthanide (Ln) and transition metal solid materials---including LnO, LnS, LnF, TaO, ZrO, TiO, and TiO---were identified by time-of-flight mass spectrometry. Variations in ion yields were investigated as a function of the composition of the precursor material, laser irradiance, and ion sampling delay after ablation. The compositions of the

John K. Gibson

1995-01-01

422

Bibliography of Soviet laser developments, Number 52, March - April 1981  

SciTech Connect

Coverage includes basic research on solid state, liquid, gas, and chemical lasers; components, nonlinear optics, spectroscopy of laser materials; ultrashort pulse generation; crystal growing; theoretical aspects of advanced lasers; and general laser theory. Laser applications are listed under biological effects; communications; beam propagation; computer technology; holography; laser-induced chemical reactions; measurement of laser parameters; laser measurement application; laser-excited; optical effects; laser spectroscopy; beam-target interaction; and plasma generation and diagnostics.

Not Available

1982-05-17

423

Experimental Verification of the Chemical Sensitivity of Two-Site Double Core-Hole States Formed by an X-Ray Free-Electron Laser  

NASA Astrophysics Data System (ADS)

We have performed x-ray two-photon photoelectron spectroscopy using the Linac Coherent Light Source x-ray free-electron laser in order to study double core-hole (DCH) states of CO2, N2O, and N2. The experiment verifies the theory behind the chemical sensitivity of two-site DCH states by comparing a set of small molecules with respect to the energy shift of the two-site DCH state and by extracting the relevant parameters from this shift.

Saln, P.; van der Meulen, P.; Schmidt, H. T.; Thomas, R. D.; Larsson, M.; Feifel, R.; Piancastelli, M. N.; Fang, L.; Murphy, B.; Osipov, T.; Berrah, N.; Kukk, E.; Ueda, K.; Bozek, J. D.; Bostedt, C.; Wada, S.; Richter, R.; Feyer, V.; Prince, K. C.

2012-04-01

424

Mixing enhancement in a multi-stream injection nozzle  

Microsoft Academic Search

We present quantitative analysis of image sequences of multi-stream injection nozzle flows with several different injection geometries in an experiment simulating mixing in a chemical oxygen-iodine laser. To visualize mixing, image sequences were acquired with planar laser-induced fluorescence (PLIF) in iodine that was injected into the main flow. The injection nozzle consisted of a slot, ejector, and injector block, with

Peter Vorobieff; C. Randall Truman; Adam M. Ragheb; Gregory S. Elliott; Julia K. Laystrom-Woodard; Darren M. King; David L. Carroll; Wayne C. Solomon

2011-01-01

425

Mixing enhancement in a multi-stream injection nozzle  

Microsoft Academic Search

We present quantitative analysis of image sequences of multi-stream injection nozzle flows with several different injection\\u000a geometries in an experiment simulating mixing in a chemical oxygen-iodine laser. To visualize mixing, image sequences were\\u000a acquired with planar laser-induced fluorescence (PLIF) in iodine that was injected into the main flow. The injection nozzle\\u000a consisted of a slot, ejector, and injector block, with

Peter Vorobieff; C. Randall Truman; Adam M. Ragheb; Gregory S. Elliott; Julia K. Laystrom-Woodard; Darren M. King; David L. Carroll; Wayne C. Solomon

426

Laser femtochemistry.  

PubMed

Femtochemistry is concerned with the very act of the molecular motion that brings about chemistry, chemical bond breaking, or bond formation on the femtosecond (10(-15) second) time scale. With lasers it is now possible to record snapshots of chemical reactions with sub-angstrom resolution. This strobing of the transition-state region between reagents and products provides real time observations that are fundamental to understanding the dynamics of the chemical bond. PMID:17730575

Zewail, A H

1988-12-23

427

Direct Chemical Analysis of Solids by Laser Ablation in an Ion-Storage Time-of-Flight Mass Spectrometer  

SciTech Connect

A laser ablation/ionization mass spectrometer system is described for the direct analysis of solids, particles, and fibers. The system uses a quadrupole ion trap operated in an ion-storage (IS) mode, coupled with a reflectron time-of-flight mass spectrometer (TOF-MS). The sample is inserted radially into the ring electrode and an imaging system allows direct viewing and selected analysis of the sample. Measurements identified trace contaminants of Ag, Sn, and Sb in a Pb target with single laser-shot experiments. Resolution (m/{micro}m) of 1500 and detection limits of approximately 10 pg have been achieved with a single laser pulse. The system configuration and related operating principles for accurately measuring low concentrations of isotopes are described.

Klunder, G L; Grant, P M; Andresen, B D; Russo, R E

2003-09-29

428

Chemical characterization of single particles by laser ablation/desorption in a quadrupole ion trap mass spectrometer  

SciTech Connect

Particles are introduced into the center of the space surrounded by the hyperbolic electrode surfaces of a quadrupole ion trap mass spectrometer. Ions are desorbed or ablated from the surfaces of the particles with laser pulses from a Nd:YAG laser as the particles fall through the trap. The ions are trapped and subsequently mass analyzed using the mass-selective instability mode of operation of the ion trap. Desorption experiments were performed with approximately 100 [mu]m silicon carbide particles with an average of a few nanograms of adsorbed trimethylphenyl-ammonium chloride, tetraphenylphosphonium bromide, or 2,4,6-trinitrotoluene per particle. A conservative detection limit of 0.7 fm per particle was determined for tetraphenylphosphonium bromide. Ablation experiments were performed with approximately 50 [mu]m nickel particles for isotope ratio measurements with good agreement between accepted and average experimental values. 22 refs., 5 figs., 1 tab.

Dale, J.M.; Yang, M.; Whitten, W.B.; Ramsey, J.M. (Oak Ridge National Lab., TN (United States))

1994-10-15

429

Unusual mechanism for H{sub 3}{sup +} formation from ethane as obtained by femtosecond laser pulse ionization and quantum chemical calculations  

SciTech Connect

The formation of H{sub 3}{sup +} from saturated hydrocarbon molecules represents a prototype of a complex chemical process, involving the breaking and the making of chemical bonds. We present a combined theoretical and experimental investigation providing for the first time an understanding of the mechanism of H{sub 3}{sup +} formation at the molecular level. The experimental approach involves femtosecond laser pulse ionization of ethane leading to H{sub 3}{sup +} ions with kinetic energies on the order of 4 to 6.5 eV. The theoretical approach involves high-level quantum chemical calculation of the complete reaction path. The calculations confirm that the process takes place on the potential energy surface of the ethane dication. A surprising result of the theoretical investigation is, that the transition state of the process can be formally regarded as a H{sub 2} molecule attached to a C{sub 2}H{sub 4}{sup 2+} entity but IRC calculations show that it belongs to the reaction channel yielding C{sub 2}H{sub 3}{sup +}+ H{sub 3}{sup +}. Experimentally measured kinetic energies of the correlated H{sub 3}{sup +} and C{sub 2}H{sub 3}{sup +} ions confirm the reaction path suggested by theory.

Kraus, Peter M.; Schwarzer, Martin C.; Schirmel, Nora; Urbasch, Gunter; Frenking, Gernot; Weitzel, Karl-Michael [Fachbereich Chemie, Physikalische Chemie, Philipps-Universitaet Marburg, Hans-Meerwein-Strasse, D-35032 Marburg (Germany)

2011-03-21

430

Tuning the size of aluminum oxide nanoparticles synthesized by laser ablation in water using physical and chemical approaches.  

PubMed

Colloidal solution of nano-sized spherical Al(2)O(3) particles were produced by nanosecond laser ablation upon irradiation on a corundum target in a distilled water environment. The effects of target inclination along the direction of laser irradiation and defocusing of the laser beam have been investigated in this study. The effect of the pH of the aqueous solution has also been studied. Synthesized particles were analyzed using transmission electron microscopy (TEM) to investigate particle shape and size distributions. Ablated nanoparticles (NPs) were spherical in shape, with the average particle size ranging from 8 to 18 nm in different operating conditions. Target inclination resulted in a decrease in the average particle size. Laser defocusing at the same power and thus with reduced fluence caused a decrease in the average size and standard deviation (SD), whereas defocusing that maintained the same fluence caused the reverse effect. Phase identification of NPs performed with high resolution TEM lattice images and fast Fourier transform indicated both a metastable ?-Al(2)O(3) phase and a stable ?-Al(2)O(3) phase. X-ray diffraction analysis was also performed, which showed peaks of both ?-Al(2)O(3) and ?-Al(2)O(3) with the presence of ?- and ?-AlO(OH) polymorphs in acidic and alkaline solution, respectively. Surface conditions of the ablated particles representing the acidic and alkaline conditions were found to have a significant influence on both the size and crystallographic phase, which indicates it may be possible to induce size and phase transitions by changing the surface chemistry. PMID:23177203

Al-Mamun, Sharif Abdullah; Nakajima, Reiko; Ishigaki, Takamasa

2012-10-26

431

Effect of chemical and Er:YAG laser treatment on bond strength of root canal resin-based sealers.  

PubMed

Different treatments of dentin walls, as laser irradiation, prior to obturation can influence the adhesion ability of endodontic sealers. Therefore, the objective of this study was to compare in vitro the shear bond strength of four resin-based sealers to dentin treated with citric acid solution or erbium: yttrium, aluminum, garnet (Er:YAG) irradiation. A total of 240 slices with 1.6 mm of thickness were cut using middle third of 84 teeth. Each slice was widened using a #45 taper.06 rotary K3 instrument. The sample was divided into groups according to dentin pretreatment (15 % citric acid or Er:YAG laser) and sealer used (AH Plus, Acroseal, EndoREZ, or RealSeal). Shear bond strength was measured using a universal materials testing machine. As results, significant differences were found when comparing sealers between all groups (p < 0.05) by Kruskal-Wallis test, regardless of the pretreatment used. Comparing pretreatments, 15 % citric acid solution had better outcomes than Er:YAG laser, with significant differences in all groups, except for Acroseal groups (p < 0.05). It was concluded that RealSeal and 15 % citric acid solution achieved the best results regarding the sealer and pretreatment used, respectively. PMID:22710741

Akisue, Eduardo; Araki, Angela Toshie; Michelotto, Andr Luiz Costa; Moura-Netto, Cacio; Gavini, Giulio

2012-06-19

432

Semiconductor lasers in China  

Microsoft Academic Search

This paper reviews the development of semiconductor lasers, especially the breakthrough on quantum well lasers in China. Regarding on the super thin material growth, the developing history of Molecular beam epitaxy and metalorganic chemical vapor deposition are briefly introduced. Taking some kinds of lasers as examples, the characteristics of long wavelength MQW F-P LD and MQW DFB LD, 808nm high

Liang-Hui Chen

1996-01-01

433

Investigation of the chemical stability of the laser-induced fluorescence tracers acetone, diethylketone, and toluene under IC engine conditions using Raman spectroscopy.  

PubMed

This paper reports on an investigation of the chemical stability of the common laser-induced fluorescence (LIF) tracers acetone, diethylketone, and toluene. Stability is analyzed using linear Raman spectroscopy inside a heated pressure cell with optical access, which is used for the LIF calibration of these tracers. The measurements examine the influence of temperature, pressure, and residence time on tracer oxidation, which occurs without a rise in temperature or pressure inside the cell, highlighting the need for optical detection. A comparison between the three different tracers shows large differences, with diethylketone having the lowest and toluene by far the highest stability. An analysis of the sensitivity of the measurement shows that the detection limit of the oxidized tracer is well below 3% molar fraction, which is typical for LIF applications in combustion devices such as internal combustion (IC) engines. Furthermore, the effect on the LIF signal intensity is examined in an isothermal turbulent mixing study. PMID:24085091

Trost, Johannes; Zigan, Lars; Eichmann, Simone C; Seeger, Thomas; Leipertz, Alfred

2013-09-01

434

Tunable lasers- an overview  

SciTech Connect

This overview of tunable lasers describes their applicability to spectroscopy in the ultraviolet and middle infrared ranges; to rapid on-line diagnostics by ultrashort cavity lasers; to exploration, by the free electron laser, for its wide tuning in the far infrared to submillimeter region; to remote detection, in areas such as portable pollution monitors, on-line chemical analyzers, auto exhaust analyzers, and production line controls; to photochemistry; and to other potential areas in diagnostics, communications, and medical and biological sciences. The following lasers are characterized by their tunability: solid state lasers, primarily alexandrite, with a tuning range of ca 1000 Angstroms; color center lasers; semiconductor lasers; dye lasers; gas lasers, where high-pressure CO/sub 2/ discharges are the best known example for a wide tunability range, and research is continuing in systems such as the alkali dimers; and, at wavelengths beyond 10 micrometers, the possibilities beyond Cerenkov and free electron lasers.

Guenther, B.D.; Buser, R.G.

1982-08-01

435

Investigations of the fabrication and the surface-enhanced Raman scattering detection applications for tapered fiber probes prepared with the laser-induced chemical deposition method.  

PubMed

The process of depositing nanoparticles onto tapered fiber probes with the laser-induced chemical deposition method (LICDM) and the surface-enhanced Raman scattering (SERS) detection performance of the prepared probes are experimentally investigated in this paper. Our results show that the nanoparticle-deposited tapered fiber probes prepared with the LICDM method depend strongly on the value of the cone angle. For small-angle tapered probes the nanoparticle-deposited areas are only focused at the taper tips, because the taper surfaces are mainly covered by a relatively low-intensity evanescent field. By lengthening the reaction time or increasing the induced power or solution concentration, it is still possible to deposit nanoparticles on small-angle tapers with the light-scattering effect. With 4-aminothiophenol as the testing molecule, it was found that for given preparation conditions, the cone angles for the tapered probes with the highest SERS spectral intensities for different excitation laser powers are almost the same. However, such an optimal cone angle is determined by the combined effects of both the localized surface plasmon resonance strength and the transmission loss generated by the nanoparticles deposited. PMID:24085073

Fan, Qunfang; Cao, Jie; Liu, Ye; Yao, Bo; Mao, Qinghe

2013-09-01

436

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

NASA Astrophysics Data System (ADS)

This article reports on the development and the first applications of a new spectrometer which enables the precise and time-resolved measurement of both the energy loss and the charge-state distribution of ion beams with 10 < Z < 30 at energies of 4-8 MeV/u after their interaction with a laser-generated plasma. The spectrometer is based on five 20 7 mm2 large and 20 ?m thick polycrystalline diamond samples produced via the Chemical Vapour Deposition (CVD) process and was designed with the help of ion-optical simulations. First experiments with the spectrometer were successfully carried out at GSI using 48Ca ions at an energy of 4.8 MeV/u interacting with a carbon plasma generated by the laser irradiation of a thin foil target. Owing to the high rate capability and the short response time of the spectrometer, pulsed ion beams with 103-104 ions per bunch at a bunch frequency of 108 MHz could be detected. The temporal evolution of the five main charge states of the calcium ion beams as well as the corresponding energy loss values could be measured simultaneously. Due to the outstanding properties of diamond as a particle detector, a beam energy resolution ?EE ~ 0.1% could be reached using the presented experimental method, while a precision of 10% in the energy loss and charge-state distribution data was obtained.

Cayzac, Witold; Frank, Alexander; Schumacher, Dennis; Roth, Markus; Blaevi?, Abel; Wamers, Felix; Trger, Michael; Berdermann, Elni; Voss, Bernd; Hessling, Thomas

2013-04-01

437

The influence of multivariate analysis methods and target grain size on the accuracy of remote quantitative chemical analysis of rocks using laser induced breakdown spectroscopy  

NASA Astrophysics Data System (ADS)

Laser-induced breakdown spectroscopy (LIBS) was used to quantitatively analyze 195 rock slab samples with known bulk chemical compositions, 90 pressed-powder samples derived from a subset of those rocks, and 31 pressed-powder geostandards under conditions that simulate the ChemCam instrument on the Mars Science Laboratory Rover (MSL), Curiosity. The low-volatile (<2 wt.%) silicate samples (90 rock slabs, corresponding powders, and 22 geostandards) were split into training, validation, and test sets. The LIBS spectra and chemical compositions of the training set were used with three multivariate methods to predict the chemical compositions of the test set. The methods were partial least squares (PLS), multilayer perceptron artificial neural networks (MLP ANNs) and cascade correlation (CC) ANNs. Both the full LIBS spectrum and the intensity at five pre-selected spectral channels per major element (feature selection) were used as input data for the multivariate calculations. The training spectra were supplied to the algorithms without averaging ( i.e. five spectra per target) and with averaging ( i.e. all spectra from the same target averaged and treated as one spectrum). In most cases neural networks did not perform better than PLS for our samples. PLS2 without spectral averaging outperformed all other procedures on the basis of lowest quadrature root mean squared error (RMSE) for both the full test set and the igneous rocks test set. The RMSE for PLS2 using the igneous rock slab test set is: 3.07 wt.% SiO 2, 0.87 wt.% TiO 2, 2.36 wt.% Al 2O 3, 2.20 wt.% Fe 2O 3, 0.08 wt.% MnO, 1.74 wt.% MgO, 1.14 wt.% CaO, 0.85 wt.% Na 2O, 0.81 wt.% K 2O. PLS1 with feature selection and averaging had a higher quadrature RMSE than PLS2, but merits further investigation as a method of reducing data volume and computation time and potentially improving prediction accuracy, particularly for samples that differ significantly from the training set. Precision and accuracy were influenced by the ratio of laser beam diameter (490 ?m) to grain size, with coarse-grained rocks often resulting in lower accuracy and precision than analyses of fine-grained rocks and powders. The number of analysis spots that were normally required to produce a chemical analysis within one standard deviation of the true bulk composition ranged from 10 for fine-grained rocks to >20 for some coarse-grained rocks.

Anderson, Ryan B.; Morris, Richard V.; Clegg, Samuel M.; Bell, James F.; Wiens, Roger C.; Humphries, Seth D.; Mertzman, Stanley A.; Graff, Trevor G.; McInroy, Rhonda

2011-10-01

438

Widely tunable mode-hop free external cavity quantum cascade lasers for high resolution spectroscopy and chemical sensing  

Microsoft Academic Search

Recent progress in the development of room temperature, continuous wave, widely tunable, mode-hop-free mid-infrared external\\u000a cavity quantum cascade laser (EC-QCL) spectroscopic sources is reported. A single mode tuning range of 155cm-1 (??8% of the center wavelength) with a maximum power of 11.1mW and 182cm-1 (??15% of the center wavelength) with a maximum power of 50mW was obtained for 5.3 and

G. Wysocki; R. Lewicki; R. F. Curl; F. K. Tittel; L. Diehl; F. Capasso; M. Troccoli; G. Hofler; D. Bour; S. Corzine; R. Maulini; M. Giovannini; J. Faist

2008-01-01

439

Laser weapons  

NASA Astrophysics Data System (ADS)

The potential for deploying lasers as an effective antimissile system is assessed. High intensity and precise collimation are noted as essential for lasers as weapons, although size and material properties determine the actual performance. Gas-dynamic, electron, and chemical lasers are reviewed as prime weapons candidates. Space-, ground-, and ship-based uses are considered; each demands precision pointing, involving movable mirrors, target tracking and condition sensors, and central processing for target choice, along with large capacity power generation and storage. Laser propagation in the atmosphere is degraded by absorption, scattering, thermal blooming, turbulence (causes diffraction), and plasma formation ahead of the beam. Different modes of damaging missiles are reviewed, and it is found that mirrored surfaces, ablative coatings, and fluid layers have significant abilities to protect a missile in-flight. Destroying an ICBM in the boost phase is calculated to require a one million MW generator, far beyond current power engineering capabilities. Conventional weapons are viewed as more effective than lasers, although high energy laser research may have definite applications in areas such as chemical engineering

Tsipis, K.

1981-12-01

440

Fourier analysis applied on in situ laser reflectometry during III-nitride metal organic chemical vapor deposition growth  

Microsoft Academic Search

In this article we present the Fourier analysis of kinetic reflectometry spectra acquired during metalorganic chemical vapor deposition. We can show that offset errors due to background radiation can be completely removed by the method itself without using filters or lock-in amplifiers. Additionally, calibration of the reflected intensity is needed as long as the response of the detector is linear

C. Simbrunner; H. Sitter; A. Bonanni

2007-01-01

441

Remote explosive and chemical agent detection using broadly tunable mid-infrared external cavity quantum cascade lasers  

Microsoft Academic Search

Terrorists both with IEDs and suicide bombers are targeting civilian infrastructures such as transportation systems. Although explosive detection technologies exist and are used effectively in aviation, these technologies do not lend themselves well to protecting open architecture soft targets, as they are focused on a checkpoint form factor that limits throughput. However, remote detection of explosives and other chemicals would

Timothy Rayner; Miles Weida; Michael Pushkarsky; Timothy Day

2007-01-01

442

In situ micro Raman investigation of the laser crystallization in Si thin films plasma enhanced chemical vapor deposition-grown from He-diluted SiH4  

NASA Astrophysics Data System (ADS)

A cw Ar+ laser crystallization has been performed locally (on a 2 ?m sized spot), using a Raman microscope, on plasma enhanced chemical vapor deposition-grown Si films. The deposition has been carried out from differently He-diluted SiH4 so that no high temperature dehydrogenation has been required before the laser treatment. X-ray diffraction patterns and Raman spectra of the deposited films reveal their amorphous nature whereas infrared spectra would indicate a larger degree of local order in the high dilution (HD) material (SiH4/He=0.02) if compared to the low dilution (LD) one (SiH4/He~3). Atomic force microscopy and scanning electron microscopy images show large, well defined outgrowths, few hundreds of nanometers-sized, on the surface of the HD film whereas these are few tens of nanometers-sized in the case of the LD film. The threshold laser power densities (LPDs) required to attain the crystallization of the HD and the LD materials (in the range of times of irradiation investigated) are 1.2105 and 2.0105 W cm-2, respectively. The relative ease to crystallize the HD material possibly originates from the fact that the heavy dilution of the reacting gas implies a lower rate of growth and so a larger degree of order. Large crystalline fractions (~0.8) have been observed for the laser-treated HD material. Using a phenomenological model, the diameters of the nanocrystallites from the Raman shift of the crystalline peaks have been estimated. The size of the small crystals increases with the time of irradiation (up to a certain time). The smallest nanocrystals would have been fabricated irradiating the LD material at the threshold LPD for the shortest time of irradiation considered in this work. This low temperature process is of great technological interest (e.g., optoelectronics, microelectronics) because it allows the patterning down to a micrometric scale of (amorphous) a-Si:H films deposited onto glass and/or plastic substrates.

Santato, Clara; Mattei, Giorgio; Ruihua, Wu; Mecarini, Federico

2004-05-01

443

High-power lasers  

SciTech Connect

Since the first demonstrations of laser beams in the early 1960s, technological advances have extended the list of potential applications. Already proven in a variety of industrial applications, single lasers are used for welding, cutting, surface hardening, and surface alloying. Research on high-energy laser-induced thermonuclear fusion is underway in several laboratories. Research efforts include glass and chemical lasers and a magnetic confinement approach. Uranium isotope separation programs are using both visible and infrared laser light to develop a viable uranium enrichment process. Future research will explore laser space propulsion as a way to construct orbiting solar power stations.

Reilly, J.P.

1978-01-01

444

Semiconductor lasers in China  

NASA Astrophysics Data System (ADS)

This paper reviews the development of semiconductor lasers, especially the breakthrough on quantum well lasers in China. Regarding on the super thin material growth, the developing history of Molecular beam epitaxy and metalorganic chemical vapor deposition are briefly introduced. Taking some kinds of lasers as examples, the characteristics of long wavelength MQW F-P LD and MQW DFB LD, 808nm high power lasers and visible lasers are also demonstrated. The low dimension lasers including quantum wire and quantum dot are under way.

Chen, Liang-Hui

1996-09-01

445

Infrared scattering scanning near-field optical microscopy using an external cavity quantum cascade laser for nanoscale chemical imaging and spectroscopy of explosive residues  

NASA Astrophysics Data System (ADS)

Infrared scattering scanning near-field optical microscopy (s-SNOM) is an apertureless superfocusing technique that uses the antenna properties of a conducting atomic force microscope (AFM) tip to achieve infrared spatial resolution below the diffraction limit. The instrument can be used either in imaging mode, where a fixed wavelength light source is tuned to a molecular resonance and the AFM raster scans an image, or in spectroscopy mode where the AFM is held stationary over a feature of interest and the light frequency is varied to obtain a spectrum. In either case, a strong, stable, coherent infrared source is required. Here we demonstrate the integration of a broadly tunable external cavity quantum cascade laser (ECQCL) into an s-SNOM and use it to obtain infrared spectra of microcrystals of chemicals adsorbed onto gold substrates. Residues of the explosive compound tetryl was deposited onto gold substrates. s-SNOM experiments were performed in the 1260-1400cm-1 tuning range of the ECQCL, corresponding to the N02 symmetric stretch vibrational fingerprint region. Vibrational infrared spectra were collected on individual chemical domains with a collection area of ~500 nm2 and compared to ensemble averaged far-field reflection-absorption infrared spectroscopy (RAIRS) results.

Craig, Ian M.; Phillips, Mark C.; Taubman, Matthew S.; Josberger, Erik E.; Raschke, Markus B.

2013-01-01

446

Bibliography of soviet laser developments, Number 59, May - June 1982  

SciTech Connect

This is the Soviet Laser Bibliography for May-June 1982, and is No. 59 in a continuing series on Soviet laser developments. The coverage includes basic research on solid state, liquid, gas, and chemical lasers; components; nonlinear optics; spectroscopy of laser materials; ultrashort pulse generation; theoretical aspects of advanced lasers; and general laser theory. Laser applications are listed under biological effects; communications; beam propagation; computer technology; holography; laser-induced chemical reactions; measurement of laser parameters; laser measurement applications; laser-excited optical effects; laser spectroscopy; beam-target interaction; and plasma generation and diagnostics.

Not Available

1983-06-01

447

Bibliography of Soviet laser developments, September-October 1987  

SciTech Connect

This is the Soviet Laser Bibliography for September-October 1987, and is No. 91 in a continuing series on Soviet laser developments. The coverage includes basic research on solid-state, liquid, gas, and chemical lasers; components; nonlinear optics; spectroscopy of laser materials; ultrashort pulse generation; crystal growing; theoretical aspects of advanced lasers; and general laser theory. Laser applications are listed under biological effects; communications systems; beam propagation; adaptive optics; computer technology; holography; laser-induced chemical reactions; measurement of laser parameters; laser measurement applications; laser-excited optical effects; laser spectroscopy; beam-target interaction; and plasma generation and diagnostics.

Not Available

1988-10-01

448

Bibliography of Soviet laser developments: January-February 1988  

SciTech Connect

This is the Soviet Laser Bibliography for January-February 1988, and is No. 93 in a continuing series on Soviet laser developments. The coverage includes basic research on solid-state, liquid, gas, and chemical lasers; components; nonlinear optics; spectroscopy of laser materials; ultrashort pulse generation; theoretical aspects of advanced lasers; and general laser theory. Laser applications are listed under biological effects; communications systems; beam propagation; adaptive optics; computer technology; holography; laser-induced chemical reactions; measurement of laser parameters; laser measurement applications; laser-excited optical effects; laser spectroscopy; beam-target interaction; and plasma generation and diagnostics.

Not Available

1989-02-21

449

Bibliography of Soviet laser developments, number 46, March - April 1980  

SciTech Connect

This is the Soviet Laser Bibliography for March-April 1980, and is No. 46 in a continuing series on Soviet laser developments. The coverage includes basic research on solid state, liquid, gas, and chemical lasers; components; nonlinear optics; spectroscopy of laser materials; ultrashort pulse generation; crystal growing; theoretical aspects of advanced lasers; and general laser theory. Laser applications are listed under biological effects; communications; beam propagation; computer technology; holography; laser-induced chemical reactions; measurement of laser parameters; laser measurement applications; laser-excited optical effects; laser spectroscopy; beam-target interaction; and plasma generation and diagnostics.

Not Available

1981-02-05

450