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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

Multikilowatt supersonic chemical oxygen iodine laser  

Microsoft Academic Search

The chemical oxygen iodine laser (COIL) is an attractive candidate for efficient power scaling at short wavelengths. High specific power output from supersonic operation leads to compact devices. The German Aerospace Research Establishment (DLR) started experimental investigations of a multikilowatt supersonic COIL at its Lampoldshausen rocket test site in 1994. The excited oxygen is produced by a rotating disk generator.

Juergen Handke; Wolfgang O. Schall; Willy L. Bohn; Lutz V. Entress-Fuersteneck; Karin Gruenewald; G. R. Kwirandt; Anke Werner

1996-01-01

3

Chemical kinetics of discharge-driven oxygen-iodine lasers  

NASA Astrophysics Data System (ADS)

Oxygen-iodine lasers that utilize electrical discharges to produce O II(a1?) 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 laser (COIL). The reactions of O with iodine include channels that are both beneficial and detrimental to the laser. The beneficial reactions result in the dissociation of I II while the detrimental processes cause direct and indirect removal of I(2P 1/2) (denoted I*, the upper level of the laser). We have examined kinetic processes relevant to the laser through studies of photo-initiated reactions in N IIO/CO II/I II mixtures. The reactions have been monitored using absorption spectroscopy, laser induced fluorescence and time-resolved emission spectroscopy. It has been established that deactivation of I* by O atoms is a critical energy loss process. We have determined a rate constant of (1.2+/-0.1)×10 -11 cm 3 s -1 for this reaction. As part of this effort the branching fraction for the formation of O II(a) from the reaction of O(1D) with N IIO was determined to be 0.38. This result has implications for lasers based on photolysis of O 3/N IIO/I II mixtures and the formation of O II(a) in the upper atmosphere.

Azyazov, Valeriy N.; Kabir, Md. Humayun; Antonov, Ivan O.; Heaven, Michael C.

2007-05-01

4

Overview on the chemical oxygen-iodine laser technology  

NASA Astrophysics Data System (ADS)

The "Chemical Oxygen-Iodine Laser" (COIL) has passed through a tremendous development from the first milliwatt to a multi-kilowatt power, and thus offered a great opportunity for investigations in the COIL technology based on a multidisciplinary science. This overview has been aimed at a demonstration of enormous endeavor of the international COIL community in the last years to bring this laser system soon to the end-users by a focusing on advanced concepts of the hardware design, improvement and scaling-up the existing facilities. The overall COIL technology is considered as a sequence of the coexistent technologies of main laser components with a mutual impact: a technology of the singlet oxygen generator, gasdynamic mixing and expansion nozzle, energy extraction and optical resonator, and the exhaust and pressure recovery system. Advanced concepts of the named technologies based on inherent supporting research disciplines - a computational modeling, kinetic studies and diagnostic techniques - are briefly described. A critical insight into the COIL performance via an energy flow, energy losses, power extraction, and a chemical efficiency of this laser system utilizes the established heuristic phenomenology. The paper ends with a reference to developed projects and suggested potential applications of the chemical oxygen-iodine laser technology.

Kodymová, Jarmila

2007-05-01

5

Cutting Performance of a Chemical Oxygen-Iodine Laser William P. Latham, James A. Rothenflue, and Charles A. Helms  

E-print Network

Cutting Performance of a Chemical Oxygen-Iodine Laser William P. Latham, James A. Rothenflue. Green Street Urbana,IL 61801 . Abstract Chemical Oxygen-Iodine Laser (COIL) is a member of the class cutting and drilling. Chemical Oxygen- Iodine Laser (COIL) technology has received considerable interest

Carroll, David L.

6

Plasma chemical oxygen-iodine laser: problems of development  

NASA Astrophysics Data System (ADS)

Great success has been obtained in the R&D of a chemical oxygen-iodine laser (COIL) operating on the electronic transition of the iodine atom, which gets an excitation from the energy donor -singlet delta oxygen (SDO). The latter is normally produced in a chemical SDO generator using very toxic and dangerous chemicals, which puts a limit for civilian applications of COIL that is still a very unique apparatus. Totally new non-chemical SDO generator is needed to allow oxygen-iodine laser to achieve its full potential as a non-hazardous efficient source of high-power laser radiation. There was interest in producing SDO in electric discharge plasma since the 50's long before COIL appearing. The idea of using SDO as a donor for iodine laser was formulated in the 70's. However, the injection of iodine molecules into a low- pressure self-sustained discharge did not result in iodine lasing. One of the main factors that could prevent from lasing in many experiments is a rather high threshold yield approximately 15 percent at 300K, which is needed for obtaining an inversion population. An analysis of different attempts of producing SDO in different kinds of electric discharge plasma has been done which demonstrates that high yield at gas pressure of practical interest for modern COIL technology can be obtained only in non-self sustained electric discharge plasma. The reason is that the value of relatively low reduced electrical field strength E/N approximately 1E-16 V.cm2, which is an order of magnitude less than that for the self-sustained discharge, is extremely important for the efficient SDO production. Although different kinds of non-self sustained discharges can be used for SDO production, we got started experiments with e-beam sustained discharge in gas mixtures containing oxygen. High specific input energy up to approximately 3 - 5 kJ/ has been experimentally obtained. Theoretical calculations have been done for different experimental conditions indicating a feasibility of reasonable SDO yield. Experimental and theoretical research of self-sustained electric discharge in SDO produced in a chemical generator, which is very important for getting plasma-chemical kinetic data needed for an estimation of SDO yield, is also discussed.

Ionin, Andrei A.; Napartovich, Anatoly P.; Yuryshev, Nikolai N.

2002-05-01

7

Chemical oxygen iodine laser (COIL) technology and development  

NASA Astrophysics Data System (ADS)

In the late 1960's researchers realized that producing a population inversion in a moving medium could be used to generate high-energy laser beams. The first lasers to scale to the 10 kW size with good beam quality were supersonic flows of N2 - CO2, emitting radiation from the CO2 at 10.6 microns. In the 1970's gas dynamic CO2 lasers were scaled to hundreds of kilowatts and engineered into a KC-135 aircraft. This aircraft (The Airborne Laser Laboratory) was used to shoot down Sidewinder AIM-9B missiles in the early 1980"s. During this same time period (1970-1990) hydrogen fluoride and deuterium fluoride lasers were scaled to the MW scale in ground-based facilities. In 1978, the Iodine laser was invented at the Air Force Research Laboratory and scaled to the 100 kW level by the early 1990"s. Since the 60s, the DOD Chemical Laser development efforts have included CO2, CO, DF, HF, and Iodine. Currently, the DOD is developing DF, HF, and Iodine lasers, since CO2 and CO have wavelengths and diffraction limitations which make them less attractive for high energy weapons applications. The current military vision is to use chemical lasers to prove the principles and field ground and air mounted laser systems while attempting to develop weight efficient solid-state lasers at the high power levels for use in future Strategic and Tactical situations. This paper describes the evolution of Chemical Oxygen Iodine Lasers, their selection for use in the Airborne Laser (ABL), and the Advanced Tactical Laser (ATL). COIL was selected for these early applications because of its power scalability, its short wavelength, its atmospheric transmittance, and its excellent beam quality. The advantages and challenges are described, as well as some of the activities to improve magazine depth and logistics supportability. COIL lasers are also potentially applicable to mobile ground based applications, and future space based applications, but challenges exist. In addition, COIL is being considered for civil commercial applications in the US and overseas.

Duff, Edward A.; Truesdell, Keith A.

2004-09-01

8

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

9

A 12-kW continuous-wave chemical oxygen-iodine laser  

SciTech Connect

A 12-kW continuous-wave chemical oxygen-iodine laser, provided with an original jet-type singlet oxygen generator, is developed and tested. The experimental and numerical techniques applied for the diagnostics and mathematical simulation of processes in the laser active medium are introduced. Some of the calculation and experimental results are presented. (lasers)

Boreysho, A S; Mal'kov, V M; Savin, Aleksandr V; Vasil'ev, D N; Evdokimov, I M; Trilis, A V; Strakhov, S Yu [Institute of Laser Instruments and Technologies, D F Ustinov 'VOENMEKh' Baltic State Technical University, St Petersburg (Russian Federation)

2003-04-30

10

Cutting performance of a chemical oxygen-iodine laser on aerospace and industrial materials William P. Latham, Kip R. Kendrick, James A. Rothenflue  

E-print Network

Cutting performance of a chemical oxygen-iodine laser on aerospace and industrial materials William Lab, 104 5. Wright St., Urbana, Illinois 61801 ABSTRACT A chemical oxygen-iodine laser (COIL) was used:YAG lasers are used for such applications. More recently, the chemical oxygen-iodine laser (COIL) has

Carroll, David L.

11

Output Power Enhancement of a Chemical Oxygen-Iodine Laser by Predissociated Iodine Injection  

Microsoft Academic Search

Output power enhancement of a chemical oxygen-iodine laser (COIL) by an injection of predissociated iodine was studied. Iodine molecules were dissociated into atoms by the microwave discharge prior to injection. It was determined that predissociation caused a negative effect on the output power enhancement when this technique was applied to a conventional supersonic COIL@. Model calculations revealed that the existence

Masamori Endo; Daichi Sugimoto; Hideo Okamoto; Kenzo Nanri; Taro Uchiyama; Shuzaburo Takeda; Tomoo Fujioka

2000-01-01

12

40 IEEE JOURNAL OF QUANTUM ELECTRONICS, VOL. 36, NO. 1, JANUARY 2000 High-Performance Chemical OxygenIodine Laser  

E-print Network

Oxygen­Iodine Laser Using Nitrogen Diluent for Commercial Applications D. L. Carroll, D. M. King, L. Fockler, D. Stromberg, W. C. Solomon, L. H. Sentman, and C. H. Fisher Abstract--A chemical oxygen­iodine; these are the highest reported chemical effi- ciencies with room-temperature nitrogen diluent. A long duration, high

Carroll, David L.

13

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

14

BRIEF COMMUNICATIONS: Chemical oxygen-iodine laser utilizing low-strength hydrogen peroxide  

Microsoft Academic Search

Efficient operation of a chemical oxygen-iodine laser was achieved using low-strength (50%) hydrogen peroxide. An output power of 5 W was obtained when the chlorine consumption was 1.2 mmol\\/sec. Bibtex entry for this abstract Preferred format for this abstract (see Preferences) Find Similar Abstracts: Use: Authors Title Abstract Text Return: Query Results Return items starting with number Query Form Database:

Nikolai P. Vagin; A. F. Konoshenko; P. G. Kryukov; D. Kh Nurligareev; V. S. Pazyuk; V. N. Tomashov; Nikolai N. Yuryshev

1984-01-01

15

Liquid-jet O2(1Delta) generator for chemical oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

Results of experimental and theoretical study of the liquid jet O2(1(Delta) ) generator in P.N. Lebedev Institute Samara Branch are presented. This study includes hydrodynamic and gasdynamic effects, heat and mass transfer, droplet generation and separation. The dependence of O2(1(Delta) ) and Cl2 yields on geometrical and physical parameters of generator are presented. High O2(1(Delta) ) yield and operation of small scale subsonic chemical oxygen-iodine laser up to 100 torr of active gas pressure in jet liquid generator have been achieved. Counterflowing jet liquid O2(1(Delta) ) generator is a very perspective for high power supersonic oxygen-iodine laser without water vapor trap and droplet separator.

Zagidullin, Marsel V.

1995-03-01

16

LASERS: Efficient chemical oxygeniodine laser with a high total pressure of the active medium  

NASA Astrophysics Data System (ADS)

A new concept of obtaining a high total pressure of the active medium of a chemical oxygeniodine laser (OIL) is proposed and verified. The nozzle unit of the laser consists of the alternating vertical arrays of cylindrical nozzles to produce high-pressure nitrogen jets, plane slotted nozzles for the flow of O2(1?) oxygen, and vertical arrays of cylindrical nozzles to inject the N2 — I2 mixture between the first two streams. For a molar chlorine flow rate of 39.2 mmol s-1, the output power was 700 W and the chemical efficiency was 19.7 %. The combined use of the ejector nozzle unit proposed to obtain the active medium and a super-sonic diffuser allows a significant simplification of the ejection system for the exhaust active medium of the OIL.

Zagidullin, M. V.; Nikolaev, V. D.; Svistun, M. I.; Khvatov, N. A.; Heiger, G. D.; Madden, T. J.

2001-01-01

17

Chemical oxygen iodine laser (COIL) technology and development  

Microsoft Academic Search

In the late 1960's researchers realized that producing a population inversion in a moving medium could be used to generate high-energy laser beams. The first lasers to scale to the 10 kW size with good beam quality were supersonic flows of N2 - CO2, emitting radiation from the CO2 at 10.6 microns. In the 1970's gas dynamic CO2 lasers were

Edward A. Duff; Keith A. Truesdell

2004-01-01

18

Unstable resonators of high-power chemical oxygen-iodine lasers  

SciTech Connect

Configurations of unstable resonators are considered depending on the basic parameters of a high-power chemical oxygen-iodine laser and the design of an unstable resonator is proposed which provides the compensation of the inhomogeneity of the small-signal gain downstream of the active medium, a high energy efficiency, and stability to intracavity aberrations. The optical scheme of this resonator is presented and its properties are analysed by simulating numerically the kinetics of the active medium and resonator itself in the diffraction approximation. (laser beams and resonators)

Savin, A V; Strakhov, S Yu; Druzhinin, S L [Institute of Laser Instruments and Technologies, D F Ustinov 'VOENMEKh' Baltic State Technical University, St Petersburg (Russian Federation)

2006-09-30

19

Active-medium inhomogeneities and optical quality of radiation of supersonic chemical oxygen-iodine lasers  

SciTech Connect

Optical inhomogeneities of the active medium of a supersonic chemical oxygen-iodine laser (COIL) and their effect on the radiation parameters are studied in the case when an unstable resonator is used. Classification of optical inhomogeneities and the main factors affecting the quality of COIL radiation are considered. The results of numerical simulation of a three-dimensional gas-dynamic active medium and an unstable optical resonator in the diffraction approximation are presented. The constraints in the fabrication of large-scale COILs associated with a deterioration of the optical quality of radiation are determined. (lasers)

Boreysho, A S; Druzhinin, S L; Lobachev, V V; Savin, A V; Strakhov, S Yu; Trilis, A V [Institute of Laser Instruments and Technologies, D F Ustinov 'VOENMEKh' Baltic State Technical University, St Petersburg (Russian Federation)

2007-09-30

20

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

21

Optical resonator with nonuniform magnification for improving beam uniformity of chemical oxygen iodine lasers  

NASA Astrophysics Data System (ADS)

Unstable resonator with nonuniform magnification for improving the beam uniformity of chemical oxygen iodine lasers is explored for the first time. The magnification of the resonator is a function of the radial coordinate of the polar coordinate system on the front mirror surface. A resonator was designed to have a lower magnification at the center of the resonator than at the edge. The resonator consists of two aspherical mirrors. Method for designing the resonator is given. The energy conservation law and the aplanatic condition were used to derive the designing principle of the two aspherical mirrors. The design result was fitted to polynomial form which is suitable for manufacturing. Numerical experiment was carried out to evaluate the performance of the resonator. The computation was based on coupled simulation of wave optics model and computational fluid mechanics model. Results proved the effectiveness of the design method. The design tends to enhance the intensity near the center of the output beam and cripple that near the edge. Further analysis revealed that this effect is induced because rays of light are reflected more densely at the center of the pupil than at the edge. Therefore, this design affords for a potential approach for improving the near field uniformity of chemical oxygen iodine lasers.

Wu, Kenan; Sun, Yang; Huai, Ying; Jia, Shuqin; Chen, Xi; Jin, Yuqi

2015-02-01

22

Proceedings of the International Conference on Lasers `95, eds. V.J. Corcoran and T.A. Goldman, STS Press, McLean VA, 1996, pp. 225-231. OPTIMIZING HIGH PRESSURE CHEMICAL OXYGEN-IODINE LASERS  

E-print Network

Press, McLean VA, 1996, pp. 225-231. OPTIMIZING HIGH PRESSURE CHEMICAL OXYGEN-IODINE LASERS David L laser model was baselined to existing oxygen-iodine research assessment and device improvement chemical* by N2. I. Introduction The typical chemical oxygen-iodine laser (COIL) utilizes an energy transfer from

Carroll, David L.

23

High-performance chemical oxygen-iodine laser using nitrogen diluent for commercial applications  

SciTech Connect

A chemical oxygen-iodine laser (COIL), the VertiCOIL device, was transferred from the Air Force Research Laboratory (AFRL) to the University of Illinois at Urbana-Champaign (UIUC) and made operational. The performance of the high-power VertiCOIL laser was measured with nitrogen diluent. New nozzle designs were investigated and implemented to optimize nitrogen performance. Nitrogen diluent chemical efficiencies of 23% were achieved; these are the highest reported chemical efficiencies with room-temperature nitrogen diluent. A long duration, high chemical efficiency test was demonstrated with nitrogen diluent; a chemical efficiency of 18.5% at 30 mmol/s of chlorine was maintained for 45 min. The highest performance was obtained with new iodine injector blocks and a larger throat height. The new iodine injector blocks moved the injectors closer to the throat by 0.7 cm and the throat height was increased from 0.897 to 1.151 cm (0.353 to 0.453 in). The performance enhancements were in qualitative agreement with the system design predictions of the Blaze II chemical laser model. Three-dimensional computational fluid dynamics calculations using the general aerodynamic simulation program code confirmed the principle design change of moving the iodine injectors closer to throat. Several researchers have suggested that COIL has a significant future as an industrial laser and have identified decommissioning and decontamination (D and D) of nuclear facilities as an important market for COIL.

Carroll, D.L.; King, D.M.; Fockler, L.; Stromberg, D.; Solomon, W.C.; Sentman, L.H.; Fisher, C.H.

2000-01-01

24

Regeneration of basic hydrogen peroxide for chemical oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

Regeneration of Basic Hydrogen Peroxide (BHP) for Chemical Oxygen Iodine Laser (COIL) has been studied. The apparatus is an electrolyte H2O2 generator, which is composed of anode chamber, cathode chamber with gas diffusion electrode and cation exchange membrane. BHP containing 5 to 10 weight percent (wt%) of H2O2 is supplied to the apparatus and the change in the H2O2 concentration is measured for various operational conditions. A 5.11wt% BHP is regenerated with current efficiency of 92% and a 10.4wt% BHP is regenerated with current efficiency of 73%. It is found that the BHP flow rate and temperature of the BHP are critical to obtain high current efficiency.

Hano, Masami; Wakita, Syuhei; Uno, Masaharu; Endo, Masamori; Nanri, Kenzo; Takeda, Shuzaburo; Fujioka, Tomoo

2003-11-01

25

Output Power Enhancement of a Chemical Oxygen-Iodine Laser by Predissociated Iodine Injection  

NASA Astrophysics Data System (ADS)

Output power enhancement of a chemical oxygen-iodine laser (COIL) by an injection of predissociated iodine was studied. Iodine molecules were dissociated into atoms by the microwave discharge prior to injection. It was determined that predissociation caused a negative effect on the output power enhancement when this technique was applied to a conventional supersonic COIL@. Model calculations revealed that the existence of atomic iodine at the plenum caused the dissipation of stored energy. It was demonstrated that decreasing the mixing point pressure was crucial to obtain output power enhancement by the predissociation technique. For this purpose, a low-pressure transonic mixing scheme with a grid nozzle array was developed. A 9% enhancement of output power was demonstrated.

Endo, Masamori; Sugimoto, Daichi; Okamoto, Hideo; Nanri, Kenzo; Uchiyama, Taro; Takeda, Shuzaburo; Fujioka, Tomoo

2000-02-01

26

Chemical oxygen-iodine laser with a cryosorption vacuum pump with different buffer gases  

NASA Astrophysics Data System (ADS)

A traditional pressure recovery system is the major obstacle to mobile chemical oxygen-iodine laser (COIL) for its huge volume. A cryosorption vacuum pump was used as the pressure recovery system for different buffer gases. It made COIL become a flexible, quiet and pressure-tight. Experiments were carried out on a verti- COIL, which was designed for N2 and energized by a square-pipe jet singlet oxygen generator (JSOG). 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. The great volume efficiency interested researchers.

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

2015-02-01

27

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

28

Enhancement of the efficiency and control of emission parameters of an unstable-resonator chemical oxygen-iodine laser  

SciTech Connect

The outlook is considered for the development of a high-power supersonic flowing chemical oxygen-iodine 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 oxygen-iodine 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. (control of laser radiation parameters)

Boreisho, A S; Lobachev, V V; Savin, A V; Strakhov, S Yu; Trilis, A V [Institute of Laser Instruments and Technologies, D F Ustinov 'VOENMEKh' Baltic State Technical University, St Petersburg (Russian Federation)

2007-07-31

29

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

30

Highly efficient cw chemical oxygen-iodine laser with transsonic iodine injection and a nitrogen buffer gas  

SciTech Connect

Methods of increasing the efficiency of low-pressure chemical oxygen-iodine lasers (COILs) with transsonic injection of molecular iodine, in which nitrogen is used as a buffer gas, are studied. A two-layer gas-dynamic model is used for a parametric analysis of physicochemical processes occurring in the transsonic iodine injector and in the COIL resonator, including mixing and generation of radiation. The 3D-RANS computer simulation software is used to study the flow structures resulting from an injection of iodine-containing flow into the transsonic zone of the oxygen nozzle. Experiments with a 10-kW modified laser have resulted in a chemical efficiency of 31.5% for a lasing power of 13.5 kW. The results of experimental studies of the cryosorption COIL exhaust system are presented. (lasers)

Boreysho, A S; Barkan, A B; Vasil'ev, D N; Evdokimov, I M; Savin, A V [D. F. Ustinov Voenmekh Baltic State Technical University, Laser Systems Ltd., St. Petersburg (Russian Federation)

2005-06-30

31

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

NASA Astrophysics Data System (ADS)

The outlook is considered for the development of a high-power supersonic flowing chemical oxygen—iodine 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 oxygen—iodine 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

32

Data acquisition and control system with a programmable logic controller (PLC) for a pulsed chemical oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

A user-friendly data acquisition and control system (DACS) for a pulsed chemical oxygen -iodine laser (PCOIL) has been developed. It is implemented by an industrial control computer?a PLC, and a distributed input/output (I/O) module, as well as the valve and transmitter. The system is capable of handling 200 analogue/digital channels for performing various operations such as on-line acquisition, display, safety measures and control of various valves. These operations are controlled either by control switches configured on a PC while not running or by a pre-determined sequence or timings during the run. The system is capable of real-time acquisition and on-line estimation of important diagnostic parameters for optimization of a PCOIL. The DACS system has been programmed using software programmable logic controller (PLC). Using this DACS, more than 200 runs were given performed successfully.

Yu, Haijun; Li, Guofu; Duo, Liping; Jin, Yuqi; Wang, Jian; Sang, Fengting; Kang, Yuanfu; Li, Liucheng; Wang, Yuanhu; Tang, Shukai; Yu, Hongliang

2015-02-01

33

Optically (solar) pumped oxygen-iodine lasers  

NASA Astrophysics Data System (ADS)

We present the results of theoretical and experimental studies demonstrating the possibility of developing an oxygen-iodine laser (OIL) with direct optical pumping of molecular oxygen involving inter-molecular interaction with charge transfer from donor molecule (buffer gas) to acceptor molecule (oxygen). This interaction lifts degeneracy of the lower energy states of molecular oxygen and increases its absorption cross section in the visible spectral region and the UV Herzberg band, where high quantum yield of singlet oxygen is achieved (QY ˜ 1 and QY ˜ 2, respectively) at the same time. A pulse-periodic optical pump sources with pulse energy of ˜50 kJ, pulse duration of ˜25 ?s, and repetition rate of ˜10 Hz, which are synchronized with the mechanism of singlet oxygen generation, are developed. This allows implementation of a pulse-periodic oxygen-iodine laser with an efficiency of ˜25%, optical efficiency of ˜40%, and parameter L/ T ˜ 1/1.5, where T is the thermal energy released in the laser active medium upon generation of energy L. It is demonstrated that, under direct solar pumping of molecular oxygen, the efficiency parameter of the OIL can reach L/ T ˜ 1/0.8 in a wide range of scaling factors.

Danilov, O. B.; Zhevlakov, A. P.; Yur'ev, M. S.

2014-07-01

34

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

Microsoft Academic Search

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

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

2000-01-01

35

Proceedings of the International Conference on Lasers '98, ed. V.J. Corcoran, STS Press, McLean VA, 1999, in press. PERFORMANCE OF A HIGH POWER CHEMICAL OXYGEN-IODINE LASER  

E-print Network

, 1999, in press. PERFORMANCE OF A HIGH POWER CHEMICAL OXYGEN-IODINE LASER USING NITROGEN DILUENT D was maintained for 45 minutes. The highest performance was obtained with new iodine injector blocks and a larger throat height. The new iodine injector blocks moved the injectors closer to the throat by 0.7 cm

Carroll, David L.

36

g... production in flowing ArO2 surface-wave microwave discharges: Possible use for oxygen-iodine laser excitation  

E-print Network

O2,,a 1 g... production in flowing Ar­O2 surface-wave microwave discharges: Possible use for oxygen-iodine be effectively used for the oxygen-iodine laser excitation. It is demonstrated that at pressures higher than 10 chemical oxygen-iodine laser operates on the electronic transition of the iodine atom at 1315 nm, where

Guerra, Vasco

37

Gain recovery in an electric oxygen-iodine laser J. W. Zimmerman,1,a  

E-print Network

Gain recovery in an electric oxygen-iodine laser J. W. Zimmerman,1,a G. F. Benavides,2 A. D. Palla online 14 January 2009 Recent investigations of an electric oxygen-iodine laser system have shown American Institute of Physics. DOI: 10.1063/1.3064163 The electrically driven oxygen-iodine laser Electri

Carroll, David L.

38

Spatial and recovery measurements of gain in an electric oxygen-iodine laser  

E-print Network

Spatial and recovery measurements of gain in an electric oxygen- iodine laser G. F. Benavidesa ABSTRACT Recent investigations of an Electric Oxygen-Iodine Laser system have shown that computational oxygen-iodine laser kinetics rates. Understanding of this kinetic process should enable us to accommodate

Carroll, David L.

39

Numerical study of He/CF{sub 3}I pulsed discharge used to produce iodine atom in chemical oxygen-iodine laser  

SciTech Connect

The pulsed discharge for producing iodine atoms from the alkyl and perfluoroalky iodides (CH{sub 3}I, CF{sub 3}I, etc.) is the most efficient method for achieving the pulse operating mode of a chemical oxygen-iodine laser. In this paper, a one-dimensional fluid model is developed to study the characteristics of pulsed discharge in CF{sub 3}I-He mixture. By solving continuity equation, momentum equation, Poisson equation, Boltzmann equation, and an electric circuit equation, the temporal evolution of discharge current density and various discharge products, especially the atomic iodine, are investigated. The dependence of iodine atom density on discharge parameters is also studied. The results show that iodine atom density increases with the pulsed width and pulsed voltage amplitude. The mixture ratio of CF{sub 3}I and helium plays a more significant role in iodine atom production. For a constant voltage amplitude, there exists an optimal mixture ratio under which the maximum iodine atom concentration is achieved. The bigger the applied voltage amplitude is, the higher partial pressure of CF{sub 3}I is needed to obtain the maximum iodine atom concentration.

Zhang Jiao; Wang Yanhui; Wang Dezhen [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China); Duo Liping; Li Guofu [Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116024 (China)

2013-04-15

40

Chemical Oxygen-Iodine Layer Device Simulation Using the 3D, unsteady Navier-Stokes Equations  

Microsoft Academic Search

The time-dependent, chemically reacting, viscous fluid dynamics within the chemical oxygen-iodine laser (COIL) flowfield are simulated using the unsteady, laminar, multi-component Navier-Stokes equations. The solutions of these equations are generated within simulations of COIL hardware at standard operating conditions; conditions predicted in previous simulations to be unsteady. These current simulations ascertain the effect of the flow unsteadiness upon the laser

T. J. Madden

2007-01-01

41

Overview of iodine generation for oxygen-iodine lasers  

NASA Astrophysics Data System (ADS)

A review of the methods for generation of iodine for oxygen-iodine lasers (OIL) is presented. The chemical and physical methods for production of both atomic (AI) and molecular (MI) iodine have been searched in order to improve the efficiency and/or technology of OILs. These trials were motivated by the estimations that a substantial part of singlet oxygen (SO) could be saved with these methods and the onset of the laser active medium will be accelerated. Vapour of MI can be generated by the evaporation of solid or pressurized liquid I2, or synthesized in situ by the reaction of Cl2 with either HI or CuI2. The chemical methods of generation of AI are based on the substitution of I atom in a molecule of HI or ICl by another halogen atom produced usually chemically. The discharge methods include the dissociation of various iodine compounds (organic iodides, I2, HI) in the RF, MW, DC-pulsed or DC-vortex stabilized discharge. Combined methods use discharge dissociation of molecules (H2, F2) to gain atoms which subsequently react to replace AI from the iodine compound. The chemical methods were quite successful in producing AI (up to the 100% yield), but the enhancement of the laser performance was not reported. The discharge methods had been subsequently improving and are today able to produce up to 0.4 mmol/s of AI at the RF power of 500 W. A substantial enhancement of the discharge- OIL performance (up to 40%) was reported. In the case of Chemical-OIL, the enhancement was reported only under the conditions of a low I2/O2 ratio, where the "standard" I2 dissociation by SO is slow. The small-signal gain up to 0.3 %/cm was achieved on the supersonic COIL using the HI dissociated in the RF discharge. Due to the complicated kinetics of the RI-I-I2-SO system and a strong coupling with the gas flow and mixing, the theoretical description of the problem is difficult. It, however, seems that we can expect the major improvement of the OIL performance for those systems, where the SO yield is rather low (DOIL) or for the high-pressure COIL, where the quenching processes are important and the shortage of the distance needed for the preparation of active media is essential.

Jirásek, Vít.

2012-01-01

42

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

43

Development of the electric discharge oxygen-iodine laser David L. Carrolla  

E-print Network

Development of the electric discharge oxygen-iodine laser David L. Carrolla , Joseph T. Verdeyena ABSTRACT In the hybrid electric discharge Oxygen-Iodine laser (ElectricOIL), the desired O2(a1. As the development of this type of iodine laser continues, the roles of oxygen atoms and NO/NO2 are found to be very

Carroll, David L.

44

Mixing effects in postdischarge modeling of electric discharge oxygen-iodine laser experiments  

E-print Network

Mixing effects in postdischarge modeling of electric discharge oxygen-iodine laser experiments; accepted 16 May 2006; published online 26 July 2006 In an electric discharge oxygen-iodine laser, laser action at 1315 nm on the I 2 P1/2 I 2 P3/2 transition of atomic iodine is obtained by a near resonant

Carroll, David L.

45

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

E-print Network

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

Carroll, David L.

46

Recent Electric Oxygen-Iodine Laser Experiments and Modeling David L. Carrolla  

E-print Network

Recent Electric Oxygen-Iodine Laser Experiments and Modeling David L. Carrolla , Gabriel F and modeling have led to a continuing evolution of the Electric Oxygen-Iodine Laser (ElectricOIL) system. A new with BLAZE-V shows that an iodine pre-dissociator can have a dramatic impact upon gain and laser performance

Carroll, David L.

47

Enhanced performance of an electric oxygen-iodine laser D. L. Carrolla  

E-print Network

Enhanced performance of an electric oxygen-iodine laser D. L. Carrolla , G. F. Benavidesa,b , J. W and modeling have led to continued enhancements in the Electric Oxygen-Iodine Laser (ElectricOIL) system. This continuous wave (cw) laser operating on the 1315 nm transition of atomic iodine is pumped by the production

Carroll, David L.

48

Evolution of the electric discharge oxygen-iodine laser David L. Carrolla  

E-print Network

Evolution of the electric discharge oxygen-iodine laser David L. Carrolla , Gabriel F. Benavidesa and modeling have led to a continuing evolution of the Electric Oxygen-Iodine Laser (ElectricOIL) system. This continuous wave (cw) laser operating on the 1315 nm transition of atomic iodine is pumped by the production

Carroll, David L.

49

Enhancement of electric oxygen-iodine laser performance using larger mode volume resonators  

E-print Network

Enhancement of electric oxygen-iodine laser performance using larger mode volume resonators Brian S iodine via a 100% increase in the resonator mode volume. O2 a1 is produced by a single rf.4130, 140.4780, 230.5750. The electrically driven oxygen-iodine laser (Electric- OIL) that was first

Carroll, David L.

50

Super-linear Enhancement of the Electric Oxygen-Iodine Laser David L. Carrolla  

E-print Network

Super-linear Enhancement of the Electric Oxygen-Iodine Laser David L. Carrolla , Brian S. Woodardb., Urbana, Illinois, 61801, United States ABSTRACT Continuing experiments with Electric Oxygen-Iodine Laser output on the 1315-nm transition of atomic iodine. The peak output power observed was 538 W. Keywords

Carroll, David L.

51

Electric Oxygen-Iodine Laser Performance Enhancement using Larger Discharge and Resonator Mode Volumes  

E-print Network

Electric Oxygen-Iodine Laser Performance Enhancement using Larger Discharge and Resonator Mode transition of atomic iodine for only a 50% increase in gain length (5.1 cm to 7.6 cm), flow rates that significantly higher power was available in the electric oxygen-iodine laser gas flow which could be extracted

Carroll, David L.

52

Enhancement of electric oxygen-iodine laser performance using a rectangular discharge and longer gain length  

E-print Network

Enhancement of electric oxygen-iodine laser performance using a rectangular discharge and longer transition of atomic iodine via a 50% increase in gain length, flow rates, and discharge power. O2 a 1 of Physics. doi:10.1063/1.3269811 The electrically driven oxygen-iodine laser Electri- cOIL that was first

Carroll, David L.

53

Systematic development of the electric discharge oxygen-iodine laser David L. Carrolla  

E-print Network

1 Systematic development of the electric discharge oxygen-iodine laser David L. Carrolla , Gabriel have led to continued improvements in the hybrid Electric Oxygen-Iodine Laser (ElectricOIL) system molecular iodine injection and partially pre-dissociated iodine are presented. A gain of 0.17% cm-1

Carroll, David L.

54

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

55

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

56

Gain and continuous-wave laser power enhancement with a multiple discharge electric oxygen-iodine laser  

E-print Network

Gain and continuous-wave laser power enhancement with a multiple discharge electric oxygen-iodine transition of atomic iodine via an increase in flow rates and pressure using multiple discharges in an electric oxygen-iodine laser. O2 a 1 is produced by two parallel radio-frequency-excited electric

Carroll, David L.

57

New concepts of the chemistry of electric-discharge oxygen-iodine lasers  

NASA Astrophysics Data System (ADS)

The chemistry of electric discharge driven oxygen iodine lasers (EOIL) has long been believed to have O2(a1?g) as the sole energy carrier for excitation of the lasing state I(2P1/2), and O(3P) as the primary quencher of this state. In many sets of experimental measurements over a wide range of conditions, we have observed persistent evidence to the contrary. In this paper, we review our experimental data base in both room-temperature discharge-flow measurements and EOIL reactor results, in comparison to model predictions and kinetics analysis, to identify the missing production and loss terms in the EOIL reaction mechanism. The analysis points to a significantly higher level of understanding of this energetic chemical system, which can support advanced concepts in power scaling investigations.

Rawlins, Wilson T.; Lee, Seonkyung; Hicks, Adam J.; Konen, Ian M.; Oakes, David B.; Plumb, Emily P.; Davis, Steven J.

2011-03-01

58

The research of Iodine pool pressure of chemical oxygen-iodine laser in non-equilibrium condition and its automatic control system design  

NASA Astrophysics Data System (ADS)

In the working process of chemical oxy-iodigenne laser(COIL), the change of iodine pool pressure is complicated. As a result, it causes some mis-judgements, such as the damage of heater and the leakage of iodine steam. Further more, when the heater electric circuit is in a single working status, and after the heater switch is on or off, there exists a buffer time for the stabilization of iodine pool pressure, which is a relatively long time, and the minimum buffer pressure exceeds to 19 torr . Of course, it increases the preparing time for steady operation of laser, and reduces the quality of laser beam. In this paper, we study the iodine pool pressure of COIL in non-equilibrium condition, and analyze the mutation and the serious buffer phenomenon of iodine steam pressure. At the same time, we design an automatic control system for iodine pool pressure, which consists of five modules, such as data collection, automatic control, manual control, heater electric circuit, and the setting and display of pressure. This system uses two kinds of heater electric circuits, in this way, the serious buffer phenomenon of iodine pool pressure is effectively avoided. As a result, the maximal buffer pressure reduces to 4 torr, this makes sure that the iodine steam pressure is suitable for the operation of COIL, which produces a good condition for the steady operation of laser system and an excellent laser output.

Zhou, Songqing; Qu, Pubo; Ren, Weiyan

2013-05-01

59

Production of resonator optics for the 1315 nm oxygen iodine laser  

NASA Astrophysics Data System (ADS)

The design of mirror coatings for the oxygen iodine laser was complicated by the need for an alignment beam. Dual wavelength reflectors were required. A 2:1 stack design was a possible solution, which could be conveniently monitored in reflection. The achievement of particular phase shifts was a more difficult task and required the use of thin corrective layers.

Carniglia, C. K.; Pond, B.

1988-01-01

60

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

E-print Network

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

Carroll, David L.

61

Oxygen Discharge and Post-Discharge Kinetics Experiments and Modeling for the Electric Oxygen-Iodine Laser System  

E-print Network

Oxygen Discharge and Post-Discharge Kinetics Experiments and Modeling for the Electric Oxygen-Iodine/2) transition of atomic iodine has been obtained by a near resonant energy transfer from O2(a1 ) produced using a low-pressure oxygen/helium/nitric oxide discharge. In the electric discharge oxygen-iodine laser

Carroll, David L.

62

Problems of development of oxygen-iodine laser with electric discharge production of singlet delta oxygen  

NASA Astrophysics Data System (ADS)

Great success has been obtained in the R&D of a chemical oxygen-iodine laser (COIL) operating on the electronic transition of the iodine atom, which gets an excitation from the energy donor -singlet delta oxygen (SDO). The latter is normally produced in a chemical SDO generator using very toxic and dangerous chemicals, which puts a limit for civilian applications of COIL that is still a very unique apparatus. Totally new non-chemical SDO generator is needed to allow oxygen-iodine laser to achieve its full potential as a non-hazardous efficient source of high-power laser radiation. There was interest in producing SDO in electric discharge plasma since the 50's long before COIL appearing. The idea of using SDO as a donor for iodine laser was formulated in the 70's. However, the injection of iodine molecules into a low- pressure self-sustained discharge did not result in iodine lasing. One of the main factors that could prevent from lasing in many experiments is a rather high threshold yield ~15% at 300K, which is needed for obtaining an inversion population. An analysis of different attempts of producing SDO in different kinds of electric discharge plasma has been done which demonstrates that high yield at gas pressure of practical interest (p > 10 Torr) for modern COIL technology can be obtained only in non-self sustained electric discharge plasma. The reason is that the value of relatively low reduced electrical field strength E/N ~10-16 V.cm2, which is an order of magnitude less than that for the self-sustained discharge, is extremely important for the efficient SDO production. Although different kinds of non-self sustained discharges can be used for SDO production, we got started experiments with e-beam sustained discharge in gas mixtures containing oxygen. High specific input energy up to ~3 - 5 kJ/l. atm [O2] has been experimentally obtained. Theoretical calculations have been done for different experimental conditions indicating a feasibility of reasonable SDO yield. Experimental and theoretical research of self-sustained electric discharge in SDO produced in a chemical generator, which is very important for getting plasma-chemical kinetic data needed for an estimation of SDO yield, is also discussed.

Ionin, Andrei A.; Napartovich, Anatoly P.; Yuryshev, Nikolai N.

2002-09-01

63

REVIEW: Excited states in the active media of oxygeniodine lasers  

NASA Astrophysics Data System (ADS)

A review of investigations of kinetic processes in active media oxygeniodine lasers (OILs) performed in the last decade is presented. The mechanisms of pumping and quenching of electronically and vibrationally excited O2 and I2 molecules are considered, and dissociation mechanisms of I2 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.

Azyazov, V. N.

2009-11-01

64

Active medium gain study of electric-discharge oxygen-iodine laser  

Microsoft Academic Search

The paper reports on experimental studies of the active medium gain in supersonic electric-discharge oxygen-iodine laser (DOIL) based on traveling mw discharge. The measurements have included: absolute concentration, yield, and energy efficiency of production of SO in pure oxygen and oxygen-helium mixes at an oxygen partial pressure 3 to 15 Torr. For the gas flow to get rid of atomic

Yuriy Kolobyanin; Yuriy Adamenkov; Boris Vyskubenko; Leonid Goryachev; Sergey Ilyin; Anatoliy Kalashnik; Tatiana Rakhimova; Georgiy Rogozhnikov

2007-01-01

65

Comparing the efficiency of supersonic oxygen-iodine laser with different mixing designs  

NASA Astrophysics Data System (ADS)

The paper presents experimental studies of supersonic oxygen-iodine laser (OIL) using twisted-flow singlet oxygen generator (SOG) over a wide range of the singlet oxygen pressures and the buffer gas flow rates. The experiments used different designs of the nozzle unit and mixing system for singlet oxygen and iodine gas with the carrier gas (such as nitrogen or helium). For a wide range of the key parameters, the study looked at the efficiency of supersonic OIL with variation of the singlet oxygen pressure. The measurements were made for different positions of the iodine injection plane with respect to the critical cross-section (both in the subsonic part of the nozzle and in the supersonic flow). The gas pressure at the nozzle unit entry was varied from 50 to 250 Torr. The total pressure loss have been found for different mixing designs. Experimental curves are given for energy performance and chemical efficiency of the supersonic OIL as a function of the key parameters. Comparison is made between the calculated and experimental data. For the optimum conditions of OIL operation, chemical efficiency of 25-30% has been achieved.

Vyskubenko, Boris A.; Adamenkov, A. A.; Bakshin, V. V.; Efremov, V. I.; Ilyin, S. P.; Kolobyanin, Yu. V.; Krukovsky, I. M.; Kudryashov, E. A.; Moiseyev, V. B.

2003-11-01

66

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

SciTech Connect

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 {Pi}. It is shown that the simplified two-level laser model satisfactorily predicts the output characteristics of OILs with a stable resonator at {tau}{sub d} {<=} 7. Efficient energy extraction from the OIL active medium is achieved in the case of {tau}{sub d} = 5 - 7, {Pi} = 4 - 8. (lasers)

Mezhenin, A V; Azyazov, V N

2012-12-31

67

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

68

Singlet oxygen generation in gas discharge for oxygen-iodine laser pumping  

NASA Astrophysics Data System (ADS)

The possibility of development of effective discharged singlet oxygen (SO) generator (DSOG) for oxygen-iodine laser (OIL) is studied in detail. Researches of kinetics of oxygen atoms and oxygen molecules in the lowest metastable singlet states have been carried out in the different discharges and its afterglow (DC discharges, E-beam controlled discharge and RF discharges) in both CW and pulsed mode in a wide range of conditions (pressures, gas mixtures, energy deposits etc.). The models developed for all the discharges have allowed us to analyze SO generation and loss mechanisms and to find out the key-parameters controlling the highest SO yield. It is shown that in addition to spatial plasma uniformity at low E/N and high specific energy deposit per oxygen molecule, DSOG must be oxygen atom free to avoid fast three-body quenching of SO by atomic oxygen with increasing pressure and thereby to provide pressure scaling (in tens Torrs) for applying to real OIL systems.

Lopaev, D. V.; Braginsky, O. V.; Klopovsky, K. S.; Kovalev, A. S.; Mankelevich, Yu. A.; Popov, N. A.; Rakhimov, A. T.; Rakhimova, T. V.; Vasilieva, A. N.

2004-09-01

69

Oxygen assisted iodine atoms production in an RF discharge for a cw oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

Results of experiments and modeling of CH3I dissociation in a 40 MHz RF discharge in a discharge chamber of original design to produce iodine atoms for cw oxygen-iodine laser are presented. In experiments a substantial increase in CH3I dissociation efficiency due to addition of oxygen into Ar:CH3I mixture was observed. Complete CH3I dissociation in Ar:CH3I:O2 mixture occurred at 200 W discharge power. Fraction of discharge power spent on iodine atoms production was equal to 16% at 0.17 mmol/s CH3I flow rate. The rate of carbon atoms production as a function of molecular oxygen and water contents in CH3I:Ar mixtures was studied with the help of numerical modeling. It was found that addition of water vapor resulted in increase while addition of molecular oxygen and HI in decrease of the rate of carbon atoms production. Due to diffusion most of carbon atoms had enough time to deposit on the walls of the discharge chamber. However, contrary to the situation in a DC discharge, in the RF discharge accumulation of carbon on the walls of the discharge chamber did not hamper discharge stability and iodine production, as it was observed in our experiments.

Mikheyev, Pavel A.; Demyanov, Andrey V.; Ufimtsev, Nikolay I.; Kochetov, Igor V.; Azyazov, Valeriy N.; Napartovich, Anatoly P.

2015-02-01

70

Active medium gain study of electric-discharge oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

The paper reports on experimental studies of the active medium gain in supersonic electric-discharge oxygen-iodine laser (DOIL) based on traveling mw discharge. The measurements have included: absolute concentration, yield, and energy efficiency of production of SO in pure oxygen and oxygen-helium mixes at an oxygen partial pressure 3 to 15 Torr. For the gas flow to get rid of atomic oxygen, both heterogeneous mercury oxide coatings of the tube walls and homogeneous additives to the work mix, such as nitrogen oxide, have been used. The active medium of DOIL was formed using a nozzle array of the type of ejector sized as 10*50 mm2. The singlet oxygen-helium mix was supplied through three rows of sonic cylindrical nozzles, while the iodine-carrier gas mix - through two rows of supersonic conical nozzles with a half-opening angle of 10°(arc). The gas-phase iodine was produced in a quartz cell filled with iodine crystals. Room-temperature iodine vapors were picked up with a carrier gas (nitrogen or helium) and thus delivered into the nozzle array. The active medium was investigated by the high-resolution laser diode spectroscopy approach that used the laser type Vortex 6025 purchased from New Focus, Inc. The laser medium gain factor was determined by the intra-cavity approach having a sensitivity about 1*10 -6 cm -1. The static temperature of the medium was determined from the measurements of gain half-width. The gain of the active medium of electric-discharge OIL has been investigated. The DOIL in use was operating on a mix composed as O II:He=1:1 at a total pressure of 6 Torr and flowrate - about 1 mmol/s. With helium as an iodine carrier gas at a flowrate ~3 mmol/s, we have recorded a positive gain in the DOIL medium.

Kolobyanin, Yuriy; Adamenkov, Yuriy; Vyskubenko, Boris; Goryachev, Leonid; Ilyin, Sergey; Kalashnik, Anatoliy; Rakhimova, Tatiana; Rogozhnikov, Georgiy

2007-05-01

71

Oxygen discharge and post-discharge kinetics experiments and modeling for the electric oxygen-iodine laser system.  

PubMed

Laser oscillation at 1315 nm on the I(2P1/2)-->I(2P3/2) transition of atomic iodine has been obtained by a near resonant energy transfer from O2(a1Delta) produced using a low-pressure oxygen/helium/nitric oxide discharge. In the electric discharge oxygen-iodine laser (ElectricOIL) the discharge production of atomic oxygen, ozone, and other excited species adds levels of complexity to the singlet oxygen generator (SOG) kinetics which are not encountered in a classic purely chemical O2(a1Delta) generation system. The advanced model BLAZE-IV has been introduced to study the energy-transfer laser system dynamics and kinetics. Levels of singlet oxygen, oxygen atoms, and ozone are measured experimentally and compared with calculations. The new BLAZE-IV model is in reasonable agreement with O3, O atom, and gas temperature measurements but is under-predicting the increase in O2(a1Delta) concentration resulting from the presence of NO in the discharge and under-predicting the O2(b1Sigma) concentrations. A key conclusion is that the removal of oxygen atoms by NOX species leads to a significant increase in O2(a1Delta) concentrations downstream of the discharge in part via a recycling process; however, there are still some important processes related to the NOX discharge kinetics that are missing from the present modeling. Further, the removal of oxygen atoms dramatically inhibits the production of ozone in the downstream kinetics. PMID:17461557

Palla, A D; Zimmerman, J W; Woodard, B S; Carroll, D L; Verdeyen, J T; Lim, T C; Solomon, W C

2007-07-26

72

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

73

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

74

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

75

Generation of singlet oxygen for an oxygen-iodine laser in a radio-frequency discharge  

SciTech Connect

The generation of singlet oxygen (SO) in a radio-frequency discharge (13.56 MHz) in the gas flow was investigated experimentally and theoretically. The oxygen pressure was varied from 2 to 20 Torr and the energy deposition in gas from 10 to 2000 J mmol{sup -1}. The saturation of the SO concentration with increasing the energy deposition was shown to arise from the three-body process of SO quenching by atomic oxygen. Removing atomic oxygen allowed a 2.5-fold increase in the ultimate SO concentration at the discharge output. For an oxygen pressure of 15 Torr, the SO fraction amounts to 10%. (active media. lasers)

Braginskii, O V; Vasil'eva, A N; Klopovskii, K S; Kovalev, A S; Lopaev, D V; Mankelevich, Yu A; Popov, N A; Rakhimov, Aleksandr T; Rakhimova, T V [D.V. Skobel'tsyn Institute of Nuclear Physics, M.V. Lomonosov Moscow State University, Moscow (Russian Federation)

2005-01-31

76

Proceedings of the eighth international symposium on gas flow and chemical lasers  

SciTech Connect

This book covers the proceedings of the 8th International Symposium on Gas Flow and Chemical Lasers. Topics covered include: excimer lasers, short wavelength lasers, chemical oxygen iodine lasers, CO{sub 2}, CO and NO{sub 2} lasers, gas-dynamic lasers, optics, laser-matter interactions, and laser applications.

Orza, J.M.

1991-01-01

77

Short wavelength chemical laser status update  

NASA Astrophysics Data System (ADS)

Future high energy laser weapon systems will require very high brightness levels. Two short wavelength chemical lasers (SWCLs), the chemical oxygen iodine laser and hydrogen fluoride overtone, are already becoming candidates for strategic missions. This paper will discuss chemical lasers operating at still shorter wavelengths in and near the visible. These lasers offer potential for even further brightness enhancements. Since, for constant output energy, the brightness of a laser scales inversely with the square of its wavelength, SWCLs offer potential system benefits. Gain measurements have been made on several SWCL candidates, but these devices are still in the developmental stage and require further demonstration and scaling before they can become viable candidates to perform strategic missions. The Strategic Defense Initiative Organization (SDIO) sponsors research in a number of the more promising SWCL technology areas through its agents at the Air Force Office of Scientific Research (AFOSR) and the U.S. Army Missile Command (MICOM). This paper provides an overview of the status of research and experiments aimed at developing visible SWCLs.

Patterson, S. P.; Duncan, W. A.; Graves, B. R.; Perram, Glen; Jones, C. R.

78

International Symposium on Gas Flow and Chemical Lasers, 8th, Madrid, Spain, Sept. 10-14, 1990, Proceedings  

SciTech Connect

Papers are presented on current research developments and applications related to high-powered lasers. Recent advances in excimer laser technology, electron-beam-pumped excimer lasers, discharge technology for excimer lasers, and pulsed XeF lasers are examined. Consideration is given to short-wavelength lasers, chemical oxygen iodine lasers, and vibrational chemical lasers. Papers are presented on CO2, CO, N2O lasers, coupled CO2 lasers, laser induced perturbation in pulsed CO2 lasers, construction of sealed-off CO2 lasers, and computer modeling of discharge-excited CO gas flow. Topics discussed include gas-dynamic lasers, discharge and flow effects, matrix and laser optics and laser beam parameters. Laser-matter interactions, laser-induced surface plasma, plasma motion velocity along laser beams and thermocapillary effects are also discussed. Applications of laser technology are examined and high-speed laser welding, welding results, laser ablation, laser steel processing, and numerical modeling of laser-matter interaction in high-intensity laser applications are considered.

Orza, J.M.; Domingo, C.

1991-01-01

79

Singlet oxygen generator for a solar powered chemically pumped iodine laser  

NASA Technical Reports Server (NTRS)

The potential of solid phase endoperoxides as a means to produce single-delta oxygen in the gas phase in concentrations useful to chemical oxygen-iodine lasers was investigated. The 1,4 - endoperoxide of ethyl 3- (4-methyl - 1-naphthyl) propanoate was deposited over an indium-oxide layer on a glass plate. Single-delta oxygen was released from the endoperoxide upon heating the organic film by means of an electrical discharge through the conductive indium oxide coating. The evolution of singlet-delta oxygen was determined by measuring the dimol emission signal at 634 nm. Comparison of the measured signal with an analytic model leads to two main conclusions: virtually all the oxygen being evolved is in the singlet-delta state and in the gas phase, and there is no significant quenching other than energy pooling on the time scale of the experiment (approximately 10 msec). The use of solid phase endoperoxide as a singlet-delta oxygen generator for an oxygen-iodine laser appears promising.

Busch, G. E.

1984-01-01

80

Excimer laser chemical problems  

SciTech Connect

Techniques need to be developed to maintain XeF and XeCl laser performance over long periods of time without degradation resulting from chemical processes occurring within the laser. The dominant chemical issues include optical damage, corrosions of laser materials, gas contamination, and control of halogen concentration. Each of these issues are discussed and summarized. The methods of minimizing or controlling the chemical processes involved are presented.

Tennant, R.; Peterson, N.

1982-01-01

81

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

E-print Network

Gain and continuous-wave laser oscillation on the 1315 nm atomic iodine transition pumped by an air on the 1315 nm transition of atomic iodine using the energy transferred to I 2 P1/2 from O2 a1 produced American Institute of Physics. DOI: 10.1063/1.2957678 The classical chemical oxygen iodine laser COIL re

Carroll, David L.

82

Orbital debris removal analysis using the airborne laser chemical oxgyen iodine laser located at the AMOS site on Maui  

NASA Astrophysics Data System (ADS)

In 1995, the NASA Project ORION investigated the feasibility of orbital debris removal using ground-based sensors and lasers (Ref. 1). This study focused on high peak-power pulsed lasers capable of initiating plasma blow-off impulse. The conclusions drawn by this study indicated that a neodymium glass laser might represent the most cost effective and technologically viable solution. Large, repetitively pulsed neodymium glass lasers have been developed by Lawrence Livermore National Laboratory for inertial confinement fusion (ICF). However, the goal of ICF is to focus the high power laser beams on a small, stationary target at very close range. The orbital debris removal problem requires the mating of a high power laser to large diameter optics equipped with laser guide star adaptive optics. The target is a rapidly moving object located many hundreds of kilometers in distance. Since the conclusion of that study, the Air Force Airborne Laser (ABL) program, utilizing a continuous wave Chemical Oxygen- Iodine Laser (COIL), has progressed dramatically. This program integrates a high average power COIL with large diameter optics, which are adaptively controlled to correct for atmospheric turbulence. The target of the Airborne Laser is a rapidly ascending ballistic missile located hundreds of kilometers in range. The similarities between the Airborne Laser and the orbital debris removal mission motivate the examination of ABL COIL technology and its associated optical hardware for the orbital debris removal mission.

Campbell, Jonathan W.; Dent, William V.

2000-10-01

83

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

84

Gain and continuous-wave laser power enhancement with a secondary discharge to predissociate molecular iodine  

E-print Network

molecular iodine in an electric oxygen-iodine laser G. F. Benavides,1 J. W. Zimmerman,2 B. S. Woodard,2 D. L and 38% enhancement in continuous-wave laser power on the 1315 nm transition of atomic iodine through the addition of a secondary discharge to predissociate the molecular iodine in an electric oxygen-iodine laser

Carroll, David L.

85

High energy chemical laser system  

Microsoft Academic Search

A high energy chemical laser system is described wherein explosive ; gaseous mixtures of a reducing agent providing hydrogen isotopes and interhalogen ; compounds are uniformly ignited by means of an electrical discharge, flash-; photolysis or an electron beam. The resulting chemical explosion pumps a lasing ; chemical species, hydrogen fluoride or deuterium fluoride which is formed in the ;

D. W. Gregg; R. K. Pearson

1975-01-01

86

Short wavelength chemical laser development  

NASA Astrophysics Data System (ADS)

Short wavelength chemical lasers (SWCL) operating in the near infrared are becoming candidates for strategic missions. Chemical lasers which operate at short wavelengths at or near the visible are discussed. These lasers offer potential brightness enhancements which will be required for future high energy laser systems. Recent progress in basic research and efforts to demonstrate lasing are reviewed. Several systems are described and a critique of recent reports of chemically generated gain in the BiF(A-x) and Na2(B-x) systems is presented. New chemistries for providing singlet electronic states of NF and NCl from halogen azides provide new opportunities for energy extraction schemes based on energy pooling. A new concept for utilizing vibrational excitation in the lasant species to enhance the excitation rate for iodine monofluoride and the development of new facilities for laser demonstration efforts are discussed.

Patterson, S. P.; Duncan, W. A.; Graves, B. R.; Perram, Glen; Jones, C. R.

1992-07-01

87

Arc driven supersonic cw HF chemical laser  

Microsoft Academic Search

The design, construction, and operational characteristics of an arc driven supersonic cw HF chemical laser of more than 1 kW power, which has been developed for laser-material investigations, are presented. Overtone lasing has also been obtained with a power of 220 W. The overtone chemical laser uses the same chemical reaction and produces the same excited populations as the conventional

Andre Sontag; Rene C. Joeckle

1993-01-01

88

Bibliography of short wavelength chemical laser research  

Microsoft Academic Search

High power short wavelength chemical laser (SWCL) systems offer great advantages for strategic and tactical military applications, including both weapons and imaging missions. The promise of very high brightness, high mass efficiency, and wavelength agility has justified a modest basic research program for more than a decade. Significant progress towards the demonstration of a visible chemical laser has been made

Glen P. Perram

1993-01-01

89

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

90

High-power mobile chemical lasers  

SciTech Connect

The prospects of equipping mobile carriers with continuous wave chemical lasers (cw CLs), which continue to be the most powerful sources of laser radiation providing the highest energy efficiency and a high optical quality of the beam, are considered. The technological problems involved in such a procedure, whose solution leads to the determination of real technical parameters of autonomous mobile laser systems, are discussed. It is shown that the technical parameters of real lasers must reflect the features of their installation and exploitation under conditions differing radically from the conditions in laboratories where their investigations are being continued. (invited paper)

Boreysho, A S [D. F. Ustinov Voenmekh Baltic State Technical University, Laser Systems Ltd., St. Petersburg (Russian Federation)

2005-05-31

91

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

92

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

93

Continuous chemical lasers of visible region  

NASA Astrophysics Data System (ADS)

The general features of continuous-wave short wavelength chemical lasers are discussed and parameters determining small signal gain are considered. H2-F-NF2 and H2-F-HN3 flames are examined as possible sources for chemical pumping of N2(A)-IF lasers. The mechanism of light amplification on Na3Br+ excimer transitions and the mechanism of enhancement of the dimole emission of singlet oxygen are discussed. A model is suggested for the enhancement of dimole emission of singlet oxygen and a possible value of the gain coefficient is calculated. Results indicate that population inversion may be created by fast relaxation of the lower laser level when using molecules as the emitting particles but the wide emission spectra requires a high pumping rate for sufficient gain. The use of atoms as emitters reduces the pumping rate but the problem of lower laser level cleaning remains unsolved.

Dvoriankin, A. N.

1991-02-01

94

Studies on supersonic flow CO chemical laser  

Microsoft Academic Search

A shock tunnel facility is fabricated and used for the study of a supersonic flow CO chemical laser. A high temperature mixture of CS2, CS, S2, S, and an inert gas is produced in a shock tube, where the thermal dissociation of CS2 is accomplished by a reflected shock wave. The shock heated mixture is exhausted through supersonic nozzles mounted

Wataru Masuda; Masato Ikarashi; Kazuhiko Shiraishi; Hiroyuki Hiraide

1989-01-01

95

Bibliography of short wavelength chemical laser research  

NASA Astrophysics Data System (ADS)

High power short wavelength chemical laser (SWCL) systems offer great advantages for strategic and tactical military applications, including both weapons and imaging missions. The promise of very high brightness, high mass efficiency, and wavelength agility has justified a modest basic research program for more than a decade. Significant progress towards the demonstration of a visible chemical laser has been made during the past few years. Highly efficient methods of chemically producing metastable electronic states at concentrations exceeding 3 x 10(exp 16) molecules/cu cm have been developed. Energy transfer from these metastables to suitable lasant species has been used to demonstrate gain in the visible. Chemically generated gain of 0.029 %/cm on the (A-X) electronic transition in bismuth fluoride has been demonstrated using pulsed thermolysis of fluorine azide and trimethyl bismuth mixtures. Recently, a table-top shock facility has been used to achieve unsaturated lasing in the same system. During the past ten years, over 400 articles and reports have resulted from this research program. This bibliography summarizes this Department of Defense sponsored research on short wavelength chemical lasers since 1980.

Perram, Glen P.

1993-05-01

96

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

97

Intense laser beams; Proceedings of the Meeting, Los Angeles, CA, Jan. 23, 24, 1992  

NASA Technical Reports Server (NTRS)

Various papers on intense laser beams are presented. Individual topics addressed include: novel methods of copper vapor laser excitation, UCLA IR FEL, lasing characteristics of a large-bore copper vapor laser (CVL), copper density measurement of a large-bore CVL, high-power XeCl excimer laser, solid state direct-drive circuit for pumping gas lasers, united energy model for FELs, intensity and frequency instabilities in double-mode CO2 lasers, comparison of output power stabilities of CO and CO2 lasers, increasing efficiency of sealed-off CO lasers, thermal effects in singlet delta oxygen generation, optical extraction from the chemical oxygen-iodine laser medium, generation and laser diagnostic analysis of bismuth fluoride. Also discussed are: high-Q resonator design for an HF overtone chemical lasers, improved coatings for HF overtone lasers, scaled atmospheric blooming experiment, simulation on producing conjugate field using deformable mirrors, paraxial theory of amplitude correction, potential capabilities of adaptive optical systems in the atmosphere, power beaming research at NASA, system evaluations of laser power beaming options, performance projections for laser beam power to space, independent assessment of laser power beaming options, removal of atmospheric CFCs by lasers, efficiency of vaporization cutting by CVL.

Wade, Richard C. (editor); Ulrich, Peter B. (editor)

1992-01-01

98

Remote Chemical Detection using Quantum Cascade Lasers  

SciTech Connect

The Infrared Technologies Program at the Pacific Northwest National Laboratory (PNNL) is focused on the science and technology of remote and in-situ chemical sensors for detecting proliferation and countering terrorism. The program is focusing on the infrared detection of gaseous species including chemical warfare agents and gases associated with the production of chemical and nuclear weapons. Several sensors under development are based on miniature infrared quantum cascade (QC) lasers constructed of semiconductor material. The QC laser is unique in that by simply changing the thickness of the semiconductor layers, the laser's wavelength can be changed to target molecular absorption features of specific chemicals. For remote sensing over long optical paths, QC lasers are applied to remote areas using the differential-absorption LIDAR technique. Using a single laser, this technique can easily monitor large areas that would require a large network of point sensors. The original remote sensing configuration, suitable for laboratory applications, consisted of an optical table, laser, beam expander, telescope, mirror, and various supporting electronic and optical components. Recently, PNNL began development of a ruggedized version to conduct experiments in real-world conditions. To reduce the effects of thermal distortion, the system had to be operated from within a large, well insulated, temperature-controlled trailer. The optical breadboard was attached to 4 shock-mounts to reduce shock and vibrational loads to the optical set-up during transport. A custom jacking system using electromechanical actuators was designed to affix the optical table directly to the ground through penetrations in the trailer floor. The jacking system allows remote sensing at longer ranges (up to 5 km) by eliminating jitter caused by wind or personnel movement within the trailer. A computer-controlled gimbal-mounted mirror was added to allow the laser beam to be accurately pointed in both the vertical and horizontal plane. Mechanical tests and finite element analysis were undertaken to verify that the gimbal drives and mounting hardware had sufficient capacity to handle the inertia of the large 22-inch diameter mirror while maintaining adequate mirror flatness. This paper will provide an overview of the remote chemical detection system and will describe innovative optical mechanical solutions developed to overcome several alignment and stability issues.

Hatchell, Brian K.; Harper, Warren W.; Gervais, Kevin L.

2006-02-01

99

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

100

Remote Chemical Sensing Using Quantum Cascade Lasers  

SciTech Connect

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, the signature chemicals are expected to occur in very low concentrations, and in mixture with ambient air or airborne waste streams that contain large numbers of other species that may interfere with spectroscopic detection, or be mistaken for signatures of illicit activity. PNNL’s emphasis is therefore on developing remote and sampling sensors with extreme sensitivity, and resistance to interferents, or selectivity. PNNL’s research activities include: 1. Identification of signature chemicals and quantification of their spectral characteristics, 2. Identification and development of laser and other technologies that enable breakthroughs in sensitivity and selectivity, 3. Development of promising sensing techniques through experimentation and modeling the physical phenomenology and practical engineering limitations affecting their performance, and 4. Development and testing of data collection methods and analysis algorithms. Close coordination of all aspects of the research is important to ensure that all parts are focused on productive avenues of investigation. Close coordination of experimental development and numerical modeling is particularly important because the theoretical component provides understanding and predictive capability, while the experiments validate calculations and ensure that all phenomena and engineering limitations are considered.

Harper, Warren W.; Schultz, John F.

2003-01-30

101

Laser-based Sensors for Chemical Detection  

SciTech Connect

Stand-off detection of hazardous materials ensures that the responder is located at a safe distance from the suspected source. Remote detection and identification of hazardous materials can be accomplished using a highly sensitive and portable device, at significant distances downwind from the source or the threat. Optical sensing methods, in particular infrared absorption spectroscopy combined with quantum cascade lasers (QCLs), are highly suited for the detection of chemical substances since they enable rapid detection and are amenable for autonomous operation in a compact and rugged package. This talk will discuss the sensor systems developed at Pacific Northwest National Laboratory and will discuss the progress to reduce the size and power while maintaining sensitivity to enable stand-off detection of multiple chemicals.

Myers, Tanya L.; Phillips, Mark C.; Taubman, Matthew S.; Bernacki, Bruce E.; Schiffern, John T.; Cannon, Bret D.

2010-05-10

102

Demonstration of an iodine laser pumped by an air-helium electric discharge  

E-print Network

Demonstration of an iodine laser pumped by an air-helium electric discharge B. S. Woodard, J. W and a continuous-wave laser on the 1315 nm transition of atomic iodine using the energy transferred to I(2 P1W in a supersonic flow cavity. Keywords: electric oxygen iodine laser, electric discharge, singlet oxygen, active

Carroll, David L.

103

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

104

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

105

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

106

Laser mass spectrometry for environmental and industrial chemical trace analysis  

PubMed

Resonant laser mass spectrometry is a promising method for chemical trace analysis since it combines selectivity, sensitivity and rapidity of measurement. It is a two-dimensional technique incorporating medium- or high-resolution UV spectroscopy and time-of-flight mass spectrometry. No sample preparation and chemical clean-up is necessary to reach detection limits in the sub-ppb range even when highly complicated mixtures of chemical species are analyzed. After an introduction to the principles of resonant laser mass spectrometry, illustrative examples of applications are presented. Drawbacks, possibilities of overcoming them, some interesting features and future developments of resonant laser mass spectrometry are discussed. PMID:10767757

Boesl

2000-03-01

107

Microstructuring and wafering of silicon with laser chemical processing  

NASA Astrophysics Data System (ADS)

Laser processing is an important application for fabrication of silicon solar cells, e.g. buried contacts, laser fired contacts or edge isolation. At Fraunhofer ISE a liquid-jet guided laser is used for Laser Chemical Processing (LCP). Both the fundamentals of laser material ablation with this system and the application of various processes for solar cell fabrication are investigated. The applications are divided into two main areas: Microstructuring and deep laser cutting (wafering) of silicon substrates. Microstructuring contains the investigation and characterization of laser induced damage and selective emitter formation for n- and p-type emitters depending on laser parameters and liquid properties. One of the most important and industrially relevant topics at the moment is the formation of a selective highly doped emitter under the metal fingers of solar cells. Wafering deals with the evaluation of suitable laser parameters, adequate chemicals or chemical additives and the understanding of ablation processes by simulation and experimental work. In this presentation newest results concerning n-type doping for varying laser and liquid parameters will be presented with regard to cell efficiency and contact resistance. Furthermore a short overview of promising LCP applications will be given, e.g. p-type doping and wafering.

Hopman, Sybille; Fell, Andreas; Mayer, Kuno; Rodofili, Andreas; Granek, Filip

2010-02-01

108

RESEARCH ARTICLE Mixing enhancement in a multi-stream injection nozzle  

E-print Network

developed at the Air Force Weapons Laboratory (McDer- mott et al. 1978). Like all chemical lasers, COIL in a chemical oxygen-iodine laser. To visualize mixing, image sequences were acquired with planar laser by stretching the mixing interface. 1 Introduction The chemical oxygen iodine laser (COIL) was originally

Carroll, David L.

109

Laser-doped silicon solar cells by Laser Chemical Processing (LCP) exceeding 20% efficiency  

Microsoft Academic Search

The introduction of selective emitters underneath the front contacts of solar cells can considerably increase the cell efficiency. Thus, cost-effective fabrication methods for this process step would help to reduce the cost per Wp of silicon solar cells. Laser Chemical Processing (LCP) is based on the waterjet-guided laser (LaserMicroJet®) developed and commercialized by Synova S.A., but uses a chemical jet.

Daniel Kray; M. Aleman; A. Fell; S. Hopman; K. Mayer; M. Mesec; R. Muller; G. P. Willeke; S. W. Glunz; B. Bitnar; D.-H. Neuhaus; R. Ludemann; T. Schlenker; D. Manz; A. Bentzen; E. Sauar; A. Pauchard; B. Richerzhagen

2008-01-01

110

Chemical and Laser Sciences Division annual report 1989  

SciTech Connect

The Chemical and Laser Sciences Division Annual Report includes articles describing representative research and development activities within the Division, as well as major programs to which the Division makes significant contributions.

Haines, N. (ed.)

1990-06-01

111

Synchronization: from pendulum clocks to chaotic lasers and chemical oscillators  

E-print Network

Synchronization: from pendulum clocks to chaotic lasers and chemical oscillators MICHAEL ROSENBLUM Christiaan Huygens reported on his observation of synchronization of two pendulum clocks which he had briefly described in his memoirs Horologium Oscillatorium (The Pendulum Clock, or Geome- trical

Potsdam, Universität

112

Numerical simulation of a supersonic flow CO chemical laser  

Microsoft Academic Search

The flow field of a supersonic flow CO chemical laser is simulated numerically. The 2D compressible Navier-Stokes equations which include species transport and vibrational relaxation equations are solved by a finite volume method utilizing a point implicit scheme. The effects of the nozzle boundary layers, diffusive mixing, and oblique shock waves on the laser performance are discussed.

Hirokazu Yamada; Koh-Ichi Masuo; Wataru Masuda; Ken-Ichi Matsuno

1991-01-01

113

Gain anisotropy in low-pressure chemical lasers  

SciTech Connect

The gain coefficient in a low-pressure chemical laser during lasing differs when viewed along the optical resonator axis and when viewed normal to the axis. Expressions for axial and normal gain coefficients are deduced. The ratio of normal-to-axial gain coefficient is evaluated for a saturated multimode chemical laser employing a Fabry-Perot resonator. The results are useful for correlating numerical code calculations with experimental power on gain measurements made normal to the optical axis.

Mirels, H.

1983-05-01

114

Chemical stabilization of the coumarin 1 dye laser  

SciTech Connect

The chemical stabilization of coumarin 1, 7-diethylamino-4-methylcoumarin, in a nitrogen laser pumped dye laser and coumarin 311, 7-dimethylamino-4-methylcoumarin, under cw conditions with sulfur-free radical chain transfer agents, are described. The mechanism for stabilization involves encounter of triplet coumarin and ground state coumarin with subsequent radical formation and radical disproportionation catalyzed by the chain transfer agents. The output of the coumarin 1 dye laser decreased 10% when the dye solution was stabilized with cysteine hydrochloride over a 12-h period. The output of the unstabilized dye laser decreased 50% during a similar period of operation.

von Trebra, R.J.; Koch, T.H.

1983-01-15

115

Project LOCOST: Laser or Chemical Hybrid Orbital Space Transport  

NASA Technical Reports Server (NTRS)

A potential mission in the late 1990s is the servicing of spacecraft assets located in GEO. The Geosynchronous Operations Support Center (GeoShack) will be supported by a space transfer vehicle based at the Space Station (SS). The vehicle will transport cargo between the SS and the GeoShack. A proposed unmanned, laser or chemical hybrid orbital space transfer vehicle (LOCOST) can be used to efficiently transfer cargo between the two orbits. A preliminary design shows that an unmanned, laser/chemical hybrid vehicle results in the fuel savings needed while still providing fast trip times. The LOCOST vehicle receives a 12 MW laser beam from one Earth orbiting, solar pumped, iodide Laser Power Station (LPS). Two Energy Relay Units (ERU) provide laser beam support during periods of line-of-sight blockage by the Earth. The baseline mission specifies a 13 day round trip transfer time. The ship's configuration consist of an optical train, one hydrogen laser engine, two chemical engines, a 18 m by 29 m box truss, a mission-flexible payload module, and propellant tanks. Overall vehicle dry mass is 8,000 kg. Outbound cargo mass is 20,000 kg, and inbound cargo mass is 6,000 kg. The baseline mission needs 93,000 kg of propellants to complete the scenario. Fully fueled, outbound mission mass is 121,000 kg. A regeneratively cooled, single plasma, laser engine design producing a maximum of 768 N of thrust is utilized along with two traditional chemical engines. The payload module is designed to hold 40,000 kg of cargo, though the baseline mission specifies less. A proposed design of a laser/chemical hybrid vehicle provides a trip time and propellant efficient means to transport cargo from the SS to a GeoShack. Its unique, hybrid propulsion system provides safety through redundancy, allows baseline missions to be efficiently executed, while still allowing for the possibility of larger cargo transfers.

Dixon, Alan; Kost, Alicia; Lampshire, Gregory; Larsen, Rob; Monahan, Bob; Wright, Geoff

1990-01-01

116

Application of laser Doppler velocimeter to chemical vapor laser system  

NASA Technical Reports Server (NTRS)

A laser Doppler velocimeter (LDV) system was used to measure iodide vapor flow fields inside two different-sized tubes. Typical velocity profiles across the laser tubes were obtained with an estimated +/-1 percent bias and +/-0.3 to 0.5 percent random uncertainty in the mean values and +/-2.5 percent random uncertainty in the turbulence-intensity values. Centerline velocities and turbulence intensities for various longitudinal locations ranged from 13 to 17.5 m/sec and 6 to 20 percent, respectively. In view of these findings, the effects of turbulence should be considered for flow field modeling. The LDV system provided calibration data for pressure and mass flow systems used routinely to monitor the research laser gas flow velocity.

Gartrell, Luther R.; Hunter, William W., Jr.; Lee, Ja H.; Fletcher, Mark T.; Tabibi, Bagher M.

1993-01-01

117

Chemical Kinetic Modeling of HMX and TATB Laser Ignition Tests  

Microsoft Academic Search

Recent high-power laser deposition experiments on octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) and 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) produced ignition times from milliseconds to seconds. Global chemical kinetic thermal decomposition models for HMX and TATB developed to predict thermal explosion experiments lasting seconds to days are applied to these laser ignition experimental data. Excellent agreement was obtained for TATB, while the calculated ignition times were longer than

CRAIG M. TARVER

2004-01-01

118

Laser studies of chemical reaction and collision processes  

SciTech Connect

This work has concentrated on several interrelated projects in the area of laser photochemistry and photophysics which impinge on a variety of questions in combustion chemistry and general chemical kinetics. Infrared diode laser probes of the quenching of molecules with {open_quotes}chemically significant{close_quotes} amounts of energy in which the energy transferred to the quencher has, for the first time, been separated into its vibrational, rotational, and translational components. Probes of quantum state distributions and velocity profiles for atomic fragments produced in photodissociation reactions have been explored for iodine chloride.

Flynn, G. [Columbia Univ., New York, NY (United States)

1993-12-01

119

Investigation of performance and mechanism for chemical laser propulsion  

NASA Astrophysics Data System (ADS)

Chemical laser propulsion (CLP) is accompanied by the release of chemical energy in the process of laser propulsion, which can improve laser propulsion performance. In this article the propulsion performance of POM propellant under the constraint of a cylindrical tube-type thruster in atmospheric and nitrogen environments, respectively, has been conducted experimentally. The results indicate that the ablation masses of a single pulse under two gas environments are close, but the momentum coupling coefficient Cm and specific impulse Isp in atmospheric environment are higher than that in nitrogen environment, which demonstrates an exothermic reaction occurred between the ablation product and the environment oxygen. To learn the mechanism of CLP the molecular spectra for ablation products of POM propellant in atmospheric and vacuum environments are measured and analyzed, respectively, and it reveals that the final product in a vacuum is CH2O, while the final products are CO2 and H2O in the atmosphere. Then the chemical reaction, composition and chemical energy release have been confirmed in the atmospheric environment. By using Arrhenius finite rate chemical reaction model with the code Fluent the flow field evolution of ablation product was simulated numerically. The results show the intensity of chemical energy release is related to the contact and mixing degree of the ablation product and the oxygen in the atmosphere, mixing more fully, the chemical energy released more intensively.

Tang, Zhiping; Li, Long

2013-05-01

120

Gain characteristics of a supersonic flow CO chemical laser  

Microsoft Academic Search

A numerical analysis is done with a CO chemical laser, which utilizes the supersonic mixing of the dissociated products of CS2 diluted in Ar with O2. It is assumed that the flow is quasi-one-dimensional and the mixing takes place instantaneously. A chemical and vibrational kinetic model encompassing twenty-four reactions and twenty-seven vibrational transitions is developed to approximate the reacting and

Wataru Masuda; Norio Ogawahara; Motoshi Tohyama

1987-01-01

121

A source of atomic oxygen for a chemical CO laser  

Microsoft Academic Search

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

T. V. Bystrova; Iu. L. Chizhov

1985-01-01

122

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

123

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

E-print Network

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

Paris-Sud XI, Université de

124

Remote Chemical Sensing Using Quantum Cascade Lasers  

Microsoft Academic Search

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

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

2004-01-01

125

Measurements of Improved ElectricOIL Performance, Gain, and Laser Power  

E-print Network

, 2005a] was enabled through an understanding of the importance that oxygen atoms play in the kinetics as O2(a)] through a three-body process [Rakhimova, 2003]. By controlling the atomic oxygen levels led to continued improvements in the Electric Oxygen-Iodine Laser (ElectricOIL) system

Carroll, David L.

126

Laser spectroscopy of chemically reactive species  

SciTech Connect

We report the observation of stimulated emission pumping spectra in the NCO radical formed in a supersonic free jet expansion by the reaction between photolytically generated CN radicals and O{sub 2}. The spectra give rotationally resolved information on high lying vibrational levels that are difficult or impossible to detect by conventional single photon spectroscopic techniques. These new data provide detailed insight into the Renner-Teller, spin-orbit and Fermi-resonance coupling in the molecule. They also provide a solid basis for future state-selected chemical and dynamical studies involving this important radical species.

Wu, Ming; Sears, T.J.

1993-02-01

127

Nozzle design in cw hydrogen fluoride chemical laser  

SciTech Connect

Different geometry nozzles used in CW Hydrogen Fluoride chemical laser are investigated. Four geometry parameters, including throat width, area ratio, axis length and base width, are considered. The flow properties, laser outcoupling power and small signal gain (SSG) of a Fabry-Perot resonator are calculated. The results show that when throat width and area ratio increase, the power and SSG peak will decrease in varying degree; they also varied when axis length changed; larger base width is related to lower cavity pressure, and smaller base width is related higher cavity pressure.

Hua, W.; Jiang, Z.; Zhao, Y. [National Univ. of Defence Technology, Hunan, Changsha (China). Dept. of Applied Physics

1996-12-31

128

Molecular dispersion spectroscopy – new capabilities in laser chemical sensing  

PubMed Central

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

2012-01-01

129

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

130

Gain anisotropy in low-pressure chemical lasers. Technical report  

SciTech Connect

Continuous-wave (cw) chemical lasers are frequently operated at pressures of the order of 1 Torr to achieve efficient lasing. At these pressures, the medium is inhomogeneously (Doppler) broadened, and the line shape (gain coefficient versus frequency), under power on operation, is a function of the viewing angle. For example, when viewed along the optical-resonator axis, the line shape may have holes because of the radiation field; when viewed from a direction orthogonal to the resonator axis, it is free of holes. This anisotropy of the gain medium is the subject of this study. The purpose is to aid in the experimental validation of numerical cw chemical laser codes wherein the line shape, as viewed along the resonator axis, is predicted, and experimental measurements of power on gain are made from an orthogonal direction. In the first portion of this study, general expressions for line shape are deduced. These expressions are then applied to determine both the axial and orthogonal gain distribution in a low-pressure multimode cw chemical laser with a Fabry-Perot (F-P) resonator.

Mirels

1986-04-15

131

Space-Based Chemical Lasers in strategic defense  

NASA Astrophysics Data System (ADS)

The Strategic Defense Initiative Organization (SDIO) has made significant progress in developing Space-Based chemical Laser (SBL) technologies and in studying the SBLs global defense capability. In this mission, a constellation of several orbiting laser platforms provides continuous global defense by intercepting threatening missiles in their boost phase, including short range ballistic missiles (SRBMs). An optional smaller constellation provides defense against launches from the low and midlatitude regions. In addition, SBLs have utility in other important related missions such as surveillance, air defense and discrimination. The hardware necessary to build such a system has been developed to the point where it is mature and ready for demonstration in space. Advances have been made in each of the following major areas of the SBL: laser device; optics/beam control; beam pointing; ATP (acquisition, tracking and pointing); uncooled optics; and laser lethality. Integration of the key laser and beam control technologies is now occurring in the ground-based ALI experiment, and a space demonstration experiment, Star LITE, is in the planning and concept development phase.

Wildt, Dan

1992-07-01

132

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

Microsoft Academic Search

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

Jun Sung Park; Seung Wook Baek

2005-01-01

133

Chemical kinetic performance losses for a hydrogen laser thermal thruster  

NASA Technical Reports Server (NTRS)

Projected requirements for efficient, economical, orbit-raising propulsion systems have generated investigations into several potentially high specific impulse, moderate thrust, advanced systems. One of these systems, laser thermal propulsion, utilizes a high temperature plasma as the enthalpy source. The plasma is sustained by a focused laser beam which maintains the plasma temperature at levels near 20,000 K. Since such temperature levels lead to total dissociation and high ionization, the plasma thruster system potentially has a high specific impulse decrement due to recombination losses. The nozzle flow is expected to be sufficiently nonequilibrium to warrant concern over the achievable specific impluse. This investigation was an attempt at evaluation of those losses. The One-Dimensional Kinetics (ODK) option of the Two-Dimensional Kinetics (TDK) Computer Program was used with a chemical kinetics rate set obtained from available literature to determine the chemical kinetic energy losses for typical plasma thruster conditions. The rates were varied about the nominal accepted values to band the possible losses. Kinetic losses were shown to be highly significant for a laser thermal thruster using hydrogen. A 30 percent reduction in specific impulse is possible simply due to the inability to completely extract the molecular recombination energy.

Mccay, T. D.; Dexter, C. E.

1985-01-01

134

Quantum cascade laser based standoff photoacoustic chemical detection.  

PubMed

Standoff chemical detection with a distance of more than 41 feet using photoacoustic effect and quantum cascade laser (QCL) operated at relatively low power, less than 40 mW, is demonstrated for the first time. The option of using QCL provides the advantages of easy tuning and modulation besides the benefit of compact size, light weight and low power consumption. The standoff detection signal can be calibrated as a function of different parameters such as laser pulse energy, gas vapor concentration and detection distance. The results yield good agreements with theoretical model. Techniques to obtain even longer detection distance and achieve outdoor operations are in the process of implementation and their projection is discussed. PMID:21997036

Chen, Xing; Cheng, Liwei; Guo, Dingkai; Kostov, Yordan; Choa, Fow-Sen

2011-10-10

135

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 devices—lasers, drills, vessel sealing devices—is 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

136

Mechanisms for Laser Control of Chemical Reactions Ben R. Torralva and Roland E. Allen  

E-print Network

Introduction For decades, chemists have dreamed of using lasers to selectively control chemical reactionsMechanisms for Laser Control of Chemical Reactions Ben R. Torralva and Roland E. Allen Department the potential for control of chemical reactions, through various mechanisms which include the following: (i

Allen, Roland E.

137

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

138

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

139

Laser Cleaning of Undyed Silk: Indications of Chemical Change  

NASA Astrophysics Data System (ADS)

Three different undyed, unweighed silk fabrics (new clean, new soiled, and naturally aged) were cleaned with a computer-controlled Q-switched Nd:YAG laser at 532nm in 30 combinations of fluence and pulse numbers. They were studied for chemical change by viscometry, X-ray diffraction, and FIB-SIMS in combination with temperature calculations. While physical changes only occurred above the tested parameters, chemical changes could be detected as low as 0.2 J cm?2 with four pulses. Yellowing was observed at lower and bleaching at higher fluence/pulse number combinations. Melting was observed in naturally aged silk cleaned with 64 pulses at 4.2 J cm?2. The temperature reached at 0.1 J cm?2 is sufficient to evaporate carbon. Excess energy is transferred into the silk substrate causing thermal degradation. Different chemical processes leading to chain scission and to crosslinking seem to occur simultaneously, even at low fluence and pulse number. An increase in pulse numbers also leads to increasing damage.

von Lerber, K.; Strlic, M.; Kolar, J.; Krüger, J.; Pentzien, S.; Kennedy, C.; Wess, T.; Sokhan, M.; Kautek, Wolfgang

140

Use of hyperosmotic chemical agent to improve the laser treatment of cutaneous vascular lesions  

E-print Network

Use of hyperosmotic chemical agent to improve the laser treatment of cutaneous vascular lesions applied to skin prior to laser irradiation. The 50% probability for a given radiant exposure RE50 following direct subcutaneous laser irradiation of 84 vessels in a dorsal skin preparation pretreated

Barton, Jennifer K.

141

Ultrafast-laser-assisted chemical restructuring of silicon and germanium surfaces  

Microsoft Academic Search

This article reports a comparative study on texturing in silicon and germanium surfaces after exposure to femtosecond laser irradiation in the gaseous environments of sulfur hexafluoride (SF6) and hydrogen chloride (HCl). The surface texturing results from the combined effect of laser-assisted chemical etching and laser ablation. Optimized processing conditions have produced features on the order of nanometers in size. We

Barada K. Nayak; Mool C. Gupta; Kurt W. Kolasinski

2007-01-01

142

Study of factors influencing the effective delivery of O2(1delta) into the resonator of the oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

Experimental studies have been performed on the processes: chlorine utilization in the bubbler type singlet oxygen generator, the quenching of O2(1(Delta) ) in the OIL path, the propagation of the gas mixture O2 + O2 (1(Delta) ) + H2O throughout forward flow-type water vapor trap.

Krukowski, I. M.; Halin, A. L.

1994-08-01

143

Laser Chemical Processing (LCP)—A versatile tool for microstructuring applications  

Microsoft Academic Search

Laser Chemical Processing (LCP) is presented as a novel microstructuring method for multiple applications. Via the combination\\u000a of a chemical liquid jet and a laser beam, thermochemical and photochemical reactions can be initiated. Due to the free choice\\u000a of the chemistry for the carrier liquid and the laser source, efficient processes can be devised for a large variety of applications.

D. Kray; A. Fell; S. Hopman; K. Mayer; G. P. Willeke; S. W. Glunz

2008-01-01

144

Microchemical systems for singlet oxygen generation  

E-print Network

Chemical Oxygen-Iodine Lasers (COIL) are a technology of interest for industrial and military audiences. COILs are flowing gas lasers where the gain medium of iodine atoms is collisionally pumped by singlet delta oxygen ...

Hill, Tyrone F. (Tyrone Frank), 1980-

2008-01-01

145

Fabrication of chemical templates via selective laser-induced desorption of hexadecanethiol self-assembled monolayers  

NASA Astrophysics Data System (ADS)

A nonlinear photothermal laser patterning technique for rapid fabrication of chemical templates is demonstrated. Hexadecanethiol monolayers on Au-coated Si substrates are processed at ? = 532 nm, a 1/e2 spot diameter of d=2.8 ?m and ambient conditions. Local laser irradiation at high laser powers and short irradiation times in the micro-/millisecond range induces desorption of thiol molecules. The laser-depleted areas are backfilled with mercaptohexadecanoic acid in order to build up chemical templates. Atomic force microscopy, scanning electron microscopy and scanning Auger electron spectroscopy are used for characterization of these templates. In agreement with a selective laser process, the results indicate the formation of flat chemical patterns with well-defined boundaries. Complementary condensation experiments demonstrate the functionality of the patterns as hydrophilic/hydrophobic templates. In particular, upon decreasing the temperature below the dew point, selective formation of water droplets on the backfilled areas is observed.

Schröter, Anja; Mathieu, Mareike; Franzka, Steffen; Feydt, Jürgen; Irsen, Stephan; Hartmann, Nils

2013-08-01

146

Optimization of an External Cavity Quantum Cascade Laser for Chemical Sensing Applications  

SciTech Connect

We describe and characterize an external cavity quantum cascade laser designed for detection of multiple airborne chemicals, and used with a compact astigmatic Herriott cell for sensing of acetone and hydrogen peroxide.

Phillips, Mark C.; Bernacki, Bruce E.; Taubman, Matthew S.; Cannon, Bret D.; Schiffern, John T.; Myers, Tanya L.

2010-03-01

147

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

148

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

149

Morphological and chemical evolution on InP(100) surface irradiated with femtosecond laser  

E-print Network

to the laser polarization direction were found by scanning electron microscopy and atomic force microscopy microscopy (AFM), and a 3D surface profiler. Ripples with ``unusual'' orientation were observed for smallMorphological and chemical evolution on InP(100) surface irradiated with femtosecond laser H

Zhou, Wei

150

Dynamic structure elucidation of chemical reactivity by laser pulses and X-ray probes.  

PubMed

Visualising chemical reactions by X-ray methods is a tantalising prospect. New light sources provide the prospect for studying atomic, electronic and energy transfers accompanying chemical change by X-ray spectroscopy and inelastic scattering. Here we assess how this adventure can illuminate inorganic and catalytic chemistry. In particular X-ray inelastic scattering provides a means of exploiting X-ray free electron lasers, as a parallel to laser Raman spectroscopy. PMID:25741902

Bartlett, Stuart A; Hamilton, Michelle L; Evans, John

2015-03-24

151

Fast infrared chemical imaging with a quantum cascade laser.  

PubMed

Infrared (IR) spectroscopic imaging systems are a powerful tool for visualizing molecular microstructure of a sample without the need for dyes or stains. Table-top Fourier transform infrared (FT-IR) imaging spectrometers, the current established technology, can record broadband spectral data efficiently but requires scanning the entire spectrum with a low throughput source. The advent of high-intensity, broadly tunable quantum cascade lasers (QCL) has now accelerated IR imaging but results in a fundamentally different type of instrument and approach, namely, discrete frequency IR (DF-IR) spectral imaging. While the higher intensity of the source provides a higher signal per channel, the absence of spectral multiplexing also provides new opportunities and challenges. Here, we couple a rapidly tunable QCL with a high performance microscope equipped with a cooled focal plane array (FPA) detector. Our optical system is conceptualized to provide optimal performance based on recent theory and design rules for high-definition (HD) IR imaging. Multiple QCL units are multiplexed together to provide spectral coverage across the fingerprint region (776.9 to 1904.4 cm(-1)) in our DF-IR microscope capable of broad spectral coverage, wide-field detection, and diffraction-limited spectral imaging. We demonstrate that the spectral and spatial fidelity of this system is at least as good as the best FT-IR imaging systems. Our configuration provides a speedup for equivalent spectral signal-to-noise ratio (SNR) compared to the best spectral quality from a high-performance linear array system that has 10-fold larger pixels. Compared to the fastest available HD FT-IR imaging system, we demonstrate scanning of large tissue microarrays (TMA) in 3-orders of magnitude smaller time per essential spectral frequency. These advances offer new opportunities for high throughput IR chemical imaging, especially for the measurement of cells and tissues. PMID:25474546

Yeh, Kevin; Kenkel, Seth; Liu, Jui-Nung; Bhargava, Rohit

2015-01-01

152

Optimization of shunt isolation processing for silicon solar cells via laser and chemical etching  

NASA Astrophysics Data System (ADS)

We employ laser scribing combined with chemical etching process to isolate the shunts in industrial off-spec or non-prime crystalline solar cells. Liquid crystal sheet and Infrared camera measurements have been carried out to reveal the existence of the shunts and hot spot temperature under reverse bias. Following laser scribing with proper laser parameters, chemical etching has been used to further optimize the isolation effect. Through illuminated current-voltage characteristic measurements, the improved open circuit voltage, fill factor and efficiency have been obtained. These results demonstrate that this combined shunt isolation process has great potential for its application in the solar cells.

Hao, H. L.; Zhong, S. H.; Zhang, X.; Shen, W. Z.

2014-08-01

153

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

154

Simulation of a two-frequency cw chemical HF-HBr laser  

SciTech Connect

An autonomous cw chemical HF-HBr laser emitting simultaneously at {approx}2.7 {mu}m (HF molecules) and {approx}4.2 {mu}m (HBr molecules) is studied numerically by using complete Navier-Stokes equations. It is shown that the output power of the HBr laser per unit area of the nozzle array can achieve {approx}20 W cm{sup -2} for the laser region length {approx}20 cm. The relation between the radiation intensities emitted by HF and HBr molecules is controlled by diluting the secondary fuel by bromine. (lasers)

Aleksandrov, B P; Katorgin, B I; Stepanov, A A [Open Joint-Stock Company, V. P. Glushko Energomash Research and Production Assocation, Khimki-1, Moscow region (Russian Federation)

2008-10-31

155

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

156

CO2 laser scribe of chemically strengthened glass with high surface compressive stress  

NASA Astrophysics Data System (ADS)

Chemically strengthened glass is finding increasing use in handheld, IT and TV cover glass applications. Chemically strengthened glass, particularly with high (>600MPa) compressive stress (CS) and deeper depth of layer (DOL), enable to retain higher strength after damage than non-strengthened glass when its surface is abraded. Corning Gorilla® Glass has particularly proven to be advantageous over competition in this attribute. However, due to high compressive stress (CS) and Central Tension (CT) cutting ion-exchanged glass is extremely difficult and often unmanageable where ever the applications require dicing the chemically strengthened mother glass into smaller parts. We at Corning have developed a CO2 laser scribe and break method (LSB) to separate a single chemically strengthened glass sheet into plurality of devices. Furthermore, CO2 laser scribe and break method enables debris-free separation of glass with high edge strength due to its mirror-like edge finish. We have investigated laser scribe and break of chemically strengthened glass with surface compressive stress greater than 600 MPa. In this paper we present the results of CO2 scribe and break method and underlying laser scribing mechanisms. We demonstrated cross-scribe repetitively on GEN 2 size chemically strengthened glass substrates. Specimens for edge strength measurements of different thickness and CS/DOL glass were prepared using the laser scribe and break technique. The specimens were tested using the standard 4-point bend method and the results are presented.

Li, Xinghua; Vaddi, Butchi R.

2011-03-01

157

The effects of motive gas physical properties on the performance of ejector for chemical lasers  

NASA Astrophysics Data System (ADS)

Axi-symmetric annular type ejector has been developed as a pressure recovery system for HF/DF chemical laser. Ejector was tested using air as operating gases and low-pressure entrained flow was obtained. In this paper, we changed motive gas since operating gases for chemical laser system are products of chemical reaction. By selection of motive gas, physical properties of operating gas changes, therefore the performance of ejector is different for each motive gas, i.e., specific heat at constant pressure (CP) and average molecular weight (MW) on the effectiveness of ejection. The research was carried out by both numerical analysis using commercial CFD code, FLUENT and experiments.

Jin, Jungkun; Kim, Sehoon; Kwon, Hyuckmo; Kwon, Sejin

2005-03-01

158

Synthesis of carbon nanotubes by laser-assisted alcohol chemical vapor deposition  

NASA Astrophysics Data System (ADS)

A laser-assisted alcohol chemical vapor deposition (CVD) process was carried out on a quartz substrate without a thick absorption layer, as a result of which, the substrate retained its transparency. The thickness of the carbon nanotube (CNT) film grown with 120 s of laser irradiation was 16.6 ?m, which was three orders of magnitude thicker than the CNT film grown without laser irradiation. The area of growth enhancement was nearly the same size as the laser spot, which implies that this method can be used for position-controlled CNT growth. In addition, the laser-assisted method can be used to decrease the process temperature. Raman spectra also showed the enhancement of CNT growth from the higher signal intensity of the G and D bands from the laser-irradiated sample.

Akahane, Kouichi; Yamamomto, Naokatsu; Maeda, Makoto; Takai, Hiroshi; Nakamura, Shin-ichi; Yamaguchi, Hiroshi; Sotobayashi, Hideyuki

2014-02-01

159

Materials for high-energy laser windows: oxyfluoride glass vs. fusion-cast CaF2  

NASA Astrophysics Data System (ADS)

The process of selecting suitable materials for high-energy laser windows involves considerations realting to (a) the flexural strength, (b) the thermal stresses, and (c) the optical distortion. Optical distortion ocnsiderations strongly favor low-absorbtion materials ythat exhibit a negitive thermo-optic coefficient (dn/dT) in conjunction with minimal stress-birefringence (qd\\overline -q? ~=0). For this reason, calcium floride has been the primary candidate for many years, but the efforts to strengthen this material have not been successful. Recently, a new glass compostion-oxyfloride glass (OFG)-has been promoted as an ideal solution in the sense that it will allow fabricating large "athermal" windows for operation at the chemical oxygen-iodine laser wavelength. It is, therefore, of interest to properly assess the merits of OFG in comparison to CaF2, which we do here on the basis of available (Dec '04) property data for fusion-cast CaF2 and OFG. Oxyfloride glass was found to be deficient in regard to thermal diffusivity, which may lead to excessive coating-induced compressive stresses, and stress- birefringence, which rules out creating a distortion-free window. It is suggested that future efforts should be directed at strengthening CaF2 in view of this material's exceptionally low absorbtion and almost no stress-birefringence

Klein, Claude A.

2005-05-01

160

JOURNAL DE PHYSIQUE CoZZoque C9, suppZ6ment au noll, Tome 41, novembre 1980, page ~ 9 -1 DEUTERIUM FLUORIDE CW CHEMICAL LASERS  

E-print Network

FLUORIDE CW CHEMICAL LASERS Leroy E. Wilson Air Force Weapons Laboratory, KirtZand Air Force Base, New fluoride (DF) cw chemical lasers. The fundamental principles of the laser are explained. The advantages and disadvantages of the laser system are discussed. The characteristics of the DF laser beam, the perfor- mance

Paris-Sud XI, Université de

161

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

162

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

163

Numerical analysis for the power of a supersonic flow CO chemical laser  

Microsoft Academic Search

A numerical analysis is presented for a CO chemical laser, which utilizes the supersonic mixing of dissociated products of CS2 diluted in Ar with O2. It is assumed that the flow is quasi-one-dimensional and that nozzle flows undergo instantaneous mixing at nozzle exits. The constant gain method is applied to estimate the laser power. The present results show that the

Wataru Masuda; Motoshi Tohyama

1988-01-01

164

Computer simulation of c-w HF chemical laser unstable resonator performance. Technical report  

SciTech Connect

Inadequacies in the treatment of the fluid-dynamic mixing that were not apparent in Fabry-Perot or stable resonator models were revealed with a wave optics-unstable resonator model. The unstable resonator data as a function of resonator size and size of the laser were shown to provide a severe test of a couples, wave optics, chemical kinetic, fluid-dynamic model of a chemical laser. A mechanism for the observed time-dependent oscillations that occur on lines whose saturated gain does not fill the unstable resonator was proposed. According to the proposed mechanism, the time-dependent oscillations are the result of a competition between chemical pumping and radiative deactivation of upper laser levels of HF. The oscillations occur only if the media is not strongly coupled to the optical fields diffractively or geometrically. Computer calculations supported the proposed mechanism and new unstable resonator experiments were suggested.

Sentman, L.H.; Gilmore, J.O.

1987-08-01

165

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

SciTech Connect

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 orbits of the protected spacecrafts) are determined. The possibility of launching the proposed spaceborne laser station to the orbit with the help of a 'Proton-M' carrier rocket is considered. (laser applications)

Avdeev, A V; Bashkin, A S; Katorgin, Boris I; Parfen'ev, M V

2011-07-31

166

Chemical detection and laser wavelength stabilization employing spectroscopic absorption via laser compliance voltage sensing  

DOEpatents

Systems and methods are disclosed that provide a direct indication of the presence and concentration of an analyte within the external cavity of a laser device that employ the compliance voltage across the laser device. The systems can provide stabilization of the laser wavelength. The systems and methods can obviate the need for an external optical detector, an external gas cell, or other sensing region and reduce the complexity and size of the sensing configuration.

Taubman, Matthew S; Phillips, Mark C

2014-03-18

167

Short pulse laser ablation is photomechanical, not thermal or chemical  

Microsoft Academic Search

Proposed mechanisms for pulsed laser ablation of biological tissue include photochemical, photothermal and photomechanical models. The principal observed effects which the correct model must explain include the high efficiency of the process, typically an order of magnitude less energy is required than for long pulse or cw ablation, and the minimal thermal damage to surrounding tissue. The photomechanical model postulates

I. Itzkan; D. Albagli; M. Dark; L. T. Perelman; C. von Rosenberg; M. S. Feld

1994-01-01

168

Theoretical investigation of an annular supersonic model of a chemical DF--CO/sub 2/ laser  

SciTech Connect

An investigation was made of an annular supersonic model of a chemical DF--CO/sub 2/ laser. It was shown that such a model enables higher laser energy characteristics to be obtained (compared with those in a plane model), a considerable reduction to be made in the radiation loading on the mirrors of the optical system, and much higher initial static pressures to be used. It was established that in the case of a strong radial expansion of the gas stream, the laser energetics are extremely sensitive to changes in the initiation level of the chain reaction.

Konoplev, N.A.; Stepanov, A.A.; Shcheglov, V.A.

1981-02-01

169

Direct chemical analysis of frozen ice cores by UV-laser ablation ICPMS Wolfgang Muller,*a  

E-print Network

Direct chemical analysis of frozen ice cores by UV-laser ablation ICPMS Wolfgang Muller,*a J recrystalli- zation of ice with increasing depth. Using 193 nm excimer laser-ablation ICPMS (UV-LA-ICPMS), we in this study. A custom- built cryo-sample holder is loaded into a standard Laurin two-volume laser-ablation

Royal Holloway, University of London

170

Laser treatment of alumina surface with chemically distinct carbide particles  

NASA Astrophysics Data System (ADS)

Laser treatment of pre-prepared alumina tile surface with a carbon film containing a mixture of 3 wt% TiC and 3 wt% B4C hard particles was conducted. Morphological and metallurgical changes at the laser treated surface were examined using optical and electron scanning microscopes, energy dispersive spectroscopy, and X-ray diffraction. Microhardness and fracture toughness of the treated surface were measured together with indentation tests. Residual stress generated at the surface region was determined from the X-ray diffraction data. It was found that TiC and B4C hard particles cause micro-crack formation in the vicinity of hard particles on the surface. This behavior is attributed to the differences between the thermal expansion coefficients of these particles. The laser treated surface is composed of a dense layer with fine sized grains and columnar structures formed below the dense layer. The presence of hard particles enhances the microhardness and lowers the fracture toughness of the surface. The formation of nitride compounds (AlN and AlON) contributes to volume shrinkage in the dense layer. Residual stress formed in the surface region is compressive.

Yilbas, Bekir S.; Ali, Haider

2014-12-01

171

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

SciTech Connect

Extending spatial resolution in laser-based chemical analysis to the nanoscale becomes increasingly important as nanoscience and nanotechnology develop. Implementation of femtosecond laser pulses arises as a basic strategy for increasing resolution since it is associated with spatially localized material damage. In this work we study femtosecond laser far- and near-field processing of silicon (Si) at two distinct wavelengths (400 and 800 nm), for nanoscale chemical analysis. By tightly focusing femtosecond laser beams in the far-field we were able to produce sub-micrometer craters. In order to further reduce the crater size, similar experiments were performed in the near-field through sub-wavelength apertures, resulting to the formation of sub-30 nm craters. Laser Induced Breakdown Spectroscopy (LIBS) was used for chemical analysis with a goal to identify the minimum crater size from which spectral emission could be measured. Emission from sub-micrometer craters (full-with-at-half-maximum) was possible, which are among the smallest ever reported for femtosecond LIBS.

Zormpa, Vasileia; Mao, Xianglei; Russo, Richard E.

2010-02-02

172

Feasibility study of a novel pressure recovery system for CO2-COIL based on chemical absorption  

NASA Astrophysics Data System (ADS)

A chemical oxygen-iodine laser (COIL) is an electronic transition, low pressure, high throughput system. The use of this laser demands a suitable pressure recovery system. This paper proposed a novel pressure recovery system based on chemical absorption and the feasibility for COIL with CO2 as buffer gas (CO2-COIL) was investigated. The novel pressure recovery system works by chemisorbing the CO2-COIL effluents into two fixed-beds maintained at initial temperature of around 293-323K. Compared with the cryosorption system for N2-COIL based on physical absorption, the novel chemisorptions based pressure recovery system has a simpler logistics and a shorter run-to-run preparation time. Two kinds of solid chemo-sorbents were designed and synthesized. One was used for chemisorbing the oxidizing gases such as O2 ,Cl2 and I2, another was used for chemisorbing the acidic gas such as CO2. The capacities of the two sorbents were measured to be 3.12 mmol?O2?/g and 3.84 mmol (CO2) /g, respectively. It indicated that the synthesized sorbents could effectively chemosorb the CO2-COIL effluents. Secondly, analog test equipment was set up and used to study the feasibility of the novel pressure recovery system used for CO2-COIL. The test results showed that the novel pressure recovery system could maintain the pressure under 6 Torr for tens seconds under the continuous gas flow. It showed that the novel pressure recovery system for CO2-COIL based on chemical absorption is feasible.

Li, Qingwei; Jin, Yuqi; Geng, Zicai; Li, Yongzhao; Zhang, Yuelong; Sang, Fengting

2015-02-01

173

A new chemical etching technique for formation of cavity facets of (GaAl)As lasers  

Microsoft Academic Search

A new chemical etching technique which offers excellent cavity facets of Ga \\/SUB 1-x\\/ Al \\/SUB x\\/ As lasers is reported. This technique is based on our finding that the crystallographic anisotropy in the conventional etching process of Ga \\/SUB 1-x\\/ Al \\/SUB x\\/ As multilayers depends strongly on the AlAs mode fraction x in every layer. A suitable combination

M. Wada; K. Hamada; T. Shibutani; H. Shimizu; M. Kume; K. Itoh; G. Kano; I. Teramoto

1985-01-01

174

Numerical simulation of a supersonic flow CO chemical laser using a leaky stream tube approach  

Microsoft Academic Search

A leaky stream tube approach is used to simulate a supersonic flow CO chemical laser. Downstream of the nozzle exits, the flow field is divided into three stream tubes: two stream tubes for the dissociated products of CS2 diluted in Ar and for O2 and the third one located between these two. It is shown that the dependence of the

Wataru Masuda; Motoshi Tohyama

1988-01-01

175

Investigation on the theoretical modeling of a supersonic flow CO chemical laser  

Microsoft Academic Search

Small signal gain coefficients of a supersonic flow CO chemical laser are calculated using a theoretical model which was developed previously and compared with the corresponding experimental results. It is shown that the model predicts the gain characteristics only qualitatively. The measured small signal gain coefficients are rather small compared with the calculated results. In the present investigation, the theoretical

Wataru Masuda; Hiroyuki Hiraide

1990-01-01

176

Effect of excimer laser irradiation on crystallinity and chemical bonding of biodegradable polymer  

E-print Network

: Biodegradable polymer Poly(L-lactic acid) Laser irradiation Chemical modification Crystallinity Radical mobility a b s t r a c t The biodegradable polymer such as poly(L-lactic acid) (PLLA) is promising in drug. Blending PLA with another biodegradable polymer, poly(glycolic acid), to adjust the degradation rate

Yao, Y. Lawrence

177

Monte Carlo simulation of laser induced chemical vapor deposition Yehuda Zeiri, Uzi Atzmony, and Joseph Bloch  

E-print Network

Monte Carlo simulation of laser induced chemical vapor deposition Yehuda Zeiri, Uzi Atzmony 21 September 1989; accepted for publication 30 November 1990) We have used a Monte Carlo method developed a Monte Carlo procedure which was used to simulate the LICVD process. The beam inten- sities used

Zeiri, Yehuda

178

Overview of the SDI (Strategic Defense Initiative) Program in short wavelength chemical lasers  

SciTech Connect

Advanced chemical lasers promise to be effective space-based weapons against responsive threats. In this program, we are developing both CW and pulsed concepts for achieving this goal. Certain approaches may also be appropriate as ground-based weapons and fusion drivers. 12 refs., 1 fig., 5 tabs.

Jones, C.R.

1988-01-01

179

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

SciTech Connect

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

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

1980-01-01

180

Kinetics and reaction mechanisms of laser-assisted chemical vapor deposition of polycrystalline silicon dots from silane  

Microsoft Academic Search

Polycrystalline silicon dots have been deposited on silicon-coated SiO2 substrates from silane irradiated with a continuous wave (cw) argon ion laser and a cw CO2 laser. Various experimental configurations were adopted for laser-assisted chemical vapor deposition of Si dots. The cw argon ion laser was focused either directly on the surface of absorbent polycrystalline Si films acting as substrates (front

Y. Pauleau; D. Tonneau

2002-01-01

181

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

182

Generation of cavitation luminescence by laser-induced exothermic chemical reaction  

SciTech Connect

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. [Department of Chemistry, Brown University, Providence, Rhode Island 02912 (United States)] [Department of Chemistry, Brown University, Providence, Rhode Island 02912 (United States)

2013-08-14

183

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

184

Laser/Plasma/Chemical-Vapor Deposition Of Diamond  

NASA Technical Reports Server (NTRS)

Proposed process for deposition of diamond films includes combination of plasma induced in hydrocarbon feed gas by microwave radiation and irradiation of plasma and substrate by lasers. Deposition of graphite suppressed. Reaction chamber irradiated at wavelength favoring polymerization of CH2 radical into powders filtered out of gas. CH3 radicals, having desired sp3 configuration, remains in gas to serve as precursors for deposition. Feed gas selected to favor formation of CH3 radicals; candidates include CH4, C2H4, C2H2, and C2H6. Plasma produced by applying sufficient power at frequency of 2.45 GHz and adjusting density of gas to obtain electron kinetic energies around 100 eV in low-pressure, low-temperature regime.

Hsu, George C.

1989-01-01

185

Development of a new laser heating system for thin film growth by chemical vapor deposition  

NASA Astrophysics Data System (ADS)

We have developed a new laser heating system for thin film growth by chemical vapor deposition (CVD). A collimated beam from a high-power continuous-wave 808 nm semiconductor laser was directly introduced into a CVD growth chamber without an optical fiber. The light path of the heating laser inside the chamber was isolated mechanically from the growth area by bellows to protect the optics from film coating. Three types of heat absorbers, (10 × 10 × 2 mm3) consisting of SiC, Ni/NiOx, or pyrolytic graphite covered with pyrolytic BN (PG/PBN), located at the backside of the substrate, were tested for heating performance. It was confirmed that the substrate temperature could reach higher than 1500 °C in vacuum when a PG/PBN absorber was used. A wide-range temperature response between 400 °C and 1000 °C was achieved at high heating and cooling rates. Although the thermal energy loss increased in a H2 gas ambient due to the higher thermal conductivity, temperatures up to 1000°C were achieved even in 200 Torr H2. We have demonstrated the capabilities of this laser heating system by growing ZnO films by metalorganic chemical vapor deposition. The growth mode of ZnO films was changed from columnar to lateral growth by repeated temperature modulation in this laser heating system, and consequently atomically smooth epitaxial ZnO films were successfully grown on an a-plane sapphire substrate.

Fujimoto, Eiji; Sumiya, Masatomo; Ohnishi, Tsuyoshi; Lippmaa, Mikk; Takeguchi, Masaki; Koinuma, Hideomi; Matsumoto, Yuji

2012-09-01

186

Laser Microdissection and Atmospheric Pressure Chemical Ionization Mass Spectrometry Coupled for Multimodal Imaging  

SciTech Connect

This paper describes the coupling of ambient laser ablation surface sampling, accomplished using a laser capture microdissection system, with atmospheric pressure chemical ionization mass spectrometry for high spatial resolution multimodal imaging. A commercial laser capture microdissection system was placed in close proximity to a modified ion source of a mass spectrometer designed to allow for sampling of laser ablated material via a transfer tube directly into the ionization region. Rhodamine 6G dye of red sharpie ink in a laser etched pattern as well as cholesterol and phosphatidylcholine in a cerebellum mouse brain thin tissue section were identified and imaged from full scan mass spectra. A minimal spot diameter of 8 m was achieved using the 10X microscope cutting objective with a lateral oversampling pixel resolution of about 3.7 m. Distinguishing between features approximately 13 m apart in a cerebellum mouse brain thin tissue section was demonstrated in a multimodal fashion including co-registered optical and mass spectral chemical images.

Lorenz, Matthias [ORNL; Ovchinnikova, Olga S [ORNL; Kertesz, Vilmos [ORNL; Van Berkel, Gary J [ORNL

2013-01-01

187

Chemical imaging of latent fingerprints by mass spectrometry based on laser activated electron tunneling.  

PubMed

Identification of endogenous and exogenous chemicals contained in latent fingerprints is important for forensic science in order to acquire evidence of criminal identities and contacts with specific chemicals. Mass spectrometry has emerged as a powerful technique for such applications without any derivatization or fluorescent tags. Among these techniques, MALDI (Matrix Assisted Laser Desorption Ionization) provides small beam size but has interferences with MALDI matrix materials, which cause ion suppressions as well as limited spatial resolution resulting from uneven distribution of MALDI matrix crystals with different sizes. LAET (Laser Activated Electron Tunneling) described in this work offers capabilities for chemical imaging through electron-directed soft ionization. A special film of semiconductors has been designed for collection of fingerprints. Nanoparticles of bismuth cobalt zinc oxide were compressed on a conductive metal substrate (Al or Cu sticky tape) under 10 MPa pressure. Resultant uniform thin films provide tight and shining surfaces on which fingers are impressed. Irradiation of ultraviolet laser pulses (355 nm) on the thin film instantly generates photoelectrons that can be captured by adsorbed organic molecules and subsequently cause electron-directed ionization and fragmentation. Imaging of latent fingerprints is achieved by visualization of the spatial distribution of these molecular ions and structural information-rich fragment ions. Atomic electron emission together with finely tuned laser beam size improve spatial resolution. With the LAET technique, imaging analysis not only can identify physical shapes but also reveal endogenous metabolites present in females and males, detect contacts with prohibited substances, and resolve overlapped latent fingerprints. PMID:25647159

Tang, Xuemei; Huang, Lulu; Zhang, Wenyang; Zhong, Hongying

2015-03-01

188

Laser spectroscopy of chemically reactive species. [NCO radical  

SciTech Connect

We report the observation of stimulated emission pumping spectra in the NCO radical formed in a supersonic free jet expansion by the reaction between photolytically generated CN radicals and O[sub 2]. The spectra give rotationally resolved information on high lying vibrational levels that are difficult or impossible to detect by conventional single photon spectroscopic techniques. These new data provide detailed insight into the Renner-Teller, spin-orbit and Fermi-resonance coupling in the molecule. They also provide a solid basis for future state-selected chemical and dynamical studies involving this important radical species.

Wu, Ming; Sears, T.J.

1993-01-01

189

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

NASA Technical Reports Server (NTRS)

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 sumary is made of probable minimum conditions that must be achieved for laser power, targeting accuracy, number of satellites, and total sources for power needed.

Grabbe, Crockett L.

1988-01-01

190

Excimer laser induced surface chemical modification of polytetrafluoroethylene  

NASA Astrophysics Data System (ADS)

Polytetrafluoroethylene has a notoriously non adhesive and non reactive character. Its successful surface photochemical modification was performed by irradiating the polytetrafluoroethylene/liquid triethylamine interface with an ArF excimer laser ( ?=193 nm). Due to the photochemical treatment the polytetrafluoroethylene surface became more hydrophilic. The water receding contact angle decreased from 94° to 43°. The reaction cross section was determined from the decrease of the contact angles. It was found to be as high as 6.4×10 -18 cm 2. XPS measurements evidenced the removal of fluorine from the polytetrafluoroethylene, incorporation of alkyl carbon and nitrogen. Photochemical dissociation path of the triethylamine makes probable that it bonded to the fluoropolymer backbone via the ?-carbon atom of an ethyl group. A radical, or a photoinduced electron transfer mechanism was suggested to describe this reaction. A selective area electroless plating of silver was performed after pretreating the sample with patterned photomodification. The increased adhesion of the sample was proved by gluing with epoxy resin. As a result of the surface modification the tensile strength of gluing increased by 210× and reached 24% of the value characteristic for the bulk material.

Révész, K.; Hopp, B.; Bor, Z.

1997-02-01

191

COMPONENTS OF LASER SYSTEMS: Transport of high-pressure O2(1?)  

NASA Astrophysics Data System (ADS)

Calculations and experimental studies were made of the influence of heat evolution on the transport of high-pressure singlet oxygen used in a supersonic oxygen—iodine laser. The heat release as a result of relaxation of O2(1?) slowed down the motion of the gas in the singlet-oxygen generator and also in the duct along which the oxygen was transported. Moreover, the heat reduced the mass flow rate of the gas and the efficiency of the singlet-oxygen generator in the supersonic laser.

Azyazov, V. N.; Zagidullin, M. V.; Nikolaev, V. D.; Svistun, M. I.; Khvatov, N. A.

1994-03-01

192

Personnel protection equipment for use with laser chemicals  

SciTech Connect

The NASA White Sands Test facility (WSTF) recently built the fluid distribution system for the Army's High Energy Laser System Test Facility (HELSTF). As part of the effort, WSTF personnel were required to activate the fluorine system. To insure adequate personnel protection during the fluorine system activation, a project was undertaken to evaluate and qualify personnel protection equipment to be used during the activation (passivation) activity. Previous work in the late 60's and early 70's showed that very few materials were totally satisfactory for use with fluorine. Little if any work has been done to measure the degree of protection afforded against either fluorine gas or hydrofluoric acid (HF), the principal residual reactive material. Two general types of tests were conducted to evaluate materials. These were (1) fluorine and HF gas permeation tests, and (2) high-velocity fluorine gas-impingement tests. The gas permeation tests were designed to exposure one side of the material to the gas at concentrations of up to 27% F2 or 1.5% HF in designed to expose one side of the material to the gas at concentrations of up to 27% F2 or 1.5% HF in GN2 with a gas purge on the opposite side leading to the detection system. The tests showed that all of the materials tested which included ILC Dover Chloropel, glove materials - Neoprene, Viton, leather, butyl rubber, face shield materials, etc., where neither permeated by HF at a 1200 ppm level nor by F2 in GN2 at concentrations as high as 27% by volume. The gas-impingement tests were designed to represent a high-pressure gas leak or the cracking of a B-nut on a system containing residual fluorine gas.

Smith, I.D.; Roepke, J.

1984-08-01

193

Simulation supported description of the local doping formation using laser chemical processing (LCP)  

NASA Astrophysics Data System (ADS)

We present an enhanced model to describe the physics of laser chemical processing (LCP), a liquid jet guided laser technique, for local doping processes applied to crystalline silicon solar cells. The main improvement of the numerical model is the consideration of the inhomogeneous laser light intensity profile within the liquid jet cross section. Measurements of the intensity profile show local superelevations of up to factor five compared to the average intensity. A measured intensity profile was implemented into the numerical model and yields good agreement between simulated and measured dopant distributions. Inhomogeneities of the spatial dopant distribution are observed and their impact on LCP line scans for producing doped lines is investigated with respect to solar cell manufacturing.

Fell, Andreas; Hopman, Sybille; Granek, Filip

2011-07-01

194

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

195

Time evolution studies of laser induced chemical changes in InAs nanowire using Raman spectroscopy  

SciTech Connect

We report the study of time evolution of chemical changes on the surface of an InAs nanowire (NW) on laser irradiation in different power density regime, using Raman spectroscopy for a time span of 8–16 min. Mixture of metastable oxides like InAsO{sub 4,} As{sub 2}O{sub 3} are formed upon oxidation, which are reflected as sharp Raman peaks at ?240–254 and 180–200?cm{sup ?1}. Evidence of removal of arsenic layer by layer is also observed at higher power density. Position controlled laser induced chemical modification on a nanometer scale, without changing the core of the NW, can be useful for NW based device fabrication.

Pal, Suparna; Aggarwal, R.; Kumari Gupta, Vandna; Ingale, Alka [Laser Physics Application Section, Raja Ramanna Centre for Advanced Technology, Indore 452013, MP (India)

2014-07-07

196

Time evolution studies of laser induced chemical changes in InAs nanowire using Raman spectroscopy  

NASA Astrophysics Data System (ADS)

We report the study of time evolution of chemical changes on the surface of an InAs nanowire (NW) on laser irradiation in different power density regime, using Raman spectroscopy for a time span of 8-16 min. Mixture of metastable oxides like InAsO4, As2O3 are formed upon oxidation, which are reflected as sharp Raman peaks at ˜240-254 and 180-200 cm-1. Evidence of removal of arsenic layer by layer is also observed at higher power density. Position controlled laser induced chemical modification on a nanometer scale, without changing the core of the NW, can be useful for NW based device fabrication.

Pal, Suparna; Aggarwal, R.; Kumari Gupta, Vandna; Ingale, Alka

2014-07-01

197

Influence of exothermic chemical reactions on laser-induced shock waves.  

PubMed

Differences in the excitation of non-energetic and energetic residues with a 900 mJ, 6 ns laser pulse (1064 nm) have been investigated. Emission from the laser-induced plasma of energetic materials (e.g. triaminotrinitrobenzene [TATB], cyclotrimethylene trinitramine [RDX], and hexanitrohexaazaisowurtzitane [CL-20]) is significantly reduced compared to non-energetic materials (e.g. sugar, melamine, and l-glutamine). Expansion of the resulting laser-induced shock wave into the air above the sample surface was imaged on a microsecond timescale with a high-speed camera recording multiple frames from each laser shot; the excitation of energetic materials produces larger heat-affected zones in the surrounding atmosphere (facilitating deflagration of particles ejected from the sample surface), results in the formation of additional shock fronts, and generates faster external shock front velocities (>750 m s(-1)) compared to non-energetic materials (550-600 m s(-1)). Non-explosive materials that undergo exothermic chemical reactions in air at high temperatures such as ammonium nitrate and magnesium sulfate produce shock velocities which exceed those of the inert materials but are less than those generated by the exothermic reactions of explosive materials (650-700 m s(-1)). The most powerful explosives produced the highest shock velocities. A comparison to several existing shock models demonstrated that no single model describes the shock propagation for both non-energetic and energetic materials. The influence of the exothermic chemical reactions initiated by the pulsed laser on the velocity of the laser-induced shock waves has thus been demonstrated for the first time. PMID:25182866

Gottfried, Jennifer L

2014-10-21

198

Ultrahigh-spatial-resolution chemical and magnetic imaging by laser-based photoemission electron microscopy  

NASA Astrophysics Data System (ADS)

We report the first experiments carried out on a new chemical and magnetic imaging system, which combines the high spatial resolution of a photoemission electron microscope (PEEM) with a continuous-wave deep-ultraviolet laser. Threshold photoemission is sensitive to the chemical and magnetic structures of the surface of materials. The spatial resolution of PEEM is limited by space charging when using pulsed photon sources as well as aberrations in the electron optics. We show that the use of a continuous-wave laser enabled us to overcome such a limit by suppressing the space-charge effect, allowing us to obtain a resolution of approximately 2.6 nm. With this system, we demonstrated the imaging of surface reconstruction domains on Si(001) by linear dichroism with normal incidence of the laser beam. We also succeeded in magnetic imaging of thin films with the use of magnetic circular dichroism near the Fermi level. The unique features of the ultraviolet laser will give us fast switching of the incident angles and polarizations of the photon source, which will be useful for the characterization of antiferromagnetic materials as well as ferromagnetic materials.

Taniuchi, Toshiyuki; Kotani, Yoshinori; Shin, Shik

2015-02-01

199

Measurements of small signal gain coefficients of a supersonic flow CO chemical laser  

Microsoft Academic Search

Small signal gain coefficients of a supersonic flow CO chemical laser are measured using a shock tunnel facility. A high temperature mixture of CS2, CS, S2, S, and Ar is produced in a shock tube, where the thermal dissociation of CS2, diluted in Ar is accomplished by a reflected shock wave. The shock-heated mixture is exhausted through two-dimensional supersonic nozzles

Wataru Masuda; Masato Ikarashi; Kazuhiko Shiraishi

1990-01-01

200

Theoretical study of a new energy extraction scheme of a chemically pumped pulsed iodine laser amplifier  

Microsoft Academic Search

A new energy extraction scheme of a chemically pumped pulsed large-scale iodine laser based on a high-pressure pulsed singlet oxygen generator is proposed. In previous investigations only low-pressure oxygen generators have been considered. Since they require a high iodine density for an efficient amplifier operation, the lifetime of the stored energy is correspondingly small and thus only small-sized iodine amplifiers

M. Endo; K. Kodama; Y. Handa; T. Uchiyama

1993-01-01

201

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

Microsoft Academic Search

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

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

2010-01-01

202

Laser induced surface chemical epitaxy: A novel thin film deposition technique  

Microsoft Academic Search

This report identifies a new deposition technique, laser induced surface chemical epitaxy, and describes experimental studies of the surface chemistry relevant to the feasibility of the technique. The experiments focus on the thermal and photo-induced surface chemistry of two organometallic molecules, dimethyl cadmium and dimethyl tellurium, on a variety of surfaces including GaAs, Au, Si, and SiO2. These studies followed

Charter D. Stinespring; Andrew Freedman

1987-01-01

203

Synthesis of Cobalt Oxides Thin Films Fractal Structures by Laser Chemical Vapor Deposition  

PubMed Central

Thin films of cobalt oxides (CoO and Co3O4) fractal structures have been synthesized by using laser chemical vapor deposition at room temperature and atmospheric pressure. Various factors which affect the density and crystallization of cobalt oxides fractal shapes have been examined. We show that the fractal structures can be described by diffusion-limited aggregation model and discuss a new possibility to control the fractal structures. PMID:24672354

Haniam, P.; Kunsombat, C.; Chiangga, S.; Songsasen, A.

2014-01-01

204

Chemical electric-discharge HF laser with a technological efficiency in excess of 100 percent  

Microsoft Academic Search

Experimental data are presented on the performance of a chemical HF laser in which the reaction is initiated by a transverse electric discharge formed in a mixture of F2:O2:SF6:H2 (8:1:8:2) by using a three-electrode system. It is shown, in particular, that the lasing power first increases with the active mixture pressure to a maximum and then decreases. The optimal pressure,

S. D. Velikanov; A. F. Zapol'Skii; M. V. Sinitsyn

1988-01-01

205

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

206

On the role of chemical reactions in initiating ultraviolet laser ablation in poly(methyl methacrylate)  

SciTech Connect

The role of chemical reactions is investigated versus the thermal and mechanical processes occurring in a polymer substrate during irradiation by a laser pulse and subsequent ablation. Molecular dynamics simulations with an embedded Monte Carlo based reaction scheme were used to study ultraviolet ablation of poly(methyl methacrylate) at 157 nm. We discuss the onset of ablation, the mechanisms leading to ablation, and the role of stress relaxation of the polymer matrix during ablation. Laser induced heating and chemical decomposition of the polymer substrate are considered as ablation pathways. It is shown that heating the substrate can set off ablation via mechanical failure of the material only for very short laser pulses. For longer pulses, the mechanism of ejection is thermally driven limited by the critical number of bonds broken in the substrate. Alternatively, if the photon energy goes towards direct bond breaking, it initiates chemical reactions, polymer unzipping, and formation of gaseous products, leading to a nearly complete decomposition of the top layers of substrates. The ejection of small molecules has a hollowing out effect on the weakly connected substrates which can lead to lift-off of larger chunks. Excessive pressure buildup upon the creation of gaseous molecules does not lead to enhanced yield. The larger clusters are thermally ejected, and an entrainment of larger polymer fragments in gaseous molecules is not observed.

Prasad, Manish; Conforti, Patrick F.; Garrison, Barbara J. [Department of Chemistry, 104 Chemistry Building, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

2007-05-15

207

Laser-based standoff detection of surface-bound explosive chemicals  

NASA Astrophysics Data System (ADS)

Avoiding or minimizing potential damage from improvised explosive devices (IEDs) such as suicide, roadside, or vehicle bombs requires that the explosive device be detected and neutralized outside its effective blast radius. Only a few seconds may be available to both identify the device as hazardous and implement a response. As discussed in a study by the National Research Council, current technology is still far from capable of meeting these objectives. Conventional nitrocarbon explosive chemicals have very low vapor pressures, and any vapors are easily dispersed in air. Many pointdetection approaches rely on collecting trace solid residues from dust particles or surfaces. Practical approaches for standoff detection are yet to be developed. For the past 5 years, SRI International has been working toward development of a novel scheme for standoff detection of explosive chemicals that uses infrared (IR) laser evaporation of surfacebound explosive followed by ultraviolet (UV) laser photofragmentation of the explosive chemical vapor, and then UV laser-induced fluorescence (LIF) of nitric oxide. This method offers the potential of long standoff range (up to 100 m or more), high sensitivity (vaporized solid), simplicity (no spectrometer or library of reference spectra), and selectivity (only nitrocompounds).

Huestis, David L.; Smith, Gregory P.; Oser, Harald

2010-04-01

208

Effects of injection of various gases on the gain characteristics of a supersonic flow CO chemical laser  

Microsoft Academic Search

Experimental studies are conducted on a supersonic flow CO chemical laser to obtain data on the reaction zone structure and the small signal gain coefficients when various gas additives are injected at the reactant interface. The additives are Ar, O2, N2O and CO. It is shown that the chemiluminescence from the laser cavity and the flow structure do not depend

Wataru Masuda; Masashi Satoh; Takayuki Uchida

1991-01-01

209

Visual observation and numerical analysis on the reaction zone structure of a supersonic flow CO chemical laser  

Microsoft Academic Search

The cavity flow field of a supersonic flow CO chemical laser is observed visually and then simulated numerically- The effects of the nozzle boundary layers, the cavity boundary layers and the mixing process on the laser performance are studied. The thin shear layer approximation is applied to the mixing region and the resulting equations are solved by the Crank-Nicolson predictor-corrector

Wataru Masuda

1991-01-01

210

Be-implanted GaAs/GaAlAs double heterostructure stripe geometry lasers grown by metalorganic chemical vapor deposition  

NASA Astrophysics Data System (ADS)

Be-implanted double heterostructure stripe geometry GaAs lasers grown by metalorganic chemical vapor deposition are described. Near-field and far-field patterns of the lasers are given. A regrowth process was used in order to introduce the highly conductive GaAs cap layer over the implanted structure.

Shtrikman, Hadas; Fekete, D.

1984-09-01

211

Potential phase control of chromium oxide thin films prepared by laser-initiated organometallic chemical vapor deposition  

E-print Network

Potential phase control of chromium oxide thin films prepared by laser-initiated organometallic used laser-initiated chemical vapor deposition to grow the chromium oxide thin films through chromium oxide CrO2 with Tc 397 K Ref. 5 has been predicted to be half metallic metallic for one spin

Idzerda, Yves

212

Laser Diagnostics Of Nascent Gaseous Product Species Formed In Chemical Reactions On Surfaces  

NASA Astrophysics Data System (ADS)

Examples from this laboratory illustrating laser probing of gaseous products formed in chemical reactions on surfaces are taken from the areas of catalytic reactions, silicon etching, and surface photochemistry. The emphasis will be on the unique advantages of laser diagnostics in these dynamical and mechanistic studies in which the chemical reaction product species undergo no collisions after leaving the surface before detection by the laser. UHV experiments on the catalytic oxidation of H2, D2 and NH3 by N02 and H2 by NO2 used the laser-induced fluorescence (LIF) technique to measure the apparent desorption energies of OH radicals and the rotational energy accommodation of the desorbing OH, OD and NO reaction products. The observed different degrees of "rotational cooling" in the different products will be discussed. In multiphoton ionization mass spectrometry experiments (MPI/MS) spectroscopies of three different MPI processes for the SiF2 radical were studied and two of these were applied to the study of silicon etching by XeF2, F2, and NF3. The only observed gaseous products were SiF4 and the SiF2 radical and their apparent production energies correlated with the case of surface fluorine atom production. In the area of surface photochemistry, an excimer laser was used to photolyze iodobenzene, trimethylgallium, and copper acetylacetonate adsorbed on a cold surface. The time-of-flight (TOF) spectra of the fragments or reaction products were measured by using a mass spectrometer equipped with multiphoton (MPI) or electron (EI) ionization.

Hsu, David S.

1989-08-01

213

Sensing signatures mediated by chemical structure of molecular solids in laser-induced plasmas.  

PubMed

Laser ablation of organic compounds has been investigated for almost 30 years now, either in the framework of pulse laser deposition for the assembling of new materials or in the context of chemical sensing. Various monitoring techniques such as atomic and molecular fluorescence, time-of-flight mass spectrometry, and optical emission spectroscopy have been used for plasma diagnostics in an attempt to understand the spectral signature and potential origin of gas-phase ions and fragments from organic plasmas. Photochemical and photophysical processes occurring within these systems are generally much more complex than those suggested by observation of optical emission features. Together with laser ablation parameters, the structural and chemical-physical properties of molecules seem to be closely tied to the observed phenomena. The present manuscript, for the first time, discusses the role of molecular structure in the optical emission of organic plasmas. Factors altering the electronic distribution within the organic molecule have been found to have a direct impact on its ensuing optical emissions. The electron structure of an organic molecule, resulting from the presence, nature, and position of its atoms, governs the breakage of the molecule and, as a result, determines the extent of atomization and fragmentation that has proved to directly impact the emissions of CN radicals and C2 dimers. Particular properties of the molecule respond more positively depending on the laser irradiation wavelength, thereby redirecting the ablation process through photochemical or photothermal decomposition pathways. It is of paramount significance for chemical identification purposes how, despite the large energy stored and dissipated by the plasma and the considerable number of transient species formed, the emissions observed never lose sight of the original molecule. PMID:25668318

Serrano, Jorge; Moros, Javier; Laserna, J Javier

2015-03-01

214

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

PubMed

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) gamma-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, C(3)H(6)N(6), shielded by 15-mm-thick iron and 4-mm-thick lead plates is demonstrated. The NRF gamma-rays of (12)C and (14)N of the melamine are measured by using the LCS gamma-rays of the energies of up to 5.0 MeV. The observed ratio ((12)C/(14)N)(exp)=0.39+/-0.12 is consistent with (C/N)(melamine)=0.5. PMID:19405694

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

2009-04-01

215

Analysis of the optical extraction efficiency in gas-flow lasers with different types of resonator  

SciTech Connect

The celebrated Rigrod model [J. Appl. Phys. {bold 34,} 2602 (1963)] has recently been shown to be inadequate for calculating the output power of gas-flow lasers when the quenching of excited species is slow and the optical extraction efficiency is high [Opt. Lett. {bold 20,} 1480 (1995)]. The previous analysis of two-level systems is presented here in detail and extended to include the chemical oxygen-iodine laser (COIL). For both two-level systems and COIL{close_quote}s, we obtained simple analytic formulas for the output power, which should be used instead of the Rigrod model. We present the formulas for Fabry{endash}Perot, stable, and unstable resonators. Both the saturation parameter and the extraction efficiency differ from those appearing in the Rigrod model. The highest extraction efficiency is achievable for both stable and unstable resonators with uniform intensity distribution over the resonator cross section and is greater than that calculated by the Rigrod model. A rather surprising conclusion is that the extraction efficiency of unstable resonators can be increased substantially if one increases the length of the part of the mirrors lying downstream of the optical axis. The derived formulas are applied to describe published experimental results of supersonic COIL{close_quote}s. The dependence of the power on the threshold gain is evaluated and from this the plenum yield of singlet oxygen is estimated. The value of the yield is in better agreement with experimental measurements than that obtained by the Rigrod model. {copyright} {ital 1996 Optical Society of America.}

Barmashenko, B.D.; Rosenwaks, S. [Department of Physics, Ben Gurion University of the Negev, Beer Sheva 84105 (Israel)

1996-12-01

216

Photothermal temperature control of a chemical reaction on a microchip using an infrared diode laser.  

PubMed

We have demonstrated that a miniaturized device with IR laser heating of the solvent, based on a photothermal effect, is capable of fast and localized control of an enzymatic reaction on a microchip under flow conditions. Using noncontact spectroscopic temperature-sensing techniques, we measured temperature dynamics and spatial distribution and compared the measurements with results of numerical simulation analysis. The device was operated at ultrafast heating and cooling rates of 67 and 53 degrees C/s, respectively, which is 30 times faster than conventional systems and 3-6 times faster than electrothermal miniaturized thermocyclers. The IR laser-mediated heater is characterized by a significantly reduced heated volume of only 5 nL, compared to existing chip-based systems with electrothermal heating. Direct heating of a sample with extremely small heat capacity led us to a fast heating rate, and efficient heat removal through heat transfer to the glass substrate resulted in a fast cooling rate. Reproducible temperature levels with dwell times shorter than 0.5 s were achieved. The enzyme reaction on a chip was successfully controlled with 0.6-s time resolution, using periodic photothermal heating by IR laser. The IR diode laser is compact and thus suits well the miniaturized system design. Our work gives the basis for integration in a chip format of a variety of chemical processes that require fast temperature control. PMID:11534733

Slyadnev, M N; Tanaka, Y; Tokeshi, M; Kitamori, T

2001-08-15

217

Synthesis of graphene pattern using laser-induced chemical vapor deposition  

NASA Astrophysics Data System (ADS)

In this study, Graphene patterns using laser-induced chemical vapor deposition (LCVD) with a visible CW laser (? = 532 nm) irradiation at room temperature was investigated. Optically-pumped solid-state laser with a wavelength of 532 nm irradiates a thin nickel foil to induce a local temperature rise, thereby allowing the direct writing of graphene patterns about ~10 ?m in width with high growth rate on precisely controlled positions. It is demonstrate that the fabrication of graphene patterns can be achieved with a single scan for each graphene pattern using LCVD with no annealing or preprocessing of the substrate. The scan speed reaches to about ~200 ?m/s, which indicates that the graphene pattern with an unite area (10×10 ?m) can be grown in 0.05 sec. The number of graphene layers was controlled by laser scan speed on a substrate. The fabricated graphene patterns on nickel foils were directly transferred to desired positions on patterned electrodes. The position-controlled transfer with rapid single-step fabrication of graphene patterns provides an innovative pathway for application of electrical circuits and devices.

Park, Jongbok; Hann, Swook; Lu, Yongfeng

2014-03-01

218

Volume 112, number 2 CHEMICAL PHYSICS LETTERS 30 November 1984 PICOSECOND LASER STUDIES OF THE EFFEC?S OF REACTANTS  

E-print Network

Volume 112, number 2 CHEMICAL PHYSICS LETTERS 30 November 1984 PICOSECOND LASER STUDIES-triplet enera splitting changes from 1400 to 950 cm-l in going from iso- octane to acetonitrile. The polarity. Because the chemistry 111 #12;Volume 112, number 2 CHEMICAL PHYSICS LEl-l-ERS 30 November 1984

Eisenthal, Kenneth B.

219

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

PubMed Central

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 600°C. 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

2013-01-01

220

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

NASA Astrophysics Data System (ADS)

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 600°C. 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.

Seral-Ascaso, Andrés; Garriga, Rosa; Sanjuán, María Luisa; Razal, Joselito M.; Lahoz, Ruth; Laguna, Mariano; de la Fuente, Germán F.; Muñoz, Edgar

2013-05-01

221

Colour and chemical changes of the lime wood surface due to CO2 laser thermal modification  

NASA Astrophysics Data System (ADS)

We studied colour and main wood components changes of lime wood caused by CO2 laser beam irradiation. The dry surface of lime wood (Tilia vulgaris L.) was irradiated with the CO2 laser beam (wavelength of 10.6 ?m) at different exposures (expressed as the irradiation dose). Colour changes were monitored by the spectrophotometer, chemical changes were observed by the ATR-FTIR spectroscopy and carbohydrates were analysed by the HPLC method. With the growth of the irradiation dose (from 8.1 to 28.7 J cm-2) lightness (?L*) decrease and increase of the total colour difference (?E*) were observed. Higher values of the input energy lead to accelerating the mutual reaction of the functional groups resulting in the subsequent condensation of lignin. The total decrease in saccharides at the highest irradiation dose reaches 27.39% of the initial amount of saccharides in the reference sample. We have observed degradation and loss of hemicelluloses.

Kubovský, Ivan; Ka?ík, František

2014-12-01

222

Laser nanolithography and chemical metalization for the manufacturing of 3D metallic interconnects  

NASA Astrophysics Data System (ADS)

We present a developed method based on direct laser writing (DLW) and chemical metallization (CM) for microfabrication of three-dimensional (3D) metallic structures. Such approach enables manufacturing of free­-form electro conductive interconnects which can be used in integrated electric circuits such micro-opto-electro mechanical systems (MOEMS). The proposed technique employing ultrafast high repetition rate laser enables efficient fabrication of 3D microstructures on dielectric as well as conductive substrates. The produced polymer links out of organic-inorganic composite matrix after CM serve as interconnects of separate metallic contacts, their dimensions are: height 15?m, width 5?m, length 35-45 ?m and could provide 300 n?m resistivity measured in a macroscopic way. This proves the techniques potential for creating integrated 3D electric circuits at microscale.

Jonavi?ius, Tomas; RekštytÄ--, Sima; Žukauskas, Albertas; Malinauskas, Mangirdas

2014-03-01

223

CHEMICAL LASERS AND THEIR MEDIA: Optically pumped pulsed IF(B?X) laser utilizing a CF3I-NF2-He mixture  

NASA Astrophysics Data System (ADS)

Stimulated emission has been obtained and studied for an IF(B?X) laser utilizing optical excitation of IF molecules formed as a result of photolysis of a CF3I-NF2-He mixture containing all the main components of the proposed IF chemical laser, apart from H2 molecules. At helium pressures above 300 Torr, lasing occurred from the ?' = 0 level filled by VT relaxation. The stimulated emission spectrum of the IF laser was tunable between the ?' = 0??'' = 3, 4, 5, 6, 7 discrete electronic-vibrational bands in the ? = 585-675 nm wavelength range.

Zolotarev, V. A.; Kryukov, P. G.; Podmar'kov, Yu P.; Frolov, M. P.; Shcheglov, V. A.

1988-05-01

224

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

225

Optical cavity temperature measurement based on the first overtones spontaneous emission spectra for HF chemical laser  

NASA Astrophysics Data System (ADS)

An optical cavity temperature test method has been established for the HF chemical laser. This method assumes that in HF optical cavity the rotational distribution of vibrationally excited HF molecules meets the statistical thermodynamic distribution, the first overtones (v = 3-1 and 2-0) spontaneous emission spectral intensity distribution is obtained by using OMA V, the optical cavity temperature is calculated by linear fitting the rotational thermal equilibrium distribution formula for each HF vibrationally excited state. This method is simple, reliable, and repeatable. This method can be used to test the optical cavity temperature not only without lasing, but also with lasing.

Tang, Shukai; Li, Liucheng; Duo, Liping; Wang, Yuanhu; Yu, Haijun; Jin, Yuqi; Sang, Fengting

2015-02-01

226

Initiation with an electron beam of chemical reactions of interest for visible wavelength lasers  

NASA Technical Reports Server (NTRS)

A description is given of the first results obtained with a new shock tube-electron beam facility designed to provide a versatile means for the systematic search for laser operation among several candidate metal atom-oxidizer systems. According to the current experimental approach, metal atoms are obtained in the vapor phase by the dissociation of metal compounds. A shock tube is employed to provide a short duration flow through an array of 29 supersonic flow-mixing nozzles. A high energy electron accelerator is used for the rapid initiation of chemical reaction in a mixed flow of encapsulated metal and oxidizer.

Whittier, J. S.; Cool, T. A.

1976-01-01

227

JOURNAL DE PHYSIQUE CoZZoque C9, suppldment au nO1l, Tome 41, novembre 1980, page C9-251 'HIGH POWER AND SINGLE L I N E OPERATIONS OF AN -Hk-CHEMICAL LASER  

E-print Network

can be properly of HBr chemical laser using an electrically used for laser isotope separation of hydro POWER AND SINGLE L I N E OPERATIONS OF AN -Hk-CHEMICAL LASER K. Toyoda, H. ~sada*and S. Namba Riken, the Institute of Physical and Chemical Research, 2-1 Hirosawa, Wako-Shi, Saitama 351, Japan. R6sumd.- Un laser

Boyer, Edmond

228

Multiline multimode c-w (continuous-wave) chemical laser performance. Technical report  

SciTech Connect

Effects of translational rotational nonequilibrium large-scale c-w chemical laser performance are evaluated for the case of a Fabry-Perot resonator with multiple longitudinal modes. Numerical results are presented for the limit Delta nu Sub c << Delta nu sub h << Delta nu sub d, where Delta nu sub c, Delta nu sub h, and Delta nu sub d denote longitudinal mode separation, homogeneous width, and Doppler width, respectively. Results include the effect of threshold gain on the power in each longitudinal mode, the power associated with each rotational energy level, and the net laser power. In the case of a saturated laser, an increase of threshold gain results in an increase in the output from strong rotational transitions at the expense of the output from weak rotational transitions. Total output is reduced. With further increase of threshold gain, the output from all rotational transitions is reduced. The case of rotational nonequilibrium and translational equilibrium is also considered. The latter case, a common assumption, is shown to provide net output power that is intermediate between the values for rotational and translational equilibrium and for rotational and translational nonequilibrium.

Mirels, H.

1989-07-01

229

Modeling of dual emission laser induced fluorescence for slurry thickness measurements in chemical mechanical polishing  

NASA Astrophysics Data System (ADS)

Dual emission laser induced fluorescence (DELIF) is a technique for measuring the instantaneous thin fluid film thickness in dynamic systems. Two fluorophores within the system produce laser induced emissions that are filtered and captured by two cameras. The ratio of the images from these cameras is used to cancel the effect of the laser beam profile on the image intensity. The resultant intensity ratio can be calibrated to a fluid film thickness. The utilization of a 2-dye system when applied to Chemical Mechanical Polishing (CMP) is complicated by the fluorescence of the polymeric polishing pad and the light scattering particles in the polishing slurry. We have developed a model of DELIF for CMP with 1-dye employing the polishing pad as the second fluorophore. While scattering particles in the slurry decrease the overall intensity of the individual images, the contrast in the image ratio increases. Using the 1-dye DELIF system to measure thin slurry films, our model results indicate that a cubic calibration may be needed. However, experimental results suggest a linear calibration is achieved for slurry films between 0 and 133 ?m thick with scattering coefficients as high as 8.66 mm-1 at a wavelength equal to 410 nm.

Gray, Caprice; Rogers, Chris B.; Manno, Vincent P.; White, Robert D.

2011-07-01

230

Double-core-hole spectroscopy for chemical analysis with an intense X-ray femtosecond laser  

PubMed Central

Theory predicts that double-core-hole (DCH) spectroscopy can provide a new powerful means of differentiating between similar chemical systems with a sensitivity not hitherto possible. Although DCH ionization on a single site in molecules was recently measured with double- and single-photon absorption, double-core holes with single vacancies on two different sites, allowing unambiguous chemical analysis, have remained elusive. Here we report that direct observation of double-core holes with single vacancies on two different sites produced via sequential two-photon absorption, using short, intense X-ray pulses from the Linac Coherent Light Source free-electron laser and compare it with theoretical modeling. The observation of DCH states, which exhibit a unique signature, and agreement with theory proves the feasibility of the method. Our findings exploit the ultrashort pulse duration of the free-electron laser to eject two core electrons on a time scale comparable to that of Auger decay and demonstrate possible future X-ray control of physical inner-shell processes. PMID:21969540

Berrah, Nora; Fang, Li; Murphy, Brendan; Osipov, Timur; Ueda, Kiyoshi; Kukk, Edwin; Feifel, Raimund; van der Meulen, Peter; Salen, Peter; Schmidt, Henning T.; Thomas, Richard D.; Larsson, Mats; Richter, Robert; Prince, Kevin C.; Bozek, John D.; Bostedt, Christoph; Wada, Shin-ichi; Piancastelli, Maria N.; Tashiro, Motomichi; Ehara, Masahiro

2011-01-01

231

Chemical models for simulating single-walled nanotube production in arc vaporization and laser ablation processes  

NASA Technical Reports Server (NTRS)

Chemical kinetic models for the nucleation and growth of clusters and single-walled carbon nanotube (SWNT) growth are developed for numerical simulations of the production of SWNTs. Two models that involve evaporation and condensation of carbon and metal catalysts, a full model involving all carbon clusters up to C80, and a reduced model are discussed. The full model is based on a fullerene model, but nickel and carbon/nickel cluster reactions are added to form SWNTs from soot and fullerenes. The full model has a large number of species--so large that to incorporate them into a flow field computation for simulating laser ablation and arc processes requires that they be simplified. The model is reduced by defining large clusters that represent many various sized clusters. Comparisons are given between these models for cases that may be applicable to arc and laser ablation production. Solutions to the system of chemical rate equations of these models for a ramped temperature profile show that production of various species, including SWNTs, agree to within about 50% for a fast ramp, and within 10% for a slower temperature decay time.

Scott, Carl D.

2004-01-01

232

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

233

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

2011-03-01

234

Direct spatiotemporal analysis of femtosecond laser-induced plasma-mediated chemical reactions  

NASA Astrophysics Data System (ADS)

Localized, micron to millimetre-scale plasmas resulting from the fleeting interaction between ultrashort laser pulses and matter have been studied extensively in inert atmospheres. In spite of recent interest in reactive plasmas as a nanofabrication tool, ultrashort pulsed laser ablation in reactive gas atmospheres has undergone little study. In this study, we develop a methodology combining time-resolved optical emission spectroscopy and spectrally filtered time-gated fast photography to directly observe and analyse plasma-mediated chemical reactions that occur when laser ablation is performed in reactive gases. Specifically, we compare the ablation of silicon dioxide in an atmosphere of xenon difluoride gas to its ablation in nitrogen and xenon atmospheres. We show that when xenon difluoride molecules are collisionally driven into an excited state by the silicon plasma produced during laser-induced decomposition of the solid substrate, the gas undergoes dissociation. The resulting fluorine radicals react spontaneously with the silicon plasma to produce volatile fluorinated silicon compounds. In particular, mass spectroscopy shows that the primary reaction byproduct is SiF2 with small amounts of SiF and SiF4. The high spatial and temporal resolution of our methodology reveals a slowly expanding plume having an atomic silicon core with a XeF? shell that persists for less than 300 ns. As the silicon is fluorinated, the optical emission due to excited silicon is quenched. The absence of a silicon signal after 300 ns establishes this as the upper limit of the reaction lifetime given the conditions of the experiment.

Straw, Marcus; Randolph, Steven

2014-03-01

235

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

236

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

237

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

238

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

239

A pulsed laser ablation/plasma chemical vapor deposition tandem system for combinatorial device fabrication  

NASA Astrophysics Data System (ADS)

In electronic device fabrication, we frequently encounter the situations to deposit thin films of semiconductors, ceramics, and metals sequentially. Since the appropriate methods for depositing these films are frequently different, it should be beneficial for the research of new devices to develop a system that enables the depositions of different films not only sequentially but also in parallel by the procedure as prescribed. In this paper, we report on a tandem system composed of a pulsed laser deposition (PLD) and two plasma chemical vapor deposition (PCVD) chambers and its application in the fabrication of a prototype structure directed towards the field effect a-Si:H solar cell. PLD and PCVD were used to deposit conductive and semiconductive/insulative film layers, respectively. An exchangeable masking scheme was designed and installed in the system so we could make several device structures in parallel and quickly optimize the device and process parameters by the combinatorial methodology.

Matsuki, N.; Abiko, Y.; Kobayashi, M.; Miyazaki, K.; Fujioka, H.; Koinuma, H.

240

Temperature engineered growth of low-threshold quantum well lasers by metalorganic chemical vapor deposition  

NASA Astrophysics Data System (ADS)

A new technique is demonstrated for the formation of narrow active regions in quantum well lasers. In temperature engineered growth, the substrate temperature is varied during the growth of epitaxial layers by metalorganic chemical vapor deposition on nonplanar substrates, allowing two-dimensional control of device features. Buried heterostructure designs with submicron active region stripe widths are obtained without the need for fine process control of lateral dimensions. The contact area above the active region is coplanar with the surrounding surface and wide enough to allow easy contacting and heat sinking. Carrier confinement is accomplished by lateral thickness variation of the quantum well active region resulting in a local strip of minimum band gap. Lasers grown in this manner exhibit cw threshold currents as low as 3.8 mA (3.4 mA pulsed), having an as-grown active region width of 0.5 micron. The near-field optical profile indicates stable, single transverse mode operation and minimal current leakage in these devices.

Dzurko, K. M.; Menu, E. P.; Beyler, C. A.; Osinski, J. S.; Dapkus, P. D.

1989-01-01

241

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

NASA Astrophysics Data System (ADS)

Several pigments (malachite CuCO3?Cu(OH)2, azurite 2CuCO3?Cu(OH)2, yellow ochre (goethite ?-FeOOH, gypsum CaSO4?2H2O), St. John's white CaCO3 formed from slaked lime) and respective mural paintings specimens were subjected to the free-running Er:YAG laser radiation in order to study their damage thresholds, in a broad range of laser fluences, both in dry and wet conditions. The specimens' damage thresholds were evaluated by spectroscopic methods, colorimetric measurements and microscopic observation. The pigments containing -OH groups were found to be more sensitive than St. John's white; hence the most sensitive paint layers in dry conditions are those containing malachite, azurite (both 1.3 J/cm2) and yellow ochre (2.5 J/cm2) as compared to the ones containing St. John's white (15.2 J/cm2). The presence of wetting agents (w.a.) attenuated the pigments chemical alteration. The damage thresholds of all the paint layers, in presence of w.a., were found to be around 2.5 J/cm2. The alteration was caused by thermo-mechanical damage and by binding medium ablation of a fresco and a secco prepared specimens, respectively.

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

2011-08-01

242

Numerical simulation for the power of a supersonic flow CO chemical laser using a leaky stream tube approach  

Microsoft Academic Search

The effects of the mixing process on the power of a supersonic flow CO chemical laser are studied numerically using a leaky stream tube approach. Downstream of the nozzle exits, the flow field is divided into three stream tubes, two stream tubes for the dissociated products of CS2 diluted in Ar and for O2, and a third stream tube between

Wataru Masuda; Satoru Sasagawa; Motoshi Tohyama

1990-01-01

243

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

244

Injectorless Quantum Cascade Laser with very low voltage-defect grown by metal-organic chemical vapor deposition  

E-print Network

Injectorless Quantum Cascade Laser with very low voltage-defect grown by metal-organic chemical, increasing the upper state LO-phonon non-raditive lifetime with quantum confinement Recently, a heterogeneous/17/25/300 nm). The output power and applied voltage versus current (L-I-V) characteristics is obtained

Mohseni, Hooman

245

Emission of a pulsed purely rotational transition chemical H{sub 2}-F{sub 2} laser  

SciTech Connect

The possibility of obtaining efficient emission at purely rotational transitions of HF molecules in a pulsed chemical hydrogen fluoride laser is studied theoretically. The operation of a H{sub 2}-F{sub 2} laser with a gas pressure of 1.1 atm emitting at the v, j {yields} v, j - 1 (v = 1 - 6, j = 10 - 14) transitions is simulated taking into account resonance VR processes. The total specific laser energy release calculated over all the vibrational levels is 5.5 J L{sup -1} on purely rotational transitions at {lambda}{approx}17 {mu}m (j = 14), 3.5 J L{sup -1} at {lambda}{approx}18.5 {mu}m (j = 13), and 2.5 J L{sup -1} at {lambda}{approx}20 {mu}m (j = 12). (lasers and amplifiers)

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

2008-04-30

246

A modular architecture for multi-channel external cavity quantum cascade laser-based chemical sensors: a systems approach  

SciTech Connect

A multi-channel laser-based chemical sensor platform is presented, in which a modular architecture allows the exchange of complete sensor channels without disruption to overall operation. Each sensor channel contains custom optical and electronics packages, which can be selected to access laser wavelengths, interaction path lengths and modulation techniques optimal for a given application or mission. Although intended primarily to accommodate mid-infrared (MIR) external cavity quantum cascade lasers (ECQCLs)and astigmatic Herriott cells, channels using visible or near infrared (NIR) lasers or other gas cell architectures can also be used, making this a truly versatile platform. Analog and digital resources have been carefully chosen to facilitate small footprint, rapid spectral scanning, ow-noise signal recovery, failsafe autonomous operation, and in-situ chemometric data analysis, storage and transmission. Results from the demonstration of a two-channel version of this platform are also presented.

Taubman, Matthew S.; Myers, Tanya L.; Bernacki, Bruce E.; Stahl, Robert D.; Cannon, Bret D.; Schiffern, John T.; Phillips, Mark C.

2012-04-01

247

InAs/InGaAsP/InP Quantum Dot Lasers Grown by Metalorganic Chemical Vapor Deposition  

NASA Astrophysics Data System (ADS)

We demonstrate InAs/InGaAsP/InP quantum dot (QD) lasers grown by metalorganic chemical vapor deposition. The active region of the lasers consists of five layers of InAs QDs. Ridge waveguide lasers with 6 ?m width have been fabricated by standard optical lithography and wet etching. Under continuous wave operation at room temperature, a low threshold current density of 447A/cm2 per QD layer is achieved for a QD laser with a cavity length of 2 mm. Moreover, the lasing redshifts from 1.61 ?m to 1.645 ?m as the cavity length increases from 1.5 mm to 4 mm. A high characteristic temperature of up to 88K is obtained in the temperature range between 10°C and 40°C.

Luo, Shuai; Ji, Hai-Ming; Gao, Feng; Yang, Xiao-Guang; Liang, Ping; Zhao, Ling-Juan; Yang, Tao

2013-06-01

248

Laser enhanced chemical reaction studies. Technical progress report, January 1, 1982-October 31, 1984  

SciTech Connect

Experimental studies of dynamic molecular processes are described with particular emphasis on the development of a powerful new infrared diode laser probe technique. This technique allows us to determine the final states of CO/sub 2/ (and other moledules) produced by collisions, photofragmentation, or chemical reactions with a spectral resolution of 0.001 cm/sup -1/ and a time resolution of 10/sup -7/ s. Such high spectral resolution provides a detailed picture of the vibrational and rotational states of molecules produced by these dynamic events. We have used this experimental method to probe collisions between hot hydrogen atoms and CO/sub 2/ and to study the final state energy distribution of CO/sub 2/ produced as a result of photodissociation of pyruvic acid. Infrared and uv fluorescence technique have also been used to investigate collisions between hot hydrogen atoms and CO, CO/sub 2/, CH/sub 3/F; photofragmentation of 1,3,5-triazine; chemical reactions between hot hydrogen atoms and N/sub 2/O; photochemical studies of Br/sub 2/ trapped in rare gas matrices; infrared multiphoton dissociation of C/sub 4/F/sub 8/; and vibrational relaxtion of (COF)/sub 2/. Progress in these interconnected experimental areas is briefly described.

Flynn, G.

1984-01-01

249

Chemical stabilization of laser dyes. Final report, 1 July 1981-1 October 1984  

SciTech Connect

Coumarin laser dyes upon excitation degrade to produce products which absorb at the lasing wavelength. This results in attenuation of dye laser output. Modes of degradation of coumarin dye lasers under both anaerobic and aerobic conditions were determined and methods of stabilization of dye lasers were established.

Koch, T.H.

1984-11-01

250

Physico-chemical properties of Pd nanoparticles produced by Pulsed Laser Ablation in different organic solvents  

NASA Astrophysics Data System (ADS)

Palladium nanoparticles are arousing an increasing interest because of their strong activity in heterogeneous catalysis in a wide range of reactions. Driven by the interest of producing Pd nanoparticles to be deposited for catalysis over hydrophobic supports, we investigated their synthesis via Pulsed Laser Ablation in Liquid in several organic solvents, as acetone, ethanol, 2-propanol, toluene, n-hexane. The colloids were produced by using a Nd:YAG ns laser and without the addition of surfactant agents. The morphology, composition, stability and oxidation state of the obtained nanoparticles were investigated by TEM-EDS analysis, UV-vis spectroscopy, X-ray Photoelectron Spectroscopy and micro-Raman spectroscopy. The results evidence that the nature of the solvent influences both the yield and the physico-chemical properties of the produced nanoparticles. While in acetone and alcohols spheroidal, non aggregated and stable particles are obtained, in case of toluene and n-hexane few unstable particles surrounded by a gel-like material are produced. Raman/XPS measurements suggest the presence of amorphous or graphitic carbon onto crystalline Pd nanoparticles, which could have hindered their growth and determined the observed smaller sizes if compared to nanoparticles produced in water. The stability of Pd colloids obtained in acetone and alcohols was attributed to adsorbed anions like enolates or alcoholates; non polar solvents like toluene and n-hexane, unable to give rise to adsorbed anionic species, cannot provide any stabilization to the palladium nanoparticles. XPS analyses also evidenced a partial oxidation of particles surface, with a ratio Pd 2+:Pd 0 of 1:2.5 and 1:4 in acetone and ethanol, respectively.

Cristoforetti, Gabriele; Pitzalis, Emanuela; Spiniello, Roberto; Ishak, Randa; Giammanco, Francesco; Muniz-Miranda, Maurizio; Caporali, Stefano

2012-01-01

251

Chemical composition and charge stability of highly crystalline pulsed-laser-deposited polytetrafluoroethylene films on metal substrates  

NASA Astrophysics Data System (ADS)

KrF excimer-laser ablation of sintered-powder polytetrafluoroethylene (PTFE) targets is used for the deposition of high-quality PTFE films on metallic microstructures and metal backplates for electroacoustic applications. The films are found to be highly crystalline, consisting of large spherulites with diameters up to 1 mm. X-ray photoelectron spectroscopy of the films revealed the chemical similarity of press-sinter target pulsed-laser-deposited films with bulk PTFE. Negatively charged PTFE films on stainless steel backplates exhibit an exceptional charge stability with practically no decrease of the surface potential up to 225 °C in open-circuit thermally stimulated discharge.

Huber, N.; Heitz, J.; Bäuerle, D.; Schwödiauer, R.; Bauer, S.; Niino, H.; Yabe, A.

252

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

253

Atmospheric pressure laser-induced acoustic desorption chemical ionization mass spectrometry for analysis of saturated hydrocarbons.  

PubMed

We present atmospheric pressure laser-induced acoustic desorption chemical ionization (AP/LIAD-CI) with O(2) carrier/reagent gas as a powerful new approach for the analysis of saturated hydrocarbon mixtures. Nonthermal sample vaporization with subsequent chemical ionization generates abundant ion signals for straight-chain, branched, and cycloalkanes with minimal or no fragmentation. [M - H](+) is the dominant species for straight-chain and branched alkanes. For cycloalkanes, M(+•) species dominate the mass spectrum at lower capillary temperature (<100 °C) and [M - H](+) at higher temperature (>200 °C). The mass spectrum for a straight-chain alkane mixture (C(21)-C(40)) shows comparable ionization efficiency for all components. AP/LIAD-CI produces molecular weight distributions similar to those for gel permeation chromatography for polyethylene polymers, Polywax 500 and Polywax 655. Coupling of the technique to Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) for the analysis of complex hydrocarbon mixtures provides unparalleled mass resolution and accuracy to facilitate unambiguous elemental composition assignments, e.g., 1754 peaks (rms error = 175 ppb) corresponding to a paraffin series (C(12)-C(49), double-bond equivalents, DBE = 0) and higher DBE series corresponding to cycloparaffins containing one to eight rings. Isoabundance-contoured plots of DBE versus carbon number highlight steranes (DBE = 4) of carbon number C(27)-C(30) and hopanes of C(29)-C(35) (DBE = 5), with sterane-to-hopane ratio in good agreement with field ionization (FI) mass spectrometry analysis, but performed at atmospheric pressure. The overall speciation of nonpolar, aliphatic hydrocarbon base oil species offers a promising diagnostic probe to characterize crude oil and its products. PMID:22881221

Nyadong, Leonard; Quinn, John P; Hsu, Chang S; Hendrickson, Christopher L; Rodgers, Ryan P; Marshall, Alan G

2012-08-21

254

Chemical stabilization of laser dyes. Final report, 1 April 1987-31 March 1990  

SciTech Connect

Irradiation of ethanol solutions of coumarin laser dye lasers produces products which absorb at the lasing wavelength. This results in attenuation of dye laser output through interference of stimulated emission. A major photoprocess which produces material which absorbs at the lasing wavelength is dye sensitized solvent oxidative oligomerization, producing aldehydic and ketonic products. A dye laser stabilization technique is removal of these carbonyl compounds as they are formed by reduction with a polymer bound borohydride reducing agent.

Koch, T.H.

1990-04-10

255

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

256

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

NASA Astrophysics Data System (ADS)

Laser-induced acoustic desorption (LIAD) was successfully coupled to a conventional atmospheric pressure chemical ionization (APCI) source in a commercial 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. From the four APCI reagent systems tested, neat carbon disulfide provided the best results. 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 but minor amount of fragmentation was observed for these two 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 predominantly form stable molecular ions.

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

2011-03-01

257

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

258

Coupled molecular dynamics-Monte Carlo model to study the role of chemical processes during laser ablation of polymeric materials  

SciTech Connect

The coarse grained chemical reaction model is enhanced to build a molecular dynamics (MD) simulation framework with an embedded Monte Carlo (MC) based reaction scheme. The MC scheme utilizes predetermined reaction chemistry, energetics, and rate kinetics of materials to incorporate chemical reactions occurring in a substrate into the MD simulation. The kinetics information is utilized to set the probabilities for the types of reactions to perform based on radical survival times and reaction rates. Implementing a reaction involves changing the reactants species types which alters their interaction potentials and thus produces the required energy change. We discuss the application of this method to study the initiation of ultraviolet laser ablation in poly(methyl methacrylate). The use of this scheme enables the modeling of all possible photoexcitation pathways in the polymer. It also permits a direct study of the role of thermal, mechanical, and chemical processes that can set off ablation. We demonstrate that the role of laser induced heating, thermomechanical stresses, pressure wave formation and relaxation, and thermochemical decomposition of the polymer substrate can be investigated directly by suitably choosing the potential energy and chemical reaction energy landscape. The results highlight the usefulness of such a modeling approach by showing that various processes in polymer ablation are intricately linked leading to the transformation of the substrate and its ejection. The method, in principle, can be utilized to study systems where chemical reactions are expected to play a dominant role or interact strongly with other physical processes.

Prasad, Manish; Conforti, Patrick F.; Garrison, Barbara J. [Department of Chemistry, 104 Chemistry Building, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

2007-08-28

259

Adhesion of fibroblasts on micro- and nanostructured surfaces prepared by chemical vapor deposition and pulsed laser treatment  

Microsoft Academic Search

The development of micro- and nanostructured surfaces which improve the cell-substrate interaction is of great interest in today's implant applications. In this regard, Al\\/Al2O3 bi-phasic nanowires were synthesized by chemical vapor deposition of the molecular precursor (tBuOAlH2)2. Heat treatment of such bi-phasic nanowires with short laser pulses leads to micro- and nanostructured Al2O3 surfaces. Such surfaces were characterized by scanning

M. Veith; O. C. Aktas; W. Metzger; D. Sossong; H. Ullah Wazir; I. Grobelsek; N. Pütz; G. Wennemuth; T. Pohlemann; M. Oberringer

2010-01-01

260

Comparative optical and structural studies of CdSe films grown by chemical bath deposition and pulsed laser deposition  

Microsoft Academic Search

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

M. A. Hernandez-Perez; J. Aguilar-Hernandez; G. Contreras-Puente; J. R. Vargas-García; E. Rangel-Salinas

2008-01-01

261

The physical-chemical and electrophysical properties of high-temperature insulating ceramics for chemical-element-vapor lasers  

NASA Astrophysics Data System (ADS)

Consideration is given to the characteristics of high-temperature ceramics (e.g., alpha-Al2O3, ZrO2, BeO, AlN, and BN) widely used in vapor lasers. Pyrolithic boron nitride is found to exhibit the best characteristics for vapor-laser systems. A system is described which is capable of measuring the low-voltage and high-voltage electrophysical characteristics of dielectrics in various gases at pressures of 1-100,000 Pa and temperatures up to 2500 K. Experimental results on the high-voltage characteristics of boron pyronitride are presented.

Buzhinskii, O. I.; Lopatin, V. V.; Chernenko, V. P.

1981-08-01

262

Standoff detection of explosives and chemical agents using broadly tuned external-cavity quantum cascade lasers (EC-QCLs)  

NASA Astrophysics Data System (ADS)

Civilian soft targets such as transportation systems are being targeted by terrorists using IEDs and suicide bombers. Having the capability to remotely detect explosives, precursors and other chemicals would enable these assets to be protected with minimal interruption of the flow of commerce. Mid-IR laser technology offers the potential to detect explosives and other chemicals in real-time and from a safe standoff distance. While many of these agents possess "fingerprint" signatures in the mid-IR (i.e. in the 3-20 micron regime), their effective interrogation by a practical, field-deployable system has been limited by size, complexity, reliability and cost constraints of the base laser technology. Daylight Solutions has addressed these shortcomings by developing compact, portable, broadly tunable mid-IR laser sources based upon external-cavity quantum cascade technology. This technology is now being applied by Daylight in system level architectures for standoff and remote detection of explosives, precursors and chemical agents. Several of these architectures and predicted levels of performance will be presented.

Takeuchi, Eric B.; Rayner, Timothy; Weida, Miles; Crivello, Salvatore; Day, Timothy

2007-10-01

263

High-resolution chemical depth profiling of solid material using a miniature laser ablation/ionization mass spectrometer.  

PubMed

High-resolution chemical depth profiling measurements of copper films are presented. The 10 ?m thick copper test samples were electrodeposited on a Si-supported Cu seed under galvanostatic conditions in the presence of particular plating additives (SPS, Imep, PEI, and PAG) used in the semiconductor industry for the on-chip metallization of interconnects. To probe the trend of these plating additives toward inclusion into the deposit upon growth, quantitative elemental mass spectrometric measurements at trace level concentration were conducted by using a sensitive miniature laser ablation ionization mass spectrometer (LIMS), originally designed and developed for in situ space exploration. An ultrashort pulsed laser system (? ? 190 fs, ? = 775 nm) was used for ablation and ionization of sample material. We show that with our LIMS system, quantitative chemical mass spectrometric analysis with an ablation rate at the subnanometer level per single laser shot can be conducted. The measurement capabilities of our instrument, including the high vertical depth resolution coupled with high detection sensitivity of ?10 ppb, high dynamic range ?10(8), measurement accuracy and precision, is of considerable interest in various fields of application, where investigations with high lateral and vertical resolution of the chemical composition of solid materials are required, these include, e.g., wafers from semiconductor industry or studies on space weathered samples in space research. PMID:25642789

Grimaudo, Valentine; Moreno-García, Pavel; Riedo, Andreas; Neuland, Maike B; Tulej, Marek; Broekmann, Peter; Wurz, Peter

2015-02-17

264

Chemical-assisted femtosecond laser writing of lab-in-fibers.  

PubMed

The lab-on-chip (LOC) platform has presented a powerful opportunity to improve functionalization, parallelization, and miniaturization on planar or multilevel geometries that has not been possible with fiber optic technology. A migration of such LOC devices into the optical fiber platform would therefore open the revolutionary prospect of creating novel lab-in-fiber (LIF) systems on the basis of an efficient optical transport highway for multifunctional sensing. For the LIF, the core optical waveguide inherently offers a facile means to interconnect numerous types of sensing elements along the optical fiber, presenting a radical opportunity for optimizing the packaging and densification of diverse components in convenient geometries beyond that available with conventional LOCs. In this paper, three-dimensional patterning inside the optical fiber by femtosecond laser writing, together with selective chemical etching, is presented as a powerful tool to form refractive index structures such as optical waveguides and gratings as well as to open buried microfluidic channels and optical resonators inside the flexible and robust glass fiber. In this approach, optically smooth surfaces (~12 nm rms) are introduced for the first time inside the fiber cladding that precisely conform to planar nanograting structures when formed by aberration-free focusing with an oil-immersion lens across the cylindrical fiber wall. This process has enabled optofluidic components to be precisely embedded within the fiber to be probed by either the single-mode fiber core waveguide or the laser-formed optical circuits. We establish cladding waveguides, X-couplers, fiber Bragg gratings, microholes, mirrors, optofluidic resonators, and microfluidic reservoirs that define the building blocks for facile interconnection of inline core-waveguide devices with cladding optofluidics. With these components, more advanced, integrated, and multiplexed fiber microsystems are presented demonstrating fluorescence detection, Fabry-Perot interferometric refractometry, and simultaneous sensing of refractive index, temperature, and bending strain. The flexible writing technique and multiplexed sensors described here open powerful prospects to migrate the benefits of LOCs into a more flexible and miniature LIF platform for highly functional and distributed sensing capabilities. The waveguide backbone of the LIF inherently provides an efficient exchange of information, combining sensing data that are attractive in telecom networks, smart catheters for medical procedures, compact sensors for security and defense, shape sensors, and low-cost health care products. PMID:25120138

Haque, Moez; Lee, Kenneth K C; Ho, Stephen; Fernandes, Luís A; Herman, Peter R

2014-10-01

265

Electromagnetic launch, then lessening chemical thrust over time as laser beam powered ion thrust grows{emdash}to any orbit  

SciTech Connect

The ElectroMagnetic (EM) Launch Tube (LT), using High-Temp SuperConduction (HTSC) EM launch coils if developed, will be built in a tall building, or, if not, at a steep angle up the west slope of an extinct volcano. The Reusable Launch Vehicle (RLV) exits the LT at such high velocity that the otherwise violent entry into the atmosphere is made possible by Special-Laser-Launch-Assist (SLLA), which ionizes and expands the atmosphere immediately ahead of the RLV. At first a brief period of chemical thrust is followed by a long period of ion thrust during ascent to orbit. As decades pass and greater ion thrust is developed, the period of chemical thrust shortens until it is no longer needed. The RLV{close_quote}s ion thrusters are powered by laser/maser, beamed first from the launch site, then from two large Solar-Power-Satellites (SPS) 180{degree} apart in Medium Earth Orbit (MEO) orbit. In orbit, the RLV is limited in where it can go only by the amount of propellant it carries or is stored in various orbits. The RLV can land at a launch site on Earth by using both chemical and ion thrust at first, and later by ion thrust alone as developments cause a far lighter RLV to carry no chemical engines/fuel/tanks. {copyright} {ital 1996 American Institute of Physics.}

Morse, T.M. [AT& T Technologies Planning Engineer (Retired), 334 Lakeview Shores Loop, Mooresville, North Carolina 28115 (United States)

1996-03-01

266

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

NASA Astrophysics Data System (ADS)

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 35 m for dimethyl methylphosphonate (DMMP) detection and 60, 90 and 140 m for cyclohexane detection. The prototype systems consisted of a Raman spectrometer equipped with a CCD detector (for CW measurements) and an I-CCD camera with time-gated electronics (for pulsed laser measurements), a reflecting telescope, a fiber optic assembly, a single-line CW laser source (514.5, 488.0, 351.1 and 363.8 nm) and a frequency-doubled single frequency Nd:YAG 532 nm laser (5 ns pulses at 10 Hz). The telescope was coupled to the spectrograph using an optical fiber, and filters were used to reject laser radiation and Rayleigh scattering. Two quartz convex lenses were used to collimate the light from the telescope from which the telescope-focusing eyepiece was removed, and direct it to the fiber optic assembly. To test the standoff sensing system, the Raman Telescope was used in the detection of liquid TIC: benzene, chlorobenzene, toluene, carbon tetrachloride, cyclohexane and carbon disulfide. Other compounds studied were CWAS: dimethylmethyl phosphonate, 2-chloroethyl ethyl sulfide and 2-(butylamino)-ethanethiol. Relative Raman scattering cross sections of liquid CWAS were measured using single-line sources at 532.0, 488.0, 363.8 and 351.1 nm. Samples were placed in glass and quartz vials at the standoff distances from the telescope for the Remote Raman measurements. The mass of DMMP present in water solutions was also quantified as part of the system performance tests.

Ortiz-Rivera, William; Pacheco-Londoño, Leonardo C.; Hernández-Rivera, Samuel P.

2010-09-01

267

Control of electroosmotic flow in laser-ablated and chemically modified hot imprinted poly(ethylene terephthalate glycol) microchannels.  

PubMed

The fabrication of microchannels in poly(ethylene terephthalate glycol) (PETG) by laser ablation and the hot imprinting method is described. In addition, hot imprinted microchannels were hydrolyzed to yield additional charged organic functional groups on the imprinted surface. The charged groups are carboxylate moieties that were also used as a means for the further reaction of different chemical species on the surface of the PETG microchannels. The microchannels were characterized by fluorescence mapping and electroosmotic flow (EOF) measurements. Experimental results demonstrated that different fabrication and channel treatment protocols resulted in different EOF rates. Laser-ablated channels had similar EOF rates (5.3+/-0.3 x 10(-4) cm(2)/Vs and 5.6+/-0.4 x 10(-4) cm(2)/Vs) to hydrolyzed imprinted channels (5.1+/-0.4 x 10(-4) cm(2)/Vs), which in turn demonstrated a somewhat higher flow rate than imprinted PETG channels that were not hydrolyzed (3.5+/-0.3 x 10(-4) cm(2)/Vs). Laser-ablated channels that had been chemically modified to yield amines displayed an EOF rate of 3.38+/- 0.1 x 10(-4) cm(2)/Vs and hydrolyzed imprinted channels that had been chemically derivatized to yield amines showed an EOF rate of 2.67+/-0.6 cm(2)/Vs. These data demonstrate that surface-bound carboxylate species can be used as a template for further chemical reactions in addition to changing the EOF mobility within microchannels. PMID:11891713

Henry, Alyssa C; Waddell, Emanuel A; Shreiner, Rubina; Locascio, Laurie E

2002-03-01

268

Remote explosive and chemical agent detection using broadly tunable mid-infrared external cavity quantum cascade lasers  

NASA Astrophysics Data System (ADS)

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 enable these kinds of targets to be protected without interrupting the flow of commerce. Tunable mid-IR laser technology offers the opportunity to detect explosives and other chemicals remotely and quickly. Most chemical compounds, including explosives, have their fundamental vibrational modes in the mid-infrared region (3 to 15?m). There are a variety of techniques that focus on examining interactions that have proven effective in the laboratory but could never work in the field due to complexity, size, reliability and cost. Daylight Solutions has solved these problems by integrating quantum cascade gain media into external tunable cavities. This has resulted in miniaturized, broadly tunable mid-IR laser sources. The laser sources have a capability to tune to +/- 5% of their center wavelength, which means they can sweep through an entire absorption spectrum to ensure very good detection and false alarm performance compared with fixed wavelength devices. These devices are also highly portable, operate at room temperature, and generate 10's to 100's of mW in optical power, in pulsed and continuous wave configurations. Daylight Solutions is in the process of developing a variety of standoff explosive and chemical weapon detection systems using this technology.

Rayner, Timothy; Weida, Miles; Pushkarsky, Michael; Day, Timothy

2007-04-01

269

Injecting parameters design and performance test of the pre-igniter for continuous wave DF/HF chemical lasers  

NASA Astrophysics Data System (ADS)

Combustion-driven continuous wave (CW) DF/HF chemical lasers cannot be inflamed successfully sometimes because the spark-plug-igniter is intolerant of ablation especially after long-time operation which deeply affected the reliability of the lasers. In this paper, a pre-igniter is designed as a new igniter system to produce F2 to solve the problem. Based on the engineering practices and the principle that high-intensity spontaneous combustion will happen when mixing F2 and H2. The results of NF3 and H2 reacting with different mole ratios were calculated by CEA software. The operation reliability of the pre-igniter, the mole concentration of F2 in the mixing gas, and the equilibrium temperature were validated by a series of experiments. The experimental results were consistent with the calculated data: with the mole ratio of NF3 to H2 increasing, the equilibrium temperature decreased gradually and finally leveled off; the mole concentration of F2 in the mixing gas first increased and then decreased, achieving the maximum of about 40% when the mole ratio of NF3 to H2 was about 3.2. Experimental results outlined that the pre-igniter performed reliability and could produce high output of F2. The ignition system with a pre-igniter and a spark plug could provide a new alternative for combustion-driven CW DF/HF chemical lasers.

Huang, Bing; Yuan, Shengfu; Yang, Lijia; Fang, Xiaoting

2014-11-01

270

Excimer laser-assisted chemical process for formation of hydrophobic surface of Si (001)  

NASA Astrophysics Data System (ADS)

Silicon (Si) wettability is one of the important parameters in the development of Si-based biosensing and lab-on-chip devices. We report on UV laser induced hydrophobicity of Si (001) wafers immersed in methanol during the irradiation with an ArF excimer laser. The irradiation with 800 pulses of the laser operating at 65 mJ/cm2 allowed to significantly increase the hydrophobicity of investigated samples as characterized by the static contact angle change from 77° to 103°. Owing to the irradiation with relatively low laser fluence, no measurable change in surface morphology of the irradiated samples has been observed with atomic force microscopy measurements. The nature of the hydrophobic surface of investigated samples is consistent with X-ray photoelectron spectroscopy analysis that indicates formation of Si-O-CH3 bonds on the surface of the laser-irradiated material.

Liu, Neng; Hassen, Walid M.; Dubowski, Jan J.

2014-10-01

271

System and method for laser assisted sample transfer to solution for chemical analysis  

DOEpatents

A system and method for laser desorption of an analyte from a specimen and capturing of the analyte in a suspended solvent to form a testing solution are described. The method can include providing a specimen supported by a desorption region of a specimen stage and desorbing an analyte from a target site of the specimen with a laser beam centered at a radiation wavelength (.lamda.). The desorption region is transparent to the radiation wavelength (.lamda.) and the sampling probe and a laser source emitting the laser beam are on opposite sides of a primary surface of the specimen stage. The system can also be arranged where the laser source and the sampling probe are on the same side of a primary surface of the specimen stage. The testing solution can then be analyzed using an analytical instrument or undergo further processing.

Van Berkel, Gary J; Kertesz, Vilmos

2014-01-28

272

Laser-Patterned Desorption Of GaAs In An Inverted Metalorganic Chemical Vapor Deposition Reactor  

NASA Astrophysics Data System (ADS)

A new laser-assisted processing technique for thinning or removing GaAs and AlGaAs quantum well (QW) layers during epitaxial growth is demonstrated. In the particular application reported here, epitaxial growth of an optoelectronic device structure is interrupted while the QW active layer is locally heated with superimposed Ar+ and Nd:YAG laser beams. The evaporation rate of the GaAs or AlGaAs is greatly increased by the optically induced heating, resulting in a local thinning of the QW. After exposure, epitaxial growth is resumed, burying the patterned QW within the crystal. Transmission electron microscopy and photoluminescence are used to characterize the spatial variation of the energy bandgap. Broad area and high power laser diodes are fabricated from the modified region of the wafer. As expected, the wavelength of operation varies from laser to laser, consistent with the spatial variation in the energy bandgap.

Epler, John E.; Treat, David W.; Chung, Harlan F.; Paoli, Thomas L.

1989-06-01

273

Influence of pulse duration on the doping quality in laser chemical processing (LCP)—a simulative approach  

NASA Astrophysics Data System (ADS)

The laser chemical processing (LCP) technique for the local doping of crystalline silicon solar cells is investigated. Here, a liquid jet containing a dopant source acts as a waveguide for pulsed laser light, which results in the melting and subsequent doping of the silicon surface. Typical LCP pulse durations are in the 15 ns range, giving satisfactory results for specific parameter settings. While great potential is assumed to exist, optimization of the pulse duration has until now not been deeply investigated, because it is hard to change this parameter in laser systems. Therefore, this paper accesses the influence of the pulse duration by a simulative approach. The model includes optics, thermodynamics, and melt dynamics induced by the liquid jet and dopant diffusion into the silicon melt. It is solved by coupling our existing finite differences Matlab-code LCPSim with the commercial fluid flow solver Ansys Fluent. Simulations of axial symmetric single pulses were performed for pulse durations ranging from 15 ns to 500 ns. Detailed results are given, which show that for longer pulse durations lateral heat conduction significantly homogenizes the inhomogeneous dopant distribution caused by the speckled intensity profile within the liquid jet cross section. The melt expulsion by the liquid jet is low enough that a sufficiently doped layer remains after full resolidification for all pulse durations. Last, temperature gradients are evaluated to give an indication on the amount of laser damage induced by thermal stress.

Fell, Andreas; Granek, Filip

2013-03-01

274

Tuning complex transition metal hydroxide nanostructures as active catalysts for water oxidation by a laser-chemical route.  

PubMed

Diverse transition metal hydroxide nanostructures were synthesized by laser-induced hydrolysis in a liquid precursor solution for alkaline oxygen evolution reaction (OER). Several active OER catalysts with fine control of composition, structure, and valence state were obtained including (Lix)[Ni0.66Mn0.34(OH)2](NO3)(CO3) · mH2O, Lix[Ni0.67Co0.33(OH)2](NO3)0.25(ORO)0.35 · mH2O, etc. An operate overpotential less than 0.34 V at current density of 10 mA cm(-2) was achieved. Such a controllable laser-chemical route for assessing complex nanostructures in liquids opens many opportunities to design novel functional materials for advanced applications. PMID:25723892

Niu, Kai-Yang; Lin, Feng; Jung, Suho; Fang, Liang; Nordlund, Dennis; McCrory, Charles C L; Weng, Tsu-Chien; Ercius, Peter; Doeff, Marca M; Zheng, Haimei

2015-04-01

275

Optically pumped deep-ultraviolet AlGaN multi-quantum-well lasers grown by metalorganic chemical vapor deposition  

NASA Astrophysics Data System (ADS)

A 245.3 nm deep ultraviolet optically pumped AlGaN based multiple-quantum-well laser operating at room temperature is described. Epitaxial growth was performed by metalorganic chemical vapor deposition on a c-plane bulk AlN substrate at a growth temperature of ~ 1130 °C. The wafer was fabricated into cleaved bars with a cavity length of ~1.45 mm and the lasing threshold was determined to be 297 kW/cm2 under pulsed 193 nm ArF excimer laser excitation. A further ~20% reduction in threshold pumping power density was observed with six pairs of SiO2/HfO2 distributed Bragg reflector deposited at the rear side of facets.

Liu, Yuh-Shiuan; Kao, Tsung-Ting; Satter, Md. Mahbub; Lochner, Zachary; Li, Xiao-Hang; Shen, Shyh-Chiang; Yoder, P. Douglas; Detchprohm, Theeradetch; Dupuis, Russell D.; Wei, Yong; Xie, Hongen; Fischer, Alec; Ponce, Fernando A.

2014-02-01

276

Chemical stabilization of laser dyes. Final report, 1 December 1984-28 February 1987  

SciTech Connect

Coumarin laser dyes upon excitation degrade to produce products that absorb at the lasing wavelength. This results in attenuation of dye laser output through interference of stimulated emission. The roles of singlet oxygen and excitation intensity on dye degradation were explored. Singlet oxygen is formed but its reactions with the dye do not appear to be a major cause of dye laser output deterioration. High light intensity results in dye-sensitized, solvent oligomerization to yield materials that interfere with dye-stimulated emission. 1, 4-Diazabicyclo2,2,2octane (DABCO)inhibits this oligomerization.

Koch, T.H.

1987-05-07

277

Laser ablation of maskant used in chemical milling process for aerospace applications  

Microsoft Academic Search

Chemical etching is a non-traditional machining process where a chemical solution is used to remove unwanted material by dissolution. To shape the etched area, before the process, a chemical inert paint (maskant) is applied on the surface. Then the maskant is trimmed away and the uncovered area is subject to the etching. The maskant cut could be obtained mechanically or

C. Leone; V. Lopresto; F. Memola Capece Minutolo; I. de Iorio; N. Rinaldi

2010-01-01

278

Identification of vapor-phase chemical warfare agent simulants and rocket fuels using laser-induced breakdown spectroscopy  

SciTech Connect

Application of laser-induced breakdown spectroscopy (LIBS) to the identification of security threats is a growing area of research. This work presents LIBS spectra of vapor-phase chemical warfare agent simulants and typical rocket fuels. A large dataset of spectra was acquired using a variety of gas mixtures and background pressures and processed using partial least squares analysis. The five compounds studied were identified with a 99% success rate by the best method. The temporal behavior of the emission lines as a function of chamber pressure and gas mixture was also investigated, revealing some interesting trends that merit further study.

Stearns, Jaime A.; McElman, Sarah E.; Dodd, James A.

2010-05-01

279

PHYSICO-CHEMICAL DYNAMICS OF NANOPARTICLE FORMATION DURING LASER DECONTAMINATION AND CHARACTERIZATION  

EPA Science Inventory

Improvement of understanding on nanoparticle production during simultaneous laser-based decontamination and characterization is imperative to the acceleration of decommission and deactivation (D&D) missions of US Department of Energy (DOE). Many researchers, mostly in material re...

280

SITE - EMERGING TECHNOLOGIES: LASER INDUCED PHOTO- CHEMICAL OXIDATIVE DESTRUCTION OF TOXIC ORGANICS IN LEACHATES AND GROUNDWATERS  

EPA Science Inventory

The technology described in this report has been developed under the Emerging Technology Program of the Superfund Innovative Technology Evaluation (SITE) Program to photochemically oxidize organic compounds in wastewater by applying ultraviolet radiation using an excimer laser. T...

281

Use of external cavity quantum cascade laser compliance voltage in real-time trace gas sensing of multiple chemicals  

NASA Astrophysics Data System (ADS)

We describe a prototype trace gas sensor designed for real-time detection of multiple chemicals. The sensor uses an external cavity quantum cascade laser (ECQCL) swept over its tuning range of 940-1075 cm-1 (9.30-10.7 ?m) at a 10 Hz repetition rate. The sensor was designed for operation in multiple modes, including gas sensing within a multi-pass Heriott cell and intracavity absorption sensing using the ECQCL compliance voltage. In addition, the ECQCL compliance voltage was used to reduce effects of long-term drifts in the ECQCL output power. The sensor was characterized for noise, drift, and detection of chemicals including ammonia, methanol, ethanol, isopropanol, Freon- 134a, Freon-152a, and diisopropyl methylphosphonate (DIMP). We also present use of the sensor for mobile detection of ammonia downwind of cattle facilities, in which concentrations were recorded at 1-s intervals.

Phillips, Mark C.; Taubman, Matthew S.; Kriesel, Jason

2015-01-01

282

Chemical-free inactivated whole influenza virus vaccine prepared by ultrashort pulsed laser treatment.  

PubMed

There is an urgent need for rapid methods to develop vaccines in response to emerging viral pathogens. Whole inactivated virus (WIV) vaccines represent an ideal strategy for this purpose; however, a universal method for producing safe and immunogenic inactivated vaccines is lacking. Conventional pathogen inactivation methods such as formalin, heat, ultraviolet light, and gamma rays cause structural alterations in vaccines that lead to reduced neutralizing antibody specificity, and in some cases, disastrous T helper type 2-mediated immune pathology. We have evaluated the potential of a visible ultrashort pulsed (USP) laser method to generate safe and immunogenic WIV vaccines without adjuvants. Specifically, we demonstrate that vaccination of mice with laser-inactivated H1N1 influenza virus at about a 10-fold lower dose than that required using conventional formalin-inactivated influenza vaccines results in protection against lethal H1N1 challenge in mice. The virus, inactivated by the USP laser irradiation, has been shown to retain its surface protein structure through hemagglutination assay. Unlike conventional inactivation methods, laser treatment did not generate carbonyl groups in protein, thereby reducing the risk of adverse vaccine-elicited T helper type 2 responses. Therefore, USP laser treatment is an attractive potential strategy to generate WIV vaccines with greater potency and safety than vaccines produced by current inactivation techniques. PMID:25423046

Tsen, Shaw-Wei David; Donthi, Nisha; La, Victor; Hsieh, Wen-Han; Li, Yen-Der; Knoff, Jayne; Chen, Alexander; Wu, Tzyy-Choou; Hung, Chien-Fu; Achilefu, Samuel; Tsen, Kong-Thon

2015-05-01

283

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

284

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·Hz-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·cm-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; Strämke, Siegfried; Röpcke, Jürgen

2011-08-01

285

Stabilization, injection and control of quantum cascade lasers, and their application to chemical sensing in the infrared.  

PubMed

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 and 20 microm, which includes the molecular fingerprint region of the infrared. 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 QCLs to optical cavities, achieving relative linewidths down to 5.6 Hz. We report injection 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, including the resonant sideband technique known as NICE-OHMS. Sensitivities of 9.7 x 10(-11) cm(-1) Hz(-1/2) have been achieved in pure nitrous oxide. PMID:15561632

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

2004-12-01

286

Elemental chemical analysis of submerged targets by double-pulse laser-induced breakdown spectroscopy.  

PubMed

Double-pulse laser-induced plasma spectroscopy (DP-LIPS) is applied to submerged targets to investigate its feasibility for elemental analysis. The role of experimental parameters, such as inter-pulse delay and detection time, has been discussed in terms of the dynamics of the laser-induced bubble produced by the first pulse and its confinement effect on the plasma produced by the second laser pulse. The analytical performance of this technique applied to targets in a water environment are discussed. The elemental analysis of submerged copper alloys by DP-LIPS has been compared with conventional (single-pulse) LIBS in air. Theoretical investigation of the plasma dynamics in water bubbles and open air has been performed. PMID:16544131

De Giacomo, A; Dell'Aglio, M; Casavola, A; Colonna, G; De Pascale, O; Capitelli, M

2006-05-01

287

Development of Efficient Mid-IR Interband Cascade Lasers for Chemical Sensing  

NASA Technical Reports Server (NTRS)

Significant progress has been made: Above room temperature (up to 350K) pulsed operation has been demonstrated. CW operation temperature has been raised up to 237 K. DFB IC lasers have been applied for the detection of trace gases such as CH4, HCl, and H2CO. Devices have been operated continuously over several hundred hours without degradation. Main challenge remains for many potential applications of ICLs. CW operation at room temperature and above with significant output powers. There is still significant room for improvement: Laser design and material quality - many parameters have not been optimized. Device fabrication and thermal management (passivation, better mounting, etc.). Significantly higher output power can be achieved with laser arrays.

Yang, Rui Q.; Hill, Cory J.; Yang, Baohua; Qiu, Yueming; Jan, Darrell

2006-01-01

288

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

289

Characterization of Nonpolar Lipids and Selected Steroids by Using Laser-Induced Acoustic Desorption/Chemical Ionization, Atmospheric Pressure Chemical Ionization, and Electrospray Ionization Mass Spectrometry†  

PubMed Central

Laser-induced acoustic desorption (LIAD) combined with ClMn(H2O)+ chemical ionization (CI) was tested for the analysis of nonpolar lipids and selected steroids in a Fourier-transform ion cyclotron resonance mass spectrometer (FT-ICR). The nonpolar lipids studied, cholesterol, 5?-cholestane, cholesta-3,5-diene, squalene, and ?-carotene, were found to solely form the desired water replacement product (adduct-H2O) with the ClMn(H2O)+ ions. The steroids, androsterone, dehydroepiandrosterone (DHEA), estrone, estradiol, and estriol, also form abundant adduct-H2O ions, but less abundant adduct-2H2O ions were also observed. Neither (+)APCI nor (+)ESI can ionize the saturated hydrocarbon lipid, cholestane. APCI successfully ionizes the unsaturated hydrocarbon lipids to form exclusively the intact protonated analytes. However, it causes extensive fragmentation for cholesterol and the steroids. The worst case is cholesterol that does not produce any stable protonated molecules. On the other hand, ESI cannot ionize any of the hydrocarbon analytes, saturated or unsaturated. However, ESI can be used to protonate the oxygen-containing analytes with substantially less fragmentation than for APCI in all cases except for cholesterol and estrone. In conclusion, LIAD/ClMn(H2O)+ chemical ionization is superior over APCI and ESI for the mass spectrometric characterization of underivatized nonpolar lipids and steroids. PMID:21528012

Jin, Zhicheng; Daiya, Shivani; Kenttämaa, Hilkka I.

2011-01-01

290

Characterization of nonpolar lipids and steroids by using laser-induced acoustic desorption/chemical ionization, atmospheric pressure chemical ionization, and electrospray ionization mass spectrometry  

SciTech Connect

Laser-induced acoustic desorption (LIAD) combined with ClMn(H{sub 2}O){sup +} chemical ionization (CI) was tested for the analysis of nonpolar lipids and selected steroids in a Fourier-transform ion cyclotron resonance mass spectrometer (FT-ICR). The nonpolar lipids studied, cholesterol, 5?-cholestane, cholesta-3,5-diene, squalene, and ?-carotene, were found to solely form the desired water replacement product (adduct-H{sub 2}O) upon reaction with the ClMn(H{sub 2}O){sup +} ions. The steroids, androsterone, dehydroepiandrosterone (DHEA), estrone, estradiol, and estriol, also form abundant adduct-H{sub 2}O ions, but less abundant adduct-2H{sub 2}O ions were also observed. Neither (+)APCI nor (+)ESI can ionize the saturated hydrocarbon lipid, cholestane. APCI successfully ionizes the unsaturated hydrocarbon lipids to form exclusively the intact protonated analytes. However, it causes extensive fragmentation for cholesterol and the steroids. The worst case is cholesterol that does not produce any stable protonated molecules. On the other hand, ESI cannot ionize any of the hydrocarbon analytes, saturated or unsaturated. However, ESI can be used to protonate the oxygen-containing analytes with substantially less fragmentation than for APCI in all cases except for cholesterol and estrone. In conclusion, LIAD/ClMn(H{sub 2}O){sup +} chemical ionization is superior over APCI and ESI for the mass spectrometric characterization of underivatized nonpolar lipids and steroids.

Jin, Z.; Daiya, S.; Kenttämaa, Hilkka I.

2011-01-01

291

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...

292

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 ...

293

An embedded stripe Be-implanted GaAs/GaAlAs double heterostructure laser grown by metalorganic chemical vapor deposition  

NASA Astrophysics Data System (ADS)

A planar GaAs/GaAlAs double heterostructure stripe geometry laser with laterally effective step change of the refraction index is described. The planar structure is achieved by regrowing an embedded stripe selectively on a Be-implanted stripe, using metalorganic chemical vapor deposition. The near-field and the far-field patterns confirm the index guiding mechanism of the light. The threshold current is comparable to those of similar lasers grown by uninterrupted growth process either by liquid phase epitaxy or by metalorganic chemical vapor deposition.

Fekete, D.

1984-11-01

294

Optical-chemical relationships for carbonaceous aerosols observed at Jeju Island, Korea with a 3-laser photoacoustic spectrometer  

NASA Astrophysics Data System (ADS)

Transport of aerosols in pollution plumes from the mainland Asian continent was observed in situ at Jeju, South Korea during the Cheju Asian Brown Cloud Plume-Asian Monsoon Experiment (CAPMEX) field campaign throughout August and September 2008 using a 3-laser photoacoustic spectrometer. Transport of mixed sulfate, carbonaceous, and nitrate aerosols from various Asian pollution plumes to Jeju accounted for 76% of the deployment days, showing large variations in their measured chemical and optical properties. Our analysis of eight distinct episodes, spanning a wide range of chemical composition, optical properties, and source regions, reveals that at episodes with higher OC/SO2-4 and NO-3/SO2-4 composition ratios exhibit lower single scatter albedo at shorter wavelengths (?405); significantly lower [?405meas = 0.79±0.06, ?405calc = 0.86±0.01] than predicted by an optical model that assumes constant complex index of refraction with wavelength (an optical model of soot). We attribute this discrepancy to enhanced absorption by organic material. Organic carbon absorption accounts for up to 50% of the measured aerosol absorption at 405 nm for the high OC/SO2-4 episode. Coatings of elemental carbon aerosol cores are hypothesized to increase absorption by factors up to 6 at visible wavelengths. Carbonaceous aerosol absorption can alter global radiative forcing estimates substantially, underscoring the need to understand and predict chemical composition effects on optical properties.

Flowers, B. A.; Dubey, M. K.; Mazzoleni, C.; Stone, E. A.; J.. Schauer, J.; Kim, S.-W.

2010-04-01

295

Fabrication of honeycomb texture on poly-Si by laser interference and chemical etching  

NASA Astrophysics Data System (ADS)

In this paper, we present a laser-interference method to fabricate honeycomb textures on poly-Si wafer for reflection reduction. When exposed to three interfering pulsed laser beams at 532 nm, the Si surface was periodically melted in accordance with the interference pattern. As a result, concave holes were generated on the surface because the melted material overflowed and condensed at the periphery. Subsequent acid etching revealed uniform and clean honeycomb textures. The texture depth could be controlled by varying the irradiation condition and a minimum reflectance of 10% was obtained. Transmission electron microscopy analysis showed that no irradiation-induced damage remained after etching. This approach can be a cost-effective alternative to lithographic processes for fabricating high-efficiency poly-Si solar cells.

Yang, Bogeum; Lee, Myeongkyu

2013-11-01

296

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

297

Chemical sensing with pulsed QC-DFB lasers operating at 15.6 micrometers  

NASA Technical Reports Server (NTRS)

Pulsed thermoelectrically cooled QC-DFB lasers operating at 15.6 micrometers were characterized for spectroscopic gas sensing applications. A new method for wavelength scanning based on repetition rate modulation was developed. A non-wavelength-selective pyroelectric detector was incorporated in the sensor configuration giving the advantage of room-temperature operation and low cost. Absorption lines of CO2 and H2O were observed in ambient air, providing information about the concentration of these species.

Kosterev, A. A.; Curl, R. F.; Tittel, F. K.; Rochat, M.; Beck, M.; Hofstetter, D.; Faist, J.

2002-01-01

298

Laser-Shot-Induced Chemical Reactions inside Nanotubes: a TDDFT investigation  

NASA Astrophysics Data System (ADS)

We present the application of the time-dependent density functional theory (TDDFT) on ultrafast laser pulse which induces dynamics in molecules encapsulated by a nanotube. A strong laser pulse polarized perpendicular to the tube axis induces a giant bond-stretch of an HCl molecule inside both C and BN nanotubes. Depending on the initial orientation of the HCl molecule, the subsequent laser-induced dynamics is different [1]. We also observed a radial motion of the nanotube and vacancies appear on the tube wall when the HCl is perpendicular to tube axis. Furthermore, the disintegration of HCl molecules took place when their molecular axis tilted to tube axis. These simulations are important to analyze light-induced nanochemistry and manipulation of nanostructures encapsulated in organic and inorganic nanotubes. The computational scheme used in present work was a combination of the molecular dynamics and real-time propagation of electron wave functions under presence of strong optical field [2,3]. The energy conservation rule was checked to monitor the numerical stability. [1] Y. Miyamoto, H. Zhang, and A, Rubio, submitted., [2] O. Sugino and Y. Miyamoto, Phys. Rev. B59, 2579 (1999). [3] A. Castro, E. Rasanen, A. Rubio and E. K. U. Gross, Eur. Phys. Lett. 87, 53001 (2009).

Zhang, Hong; Miyamoto, Yoshiyuki; Rubio, Angel

2011-03-01

299

Kr/sup +/ laser-induced chemical vapor deposition of W  

SciTech Connect

Kr/sup +/ laser-induced pyrolytic direct writing of W stripes by H/sub 2/ reduction of WF/sub 6/ has been investigated. The reproducibility of the process and the morphology and electrical properties of deposits depend heavily on the partial pressures of both WF/sub 6/ and H/sub 2/; the best results have been obtained with p(WF/sub 6/) = 5 mbar and 100 mbarless than or equal top(H/sub 2/)less than or equal to800 mbar. For a laser focus of 2w/sub 0/ = 7 ..mu..m and laser powers between 30 and 200 mW, the widths of stripes varied between 1.5 and 15 ..mu..m with corresponding thicknesses between 0.1 to 3 ..mu..m. The width of stripes is independent of the scanning speed within the range 20 ..mu..m/sless than or equal toV/sub s/ less than or equal to400 ..mu..m/s. The electrical resistivities of these stripes were about a factor of 1.3--2.3 larger than the bulk value.

Zhang, G.Q.; Szoerenyi, T.; Baeuerle, D.

1987-07-15

300

Laser weapons  

Microsoft Academic Search

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

Kosta Tsipis

1981-01-01

301

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

NASA Astrophysics Data System (ADS)

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

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

2003-03-01

302

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

303

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

304

Comparison of the structural and chemical composition of two unique micro/nanostructures produced by femtosecond laser interactions on nickel  

SciTech Connect

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. [Department of Electrical Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68588 (United States)] [Department of Electrical Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68588 (United States)

2013-09-16

305

Chemical generation of electronically excited nitrogen N2(A3 epsilon+ mu) and lasers on electronic transitions  

NASA Astrophysics Data System (ADS)

A numerical modeling of H2-F-HN3 and H2-F-NF2 flames was done in order to investigate the use of these flames as a pumping source for a N2(A)-IF electronic energy transfer (EET) laser. Equations for concentrations of different chemical species, populations of the ground and excited states of molecules, and energy-exchange processes were included in the model. The main processes determining the kinetics of electronically excited particles in H2-F-NF2 and H2-F-NH3 flames leading to the formation of N2(A) are listed. Results indicate the possibility of high concentrations of NA2(A) generation in these media. Electronically excited NA2(A) may be used as an energy donor to pump acceptors radiating in the visible region and the media considered appear to be promising sources for optical pumping.

Dvoriankin, A. N.; Makarov, V. N.

1991-02-01

306

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

307

CONTROL OF LASER RADIATION PARAMETERS: Two-coordinate control of the radiation pattern of a chemical non-chain electric-discharge DF laser by using space—time 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

308

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 (CdCl 2) and cadmium acetate (Cd(CH 3COO) 2) solutions were employed as Cd 2+ source while a freshly prepared sodium selenosulfite (Na 2SeSO 3) solution provided the Se 2- 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/cm 2 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-García, J. R.; Rangel-Salinas, E.

2008-05-01

309

Volume 70, number 1 CHEMICAL PHYSICS LETI'ERS 15 February 1980 SEMICLASSICAL THEORY OF WBRATIONAL COLLISIONS IN A LASER FtELD  

E-print Network

Volume 70, number 1 CHEMICAL PHYSICS LETI'ERS 15 February 1980 SEMICLASSICAL THEORY OF WBRATIONAL COLLISIONS IN A LASER FtELD shlh-I CHU Department of CJzemJstry. UnwersHy of Kansas. Lawrence. Kansas 6604.5. USA Received 26 November 1979 A semtclasslcal theory of multlphoton enhancement of vibrational

Chu, Shih-I

310

Facilities: NHMFL 9.4 Tesla Fourier Transform Ion Cyclotron Resonance Mass Spectrometer Citation: Atmospheric Pressure Laser-Induced Acoustic Desorption Chemical Ionization Mass Spectrometry  

E-print Network

: Atmospheric Pressure Laser-Induced Acoustic Desorption Chemical Ionization Mass Spectrometry for Analysis hydrocarbons (the primary components of gasoline) are difficult to analyze by mass spectrometry, because with the ability of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to analyze complex

Weston, Ken

311

Laser-induced Fluorescence Spectroscopy for applications in chemical sensing and optical refrigeration  

NASA Astrophysics Data System (ADS)

Laser-induced breakdown spectroscopy (LIBS) is an innovative technique that has been used as a method for fast elemental analysis in real time. Conventional ultraviolet-visible (UV-VIS) LIBS has been applied to detect the elemental composition of different materials, including explosives, pharmaceutical drugs, and biological samples. The extension of conventional LIBS to the infrared region (˜1-12 mum) promises to provide additional information on molecular emission signatures due to rotational-vibrational transitions. In this research, a pulsed Nd: YAG laser operating at 1064 nm was focused onto several sodium compounds (NaCl, NaClO3, Na2CO3 and NaClO4) and potassium compounds (KCl, KClO3, K2CO3 and KClO4) to produce an intense plasma at the target surface. Several distinct infrared (IR) atomic emission signatures were observed from all sodium and potassium containing compounds. The atomic emission lines observed from the investigated samples matched assigned transitions of neutral sodium and potassium atoms published in the National Institute of Standards and Technology (NIST) atomic database. In addition to the intense atomic lines, the rst evidence of molecular LIBS emission structures were observed at ˜10.0 m in KClO3 and NaClO3 for the chlorate anion (ClO3 --1), at ˜6.7 to 8.0 mum in KNO3 and NaNO 3 for the nitrate anion (NO3--1 ), ˜8.0 to 10.0 mum in KClO4 and NaClO4 for perchlorate anion (ClO4--1 ), and ˜6.88 mum and 11.53 mum in Na2CO3 for the carbonate anion (CO3--1 ). The observed molecular emission showed strong correlation with the conventional Fourier Transform Infrared Spectrometry (FTIR) absorption spectra of the investigated samples. IR LIBS was also applied to determine the limit of detection (LOD) for the perchlorate anion in KClO4 using the 8.0 -11.0 mum IR-LIBS emission band. The calibration curve of ClO4 in KClO4 was constructed using peak and integrated emission intensities for known concentrations of mixed KClO4/NH4NO3 samples. The limit of detection for ClO4, was determined to be 14.7 +/- 0.5 wt%/wt for the given experimental conditions. In the second part of this research, the temperature-dependent absorption and emission properties of Tm doped KPb2Cl5 (KPC) and KPb2Br5 (KPB) were evaluated for applications in laser cooling. A Tm doped Y3Al5O12 (YAG) crystal was also included for comparative studies. Under laser pumping, all crystals exhibited broad IR fluorescence at room temperature with a mean fluorescence wavelength of ˜1.82 mum and bandwidth of 0.14 mum (FWHM) for Tm:KPC/KPB and ˜1.79 mum for Tm:YAG. Initial experiments on laser-induced heating/cooling were performed using a combined IR imaging and fluorescence thermometry setup. Employing a continuous-wave laser operating at 1.907 mum, Tm: KPC and Tm: KPB crystals revealed a very small heat load resulting in temperature increase of ˜ 0.3 ( +/- 0.1)°C. The heat loading in Tm:YAG was signicantly larger and resulted in a temperature increase of ˜0.9 (+/-0.1)°C. The results derived from IR imaging were also conrmed by the fluorescence thermometry experiments, which showed only minimal changes in the FIR intensity ratio of the green Er3+ fluorescence lines from Er:KPC.

Kumi Barimah, Eric

312

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

313

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

314

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

315

Laser fluorescence studies of the chemical interactions of sodium species with sulfur bearing fuels  

NASA Technical Reports Server (NTRS)

By using a large matrix of fuel rich and fuel lean H2/O2/N2 and fuel rich C2H2/O2/N2 flames, the behavior of sodium and its interactions with sulfur at high temperatures was extensively characterized. OH concentrations were measured for each flame using the previously validated laser induced fluorescence technique. Sodium atomic concentrations were obtained by the saturated laser fluorescence method. Measurements were made in the absence and presence of up to 2% sulfur. In oxygen rich systems sodium is depleted by NaO2 and NaOH formation. The relative amounts of each are controlled by the degree of nonequilibration of the flame radicals and by the temperature. The bond strength of NaO2 was established. For the first time, a complete understanding of the complex behavior of sodium in fuel lean H2/O2 flames has emerged and computer modeling has permitted various rate constants of Na, NaO2 and NaOH reactions to be approximately fixed.

Steinberg, M.; Schofield, K.

1983-01-01

316

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

317

High spatial resolution chemical imaging of surfaces by combination of a field-emission ion gun and intense laser radiation  

NASA Astrophysics Data System (ADS)

Scanning surface analysis by laser ionization (SALI) has been developed to provide chemical images of surfaces. SALI is a recently developed technique that uses nonselective photoionization of sputtered or desorbed neutral atoms and molecules emitted from a sample close to but above (~ 1 mm) the surface, followed by time-of-flight mass spectrometry (TOF-MS). In this new development, specifically nonresonant multiphoton ionization (NRMPI) and sputtering using a field-emission liquid-metal ion gun are employed. The reason for decoupling the sputtering and ionization is that in nearly all situations, the neutral particles constitute the dominant channel for the sputtered material; therefore, SALI is much less sensitive than scanning secondary ion mass spectrometry (SIMS) to changes in the chemical matrix, and also SALI delivers a much more uniform sensitivity between different species than SIMS. Furthermore, the mass multiplex advantage of TOF-MS allows an entire mass spectrum of the sample to be mapped out in one scan of the surface. Initial results with a transmission electron microscopy (TEM) grid and an electronic device are presented.

Mouncey, Simon P.; Moro, Lorenza; Becker, Christopher H.

1991-10-01

318

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

Microsoft Academic Search

Chemically amplified photoresists require a post exposure bake (PEB), typically on a hot plate at 90-150°C 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,

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

2010-01-01

319

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

320

Direct (222 nm) photopolymerisation of acrylates. A laser flash photolysis and quantum chemical study  

NASA Astrophysics Data System (ADS)

Direct excitation of acrylates at 222 nm leads primarily to the formation of a triplet state which is calculated to be highly localised at the vinyl double bond. This triplet state undergoes different reactions like inter- and intramolecular hydrogen transfer as well as addition to a ground state molecule. The latter process, leading to a true biradical, proceeds with a bimolecular rate constant of 7×10 8 (butyl acrylate) or 2×10 9 dm 3 mol -1 s -1 (butanediol diacrylate). In oxygen containing solutions, peroxyl radicals are formed with strong absorption bands around 260 and 430 nm. Quantum chemical calculations support the interpretation.

Knolle, W.; Scherzer, T.; Naumov, S.; Mehnert, R.

2003-06-01

321

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

322

Chemical kinetic studies of atmospheric reactions using tunable diode laser spectroscopy  

NASA Technical Reports Server (NTRS)

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 while minimizing both the sample volume and the interference fringes inherent in conventional 'White' cells. Computerized signal processing using rapid scan (300 kHz), sweep integration with 100 percent duty cycle allows substantial noise reduction while retaining the advantages of using direct absorption for absolute absorbance measurements and simultaneous detection of multiple species. Peak heights and areas are determined by curve fitting using nonlinear least square methods. We have applied these techniques to measurements of: (1) heterogeneous uptake chemistry of atmospheric trace gases (HCl, H2O2, and N2O5) on aqueous and sulfuric acid droplets; (2) vapor pressure measurements of nitric acid and water over prototypical stratospheric aerosol (nitric acid trihydrate) surfaces; and (3) discharge flow tube kinetic studies of the HO2 radical using isotopic labeling for product channel and mechanistic analysis. Results from each of these areas demonstrate the versatility of TDL absorption spectroscopy for atmospheric chemistry applications.

Worsnop, Douglas R.; Nelson, David D.; Zahniser, Mark S.

1993-01-01

323

Chemical Production by Pulse-Laser Irradiation on Ices: Simulation of Impact Shock-Induced Chemistry on Icy Satellites  

NASA Astrophysics Data System (ADS)

Several icy satellites of the outer planets show a variety of impact cratering features. The effect of impact by extraterrestrial objects into the surface is commonly related to physical changes. Most of the research applied to impacts on ices has been developed to study and understand the cratering formation process and their physical, geophysical characteristics. Chemical changes and synthesis occurring on icy planetary surfaces are generally explained by the influence of UV photons and high-energy charged particles on ices. Nonetheless, impact process onto ices could be a source of local or global endogenic process and could be especially advantageous as an efficient energy source for driving interesting chemistry. Upon impact on icy surface, the kinetic energy of the impacting body is transferred to the ground liberating a great deal of stress energy which could initiate in situ aqueous melts of the ice, hydrolysis and other chemical reactions in the fracture zone beneath the crater. Here we present a novel experimental method to study the chemistry in planetary ices induced by impact shocks. Impact shocks were simulated in laboratory using a powerful pulsed laser (Q-switched Nd-YAG laser, 1064 nm). We have irradiated at 77K icy mixtures of H2O / CO2, H2O / Na2CO3, H2O / CH3OH and finally H2O / CH3OH / (NH4)2SO4. GC-MS and FTIR analyses show that hydrogen peroxide, carbon monoxide and methanol are formed in irradiated H2O / CO2 ices. Ice containing sodium carbonate generates under simulated impact CO and CO2 which are also produced in impacted H2O / CH3OH and H2O / CH3OH / (NH4)2SO4 ices. But, in both latter icy mixtures, methane and more complex molecules are also formed. We have detected acetone, methyl formate and dimethyl formal. Adding ammonium sulfate to ice containing methanol induces the production of N2O, HCN and CH3CN.

Nna-Mvondo, Delphine; Khare, B. N.; Ishihara, T.; McKay, C. P.; Cruikshank, D. P.; Borucki, W. J.

2007-12-01

324

Comparison of silver nanoparticles confined in nanoporous silica prepared by chemical synthesis and by ultra-short pulsed laser ablation in liquid  

NASA Astrophysics Data System (ADS)

Hexagonally ordered mesoporous silica materials, MCM-41 and SBA-15, have been synthesized and loaded with Ag nanoparticles, utilizing both chemical synthesis and ultra-short pulsed laser ablation in liquid. In laser ablation, a silver target, immersed in aqueous suspension of ordered mesoporous silica SBA-15, was irradiated by ultra-short laser pulses to generate silver nanoparticles. For comparison, samples of similar silver contents were prepared either by incorporating silver into the SBA-15 during a hydrothermal synthesis or by introducing silver in MCM-41 by template ion-exchange. Samples were characterized by XRD, N2 physisorption, TEM and UV-vis spectroscopy. All preparations contained significant amount of 5-50 nm size silver agglomerates on the outer surface of the silica particles. The laser ablation process did not cause significant destruction of the SBA-15 structure and metallic silver (Ag0) nanoparticles were mainly generated. It is demonstrated that by laser ablation in aqueous silica suspension smaller and more uniform metallic silver particles can be produced and loaded on the surface of the silica support than by synthesis procedures. Catalytic properties of the samples have been tested in the total oxidation of toluene. Because of its favorable Ag dispersity, the Ag/SBA-15 catalyst, generated by the laser ablation method, had better catalytic stability and, relative to its Ag load, higher activity than the conventional Ag/SBA-15 preparations.

Szegedi, Á.; Popova, M.; Valyon, J.; Guarnaccio, A.; De Stefanis, A.; De Bonis, A.; Orlando, S.; Sansone, M.; Teghil, R.; Santagata, A.

2014-10-01

325

Sixteen micron chemical laser study. Quarterly technical progress report, January 1, 1978March 31, 1978. Report No. 2. [In Br--F system for UFâ laser isotope separation  

Microsoft Academic Search

Objective is to develop new coherent sources in the 16..mu.. region, for laser isotope separation of UFâ. No laser emission in this region was detected in gaseous mixtures containing Br and F sources in a longitudinally discharged flow tube device, a multi-pin transversely discharged flow tube device, and a shock tube. (DLC)

Blauer

1978-01-01

326

Design and chemical synthesis of iodine-containing molecules for application to solar-pumped I* lasers  

NASA Technical Reports Server (NTRS)

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 correlate with increasing radical stability. This expectation was based upon the analysis, previously reported, of the structures and absorption maxima of compounds studied earlier. A previously unknown substance was prepared, a prototypical target molecule, perfluoro-3-iodocyclopent-1-ene. It was obtained by reaction of perfluorocyclopentene with sulfur trioxide under the influence of antimony pentafluoride catalyst, followed by treatment of the resulting allylic fluorosulfonate with sodium iodide in sulfoland solvent. Preliminary data indicate that the absorption maximum for the iodo fluorocarbon is not shifted significantly to longer wavelength. It is not certain whether this result reflects an unexpected influence of the cyclic structure upon the position of the absorption maximum.

Shiner, C. S.

1986-01-01

327

A hyphenated optical trap capillary electrophoresis laser induced native fluorescence system for single-cell chemical analysis  

PubMed Central

Single-cell measurements allow a unique glimpse into cell-to-cell heterogeneity; even small changes in selected cells can have a profound impact on an organism’s physiology. Here an integrated approach to single-cell chemical sampling and assay are described. Capillary electrophoresis (CE) with laser-induced native fluorescence (LINF) has the sensitivity to characterize natively-fluorescent indoles and catechols within individual cells. While the separation and detection approaches are well established, the sampling and injection of individually selected cells requires new approaches. We describe an optimized system that interfaces a single-beam optical trap with CE and multichannel LINF detection. A cell is localized within the trap and then the capillary inlet is positioned near the cell using a computer-controlled micromanipulator. Hydrodynamic injection allows cell lysis to occur within the capillary inlet, followed by the CE separation and LINF detection. The use of multiple emission wavelengths allows improved analyte identification based on differences in analyte fluorescence emission profiles and migration time. The system enables injections of individual rat pinealocytes and quantification of their endogenous indoles, including serotonin, N-acetyl-serotonin, 5-hydroxyindole-3-acetic acid, tryptophol and others. The amounts detected in individual cells incubated in 5-hydroxytryptophan ranged from 10?14 mol to 10?16 mol, an order of magnitude higher than observed in untreated pinealocytes. PMID:22543409

Cecala, Christine; Rubakhin, Stanislav S.; Mitchell, Jennifer W.; Gillette, Martha U.; Sweedler, Jonathan V.

2013-01-01

328

High Temperature Nanocomposites For Nuclear Thermal Propulsion and In-Space Fabrication by Hyperbaric Pressure Laser Chemical Vapor Deposition  

NASA Astrophysics Data System (ADS)

Nuclear Thermal Propulsion (NTP) is an indispensable technology for the manned exploration of the solar system. By using Hyperbaric Pressure Laser Chemical Vapor Deposition (HP-LCVD), the authors propose to design and build a promising next-generation fuel element composed of uranium carbide UC embedded in a latticed matrix of highly refractory Ta4HfC5 for an NTP rocket capable of sustaining temperatures up to 4000 K, enabling an Isp of up to 1250 s. Furthermore, HP-LCVD technology can also be harnessed to enable 3D rapid prototyping of a variety of materials including metals, ceramics and composites, opening up the possibility of in-space fabrication of components, replacement parts, difficult-to-launch solar sails and panels and a variety of other space structures. Additionally, rapid prototyping with HP-LCVD makes a feasible "live off the land" strategy of interplanetary and interstellar exploration ­ the precursors commonly used in the technology are found, often in abundance, on other solar system bodies either as readily harvestable gas (e.g. methane) or as a raw material that could be converted into a suitable precursor (e.g. iron oxide into ferrocene on Mars).

Maxwell, J. L.; Webb, N. D.; Espinoza, M.; Cook, S.; Houts, M.; Kim, T.

329

Periodic nanostructuring of Er /Yb-codoped IOG1 phosphate glass by using ultraviolet laser-assisted selective chemical etching  

NASA Astrophysics Data System (ADS)

The patterning of submicron period (?500nm) Bragg reflectors in the Er /Yb-codoped IOG1 Schott, phosphate glass is demonstrated. A high yield patterning technique is presented, wherein high volume damage is induced into the glass matrix by exposure to intense ultraviolet 213nm, 150ps Nd:YAG laser radiation and, subsequently, a chemical development in potassium hydroxide (KOH)/ethylenediamine tetra-acetic acid (EDTA) aqueous solution selectively etches the exposed areas. The electronic changes induced by the 213nm ultraviolet irradiation are examined by employing spectrophotometric measurements, while an estimation of the refractive index changes recorded is provided by applying Kramers-Kronig transformation to the absorption change data. In addition, real time diffraction efficiency measurements were obtained during the formation of the volume damage grating. After the exposure, the growth of the relief grating pattern in time was measured at fixed time intervals and the dependence of the grating depth on the etching time and exposure conditions is presented. The gratings fabricated are examined by atomic and scanning electron microscopies to reveal the relief topology of the structures. Gratings with average depth of 120nm and excellent surface quality were fabricated by exposing the IOG1 phosphate glass to 36 000 pulses of 208mJ/cm2 energy density, followed by developing in the KOH/EDTA agent for 6min.

Pappas, C.; Pissadakis, S.

2006-12-01

330

Direct monitoring of chemical transformations by combining thin layer chromatography with nanoparticle-assisted laser desorption/ionization mass spectrometry.  

PubMed

A nanomaterial-assisted method that combines thin layer chromatography (TLC) with matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) was developed to directly monitor chemical transformations. A substrate-dependent extraction strategy was studied and successfully used to identify target molecules from the depths of a developed TLC plate. By using this strategy, a hydrophobic sample of interest was enriched on the surface of the TLC plate in the presence of acetonitrile, in contrast to using water and methanol to identify hydrophilic samples. The successful enrichment of samples by specific solvents provided stable desorption/ionization efficiencies of compounds of interest and led to very good sensitivity near the attomole scale. The method was then used to monitor 4-dimethylaminopyridine (DMAP)-catalyzed acylation in preparation of bifunctional sulfonamides. The labile DMAP-acyl intermediate and final sulfonamide product were clearly identified on TLC plates without external purification or sample preparation. Furthermore, in combination with collision-induced dissociation (CID) to provide structural information, the technique was successfully used in the natural product discovery of anti-inflammatory flavonoids from Helminthostachys zeylanica, a traditional Chinese herb. The newly proposed method provides a very low background from silica supports or organic matrices in the low molecular weight range (100-1000 Da). The technique may greatly accelerate studies of metabolomics, drug discovery, and organic synthesis. PMID:23330148

Chen, Chun-Chi; Yang, Yung-Lin; Ou, Chun-Lin; Chou, Chih-Hung; Liaw, Chih-Chuang; Lin, Po-Chiao

2013-03-01

331

First-Principles Simulations of Chemical Reactions in an HCl Molecule Embedded inside a C or BN Nanotube Induced by Ultrafast Laser Pulses  

NASA Astrophysics Data System (ADS)

We show by first-principles simulations that ultrafast laser pulses induce different chemical reactions in a molecule trapped inside a nanotube. A strong laser pulse polarized perpendicular to the tube axis induces a giant bond stretch of an encapsulated HCl molecule in semiconducting carbon nanotube or in a BN nanotube. Depending on the initial orientation of the HCl molecule, the subsequent laser-induced dynamics is different: either complete disintegration or rebonding of the HCl molecule. Radial motion of the nanotube is always observed and a vacancy appears on the tube wall when the HCl is perpendicular to the tube axis. Those results are important to analyze confined nanochemistry and to manipulate molecules and nanostructures encapsulated in organic and inorganic nanotubes.

Miyamoto, Yoshiyuki; Zhang, Hong; Rubio, Angel

2010-12-01

332

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

Microsoft Academic Search

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

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

333

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

334

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

335

Laser-assisted hatching of embryos is better than the chemical method for enhancing the pregnancy rate in women with advanced age  

Microsoft Academic Search

Objective: Assisted hatching may enhance embryo implantation. This study was conducted to examine the efficacy of the laser- and chemical-assisted hatching for promotion of implantation (IR), pregnancy (PR), and delivery rate (DR) in older women undergoing IVF cycles.Design: Prospective study.Setting: An IVF unit of a medical center.Patient(s): A total of 601 embryos from 141 women aged ?38 years underwent controlled

Yao-Yuan Hsieh; Chun-Chia Huang; Tzu-Chun Cheng; Chi-Chen Chang; Horng-Der Tsai; Maw-Sheng Lee

2002-01-01

336

Airborne intercomparison of HOx measurements using laser-induced fluorescence and chemical ionization mass spectrometry during ARCTAS  

NASA Astrophysics Data System (ADS)

The hydroxyl (OH) and hydroperoxyl (HO2) radicals, collectively called HOx, play central roles in tropospheric chemistry. Accurate measurements of OH and HO2 are critical to examine our understanding of atmospheric chemistry. Intercomparisons of different techniques for detecting OH and HO2 are vital to evaluate their measurement capabilities. Three instruments that measured OH and/or HO2 radicals were deployed on the NASA DC-8 aircraft throughout Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) in the spring and summer of 2008. One instrument was the Penn State Airborne Tropospheric Hydrogen Oxides Sensor (ATHOS) for OH and HO2 measurements based on Laser-Induced Fluorescence (LIF) spectroscopy. A second instrument was the NCAR Selected-Ion Chemical Ionization Mass Spectrometer (SI-CIMS) for OH measurement. A third instrument was the NCAR Peroxy Radical Chemical Ionization Mass Spectrometer (PeRCIMS) for HO2 measurement. Formal intercomparison of LIF and CIMS was conducted for the first time on a same aircraft platform. The three instruments were calibrated by quantitative photolysis of water vapor by ultraviolet (UV) light at 184.9 nm with three different calibration systems. The absolute accuracies were ±32% (2?) for the LIF instrument, ±65% (2?) for the SI-CIMS instrument, and ±50% (2?) for the PeRCIMS instrument. In general, good agreement was obtained between the CIMS and LIF measurements of both OH and HO2 measurements. Linear regression of the entire data set yields [OH]CIMS = 0.89 × [OH]LIF + 2.8 × 104 cm-3 with a correlation coefficient r2 = 0.72 for OH, and [HO2]CIMS = 0.86 × [HO2]LIF + 3.9 parts per trillion by volume (pptv, equivalent to pmol mol-1) with a correlation coefficient r2 = 0.72 for HO2. In general, the difference between CIMS and LIF instruments for OH and HO2 measurements can be explained by their combined measurement uncertainties. Comparison with box model results shows some similarities for both the CIMS and LIF measurements. First, the observed-to-modeled HO2 ratio increases greatly for higher NO mixing ratios, indicating that the model may not properly account for HOx sources that correlate with NO. Second, the observed-to-modeled OH ratio increases with increasing isoprene mixing ratios, suggesting either incomplete understanding of isoprene chemistry in the model or interferences in the measurements in environments where biogenic emissions dominate ambient volatile organic compounds.

Ren, X.; Mao, J.; Brune, W. H.; Cantrell, C. A.; Mauldin, R. L., III; Hornbrook, R. S.; Kosciuch, E.; Olson, J. R.; Crawford, J. H.; Chen, G.; Singh, H. B.

2012-08-01

337

Airborne intercomparison of HOx measurements using laser-induced fluorescence and chemical ionization mass spectrometry during ARCTAS  

NASA Astrophysics Data System (ADS)

The hydroxyl (OH) and hydroperoxyl (HO2) radicals, collectively called HOx, play central roles in tropospheric chemistry. Accurate measurements of OH and HO2 are critical to examine our understanding of atmospheric chemistry. Intercomparisons of different techniques for detecting OH and HO2 are vital to evaluate their measurement capabilities. Three instruments that measured OH and/or HO2 radicals were deployed on the NASA DC-8 aircraft throughout Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS), in the spring and summer of 2008. One instrument was the Penn State Airborne Tropospheric Hydrogen Oxides Sensor (ATHOS) for OH and HO2 measurements based on Laser-Induced Fluorescence (LIF) spectroscopy. A second instrument was the NCAR Selected-Ion Chemical Ionization Mass Spectrometer (SI-CIMS) for OH measurement. A third instrument was the NCAR Peroxy Radical Chemical Ionization Mass Spectrometer (PeRCIMS) for HO2 measurement. Formal intercomparison of LIF and CIMS was conducted for the first time on a same aircraft platform. The three instruments were calibrated by quantitative photolysis of water vapor by UV light at 184.9 nm with three different calibration systems. The absolute accuracies were ±32% (2?) for the LIF instrument, ±65% (2?) for the SI-CIMS instrument, and ±50% (2?) for the PeRCIMS instrument. In general, good agreement was obtained between the CIMS and LIF measurements of both OH and HO2 measurements. Linear regression of the entire data set yields [OH]CIMS = 0.89 × [OH]LIF + 2.8 × 105 cm-3 with a correlation coefficient, r2 = 0.72 for OH and [HO2]CIMS = 0.86 × [HO2]LIF + 3.9 parts per trillion by volume (pptv, equivalent to pmol mol-1) with a correlation coefficient, r2 = 0.72 for HO2. In general, the difference between CIMS and LIF instruments for OH and HO2 measurements can be explained by their combined measurement uncertainties. Comparison with box model results shows some similarities for both the CIMS and LIF measurements. First, the observed-to-modeled HO2 ratio increases greatly for higher NO mixing ratios, indicating that the model may not properly account for HOx sources that correlate with NO. Second, the observed-to-modeled OH ratio increases with increasing isoprene mixing ratios, suggesting either incomplete understanding of isoprene chemistry in the model or interferences in the measurements in environments where biogenic emissions dominate ambient volatile organic compounds.

Ren, X.; Mao, J.; Brune, W. H.; Cantrell, C. A.; Mauldin, R. L., III; Hornbrook, R. S.; Kosciuch, E.; Olson, J. R.; Crawford, J. H.; Chen, G.; Singh, H. B.

2012-03-01

338

A laser-based instrument for the study of ultrafast chemical dynamics by soft x-ray-probe photoelectron spectroscopy  

Microsoft Academic Search

A laser-based instrument is described for the study of femtosecond dissociation dynamics of gas phase molecules via time-resolved vacuum ultraviolet and soft x-ray photoelectron spectroscopy. Visible or UV pump pulses are generated with nonlinear crystal techniques on a Ti:sapphire laser output, while soft x-ray probe pulses are created via high-order harmonic generation of the same laser in rare gases. Here

Lora Nugent-Glandorf; Michael Scheer; David A. Samuels; Veronica Bierbaum; Stephen R. Leone

2002-01-01

339

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

340

Tunable laser flash absorption: a new technique for measuring rates and yields of chemical reactions at high temperatures  

Microsoft Academic Search

The flash absorption technique, whereby light from an excimer laser is used to measure the kinetic behavior of absorbing species in the high temperature region behind a shock front with a linear array detector, has been extended by using tunable light from a high resolution, pulsed dye laser. The use of narrowband, tunable light allows us to access isolated rovibronic

William A. VonDrasek; Shigeo Okajima; John H. Kiefer; Paul J. Ogren; Jan P. Hessler

1990-01-01

341

J. Phys. Chem. 1083, 87, 2153-2161 2153 Electronic-to-Vibrational Energy Transfer from I * (5 2P1,2)to 12( 25< Y <43)  

E-print Network

relaxation of 12(u=40)by argon,helium, and I2at room temperature are (7.3f 0.3) X lo5s-l torr-l, (1.02f 0 implicationsfor the mechanism of I2 dissociation in the chemical oxygen/iodine laser. A chain- branchingmechanism oxy- gen/iodine laser. Previous investigationsof this system2-10 had resulted in the following

Houston, Paul L.

342

Effect of KrF excimer laser irradiation on low-temperature preparation of lead titanium oxide film by metalorganic chemical vapor deposition  

SciTech Connect

Effect of KrF excimer laser irradiation on the preparation of PbTiO{sub 3} film by metalorganic chemical vapor deposition (MOCVD) was studied from the view points of composition, deposition amount, crystallinity and the morphology of the film. The crystalline PbTiO{sub 3} films with stoichiometric composition was prepared at 380 C with the irradiation of KrF excimer laser (248nm) using Pb(DPM){sub 2} and Ti(O{center_dot}i-Pr){sub 4} as the MOCVD gas source. On the other hand, the film without irradiation had the Pb-poor composition and was amorphous. The deposition amount of irradiated film was 1.5 times as high as that of non-irradiated film. It was supposed that this was not due to the heat effect with irradiation, but due to the photochemical effect.

Yamazaki, Yasuo; Hioki, Tsuyosi; Funakubo, Hiroshi; Shinozaki, Kazuo; Mizutani, Nobuyasu [Tokyo Institute of Technology (Japan). Dept. of Inorganic Materials] [Tokyo Institute of Technology (Japan). Dept. of Inorganic Materials

1995-09-01

343

Topical Meeting on Laser Applications to Chemical Analysis III, Salt Lake City, UT, Jan. 27-31, 1992, Proceedings  

NASA Astrophysics Data System (ADS)

Various papers on lasers, photonics, and environmental optics are presented. Individual topics addressed include: tunable diode laser ratio measurements of atmospheric constituents employing dual fitting analysis and jump scanning, ultrasensitive spectral trace detection of individual molecular components in an atmospheric binary mixture, applications of a tunable CO2 sideband lasers for high-resolution spectroscopic measurements of atmospheric gases, molecular analysis by ionization of laser-desorbed neutral species, spatially resolved multispecies and temperature analysis in hydrogen flames, intense backward Raman lasers in CH4 and H2, time-resolved emission studies of ArF-laser-produced microplasmas. Also discussed are: measurements of the refractive index of PbEuTe in the 3-10 micron region of the infrared, high-efficiency and compact blue source: intracavity frequency tripling by using LBO and BBO without the influence of birefringence, radiation and collisional energy transfer among the A 2Pi(i) and X 2Sigma(+) states of CN, wager-vapor absorption line measurements in the 940-nm band using a Raman-shifted dye laser, Gaussian-Schell model source in 1D first-order systems with loss or gain. (For individual items see A93-28552 to A93-28566)

Miziolek, Andrzej W.; Long, S. R.; Crosley, David R.

1993-02-01

344

New gas lasers committee report on electronic transition chemically and electrically excited lasers. Meeting of 20--22 September 1972. Technical report 1 Sep1 Dec 1972  

Microsoft Academic Search

The ideas generated by a committee of consultants are summarized. The purpose of the meeting was to recommend an approach for finding new efficient gas lasers where the inversion is obtained from an electronic transition of the gas. Probable criteria such as quantum efficiency, concentration, lifetime, gain, etc., have been suggested for a suitable system to aid in sorting among

L. E. Wilson; S. Benson; T. Cool; A. Javan; A. Kuppermann

1973-01-01

345

The role of physical and chemical properties of Pd nanostructured materials immobilized on inorganic carriers on ion formation in atmospheric pressure laser desorption/ionization mass spectrometry.  

PubMed

Fundamental parameters influencing the ion-producing efficiency of palladium nanostructures (nanoparticles [Pd-NP], nanoflowers, nanofilms) during laser irradiation were studied in this paper. The nanostructures were immobilized on the surface of different solid inorganic carrier materials (porous and mono-crystalline silicon, anodic porous aluminum oxide, glass and polished steel) by using classical galvanic deposition, electroless local deposition and sputtering. It was the goal of this study to investigate the influence of both the nanoparticular layer as well as the carrier material on ion production for selected analyte molecules. Our experiments demonstrated that the dimensions of the synthesized nanostructures, the thickness of the active layers, surface disorders, thermal conductivity and physically or chemically adsorbed water influenced signal intensities of analyte ions during surface-assisted laser desorption/ionization (SALDI) while no effects such as plasmon resonance, photoelectric effect or catalytic activity were expected to occur. Excellent LDI abilities were seen for Pd-NPs immobilized on steel, while Pd nanoflowers on porous silicon exhibited several disadvantages; viz, strong memory effects, dependency of the analytical signal on amount of physically and chemically adsorbed water inside porous carrier, reduced SALDI activity from unstable connections between Pd and semiconductor material, decrease of the melting point of pure silicon after Pd immobilization and resulting strong laser ablation of metal/semiconductor complex, as well as significantly changed surface morphology after laser irradiation. The analytical performance of Pd-NP/steel was further improved by applying a hydrophobic coating to the steel surface before galvanic deposition. This procedure increased the distance between Pd-NPs, thus reducing thermal stress upon LDI; it simultaneously decreased spot sizes of deposited sample solutions. PMID:24913399

Silina, Yuliya E; Koch, Marcus; Volmer, Dietrich A

2014-06-01

346

Design of Laser Based Monitoring Systems for Compliance Management of Odorous and Hazardous Air Pollutants in Selected Chemical Industrial Estates at Hyderabad, India  

NASA Astrophysics Data System (ADS)

Industrialization can no longer sustain without internalization of the concerns of the receiving environment and land-use. Increased awareness and public pressure, coupled with regulatory instruments and bodies exert constant pressure on industries to control their emissions to a level acceptable to the receiving environment. However, when a group of industries come-up together as an industrial estate, the cumulative impacts of all the industries together often challenges the expected/desired quality of receiving environment, requiring stringent pollution control and monitoring measures. Laser remote sensing techniques provide powerful tools for environmental monitoring. These methods provide range resolved measurements of concentrations of various gaseous pollutants and suspended particulate matter (SPM) not only in the path of the beam but over the entire area. A three dimensional mapping of the pollutants and their dispersal can be estimated using the laser remote sensing methods on a continuous basis. Laser Radar (Lidar) systems are the measurements technology used in the laser remote sensing methods. Differential absorption lidar (DIAL) and Raman Lidar technologies have proved to be very useful for remote sensing of air pollutants. DIAL and Raman lidar systems can be applied for range resolved measurements of molecules like SO2, NO2, O3 Hg, CO, C2H4, H2O, CH4, hydrocarbons etc. in real time on a continuous basis. This paper describes the design details of the DAIL and Raman lidar techniques for measurement of various hazardous air pollutants which are being released into the atmosphere by the chemical industries operating in the Bachupally industrial Estate area at Hyderabad, India. The relative merits of the two techniques have been studied and the minimum concentration of pollutants that can be measured using these systems are presented. A dispersion model of the air pollutants in the selected chemical industrial estates at Hyderabad has been developed.

Sudhakar, P.; Kalavathi, P.; Ramakrishna Rao, D.; Satyanarayna, M.

2014-12-01

347

Femtosecond-laser-produced low-density plasmas in transparent biological media: a tool for the creation of chemical, thermal, and thermomechanical effects below the optical breakdown threshold  

NASA Astrophysics Data System (ADS)

The irradiance threshold for femtosecond optical breakdown in aqueous media is approximately equals 1.0x1013W cm-2. At the breakdown threshold, a plasma with a free electron density of about 1021cm-3 is generated, and the energy density in the breakdown region is sufficiently high to cause the formation of a bubble which can be experimentally observed. We found previously that plasmas with a free electron density <1021cm-3 are formed also in a fairly large irradiance range below the breakdown threshold. The present study investigates the chemical, thermal, and thermomechanical effects produced by these low-density plasmas. We use a rate equation model considering multiphoton ionization and produced by these low-density plasmas. We use a rate equation model considering multiphoton ionization and avalanche ionization to numerically simulate the temporal evolution of the free electron density during the laser pulse for a given irradiance, and to calculate the irradiance dependence of the free-electron density and volumetric energy density reached at the end of the laser pulse. The value of the energy density created by each laser pulse is then used to calculate the temperature distribution in the focal region after application of a single laser pulse and of series of pulses. The results of the temperature calculations yield, finally, the starting point for calculations of the thermoelastic stresses that are generated during the formation of the low-density plasmas. We found that, particularly for short wavelengths, a large 'tuning range' exists for the creation of spatially extremely confined chemical, thermal and mechanical effects via free electron generation through nonlinear absorption. Photochemical effects dominate at the lower end of this irradiance range, whereas at the upper end they are mixed with thermal effects and modified by thermoelastic stresses. Above the breakdown threshold, the spatial confinement is partly destroyed by cavitation bubble formation, and the laser-induced effects become more disruptive. Our simulations revealed that the highly localized ablation of intracellular structures and intranuclear chromosome dissection recently demonstrated by other researchers are probably mediated by free-electron- induced chemical bond breaking and not related to heating or thermoelastic stresses. We conclude that low density plasmas below the optical breakdown threshold can be a versatile tool for the manipulation of transparent biological media and other transparent materials. (enabling, e.g., the generation of optical waveguides in bulk glass). Low density plasmas may, however, also be a potential hazard in multiphoton microscopy and higher harmonic imaging.

Vogel, Alfred; Noack, Joachim; Huettmann, Gereon; Paltauf, Guenther

2002-04-01

348

Development of advanced generator of singlet oxygen for a COIL  

Microsoft Academic Search

The generator of singlet oxygen (SOG) remains still a challenge for a chemical oxygen-iodine laser (COIL). Hitherto, only chemical generators based on the gas-liquid reaction system (chlorine-basic hydrogen peroxide) can supply singlet oxygen, O2(1Delta), in enough high yields and at pressures to maintain operation of the high power supersonic COIL facilities. Employing conventional generators of jet-type or rotating disc-type makes

Jarmila Kodymova; Otomar Spalek; Vít Jirásek; Miroslav Censký; Jan Hrubý

2006-01-01

349

Effect of pulsed laser irradiation on the structure of GeTe films deposited by metal organic chemical vapor deposition: A Raman spectroscopy study  

SciTech Connect

Phase changes between amorphous and crystallized states were induced by laser irradiation with nanosecond pulses in Ge{sub x}Te{sub y} films grown by metal organic chemical vapor deposition. The different phases were obtained by adjusting the pulse energy and could be distinguished by their different optical reflectivities. The corresponding structural changes were studied by Raman spectroscopy, showing marked differences for the two phases. A clear correlation is found between optical reflectivity levels, crystallographic state and the evolution of Ge-Ge, Te-Te, and Ge-Te Raman bands.

Salicio, O.; Wiemer, C.; Fanciulli, M. [CNR-INFM MDM Laboratory, via C. Olivetti 2, 20041 Agrate Brianza (Italy); Gawelda, W.; Siegel, J.; Afonso, C. N. [Laser Processing Group, Instituto de Optica, CSIC, Serrano 121, E-28006 Madrid (Spain); Plausinaitiene, V.; Abrutis, A. [Department of General and Inorganic Chemistry, Faculty of Chemistry, Vilnius University, Naugarduko 24, LT-2006 VU (Lithuania)

2009-02-01

350

Preparation of the c-axis oriented AlN film by laser chemical vapor deposition using a newly proposed Al(acac)3 precursor  

NASA Astrophysics Data System (ADS)

Highly oriented AlN film was prepared on a c-plane sapphire substrate by laser chemical vapor deposition using a newly proposed aluminum acetylacetonate precursor and ammonia gas as source reactants. The c-axis oriented AlN films were obtained on the c-plane sapphire substrate at deposition temperatures from 900 to 1230 K. AlN film prepared at 1047 K showed an epitaxial relation as (//( [//[. The full width at half maximum (FWHM) of the X-ray rocking curve for AlN (0002) plane increased with increasing deposition temperature. The c-axis lattice parameter decreased with increasing deposition temperature.

You, Yu; Ito, Akihiko; Tu, Rong; Goto, Takashi

2013-02-01

351

Passively Q-switched mode-locking Nd:GdVO4 laser with a chemically reduced graphene oxide saturable absorber  

NASA Astrophysics Data System (ADS)

A diode-pumped passively Q-switched mode-locking Nd:GdVO4 laser using a chemically reduced graphene oxide saturable absorber was demonstrated. The repetition rate and pulse width of the Q-switching envelopes were 5.7 MHz and 100 ns, respectively, while those of the mode-locking pulses that were modulated in the Q-switching envelopes were 139 MHz and 10 ps. At the maximum pump power of 7 W, the average output power was 1.38 W, corresponding to a slope efficiency of 25%.

Pan, Shu-Di; Cui, Liang; Liu, Jing-Quan; Teng, Bing; Liu, Jian-Hua; Ge, Xiao-Hui

2014-12-01

352

InGaAs-GaAs strained-layer quantum well buried heterostructure lasers (lambda > 1 µm) by metalorganic chemical vapor deposition  

NASA Astrophysics Data System (ADS)

Data are presented on long-wavelength (?>1 ?m) strained-layer InGaAs-GaAs quantum well buried heterostructure lasers grown by a two-step metalorganic chemical vapor deposition (MOCVD) process. Wet chemical etched mesas with an active region width of 3.5 ?m are formed in a step-graded InGaAs-GaAs quantum well structure using an oxide mask. Selective MOCVD regrowth is used to form the buried heterostructure. Data are presented for devices having output powers of greater than 130 mW/facet, pulsed threshold currents of less than 7 mA, and internal quantum efficiencies of greater than 60%, for an emission wavelength of 1.074 ?m. The near-field patterns indicate stable index-guided fundamental mode operation to greater than 30Ith.

York, P. K.; Beernink, K. J.; Fernández, G. E.; Coleman, J. J.

1989-02-01

353

Separation of isotopes with lasers  

Microsoft Academic Search

The advantages of using laser radiation for separation of isotopes accrue from the unique property of laser radiation to act on a specific desired isotope within a natural isotope mixture rather than on the mixture as a whole. Some theoretical aspects of the application of dye lasers, chemical lasers, and molecular lasers to the separation of isotopes are examined. The

N. V. Karlov; A. M. Prokhorov

1976-01-01

354

Experimental performances of pre-swirling jet singlet oxygen generator  

NASA Astrophysics Data System (ADS)

Singlet oxygen generator (SOG) is the key part of chemical oxygen iodine laser (COIL) which supplies chemical energy for chemical oxygen iodine laser. A novel pre-swirling jet singlet oxygen generator (PJSOG) with rapid separation technology is put forward. In this paper, experimental performances of PJSOG have been studied by means of theoretical and experimental analysis. With excellent phase dispersion and rapid separation performances, PJSOG has several or several decade times specific area than traditional SOGs and high separation efficiency. It can reach more than 95% chlorine utilization and about 60% O2 ( 1?) yield. The operating stability has also been studied in this paper. The stable running time of PJSOG increased with liquid flow structure improvement. With high separation efficiency, high O2 ( 1?) output coefficient, high utilization coefficient of Cl2 and excellent operating stability, the novel PJSOG must be a promising technology in further research.

Liu, Zhendong; Chen, Wenwu; Xu, Xiaobo; Dai, Yuqiang; Wang, Jinglong; Liu, Yushi; Lv, Guosheng; Jin, Yuqi; Sang, Fengting

2015-02-01

355

Continuous wave laser assisted chemical material removal from Mo, W, and Si at faint red hot temperatures (700-800 C)  

NASA Astrophysics Data System (ADS)

Continuous-wave CO2 and argon ion laser assisted chemical etching of Mo and W in air and Mo, W, and Si in a 7-percent F2 mixture in He is reported. At room temperature, these materials are hardly etched in air or the F2 mixture. At faint red hot temperatures (700-800 C), however, they react strongly with the fluorine to produce volatile MoF6, WF6, and SiF4 which allow the etching process to continue. Using 50 W/sq cm of the CW CO2 laser radiation on a 275-micron-thick Si wafer in 30 Torr of the F2 mixture yielded an etch rate of about 1 micron/s (on both sides) and submicron surface smoothness. Using 4 W of the 4880 A Ar ion laser beam focused tightly on a 30-micron-thick Mo film in air, perforated the film at a rate of 2 micron/s by producing the volatile MoO3 at the elevated temperature.

Koren, G.

1985-11-01

356

Lasers '90; Proceedings of the 13th International Conference on Lasers and Applications, San Diego, CA, Dec. 10-14, 1990  

NASA Astrophysics Data System (ADS)

Various papers on lasers are presented. The general topics considered are: X-ray lasers; FELs, solid state lasers; techniques and phenomena of ultrafast lasers; optical filters and free space laser communications, discharge lasers; tunable lasers; application of lasers in medicine and surgery; lasers in materials processing; high power lasers; dynamic gratings, wave mixing, and holography; up-conversion lasers; lidar and laser radar; laser resonators; excimer lasers; laser propagation; nonlinear and quantum optics; blue-green technology; imaging; laser spectroscopy; chemical lasers; dye lasers; lasers in chemistry.

Harris, Dennis G.; Herbelin, John

357

Design and chemical synthesis of iodine-containing molecules for application to solar-pumped I* lasers  

NASA Technical Reports Server (NTRS)

Research is directed toward the design and synthesis of new media for solar-pumped I* lasers. Since the most effective existing lasants are perfluoroalkyl iodides, a strategy was proposed for the development of improved materials of this type with absorption maxima at 300 nm. Absorption spectra were synthesized and measured for prototypical species containing iodine bound to boron, iron, and cobalt.

Shiner, Christopher S.

1986-01-01

358

Chemical and Isotopic Analysis of Trace Organic Matter on Meteorites and Interstellar Dust Using a Laser Microprobe Instrument  

NASA Technical Reports Server (NTRS)

Polycyclic Aromatic Hydrocarbons (PAHs) are of considerable interest today because they are ubiquitous on Earth and in the interstellar medium (ISM). In fact, about 20% of cosmic carbon in the galaxy is estimated to be in the form of PAHs. Investigation of these species has obvious uses for determining the cosmochemistry of the solar system. Work in this laboratory has focused on four main areas: 1) Mapping the spatial distribution of PAHs in a variety of meteoritic samples and comparing this distribution with mineralogical features of the meteorite to determine whether a correlation exists between the two. 2) Developing a method for detection of fullerenes in extraterrestrial samples using microprobe Laser Desorption Ionization Mass Spectroscopy and utilizing this technique to investigate fullerene presence, while exploring the possibility of spatially mapping the fullerene distribution in these samples through in situ detection. 3) Investigating a possible formation pathway for meteoritic and ancient terrestrial kerogen involving the photochemical reactions of PAHs with alkanes under prebiotic and astrophysically relevant conditions. 4) Studying reaction pathways and identifying the photoproducts generated during the photochemical evolution of PAH-containing interstellar ice analogs as part of an ongoing collaboration with researchers at the Astrochemistry Lab at NASA Ames. All areas involve elucidation of the solar system formation and chemistry using microprobe Laser Desorption Laser Ionization Mass Spectrometry. A brief description of microprobe Laser Desorption Ionization Mass Spectroscopy, which allows selective investigation of subattomole levels of organic species on the surface of a sample at 10-40 micrometer spatial resolution, is given.

Zare, Richard N.; Boyce, Joseph M. (Technical Monitor)

2001-01-01

359

Bibliography of Soviet laser developments, no. 38, November - December 1978  

NASA Astrophysics Data System (ADS)

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; beam-target interaction; and plasma generation and diagnostics.

1979-09-01

360

Laser propulsion  

NASA Technical Reports Server (NTRS)

The use of an earth-based high-power laser beam to provide energy for earth-launched rocket vehicle is investigated. The laser beam energy is absorbed in an opaque propellant gas and is converted to high-specific-impulse thrust by expanding the heated propellant to space by means of a nozzle. This laser propulsion scheme can produce specific impulses of several thousand seconds. Payload to gross-weight fractions about an order of magnitude higher than those for conventional chemical earth-launched vehicles appear possible. There is a potential for a significant reduction in cost per payload mass in earth orbit.

Rom, F. E.; Putre, H. A.

1972-01-01

361

IEEE JOURNAL OF QUANTUM ELECTRONICS, VOL. 48, NO. 6, JUNE 2012 741 Superlinear Enhancement of Discharge Driven  

E-print Network

outcoupled power of 538 W. Index Terms--All-gas laser, discharge oxygen iodine laser (DOIL), electric oxygen of Discharge Driven Electric Oxygen-Iodine Laser by Increasing g0L Gabriel F. Benavides, Brian S. WoodardOIL devices utilizing a new concentric discharge geometry with improved O2(a1 ) production at higher discharge

Carroll, David L.

362

Laser satellite power systems  

SciTech Connect

A laser satellite power system (SPS) converts solar power captured by earth-orbiting satellites into electrical power on the earth's surface, the satellite-to-ground transmission of power being effected by laser beam. The laser SPS may be an alternative to the microwave SPS. Microwaves easily penetrate clouds while laser radiation does not. Although there is this major disadvantage to a laser SPS, that system has four important advantages over the microwave alternative: (1) land requirements are much less, (2) radiation levels are low outside the laser ground stations, (3) laser beam sidelobes are not expected to interfere with electromagnetic systems, and (4) the laser system lends itself to small-scale demonstration. After describing lasers and how they work, the report discusses the five lasers that are candidates for application in a laser SPS: electric discharge lasers, direct and indirect solar pumped lasers, free electron lasers, and closed-cycle chemical lasers. The Lockheed laser SPS is examined in some detail. To determine whether a laser SPS will be worthy of future deployment, its capabilities need to be better understood and its attractiveness relative to other electric power options better assessed. First priority should be given to potential program stoppers, e.g., beam attenuation by clouds. If investigation shows these potential program stoppers to be resolvable, further research should investigate lasers that are particularly promising for SPS application.

Walbridge, E.W.

1980-01-01

363

Tunable laser flash absorption: a new technique for measuring rates and yields of chemical reactions at high temperatures.  

PubMed

The flash absorption technique, whereby light from an excimer laser is used to measure the kinetic behavior of absorbing species in the high temperature region behind a shock front with a linear array detector, has been extended by using tunable light from a high resolution, pulsed dye laser. The use of narrowband, tunable light allows us to access isolated rovibronic transitions and, thereby, obtain state-specific kinetic information. If the oscillator strength of the transition and the absorption line profile are known, the absolute concentration may be determined. We demonstrate the technique by measuring the temporal development of the hydroxyl radical as it is formed after propane has been thermally dissociated in the presence of oxygen. We conclude that accurate kinetic measurements can be made with hydroxyl concentrations of 10(15) cm(-3) This technique may also be applied to study any species which absorbs below 50,000 cm(-1). PMID:20577484

Vondrasek, W A; Okajima, S; Kiefer, J H; Ogren, P J; Hessler, J P

1990-11-20

364

Photoexcitation of lasers and chemical reactions for NASA missions: A theoretical study. [optical pumping in high pressure gas  

NASA Technical Reports Server (NTRS)

The possibility of obtaining CW laser oscillation by optical pumping in the infrared at an elevated gas pressure is reviewed. A specific example utilizing a mixture of CO and NO gases is included. The gas pressures considered are in excess of several atmospheres. Laser frequency tuning over a broad region becomes possible at such elevated gas pressures due to collisional broadening of the amplifying transitions. The prior-rate and surprisal analysis are applied to obtain detailed VV and VT rates for CO and NO molecules and the transfer rates in a CO-NO gas mixture. The analysis is capable of giving temperature dependence of the rate constants. Computer estimates of the rates are presented for vibrational levels up to v = 50. The results show that in the high-lying vibrational states the VV transfer rates with Delta nu = 2 become appreciable.

Javan, A.; Guerra, M.

1981-01-01

365

Development of a deep-sea laser-induced breakdown spectrometer for in situ multi-element chemical analysis  

NASA Astrophysics Data System (ADS)

Spectroscopy is emerging as a technique that can expand the envelope of modern oceanographic sensors. The selectivity of spectroscopic techniques enables a single instrument to measure multiple components of the marine environment and can form the basis for versatile tools to perform in situ geochemical analysis. We have developed a deep-sea laser-induced breakdown spectrometer (ChemiCam) and successfully deployed the instrument from a remotely operated vehicle (ROV) to perform in situ multi-element analysis of both seawater and mineral deposits at depths of over 1000 m. The instrument consists of a long-nanosecond duration pulse-laser, a spectrometer and a high-speed camera. Power supply, instrument control and signal telemetry are provided through a ROV tether. The instrument has two modes of operation. In the first mode, the laser is focused directly into seawater and spectroscopic measurements of seawater composition are performed. In the second mode, a fiber-optic cable assembly is used to make spectroscopic measurements of mineral deposits. In this mode the laser is fired through a 4 m long fiber-optic cable and is focused onto the target's surface using an optical head and a linear stage that can be held by a ROV manipulator. In this paper, we describe the instrument and the methods developed to process its measurements. Exemplary measurements of both seawater and mineral deposits made during deployments of the device at an active hydrothermal vent field in the Okinawa trough are presented. Through integration with platforms such as underwater vehicles, drilling systems and subsea observatories, it is hoped that this technology can contribute to more efficient scientific surveys of the deep-sea environment.

Thornton, Blair; Takahashi, Tomoko; Sato, Takumi; Sakka, Tetsuo; Tamura, Ayaka; Matsumoto, Ayumu; Nozaki, Tatsuo; Ohki, Toshihiko; Ohki, Koichi

2015-01-01

366

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

2013-02-15

367

Investigation of laser diagnostics of PACVD (Plasma Assisted Chemical Vapor Deposition) processes for depositing hard face coatings  

SciTech Connect

The goal of this project is to improve the understanding of the mechanisms which govern the nonequilibrium reactive plasma of the mechanisms which govern the atomistic or molecular deposition of hard face coatings for erosion resistant applications. The goal is to provide a predictive capability that is severely lacking in the present science base of PACVD processing for depositing hard face coatings. Advanced laser diagnostics will be used to probe the plasma for improving process control. 2 figs.

Roman, W.C.

1990-06-01

368

Infrared laser enhanced reactions: Temperature resolution of the chemical dynamics of the O3† + NO reaction systen  

Microsoft Academic Search

The rate constant for the decay of vibrationally excited ozone, O3†, in the O3† + NO reaction system has been measured from 153 to 373 K. Vibrationally excited O3 was produced in the asymmetric stretch normal mode by absorption of square wave modulated emission from a CO2 laser tuned to the P (30) 9.6 ?m transition. Under appropriate experimental conditions,

Michael J. Kurylo; Walter Braun; Chieu Nguyen Xuan; Andrew Kaldor

1975-01-01

369

Chemical characterization of single micro- and nano-particles by optical catapulting-optical trapping-laser-induced breakdown spectroscopy  

NASA Astrophysics Data System (ADS)

Spectral identification of individual micro- and nano-sized particles by the sequential intervention of optical catapulting, optical trapping and laser-induced breakdown spectroscopy is presented. The three techniques are used for different purposes. Optical catapulting (OC) serves to put the particulate material under inspection in aerosol form. Optical trapping (OT) permits the isolation and manipulation of individual particles from the aerosol, which are subsequently analyzed by laser-induced breakdown spectroscopy (LIBS). Once catapulted, the dynamics of particle trapping depends both on the laser beam characteristics (power and intensity gradient) and on the particle properties (size, mass and shape). Particles are stably trapped in air at atmospheric pressure and can be conveniently manipulated for a precise positioning for LIBS analysis. The spectra acquired from the individually trapped particles permit a straightforward identification of the material inspected. Variability of LIBS signal for the inspection of Ni microspheres was 30% relative standard deviation. OC-OT-LIBS permits the separation of particles in a heterogeneous mixture and the subsequent analysis of the isolated particle of interest. In order to evaluate the sensitivity of the approach, the number of absolute photons emitted by a single trapped particle was calculated. The limit of detection (LOD) for Al2O3 particles was calculated to be 200 attograms aluminium.

Fortes, Francisco J.; Fernández-Bravo, Angel; Javier Laserna, J.

2014-10-01

370

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

371

Performance of chemical vapor deposition fabricated graphene absorber mirror in Yb3+ : Sc2SiO5 mode-locked laser  

NASA Astrophysics Data System (ADS)

A reflective graphene saturable absorber mirror (SAM) was successfully fabricated by chemical vapor deposition technology. A stable diode-pumped passively mode-locked Yb3+:Sc2SiO5 laser using a graphene SAM as a saturable absorber was accomplished for the first time. The measured average output power amounts to 351 mW under the absorbed pump power of 12.5 W. Without prisms compensating for dispersion, the minimum pulse duration of 7 ps with a repetition rate of 97 MHz has been obtained at the central wavelength of 1063 nm. The corresponding peak power and the maximum pulse energy were 516 W and 3.6 nJ, respectively.

Cai, Wei; Li, Yaqi; Zhu, Hongtong; Jiang, Shouzhen; Xu, Shicai; Liu, Jie; Zheng, Lihe; Su, Liangbi; Xu, Jun

2014-12-01

372

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

373

Chemical analysis of pharmaceuticals and explosives in fingermarks using matrix-assisted laser desorption ionization/time-of-flight mass spectrometry.  

PubMed

Chemical analysis of latent fingermarks, "touch chemistry," has the potential of providing intelligence or forensically relevant information. Matrix-assisted laser desorption ionization/time-of-flight mass spectrometry (MALDI/TOF MS) was used as an analytical platform for obtaining mass spectra and chemical images of target drugs and explosives in fingermark residues following conventional fingerprint development methods and MALDI matrix processing. There were two main purposes of this research: (1) develop effective laboratory methods for detecting drugs and explosives in fingermark residues and (2) determine the feasibility of detecting drugs and explosives after casual contact with pills, powders, and residues. Further, synthetic latent print reference pads were evaluated as mimics of natural fingermark residue to determine if the pads could be used for method development and quality control. The results suggest that artificial amino acid and sebaceous oil residue pads are not suitable to adequately simulate natural fingermark chemistry for MALDI/TOF MS analysis. However, the pads were useful for designing experiments and setting instrumental parameters. Based on the natural fingermark residue experiments, handling whole or broken pills did not transfer sufficient quantities of drugs to allow for definitive detection. Transferring drugs or explosives in the form of powders and residues was successful for preparing analytes for detection after contact with fingers and deposition of fingermark residue. One downfall to handling powders was that the analyte particles were easily spread beyond the original fingermark during development. Analyte particles were confined in the original fingermark when using transfer residues. The MALDI/TOF MS was able to detect procaine, pseudoephedrine, TNT, and RDX from contact residue under laboratory conditions with the integration of conventional fingerprint development methods and MALDI matrix. MALDI/TOF MS is a nondestructive technique which provides chemical information in both the mass spectra and chemical images. PMID:24447453

Kaplan-Sandquist, Kimberly; LeBeau, Marc A; Miller, Mark L

2014-02-01

374

The effect of deposition atmosphere on the chemical composition of TiN and ZrN thin films grown by pulsed laser deposition  

NASA Astrophysics Data System (ADS)

Very thin TiN and ZrN films (<500 nm) were grown on (1 0 0) Si substrates at temperatures up to 500 °C by the pulsed laser deposition (PLD) technique using a KrF excimer laser under residual vacuum or various mixtures of CH4 or N2. Auger electron spectroscopy investigations found that films contained a relatively low oxygen concentration, usually below 3.0 at%. Films deposited under residual vacuum or very low N2 pressures (<3 × 10-3 Pa) contained 3-6 at% C atoms in the bulk. This fraction grew to 8-10 at% when the deposition was performed under an atmosphere of 2 × 10-3 Pa CH4. To avoid C atoms incorporation into the bulk a deposition pressure of 10 Pa N2 was required. X-ray photoelectron spectroscopy investigations found that oxygen was mostly bonded in an oxynitride type of compound, while carbon was bonded into a metallic carbide. The presence of C atoms in the chemical composition of the TiN or ZrN improved the measured hardness of the films.

Craciun, D.; Socol, G.; Stefan, N.; Dorcioman, G.; Hanna, M.; Taylor, C. R.; Lambers, E.; Craciun, V.

2014-05-01

375

2-?m wavelength all-fiber Q-switched double-clad fiber laser using monopiece single-layer chemical-vapor-deposition graphene  

NASA Astrophysics Data System (ADS)

We demonstrate a large-energy 2-?m double-clad Tm-doped fiber laser (DC-TDFL) Q-switched by a monopiece single-layer graphene nanosheet. The single-layer graphene is fabricated by the chemical vapor deposition (CVD) method, and then transferred onto the facet of a fiber ferrule for constructing a fiber-compatible saturable absorber (SA). The Q-switching operation of the DC-TDFL at 1980 nm is achieved and has a large pulse energy of 1.06 ?J (corresponding to the average output power of 28.6 mW). The narrowest pulse duration is 2.7 ?s, and the pulse repetition rate can be tuned from 8 to 27 kHz by changing the pump power from 2.35 to 2.82 W. To the best of our knowledge, this work is not only the first demonstration of a 2-?m Q-switched all-fiber laser using monopiece single-layer CVD graphene as a SA, but also generates the largest pulse energy from graphene-based all-fiber DC-TDFLs.

Huang, Yizhong; Luo, Zhengqian; Liu, Chun; Wu, Duanduan; Li, Yingyue; Le, Lili

2014-10-01

376

Laser-assisted one-pot fabrication of calcium phosphate-based submicrospheres with internally crystallized magnetite nanoparticles through chemical precipitation.  

PubMed

In this paper, we have further developed our simple (one-pot) and rapid (short irradiation time) laser fabrication process of submicrometer spheres composed of amorphous calcium iron phosphate. In our previous process, laser irradiation was applied to a calcium phosphate (CaP) reaction mixture supplemented with ferric ions (Fe(3+)) as a light-absorbing agent. Because the intention of the present study was to fabricate magnetite-encapsulated CaP-based submicrometer spheres, ferrous ions (Fe(2+)) were used as a light-absorbing agent rather than ferric ions. The ferrous ions served as a light-absorbing agent and facilitated the fabrication of submicrometer and micrometer spheres of amorphous calcium iron phosphate. The sphere formation and growth were better promoted by the use of ferrous ions as compared with the use of ferric ions. The chemical composition of the spheres was controllable through adjustment of the experimental conditions. By the addition of sodium hydroxide to the CaP reaction mixture supplemented with ferrous ions, fabrication of CaP-based magnetic submicrometer spheres was successfully achieved. Numerous magnetite and wüstite nanoparticles were coprecipitated or segregated into the CaP-based spherical amorphous matrix via light-material interaction during the CaP precipitation process. The magnetic properties of the magnetite and wüstite formed in the CaP-based spheres were investigated by magnetization measurements. The present process and the resulting CaP-based spheres are expected to have great potential for biomedical applications. PMID:25742691

Nakamura, Maki; Oyane, Ayako; Sakamaki, Ikuko; Ishikawa, Yoshie; Shimizu, Yoshiki; Kawaguchi, Kenji

2015-04-14

377

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

378

Optical pumping of chemical HF lasers on the basis of NF{sub 3}-H{sub 2} and ClF{sub 5}-H{sub 2} mixtures by an open surface discharge in the bleaching-wave mode  

SciTech Connect

Lasing on HF upon optical pumping by emission of an open discharge, using NF{sub 3} and ClF{sub 5} as donors of fluorine atoms, was obtained for the first time in a chemical laser and the bleaching-wave mode was realised in a chemical HF laser. An open surface discharge was used as a pump source. The velocity of the bleaching wave, which was formed under its action, reached {approx}8 km s{sup -1}. The formation of this wave leads to a rapid (with an ultrasonic velocity) replacement of the working medium in the lasing region, which provides a quantum laser efficiency close to unity. The optimum compo-sition of the working mixture was found to be NF{sub 3}:H{sub 2}:Kr =6:10:125 Torr. For this composition, the output laser energy in a 3.2-{mu}s pulse reached {approx}0.4 J and the specific output energy was 3.5 J litre{sup -1}. Approximately the same output characteristics of laser emission (0.35 J in a 3.5-{mu}s pulse in the ClF{sub 5}:H{sub 2}:Kr=3:20:50 Torr mixture) were obtained in the system using ClF{sub 5} as donors of fluorine atoms. (lasers, active media)

Artem'ev, Mikhail Yu; Mikheev, L D; Nesterov, V M; Cheremiskin, V I [P.N. Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Bashkin, A S [Open Joint-Stock Company, V.P. Glushko Energomash Research and Production Assocation, Khimki-1, Moscow region (Russian Federation); Sentis, M L [Laboratoire Lasers, Plasmas et Procedes Photoniques, FRE 2165 CNRS - Aix-Marseille II University (France)

2001-07-31

379

Time-Resolved O3 Chemical Chain Reaction Kinetics Via High-Resolution IR Laser Absorption Methods  

NASA Technical Reports Server (NTRS)

Excimer laser photolysis in combination with time-resolved IR laser absorption detection of OH radicals has been used to study O3/OH(v = 0)/HO2 chain reaction kinetics at 298 K, (i.e.,(k(sub 1) is OH + 03 yields H02 + 02 and (k(sub 2) is H02 + 03 yields OH + 202). From time-resolved detection of OH radicals with high-resolution near IR laser absorption methods, the chain induction kinetics have been measured at up to an order of magnitude higher ozone concentrations ([03] less than or equal to 10(exp 17) molecules/cu cm) than accessible in previous studies. This greater dynamic range permits the full evolution of the chain induction, propagation, and termination process to be temporally isolated and measured in real time. An exact solution for time-dependent OH evolution under pseudo- first-order chain reaction conditions is presented, which correctly predicts new kinetic signatures not included in previous OH + 03 kinetic analyses. Specifically, the solutions predict an initial exponential loss (chain "induction") of the OH radical to a steady-state level ([OH](sub ss)), with this fast initial decay determined by the sum of both chain rate constants, k(sub ind) = k(sub 1) + k(sub 2). By monitoring the chain induction feature, this sum of the rate constants is determined to be k(sub ind) = 8.4(8) x 10(exp -14) cu cm/molecule/s for room temperature reagents. This is significantly higher than the values currently recommended for use in atmospheric models, but in excellent agreement with previous results from Ravishankara et al.

Kulcke, Axel; Blackmon, Brad; Chapman, William B.; Kim, In Koo; Nesbitt, David J.

1998-01-01

380

Elastic constants of chemical-vapor-deposition diamond thin films: resonance ultrasound spectroscopy with laser-Doppler interferometry  

Microsoft Academic Search

Polycrystalline thin films show transverse isotropy (or hexagonal symmetry) and show five independent elastic constants because of columnar structure, texture, residual stress, and local incohesive bonds (or microcracks). In this paper, we developed an advanced method for measuring the anisotropic elastic constants of thin films using resonance ultrasound spectroscopy and determined the elastic constants of chemical-vapor-deposition diamond thin films. Mechanical

Nobutomo Nakamura; Hirotsugu Ogi; Masahiko Hirao

2004-01-01

381

Evaluation of the laser-induced breakdown spectroscopy technique for determination of the chemical composition of copper concentrates  

NASA Astrophysics Data System (ADS)

Laser-induced breakdown spectroscopy (LIBS), like many other spectroscopic techniques, is a comparative method. Typically, in qualitative analysis, synthetic certified standard with a well-known elemental composition is used to calibrate the system. Nevertheless, in all laser-induced techniques, such calibration can affect the accuracy through differences in the overall composition of the chosen standard. There are also some intermediate factors, which can cause imprecision in measurements, such as optical absorption, surface structure and thermal conductivity. In this work the calibration performed for the LIBS technique utilizes pellets made directly from the tested materials (old well-characterized samples). This choice produces a considerable improvement in the accuracy of the method. This technique was adopted for the determination of trace elements in industrial copper concentrates, standardized by conventional atomic absorption spectroscopy with a flame atomizer. A series of copper flotation concentrate samples was analyzed for three elements: silver, cobalt and vanadium. We also proposed a method of post-processing the measurement data to minimize matrix effects and permit reliable analysis. It has been shown that the described technique can be used in qualitative and quantitative analyses of complex inorganic materials, such as copper flotation concentrates. It was noted that the final validation of such methodology is limited mainly by the accuracy of the characterization of the standards.

?azarek, ?ukasz; Anto?czak, Arkadiusz J.; Wójcik, Micha? R.; Drzyma?a, Jan; Abramski, Krzysztof M.

2014-07-01

382

Laser Safety Device  

NASA Technical Reports Server (NTRS)

A major focus of work done at Air Products and Chemicals' Laser Application Laboratory is on use of ultraviolet radiation using high energy excimer lasers. Because light within the wavelength of excimer lasers is invisible, it can cause serious damage to eyes and tissue. To contain the laser beam, Air Products Incorporated a Jet Propulsion Laboratory invention described in a technical support package into its beam stops. The technology interrupts the laser pathway and allows workers to remain in the target area without shutting off the laser.

1992-01-01

383

Infrared Scattering Scanning Near-Field Optical Microscopy Using An External Cavity Quantum Cascade Laser For Nanoscale Chemical Imaging And Spectroscopy of Explosive Residues  

SciTech Connect

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 1260-1400 cm?1 tuning range of the ECQCL, corresponding to the NO2 symmetric stretch vibrational fingerprint region. Vibrational infrared spectra were collected on individual chemical domains with a collection area of *500nm2 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 Bernd

2013-02-04

384

Bibliography of Soviet laser developments, number 44, November - December 1979  

NASA Astrophysics Data System (ADS)

This is the Soviet Laser Bibliography for November-December 1979, and is No. 44 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.

1980-08-01

385

Coupled simulation of chemical lasers based on intracavity partially coherent light model and 3D CFD model.  

PubMed

Coupled simulation based on intracavity partially coherent light model and 3D CFD model is firstly achieved in this paper. The dynamic equation of partially coherent intracavity field is derived based on partially coherent light theory. A numerical scheme for the coupled simulation as well as a method for computing the intracavity partially coherent field is given. The presented model explains the formation of the sugar scooping phenomenon, and enables studies on the dependence of the spatial mode spectrum on physical parameters of laser cavity and gain medium. Computational results show that as the flow rate of iodine increases, higher order mode components dominate in the partially coherent field. Results obtained by the proposed model are in good agreement with experimental results. PMID:22274214

Wu, Kenan; Huai, Ying; Jia, Shuqin; Jin, Yuqi

2011-12-19

386

The gas flow lasers - A review of theoretical and experimental development  

Microsoft Academic Search

The current trends and principles of gas flow lasers, chemical lasers, and electrically excited supersonic lasers are reviewed with an emphasis on gas dynamic lasers. The principles, aeodynamics and characteristics of 16- and 9-micron CO2 gasdynamic lasers are analyzed. The performance characteristics of supersonic flow chemical lasers, such as HF, DF, and CO lasers, and electrically excited supersonic flow CO

W. Masuda

1985-01-01

387

Novel two-step laser ablation and ionization mass spectrometry (2S-LAIMS) of actor-spectator ice layers: Probing chemical composition of D{sub 2}O ice beneath a H{sub 2}O ice layer  

SciTech Connect

In this work, we report for the first time successful analysis of organic aromatic analytes imbedded in D{sub 2}O ices by novel infrared (IR) laser ablation of a layered non-absorbing D{sub 2}O ice (spectator) containing the analytes and an ablation-active IR-absorbing H{sub 2}O ice layer (actor) without the analyte. With these studies we have opened up a new method for the in situ analysis of solids containing analytes when covered with an IR laser-absorbing layer that can be resonantly ablated. This soft ejection method takes advantage of the tenability of two-step infrared laser ablation and ultraviolet laser ionization mass spectrometry, previously demonstrated in this lab to study chemical reactions of polycyclic aromatic hydrocarbons (PAHs) in cryogenic ices. The IR laser pulse tuned to resonantly excite only the upper H{sub 2}O ice layer (actor) generates a shockwave upon impact. This shockwave penetrates the lower analyte-containing D{sub 2}O ice layer (spectator, a non-absorbing ice that cannot be ablated directly with the wavelength of the IR laser employed) and is reflected back, ejecting the contents of the D{sub 2}O layer into the vacuum where they are intersected by a UV laser for ionization and detection by a time-of-flight mass spectrometer. Thus, energy is transmitted from the laser-absorbing actor layer into the non-absorbing spectator layer resulting its ablation. We found that isotope cross-contamination between layers was negligible. We also did not see any evidence for thermal or collisional chemistry of PAH molecules with H{sub 2}O molecules in the shockwave. We call this “shockwave mediated surface resonance enhanced subsurface ablation” technique as “two-step laser ablation and ionization mass spectrometry of actor-spectator ice layers.” This method has its roots in the well-established MALDI (matrix assisted laser desorption and ionization) method. Our method offers more flexibility to optimize both the processes—ablation and ionization. This new technique can thus be potentially employed to undertake in situ analysis of materials imbedded in diverse media, such as cryogenic ices, biological samples, tissues, minerals, etc., by covered with an IR-absorbing laser ablation medium and study the chemical composition and reaction pathways of the analyte in its natural surroundings.

Yang, Rui, E-mail: ryang73@ustc.edu; Gudipati, Murthy S., E-mail: gudipati@jpl.nasa.gov [Science Division, Jet Propulsion Laboratory, California Institute of Technology, Mail Stop 183-301, 4800 Oak Grove Drive, Pasadena, California 91109 (United States)

2014-03-14

388

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

SciTech Connect

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

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

2013-04-15

389

Optical-chemical-microphysical relationships and closure studies for mixed carbonaceous aerosols observed at Jeju Island; 3-laser photoacoustic spectrometer, particle sizing, and filter analysis  

NASA Astrophysics Data System (ADS)

Transport of aerosols in pollution plumes from the mainland Asian continent was observed in situ at Jeju, South Korea during the Cheju Asian Brown Cloud Plume-Asian Monsoon Experiment (CAPMEX) field campaign throughout August and September 2008 using a 3-laser photoacoustic spectrometer (PASS-3), chemical filter analysis, and size distributions. The PASS-3 directly measures the effects of morphology (e.g. coatings) on light absorption that traditional filter-based instruments are unable to address. Transport of mixed sulfate, carbonaceous, and nitrate aerosols from various Asian pollution plumes to Jeju accounted for 74% of the deployment days, showing large variations in their measured chemical and optical properties. Analysis of eight distinct episodes, spanning wide ranges of chemical composition, optical properties, and source regions, reveals that episodes with higher organic carbon (OC)/sulfate (SO42-) and nitrate (NO3-)/SO42- composition ratios exhibit lower single scatter albedo at shorter wavelengths (?405). We infer complex refractive indices (n-ik) as a function of wavelength for the high, intermediate, and low OC/SO42- pollution episodes by using the observed particle size distributions and the measured optical properties. The smallest mean particle diameter corresponds to the high OC/SO42- aerosol episode. The imaginary part of the refractive index (k) is greater for the high OC/SO42- episode at all wavelengths. A distinct, sharp increase in k at short wavelength implies enhanced light absorption by OC, which accounts for 50% of the light absorption at 405 nm, in the high OC/SO42- episode. Idealized analysis indicates increased absorption at 781 nm by factors greater than 3 relative to denuded black carbon in the laboratory. We hypothesize that coatings of black carbon cores are the mechanism of this enhancement. This implies that climate warming and atmospheric heating rates from black carbon particles can be significantly larger than have been estimated previously. The results of this study demonstrate ways in which atmospheric processing and mixing can amplify particle light absorption for carbonaceous aerosol, significantly at short wavelength, underscoring the need to understand and predict chemical composition effects on optical properties to accurately estimate the climate radiative forcing by mixed carbonaceous aerosols.

Flowers, B. A.; Dubey, M. K.; Mazzoleni, C.; Stone, E. A.; Schauer, J. J.; Kim, S.-W.; Yoon, S. C.

2010-11-01

390

Laser-induced breakdown spectroscopy (LIBS) technique for the determination of the chemical composition of complex inorganic materials  

NASA Astrophysics Data System (ADS)

Laser-induced breakdown spectroscopy (LIBS) is a fast, fully optical method, that needs little or no sample preparation. In this technique qualitative and quantitative analysis is based on comparison. The determination of composition is generally based on the construction of a calibration curve namely the LIBS signal versus the concentration of the analyte. Typically, to calibrate the system, certified reference materials with known elemental composition are used. Nevertheless, such samples due to differences in the overall composition with respect to the used complex inorganic materials can influence significantly on the accuracy. There are also some intermediate factors which can cause imprecision in measurements, such as optical absorption, surface structure, thermal conductivity etc. This paper presents the calibration procedure performed with especially prepared pellets from the tested materials, which composition was previously defined. We also proposed methods of post-processing which allowed for mitigation of the matrix effects and for a reliable and accurate analysis. This technique was implemented for determination of trace elements in industrial copper concentrates standardized by conventional atomic absorption spectroscopy with a flame atomizer. A series of copper flotation concentrate samples was analyzed for contents of three elements, that is silver, cobalt and vanadium. It has been shown that the described technique can be used to qualitative and quantitative analyses of complex inorganic materials, such as copper flotation concentrates.

?azarek, ?ukasz; Anto?czak, Arkadiusz J.; Wójcik, Micha? R.; Kozio?, Pawe? E.; Stepak, Bogusz; Abramski, Krzysztof M.

2014-08-01

391

Defect structure and chemical bonding of p-type ZnO:Sb thin films prepared by pulsed laser deposition  

NASA Astrophysics Data System (ADS)

X-ray photoelectron spectroscopy and x-ray diffraction were used to understand the local environment of Sb in pulsed laser deposited ZnO:Sb films, which switched to p-type electrical conductivity from as-deposited n-type behavior after being annealed at 600 °C under an O2 flow. Tensile in-plane stress was observed in the as-deposited n-type films, and its magnitude increased after the annealing induced p-type switch. This stress can be explained by larger Sb sitting on smaller Zn sites in both the as-deposited and annealed films. Annealing resulted in oxygen incorporation and a more electronegative environment for the cations, as indicated by shifts to higher binding energy of both the Zn2p and Sb3d XPS peaks. The XPS results also show the formation of Sb2O5 in the p-type samples, and indicate a reorganization of the local coordination of Sb. Based on these results and density functional theory computations of the formation and ionization energies of defect complexes, we propose that ?ft[ S{{b}Zn}-2{{V}Zn} \\right]\\prime acceptor complexes are responsible for the p-type conductivity.

Santos-Ortiz, Reinaldo; Jha, Jitendra Kumar; Sun, Wei; Nyandoto, Gilbert; Du, Jincheng; Shepherd, Nigel D.

2014-11-01

392

Lasers - Present and future research  

Microsoft Academic Search

Laser research is reviewed in regards to applications and with particular attention to work in French laboratories. Inertial confinement fusion requires high energy deposition in 0.1-10 ns times, and efforts to devise suitable laser systems are outlined. Exciplex lasers are presented, including halogen and rare-gas halide lasers, rare gas and alkaline dimers, and trimer lasers. Optical and chemical pumping of

P. Philippe

1981-01-01

393

On the role of laser irradiation in the processes of laser desorption/ionisation from silicon surfaces  

SciTech Connect

The role of laser irradiation in the processes of laser desorption/ionisation from silicon surfaces is considered. The basic functions of laser irradiation (chemical activation of the ion emitter surface, laser-induced ionisation of chemical compounds and ion desorption) are established and analysed. (interaction of laser radiation with matter)

Zhabin, S N; Pento, A N; Grechnikov, A A; Borodkov, A S; Sartakov, B G; Simanovsky, Ya O; Nikiforov, S M; Alimpiev, S S

2011-09-30

394

Metallurgical and chemical characterization of copper alloy reference materials within laser ablation inductively coupled plasma mass spectrometry: Method development for minimally-invasive analysis of ancient bronze objects  

NASA Astrophysics Data System (ADS)

The chemical composition of ancient metal objects provides important information for manufacturing studies and authenticity verification of ancient copper or bronze artifacts. Non- or minimal-destructive analytical methods are preferred to mitigate visible damage. Laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) enables the determination of major elements as well as impurities down to lower ppm-levels, however, accuracy and precision of analysis strongly depend on the homogeneity of reference materials used for calibration. Moreover, appropriate analytical procedures are required e.g. in terms of ablation strategies (scan mode, spot size, etc.). This study reviews available copper alloy (certified) reference materials — (C)RMs from different sources and contributes new metallurgical data on homogeneity and spatial elemental distribution. Investigations of the standards were performed by optical and scanning electron microscopy with X-ray spectrometry (SEM-EDX) for the following copper alloy and bronze (certified) reference materials: NIST 454, BAM 374, BAM 211, BAM 227, BAM 374, BAM 378, BAS 50.01-2, BAS 50.03-4, and BAS 50.04-4. Additionally, the influence of inhomogeneities on different ablation and calibration strategies is evaluated to define an optimum analytical strategy in terms of line scan versus single spot ablation, variation of spot size, selection of the most appropriate RMs or minimum number of calibration reference materials.

Walaszek, Damian; Senn, Marianne; Faller, Markus; Philippe, Laetitia; Wagner, Barbara; Bulska, Ewa; Ulrich, Andrea

2013-01-01

395

The influence of laser-induced nanosecond rise-time stress waves on the microstructure and surface chemical activity of single crystal Cu nanopillars  

NASA Astrophysics Data System (ADS)

An apparatus and test procedure for fabrication and loading of single crystal metal nanopillars under extremely high pressures (>1 GPa) and strain rates (>107 s-1), using laser-generated stress waves, are presented. Single-crystalline Cu pillars (˜1.20 ?m in tall and ˜0.45 ?m in diameter) prepared via focused ion beam milling of Cu(001) substrates are shock-loaded using this approach with the dilatational stress waves propagating along the [001] axis of the pillars. Transmission electron microscopy observations of shock-loaded pillars show that dislocation density decreases and that their orientation changes with increasing stress wave amplitude, indicative of dislocation motion. The shock-loaded pillars exhibit enhanced chemical reactivity when submerged in oil and isopropyl alcohol solutions, due likely to the exposure of clean surfaces via surface spallation and formation of surface steps and nanoscale facets through dislocation motion to the surface of the pillars, resulting in growth of thin oxide films on the surfaces of the pillars.

Youssef, G.; Crum, R.; Prikhodko, S. V.; Seif, D.; Po, G.; Ghoniem, N.; Kodambaka, S.; Gupta, V.

2013-02-01

396

The influence of laser-induced nanosecond rise-time stress waves on the microstructure and surface chemical activity of single crystal Cu nanopillars  

PubMed Central

An apparatus and test procedure for fabrication and loading of single crystal metal nanopillars under extremely high pressures (>1?GPa) and strain rates (>107?s?1), using laser-generated stress waves, are presented. Single-crystalline Cu pillars (?1.20??m in tall and ?0.45??m in diameter) prepared via focused ion beam milling of Cu(001) substrates are shock-loaded using this approach with the dilatational stress waves propagating along the [001] axis of the pillars. Transmission electron microscopy observations of shock-loaded pillars show that dislocation density decreases and that their orientation changes with increasing stress wave amplitude, indicative of dislocation motion. The shock-loaded pillars exhibit enhanced chemical reactivity when submerged in oil and isopropyl alcohol solutions, due likely to the exposure of clean surfaces via surface spallation and formation of surface steps and nanoscale facets through dislocation motion to the surface of the pillars, resulting in growth of thin oxide films on the surfaces of the pillars. PMID:23526837

Youssef, G.; Crum, R.; Prikhodko, S. V.; Seif, D.; Po, G.; Ghoniem, N.; Kodambaka, S.; Gupta, V.

2013-01-01

397

The influence of laser-induced nanosecond rise-time stress waves on the microstructure and surface chemical activity of single crystal Cu nanopillars.  

PubMed

An apparatus and test procedure for fabrication and loading of single crystal metal nanopillars under extremely high pressures (>1?GPa) and strain rates (>10(7)?s(-1)), using laser-generated stress waves, are presented. Single-crystalline Cu pillars (?1.20??m in tall and ?0.45??m in diameter) prepared via focused ion beam milling of Cu(001) substrates are shock-loaded using this approach with the dilatational stress waves propagating along the [001] axis of the pillars. Transmission electron microscopy observations of shock-loaded pillars show that dislocation density decreases and that their orientation changes with increasing stress wave amplitude, indicative of dislocation motion. The shock-loaded pillars exhibit enhanced chemical reactivity when submerged in oil and isopropyl alcohol solutions, due likely to the exposure of clean surfaces via surface spallation and formation of surface steps and nanoscale facets through dislocation motion to the surface of the pillars, resulting in growth of thin oxide films on the surfaces of the pillars. PMID:23526837

Youssef, G; Crum, R; Prikhodko, S V; Seif, D; Po, G; Ghoniem, N; Kodambaka, S; Gupta, V

2013-02-28

398

Relation between crystallinity and chemical nature of surface on wettability: A study on pulsed laser deposited TiO{sub 2} thin films  

SciTech Connect

Pure titania (TiO{sub 2}) polycrystalline thin films in rutile, anatase and mixed phase have been grown on amorphous glass substrates by pulsed laser deposition method at various oxygen gas pressure. Wettability investigations have been carried out on these films. Consistent with our previous report [J. Phys. D: Appl. Phys. 41, 155308 (2008)] it has been observed that for nearly same surface roughness large contact angle or superhydrophobicity is present when sample has a pure single phase and lower contact angle or hydrophobicity when mixed phases were present. Structural characterizations suggest that in addition to roughness, pure phase film surface associated with hydrophobic sites and mixed phase film surface show association of both hydrophobic and hydrophilic sites, which might be inducing specific wetting character. UV treatment induces superhydrophilicity in the films. It was observed that UV irradiation causes nonequilibrium state on the TiO{sub 2} surface, leading to changes in the electron density, which in turn produces decrement in the crystallinity and lattice expansion. Reversible changes in the wetting state on the pure phase surfaces were observed to be faster than those on the mixed phase surfaces. We tried to establish the possible relation between crystalline phases, chemical nature of surface on reversible wettability besides the main governing parameter viz. surface roughness.

Shirolkar, Mandar M. [DST Unit on Nanoscience, Indian Institute of Science Education and Research, Pune, 411021 (India); Department of Physics, University of Pune, 411007 (India); Phase, Deodatta; Sathe, Vasant; Choudhary, Ram Janay [UGC-DAE Consortium for Scientific Research Indore Centre, Indore, 452017 (India); Rodriguez-Carvajal, J. [Laboratoire Leon Brillouin (CEA-CNRS), CEA/Saclay, 91191 Gif-sur-Yvette Cedex (France); Kulkarni, Sulabha K. [DST Unit on Nanoscience, Indian Institute of Science Education and Research, Pune, 411021 India (India); Banasthali University, Banasthali, 304022 Rajasthan (India)

2011-06-15

399

Reactions of Laser-Ablated U Atoms with HF: Infrared Spectra and Quantum Chemical Calculations of HUF, UH, and UF in Noble Gas Solids.  

PubMed

Reactions of laser-ablated U atoms with HF produce HUF as the major product and UH and UF as minor products, which are identified from their argon and neon matrix infrared spectra. Our assignment of HUF is confirmed by the observation of DUF and close agreement with observed and calculated vibrational frequencies and deuterium shifts in the vibrational frequencies. Our previous observation of the UH diatomic molecule from argon matrix experiments with H2, HD, and D2 as reagents is confirmed through its present observation with HF and DF, and with recent higher level quantum chemical calculations. The HF reaction provides a lower concentration of F in the system and thus simplifies the fluorine chemistry relative to similar U atom reactions with F2, and the new matrix identification of UF here is consistent with recent high level calculations on UF. In addition, we find evidence for the higher oxidation state secondary reaction products UHF2, UHF3, and UH2F2. PMID:25080179

Vent-Schmidt, Thomas; Andrews, Lester; Riedel, Sebastian

2014-08-12

400

The influence of laser-induced nanosecond rise-time stress waves on the microstructure and surface chemical activity of single crystal Cu nanopillars  

SciTech Connect

An apparatus and test procedure for fabrication and loading of single crystal metal nanopillars under extremely high pressures (>1 GPa) and strain rates (>10{sup 7} s{sup -1}), using laser-generated stress waves, are presented. Single-crystalline Cu pillars ({approx}1.20 {mu}m in tall and {approx}0.45 {mu}m in diameter) prepared via focused ion beam milling of Cu(001) substrates are shock-loaded using this approach with the dilatational stress waves propagating along the [001] axis of the pillars. Transmission electron microscopy observations of shock-loaded pillars show that dislocation density decreases and that their orientation changes with increasing stress wave amplitude, indicative of dislocation motion. The shock-loaded pillars exhibit enhanced chemical reactivity when submerged in oil and isopropyl alcohol solutions, due likely to the exposure of clean surfaces via surface spallation and formation of surface steps and nanoscale facets through dislocation motion to the surface of the pillars, resulting in growth of thin oxide films on the surfaces of the pillars.

Youssef, G.; Crum, R.; Seif, D.; Po, G. [Department of Mechanical and Aerospace Engineering, University of California Los Angeles, 420 Westwood Plaza, Los Angeles, California 90095-1597 (United States); Prikhodko, S. V.; Kodambaka, S. [Department of Materials Science and Engineering, University of California Los Angeles, 410 Westwood Plaza, Los Angeles, California 90095-1595 (United States); Ghoniem, N.; Gupta, V. [Department of Mechanical and Aerospace Engineering, University of California Los Angeles, 420 Westwood Plaza, Los Angeles, California 90095-1597 (United States); Department of Materials Science and Engineering, University of California Los Angeles, 410 Westwood Plaza, Los Angeles, California 90095-1595 (United States)

2013-02-28

401

Carbamazepine in municipal wastewater and wastewater sludge: ultrafast quantification by laser diode thermal desorption-atmospheric pressure chemical ionization coupled with tandem mass spectrometry.  

PubMed

In this study, the distribution of the anti-epileptic drug carbamazepine (CBZ) in wastewater (WW) and aqueous and solid phases of wastewater sludge (WWS) was carried out. A rapid and reliable method enabling high-throughput sample analysis for quicker data generation, detection, and monitoring of CBZ in WW and WWS was developed and validated. The ultrafast method (15s per sample) is based on the laser diode thermal desorption-atmospheric pressure chemical ionization (LDTD-APCI) coupled to tandem mass spectrometry (MS/MS). The optimization of instrumental parameters and method application for environmental analysis are presented. The performance of the novel method was evaluated by estimation of extraction recovery, linearity, precision and detection limit. The method detection limits was 12 ng L(-1) in WW and 3.4 ng g(-1) in WWS. The intra- and inter-day precisions were 8% and 11% in WW and 6% and 9% in WWS, respectively. Furthermore, three extraction methods, ultrasonic extraction (USE), microwave-assisted extraction (MAE) and accelerated solvent extraction (ASE) with three different solvent condition such as methanol, acetone and acetonitrile:ethyle acetate (5:1, v/v) were compared on the basis of procedural blank and method recovery. Overall, ASE showed the best extraction efficiency with methanol as compared to USE and MAE. Furthermore, the quantification of CBZ in WW and WWS samples showed the presence of contaminant in all stages of the treatment plant. PMID:22967548

Mohapatra, D P; Brar, S K; Tyagi, R D; Picard, P; Surampalli, R Y

2012-09-15

402

Influence of plasma density on the chemical composition and structural properties of pulsed laser deposited TiAlN thin films  

SciTech Connect

Incorporation of substitutional Al into the TiN lattice of the ternary alloy TiAlN results in a material with improved properties compared to TiN. In this work, TiAlN thin films were grown by the simultaneous ablation of Ti and Al targets in a nitrogen containing reactive atmosphere. The deposit was formed on silicon substrates at low deposition temperature (200?°C). The dependence of the Al content of the films was studied as a function of the ion density of the plasma produced by the laser ablation of the Al target. The plasma parameters were measured by means of a planar Langmuir probe and optical emission spectroscopy. The chemical composition of the films was measured by energy dispersive X-ray spectroscopy. The results showed a strong dependence of the amount of aluminum incorporated in the films with the plasma density. The structural characterization of the deposits was carried out by Raman spectroscopy, X-ray diffraction, and transmission electron microscopy, where the substitutional incorporation of the Al into the TiN was demonstrated.

Quiñones-Galván, J. G.; Camps, Enrique [Departamento de Física, Instituto Nacional de Investigaciones Nucleares, Apartado Postal 18-1027, México D.F. C.P. 11801 (Mexico); Muhl, S. [Instituto de Investigaciones en Materiales, UNAM, México D.F. C.P. 04510 (Mexico); Flores, M. [Departamento de Ingeniería de Proyectos, CUCEI, Universidad de Guadalajara, Apdo. Postal 307, C.P. 45101 Zapopan, Jalisco (Mexico); Campos-González, E. [Departamento de Física, CINVESTAV-IPN, Apdo. Postal 14-740, México D.F. 07360 (Mexico)

2014-05-15

403

Laser-assisted electrochemistry  

SciTech Connect

The effect of laser irradiation on electrodeposition processes has been investigated. These studies demonstrated that the addition of laser irradiation to an electroplating process can dramatically enhance plating rates and current efficiencies, as well as improve the morphology of the resultant electrodeposit. During the course of these investigations, the mechanism for the laser enhancement of electrodeposition processes was determined. Experimental evidence was obtained to show that laser irradiation of the substrate results in increased metal ion concentrations at the surface of the electrode due to a laser-induced Soret effect. The laser-induced Soret effect has important implications for laser-assisted electrochemical processing. The increase in the surface concentration of ions allows efficient electrodeposition from dilute solutions. As such, laser- assisted electrodeposition may develop into an environmentally conscious manufacturing process by reducing waste and limiting worker exposure to toxic chemicals.

Glenn, D.F.

1995-05-01

404

Singlet oxygen (1O) generation upon 1270 nm laser irradiation of ground state oxygen (3O) dissolved in organic solvents: Simultaneous and independent determination of 1O production rate and reactivity with chemical traps  

NASA Astrophysics Data System (ADS)

Direct photo-production of singlet oxygen, via 1270 nm laser excitation of molecular oxygen, has been the focus of recent articles. The chemical traps 1,3-diphenylisobenzofuran and rubrene are used to monitor singlet oxygen production in organic solvents through the O[3?g-]?O[1?g] transition. In this Letter evolution of the trap concentration is monitored continuously and we propose a new and simple method to measure singlet oxygen production rate. We derive an analytical expression for the trap disappearance rate that allows simultaneous and independent determination of the 1270 nm absorption cross section and the half quenching concentration with the chemical trap.

Sivéry, A.; Anquez, F.; Pierlot, C.; Aubry, J. M.; Courtade, E.

2013-01-01

405

Laser demonstration and performance characterization of optically pumped Alkali Laser systems  

Microsoft Academic Search

Diode Pumped Alkali Lasers (DPALs) offer a promising approach for high power lasers in military applications that will not suffer from the long logistical trails of chemical lasers or the thermal management issues of diode pumped solid state lasers. This research focuses on characterizing a DPAL-type system to gain a better understanding of using this type of laser as a

Clifford V. Sulham

2010-01-01

406

Pulsed DF laser effects  

Microsoft Academic Search

Laser effects caused by pulsed DF laser beams have been investigated under one-dimensional plasma conditions. The high energy pulse from a 50-liter photoinitiated chemical laser was utilized to measure both metal and fiberglass target responses to incident fluences up to 150 J\\/sq cm. In thermal coupling experiments with aluminum, the absorbed fluence showed enhancement just above the plasma threshold, reaching

W. E. Maher; R. B. Hall

1981-01-01

407

Laser isotope separation  

Microsoft Academic Search

This work describes the atomic route to laser isotope separation. This is a process which uses intense pulsed lasers to photoionize one isotopic species of a chemical element, after which these ions are extracted electromagnetically. The paper describes only the isotopic enrichment of uranium for nuclear fuel cycles. It makes brief mention of the traditional cascade processes used at present,

P. T. Greenland

1990-01-01

408

Pseudo-elastic and bio-chemical properties of Ti-Ni shape memory alloy wires micro-welded by YAG laser  

NASA Astrophysics Data System (ADS)

In order to investigate the applicability of laser micro welding to the fabrication of medical devices, Ti-Ni based shape memory alloy biomaterials wires were micro spot melted by using YAG laser. By the optimization of laser conditions such as laser power or pulse duration, sound spot melted wires free from any defects were prepared and the width of the melted metal was reduced to about 0.2 mm for the 0.15 mm diameter wires. Compared with the SUS304 wires, melting of shape memory alloy wires needed more precise control of laser conditions although it needed smaller power input. Melted metal exhibited a rapidly quenched microstructure. The spot melted wires showed 70% of tensile strength and almost the same super-elastic behavior compared with base materials. Besides, it was confirmed by immersion test and by measurement of anodic polarization curve that NT-E4 wires still retain a sound corrosion resistance in a quasi biological environment by laser spot melting. Crosswise or parallel joints was also successfully prepared by laser spot welding of wires, suggesting the laser micro welding is applicable to the fabrication of biomedical devices.

Uenishi, Keisuke; Takatsugu, Masaya; Kobayashi, Kojiro F.

2003-11-01

409

FINAL REPORT. PARTICLE GENERATION BY LASER ABLATION IN SUPPORT OF CHEMICAL ANALYSIS OF HIGH LEVEL MIXED WASTE FROM PLUTONIUM PRODUCTION OPERATIONS  

EPA Science Inventory

We 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 consi...

410

Laser Therapy  

MedlinePLUS

... How to Choose the Best Skin Care Products Laser Resurfacing Uses for Laser Resurfacing Learn more about specific conditions where laser ... skin Scars Sun-damaged skin Wrinkles What is laser resurfacing? Laser resurfacing is a procedure that uses ...

411

Instabilities and structure formation in laser processing  

SciTech Connect

This paper gives an overview on different types of instabilities and structure formation in various fields of laser processing. Among the examples discussed in detail are non-coherent structures observed in laser-induced chemical vapor deposition (LCVD), in laser-induced surface modifications, and in laser ablation of polymers.

Baeuerle, D.; Arenholz, E.; Arnold, N.; Heitz, J.; Kargl, P.B. [Johannes-Kepler-Univ. Linz (Austria). Angewandte Physik

1996-12-31

412

Lasers '85; Proceedings of the Eighth International Conference, Las Vegas, NV, Dec. 2-6, 1985  

SciTech Connect

The present conference on laser technology development encompasses issues in such areas as VUV and X-ray lasers; optical phase conjugation and nonlinear optics; laser applications in medicine; methods for optical processing; laser and nonlinear spectroscopy; ultrashort-pulse lasers and their applications; frequency selection in pulsed lasers; and interactions between laser beams, material surfaces, and material volumes. Also treated are laser applications in the Strategic Defense Initiative program, chemical laser design and performance, the lasing of biophysical materials, laser diagnostics in fluids and plasma, semiconductor laser diodes and arrays, solid state lasers, radiation- and solar-pumped lasers, laser cavities and propagation, remote sensing with lasers and fiber-optics, coupled resonators and diode lasers, industrial applications of lasers, excimer lasers, optoelectronics, CO/sub 2/ lasers, fiber-optic sensors, alexandrite lasers, free electron lasers, and IR and visible wavelength lasers.

Wang, C.P.

1986-01-01

413

Laser ablation in analytical chemistry—a review  

Microsoft Academic Search

Laser ablation is becoming a dominant technology for direct solid sampling in analytical chemistry. Laser ablation refers to the process in which an intense burst of energy delivered by a short laser pulse is used to sample (remove a portion of) a material. The advantages of laser ablation chemical analysis include direct characterization of solids, no chemical procedures for dissolution,

Richard E Russo; Xianglei Mao; Haichen Liu; Jhanis Gonzalez; Samuel S Mao

2002-01-01

414

Lasers '86; Proceedings of the Ninth International Conference on Lasers and Applications, Orlando, FL, Nov. 3-7, 1986  

SciTech Connect

Laser physics, technology, and applications are examined in reviews and reports. Topics addressed include VUV and X-ray lasers, vibrational energy transfer and kinetics, medical applications, ultrashort lasers and spectroscopy, surface and material interactions, lasers in atmospheric physics, and fiber-optic systems. Consideration is given to alexandrite lasers, four-wave mixing and nonlinear optics, chemical lasers, semiconductor lasers, photothermal and photoacoustic spectroscopy, dye lasers, optical phase conjugation and SBS, excimer lasers, SDI laser applications, remote-sensing with lasers, FELs, and applications in chemistry. Diagrams, drawings, graphs, and photographs are provided.

Mcmillan, R.W.

1987-01-01

415

Laser rocket system analysis  

NASA Technical Reports Server (NTRS)

The laser rocket systems investigated in this study were for orbital transportation using space-based, ground-based and airborne laser transmitters. The propulsion unit of these systems utilizes a continuous wave (CW) laser beam focused into a thrust chamber which initiates a plasma in the hydrogen propellant, thus heating the propellant and providing thrust through a suitably designed nozzle and expansion skirt. The specific impulse is limited only by the ability to adequately cool the thruster and the amount of laser energy entering the engine. The results of the study showed that, with advanced technology, laser rocket systems with either a space- or ground-based laser transmitter could reduce the national budget allocated to space transportation by 10 to 345 billion dollars over a 10-year life cycle when compared to advanced chemical propulsion systems (LO2-LH2) of equal capability. The variation in savings depends upon the projected mission model.

Jones, W. S.; Forsyth, J. B.; Skratt, J. P.

1979-01-01

416

Direct chemical-analysis of uv laser-ablation products of organic polymers by using selective ion monitoring mode in gas-chromatography mass-spectrometry  

USGS Publications Warehouse

Trace quantities of laser ablated organic polymers were analyzed by using commercial capillary column gas chromatography/mass spectrometry; the instrument was modified so that the laser ablation products could be introduced into the capillary column directly and the constituents of each peak in the chromatogram were identified by using a mass spectrometer. The present study takes advantage of the selective ion monitoring mode for significantly improving the sensitivity of the mass spectrometer as a detector, which is critical in analyzing the trace quantities and confirming the presence or absence of the species of interest in laser ablated polymers. The initial composition of the laser ablated polymers was obtained by using an electron impact reflectron time-of-flight mass spectrometer and the possible structure of the fragments observed in the spectra was proposed based on the structure of the polymers.

Choi, Y.; Lee, H.W.; Fountain, S.T.; Lubman, D.M.

1994-01-01

417

Lasers Radiation  

MedlinePLUS

... and instruments, including their uses, risks and benefits. Laser Safety Information April. 4, 2014. Laser Institute of America ... Labor, Occupational Safety & Health Administration This webpage discusses laser safety standards in the workplace. Laser Toys: Not Always ...

418

Laser propulsion for orbit transfer - Laser technology issues  

NASA Technical Reports Server (NTRS)

Using reasonable near-term mission traffic models (1991-2000 being the assumed operational time of the system) and the most current unclassified laser and laser thruster information available, it was found that space-based laser propulsion orbit transfer vehicles (OTVs) can outperform the aerobraked chemical OTV over a 10-year life-cycle. The conservative traffic models used resulted in an optimum laser power of about 1 MW per laser. This is significantly lower than the power levels considered in other studies. Trip time was taken into account only to the extent that the system was sized to accomplish the mission schedule.

Horvath, J. C.; Frisbee, R. H.

1985-01-01

419

Quantitative chemical imaging of element diffusion into heterogeneous media using laser ablation inductively coupled plasma mass spectrometry, synchrotron micro-X-ray fluorescence, and extended X-ray absorption fine structure spectroscopy.  

PubMed

Quantitative chemical imaging of trace elements in heterogeneous media is important for the fundamental understanding of a broad range of chemical and physical processes. The primary aim of this study was to develop an analytical methodology for quantitative high spatial resolution chemical imaging based on the complementary use of independent microanalytical techniques. The selected scientific case study is focused on high spatially resolved quantitative imaging of major elements, minor elements, and a trace element (Cs) in Opalinus clay, which has been proposed as the host rock for high-level radioactive waste repositories. Laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS), providing quantitative chemical information, and synchrotron radiation based micro-X-ray fluorescence (SR-microXRF), providing high spatial resolution images, were applied to study Cs migration into Opalinus clay rock. The results indicate that combining the outputs achievable by the two independent techniques enhances the imaging capabilities significantly. The qualitative high resolution image of SR-microXRF is in good agreement with the quantitative image recorded with lower spatial resolution by LA-ICPMS. Combining both techniques, it was possible to determine that the Opalinus clay sample contains two distinct domains: (i) a clay mineral rich domain and (ii) a calcium carbonate dominated domain. The two domains are separated by sharp boundaries. The spatial Cs distribution is highly correlated to the distribution of the clay. Furthermore, extended X-ray absorption fine structure analysis indicates that the trace element Cs preferentially migrates into clay interlayers rather than into the calcite domain, which complements the results acquired by LA-ICPMS and SR-microXRF. By using complementary techniques, the quantification robustness was improved to quantitative micrometer spatial resolution. Such quantitative, microscale chemical images allow a more detailed understanding of the chemical reactive transport process into and within heterogeneous media to be gained. PMID:21623637

Wang, H A O; Grolimund, D; Van Loon, L R; Barmettler, K; Borca, C N; Aeschlimann, B; Günther, D

2011-08-15

420

InGaP/InGaAsP/GaAs 0.808 microns separate confinement laser diodes grown by metalorganic chemical vapor deposition  

NASA Astrophysics Data System (ADS)

Aluminum-free InGaP/InGaAsP/GaAs separate confinement heterostructures have been grown and used for broad-area stripe diode laser fabrication. The lasers demonstrated a uniform near-field pattern and emission spectrum at lambda = 0.808 micron witha full width at half maximum less than or = 2 nm, meeting the necessary requirements for Nd:YAG pumping systems. A threshold current density of 470 A/sq. cm and differential efficiency of 0.7 W/A with series resistance of 0.12 Ohms for 1.37 mm-long diodes have been measured.

Diaz, J.; Eliashevich, I.; Mobarhan, K.; Kolev, E.; Wang, L. J.; Garbuzov, D. Z.; Razeghi, M.

1994-02-01

421

Mixed-layered bismuth-oxygen-iodine materials for capture and waste disposal of radioactive iodine  

SciTech Connect

Materials and methods of synthesizing mixed-layered bismuth oxy-iodine materials, which can be synthesized in the presence of aqueous radioactive iodine species found in caustic solutions (e.g. NaOH or KOH). This technology provides a one-step process for both iodine sequestration and storage from nuclear fuel cycles. It results in materials that will be durable for repository conditions much like those found in Waste Isolation Pilot Plant (WIPP) and estimated for Yucca Mountain (YMP). By controlled reactant concentrations, optimized compositions of these mixed-layered bismuth oxy-iodine inorganic materials are produced that have both a high iodine weight percentage and a low solubility in groundwater environments.

Krumhansl, James L; Nenoff, Tina M

2013-02-26

422

DARPA-NRL laser program. Report to Defense Advanced Research Projects Agency  

Microsoft Academic Search

The DARPA-NRL Laser Program is concerned with the development of laser technology in three project areas: chemical infrared lasers, electrical infrared lasers and electronic-state lasers. The chemical infrared laser program includes studies of pulsed HCl laser systems and molecular energy transfer processes. Data have been collected which suggests that intramolecular energy transfer occurs in SF6 at a rate 1,000 times

J. R. Airey; R. Burnham; L. Champagne; N. Dejeu; J. Eversole

1976-01-01

423

Volume 154, number 5 CHEMICAL PHYSICS LETTERS 3 February 1989 A SOLID STATE RARE GAS HALIDE LASER: XeF IN CRYSTALLINE ARGON  

E-print Network

: XeF IN CRYSTALLINE ARGON N. SCHWENTNER ' Institutfiir Atom- und Festkiirperphysik, Freie Universitdt in crystalline argon. Conversion efficiencies as high as 30% are observed. Gain measurements indicate demonstration of an optically pumped visible laser in a rare gas crystal. The sys- tem, XeF in crystalline argon

Apkarian, V. Ara

424

High power laser coupling. Final report. [HF laser weapons  

Microsoft Academic Search

A photoinitiated pulsed chemical laser has been developed for laser effects studies. This laser has produced 292 J at 2.8 ..mu..m (HF) and 144 J at 3.8 ..mu..m (DF). The threshold conditions for forming absorbing plasmas at atmospheric pressure have been extensively studied for both wavelengths and for seven materials. These thresholds have been measured in terms of both irradiance

R. B. Hall; W. E. Maher; D. J. Nelson; D. B. Nichols

1977-01-01

425

Excimer laser photoresist stripping  

NASA Astrophysics Data System (ADS)

A new method for stripping the most challenging photoresists on deep sub-micron technology semiconductor wafers has been developed. The method uses a combination of UV excimer laser ablation and reactive chemistry to strip the photoresist in a single dry process, eliminating the wet acids or solvents often used following ashing of high dose implantation (HDI) and reactive ion etching (RIE). The stripping process combines new removal mechanisms: chemical assisted UV excimer laser ablation/etching, laser induced chemical etching of side walls and residues, and enhanced combustion. During the laser pulses photolysis of the process gas occurs, UV laser radiation breaks the photoresist polymer chain bonds, and the photoresist (including foreign materials imbedded in it) is ablated. The combustion is ignited by the ablative impact of laser radiation and enhanced by the radicals formed during photo-thermal decomposition of the process gases. Following this process, the volatilized products and gases are evacuated. The optimum laser stripping conditions were developed to provide a wide process window for the most challenging stripping conditions, such as after HDI and RIE (metal, polysilicon), without causing damage to the wafer devices. A photoresist stripping system based on the described technology was designed and built. The system has been designated as the L-StripperTM and provides stripping time of 0.15 s/(micrometer cm2).

Genut, Menachem; Tehar-Zahav, Ofer; Iskevitch, Eli; Livshits, Boris

1996-06-01

426

USE OF MULTI-PHOTON LASER-SCANNING MICROSCOPY TO DESCRIBE THE DISTRIBUTION OF XENOBIOTIC CHEMICALS IN FISH EARLY LIFE STAGES  

EPA Science Inventory

To better understand the mechanisms by which persistent bioaccumulative toxicants (PBTs) produce toxicity during fish early life stages (ELS), dose response relationships need to be determined in relation to the dynamic distribution of chemicals in sensitive tissues. In this stud...

427

A tomographic technique for the simultaneous imaging of temperature, chemical species, and pressure in reactive flows using absorption spectroscopy with frequency-agile lasers  

E-print Network

This paper proposes a technique that can simultaneously retrieve distributions of temperature, concentration of chemical species, and pressure based on broad bandwidth, frequency-agile tomographic absorption spectroscopy. The technique holds...

Cai, Weiwei; Kaminski, Clemens F.

2014-01-21

428

Atomic Vapor Laser Isotope Separation  

Microsoft Academic Search

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

James I. Davis

1983-01-01

429

Engineering Light: Quantum Cascade Lasers  

SciTech Connect

Quantum cascade lasers are ideal for environmental sensing and medical diagnostic applications. Gmachl discusses how these lasers work, and their applications, including their use as chemical trace gas sensors. As examples of these applications, she briefly presents results from her field campaign at the Beijing Olympics, and ongoing campaigns in Texas, Maryland, and Ghana.

Claire Gmachl

2010-03-17

430

Engineering Light: Quantum Cascade Lasers  

ScienceCinema

Quantum cascade lasers are ideal for environmental sensing and medical diagnostic applications. Gmachl discusses how these lasers work, and their applications, including their use as chemical trace gas sensors. As examples of these applications, she briefly presents results from her field campaign at the Beijing Olympics, and ongoing campaigns in Texas, Maryland, and Ghana.

Claire Gmachl

2010-09-01

431

A high-repetition rate scheme for synchrotron-based picosecond laser pump/x-ray probe experiments on chemical and biological systems in solution  

SciTech Connect

We present the extension of time-resolved optical pump/x-ray absorption spectroscopy (XAS) probe experiments towards data collection at MHz repetition rates. The use of a high-power picosecond laser operating at an integer fraction of the repetition rate of the storage ring allows exploitation of up to two orders of magnitude more x-ray photons than in previous schemes based on the use of kHz lasers. Consequently, we demonstrate an order of magnitude increase in the signal-to-noise of time-resolved XAS of molecular systems in solution. This makes it possible to investigate highly dilute samples at concentrations approaching physiological conditions for biological systems. The simplicity and compactness of the scheme allows for straightforward implementation at any synchrotron beamline and for a wide range of x-ray probe techniques, such as time-resolved diffraction or x-ray emission studies.

Lima, Frederico A.; Milne, Christopher J.; Amarasinghe, Dimali C. V.; Rittmann-Frank, Mercedes Hannelore; Veen, Renske M. van der; Reinhard, Marco; Pham, Van-Thai; Karlsson, Susanne; Mourik, Frank van; Chergui, Majed [Laboratoire de Spectroscopie Ultrarapide, Ecole Polytechnique Federale de Lausanne, ISIC, FSB, 1015 Lausanne (Switzerland); Johnson, Steven L.; Grolimund, Daniel; Borca, Camelia; Huthwelker, Thomas; Janousch, Markus [Swiss Light Source, Paul Scherrer Institut, 5232 Villigen (Switzerland); Abela, Rafael [SwissFEL, Paul Scherrer Institut, 5232 Villigen (Switzerland)

2011-06-15

432

Investigation of statistics strategies for improving the discriminating power of laser-induced breakdown spectroscopy for chemical and biological warfare agent simulants  

Microsoft Academic Search

Laser-induced breakdown spectroscopy spectra of bacterial spores, molds, pollens and nerve agent simulants have been acquired. The performance of several statistical methodologies–linear correlation, principal components analysis, and soft independent model of class analogy–has been evaluated for their ability to differentiate between the various samples. The effect of data selection (total spectra, peak intensities, and intensity ratios) and pre-treatments (e.g., averaging)

Chase A. Munson; Frank C. De Lucia; Thuvan Piehler; Kevin L. McNesby; Andrzej W. Miziolek

2005-01-01

433

Method for laser induced isotope enrichment  

DOEpatents

Methods for separating isotopes or chemical species of an element and causing enrichment of a desired isotope or chemical species of an element utilizing laser ablation plasmas to modify or fabricate a material containing such isotopes or chemical species are provided. This invention may be used for a wide variety of materials which contain elements having different isotopes or chemical species.

Pronko, Peter P.; Vanrompay, Paul A.; Zhang, Zhiyu

2004-09-07

434

PROCEEDINGS288 -;-m__c_ LASER ABLATION  

E-print Network

TAIP CONFERENCE PROCEEDINGS288 -;-m__c_ LASER ABLATION: MECHANISMSAND ..'m . . APPLICATIONS States of America. #12;Extending Laser Fusion Concepts Into the Lower Power ( 5 1 GW Heights, NY 10598 USA Claude PHIPPS Chemical and Laser Science Div., Los Alamos National Lab. Los Alamos

Vertes, Akos

435

Laser satellite power systems: concepts and issues  

SciTech Connect

A laser satellite power system (SPS) converts solar power captured by earth-orbiting satellites into electrical power on the earth's surface, the satellite-to-ground transmission of power being effected by a laser beam. The laser SPS is an alternative to the microwave SPS. Lasers and how they work are described, as are the types of lasers - electric discharge, direct and indirect solar pumped, free electron, and closed-cycle chemical - that are candidates for application in a laser SPS. The advantages of a laser SPS over the microwave alternative are pointed out. One such advantage is that, for the same power delivered to the utility busbar, land requirements for a laser system are much smaller (by a factor of 21) than those for microwave system. The four laser SPS concepts that have been presented in the literature are described and commented on. Finally key issues for further laser SPS research are discussed.

Walbridge, E.W.

1982-01-01

436

CW bismuth fibre laser  

Microsoft Academic Search

A new fibre laser based on a bismuth-doped aluminosilicate glass fibre is proposed and fabricated. CW lasing is obtained in the spectral region between 1150 and 1300 nm. The fibres are fabricated by the method of modified chemical vapour deposition. Bibtex entry for this abstract Preferred format for this abstract (see Preferences) Find Similar Abstracts: Use: Authors Title Abstract Text

Evgenii M. Dianov; V. V. Dvoyrin; V. M. Mashinsky; A. A. Umnikov; M. V. Yashkov; A. N. Gur'yanov

2005-01-01

437

Heterogeneous losses of externally generated I atoms for OIL  

NASA Astrophysics Data System (ADS)

Usage of an external iodine atom generator can improve energy efficiency of the oxygen-iodine laser (OIL) and expand its range of operation parameters. However, a noticeable part of iodine atoms may recombine or undergo chemical bonding during transportation from the generator to the injection point. Experimental results reported in this paper showed that uncoated aluminum surfaces readily bounded iodine atoms, while nickel, stainless steel, Teflon or Plexiglas did not. Estimations based on experimental results had shown that the upper bound of probability of surface iodine atom recombination for materials Teflon, Plexiglas, nickel or stainless steel is ?rec <= 10-5.

Torbin, A. P.; Mikheyev, P. A.; Ufimtsev, N. I.; Voronov, A. I.; Azyazov, V. N.

2012-01-01

438

USE OF WHOLE BODY CHEMICAL RESIDUE ANALYSIS AND LASER SCREENING CONFOCAL MICROSCOPY TO DESCRIBE DISTRIBUTION OF PBTS IN FISH EARLY LIFE STAGES  

EPA Science Inventory

Fish early life stages (ELS) are more sensitive than juveniles or adults to many persistent bioaccumulative toxicants (PBTs). To better understand the mechanisms by which these chemicals produce toxicity during fish ELS, dose-response relationships need to be determined in relat...

439

Chemical Peels  

MedlinePLUS

... How to Choose the Best Skin Care Products Chemical Peels Uses for Chemical Peels Learn more about specific conditions where chemical ... damaged skin Sagging skin Wrinkles What is a chemical peel? A chemical peel is a technique used ...

440

Laser-heated thruster  

NASA Technical Reports Server (NTRS)

The development of a computer program for the design of the thrust chamber for a CW laser heated thruster was examined. Hydrodgen was employed as the propellant gas and high temperature absorber. The laser absorption coefficient of the mixture/laser radiation combination is given in temperature and species densities. Radiative and absorptive properties are given to determine radiation from such gas mixtures. A computer code for calculating the axisymmetric channel flow of a gas mixture in chemical equilibrium, and laser energy absorption and convective and radiative heating is described. It is concluded that: (1) small amounts of cesium seed substantially increase the absorption coefficient of hydrogen; (2) cesium is a strong radiator and contributes greatly to radiation of cesium seeded hydrogen; (3) water vapor is a poor absorber; and (4) for 5.3mcm radiation, both H2O/CO and NO/CO seeded hydrogen mixtures are good absorbers.

Kemp, N. H.; Lewis, P. F.

1980-01-01

441

Laser energy conversion  

NASA Technical Reports Server (NTRS)

Laser radiation could possibly provide a feasible approach for the transmission of energy between stations and vehicles in space and on earth. The transmitted energy could be used for the operational requirements of the receiving space station, lunar base, or spacecraft. In addition, laser energy could also be employed to provide power for the propulsion of vehicles in space. The present status of development regarding the various technological areas involved in an implementation of these objectives is examined, taking into account the possibility of further advances needed to satisfy the technical requirements. Attention is given to laser-induced chemistry for converting the radiation energy into chemical energy. Other subjects considered are related to photovoltaics, optical diodes, thermo-electronics, laser rockets, and photon engines.

Billman, K. W.

1975-01-01

442

Remote sensing of chemical warfare agent by CO2 -lidar  

NASA Astrophysics Data System (ADS)

The possibilities of remote sensing of chemical warfare agent by differential absorption method were analyzed. The CO2 - laser emission lines suitable for sounding of chemical warfare agent with provision for disturbing absorptions by water vapor were choose. The detection range of chemical warfare agents was estimated for a lidar based on CO2 - laser The other factors influencing upon echolocation range were analyzed.

Geiko, Pavel P.; Smirnov, Sergey S.

2014-11-01

443

A borane laser  

NASA Astrophysics Data System (ADS)

Emission from electronically excited species forms the basis for an important class of light sources—lasers. So far, commercially available solution-processed blue-emitting laser materials are based on organic compounds or semiconductor nanocrystals that have significant limitations: either low solubility, low chemical- and/or photo-stability and/or uncompetitive prices. Here we report a novel and competitive alternative to these existing laser materials that is based on boron hydrides, inorganic cluster compounds with a rich and diverse chemistry. We demonstrate that solutions of the borane anti-B18H22 show, under pulsed excitation, blue laser emission at 406?nm with an efficiency (ratio of output/input energies) of 9.5%, and a photostability superior to many of the commercially available state-of-the-art blue laser dyes. This demonstration opens the doors for the development of a whole new class of laser materials based on a previously untapped resource for laser technology—the boranes.

Cerdán, Luis; Braborec, Jakub; Garcia-Moreno, Inmaculada; Costela, Angel; Londesborough, Michael G. S.

2015-01-01

444

A borane laser.  

PubMed

Emission from electronically excited species forms the basis for an important class of light sources-lasers. So far, commercially available solution-processed blue-emitting laser materials are based on organic compounds or semiconductor nanocrystals that have significant limitations: either low solubility, low chemical- and/or photo-stability and/or uncompetitive prices. Here we report a novel and competitive alternative to these existing laser materials that is based on boron hydrides, inorganic cluster compounds with a rich and diverse chemistry. We demonstrate that solutions of the borane anti-B18H22 show, under pulsed excitation, blue laser emission at 406?nm with an efficiency (ratio of output/input energies) of 9.5%, and a photostability superior to many of the commercially available state-of-the-art blue laser dyes. This demonstration opens the doors for the development of a whole new class of laser materials based on a previously untapped resource for laser technology-the boranes. PMID:25583133

Cerdán, Luis; Braborec, Jakub; Garcia-Moreno, Inmaculada; Costela, Angel; Londesborough, Michael G S

2015-01-01

445

Energy transmission by laser  

NASA Astrophysics Data System (ADS)

Laser spark obtained by using a conical optics is much more appropriate to form conducting channels in atmosphere. Only two types of lasers are actively considered to be used in forming high-conductivity channels in atmosphere, controlled by laser spark: pulsed sub-microsecond gas and chemical lasers (CO2, DF) and short pulse solid-state and UV lasers. Main advantage of short pulse lasers is their ability in forming of superlong ionised channels with a characteristic diameter of ~ 100 mkm in atmosphere along the beam propagation direction. At estimated electron densities below 1016 cm-3 in these filaments and laser wavelengths in the range of 0.5 - 1.0 mm, the plasma barely absorbs laser radiation. In this case, the length of the track composed of many filaments is determined by the laser intensity and may reach many kilometers at a femtosecond pulse energy of ~ 100 mJ. However, these lasers could not be used to form high-conductivity long channels in atmosphere. The ohmic resistance of this type a conducting channels turned out to be very high, and the gas in the channels could not be strongly heated (< 1 J). An electric breakdown controlled by radiation of femtosecond solid-state laser was implemented in only at a length of 3 m with a voltage of 2 MV across the discharge gap (670 kV/m). Not so long ago scientific group from P.N. Lebedev has improved that result, the discharge gap -1m had been broken under KrF laser irradiation when switching high-voltage (up to 390 kV/m) electric discharge by 100-ns UV pulses. Our previous result - 16 m long conducting channel controlled by a laser spark at the voltage - 3 MV - was obtained more than 20years ago in Russia and Japan by using pulsed CO2 laser with energy - 0.5 kJ. An average electric field strength was < 190 kV/m. It is still too much for efficient applications.

Apollonov, V. V.

2015-02-01

446

Chemical Changes  

NSDL National Science Digital Library

In this activity you will learn what a chemical change is. The first step to understanding chemical changes is to recognize the difference between chemical properties and physical properties. Click here for an example: Chemical and Physical Changes What are the signs of a chemical reaction occuring? Signs of Chemical Change What variables affect a chemical reaction? Variables ...

Mr. Jolley

2005-10-25

447

Pulsed excimer laser processing for cost-effective solar cells  

NASA Technical Reports Server (NTRS)

The application of excimer laser in the fabrication of photovoltaic devices was investigated extensively. Processes included junction formation, laser assisted chemical vapor deposition metallization, and laser assisted chemical vapor deposition surface passivation. Results demonstrated that implementation of junction formation by laser annealing in production is feasible because of excellent control in junction depth and quality. Both metallization and surface passivation, however, were found impractical to be considered for manufacturing at this stage.

Wong, David C.

1985-01-01

448

A tomographic technique for the simultaneous imaging of temperature, chemical species, and pressure in reactive flows using absorption spectroscopy with frequency-agile lasers  

SciTech Connect

This paper proposes a technique that can simultaneously retrieve distributions of temperature, concentration of chemical species, and pressure based on broad bandwidth, frequency-agile tomographic absorption spectroscopy. The technique holds particular promise for the study of dynamic combusting flows. A proof-of-concept numerical demonstration is presented, using representative phantoms to model conditions typically prevailing in near-atmospheric or high pressure flames. The simulations reveal both the feasibility of the proposed technique and its robustness. Our calculations indicate precisions of ?70?K at flame temperatures and ?0.05 bars at high pressure from reconstructions featuring as much as 5% Gaussian noise in the projections.

Cai, Weiwei; Kaminski, Clemens F., E-mail: cfk23@cam.ac.uk [Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge CB2 3RA (United Kingdom)

2014-01-20

449

Chemical Mechanical Planarization- Chemical  

NSDL National Science Digital Library

This website includes an animation which illustrates the chemical action of slurry in the chemical-mechanical planarization process. Objective: Explain the mechanical and chemical ste