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1

Micro Chemical Oxygen-Iodine Laser (COIL).  

National Technical Information Service (NTIS)

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

C. Livermore-Clifford

2007-01-01

2

The standard chemical oxygen-iodine laser kinetics package  

Microsoft Academic Search

This report presents the Air Force Weapons Laboratory Standard Chemical Oxygen-Iodine Laser Kinetics Package. A complete reaction scheme including recommended rate coefficients for modeling the gas phase kinetics of chemical oxygen-iodine lasers (COIL) was established to provide a common basis for the research and development of COIL devices. A review of the experimental kinetic data base from which this model

Glen P. Perram; Gordon D. Hager

1988-01-01

3

Chemical oxygen-iodine laser (COIL) thermal management  

NASA Astrophysics Data System (ADS)

The chemical oxygen-iodine laser (COIL) has been studied at the Phillips Laboratory since its invention in 1978. One of the most difficult challenges in COIL technology is to produce constant power for more than a few seconds; an essential feature for most applications. The key to developing a laser with these operational characteristics is management of the heat released during the production of singlet delta oxygen. Approximately 10 joules is deposited into the singlet delta oxygen generator (SOG) for every joule extracted as laser power. A recent test series demonstrated run times of 120 seconds at 9 kW by controlling the SOG reaction temperature with a flowing aqueous solution of cold hydroperoxide (BHP). This method of managing the energy released is quite effective but requires a large reservoir of cold BHP.

Truesdell, Keith A.; Helms, Charles A.; Longergan, Thomas; Wisniewski, Charles F.; Scott, Joseph E.; Healey, Keith P.

1995-03-01

4

Applications of the chemical oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

The Chemical Oxygen-Iodine Laser (COIL) has been developed at the Air Force Research Laboratory for military applications. For example, the COIL is to be use as the laser device for the ABL. A high power laser is useful for applications that require the delivery of a substantial amount of energy to a very small focused laser spot. The COIL is a member of the class of high power lasers that are also useful for industrial applications, including the materials processing task of high speed cutting and drilling. COIL technology has received considerable interest over the last several years due to its short, fiber- deliverable wavelength, scalability to very high powers, and demonstrated nearly diffraction-limited optical quality. These unique abilities make it an ideal candidate for nuclear reactor decommissioning and nuclear warhead dismantlement. Japanese researchers envision using a COIL for disaster cleanup and survivor rescue. It is also being studied by the oil and gas industry for well drilling. Any commercial or industrial application that requires very rapid, precise, and noninvasive cutting or drilling, could be readily accomplished with a COIL. Because of the substantial power levels available with a COIL, the laser could also be used for broad area applications such as paint stripping. This paper includes a collection of experiments accomplished at the Air Force Research Laboratory Chemical Laser Facility, including metal cutting, hole drilling, high power fiber optic transmission, and rock crushing.

Latham, William P.; Kendrick, Kip R.; Quillen, Brian

2000-01-01

5

Standard chemical oxygen-iodine laser kinetics package. Revision. Final report, August 1987March 1988  

Microsoft Academic Search

It has been long recognized that continuous-wave (CW) chemical lasers represent an extremely complex interaction between fluid mechanics, chemical kinetics, and optical physics. The chemical oxygen-iodine laser presents additional problems in that the energy-storage medium, singlet oxygen, is generated by a liquid-gas phase reaction. The kinetics of chemical oxygen-iodine lasers can be divided into five categories: (1) the chemistry of

G. P. Perram; G. D. Hager

1988-01-01

6

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

7

Standard Chemical Oxygen-Iodine Laser Kinetics Package. Final report, August 1987March 1988  

Microsoft Academic Search

This report presents the Air Force Weapons Laboratory Standard Chemical Oxygen-Iodine Laser Kinetics Package. A complete reaction scheme including recommended rate coefficients for modeling the gas-phase kinetics of chemical oxygen-iodine lasers (COIL) was established to provide a common basis for the research and development of COIL devices. A review of the experimental kinetic data base from which this model was

G. P. Perram; G. D. Hager

1988-01-01

8

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

9

Optimization of jet singlet oxygen generator for chemical oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

Experimental investigation of a jet singlet oxygen generator for a supersonic chemical oxygen-iodine laser was performed aimed to evaluation of the effects of BHP temperature and composition on the water content and other output generator parameters. Laser experiments on a small-scale system were realized to prove the obtained results.

Spalek, Otomar; Kodymova, Jarmila; Zagidullin, Marsel V.; Nikolaev, Valeri D.

1997-04-01

10

Application of a telescopic resonator to high-power chemical oxygen-iodine lasers  

Microsoft Academic Search

The application of an intraresonator telescope to high-power chemical oxygen-iodine lasers to decrease the output beam divergence is analyzed and demonstrated. A theoretical formula based on the ABCD matrix theory is developed to analyze the characteristics of the telescopic resonator. Calculations are carried out using Galilean type telescopes with magnification factors in the range of two to four, and our

Sanichiro Yoshida; Kouki Shimizu; Hari Tahil; Ikuzo Tanaka

1994-01-01

11

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

12

Application of a telescopic resonator to high-power chemical oxygen-iodine lasers  

SciTech Connect

The application of an intraresonator telescope to high-power chemical oxygen-iodine lasers to decrease the output beam divergence is analyzed and demonstrated. A theoretical formula based on the ABCD matrix theory is developed to analyze the characteristics of the telescopic resonator. Calculations are carried out using Galilean type telescopes with magnification factors in the range of two to four, and the high-power chemical oxygen-iodine laser as an analysis model. By locating the telescope at a proper position on the optical axis, the overall telescopic resonator can be conveniently tailored to the hardware of this model laser in a way that the beam divergence and the resonator stability can be improved simultaneously. Experiments are carried out for one of the conditions used in the calculations. Measured divergence angles are in excellent agreement with the theoretical values.

Yoshida, Sanichiro; Shimizu, Kouki; Tahil, Hari; Tanaka, Ikuzo (Inst. of Research and Innovation, Chiba (Japan). Laser Lab.)

1994-01-01

13

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

14

Semi-gas kinetics model for performance modeling of flowing chemical oxygen-iodine lasers (COIL)  

NASA Astrophysics Data System (ADS)

A semi-gas kinetics (SGK) model for performance analyses of flowing chemical oxygen-iodine laser (COIL) is presented. In this model, the oxygen-iodine reaction gas flow is treated as a continuous medium, and the effect of thermal motions of particles of different laser energy levels on the performances of the COIL is included and the velocity distribution function equations are solved by using the double-parameter perturbational method. For a premixed flow, effects of different chemical reaction systems, different gain saturation models and temperature, pressure, yield of excited oxygen, iodine concentration and frequency-shift on the performances of the COIL are computed, and the calculated output power agrees well with the experimental data. The results indicate that the power extraction of the SGK model considering 21 reactions is close to those when only the reversible pumping reaction is considered, while different gain saturation, models and adjustable parameters greatly affect the output power, the optimal threshold gain range, and the length of power extraction.

Gao, Zhi; Hu, Limin; Shen, Yiqing

2004-05-01

15

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

16

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

17

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

18

Operational characteristics of high-pressure subsonic mode chemical oxygen-iodine lasers  

NASA Astrophysics Data System (ADS)

High-pressure subsonic mode operation of chemical oxygen- iodine laser (COIL) is studied. In this mode, the singlet oxygen generated by the liquid-jet singlet oxygen generator (SOG) is directly utilized in the optical cavity without supersonic expansion. Drastic reduction of the required vacuum pump capacity, and iodine consumption was obtained. We have demonstrated a 25.0 percent of chemical efficiency with a small-scale device. The scale-up version of the COIL is developed and initial tests are conducted. The device is so designed that it will operate for 2 hours at 1kW laser output. Due to the inadequate heat exchanger of basic hydrogen peroxide (BHP), performance of the system was not yet satisfactory. However, a 30-minute continuous operation o the counter-flow type jet SOG with recirculation of BHP was demonstrated for the first time.

Endo, Masamori; Sugimoto, Daichi; Tei, Kazuyoku; Takeda, Shuzaburo; Nanri, Kenzo; Fujioka, Tomoo

2000-05-01

19

Chemical oxygen-iodine laser with a centrifugal spray generator of singlet oxygen  

NASA Astrophysics Data System (ADS)

A chemical oxygen-iodine laser driven by the centrifugal spray generator of singlet oxygen was developed and experimentally studied. Modeling and experimental studies showed that the designed generator can produce singlet oxygen, O2(1?g), with a high efficiency (chlorine utilization 0.68 - 0.87 and O2(1?g) yield 0.35 - 0.7) even at very high generator pressures (25 - 70 kPa), which cannot be attained by other O2(1?g) generators. This high-pressure operation should be beneficial for a pressure recovery system of the laser. Another specific feature of the generator is a very high BHP utilization (0.24-0.6). The developed separator can effectively remove even small droplets (> 1 ?m) from gas at the generator exit. Preliminary experiments on the COIL driven the centrifugal spray generator provided the small signal gain up to 0.5 % cm-1.

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

2010-09-01

20

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

NASA Astrophysics Data System (ADS)

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

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

2000-05-01

21

Centrifugal spray generator of singlet oxygen for a chemical oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

A centrifugal spray generator of singlet oxygen, O2(1?g), for driving a chemical oxygen-iodine laser was developed and its operation was experimentally studied. Modeling of the liquid separation from the gas flow showed that the separator designed could remove droplets larger than 0.5 ?m from gas, which is very important for the laser operation. This result was confirmed by experiments. Experimental studies proved that O2(1?g) could be produced with a high efficiency (chlorine utilization 0.68-0.87 and O2(1?g) yield 0.35-0.7) even at very high generator pressures (25-70 kPa), which cannot be attained by other O2(1?g) generators.

Špalek, O.; Hrubý, J.; ?enský, M.; Jirásek, V.; Kodymová, J.

2010-09-01

22

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

23

Real-time data acquisition and control system for a chemical oxygen iodine laser  

NASA Astrophysics Data System (ADS)

A user-friendly data acquisition and control system (DACS) for a chemical oxygen-iodine laser (COIL) has been developed. The system is capable of handling 117 analogue/digital channels for performing various operations such as on-line acquisition, control, display, safety measures and status indication of various subsystems. 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 COIL. The DACS system has been programmed using Advantech-GeniDAQ software. This software has also been used to convert the acquired data into graphical form. Using this DACS, more than 200 runs were given performed successfully.

Mainuddin; Tyagi, R. K.; Rajesh, R.; Singhal, Gaurav; Dawar, A. L.

2003-08-01

24

Lasing in supersonic chemical oxygen-iodine lasers: recent modeling and comparison with experiment  

NASA Astrophysics Data System (ADS)

Simple models are developed, describing the power extraction in chemical oxygen-iodine lasers (COILs) with stable and unstable resonators. For stable resonators the model is applied to the ejector high pressure COIL and the results are compared with the experimental data (see also a preceding paper by Rosenwaks et al.). The positive and negative branch unstable resonators with cylindrical mirrors that have been recently used in COILs are studied theoretically using a geometrical optics model. The optical extraction efficiency, spatial distributions of the intracavity radiation intensity in the flow direction and the intensity in the far field are calculated for both kinds of resonators as a function of both the resonator and COIL parameters. The optimal resonator magnifications corresponding to the maximum intensity in the far field are found.

Barmashenko, Boris D.; Waichman, Karol; Rosenwaks, Salman

2010-09-01

25

Gain and Temperature in a Slit Nozzle Supersonic Chemical Oxygen-Iodine Laser with Transonic and Supersonic Injection of Iodine.  

National Technical Information Service (NTIS)

Spatial distributions of the gain and temperature across the flow were studied for transonic and supersonic schemes of the iodine injection in a slit nozzle supersonic chemical oxygen-iodine laser as a function of the iodine and secondary nitrogen flow ra...

B. D. Barmashenko D. Furman E. Bruins S. Rosenwaks V. Rybalkin

2002-01-01

26

Chemical oxygen-iodine laser for decommissioning and dismantlement of nuclear facilities  

NASA Astrophysics Data System (ADS)

Conceptual designs of a chemical oxygen-iodine laser (COIL) facility for decommissioning and dismantlement (DD) of nuclear facility is proposed. The requisite output power and beam quality was determined base don our preliminary experiments of nonmetal material processing. Assuming the laser power of 30kW, it is derived that the beam quality of M2 equals 36 required to cut a biological shield wall of a nuclear power plant at a cutting speed of 10mm/min. Then the requisite specification of an optical fiber to deliver the laser is calculated. It turned to be quite extreme, core diameter of 1.7mm and NA equals 0.018. The mass flow and heat balance of proposed facility is calculated based on our recent COIL studies. With the high-pressure subsonic mode, the vacuum pump size is minimized compared to the supersonic operation. Finally, the size of the facility is estimated assuming tow-hour continuous operation. It is revealed that such a system can be packed in five railway containers.

Tei, Kazuyoku; Sugimoto, Daichi; Endo, Masamori; Takeda, Shuzaburo; Fujioka, Tomoo

2000-01-01

27

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

28

Removal of Water Vapor in a Mist Singlet Oxygen Generator for Chemical Oxygen Iodine Laser  

NASA Astrophysics Data System (ADS)

The mist singlet oxygen generator (Mist-SOG) for a chemical oxygen iodine laser (COIL) has been developed in order to increase basic hydrogen peroxide (BHP) utilization. It was clarified that the Mist-SOG generated much more water vapor than conventional SOGs because the heat capacity of BHP is small. The water vapor deactivates the excited iodine and depresses the laser power. Therefore, a jet-cold trap was developed in order to remove the water vapor while maintaining a minimum deactivation of singlet oxygen. In this method, a nozzle was used to spray chilled H2O2 at 238 K as a thin layer directly to the gas flow to achieve a large specific surface area for water vapor. As a result, the water vapor mole fraction was reduced to 7% from 18% with the BHP utilization of 21% at the Cl2 consumption rate of 3.5 mmol/s (Cl2 input flow rate of 8.0 mmol/s) for 65-?m-diameter BHP droplets.

Muto, Shigeki; Endo, Masamori; Nanri, Kenzo; Fujioka, Tomoo

2004-02-01

29

Spray generator of singlet oxygen for a chemical oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

A spray type of singlet oxygen generator for driving the Chemical Oxygen-Iodine Laser was developed. Singlet oxygen, O2(1?g), is generated by a fast reaction of chlorine with basic hydrogen peroxide solution in the form of a dense spray. A mathematical model of this reaction system showed that O2(1?g) can be generated in this system with a high yield (0.70-0.80), high utilization of chlorine (0.75-0.95), and effective utilization of liquid (0.36-0.54) at very high generator pressures (35-75 kPa). Experimental studies of this reaction system without an efficient separation of liquid proved an efficient O2(1?g) production characterized by a rather high product of chlorine utilization and O2(1?g) yield (0.4-0.9) at very high generator pressures (30-80 kPa). This pressure is much higher than the operation pressure used in other generators, which should be beneficial for a pressure recovery system of the COIL. These results provided the basis for designing a centrifugal spray generator with an efficient separation of liquid from the gas flow, which is the subject of the following paper.

Jirásek, V.; Hrubý, J.; Špalek, O.; ?enský, M.; Kodymová, J.

2010-09-01

30

Effects of translational nonequilibrium on the performance of a flowing chemical oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

The effect of the translational nonequilibrium on performance modeling of flowing chemical oxygen-iodine lasers (COIL) is emphasized in this paper. The spectral line broadening (SLB) model is a basic factor for predicting the performances of flowing COIL. The Voigt profile function is a well-known SLB model and is usually utilized. In the case of gas pressure in laser cavity less than 5 torr, a low pressure limit expression of the Voigt profile function is used. These two SLB models imply that all lasing particles can interact with monochromatic laser radiation. Basically, the inhomogeneous broadening effects are not considered in these two SLB models and they cannot predict the spectral content. The latter requires consideration of finite translational relaxation rate. Unfortunately, it is rather difficult to solve simultaneously the Navier-Stokes (NS) equations and the conservation equations of the number of lasing particles per unit volume and per unit frequency interval. In the operating condition of flowing COIL, it is possible to obtain a perturbational solution of the conservational equations for lasing particles and deduce a new relation between the gain and the optical intensity, i.e., a new gain-saturation relation. By coupling the gain-saturation relation with other governing equations (such as the NS equations, chemical reaction equations and the optical model of gain-equal-loss), we have numerically calculated the performances of flowing COIL. The present results are compared with those obtained by the common rate-equation (RE) model, in which the Voigt profile function and its low pressure limit expression are used. The difference of different model"s results is great. For instance, in the case of lasing frequency coinciding with the central frequency of line profile and very low gas pressure, the gain saturation relation of the present model is quite different with that of the RE model.

Gao, Zhi; Yan, Hai-Xing; Hu, Li-Min

2003-12-01

31

High-power oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

At VNIIEF work on chemical oxygen-iodine laser (COIL) was begun in 1982 at the Laboratory of Gas-Flow Chemical Lasers. The present report is a review of work performed at this laboratory, the same year generation at the 10 mW level was obtained. A year later the output power was increased up to 180 W. In 1986 optimization of the set-up operation allowed us to increase the laser power up to 900 W. Later a new research set-up was created. In 1990 it produced the output power of approximately 4 kW in 20 seconds.

Kalinovsky, Vitali S.; Kirillov, Gennadi A.; Konovalov, V. V.; Nikolaev, V. D.

1993-04-01

32

Multiphase reacting flow modeling of singlet oxygen generators for chemical oxygen iodine lasers.  

SciTech Connect

Singlet oxygen generators are multiphase flow chemical reactors used to generate energetic oxygen to be used as a fuel for chemical oxygen iodine lasers. In this paper, a theoretical model of the generator is presented along with its solutions over ranges of parameter space and oxygen maximizing optimizations. The singlet oxygen generator (SOG) is a low-pressure, multiphase flow chemical reactor that is used to produce molecular oxygen in an electronically excited state, i.e. singlet delta oxygen. The primary product of the reactor, the energetic oxygen, is used in a stage immediately succeeding the SOG to dissociate and energize iodine. The gas mixture including the iodine is accelerated to a supersonic speed and lased. Thus the SOG is the fuel generator for the chemical oxygen iodine laser (COIL). The COIL has important application for both military purposes--it was developed by the US Air Force in the 1970s--and, as the infrared beam is readily absorbed by metals, industrial cutting and drilling. The SOG appears in various configurations, but the one in focus here is a crossflow droplet generator SOG. A gas consisting of molecular chlorine and a diluent, usually helium, is pumped through a roughly rectangular channel. An aqueous solution of hydrogen peroxide and potassium hydroxide is pumped through small holes into the channel and perpendicular to the direction of the gas flow. So doing causes the solution to become aerosolized. Dissociation of the potassium hydroxide draws a proton from the hydrogen peroxide generating an HO{sub 2} radical in the liquid. Chlorine diffuses into the liquid and reacts with the HO{sub 2} ion producing the singlet delta oxygen; some of the oxygen diffuses back into the gas phase. The focus of this work is to generate a predictive multiphase flow model of the SOG in order to optimize its design. The equations solved are the so-called Eulerian-Eulerian form of the multiphase flow Navier-Stokes equations wherein one set of the equations represents the gas phase and another equation set of size m represents the liquid phase. In this case, m is representative of the division of the liquid phase into distinct representations of the various droplet sizes distributed in the reactor. A stabilized Galerkin formulation is used to solve the equation set on a computer. The set of equations is large. There are five equations representing the gas phase: continuity, vector momentum, heat. There are 5m representing the liquid phase: number density, vector momentum, heat. Four mass transfer equations represent the gas phase constituents and there are m advection diffusion equations representing the HO{sub 2} ion concentration in the liquid phase. Thus we are taking advantage of and developing algorithms to harness the power of large parallel computing architectures to solve the steady-state form of these equations numerous times so as to explore the large parameter space of the equations via continuation methods and to maximize the generation of singlet delta oxygen via optimization methods. Presented here will be the set of equations that are solved and the methods we are using to solve them. Solutions of the equations will be presented along with solution paths representing varying aerosol loading-the ratio of liquid to gas mass flow rates-and simple optimizations centered around maximizing the oxygen production and minimizing the amount of entrained liquid in the gas exit stream. Gas-entrained liquid is important to minimize as it can destroy the lenses and mirrors present in the lasing cavity.

Salinger, Andrew Gerhard; Pawlowski, Roger Patrick; Hewett, Kevin B. (Air Force Research Laboratory, Albuquerque, NM); Madden, Timothy J. (Air Force Research Laboratory, Albuquerque, NM); Musson, Lawrence Cale

2008-08-01

33

Comparison of one- and three-dimensional computational fluid dynamics models of the supersonic chemical oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

A simple one-dimensional (1D) computational fluid dynamics (CFD) model of the chemical oxygen iodine laser (COIL) with supersonic mixing is compared with three-dimensional (3D) CFD models and with experimental measurements of the COIL parameters. Dependence of the gain, iodine dissociation fraction and temperature at the resonator optical axis and of the output lasing power on the iodine flow rate predicted by the 1D model is in good agreement with that found using 3D models and experimental results. Hence the 1D model can be used instead of much more complicated 3D models for estimates of the working parameters of supersonic COILs.

Brami-Rosilio, I.; Barmashenko, B. D.; Rosenwaks, S.

2012-09-01

34

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

35

Parametric studies of a small-scale chemical oxygen-iodine laser/jet generator system: recent achievements  

NASA Astrophysics Data System (ADS)

Recent results of parametric studies of an efficient supersonic chemical oxygen-iodine laser are presented. The laser is energized by a jet type singlet oxygen generator, operated without primary buffer gas and applies simple nozzle geometry and transonic mixing of iodine and oxygen. Output power of 190 W with chemical efficiency of 18% was obtained in a 5 cm gain length for Cl2 flow rate of 11.8 mmole/s. The power is studied as a function of the distance between the optical axis and the supersonic nozzle exit plane, the molar flow rates of various reagents, the BHP and gas pressures in the generator, the type of the secondary buffer gas (N2 or He) and the stagnation temperature of the gas. It is found that the power under the present operation conditions is almost unaffected by water vapor in the medium. The role of buffer gas under different conditions is discussed.

Furman, Dov; Barmashenko, Boris D.; Rosenwaks, Salman

1998-05-01

36

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

SciTech Connect

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

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

1996-09-01

37

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

38

Oxygen-iodine laser research at RFNC-VNIIEF  

Microsoft Academic Search

The paper presents the most important efforts in the Chemical Oxygen-Iodine Laser (COIL) research carried on at Russian Federal Nuclear Center VNIIEF and some of their results. In particular, they include experimental data on the laser generation output of subsonic COIL on the water vapor concentration in singlet oxygen, calculated generation values of a supersonic COIL having high singlet oxygen

Anatoliy A. Adamenkov; Yuri N. Deryugin; Boris A. Vyskubenko; S. P. Ilyin; V. V. Kalinovsky; Yuriy V. Kolobyanin; V. V. Konovalov; Ivan M. Krukovsky; Evgeniy A. Kudryashov; V. D. Nikolaev

1998-01-01

39

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

NASA Astrophysics Data System (ADS)

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

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

2003-06-01

40

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

NASA Astrophysics Data System (ADS)

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

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

1989-04-01

41

Numerical analysis of spatial evolution of the small signal gain in a chemical oxygen–iodine laser operating without primary buffer gas  

Microsoft Academic Search

A chemical oxygen–iodine laser (COIL) that operates without primary buffer gas has become a new way of facilitating the compact integration of laser systems. To clarify the properties of spatial gain distribution, three-dimensional (3-D) computational fluid dynamics (CFD) technology was used to study the mixing and reactive flow in a COIL nozzle with an interleaving jet configuration in the supersonic

Zongmin Hu; Zonglin Jiang; Rhoshin Myong; Taehwan Cho

2008-01-01

42

Numerical study on the performance of nozzle flow for supersonic chemical oxygen–iodine lasers  

Microsoft Academic Search

Laser performance is greatly dependent on its operating conditions due to the strong coupling among multi-physics such as\\u000a gas-dynamics, chemical reaction kinetics and optics in the mixing nozzle of COIL. In this paper, 3D CFD technology is used\\u000a to simulate the mixing and reactive flow of subsonic cross jet scheme at different conditions. Results obtained show that\\u000a the jet penetration

Zongmin Hu; Junming Lü; Zonglin Jiang; Rho-Shin Myong; Tae-Hwan Cho

2008-01-01

43

Gain and temperature in a slit nozzle supersonic chemical oxygen-iodine laser with transonic and supersonic injection of iodine  

NASA Astrophysics Data System (ADS)

Spatial distributions of the gain and temperament across the flow were studied for transonic and supersonic schemes of the iodine injection in a slit nozzle supersonic chemical oxygen-iodine laser as a function of the iodine and secondary nitrogen flow rate, jet penetration parameter and gas pumping rate. The mixing efficiency for supersonic injection of iodine is found to be much larger than for transonic injection, the maximum values of the gain being approximately 0.65 percent/cm for both injection schemes. Measurements of the gain distribution as a function of the iodine molar flow rate nI2 were carried out. For transonic injection the optimal value of nI2 at the flow centerline is smaller than that at the off axis location. The temperature is distributed homogeneously across the flow, increasing only in the narrow boundary layers near the walls. Opening a leak downstream of the cavity in order to decease the Mach number results in a decrease of the gain and increase of the temperature. The mixing efficiency in this case is much larger than for closed leak.

Rosenwaks, Salman; Barmashenko, Boris D.; Bruins, Esther; Furman, Dov; Rybalkin, Victor; Katz, Arje

2002-05-01

44

Numerical study on the performance of nozzle flow for supersonic chemical oxygen-iodine lasers  

NASA Astrophysics Data System (ADS)

Laser performance is greatly dependent on its operating conditions due to the strong coupling among multi-physics such as gas-dynamics, chemical reaction kinetics and optics in the mixing nozzle of COIL. In this paper, 3D CFD technology is used to simulate the mixing and reactive flow of subsonic cross jet scheme at different conditions. Results obtained show that the jet penetration depth plays a dominant role in the spatial distribution of small signal gains. In the case of over-penetration, unsteady flow structures are induced by impinging between the opposing jets. The optimum spatial distribution of the chemical performance cannot be obtained even if the full penetration condition is achieved through the subsonic transverse jet mixing scheme in the COIL nozzle flow.

Hu, Zongmin; Lü, Junming; Jiang, Zonglin; Myong, Rho-Shin; Cho, Tae-Hwan

2008-04-01

45

Advanced Nozzle Concepts for the Chemical Oxygen-Iodine Laser (COIL).  

National Technical Information Service (NTIS)

This report results from a contract tasking P. N. Lebedev Physical Institute as follows: Iodine lasers offer the possibility of producing high average powers at a wavelength compatible with conventional fiber optic delivery systems, making them attractive...

V. D. Nikolaev

2006-01-01

46

Oxygen-iodine laser research at RFNC-VNIIEF  

NASA Astrophysics Data System (ADS)

The paper presents the most important efforts in the Chemical Oxygen-Iodine Laser (COIL) research carried on at Russian Federal Nuclear Center VNIIEF and some of their results. In particular, they include experimental data on the laser generation output of subsonic COIL on the water vapor concentration in singlet oxygen, calculated generation values of a supersonic COIL having high singlet oxygen pressure at the nozzle inlet, and experiments with the twisted-aerosol- flow singlet oxygen generator (TASOG) for up to 100 Torr pressures. Requirements are discussed for the supersonic high- pressure COIL components, such as singlet oxygen generator and the system for singlet oxygen mixing with iodine.

Adamenkov, Anatoliy A.; Deryugin, Yuri N.; Vyskubenko, Boris A.; Ilyin, S. P.; Kalinovsky, V. V.; Kolobyanin, Yuriy V.; Konovalov, V. V.; Krukovsky, Ivan M.; Kudryashov, Evgeniy A.; Nikolaev, V. D.

1998-12-01

47

Electric Oxygen Iodine Laser: A Study for Scaling.  

National Technical Information Service (NTIS)

Energy transfer reactions that could potentially limit scaling of the electric oxygen iodine laser (EOIL) were examined. Quenching of excited iodine atoms (I*) by atomic oxygen has been identified as a significant energy loss channel. The rate constant fo...

M. C. Heaven

2009-01-01

48

Oxygen-iodine laser in Russian Federal Nuclear Center VNIIEF  

NASA Astrophysics Data System (ADS)

The paper reports on the experimental investigations into supersonic oxygen-iodine laser (COIL). Study efficiency results of the COIL unit driven by the singlet oxygen generator (SOG) with twisted gas flow (TA-SOG) are given for supersonic iodine- oxygen mixing at a broadly ranged singlet oxygen pressure and buffer gas flowrate. The measurements were performed for variations of the throat sizes and the positions of the iodine injection plane in supersonic nozzle part. The gas pressure at the input of the nozzle unit was varied from 50 to 150 Torr. The chemical efficiency achieved under optimal operational COIL conditions was 33%.

Vyskubenko, Boris A.; Adamenkov, Anatoly A.; Bakshin, Victor V.; Buzoverya, Vladimir V.; Vdovkin, Leonid A.; Deryugin, Yuri N.; Efremov, Valentin I.; Ilyin, Sergey P.; Kalinovskiy, Vladimir V.; Kolobyanin, Yuriy V.; Konovalov, Vladimir V.; Kudryashov, Evgeniy A.; Moiseev, Vladimir B.; Nickolaev, Victor D.

2005-03-01

49

Buffer gas mixing with active gas on chemical oxygen-iodine laser performance with jet type SOG  

NASA Astrophysics Data System (ADS)

The increasing of stagnation pressure and Re number of gas flow is a very important for supersonic oxygen-iodine laser (COIL). This goal can be achieved with the aid of high pressure singlet oxygen generator (SOG) and high dilution of oxygen with buffer gas of high molecular weight downstream of SOG. The study of COIL operated with jet type SOG at 10 and 20 mmole/s of chlorine flow rate and 50 torr output of pure oxygen is presented. Two experimental set-up were tested. In the first one the mixing of chlorine with buffer gas was provided upstream of SOG gas inlet. In the second one the pure chlorine was injected into SOG and oxygen was mixed with buffer gas downstream of SOG outlet. The stability of jet SOG in the first set-up strongly depended on partial buffer gas pressure and its molecular weight: at higher pressures and molecular weight the stability of SOG operation was worse. In the second set-up the operation of SOG didn't depend on buffer gas pressure and its molecular weight. COIL output power was highest for first set-up with dilution of chlorine by buffer gas until SOG stable operated. In the second set-up the output power was in twice less and strongly depend on type and position of buffer gas injector between SOG and iodine injector. This dependence strongly demonstrated the importance of gas mixing to molecular level for achieving highest COIL power. Another problem considered in this work is connected with BHP heating that important for recirculation of liquid in long time duration COIL operating system. The correlation of BHP heating and O2(1(Delta) ) yield is presented. It is shown that nacsent O2(1(Delta) ) yield is close to 100%.

Zagidullin, Marsel V.; Nikolaev, Valeri D.; Svistun, Michael I.; Safonov, Vladimir S.; Ufimtsev, Nikolay I.

1996-03-01

50

Oxygen-iodine laser in Russian Federal Nuclear Center VNIIEF  

Microsoft Academic Search

The paper reports on the experimental investigations into supersonic oxygen-iodine laser (COIL). Study efficiency results of the COIL unit driven by the singlet oxygen generator (SOG) with twisted gas flow (TA-SOG) are given for supersonic iodine- oxygen mixing at a broadly ranged singlet oxygen pressure and buffer gas flowrate. The measurements were performed for variations of the throat sizes and

Boris A. Vyskubenko; Anatoly A. Adamenkov; Victor V. Bakshin; Vladimir V. Buzoverya; Leonid A. Vdovkin; Yuri N. Deryugin; Valentin I. Efremov; Sergey P. Ilyin; Vladimir V. Kalinovskiy; Yuriy V. Kolobyanin; Vladimir V. Konovalov; Evgeniy A. Kudryashov; Vladimir B. Moiseev; Victor D. Nickolaev

2005-01-01

51

Development of the electric discharge oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

In the hybrid electric discharge Oxygen-Iodine laser (ElectricOIL), the desired O II(a1?) is produced using a low-to-medium pressure electric discharge. The discharge production of atomic oxygen, ozone, and other excited species adds higher levels of complexity to the post-discharge kinetics which are not encountered in a classic purely chemical O II(a1?) generation system. Experimental studies over the past six years using electric discharges have demonstrated O II(a) yields greater than 20%, gain, and cw laser power. Several modeling studies have also been performed for ElectricOIL and similar systems. As the development of this type of iodine laser continues, the roles of oxygen atoms and NO/NO II are found to be very significant in both the discharge region and downstream of the discharge region. A series of O II(1?) emission, I* emission, O-atom titrations, gain, and O II(1?) yield, NO II* emission, and laser power measurements have been taken to explore the complex phenomena that are being observed. As the overall system is better understood improvements are being made in laser power and efficiency.

Carroll, David L.; Verdeyen, Joseph T.; King, Darren M.; Palla, Andrew D.; Laystrom, Julia K.; Benavides, Gabriel F.; Zimmerman, Joseph W.; Woodard, Brian S.; Solomon, Wayne C.

2007-05-01

52

Advancement and problems of fullerene-oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

The methods of improving the efficiency of a fullerene-oxygen-iodine laser are investigated. In the course of this research, we developed new fullerene coatings that possess better mechanical and radiative hardness, as well as higher efficiency of singlet oxygen generation. We show that, by using these coatings, the energy yield per unit volume of the active medium can be increased to 9 J/l, which is almost two times higher than the previous result. The energy efficiency of the laser can also be increased by a factor of nearly two. At the same time, several problems were revealed that hinder the further improvement of the laser efficiency and its long-term operation with stable parameters of the output radiation. We outline principal approaches to further optimization of the laser design that would help to overcome the negative factors and make it possible to create a fullerene-oxygen-iodine laser with high and stable parameters of the output radiation.

Grenishin, A. S.; Kiselev, V. M.; Kislyakov, I. M.; Pavlova, A. L.; Sosnov, E. N.

2010-01-01

53

Electric discharge oxygen-iodine laser: three decades from the idea to the laser development  

Microsoft Academic Search

The overview of experimental research aimed at the research and development of an electric discharge oxygen-iodine laser (DOIL) since the first negative attempt of launching a DOIL in the 1970's is presented. The problem is tightly connected with the development of singlet delta oxygen (SDO) electric generator, which could substitute in future for SDO chemical one used for a high-power

Andrey Ionin

2006-01-01

54

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

55

An Electronic Transition Chemical Laser.  

National Technical Information Service (NTIS)

This report covers unclassified laser research performed at the Air Force Weapons Laboratory. The two reports included herein describe the first operation of an oxygen-iodine chemical laser and the first transverse flow high efficiency oxygen-iodine chemi...

W. E. McDermott N. R. Pchelkin D. J. Bernard R. R. Bousek

1978-01-01

56

Frequency-doubled pulsed chemical oxygen-iodine laser as an efficient pump source for high-power solid state lasers  

Microsoft Academic Search

Output laser parameters are enhanced significantly by using laser pumping. An excellent example is usage of laser diodes for solid-state laser pumping. Although there are permanent advances towards development of this technique, its application for laser systems of more than 100 J output requires time, significant effort and expense. I propose another pumping source based on a rather simple and

P. G. Kryukov

1995-01-01

57

Method, System and Apparatus for an Enhanced Electrically Pumped Oxygen Iodine Laser.  

National Technical Information Service (NTIS)

In one embodiment of the present invention an oxygen iodine laser includes a gas mixing section. Ground state oxygen and a carrier gas are introduced into the first gas mixing section, sometimes separately. The laser includes a discharge region to generat...

D. L. Carroll D. M. King J. T. Verdeyen W. C. Solomon

2005-01-01

58

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.

2011-02-01

59

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

60

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

NASA Astrophysics Data System (ADS)

In an electric discharge oxygen-iodine laser, laser action at 1315 nm on the I(2P1/2)-->I(2P3/2) transition of atomic iodine is obtained by a near resonant energy transfer from O2(a 1?) which is produced using a low-pressure electric discharge. The discharge production of atomic oxygen, ozone, and other excited species adds higher levels of complexity to the postdischarge kinetics which are not encountered in a classic purely chemical O2(a 1?) generation system. Mixing effects are also present. In this paper we present postdischarge modeling results obtained using a modified version of the BLAZE-II gas laser code. A 28 species, 105 reaction chemical kinetic reaction set for the postdischarge kinetics is presented. Calculations were performed to ascertain the impact of a two stream mixing mechanism on the numerical model and to study gain as a function of reactant mass flow rates. The calculations were compared with experimental data. Agreement with experimental data was improved with the addition of new kinetics and the mixing mechanism.

Palla, Andrew D.; Carroll, David L.; Verdeyen, Joseph T.; Solomon, Wayne C.

2006-07-01

61

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

62

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.

2003-12-01

63

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

64

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

65

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

66

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 O2: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

67

Chemistry of I(2P1/2) excitation in a hybrid catalytic electric-discharge oxygen-iodine laser  

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 examine comparisons of kinetics analysis and model predictions to experimental results from a supersonic EOIL research reactor. This analysis leads to identification of important additional production and loss terms for the lasing species, I(2P1/2), in the EOIL reaction mechanism. These mechanisms are also relevant to the catalytically enhanced EOIL excitation mechanism. Exploitation of this chemistry can lead to substantial increases in gain and power extraction efficiency in larger-scale EOIL systems. The analysis points to a significantly higher level of understanding of this energetic chemical system, which can support application of advanced concepts in power scaling investigations.

Rawlins, Wilson T.; Lee, Seonkyung; Davis, Steven J.

2012-02-01

68

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

69

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

70

Kinetics and scaling of gain and lasing in a 1-5 kW microwave discharge oxygen iodine laser  

NASA Astrophysics Data System (ADS)

Scaling of Electric Oxygen-Iodine Laser (EOIL) systems to higher powers requires extension of electric discharge powers into the kW range and beyond, with high efficiency and singlet oxygen yield. This paper describes the implementation of a moderate-power (1 to 5 kW) microwave discharge at 30 to 70 Torr pressure in a supersonic flow reactor designed for systematic investigations of the scaling of gain and lasing with power and flow conditions. The 2450 MHz microwave discharge is confined near the flow axis by a swirl flow. The discharge effluent, containing active species including O2(a1?), O(3P), and O3, passes through a 2-D flow duct equipped with a supersonic nozzle and cavity. I2 is injected upstream of the supersonic nozzle. The apparatus is water-cooled, and is modular to permit a variety of inlet, nozzle, and optical configurations. A comprehensive suite of optical emission and absorption diagnostics monitors the absolute concentrations of O2(a), O(3P), O3, I2, I(2P3/2), I(2P1/2), small-signal gain, and temperature in both the subsonic and supersonic flow streams. The experimental results include numerous observations of positive gain and lasing in supersonic flow, and the scaling of gain with a variety of flow and reaction rate conditions. The results are compared with kinetics modeling predictions to highlight key discrepancies as well as areas of agreement. The observed gains are generally lower than the predicted values, due in part to chemical kinetics effects and also due to mixing limitations specific to the reagent injection design. We discuss in detail the observed effects related to O-atom chemistry, and their import for scaling the gain to higher levels. We also will present initial beam quality measurements.

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

2010-02-01

71

Compact cw supersonic chemical oxygen-iodine laser (COIL)  

NASA Astrophysics Data System (ADS)

A closed-loop flowing basic hydrogen peroxide (BHP) system with real-time cooling was constructed and coupled to a supersonic COIL, resulting in a 20-min. continuous run at an average power of 500 W. An overall BHP heat transfer coefficient of 150 BTU/(hr(DOT)ft2(DOT) degree(s)F) was measured.

Phipps, Steven P.; Helms, Charles A.; Truesdell, Keith A.; Healey, Keith P.

1995-03-01

72

Catalytic enhancement of singlet oxygen production and optical gain in electric discharge oxygen-iodine laser systems  

NASA Astrophysics Data System (ADS)

We are investigating catalytically enhanced production of singlet oxygen, O2(a1?g), observed by reaction of O2/He discharge effluents over an iodine oxide film surface in a microwave discharge-flow reactor at 320 K. We have previously reported a two-fold increase in the O2(a) yields by this process, and corresponding enhancement of I(2P1/2) excitation and small-signal gain upon injection of I2 and NO2. In this paper we review observed I* excitation behavior and correlations of the catalytically generated O2(a) with atomic oxygen over a large range of discharge-flow conditions to develop a conceptual reaction mechanism for the phenomena. We describe a first-generation catalytic module for the PSI supersonic MIDJet/EOIL reactor, and tests with this module for catalyst coating deposition and enhancement of the small-signal gain observed in the supersonic flow. The results present compelling evidence for catalytic production of vibrationally excited O2(X,v) and its participation in the I* excitation process. The observed catalytic effects could significantly benefit the development of high-power electrically driven oxygen-iodine laser systems.

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

2011-02-01

73

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

74

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

Microsoft Academic Search

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

Jose M. Orza; C. Domingo

1991-01-01

75

Development of a mist singlet oxygen generator for a chemical oxygen-iodine laser  

NASA Astrophysics Data System (ADS)

Mist singlet oxygen generator (Mist-SOG) has been developed in order to increase the BHP utilization. On the other hand, Mist-SOG generates much more water vapor than conventional SOG because the heat capacity of the BHP is small. It is well known that the water vapor deactivates the excited iodine. In order to remove the water vapor, we developed a jet-cold trap. In this method, a nozzle sprayed a chilled H2O2 at 238K with a thin layer form to the gas flow directly in order to get the large specific surface for the water vapor. As a result of experiment, Water vapor partial pressure reduced from 3.3 Torr at the BHP flow rate of 2.2 ml/s and Cl2 flow rate of 3.5 mmol/s for the 65?m BHP droplets.

Muto, Shigeki; Endo, Masamori; Nanri, Kenzo; Fujioka, Tomoo

2003-11-01

76

Electrochemical regeneration of basic hydrogen peroxide for chemical oxygen iodine laser  

NASA Astrophysics Data System (ADS)

A 3.6M basic hydrogen peroxide solution is electrochemically regenerated. The apparatus was originally developed for electrolytic H2O2 production, generating dilute (<0.2M) BHP for paper manufacturing. To suppress decomposition by various mechanisms, they are identified and quantified. Both caffeine and peracetic acid are found effective to suppress autodecomposition. Theoretical prediction of the current efficiency is made to find an optimum operational condition. A BHP of 3.614M is regenerated to 3.657M with a current efficiency of 67%.

Endo, Masamori; Hano, Masami; Wakita, Syuhei; Uno, Masaharu; Takeda, Shuzaburo

2005-03-01

77

Short Wavelength Chemical Laser (SWCL) Workshop  

NASA Astrophysics Data System (ADS)

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

Watt, W.

1984-12-01

78

Short wavelength chemical lasers  

SciTech Connect

Experimental results on the operation of HF chemical lasers on the v = 2 to v = 0 overtone transitions are presented. Two separate CW laser devices with gain lengths of 15 and 30 cm produced 21 and 56 W of overtone power. The comparable power on fundamental transitions of the same lasers was 97 and 180 W. Thus, these overtone HF lasers produce 22 and 31 percent of the available fundamental power, much higher percentages than previous overtone chemical lasers. The implications of this new short wavelength chemical laser for high power lasers are discussed briefly. 17 references.

Jeffers, W.Q.

1989-01-01

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

Visible chemical lasers  

NASA Astrophysics Data System (ADS)

Applications for visible chemical lasers, which show great potential as highly efficient, wavelength agile, deployable, high brightness laser systems are discussed. These systems provide important and unique opportunities for both directed energy weapons and diagnostic applications. Issues discussed in this paper include concepts, requirements and approaches to visible chemical lasers. A survey of candidate energy transfer system is also given, with emphasis on excited NF and nitrogen driven lasers. The long term, low level investment in this techonology area during the past decade firmly establishes the opportunity for a lasing demonstration in the near term.

Perram, Glen P.

81

Chemical hydrogen fluoride lasers  

NASA Astrophysics Data System (ADS)

A brief review of the investigation results of chemical lasers based on the chain and nonchain reaction of fluorine with hydrogen (deuterium) made in the Russian Federal Nuclear Center (VNIIEF) is presented in this report.

Borisov, V. P.; Velikanov, S. D.; Zapolsky, A. F.; Kormer, S. B.; Synitsin, M. V.; Urlin, Vitali D.; Frolov, Y. N.; Shurov, V. V.

1996-02-01

82

Chemical Laser Diluents.  

National Technical Information Service (NTIS)

The purpose of this study was to monitor the effects of diluents on a HCl laser. The initial plans were to obtain an HCl laser with a mixture of helium, hydrogen, and chlorine, and then try other chemicals. However, it was found in the present study that ...

J. K. McDonald

1975-01-01

83

Chemical laser systems analysis  

SciTech Connect

This paper presents a means by which the chemical laser device weight can be minimized with respect to its performance and the device power minimized with respect to the target range. Chemical laser performance parameters such as the specific power and nozzle power flux are then used in conjunction with weight and propagation models to determine system effectiveness. A measure of merit is given by which systems can be contrasted. An illustrative example is included in which DF and Iodine laser systems are compared for an airborne scenario. 14 references.

Doughty, J.R.

1988-11-01

84

Multi-Disciplinary Research for High Energy Chemical Lasers, Closed- Cycle ElectricOIL Technology.  

National Technical Information Service (NTIS)

The program was initiated in July 2002. Work during this grant resulted in more than 50 publications in several major breakthroughs by the MRI team: (1) the first measurement of laser gain in a discharge driven oxygen- iodine system was demonstrated in a ...

W. C. Solomon

2007-01-01

85

Chemical laser modeling with genetic algorithms  

Microsoft Academic Search

A genetic algorithm technique was implemented to determine a set of unknown parameters that best matched the Blaze II chemical laser model predictions with experimental data. This is the first known application of the genetic algorithm technique for modeling lasers, chemically reacting flows, and chemical lasers. Overall, the genetic algorithm technique worked exceptionally well for this chemical laser modeling problem

David L. Carroll

1996-01-01

86

Efficient Pulsed Chemical Laser.  

National Technical Information Service (NTIS)

Output pulse observations are presented for a He-diluted CO2 laser pumped by vibrational-vibration (VV) energy transfer from vibrationally excited DF produced by the D2-F2 chain reaction. Flash photolysis of the F2 initiated the reaction. A 290-cc reactio...

A. Chang J. S. Whittier S. N. Suchard

1973-01-01

87

HCl Chemical Laser.  

National Technical Information Service (NTIS)

Several types of HCl lasers were observed in the region of the electromagnetic spectrum from about 3.5 to 3.9 micrometers. A number of reactants were screened in a pulsed electrical discharge system, and HCl lasing was observed from 26 transitions between...

H. C. Gardner J. A. Merritt

1973-01-01

88

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

89

Gas laser chemical pump fluidization  

SciTech Connect

An improvement to the chemical pump as currently used to pump a gas laser cavity is achieved by employing a chemical pump with a fluidized bed, i.e., a bed of particles of a reactive material wherein the particles are suspended in a column by an inert driving fluid. The driving fluid which is nonreactive with the particles of reactive material can be selected from the group consisting of helium and argon. In addition to its function to fluidize the particles of reactive material, the driving fluid can function for some designs to load or unload the particle bed material. The reactive material is selected from the materials consisting of lithium, sodium, potassium, rubidium, cesium, calcium, strontium, barium, titanium, zirconium, hafnium, and alloys of the same which are reactive with the laser effluent gases which include various mixtures of hydrogen, deuterium, nitrogen, hydrogen fluoride, deuterium fluoride, and other combustion products. The reactive materials form solids or liquids from the effluent gases which are brought into intimate contact with the fluidized bed. Fluidization of the bed results from flow of the laser effluent gases as augmented by the driving fluid to maintain the proper fluidization and particle motion to maintain the reaction required for retention of the low pressure necessary for efficient operation of the laser. The particle motion also serves to reduce the temperature gradients in the bed and increases the heat transfer from the bed to the container walls.

Martin, W.D.

1980-04-01

90

Quantum cascade lasers in chemical physics  

NASA Astrophysics Data System (ADS)

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

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

2010-02-01

91

Chemical Stabilization of Laser Dyes.  

National Technical Information Service (NTIS)

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...

T. H. Koch

1984-01-01

92

HF\\/DF chemical laser performance modification by chemical additives  

Microsoft Academic Search

The premixed DF supersonic flow chemical laser promises favorable operational characteristics. To establish feasibility, an experimental program has been initiated to develop the chemical inhibition and ignition techniques required to achieve premixed supersonic flow HF\\/DF chemical laser operation. This report documents the available results. Premixing the inhibition by 1 to 4% O2 has been achieved in 5 g\\/sec and 50

S. C. Kurzius

1974-01-01

93

High-pressure chemical waveguide laser  

Microsoft Academic Search

The exothermic chain reactions between deuterium and fluorine have been used to produce laser emission from carbon dioxide in a high-pressure chemical waveguide laser. Chemical chain reactions initiated by flash photolysis of this system produced 10.6-micron radiation from a 3-mm-diam laser tube having an effective length of 50 cm. Lasing occurs in stable D2-F2-CO2-He mixtures at pressures as high as

T. O. Poehler; R. E. Walker; J. W. Leight

1975-01-01

94

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

95

Chemically-Assisted Pulsed Laser-Ramjet  

NASA Astrophysics Data System (ADS)

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

Horisawa, Hideyuki; Kaneko, Tomoki; Tamada, Kazunobu

2010-10-01

96

Laser Applications to Chemical and Environmental Analysis.  

National Technical Information Service (NTIS)

The seventh topical meeting on Lasers and Applications to Chemical and Environmental Analysis continued the tradition of state-of-the-art research and applications and was presented in an informal atmosphere designed to foster communication among research...

J. A. Thorner

2000-01-01

97

Alpha high-power chemical laser program  

Microsoft Academic Search

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

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

1993-01-01

98

Laser spectroscopy for studying chemical processes  

Microsoft Academic Search

In recent years, various methods have been developed to observe and to influence the course of chemical reactions using laser radiation. By selectively increasing the translational, rotational, and vibrational energies and by controlling the relative orientation of the reaction partners with tunable infrared and UV lasers, direct insight can be gained into the molecular course of the breaking and re-forming

J. Wolfrum

1988-01-01

99

Cryosorption-pumped CW chemical laser  

Microsoft Academic Search

A miniature CW chemical laser is described which can serve as a convenient multiline source in the IR. It employs condensible carrier gases with cryosorption pumping only (thus no moving parts) to deliver 300 and 200 mW, respectively, of HF and HCl radiation. Five laser reactions with a total of nine lines each of HCl and HF in the regions

K. R. Newton; R. B. Bernstein

1978-01-01

100

Chemical aerosol detection using femtosecond laser pulses  

Microsoft Academic Search

Many chemical warfare agents are dispersed as small aerosol particles. In the past, most electro-optical excitation and detection schemes have used continuous or pulsed lasers with pulse lengths ranging from nanoseconds to microseconds. In this paper, we present interesting ongoing new results on femtosecond imaging and on the time dependent solutions to the scattering problem of a femtosecond laser pulse

Dennis R. Alexander; Mark L. Rohlfs; John C. Stauffer

1997-01-01

101

High-Energy Pulsed CO Chemical Laser.  

National Technical Information Service (NTIS)

A high-energy pulsed CO chemical laser has been constructed. Fibrationally excited CO molecules are produced via the reaction O + CS yields, (CO+) s. A laser output of 240 mJ/pulse is obtained when a mixture of CS2 and O2 is flash photolyzed without any a...

J. J. Tiee C. R. Quick C. D. Harper A. B. Petersen C. Wittig

1975-01-01

102

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

103

Chemical stabilization of laser dyes  

NASA Astrophysics Data System (ADS)

Coumarin laser dyes upon excitation degrade to produce products which 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 which interfere with dye stimulated emission. 1, 4-Diazabicyclo2,2,2octane (DABCO)inhibits this oligomerization.

Koch, Tad H.

1987-05-01

104

Long pulse chemical laser. Final technical report  

Microsoft Academic Search

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-COâ 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,

R. L. Bardon; R. E. Breidenthal; V. R. Buonadonna

1989-01-01

105

A spectroscopic study of CW chemical lasers.  

NASA Technical Reports Server (NTRS)

A subsonic transverse-flow chemical laser has been instrumented to permit measurements of vibration-rotation state populations and laser output spectra under flow conditions typical of present CW hydrogen halide laser operation. Measurements are presented for the F + HI, F + HBr, F + CH4, F + HCl, F + H2, Cl + HI, and Cl + HBr atom-exchange reaction systems. CW operation was found to be characterized by relatively modest departures from Maxwell-Boltzmann vibrational energy distributions at all stages of reaction in contrast to pulsed operation based on similar reactions.

Rosen, D. I.; Sileo, R. N.; Cool, T. A.

1973-01-01

106

Long pulse chemical laser. Final technical report.  

National Technical Information Service (NTIS)

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...

R. L. Bardon R. E. Breidenthal V. R. Buonadonna

1989-01-01

107

CO Chain-Reaction Chemical Laser Research.  

National Technical Information Service (NTIS)

A chain-reaction CO chemical laser fueled by carbon monosulfide (CS) and molecular oxygen (O2) has been demonstrated. Initiation by the chain carriers (either O-atoms or S-atoms) is necessary; the chain length lambda* increases rapidly with CS/CS2 fuel mo...

W. Q. Jeffers H. Y. Ageno C. E. Wiswall

1976-01-01

108

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

109

XIII International Symposium on Gas Flow and Chemical Lasers and High- Power Laser Conference.  

National Technical Information Service (NTIS)

The Final Proceedings for XIII Int'I Symposium on Gas Flow & Chemical Lasers and High Power Laser Conference, 18 September 2000-22 September 2000 This is an interdisciplinary conference. Topics include CO2 and CO lasers, metal vapor lasers, chemical laser...

A. Lapucci M. Ciofini

2000-01-01

110

Microstructuring and wafering of silicon with laser chemical processing  

Microsoft Academic Search

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

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

2010-01-01

111

Chemically assisted laser ablation ICP mass spectrometry.  

PubMed

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

Hirata, Takafumi

2003-01-15

112

Laser Velocimetry of Chemical Vapor Deposition Flows  

NASA Technical Reports Server (NTRS)

Laser velocimetry (LV) is being used to measure the gas flows in chemical vapor deposition (CVD) reactors. These gas flow measurements can be used to improve industrial processes in semiconductor and optical layer deposition and to validate numerical models. Visible in the center of the picture is the graphite susceptor glowing orange-hot at 600 degrees C. It is inductively heated via the copper cool surrounding the glass reactor.

1993-01-01

113

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

114

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

NASA Astrophysics Data System (ADS)

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.; Ulrich, Peter B.

115

Chemical and Laser Sciences Division annual report, 1988  

SciTech Connect

This annual report from the Chemical and Laser Sciences Division at Los Alamos contains both programmatic and technical information on the following research: KrF lasers for inertial confinement fusion; free electron lasers; neutral particle beam sensing; chemical sensing; mass spectroscopy; orbit simulations; high temperature kinetics; and microwave absorption spectrometers. (JEF)

Not Available

1989-06-01

116

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

117

Mid-IR semiconductor lasers for chemical sensing  

NASA Technical Reports Server (NTRS)

The development of mid-IR semiconductor diode lasers based on type-II interband cascade structures is presented. How these diode lasers can be developed to meet the requirements in chemical sensing applications is discussed.

Hill, C. J.; Yang, R. Q.

2003-01-01

118

Optical design method for controlling laser beam profiles  

Microsoft Academic Search

By properly designing the laser optical resonator, an optimal match between brightness and coherence can be achieved. This paper discusses one such design for an oxygen iodine laser and shows measured beam profiles. The laser mode was shaped and optically relayed to a test specimen. Very uniform beams of high brightness were measured at the plane of the test sample.

Burton D. O'Neil; Vance A. Hedin; Carol E. Hines

1994-01-01

119

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

120

Sensitivity analysis for chemical laser design: a model problem  

Microsoft Academic Search

Modeling the performance of chemical lasers requires coupling an analysis of the chemically reacting flow to one that predicts the laser intensity in the optical cavity. The continuous sensitivity equation method (CSEM), applied to such coupled systems, naturally leads to a coupled system of linear equations for the sensitivities. We introduce a model problem, based on one-dimensional gas dynamics with

J. T. Borggaard; E. M. Cliff

2000-01-01

121

Laser-Beam-Absorption Chemical-Species Monitor  

NASA Technical Reports Server (NTRS)

Apparatus measures concentration of chemical species in fluid medium (e.g., gaseous industrial process stream). Directs laser beam through medium, and measures intensity of beam after passage through medium. Relative amount of beam power absorbed in medium indicative of concentration of chemical species; laser wavelength chosen to be one at which species of interest absorbs.

Gersh, Michael; Goldstein, Neil; Lee, Jamine; Bien, Fritz; Richtsmeier, Steven

1996-01-01

122

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

123

Remote chemical sensing with quantum cascade lasers  

NASA Astrophysics Data System (ADS)

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

Harper, Warren W.; Strasburg, Jana D.

2004-09-01

124

Mixing enhancement in chemical lasers. I. Experiments  

SciTech Connect

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

Driscoll, R.J.

1986-07-01

125

Chemical imaging sensor and laser beacon.  

PubMed

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

Carrieri, Arthur H

2003-05-20

126

Laser-induced gas breakdown - Spectroscopic and chemical studies.  

NASA Technical Reports Server (NTRS)

Discussion of the results of several experimental investigations on laser-induced gas breakdown. The experiments included time-resolved spectroscopy, direct detection of H atoms with a TiO2 probe, and chemical reactions; each of them provided insight into the behavior of the medium at different times. Chemical reactions and explosions have been initiated by the laser beam when a plasma was created. No primary multiphotonic absorption and no macroscopic chemical reactions were observed below the breakdown threshold.

De Montgolfier, PH.; Dumont, P.; Mille, Y.; Villermaux, J.

1972-01-01

127

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

128

Atmospheric propagation properties of various laser systems  

NASA Astrophysics Data System (ADS)

Atmospheric propagation properties of various laser systems, including diode pumped alkali lasers (DPALs) and the Chemical Oxygen Iodine Laser (COIL), are of importance. However, there appears to be a lack of highly accurate transmission characteristics of these systems associated with their operating conditions. In this study laser propagation of the rubidium-based DPAL and the COIL has been simulated utilizing integrated cavity output spectroscopy. This technique allowed for the simulation of laser propagation approaching distances of 3 kilometers on a test stand only 35 cm long. The spectral output from these simulations was compared to the HITRAN database with excellent agreement. The spectral prole and proximity of the laser line to the atmospheric absorbers is shown. These low pressure spectral proles were then extrapolated to higher pressures using an in-house hyperne model. These models allowed for the comparison of proposed systems and their output spectral prole. The diode pumped rubidium laser at pressures under an atmosphere has been shown to interact with only one water absorption feature, but at pressures approaching 7 atmospheres the D1 transition may interact with more than 6 water lines depending on resonator considerations. Additionally, a low pressure system may have some slight control of the overlap of the output prole with the water line by changing the buer gases.

Pitz, Greg A.; Glass, Sara; Kamer, Brian; Klennert, Wade L.; Hostutler, David A.

2012-05-01

129

Remote chemical sensing by laser optical pumping  

SciTech Connect

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

Stevens, C.G.; Magnotta, F.

1996-08-01

130

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

131

Laser cutting with chemical reaction assist  

DOEpatents

A method for cutting with a laser beam where an oxygen-hydrocarbon reaction is used to provide auxiliary energy to a metal workpiece to supplement the energy supplied by the laser. Oxygen is supplied to the laser focus point on the workpiece by a nozzle through which the laser beam also passes. A liquid hydrocarbon is supplied by coating the workpiece along the cutting path with the hydrocarbon prior to laser irradiation or by spraying a stream of hydrocarbon through a nozzle aimed at a point on the cutting path which is just ahead of the focus point during irradiation.

Gettemy, Donald J. (Los Alamos, NM) [Los Alamos, NM

1992-01-01

132

Laser cutting with chemical reaction assist  

DOEpatents

A method is described for cutting with a laser beam where an oxygen-hydrocarbon reaction is used to provide auxiliary energy to a metal workpiece to supplement the energy supplied by the laser. Oxygen is supplied to the laser focus point on the workpiece by a nozzle through which the laser beam also passes. A liquid hydrocarbon is supplied by coating the workpiece along the cutting path with the hydrocarbon prior to laser irradiation or by spraying a stream of hydrocarbon through a nozzle aimed at a point on the cutting path which is just ahead of the focus point during irradiation. 1 figure.

Gettemy, D.J.

1992-11-17

133

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

134

Laser micromachining of chemically altered polymers  

SciTech Connect

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

Lippert, T.

1998-08-01

135

Standoff chemical detection using quantum cascade lasers and photoacoustic sensing  

NASA Astrophysics Data System (ADS)

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

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

2011-05-01

136

Pulsed chemical HF laser with a large discharge gap  

SciTech Connect

The characteristics of the radiation emitted by an electric-discharge pulsed chemical HF laser with a discharge gap of 10 cm are studied. The discharge was stabilised by a semiconducting ferroelectric ceramic layer deposited on plane metal electrodes. The specific energy and technical efficiency were 3 J L{sup -1} and 3.4%, respectively, for a laser operating on a nonchain reaction in SF{sub 6}-H{sub 2} mixture and 25 J L{sup -1} and 26%, respectively, for a laser operating on a chain reaction in F{sub 2}-O{sub 2}-SF{sub 6}-H{sub 2} mixture. (lasers)

Azarov, M A; Klimuk, Evgenii A; Kutumov, Konstantin A; Troshchinenko, G A [Russian Science Centre 'Applied Chemistry', St Petersburg (Russian Federation); Lacour, Bernard M [Laboratoire de Physique des Gaz et des Plasmas, Universite Paris-Sud, Orsay (France)

2004-11-30

137

High power semiconductor laser arrays by metalorganic chemical vapor deposition  

NASA Astrophysics Data System (ADS)

Semiconductor injection lasers have the capability of producing very high output powers if a large array of diodes can be fabricated. The development of useful high power semiconductor lasers depends on fabrication processes which overcome the problems associated with high power laser operation. Developments in semiconductor fabrication processes which have led to the fabrication of large linear arrays capable of high power operation are described. Much of this work has been devoted to the fabrication of low threshold current, high efficiency laser diodes using the graded barrier quantum well (GBQW) structure grown by metalorganic chemical vapor deposition (MOCVD). The effects of various processing methods in the optical properties of the laser, such as the threshold current, efficiency, emission wavelength, and near- and far-field radiation patterns, are described and explained. Low threshold current operation with stable radiation patterns have been observed in several types of laser devices. One problem which has prevented high power semiconductor laser operation is lateral lasing and amplified spontaneous emission processes which limit the width of most semiconductor lasers to less than approximately 200 microns. This problem has been solved through the use of a non-planar active region, which allows the width of the laser array to be increased to at least several millimeters. The characteristics of these non-planar laser arrays are presented.

Zmudzinski, Charles Alan

138

Investigation of Molecular and Chemical Laser Systems.  

National Technical Information Service (NTIS)

Results of studies conducted in two research areas are reported. Experimental studies aimed at developing a c.w. atomic I laser at 1.315 micrometers explored several excitation mechanisms that lead to the production of the excited state of I(doublet P(1/2...

G. J. Wolga R. A. McFarlane

1974-01-01

139

Fluid dynamic issues in continuous wave short wavelength chemical lasers  

SciTech Connect

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

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

1988-01-01

140

Investigation of Iron Films Produced by Laser Chemical Vapor Deposition  

NASA Astrophysics Data System (ADS)

We are investigating a technique for the Laser Chemical Vapor Deposition of thin films at atmospheric pressure and room temperature. (P.C. Chen and A. Visnapuu, J. Mat. Sci. Lett. 14 (1995) 1289.) Our work has centered on the deposition of iron onto graphite. An infrared laser heats the substrate, causing ironpentacarbonyl vapor to dissociate and allowing the iron to adhere to the substrate. We have used a variety of laser powers, deposition times, and graphite surface preparations. Samples created using this technique show evidence of thin film interference. SIMS analysis shows very little contamination in the iron film, as well as some intermixture between the film and the substrate.

Curry, Candace A.; Burns-Kaurin, Michael G.

1997-03-01

141

Chemical ionization Fourier transform mass spectrometry of chemical warfare agent simulants using laser produced metal ions  

Microsoft Academic Search

In an initial investigation of the potential utility of chemical ionization (CI) mass spectrometry of selected analogs of chemical warfare agents using metal ions, the reactions of manganese ions with chloroalkyl sulfides and organophosphonates have been followed in a Fourier transform mass spectrometer. Mn{sup +} ions, produced by UV laser radiation focused on a stainless steel target, react rapidly with

Chih-Cong Chou; S. Randolph Long

1990-01-01

142

Laser absorption techniques for spectroscopy and chemical kinetics studies in a shock tube  

Microsoft Academic Search

Recent laboratory work to develop advanced laser-based diagnostics for shock tube applications is overviewed. Tunable laser absorption techniques have received primary emphasis, with applications to fundamental studies of spectroscopic parameters and investigations of chemical kinetics. Laser sources have included a discretely tunable CO infrared laser, a continuously tunable infrared diode laser and a continuously tunable ultraviolet\\/visible ring dye laser.

R. K. Hanson; S. Salimian; E. C. Rea Jr.

1984-01-01

143

Laser-Assisted Chemical Polishing of Silicon (112) Wafers  

NASA Astrophysics Data System (ADS)

Pulsed laser-assisted chemical etching (PLACE) offers an advanced, novel substrate preparation method for molecular beam epitaxy (MBE) growth of mercury cadmium telluride on silicon (112) wafers. By controlling the laser fluence, the chemical etch process is refined into a final polish step. PLACE offers surface roughness on the order of chemical mechanical polishing standards and has been verified by 488-nm Raman and high-resolution x-ray diffraction as causing no surface or subsurface damage. To the contrary, experiments show that using PLACE not only alters the surface chemically but also removes subsurface damage through recrystallization reaching micron depths. The process occurs in a modular vacuum chamber that could conceivably be transferred between tools so that vacuum is not broken between polishing and MBE deposition. PLACE can achieve ultra-high-purity and fine dimensional control since it is a dry process relying on pyrolytic vapor-phase reactions initiated, and constrained, by a pulsed laser. Since the process is a function of laser fluence and optics, it is imminently scalable to 6-inch wafer sizes and beyond.

Dandekar, Niru; Chivas, Robert; Silverman, Scott; Kou, Xiaolu; Goorsky, Mark

2012-10-01

144

High gain CO chemical laser produced in a shock tunnel  

Microsoft Academic Search

Experimental theoretical results are presented of small signal gain in a CO chemical laser produced in a shock tunnel. The thermal dissociation of CS2 into CS + S is effected by a reflected shock wave. The dissociated products, diluted in Ar, expand through a supersonic nozzle having an area ratio of 40 into a combustion chamber. At the nozzle exit,

M. Tilleman; J. Stricker

1982-01-01

145

Combustion-driven blowdown facilities for chemical laser research  

NASA Astrophysics Data System (ADS)

The importance of fluid dynamic phenomena in the development of high-energy/high-power lasers (HELs) is outlined, and the value of blowdown test facility (BDF) concepts in short wavelength chemical laser studies is shown, with emphasis on the NF(a)/BiF(A-X) transfer laser mechanism. The general characteristics and advantages of the BDF approach applied to HEL studies are shown, and the simple operating principles of the BDF concept are illustrated. Simplified parametric calculations are made for the BDF for its application to the investigation of short wavelength all-chemically pumped electronic transition HELs (SWCL) mechanisms. The procedure used for a nonequilibrium combustor operation is described, and an original alternate combustor charging procedure is shown. Results are reported from a brief series of HF fundamental transitional lasing experiments.

Warren, Walter R., Jr.; Schneider, Leo E.; Rodriguez, James N.

1991-06-01

146

Plasma cathode preionized atmospheric pressure HF chemical laser  

NASA Astrophysics Data System (ADS)

The performance of an electric discharge, plasma-cathode-preionized, atmospheric-pressure HF chemical laser was investigated and the laser was geometrically optimized. The preionization electron density was measured at atmospheric pressure in helium and in a mixture of SF 6 + H 2 diluted by helium. The measured preionization density is ne ? 6.7 × 10 9-2 × 10 10cm -3, which is higher than the minimum critical density required for a self-sustained, homogeneous discharge of atmospheric-pressure electronegative gases. We have found improvement in laser specific energy for a diluted gas mixture of SF 6 + H 2 due to reduction in SF 6 concentration. The effects of inter-electrode gap height and plasma cathode grid width on laser performance were also investigated and are reported.

Kalisky, Y.; Waichman, K.; Kamin, S.; Chuchem, D.

1997-02-01

147

A UV laser source for biological and chemical sensing  

NASA Astrophysics Data System (ADS)

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

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

2004-01-01

148

Reacting Flow and Pressure Recovery Processes in HF/DF Chemical Lasers.  

National Technical Information Service (NTIS)

Several properties of gas dynamic processes that occur in flowing gas lasers are discussed and their importance in establishing laser performance is outlined. The continuous HF (or DF) supersonic diffusion chemical laser is chosen to illustrate the coupli...

W. R. Warren

1973-01-01

149

Production of Singlet Oxygen within a Flow Discharge  

Microsoft Academic Search

The Airborne laser program is an Air Force sponsored program to place a laser on the battle field for use as a tactical weapon. The chemical oxygen iodine laser offers the powers necessary for this weapons application, but it requires significant logistical support. The goal of this current research program is to demonstrate an oxygen-iodine laser with electrical discharge production

Matthew Lange; Greg Pitz; Glen Perram

2008-01-01

150

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

151

Femtosecond laser-induced breakdown spectroscopy of surface nitrate chemicals.  

PubMed

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

Ahmido, Tariq; Ting, Antonio; Misra, Prabhakar

2013-05-01

152

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.

Nikodem, Michal; Wysocki, Gerard

2012-01-01

153

Laser-induced chemical changes in art materials  

NASA Astrophysics Data System (ADS)

Lasers can induce subtle and not so subtle changes in material structure. We have found that certain pigments can undergo chemical and crystallographic changes and concomitant color shifts. Minerals and the related pigments may experience a loss of hydroxyl groups or other chemical reordering. The organic component of skeletal, keratinaceous, and cellulosic materials can be pyrolized, ablated, or etched. Polymers can discolor, undergo structural weakening, or be volatilized. A few of these processes have been investigated with regards to changes on ivory and bone, selected pigments and the removal of dye-based pen ink from porous substrates.

Abraham, Margaret H.; Scheerer, Stefanie; Madden, Odile; Adar, Fran

2001-10-01

154

Scaling laws for pulsed chain-reaction chemical lasers  

NASA Astrophysics Data System (ADS)

Scaling laws for pulsed chain-reaction chemical lasers are deduced with the use of a two-level vibrational model. The performance of a saturated laser depends only on the parameter K = t sub cd/t sub p, where t sub cd and t sub p are the characteristic collisional deactivation and characteristic pumping times, respectively. The normalized output energy per unit volume per pulse of a saturated HF chain-reaction laser is 2E/Epsilon H sub 2,0 = K(1 + 0(K)), where E is output energy per unit volume per pulse, Epsilon is energy per mole of photons, and H sub 2, 0 is the initial concentration of H sub 2 in moles per unit volume. In the range 0.02 < or = thi << 1 the normalized output energy from a saturated HF laser can be expressed as 2E/Epsilon H sub 2, 0 = thi, where thi approx. = (F/F sub 2) sub 0 1/2(F sub 2/H sub 2)0(1 + 0.094(F sub 2/H sub 2) sub 0) to the minus 1/2 power. In the latter regime the product Et sub e is a constant for a saturated laser (t sub e = pulse length). Corrections for multiple vibrational levels are given in an Appendix.

Mirels, H.; Hofland, R., Jr.; Whittier, J. S.

1981-08-01

155

Space-Based Chemical Lasers in strategic defense  

SciTech Connect

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, D. (SDIO, Washington, DC (United States))

1992-07-01

156

Ultrafast X-ray Laser Studies of Chemical Dynamics  

NASA Astrophysics Data System (ADS)

First light at the LCLS x-ray free electron laser at the SLAC National Accelerator Laboratory marked the beginning of hard x-ray laser science 2009. With pulse energies in excess of a milliJoule and pulse durations as short as 5 femtoseconds in duration, the LCLS provides a novel and potentially transformative approach for investigating chemical dynamics in complex systems. Understanding the coupled evolution of electrons and nuclei during chemical transformations remains the central and vexing challenge in the study of chemical reaction dynamics. Ultrafast optical electronic spectroscopy can monitor both the nuclear and the electronic evolution that occurs during a chemical reaction, but this joint sensitivity often impedes the robust interpretation of experimental measurement. The LCLS provides the opportunity to simultaneously measure electronic dynamics with x-ray fluorescence and nuclear dynamics with elastic x-ray scattering, providing a robust means for disentangling the coupled motions of electrons and nuclei during excited state internal conversion and intersystem crossing. These exciting new opportunities will be discussed in the context of recent studies of photo-induced spin crossover dynamics in iron(II) tris-bipyridine. [Fe(bpy)3]^2+.

Gaffney, Kelly

2012-02-01

157

Physical and Chemical Changes of Polystyrene Nanospheres Irradiated with Laser  

SciTech Connect

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

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

2011-05-25

158

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

159

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

160

Chemical and Laser Sciences Division: Annual report, 1987  

SciTech Connect

As the Chemical and Laser Sciences Division concludes its first year, the Division personnel can be proud of their many scientific and technical accomplishments. Among the important milestones which the Division achieved were significant demonstrations of the process performance in the Special Isotope Separation program, of beam sensing techniques for the NPB program, and of optical angular multiplexing and energy extraction from the ICF KrF laser. In addition, the Los Alamos FTS was brought to operational status and the Bright Source attained intensities on the order of 10/sup 17/ W/cm/sup 2/. A few highlights of these and other research and development activities are presented in the following sections of this report.

Not Available

1988-01-01

161

Physics and technique fundamentals of laser chemical hardening of the machine elements and metal cutting tools  

Microsoft Academic Search

The results of the experimental investigations of microstructures and properties of various materials subjected to the laser chemical heat treatment are presented. Optimization criteria of the laser radiation modes and conditions and also the chemical compositions of the coatings received by means of electrical-spark alloying, ion-plasma spraying, chemical deposition and dross cladding for the purpose of producing composite material having

G. I. Brover; V. N. Waravka; V. N. Pustowoit; A. V. Litwin

1996-01-01

162

Chemical and structural modifications of laser treated iron surfaces: investigation of laser processing parameters  

Microsoft Academic Search

This study focuses on the chemical, morphological and structural characterization of iron surfaces treated by laser in ambient air. Incorporation of nitrogen over a 1–2?m thickness (10–30at.% at the profile maximum) and superficial oxidation on 200–400nm depth have been evidenced by nuclear reaction analyses. X-ray diffraction at grazing incidence has shown the formation of FeO and Fe3O4 oxide phases as

A. L Thomann; A. Basillais; M. Wegscheider; C. Boulmer-Leborgne; A. Pereira; P. Delaporte; M. Sentis; T. Sauvage

2004-01-01

163

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

164

Study of factors influencing the effective delivery of O2(1-delta) 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.; Khalin, A. L.

1994-08-01

165

Laser chemical etching of waveguides and quasi-optical devices  

NASA Astrophysics Data System (ADS)

The terahertz (THz) frequency domain, located at the frontier of radio and light, is the last unexplored region of the electromagnetic spectrum. As technology becomes available, THz systems are finding applications to fields ranging all the way from astronomical and atmospheric remote sensing to space telecommunications, medical imaging, and security. In Astronomy the THz and far infrared (IR) portion of the electromagnetic spectrum (? = 300 to 10 ?m) may hold the answers to countless questions regarding the origin and evolution of the Universe, galaxy, star and planet formation. Over the past decade, advances in telescope and detector technology have for the first time made this regime available to astronomers. Near THz frequencies, metallic hollow waveguide structures become so small, (typically much less than a millimeter), that conventional machining becomes extremely difficult, and in many cases, nearly impossible. Laser induced, micro-chemical etching is a promising new technology that can be used to fabricate three dimensional structures many millimeters across with micrometer accuracy. Laser micromachining of silicon possesses a significant edge over more conventional techniques. It does not require the use of masks and is not confined to crystal planes. A non-contact process, it eliminates tool wear and vibration problems associated with classical milling machines. At the University of Arizona we have constructed the first such laser micromachining system optimized for the fabrication of THz and far IR waveguide and quasi-optical components. The system can machine structures up to 50 mm in diameter, down to a few microns accuracy in a few minutes and with a remarkable surface finish. A variety of THz devices have been fabricated using this technique, their design, fabrication, assembly and theoretical performance is described in the chapters that follow.

Drouet D'Aubigny, Christian Yann Pierre

2003-11-01

166

Laser enhanced chemical reaction studies. Technical progress report  

SciTech Connect

A powerful infrared diode laser probe was used to determine final states of small (2-5 atom) molecules produced by collisions, photofragmentation, or chemical reactions with spectral resolution 0.0003 cm{sup {minus}1} and time resolution 10{sup {minus}7}s. Besides picturing the vibrational rotational quantum states of product molecules, this also provides a picture of the translational motion of recoiling fragments through the infrared Doppler line width profile. This method was used to probe collisions between cool bath molecules and vibrationally hot molecules, in order to understand the quenching mechanism for unimolecular chemical reactions. Long-range collisions appear to dominate production of bath molecules which become vibrationally excited during this quenching process. Glimpses are being provided of the separate behavior of translational and rotational degrees of freedom of recoiling bath molecules during relaxation of highly vibrationally excited donors. A study was completed of collisions between hot H atoms and CO{sub 2}, by measuring probability for excitation of the antisymmetric vibrational overtone level CO{sub 2}(00{sup 0}2). Comparison with a 00{sup 0}1 fundamental level study suggests that translational and rotational energy distributions in this collision can be described by classical mechanics, but that vibrational excitation probabilities require full quantum treatment. Relaxation of hot pyrazine by CO{sub 2} was studied. Multiphoton ionization studies have been begun.

Flynn, G.

1993-12-31

167

Metal film deposition by laser breakdown chemical vapor deposition  

SciTech Connect

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

Jervis, T.R.

1985-01-01

168

Numerical analysis on the beam quality improvements of high power chemical laser system with water cooled mirrors  

Microsoft Academic Search

Chemical laser is one of the most widely used high power infrared sources. Thermal deformation of mirrors in a resonator is a key factor which hinders the improvement of the beam quality in high power chemical lasers, and it has been a matter of the utmost concern in the design of high power chemical laser systems. Water-cooled technique is one

Kai Han; Bin Li; Xiao-Jun Xu

2011-01-01

169

Laser applications to chemical analysis: an introduction by the feature editors  

NASA Astrophysics Data System (ADS)

This issue of Applied Optics features papers on the application of laser technology to chemical analysis. Many of the contributions, although not all, result from papers presented at the Fourth OSA Topical Meeting on Laser Applications to Chemical Analysis, which was held at Jackson Hole, Wyoming, March, 1994. This successful meeting, with nearly one hundred participants, continued the tradition of earlier LACA meetings to focus on the optical science of laser-based measurements of temperature and trace chemical assays in a wide variety of practical applications.

Jeffries, Jay B.; Ramsey, J. Michael; Lucht, Robert P.

1995-06-01

170

High gain CO chemical laser produced in a shock tunnel  

NASA Astrophysics Data System (ADS)

Experimental theoretical results are presented of small signal gain in a CO chemical laser produced in a shock tunnel. The thermal dissociation of CS2 into CS + S is effected by a reflected shock wave. The dissociated products, diluted in Ar, expand through a supersonic nozzle having an area ratio of 40 into a combustion chamber. At the nozzle exit, molecular oxygen is injected supersonically. The two streams mix and combustion occurs where vibrationally excited CO is produced by the CS + O - CO (v) + S reaction. Gain measurements of the P7(14) line are made at distances of 5.5 and 11.5 cm downstream of the oxygen injection point, the stagnation pressure being 25 atm. The stagnation temperatures are varied in the range of 2500-4600 K and mixtures of CS2:Ar between 5:95 and 30:70 are tested. A maximum gain of 8% per cm is observed for CS2:Ar = 20:80 at a stagnation temperature of about 4000 K and a distance of 11.5 cm. A semiempirical model describing the fuel-diluent expansion through the supersonic nozzle and the fuel-oxidizer mixing process is then developed.

Tilleman, M.; Stricker, J.

171

Toxicological characterization of chemicals produced from laser irradiation of graphite composite materials  

SciTech Connect

One of the major potential hazards associated with laser machining of graphite composite materials is the toxic fumes and gases that are generated. When exposed to the intense energy of the laser beam, the organic polymer matrix of the composite material may decompose into various toxic by-products. To advance the understanding of the laser machining process from a health and safety viewpoint, this particular study consisted of the following steps: collect and analyze gaseous by-products generated during laser machining; collect particulates generated during laser machining and chemically extract them to determine the chemical species that may have absorbed or recondensed onto these particles; and review and evaluate the toxicity of the identified chemical species.

Kwan, J.

1990-11-01

172

Optical thin films grown by surface chemical reaction for high-power lasers  

NASA Astrophysics Data System (ADS)

We developed a novel coating method using chemical reactions of gaseous reactants on a surface. A self-limiting nature of surface chemical reactions allows precisely controlled growth of films with high uniformity and controllability of thickness over large area. The nonuniformity of thickness distribution was under 1% over 240 mm in diameter. The film thickness had proportional relationship with a number of chemical reactions. TiO2 films at growth temperature of 25 degree(s)C had a laser-induced damage threshold of 5 J/cm2 for 1-ns, 1.06-micrometers laser pulses. The laser damage resistance of TiO2 films decreased at higher growth temperature. TiO2 films grown at the high temperature had higher crystallinity. We clarified that the laser damages resulted from the local sites that absorbed the laser energy.

Zaitsu, Shin-ichi; Motokoshi, Shinji; Jitsuno, Takahisa; Nakatsuka, Masahiro; Yamanaka, Tatsuhiko

2001-04-01

173

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

National Technical Information Service (NTIS)

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

D. E. Kotecki

1988-01-01

174

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

SciTech Connect

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

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

1990-05-28

175

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

National Technical Information Service (NTIS)

A laser ablation/ionization mass spectrometer system is described for the direct chemical analysis of solids. An Nd:YAG laser is used for ablation and ionization of the sample in a quadrupole ion trap operated in an ion-storage (IS) mode that is coupled w...

J. K. Holt E. J. Nelson G. L. Klunder

2005-01-01

176

Pressure Recovery in a Constant-Area Diffuser for Chemical Lasers with Nozzle Base Relief.  

National Technical Information Service (NTIS)

A study of pressure recovery in a supersonic flow in which energetic exothermic reactions occur has been performed that is applicable for a cw chemical laser. Analytical and experimental work has shown that typical HF(DF) laser flows can be recovered to a...

D. A. Durran S. W. Liu

1975-01-01

177

Numerical Methods for Two-Dimensional CW Chemical Laser Power Calculations.  

National Technical Information Service (NTIS)

The current status of two-dimensional chemical laser modeling at Los Alamos is reviewed, with emphasis on numerical methods for coupling the radiation field to the fluid dynamics so that laser power can be calculated. The primary computational model is em...

J. D. Ramshaw T. D. Butler

1977-01-01

178

Laser structuring and modification of polymer surfaces for chemical and medical microcomponents  

Microsoft Academic Search

In the production of micro devices the surface properties become more and more important for chemistry, biotechnology and medical technology with respect to wetting properties and chemical composition of the surface. Typical applications are implants as well as micro fluidic systems or miniaturized devices for DNA- and proteome analysis (biochips). In this paper newly designed laser technologies based on UV-laser

Elke A. Bremus-Koebberling; Ulrike Meier-Mahlo; Oliver Henkenjohann; Stefan Beckemper; Arnold Gillner

2004-01-01

179

Effect of high-power IR laser radiation on chemically active polymers  

SciTech Connect

We have investigated the decomposition of the chemically active polymer cellulose nitrate upon exposure to IR laser radiation. For diagnostics of processes occurring in the condensed phase, we use dynamic mass spectrometry of decomposition products accelerated into a vacuum. We establish an important dependence of the composition of decomposition products on the absorption coefficient of the polymer. We observe the efficient occurrence of secondary chemical reactions in the condensed phase upon bulk decomposition of cellulose nitrate by highpower laser radiation.

Bakhirkin, Y.A.; Bykovskii, Y.A.; Chistyakov, A.A.; Ukraintsev, V.A.

1986-07-01

180

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

181

Surface chemical reaction of laser ablated aluminum sample for detonation initiation  

SciTech Connect

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

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

2011-05-01

182

Characteristics of a CW HF chemical laser calculated from a simplified two-dimensional model  

Microsoft Academic Search

A two-dimensional simplified model of an HF chemical laser is introduced. Using an implicit finite difference scheme, the solution of two adjacent parallel streams with diffusion mixing and chemical reaction is generated. A contour of mixing and reaction boundary is obtained without presupposition. The distribution of the HF(v) concentrations, gas temperature and the optical small signal gain (alpha sub V,

Zhou Xuehua; Chen Liyin; Chen Haitao

1986-01-01

183

Predictions of Chemical Species via Diode Laser Spectroscopy  

NASA Technical Reports Server (NTRS)

A technique to predict temperature and chemical species in flames from absorbance measurement of one chemical species is presented. Predicted temperature and mole fractions of methane and water agreed well with measured and published results.

Chen, Shin-Juh; Silver, Joel A.; Dahm, Werner J. A.; Piltch, Nancy D.; Salzman, Jack (Technical Monitor)

2001-01-01

184

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

185

Personnel Protection Equipment for Use with Laser Chemicals.  

National Technical Information Service (NTIS)

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 ...

I. D. Smith J. Roepke

1984-01-01

186

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

187

Measurements of 4.2 micron CO2 pressure broadening by using an HBr chemical laser  

Microsoft Academic Search

The pressure broadening of CO2(0000?00°1) transitions has been studied by using an HBr chemical laser. By measuring the absorption of the HBr laser beams by CO2 gas, the coefficients of broadening have been obtained as a function of the rotational quantum number J. The coefficient is expressed as ??= (5.2±0.5)?(0.05±0.01) J (MHz\\/Torr). This equation is in good agreement with data

Hitoshi Oodate; Tomoo Fujioka

1978-01-01

188

High rate, large area laser-assisted chemical vapor deposition of nickel from nickel carbonyl  

Microsoft Academic Search

High-power diode lasers (HPDL) are being increasingly used in industrial applications. Deposition of nickel from nickel carbonyl (Ni(CO)4 ) precursor by laser-induced chemical vapor deposition (CVD) was studied with emphasis on achieving high deposition rates. An HPDL system was used to provide a novel energy source facilitating a simple and compact design of the energy delivery system. Nickel deposits on

Vlad Paserin

2009-01-01

189

Concepts for scalable CDMA-networked M\\/LWIR semiconductor laser standoff chemical detection system  

Microsoft Academic Search

Mid-wave\\/Long-wave IR (3-14 mum) semiconductor lasers such as QC and Sb can be used for standoff chemical agent sensing in a network architecture that is different from conventional absorption lidars. Compact, potentially inexpensive semiconductor lasers may allow using them in a large number that form a cooperative network in which, the integrated sensing information is much more than the sum

Yi Wang; Yang Wang; Chuan Peng; Huanlin Zhang; Anush Seetharaman; Han Q. Le

2004-01-01

190

Recent Advances in Infrared Semiconductor Laser based Chemical Sensing Technologies  

NASA Astrophysics Data System (ADS)

Recent advances in the development of sensors based on the use of quantum cascade lasers (QCLs) for the sensitive, selective detection, quantification and monitoring of both small and large molecular gas species with resolved and unresolved spectroscopic features respectively will be described.

Tittel, F. K.; Curl, R. F.; Dong, L.; Doty, J. H.; Kosterev, A. A.; Lewicki, R.; Thomazy, D.; Wysocki, G.

191

Ultrasensitive standoff chemical sensing based on nonlinear multi-photon laser wave-mixing spectroscopy  

NASA Astrophysics Data System (ADS)

Nonlinear multi-photon laser wave mixing is presented as an ultrasensitive optical detection method for chem/bio agents in thin films and gas- and liquid-phase samples. Laser wave mixing is an unusually sensitive optical absorption-based detection method that offers significant inherent advantages including excellent sensitivity, small sample requirements, short optical path lengths, high spatial resolution, high spectral resolution and standoff remote detection capability. Wave mixing can detect trace amounts of chemicals even when using micrometer-thin samples, and hence, it can be conveniently interfaced to fibers, microarrays, microfluidic systems, lab-on-a-chip, capillary electrophoresis and other capillary- or fiber-based chemical separation systems. The wave-mixing signal is generated instantaneously as the two input laser beams intersect inside the analyte of interest. Laser excitation wavelengths can be tuned to detect multiple chemicals in their native form since wave mixing can detect both fluorescing and non-fluorescing samples at parts-pertrillion or better detection sensitivity levels. The wave-mixing signal is a laser-like coherent beam, and hence, it allows reliable and effective remote sensing of chemicals. Sensitive wave-mixing detectors offer many potential applications including sensitive detection of biomarkers, early detection of diseases, sensitive monitoring of environmental samples, and reliable detection of hazardous chem/bio agents with a standoff detection capability.

Gregerson, Marc; Hetu, Marcel; Iwabuchi, Manna; Jimenez, Jorge; Warren, Ashley; Tong, William G.

2012-10-01

192

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

193

Co-catalytic Absorption Layers for Controlled Laser-Induced Chemical Vapor Deposition of Carbon Nanotubes.  

PubMed

The concept of co-catalytic layer structures for controlled laser-induced chemical vapor deposition of carbon nanotubes is established, in which a thin Ta support layer chemically aids the initial Fe catalyst reduction. This enables a significant reduction in laser power, preventing detrimental positive optical feedback and allowing improved growth control. Systematic study of experimental parameters combined with simple thermostatic modeling establishes general guidelines for the effective design of such catalyst/absorption layer combinations. Local growth of vertically aligned carbon nanotube forests directly on flexible polyimide substrates is demonstrated, opening up new routes for nanodevice design and fabrication. PMID:24564273

Michaelis, F Benjamin; Weatherup, Robert S; Bayer, Bernhard C; Bock, Maximilian C D; Sugime, Hisashi; Caneva, Sabina; Robertson, John; Baumberg, Jeremy J; Hofmann, Stephan

2014-03-26

194

LDRD final report on high power broadly tunable Mid-IR quantum cascade lasers for improved chemical species detection.  

SciTech Connect

The goal of our project was to examine a novel quantum cascade laser design that should inherently increase the output power of the laser while simultaneously providing a broad tuning range. Such a laser source enables multiple chemical species identification with a single laser and/or very broad frequency coverage with a small number of different lasers, thus reducing the size and cost of laser based chemical detection systems. In our design concept, the discrete states in quantum cascade lasers are replaced by minibands made of multiple closely spaced electron levels. To facilitate the arduous task of designing miniband-to-miniband quantum cascade lasers, we developed a program that works in conjunction with our existing modeling software to completely automate the design process. Laser designs were grown, characterized, and iterated. The details of the automated design program and the measurement results are summarized in this report.

Wanke, Michael Clement; Hudgens, James J.; Fuller, Charles T.; Samora, Sally; Klem, John Frederick; Young, Erik W.

2006-01-01

195

Physico-Chemical Dynamics of Nanoparticle Formation during Laser Decontamination  

SciTech Connect

Laser-ablation based decontamination is a new and effective approach for simultaneous removal and characterization of contaminants from surfaces (e.g., building interior and exterior walls, ground floors, etc.). The scientific objectives of this research are to: (1) characterize particulate matter generated during the laser-ablation based decontamination, (2) develop a technique for simultaneous cleaning and spectroscopic verification, and (3) develop an empirical model for predicting particle generation for the size range from 10 nm to tens of micrometers. This research project provides fundamental data obtained through a systematic study on the particle generation mechanism, and also provides a working model for prediction of particle generation such that an effective operational strategy can be devised to facilitate worker protection.

Cheng, M.D.

2005-06-01

196

Laser induced vibrational energy transfer and chemical reactions  

Microsoft Academic Search

Fluorescence risetimes and falltime were studied in approximately 5 micron and 14 microns regions after Nu sub 2 mode of CD3Br is excited by a Q-switched CO2 laser. Around 5 micron, activation occurs in approximately 10 gas kinetic collisions and in the region beyond 14 microns, activation requires 77 collisions. Deactivation of both signals occurs at about the same rate,

S. T. Lin

1978-01-01

197

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

198

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

NASA Astrophysics Data System (ADS)

Laser-tissue interaction may generate by energy absorption a complex mixture of gaseous, volatile, semi-volatile and particular substances. At the time about 150 different components are known from IR-laser interaction with different organ tissues like liver, fat, muscle and skin. The laser-tissue interaction process thereby is dominated by heating processes, which is confirmed by the similarity of formed chemical products in comparison with conventional cooking processes for food preparation. With the identified chemical substances and relative amounts in backmind a walk along the think path of risk assessment with special reference to pyrolysis products is given. The main way of intake of pyrolysis products is the inhalative one, which results from the fine aerosols formed and the high spreading energy out of the irradiated source. The liberated amounts of irritative chemicals as (unsaturated) aldehydes, heterocycles of bad odor and possibly cancerogenic acting substances relates to some (mu) g/g of laser vaporized tissue. With regard to this exposure level in a hypothetic one cubic meter volume the occupational limit settings are far away. Even indoor air exposure levels are in nearly all cases underwent, for the content of bad smelling substances forces an effective ventilation. Up to now no laser typical chemical substance could be identified, which was not elsewhere known by frying or baking processes of meat, food or familiar. Starting with the GRAS concept of 1957 the process of risk assessment by modified food products and new ingredients is still improofing. The same process of risk assessment is governing the laser pyrolysis products of mammalian tissues. By use of sufficient suction around the laser tissue source the odor problems as well as the toxicological problems could be solved.

Weber, Lothar W.; Meier, Thomas H.

1996-01-01

199

Synthesis of carbon nanotubes by laser-assisted chemical vapor deposition  

Microsoft Academic Search

With recent advances in the aligned growth of carbon nanotubes (CNTs), there are great interests in CNT-based field-emission and electronic applications. In conventional thermal chemical vapor deposition, substrates as well as chambers need to be globally heated to a sufficiently-high reaction temperature. In this paper, we report a method for direct synthesis of CNTs on pre-defined electrodes using laser-assisted chemical

J. Shi; Y. F. Lu; X. W. Wang

2006-01-01

200

Fabrication of microchannels in glass using focused femtosecond laser radiation and selective chemical etching  

Microsoft Academic Search

We use the combination of femtosecond laser dielectric modification and selective chemical etching to fabricate high-quality microchannels in glass. The photoinduced modification morphology has been studied in fused silica and in borosilicate glass BK7, using ultra-high spatial resolution techniques of selective chemical etching followed by atomic force or scanning electron microscopy. The analysis shows that the high differential etch rate

C. Hnatovsky; R. S. Taylor; E. Simova; P. P. Rajeev; D. M. Rayner; V. R. Bhardwaj; P. B. Corkum

2006-01-01

201

The possibility of stimulated emission at 16 microns from a repetitively pulsed DF-CO2 chemical laser  

Microsoft Academic Search

The feasibility of a DF-CO2 chemical laser emitting at 16 microns is studied theoretically. It is shown that for typical compositions the radiation power density of a repetitively pulsed laser can amount to 0.5-2.5 W\\/cu cm. Factors which can lead to an enhancement of the energy characteristics of the laser are examined.

A. S. Biriukov; N. A. Konoplev; A. A. Stepanov; V. A. Shcheglov

1981-01-01

202

Chemical Changes Associated with Increased Acid Resistance of Er:YAG Laser Irradiated Enamel  

PubMed Central

Background. An increase in the acid resistance of dental enamel, as well as morphological and structural changes produced by Er:YAG laser irradiation, has been reported. Purpose. To evaluate the chemical changes associated with acid resistance of enamel treated with Er:YAG laser. Methods. Forty-eight enamel samples were divided into 4 groups (n = 12). Group I (control); Groups II, III, and IV were irradiated with Er:YAG at 100?mJ (12.7?J/cm2), 200?mJ (25.5?J/cm2), and 300?mJ (38.2?J/cm2), respectively. Results. There were significant differences in composition of irradiated groups (with the exception of chlorine) and in the amount of calcium released. Conclusions. Chemical changes associated with an increase in acid resistance of enamel treated with Er:YAG laser showed a clear postirradiation pattern characterized by a decrease in C at.% and an increase in O, P, and Ca at.% and no changes in Cl at.%. An increased Ca/P ratio after Er:YAG laser irradiation was associated with the use of higher laser energy densities. Chemical changes produced by acid dissolution showed a similar trend among experimental groups. Stable or increased Ca/P ratio after acid dissolution was observed in the irradiated groups, with reduction of Ca released into the acid solution.

Olea-Mejia, Oscar Fernando; Garcia-Fabila, Maria Magdalena; Rodriguez-Vilchis, Laura Emma; Sanchez-Flores, Ignacio; Centeno-Pedraza, Claudia

2014-01-01

203

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

NASA Astrophysics Data System (ADS)

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

Catrin, Rodolphe; Gachot, Carsten; Marchand, Günter; Schmid, Ulrich; Mücklich, Frank

2009-05-01

204

LIBS and LITE Emission Based Laser Remote Sensing of Chemical Species and Enhanced Modeling of Atmospheric Absorption  

Microsoft Academic Search

Laser-Induced Breakdown spectroscopy (LIBS) and Laser-Induced Thermal Emission (LITE) emission based laser remote sensing were investigated with the application to the remote measurements of trace chemical species. In particular, UVvisible LIBS and Mid-IR LITE systems were developed and measurements of remote targets and chemical surfaces were studied. The propagation through the atmosphere of the multi-wavelength backscattered LIBS and LITE optical

Dzianis V. Pliutau

2010-01-01

205

Temporal Stability of Single-Line CW HF Chemical Laser with Unstable Resonator.  

National Technical Information Service (NTIS)

The temporal stability of the output from a single-line cw HF chemical laser with an unstable resonator was investigated experimentally to determine if large-scale output power fluctuations, associated with a 'mode-medium' instability of the type original...

E. B. Turner R. A. Chodzko H. Mirels

1977-01-01

206

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

207

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

Microsoft Academic Search

Visible chemical laser amplifiers have been generated in select wavelength regions near 527, 492, and 460 nm employing the highly efficient and selective formation of sodium dimer electronically excited states from the sodium trimer-halogen atom, Na3-X, (x = Cl, Br, I) reactions. Witha focus to increasing amplifier gain length and amplifying medium concentration, an extended path length slit source device

James L. Gole

1995-01-01

208

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

Microsoft Academic Search

Two successful approaches to the formation of electronically inverted atomic diatomic configurations based on (1) highly efficient near resonant intermolecular energy transfer, and (2) highly efficient and selective fast direct chemical reaction are outlined. Near resonant energy transfer pumping from selectively formed metastable states of SiO and GeO is used to form thallium, gallium, sodium, and potassium atom laser amplifiers

James L. Gole

1992-01-01

209

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

Microsoft Academic Search

Localized laser chemical vapor deposition (LLCVD) has become an important process for the direct generation of thin film microstructures, and is finding novel applications in microelectronics processing. Understanding the fundamental dynamics associated with thin film growth by LLCVD is necessary to control interface and thin film properties, and maintain reproducibility of deposit formation. In this dissertation, the nucleation and initial

David Edward Kotecki

1988-01-01

210

Sensing chemically excited metastable populations by CO2 laser gain measurements  

Microsoft Academic Search

For chemical laser applications it is desirable to populate metastable states which are not easily detected except in connection with a subsequent transfer of energy to a more efficient emitter. The vibrational states of the carbon dioxide molecule make it possible to monitor the transitions of a molecule which can be nonselectively excited by transfer over a broad range of

D. J. Benard

1976-01-01

211

CN photodissociation and predissociation chemical lasers - Molecular electronic and vibrational laser emissions  

Microsoft Academic Search

Flash photolysis of HCN, ClCN, BrCN, ICN, (CN)2, CH3NC, CF3CN, and C2F5CN at wavelengths greater than or equal to 1550 A was used in the photodissociation and predissociation of molecular electronic and vibrational lasers. To formulate a state-to-state photochemical reaction mechanism of electronically and vibrationally excited CN radicals, fluorescence and spectroscopy measurements were used in combination with observed laser transitions

G. A. West; M. J. Berry

1974-01-01

212

Solutions of the full Navier-Stokes equations for reacting three-dimensional chemical laser cavity and diffuser flow fields  

NASA Astrophysics Data System (ADS)

This paper addresses a computer model that is capable of predicting chemical laser performance and pressure recovery for complex three-dimensional chemical laser configurations. The time-dependent numerical technique allows for complex arbitrary geometrical boundaries, the solution of the full three-dimensional Navier-Stokes equations with a turbulent kinetic energy model, and chemical vibrational and rotational nonequilibrium chemistry (including gain calculations). Calculations are compared with measurements for both (1) a three-dimensional viscous chemical laser cavity flow with swirl-inducing trip injection, and (2) a radial vane diffuser with multiple internal shock/boundary layer interactions.

Hendricks, W. L.; Mikatarian, R. R.; Gross, B. J.; Rapagnani, N. L.

1981-06-01

213

Windows for HF/DF chemical lasers - CaF2 or ZnSe  

NASA Astrophysics Data System (ADS)

An investigation of laser-driven phenomena occurring in CaF2 and ZnSe window materials which affect the performance of high energy laser systems at chemical wavelengths is reported. The systems studied comprised an optical cavity, relay tube, beam expander, and output window to the focus. An analysis of the cumulative phaseshifts due to beam defocusing and distortion caused by thermally generated aberrations in the window is performed to determine an expression for the degradation in focal intensity. Optical distortion coefficients are derived for laser beams passing through a solid window, and specifically for polycrystalline CaF2 and ZnSe, along with other elastic, optical, and elastic properties. Performance evaluations are analytically compared for the two materials, and CVD ZnSe windows are found suitable for maximizing peak irradiance, while CaF2 is useful for optimizing energy delivery capabilities of HF/DF lasers.

Klein, C. A.

214

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

215

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

216

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

SciTech Connect

We have made a detailed study of the care that must be taken to correctly measure OH radical concentrations in flames. A large part of these studies has concerned collisional quenching of hydride radical species (OH, NH, and NH{sub 2}), in particular the dependence upon rotational level and collision velocity (temperature). The results on OH and NH have shown unique and interesting behavior from the viewpoint of fundamental molecular dynamics, pointing to quenching often governed by collisions on an anisotropic, attractive surface, whereas NH{sub 2} quenching appears to depend on state-mixing considerations, not dynamic control. This state-specific behavior of these small, theoretically tractable hydrides has direct ramifications for quantitative flame diagnostics. Our other effort in the diagnostic area has been repeated but unsuccessful searches for laser induced fluorescence in the vinyl radical.

Crosley, D.R.

1991-01-22

217

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

218

Chemical bond formation during laser bonding of Teflon ® FEP and titanium  

NASA Astrophysics Data System (ADS)

Teflon ® FEP (fluorinated ethylene propylene) is resistant to most chemical solvents, is heat sealable and has low moisture uptake, which make this polymer attractive as a packaging materials for electronics and implantable devices. Teflon ® FEP/Ti microjoints were fabricated by using focused infrared laser irradiation. Teflon ® FEP/Ti interfaces were studied by using X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS). The XPS results give evidence for the formation of Ti-F bonds in the interfacial region. The AES and SEM-EDS results show that the chemical bond formation occurs only in the actual bond area. No evidence for chemical bond formation was found in the heat affected zone surrounding the laser bonds.

Georgiev, Grigor L.; Baird, Ronald J.; McCullen, Erik F.; Newaz, Golam; Auner, Gregory; Patwa, Rahul; Herfurth, Hans

2009-05-01

219

Solutions of the full Navier-Stokes equations for reacting three-dimensional chemical laser cavity and diffuser flow fields  

Microsoft Academic Search

This paper addresses a computer model that is capable of predicting chemical laser performance and pressure recovery for complex three-dimensional chemical laser configurations. The time-dependent numerical technique allows for complex arbitrary geometrical boundaries, the solution of the full three-dimensional Navier-Stokes equations with a turbulent kinetic energy model, and chemical vibrational and rotational nonequilibrium chemistry (including gain calculations). Calculations are compared

W. L. Hendricks; R. R. Mikatarian; B. J. Gross; N. L. Rapagnani

1981-01-01

220

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

221

Feasibility studies of a visible chemical laser from the detonation products of lead azide  

SciTech Connect

The feasibility of a visible-range lasing scheme based on the 3P1 0 to 1D2 transition at 722.9 nm that occurs through the detonation of lead azide is presently demonstrated via high-speed framing photography. Further support for this phenomenon is obtained through measurements of the transmission of an HeNe laser beam through the detonation products and from the temporal behavior of these products' chemiluminescence. This scheme indicates that it is possible to employ a primary explosive as a source of premixed chemical-laser reagents. 28 refs.

Bar, I.; Ben-Porat, T.; Cohen, A.; Heflinger, D.; Tzuk, Y.; Rosenwaks, S. (Negev, University, Beersheba (Israel))

1992-07-01

222

Multiwavelength laser array by chemical beam epitaxy patterned InP substrates  

NASA Astrophysics Data System (ADS)

A multiwavelength laser array has been obtained through growth on patterned InP substrates using chemical beam epitaxy. This technique makes use of interfacet migration of reactant species to obtained compositional and/or thickness variation with position on a set of patterned ridges. Results obtained on 100-line InP substrates with prepatterned ridges of various sizes oriented in the 0 -1 1-line direction are presented. A variation in lasing wavelength from 1560 to 1582 nm is obtained from lasers processed on ridges with different sizes.

Kapre, R. M.; Tsang, W. T.; Chen, Y. K.; Sergent, A. M.

1993-04-01

223

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

224

Chemical characterization of aerosol particles by laser Raman spectroscopy. Revision  

SciTech Connect

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

Fung, K.H.

1999-12-01

225

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

226

Optical properties and surface structure comparison of tooth whitening using four laser systems and chemical action agents  

NASA Astrophysics Data System (ADS)

The purpose of the study is to evaluate the effect of various laser techniques for bleaching teeth in office vital whitening. Hydrogen peroxide (30% concentration) and carbamide peroxide (10% solution) were used for chemical activation of bleaching process. Extracted non-carcious upper central incisors were exposed to laser radiation. Four different laser systems (Nd:YAG laser SHG, wavelength 0.53 ?m, CTE:YAG laser, wavelength 2.7 ?m, Nd:YAG laser, wavelength 1.06 ?m, and alexandrite laser, wavelength 0.75 ?m) were applied to accelerate the speed of the process. The end of chemical exposition was verified by the change of bleaching agent color. The color change was determined by stereomicroscope (Nikon SMZ 2T, Japan), the quality of surface structure was checked by scanning electron microscope Joel (Japan). The speed of bleaching rnaged from 630 s (chemical methods only) to 250-340 s (chemicals + alexandrite laser radiation). The Alexandrite laser application was considered an elective process to decrease the time of bleaching without modifying the surface.

Dostalova, Tatjana; Jelinkova, Helena; Koranda, Pavel; Nemec, Michal; Sulc, Jan; Housova, Devana; Miyagi, Mitsunobu; Kokta, Milan R.

2003-06-01

227

ACTIVE MEDIA: Chemical hydrogen fluoride laser on a thermal chain explosion initiated by resonance IR radiation  

NASA Astrophysics Data System (ADS)

Characteristics of a chemical H2—F2 laser initiated by resonant vibrational excitation of HF molecules upon the development of a thermal chain branching reaction are theoretically studied. After the addition of N2F2 or F2SO3 molecules with partial pressure of 20 Torr to the HF: H2: F2: O2: He = 0.5: 76: 228: 23: 100-Torr mixture, a specific output energy of a hydrogen fluoride laser initiated by a 2-?s pulse from an H2—F2 laser with the energy density of 0.01-10 J cm-2 amounted to 30-60 J litre-1, exceeding the specific initiation energy by a factor of 100 —4000.

Igoshin, Valerii I.; Pichugin, S. Yu; Stukalina, I. L.

2000-07-01

228

Chemical taggant detection and analysis by laser-induced breakdown spectroscopy.  

PubMed

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. PMID:19122697

Wise, Steven H; Almirall, Jose R

2008-11-01

229

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

230

Optical thin films grown by surface chemical reaction for high-power lasers  

NASA Astrophysics Data System (ADS)

We prepared optical thin films grown with surface chemical reactions using TiCl4 and H2O for TiO2. The nonuniformity of thickness distribution was under 1% over 240 mm in diameter. The structure of TiO2 film grown at 25 degrees Celsius was amorphous. The structure changed into polycrystalline with an increase of growth temperature up to 400 degrees Celsius. Secondary ion mass spectrometry showed that chloride residents presented in the films at every growth temperature. However, these chloride residents could be removed by thermal annealing at 400 degrees Celsius. The TiO2 film at the growth temperature of 25 degrees Celsius had a laser-induced damage threshold of 5 J/cm2 for 1-ns, 1064 nm laser pulse. The damage threshold of TiO2 films decreased at higher growth temperature. Chloride in the films had no influence on the laser-induced damage threshold.

Zaitsu, Shin-ichi; Motokoshi, Shinji; Jitsuno, Takahisa; Nakatsuka, Masahiro; Yamanaka, Tatsuhiko

2000-04-01

231

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

PubMed

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

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

2013-10-01

232

Direct measurement of chemical composition of SOx in impact vapor using a laser gun  

NASA Astrophysics Data System (ADS)

The final chemical composition of vapor clouds created by the impacts higher than 10 km/s is important to investigate the evolution of the planetary surface environment and life. However, no previous experimental study has observed directly it because of experimental difficulties. In this study, we conducted hypervelocity impact experiments using a laser gun and measured the chemical compositions of the impact-generated sulfuric oxides directly. The result clearly shows that the sulfur oxides released by hypervelocity impacts are dominated by SO3, not SO2.

Ohno, Sohsuke; Kadono, T.; Kurosawa, Kosuke; Hamura, Taiga; Sakaiya, Tatsuhiro; Sugita, S.; Shigemori, K.; Hironaka, Yoichiro; Sano, T.; Watari, Takeshi; Otani, K.; Matsui, T.

2012-03-01

233

Structuring of sapphire by laser-assisted methods, ion-beam implantation, and chemical wet etching  

Microsoft Academic Search

Sapphire is an attractive material for micro- and opto-electronic systems applications because of its excellent mechanical and chemical properties. However, because of its hardness, sapphire is difficult to machine. Titanium-doped sapphire is a well-known broadly tunable and short-pulse laser material and a promising broadband light source for applications in low-coherence interferometry. We investigated several methods to fabricate rib structures in

A. Crunteanu; P. Hoffmann; M. Pollnau; C. Buchal

2002-01-01

234

Chemical production of vibrationally excited HBr for a continuous wave laser  

Microsoft Academic Search

Bromine has been added to the hydrogen cavity fuel of a cw supersonic mixing HF chemical laser. The hydrogen atoms produced in the F+H2-->HF(vHBr(v<=6)+Br. Infrared chemiluminescence measurements indicate unsaturated gain coefficients of about (2+\\/-1) ×10-3 cm-1 for J=4 through J=8 for v=3, 2, and 1 levels of HBr. The current 3-cm gain length is not sufficient for lasing without the

Donald J. Miller; William L. Shackleford; George Emanuel

1979-01-01

235

Selection of a Master-Oscillator Scheme for a Chemical IR-Initiated Laser  

Microsoft Academic Search

The results of experimental and theoretical studies of operation regimes of a pulsed chemical D2–F2–CO2 UV initiated laser are presented. The influence of particular mixture components, the power of the UV radiation source, and the resonator's characteristics on the output radiation parameters are experimentally studied on the “Kaiman” setup. The results of theoretical simulation obtained using the proposed scheme correspond

A. O. Alexandrov; L. P. Feoktistov; M. P. Frolov; Ya. M. Kravets; V. G. Louzhnov; A. S. Maiorov; A. P. Pashenko; Yu. P. Podmar'kov; Yu. A. Satov; N. G. Shchepetov; Yu. B. Smakovskii; V. N. Smol'skii; A. N. Starodub; B. L. Vasin; N. N. Yuryshev; N. P. Zaretskii

2003-01-01

236

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

Microsoft Academic Search

A determination was made of the energy, spectrum, and duration of emission of radiation generated as a result of vibrational-rotational transitions in HF and HCl molecules in a chemical laser utilizing ClF-H2-He mixtures and subjected to short-pulse initiation of the pump reactions by a transverse electric discharge preceded by photopreionization. When the total energy of the output radiation pulses due

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

1984-01-01

237

BRIEF COMMUNICATIONS: Investigation of a chemical HF laser utilizing a highpressure H2SF6 mixture  

Microsoft Academic Search

An investigation was made of the energy characteristics of a chemical HF laser utilizing an H2-SF6 mixture and excited by a beam of relativistic electrons. Efficient lasing was obtained at gas mixture pressures up to 4.5 atm, a specific output energy of 50 J\\/liter being obtained at 1.5 atm. It should be possible to tune continuously the lasing frequency in

A. S. Bashkin; A. N. Oraevskii; V. N. Tomashov; Nikolai N. Yuryshev

1982-01-01

238

Operating characteristics of a high pressure DF-CO2 CW chemical transfer laser  

Microsoft Academic Search

High pressure operation (200 torr) of a subsonic NO-initiated DF-CO2 transfer chemical laser has been successfully demonstrated. Small-signal gains of 1.6, 1.5, and 1.4%\\/cm have been measured at cavity pressures 100, 140, and 200 torr, respectively, with gain widths of up to 5 cm at 200 torr. The experimental results were found to be in excellent agreement with theoretical predictions

G. D. Hager; L. M. Wood; M. L. Chazen; F. B. Bossler; L. Shub; W. C. Solomon

1979-01-01

239

Comprehensive kinetics model for DF-CO2 transfer chemical lasers  

Microsoft Academic Search

A computer model of the DF-CO2 CW transfer chemical laser (TCL) which treats the first nine vibrational states of DF and the first thirty-nine vibrational states of CO2 is described in detail. Information theory, as it now exists, was used to correlate the large number of possible energy transfer processes involving the CO2 molecule with the rather small body of

J. A. Blauer; S. W. Zelazny; W. C. Solomon; G. D. Hager

1979-01-01

240

Operating characteristics of a high pressure DF-CO2CW chemical transfer laser  

Microsoft Academic Search

Interest in the DF-CO2transfer chemical laser (TCL) is stimulated by its potential to yield high specific efficiencies and high gain coefficients at high optical cavity pressures. Previous technology studies of the DF-CO2TCL for the most part have been limited to operation at cavity pressures of 100 torr or less. Recently, high pressure operation (233 torr) of a supersonic TCL has

G. D. Hager; L. Wood; M. Chazen; F. Bossler; L. Shub; W. Solomon

1979-01-01

241

Comprehensive kinetics model for DF-CO2transfer chemical lasers  

Microsoft Academic Search

A computer model of the DF-CO2CW transfer chemical laser (TCL) which treats the first nine vibrational states of DF and the first thirty-nine vibrational states of CO2is described in detail. Information theory, as it now exists, was used to correlate the large number of possible energy transfer processes involving the CO2molecule with the rather small body of published experimental data.

J. Blauer; S. Zelazny; G. Hager; W. Solomon

1979-01-01

242

Synthesis of cobalt oxides thin films fractal structures by laser chemical vapor deposition.  

PubMed

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

243

Measurement Of Atmospheric Peroxy Radicals By Chemical Conversion And Laser-induced Fluorescence Technique  

Microsoft Academic Search

A new method for measuring atmospheric peroxy radicals is described based on chemical conversion and laser-induced fluorescence (LIF) technique. Peroxy radicals are quantitatively converted into hydroperoxyl radicals (HO2) by the reactions with NO in a low-pressure reactor. The produced HO2 is then detected with an LIF instrument. The characterization and response of this instrument has been evaluated through the laboratory

X. Ren; C. Naik; J. Mao; H. Harder; M. Martinez; R. Lesher; W. H. Brune

2005-01-01

244

Modeling of HF chemical laser flowfields using the Direct Simulation Monte Carlo method  

SciTech Connect

A methodology, based on the Direct Simulation Monte Carlo (DSMC) approach, has been developed to screen injector concepts for high-energy chemical lasers. This methodology involves modeling the associated complex three-dimensional, reacting, multispecies flowfields and has been validated by comparison with experimental measurements. The method enables screening of new high-performance injector concepts and has the potential of greatly minimizing idea-to-implementation time and cost. 5 refs.

McGregor, R.D.; Haflinger, D.E.; Lohn, P.D.; Sollee, J.L.; Behrens, H.W.; Duncan, W.A. (TRW Space AND Technology Group, Redondo Beach, CA (United States) U.S. Army, Missile Command, Redstone Arsenal, Al (United States))

1992-07-01

245

Miniaturized optical fiber Fabry-Perot interferometer fabricated by femtosecond laser irradiation and selective chemical etching  

NASA Astrophysics Data System (ADS)

A U-shaped optical fiber inline microchannel was fabricated by femtosecond laser irradiation and subsequent selective chemical wet etching. A high quality micro-cavity embedded inside the channel was obtained to construct a Fabry-Perot interferometer (FPI). A fringe visibility of 20 dB in spectrum domain was achieved. High temperature survivability of this micro device was also demonstrated. The proposed assembly-free optical fiber inline interferometer is attractive for sensing applications in high-temperature harsh environments.

Yuan, Lei; Lan, Xinwei; Huang, Jie; Wang, Hanzheng; Cheng, Baokai; Liu, Jie; Xiao, Hai

2014-03-01

246

Active coherent laser spectrometer for remote detection and identification of chemicals  

NASA Astrophysics Data System (ADS)

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

MacLeod, Neil A.; Weidmann, Damien

2012-10-01

247

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

248

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

249

Characterizing effects and benefits of beam defocus on high energy laser performance under thermal blooming and turbulence conditions for air-to-ground engagements  

NASA Astrophysics Data System (ADS)

This dissertation makes contributions towards knowledge of optimizing of laser weapon performance when operating in the air-to-ground (ATG) regime in thermal blooming conditions. Wave optics modeling techniques were used to represent laser weapon performance in a high fidelity sense to allow progress to be made toward improving lower-fidelity scaling laws that can be used in systems level analysis which has need for better representations of thermal blooming. Chemical-oxygen iodine laser (COIL) based weapon systems that operate near the ground will experience thermal blooming due to atmospheric absorption if output power is sufficiently high. The thermal lens in the ATG case is predominantly in the far-field of the optical system which puts the problem outside the envelope for most classical phase correction techniques. Focusing the laser beyond the target (defocus) in the air-to-ground regime is shown to improve irradiance at the target and can be thought of as reducing the thermal blooming distortion number, ND, rather than phase correction. Improvement is shown in a baseline scenario presented and all variations from it explored herein. The Breaux ND is examined for potential use in a defocus scaling law, and a correction factor due to Smith (1977), developed for a different context, is proposed to address deficiencies. Optimal defocus settings and expected improvement are presented as a function of Breaux ND. Also, the generally negative interaction between turbulence and thermal blooming is investigated and shown to further limit performance potential of ATG laser weapons. This negative interaction can impact the weapon design trade space and operational methods for minimizing the interaction and thermal blooming are explored in a case study.

Long, Scott N.

250

Ambient diode laser desorption dielectric barrier discharge ionization mass spectrometry of nonvolatile chemicals.  

PubMed

In this work, the combined use of desorption by a continuous wave near-infrared diode laser and ionization by a dielectric barrier discharge-based probe (laser desorption dielectric barrier discharge ionization mass spectrometry (LD-DBDI-MS)) is presented as an ambient ionization method for the mass spectrometric detection of nonvolatile chemicals on surfaces. A separation of desorption and ionization processes could be verified. The use of the diode laser is motivated by its low cost, ease of use, and small size. To achieve an efficient desorption, the glass substrates are coated at the back side with a black point (target point, where the sample is deposited) in order to absorb the energy offered by the diode laser radiation. Subsequent ionization is accomplished by a helium plasmajet generated in the dielectric barrier discharge source. Examples on the application of this approach are shown in both positive and negative ionization modes. A wide variety of multiclass species with low vapor pressure were tested including pesticides, pharmaceuticals and explosives (reserpine, roxithromycin, propazine, prochloraz, spinosad, ampicillin, dicloxacillin, enrofloxacin, tetracycline, oxytetracycline, erythromycin, spinosad, cyclo-1,3,5,7-tetramethylene tetranitrate (HMX), and cyclo-1,3,5-trimethylene trinitramine (RDX)). A comparative evaluation revealed that the use of the laser is advantageous, compared to just heating the substrate surface. PMID:23419061

Gilbert-López, Bienvenida; Schilling, Michael; Ahlmann, Norman; Michels, Antje; Hayen, Heiko; Molina-Díaz, Antonio; García-Reyes, Juan F; Franzke, Joachim

2013-03-19

251

Laser-induced IR fluorescence spectra of simulant chemical threat agent and exhaust vapors. Technical report  

SciTech Connect

Infrared (IR) fluorescence spectra have been measured for several agent/exhaust simulants illuminated by a slowly (10-200 Hz) chopped infrared absorption spectra when excited by a grating tuned 5 watt CO{sub 2} (9 - 11 microns) laser. Utilizing a calibrated spectral measurement apparatus, the spectra are presented in terms of the actual quantity of fluorescence energy emitted from a unit volume of vapor and wavelength span for a given set of excitation conditions (laser wavelength, power, and chop frequency) and simulant pressure. The addition of air to small quantities (10 - 30 Torr) of the simulants quenches, but does not completely extinguish, the fluorescence. A linear increase in the infrared fluorescence intensity with laser chopping period is observed along with very slow (msec) rise and decay times of the fluorescence signal. These observations are attributed to the bulk heating of the vapor or vapor-air mixture along the laser beam path due to the slow chopping frequencies. These results indicate the possible utilization of laser-induced infrared fluorescence in remote sensing of chemical vapors of interest to the Army (agents/vehicle exhausts).

Bossoli, R.B.; Thomson, G.M.

1990-04-01

252

BRIEF COMMUNICATIONS: Dependence of the power of a chemical CO laser on the reaction mixture flow rate  

Microsoft Academic Search

Operation of a chemical CO laser was studied experimentally as a function of the flow rate of a CS2-N2O-O2 working mixture pumped through the optical resonator cavity. A cw laser radiation power of ~ 730 W was reached at a gas flow rate of about 25 g\\/s.

V. A. Dudkin; V. B. Rukhin

1991-01-01

253

On the possibility of simultaneous emission of an autonomous cw HF-DF chemical laser in two spectral ranges  

SciTech Connect

The efficiencies of different fuel compositions used in the combustion chamber of an autonomous cw chemical HF-DF laser for obtaining high specific energy parameters during simultaneous lasing in HF and DF molecules in two spectral ranges are theoretically analysed. It is shown that mirrors with the reflectance above 99% in these spectral ranges can be manufactured in principle. (lasers)

Bashkin, A S; Gurov, L V; Katorgin, B I; Petrova, S N [Open Joint-Stock Company, V.P. Glushko Energomash Research and Production Assocation, Khimki-1, Moscow region (Russian Federation); Polinovsky, D V [Moscow Aviation Institute (State Technical University), Moscow (Russian Federation)

2008-05-31

254

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

Microsoft Academic Search

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

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

2006-01-01

255

Laser micromachined and laminated microchannel components for chemical sensors and heat transfer applications  

NASA Astrophysics Data System (ADS)

The fabrication of microchannel chemical sensors with seven laminated individual functional modules is described. The sensors, used to detect chromium in nuclear and chemical waste streams, were fabricated using laser micromachining, bulk silicon micromachining, photolithographic techniques, sputter coating deposition, and anodic and adhesive bonding processes. The size of the sensor was 2 cm by 2.2 cm, with a total thickness of 2.2 cm. It consisted of two or more reservoir modules to hold the liquids being evaluate, two or more micropump modules to pump the liquids through the sensor, a chemical mixing module, a reaction module, and a sensor module with electrical circuitry for connection to external measurement equipment. The fluids were directed through the layers by interconnecting flow channels. The reservoir modules were fabricated by machining Pyrex and anodic bonding to silicon. The chemical mixing module was fabricated by wet etching Pyrex and anodic bonding to silicon. The reaction module contained a serpentine 200- micrometers -wide channel, and was formed by laser micromachining polyimide. The first prototype of this sensor employed external micropumps, while the second prototype will use off-the-shelf piezoelectric micropumps. The detector layer consisted of iridium, silver, and platinum sensor pads connected to gold contact strips. The modules were joined using adhesive bonding, and an electrostatic technique was used for silicon-Pyrex bonding.

Martin, Peter M.; Bennett, Wendy D.; Hammerstrom, D. J.; Johnston, John W.; Matson, Dean W.

1997-09-01

256

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

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

257

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

258

Study on the surface chemical properties of UV excimer laser irradiated polyamide by XPS, ToF-SIMS and CFM  

NASA Astrophysics Data System (ADS)

Polyamide (nylon 6) was irradiated by a pulsed ultraviolet (UV) excimer laser with a fluence below its ablation threshold. Chemical modifications on laser treated nylon were studied by X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (Tof-SIMS) and chemical force microscopy (CFM). XPS study provides information about changes in chemical composition and the chemical-state of atom types on the fiber surface. The high sensitivity of ToF-SIMS to the topmost layers was used to detect crosslinking after the laser treatment. Gold-coated AFM tips modified with ?COOH terminated self-assembled alkanethiol monolayers (SAMs) were used to measure adhesion forces on the untreated and laser treated samples. XPS results revealed that the irradiated samples have higher oxygen content than prior to laser irradiation. Tof-SIMS analysis illustrated that carbonyl groups in nylon 6 decrease significantly but hydroxyl groups increase after low-fluence laser irradiation. The adhesion force measurements by CFM showed spatial distribution of hydroxyl groups on nylon 6 after the laser treatment.

Yip, Joanne; Chan, Kwong; Sin, Kwan Moon; Lau, Kai Shui

2003-01-01

259

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

260

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

261

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

Microsoft Academic Search

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

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

2010-01-01

262

'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.

2013-01-01

263

Laser ablation of phenylazide in an argon matrix: direct observation and chemical reactivity of ablated fragments  

NASA Astrophysics Data System (ADS)

Ablation of pentafluorophenylazide (FPA) in an Ar matrix at 8-10 K was carried out upon irradiation with ns-pulsed UV lasers in a vacuum. The plume of ablated products was monitored by a time-resolved imaging/spectroscopic technique using a gated and intensified CCD camera system. A large amount of pentafluorophenylnitrene (FPN) having a high kinetic energy ( 6 eV) was ejected as fragments from the matrix film during ablation. A quantitative formation of triplet FPN from the photolysis of the FPA was observed by spectroscopic measurements in the IR and UV-visible regions, and was confirmed by a theoretical IR spectrum calculated according to density functional theory. A FPN beam is useful for chemical surface modification of organic materials, such as aromatic polyester and alkylthiol. A surface analysis of these materials by X-ray photoelectron spectroscopy and Fourier transform infrared reflection absorption spectroscopy showed that the FPN was immobilized onto the surface through chemical bonds. This technique for the chemical surface modification of materials is made possible by a pulsed beam of reactive fragments with a high density in the laser ablation process.

Niino, H.; Sato, T.; Yabe, A.

264

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

265

Supersonic jet/multiphoton ionization spectrometry of chemical species resulting from thermal decomposition and laser ablation of polymers  

SciTech Connect

The chemical species resulting from thermal decomposition and laser ablation of polymers are measured by excitation/fluorescence and multiphoton ionization/mass spectrometries after supersonic jet expansion for rotational cooling to simply the optical spectrum. The signal of minor chemical species occurred is strongly enhanced by resonant excitation and multiphoton ionization, and even the isomer can be clearly differentiated. For example, p-cresol occurred by thermal decomposition of polycarbonate is detected selectively by mass-selected resonant multiphoton ionization spectrometry. Various chemical species occurred by laser ablation of even a polystyrene foam are also measured by this technique.

Hozumi, Masami; Murata, Yoshiaki; Cheng-Huang Lin; Imasaka, Totaro [Department of Chemical Science and Technology, Faculty of Engineering, Hakozaki, Higashi-Ku, Fukuoka 812 (Japan)

1995-04-01

266

Chemical and explosive detections using photo-acoustic effect and quantum cascade lasers  

NASA Astrophysics Data System (ADS)

Photoacoustic (PA) effect is a sensitive spectroscopic technique for chemical sensing. In recent years, with the development of quantum cascade lasers (QCLs), significant progress has been achieved for PA sensing applications. Using high-power, tunable mid-IR QCLs as laser sources, PA chemical sensor systems have demonstrated parts-pertrillion- level detection sensitivity. Many of these high sensitivity measurements were demonstrated locally in PA cells. Recently, we have demonstrated standoff PA detection of isopropanol vapor for more than 41 feet distance using a quantum cascade laser and a microphone with acoustic reflectors. We also further demonstrated solid phase TNT detections at a standoff distance of 8 feet. To further calibrate the detection sensitivity, we use nerve gas simulants that were generated and calibrated by a commercial vapor generator. Standoff detection of gas samples with calibrated concentration of 2.3 ppm was achieved at a detection distance of more than 2 feet. An extended detection distance up to 14 feet was observed for a higher gas concentration of 13.9 ppm. For field operations, array of microphones and microphone-reflector pairs can be utilized to achieve noise rejection and signal enhancement. We have experimentally demonstrated that the signal and noise spectra of the 4 microphone/4 reflector system with a combined SNR of 12.48 dB. For the 16-microphone and one reflector case, an SNR of 17.82 was achieved. These successful chemical sensing demonstrations will likely create new demands for widely tunable QCLs with ultralow threshold (for local fire-alarm size detection systems) and high-power (for standoff detection systems) performances.

Choa, Fow-Sen

2013-12-01

267

Chemical production of vibrationally excited HBr for a continuous wave laser  

Microsoft Academic Search

Bromine has been added to the hydrogen cavity fuel of a cw supersonic mixing HF chemical laser. The hydrogen atoms produced in the F+H2?HF(v?3)+H reaction are used to continuously produce vibrationally excited HBr by the reaction H+Br2?HBr(v?6)+Br. Infrared chemiluminescence measurements indicate unsaturated gain coefficients of about (2±1) ×10?3 cm?1 for J=4 through J=8 for v=3, 2, and 1 levels of

Donald J. Miller; William L. Shackleford; George Emanuel

1979-01-01

268

Hybrid chemical etching of femtosecond laser irradiated structures for engineered microfluidic devices  

NASA Astrophysics Data System (ADS)

We report on the fabrication of 3D buried micro-structures in fused silica glass using the selective chemical etching along femtosecond laser irradiated zones. Specifically, we have exploited a novel approach combining two different etching agents in successive steps. The widely used hydrofluoric acid solution, which provides fast volume removal, and potassium hydroxide solution, which exhibits high selectivity, are used to fabricate microfluidic structures. We demonstrate that this hybrid approach takes advantage of both of the individual etchants’ special characteristics and facilitates prototyping and fabrication of complex geometries for microfluidic devices.

LoTurco, S.; Osellame, R.; Ramponi, R.; Vishnubhatla, K. C.

2013-08-01

269

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

SciTech Connect

We are developing a new technique for the chemical characterization of microparticles based upon the use of electrodynamic traps. The electrodynamic trap has achieved widespread use in the mass spectrometry community in the form of the ion trap mass spectrometer or quadrupole ion trap. Small macroscopic particles can be confined or levitated within the electrode structure of a three-dimensional quadrupole electrodynamic trap in the same way as fundamental charges or molecular ions by using a combination of ac and dc potentials. Our concept is to use the same electrode structure to perform both microparticle levitation and ion trapping/mass analysis. The microparticle will first be trapped and spatially stabilized within the trap for characterization by optical probes, i.e., absorption, fluorescence, or Raman spectroscopy. After the particle has been optically characterized, it is further characterized using mass spectrometry. Ions are generated from the particle surface using laser ablation or desorption. The characteristics of the applied voltages are changed to trap the ions formed by the laser with the ions subsequently mass analyzed. The work described in this paper focuses on the ability to perform laser desorption experiments on microparticles contained within the ion trap.

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

1991-01-01

270

Low temperature selective epitaxy of III V compounds by laser assisted chemical vapor deposition  

NASA Astrophysics Data System (ADS)

Laser Assisted Chemical Vapor Deposition (LCVD) is a new approach for low temperature selective epitaxy of III-V compounds with great potential for maskless multicomponent device integration on the same wafer. GaAs substrates were thermally biased to temperatures as low as 250°C and exposed simultaneously to fluxes of trimethylgallium (TMG) and arsine (AsH 3). Ar ion laser scanning of the substrate, at carefully selected growth conditions, resulted in epitaxial selective deposition at rates as low as a few Å/s per scan. The LCVD growth rates as a function of deposition temperatures are reported for different laser powers and seem to follow an Arrhenius type relation. Activation energies in the range 10-13 kcal/mol were estimated for growth temperatures in the range 250-400°C. X-ray diffraction topography is demonstrated as a powerful nondestructive tool for structural characterization. We have utilized this technique to optimize the LCVD growth conditions in order to achieve device quality films that are free from lattice distortion. Low temperature photoluminescence shows the presence of impurity peaks that can be related to carbon.

Karam, N. H.; Liu, H.; Yoshida, I.; Jiang, B.-L.; Bedair, S. M.

1988-12-01

271

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

272

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.

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

273

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

PubMed

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

2011-10-11

274

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

SciTech Connect

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

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

1991-01-01

275

Fabrication of high-aspect ratio, micro-fluidic channels and tunnels using femtosecond laser pulses and chemical etching  

Microsoft Academic Search

We present novel results obtained in the fabrication of high-aspect ratio micro-fluidic microstructures chemically etched from fused silica substrates locally exposed to femtosecond laser radiation. A volume sampling method to generate three-dimensional patterns is proposed and a systematic SEM-based analysis of the microstructure is presented. The results obtained gives new insights toward a better understanding of the femtosecond laser interaction

Yves Bellouard; Ali Said; Mark Dugan; Philippe Bado

2004-01-01

276

Development of a measurement system of peroxy radicals using a chemical amplification\\/laser-induced fluorescence technique  

Microsoft Academic Search

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

Yasuhiro Sadanaga; Jun Matsumoto; Ken-Ichi Sakurai; Ryoko Isozaki; Shungo Kato; Tomoki Nomaguchi; Hiroshi Bandow; Yoshizumi Kajii

2004-01-01

277

Probing the heat affected zone by chemical modifications in femtosecond pulse laser ablation of titanium nitride films in air  

Microsoft Academic Search

A new approach is presented to quantify the so-called ``heat affected zone'' (HAZ) during femtosecond laser pulse processing. Ablation of titanium nitride (TiN) thin films (~3 mum thickness) by multiple femtosecond laser pulses (tau=130 fs, lambda=800 nm) in air environment was studied by means of two different surface analytical methods both being sensitive to chemical alterations at the surface. Scanning

Jörn Bonse; Jörg Krüger

2010-01-01

278

Chemical studies of intraocular lenses after experimental generation of lesions by a short-pulsed Nd-YAG laser  

Microsoft Academic Search

It is theoretically possible that lesions generated by a Q-switched Nd-YAG laser could lead to chemical changes in polymethylmethacrylate (PMMA) intraocular lenses. These changes could be of clinical relevance. Therefore, we measured the residual monomer content of intraocular lenses before and after generation of lesions by means of a short-pulsed Nd-YAG laser. Despite the explosive destruction of the lens surface

O. F. Scheiffarth; K. Ludwig; R. Birngruber; V.-P. Gabel; L. Meyer

1984-01-01

279

Experimental investigation of CO chemical laser produced by supersonically mixing CS\\/S with O2 in a shock tunnel  

Microsoft Academic Search

Experimental results of small-signal gain in a CO chemical laser operating with very high values of CS:CS2 and S:CS are presented. The laser is produced in a shock tunnel in which complete thermal dissocation of CS2 into CS + S is accomplished by a reflected shock wave. The dissociated products, which are diluted in Ar, expand through a supersonic nozzle

J. Stricker; M. Tilleman

1981-01-01

280

Singlet oxygen kinetics in a double microwave discharge  

Microsoft Academic Search

Chemical lasers offer the highest powers necessary for many weapons applications, but require significant logistical support in the delivery of specialized fuels to the battlefield. In the Chemical Oxygen-Iodine Laser (COIL), which is the weapon aboard the Airborne Laser (ABL), gaseous chlorine and liquid basic hydrogen peroxide are used to generate the singlet oxygen energy reservoir. The goal of the

Greg A. Pitz; Matthew A. Lange; Glen P. Perram

2004-01-01

281

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

282

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

283

InGaAsP\\/InP buried-heterostructure lasers \\/lambda = 1.5 microns\\/ with chemically etched mirrors  

Microsoft Academic Search

The monolithic fabrication of buried heterostructure InGaAsP\\/InP lasers operating at a wavelength of 1.5 microns with chemically etched mirrors is reported. The buried heterostructure lasers were prepared from InGaAsP\\/InP DH wafers reverse-mesa etched with a Br2:CH3OH solution, with the reverse-mesa walls buried by subsequent LPE growth. To fabricate the etched mirror laser, Au-Zn metal was evaporated onto the epitaxial-layer side

S. Adachi; H. Kawaguchi; K. Takahei; Y. Noguchi

1981-01-01

284

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

Microsoft Academic Search

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

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

2011-01-01

285

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

Microsoft Academic Search

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

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

2011-01-01

286

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

Microsoft Academic Search

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

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

2010-01-01

287

Properties of aluminum oxide thin films deposited by pulsed laser deposition and plasma enhanced chemical vapor deposition  

Microsoft Academic Search

The chemical, structural, mechanical and optical properties of thin aluminum oxide films deposited at room temperature (RT) and 800 °C on (100) Si and Si–SiO2 substrates by pulsed laser deposition and plasma enhanced chemical vapor deposition are investigated and compared. All films are smooth and near stoichiometric aluminum oxide. RT films are amorphous, whereas ? type nano-crystallized structures are pointed out

C. Cibert; H. Hidalgo; C. Champeaux; P. Tristant; C. Tixier; J. Desmaison; A. Catherinot

2008-01-01

288

Ar+ and CuBr laser-assisted chemical bleaching of teeth: estimation of whiteness degree  

NASA Astrophysics Data System (ADS)

In this work the results of adaptation of impartial methods for color determination aimed at developing of techniques for estimation of human teeth whiteness degree, sufficiently handy for common use in clinical practice are presented. For approbation and by the way of illustration of the techniques, standards of teeth colors were used as well as model and naturally discolored human teeth treated by two bleaching chemical compositions activated by three light sources each: Ar+ and CuBr lasers, and a standard halogen photopolymerization lamp. Typical reflection and fluorescence spectra of some samples are presented; the samples colors were estimated by a standard computer processing in RGB and B coordinates. The results of the applied spectral and colorimetric techniques are in a good agreement with those of the standard computer processing of the corresponding digital photographs and complies with the visually estimated degree of the teeth whiteness judged according to the standard reference scale commonly used in the aesthetic dentistry.

Dimitrov, S.; Todorovska, Roumyana; Gizbrecht, Alexander I.; Raychev, L.; Petrov, Lyubomir P.

2003-11-01

289

Direct measurement of chemical composition of SOx in impact vapor using a laser gun  

NASA Astrophysics Data System (ADS)

The SO3/SO2 ratio of the impact vapor cloud is a key parameter for understanding the environmental perturbation caused by the impact-induced SOx and the killing mechanism of. the mass extinction at the K-Pg boundary. We conducted hypervelocity impact experiments using a high-speed laser gun (GEKKO XII-HIPER, ILE, Osaka University) and measured the chemical compositions of the SOx released from CaSO4. The experimental result indicates that SOx are dominated by SO3. It implies that the SOx generated by the K-Pg impact would have been also dominated by SO3, because the SO3/SO2 ratio of natural planetary scale impact vapor clouds would have been larger than that of the experimental result of this study.

Ohno, Sohsuke; Kadono, Toshihiko; Kurosawa, Kosuke; Hamura, Taiga; Sakaiya, Tatsuhiro; Sugita, Seiji; Shigemori, Keisuke; Hironaka, Yoichiro; Watari, Takeshi; Matsui, Takafumi

2011-06-01

290

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

SciTech Connect

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

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

2012-01-23

291

BRIEF COMMUNICATIONS: Investigation of the energy characteristics of a chemical CO2 laser utilizing a O3+D2+CO2 mixture  

Microsoft Academic Search

The operating parameters of a chemical CO2 laser were optimized in order to achieve maximum output energy. The results obtained under pulse operation conditions were used in an estimate of possible parameters of a chemical cw CO2 laser utilizing a O3 + D2 + CO2 + He mixture.

A. S. Bashkin; A. N. Oraevskii; V. N. Tomashov; Nikolai N. Yuryshev

1975-01-01

292

Laser Initiated Chemical Deposition of Both Ferromagnetic and Antiferromagnetic Chromium Oxide  

NASA Astrophysics Data System (ADS)

The ferromagnetic chromium oxide CrO2 has been predicted to be half-metallic. This makes it as an attactive material for tunnel junction. The antiferromagnetic chromium oxide Cr_2O3 is suitable for tunnel junction barrier both below and above the Neel temperature. We have used both the laser initiated chemical vapor deposition and laser induced deposition from solution to grow the films of chromium oxide. For the solution based deposition procedure, we were able to obtain both thin films as well as dots(about 220nm and 300nm diameter) with a very little distribution in sizes. This indicates that under some conditions, the solution based deposition is uniform and the deposition of dots depends on surface nucleation sites. Vapor deposition is based on the photolysis of Cr(CO)6 in oxgen environment. This latter deposition process results in two phase Cr_2O3 and CrO2 thin films that depend on the differentO2 partial pressure. Both the techniques and the magnetic properties of these chromium oxide thin films will be presented.

Cheng, Rui-Hua; Borca, C. N.; Zhong, Zhenchen; Bosley, J.; Dowben, Peter

2000-03-01

293

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

SciTech Connect

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

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

2007-07-15

294

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

Microsoft Academic Search

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

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

1995-01-01

295

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

296

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

297

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

NASA Astrophysics Data System (ADS)

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

Kwok, Kinghong

298

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

299

Characterization of AlGaInN diode lasers with mirrors from chemically assisted ion beam etching  

NASA Astrophysics Data System (ADS)

Current-injection InGaAlN heterostructure laser diodes grown by metalorganic chemical vapor deposition on sapphire substrates are demonstrated with mirrors fabricated by chemically assisted ion beam etching. Due to the independent control of physical and chemical etching, smooth vertical sidewalls with a root-mean-squared roughness of 4-6 nm have been achieved. The diodes lased under pulsed current-injection conditions at wavelengths in the range from 419 to 423 nm. The lowest threshold current density was 25 kA/cm2. Lasing was observed in both gain-guided and ridge-waveguide test diodes, with cavity lengths from 300 to 1000 ?m and output powers of 10-20 mW were achieved. Laser performance is illustrated with light output-current and current-voltage characteristics and with a high-resolution optical spectrum.

Kneissl, M.; Bour, D. P.; Johnson, N. M.; Romano, L. T.; Krusor, B. S.; Donaldson, R.; Walker, J.; Dunnrowicz, C.

1998-03-01

300

Influence of the oxidiser gas composition on the overtone generation efficiency of a supersonic cw chemical HF laser  

SciTech Connect

An experimental investigation was made of the influence of the chemical composition of the oxidiser gas in an atomic-fluorine generator on the efficiency of generation of radiation representing the first overtone of the HF molecule in a self-contained supersonic cw chemical HF laser with the active medium 70 cm long. The optimal chemical composition was different for the fundamental and overtone transitions. A specific output energy of 84 J g{sup -1} at a specific mass flow rate of 0.13 g s{sup -1} cm{sup -2} through the nozzle array was achieved by optimisation of a linear three-mirror optical cavity at the 1.33 - 1.35 {mu}m wavelengths. The overtone radiation power generated in the whole of the active medium was 7.5 kW, corresponding to a 41% efficiency of energy conversion to an overtone. (lasers, active media)

Konkin, S V; Fedorov, Igor' A; Rebone, Vitalii K; Rotinyan, Mikhail A; Tret'yakov, Nikolai E; Galaev, I I; Moroz, M V; Tomashevich, N N [Russian Science Centre 'Applied Chemistry', St Petersburg (Russian Federation)

1998-08-31

301

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

NASA Astrophysics Data System (ADS)

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

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

2011-09-01

302

Measurement of low-level gain in a visible chemical laser amplifier  

NASA Astrophysics Data System (ADS)

High precision zero power gain measurements are used to demonstrate that the energy transfer sequence SiO*(b3II) + Na(3s2S) yields SiO(X1(Sigma) +) + Na*(4d2D); Na*(4d2D); Na*(4d2D) yields Na(3p2P) + hv(569 nm); Na*$(4d(superscript 2D) + hv(569 nm) yields Na(3p2P) + 2hv(569 nm) represents a viable visible chemical laser amplifier candidate. Dual beam radiometry is used to advantage in a sensitive and stable measurement system, which provides correction for: 1. source intensity fluctuations, 2. variations in source spectral density, 3. variations in detector spectral response, and 4. gain variations in detector and amplification stages. Experiments are performed to determine the amplification of a probe beam at 569 nm by an extended path length (nominal gain length approximately 5 cm) reaction energy transfer zone. For these quantitative gain measurements, the stability of the probe signal sets a limit on the sensitivity of the measurement. Considerable effort was expended to insure equivalent path lengths for probe and reference beams to compensate for source output variations so that the reference signal possesses the same temporal behavior as the probe, and the probe and reference optical systems image the same portion of the source on the detector. A gain coefficient, conservatively estimated as 0.8 to 1.5 X 10-3 cm-1, was measured. Based on this result, a Rigrod analysis indicates an expected full laser cavity output power between one and ten watts.

Stephens, James M.; Stout, John; Abraham, Joseph; Neumann, Martin; Gole, James L.; Sentman, Lee H.; Zaczek, Mariusz

2001-12-01

303

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

NASA Astrophysics Data System (ADS)

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

Patel, C. K. N.

2008-01-01

304

A high efficiency HF/H2/F2/ chemical laser initiated with a surface-spark ultraviolet flash  

NASA Astrophysics Data System (ADS)

A novel Teflon-resin surface-spark-discharge UV flash driven by a high-voltage and low-inductance coaxial Marx generator has been used to initiate a high-efficiency H2/F2 chemical laser. An HF laser output energy of 8.5 J/pulse (14.6 J/l) and an electrical efficiency of 9.7% at a total pressure of 700 torr and at a charging voltage of 108 kV have been obtained. A maximum electrical efficiency of 12.6% has been obtained under optimized conditions.

Hokazono, H.; Hishinuma, K.; Watanabe, K.; Obara, M.; Fujioka, T.

1982-03-01

305

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

Microsoft Academic Search

.   KrF excimer-laser ablation of sintered-powder polytetrafluoroethylene (PTFE) targets is used for the deposition of high-quality\\u000a PTFE films on metallic microstructures and metal backplates for electroacoustic applications. The films are found to be highly\\u000a crystalline, consisting of large spherulites with diameters up to 1 mm. X-ray photoelectron spectroscopy of the films revealed\\u000a the chemical similarity of press-sinter target pulsed-laser-deposited films with

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

2001-01-01

306

Advanced COIL technologies for field applications  

NASA Astrophysics Data System (ADS)

Chemical oxygen-iodine laser (COIL) has a great potential for applications such as decommissioning and dismantlement (D&D) of nuclear reactor, rock destruction and removal and extraction of a natural resource (Methane hydrate) because of the unique characteristics such as power scalability, high optical beam quality and optical fiber beam. Five-kilowatt Chemical oxygen-iodine laser (COIL) test facility has been developed. The chemical efficiency of 27% has been demonstrated with a moderate beam quality for optical fiber coupling. Our research program contains conventional/ejector-COIL scheme, Jet-SOG/Mist-SOG optimization, fiber delivery and long-term operation.

Tei, Kazuyoku; Sugimoto, Daichi; Ito, T.; Watanabe, G.; Vyskubenko, O.; Takeuchi, N.; Muto, S.; Kenzo, N.; Fujioka, Tomoo

2005-01-01

307

Design and performance of a Petawatt subpicosecond N2O-laser pumped by HF — chemical laser radiation  

Microsoft Academic Search

Progress on developing a petawatt laser source in 10?m region is described. Analysis of optical pumping N2O containing active media by pulsed multifrequency HF laser has been performed. It is shown that amplification of ultrashort pulses should be carried out in the gain band centered at 930cm?1. Amplification of seed ultrashort (?1ps) pulses in atmospheric and high pressure N2O (up

B. G. Bravy; Yu. A. Chernyshev; V. M. Gordienko; E. F. Makarov; V. T. Platonenko; G. K. Vasiliev

2006-01-01

308

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

309

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

SciTech Connect

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

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

2013-01-01

310

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

311

Measurement Of Atmospheric Peroxy Radicals By Chemical Conversion And Laser-induced Fluorescence Technique  

NASA Astrophysics Data System (ADS)

A new method for measuring atmospheric peroxy radicals is described based on chemical conversion and laser-induced fluorescence (LIF) technique. Peroxy radicals are quantitatively converted into hydroperoxyl radicals (HO2) by the reactions with NO in a low-pressure reactor. The produced HO2 is then detected with an LIF instrument. The characterization and response of this instrument has been evaluated through the laboratory experiments as well as numeric simulations. Relative responses of different organic groups of peroxy radicals to HO2 were measured and the conversion coefficients agree generally well with the model calculations. The dependence of conversion coefficients on different experiment conditions was investigated. For HO2, the LIF signal is calibrated with an HO2 source produced by the photolysis of H2O via a low-pressure mercury lamp. Field measurements of peroxy radicals using this method were conducted at a rural site and preliminary results are presented. The estimated accuracy of the derived HOxROx concentrations is about 40% with a 2? confidence level. Typical detection limit is about 0.2 pptv for 1-minute averaging times.

Ren, X.; Naik, C.; Mao, J.; Harder, H.; Martinez, M.; Lesher, R.; Brune, W. H.

2005-12-01

312

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

SciTech Connect

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

Stiglich, S.W.

1989-12-01

313

Effects of specific heat ratio on a simulated chemical-laser-cavity flow. Master's thesis  

SciTech Connect

Mixing of primary cold flow air and secondary helium to control the ratio of specific heats for the medium flowing through a simulated chemical laser nozzle/lasing cavity was accomplished. The effects of a range of mixture specific heat ratios on flowfield behavior were examined using static pressure ports in the test cavity. Schlieren photography and high speed filming aided description of the flow dynamics. Results indicated that boundary layer effects became evident in the nozzles as specific heat ratios increased. Large pressure fluctuations were observed in the cavity when helium was introduced into the flow to raise the specific heat ratio. This unstable behavior was attributed to the helium mass flow into the mixer and the mixer design itself. Use of the air/helium mixer brought about the pressure fluctuations earlier in a test run than with than with the mixer removed under the same conditions. Favorable pressure conditions for lasing were achieved for at least two seconds for the supersonic nozzles' design specific heat ratio of 1.51. Adverse pressure behavior was also attributed to three dimensional viscous effects along the cavity walls. (JHD)

Botts, C.D.

1990-12-01

314

Chemical transformations of the polyimide Kapton brought about by ultraviolet laser radiation  

Microsoft Academic Search

By the use of ultraviolet laser pulses of microsecond and millisecond duration it is shown that the chemistry of the transformations of Kapton by UV laser radiation is strongly dependent on the intensity (power\\/unit area) of the laser beam. With these long pulses, the polymer was not ablated. The decomposition resulted in 51% of the polymer weight being converted to

R. Srinivasan; R. R. Hall; W. D. Loehle; W. D. Wilson; D. C. Allbee

1995-01-01

315

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

316

Chemically assisted femtosecond laser machining for applications in LiNbO3 and LiTaO3  

NASA Astrophysics Data System (ADS)

We introduce and optimize a fabrication procedure that employs both femtosecond laser machining and hydrofluoric acid etching for cutting holes or voids in slabs of lithium niobate and lithium tantalate. The fabricated structures have 3 ?m lateral resolution, a lateral extent of at least several millimeters, and cut depths of up to 100 ?m. Excellent surface quality is achieved by initially protecting the optical surface with a sacrificial silicon dioxide layer that is later removed during chemical etching. To optimize cut quality and machining speed, we explored various laser-machining parameters, including laser polarization, repetition rate, pulse duration, pulse energy, exposure time, and focusing, as well as scanning, protective coating, and etching procedures. The resulting structures significantly broaden the capabilities of terahertz polaritonics, in which lithium niobate and lithium tantalate are used for terahertz wave generation, imaging, and control. The approach should be applicable to a wide range of materials that are difficult to process by conventional methods.

Sivarajah, Prasahnt; Werley, Christopher A.; Ofori-Okai, Benjamin K.; Nelson, Keith A.

2013-09-01

317

Lasers.  

National Technical Information Service (NTIS)

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

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

1991-01-01

318

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

Microsoft Academic Search

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

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

1975-01-01

319

BRIEF COMMUNICATIONS: Investigation of a pulsed chemical H2-F2 laser at high pressures of the working mixture  

Microsoft Academic Search

A report is given of the experimental results and qualitative analysis of the operation of a chemical H2-F2 laser at pressures up to 5 atm in the mixture. The mixture was initiated optically with a flux of 1.5×1023 photons·cm-2·sec-1 using pulses of 0.7 musec duration. Reduction of the duration of the initiation pulses at a constant pump energy increased the

Yu A. Kolchin; V. B. Kolovskii; S. Ya Pshezhetskii; N. F. Chebotarev

1978-01-01

320

Ex situ ellipsometry characterization of excimer laser annealed amorphous silicon thin films grown by low pressure chemical vapor deposition  

Microsoft Academic Search

Spectroscopic ellipsometry was used to monitor excimer laser annealed thin (?100 nm) amorphous silicon (a-Si) films grown on quartz substrates by low pressure chemical vapor deposition (LPCVD). The peak position of the imaginary part of the complex dielectric function &egr;2 was used to determine the degree of crystallization of the a-Si. The amplitude of &egr;2 at the Si E1 transition

Chau-Hong Kuo; In-Cha Hsieh; Dieter K. Schroder; George N. Maracas; Sheau Chen; Thomas W. Sigmon

1997-01-01

321

Reversible laser chemically induced phase transformations in thin-film Ba2YCu3O(x) superconductors  

NASA Astrophysics Data System (ADS)

Phase transformations of a thin film of Ba2YCu3O(x) were induced with a focused laser beam in chemical ambients. The transformations, involving superconductive and nonsuperconductive phases, are achieved rapidly and with a high degree of spatial control. They are fully reversible, and the appropriate processing parameters have been studied. These effects are interpreted within present models, which relate the superconducting properties of Ba2YCu3O(x) to its oxygen content and crystalline structure.

Rothschild, M.; Sedlacek, J. H. C.; Black, J. G.; Ehrlich, D. J.

1988-02-01

322

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

Microsoft Academic Search

We have used laser-initiated chemical vapor deposition to grow the chromium oxide thin films through the oxidation of Cr(CO)6 in an oxygen environment. While both Cr2O3 and CrO2 are present in the film, the relative weight of each phase depends on the oxygen partial pressure. The Curie temperature of the film increases and approaches the bulk TC of CrO2 (397

Ruihua Cheng; C. N. Borca; P. A. Dowben; Shane Stadler; Y. U. Idzerda

2001-01-01

323

A refractometer based on a micro-slot in a fiber Bragg grating formed by chemically assisted femtosecond laser processing.  

PubMed

A liquid core waveguide as a refractometer is proposed. Microtunnels were created in standard optical fiber using tightly focused femtoscond laser inscription and chemical etching. A 1.2(h)x125(d) x500(l) mum micro-slot engraved along a fiber Bragg grating (FBG) was used to construct liquid core waveguide by filling the slot with index matching oils. The device was used to measure refractive index and sensitivity up to 10- 6/pm was obtained. PMID:19550870

Zhou, Kaiming; Lai, Yicheng; Chen, Xianfeng; Sugden, Kate; Zhang, Lin; Bennion, Ian

2007-11-26

324

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

325

Organic chemical analysis on a microscopic scale using two-step laser desorption/laser ionization mass spectrometry  

NASA Technical Reports Server (NTRS)

The distribution of PAHs in the Allende meteorite has been measured using two-step laser desorption and laser multiphoton-ionization mass spectrometry. This method enables in situ analysis (with a spatial resolution of 1 mm or better) of selected organic molecules. Results show that PAH concentrations are locally high compared to the average concentration found by analysis of pulverized samples, and are found primarily in the fine-grained matrix; no PAHs were detected in the interiors of individual chondrules at the detection limit (about 0.05 ppm).

Kovalenko, L. J.; Philippoz, J.-M.; Bucenell, J. R.; Zenobi, R.; Zare, R. N.

1991-01-01

326

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

National Technical Information Service (NTIS)

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

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

2003-01-01

327

Laboratory Evaluation of Laser-Induced Breakdown Spectroscopy (LIBS) as a New in situ Chemical Sensing Technique for the Deep Ocean.  

National Technical Information Service (NTIS)

Laser-induced breakdown spectroscopy (LIBS) possesses many of the characteristics required for in situ chemical sensing, and is a promising technique for field measurements in extreme environments. In this work, laboratory experiments validate the LIBS te...

A. P. Michel

2007-01-01

328

Monolithic integrated InGaAsP/InP distributed feedback laser with Y-branching waveguide and a monitoring photodetector grown by metalorganic chemical vapor deposition  

SciTech Connect

We have fabricated an integrated 1.5 ..mu..m distributed feedback laser (DFB) with a Y-branching waveguide and a monitoring photodetector, grown entirely by metalorganic chemical vapor deposition. The integrated device is designed to resolve the frontface-backface mistracking problem of the DFB laser and to demonstrate monolithic integration of fundamental building blocks for photonic integrated circuits.

Liou, K.; Koren, U.; Chandrasekhar, S.; Koch, T.L.; Shahar, A.; Burrus, C.A.; Gnall, R.P.

1989-01-09

329

Tandem Chemical Laser Measurements of Vibrational Energy Distribution in the Dichloroethylene Photoelimination Reactions  

Microsoft Academic Search

Equal-gain temperature measurements with two laser tubes in the same optical cavity (a ``tandem'' laser) are described. In this way, rate constant ratios can be measured for vibrational transitions that do not have highest gain. The HCl laser emissions caused by photolysis of the 1, 1- and cis-1, 2-dichloroethylenes were examined in this manner. For 1, 1-dichloroethylene, k3?k2=0.85± 0.02 and

Mario J. Molina; George C. Pimentel

1972-01-01

330

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

NASA Astrophysics Data System (ADS)

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

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

1994-03-01

331

Collisional Dynamics and Spectroscopic Studies of Highly Excited Rovibrational Levels of I(2)X(0(+) sub g) via Stimulated Emission Pumping.  

National Technical Information Service (NTIS)

Highly excited vibrational levels of iodine 2 (X) are thought to play an important role in the mechanism of iodine dissociation in the chemical oxygen iodine laser. It has been proposed that Iodine 2 is dissociated in the laser with processes such as Iodi...

M. L. Nowlin

1994-01-01

332

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

333

Morphological and Chemical Changes of Deciduous Enamel Produced by Er:YAG Laser, Fluoride, and Combined Treatment.  

PubMed

Abstract Objective: The purpose of this study was to evaluate in vitro morphological and chemical changes on human deciduous enamel produced by Er:YAG laser irradiation, fluoride application, combined treatment, and acid dissolution. Background data: Er:YAG laser has been proposed as a potential preventive dental caries strategy. There is scarce information regarding deciduous enamel. Methods: Eighty enamel samples were assigned to eight groups (n=10): G1, control; G2, G3, and G4, Er:YAG laser irradiation at 7.5, 12.7, and 39.8?J/cm(2), respectively; G5, fluoride application; G6, G7, and G8, irradiation at previous densities plus fluoride application. Morphology was evaluated by scanning electron microscopy, and chemical composition was determined by energy dispersive X-ray spectroscopy before treatment (BT), after treatment (AT), and after acid dissolution (AAD). One way and repeated measures analysis of variance (ANOVA) were used (p?0.05). Results: Morphology of lased surfaces included craters, exposed prisms, fractures, and melting. No morphological modifications appeared after fluoride application, or AAD. Chemically, AT: C atomic percentage (at%) decreased in G3, G4, and G8; O at% decreased in G5-G8; F content was higher for G7; trace elements remained under 1.0 at%; Ca at % increased in G4, G7, and G8; there were increments in P at% in G4 and G8; and Ca/P increased in G4, G7, and G8. AAD: F at% dropped to 0.00 in G5-G8; and P at% increased in G7. Conclusions: Morphological changes of Er:YAG irradiated enamel represented mild to severe damages. Conditions employed in this study are not recommended for deciduous caries prevention. Er:YAG energy density influenced chemical changes in enamel to enhance its structure. Acid dissolution removed fluoride from enamel surface. PMID:24717124

Zamudio-Ortega, Carmen M; Contreras-Bulnes, Rosalía; Scougall-Vilchis, Rogelio J; Morales-Luckie, Raúl A; Olea-Mejía, Oscar F; Rodríguez-Vilchis, Laura E; García-Fabila, María M

2014-05-01

334

Pulsed laser deposition of chromium oxides thin films: chemical stabilizations by capping and doping  

Microsoft Academic Search

The half-metallic ferromagnetic chromium dioxide (Tc = 390 K) is a prospective material for spintronics applications. We employed pulsed laser deposition (PLD) to grow thin films of various chromium oxides. The experiments have been carried out in oxygen at different dynamical pressures, using a KrF* laser source (lambda = 248 nm, tauFWHM >= 30 ns), various chromium oxide targets, such

Carmen-Daniela Stanoi; Gabriel Socol; Carmen Ristoscu; Emanuel Axente; D. Caiteanu; Ion N. Mihailescu; Cristiana E. Grigorescu; Beatrice Bastide; Odile Monnereau; Laurence Tortet; T. Zhang

2004-01-01

335

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.

2014-03-01

336

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

SciTech Connect

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

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

2004-12-01

337

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

NASA Astrophysics Data System (ADS)

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

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

1998-05-01

338

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

339

Detection of chemical changes in bone after irradiation with Er,Cr:YSGG laser  

NASA Astrophysics Data System (ADS)

The use of laser for bone cutting can be more advantageous than the use of drill. However, for a safe clinical application, it is necessary to know the effects of laser irradiation on bone tissues. In this study, the Fourier Transform Infrared spectroscopy (FTIR) was used to verify the molecular and compositional changes promoted by laser irradiation on bone tissue. Bone slabs were obtained from rabbit's tibia and analyzed using ATR-FTIR. After the initial analysis, the samples were irradiated using a pulsed Er,Cr:YSGG laser (2780nm), and analyzed one more time. In order to verify changes due to laser irradiation, the area under phosphate (1300-900cm-1), amides (1680-1200cm-1), water (3600-2400cm-1), and carbonate (around 870cm-1 and between 1600-1300cm-1) bands were calculated, and normalized by phosphate band area (1300-900cm-1). It was observed that Er,Cr:YSGG irradiation promoted a significant decrease in the content of water and amides I and III at irradiated bone, evidencing that laser procedure caused an evaporation of the organic content and changed the collagen structure, suggesting that these changes may interfere with the healing process. In this way, these changes should be considered in a clinical application of laser irradiation in surgeries.

Benetti, Carolina; Santos, Moises O.; Rabelo, Jose S.; Ana, Patrícia A.; Correa, Paulo R.; Zezell, Denise M.

2011-02-01

340

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

PubMed

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 microm where water is the main absorber and 6.45 microm where both water and protein absorb. The picosecond pulses of the superpulse are treated as a train of impulses. We find that the heating rates are sufficient to superheat the outer saline layers on the nanosecond time scale, leading to explosive vaporization. We also find that competition between the layer-specific heating rates and thermal diffusion results in a wavelength-dependent separation in layer temperatures. We consider the onset of both chemical bond breaking and the helix-coil transition of protein prior to vaporization in terms of the thermal, chemical, and structural properties of the system as well as laser wavelength and pulse structure. There is no evidence for thermal bond breaking on these time scales. At 6.45 microm, but not 3 microm, there is evidence for a significant helix-coil transition. While the native protein is ductile, the denatured protein exhibits brittle fracture. This model provides a dynamic mechanism to account for the preferential ablative properties observed with FEL radiation tuned near 6.45 microm. PMID:12188758

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

2002-06-01

341

Passively mode-locked fiber laser by using monolayer chemical vapor deposition of graphene on D-shaped fiber.  

PubMed

We demonstrate a monolayer graphene saturable absorber (SA) based on D-shaped fiber for operation of the mode-locked fiber laser. The monolayer graphene is grown by chemical vapor deposition (CVD) on Cu substrate and transferred onto the polymer, and then covered with D-shaped fiber, which allows light-graphene interaction via the evanescent field of the fiber. Due to the side-coupled interaction, the length of graphene is long enough to avoid optical power-induced thermal damage. Using such a graphene-based SA, stable mode-locked solitons with 4.5 nm spectral bandwidth and 713 fs pulsewidth at the 1563 nm wavelength have been obtained under 280 mW pump power. The influence of total cavity dispersion on the optical spectrum and pulse is also investigated by adding different lengths of single-mode fiber in the laser cavity. PMID:24921867

Chen, Tao; Liao, Changrui; Wang, D N; Wang, Yiping

2014-05-01

342

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

NASA Technical Reports Server (NTRS)

This work is directed toward the design and chemical synthesis of new media for solar-pumped I* lasers. In view of the desirability of preparing a perfluoroalkyl iodide absorbing strongly at 300 nm, the relationship betwen perfluoroalkyl iodide structure and the corresponding absorption wavelength was reexamined. Analysis of existing data suggests that, in this family of compounds, the absorption maximum shifts to longer wavelength, as desired, as the C-I bond in the lasant is progressively weakened. Weakening of the C-I bond correlates, in turn, with increasing stability of the perfluoroalkyl radical formed upon photodissociation of the iodide. The extremely promising absorption characteristics of perfluoro-tert-butyl iodide can be accounted for on this basis. A new technique of diode laser probing to obtain precise yields of I* atoms in photodissociation was also developed.

Shiner, C. S.

1985-01-01

343

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

344

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...

345

Theoretical Study of Laser-Stimulated Chemical Vapor Deposition Processes of Importance in Microelectronics.  

National Technical Information Service (NTIS)

Recent experiments have demonstrated that laser radiation incident on a gas surface interface can stimulate and control the process of vapor deposition onto the surface. This research project has been a theoretical analysis of the deposition and related l...

T. F. George

1983-01-01

346

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...

347

Fabrication of Microstructures on Photosensitive Glass using a Femtosecond Laser Process and Chemical Etching.  

National Technical Information Service (NTIS)

In this study a method for the fabrication of microstructures on the surface of an inside photosensitive glass by femtosecond laser-induced modification was developed. This technique was followed by heat treatment to crystallize the modified area, and the...

C. W. Cheng C. W. Chien J. S. Chen P. X. Lee

2009-01-01

348

F2-laser ablation of Fabry–Perot cavities in optical fibres: chemical sensors  

Microsoft Academic Search

The authors have previously reported on the micro-machining of intrinsic fibre Fabry–Perot cavities in fused silica optical fibres using a 157 nm excimer laser. The current paper reports on a technique for estimating the depth of the cavity by measuring the transmitted light intensity during the micro-machining of optical fibres using a 157 nm laser. Single and multiple cavities were

V R Machavaram; R A Badcock; G F Fernando

2012-01-01

349

Chemical and structural modifications of laser treated WTi surfaces at different ambient conditions  

Microsoft Academic Search

In this work we have studied the influence of laser modification on the composition and structure of tungsten titanium (WTi)\\u000a thin films, deposited on n-type (100) silicon wafers. After deposition, the samples were multi-pulse laser irradiated in a nitrogen, oxygen, and helium\\u000a ambient. The composition of the WTi\\/Si sample was determined by Elastic Recoil Detection Analysis (ERDA). Surface morphology\\u000a was

S. Petrovic; D. Perusko; D. Milovanovic; Z. Siketic; M. Jaksic; J. Kovac; B. Gakovic; M. Milosavljevic; M. Trtica

2011-01-01

350

Technical analysis of a proposed ship-to-ship chemical laser transmission experiment  

Microsoft Academic Search

Equipment and procedures for performing a DF laser ship-to-ship transmission experiment are described. A low-power, CW DF laser, a Fourier Transform Spectrometer, and a 32 inch diameter optical tracking system with 50 microradian resolution will be installed aboard the aircraft carrier USS LEXINGTON. A 60 inch-diameter tracking receiver and aerosol and meteorological equipment will be installed aboard an escort ship.

D. H. Leslie

1982-01-01

351

Chemical and structural modifications of laser treated WTi surfaces at different ambient conditions  

NASA Astrophysics Data System (ADS)

In this work we have studied the influence of laser modification on the composition and structure of tungsten titanium (WTi) thin films, deposited on n-type (100) silicon wafers. After deposition, the samples were multi-pulse laser irradiated in a nitrogen, oxygen, and helium ambient. The composition of the WTi/Si sample was determined by Elastic Recoil Detection Analysis (ERDA). Surface morphology was monitored by Atomic Force Microscopy (AFM). In the experiment, typical laser output parameters were: wavelength 1064 nm, pulse duration 150 ps, and laser pulse energy 30 mJ. Surface concentrations of W and Ti, as well as the concentration of gas components nitrogen and oxygen were determinated before and after the action of laser radiation in different ambient conditions. The contents of W and Ti decreased after irradiation due to adsorbed gases from the surrounding atmosphere. After surface irradiation in the inert ambient (He), the concentrations of the components were not significantly changed. In other cases, oxygen was the dominant component at the surface, probably due to the high affinity of thin film components. Also, the morphological changes occurred at the surface of WTi, as an increase in the surface roughness and formation of the granular structures are a result of laser-induced surface oxidation and recrystallization.

Petrovi?, S.; Peruško, D.; Milovanovi?, D.; Siketi?, Z.; Jakši?, M.; Kova?, J.; Gakovi?, B.; Milosavljevi?, M.; Trtica, M.

2011-11-01

352

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

353

HF Laser.  

National Technical Information Service (NTIS)

A review is made of the research and development of the HF chemical laser and related work. Many gaseous compounds are used as laser media successfully; reaction kinetics and technological problems are described. The hybrid chemical laser of HF-CO sub 2 s...

K. Suzuki M . Iwasaki

1977-01-01

354

Technical analysis of a proposed ship-to-ship chemical laser transmission experiment  

NASA Astrophysics Data System (ADS)

Equipment and procedures for performing a DF laser ship-to-ship transmission experiment are described. A low-power, CW DF laser, a Fourier Transform Spectrometer, and a 32 inch diameter optical tracking system with 50 microradian resolution will be installed aboard the aircraft carrier USS LEXINGTON. A 60 inch-diameter tracking receiver and aerosol and meteorological equipment will be installed aboard an escort ship. Precise absolute transmittance measurements using the laser source, and high resolution infrared spectral measurements using the spectrometer, will be performed between the two ships at separations from 1 to 5 kilometers. The expected precision of the derived data is discussed. The contribution of the experiment results toward improving DF laser propagation model-validation is analysed in great detail. Five appendices contain discussions of tracker and optical engineering details and a discussion proposing related LIDAR measurements. Successful completion of the project, we conclude, will provide the Navy and HEL community with a dual large aperture tracking system for performing significant atmospheric transmission measurements using a ship-based, combustion-driven DF laser.

Leslie, D. H.

1982-02-01

355

Depth profile analysis of the chemical and morphological changes in CO2-laser-irradiated dental enamel  

NASA Astrophysics Data System (ADS)

Previous studies have shown that IR irradiation of dental enamel at specific wavelengths results in chemical changes in the mineral phase that reduce the progression of sub- surface caries-like lesions. The inhibition of lesion progression has been correlated to the decomposition of carbonate in the irradiated enamel mineral. The present study investigated loss of the carbonate component as a function of depth with 1 micrometers resolution by measuring the strength of the spectrum in the region of the carbonate absorption bands near 1400 cm-1. Bovine enamel samples were laser treated at (lambda) equals 9.6 micrometers with a pulse duration of either 2 microsecond(s) or 100 microsecond(s) . The depth of treatment was compared with numerical simulation of the temperature rise in enamel due to laser heating. The temperature rise needed to initiate carbonate loss was 400 degrees C, but complete carbonate loss did not occur until surface temperatures were reached which exceeded the melting temperature. The depth of the treatment varied depending upon the absorption coefficient, pulse duration, and fluence of the laser irradiation.

Zuerlein, Michael J.; Fried, Daniel; Featherstone, John D.

1999-05-01

356

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

357

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

358

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

359

Pulsed laser deposition of chromium oxides thin films: chemical stabilizations by capping and doping  

NASA Astrophysics Data System (ADS)

The half-metallic ferromagnetic chromium dioxide (Tc = 390 K) is a prospective material for spintronics applications. We employed pulsed laser deposition (PLD) to grow thin films of various chromium oxides. The experiments have been carried out in oxygen at different dynamical pressures, using a KrF* laser source (? = 248 nm, ?FWHM >= 30 ns), various chromium oxide targets, such as CrO3, Cr8O21 (the latter ones both pure and doped with Y and Sb respectively, for stabilization purposes) and sapphire substrates (c-cut). We optimized the laser fluence. To avoid CrO2 reduction to Cr2O3 in very thin films when kept in atmospheric air, we applied a protection with gold. X-ray diffraction, electron microscopy and Raman spectroscopy evidence uniform films containing CrO2.

Stanoi, Carmen-Daniela; Socol, Gabriel; Ristoscu, Carmen; Axente, Emanuel; Caiteanu, D.; Mihailescu, Ion N.; Grigorescu, Cristiana E.; Bastide, Beatrice; Monnereau, Odile; Tortet, Laurence; Zhang, T.

2004-10-01

360

Molecular dispersion spectroscopy for chemical sensing using chirped mid-infrared quantum cascade laser.  

PubMed

A spectroscopic method of molecular detection based on dispersion measurements using a frequency-chirped laser source is presented. An infrared quantum cascade laser emitting around 1912 cm(-1) is used as a tunable spectroscopic source to measure dispersion that occurs in the vicinity of molecular ro-vibrational transitions. The sample under study is a mixture of nitric oxide in dry nitrogen. Two experimental configurations based on a coherent detection scheme are investigated and discussed. The theoretical models, which describe the observed spectral signals, are developed and verified experimentally. The method is particularly relevant to optical sensing based on mid-infrared quantum cascade lasers as the high chirp rates available with those sources can significantly enhance the magnitude of the measured dispersion signals. The method relies on heterodyne beatnote frequency measurements and shows high immunity to variations in the optical power received by the photodetector. PMID:21164961

Wysocki, Gerard; Weidmann, Damien

2010-12-01

361

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

NASA Astrophysics Data System (ADS)

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

Lang, Norbert; Hempel, Frank; Strämke, Siegfried; Röpcke, Jürgen

2011-08-01

362

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

363

Identification and quantification of selected chemicals in laser pyrolysis products of mammalian tissues  

NASA Astrophysics Data System (ADS)

Liver and muscle tissue have been irradiated with a surgical CO2-laser. The prefiltered fumes were adsorbed on different sorbents (activated charcoal type NIOSH and Carbotrap) and desorbed with different solvents (carbondisulphide and acetone). Analysis was done by gas chromatography/mass spectrometry. An updated list of identified substances is shown. Typical Maillard reaction products as found in warmed over flavour as aldehydes, aromatics, heterocyclic and sulphur compounds were detected. Quantification of some toxicological relevant substances is presented. The amounts of these substances are given in relation to the laser parameters and different tissues for further toxicological assessment.

Spleiss, Martin; Weber, Lothar; Meier, Thomas H.; Treffler, Bernd

1995-01-01

364

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

NASA Astrophysics Data System (ADS)

CeO 2 films were prepared on LaMnO 3/MgO/Gd 2Zr 2O 7 multi-coated Hastelloy C276 tapes by laser chemical vapor deposition at different laser power ( PL) from 46 to 101 W. Epitaxial (1 0 0) CeO 2 films were prepared at PL = 46-93 W (deposition temperature, Tdep = 705-792 K). Epitaxial CeO 2 films had rectangular-shaped grains at PL = 46-77 W ( Tdep = 705-754 K), while square-shaped grains were obtained at PL = 85-93 W ( Tdep = 769-792 K). CeO 2 films showed a columnar microstructure. Epitaxial (1 0 0) CeO 2 films with rectangular grains exhibited full width at half maximum of ?-scan on (2 0 0) reflection and ?-scan on (2 2 0) reflection of 3.4-3.2° and 6.0-7.2°, respectively. The deposition rate of the epitaxial (1 0 0) CeO 2 films had a maximum of 4.6 ?m h -1 at PL = 77 W ( Tdep = 754 K).

Zhao, Pei; Ito, Akihiko; Tu, Rong; Goto, Takashi

2010-08-01

365

Optically pumped laser oscillation at about 2.9 microns of a HgCdTe layer grown by metalorganic chemical vapor deposition  

Microsoft Academic Search

Photopumped pulsed stimulated emission at 2.9 microns in an HgCdTe layer grown by metalorganic chemical vapor deposition on a CdTe substrate was studied as a function of temperature. The threshold power of the HgCdTe laser (photoexcited by a GaAs diode laser) increased from 0.04 W at 12 K to 1.58 W at 150 K. Above 50 K, the temperature dependence

A. Ravid; A. Zussman; G. Cinader; A. Oron

1989-01-01

366

Hexagonal Truncated Pyramidal Light Emitting Diodes through Wafer Bonding of ZnO to GaN, Laser Lift-off, and Photo Chemical Etching  

Microsoft Academic Search

We report on a hexagonal pyramidal light emitting diodes (LEDs) produced by direct wafer bonding of a metal organic chemical vapor deposition (MOCVD) grown GaN LED on sapphire to a n-type ZnO wafer, laser lift off, and photochemical etching of the nitrogen face of the GaN LED. Laser lift off was used to remove the sapphire of the GaN wafer,

Daniel B. Thompson; Akihiko Murai; Michael Iza; Stuart Brinkley; Steven P. DenBaars; Umesh K. Mishra; Shuji Nakamura

2008-01-01

367

Structural and chemical characterization of free-standing GaN films separated from sapphire substrates by laser lift-off  

Microsoft Academic Search

Laser lift-off of GaN heteroepitaxial layers from sapphire substrates is a promising method for electronic device integration and GaN substrate creation. Of critical importance is the structural and chemical quality of the GaN layers following laser processing. In this letter, transmission electron microscopy techniques are used to characterize the modifications that occur at the resulting GaN surfaces. Structural alteration and

E. A. Stach; M. Kelsch; E. C. Nelson; W. S. Wong; T. Sands; N. W. Cheung

2000-01-01

368

Laser temperature-jump spectrophotometer using stimulated Raman effect in H2 gas for the study of nanosecond fast chemical relaxation times  

Microsoft Academic Search

A laser temperature-jump spectrophotometer for the study of chemical relaxation times with a heating time of about 18 nsec is described. The stimulated Raman effect in hydrogen gas at 80-atm pressure produces a frequency shift of a neodymium-glass laser from 1.06 to 1.89 ?, at which the absorbance of water is very high. The use of H2 as a Raman

Syed Ameen

1975-01-01

369

Observation of chemical shifts of Si 2p level by an x-ray photoelectron spectroscopy system with a laser-plasma x-ray source  

Microsoft Academic Search

An x-ray photoelectron spectroscopy system with a laser-plasma x-ray source is shown to have energy resolution high enough to observe chemical shifts of Si 2p electrons in SiO2, Si3N4, and pure Si. A boron nitride (BN) plasma x-ray source is produced by irradiation of 100 mJ Q-switched YAG laser pulses. A single line emission at 4.86 nm is selected from

Hiroyuki Kondo; Toshihisa Tomie; Hideaki Shimizu

1998-01-01

370

Effect of deposition temperature on chemical composition and electronic properties of amorphous carbon nitride ( a-CNx) thin films grown by plasma assisted pulsed laser deposition  

Microsoft Academic Search

The effect of deposition temperature and nitrogen inclusion in amorphous carbon (a-C) films, deposited by plasma enhanced pulsed laser deposition, on chemical composition and electronic transport has been studied. a-CNx films were deposited on Si (100) by pulsed ArF laser ablation of a graphite target, under N2 atmosphere. A radiofrequency (13.56MHz RF) apparatus was used to generate plasma of excited

E. Cappelli; D. M. Trucchi; S. Kaciulis; S. Orlando; A. Zanza; A. Mezzi

2011-01-01

371

Vibrational Energy Transfer in HF/DF - CO2 Chemical Laser Systems.  

National Technical Information Service (NTIS)

The experimental method of laser induced vibrational fluorescence has been used to measure the overall rate, k(12), with which the (001) vibrational energy level of CO2 in the lowest electronic state is deactivated through collisions with DF and HF in the...

R. A. McFarlane G. J. Wolga

1971-01-01

372

Reliability of AlGaAs\\/GaAs laser diodes grown by metalorganic chemical vapor deposition  

Microsoft Academic Search

The results from an extensive life test of wide stripe laser diodes operating in the 808 nm wavelength region and at a heatsink temperature of -20 C are reported. Devices were mounted p-side down on BeO heatsinks with indium solder. Stringent screening and burn-in criteria were applied to the device population prior to selection for long term test.

D. Dreisewerd; W. Fritz; D. Begley; S. Schwedt; G. Elliott

1988-01-01

373

Reliability of AlGaAs/GaAs laser diodes grown by metalorganic chemical vapor deposition  

NASA Astrophysics Data System (ADS)

The results from an extensive life test of wide stripe laser diodes operating in the 808 nm wavelength region and at a heatsink temperature of -20 C are reported. Devices were mounted p-side down on BeO heatsinks with indium solder. Stringent screening and burn-in criteria were applied to the device population prior to selection for long term test.

Dreisewerd, D.; Fritz, W.; Begley, D.; Schwedt, S.; Elliott, G.

1988-01-01

374

Highly uniform and reproducible vertical-cavity surface emitting lasers grown by metalorganic chemical vapor deposition  

SciTech Connect

We show that the uniformity of the lasing wavelength of vertical-cavity surface emitting lasers (VCSELs) can be as good as {plus_minus}0.3% across a entire 3 in. wafer in MOCVD growth with a similar run-to-run reproducibility.

Hou, H.Q.; Chui, H.C.; Choquette, K.D.; Hammons, B.E.; Breiland, W.G.; Geib, K.M.

1996-01-01

375

Laser-induced breakdown spectroscopy (LIBS): a promising versatile chemical sensor technology for hazardous material detection  

Microsoft Academic Search

A series of laboratory experiments have been performed highlighting the potential of laser-induced breakdown spectroscopy (LIBS) as a versatile sensor for the detection of terrorist threats. LIBS has multiple attributes that provide the promise of unprecedented performance for hazardous material detection and identification. These include: 1) real-time analysis, 2) high sensitivity, 3) no sample preparation, and 4) the ability to

Frank C. DeLucia; Alan C. Samuels; Russell S. Harmon; Roy A. Walters; Kevin L. McNesby; Aaron LaPointe; Andrzej W. Miziolek

2005-01-01

376

Relationship between the chemical and morphological characteristics of human dentin after Er:YAG laser irradiation.  

PubMed

The effects of laser etching on dentin are studied by microenergy-dispersive x-ray fluorescence spectrometry (?-EDXRF) and scanning electron microscopy (SEM) to establish the correlation of data obtained. Fifteen human third molars are prepared, baseline ?-EDXRF mappings are performed, and ten specimens are selected. Each specimen received four treatments: acid etching (control-CG) or erbium:yttrium-aluminum-garnet (Er:YAG) laser irradiation (I-100 mJ, II-160 mJ, and III-220 mJ), and maps are done again. The Ca and P content are significantly reduced after acid etching (p<0.0001) and increased after laser irradiation with 220 mJ (Ca: p<0.0153 and P: p=0.0005). The Ca/P ratio increased and decreased after CG (p=0.0052) and GI (p=0.0003) treatments, respectively. CG treatment resulted in lower inorganic content (GI: p<0.05, GII: p<0.01, and GIII: p<0.01) and higher Ca/P ratios than laser etching (GI: p<0.001, GII: p<0.01, and GIII: p<0.01). The SEM photomicrographies revealed open (CG) and partially open dentin tubules (GI, GII, and GIII). ?-EDXRF mappings illustrated that acid etching created homogeneous distribution of inorganic content over dentin. Er:YAG laser etching (220 mJ) produced irregular elemental distribution and changed the stoichiometric proportions of hydroxyapatite, as showed by an increase of mineral content. Decreases and increases of mineral content in the ?-EDXRF images are correlated to holes and mounds, respectively, as found in SEM images. PMID:23797898

Soares, Luís Eduardo Silva; Martin, Ovídio César Lavesa; Moriyama, Lilian Tan; Kurachi, Cristina; Martin, Airton Abrahão

2013-01-01

377

Long-wavelength InGaAsP\\/InP multiquantum well distributed feedback and distributed Bragg reflector lasers grown by chemical beam epitaxy  

Microsoft Academic Search

We demonstrated the successful operation of long-wavelength InGaAsP low threshold-current index-coupled and gain-coupled DFB lasers grown by chemical beam epitaxy (CBE). For index-coupled DFB lasers, buried-heterostructure six-QW DFB lasers (250 ?m long and as-cleaved) operated at 1.55 ?m with CW threshold currents 10-15 mA and slope efficiencies up to 0.35 mW\\/mA (both facets). A side-mode suppression ratio (SMSR) as high

W. T. Tsang; M. C. Wu; Y. K. Chen; F. S. Choa; R. A. Logan; S. N. G. Chu; A. M. Sergent; P. Magill; K. C. Reichmann; C. A. Burrus

1994-01-01

378

Modification of Electronic and Chemical Structure at Metal/CdTe Interfaces by Pulsed Laser Annealing,  

National Technical Information Service (NTIS)

We have measured the effects of metallization and thermal processing on the chemical interaction, band bending, and deep level formation at Gold and Indium-Cadmium Telluride interfaces using soft x-ray photoemission, photoluminescence, cathodoluminescence...

J. L. Shaw R. E. Viturro L. J. Brillson D. Kilday G. Margaritondo

1988-01-01

379

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

380

Chemical composition and growing kinetics of titanium nitrided layers under CO2 laser irradiation  

NASA Astrophysics Data System (ADS)

The growth and morphology of nitrided layers formed during the solid phase nitriding of pure titanium by CO2 laser were investigated. In the case of a laser treatment carried out under isothermal conditions, it was shown that CO2 photons irradiation of the substrate does not produce any specific assisted nitride growth: nitriding kinetics, nitride composition and structure were similar to those obtained after nitriding using a classical heating system. From the nitriding kinetics, nitrogen diffusion coefficients were determined using an analytical solution of Fick's equation. This allows to plot the evolution of the nitrogen concentration with respect to depth and to compare calculated profiles to those determined experimentally by Nuclear Reaction Microanalysis.

Laurens, Patricia; L'Enfant, Herve; Dubois, Thierry; Saint Catherine, Marie C.

1997-08-01

381

Light emission from tungsten nanoparticles during laser-assisted chemical vapor deposition of tungsten  

NASA Astrophysics Data System (ADS)

Recently we reported that phosphorescent light emission was observed upon irradiation of WF6/H2/noble gas (Ar, Kr, Ne, Xe) mixtures by ArF excimer laser [P. Heszler, P. Mogyorósi, and J.-O. Carlsson, J. Appl. Phys. 78, 5277 1995], originating from tungsten nanoparticles. In this work results of additional measurements on the same system are presented, and we conclude that the reported phosphorescence is a blackbody-like radiation. Taking into account the emissivity of the particles calculated on the base of the Mie theory, it was possible to determine the dependence of the temperature of the tungsten nanoparticles on time after the laser pulse by means of time-resolved spectroscopy. It is shown that surface reactions on the hot nanoparticles contribute significantly to the growth. The size distribution was found lognormal by transmission electron microscopy measurements.

Heszler, P.; Landström, L.; Lindstam, M.; Carlsson, J. O.

2001-04-01

382

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

383

Low-threshold quantum well lasers grown by metalorganic chemical vapor deposition on nonplanar substrates  

Microsoft Academic Search

Low-threshold quantum-well lasers having as-grown optical and electronic confinement fabricated by a single-step growth on nonplanar substrates are discussed. Several devices using various approaches for delineating narrow active regions by this technique are described. Fully planar index-guided arrays grown over a nonplanar substrate exhibit a threshold current of 8 mA per element. A technology called temperature engineered growth, which permits

Kenneth M. Dzurko; Eric P. Menu; Christopher A. Beyler; Julian S. Osinski; P. Daniel Dapkus

1989-01-01

384

Laser based in-situ and standoff detection of chemical warfare agents and explosives  

NASA Astrophysics Data System (ADS)

Laser based detection of gaseous, liquid and solid residues and trace amounts has been developed ever since lasers were invented. However, the lack of availability of reasonably high power tunable lasers in the spectral regions where the relevant targets can be interrogated as well as appropriate techniques for high sensitivity, high selectivity detection has hampered the practical exploitation of techniques for the detection of targets important for homeland security and defense applications. Furthermore, emphasis has been on selectivity without particular attention being paid to the impact of interfering species on the quality of detection. Having high sensitivity is necessary but not a sufficient condition. High sensitivity assures a high probability of detection of the target species. However, it is only recently that the sensor community has come to recognize that any measure of probability of detection must be associated with a probability of false alarm, if it is to have any value as a measure of performance. This is especially true when one attempts to compare performance characteristics of different sensors based on different physical principles. In this paper, I will provide a methodology for characterizing the performance of sensors utilizing optical absorption measurement techniques. However, the underlying principles are equally application to all other sensors. While most of the current progress in high sensitivity, high selectivity detection of CWAs, TICs and explosives involve identifying and quantifying the target species in-situ, there is an urgent need for standoff detection of explosives from safe distances. I will describe our results on CO2 and quantum cascade laser (QCL) based photoacoustic sensors for the detection of CWAs, TICs and explosives as well the very new results on stand-off detection of explosives at distances up to 150 meters. The latter results are critically important for assuring safety of military personnel in battlefield environment, especially from improvised explosive devices (IEDs), and of civilian personnel from terrorist attacks in metropolitan areas.

Patel, C. Kumar N.

2009-09-01

385

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

386

Analysis of lasing in COILs with positive and negative branch unstable resonators using a simple geometrical-optics model  

NASA Astrophysics Data System (ADS)

A simple geometrical optics model is developed, describing the power extraction in chemical oxygen-iodine lasers with unstable resonators. The positive and negative branch unstable resonators with cylindrical mirrors that were recently used in the COIL are studied. The optical extraction efficiency and intensity spatial distributions in the flow direction for both kinds of resonators are calculated.

Barmashenko, Boris D.

2008-10-01

387

Roughening Hexagonal Surface Morphology on Laser Lift-Off (LLO) N-Face GaN with Simple Photo-Enhanced Chemical Wet Etching  

Microsoft Academic Search

A photo-enhanced chemical wet etching technique is presented to form a roughened surface morphology with hexagonal symmetry on laser lift-off (LLO) N-face GaN grown by metalorganic chemical vapor deposition (MOCVD). An aqueous solution of KOH was used as etch electrolyte. The etched surface showed cones with hexagonal pyramid structures bound by \\\\{10\\\\bar{1}\\\\bar{1}\\\\} facets. A detailed analysis of the etch rates

Yan Gao; Tetsuo Fujii; Rajat Sharma; Kenji Fujito; Steven P. Denbaars; Shuji Nakamura; Evelyn L. Hu

2004-01-01

388

A thermo-chemical model of liquid iron oxidation during plasma arc or laser cutting  

NASA Astrophysics Data System (ADS)

It is suggested that if liquid iron is in contact with an atmosphere of gaseous oxygen, the chemical reaction of oxidation inside the liquid metal is of a homogeneous type, as opposed to the heterogeneous reaction of oxidation which takes place in a solid metal. A system of equations describing the inter-related chemical and heat processes is formulated and solved numerically. The obtained solution demonstrated the existence of a relatively narrow reaction zone that moves inwards through the metal. It was shown that the temperature in the reaction zone could be rather high as a result of the following sequence of events: a chemical reaction heats the metal, which boosts the oxygen diffusion and the oxygen supply to the reaction zone, which in turn increases the rate of oxidation. Thermal conductivity and depletion of the reagents stop this explosive-like process. Calculations showed that after some initial period, the reaction zone motion follows the parabolic law.

Nemchinsky, Valerian

2012-11-01

389

Electrical conductivity of BaTi4O9 film prepared by laser chemical vapor deposition method  

NASA Astrophysics Data System (ADS)

A BaTi4O9 film was prepared on a Pt/Ti/SiO2/Si substrate by a laser chemical vapor deposition method and was investigated by impedance spectroscopy over ranges of temperature (300-1073 K) and frequency (102-107 Hz). Plots between real and imaginary parts of the impedance ( Z' and Z'') suggest the presence of two relaxation regimes, which were attributed to grain and grain boundary responses. The conduction of both grains and grain boundaries obeys the Arrhenius format with activation energies of respectively 1.45 and 1.24 eV. The close activation energies indicate that the conduction in BaTi4O9 film is mainly by oxygen vacancies.

Guo, Dongyun; Goto, Takashi; Wang, Chuanbin; Shen, Qiang; Zhang, Lianmeng

2012-06-01

390

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

391

Effects of imiquimod and low-intensity laser (?660 nm) in chemically induced oral carcinomas in hamster buccal pouch mucosa.  

PubMed

Squamous cell carcinoma (SCC) is the most common neoplasm of the oral cavity. It is aggressive, highly proliferative, and metastatic. This study aimed to evaluate the effect of LLLT and imiquimod on DMBA chemically induced lesions on the oral mucosa of hamsters. SCCs were induced on 25 hamsters. Animals of G1 (control 1) were killed and the presence of tumors confirmed; G2 (control 2) suffered no interventions for additional 4 weeks; animals of G3 (laser treatment) were irradiated (?660 nm, 50 mW, CW, Ø=3 mm, 0.07 cm(2), 714.2 mW/cm(2), 133 s, 95 J/cm(2), 6.65 J) at every other day for 4 weeks; animals of G4 (imiquimod treatment) received 5 % imiquimod three times a week for 4 weeks; and animals of G5 (imiquimod and laser treatment) received both treatments for the same period. Samples were taken and underwent histological analysis by light microscopy and were investigated using immunohistochemistry for S-100(+) dendritic cells. In G1, G2, and G3, the evaluations showed malignant tumors and the absence of S-100(+) dendritic cells in the tumor stroma. In G4, 60 % of the animals had no malignant tumors, and S-100(+) dendritic cells were present in the stroma of the tumors as well as dysplasia. In G5, 40 % of the animals presented SCC, with scarce or no S-100(+) dendritic cells. The imiquimod treatment played a direct effect on SCC, demonstrated by the increased number of S-100(+) dendritic cells, which could suggest an important role of immune surveillance against neoplastic proliferation. Furthermore, its association with laser needs to be further investigated. PMID:22941426

de C Monteiro, Juliana S; de Oliveira, Susana C P S; Reis Júnior, João Alves; Gurgel, Clarissa Araújo Silva; de Souza, Suzana C O Machado; Pinheiro, Antônio Luiz Barbosa; dos Santos, Jean Nunes

2013-05-01

392

Recovery of a chemical vapor deposited diamond detection system from strong pulses of laser produced x rays  

SciTech Connect

We are planning an experiment that will study the response of a chemical vapor deposited (CVD) diamond detector to a strong x-ray pulse followed by a second weaker pulse arriving 50-300 ns later, with a contrast in amplitude of about 1000. These tests will be performed at the LLNL Jupiter laser facility and are intended to produce charge carrier densities similar to those expected during a DT implosion at the National Ignition Facility, where a large 14.1 MeV neutron pulse is followed by a weak downscattered neutron signal produced by slower 6-10 MeV neutrons. The areal density {rho}R is proportional to the number of downscattered neutrons. The challenge of measuring {rho}R resides consequently in the effects of the first strong pulse on the weaker later pulse, which may include the saturation of the diamond wafer, saturation of the oscilloscope, or saturation of the associated power and data acquisition electronics. We are presenting the preparation of a double pulse experiment that will use a system of three polycrystalline CVD diamond detectors irradiated by 8.6 keV x rays produced by two laser beams incident on a zinc target.

Dauffy, L. S.; Koch, J. A.; Izumi, N.; Tommasini, R. [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94551 (United States)

2006-10-15

393

Mid-IR quantum cascade lasers as an enabling technology for a new generation of chemical analyzers for liquids  

NASA Astrophysics Data System (ADS)

This presentation introduces a chemical analyzer (The ERACHECK) which is based on quantum cascade laser technology for measuring oil-in-water. Using these mid-IR lasers, it was possible to develop a portable, robust and highly precise analyzer for the measurement of oil-in-water, a parameter which is vital in the petrochemical industry for process control and environmental analysis. The overall method employs a liquid-liquid extraction step of the aqueous sample using a cyclic, aliphatic hydrocarbon such as cyclohexane. Quantification is based on measurement of the C-H deformation vibrations of the extracted hydrocarbons in the cyclic extraction solvent. The developed method is linear from 0.5 - 2000 ppm of oil in water, with precisions well below 15% in terms of r.s.d for repeated measurements. The portability of the ERACHECK and its robustness has been key for its successful use on oil rigs as well as petrochemical production sites on land. The values provided by the ERACHECK correlate well with those obtained by the former CFC (Freon 113) based method for oil in water, which is no longer in use in industrialized countries due to the ozone depleting effect of the CFCs employed.

Lendl, B.; Reidl-Leuthner, C.; Ritter, W.

2011-01-01

394

Hexagonal GaN 1- xP x growth by laser-assisted metalorganic chemical vapor deposition  

NASA Astrophysics Data System (ADS)

The growth of nitride-rich GaN 1- xP x using laser-assisted metalorganic chemical vapor deposition (LA-MOCVD) in order to obtain N-rich GaN 1- xP x with a larger composition ratio ( x) was tried for the first time. An ArF (193 nm) laser was used for the low temperature decomposition of source gases. Trimethylgallium (TMG), ammonia (NH 3) and tertialbutylphosphine (TBP) were used as source gases. As a result, N-rich GaN 1- xP x was grown at 800-950°C. A higher growth rate of 30 ?m/h was obtained by this method. Using a secondary ion mass spectrometry (SIMS), we confirmed that the P incorporation was about 9% into GaN 1- xP x. This composition ( x) was higher than that using a conventional MOCVD. Furthermore, the photoluminescence (PL) spectra of GaN 1- xP x was measured. It was observed that the peak shift of the GaN 1- xP x band-edge emission was over 100 meV compared with that of GaN. This larger peak shift at the band-edge emission was obtained by applying thermal annealing after growth.

Kikawa, Junjiroh; Yoshida, Seikoh; Itoh, Yoshiteru

2001-07-01

395

A comparative study of CW HF chemical laser Fabry-Perot and stable resonator performance  

NASA Astrophysics Data System (ADS)

In the present experimental determination of CW HF laser performance as a function of SF6 and H2 reactant flow rates at low and high pressure, for Fabry-Perot (F-P) and stable resonators in vacuum and external mirror mounts, F-P power was less than the corresponding stable resonator power; in addition, beam diameters were 50-100 percent larger than the corresponding stable resonator beam diameters. The separate baselining of the F-P and stable resonator models undertaken is noted to account for several aspects of the resonator modes which are not included in either the F-P or stable resonator models.

Sentman, L. H.; Tsioulos, G.; Bichanich, J.; Carroll, D.; Theodoropoulos, P.

396

Solution-based synthesis of crystalline silicon from liquid silane through laser and chemical annealing.  

PubMed

We report a solution process for the synthesis of crystalline silicon from the liquid silane precursor cyclohexasilane (Si(6)H(12)). Polysilane films were crystallized through thermal and laser annealing, with plasma hydrogenation at atmospheric pressure generating further structural changes in the films. The evolution from amorphous to microcrystalline is characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy and impedance spectroscopy. A four-decade enhancement in the electrical conductivity is attributed to a disorder-order transition in a bonded Si network. Our results demonstrate a potentially attractive approach that employs a solution process coupled with ambient postprocessing to produce crystalline silicon thin films. PMID:22545711

Iyer, Ganjigunte R S; Hobbie, Erik K; Guruvenket, Srinivasan; Hoey, Justin M; Anderson, Kenneth J; Lovaasen, John; Gette, Cody; Schulz, Douglas L; Swenson, Orven F; Elangovan, Arumugasamy; Boudjouk, P

2012-05-01

397

Quenching of NF singlet states in a hybrid chemical-laser system  

NASA Astrophysics Data System (ADS)

Quenching of NF (a1 Delta) and NF (b1 Sigma) was studied in a subscale upconversion gain medium that was based on energy transfer from NF (b1 Sigma) to IF. Quenching of NF (b1 Sigma) by IF was also found to occur at gas-kinetic rates that were large compared to the energy-transfer rate, indicating low efficiency for the laser. Significant quenching of NF (b Sigma) by IF was also found to occur at a slower rate than was evident for the NF (b1 Sigma) state.

Benard, D. J.; Chowdhury, M. A.; Pritt, A. T.

1986-12-01

398

Chemically driven visible laser amplifiers and oscillators based on fast intermolecular electronic energy transfer  

Microsoft Academic Search

Near-resonant intermolecular energy transfer from selectively formed metastable states of SiO and GeO is used to form continuous sodium and potassium based laser amplifiers. These materials are brought into contact with the appropriate atomic receptors to energy transfer pump X 2S1\\/2 Na atoms (SiO) to excited 4d2D and 5s2S states and 2S1\\/2 K atoms (GeO) to the excited 5d2D state.

J. L. Gole; K. K. Shen; H. Wang; C. B. Winstead; J. Stephens

1993-01-01

399

Surface morphology studies of laser irradiated and chemically metalized polyamide composites  

Microsoft Academic Search

Most of polymers need surface treatment prior to be electroless metalized. Conventionally, polymer substrates are cleaned with solvents to remove surface contaminants, then chemically etched to obtain a micro-roughened oxidized surface, and finally seeded with a catalyst such as palladium. In this work, the method consisting in compositional and physical modifications of polyamide (PA6) was applied. Granulated PA6 was mechanically

Piotr Rytlewski; Marian ?enkiewicz; Adam Tracz; Krzysztof Moraczewski; Waldemar Mróz

2011-01-01

400

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

401

Small-Signal-Gain and Time-Resolved Spectroscopy of the D2-F2/CO2 Pulsed Chemical Transfer Laser System.  

National Technical Information Service (NTIS)

The authors report measurements of the small-signal-gain and time-resolved spectral output of a flash-initiated D2-F2/CO2 chemical transfer laser system. Small-signal-gain measurements indicate a possible lack of rotational equilibration among the rotatio...

S. N. Suchard

1974-01-01

402

Selective reactivity, ultrafast energy transfer and the development of chemically pumped visible lasers. Final report, 1 August 1989-30 September 1992  

Microsoft Academic Search

Two successful approaches to the formation of electronically inverted atomic diatomic configurations based on (1) highly efficient near resonant intermolecular energy transfer and (2) highly efficient and selective fast direct chemical reaction are outlined. Near resonant energy transfer pumping from selectively formed metastable states of SiO and GeO is used to form thallium, gallium, sodium, and potassium atom laser amplifiers

Gole

1992-01-01

403

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

404

Pulsed chemical laser technology-development test plan: single-pulse diagnostic testing  

SciTech Connect

Single-pulse DF and DF/CO/sub 2/ transfer laser testing will be conducted to expand the data base for verification and extension of performance scaling relations. Scaling relations are currently based on the analytical effort completion under Task I and the comparison of this analysis with the available data. Tests will explore the effects on performance of gas composition with constituents including F/sub 2/, D/sub 2/, O/sub 2/, HF, NF/sub 2/, He, N/sub 2/, and CO/sub 2/ at both DF and CO/sub 2/ wavelengths. Tests will explore the nature of the medium in terms of F-atom initiation level and gain, the nature of the initiating electron-beam source in terms of energy deposition level and uniformity and pulse length, and laser yield in terms of total energy, pulse shape, and time resolved spectra. The system will operate at pressures ranging from 200 to 760 torr.

Moran, J.P.

1986-04-15

405

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

406

Computation of streamwise vorticity in a compressible flow of a winglet nozzle-based COIL device  

Microsoft Academic Search

Chemical oxygen iodine laser (COIL) is a high-power laser with potential applications in both military as well as in the industry. COIL is the only chemical laser based on electronic transition with a wavelength of 1.315?m, which falls in the near-infrared (IR) range. Thus, COIL beam can also be transported via optical fibers for remote applications such as dismantling of

Gaurav Singhal; A. L. Dawar; P. M. V. Subbarao; M. Endo

2008-01-01

407

Particle generation by laser ablation in support of chemical analysis of high level mixed waste from plutonium production operations. 1998 annual progress report  

SciTech Connect

'The authors goal is to provide fundamental mechanistic studies of laser produced particulate formation in support of the use of Laser Assisted-Inductively Coupled Plasma-Mass Spectroscopy (LA-ICP-MS) to be used for analysis of radioactive/toxic materials. The work reported here represents the first nine months of this 3-year project. The major focus of these studies is determining the detailed mechanisms and character of the particulates generated by laser ablation of solid targets relevant to sampling materials for chemical analysis using inductively coupled mass spectroscopy, ICP-MS. In this application, particles generated by laser ablation must be transported to the plasma torch of the ICP-MS, often through a hollow tube with an interior diameter of a few mm. Proper digestion and ionization of particles in the plasma limits particle sizes to under a micron. Thus the production of submicron particles which truly represent the stoichiometry of the specimen is of critical importance.'

Dickinson, J.T. [Washington State Univ., Pullman, WA (US); Alexander, M.L. [Pacific Northwest National Lab., Richland, WA (US)

1998-06-01

408

Improving the performance of high-laser-damage-threshold, multilayer dielectric pulse-compression gratings through low-temperature chemical cleaning.  

PubMed

A low-temperature chemical cleaning approach has been developed to improve the performance of multilayer dielectric pulse-compressor gratings for use in the OMEGA EP laser system. X-ray photoelectron spectroscopy results guided the selection of targeted cleaning steps to strip specific families of manufacturing residues without damaging the grating's fragile 3D profile. Grating coupons that were cleaned using the optimized method consistently met OMEGA EP requirements on diffraction efficiency and 1054 nm laser-damage resistance at 10 ps. The disappearance of laser-conditioning effects for the highest-damage-threshold samples suggests a transition from a contamination-driven laser-damage mechanism to defect-driven damage for well-cleaned components. PMID:23478773

Howard, Heather P; Aiello, Anthony F; Dressler, Justin G; Edwards, Nicholas R; Kessler, Terrance J; Kozlov, Alexei A; Manwaring, Ian R T; Marshall, Kenneth L; Oliver, James B; Papernov, Semyon; Rigatti, Amy L; Roux, Alycia N; Schmid, Ansgar W; Slaney, Nicholas P; Smith, Christopher C; Taylor, Brittany N; Jacobs, Stephen D

2013-03-10

409

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

410

Design and performance of a sensor system for detection of multiple chemicals using an external cavity quantum cascade laser  

NASA Astrophysics Data System (ADS)

We describe the performance of a sensor system designed for simultaneous detection of multiple chemicals with both broad and narrow absorption features. The sensor system consists of a broadly tunable external cavity quantum cascade laser (ECQCL), multi-pass Herriott cell, and custom low-noise electronics. The ECQCL features a fast wavelength tuning rate of 2265 cm-1/s (15660 nm/s) over the range of 1150-1270 cm-1 (7.87-8.70 ?m), which permits detection of molecules with broad absorption features and dynamic concentrations, while the 0.2 cm-1 spectral resolution of the ECQCL system allows measurement of small molecules with atmospherically broadened absorption lines. High-speed amplitude modulation and low-noise electronics are used to improve the ECQCL performance for direct absorption measurements. We demonstrate simultaneous detection of Freon-134a (1,1,1,2-tetrafluoroethane), ammonia (NH3), and nitrous oxide (N2O) at low-ppb concentrations in field measurements of atmospheric chemical releases from a point source.

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

2010-01-01

411

Exploring the nanoworld with terahertz and infrared laser spectrometers and chemical nanoscopes  

Microsoft Academic Search

Research on biomolecules, proteins, and living cells requires extremely sensitive spectrometers to harvest the response from precious, small quantity samples. Exploring the large biological parameter space of different mutations, concentrations, pH-values and temperatures demands fast data acquisition and high signal-to-noise ratios for satisfying statistics. We developed terahertz and infrared spectrometers to facilitate the study of biological samples. A chemical nanoscope

E. Briindermann

2007-01-01

412

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

413

Chemical imaging of trichome specialized metabolites using contact printing and laser desorption/ionization mass spectrometry.  

PubMed

Cell transfer by contact printing coupled with carbon-substrate-assisted laser desorption/ionization was used to directly profile and image secondary metabolites in trichomes on leaves of the wild tomato Solanum habrochaites. Major specialized metabolites, including acyl sugars, alkaloids, flavonoids, and terpenoid acids, were successfully detected in positive ion mode or negative ion mode, and in some cases in both modes. This simple solvent-free and matrix-free sample preparation for mass spectrometry imaging avoids tedious sample preparation steps, and high-spatial-resolution images were obtained. Metabolite profiles were generated for individual glandular trichomes from a single Solanum habrochaites leaf at a spatial resolution of around 50 ?m. Relative quantitative data from imaging experiments were validated by independent liquid chromatography-mass spectrometry analysis of subsamples from fresh plant material. The spatially resolved metabolite profiles of individual glands provided new information about the complexity of biosynthesis of specialized metabolites at the cellular-resolution scale. In addition, this technique offers a scheme capable of high-throughput profiling of metabolites in trichomes and irregularly shaped tissues and spatially discontinuous cells of a given cell type. PMID:24220760

Li, Chao; Wang, Zhenzhen; Jones, A Daniel

2014-01-01

414

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

415

High-rate deposition of YBa2Cu3O7-? high-temperature superconducting films by IR-laser-assisted chemical vapor deposition  

NASA Astrophysics Data System (ADS)

We applied an infrared- (IR-) laser-assisted chemical vapor deposition technique to YBa2Cu3O7-? (YBCO) film fabrication in order to enhance the deposition rate to one suitable for commercial applications. IR-laser illumination during deposition effectively suppressed outgrowth of a-axis oriented grains, which strongly diminish the film’s current-carrying capacity. As a result, high-performance YBCO films with critical current densities of greater than 1 × 106 A cm-2 were successfully obtained at high deposition rates of up to 58 ?m h-1 (˜1 ?m min-1) by this method.

Miyata, S.; Matsuse, K.; Ibi, A.; Izumi, T.; Shiohara, Y.; Goto, T.

2013-04-01

416

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.

2014-05-01

417

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

SciTech Connect

The patterning of submicron period ({approx_equal}500 nm) 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 213 nm, 150 ps 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 213 nm 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 120 nm and excellent surface quality were fabricated by exposing the IOG1 phosphate glass to 36 000 pulses of 208 mJ/cm{sup 2} energy density, followed by developing in the KOH/EDTA agent for 6 min.

Pappas, C.; Pissadakis, S. [Foundation for Research and Technology-Hellas, Institute of Electronic Structure and Laser, Vasilika Vouton, P.O. Box 1527, Heraklion 71 110 (Greece)

2006-12-01

418

A study of laser-induced blue emission with nanosecond decay of silicon nanoparticles synthesized by a chemical etching method.  

PubMed

Silicon nanoparticles (Si NPs), exhibiting a strong visible photoluminescence (PL), have found many applications in optoelectronics devices, biomedical tags and flash memories. Chemical etching is a well-known method for synthesizing orange-luminescent, hydride-capped silicon nanoparticles (H/Si NPs). However, a blueshift in emission wavelength occurs when reducing the particle size to exciton Bohr radius or less. In this paper, we attempted to synthesize and characterize H/Si NPs that emit lower wavelengths at room temperature. We proved that our method succeeded in synthesizing H/Si NPs with emission in the blue region. The wavelength-resolved and time-resolved studies of the PL were executed for H/Si NPs in methanol (MeOH), pyridine (py) and furan, using the 355 nm pulsed radiation from a Nd:YAG laser. In addition, excitation wavelength-dependent and PL studies were executed using the spectrofluorometer with a xenon (Xe) broad band light source. We noticed solvent-dependent PL spectra with sharp peaks near 420 nm and a short lifetime less than 100 ns. The morphology and particle size were investigated by high resolution transmission electron microscope (HRTEM). Particles as small as one nanometer were observed in MeOH and py suspensions while two-nanometer particles were observed in the furan suspension. PMID:19671981

Bagabas, Abdulaziz A; Gondal, Mohammed A; Dastageer, Mohammed A; Al-Muhanna, Abdulrahman A; Alanazi, Thaar H; Ababtain, Moath A

2009-09-01

419

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

420

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.

421

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

PubMed

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

2012-07-01

422

Growth of normally-immiscible materials (NIMs), binary alloys, and metallic fibers by hyperbaric laser chemical vapor deposition  

NASA Astrophysics Data System (ADS)

This work demonstrates that two or more elements of negligible solubility (and no known phase diagram) can be co-deposited in fiber form by hyperbaric-pressure laser chemical vapor deposition (HP-LCVD). For the first time, Hg-W alloys were grown as fibers from mixtures of tungsten hexafluoride, mercury vapor, and hydrogen. This new class of materials is termed normally-immiscible materials (NIMs), and includes not only immiscible materials, but also those elemental combinations that have liquid states at exclusive temperatures. This work also demonstrates that a wide variety of other binary and ternary alloys, intermetallics, and mixtures can be grown as fibers, e.g. silicon-tungsten, aluminum-silicon, boron-carbon-silicon, and titanium-carbon-nitride. In addition, pure metallic fibers of aluminum, titanium, and tungsten were deposited, demonstrating that materials of high thermal conductivity can indeed be grown in three-dimensions, provided sufficient vapor pressures are employed. A wide variety of fiber properties and microstructures resulted depending on process conditions; for example, single crystals, fine-grained alloys, and glassy metals could be deposited.

Maxwell, J. L.; Black, M. R.; Chavez, C. A.; Maskaly, K. R.; Espinoza, M.; Boman, M.; Landstrom, L.

2008-06-01

423

Impedance Spectroscopy of Dielectric BaTi5O11 Film Prepared by Laser Chemical Vapor Deposition Method  

NASA Astrophysics Data System (ADS)

BaTi5O11 film was prepared on Pt/Ti/SiO2/Si substrate by the laser chemical vapor deposition method. A single-phase BaTi5O11 film with (overline{3} 22)/(overline{2} 23) preferred orientation and columnar cross-section was obtained at high deposition rate (154.8 ?m h-1). The dielectric constant ( ? r) of the BaTi5O11 film was 21, measured at 300 K and 1 MHz. The electrical properties of the BaTi5O11 film were investigated by ac impedance spectroscopy from 300 K to 1073 K at 102 Hz to 107 Hz. Plots of the real and imaginary parts of the impedance ( Z' and Z?) and electrical modulus ( M' and M?) in the above frequency and temperature range suggested the presence of two relaxation regimes, which were attributed to grain and grain boundary responses. The ac conductivity plots as a function of frequency showed three types of conduction process at elevated temperature. The frequency-independent plateau at low frequency was due to dc conductivity. The mid-frequency conductivity was due to grain boundaries, while the high-frequency conductivity was due to grains.

Guo, Dongyun; Goto, Takashi; Wang, Chuanbin; Shen, Qiang; Zhang, Lianmeng

2012-04-01

424

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 (~500 nm) 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 213 nm, 150 ps 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 213 nm 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 120 nm and excellent surface quality were fabricated by exposing the IOG1 phosphate glass to 36 000 pulses of 208 mJ/cm2 energy density, followed by developing in the KOH/EDTA agent for 6 min.

Pappas, C.; Pissadakis, S.

2006-12-01

425

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

SciTech Connect

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 [Green Innovation Research Laboratories, NEC Corporation, 34 Miyukigaoka, Tsukuba 305-8501 (Japan); Zhang Hong [School of Physical Science and Technology, Sichuan University, Chengdu 610065 (China); Rubio, Angel [Nano-Bio Spectroscopy group and ETSF Scientific Development Centre, Department Fisica de Materiales, Universidad del Pais Vasco, Avenida de Tolosa 72, E-20018 San Sebastian (Spain)

2010-12-10

426

First-principles simulations of chemical reactions in an HCl molecule embedded inside a C or BN nanotube induced by ultrafast laser pulses.  

PubMed

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. PMID:21231562

Miyamoto, Yoshiyuki; Zhang, Hong; Rubio, Angel

2010-12-10

427

Laser-induced chemical reactions. [H + H/sub 2/; F + H/sub 2/; H + HF; Cl + H/sub 2/; H + HCl; H + LiF  

SciTech Connect

A classical model for the interaction of laser radiation with a molecular system is derived. This model is used to study the enhancement of a chemical reaction via a collision induced absorption. It was found that an infrared laser will in general enhance the rate of a chemical reaction, even if the reactants are infrared inactive. Results for an illustrative analytically solvable model are presented, as well as results from classical trajectory studies on a number of systems. The collision induced absorption spectrum in these systems can be written as the Fourier transform of a particular dipole correlation function. This is used to obtain the collision induced absorption spectrum for a state-selected, mono-energetic reactive collision system. Examples treated are a one-dimensional barrier problem, reactive and nonreactive collisions of H + H/sub 2/, and a modified H + H/sub 2/ potential energy surface which leads to a collision intermediate. An extension of the classical model to treat laser-induced electronically nonadiabatic collision processes is constructed. The model treats all degrees of freedom, molecular, electronic and radiation, in a dynamically consistent framework within classical mechanics. Application is made to several systems. Several interesting phenomena are discovered including a Franck-Condon-like effect causing maxima in the reaction probability at energies much below the classical threshold, laser de-enhancement of chemical reactions and an isotope effect. In order to assess the validity of the classical model for electronically nonadiabatic process (without a laser field), a model problem involving energy transfer in a collinear atom-diatom system is studied, and the results compared to the available quantum mechanical calculation. The calculations are in qualitative agreement.

Orel, A.E.

1980-12-01

428

Versatile chemical molecule sensing using multi-wavelength fiber laser based on inter-core interference in twin-core photonic crystal fiber  

NASA Astrophysics Data System (ADS)

We propose and experimentally demonstrate a new chemical molecule sensing scheme using multi-wavelength fiber laser based on inter-core interference in twin-core photonic crystal fiber. In our proposed multi-wavelength fiber laser, two separated cores are integrated in a single photonic crystal fiber and surrounded by air channels. The anti-symmetrical super-modes participate in inter-core interference, which leads to the formation of twin-core photonic crystal fiber-based wavelength-selective comb filter. Most of the evanescent waves are localized in the 13 air channels around the two integrated cores, where light-matter interaction takes in place. The presence of chemical molecules in the air channels of TC-PCF leads to perturbation of the inter-core effective index difference between the two propagating core modes and the associated lasing wavelength shift.

Kim, Bongkyun; Naeem, Khurram; Han, Jihee; Chung, Youngjoo

2013-03-01

429

Crystalline SiGe films grown on Si substrates using laser-assisted plasma-enhanced chemical vapor deposition at low temperature  

NASA Astrophysics Data System (ADS)

Compared with conventional plasma-enhanced chemical vapor deposition, laser-assisted plasma-enhanced chemical vapor deposition (LAPECVD) can be used to deposit crystalline SiGe films on Si substrates at low temperature. In the LAPECVD system, a CO2 laser with a wavelength of 10.6 ?m was utilized to assist the pyrolytical decomposition of SiH4 and GeH4 reactant gases. The resultant Si0.78Ge0.22 films were obtained and verified through the use of the Auger electron spectroscopy measurement. As the diffraction pattern of a glancing incident angle X-ray diffraction measurement had indicated, several significant diffraction peaks corresponding to a diamond-cubic structure at (111), (220), and (311) were clearly observed. Crystalline SiGe films were also identified by the electron diffraction pattern of high-resolution transmission electron microscopy images.

Lee, Ching-Ting; Cheng, Jun-Hung; Lee, Hsin-Ying

2007-08-01

430

CO2 laser-based differential absorption lidar system for range-resolved and long-range detection of chemical vapor plumes  

NASA Astrophysics Data System (ADS)

A dual CO2 laser-based differential absorption lidar (DIAL) system has been constructed and demonstrated for range-resolved mapping of chemical vapor plumes. The system acquires high range resolution through the use of plasma-shutter pulse clippers that extinguish the nitrogen tail of the CO2-laser output. A programmable servomotor-driven scanner allows full hemispherical coverage of the interrogated field. A high-speed direct-detection receiver subsystem is used to gather, process, and display vapor-concentration data in near real time. Data demonstrating range-resolved detection of low concentrations of chemical plumes from ranges of 1 to 2 km are presented. In the column-content detection mode, trace levels of secondary vapors from various organophosphate liquids were monitored. Detection of an SF6 vapor plume released 16 km from the DIAL system is also adduced.

Carlisle, Clinton B.; van der Laan, Jan E.; Carr, Lewis W.; Adam, Philippe; Chiaroni, Jean-Pierre

1995-09-01

431

CO(2) laser-based differential absorption lidar system for range-resolved and long-range detection of chemical vapor plumes.  

PubMed

A dual CO(2) laser-based differential absorption lidar (DIAL) system has been constructed and demonstrated for range-resolved mapping of chemical vapor plumes. The system acquires high range resolution through the use of plasma-shutter pulse clippers that extinguish the nitrogen tail of the CO(2)-laser output. Aprogrammable servomotor-driven scanner allows full hemispherical coverage of the interrogated field. A high-speed direct-detection receiver subsystem is used to gather, process, and display vapor-concentration data in near real time. Data demonstrating range-resolved detection of low concentrations of chemical plumes from ranges of 1 to 2 km are presented. In the column-content detection mode, trace levels of secondary vapors from various organophosphate liquids were monitored. Detection of an SF(6) vapor plume released 16 km from the DIAL system is also adduced. PMID:21060462

Carlisle, C B; van der Laan, J E; Carr, L W; Adam, P; Chiaroni, J P

1995-09-20

432

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

433

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

434

Laser-induced metal-organic chemical vapor deposition (MOCVD) of Cu(hfac)(TMVS) on amorphous Teflon AF1600: an XPS study of the interface  

Microsoft Academic Search

Pulsed KrF excimer laser radiation (248 nm) was used to activate copper deposition from Cu(hfac)(TMVS) onto Teflon AF1600. The interface was examined using X-ray photoelectron spectroscopy (XPS) for thicknesses up to several monolayers. We found that Teflon carbons are the only substrate atoms involved in chemical bonding. Cu0 and CuI-hfac were found to be uniformly distributed throughout the deposited film

D. Popovici; G Czeremuzkin; M Meunier; E Sacher

1998-01-01

435

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

436

Intercomparison of peroxy radical measurements at a rural site using laser-induced fluorescence and Peroxy Radical Chemical Ionization Mass Spectrometer (PerCIMS) techniques  

Microsoft Academic Search

Two different instruments were deployed to measure hydroperoxy radical (HO2) and total peroxy radicals during May and June 2002 at a rural site located at Rock Springs near State College, Pennsylvania. One instrument was the Penn State Ground-Based Tropospheric Hydrogen Oxides Sensor (GTHOS), which measured HO2 by laser-induced fluorescence (LIF) of OH following the chemical conversion of HO2 to OH

Xinrong Ren; Gavin D. Edwards; Christopher A. Cantrell; Robert L. Lesher; Andrew R. Metcalf; Terry Shirley; William H. Brune

2003-01-01

437

Spatially-resolved temperature diagnostic for supersonic flow using cross-beam Doppler-limited laser saturation spectroscopy  

NASA Astrophysics Data System (ADS)

Optical techniques for measuring the temperature in three-dimensional supersonic reactive flows have typically depended on lineshape measurements using single-beam laser absorption spectroscopy. However, absorption over extended path lengths in flows with symmetric, turbulent eddies can lead to systematically high extracted temperatures due to Doppler shifts resulting from flow along the absorption path. To eliminate these problems and provide full three-dimensional spatial resolution, two variants of laser saturation spectroscopy have been developed and demonstrated, for the first time, which utilize two crossed and nearly copropogating laser beams. Individual rotational lines in the visible I2 X 1Sigma 0+g ? B 3pi 0+u transition were used to develop the two diagnostic to support research on the Chemical Oxygen-Iodine Laser (COIL), the weapon aboard the USAF Airborne Laser. Cross-Beam Saturation Absorption Spectroscopy (CBSAS) and Cross-Beam Inter-Modulated Fluorescence (CBIMF) were demonstrated as viable methods for recording the spectral signal of an I2 ro-vibrational line in a small three-dimensional volume using a tunable CW dye laser. Temperature is extracted by fitting the recorded signal with a theoretical signal constructed from the Doppler-broadened hyperfine components of the ro-vibrational line. The CBIMF technique proved successful for extracting the temperature of an I2-seeded, Ar gas flow within a small, Mach 2, Laval nozzle where the overlap volume of the two 1 mm diameter laser beams was 2.4 mm 3. At a test point downstream of the nozzle throat, the average temperature of 146 K +/- 1.5 K extracted from measurements of the I2 P(46) 17-1 spectral line compared favorably with the 138 K temperature calculated from isentropic, one-dimensional flow theory. CBIMF provides sufficient accuracy for characterizing the temperature of the gas flow in a COIL device, and could be applied to other areas of flow-field characterization and nozzle design. In contrast, the CBSAS signal was not sufficiently strong for reliable temperature extraction from the 2.4 mm3 overlap volume required in the nozzle experiments. Otherwise, the CBSAS technique could have greater success for application in flow field test environments that allow the use of a larger overlap-volume. CBIMF and CBSAS measurements were also made in a static cell at 293 K. At 50 mTorr of I2, the standard error in temperature from CBIMF measurements of the I2 P(46) 17-1 line was approximately 0.5 K. For CBSAS, the standard error in temperature was approximately 3 K at 50 mTorr of I2. Accuracy improved with increasing I2 pressure. In addition, the spatial-resolution capability of CBIMF and CBSAS was demonstrated in a static cell with an applied temperature gradient ranging from 300 to 365 K. Extracted temperatures were compared to thermocouple measurements at multiple positions in the gradient. Agreement between extracted temperatures and thermocouple measurements was better at the lower temperatures. Doppler-free measurements of several I2 hyperfine spectra were also performed to support development of the theoretical model. Saturation Absorption Spectroscopy was used to obtain Ar pressure broadening rates of 8.29 +/- 0.30 MHz/Torr for the I2 P(70) 17-1 hyperfine spectrum, and 10.70 +/- 0.41 MHz/Torr for the I2 P(10) 17-1 hyperfine spectrum.

Phillips, Grady T.

438

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

439

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

440

Total microcystins analysis in water using laser diode thermal desorption-atmospheric pressure chemical ionization-tandem mass spectrometry.  

PubMed

A new approach for the analysis of the cyanobacterial microcystins (MCs) in environmental water matrices has been developed. It offers a cost efficient alternative method for the fast quantification of total MCs using mass spectrometry. This approach permits the quantification of total MCs concentrations without requiring any derivatization or the use of a suite of MCs standards. The oxidation product 2-methyl-3-methoxy-4-phenylbutyric acid (MMPB) was formed through a Lemieux oxidation and represented the total concentration of free and bound MCs in water samples. MMPB was analyzed using laser diode thermal desorption-atmospheric pressure chemical ionization coupled to tandem mass spectrometry (LDTD-APCI-MS/MS). LDTD is a robust and reliable sample introduction method with ultra-fast analysis time (<15 s sample(-1)). Several oxidation and LDTD parameters were optimized to improve recoveries and signal intensity. MCs oxidation recovery yield was 103%, showing a complete reaction. Internal calibration with standard addition was achieved with the use of 4-phenylbutyric acid (4-PB) as internal standard and showed good linearity (R(2)>0.999). Limits of detection and quantification were 0.2 and 0.9 ?g L(-1), respectively. These values are comparable with the WHO (World Health Organization) guideline of 1 ?g L(-1) for total microcystin-LR congener in drinking water. Accuracy and interday/intraday variation coefficients were below 15%. Matrix effect was determined with a recovery of 91%, showing no significant signal suppression. This work demonstrates the use of the LDTD-APCI-MS/MS interface for the screening, detection and quantification of total MCs in complex environmental matrices. PMID:24745740

Roy-Lachapelle, Audrey; Fayad, Paul B; Sinotte, Marc; Deblois, Christian; Sauvé, Sébastien

2014-04-11

441

Lasers '92; Proceedings of the International Conference on Lasers and Applications, 15th, Houston, TX, Dec. 7-10, 1992  

NASA Technical Reports Server (NTRS)

Papers from the conference are presented, and the topics covered include the following: x-ray lasers, excimer lasers, chemical lasers, high power lasers, blue-green lasers, dye lasers, solid state lasers, semiconductor lasers, gas and discharge lasers, carbon dioxide lasers, ultrafast phenomena, nonlinear optics, quantum optics, dynamic gratings and wave mixing, laser radar, lasers in medicine, optical filters and laser communication, optical techniques and instruments, laser material interaction, and industrial and manufacturing applications.

Wang, Charles P. (editor)

1993-01-01

442

PhotoChemical Synthesis of Iron Oxide Nanowires Induced by Pulsed Laser Ablation of Iron Powder in Liquid Media  

Microsoft Academic Search

Iron oxide nanowires are synthesized by photochemical method through nanosecond pulsed laser ablation of iron powder in liquid media. The synthesis is tried using various wavelengths (248 and 532 nm) of pulsed laser at different liquids (water, ethanol, methanol, isopropanol and glycol). The solution of iron oxide nanowires is obtained only in methanol when the iron powder (size 60 mu

S. Mollah; S. J. Henley; C. E. Giusca; S. R. P. Silva

2010-01-01

443

Chemical Laser Studies.  

National Technical Information Service (NTIS)

Pressure limits of detonations in hydrogen-chlorine and hydrogen-chlorine-40% argon mixtures were established experimentally. At 300 K no mixture of hydrogen, chlorine and argon could be detonated below 16 torr. Replacement of excess hydrogen with argon c...

J. R. Bowen

1975-01-01

444

Femtosecond Laser Etching of GaN and InGaN Thin Films Grown by Metal Organic Chemical Vapor Deposition  

NASA Astrophysics Data System (ADS)

In this work a possibility of selective GaN and InGaN layer etching via femtosecond laser ablation was investigated. The samples of different indium concentrations were grown by metal organic chemical vapor deposition (MOCVD) technique on sapphire substrates. Prior to the laser treatment all samples were characterized by the means of photoluminescence and X-ray diffraction techniques. Further the laser-induced damage thresholds (LIDT) were estimated in multiple pulse (S-on-1) and single pulse (1-on-1) regimes for 1030, 515, and 343 nm wavelengths covering NIR--UV spectral regions. Experimental results indicated a strong interrelation between LIDT, indium concentration and band-gap. An abrupt change in single pulse LIDT is observed when the multi-photon absorption experiences transition from three to two photon absorption. Furthermore an overview of typical laser induced damage morphologies is performed and discussed. A selective smooth etching of GaN and InGaN layers was obtained when exposing with multiple pulses in UV range.

Š?iuka, Mindaugas; Grinys, Tomas; Dmukauskas, Mantas; Plerpait?, Viktorija; Melninkaitis, Andrius

2013-08-01

445

Laser Systems  

NASA Technical Reports Server (NTRS)

Tunable diode lasers are employed as radiation sources in high resolution infrared spectroscopy to determine spectral characteristics of gaseous compounds. With other laser systems, they are produced by Spectra-Physics, and used to monitor chemical processes, monitor production of quantity halogen lamps, etc. The Laser Analytics Division of Spectra-Physics credits the system's reliability to a program funded by Langley in the 1970s. Company no longer U.S.-owned. 5/22/97

1985-01-01

446

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

Microsoft Academic Search

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

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

2005-01-01

447

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

448