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Sample records for photodissociation iodine laser

  1. Solar-pumped photodissociation iodine laser

    NASA Technical Reports Server (NTRS)

    Lee, J. H.; Weaver, W. R.; Humes, D. H.; Williams, M. D.; Lee, M. H.

    1986-01-01

    The scientific feasibility of a solar-pumped iodine photodissociation laser for space applications is under investigation. Recently, a 2-W CW output for more than one hour was achieved using n-C3F7I vapor as the laser material and a vortex-stabilized argon arc as the light source.

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

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

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

  4. Analysis of the effect of anhydride of trifluoroacetanhydride in the working mixture composition on the operation of iodine photodissociation laser

    NASA Astrophysics Data System (ADS)

    Vinogradskii, L. M.; Polozov, A. A.; Khudikov, N. M.

    2015-12-01

    The effect of the (CF3CO)2O (trifluoroacetanhydride) buffer additive on the operation of an iodine photodissociation laser is studied experimentally. Comparative experiments for determining the laser energy of the iodine laser with the replacement of the working substance with this buffer additive and without it and with widely used buffer gas SF6 (sulfur hexafluoride) are carried out. Optical inhomogeneities in the working volume, emerging during pumping of working mixtures based on i-C3F7I (perfluoroalkyl iodide) with buffer additives (CF3CO)2O and C6F14 (perfluorohexane), are measured. The results of experiments are analyzed.

  5. LASERS: Pulse-periodic iodine photodissociation laser with a high output energy

    NASA Astrophysics Data System (ADS)

    Abashev, R. T.; Kamrukov, A. S.; Kozlov, N. P.; Korolenko, V. G.; Ovchinnikov, P. A.; Protasov, Yu S.; Rychkov, M. L.; Telenkov, I. I.

    1991-05-01

    A description is given of a pulse-periodic iodine laser pumped by high-power nonmagnetic plasma-dynamic flashlamps and incorporating a thermal closed circulation system for the active medium (n-C4F9I-C6F14 mixture) based on a condensation-evaporation cycle. An investigation was made of the energy balance and the output characteristics of the laser under single-pulse and pulse-periodic conditions at a repetition frequency of 17-50 mHz. The laser output energy was ~ 0.5 kJ, the pulse duration was 35-40 μs, the angular divergence was ~ 0.56 mrad, and the efficiency in terms of the electrical energy deposited in the pumping system was ~ 1 %. Stimulated emission during the complete laser pulse was achieved at the frequency of the unperturbed F' = 3 →F = 4 electronic transition in the hyperfine structure of the iodine atom.

  6. Picosecond dynamics of reactions in the liquid phase: studies of iodine photodissociation and development of new laser techniques

    SciTech Connect

    Berg, M.A.

    1985-09-01

    Iodine photodissociation and recombination was studied as a model for processes common to chemical reaction in the liquid phase. Picosecond transient absorption measurements from 1000 to 295 nm were used to monitor the dynamics in a variety of solvents. Most of the atoms which undergo geminate recombination were found to do so in less than or equal to 15 ps, in agreement with the results of existing molecular dynamics simulations. Vibrational relaxation times vary from approx.15 ps near the middle of the ground state well to approx.150 ps for complete relaxation to v = 0. The prediction of strong resonant vibrational energy transfer to chlorinated methane solvents was not supported, but some evidence for this mechanism was found for alkane solvents. Current theory is unable to explain the large variation (65 to 2700 ps) of the excited A'-state lifetime in various solvents. The 10-Hz amplified, synchronously-pumped dye laser which was used in these studies is described and characterized. SERS (Stimulated Electronic Raman Scattering) and difference frequency mixing were used in the generation of the infrared and far-infrared, respectively. 54 refs., 38 figs., 3 tabs. (WRF)

  7. Synchronizing single-shot high-energy iodine photodissociation laser PALS and high-repetition-rate femtosecond Ti:sapphire laser system

    NASA Astrophysics Data System (ADS)

    Dostal, J.; Dudzak, R.; Pisarczyk, T.; Pfeifer, M.; Huynh, J.; Chodukowski, T.; Kalinowska, Z.; Krousky, E.; Skala, J.; Hrebicek, J.; Medrik, T.; Golasowski, J.; Juha, L.; Ullschmied, J.

    2017-04-01

    A system of precise pulse synchronization between a single-shot large-scale laser exploiting an acousto-optical modulator and a femtosecond high repetition rate laser is reported in this article. This opto-electronical system has been developed for synchronization of the sub-nanosecond kJ-class iodine photodissociation laser system (Prague Asterix Laser System—PALS) with the femtosecond 25-TW Ti:sapphire (Ti:Sa) laser operating at a repetition rate 1 kHz or 10 Hz depending on the required energy level of output pulses. At 1 kHz synchronization regime, a single femtosecond pulse of duration about 45 fs and a small energy less than 1 mJ are exploited as a probe beam for irradiation of a three-frame interferometer, while at 10 Hz repetition rate a single femtosecond pulse with higher energy about 7-10 mJ is exploited as a probe beam for irradiation of a two-channel polaro-interferometer. The synchronization accuracy ±100 ps between the PALS and the Ti:Sa laser pulses has been achieved in both regimes of synchronization. The femtosecond interferograms of laser-produced plasmas obtained by the three-frame interferometer and the femtosecond polarimetric images obtained by the two-frame polaro-interferometer confirm the full usefulness and correct functionality of the proposed method of synchronization.

  8. Photodissociation Dye Laser

    DTIC Science & Technology

    1975-04-01

    Chemical Properties of Free Radicals 5 C. Criteria for the Selection of Photodissociation Dye Laser Molecules 6 III. EXPERIMENTAL EFFORT AND...nanoseconds. In radicl systems, however, there is evidence both theoretical and experimental, that the first doublet-doublet electronic tra-jitions are...Properties, of Free Radicals Recombination is only one of many possible reaction paths that can occur in a radical system. Because they are characterized

  9. Investigation of the excited state iodine lifetime in the photodissociation of perfluoroalkyl iodides

    NASA Technical Reports Server (NTRS)

    Cobb, Stephen H.

    1991-01-01

    An evaluation of prospective laser materials for a space-based solar pumped laser system over the past decade has resulted in the identification of the iodine photodissociation laser as that system best suited to solar-pumped high energy operation. The active medium for the solar-pumped iodine photodissociation laser is from the family of perfluoroalkyl iodides. These lasants have the general form C(n)F(2n + 1)I, often abbreviated as RI. These iodides are known to exhibit photodissociaiton of the C-I bond when irradiated by near UV photons. The focus was on the experimental determination of the lifetime of the excited iodine atom following photodissociation of C4F9I, and also to monitor fluorescence from the iodine molecule at 500 nm to determine if I2 is being produced in the process. Photodissociation is achieved using an XeCl excimer laser with an output wavelength of 308 nm. The XeCl beam is focused into the middle of a cylindrical quartz cell containing the lasant. The laser pulse is detected with a fast risetime photomultiplier tube as it exits the cell. Other aspects of the investigation are discussed.

  10. Direct solar-pumped iodine laser amplifier

    NASA Technical Reports Server (NTRS)

    Han, K. S.

    1985-01-01

    This semiannual progress report covers the period from April 1, 1985 to Sept. 30, 1985 under NASA grant NAS1-441 entitled direct solar pumped iodine laser amplifier. During this period the parametric studies of the iodine laser oscillator pumped by a Vortek simulator was carried out before the amplifier studies. The amplifier studies are postponed to the extended period following completion of the parametric studies. In addition, the kinetic modeling of a solar pumped iodine laser amplifier, and the experimental work for a solar pumped dye laser amplifier are in progress. This report contains three parts: (1) the radiation characteristics of solar simulator and the parametric characteristics of photodissociation iodine laser continuously pumped by a Vortek solar simulator; (2) kinetic modeling of a solar pumped iodine laser amplifier; and (3) the study of the dye laser amplifier pumped by a Tamarack solar simulator.

  11. Metal dihalide photodissociation cyclic laser

    SciTech Connect

    Celto, J.E.; Schimitschek, E.J.; Trias, J.A.

    1980-10-21

    A pulsed laser produces emitted laser energy by photodissociation of metal dihalide and cyclic recombination. A metal dihalide selected from sub-group ii-b of the periodic table of elements is contained within an elongated sealed enclosure. Ultraviolet photons supplied from another laser employed as an excitation pump causes dissociation of the metal dihalide for achieving the ultimate laser action. An inert buffer gas is included within the enclosure for aiding photon energy transfer uniformity and to provide vibrational relaxation of the lasing medium in its electronic states. Two reflective surfaces, one of which is only partially reflective, are aligned with the principal axis of the laser assembly for producing an optical resonator for the emitted laser energy.

  12. Laser photoluminescence spectroscopy of photodissociation fragments

    NASA Technical Reports Server (NTRS)

    Jackson, W. M.; Cody, R. J.

    1974-01-01

    Laser induced photoluminescence spectroscopy has been used to study the energy partitioning among CN fragments produced by the photodissociation of C2N2. The CN radicals are produced in both the A 2Pi and the X 2Sigma+ states. The A state is formed primarily in the nu-prime = 0 level, and the X state is formed in the lower vibrational levels. Since the photodissociation process does not produce the maximum amount of vibrational excitation in the CN fragments, it is suggested that the excess energy goes into either translational and/or rotational excitation of the CN.

  13. A 10-watt CW photodissociation laser with IODO perfluoro-tert-butane

    NASA Technical Reports Server (NTRS)

    Tabibi, Bagher; Venable, Demetrius D.

    1989-01-01

    NASA has been investigating the feasibility of direct solar-pumped laser systems for power beaming in space. Among the various gas, liquid, and solid laser systems being proposed as candidates for solar-pumped lasers, the iodine photodissociation gas laser has demonstrated its potential for space application. Of immediate attention is the determination of system requirements and the choice of lasants to improve the system efficiency. The development of an efficient iodine laser depends on the availability of a suitable iodide which has favorable laser kinetics, chemically reversibility, and solar energy utilization. Among the various alkyliodide lasants comparatively tested in a long-pulse system, perfluoro- tert-butyl iodide, T-C4F9I, was found to be the best. However, the operating conditions for the laser medium in a continuously pumped and continuous-flow iodine laser differ considerably from those in the pulsed regime. The results of the continuous wave (CW)) laser performance from t-C4F9I are reported. Perfluoro- n-propyl iodide, n-C3F7I is used for comparison because of its universal use in photodissociation iodine lasers.

  14. High power CW iodine laser pumped by solar simulator

    NASA Technical Reports Server (NTRS)

    Lee, Ja H.; Lee, Min H.; Weaver, Willard R.

    1987-01-01

    An iodine photodissociation laser was pumped by a long Ar arc as the solar simulator to produce a 10-W CW output. Continuous lasing for 1 h was achieved with a flow of the laser material n-C3F7I. The 10-W CW output is the highest produced to date and establishes the feasibility of developing a solar-pumped laser for space power transmission.

  15. XeCl laser pumped iodine laser using t-C4F9I

    NASA Technical Reports Server (NTRS)

    Hwang, In Heon; Han, Kwang S.; Lee, Ja H.

    1989-01-01

    An iodine photodissociation laser using t-C4F9I as the active material was pumped by a XeCl laser. An iodine laser output energy of 3 mJ with pulse duration of 25 ns was obtained when the pumping pulse energy was 80 mJ, the iodine pressure was 70 torr, and the reflectance of the output mirror was 85 percent. The high pumping efficiency and low threshold pump power achieved in this experiment are attributable to the high absorption cross section at the pump laser wavelength (308 nm) of the iodide used.

  16. XeCl laser pumped iodine laser using t-C4F9I

    NASA Technical Reports Server (NTRS)

    Hwang, In Heon; Han, Kwang S.

    1989-01-01

    An iodine photodissociation laser using t-C4F9I as the active material was pumped by an XeCl laser. An iodine laser output energy of 3 mJ with pulse duration of 25 ns was obtained when the pumping pulse energy was 80 mJ, the iodide pressure was 70 torr, and the reflectance of the output mirror was 85 percent. The high pumping efficiency and low threshold pump power achieved in this experiment are attributable to the high absorption cross section at the pump laser wavelength (308 nm) of the iodide used.

  17. Development of laser-ion beam photodissociation methods

    SciTech Connect

    Russell, D.H.

    1990-08-01

    During this report period our research efforts have concentrated on studies of the dissociation reactions of model peptides and other biologically important molecules. In addition, a considerable amount of research effort has been directed toward improving the apparatus used for laser-ion beam photodissociation. The instrumental improvements include some changes on the original apparatus, but most of this effort involved designing a second generation laser-ion beam photodissociation instrument.

  18. Study of carboxyhemoglobin photodissociation with laser flash-photolysis

    NASA Astrophysics Data System (ADS)

    Kuzmin, Vasiliy V.; Salmin, Vladimir V.; Salmina, A. B.; Provorov, Alexander S.

    2004-08-01

    Assessment of the carboxyhemoglobin photodissociation has been performed under the native conditions. This investigation has a great importance for the development and creation of completely new approach for the treatment of carbon monoxide poisoning based on the photoinduced dissociation of carboxyhemoglobin. Photodissociation was registered on the experimental setup with crossing laser beams were pulsed Nd:YAG laser at the second harmonics wavelength (λ=532 nm) was used as a source of photolyzing radiation. Buffered solutions of whole human peripheral blood (PBS, pH=7.4) and diluted hemolized human peripheral blood were used. We found optimal parameters for the registration of the photodissociation such as using of buffered solutions of the whole human peripheral blood with the concentration of carboxyhemoglobin around 50% detection of dissociation of carboxyhemoglobin at the maximum of absorption within the Soret's band (435 nm). Dependence of photodissociation efficiency on the concentration of the complex in the tested solutions, as well as on the photolysis radiation intensity in both types of solutions was proved.

  19. Direct solar-pumped iodine laser amplifier

    NASA Technical Reports Server (NTRS)

    Han, K. S.

    1986-01-01

    During this period the parametric studies of the iodine laser oscillator pumped by a Vortek simulator were carried out before amplifier studies. The amplifier studies are postponed to the extended period after completing the parametric studies. In addition, the kinetic modeling of a solar-pumped iodine laser amplifier, and the experimental work for a solar pumped dye laser amplifier are in progress. This report contains three parts: (1) a 10 W CW iodine laser pumped by a Vortek solar simulator; (2) kinetic modeling to predict the time to lasing threshold, lasing time, and energy output of solar-pumped iodine laser; and (3) the study of the dye laser amplifier pumped by a Tamarack solar simulator.

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

    SciTech Connect

    Censky, M; Spalek, O; Jirasek, V; Kodymova, J; Jakubec, I

    2009-11-30

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

  1. Role of molecular photodissociation in ultrafast laser surgery

    NASA Astrophysics Data System (ADS)

    Wang, Jenny; Schuele, Georg; Huie, Phil; Palanker, Daniel V.

    2015-03-01

    Transparent ocular tissues such as cornea and crystalline lens can be precisely ablated or dissected using ultrafast ultraviolet, visible, and infrared lasers. In refractive or cataract surgery, cutting of the cornea, lens, and lens capsule is typically produced by dielectric breakdown in the focus of a short-pulse laser which results in explosive vaporization of the interstitial water and mechanically ruptures the surrounding tissue. Here, we report that tissue can also be disrupted below the threshold of bubble appearance using 400 nm femtosecond pulses with minimal mechanical damage. Using gel electrophoresis and liquid chromatography/mass spectrometry, we assessed photodissociation of proteins and polypeptides by 400 nm femtosecond pulses both below and above the cavitation bubble threshold. Negligible protein dissociation was observed with 800 nm femtosecond lasers even above the threshold of dielectric breakdown. Scanning electron microscopy of the cut edges in porcine lens capsule demonstrated that plasma-mediated cutting results in the formation of grooves. Below the cavitation bubble threshold, precise cutting could still be produced with 400 nm femtosecond pulses, possibly due to molecular photodissociation of the tissue structural proteins.

  2. Direct solar-pumped iodine laser amplifier

    NASA Astrophysics Data System (ADS)

    Han, Kwang S.; Kim, K. H.; Stock, L. V.

    1987-02-01

    The improvement on the collection system of the Tarmarack Solar Simulator beam was attemped. The basic study of evaluating the solid state laser materials for the solar pumping and also the work to construct a kinetic model algorithm for the flashlamp pumped iodine lasers were carried out. It was observed that the collector cone worked better than the lens assembly in order to collect the solar simulator beam and to focus it down to a strong power density. The study on the various laser materials and their lasing characteristics shows that the neodymium and chromium co-doped gadolinium scandium gallium garnet (Nr:Cr:GSGG) may be a strong candidate for the high power solar pumped solid state laser crystal. On the other hand the improved kinetic modeling for the flashlamp pumped iodine laser provides a good agreement between the theoretical model and the experimental data on the laser power output, and predicts the output parameters of a solar pumped iodine laser.

  3. Direct solar-pumped iodine laser amplifier

    NASA Technical Reports Server (NTRS)

    Han, Kwang S.; Kim, K. H.; Stock, L. V.

    1987-01-01

    The improvement on the collection system of the Tarmarack Solar Simulator beam was attemped. The basic study of evaluating the solid state laser materials for the solar pumping and also the work to construct a kinetic model algorithm for the flashlamp pumped iodine lasers were carried out. It was observed that the collector cone worked better than the lens assembly in order to collect the solar simulator beam and to focus it down to a strong power density. The study on the various laser materials and their lasing characteristics shows that the neodymium and chromium co-doped gadolinium scandium gallium garnet (Nr:Cr:GSGG) may be a strong candidate for the high power solar pumped solid state laser crystal. On the other hand the improved kinetic modeling for the flashlamp pumped iodine laser provides a good agreement between the theoretical model and the experimental data on the laser power output, and predicts the output parameters of a solar pumped iodine laser.

  4. Single photon excimer laser photodissociation of highly vibrationally excited polyatomic molecules

    SciTech Connect

    Tiee, J.J.; Wampler, F.B.; Rice, W.W.

    1980-01-01

    The ir + uv photodissociation of SF/sub 6/ has been performed using CO/sub 2/ and ArF lasers. The two-color photolysis significantly enhances the photodissociation process over ArF irradiation alone and is found to preserve the initial isotopic specificity of the ir excitation process.

  5. Development of laser-ion beam photodissociation methods. Progress report, December 1, 1992--November 30, 1993

    SciTech Connect

    Russell, D.H.

    1992-08-01

    Research efforts were concentrated on developing the tandem magnetic sector (EB)/reflection-time-of-flight (TOF) instrument, preliminary experiments with tandem TOF/TOF instruments, developing method for performing photodissociation with pulsed lasers, experiments with laser ionization of aerosol particles, matrix-assisted laser desorption ionization (MALDI), and ion-molecule reaction chemistry of ground and excited state transition metal ions. This progress report is divided into: photodissociation, MALDI (including aerosols), and ion chemistry fundamentals.

  6. Direct solar-pumped iodine laser amplifier

    NASA Technical Reports Server (NTRS)

    Han, Kwang S.; Hwang, In Heon

    1990-01-01

    The optimum conditions of a solar pumped iodine laser are found in this research for the case of a continuous wave operation and a pulsed operation. The optimum product of the pressure(p) inside the laser tube and the tube diameter(d) was pd=40 approx. 50 torr-cm on the contrary to the case of a high intensity flashlamp pumped iodine laser where the optimum value of the product is known to be pd=150 torr-cm. The pressure-diameter product is less than 1/3 of that of the high power iodine laser. During the research period, various laser materials were also studied for solar pumping. Among the laser materials, Nd:YAG is found to have the lowest laser threshold pumping intensity of about 200 solar constant. The Rhodamine 6G was also tested as the solar pumped laser material. The threshold pumping power was measured to be about 20,000 solar constant. The amplification experiment for a continuously pumped iodine laser amplifier was performed using Vortek solar simulator and the amplification factors were measured for single pass amplification and triple pass amplification of the 15 cm long amplifier tube. The amplification of 5 was obtained for the triple pass amplification.

  7. Fullurene-oxygen-iodine laser (FOIL): physical principles

    NASA Astrophysics Data System (ADS)

    Danilov, Oleg B.; Belousova, Inna M.; Mak, Artur A.; Belousov, Vlidilen P.; Grenishin, A. S.; Kiselev, V. M.; Krys'ko, A. V.; Murav'eva, T. D.; Ponomarev, Alexander N.; Sosnov, Eugene N.

    2005-03-01

    The paper considers the physical principles of developing the fullerene - oxygen - iodine laser (FOIL) with optical (sunlight in particular) pumping. Kinetic scheme of such a laser is considered. It is shown that the utmost efficiency of FOIL may exceed 40% of the energy, absorbed by fullerenes. Presented are the experimental results of singlet oxygen generation in liquid media (solutions and suspensions) and in solid-state structures, containing either fullerenes or fullerene-like nanopartickles (FNP). In experiment was shown the possibility of the singlet oxygen transfer to the gaseous phase by means of organizing of the solution (suspension) the boiling as well as of the gasodynamic wave of desorption from the solid-state structures, containing fullerenes or FNP. We present the preliminary experimental results of pulsed generation in optically pumped FOIL with the use of primary photodissociation of iodide for preparation of the atomic iodine in the generation zone. In the experiments on FOIL generation was implemented the principle of spectral separation of optical pumping.

  8. Fullerene-oxygen-iodine laser (FOIL): physical principles

    NASA Astrophysics Data System (ADS)

    Danilov, Oleg B.; Belousova, Inna M.; Mak, Artur A.; Belousov, Vlidilen P.; Grenishin, A. S.; Kiselev, V. M.; Krys'ko, A. V.; Murav'eva, T. D.; Ponomarev, Alexander N.; Sosnov, Eugene N.

    2004-06-01

    The paper considers the physical principles of developing the fullerene-oxygen-iodine laser (FOIL) with optical (sunlight in particular) pumping. Kinetic scheme of such a laser is considered. It is shown that the utmost efficiency of FOIL may exceed 40% of the energy, absorbed by fullerenes. Presented are the experimental results of singlet oxygen generation in liquid media (solutions and suspensions) and in solid-state structures, containing either fullerenes or fullerene-like nanoparticles (FNP). In experiment was shown the possibility of the singlet oxygen transfer to the gaseous phase by means of organizing of the solution (suspension) the boiling as well as of the gasodynamic wave of desorption from the solid-state structures, containing fullerenes or FNP. We present the preliminary experimental results of pulsed generation in optically pumped FOIL with the use of primary photodissociation of iodide for preparation of the atomic iodine in the generation zone. In the experiments on FOIL generation was implemented the principle of spectral separation of optical pumping.

  9. Fullerene-oxygen-iodine laser (FOIL): physical principles

    NASA Astrophysics Data System (ADS)

    Danilov, Oleg B.; Belousova, Inna M.; Mak, Artur A.; Belousov, Vlidilen P.; Grenishin, A. S.; Kiselev, V. M.; Krys'ko, A. V.; Murav'eva, T. D.; Ponomarev, Alexander N.; Sosnov, Eugene N.

    2004-09-01

    The paper considers the physical principles of developing the fullerene-oxygen-iodine laser (FOIL) with optical (sunlight in particular) pumping. Kinetic scheme of such a laser is considered. It is shown that the utmost efficiency of FOIL may exceed 40% of the energy, absorbed by fullerenes. Presented are the experimental results of singlet oxygen generation in liquid media (solutions and suspensions) and in solid-state structures, containing either fullerenes or fullerene-like nanoparticles (FNP). In experiment was shown the possibility of the singlet oxygen transfer to the gaseous phase by means of organizing of the solution (suspension) the boiling as well as of the gasodynamic wave of desorption from the solid-state structures, containing fullerenes or FNP. We present the preliminary experimental results of pulsed generation in optically pumped FOIL with the use of primary photodissociation of iodide for preparation of the atomic iodine in the generation zone. In the experiments on FOIL generation was implemented the principle of spectral separation of optical pumping.

  10. Direct solar-pumped iodine laser amplifier

    NASA Technical Reports Server (NTRS)

    Han, Kwang S.; Hwang, In H.; Stock, Larry V.

    1988-01-01

    A XeCl laser which was developed earlier for an iodine laser oscillator was modified in order to increase the output pulse energy of XeCl laser so that the iodine laser output energy could be increased. The electrical circuit of the XeCl laser was changed from a simple capacitor discharge circuit of the XeCl laser to a Marx system. Because of this improvement the output energy from the XeCl laser was increased from 60 mj to 80 mj. Subsequently, iodine laser output energy was increased from 100 mj to 3 mj. On the other hand, the energy storage capability and amplification characteristics of the Vortek solar simulator-pumped amplifier was calculated expecting the calculated amplification factor is about 2 and the energy extraction efficiency is 26 percent due to the very low input energy density to the amplifier. As a result of an improved kinetic modeling for the iodine solar simulator pumped power amplifier, it is found that the I-2 along the axis of the tube affects seriously the gain profile. For the gas i-C3F7I at the higher pressures, the gain will decrease due to the I-2 as the pumping intensity increases, and at these higher pressures an increase in flow velocity will increase the gain.

  11. Direct solar-pumped iodine laser amplifier

    NASA Technical Reports Server (NTRS)

    Han, Kwang S.; Hwang, In Heon; Stock, Larry V.

    1989-01-01

    This semiannual progress report covers the period from September 1, 1988 to February 28, 1989 under NASA grant NAG-1-441 entitled, Direct Solar-Pumped Iodine Laser Amplifier. During this period, the research effort was concentrated on the solar pumped master oscillator power amplifier (MOPA) system using n-C3F7I. In the experimental work, the amplification measurement was conducted to identify the optimum conditions for amplification of the center's Vortek solar simulator pumped iodine laser amplifier. A modeling effort was also pursued to explain the experimental results in the theoretical work. The amplification measurement of the solar simulator pumped iodine laser amplifier is the first amplification experiment on the continuously pumped amplifier. The small signal amplification of 5 was achieved for the triple pass geometry of the 15 cm long solar simulator pumped amplifier at the n-C3F7I pressure of 20 torr, at the flow velocity of 6 m/sec and at the pumping intensity of 1500 solar constants. The XeCl laser pumped iodine laser oscillator, which was developed in the previous research, was employed as the master oscillator for the amplification measurement. In the theoretical work, the rate equations of the amplifier was established and the small signal amplification was calculated for the solar simulator pumped iodine laser amplifier. The amplification calculated from the kinetic equations with the previously measured rate coefficients reveals very large disagreement with experimental measurement. Moreover, the optimum condition predicted by the kinetic equation is quite discrepant with that measured by experiment. This fact indicates the necessity of study in the measurement of rate coefficients of the continuously pumped iodine laser system.

  12. Overview of iodine generation for oxygen-iodine lasers

    NASA Astrophysics Data System (ADS)

    Jirásek, Vít.

    2012-01-01

    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

  13. A computer modeling study of isotopically selective, laser photodissociation of OCS in cryogenic solutions

    SciTech Connect

    Zittel, P.F.

    1991-12-23

    Computer model calculations are presented for enrichments of carbon, oxygen, and sulfur isotopes by two-step, IR/UV, laser photodissociation of OCS in rare gas liquid solutions. The model calculations are based on previously measured fundamental physical properties, including spectroscopic parameters of the IR absorption bands of OCS in cryogenic solution, UV photodissociation cross sections for specific vibrational levels of OCS, and rates for vibrational relaxation of OCS by cryogenic solvents. Results are presented for both pulsed and continuous wave laser sources. Photodissociation through both the 2{nu}{sub 2} and {nu}{sub 1} intermediate vibrational levels of OCS is investigated. The laser characteristics required to obtain optimum enrichments are determined by modeling the dependence of enrichment on laser wavelength and intensity, as well as pulse width and timing for pulsed sources. Optimum carbon and oxygen isotope enrichment factors of 9--14 are found for two-step photodissociation through the OCS(2{nu}{sub 2}) vibrational level, using pulsed CO{sub 2} and KrF excimer laser sources. Optimum sulfur isotope enrichment factors of 5--6 are found for photodissociation through the OCS({nu}{sub 1}) level, using a pulsed 12 {mu}m laser and a KrF excimer laser. The enrichments found for continuous wave laser sources are smaller than those for pulsed sources. 19 figs., 4 tabs.

  14. A computer modeling study of isotopically selective, laser photodissociation of OCS in cryogenic solutions

    SciTech Connect

    Zittel, P.F.

    1991-12-23

    Computer model calculations are presented for enrichments of carbon, oxygen, and sulfur isotopes by two-step, IR/UV, laser photodissociation of OCS in rare gas liquid solutions. The model calculations are based on previously measured fundamental physical properties, including spectroscopic parameters of the IR absorption bands of OCS in cryogenic solution, UV photodissociation cross sections for specific vibrational levels of OCS, and rates for vibrational relaxation of OCS by cryogenic solvents. Results are presented for both pulsed and continuous wave laser sources. Photodissociation through both the 2{nu}{sub 2} and {nu}{sub 1} intermediate vibrational levels of OCS is investigated. The laser characteristics required to obtain optimum enrichments are determined by modeling the dependence of enrichment on laser wavelength and intensity, as well as pulse width and timing for pulsed sources. Optimum carbon and oxygen isotope enrichment factors of 9--14 are found for two-step photodissociation through the OCS(2{nu}{sub 2}) vibrational level, using pulsed CO{sub 2} and KrF excimer laser sources. Optimum sulfur isotope enrichment factors of 5--6 are found for photodissociation through the OCS({nu}{sub 1}) level, using a pulsed 12 {mu}m laser and a KrF excimer laser. The enrichments found for continuous wave laser sources are smaller than those for pulsed sources. 19 figs., 4 tabs.

  15. Electric Oxygen Iodine Laser: A Study for Scaling

    DTIC Science & Technology

    2009-09-03

    active components in the flow is small, resulting in a low gain coefficient . To produce a high- power oxygen iodine laser system it will be necessary... iodine laser: A study for scaling Sb. GRANT NUMBER F A9550-07-l-0529 Sc. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Sd. PROJECT NUMBER Michael C. Heaven Se...potentially limit scaling of the electric oxygen iodine laser (EOIL) were examined. Quenching of excited iodine atoms (I*) by atomic oxygen has been

  16. Direct solar-pumped iodine laser amplifier

    NASA Technical Reports Server (NTRS)

    Han, Kwang S.

    1987-01-01

    This semiannual progress report covers the period from March 1, 1987 to September 30, 1987 under NASA grant NAG1-441 entitled 'Direct solar-pumped iodine laser amplifier'. During this period Nd:YAG and Nd:Cr:GSGG crystals have been tested for the solar-simulator pumped cw laser, and loss mechanisms of the laser output power in a flashlamp-pumped iodine laser also have been identified theoretically. It was observed that the threshold pump-beam intensities for both Nd:YAG and Nd:Cr:GSGG crystals were about 1000 solar constants, and the cw laser operation of the Nd:Cr:GSGG crystal was more difficult than that of the Nd:YAG crystal under the solar-simulator pumping. The possibility of the Nd:Cr:GSGG laser operation with a fast continuously chopped pumping was also observed. In addition, good agreement between the theoretical calculations and the experimental data on the loss mechanisms of a flashlamp-pumped iodine laser at various fill pressures and various lasants was achieved.

  17. A model for a continuous-wave iodine laser

    NASA Technical Reports Server (NTRS)

    Hwang, In H.; Tabibi, Bagher M.

    1990-01-01

    A model for a continuous-wave (CW) iodine laser has been developed and compared with the experimental results obtained from a solar-simulator-pumped CW iodine laser. The agreement between the calculated laser power output and the experimental results is generally good for various laser parameters even when the model includes only prominent rate coefficients. The flow velocity dependence of the output power shows that the CW iodine laser cannot be achieved with a flow velocity below 1 m/s for the present solar-simulator-pumped CW iodine laser system.

  18. A model for a continuous-wave iodine laser

    NASA Technical Reports Server (NTRS)

    Hwang, In H.; Tabibi, Bagher M.

    1990-01-01

    A model for a continuous-wave (CW) iodine laser has been developed and compared with the experimental results obtained from a solar-simulator-pumped CW iodine laser. The agreement between the calculated laser power output and the experimental results is generally good for various laser parameters even when the model includes only prominent rate coefficients. The flow velocity dependence of the output power shows that the CW iodine laser cannot be achieved with a flow velocity below 1 m/s for the present solar-simulator-pumped CW iodine laser system.

  19. Recombination of photodissociated iodine: A time-resolved x-ray-diffraction study

    SciTech Connect

    Wulff, M.; Bratos, S.; Plech, A.; Vuilleumier, R.; Mirloup, F.; Lorenc, M.; Kong, Q.; Ihee, H.

    2006-01-21

    A time-resolved x-ray-diffraction experiment is presented that aims to study the recombination of laser-dissociated iodine molecules dissolved in CCl{sub 4}. This process is monitored over an extended time interval from pico- to microseconds. The variations of atom-atom distances are probed with a milliangstrom resolution. A recent theory of time-resolved x-ray diffraction is used to analyze the experimental data; it employs the correlation function approach of statistical mechanics. The most striking outcome of this study is the experimental determination of time-dependent I-I atom-atom distribution functions. The structure of the CCl{sub 4} solvent changes simultaneously; the solvent thus appears as a reaction partner rather than an inert medium hosting it. Thermal expansion of the system is nonuniform in time, an effect due to the presence of the acoustic horizon. One concludes that a time-resolved x-ray diffraction permits real-time visualization of solvent and solute motions during a chemical reaction.

  20. Direct solar-pumped iodine laser amplifier

    NASA Technical Reports Server (NTRS)

    Han, Kwang S.; Hwang, In Heon; Kim, Khong Hon; Stock, Larry V.

    1988-01-01

    A XeCl laser pumped iodine laser oscillator was developed which will be incorporated into the Master Oscillator Power Amplifier (MOPA) system. The developed XeCl laser produces output energy of about 60 mJ per pulse. The pulse duration was about 10 nsec. The kinetic model for the solar-pumped laser was refined and the algorithm for the calculation of a set of rate equations was improved to increase the accuracy and the efficiency of the calculation. The improved algorithm was applied to explain the existing experimental data taken from a flashlamp pumped iodine laser for three kinds of lasants, i-C3F7I, n-C4F9I, and t-C4F9I. Various solid laser materials were evaluated for solar-pumping. The materials studied were Nd:YAG, Nd:YLF, and Cr:Nd:GSGG crystals. The slope efficiency of 0.17 percent was measured for the Nd:YLF near the threshold pump intensity which was 211 solar constants (29W/sq cm). The threshold pump intensity of the Nd:YAG was measured to be 236 solar constants (32W/sq cm) and the near-threshold slope efficiency was 0.12 percent. True CW laser operation of Cr:Nd:GSGG was possible only at pump intensities less than or equal to 1,500 solar constants (203 W/sq cm). This fact was attributed to the high thermal focusing effect of the Cr:Nd:GSGG rod.

  1. Effect of laser-induced photodissociation of oxyhemoglobin on biomedical processes

    NASA Astrophysics Data System (ADS)

    Asimov, Mustafo M.; Asimov, Rustam M.; Mirshahi, M.; Gisbrecht, Alexander

    2001-04-01

    In the present report we draw attention to the phenomenon of laser-induced photodissociation of oxyhemoglobin in cutaneous blood vessels as an important factor in biostimulating and therapeutic action of low energy laser radiation. Calculations of absorption efficiency of laser radiation both by oxyhemoglobin and carbon monoxide hemoglobin were carried out by a computer simulation using Kubelka-Munk model of tissue. It has been shown that the absorption of the oxyhemoglobin in the visible region corresponding to the Q-band of absorption spectra possesses a relatively high selectivity. The obtained results are discussed in terms of developing new methods for wound healing, as well as for carbon monoacid poisoning. Some aspects of the laser-induced photodissociation of oxyhemoglobin complexes are discussed in view of its practical use for developing new diagnostic methods. An attractive way to use this phenomenon is monitoring of local concentrations of oxygen by laser light irradiation.

  2. Optically (solar) pumped oxygen-iodine lasers

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

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

  3. Oxyhemoglobin photodissociation efficiency in biological tissue exposed to laser radiation

    NASA Astrophysics Data System (ADS)

    Barun, V. V.; Ivanov, A. P.

    2011-09-01

    We have obtained quantitative data on the differential (with respect to depth) and the integrated oxyhemoglobin photodissociation efficiency in the dermis when the skin surface is exposed to a light beam in the wavelength range 300-650 nm. With this aim, we have used our own previously developed optical model for skin tissue and analytical procedure for calculating the characteristics of optical fields in a medium. We have estimated the number of oxygen molecules formed at different depths in the medium, and also their integrated number over the entire thickness of the dermis as a function of the irradiation wavelength. We consider models for a dermis that is homogeneous with respect to depth and a dermis that has a layered structure. We show that the spectral photodissociation efficiency has a number of maxima associated with the absorption spectrum of oxyhemoglobin and the optical properties of all the layers of skin tissue. We discuss the effect of the epidermis on these maxima.

  4. Demonstration of a new laser diagnostic based on photodissociation spectroscopy for imaging mixture fraction in a non-premixed jet flame.

    PubMed

    Zhao, Yan; Tong, Chenning; Ma, Lin

    2010-04-01

    The study of turbulent combustion calls for new diagnostics that can measure multidimensional mixture fraction under a wide range of flame conditions. A laser diagnostic technique based on photodissociation spectroscopy (PDS) is proposed to address this need. This paper describes the concept of the PDS-based diagnostic, reports its experimental demonstration in a non-premixed jet flame, and assesses its performance and applicable range. This new technique is centered around the creative use of photodissociation (PD) for flow visualization. A carefully chosen PD precursor is seeded into the flow of interest to measure mixture fraction. The precursor is chosen such that (1) both the precursor itself and the products formed from the precursor (if it reacts) can be completely and rapidly photodissociated; thus, the concentration of one of the photofragments forms a conserved scalar and can be used to infer the mixture fraction, and (2) the target photofragment offers friendly spectroscopic properties (e.g., strong laser-induced fluorescence signals and/or simple signal interpretation) so multidimensional imaging can be readily obtained. Molecular iodine (I(2)) was identified as a precursor satisfying both requirements and was seeded into a carbon monoxide (CO)-air jet flame for single-shot two-dimensional imaging of mixture fraction. This demonstration illustrates the potential of the PDS-based technique to overcome the limitations of existing techniques and to provide multidimensional measurements of mixture fraction in a variety of reactive flows.

  5. Ultraviolet photodissociation of iodine monochloride (ICl) at 235, 250, and 265 nm

    SciTech Connect

    Diamantopoulou, N.; Kitsopoulos, Theofanis N.; Kartakoulis, A.; Glodic, P.; Samartzis, Peter C.

    2011-05-21

    ICl photolysis in the ultraviolet region of the spectrum (235-265 nm) is studied using the Slice Imaging technique. The Cl*({sup 2}P{sub 1/2})/Cl({sup 2}P{sub 3/2}) and the I*({sup 2}P{sub 1/2})/I({sup 2}P{sub 3/2}) branching ratio between the I({sup 2}P{sub 3/2}) + Cl({sup 2}P{sub 3/2})/Cl*({sup 2}P{sub 1/2}) and I*({sup 2}P{sub 1/2}) + Cl({sup 2}P{sub 3/2})/Cl*({sup 2}P{sub 1/2}) channels is extracted from the respective iodine and chlorine photofragment images. We find that ground state chlorine atoms (Cl({sup 2}P{sub 3/2})) are formed nearly exclusively with excited state iodine atoms (I*({sup 2}P{sub 1/2})), while excited spin-orbit chlorine atoms (Cl*({sup 2}P{sub 1/2})) are concurrently produced only with ground state iodine atoms (I({sup 2}P{sub 3/2})). We conclude that photolysis of ICl in this UV region is a relatively ''clean'' source of spin-orbit excited chlorine atoms that can be used in crossed molecular beam experiments.

  6. Development of laser-ion beam photodissociation methods. Progress report, December 1, 1991--November 30, 1992

    SciTech Connect

    Russell, D.H.

    1992-08-01

    During this report period our research efforts have concentrated on the continued development of the tandem magnetic sector (EB)/reflectron-time-of-flight (TOF) instrument, preliminary experiments with the tandem TOF/TOF E/R-TOF instrument, developing the methodology for performing photodissociation with pulsed lasers on the EB/R-TOF instrument, preliminary experiments with laser ionization on the aerosol-particle beam apparatus, development of a vacuum ultra-violet laser for photoionization/photoexcitation of gas phase ions, and fundamental studies on matrix-assisted laser desorption ionization (MALDI).

  7. Experimental analysis of chemical oxygen-iodine lasers

    NASA Astrophysics Data System (ADS)

    Bonnet, J.; David, D.; Georges, E.; Leporcq, B.; Pigache, D.; Verdier, C.

    The dissociation, excitation and quenching of iodine was examined in two lasers to build a data base for the kinetics of oxygen-iodine lasers. I2 mixed with Ar was pumped into a pyrex cavity in a small laser, and mixed with O2 in a larger laser. Measurements were made of the 1270 nm emission of O(2)1Delta in the larger laser. Excited I and I2 luminescence intensity profiles and the excited I emission profile in the presence of water vapor were obtained. Rising water vapor pressure decreased the luminescence and laser power by increasing the I2 dissociation time. In the larger laser, iodine, although injected, never reached the channel midplane, thus reducing the laser output to proportionally less than that of the smaller laser. A new injector will be tested in an attempt to achieve higher lasing powers.

  8. Photodissociation of nitrogen dioxide by pulsed laser light at 6943 A.

    NASA Technical Reports Server (NTRS)

    Gerstmayr, J. W.; Harteck, P.; Reeves, R. R.

    1972-01-01

    Nitrogen dioxide was photodissociated using a pulsed ruby laser at 6943 A. The energy of a single photon at this wavelength was equivalent to only 57% of the dissociation energy. The mechanism proposed to account for the results was the consecutive absorption of two photons, the first resulting in a short-lived excited state. The second photon is then absorbed by the excited species resulting in dissociation.

  9. Amplified spontaneous emission in solar-pumped iodine laser

    NASA Technical Reports Server (NTRS)

    Cho, Yong S.; Hwang, In H.; Han, Kwang S.; Lee, Ja H.

    1992-01-01

    The amplified spontaneous emission (ASE) from a long pulse, solar-simulating radiation pumped iodine laser amplifier is studied. The ASE threshold pump intensity is almost proportional to the inverse of the laser gain length when the gas pressure is constant in the laser tube.

  10. Amplified spontaneous emission in solar-pumped iodine laser

    NASA Technical Reports Server (NTRS)

    Cho, Yong S.; Hwang, In H.; Han, Kwang S.; Lee, Ja H.

    1992-01-01

    The amplified spontaneous emission (ASE) from a long pulse, solar-simulating radiation pumped iodine laser amplifier is studied. The ASE threshold pump intensity is almost proportional to the inverse of the laser gain length when the gas pressure is constant in the laser tube.

  11. Evidence for quantum effects in laser driven photodissociation of methylamines

    NASA Astrophysics Data System (ADS)

    Bar, Ilana; Epshtein, Michael; Portnov, Alexander

    2015-03-01

    Non-adiabatic dynamics at conical intersections (CI) extensively affects the photostability of biomolecules by efficiently photoinducing decay routes that dissipate harmful excess ultraviolet energy. Here the photodissociation of the model test molecules, methylamine (CH3NH2) and its partially deuterated isotopologue (CD3NH2) , excited to different specific vibrational modes in the electronically excited state has been investigated by H(D) photofragments detection with two-color reduced-Doppler ion imaging. The H products, resulting from N-H bond cleavage via two dissociation pathways, showed anomalous distributions for some of the vibronic states, as indicated by dynamic resonances in the product branching ratio and in the anisotropy parameters. This vibronic-specific control is attributed to distinctive dynamical interferences of the initially prepared wavepackets, affecting the passage efficiency through the S1/S0 CIs. It is suggested that the H product distributions are extremely sensitive to the positions and energies of the CIs in the two molecules, rather than to the unique initial nuclear motion that promotes the coupling between the two electronic states. These observations reveal uniquely detailed insights into the dynamics of state-specific control of internal conversion.

  12. Photo-dissociation quantum yields of mammalian oxyhemoglobin investigated by a nanosecond laser technique

    SciTech Connect

    Yang Ningli; Zhang Shuyi . E-mail: zhangsy@nju.edu.cn; Kuo Paokuang; Qu Min; Fang Jianwen; Li Jiahuang; Hua Zichun

    2007-02-23

    The photo-dissociations of oxyhemoglobin of several mammals, such as human, bovine, pig, horse, and rabbit, have been studied. By means of optical pump-probe technique, the quantum yields for photo-dissociation of these oxyhemoglobin have been determined at pH 7 and 20 {sup o}C. A nanosecond laser at 532 nm is used as the pumping source, and a xenon lamp through a monochrometer provides a probe light at 432 nm. The experimental results show that the quantum yields of these mammalian oxyhemoglobin are different from each other, especially for that of rabbit. By analyzing the amino acid sequences and tetramer structures as well as the flexibility and hydrophobicity of the different hemoglobin, possible explanations for the differences are proposed.

  13. Laser Induced Fluorescence of the Iodine Ion

    DTIC Science & Technology

    2014-09-01

    Fluorescence of the Iodine Ion 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER William A. Hargus, Jr. 5e. TASK NUMBER...SUPPLEMENTARY NOTES Briefing Charts presented at Gaseous Electronics Conference; Raleigh, NC; 5 November 2014. PA#14517 14. ABSTRACT Iodine (I2) has been...discussed seriously as a propellant for Hall effect and other electrostatic thrusters as early as 2000. Atomic iodine has a mass of 126.9 amu, but as

  14. Space interferometry application of laser frequency stabilization with molecular iodine.

    PubMed

    Leonhardt, Volker; Camp, Jordan B

    2006-06-10

    A number of planned space interferometry missions, including the Laser Interferometer Space Antenna (LISA) gravitational wave detector, require a laser system with high-frequency stability over long time scales. A 1064 nm wavelength nonplanar ring oscillator (NPRO) laser stabilized to a resonant transition in molecular iodine is suitable for these missions, providing high-frequency stability at an absolute reference frequency. The iodine stabilized laser also offers low sensitivity to temperature and alignment fluctuations and allows frequency tuning. We have evaluated the noise performance of a NPRO laser stabilized to iodine using frequency modulation spectroscopy and have found an Allan standard deviation of 10(-14) over 100 s. Simplified optical configurations and the radiation hardness of the frequency-doubling crystals have also been investigated.

  15. Laser-induced photodissociation of oxyhemoglobin: Optical method of elimination of hypoxia (oxygen deficiency in biotissue)

    NASA Astrophysics Data System (ADS)

    Asimov, M. M.; Thanh, Nguyen Cong

    2011-08-01

    We consider the effect of laser-induced in vivo photodissociation of blood oxyhemoglobin on gas exchange in biological tissues. An optical method of laser-induced oxygenation of biotissues is developed and proposed. We show that, in the region of the action of the laser radiation, the degree of oxygenation of a tissue increases. We experimentally confirm that the phenomenon of laser-induced in vivo photodissociation of oxyhemoglobin opens up a new possibility of controlling the local concentration of free molecular oxygen in tissues, eliminating tissue hypoxia, and stimulating aerobic metabolism of cells. We show that the efficiency of the proposed method of laser-induced oxygenation of biotissues proves to be comparable with the efficiency of the hyperbaric oxygenation, but has the advantage of the locality of the action. The proposed optical method of local oxygenation of biotissues will make it possible to eliminate the problem of hypoxia in cancerous tumor tissue and to considerably increase the efficiency of photodynamic, radiation, and chemotherapy in modern oncology.

  16. Development of Laser-Ion Beam Photodissociation Methods

    SciTech Connect

    David H. Russell

    2004-05-11

    OAK-B135 Our BES funded research is aimed at determining structure(s) of model gas-phase ions and understanding how structure influences unimolecular reactivity. The model gas-phase ions include positional isomers of di- and tri-amino acids synthesized in my laboratory, i.e., RGG, GRG, and GGR, to peptides derived from proteolytic digestion of biologically relevant proteins. We are especially interested in understanding the role of intramolecular interactions in the stabilizing ion structure and how changing the charge-site affects structure. The location of charge of gas-phase ions can be manipulated by changing the position of the charge carrying amino acid (basic vs. acidic side chains) and by derivatization of the N- and/or C-terminus. For example, the proton of [M + H]+ ions is mobile and migrates over the entire molecule, whereas Li+, Na+, and to some extent K+ prefers to bind to the C-terminal or side-chain carboxylic acid groups, and Cu+ binds exclusively to the N-terminus and/or basic side-chains such as H, K, and R. The studies are carried out using tandem TOF mass spectrometry, viz. 193 nm (6.43 eV) photodissociation, low (Elab = 10-100 eV) and high kinetic energy (Elab = 1-10 keV) collision-induced dissociation (CID) and surface-induced dissociation (SID)(Elab = 20-70 eV). These techniques are used to probe the structure of model gas-phase ions, i.e., to determine the amino acid sequence of the peptide ions or metal ion (alkali metal and/or transition metal ions) binding site(s) or the site(s) of other charge-carrying functional groups, i.e., oxidized side-chains as well as phosphate or sulfate groups. We are especially interested in understanding how metal ion binding alters the secondary/tertiary (2o/3o) structure of the peptide, i.e., intra-molecular interactions. We have also combine these studies with solution-phase studies and ion mobility spectrometry (IMS)), which can be used to study 2o/3o structure of low-internal energy (collisionally

  17. Development of Laser-Ion Beam Photodissociation Methods

    SciTech Connect

    David H. Russell

    2004-03-31

    OAK-B135 Our BES funded research is aimed at determining structure(s) of model gas-phase ions and understanding how structure influences unimolecular reactivity. The model gas-phase ions include positional isomers of di- and tri-amino acids synthesized in my laboratory, i.e., RGG, GRG, and GGR, to peptides derived from proteolytic digestion of biologically relevant proteins. We are especially interested in understanding the role of intramolecular interactions in the stabilizing ion structure and how changing the charge-site affects structure. The location of charge of gas-phase ions can be manipulated by changing the position of the charge carrying amino acid (basic vs. acidic side chains) and by derivatization of the N- and/or C-terminus. For example, the proton of [M + H]+ ions is mobile and migrates over the entire molecule, whereas Li+, Na+, and to some extent K+ prefers to bind to the C-terminal or side-chain carboxylic acid groups, and Cu+ binds exclusively to the N-terminus and/or basic side-chains such as H, K, and R. The studies are carried out using tandem TOF mass spectrometry, viz. 193 nm (6.43 eV) photodissociation, low (Elab = 10-100 eV) and high kinetic energy (Elab = 1-10 keV) collision-induced dissociation (CID) and surface-induced dissociation (SID)(Elab = 20-70 eV). These techniques are used to probe the structure of model gas-phase ions, i.e., to determine the amino acid sequence of the peptide ions or metal ion (alkali metal and/or transition metal ions) binding site(s) or the site(s) of other charge-carrying functional groups, i.e., oxidized side-chains as well as phosphate or sulfate groups. We are especially interested in understanding how metal ion binding alters the secondary/tertiary (2o/3o) structure of the peptide, i.e., intra-molecular interactions. We have also combine these studies with solution-phase studies and ion mobility spectrometry (IMS), which can be used to study 2o/3o structure of low-internal energy (collisionally

  18. Photodissociation Dye Laser Studies and High Pressure Discharge Conditioning Studies

    DTIC Science & Technology

    1976-11-01

    reflective dielectric coated mirrors served to form a resonant cavity. However, no laser action was observed from this configuration. Unfortunately, the...temperature Is kept at a minimum. How- ever, composite materials with low work function, such as various types of oxide- coated cathodes, lanthanum...34 Photochromism ," Techniques of Chemistry, Vol. Ill, Wlley-Interscience, New York (1971). d. Henry Gilman, Ed., "Organic Chemistry—An Advanced

  19. Fragment angular distribution in one- and two-color photodissociation by strong laser fields

    SciTech Connect

    Charron, E.; Giusti-Suzor, A.; Mies, F.H. Laboratoire de Chimie Physique, 11 rue Pierre et Marie Curie, 75231 Paris National Institute of Standards and Technology, Gaithersburg, Maryland 20899 )

    1994-02-01

    We present calculations for H[sub 2][sup +] photodissociation in intense short laser pulses where molecular rotation is fully included, resulting in the experimentally observed alignment of the photofragments. In addition, we show that by using a coherent superposition (phase-locked) of a fundamental radiation and its second harmonic, [ital a] [ital strong] [ital asymmetry] between the forwards and backwards proton distribution can be observed. Both the total dissociation probability and the asymmetry of the ion distribution are sensitive to the relative phase of the two colors and thus subject to coherent control.

  20. Electronically Excited C2 from Laser Photodissociated C60

    NASA Technical Reports Server (NTRS)

    Arepalli, Sivaram; Scott, Carl D.; Nikolaev, Pavel; Smalley, Richard E.

    1999-01-01

    Spectral and transient emission measurements are made of radiation from products of laser excitation of buckminsterfullerene (C60) vapor diluted in argon at 973 K. The principal radiation is from the Swan band system of C2 and, at early times, also from a black body continuum. The C2 radiation is observed only when C60 is excited by green (532 nm) and not with IR (1064 nm) laser radiation at energy densities of about 1.5 J/square cm. Transient measurements indicate that there are two characteristic periods of decay of radiation. The first period, lasting about 2 micro seconds, has a characteristic decay time of about 0.3 micro seconds. The second period, lasting at least 50 micro seconds, has a characteristic decay time of about 5 micro seconds. These characteristic times are thought to be associated with cooling of C60 molecules or nanosized carbon particles during the early period; and with electronically excited C2 that is a decomposition product of laser excited C60, C58, ... molecules during the later period.

  1. Investigation of tissue oxygenation by in vivo laser-induced photodissociation of cutaneous arterial blood oxyhemoglobin

    NASA Astrophysics Data System (ADS)

    Asimov, M. M.; Korolevich, A. N.

    2008-06-01

    A novel method of direct control of local tissue oxygenation based on laser-induced photodissociation of oxyhemoglobin in cutaneous blood vessels is discussed. New technology in selective and local increase of the concentration of free molecular oxygen in tissue that enhances metabolism of cells is demonstrated. Direct in vivo measurements of the tissue oxygen tension are carried out on human skin. Kinetics of oxygen tension in tissue is investigated under the effect of He-Ne laser radiation at the power of 1mW relatively to initial value of tissue oxygen tension. The results of experimental study the kinetics of oxygen distribution into tissue from arterial blood is presented. Biomedical applications of proposed new technology in laser therapy of pathologies where elimination of local tissue hypoxia is critical are discussed.

  2. Development of laser-ion beam photodissociation methods. Progress report, December 1991--November 1994

    SciTech Connect

    Russell, D.H.

    1994-06-01

    This project emphasizes the development of laser mass spectrometry methods for fundamental and applied studies of gas-phase processes. The current studies are focussed on the photochemistry and photophysics of peptides and other biological molecules. Matrix-assisted laser desorption ionization (MALDI) is used to produce ions that are subsequently subjected to photoexcitation and dissociation. MALDI is still very much in the developmental stages, thus a significant portion of this research focusses on fundamental studies of the MALDI ion formation/energy transfer process. The authors view is that excited state H+-transfer reactions play an important role in MALDI, consequently a significant portion of their research activities are focussed on such studies. Fundamental studies of the role of the matrix in MALDI are an integral part of this project. A new MALDI experiment, MALDI of aerosol particles generated from solutions, has been demonstrated and new developmental research in this area is planned. The authors are also actively pursuing a research program on gas-phase H+-transfer processes that mimic the MALDI process. In addition, they are developing photodissociation experiments, based on tandem time-of-flight mass spectrometers, for structural characterization of complex organic molecules. The photodissociation studies use MALDI as the ionization method. These research areas involve the development of new instrumentation, new instrument methodologies, and data processing.

  3. Photodissociation and photoexcitation of simple molecules with 1576 A f2 laser

    NASA Astrophysics Data System (ADS)

    Slanger, T. G.; Taherian, M. R.

    The Fluorine laser, operating at 1576 A, is the shortest wavelength laser with which one photon photochemical experiments are currently practical. This paper studies experiments carried out on C2N2 and on NO, the former case involving photodissociation, the latter, photoexcitation. At 1576 A, photodissociation of C2N2 leads to production of CN(A 2Pi) and CN(X2 Sigma(+)), with the CN(A) being produced in a range of vibrational levels, up to the thermodynamic limit of v=5. Radiative lifetimes have been measured for each of the six levels, and the lifetimes become shorter with increasing v, which agrees with theoretical predictions, but with no previous experimental studies. Rates coefficients for quenching the CN(A) state by the parent molecule show a correlation with the size of the energy gap between the A level and the closest lower X level, although the effect is linear and not exponetial in energy. The laser radiation is resonant with a transition in the B'-X band of NO. This results, in the collision-free case, in emission in three band systems, B' and B, whereas upon He addition, several other band systems appear. We have determined which rotational levels are involved in the initial step, and find the match to be within 0.25/cm of resonance. The branching ratio between the B'-X and B'-B systems has been found to be 155. The resonance between the laser radiation and the NO transition establishes NO as a unique monitor of the laser power.

  4. The biomedical effect of laser-induced photodissociation of oxyhemoglobin in vivo

    NASA Astrophysics Data System (ADS)

    Asimov, M. M.

    2013-11-01

    It is demonstrated that the photodissociation of oxyhemoglobin in cutaneous blood vessels and capillaries allows additional extraction of molecular oxygen, prevents hypoxia, and stimulates aerobic metabolism of cells. On the basis of the studied phenomena, a new optical technology of local oxygenation of tissue directly in the zone of laser irradiation has been developed. It is shown that the efficiency of the proposed method for laser-induced oxygenation of biotissues is comparable with the efficiency of hyperbaric oxygenation, with local action being an additional advantage. Various aspects of the applications of the new technology in modern medicine in which the elimination of local hypoxia is needed are discussed. The proposed optical method for local oxygenation of biotissues makes it possible to solve the hypoxia problem in malignant tissue and substantially increase the efficiency of photodynamic, radiation, and chemical therapy in modern oncology.

  5. Results of experiments on iodine dissociation in active medium of oxygen-iodine laser

    NASA Astrophysics Data System (ADS)

    Zagidullin, Marsel V.; Khvatov, Nickolay A.; Malyshev, Mikhail S.

    2017-01-01

    Results of experiments on dissociation of iodine molecules in the presence of singlet oxygen molecules are presented for wide range of oxygen-iodine media composition. Rate constants values have been obtained: 4.3ṡ10-17cm3/s for the reaction O2(1Δ)+O2(1Δ)->O2(1Σ) +O2(3Σ) - (1), 2.8ṡ10-13 cm3/s for the reactionO2(1Δ)+I(2P1/2)->O2(1Σ)+I(2P3/2) - (4) and 8.3ṡ10-11 cm3/s for the reaction O2(1Σ) +I2->O2(3Σ)+2I - (2). Analysis of experiments shows that for the wide range of oxygen-iodine medium composition the dissociation occurs via the chain of reactions (1), (2), O2(1Δ)+I(2P3/2)->O2(3Σ)+I(2P1/2), (4) and via cascade process I2+I(2P1/2)->I2(v)+I(2P3/2), I2(v)+O2(1Δ)→2I+O2(3Σ). Contributions of each mechanism in the dissociation of the iodine are comparable for the typical composition of the active medium of the supersonic chemical oxygen-iodine laser. The experiments did not reveal the contribution of vibrationally excited oxygen molecules in the dissociation of iodine. Thus, the experiments and the following conclusions are fully confirmed iodine dissociation mechanism previously proposed by Heidner et al. (J. Phys. Chem., 87, 2348 (1983)).

  6. Chemical kinetics of discharge-driven oxygen-iodine lasers

    NASA Astrophysics Data System (ADS)

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

    2007-05-01

    Oxygen-iodine lasers that utilize electrical discharges to produce O II(a1Δ) are currently being developed. The discharge generators differ from those used in chemical oxygen-iodine lasers in that they produce significant amounts of atomic oxygen and traces of ozone. As a consequence of these differences, the chemical kinetics of the discharge laser are markedly different from those of a conventional chemical oxygen-iodine laser (COIL). The reactions of O with iodine include channels that are both beneficial and detrimental to the laser. The beneficial reactions result in the dissociation of I II while the detrimental processes cause direct and indirect removal of I(2P 1/2) (denoted I*, the upper level of the laser). We have examined kinetic processes relevant to the laser through studies of photo-initiated reactions in N IIO/CO II/I II mixtures. The reactions have been monitored using absorption spectroscopy, laser induced fluorescence and time-resolved emission spectroscopy. It has been established that deactivation of I* by O atoms is a critical energy loss process. We have determined a rate constant of (1.2+/-0.1)×10 -11 cm 3 s -1 for this reaction. As part of this effort the branching fraction for the formation of O II(a) from the reaction of O(1D) with N IIO was determined to be 0.38. This result has implications for lasers based on photolysis of O 3/N IIO/I II mixtures and the formation of O II(a) in the upper atmosphere.

  7. Molecular Iodine Fluorescence Using a Green Helium-Neon Laser

    ERIC Educational Resources Information Center

    Williamson, J. Charles

    2011-01-01

    Excitation of molecular iodine vapor with a green (543.4 nm) helium-neon laser produces a fluorescence spectrum that is well suited for the upper-level undergraduate physical chemistry laboratory. Application of standard evaluation techniques to the spectrum yields ground electronic-state molecular parameters in good agreement with literature…

  8. Molecular Iodine Fluorescence Using a Green Helium-Neon Laser

    ERIC Educational Resources Information Center

    Williamson, J. Charles

    2011-01-01

    Excitation of molecular iodine vapor with a green (543.4 nm) helium-neon laser produces a fluorescence spectrum that is well suited for the upper-level undergraduate physical chemistry laboratory. Application of standard evaluation techniques to the spectrum yields ground electronic-state molecular parameters in good agreement with literature…

  9. Chemical oxygen iodine laser (COIL) technology and development

    NASA Astrophysics Data System (ADS)

    Duff, Edward A.; Truesdell, Keith A.

    2004-09-01

    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

  10. New approach to carbon monoxide poisoning treatment by laser-induced photodissociation of carboxyhemoglobin of cutaneous blood vessels

    NASA Astrophysics Data System (ADS)

    Asimov, Mustafo M.; Asimov, Rustam M.; Gisbrecht, Alexander

    2005-04-01

    A new approach to carbon monoxide poisoning treatment based on laser-induced photodissociation of the carboxyhemoglobin is proposed. Using the simple model of laser tissue interaction the action spectra of laser radiation on carboxyhemoglobin of cutaneous blood vessels has been calculated. The results of the calculatoins indicate that there is a relatively narrow spectral range in the visible region where one could effectively irradiate carboxyhemoglobin through the tissue not in a deep distances. In the case of deeper penetration, the action spectra of laser radiation shifts toward the longer wavelength region. Despite the similarity of the carboxyhemoglobin and oxyhemoglobin action spectra, the significant difference in quantum yields of photodissociation makes possible to develop an effective method of carbon monoxide poisoning treatment.

  11. Optically pumped oxygen-iodine laser

    NASA Astrophysics Data System (ADS)

    Zagidullin, Marsel V.; Malyshev, Mikhail S.

    2017-01-01

    A novel optical pumping scheme considering a two-step irradiation by light at wavelengths near 500 nm and 1315 nm is proposed in this work. Radiation at 500 nm is used to dissociate about 1% of iodine molecules. The radiation at 1315 nm excites atomic iodine to the 2P1/2 state. Singlet oxygen molecules are produced via the energy exchange process I(2P1/2)+O2(X3Σ)-> I(2P3/2)+O2(a1Δ), while I(2P1/2)+O2(a1Δ) energy pooling produces b1Σ oxygen. I(2P3/2) and O2(1Σ) then accelerate the dissociation of I2. After gas dynamic cooling in supersonic nozzle, active medium may reach 100 W cm-2 and small signal gain of 0.01 cm-1.

  12. Absolute frequency shifts of iodine cells for laser stabilization

    NASA Astrophysics Data System (ADS)

    Lazar, Josef; Hrabina, Jan; Jedlička, Petr; Číp, Ondřej

    2009-10-01

    We present an investigation of iodine cell purity and influence of contaminations upon frequency shifts of iodine-stabilized frequency-doubled Nd : YAG lasers. The study combines measurements of laser-induced fluorescence and evaluation through the Stern-Volmer formula, with direct measurement of frequency shifts referenced by means of an optical comb to a radiofrequency clock etalon. These indirect and direct approaches are compared and provide feedback on the cell manufacturing procedure. Significant improvement of the apparatus for the measurement of induced fluorescence is reported, leading to better repeatability of the results. The ultimate precision that can be achieved in measurements of the absolute frequency of a stabilized laser is discussed in terms of the cell quality.

  13. ArF laser photodissociation dynamics of furfuryl alcohol: LIF observation of OH state distribution

    NASA Astrophysics Data System (ADS)

    Chowdhury, Pradyot K.; Upadhyaya, Hari P.; Naik, Prakash D.

    2001-08-01

    The dynamics of furfuryl alcohol (FURFUROL) photodissociation at 193 nm is reported, using laser-induced fluorescence (LIF) of the nascent OH radical and RRKM theory. The nascent OH fragments are probed by LIF under collisionless conditions, to determine the initial product state distributions. There is no significant population (<2%) in excited vibrational levels of OH (X 2Π). However, the initial rotational state distribution is Boltzmann-like, characterized by a single rotational temperature Trot of 780±40 K. The average relative translational energy of the photofragments is determined to be 26±4 kJ mol -1. The measured rate constant for the FURFUROL dissociation vis-a-vis statistical RRKM theory, suggests a threshold dissociation energy of 357±20 kJ mol -1.

  14. Isotope separation of {sup 17}O by photodissociation of ozone with near-infrared laser irradiation

    SciTech Connect

    Hayashida, Shigeru; Kambe, Takashi; Sato, Tetsuya; Igarashi, Takehiro; Kuze, Hiroaki

    2012-04-01

    Oxygen-17 is a stable oxygen isotope useful for various diagnostics in both engineering and medical applications. Enrichment of {sup 17}O, however, has been very costly due to the lack of appropriate methods that enable efficient production of {sup 17}O on an industrial level. In this paper, we report the first {sup 17}O-selective photodissociation of ozone at a relatively high pressure, which has been achieved by irradiating a gas mixture of 10 vol% O{sub 3}-90 vol% CF{sub 4} with narrowband laser. The experiment was conducted on a pilot-plant scale. A total laser power of 1.6 W was generated by external-cavity diode lasers with all the laser wavelengths fixed at the peak of an absorption line of {sup 16}O{sup 16}O{sup 17}O around 1 {mu}m. The beams were introduced into a 25 -m long photoreaction cell under the sealed-off condition with a total pressure of 20 kPa. Lower cell temperature reduced the background decomposition of ozone, and at the temperature of 158 K, an {sup 17}O enrichment factor of 2.2 was attained.

  15. Direct solar-pumped iodine laser amplifier

    NASA Technical Reports Server (NTRS)

    Han, Kwang S.; Kim, K. H.; Stock, L. V.

    1986-01-01

    In order to evaluate the feasibility of the solar pumped dye laser, the parametric study of a dye laser amplifier pumped by a solar simulator and flashlamp was carried out, and the amplifier gains were measured at various pump beam irradiances on the dye cell. Rhodamine 6G was considered as a candidate for the solar pumped laser because of its good utilization of the solar spectrum and high quantum efficiency. The measurement shows that a solar concentration of 20,000 is required to reach the threshold of the dye. The work to construct a kinetic model algorithm which predicts the output parameter of laser was progressed. The kinetic model was improved such that there is good agreement between the theoretical model and experimental data for the systems defined previously as flashlamp pumped laser oscillator, and the long path length solar pumped laser.

  16. Iodine

    USGS Publications Warehouse

    Krukowski, S.T.

    2006-01-01

    In descending order, Chile, Japan and the United States have the largest iodine reserves. Chile produces iodine from iodate minerals while Japan and the United States produce it from sodium iodide solutions found in underground iodide solutions. Iodine is also produced from subterranean brines in Azerbaijan, Russia, Turkmenista, Indonesia and Uzbekistan. In 2005, iodine prices increased sharply to US$19 to US$23 then leveled off at US$23 to US$25.

  17. Nuclear-driven flashlamp pumping of the atomic iodine laser

    SciTech Connect

    Miley, G.H.

    1992-03-01

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

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

    SciTech Connect

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

    2014-01-31

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

  19. Excited states in the active media of oxygen - iodine lasers

    SciTech Connect

    Azyazov, V N

    2009-11-30

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

  20. Detection of OH radical in laser induced photodissociation of tetrahydrofuran at 193 nm

    NASA Astrophysics Data System (ADS)

    SenGupta, Sumana; Upadhyaya, Hari P.; Kumar, Awadhesh; Naik, Prakash D.; Bajaj, Paramanand

    2005-03-01

    On excitation at 193nm, tetrahydrofuran (THF) generates OH as one of the photodissociation products. The nascent energy state distribution of the OH radical was measured employing laser induced fluorescence technique. It is observed that the OH radical is formed mostly in the ground vibrational level, with low rotational excitation (˜3%). The rotational distribution of OH (v″=0,J) is characterized by rotational temperature of 1250±140K. Two spin-orbit states, Π3/22 and Π1/22 of OH are populated statistically. But, there is a preferential population in Λ doublet levels. For all rotational numbers, the Π+2(A') levels are preferred to the Π-2(A″) levels. The relative translational energy associated with the photoproducts in the OH channel is calculated to be 17.4±2.2kcalmol-1, giving an fT value of ˜36%, and the remaining 61% of the available energy is distributed in the internal modes of the other photofragment, i.e., C4H7. The observed distribution of the available energy agrees well with a hybrid model of energy partitioning, predicting an exit barrier of ≈16kcalmol-1. Based on both ab initio molecular orbital calculations and experimental results, a plausible mechanism for OH formation is proposed. The mechanism involves three steps, the C-O bond cleavage of the ring, H atom migration to the O atom, and the C-OH bond scission, in sequence, to generate OH from the ground electronic state of THF. Besides this high energy reaction channel, other photodissociation channels of THF have been identified by detecting the stable products, using Fourier transform infrared and gas chromatography.

  1. Development of the electric discharge oxygen-iodine laser

    NASA Astrophysics Data System (ADS)

    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

    In the hybrid electric discharge Oxygen-Iodine laser (ElectricOIL), the desired O II(a1Δ) 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(a1Δ) 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(1Δ) emission, I* emission, O-atom titrations, gain, and O II(1Δ) 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.

  2. ELEMENTS OF LASER SETUPS: Parameters of an electric-discharge generator of iodine atoms for a chemical oxygen—iodine laser

    NASA Astrophysics Data System (ADS)

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

    2009-01-01

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

  3. 20-Kw nitrogen diluent chemical oxygen-iodine laser

    NASA Astrophysics Data System (ADS)

    Yang, Tientsai T.; Bhowmik, Anup; Burde, David H.; Clark, Roy; Carroll, S.; Dickerson, Robert A.; Eblen, J.; Gylys, Vytas T.; Hsia, Y. C.; Humphreys, Richard H., Jr.; Moon, L. F.; Hurlock, Steve C.; Tomassian, A.

    2002-09-01

    A new Chemical Oxygen-Iodine Laser (COIL) has been developed and demonstrated at chlorine flow rates up to 1 gmol/s. The laser employs a cross flow jet oxygen generator operating with no diluent. The generator product flow enters the laser cavity at Mach 1 and is accelerated by mixing with 5 gmol/s, Mach 5 nitrogen diluent in an ejector nozzle array. The nitrogen also serves as the carrier for iodine. Vortex mixing is achieved through the use of mixing tabs at the nitrogen nozzle exit. Mixing approach design and analysis, including CFD analysis, led to the preferred nozzle configuration. The selected mixing enhancement design was tested in cold flow and the results are in good agreement with the CFD predictions. Good mixing was achieved within the desired cavity flow length of 20 cm and pressure recovery about 90 Torr was measured at the cavity exit. Finally, the design was incorporated into the laser and power extraction as high as 20 kw was measured at the best operating condition of 0.9 gmol/s. Stable resonator mode footprints showed desieable intensity profiles, which none of the sugar scoop profiles characteristic of the conventional COIL designs.

  4. Low threshold solar-pumped iodine laser

    NASA Technical Reports Server (NTRS)

    Deyoung, R. J.

    1986-01-01

    Solar-pumped lasing of i-C3F7I and n-C4F9I at lower solar concentrations (170 solar constants) and longer gain lengths than previous solar lasers is demonstrated, with potential application to the lasing needs of space. Two xenon arc solar simulators provide an AM0 spectrum over the 60-cm gain length, and output pulse energies of 70 mJ and an average power of 550 mW are achieved. Low pressure lasing times of 600 ms are reached, and the observed 0.074 percent slope efficiency could approach the 0.2 percent maximum theoretical efficiency. Due to less quenching of I(asterisk), n-C4F9I is found to be a superior lasant to i-C3F7I.

  5. Visible light generation of iodine atoms and I-I bonds: sensitized I(-) oxidation and I(3)(-) photodissociation.

    PubMed

    Gardner, James M; Abrahamsson, Maria; Farnum, Byron H; Meyer, Gerald J

    2009-11-11

    Direct 355 or 532 nm light excitation of TBAI(3), where TBA is tetrabutyl ammonium, in CH(3)CN at room temperature yields an iodine atom, I(*), and an iodine radical anion, I(2)(-*). In the presence of excess iodide, the iodine atom reacts quantitatively to yield a second equivalent of I(2)(-*) with a rate constant of k = 2.5 +/- 0.4 x 10(10) M(-1) s(-1). The I(2)(-*) intermediates are unstable with respect to disproportionation and yield initial reactants, k = 3.3 +/- 0.1 x 10(9) M(-1) s(-1). The coordination compound Ru(bpz)(2)(deeb)(PF(6))(2), where bpz is 2,2'-bipyrazine and deeb is 4,4'-(C(2)H(5)CO(2))(2)-2,2'-bipyridine, was prepared and characterized for mechanistic studies of iodide photo-oxidation in acetonitrile at room temperature. Ru(bpz)(2)(deeb)(2+) displayed a broad metal-to-ligand charge transfer (MLCT) absorption band at 450 nm with epsilon = 1.7 x 10(4) M(-1) cm(-1). Visible light excitation resulted in photoluminescence with a corrected maximum at 620 nm, a quantum yield phi = 0.14, and an excited state lifetime tau = 1.75 micros from which k(r) = 8.36 x 10(4) s(-1) and k(nr) = 5.01 x 10(5) s(-1) were abstracted. Arrhenius analysis of the temperature dependent excited state lifetime revealed an activation energy of approximately 2500 cm(-1) and a pre-exponential factor of 10(10) s(-1), assigned to activated surface crossing to a ligand field or MLCT excited state. Steady state light excitation of Ru(bpz)(2)(deeb)(2+) in a 20 mM TBAI acetonitrile solution resulted in ligand loss photochemistry with a quantum yield of 5 x 10(-5). The MLCT excited state was dynamically quenched by iodide with K(sv) = 1.1 x 10(5) M(-1) and k(q) = 6.6 +/- 0.3 x 10(10) M(-1) s(-1), a value consistent with diffusion-limited electron transfer. Excited state hole transfer to iodide was quantitative but the product yield was low due to poor cage escape yields, phi(CE) = 0.042 +/- 0.001. Nanosecond transient absorption was used to quantify the appearance of two

  6. Discharge pumped iodine monofluoride laser: Operating parameters and collisional kinetics

    NASA Astrophysics Data System (ADS)

    Dlabal, M. L.

    Lasing was observed at five different wavelengths ranging from 472 to 497 nm from discharge pumped iodine monofluoride (IF). At the optimum output coupling 4 mJ was measured in a 30 ns FWHM pulse with a peak power of 140 kW. The merits and deficiencies of both HI and CF3I as iodine donors are discussed. Measurements show the small signal gain to be or = 1%/cm from 478 to 497 nm, while much of the absorption is due to excited state of He. Limited line tunability is also demonstrated by using an internally mounted Littrow prism. Quenching measurements of the upper and lowr laser level show the lower level to be removed more rapidly, thereby avoiding bottlenecking. In addition, the upper level spontaneous emission lifetime is measured to 17.2 + or - 4.0 ns. Finally studies of the formation kinetics of the upper laser level of IF show I (4P) atoms to be an immediate precursor, while the F (4P) atoms are unimportant.

  7. Fragmentation due to centrifugal forces in the photodissociation of H{sub 2}{sup +} in intense laser fields

    SciTech Connect

    Fischer, Michael; Schmidt, Ruediger; Lorenz, Ulf; Schmidt, Burkhard

    2011-09-15

    By means of quantum-dynamical and classical trajectory calculations of H{sub 2}{sup +} photodissociation in strong laser fields, it is shown that for certain combinations of pulse durations and intensities the rotational dynamics can lead to fragmentation. In that case, the photofragments exhibit characteristic angular distributions. The classical calculations provide a transparent physical picture of this mechanism which is also very well established in collisions between atomic nuclei or liquid droplets: nonrotating systems are stable, whereas rotating systems fragment due to the decrease of the fragmentation barrier with increasing angular momentum.

  8. Tracing the photodissociation probability of H{sub 2}{sup +} in intense fields using chirped laser pulses

    SciTech Connect

    Prabhudesai, Vaibhav S.; Natan, Adi; Bruner, Barry D.; Diner, Adi; Silberberg, Yaron; Lev, Uri; Heber, Oded; Zajfman, Daniel; Strasser, Daniel; Schwalm, D.; Ben-Itzhak, Itzik; Hua, J. J.; Esry, B. D.

    2010-02-15

    The temporal evolution of the dissociation probabilities for various vibrational levels of H{sub 2}{sup +} is observed in terms of shifts in the kinetic energy release dissociation spectra, induced by linearly chirped intense laser pulses. In contrast to previous observations, in which no dependence on the chirp sign was observed, the energy spectrum reported here shows peak shifts, up for negative chirp and down for positive chirp. For some vibrational levels, dissociation takes place early on in the pulse; hence, care must be taken while interpreting the effect of pulse duration in photodissociation studies. This interpretation is supported by numerical solutions of the time-dependent Schroedinger equation.

  9. An alternative laser driven photodissociation mechanism of pyrrole via π*1σ/S0 conical intersection

    NASA Astrophysics Data System (ADS)

    Nandipati, K. R.; Lan, Z.; Singh, H.; Mahapatra, S.

    2017-06-01

    A first principles quantum dynamics study of N-H photodissociation of pyrrole on the S0-1π σ*(A12) coupled electronic states is carried out with the aid of an optimally designed UV-laser pulse. A new photodissociation path, as compared to the conventional barrier crossing on the π*1σ state, opens up upon electronic transitions under the influence of pump-dump laser pulses, which efficiently populate both the dissociation channels. The interplay of electronic transitions due both to vibronic coupling and the laser pulse is observed in the control mechanism and discussed in detail. The proposed control mechanism seems to be robust, and not discussed in the literature so far, and is expected to trigger future experiments on the π*1σ photochemistry of molecules of chemical and biological importance. The design of the optimal pulses and their application to enhance the overall dissociation probability is carried out within the framework of optimal control theory. The quantum dynamics of the system in the presence of pulse is treated by solving the time-dependent Schrödinger equation in the semi-classical dipole approximation.

  10. Injectant mole-fraction imaging in compressible mixing flows using planar laser-induced iodine fluorescence

    NASA Technical Reports Server (NTRS)

    Hartfield, Roy J., Jr.; Abbitt, John D., III; Mcdaniel, James C.

    1989-01-01

    A technique is described for imaging the injectant mole-fraction distribution in nonreacting compressible mixing flow fields. Planar fluorescence from iodine, seeded into air, is induced by a broadband argon-ion laser and collected using an intensified charge-injection-device array camera. The technique eliminates the thermodynamic dependence of the iodine fluorescence in the compressible flow field by taking the ratio of two images collected with identical thermodynamic flow conditions but different iodine seeding conditions.

  11. Injectant mole-fraction imaging in compressible mixing flows using planar laser-induced iodine fluorescence

    NASA Technical Reports Server (NTRS)

    Hartfield, Roy J., Jr.; Abbitt, John D., III; Mcdaniel, James C.

    1989-01-01

    A technique is described for imaging the injectant mole-fraction distribution in nonreacting compressible mixing flow fields. Planar fluorescence from iodine, seeded into air, is induced by a broadband argon-ion laser and collected using an intensified charge-injection-device array camera. The technique eliminates the thermodynamic dependence of the iodine fluorescence in the compressible flow field by taking the ratio of two images collected with identical thermodynamic flow conditions but different iodine seeding conditions.

  12. Threshold kinetics of a solar-simulator-pumped iodine laser

    NASA Technical Reports Server (NTRS)

    Wilson, J. W.; Lee, Y.; Weaver, W. R.; Humes, D. H.; Lee, J. H.

    1984-01-01

    A model of the chemical kinetics of the n-C3F7I solar-simulator-pumped iodine laser is utilized to study the major kinetic processes associated with the threshold behavior of this experimental system. Excited-state diffusion to the cell wall is the dominant limiting factor below 5 torr. Excited-state diffusion to the cell wall is the dominant limiting factor below 5 torr. Excited-state recombination with the alkyl radical and quenching by the parent gas control threshold at higher pressures. Treatment of the hyperfine splitting and uncertainty in the pressure broadening are important factors in fixing the threshold level. In spite of scatter in the experimental data caused by instabilities in the simulator high-pressure high-pressure arc, reasonable agreement is achieved between the model and experiment. Model parameters arrived at are within the uncertainty range of values found in the literature.

  13. Analysis of processes participating during intense iodine-laser-beam interactions with laser-produced plasmas

    NASA Astrophysics Data System (ADS)

    Láska, L.; Badziak, J.; Jungwirth, K.; Kálal, M.; Krása, J.; Krouský, E.; Kubeš, P.; Margarone, D.; Parys, P.; Pfeifer, M.; Rohlena, K.; Rosiński, M.; Ryć, L.; Skála, J.; Torrisi, L.; Ullschmied, J.; Velyhan, A.; Wolowski, J.

    2010-10-01

    The high-power iodine laser PALS was used to generate highly charged Ta ions and to study non-linear processes in laser-produced plasma. Longitudinal structures of the expanding plasma, obtained by using an X-ray streak camera on a time scale ∼ 2 ns, are presented. Various bright spots (moon-like, half-moon-like), expansion-path curvature and even their splitting were recorded. These phenomena are ascribed to the effect of the magnetic field that is self-generated at high laser intensities.

  14. Spectroscopy and primary processes in the photolysis of iodides for iodine photodissociation lasers (review)

    SciTech Connect

    Pravilov, A.

    1981-07-01

    An analysis is made of the general laws governing the spectroscopy of diatomic and polyatomic iodides in the UV--VUV parts of the spectrum and their spectroscopic properties are compared with published data on the primary photolysis processes. Particular attention is paid to alkyl iodides and perfluoroalkyl iodides. An attempt is made to interpret the observed dependences.

  15. Stabilized Iodine Flow for Long Run Time Chemical Oxygen-Iodine Lasers

    DTIC Science & Technology

    1992-10-01

    United States Government retains a nonexclusive royalty- free license to publish or reproduce the material contained herein, or allow others to do so, for...4 Flowchart of iodine control logic. 8 5 Variation of iodine flow on the RADICL device in the absence of active control. 11 6 Variation of iodine...flow on the RADICL device in the presence of active control. 11 7 The run helium purposely started low to observe the recovery of the control system. 13

  16. Investigation of laser-induced iodine fluorescence for the measurement of density in compressible flows

    NASA Technical Reports Server (NTRS)

    Mcdaniel, J. C., Jr.

    1982-01-01

    Laser induced fluorescence is an attractive nonintrusive approach for measuring molecular number density in compressible flows although this technique does not produce a signal that is directly related to the number density. Saturation and frequency detuned excitation are explored as means for minimizing the quenching effect using iodine as the molecular system because of its convenient absorption spectrum. Saturation experiments indicate that with available continuous wave laser sources of Gaussian transverse intensity distribution only partial saturation could be achieved in iodine at the pressures of interest in gas dynamics. Using a fluorescence lineshape theory, it is shown that for sufficiently large detuning of a narrow bandwidth laser from a molecular transition, the quenching can be cancelled by collisional broadening over a large range of pressures and temperatures. Experimental data obtained in a Mach 4.3 underexpanded jet of nitrogen seeded with iodine for various single mode argon laser detunings from a strong iodine transition at 5145 A are discussed.

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

    NASA Astrophysics Data System (ADS)

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

    2002-05-01

    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.

  18. Laser ion beam photodissociation studies of model amino acids and peptides

    SciTech Connect

    Techlenburg, R.E. Jr.; Miller, M.N.; Russell, D.H. )

    1989-02-15

    Visible (458-514.5 nm) and uv (333-385 nm) photodissociation of the (M + H){sup +} ions of dinitrophenyl (DNP) derivatized amino acids and peptides is reported. Photoexcitation of the DNP peptides by a visible proton results in fragmentation of the peptide chain with little fragmentation within the chromophore. Conversely, uv photoexcitation of the DNP peptides results in fragmentation of the chromophore as well as the peptide chain, but loss of NO or NO{sub 2} (within the chromophore) often dominates the photofragment ion spectrum. These results are rationalized with particular emphasis on energy-selective dissociation channels of large ionic systems. DNP-leucine and DNP-isoleucine (M + H){sup +} can be differentiated on the basis of photodissociation reactions which yield distonic radical cations. The rate of dissociation of photoexcited ions of DNP peptides is shown to decrease with increasing molecular weight (degrees of freedom). Lastly, comparisons between photodissociation and collision-induced dissociation as a structural probe are presented. 55 refs., 8 figs., 3 tabs.

  19. State-Resolved and State-To Photodissociation Study of CO_2 by Two-Color Vuv-Vuv Laser Pump-Probe Method

    NASA Astrophysics Data System (ADS)

    Lu, Zhou; Chang, Yih-Chung; Jackson, William M.; Ng, Cheuk-Yiu

    2014-06-01

    CO_2 is known as a strong contributor to the greenhouse effect, and its concentration in the atmosphere increases annually. Photodissociation of CO_2 is considered an important photochemical sink of CO_2 molecules which could ultimately limit the increase of CO_2 concentration in the atmosphere. Since CO_2 molecules have negligibly small absorption from the visible region down to about 200 nm, photodissociation studies of CO_2 in the vacuum ultraviolet (VUV) region below 200 nm are of great importance in understanding the photochemical decomposition processes of CO_2 molecules. State-to-state photodissociation of CO_2 has been investigated by employing two independent VUV lasers and the time-slice velocity-map-imaging-photoion (VMI-PI) method. The spin-allowed photoproduct channels, CO(X1Σ+) + O(1D), CO(X1Σ+) + O(1S), CO(a3Π) + O(3PJ), and C(3PJ) + O2(X3Σg-), and the spin-forbidden photoproduct channel, CO(X1Σ+) + O(3PJ), were directly observed from the time-slice VMI-PI images. The angular anisotropic parameters were evaluated, allowing us to estimate the lifetimes for the formations of these dissociation channels. To the authors' knowledge, the current CO_2 photodissociation studies show for the first time that all of the energetically available photodissociation channels are formed in the CO_2 photoexcitation energy of interest.

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

    NASA Technical Reports Server (NTRS)

    Shiner, C. S.

    1986-01-01

    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.

  1. Laser pulse design using optimal control theory-based adaptive simulated annealing technique: vibrational transitions and photo-dissociation

    NASA Astrophysics Data System (ADS)

    Nath, Bikram; Mondal, Chandan Kumar

    2014-08-01

    We have designed and optimised a combined laser pulse using optimal control theory-based adaptive simulated annealing technique for selective vibrational excitations and photo-dissociation. Since proper choice of pulses for specific excitation and dissociation phenomena is very difficult, we have designed a linearly combined pulse for such processes and optimised the different parameters involved in those pulses so that we can get an efficient combined pulse. The technique makes us free from choosing any arbitrary type of pulses and makes a ground to check their suitability. We have also emphasised on how we can improve the performance of simulated annealing technique by introducing an adaptive step length of the different variables during the optimisation processes. We have also pointed out on how we can choose the initial temperature for the optimisation process by introducing heating/cooling step to reduce the annealing steps so that the method becomes cost effective.

  2. Fast beam studies of free radical photodissociation

    SciTech Connect

    Neumark, D.M.

    1993-12-01

    The authors have developed a novel technique for studying the photodissociation spectroscopy and dynamics of free radicals. In these experiments, radicals are generated by laser photodetachment of a fast (6-8 keV) mass-selected negative ion beam. The resulting radicals are photodissociated with a second laser, and the photofragments are collected and detected with high efficiency using a microchannel plate detector. The overall process is: ABC{sup -} {yields} ABC + e{sup -} {yields} A + BC, AB + C. Two types of fragment detection schemes are used. To map out the photodissociation cross-section of the radical, the photodissociation laser is scanned and the total photofragment yield is measured as a function of wavelength. In other experiments, the photodissociation frequency is fixed and the photofragment masses, kinetic energy release, and scattering angle is determined for each photodissociation event.

  3. Improved production of Br atoms near zero speed by photodissociating laser aligned Br{sub 2} molecules

    SciTech Connect

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

    2014-10-28

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

  4. LASER BEAMS AND RESONATORS: Unstable resonators of high-power chemical oxygen—iodine lasers

    NASA Astrophysics Data System (ADS)

    Savin, A. V.; Strakhov, S. Yu; Druzhinin, S. L.

    2006-09-01

    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.

  5. Communication: State-to-state photodissociation study by the two-color VUV-VUV laser pump-probe time-slice velocity-map-imaging-photoion method

    NASA Astrophysics Data System (ADS)

    Gao, Hong; Song, Yu; Jackson, William M.; Ng, C. Y.

    2013-05-01

    We demonstrate that combining two independently tunable vacuum ultraviolet (VUV) lasers and the time-slice velocity-map-imaging-photoion (VMI-PI) method allows the rovibronically state-selected photodissociation study of CO in the VUV region along with the state-selective detection of product C(3P0,1,2) using the VUV-UV (1+1') resonance-enhanced photoionization and the VUV Rydberg autoionization methods. Both tunable VUV lasers are generated based on the two-photon resonance-enhanced four-wave mixing scheme using a pulsed rare gas jet as the nonlinear medium. The observed fine-structure distributions of product C(3PJ), J = 0, 1, and 2, are found to depend on the CO rovibronic state populated by VUV photoexcitation. The branching ratios for C(3P0) + O(3PJ): C(3P0) + O(1D2), C(3P1) + O(3PJ): C(3P1) + O(1D2), and C(3P2) + O(3PJ): C(3P2) + O(1D2), which were determined based on the time-slice VMI-PI measurements of C+ ions formed by J-state selective photoionization sampling of C(3P0,1,2), also reveal strong dependences on the spin-orbit state of C(3P0,1,2). By combining the measured branching ratios and fine-structure distributions of C(3P0,1,2), we have determined the correlated distributions of C(3P0,1,2) accompanying the formation of O(1D2) and O(3PJ) produced in the VUV photodissociation of CO. The success of this demonstration experiment shows that the VUV photodissociation pump-VUV photoionization probe method is promising for state-to-state photodissociation studies of many small molecules, which are relevant to planetary atmospheres as well as fundamental understanding of photodissociation dynamics.

  6. Relative quantum yield of I-asterisk(2P1/2) in the tunable laser UV photodissociation of i-C3F7I and n-C3F7I - Effect of temperature and exciplex emission

    NASA Technical Reports Server (NTRS)

    Smedley, J. E.; Leone, S. R.

    1983-01-01

    Wavelength-specific relative quantum yields of metastable I from pulsed laser photodissociation of i-C3F7I and n-C3F7I in the range 265-336 nm are determined by measuring the time-resolved infrared emission from the atomic I(P-2(1/2) P-2(3/2) transition. It is shown that although this yield appears to be unity from 265 to 298 nm, it decreases dramatically at longer wavelengths. Values are also reported for the enhancement of emission from metastable I due to exciplex formation at several temperatures. The exciplex formation emission increases linearly with parent gas pressure, but decreases with increasing temperature. Absorption spectra of i- and n-C3F7I between 303 and 497 K are presented, and the effect of temperature on the quantum yields at selected wavelengths greater than 300 nm, where increasing the temperature enhances the absorption considerably, are given. The results are discussed in regard to the development of solar-pumped iodine lasers.

  7. Relative quantum yield of I-asterisk(2P1/2) in the tunable laser UV photodissociation of i-C3F7I and n-C3F7I - Effect of temperature and exciplex emission

    NASA Technical Reports Server (NTRS)

    Smedley, J. E.; Leone, S. R.

    1983-01-01

    Wavelength-specific relative quantum yields of metastable I from pulsed laser photodissociation of i-C3F7I and n-C3F7I in the range 265-336 nm are determined by measuring the time-resolved infrared emission from the atomic I(P-2(1/2) P-2(3/2) transition. It is shown that although this yield appears to be unity from 265 to 298 nm, it decreases dramatically at longer wavelengths. Values are also reported for the enhancement of emission from metastable I due to exciplex formation at several temperatures. The exciplex formation emission increases linearly with parent gas pressure, but decreases with increasing temperature. Absorption spectra of i- and n-C3F7I between 303 and 497 K are presented, and the effect of temperature on the quantum yields at selected wavelengths greater than 300 nm, where increasing the temperature enhances the absorption considerably, are given. The results are discussed in regard to the development of solar-pumped iodine lasers.

  8. Noise-immune laser receiver - transmitters with the quantum sensitivity limit

    SciTech Connect

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

    2009-11-30

    We consider the operation principles of noise-immune near-IR receiver - transmitters with the quantum sensitivity limit, in which active quantum filters based on iodine photodissociation quantum amplifiers and iodine lasers are used. The possible applications of these devices in laser location, laser space communication, for the search for signals from extraterrestrial civilisations and sending signals to extraterrestrial civilisations are discussed. (invited paper)

  9. Determination of iodine in oyster tissue by isotope dilution laser resonance ionization mass spectrometry

    SciTech Connect

    Fassett, J.D.; Murphy, T.J. )

    1990-02-15

    The technique of laser resonance ionization mass spectrometry has been combined with isotope dilution analysis to determine iodine in oyster tissue. The long-lived radioisotope, 129I, was used to spike the samples. Samples were equilibrated with the 129I, wet ashed under controlled conditions, and iodine separated by coprecipitation with silver chloride. The analyte was dried as silver ammonium iodide upon a tantalum filament from which iodine was thermally desorbed in the resonance ionization mass spectrometry instrument. A single-color, two-photon resonant plus one-photon ionization scheme was used to form positive iodine ions. Long-lived iodine signals were achieved from 100 ng of iodine. The precision of 127I/129I measurement has been evaluated by replicate determinations of the spike, the spike calibration samples, and the oyster tissue samples and was 1.0%. Measurement precision among samples was 1.9% for the spike calibration and 1.4% for the oyster tissue. The concentration of iodine determined in SRM 1566a, Oyster Tissue, was 4.44 micrograms/g with an estimate of the overall uncertainty for the analysis of +/- 0.12 microgram/g.

  10. Determination of iodine in oyster tissue by isotope dilution laser resonance ionization mass spectrometry.

    PubMed

    Fassett, J D; Murphy, T J

    1990-02-15

    The technique of laser resonance ionization mass spectrometry has been combined with isotope dilution analysis to determine iodine in oyster tissue. The long-lived radioisotope, 129I, was used to spike the samples. Samples were equilibrated with the 129I, wet ashed under controlled conditions, and iodine separated by coprecipitation with silver chloride. The analyte was dried as silver ammonium iodide upon a tantalum filament from which iodine was thermally desorbed in the resonance ionization mass spectrometry instrument. A single-color, two-photon resonant plus one-photon ionization scheme was used to form positive iodine ions. Long-lived iodine signals were achieved from 100 ng of iodine. The precision of 127I/129I measurement has been evaluated by replicate determinations of the spike, the spike calibration samples, and the oyster tissue samples and was 1.0%. Measurement precision among samples was 1.9% for the spike calibration and 1.4% for the oyster tissue. The concentration of iodine determined in SRM 1566a, Oyster Tissue, was 4.44 micrograms/g with an estimate of the overall uncertainty for the analysis of +/- 0.12 microgram/g.

  11. Planar temperature measurement in compressible flows using laser-induced iodine fluorescence

    NASA Technical Reports Server (NTRS)

    Hartfield, Roy J., Jr.; Hollo, Steven D.; Mcdaniel, James C.

    1991-01-01

    A laser-induced iodine fluorescence technique that is suitable for the planar measurement of temperature in cold nonreacting compressible air flows is investigated analytically and demonstrated in a known flow field. The technique is based on the temperature dependence of the broadband fluorescence from iodine excited by the 514-nm line of an argon-ion laser. Temperatures ranging from 165 to 245 K were measured in the calibration flow field. This technique makes complete, spatially resolved surveys of temperature practical in highly three-dimensional, low-temperature compressible flows.

  12. Planar temperature measurement in compressible flows using laser-induced iodine fluorescence

    NASA Technical Reports Server (NTRS)

    Hartfield, Roy J., Jr.; Hollo, Steven D.; Mcdaniel, James C.

    1991-01-01

    A laser-induced iodine fluorescence technique that is suitable for the planar measurement of temperature in cold nonreacting compressible air flows is investigated analytically and demonstrated in a known flow field. The technique is based on the temperature dependence of the broadband fluorescence from iodine excited by the 514-nm line of an argon-ion laser. Temperatures ranging from 165 to 245 K were measured in the calibration flow field. This technique makes complete, spatially resolved surveys of temperature practical in highly three-dimensional, low-temperature compressible flows.

  13. Tandem time-of-flight mass spectrometer for photodissociation of biopolymer ions generated by matrix-assisted laser desorption ionization (MALDI-TOF-PD-TOF) using a linear-plus-quadratic potential reflectron.

    PubMed

    Oh, Joo Yeon; Moon, Jeong Hee; Kim, Myung Soo

    2004-08-01

    A tandem time-of-flight mass spectrometer for the study of photodissociation of biopolymer ions generated by matrix-assisted laser desorption ionization was designed and constructed. A reflectron with linear and quadratic (LPQ) potential components was used. Characteristics of the LPQ reflectron and its utility as the second stage analyzer of the tandem mass spectrometer were investigated. Performance of the instrument was tested by observing photodissociation of [M + H](+) from angiotensin II, a prototype polypeptide. Quality of the photodissociation tandem mass spectrum was almost comparable to that of the post-source decay spectrum. Monoisotopic selection of the parent ion was possible, which was achieved through the ion beam-laser beam synchronization. General theoretical considerations needed for a successful photodissociation of large biopolymer ions are also presented.

  14. Modeling of optimal conditions for oxyhemoglobin photodissociation in laser-irradiated biotissue

    NASA Astrophysics Data System (ADS)

    Barun, V. V.; Ivanov, A. P.; Bashkatov, A. N.; Genina, E. A.; Tuchin, V. V.

    2013-08-01

    Based on the theory of radiation transfer and a model that describes the structure and optical properties of biotissues, we have found spectral conditions of irradiation of the skin surface that ensure efficient generation of molecular oxygen O2 in the dermis due to the photodissociation of blood oxyhemoglobin. We show that, for maximal local O2 formation at depths z ≤ 0.2 mm, 0.2 mm < z ≤ 0.9 mm, 0.9 mm < z ≤ 2.5 mm, and z > 2.5 mm, it is more effective to use wavelengths in the intervals 418 ± 5, 575 ± 5, 585 ± 5, and 600 ± 5 nm, respectively. Physical reasons for the shift of optimal wavelengths toward the red range of the spectrum are described. We show that they are based on the selectivity of optical properties of the skin biotissue, which acts as of a kind of spectral filter the transmission curve of which depends on the depth. It is found that irradiation at a wavelength near 575 nm is optimal for the generation of a maximal amount of O2 in the intire bulk of the dermis.

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

    SciTech Connect

    Zhang Jiao; Wang Yanhui; Wang Dezhen; Duo Liping; Li Guofu

    2013-04-15

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

  16. Initial state-specific photodissociation dynamics of pyrrole via 1 π σ ∗/ S 0 conical intersection initiated with optimally controlled UV-laser pulses

    NASA Astrophysics Data System (ADS)

    Nandipati, K. R.; Kanakati, Arun Kumar; Singh, H.; Lan, Z.; Mahapatra, S.

    2017-09-01

    Optimal initiation of quantum dynamics of N-H photodissociation of pyrrole on the S0-1πσ∗(1A2) coupled electronic states by UV-laser pulses in an effort to guide the subsequent dynamics to dissociation limits is studied theoretically. Specifically, the task of designing optimal laser pulses that act on initial vibrational states of the system for an effective UV-photodissociation is considered by employing optimal control theory. The associated control mechanism(s) for the initial state dependent photodissociation dynamics of pyrrole in the presence of control pulses is examined and discussed in detail. The initial conditions determine implicitly the variation in the dissociation probabilities for the two channels, upon interaction with the field. The optimal pulse corresponds to the objective fixed as maximization of overall reactive flux subject to constraints of reasonable fluence and quantum dynamics. The simple optimal pulses obtained by the use of genetic algorithm based optimization are worth an experimental implementation given the experimental relevance of πσ∗-photochemistry in recent times.

  17. Quantitative measurement of density and velocity in compressible flows using laser-induced iodine fluorescence

    NASA Technical Reports Server (NTRS)

    Mcdaniel, J. C.

    1983-01-01

    A nonintrusive optical technique for the quantitative measurement of molecular density and velocity at a point or in an entire cross-sectional plane of a compressible flowfield is reported. Iodine molecules, seeded into the flowfield reservoir, are excited by a tunable narrow-bandwidth laser and the resulting spatially-resolved fluorescence is collected by a single- or multiple-element detector. A theoretical model for the iodine laser-induced fluorescence process is essential for quantitative measurements and is developed using a rate-equation approach. Density measurements using laser-induced fluorescence are normally complicated by collisional quenching; however, the theory predicts that the off-resonant fluorescent signal is directly proportional to density. Velocity is directly related to the Doppler shift of the iodine absorption line, determined by monitoring the broadband fluorescent signal as the laser is tuned in frequency. Experiments in a steady supersonic flowfield are compared with numerical calculations to demonstrate the accuracy of the approach for density and velocity measurement and the lack of perturbation to the flowfield by the iodine seeding. Extensions of the current approach to density and velocity measurement in lower Mach number flows, to the measurement of pressure and temperature, and to temporally-resolved measurements are discussed.

  18. Analytical evaluation of kinetics in oxygen-iodine laser nozzle flows

    NASA Astrophysics Data System (ADS)

    Quan, Victor

    1997-05-01

    The reaction processes in chemical oxygen-iodine laser nozzle flows are investigated analytically. In the transport equations for the reacting species, order-of-magnitude arguments are applied to retain the dominant terms. The effects of local flow properties on the chemical kinetics are found in terms of a transformed coordinate which is a function of the nozzle shape and inlet flow conditions. Approximate closed-form solutions for the iodine dissociation, oxygen yield, and the dissociation cost are derived. The results indicate that the chemical processes occur predominantly in the subsonic section of the nozzle where the pressure is high and velocity is low.

  19. Simultaneous multiple-point velocity measurements using laser-induced iodine fluorescence

    NASA Technical Reports Server (NTRS)

    Mcdaniel, J. C.; Hiller, B.; Hanson, R. K.

    1983-01-01

    A technique is demonstrated for measuring velocity at multiple locations in a plane of a gaseous flowfield using Doppler-shifted absorption with fluorescence detection from iodine molecules, excited by a sheet of tunable single-axial-mode argon-ion laser radiation at 514.5 nm. Measurements were made simultaneously at 10,000 points in an iodine-seeded supersonic flow field with a 100 x 100 element photodiode array camera and were found to agree well with a numerical solution for the velocity field. The accuracy with which a component of velocity can be measured is limited, in the current approach, by the iodine linewidth to about 5 m/sec.

  20. Communication: State-to-state photodissociation study by the two-color VUV-VUV laser pump-probe time-slice velocity-map-imaging-photoion method.

    PubMed

    Gao, Hong; Song, Yu; Jackson, William M; Ng, C Y

    2013-05-21

    We demonstrate that combining two independently tunable vacuum ultraviolet (VUV) lasers and the time-slice velocity-map-imaging-photoion (VMI-PI) method allows the rovibronically state-selected photodissociation study of CO in the VUV region along with the state-selective detection of product C((3)P(0,1,2)) using the VUV-UV (1+1') resonance-enhanced photoionization and the VUV Rydberg autoionization methods. Both tunable VUV lasers are generated based on the two-photon resonance-enhanced four-wave mixing scheme using a pulsed rare gas jet as the nonlinear medium. The observed fine-structure distributions of product C((3)P(J)), J = 0, 1, and 2, are found to depend on the CO rovibronic state populated by VUV photoexcitation. The branching ratios for C((3)P0) + O((3)P(J)): C((3)P0) + O((1)D2), C((3)P1) + O((3)P(J)): C((3)P1) + O((1)D2), and C((3)P2) + O((3)PJ): C((3)P2) + O((1)D2), which were determined based on the time-slice VMI-PI measurements of C(+) ions formed by J-state selective photoionization sampling of C((3)P(0,1,2)), also reveal strong dependences on the spin-orbit state of C((3)P(0,1,2)). By combining the measured branching ratios and fine-structure distributions of C((3)P(0,1,2)), we have determined the correlated distributions of C((3)P(0,1,2)) accompanying the formation of O((1)D2) and O((3)P(J)) produced in the VUV photodissociation of CO. The success of this demonstration experiment shows that the VUV photodissociation pump-VUV photoionization probe method is promising for state-to-state photodissociation studies of many small molecules, which are relevant to planetary atmospheres as well as fundamental understanding of photodissociation dynamics.

  1. Calculations on Isotope Separation by Laser Induced Photodissociation of Polyatomic Molecules. Final Report

    DOE R&D Accomplishments Database

    Lamb, W. E. Jr.

    1978-11-01

    This report describes research on the theory of isotope separation produced by the illumination of polyatomic molecules by intense infrared laser radiation. Newton`s equations of motion were integrated for the atoms of the SF{sub 6} molecule including the laser field interaction. The first year`s work has been largely dedicated to obtaining a suitable interatomic potential valid for arbitrary configurations of the seven particles. This potential gives the correct symmetry of the molecule, the equilibrium configuration, the frequencies of the six distinct normal modes of oscillation and the correct (or assumed) value of the total potential energy of the molecule. Other conditions can easily be imposed in order to obtain a more refined potential energy function, for example, by making allowance for anharmonicity data. A suitable expression was also obtained for the interaction energy between a laser field and the polyatomic molecule. The electromagnetic field is treated classically, and it would be easily possible to treat the cases of time dependent pulses, frequency modulation and noise.

  2. Flow Measurements of Translational-Rotational Nonequilibrium Using Laser-Induced Iodine Fluorescence

    NASA Astrophysics Data System (ADS)

    Cecil, Eric; McDaniel, James C.

    2011-05-01

    A shock wave impingement flow was studied under low temperature, low density conditions in a hypersonic free-jet wind tunnel. A sharp-edged flat plate was placed at zero incidence in the hypersonic core of a free-jet of nitrogen gas at Mach 12; a right circular cylinder mounted in the middle of the plate projected out normal to the plate surface. The oblique shock produced at the plate leading edge impinged on the detached bow shock wave produced by the cylinder. The symmetry plane in the flow was studied using a laser sheet-beam probe from a narrow-bandwidth laser source, which induced fluorescence in iodine molecules seeded in the gas. Fluorescence patterns produced by the sheet-beam were recorded by a charge-coupled device camera as the laser frequency was tuned in increments over a range spanning two distinct absorption lines in the iodine spectrum. The fluorescence intensity-versus-laser excitation frequency data recorded at each pixel was least-squares fitted to a nonequilibrium model of the iodine spectrum to estimate local translational and rotational temperature, velocity, and density. Contour plots of these results are presented at a resolution equal to roughly one mean-free-path of the oncoming flow at the plate leading edge. Profile plots of translational and rotational temperature on the plate are presented.

  3. Lasic -Cavity-enhanced molecular iodine laser frequency stabilization for space projects

    NASA Astrophysics Data System (ADS)

    Turazza, Oscar; Acef, O.; Auger, G.; Halloin, H.; Duburck, F.; Plagnol, E.; Holleville, D.; Dimarcq, N.; Binetruy, P.; Brillet, A.; Lemonde, P.; Devismes, E.; Prat, P.; Lours, M.; Tuckey, P.; Argence, B.

    We present work in progress at SYRTE, APC and ARTEMIS aiming at stabilizing the frequency of a Nd:YAG laser using saturated absorption spectroscopy of molecular iodine 127I2. The novel design of the LASIC project allows for robustness and compacity while achieving high-performance phase noise suppression. The project is a follow-up of the laser stabilization work started at Artemis and continued at APC. The use of a low-finesse bow-tie optical cavity around the iodine absorber, combined with an adapted high-frequency modulation of the laser phase -NICE-OHMS technique-yields shot-noise limited saturated absorption signals with cavity-enhanced signal-to-noise ratios. Residual fractional frequency instability in terms of Allan Std. Deviation is expected below 10-14 @1s integration time and down to 10-15 over several hours. The compact iodine / cavity design, and performance well above LISA requirements make this project an interesting candidate for the space-based Gravitational Waves detector. We discuss the scientific background and outline of this project within the LISA framework, as well as its potential impact on other stringent technical requirements of the LISA project (e.g. U.S.O. clock-stability, arm-length measurements. . . ). We also present other possible applications for space projects involving interferometry, laser ranging or onboard ultrastable oscillators.

  4. Improvement in Suppression of Pulsed Nd:YAG Laser Light With Iodine Absorption Cells for Filtered Rayleigh Scattering Measurements

    NASA Technical Reports Server (NTRS)

    Seasholtz, Richard G.; Buggele, Alvin E

    1997-01-01

    Filtered Rayleigh scattering using iodine absorption cells is an effective technique for obtaining density, temperature, and velocity measurements in high speed confined flows. By tuning a single frequency laser to a strong iodine absorption line, stray scattered laser light can be greatly suppressed. For example, the minimum transmission predicted by an iodine absorption model calculation is less than 10(exp -5) at the 18788.44/cm line using a 200 mm absorption cell containing iodine vapor at 0.46 T. Measurements obtained by other researches using a CW Nd:YAG laser agree with the model calculations. However, measurements made by us and by others using Q-switched, injection-seeded, frequency doubled Nd:YAG lasers only show minimum transmission of about 3 x 10(exp -3). This greatly reduces the applicability of the filtered Rayleigh scattering technique using these lasers in experiments having large amounts of stray scattered laser light. The purposes of the present study are to characterize the spectrum of the excess light transmitted by the iodine cell and to make changes to the laser to reduce the transmitted laser light. Transmission data as a function of laser frequency for the iodine absorption line at 18788.44/cm are presented. A planar mirror Fabry-Perot interferometer was used to characterize the frequency spectrum of the light passed through the cell. Measurements taken with the laser tuned to the center of the iodine absorption line show the light transmitted through the iodine cell to have a component with a bandwidth of about 40 GHz. This is probably caused by other modes in the laser that exist in spite of the single frequency injection beam. A second broadband component was also observed, possibly caused by the laser flash lamps or by fluorescence. An intracavity etalon was installed in the laser oscillator cavity to suppress the 40 GHz component. Measurements taken with the etalon tuned to the injection frequency showed a reduction in the transmitted

  5. Laser detection of spin-polarized hydrogen from HCl and HBr photodissociation: comparison of H- and halogen-atom polarizations.

    PubMed

    Sofikitis, Dimitris; Rubio-Lago, Luis; Bougas, Lykourgos; Alexander, Andrew J; Rakitzis, T Peter

    2008-10-14

    Thermal HCl and HBr molecules were photodissociated using circularly polarized 193 nm light, and the speed-dependent spin polarization of the H-atom photofragments was measured using polarized fluorescence at 121.6 nm. Both polarization components, described by the a(0)(1)(perpendicular) and Re[a(1)(1)(parallel, perpendicular)] parameters which arise from incoherent and coherent dissociation mechanisms, are measured. The values of the a(0)(1)(perpendicular) parameter, for both HCl and HBr photodissociation, are within experimental error of the predictions of both ab initio calculations and of previous measurements of the polarization of the halide cofragments. The experimental and ab initio theoretical values of the Re[a(1)(1)(parallel, perpendicular)] parameter show some disagreement, suggesting that further theoretical investigations are required. Overall, good agreement occurs despite the fact that the current experiments photodissociate molecules at 295 K, whereas previous measurements were conducted at rotational temperatures of about 15 K.

  6. Optimal buffer gas pressure for laser-induced fluorescence detection of the iodine-129 isotope in the atmosphere

    SciTech Connect

    Kireev, S.V.; Pit`ko, A.V.; Shnyrev, S.L.

    1995-06-01

    The effect of atmospheric air pressure on the intensity of iodine-129 vapor fluorescence excited by a He-Ne (633 nm) laser is studied. It is shown that to achieve the maximum intensity of fluorescence of molecular iodine-129, it is advantageous, first, to use a {sup 3}He-{sup 20}Ne laser for excitation, and second, to detect atmospheric iodine impurities in the gas mixture under analysis evacuated to 2 x 10{sup 18} - 4 x 10{sup 18} mol/cm{sup 3}. In this case, the sensitivity increases about twofold. 7 refs., 4 figs.

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

    NASA Astrophysics Data System (ADS)

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

    2000-05-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2000-05-01

    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.

  9. Nuclear-driven flashlamp pumping of the atomic iodine laser. Final report

    SciTech Connect

    Miley, G.H.

    1992-03-01

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

  10. Chemical Oxygen-Iodine Laser Device Simulation Using the 3D, Unsteady Navier-Stokes Equations

    DTIC Science & Technology

    2007-06-01

    overall rate of dimensional ( 3D ) GASP model for the COIL flowfield dissociation of I2. was executed in time accurate mode utilizing lst-order The gas... 3D , Unsteady Navier-Stokes Equations DISTRIBUTION: Approved for public release, distribution unlimited This paper is part of the following report...ADP023803 UNCLASSIFIED Chemical Oxygen-Iodine Laser Device Simulation Using the 3D , Unsteady Navier- Stokes Equations Timothy J. Madden US Air Force

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

    DTIC Science & Technology

    2006-03-01

    Branch *) The objective of this project is to develop the optimal ejector nozzle bank (with additional nozzles for injection iodine vapor at low...gain (SSG) by employing of the Rigrod dependencies of the laser power. An application of an ejector -like nozzle bank to produce a gain medium in the...sonic/supersonic jets is very slow and it is necessary to use some kind of mixing enhancement schemes. Such mixing enhancement in the ejector

  12. Performance characteristics of a chemical oxygen-iodine laser without a water vapor trap

    NASA Astrophysics Data System (ADS)

    Kikuchi, Toshio; Tsuruyama, Toru; Uchiyama, Taro

    1988-09-01

    The effect of water vapor on the operation of a chemical oxygen-iodine laser without a water vapor trap is described. The maximum CW laser power of 87 W was obtained without the water vapor trap at a Cl2 flow rate of 740 mmol/min. An alkaline H2O2 solution (90 wt pct H2O2, 50 wt pct KOH) was cooled down to about -30 C in order to control the saturated H2O2-H2O vapor pressure to less than 100 mTorr. Two porous pipes made of carbon were utilized as a singlet oxygen generator.

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

    NASA Technical Reports Server (NTRS)

    Shiner, C. S.

    1985-01-01

    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.

  14. Effect of buffer gases on broadening of the Iodine-127 resonance absorption line at a 633-nm He-Ne laser wavelength

    SciTech Connect

    Kireev, S.V.; Shnyrev, S.L.; Zaspa, Yu.P.

    1995-04-01

    Collisional broadening coefficients are measured for iodine-127 resonance absorption lines in several rare cases of atmospheric air and CO{sub 2}. The results obtained are used to determine the optimum pressure of a gaseous mixture in a measuring cell for detecting iodine-127 by a helium-neon (633 nm) laser-induced fluorescence technique of monitoring iodine in atmospheric air.

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

    SciTech Connect

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

    2011-05-31

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

  16. A unified planar measurement technique for compressible flows using laser-induced iodine fluorescence

    NASA Technical Reports Server (NTRS)

    Hartfield, Roy J., Jr.; Hollo, Steven D.; Mcdaniel, James C.

    1992-01-01

    A unified laser-induced fluorescence technique for conducting planar measurements of temperature, pressure and velocity in nonreacting, highly compressible flows has been developed, validated and demonstrated. Planar fluorescence from iodine, seeded into air, was induced by an argon-ion laser and collected using a liquid-nitrogen cooled CCD camera. In the measurement technique, temperature is determined from the fluorescence induced with the laser operated broad band. Pressure and velocity are determined from the shape and position of the fluorescence excitation spectrum which is measured with the laser operated narrow band. The measurement approach described herein provides a means of obtaining accurate, spatially-complete maps of the primary flow field parameters in a wide variety of cold supersonic and transonic flows.

  17. State of the art and perspectives of chemical oxygen-iodine lasers

    NASA Astrophysics Data System (ADS)

    Zagidullin, Marsel V.; Nikolaev, Valeri D.

    1999-01-01

    The chemical oxygen-iodine laser (COIL) is a scaleable high power laser promising for industrial applications. The principles of singlet oxygen generation in the jet type singlet oxygen generator and COIL operation are considered. The progress in high pressure jet type singlet oxygen generators allowed to develop the compact highly efficient COIL. The different types of efficient mixing schemes were tested in COIL based on the high pressure jet singlet oxygen generator. The preliminary cooling of active medium via mixing of oxygen with cold buffer nitrogen gas result in high efficiency operation of the small scale COIL with subsonic gas flow in the laser cavity. The project of COIL with high pressure of oxygen in laser cavity is discussed.

  18. A unified planar measurement technique for compressible flows using laser-induced iodine fluorescence

    NASA Technical Reports Server (NTRS)

    Hartfield, Roy J., Jr.; Hollo, Steven D.; Mcdaniel, James C.

    1992-01-01

    A unified laser-induced fluorescence technique for conducting planar measurements of temperature, pressure and velocity in nonreacting, highly compressible flows has been developed, validated and demonstrated. Planar fluorescence from iodine, seeded into air, was induced by an argon-ion laser and collected using a liquid-nitrogen cooled CCD camera. In the measurement technique, temperature is determined from the fluorescence induced with the laser operated broad band. Pressure and velocity are determined from the shape and position of the fluorescence excitation spectrum which is measured with the laser operated narrow band. The measurement approach described herein provides a means of obtaining accurate, spatially-complete maps of the primary flow field parameters in a wide variety of cold supersonic and transonic flows.

  19. Molecular iodine fluorescence spectra generated with helium-neon lasers for spectrometer calibration.

    PubMed

    Williamson, J Charles

    2010-12-01

    Gas-phase molecular iodine laser-induced fluorescence (LIF) spectra were recorded out to 815 nm at 1 cm(-1) resolution using green, yellow, and red helium-neon (HeNe) lasers as excitation sources. Nine previously unreported I(2) B←X absorption transitions accessed by these lasers were identified, and specific rovibronic transition assignments were made for two hundred LIF peaks--more than sixty per laser. These I(2) LIF peaks can be used to calibrate the vacuum wavenumber coordinate of spectrometers to better than 0.1 cm(-1) accuracy. In particular, green HeNe excitation of the I(2) R(106) 28-0 transition leads to strong fluorescence well suited for calibration, with a rotational doublet spacing of 15 cm(-1) and a doublet-to-doublet spacing of 190 cm(-1). Calibration by HeNe I(2) LIF may be an especially valuable technique for Raman spectroscopy applications.

  20. Frequency reproducibility of an iodine-stabilized Nd:YAG laser at 532 nm

    NASA Astrophysics Data System (ADS)

    Hong, Feng-Lei; Ishikawa, Jun; Zhang, Yun; Guo, Ruixiang; Onae, Atsushi; Matsumoto, Hirokazu

    2004-05-01

    We have established an ensemble of iodine-stabilized Nd:YAG lasers to verify the frequency reproducibility of the laser. The stability, repeatability and several systematic shifts of the laser frequency are investigated by heterodyne beating of the lasers. The frequency dispersion of the ensemble of lasers is evaluated to be 0.5 kHz (corresponding to a relative frequency uncertainty of 8 × 10 -13). The absolute frequency of one of the lasers (named as Y3) is measured to be 563 260 223 507 897(58) Hz using a femtosecond optical comb, when the laser was stabilized on the a10 component of the R(56)32-0 transition of 127I 2 for a cold-finger temperature of -10 °C. This group of lasers, including one transportable laser, forms an ensemble of optical frequency standards, which serves for many applications such as international comparisons, optical frequency measurements, frequency calibration services and high-resolution spectroscopy.

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

    NASA Astrophysics Data System (ADS)

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

    2006-07-01

    In an electric discharge oxygen-iodine laser, laser action at 1315nm on the I(P1/22)→I(P3/22) transition of atomic iodine is obtained by a near resonant energy transfer from O2(aΔ1) 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(aΔ1) 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.

  2. Photodissociation Regions

    NASA Technical Reports Server (NTRS)

    Hollenbach, David J.; DeVincenzi, Donald L. (Technical Monitor)

    2000-01-01

    The interstellar medium of galaxies is the reservoir out of which stars are born and into which stars inject newly created elements as they age. The physical properties of the interstellar medium are governed in part by the radiation emitted by these stars. Far-ultraviolet (6 eV< hNu < 13.6 eV) photons from massive stars dominate the heating and influence the chemistry of the neutral atomic gas and much of the molecular gas in galaxies. Predominantly neutral regions of the interstellar medium in which the heating and chemistry are regulated by far ultraviolet photons are termed Photodissociation Regions (PDRs). These regions are the origin of most of the non-stellar infrared (IR) and the millimeter and submillimeter CO emission from galaxies. The importance of PDRs has become increasingly apparent with the advances in IR and submillimeter astronomy. The IR emission from PDRs includes fine structure lines of C, C(+) and O; rovibrational lines of H2; rotational lines of CO; broad mid-IR features of polycyclic aromatic hydrocarbons; and a luminous underlying IR continuum from interstellar dust. The transition of H to H2 and C(+) to CO occurs within PDRs. Comparison of observations with theoretical models of PDRs enables one to determine the density and temperature structure, the elemental abundances, the level of ionization, and the radiation field. PDR models have been applied to interstellar clouds near massive stars, planetary nebulae, red giant outflows, photoevaporating planetary disks around newly formed stars, diffuse clouds, the neutral intercloud medium, and molecular clouds in the interstellar radiation field-in summary, much of the interstellar medium in galaxies. Theoretical PDR models explain the observed correlations of the [CII] 158, micrometers with the CO J=1-0 emission, the CO J=1-0 luminosity with the interstellar molecular mass, and the [CII] 158 micrometers plus [OI] 63 micrometers luminosity with the IR continuum luminosity. On a more global

  3. Quantitative characterization of a nonreacting, supersonic combustor flowfield using unified, laser-induced iodine fluorescence

    NASA Technical Reports Server (NTRS)

    Fletcher, D. G.; Mcdaniel, J. C.

    1989-01-01

    A calibrated, nonintrusive optical technique, laser-induced iodine fluorescence (LIIF) was used to quantify the steady, compressible flowfield of a nonreacting, supersonic combustor. The combustor was configured with single and staged, transverse-air injection into a supersonic-air freestream behind a rearward-facing step. Pressure, temperature, two-velocity components, and injectant mole fraction were measured with high spatial resolution in the three-dimensional flowfields. These experimental results provide a benchmark set of data for validation of computational fluid dynamic (CFD) codes being developed to model supersonic combustor flowfields.

  4. Quantitative characterization of a nonreacting, supersonic combustor flowfield using unified, laser-induced iodine fluorescence

    NASA Technical Reports Server (NTRS)

    Fletcher, D. G.; Mcdaniel, J. C.

    1989-01-01

    A calibrated, nonintrusive optical technique, laser-induced iodine fluorescence (LIIF) was used to quantify the steady, compressible flowfield of a nonreacting, supersonic combustor. The combustor was configured with single and staged, transverse-air injection into a supersonic-air freestream behind a rearward-facing step. Pressure, temperature, two-velocity components, and injectant mole fraction were measured with high spatial resolution in the three-dimensional flowfields. These experimental results provide a benchmark set of data for validation of computational fluid dynamic (CFD) codes being developed to model supersonic combustor flowfields.

  5. Mechanism of singlet oxygen deactivation in an electric discharge oxygen - iodine laser

    NASA Astrophysics Data System (ADS)

    Azyazov, V. N.; Mikheyev, P. A.; Pershin, A. A.; Torbin, A. P.; Heaven, M. C.

    2014-12-01

    We have determined the influence of the reaction of molecular singlet oxygen with a vibrationally excited ozone molecule O2(a 1Δ) + O3(ν) → 2O2 + O on the removal rate of O2(a 1Δ) in an electric-discharge-driven oxygen - iodine laser. This reaction has been shown to be a major channel of O2(a 1Δ) loss at the output of an electric-discharge singlet oxygen generator. In addition, it can also contribute significantly to the loss of O2(a 1Δ) in the discharge region of the generator.

  6. Theoretical shaping of femtosecond laser pulses for ultrafast molecular photo-dissociation with control techniques based on time-dependent density functional theory.

    PubMed

    Castro, Alberto

    2013-05-10

    The combination of time-dependent density functional theory and quantum optimal control formalism is used to optimize the shape of ultra-short laser pulses in order to achieve the photodissociation of the hydrogen molecule. The very short pulse durations used in this work (a few femtoseconds) do not allow for significant nuclear movement during irradiation, and thus the dissociation mechanism is sequential. During pulse irradiation, a large sudden momentum is communicated which can be understood in terms of population of excited, bound or unbound, dissociative electronic states. The target is defined in terms of the average opposing force during the action of the pulse, or equivalently, in terms of the final dissociative velocity.

  7. Performance characteristics of a transverse-flow, oxygen-iodine chemical laser in a low gas-flow velocity

    NASA Astrophysics Data System (ADS)

    Watanabe, K.; Kashiwabara, S.; Sawai, K.; Toshima, S.; Fujimoto, R.

    1983-03-01

    Performance characteristics are reported for a transverse-flow, oxygen-iodine chemical laser which operates at a low level (8 m/s) of linear flow gas velocity using a small size vacuum pump. This is the first time that dependences of laser output power have experimentally been found on Cl2 and I2 flow rates. Output powers in excess of 10 W have been efficiently extracted from a 50 x 0.5-cm rectangular flow duct. A total energy of 11 kJ from one gram of iodine has been obtained. The reaction mechanisms associated with the power decrease in high concentrations of I2 are carefully discussed.

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

    NASA Astrophysics Data System (ADS)

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

    2000-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2004-02-01

    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-μm-diameter BHP droplets.

  10. Singlet oxygen generator for a solar powered chemically pumped iodine laser

    NASA Technical Reports Server (NTRS)

    Busch, G. E.

    1984-01-01

    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.

  11. Performance model for optical extraction from a pulsed chemical oxygen-iodine laser

    NASA Astrophysics Data System (ADS)

    Copeland, D. A.; Bauer, A. H.; Jones, K. D.

    A comprehensive time-dependent gain model for pulsed optical extraction from a flowing oxygen-iodine laser medium is described. Gas flow is treated using an unsteady, premixed, quasi-one-dimensional model which accounts for gas motion and expansion as well as heat release in the cavity. The model uses a simplified, temperature-dependent, chemical kinetics package which consists of several reactions among the 3Sigma, 1Delta, and 1Sigma states of oxygen, atomic and molecular iodine, water, and helium. Hyperfine relaxation effects on the gain and optical extraction from the 3-4 line are treated using a simple four-level laser model. An efficient algorithm for solving the coupled medium and optical extraction equations is described. This gain model, in conjunction with a geometric model of an unstable confocal resonator, is used to examine energy extraction from the medium as a function of pulse repetition rate, duty cycle, and optical mode width. It is shown that the output power may exhibit flow-induced relaxation oscillations and the conditions under which these oscillations occur are discussed.

  12. Performance model for optical extraction from a Q-switched chemical oxygen-iodine laser

    NASA Astrophysics Data System (ADS)

    Copeland, D. A.; Bauer, A. H.; Jones, K. D.

    1993-03-01

    A comprehensive time-dependent model for optical extraction from a Q-switched supersonic oxygen-iodine laser is described. Gas flow is treated by using an unsteady, premixed, quasi-1D model that accounts for gas motion and expansion as well as heat release in the cavity. The model uses a simplified, temperature-dependent, chemical kinetics package that consists of several reactions among the 3Sigma, 1Delta, and 1Sigma states of oxygen, atomic and molecular iodine, water, and helium. Hyperfine relaxation effects on the gain and optical extraction from the 3-4 transition line are treated by using a simple four-level laser model. An efficient algorithm for solving the coupled medium and optical extraction equations, in conjunction with a geometric model of an unstable confocal resonator, is used to examine optical extraction from the medium as a function of pulse repetition rate, duty cycle, and optical mode width. It is shown that the output power may exhibit flow-induced relaxation oscillations.

  13. Mechanism of singlet oxygen deactivation in an electric discharge oxygen – iodine laser

    SciTech Connect

    Azyazov, V N; Mikheyev, P A; Torbin, A P; Pershin, A A; Heaven, M C

    2014-12-31

    We have determined the influence of the reaction of molecular singlet oxygen with a vibrationally excited ozone molecule O{sub 2}(a {sup 1}Δ) + O{sub 3}(ν) → 2O{sub 2} + O on the removal rate of O{sub 2}(a {sup 1}Δ) in an electric-discharge-driven oxygen – iodine laser. This reaction has been shown to be a major channel of O{sub 2}(a {sup 1}Δ) loss at the output of an electric-discharge singlet oxygen generator. In addition, it can also contribute significantly to the loss of O{sub 2}(a {sup 1}Δ) in the discharge region of the generator. (lasers)

  14. Kinematically complete final state investigations of molecular photodissociation: two- and three-body decay of laser-prepared H 3 3 s 2 A 1 '

    NASA Astrophysics Data System (ADS)

    Galster, U.; Kaminski, P.; Beckert, M.; Helm, H.; Müller, U.

    2001-12-01

    We have performed kinematically complete investigations of molecular photodissociation of triatomic hydrogen in a fast beam translational spectrometer recently built in Freiburg. The apparatus allows us to investigate laser-induced dissociation of neutral molecules into two, three, or more neutral products. The fragments are detected in coincidence and their vectorial momenta in the center-of-mass frame are determined. We demonstrate the potential of the method at the fragmentation of the 3 s 2A1'(N = 1, K = 0) state of triatomic hydrogen. In this state, three-body decay into ground state hydrogen atoms H+H+H, two-body predissociation into H+H2(v, J), and photoemission to the H3 ground state surface with subsequent two-body decay are competing channels. In the case of two-body predissociation, we determine the rovibrational population in the H2(v, J) fragment. The vibrational distribution of H2 is compared with approximate theoretical predictions. For three-body decay, we measure the six-fold differential photodissociation cross-section. To determine accurate final state distributions, the geometric collection efficiency of the apparatus is calculated by a Monte Carlo simulation, and the raw data are corrected for apparatus efficiency. The final state momentum distribution shows pronounced correlation patterns which are characteristic for the dissociation mechanism. For a three-body decay process with a discrete kinetic energy release we have developed a novel data reduction procedure based on the detection of two fragments. The final state distribution determined by this independent method agrees extremely well with that observed in the triple-coincidence data. In addition, this method allows us to fully explore the phase space of the final state and to determine the branching ratios between the two- and three-body decay processes.

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

    NASA Technical Reports Server (NTRS)

    Shiner, Christopher S.

    1986-01-01

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

  16. A 50-kW Module Power Station of Directly Solar-Pumped Iodine Laser

    NASA Technical Reports Server (NTRS)

    Choi, S. H.; Lee, J. H.; Meador, W. E.; Conway, E. J.

    1997-01-01

    The conceptual design of a 50 kW Directly Solar-Pumped Iodine Laser (DSPIL) module was developed for a space-based power station which transmits its coherent-beam power to users such as the moon, Martian rovers, or other satellites with large (greater than 25 kW) electric power requirements. Integration of multiple modules would provide an amount of power that exceeds the power of a single module by combining and directing the coherent beams to the user's receiver. The model developed for the DSPIL system conservatively predicts the laser output power (50 kW) that appears much less than the laser output (93 kW) obtained from the gain volume ratio extrapolation of experimental data. The difference in laser outputs may be attributed to reflector configurations adopted in both design and experiment. Even though the photon absorption by multiple reflections in experimental cavity setup was more efficient, the maximum secondary absorption amounts to be only 24.7 percent of the primary. However, the gain volume ratio shows 86 percent more power output than theoretical estimation that is roughly 60 percent more than the contribution by the secondary absorption. Such a difference indicates that the theoretical model adopted in the study underestimates the overall performance of the DSPIL. This fact may tolerate more flexible and radical selection of design parameters than used in this design study. The design achieves an overall specific power of approximately 5 W/kg and total mass of 10 metric tons.

  17. Theoretical Shaping of Femtosecond Laser Pulses for Molecular Photodissociation with Control Techniques Based on Ehrenfest's Dynamics and Time-Dependent Density Functional Theory.

    PubMed

    Castro, Alberto

    2016-06-03

    The combination of nonadiabatic Ehrenfest-path molecular dynamics (EMD) based on time-dependent density functional theory (TDDFT) and quantum optimal control formalism (QOCT) was used to optimize the shape of ultra-short laser pulses to achieve photodissociation of a hydrogen molecule and the trihydrogen cation H3 (+) . This work completes a previous one [A. Castro, ChemPhysChem, 2013, 14, 1488-1495], in which the same objective was achieved by demonstrating the combination of QOCT and TDDFT for many-electron systems on static nuclear potentials. The optimization model, therefore, did not include the nuclear movement and the obtained dissociation mechanism could only be sequential: fast laser-assisted electronic excitation to nonbonding states (during which the nuclei are considered to be static), followed by field-free dissociation. Here, in contrast, the optimization was performed with the QOCT constructed on top of the full dynamic model comprised of both electrons and nuclei, as described within EMD based on TDDFT. This is the first numerical demonstration of an optimal control formalism for a hybrid quantum-classical model, that is, a molecular dynamics method.

  18. Mathematical modeling of a photovoltaic-laser energy converter for iodine laser radiation

    NASA Technical Reports Server (NTRS)

    Walker, Gilbert H.; Heinbockel, John H.

    1987-01-01

    Space-based laser power systems will require converters to change laser radiation into electricity. Vertical junction photovoltaic converters are promising devices for this use. A promising laser for the laser power station is the t-C4F9I laser which emits radiation at a wavelength of 1.315 microns. This paper describes the results of mathematical modeling of a photovoltaic-laser energy converter for use with this laser. The material for this photovoltaic converter is Ga(53)In(47)As which has a bandgap energy of 0.94 eV, slightly below the energy of the laser photons (0.943 eV). Results of a study optimizing the converter parameters are presented. Calculated efficiency for a 1000 vertical junction converter is 42.5 percent at a power density of 1 x 10 to the 3d power w/sq cm.

  19. Regeneration of basic hydrogen peroxide for chemical oxygen-iodine laser

    NASA Astrophysics Data System (ADS)

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

    2003-11-01

    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.

  20. A computational fluid dynamics simulation of a supersonic chemical oxygen-iodine laser

    NASA Astrophysics Data System (ADS)

    Waichman, K.; Rybalkin, V.; Katz, A.; Dahan, Z.; Barmashenko, B. D.; Rosenwaks, S.

    2007-05-01

    The dissociation of I II molecules at the optical axis of a supersonic chemical oxygen-iodine laser (COIL) was studied via detailed measurements and three dimensional computational fluid dynamics calculations. Comparing the measurements and the calculations enabled critical examination of previously proposed dissociation mechanisms and suggestion of a mechanism consistent with the experimental and theoretical results. The gain, I II dissociation fraction and temperature at the optical axis, calculated using Heidner's model (R.F. Heidner III et al., J. Phys. Chem. 87, 2348 (1983)), are much lower than those measured experimentally. Agreement with the experimental results was reached by using Heidner's model supplemented by Azyazov-Heaven's model (V.N. Azyazov and M.C. Heaven, AIAA J. 44, 1593 (2006)) where I II(A') and vibrationally excited O II(a1Δ) are significant dissociation intermediates.

  1. Experimental investigation of a supersonic swept ramp injector using laser-induced iodine fluorescence

    NASA Technical Reports Server (NTRS)

    Hartfield, Roy J.; Hollo, Steven D.; Mcdaniel, James C.

    1990-01-01

    Planar measurements of injectant mole fraction and temperature have been conducted in a nonreacting supersonic combustor configured with underexpanded injection in the base of a swept ramp. The temperature measurements were conducted with a Mach 2 test section inlet in streamwise planes perpendicular to the test section wall on which the ramp was mounted. Injection concentration measurements, conducted in cross flow planes with both Mach 2 and Mach 2.9 free stream conditions, dramatically illustrate the domination of the mixing process by streamwise vorticity generated by the ramp. These measurements, conducted using a nonintrusive optical technique (laser-induced iodine fluorescence), provide an accurate and extensive experimental data base for the validation of computation fluid dynamic codes for the calculation of highly three-dimensional supersonic combustor flow fields.

  2. Directly solar-pumped iodine laser for beamed power transmission in space

    NASA Technical Reports Server (NTRS)

    Choi, S. H.; Meador, W. E.; Lee, J. H.

    1992-01-01

    A new approach for development of a 50-kW directly solar-pumped iodine laser (DSPIL) system as a space-based power station was made using a confocal unstable resonator (CUR). The CUR-based DSPIL has advantages, such as performance enhancement, reduction of total mass, and simplicity which alleviates the complexities inherent in the previous system, master oscillator/power amplifier (MOPA) configurations. In this design, a single CUR-based DSPIL with 50-kW output power was defined and compared to the MOPA-based DSPIL. Integration of multiple modules for power requirements more than 50-kW is physically and structurally a sound approach as compared to building a single large system. An integrated system of multiple modules can respond to various mission power requirements by combining and aiming the coherent beams at the user's receiver.

  3. Directly solar-pumped iodine laser for beamed power transmission in space

    NASA Technical Reports Server (NTRS)

    Choi, S. H.; Meador, W. E.; Lee, J. H.

    1992-01-01

    A new approach for development of a 50-kW directly solar-pumped iodine laser (DSPIL) system as a space-based power station was made using a confocal unstable resonator (CUR). The CUR-based DSPIL has advantages, such as performance enhancement, reduction of total mass, and simplicity which alleviates the complexities inherent in the previous system, master oscillator/power amplifier (MOPA) configurations. In this design, a single CUR-based DSPIL with 50-kW output power was defined and compared to the MOPA-based DSPIL. Integration of multiple modules for power requirements more than 50-kW is physically and structurally a sound approach as compared to building a single large system. An integrated system of multiple modules can respond to various mission power requirements by combining and aiming the coherent beams at the user's receiver.

  4. Experimental investigation of a supersonic swept ramp injector using laser-induced iodine fluorescence

    NASA Technical Reports Server (NTRS)

    Hartfield, Roy J.; Hollo, Steven D.; Mcdaniel, James C.

    1990-01-01

    Planar measurements of injectant mole fraction and temperature have been conducted in a nonreacting supersonic combustor configured with underexpanded injection in the base of a swept ramp. The temperature measurements were conducted with a Mach 2 test section inlet in streamwise planes perpendicular to the test section wall on which the ramp was mounted. Injection concentration measurements, conducted in cross flow planes with both Mach 2 and Mach 2.9 free stream conditions, dramatically illustrate the domination of the mixing process by streamwise vorticity generated by the ramp. These measurements, conducted using a nonintrusive optical technique (laser-induced iodine fluorescence), provide an accurate and extensive experimental data base for the validation of computation fluid dynamic codes for the calculation of highly three-dimensional supersonic combustor flow fields.

  5. 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)

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

    2007-07-01

    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.

  6. Laser Doppler velocimetry for continuous flow solar-pumped iodine laser system

    NASA Technical Reports Server (NTRS)

    Tabibi, Bagher M.; Lee, Ja H.

    1991-01-01

    A laser Doppler velocimetry (LDV) system was employed to measure the flow velocity profile of iodide vapor inside laser tubes of 36 mm ID and 20 mm ID. The LDV, which was operated in the forward scatter mode used a low power (15 mW) He-Ne laser beam. Velocity ranges from 1 m/s was measured to within one percent accuracy. The flow velocity profile across the laser tube was measured and the intensity of turbulence was determined. The flow of iodide inside the laser tube demonstrated a mixture of both turbulence and laminar flow. The flowmeter used for the laser system previously was calibrated with the LDV and found to be in good agreement.

  7. Speciation of iodine-containing proteins in Nori seaweed by gel electrophoresis laser ablation ICP-MS.

    PubMed

    Romarís-Hortas, V; Bianga, J; Moreda-Piñeiro, A; Bermejo-Barrera, P; Szpunar, J

    2014-09-01

    An analytical approach providing an insight into speciation of iodine in water insoluble fraction of edible seaweed (Nori) was developed. The seaweed, harvested in the Galician coast (Northwestern Spain), contained 67.7±1.3 μg g(-1) iodine of which 25% was water soluble and could be identifies as iodide. Extraction conditions of water insoluble residue using urea, NaOH, SDS and Triton X-100 were investigated. The protein pellets obtained in optimized conditions (after precipitation of urea extracts with acetone), were digested with trypsin and protease XIV. Size exclusion chromatography-ICP-MS of both enzymatic digests demonstrated the occurrence of iodoaminoacids putatively present in proteins. Intact proteins could be separated by gel electrophoresis after an additional extraction of the protein extract with phenol. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS PAGE) with laser ablation ICP-MS detection of (127)I indicated the presence of iodine in protein bands corresponding to molecular masses of 110 kDa, 40 kDa, 27 kDa, 20 kDa and 10 kDa. 2D IEF-SDS PAGE with laser ablation ICP-MS (127)I imaging allowed the detection of 5 iodine containing protein spots in the alkaline pI range.

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

    NASA Astrophysics Data System (ADS)

    Špalek, Otomar; Jirásek, Vít; Čenský, Miroslav; Kodymová, Jarmila

    2010-09-01

    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(1Δg), with a high efficiency (chlorine utilization 0.68 - 0.87 and O2(1Δg) yield 0.35 - 0.7) even at very high generator pressures (25 - 70 kPa), which cannot be attained by other O2(1Δg) 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 μm) 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.

  9. Subwavenumber charge-coupled device spectrometer calibration using molecular iodine laser-induced fluorescence

    SciTech Connect

    Lambert, Joseph G.; Hernandez-Diaz, Carlos; Williamson, J. Charles

    2010-01-15

    Spectrometers configured with charge-coupled devices (CCD) or other array-based detectors require calibration to convert from the pixel coordinate to a spectral coordinate. A CCD calibration method well suited for Raman spectroscopy has been developed based on the 514.5 nm Ar{sup +} laser-induced fluorescence (LIF) spectrum of room-temperature molecular iodine vapor. Over 360 primary and secondary I{sub 2} LIF calibration lines spanning 510-645 nm were identified as calibrant peaks using an instrumental resolution of 1 cm{sup -1}. Two instrument calibration functions were evaluated with these peaks: a second-order polynomial and a function derived from simple optomechanical considerations. The latter function provided better fitting characteristics. Calibration using I{sub 2} LIF was tested with measurements of both laser light scattering and Raman spectra. The I{sub 2} LIF reference spectra and the signal spectra were recorded simultaneously, with no cross talk, by separating the two signals spatially along the vertical axis of the CCD imager. In this way, every CCD image could be independently calibrated. An accuracy and a precision of {+-}0.05 cm{sup -1} were achieved with this calibration technique.

  10. Kinetics of an oxygen - iodine active medium with iodine atoms optically pumped on the 2P1/2 - 2P3/2 transition

    NASA Astrophysics Data System (ADS)

    Zagidullin, M. V.; Malyshev, M. S.; Azyazov, V. N.

    2015-08-01

    The kinetics of the processes occurring in an O2 - I2 - He - H2O gas flow in which photodissociation of molecular iodine at a wavelength close to 500 nm and excitation of atomic iodine on the 2P1/2 - 2P3/2 transition by narrow-band radiation near 1315 nm are implemented successively has been analysed. It is shown that implementation of these processes allows one to form an oxygen - iodine medium with a high degree of dissociation of molecular iodine and a relative content of singlet oxygen O2(a1Δ) exceeding 10%. Having formed a supersonic gas flow with a temperature ~100 K from this medium, one can reach a small-signal gain of about 10-2 cm-1 on the 2P1/2 - 2P3/2 transition in iodine atoms. The specific power per unit flow cross section in the oxygen - iodine laser with this active medium may reach ~100 W cm-2.

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

    NASA Astrophysics Data System (ADS)

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

    1998-05-01

    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.

  12. A flight-like absolute optical frequency reference based on iodine for laser systems at 1064 nm

    NASA Astrophysics Data System (ADS)

    Döringshoff, K.; Schuldt, T.; Kovalchuk, E. V.; Stühler, J.; Braxmaier, C.; Peters, A.

    2017-06-01

    We present an absolute optical frequency reference based on precision spectroscopy of hyperfine transitions in molecular iodine ^{127}I_2 for laser systems operating at 1064 nm. A quasi-monolithic spectroscopy setup was developed, integrated, and tested with respect to potential deployment in space missions that require frequency stable laser systems. We report on environmental tests of the setup and its frequency stability and reproducibility before and after each test. Furthermore, we report on the first measurements of the frequency stability of the iodine reference with an unsaturated absorption cell which will greatly simplify its application in space missions. Our frequency reference fulfills the requirements on the frequency stability for planned space missions such as LISA or NGGM.

  13. Femtosecond photodissociation dynamics of chloroiodomethane in the first absorption band

    NASA Astrophysics Data System (ADS)

    Murillo-Sánchez, M. L.; Marggi Poullain, S.; González-Vázquez, J.; Corrales, M. E.; Balerdi, G.; Bañares, L.

    2017-09-01

    The real time photodissociation of chloroiodomethane (CH2ICl) in the first absorption band at 268 nm is reported in comparison with the well-known methyl iodide (CH3I) in order to investigate the halogen-atom substituent effect on the time-resolved photodynamics of halomethanes. Femtosecond velocity map imaging measurements in conjunction with resonance enhanced multiphoton ionization (REMPI) to detect the iodine fragments have been performed to obtain translational energy, angular distributions and the photodissociation reaction times. High level ab initio and on-the-fly trajectory calculations have been carried out to rationalize the experimental results in terms of the excited states involved and the dissociation mechanisms.

  14. Flowfield measurements in a model scramjet combustion using laser-induced iodine fluorescence

    NASA Technical Reports Server (NTRS)

    Mcdaniel, J. C., Jr.

    1984-01-01

    Preliminary designs were completed for an iodine mixing chamber and the optical setup to be used with a modified wind tunnel in obtaining accurate, spatially resolved measurements of variables in the flowfield of a model nonreacting scramjet combustor. Schematics of the iodine-seeded wind tunnel and a sketch of the charcoal filter for removing the iodine are included along with a cutaway section of the laboratory.

  15. Design and chemical synthesis of iodine-containing molecules for application to solar-pumped I* lasers. Semiannual Progress Report, 1 January-30 June 1985

    SciTech Connect

    Shiner, C.S.

    1985-01-01

    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.

  16. Kinetic-fluid dynamics modeling of I2 dissociation in supersonic chemical oxygen-iodine lasers

    NASA Astrophysics Data System (ADS)

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

    2009-09-01

    The mechanism of I2 dissociation in supersonic chemical oxygen-iodine lasers (COILs) is studied applying kinetic-fluid dynamics modeling, where pathways involving the excited species I2(X Σ1g +,10≤v<25), I2(X Σ1g +,25≤v≤47), I2(A'Π32u), I2(AΠ31u), O2(X Σ3g -,v), O2(aΔ1g,v), O2(b Σ1g +,v), and I(P21/2) as intermediate reactants are included. The gist of the model is adding the first reactant and reducing the contribution of the second as compared to previous models. These changes, recently suggested by Azyazov, et al. [J. Chem. Phys. 130, 104306 (2009)], significantly improve the agreement with the measurements of the gain in a low pressure supersonic COIL for all I2 flow rates that have been tested in the experiments. In particular, the lack of agreement for high I2 flow rates, which was encountered in previous models, has been eliminated in the present model. It is suggested that future modeling of the COIL operation should take into account the proposed contribution of the above mentioned reactants.

  17. Solvent evaporation versus proton transfer in nucleobase-Pt(CN)(4,6)²⁻ dianion clusters: a collisional excitation and electronic laser photodissociation spectroscopy study.

    PubMed

    Sen, Ananya; Luxford, Thomas F M; Yoshikawa, Naruo; Dessent, Caroline E H

    2014-08-07

    Isolated molecular clusters of adenine, cytosine, thymine and uracil with Pt(CN)6(2-) and Pt(CN)4(2-) were studied for the first time to characterize the binding and reactivity of isolated transition metal complex ions with nucleobases. These clusters represent model systems for understanding metal complex-DNA adducts, as a function of individual nucleobases. Collisional excitation revealed that the clusters decay on the ground electronic surface by either solvent evaporation (i.e. loss of a nucleobase unit from the cluster) or via proton transfer from the nucleobase to the dianion. The Pt(CN)6(2-)-nucleobase clusters decay only by solvent evaporation, while the Pt(CN)4(2-) clusters fragment by both pathways. The enhanced proton-transfer reactivity of Pt(CN)4(2-) is attributed to the higher charge-density of the ligands in this transition metal anion. % fragmentation curves of the clusters reveal that the adenine clusters display distinctively higher fragmentation onsets, which are traced to the propensity of adenine to form the shortest intercluster H-bond. We also present laser electronic photodissociation measurements for the Pt(CN)6(2-)·Ur, Pt(CN)4(2-)·Ur and Pt(CN)4(2-)·Ur2 clusters to illustrate the potential of exploring metal complex DNA photophysics as a function of nucleobase within well-defined gaseous clusters. The spectra reported herein represent the first such measurements. We find that the electronic excited states decay with production of the same fragments (associated with solvent evaporation and proton transfer) observed upon collisional excitation of the electronic ground state, indicating ultrafast deactivation of the excited-state uracil-localized chromophore followed by vibrational predissociation.

  18. Computer-controlled multi-parameter mapping of 3D compressible flowfields using planar laser-induced iodine fluorescence

    NASA Technical Reports Server (NTRS)

    Donohue, James M.; Victor, Kenneth G.; Mcdaniel, James C., Jr.

    1993-01-01

    A computer-controlled technique, using planar laser-induced iodine fluorescence, for measuring complex compressible flowfields is presented. A new laser permits the use of a planar two-line temperature technique so that all parameters can be measured with the laser operated narrowband. Pressure and temperature measurements in a step flowfield show agreement within 10 percent of a CFD model except in regions close to walls. Deviation of near wall temperature measurements from the model was decreased from 21 percent to 12 percent compared to broadband planar temperature measurements. Computer-control of the experiment has been implemented, except for the frequency tuning of the laser. Image data storage and processing has been improved by integrating a workstation into the experimental setup reducing the data reduction time by a factor of 50.

  19. Computer-controlled multi-parameter mapping of 3D compressible flowfields using planar laser-induced iodine fluorescence

    NASA Technical Reports Server (NTRS)

    Donohue, James M.; Victor, Kenneth G.; Mcdaniel, James C., Jr.

    1993-01-01

    A computer-controlled technique, using planar laser-induced iodine fluorescence, for measuring complex compressible flowfields is presented. A new laser permits the use of a planar two-line temperature technique so that all parameters can be measured with the laser operated narrowband. Pressure and temperature measurements in a step flowfield show agreement within 10 percent of a CFD model except in regions close to walls. Deviation of near wall temperature measurements from the model was decreased from 21 percent to 12 percent compared to broadband planar temperature measurements. Computer-control of the experiment has been implemented, except for the frequency tuning of the laser. Image data storage and processing has been improved by integrating a workstation into the experimental setup reducing the data reduction time by a factor of 50.

  20. Optical Frequency Metrology of an Iodine-Stabilized He-Ne Laser Using the Frequency Comb of a Quantum-Interference-Stabilized Mode-Locked Laser

    PubMed Central

    Smith, Ryan P.; Roos, Peter A.; Wahlstrand, Jared K.; Pipis, Jessica A.; Rivas, Maria Belmonte; Cundiff, Steven T.

    2007-01-01

    We perform optical frequency metrology of an iodine-stabilized He-Ne laser using a mode-locked Ti:sapphire laser frequency comb that is stabilized using quantum interference of photocurrents in a semiconductor. Using this technique, we demonstrate carrier-envelope offset frequency fluctuations of less than 5 mHz using a 1 s gate time. With the resulting stable frequency comb, we measure the optical frequency of the iodine transition [127I2 R(127) 11-5 i component] to be 473 612 214 712.96 ± 0.66 kHz, well within the uncertainty of the CIPM recommended value. The stability of the quantum interference technique is high enough such that it does not limit the measurements. PMID:27110472

  1. Efficient photo-dissociation of CH4 and H2CO molecules with optimized ultra-short laser pulses

    NASA Astrophysics Data System (ADS)

    Rasti, S.; Irani, E.; Sadighi-Bonabi, R.

    2015-11-01

    The fragmentation dynamics of CH4 and H2CO molecules have been studied with ultra-short pulses at laser intensityof up to 1015Wcm-2. Three dimensional molecular dynamics calculations for finding the optimized laser pulses are presented based on time-dependent density functional theory and quantum optimal control theory. A comparison of the results for orientation dependence in the ionization process shows that the electron distribution for CH4 is more isotropic than H2CO molecule. Total conversion yields of up to 70% at an orientation angle of 30o for CH4 and 65% at 900 for H2CO are achieved which lead to enhancement of dissociation probability.

  2. The elementary steps of the photodissociation and recombination reactions of iodine molecules enclosed in cages and channels of zeolite crystals: A femtosecond time-resolved study of the geometry effect

    NASA Astrophysics Data System (ADS)

    Flachenecker, G.; Materny, A.

    2004-03-01

    We present femtosecond time-resolved pump-probe experiments on iodine molecules enclosed into well-defined cages and channels of different crystalline SiO2 modifications of zeolites. The new experimental results obtained from iodine in TON (Silica-ZSM-22), FER (Silica-Ferrierit), and MFI (Silicalit-1) porosils are compared with data published earlier on the iodine/DDR (Decadodecasil 3R) porosil system [Flachenecker et al., Phys. Chem. Chem. Phys. 5, 865 (2003)]. A summary of all findings is given. The processes analyzed by means of the ultrafast spectroscopy are the vibrational relaxation as well as the dissociation and recombination reactions, which are caused by the interaction of the photo-excited iodine molecules with the cavity walls of the porosils. A clear dependence of the observed dynamics on the geometry of the surrounding lattice structure can be seen. These measurements are supported by temperature-dependent experiments. Making use of a theoretical model which is based on the classical Langevin equation, an analysis of the geometry-reaction relation is performed. The Brownian dynamics simulations show that in contrast to the vibrational relaxation the predissociation dynamics are independent of the frequency of collisions with the surroundings. From the results obtained in the different surroundings, we conclude that mainly local fields are responsible for the crossing from the bound B state to the repulsive a/a' states of the iodine molecules.

  3. Influence of the gaseous mixture composition on accuracy of molecular iodine on-line detection by laser-induced fluorescence method

    NASA Astrophysics Data System (ADS)

    Kireev, S. V.; Shnyrev, S. L.

    2016-07-01

    This paper informs on research into the influence of the composition of gaseous mixtures analyzed on the accuracy of on-line molecular iodine detection by laser-induced fluorescence in various gaseous media—in atmospheric air and in technological mixtures formed during reprocessing of spent nuclear fuel. The paper shows that by considering the composition of buffer media and parts of its components, the accuracy of iodine content measurement may be increased in several times.

  4. A velocity map imaging study of the photodissociation of the methyl iodide cation.

    PubMed

    Marggi Poullain, S; Chicharro, D V; González-Vázquez, J; Rubio-Lago, L; Bañares, L

    2017-03-06

    The photodissociation dynamics of the methyl iodide cation has been studied using the velocity map imaging technique. A first laser pulse is used to ionize methyl iodide via a (2 + 1) REMPI scheme through the 5pπ → 6p Rydberg state two-photon transition. The produced CH3I(+)(X[combining tilde](2)E3/2) ions are subsequently excited at several wavelengths between 242 and 260 nm. The reported translational energy distributions for the methyl and iodine ions present a Boltzmann-type unstructured distribution at low excitation energies as well as a recoiled narrow structure at higher excitation energies highlighting two different dissociation processes. High level ab initio calculations have been performed in order to obtain a deeper understanding of the photodissociation dynamics of the CH3I(+) ion. Direct dissociation on a repulsive state from the manifold of states representing the B[combining tilde] excited state leads to CH3(+)(X[combining tilde](1)A1') + I*((2)P1/2), while the CH3 + I(+)((3)P2) channel is populated through an avoided crossing outside the Franck-Condon region. In contrast, an indirect process involving the transfer of energy from highly excited electronic states to the ground state of the ion is responsible for the observed Boltzmann-type distributions.

  5. Prototype of a Laser-Induced Fluorescence Ground-Based Instrument for Measurements of Atmospheric Iodine Monoxide (IO)

    NASA Astrophysics Data System (ADS)

    Thurlow, M. E.; Co, D. T.; Hanisco, T. F.; Lapson, L. B.; Anderson, J. G.

    2008-12-01

    High abundances of iodine monoxide (IO) are known to exist and to participate in local photochemistry of the marine boundary layer: (1) IO participates in depletion episodes of O3 and in the removal of mercury in the Arctic polar spring by enhancing atomic Br mixing ratios. Recent observations and computer simulations suggest that mercury sequestration is closely tied to halogen photochemistry and that gaseous atomic Hg depletion can be enhanced significantly by the presence of small amounts of iodine-containing compounds. (2) IO and higher- order iodine oxides are involved in the formation of new particles in coastal marine environments. Studies using smog chamber experiments simulating coastal atmospheric conditions have demonstrated that new particles can form from condensable iodine-containing vapors and that their concentrations over the open ocean are sufficient to influence marine particle formation. (3) IO has also been shown to affect the oxidizing capacity of the troposphere by altering the partitioning of NO2/NO and HO2/HO and by activating chlorine and bromine in sea salt aerosols. In the stratosphere, these same processes can lead to enhanced ozone loss rates. Detailed photochemical models that include iodine photochemistry, however, are hampered by the lack of observational data. The distribution of IO in vertical, horizontal, and temporal coordinates is unknown, so the impact of IO on global photochemistry cannot be predicted. The resolution of these important scientific issues requires an in situ IO instrument. A fully functional nanosecond Nd:YAG-pumped Ti:Sapphire laser system and a prototype IO ground-based instrument have been built in our lab. With the current setup, the laser system was situated 10 m from the field station, and the laser light was coupled via an optical fiber. With the use of highly efficient fluorescence detection optics and photon counting techniques, sensitivities of better than 0.1 ppt in 1 s for IO was achieved in the

  6. Prototype of a Laser-Induced Fluorescence Ground-Based Instrument for Measurements of Atmospheric Iodine Monoxide (IO)

    NASA Astrophysics Data System (ADS)

    Co, D. T.; Thurlow, M. E.; Hanisco, T. F.; Lapson, L. B.; Anderson, J. G.

    2007-12-01

    High abundances of iodine monoxide (IO) are known to exist and to participate in local photochemistry of the marine boundary layer: (1) IO participates in depletion episodes of O3 and in the removal of mercury in the Arctic polar spring by enhancing atomic Br mixing ratios. Recent observations and computer simulations suggest that mercury sequestration is closely tied to halogen photochemistry and that gaseous atomic Hg depletion can be enhanced significantly by the presence of small amounts of iodine-containing compounds. (2) IO and higher- order iodine oxides are involved in the formation of new particles in coastal marine environments. Studies using smog chamber experiments simulating coastal atmospheric conditions have demonstrated that new particles can form from condensable iodine-containing vapors and that their concentrations over the open ocean are sufficient to influence marine particle formation. (3) IO has also been shown to affect the oxidizing capacity of the troposphere by altering the partitioning of NO2/NO and HO2/HO and by activating chlorine and bromine in sea salt aerosols. In the stratosphere, these same processes can lead to enhanced ozone loss rates. Detailed photochemical models that include iodine photochemistry, however, are hampered by the lack of observational data. The distribution of IO in vertical, horizontal, and temporal coordinates is unknown, so the impact of IO on global photochemistry cannot be predicted. The resolution of these important scientific issues requires an in situ IO instrument. A fully functional nanosecond Nd:YAG-pumped Ti:Sapphire laser system and a prototype IO ground-based instrument have been built in our lab. With the current setup, the laser system was situated 10 m from the field station, and the laser light was coupled via an optical fiber. With the use of highly efficient fluorescence detection optics and photon counting techniques, sensitivities of better than 0.1 ppt in 1 s for IO was achieved in the

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

    SciTech Connect

    Andreeva, Tamara L; Kuznetsova, S V; Maslov, Aleksandr I; Sorokin, Vadim N

    2009-08-31

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

  8. Digital control of an iodine stabilized He-Ne laser by using a personal computer and a simple electronic system

    NASA Astrophysics Data System (ADS)

    Pantelić, Dejan V.; Panić, Bratimir M.; Kovačević, Aleksander G.

    2003-06-01

    An electronic system used for active control and optical frequency stabilization of a He-Ne laser is described. It is based on digital acquisition and signal processing, using minimum of analog electronics, and a personal computer (PC). Main functions of the system: phase sensitive detection, automatic control, and user interface, are performed in software. Simultaneous frequency and iodine cell temperature stabilization algorithm is described. Electronic system is compact (occupies only desktop PC case), inexpensive (commercial, of-the-shelf, components are mostly used), and can be easily upgraded and reprogrammed (new stabilization algorithms can be implemented). It is now a part of the primary length standard of Yugoslavia.

  9. Quantitative measurement of transverse injector and free stream interaction in a nonreacting SCRAMJET combustor using laser-induced iodine fluorescence

    NASA Technical Reports Server (NTRS)

    Fletcher, D. G.; Mcdaniel, J. C.

    1987-01-01

    A preliminary quantitative study of the compressible flowfield in a steady, nonreacting model SCRAMJET combustor using laser-induced iodine fluorescence (LIIF) is reported. Measurements of density, temperature, and velocity were conducted with the calibrated, nonintrusive, optical technique for two different combustor operating conditions. First, measurements were made in the supersonic flow over a rearward-facing step without transverse injection for comparison with calculated pressure profiles. The second configuration was staged injection behind the rearward-facing step at an injection dynamic pressure ratio of 1.06. These experimental results will be used to validate computational fluid dynamic (CFD) codes being developed to model supersonic combustor flowfields.

  10. Planar measurement of flow field parameters in a nonreacting supersonic combustor using laser-induced iodine fluorescence

    NASA Technical Reports Server (NTRS)

    Hartfield, Roy J., Jr.; Hollo, Steven D.; Mcdaniel, James C.

    1990-01-01

    A nonintrusive optical technique, laser-induced iodine fluorescence, has been used to obtain planar measurements of flow field parameters in the supersonic mixing flow field of a nonreacting supersonic combustor. The combustor design used in this work was configured with staged transverse sonic injection behind a rearward-facing step into a Mach 2.07 free stream. A set of spatially resolved measurements of temperature and injectant mole fraction has been generated. These measurements provide an extensive and accurate experimental data set required for the validation of computational fluid dynamic codes developed for the calculation of highly three-dimensional combustor flow fields.

  11. Planar measurement of flow field parameters in a nonreacting supersonic combustor using laser-induced iodine fluorescence

    NASA Technical Reports Server (NTRS)

    Hartfield, Roy J., Jr.; Hollo, Steven D.; Mcdaniel, James C.

    1990-01-01

    A nonintrusive optical technique, laser-induced iodine fluorescence, has been used to obtain planar measurements of flow field parameters in the supersonic mixing flow field of a nonreacting supersonic combustor. The combustor design used in this work was configured with staged transverse sonic injection behind a rearward-facing step into a Mach 2.07 free stream. A set of spatially resolved measurements of temperature and injectant mole fraction has been generated. These measurements provide an extensive and accurate experimental data set required for the validation of computational fluid dynamic codes developed for the calculation of highly three-dimensional combustor flow fields.

  12. Kinetics of an oxygen – iodine active medium with iodine atoms optically pumped on the {sup 2}P{sub 1/2} – {sup 2}P{sub 3/2} transition

    SciTech Connect

    Zagidullin, M V; Azyazov, V N; Malyshev, M S

    2015-08-31

    The kinetics of the processes occurring in an O{sub 2} – I{sub 2} – He – H{sub 2}O gas flow in which photodissociation of molecular iodine at a wavelength close to 500 nm and excitation of atomic iodine on the {sup 2}P{sub 1/2} – {sup 2}P{sub 3/2} transition by narrow-band radiation near 1315 nm are implemented successively has been analysed. It is shown that implementation of these processes allows one to form an oxygen – iodine medium with a high degree of dissociation of molecular iodine and a relative content of singlet oxygen O{sub 2}(a{sup 1}Δ) exceeding 10%. Having formed a supersonic gas flow with a temperature ∼100 K from this medium, one can reach a small-signal gain of about 10{sup -2} cm{sup -1} on the {sup 2}P{sub 1/2} – {sup 2}P{sub 3/2} transition in iodine atoms. The specific power per unit flow cross section in the oxygen – iodine laser with this active medium may reach ∼100 W cm{sup -2}. (active media)

  13. A Ground-Based Instrument for the Laser-Induced Fluorescence Detection of Coastal Iodine Monoxide (IO)

    NASA Astrophysics Data System (ADS)

    Hannun, R. A.; Thurlow, M. E.; O'Brien, A.; Co, D. T.; Hanisco, T. F.; Lapson, L. B.; Anderson, J.

    2011-12-01

    The photochemistry of iodine monoxide (IO) within the marine boundary layer plays a role in the catalytic loss cycles of surface ozone and potentially leads to the nucleation of marine aerosols. Biogenic emissions of molecular iodine and organo-halide precursor molecules account for the largest sources of IO in marine and coastal environments. Due to the inhomogeneous distribution of atmospheric IO in conjunction with low mixing ratios of less than 10 ppt, high sensitivity in-situ measurements are needed in order to better understand the impact of IO photochemistry in a quantifiable way. To address these challenges, a laser-induced fluorescence instrument has been developed, with a nanosecond-pulsed Nd:YAG-pumped Ti:Sapphire laser system. Through efficient optical design and fluorescence detection, we are able to operate in the sensitivity threshold of 1 ppt per minute for IO. Further design considerations included the development of a mobile, weatherproof instrument configuration, which can sustain deployment in a variety of field conditions. In order to validate the detection technique, the instrument was deployed at Shoals Marine Laboratory in Maine from August-September 2011. Instrument design considerations as well as preliminary results of the detection of IO from laminaria digitata, a kelp species present in coastal New England sites, will be presented.

  14. The photodissociation and reaction dynamics of vibrationally excited molecules

    SciTech Connect

    Crim, F.F.

    1993-12-01

    This research determines the nature of highly vibrationally excited molecules, their unimolecular reactions, and their photodissociation dynamics. The goal is to characterize vibrationally excited molecules and to exploit that understanding to discover and control their chemical pathways. Most recently the author has used a combination of vibrational overtone excitation and laser induced fluorescence both to characterize vibrationally excited molecules and to study their photodissociation dynamics. The author has also begun laser induced grating spectroscopy experiments designed to obtain the electronic absorption spectra of highly vibrationally excited molecules.

  15. Laser-induced fluorescence method of molecular iodine detection in the atmosphere in real time using copper-vapor laser at the wavelength of 510.6 nm

    NASA Astrophysics Data System (ADS)

    Kireev, S. V.; Shnyrev, S. L.

    2017-06-01

    The method of simultaneously detecting 127I2 and 127I129I in the atmospheric air is proposed. The method is based on exciting fluorescence of the molecules in question by copper-vapor laser radiation at the wavelength of 510.6 nm and registering intensities of their individual fluorescence spectral lines. The values of minimal real-time measured relative concentrations of 127I129I being mixed with 127I2 are approximately 10-6. This method can be used for the ecological monitoring of iodine-129 in the atmosphere.

  16. Pulsed chemical oxygen-iodine laser (COIL): state of the art and future

    NASA Astrophysics Data System (ADS)

    Frolov, M. P.; Ishkov, D.; Kryukov, P. G.; Pazyuk, Vladimir S.; Podmar'kov, Yu. P.; Vagin, Nikolai P.; Yuryshev, Nikolai N.

    1995-03-01

    The pulsed operation of COIL is now a subject of interest. The different approaches are used to obtain such a mode. The method of instant volumetric iodine generation is considered. The experimental results are presented. The advantage and disadvantages, problems, perspectives and possible applications are discussed.

  17. Design and chemical synthesis of iodine-containing molecules for application to solar-pumped I* lasers. Semiannual progress report, 1 July-31 December 1986

    SciTech Connect

    Shiner, C.S.

    1986-12-01

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

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

    PubMed

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

    2007-07-26

    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.

  19. Communication: XUV transient absorption spectroscopy of iodomethane and iodobenzene photodissociation

    NASA Astrophysics Data System (ADS)

    Drescher, L.; Galbraith, M. C. E.; Reitsma, G.; Dura, J.; Zhavoronkov, N.; Patchkovskii, S.; Vrakking, M. J. J.; Mikosch, J.

    2016-07-01

    Time-resolved extreme ultraviolet (XUV) transient absorption spectroscopy of iodomethane and iodobenzene photodissociation at the iodine pre-N4,5 edge is presented, using femtosecond UV pump pulses and XUV probe pulses from high harmonic generation. For both molecules the molecular core-to-valence absorption lines fade immediately, within the pump-probe time-resolution. Absorption lines converging to the atomic iodine product emerge promptly in CH3I but are time-delayed in C6H5I. We attribute this delay to the initial π → σ* excitation in iodobenzene, which is distant from the iodine reporter atom. We measure a continuous shift in energy of the emerging atomic absorption lines in CH3I, attributed to relaxation of the excited valence shell. An independent particle model is used to rationalize the observed experimental findings.

  20. Communication: XUV transient absorption spectroscopy of iodomethane and iodobenzene photodissociation.

    PubMed

    Drescher, L; Galbraith, M C E; Reitsma, G; Dura, J; Zhavoronkov, N; Patchkovskii, S; Vrakking, M J J; Mikosch, J

    2016-07-07

    Time-resolved extreme ultraviolet (XUV) transient absorption spectroscopy of iodomethane and iodobenzene photodissociation at the iodine pre-N4,5 edge is presented, using femtosecond UV pump pulses and XUV probe pulses from high harmonic generation. For both molecules the molecular core-to-valence absorption lines fade immediately, within the pump-probe time-resolution. Absorption lines converging to the atomic iodine product emerge promptly in CH3I but are time-delayed in C6H5I. We attribute this delay to the initial π → σ(*) excitation in iodobenzene, which is distant from the iodine reporter atom. We measure a continuous shift in energy of the emerging atomic absorption lines in CH3I, attributed to relaxation of the excited valence shell. An independent particle model is used to rationalize the observed experimental findings.

  1. Reduced dimer production in solar-simulator-pumped continuous wave iodine lasers based on model simulations and scaling and pumping studies

    NASA Technical Reports Server (NTRS)

    Costen, Robert C.; Heinbockel, John H.; Miner, Gilda A.; Meador, Willard E., Jr.; Tabibi, Bagher M.; Lee, Ja H.; Williams, Michael D.

    1995-01-01

    A numerical rate equation model for a continuous wave iodine laser with longitudinally flowing gaseous lasant is validated by approximating two experiments that compare the perfluoroalkyl iodine lasants n-C3F7I and t-C4F9I. The salient feature of the simulations is that the production rate of the dimer (C4F9)2 is reduced by one order of magnitude relative to the dimer (C3F7)2. The model is then used to investigate the kinetic effects of this reduced dimer production, especially how it improves output power. Related parametric and scaling studies are also presented. When dimer production is reduced, more monomer radicals (t-C4F9) are available to combine with iodine ions, thus enhancing depletion of the laser lower level and reducing buildup of the principal quencher, molecular iodine. Fewer iodine molecules result in fewer downward transitions from quenching and more transitions from stimulated emission of lasing photons. Enhanced depletion of the lower level reduces the absorption of lasing photons. The combined result is more lasing photons and proportionally increased output power.

  2. Laser source for dimensional metrology: investigation of an iodine stabilized system based on narrow linewidth 633 nm DBR diode

    NASA Astrophysics Data System (ADS)

    Rerucha, Simon; Yacoot, Andrew; Pham, Tuan M.; Cizek, Martin; Hucl, Vaclav; Lazar, Josef; Cip, Ondrej

    2017-04-01

    We demonstrated that an iodine stabilized distributed Bragg reflector (DBR) diode based laser system lasing at a wavelength in close proximity to λ =633 nm could be used as an alternative laser source to the helium-neon lasers in both scientific and industrial metrology. This yields additional advantages besides the optical frequency stability and coherence: inherent traceability, wider optical frequency tuning range, higher output power and high frequency modulation capability. We experimentally investigated the characteristics of the laser source in two major steps: first using a wavelength meter referenced to a frequency comb controlled with a hydrogen maser and then on an interferometric optical bench testbed where we compared the performance of the laser system with that of a traditional frequency stabilized He–Ne laser. The results indicate that DBR diode laser system provides a good laser source for applications in dimensional (nano)metrology, especially in conjunction with novel interferometric detection methods exploiting high frequency modulation or multiaxis measurement systems.

  3. Photodissociation of dimethylnitrosamine

    NASA Astrophysics Data System (ADS)

    Geiger, G.; Stafast, H.; Brühlmann, U.; Huber, J. Robert

    1981-05-01

    Photodissociation of (CH 3) 2N-NO following S 1(nπ *) ← S 0 excitation yields (CH 3) 2N - and NO with a quantum yield of 1.03 ± 0.10. These fragments recombine leaving no stable photopioducts. A fraction of NO produced by photolysis is vibrationally excited. The rate of the NO( v = 1) relaxation in collision with (CH 3) 2N-NO, measured by IR fluorescence, is (1.47 ± 0.03) × 10 4 s -1 Torr -1.

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

  5. Laser studies of chemical reaction and collision processes

    SciTech Connect

    Flynn, G.

    1993-12-01

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

  6. Measurement of kinetic parameters relevant to the operation of an electron-beam initiated atomic iodine laser

    SciTech Connect

    Ramirez, J.E.; Bera, R.K.; Hanrahan, R.J.

    1985-04-01

    Parameters relevant to the operation of an electron-beam initiated atomic iodine laser, which would lase on the transition 5 /sup 2/P/sub 1//sub ///sub 2/ (I*)..-->..5 /sup 2/P/sub 3//sub ///sub 2/ (I), have been measured by pulse radiolysis. Kinetic data for the parent compound quenching of I* were obtained by variation of the parent compound pressure at constant buffer gas pressure and observing I* decay rates versus time. Deactivation rates for perfluoroalkyl iodides were found to be much lower than for the corresponding alkyl iodides. Values obtained (in cm/sup 3/ molec/sup -1/ s/sup -1/) are as follows: CH/sub 3/I, (2.0 +- 0.1) x 10/sup -13/; C/sub 2/H/sub 5/I, (5.0 +- 0.3) x 10/sup -13/; CF/sub 3/I, (8.8 +- 0.3) x 10/sup -16/; C/sub 2/F/sub 5/I, (9.7 +- 1.0) x 10/sup -15/; n-C/sub 3/F/sub 7/I, (2.5 +- 0.2) x 10/sup -15/; i-C/sub 3/F/sub 7/I, (1.7 +- 0.1) x 10/sup -15/; n-C/sub 4/F/sub 9/I, (1.8 +- 0.1) x 10/sup -14/. The extent of population inversion was investigated by measuring initial excited state and ground state atomic iodine concentrations, which gives the branching ratio (I*)/(I). Values obtained are as follows: CH/sub 3/I, 2.7; CF/sub 3/I, 3.8; C/sub 2/F/sub 5/I, 2.7; i-C/sub 3/F/sub 7/I, 3.2; n-C/sub 4/F/sub 9/I, 1.8. Comparing both branching ratios and lifetimes, it is seen that CF/sub 3/I is the most promising candidate for an electron beam initiated atomic iodine laser.

  7. Coherent control over the photodissociation of CH3I

    NASA Astrophysics Data System (ADS)

    Kleiman, Valeria D.; Zhu, Langchi; Allen, Jeanette; Gordon, Robert J.

    1995-12-01

    Coherent phase control of the photodissociation of CH3I has been achieved by quantum mechanical interference between competing paths. The control was accomplished by exciting the parent molecules with three UV photons of frequency ω1 and one VUV photon of frequency ω3=3ω1. Varying the phase difference between the two laser beams resulted in a modulation of the I+ and CH+3 signals, without affecting the parent ion signal. We propose a mechanism in which control occurs over the photodissociation step to produce CH3+I*, followed by ionization of the neutral fragments by additional UV photons.

  8. Solar-pumped gas laser development

    NASA Technical Reports Server (NTRS)

    Wilson, J. W.

    1981-01-01

    The direct conversion of solar radiation into an inverted population for extraction in an optical cavity holds promise as a relatively simple system design. Broad-band photoabsorption in the visible or near-UV range is required to excite large volumes of gas and to ensure good solar absorption efficiency. The state excited must be a metastable state which is not quenched by the parent gas. The emission bandwidth must be less than approximately 10 A. The system should show chemical reversibility and an insensitivity to increasing temperature. Other properties such as good quantum efficiency and kinetic efficiency are also implied. A search of electronic-vibrational transitions in diatomic molecules satisfying these conditions is now in progress. A photodissociation-pumped atomic iodine laser is now being tested under solar pumping conditions. Photodissociation studies for thallium spin-flip metastable formation will begin in the near future.

  9. Solid-State Raman Converters for High-Average Power Chemical Oxygen Iodine Laser

    DTIC Science & Technology

    1998-01-01

    34Intraresonator stimulated Raman scattering in a nanosecond neodymium laser based on potassium gadolinium tungstate." Optika i Spectroscopiya, 62, 569 (1987). 18...stimulated Raman scattering in the active element of neodymium laser." Optika i Spectroskopiya, 59,950 (1985) (in Russian). 14. Y.RShen, The

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

    NASA Astrophysics Data System (ADS)

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

    2003-11-01

    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 65μm BHP droplets.

  11. Ultraviolet laser excitation source

    NASA Technical Reports Server (NTRS)

    Lee, J. H.; Mcfarland, D. R.; Hohl, F.

    1980-01-01

    A new intense ultraviolet light source has been developed from an array of hypocycloidal pinch (HCP) devices. The basic unit of the array is constructed with three disk electrodes and is capable of producing dense plasmas at temperatures up to 10,000,000 K. Very high input power levels to the array are possible without significantly shortening its useful life, in strong contrast with conventional xenon flashlamps. The new light source, when operated with Ar and Xe gas mixtures at high pressures (approximately 5 x 10 to the 4th Pa), produced a light output of over 100 MW in the near-UV spectral range and successfully pumped an iodine photodissociation laser at 1.315 microns. A xenon recombination laser at 2.027 microns was also pumped in the HCP array.

  12. Interpretation of In-Situ Measurements of Iodine Monoxide in Coastal Regions Using Laser-Induced Fluorescence Spectroscopy

    NASA Astrophysics Data System (ADS)

    Furneaux, K. L.; Whalley, L. K.; Heard, D. E.

    2009-04-01

    Iodine species are present in coastal and open ocean regions due to the release of I2 and iodocarbons from macro and micro algae. The photolysis of these molecules yields iodine atoms, which react with ozone to produce iodine monoxide (IO). IO is involved in ozone depletion cycles, the partitioning of HOx and NOx, and the formation and growth of new particles. A novel point source Laser Induced Fluorescence (LIF) instrument was deployed to measure IO in September 2006 at Roscoff, France as part of the Reactive Halogens in the Marine Boundary Layer (RHaMBLe) programme (1 instrument uncertainty = 23%)1. The maximum IO mixing ratio was 30 ± 7.1 pptV (10 s integration period, limit of detection = 1.4 pptV) at this semi-polluted coastal site (NOx levels = 1 - 5 ppbV). The closest macroalgae beds known to strongly emit I2 (laminaria) were ~ 300 m from the LIF instrument. IO displayed a strong anti-correlation with tidal height which is consistent with previous studies. IO was also dependent on solar irradiation and meteorological conditions. The dominant source of IO at this site was the photolysis of I2. The measurements provided by this instrument aim to address the main uncertainties associated with iodine chemistry. Co-ordinated measurement of IO by point source (LIF) and spatially averaged (Long Path Differential Optical Absorption Spectroscopy) instruments confirm the presence of IO hotspots due to non-uniform macroalgae distribution at this location (resulting in a spatially variable I2 source). The ratio of point source/spatially averaged IO is determined by meteorological conditions and distance of the instrument from macroalgae beds. Co-located point source I2 (Broadband Cavity Ringdown Spectroscopy) and IO (LIF) measurements correlated on some days but cannot be explained by our current knowledge of iodine chemistry. The influence of NOx on IO has been investigated. The detection of IO by LIF at the Roscoff site shows that IO can survive in a high NOx

  13. Apparatus for extraction and separation of a preferentially photo-dissociated molecular isotope into positive and negative ions by means of an electric field

    NASA Technical Reports Server (NTRS)

    Wilhelm, H. E. (Inventor)

    1978-01-01

    Molecules of one and the same isotope were preferentially photodissociated by a laser and an ultraviolet source, or by multiphoton absorption of laser radiation. The resultant ions were confined with a magnetic field, moved in opposite directions by an electric field, extracted from the photodissociation region by means of screening and accelerating grids, and collected in ducts.

  14. Method and apparatus for the production of pre pulse free smooth laser radiation pulses of variable pulse duration

    SciTech Connect

    Witte, K. J.; Fill, E.; Scrlac, W.

    1985-04-30

    The pulse duration of an iodine laser is adjusted between 400 ps and 20 ns primarily by changing the resonator length in the range of about 2 cm to about 100 cm and secondarily by the ratio of excitation energy to threshold energy of the laser. Iodine laser pulses without pre-pulse and substructure are achieved in that the gas pressure of the laser gas of the iodine laser is adapted to the resonator length in order to limit the band width of the amplification and thus the band width of the pulse to be produced. The longer are the laser pulses to be produced the lower is the pressure chosen. A prerequisite for the above results is that the excitation of the iodine laser occurs extremely rapidly. This is advantageously achieved by photo-dissociation of a perfluoroalkyl iodide as CF/sub 3/I by means of laser providing sufficiently short output pumping pulses, e.g. an excimer laser, as a KrF laser or XeCl laser or a frequency-multiplied Nd-glass or Nd-YAG laser, or a N/sub 2/ laser (in combination with t-C/sub 4/F/sub 9/I as laser medium). In addition to the substantial advantage of the easy variability of the pulse duration the method additionally has a number of further advantages, namely pre-pulse-free rise of the laser pulse up to the maximum amplitude; exchange of the laser medium between two pulses is not necessary at pulse repetition rates below about 1 hertz; high pulse repetion rates obtainable with laser gas regeneration; switching elements for isolating a laser oscillator from a subsequent amplifier cascade for the purpose of avoiding parasitic oscillations are not as critical as with flashlamp-pumped lasers.

  15. Frequency stabilization of an external cavity diode laser to molecular iodine at 657.483 nm.

    PubMed

    Fang, Hui-Mei; Wang, Shing-Chung; Shy, Jow-Tsong

    2006-05-01

    The saturation spectrum of the P(84) 5-5 transition of 127I2 at 657.483 nm is obtained with the third-harmonic demodulation method using an external cavity diode laser. The laser frequency is modulated by modulating the diode current instead of modulating the cavity length with a piezoelectric transducer (PZT). Current modulation allows a modulation frequency that is higher than PZT modulation. The signal-to-noise ratio of 1000 is better than previous results presented in the literature. The laser is frequency stabilized to the hyperfine component o of the P(84) 5-5 transition with a frequency stability of better than 10 kHz (2.2 x 10(-11) relative stability).

  16. Dissociation of I II in chemical oxygen-iodine lasers: experiment, modeling, and pre-dissociation by electrical discharge

    NASA Astrophysics Data System (ADS)

    Katz, A.; Waichman, K.; Dahan, Z.; Rybalkin, V.; Barmashenko, B. D.; Rosenwaks, S.

    2007-06-01

    The dissociation of I II molecules at the optical axis of a supersonic chemical oxygen-iodine laser (COIL) was studied via detailed measurements and three dimensional computational fluid dynamics calculations. Comparing the measurements and the calculations enabled critical examination of previously proposed dissociation mechanisms and suggestion of a mechanism consistent with the experimental and theoretical results obtained in a supersonic COIL for the gain, temperature and I II dissociation fraction at the optical axis. The suggested mechanism combines the recent scheme of Azyazov and Heaven (AIAA J. 44, 1593 (2006)), where I II(A' 3Π 2u), I II(A 3Π 1u) and O II(a1Δ g, v) are significant dissociation intermediates, with the "standard" chain branching mechanism of Heidner et al. (J. Phys. Chem. 87, 2348 (1983)), involving I(2P 1/2) and I II(X1Σ + g, v). In addition, we examined a new method for enhancement of the gain and power in a COIL by applying DC corona/glow discharge in the transonic section of the secondary flow in the supersonic nozzle, dissociating I II prior to its mixing with O II(1Δ). The loss of O II(1Δ) consumed for dissociation was thus reduced and the consequent dissociation rate downstream of the discharge increased, resulting in up to 80% power enhancement. The implication of this method for COILs operating beyond the specific conditions reported here is assessed.

  17. Toward understanding the dissociation of I2 in chemical oxygen-iodine lasers: Combined experimental and theoretical studies

    NASA Astrophysics Data System (ADS)

    Waichman, K.; Rybalkin, V.; Katz, A.; Dahan, Z.; Barmashenko, B. D.; Rosenwaks, S.

    2007-07-01

    The dissociation of I2 molecules at the optical axis of a supersonic chemical oxygen-iodine laser (COIL) was studied via detailed measurements and three-dimensional computational fluid dynamics calculations. The measurements, briefly reported in a recent paper [Rybalkin et al., Appl. Phys. Lett. 89, 021115 (2006)] and reanalyzed in detail here, revealed that the number N of consumed O2(aΔg1) molecules per dissociated I2 molecule depends on the experimental conditions: it is 4.5±0.4 for typical conditions and I2 densities applied for optimal operation of the COIL but increases at lower I2 densities. Comparing the measurements and the calculations enabled critical examination of previously proposed dissociation mechanisms and suggestion of a mechanism consistent with the experimental and theoretical results obtained in a supersonic COIL for the gain, temperature, I2 dissociation fraction, and N at the optical axis. The suggested mechanism combines the recent scheme of Azyazov and Heaven [AIAA J. 44, 1593 (2006)], where I2(A'Π2u3), I2(AΠ1u3), and O2(aΔg1,v) are significant dissociation intermediates, with the "standard" chain branching mechanism of Heidner III et al. [J. Phys. Chem. 87, 2348 (1983)], involving I(P1/22) and I2(XΣg +1,v).

  18. Iodine monofluoride 140-kW laser - Small signal gain and operating parameters

    NASA Technical Reports Server (NTRS)

    Dlabal, M. L.; Hutchinson, S. B.; Eden, J. G.; Verdeyen, J. T.

    1981-01-01

    Output energies in excess of 4 mJ in a 30-nsec FWHM pulse (140-kW peak power) have been obtained from a discharge-pumped IF laser for a cavity output coupling of 35%. In addition, oscillation on a new transition of the IF (E-A) band at 472.7 nm has been observed. By measurement of the output power of the laser for various values of output mirror transmission, the small signal gain and loss coefficients were found to be (3.1 + or - 0.7)%/cm and 0.3%/cm, respectively.

  19. INTERACTION OF LASER RADIATION WITH TARGETS Tomographic imaging of a target directly irradiated in experiments on the Iskra-5 iodine laser facility

    NASA Astrophysics Data System (ADS)

    Bondarenko, S. V.; Garanin, R. V.; Garanin, Sergey G.; Zhidkov, N. V.; Oreshkov, O. V.; Potapov, S. V.; Suslov, N. A.; Frolova, N. V.

    2010-12-01

    We set forth the data of experiments involving direct microtarget irradiation by the 12 second-harmonic beams (λ = 0.66 μm) of iodine laser radiation carried out on the Iskra-5 facility. For microtargets we employed glass shells ~500 μm in diameter with ~1-μm thick walls, which were filled with a DT mixture at a pressure pDT approx 3-4 atm. In one of these experiments, a tomographic image of the microtarget was recorded from the images obtained using pinhole cameras, which were arranged along seven different directions. The pinhole images were acquired in the X-ray radiation with photon energies above 1.5 keV. The procedure used for reconstructing the volume luminosity of the microtarget is described. An analysis of the tomographic image suggests that the compressed microtarget domain possesses a complex asymmetric shape; 20-30 μm sized structural elements being clearly visible. The resultant data set allowed us to estimate the initial nonuniformity of microtarget surface irradiation by the laser radiation. The rms nonuniformity of microtarget irradiance was estimated at ~60 %.

  20. Electron-beam sustained discharge in oxygen gas mixtures: singlet delta oxygen production for oxygen-iodine laser

    NASA Astrophysics Data System (ADS)

    Frolov, Mikhail P.; Hager, Gordon D.; Ionin, Andrei A.; Klimachev, Yurii M.; Kochetov, Igor V.; Kotkov, Andrei A.; McIver, John K.; Napartovich, Anatolii P.; Podmar'kov, Yurii P.; Seleznev, Leonid V.; Sinitsyn, Dmitrii V.; Vagin, Nikolai P.; Yuryshev, Nikolay N.

    2004-09-01

    Electric properties and spectroscopy of an e-beam sustained discharge (EBSD) in oxygen and oxygen gas mixtures at gas pressure up to 100 Torr were experimentally studied. The pulsed discharge in pure oxygen and its mixtures with noble gases was shown to be very unstable and characterized by low input energy. When adding small amount of carbon monoxide or hydrogen, the electric stability of the discharge increases, specific input energy (SIE) per molecular component being more than order of magnitude higher and coming up to 6.5 kJ/(l atm) for gas mixture O2:Ar:CO = 1:1:0.1. The results of experiments on spectroscopy of the singlet delta oxygen O2(a1Δg)(SDO) and O2(b1Σg+) states in the EBSD are presented. The calibration of the optical scheme for measuring the SDO absolute concentration and yield using the detection of luminescence of the SDO going from a chemical SDO generator was done. The preliminary measurement of the SDO yield demonstrated that it was ~3% for the SIE of ~1 kJ/(l atm), which is close to the results of theoretical calculations for such a SIE. Theoretical calculations demonstrated that for the SIE of 6.5 kJ/(l atm) the SDO yield may reach ~20% exceeding its threshold value needed for oxygen-iodine laser operation at room temperature, although a part of the energy loaded into the EBSD goes into the vibrational energy of the molecular admixture, (which was experimentally demonstrated by launching a CO laser operating on an oxygen-rich mixture O2:Ar:CO = 1:1:0.1 and measuring its small-signal gain).

  1. Photodissociation dynamics of pyrimidine

    SciTech Connect

    Lin Mingfu; Dyakov, Yuri A.; Tseng, C.-M.; Mebel, Alexander M.; Lin, S.H.; Lee, Yuan T.; Ni, C.-K.

    2006-02-28

    Photodissociation of pyrimidine at 193 and 248 nm was investigated separately using vacuum ultraviolet photoionization at 118.4 and 88.6 nm and multimass ion imaging techniques. Six dissociation channels were observed at 193 nm, including C{sub 4}N{sub 2}H{sub 4}{yields}C{sub 4}N{sub 2}H{sub 3}+H and five ring opening dissociation channels, C{sub 4}N{sub 2}H{sub 4}{yields}C{sub 3}NH{sub 3}+HCN, C{sub 4}N{sub 2}H{sub 4}{yields}2C{sub 2}NH{sub 2}, C{sub 4}N{sub 2}H{sub 4}{yields}CH{sub 3}N+C{sub 3}NH, C{sub 4}N{sub 2}H{sub 4}{yields}C{sub 4}NH{sub 2}+NH{sub 2}, and C{sub 4}N{sub 2}H{sub 4}{yields}CH{sub 2}N+C{sub 3}NH{sub 2}. Only the first four channels were observed at 248 nm. Photofragment translational energy distributions and dissociation rates indicate that dissociation occurs in the ground electronic state after internal conversion at both wavelengths. The dissociation rates were found to be >5x10{sup 7} and 1x10{sup 6} s{sup -1} at 193 and 248 nm, respectively. Comparison with the potential energies from ab initio calculations have been made.

  2. A Plasma Ultraviolet Source for Short Wavelength Lasers.

    DTIC Science & Technology

    1988-04-15

    Iodine photodissociation laser pumped with radiation from magnetoplasma compressions", G. N . Kashikov, V. K. Orlov, A. N . Panin, A. K. Piskunov and V. A...H DAAL3-86-G-0ee3 UNCLASIFIED F.’G 9/3 W EEEEEEEEEEommoiE EEEEEEEEEEEE Eu.... N ’ "’ II~ N .’ 1-0 L; 7, 1,,- / 41 5 u 1-25 IllII4 UNCLASSIFIED...REPORT NUMBER 2. GOVT ACCESSION NO. 3. RECIPIENT’S CATALOG NUMBER %Id AA6. ~-/h N /A N /ACo0 S TITLE (and Subtitle) S. TYPE OF REPORT & PERIOD COVERED

  3. Carrier phases for iodine in the Allende meteorite and their associated Xe-129(r)/I-127 ratios - A laser microprobe study

    NASA Technical Reports Server (NTRS)

    Kirschbaum, C.

    1988-01-01

    This paper presents the results of a study of the carrier phases of iodine in the Allende meteorite and their associated Xe-129(r)/I-127 ratios, obtained using a new high-sensitivity low-blank mass spectrometer coupled with a low-blank laser extraction system. Two types of experiments were performed: a survey of the Xe-129(r) amounts in unirradiated specimens of fine-grained assemblages and individual coarse mineral grains, and a study of the relationship between chlorine and iodine in irradiated samples of the inclusions, in which the Xe-129(r)/I-127 ratios were determined for various minerals. As a by-product of these measurements, the Ar-40/Ar-39 ages were obtained along with some results on trapped Xe components. A schematic diagram of the new mass spectrometer system is included.

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

    NASA Astrophysics Data System (ADS)

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

    2009-11-01

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

  5. Photodissociation cross section of ClOOCl at 330 nm.

    PubMed

    Jin, Bing; Chen, I-Cheng; Huang, Wen-Tsung; Lien, Chien-Yu; Guchhait, Nikhil; Lin, Jim J

    2010-04-15

    The photolysis rate of ClOOCl is crucial in the catalytic destruction of polar stratospheric ozone. In this work, we determined the photodissociation cross section of ClOOCl at 330 nm with a molecular beam and with mass-resolved detection. The photodissociation cross section is the product of the absorption cross section and the dissociation quantum yield. We formed an effusive molecular beam of ClOOCl at a nozzle temperature of 200 or 250 K and determined its photodissociation probability by measuring the decrease of the ClOOCl intensity upon laser irradiation. By comparing with a reference molecule (Cl(2)), of which the absorption cross section and dissociation quantum yield are well-known, we determined the absolute photodissociation cross section of ClOOCl at 330 nm to be (2.31 +/- 0.11) x 10(-19) cm(2) at 200 K and (2.47 +/- 0.12) x 10(-19) cm(2) at 250 K. Impurity interference has been a well-recognized problem in conventional spectroscopic studies of ClOOCl; our mass-resolved measurement directly overcomes such a problem. This measurement of the ClOOCl photolysis cross section at 330 nm is particularly useful in constraining its atmospheric photolysis rate, which in the polar stratosphere peaks near this wavelength.

  6. On the photodissociation of uranium hexafluoride in the B band

    NASA Astrophysics Data System (ADS)

    Menghini, M.; Morales, P.; Dore, P.; Schisano, M. I.

    1986-06-01

    The rate of photodissociation of uranium hexafluoride is measured for the first time as a function of wavelength in the B band. The experimental technique used tests the collision-free behavior and, with the addition of a buffer gas, the collisional effects on molecular relaxation. In both cases, the dissociation yield is strongly nonuniform. A qualitative interpretation of these results is attempted. Their relevance to the subject of laser isotopic separation and more generally of selective photochemistry is outlined.

  7. Iodine revisited.

    PubMed

    Cooper, Rose A

    2007-06-01

    Iodine is an antiseptic that has been used in wound care for more than 150 years. Traditional formulations of iodine had serious limitations that were reduced in later products. Much has been written about iodine and opinions on its clinical efficacy are divided. There have been reviews of the chemical properties of iodine, its antimicrobial activity, human physiology, cytotoxicity and its clinical effectiveness, but few have addressed all these aspects. With the recent development of iodine-containing wound care products and the continued publication of laboratory and clinical studies, it seems timely to reassess the evidence relating to the effectiveness of iodine for treating wounds. This literature review attempts to provide an appropriate chemical and physiological background of the characteristics of iodine in order to provide a sound basis for understanding the available microbiological and clinical data. It will show that understanding the factors that contribute to the activity and potential cytotoxicity of iodine are important in evaluating the clinical evidence. Although definitive studies are needed, the sustained delivery of low doses of free iodine offers the potential to inhibit a broad range of microbial species without selecting for resistant strains or inducing cytotoxic effects.

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

    SciTech Connect

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

    2009-09-15

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

  9. Effect of velocity cross-relaxation and mode separation upon the power spectrum of a chemical oxygen-iodine laser resonator

    NASA Astrophysics Data System (ADS)

    Copeland, Drew A.

    1990-06-01

    A gain model for optical extraction from the CW chemical oxygen-iodine laser medium is described. It uses a simplified, temperatuire-dependent, chemical kinetics package which consists of several reactions between molecular oxygen, atomic and molecular iodine, water, and helium. The Heidner I2 dissociation mechanism is included to allow for incomplete dissociation. Gas flow is treated using a premixed, one-dimensional stream-tube model which accounts for gas expansion and heat release in the cavity. Collisional cross-relaxation effects upon the Doppler-broadened line are treated using a Fokker-Planck diffusion model of the velocity distribution of the upper and lower laser levels. This model, in conjunction with geometric optics, multimode model of an unstable standing-wave confocal resonator, is used to examine the influence of incomplete velocity cross-relaxation and longitudinal mode separation upon the output power and mode spectrum of the laser. It is shown that lasing will occur on all available modes even when the mode separation is less than the collision linewidth.

  10. Laser plasma as an effective ion source

    NASA Astrophysics Data System (ADS)

    Masek, Karel; Krasa, Josef; Laska, Leos; Pfeifer, Miroslav; Rohlena, Karel; Kralikova, Bozena; Skala, Jiri; Woryna, Eugeniusz; Farny, J.; Parys, Piotr; Wolowski, Jerzy; Mraz, W.; Haseroth, H.; Sharkov, B.; Korschinek, G.

    1998-09-01

    Ions in different charge state and with different energy distribution are generated in the process of interaction of intense laser radiation with solid targets. Multiply charged ions of medium- and high-Z elements (Al, Co, Ni, Cu, Sn, Ta, W, Pt, Au, Pb, Bi), produced by photodissociation iodine laser system PERUN ((lambda) equals 1.315 micrometer, EL approximately 40 J, (tau) approximately 500 ps) are reported. Corpuscular diagnostics based on time-of-flight method (ion collectors and a cylindrical electrostatic ion energy analyzer) as well as Thomson parabola spectrometer were used in the experiments. The ions in maximum charge state up to about 55+ and with energies of several MeV were registered at a distance of about 2 m from the plasma plume. Measured ion current densities higher than 10 mA/cm2 in about 1 m from the target demonstrate the performance of laser ion source. A theoretical interpretation of ion spectra is attempted.

  11. Radioactive Iodine

    MedlinePlus

    ... No Comments IDD NEWSLETTER – February 2017 VOLUME 45 NUMBER 1 FEBRUARY 2017 IODINE GLOBAL NETWORK (formerly ICCIDD Global Network) is a ... 2015 (PDF File, 9.42 MB) VOLUME 44 NUMBER 4 NOVEMBER 2016 IODINE GLOBAL NETWORK (formerly ICCIDD Global Network) is a ...

  12. Formation and stimulated photodissociation of metastable molecules with emission of photon at the collision of two atoms in a laser radiation field

    NASA Astrophysics Data System (ADS)

    Gazazyan, E.; Gazazyan, A.

    2017-04-01

    The formation of metastable molecules (Feshbach resonances) at the collision of two atoms and subsequent stimulated transition to a lower unbound electronic molecular state, with emission of a photon of the laser radiation has been investigated. This can develop, in particular, for Rb 2 molecules due to resonance scattering of two Rb atoms. This process is a basis for the creation of excimer lasers. Expressions have been obtained for the cross sections of elastic and inelastic resonance scattering and the intensity of the stimulated emission of the photons.

  13. Photodissociation of Peroxynitric Acid in the Near-IR

    NASA Technical Reports Server (NTRS)

    Roehl, Coleen M.; Nizkorodov, Sergey A.; Zhang, Hui; Blake, Geoffrey A.; Wennberg, Paul O.

    2002-01-01

    Temperature-dependent near-IR photodissociation spectra were obtained for several vibrational overtone transitions of peroxynitric acid (HNO4) with a tunable OPO photolysis/OH laser-induced-fluorescence system. Band-integrated photodissociation cross-sections (definity integral of sigma(sub diss)), determined relative to that for the 3nu(sub 1), OH stretching overtone, were measured for three dissociative bands. Assuming unit quantum efficiency for photodissociation of 3nu(sub 1), we find 2nu(sub 1) + nu(sub 3)(8242/cm) = (1.21 x 10(exp -20) (independent of temperature), 2nu(sub 1) (6900/cm) = 4.09 x 10(exp 18) * e(sup (-826,5/T)) (295 K greater than T greater than 224 K), and nu(sub 1) + 2nu(sub 3) (6252/cm) = 1.87 x 10(exp -19) * e(sup (- 1410.7/T)) (278 K greater than T greater than 240 K) sq cm/molecule cm. The photodissociation cross-sections are independent of pressure over the range 2 to 40 Torr. Temperature-dependent quantum yields (phi) for these transitions were obtained using integrated absorption cross-sections (definity integral of sigma(sub abs)) of HNO4 overtone vibrations measured with a FTIR spectrometer. In the atmosphere, photodissociation in the infrared is dominated by excitation of the first overtone of the OH stretching vibration (2nu((sub 1)). Inclusion of all dissociative HNO4 overtone and combination transitions yields a daytime IR photolysis rate of approximately 1 x 10(esp -1)/s. This process significantly shortens the estimated lifetime of HNO4 in the upper troposphere and lower stratosphere.

  14. Planar Laser-Induced Iodine Fluorescence Measurements in Rarefied Hypersonic Flow

    NASA Technical Reports Server (NTRS)

    Cecil, Eric; McDaniel, James C.

    2005-01-01

    A planar laser-induced fluorescence (PLIF) technique is discussed and applied to measurement of time-averaged values of velocity and temperature in an I(sub 2)-seeded N(sub 2) hypersonic free jet facility. Using this technique, a low temperature, non-reacting, hypersonic flow over a simplified model of a reaction control system (RCS) was investigated. Data are presented of rarefied Mach 12 flow over a sharp leading edge flat plate at zero incidence, both with and without an interacting jet issuing from a nozzle built into the plate. The velocity profile in the boundary layer on the plate was resolved. The slip velocity along the plate, extrapolated from the velocity profile data, varied from nearly 100% down to 10% of the freestream value. These measurements are compared with results of a DSMC solution. The velocity variation along the centerline of a jet issuing from the plate was measured and found to match closely with the correlation of Ashkenas and Sherman. The velocity variation in the oblique shock terminating the jet was resolved sufficiently to measure the shock wave thickness.

  15. Planar Laser-Induced Iodine Fluorescence Measurements in Rarefied Hypersonic Flow

    NASA Astrophysics Data System (ADS)

    Cecil, Eric; McDaniel, James C.

    2005-05-01

    A planar laser-induced fluorescence (PLIF) technique is discussed and applied to measurement of time-averaged values of velocity and temperature in an I2-seeded N2 hypersonic free jet facility. Using this technique, a low temperature, non-reacting, hypersonic flow over a simplified model of a reaction control system (RCS) was investigated. Data are presented of rarefied Mach 12 flow over a sharp leading edge flat plate at zero incidence, both with and without an interacting jet issuing from a nozzle built into the plate. The velocity profile in the boundary layer on the plate was resolved. The slip velocity along the plate, extrapolated from the velocity profile data, varied from nearly 100% down to 10% of the freestream value. These measurements are compared with results of a DSMC solution. The velocity variation along the centerline of a jet issuing from the plate was measured and found to match closely with the correlation of Ashkenas and Sherman. The velocity variation in the oblique shock terminating the jet was resolved sufficiently to measure the shock wave thickness.

  16. In-situ measurements of iodine monoxide at coastal and open-ocean locations using laser induced fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Commane, R.; Whalley, L. K.; Furneaux, K. L.; Ingham, T.; Bloss, W. J.; Heard, D. E.

    2008-12-01

    The halogen oxides, IO and BrO, have traditionally been measured using the Long Path-Differential Optical Absorption Spectroscopy (LP-DOAS) technique. Laser Induced Fluorescence (LIF), however, provides a sensitive and selective alternative method to detect IO. LIF provides a point-source measurement of IO; comparison of IO data taken using LIF and LP-DOAS can help determine local sources of iodine at coastal sites. In-situ techniques, such as LIF, also allow a direct comparison with other co-located in-situ instruments, improving the understanding of the chemical interactions that occur. Furthermore the size, weight and flexibility of such instruments mean that they are readily deployable on ship and aircraft platforms, as well as at ground-based sites. The University of Leeds LIF-IO instruments have been operational since 2006; data taken at three contrasting locations will be presented. IO measurements were made at the Mace Head Observatory on the west coast of Ireland in 2007. The site is predominantly impacted by background air-masses from the north Atlantic. An anti-correlation between IO concentration and tidal height during the day was observable; a maximum of 33 pptV was observed during the lowest tides. A comparison with concurrent LP-DOAS measurements demonstrates local hot-spots of IO production. The release of I2 from a narrow strip of macro-algae, specifically laminaria, along this coastline acts as the major iodine source. In-situ IO measurements were also made at a second coastal site, in Roscoff, France as part of the Reactive Halogens in the Marine Boundary Layer (RHaMBLe) project. This stretch of coastline is also impacted by macro-algae and high concentrations of IO were again observable at low-tide. In contrast to Mace Head, the Roscoff site was influenced by local pollution. A negative correlation between IO and NO2 was observed during low-tide periods; a positive correlation between IO and new particle bursts was also recorded. This work

  17. Efficient photo-dissociation of CH{sub 4} and H{sub 2}CO molecules with optimized ultra-short laser pulses

    SciTech Connect

    Rasti, S.; Irani, E.; Sadighi-Bonabi, R.

    2015-11-15

    The fragmentation dynamics of CH{sub 4} and H{sub 2}CO molecules have been studied with ultra-short pulses at laser intensityof up to 10{sup 15}Wcm{sup −2}. Three dimensional molecular dynamics calculations for finding the optimized laser pulses are presented based on time-dependent density functional theory and quantum optimal control theory. A comparison of the results for orientation dependence in the ionization process shows that the electron distribution for CH{sub 4} is more isotropic than H{sub 2}CO molecule. Total conversion yields of up to 70% at an orientation angle of 30{sup o} for CH{sub 4} and 65% at 90{sup 0} for H{sub 2}CO are achieved which lead to enhancement of dissociation probability.

  18. The photodissociation and reaction dynamics of vibrationally excited molecules

    SciTech Connect

    Not Available

    1993-01-01

    We have used combined vibrational overtone excitation and laser induced fluorescence detection to study dissociation dynamics of hydroxylamine (NH[sub 2]OH), have performed our first laser induced grating experiments on water, and have begun assembling a new apparatus for preparing vibrationally excited molecules with simulated Raman excitation. We study role of vibrational excitation in photodissociation dynamics by using a vibrational state preparation technique, such as vibrational overtone excitation or stimulated Raman excitation, to create molecules with particular nuclear motions and then to excite that molecule to a dissociative electronic state.

  19. Multiphoton Photodissociation of Several Halocarbons.

    NASA Astrophysics Data System (ADS)

    Quandt, Bob

    2006-03-01

    The 2 x 193 nm photodissociations of CHCl3 , CFCl3, CF3CCl3, CCl4, CH3-CCl3 and CH3CH2-CCl3 have been examined using dispersed fluorescence. It was found that the initial photodissociation of CHCl3 forms large amounts of CH(A^2δ) while the photodissociation of CCl4 forms lesser but still significant amounts of CX(A^2δ) The photodissociations of CH3-CCl3 and CH3CH2-CCl3 produce CH3-C and CH3CH2-C presumably in the A^2δ state. The exact photoproducts of the fluorinated species are currently unknown. Fluorescence rise time measurements show that the CH(A^2δ) and CCl(A^2δ) photoproducts quickly react to form C2 (d^3πg). However, formation of C2 (d^3πg) is attenuated when the primary photoproducts are CF3C, CH3-C and CH3CH2-C and disappears completely when it is CF. In addition, the atomic and molecular halogen photoproduct channels were investigated using ab initio calculations. Intrinsic Reaction Coordinate calculations were performed at the MP2 level of theory using the LANL2DZ basis set in order to characterize the dissociation pathways for all of species investigation.. The results of the calculations show the presence of three transition states and an ion-pair isomer intermediate for all molecules. The broken symmetry structure of the transition states for the formation of molecular bromine is in agreement with the first step of the addition mechanism proposed by Cain and co-workers for CX2 +Y2 reactions.

  20. Threshold photodissociation of Cr+2

    NASA Astrophysics Data System (ADS)

    Lessen, D. E.; Asher, R. L.; Brucat, P. J.

    1991-08-01

    A one-photon photodissociation threshold for supersonically cooled Cr+2 is determined to be 2.13 eV. This threshold provides a strict upper limit to the adiabatic binding energy of the ground state of chromium dimer cation if the initial internal energy of the parent ion may be neglected. From the difference in the IPs of chromium atom and dimer, an upper limit to the dissociation of Cr2 is placed at 1.77 eV.

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

    NASA Astrophysics Data System (ADS)

    Woodard, B. S.; Zimmerman, J. W.; Benavides, G. F.; Carroll, D. L.; Verdeyen, J. T.; Palla, A. D.; Field, T. H.; Solomon, W. C.; Davis, S. J.; Rawlins, W. T.; Lee, S.

    2008-07-01

    Herein the authors report on the demonstration of gain and a continuous-wave laser on the 1315nm transition of atomic iodine using the energy transferred to I(P1/22) from O2(aΔ1) produced by a radio-frequency-excited electric discharge sustained in a dry air-He-NO gas mixture. Active oxygen and nitrogen species were observed downstream of the discharge region. Downstream of the discharge, cold gas injection was employed to raise the gas density and lower the temperature of the continuous gas flow. Gain of 0.0062%cm-1 was obtained and the laser output power was 32mW in a supersonic flow cavity.

  2. Photodissociation spectroscopy of protonated leucine enkephalin.

    PubMed

    Herburger, Andreas; van der Linde, Christian; Beyer, Martin K

    2017-02-24

    Protonated leucine enkephalin (YGGFL) was studied by ultraviolet photodissociation (UVPD) from 225 to 300 nm utilizing an optical parametric oscillator tunable wavelength laser system (OPO). Fragments were identified by absolute mass measurement in a 9.4 T Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS). Bond cleavage was preferred in the vicinity of the two aromatic residues, resulting in high ion abundances for a4, a1, b3, y2 and y1 fragments. a, b and y ions dominated the mass spectrum, and full sequence coverage was achieved for those types. Photodissociation was most effective at the short wavelength end of the studied range, which is assigned to the onset of the La π-π* transition of the tyrosine chromophore, but worked well also at the Lb π-π* chromophore absorption maxima in the 35 000-39 000 cm(-1) region. Several side-chain and internal fragments were observed. H atom loss is observed only above 41 000 cm(-1), consistent with the requirement of a curve crossing to a repulsive (1)πσ* state. It is suggested that the photochemically generated mobile H atom plays a role in further backbone cleavages, similar to the mechanism for electron capture dissociation. The b4 fragment is most intense at the Lb chromophore absorptions, undergoing additional fragmentation at higher photon energies. The high resolution of the FT-ICR MS revealed that out of all x and z-type fragments only x3 and x4 were formed, with low intensity. Other previously reported x- and z-fragments were re-assigned to internal fragments, based on exact mass measurement.

  3. Molecular Iodine Clock

    NASA Astrophysics Data System (ADS)

    Ye, Jun; Ma, Long Sheng; Hall, John L.

    2001-12-01

    We demonstrate a simple optical clock based on an optical transition of iodine molecules, providing a frequency stability superior to most rf sources. Combined with a femtosecond-laser-based optical comb to provide the phase coherent clock mechanism linking the optical and microwave spectra, we derive an rf clock signal of comparable stability over an extended period. Measurements suggest the stability ( 5×10-14 at 1 s) of the cw laser locked on the iodine transition is transferred to every comb component throughout the optical octave bandwidth (from 532 to 1064 nm) with a precision of 3.5×10-15. Characterization of the performance of the optical clock shows (in-)stability below 3×10-13 at 1 s (currently limited by the microwave sources), and 4.6×10-13 over one year.

  4. Molecular iodine clock.

    PubMed

    Ye, J; Ma, L S; Hall, J L

    2001-12-31

    We demonstrate a simple optical clock based on an optical transition of iodine molecules, providing a frequency stability superior to most rf sources. Combined with a femtosecond-laser-based optical comb to provide the phase coherent clock mechanism linking the optical and microwave spectra, we derive an rf clock signal of comparable stability over an extended period. Measurements suggest the stability ( 5x10(-14) at 1 s) of the cw laser locked on the iodine transition is transferred to every comb component throughout the optical octave bandwidth (from 532 to 1064 nm) with a precision of 3.5x10(-15). Characterization of the performance of the optical clock shows (in-)stability below 3x10(-13) at 1 s (currently limited by the microwave sources), and 4.6x10(-13) over one year.

  5. Moving in on the Action: An Experimental Comparison of Fluorescence Excitation and Photodissociation Action Spectroscopy.

    PubMed

    Wellman, Sydney M J; Jockusch, Rebecca A

    2015-06-18

    Photodissociation action spectroscopy is often used as a proxy for measuring gas-phase absorption spectra of ions in a mass spectrometer. Although the potential discrepancy between linear optical and photodissociation spectra is generally acknowledged, direct experimental comparisons are lacking. In this work, we use a quadrupole ion trap that has been modified to enable both photodissociation and laser-induced fluorescence to assess how closely the visible photodissociation action spectrum of a fluorescent dye reflects its fluorescence excitation spectrum. Our results show the photodissociation action spectrum of gaseous rhodamine 110 is both substantially narrower and slightly red-shifted (∼120 cm(-1)) compared to its fluorescence excitation spectrum. Power dependence measurements reveal that the photodissociation of rhodamine 110 requires, on average, the absorption of three photons whereas fluorescence is a single-photon process. These differing power dependences are the key to interpreting the differences in the measured spectra. The experimental results provide much-needed quantification and insight into the differences between action spectra and linear optical spectra, and emphasize the utility of fluorescence excitation spectra to provide a more reliable benchmark for comparison with theory.

  6. Iodine Deficiency

    MedlinePlus

    ... enlargement of the thyroid (goiter – see Goiter brochure ), hypothyroidism (see Hypothyroidism brochure ) and to mental retardation in infants and ... when lying down, and difficulty swallowing and breathing. HYPOTHYROIDISM – As the body’s iodine levels fall, hypothyroidism may ...

  7. Tracing iodine

    NASA Astrophysics Data System (ADS)

    Metrangolo, Pierangelo; Resnati, Giuseppe

    2011-03-01

    Pierangelo Metrangolo and Giuseppe Resnati celebrate the bicentenary of the discovery of iodine - a good time to also bring to its conclusion an international project that aims to define and categorize halogen bonding.

  8. Photodissociation of interstellar N2

    NASA Astrophysics Data System (ADS)

    Li, X.; Heays, A. N.; Visser, R.; Ubachs, W.; Lewis, B. R.; Gibson, S. T.; van Dishoeck, E. F.

    2013-07-01

    Context. Molecular nitrogen is one of the key species in the chemistry of interstellar clouds and protoplanetary disks, but its photodissociation under interstellar conditions has never been properly studied. The partitioning of nitrogen between N and N2 controls the formation of more complex prebiotic nitrogen-containing species. Aims: The aim of this work is to gain a better understanding of the interstellar N2 photodissociation processes based on recent detailed theoretical and experimental work and to provide accurate rates for use in chemical models. Methods: We used an approach similar to that adopted for CO in which we simulated the full high-resolution line-by-line absorption + dissociation spectrum of N2 over the relevant 912-1000 Å wavelength range, by using a quantum-mechanical model which solves the coupled-channels Schrödinger equation. The simulated N2 spectra were compared with the absorption spectra of H2, H, CO, and dust to compute photodissociation rates in various radiation fields and shielding functions. The effects of the new rates in interstellar cloud models were illustrated for diffuse and translucent clouds, a dense photon dominated region and a protoplanetary disk. Results: The unattenuated photodissociation rate in the Draine (1978, ApJS, 36, 595) radiation field assuming an N2 excitation temperature of 50 K is 1.65 × 10-10 s-1, with an uncertainty of only 10%. Most of the photodissociation occurs through bands in the 957-980 Å range. The N2 rate depends slightly on the temperature through the variation of predissociation probabilities with rotational quantum number for some bands. Shielding functions are provided for a range of H2 and H column densities, with H2 being much more effective than H in reducing the N2 rate inside a cloud. Shielding by CO is not effective. The new rates are 28% lower than the previously recommended values. Nevertheless, diffuse cloud models still fail to reproduce the possible detection of interstellar N2

  9. Photodissociation of Cerium Oxide Nanocluster Cations.

    PubMed

    Akin, S T; Ard, S G; Dye, B E; Schaefer, H F; Duncan, M A

    2016-04-21

    Cerium oxide cluster cations, CexOy(+), are produced via laser vaporization in a pulsed nozzle source and detected with time-of-flight mass spectrometry. The mass spectrum displays a strongly preferred oxide stoichiometry for each cluster with a specific number of metal atoms x, with x ≤ y. Specifically, the most prominent clusters correspond to the formula CeO(CeO2)n(+). The cluster cations are mass selected and photodissociated with a Nd:YAG laser at either 532 or 355 nm. The prominent clusters dissociate to produce smaller species also having a similar CeO(CeO2)n(+) formula, always with apparent leaving groups of (CeO2). The production of CeO(CeO2)n(+) from the dissociation of many cluster sizes establishes the relative stability of these clusters. Furthermore, the consistent loss of neutral CeO2 shows that the smallest neutral clusters adopt the same oxidation state (IV) as the most common form of bulk cerium oxide. Clusters with higher oxygen content than the CeO(CeO2)n(+) masses are present with much lower abundance. These species dissociate by the loss of O2, leaving surviving clusters with the CeO(CeO2)n(+) formula. Density functional theory calculations on these clusters suggest structures composed of stable CeO(CeO2)n(+) cores with excess oxygen bound to the surface as a superoxide unit (O2(-)).

  10. Iodine Satellite

    NASA Technical Reports Server (NTRS)

    Dankanich, John; Kamhawi, Hani; Szabo, James

    2015-01-01

    This project is a collaborative effort to mature an iodine propulsion system while reducing risk and increasing fidelity of a technology demonstration mission concept. 1 The FY 2014 tasks include investments leveraged throughout NASA, from multiple mission directorates, as a partnership with NASA Glenn Research Center (GRC), a NASA Marshall Space Flight Center (MSFC) Technology Investment Project, and an Air Force partnership. Propulsion technology is often a critical enabling technology for space missions. NASA is investing in technologies to enable high value missions with very small and low-cost spacecraft, even CubeSats. However, these small spacecraft currently lack any appreciable propulsion capability. CubeSats are typically deployed and drift without any ability to transfer to higher value orbits, perform orbit maintenance, or deorbit. However, the iodine Hall system can allow the spacecraft to transfer into a higher value science orbit. The iodine satellite (iSAT) will be able to achieve a (Delta)V of >500 m/s with <1 kg of solid iodine propellant, which can be stored in an unpressurized benign state prior to launch. The iSAT propulsion system consists of the 200 W Hall thruster, solid iodine propellant tank, a power processing unit, and the necessary valves and tubing to route the iodine vapor. The propulsion system is led by GRC, with critical hardware provided by the Busek Co. The propellant tank begins with solid iodine unpressurized on the ground and in-flight before operations, which is then heated via tank heaters to a temperature at which solid iodine sublimates to iodine vapor. The vapor is then routed through tubing and custom valves to control mass flow to the thruster and cathode assembly. 2 The thruster then ionizes the vapor and accelerates it via magnetic and electrostatic fields, resulting in thrust with a specific impulse >1,300 s. The iSAT spacecraft, illustrated in figure 1, is currently a 12U CubeSat. The spacecraft chassis will be

  11. Iodine in diet

    MedlinePlus

    ... products also contain iodine. Other good sources are plants grown in iodine-rich soil. ... goiter or hypothyroidism . Without enough iodine, the thyroid ... intake of iodine can reduce the function of the thyroid gland.

  12. Iodine Absorption Cells Purity Testing.

    PubMed

    Hrabina, Jan; Zucco, Massimo; Philippe, Charles; Pham, Tuan Minh; Holá, Miroslava; Acef, Ouali; Lazar, Josef; Číp, Ondřej

    2017-01-06

    This article deals with the evaluation of the chemical purity of iodine-filled absorption cells and the optical frequency references used for the frequency locking of laser standards. We summarize the recent trends and progress in absorption cell technology and we focus on methods for iodine cell purity testing. We compare two independent experimental systems based on the laser-induced fluorescence method, showing an improvement of measurement uncertainty by introducing a compensation system reducing unwanted influences. We show the advantages of this technique, which is relatively simple and does not require extensive hardware equipment. As an alternative to the traditionally used methods we propose an approach of hyperfine transitions' spectral linewidth measurement. The key characteristic of this method is demonstrated on a set of testing iodine cells. The relationship between laser-induced fluorescence and transition linewidth methods will be presented as well as a summary of the advantages and disadvantages of the proposed technique (in comparison with traditional measurement approaches).

  13. REVIEWS OF TOPICAL PROBLEMS: Gas lasers with solar excitation

    NASA Astrophysics Data System (ADS)

    Gordiets, B. F.; Panchenko, Vladislav Ya

    1986-07-01

    CONTENTS 1. Introduction 703 2. General requirements for laser media using solar excitation 704 3. Lasers with direct excitation by solar light 705 3.1. Basic characteristics of laser media. 3.2. Photodissociation Br2-CO2 lasers. 3.3. Interhalogen molecule lasers. 3.4. Iodine lasers. 3.5. Alkali metal vapor lasers. 4. Lasers with thermal conversion of solar pumping 709 4.1. General considerations. 4.2. CO2 laser with excitation in a black body cavity and with gas flow. 4.3. cw CO2 laser without gas flow. 5. Space laser media with solar excitation 713 5.1. Population inversion of molecular levels in the outer atmosphere of the Earth. 5.2. Laser effect in the atmospheres of Venus and Mars. 5.3. Terrestrial experimental technique for observing infrared emission in the atmospheres of planets. 5.4. Designs for laser systems in the atmospheres of Venus and Mars. 6. Conclusions 717 References 717

  14. The development and deployment of a ground-based, laser-induced fluorescence instrument for the in situ detection of iodine monoxide radicals

    SciTech Connect

    Thurlow, M. E. Hannun, R. A.; Lapson, L. B.; Anderson, J. G.; Co, D. T.; O'Brien, A. S.; Hanisco, T. F.

    2014-04-15

    High abundances of iodine monoxide (IO) are known to exist and to participate in local photochemistry of the marine boundary layer. Of particular interest are the roles IO plays in the formation of new particles in coastal marine environments and in depletion episodes of ozone and mercury in the Arctic polar spring. This paper describes a ground-based instrument that measures IO at mixing ratios less than one part in 10{sup 12}. The IO radical is measured by detecting laser-induced fluorescence at wavelengths longer that 500 nm. Tunable visible light is used to pump the A{sup 2}Π{sub 3/2} (v{sup ′} = 2) ← X{sup 2}Π{sub 3/2} (v{sup ″} = 0) transition of IO near 445 nm. The laser light is produced by a solid-state, Nd:YAG-pumped Ti:Sapphire laser at 5 kHz repetition rate. The laser-induced fluorescence instrument performs reliably with very high signal-to-noise ratios (>10) achieved in short integration times (<1 min). The observations from a validation deployment to the Shoals Marine Lab on Appledore Island, ME are presented and are broadly consistent with in situ observations from European Coastal Sites. Mixing ratios ranged from the instrumental detection limit (<1 pptv) to 10 pptv. These data represent the first in situ point measurements of IO in North America.

  15. The Development and Deployment of a Ground-Based, Laser-Induced Fluorescence Instrument for the In Situ Detection of Iodine Monoxide Radicals

    NASA Technical Reports Server (NTRS)

    Thurlow, M. E.; Co, D. T.; O'Brien, A. S.; Hannun, R. A.; Lapson, L. B.; Hanisco, T. F.; Anderson, J. G.

    2014-01-01

    High abundances of iodine monoxide (IO) are known to exist and to participate in local photochemistry of the marine boundary layer. Of particular interest are the roles IO plays in the formation of new particles in coastal marine environments and in depletion episodes of ozone and mercury in the Arctic polar spring. This paper describes a ground-based instrument that measures IO at mixing ratios less than one part in 1012. The IO radical is measured by detecting laser-induced fluorescence at wavelengths longer that 500 nm. Tunable visible light is used to pump the A23/2 (v = 2) ? X23/2 (v = 0) transition of IO near 445 nm. The laser light is produced by a solid-state, Nd:YAG-pumped Ti:Sapphire laser at 5 kHz repetition rate. The laser-induced fluorescence instrument performs reliably with very high signal-to-noise ratios (>10) achieved in short integration times (<1 min). The observations from a validation deployment to the Shoals Marine Lab on Appledore Island, ME are presented and are broadly consistent with in situ observations from European Coastal Sites. Mixing ratios ranged from the instrumental detection limit (<1 pptv) to 10 pptv. These data represent the first in situ point measurements of IO in North America.

  16. Solar energy conversion through ligand photodissociation

    SciTech Connect

    Hoffman, B.M.; Sima, P.D.

    1983-04-06

    A new technique for photochemical conversion of solar energy based on ligand photodissociation from metal complexes is examined. The concept is illustrated with a photogalvanic cell in which voltages are generated by photodissociation of CO from carbonylferroheme and with a cell in which the illuminated electrode is coated with an iron tetraphenylporphyrin.

  17. Combined Infrared Multiphoton Dissociation with Ultraviolet Photodissociation for Ubiquitin Characterization

    NASA Astrophysics Data System (ADS)

    Halim, Mohammad A.; Girod, Marion; MacAleese, Luke; Lemoine, Jérôme; Antoine, Rodolphe; Dugourd, Philippe

    2016-09-01

    Herein we report the successful implementation of the consecutive and simultaneous photodissociation with high (213 nm) and low (10.6 μm) energy photons (HiLoPD, high-low photodissociation) on ubiquitin in a quadrupole-Orbitrap mass spectrometer. Absorption of high-energy UV photon is dispersed over the whole protein and stimulates extensive C-Cα backbone fragmentation, whereas low-energy IR photon gradually increases the internal energy and thus preferentially dissociates the most labile amide (C-N) bonds. We noticed that simultaneous irradiation of UV and IR lasers on intact ubiquitin in a single MS/MS experiment provides a rich and well-balanced fragmentation array of a/x, b/y, and z ions. Moreover, secondary fragmentation from a/x and z ions leads to the formation of satellite side-chain ions (d, v, and w) and can help to distinguish isomeric residues in a protein. Implementation of high-low photodissociation in a high-resolution mass spectrometer may offer considerable benefits to promote a comprehensive portrait of protein characterization.

  18. Radionuclide Basics: Iodine

    MedlinePlus

    ... body; as they pass through, they can cause damage to tissue and DNA. Iodine-131: 8.02 days Iodine-129: 15.7 million years On this page: Iodine in the environment Iodine sources Iodine and health Iodine in the ...

  19. Development of a Laser-Induced Fluorescence Ground-Based Instrument for Measurements of Atmospheric Iodine Monoxide (IO)

    NASA Astrophysics Data System (ADS)

    Co, D. T.; Hanisco, T. F.; Lapson, L. B.; Anderson, J. G.

    2006-12-01

    High abundances of iodine monoxide (IO) are known to exist and to participate in local photochemistry of the marine boundary layer: (1) IO participates in depletion episodes of O3 and in the removal of mercury in the Arctic polar spring by enhancing atomic Br mixing ratios. Recent observations and computer simulations suggest that mercury sequestration is closely tied to halogen photochemistry and that gaseous atomic Hg depletion can be enhanced significantly by the presence of small amounts of iodine-containing compounds. (2) IO and higher-order iodine oxides are involved in the formation of new particles in coastal marine environments. Studies using smog chamber experiments simulating coastal atmospheric conditions have demonstrated that new particles can form from condensable iodine-containing vapors and that their concentrations over the open ocean are sufficient to influence marine particle formation. (3) IO has also been shown to affect the oxidizing capacity of the troposphere by altering the partitioning of NO2/NO and HO2/HO and by activating chlorine and bromine in sea salt aerosols. In the stratosphere, these same processes can lead to enhanced ozone loss rates. Detailed photochemical models that include iodine photochemistry, however, are hampered by the lack of observational data. The distribution of IO in vertical, horizontal, and temporal coordinates is unknown, so the impact of IO on global photochemistry cannot be predicted. The resolution of these important scientific issues requires an in situ IO sensor. A fully functional nanosecond Nd:YAG-pumped Ti:Sapphire system and an IO sensor have been built in our lab. With the use of highly efficient fluorescence detection optics and photon counting techniques, a sensitivity of better than 0.1 ppt in 1 s for IO was empirically determined with our current laboratory prototype system, sensitive enough to resolve both the dilute mixing ratios of tropospheric and stratospheric IO and fast enough to resolve

  20. Generation of iodine L-shell X-rays under excitation of large CF{sub 3}I clusters by femtosecond laser radiation

    SciTech Connect

    Gordienko, Vyacheslav M; Dzhidzhoev, M S; Zhvaniya, I A; Pribytkov, Andrei V; Trubnikov, Dmitrii N; Fedorov, D O

    2012-11-30

    The use of clusters of polyatomic molecules with a relatively low ionisation energy ({approx}10 eV) is proposed for the efficient production of X-ray radiation. We have observed for the first time the generation of characteristic X-ray radiation due to L transitions in iodine atoms under the high-intensity femtosecond laser irradiation of molecular CF{sub 3}I clusters, which were a small admixture to Ar carrier gas. The X-ray conversion efficiency amounts to {approx}10{sup -6} (for a yield of {approx}10{sup 7} photons per pulse), which is an order of magnitude higher than the efficiency we obtained in the case of argon clusters under comparable conditions. (letters)

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

    NASA Astrophysics Data System (ADS)

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

    1998-05-01

    This paper describes a series of analyses using the 3-d MINT Navier-Stokes and OCELOT wave optics codes to calculate beam quality in a COIL laser cavity. To make this analysis tractable, the problem was broken into two contributions to the medium quality; that associated with microscale disturbances primarily from the transverse iodine injectors, and that associated with the macroscale including boundary layers and shock-like effects. Results for both microscale and macroscale medium quality are presented for the baseline layer operating point in terms of single pass wavefront error. These results show that the microscale optical path difference effects are 1D in nature and of low spatial order. The COIL medium quality is shown to be dominated by macroscale effects; primarily pressure waves generated from flow/boundary layer interactions on the cavity shrouds.

  2. Absolute frequency measurement of the iodine-stabilized Ar+ laser at 514.6 nm using a femtosecond optical frequency comb

    NASA Astrophysics Data System (ADS)

    Goncharov, A.; Amy-Klein, A.; Lopez, O.; du Burck, F.; Chardonnet, C.

    The frequency of 127I2 hyperfine component a3 of the P(13) 43-0 transition at 514.6 nm has been measured with an optical clockwork based on a femtosecond laser frequency comb generator. The measured frequency at an iodine pressure of 0.12 Pa is 67.3(0.75) kHz higher than the value of 582490603.38(15) MHz, adopted by the CIPM in 2003 [9] but is in a good agreement with the value measured by [29]. In our experiment we used H-maser reference frequency located at BNM-SYRTE Observatoire de Paris and transported to our laboratory by a 43 km optical fibre link.

  3. Energy distribution in the no fragment after photodissociation of dimethylnitrosamine (CH 3) 2NNO

    NASA Astrophysics Data System (ADS)

    Dubs, Martin; Huber, J. Robert

    1984-06-01

    The vibrational and rotational state distributions as well as the translational energy have been measured for the nascent NO fragment after photodissociation of dimethylnitrosamine at 363.5 nm. Four different vibrational states (υ″ = 0-3) and rotational transitions with quantum numbers up to J″ = 50 were observed using two-photon laser-induced flourescence.

  4. Vacuum ultraviolet photoionization and photodissociation of polyatomic molecules and radicals

    SciTech Connect

    Ng, C.Y.

    1993-12-01

    In the past decade, tremendous progress has been made in understanding the photodissociation (PD) dynamics of triatomic molecules. However, the PD study of radicals, especially polyatomic radicals, has remained essentially an unexplored research area. Detailed state-to-state PD cross sections for radicals in the UV and VUV provide challenges not only for dynamical calculations, but also for ab initio quantum chemical studies. The authors have developed a laser based pump-probe apparatus for the measurement of absolute PD cross sections for CH{sub 3}S and HS is summarized.

  5. Coherent phase control of the photodissociation of HOD

    SciTech Connect

    Allendorf, S.W.; Conaway, W.E.; Krause, J.L.

    1993-07-19

    A goal of chemical reaction dynamics is to control the course of reactions. We are examining the photodissocation of HOD, which is attractive for coherent control studies. A fixed frequency laser at 600 nm and its third harmonic at 200 nm is used to simultaneously and coherently photodissociate the rovibrationally excited parent molecules. Preliminary experiments focussed on confirming individual steps of the complex experiment; results are given of three-photon dissociation of H{sub 2}O, which gives confidence for the HOD three-photon dissociation.

  6. Vector Correlation in the Photodissociation of Metal Nitrosyls

    NASA Astrophysics Data System (ADS)

    Bartz, Jeffrey A.; Peden, Amber L.; Kieda, Ryan D.

    2010-06-01

    The vector correlation in the photodissociation of metal nitrosyls has been determined using linearly-polarized laser light and velocity-mapped ion imaging. The 225-nm dissociation beam excites a doubly-degenerate metal-to-ligand charge transfer in both eta5-C5H5NiNO and Co(CO)3NO. State-resolved detection of the NO product through the A (v'=0) ← X (v"=0) transition reveals that both molecules dissociate promptly with a high degree of vector correlation.

  7. Velocity map ion imaging study of Ar2+ photodissociation

    NASA Astrophysics Data System (ADS)

    Maner, J. A.; Mauney, D. T.; Duncan, M. A.

    2017-03-01

    The argon dimer cation is produced in a plasma generated by a laser spark in a supersonic expansion. The cold ions are mass selected and investigated by photodissociation at 355 nm, with velocity map imaging of the Ar+ photofragment. Using the radius of the image, we determine the kinetic energy release and derive the ground state dissociation energy of Ar2+ as D0″ = 1.32 +0.03/-0.02 eV. Additionally, the angular distribution is described with β = 1.71-1.95, consistent with excitation of the parallel-type 2Σg+ ← 2Σu+ transition.

  8. Study of photodissociation parameters of carboxyhemoglobin

    SciTech Connect

    Kuz'min, V V; Salmin, V V; Provorov, A S; Salmina, A B

    2008-07-31

    The general properties of photodissociation of carboxyhemoglobin (HbCO) in buffer solutions of whole human blood are studied by the flash photolysis method on a setup with intersecting beams. It is shown that the efficiency of photoinduced dissociation of the HbCO complex virtually linearly depends on the photolytic irradiation intensity for the average power density not exceeding 45 mW cm{sup -2}. The general dissociation of the HbCO complex in native conditions occurs in a narrower range of values of the saturation degree than in model experiments with the hemoglobin solution. The dependence of the pulse photolysis efficiency of HbCO on the photolytic radiation wavelength in the range from 550 to 585 nm has a broad bell shape. The efficiency maximum corresponds to the electronic Q transition (porphyrin {pi}-{pi}* absorption) in HbCO at a wavelength of 570 nm. No dissociation of the complex was observed under given experimental conditions upon irradiation of solutions by photolytic radiation at wavelengths above 585 nm. (laser applications and other topics in quantum electronics)

  9. Iodine Satellite

    NASA Technical Reports Server (NTRS)

    Kamhawi, Hani; Dankanich, John; Martinez, Andres; Petro, Andrew

    2015-01-01

    The Iodine Satellite (iSat) spacecraft will be the first CubeSat to demonstrate high change in velocity from a primary propulsion system by using Hall thruster technology and iodine as a propellant. The mission will demonstrate CubeSat maneuverability, including plane change, altitude change and change in its closest approach to Earth to ensure atmospheric reentry in less than 90 days. The mission is planned for launch in fall 2017. Hall thruster technology is a type of electric propulsion. Electric propulsion uses electricity, typically from solar panels, to accelerate the propellant. Electric propulsion can accelerate propellant to 10 times higher velocities than traditional chemical propulsion systems, which significantly increases fuel efficiency. To enable the success of the propulsion subsystem, iSat will also demonstrate power management and thermal control capabilities well beyond the current state-of-the-art for spacecraft of its size. This technology is a viable primary propulsion system that can be used on small satellites ranging from about 22 pounds (10 kilograms) to more than 1,000 pounds (450 kilograms). iSat's fuel efficiency is ten times greater and its propulsion per volume is 100 times greater than current cold-gas systems and three times better than the same system operating on xenon. iSat's iodine propulsion system consists of a 200 watt (W) Hall thruster, a cathode, a tank to store solid iodine, a power processing unit (PPU) and the feed system to supply the iodine. This propulsion system is based on a 200 W Hall thruster developed by Busek Co. Inc., which was previously flown using xenon as the propellant. Several improvements have been made to the original system to include a compact PPU, targeting greater than 80 percent reduction in mass and volume of conventional PPU designs. The cathode technology is planned to enable heaterless cathode conditioning, significantly increasing total system efficiency. The feed system has been designed to

  10. Peptide Photodissociation with 157 nm Light in a Commercial Tandem Time-of-Flight Mass Spectrometer

    PubMed Central

    Zhang, Liangyi; Reilly, James P.

    2009-01-01

    Photodissociation with 157 nm light was implemented in an ABI model 4700 matrix-assisted laser desorption ionization (MALDI) tandem time-of-flight (TOF) mass spectrometer for peptide analysis. With a homemade computer program to control the light timing based on the m/z of each precursor ion, the photodissociation setup was seamlessly automated with the mass spectrometer. Peptide photodissociation in this apparatus yielded fragments similar to those observed in previous experiments with a homebuilt tandem-TOF mass spectrometer. Peptides having arginine at their C-termini yielded high-energy x-, v- and w- type fragments while peptides with N-terminal arginine produced many a- and d- type ions. Abundant immonium ions were also generated. High-quality photodissociation spectra were obtained with as little as 5 fmol of peptides. In the analysis of various tryptic peptides, photodissociation provided much more sequence information than the conventional TOF-TOF CID. Because of the high fragmentation efficiency, sensitivity was not sacrificed to achieve this. PMID:19702244

  11. H{sub 2}{sup +} photodissociation by an intense pulsed photonic Fock state

    SciTech Connect

    Paul, Amit K.; Adhikari, Satrajit; Baer, Michael; Baer, Roi

    2010-01-15

    We study the photodissociation of the H{sub 2}{sup +} molecule by ultrashort Fock-state electromagnetic pulses (EMPs). We use the Born-Oppenheimer treatment combined with an explicit photon number representation via diabatic electrophoton potential surfaces for simplification of the basic equations. We discuss the issue of the number of photon states required and show that six photon states enable good accuracy for photoproduct kinetic energies of up to 3 eV. We calculate photodissociation probabilities and nuclear kinetic-energy (KE) distributions of the photodissociation products for 800-nm, 50-TW/cm{sup 2} pulses. We show that KE distributions depend on three pulse durations of 10, 20, and 45 fs and on various initial vibrational states of the molecule. We compare the Fock-state results to those obtained by 'conventional', i.e., coherent-state, laser pulses of equivalent electric fields and durations. The effects of the quantum state of EMPs on the photodissociation dynamics are especially strong for high initial vibrational states of H{sub 2}{sup +}. While coherent-state pulses suppress photodissociation for the high initial vibrational states of H{sub 2}{sup +}, the Fock-state pulses enhance it.

  12. Photodissociation dynamics of benzoic acid

    SciTech Connect

    Dyakov, Yuri A.; Bagchi, Arnab; Lee, Yuan T.; Ni, Chi-Kung

    2010-01-07

    The photodissociation of benzoic acid at 193 and 248 nm was investigated using multimass ion imaging techniques. Three dissociation channels were observed at 193 nm: (1) C{sub 6}H{sub 5}COOH{yields}C{sub 6}H{sub 5}+COOH, (2) C{sub 6}H{sub 5}COOH{yields}C{sub 6}H{sub 5}CO+OH, and (3) C{sub 6}H{sub 5}COOH{yields}C{sub 6}H{sub 6}+CO{sub 2}. Only channels, (2) and (3), were observed at 248 nm. Comparisons of the ion intensities and photofragment translational energy distributions with the potential energies obtained from ab initio calculations and the branching ratios obtained from the Rice-Ramsperger-Kassel-Marcus theory suggest that the dissociation occurs on many electronic states.

  13. Photodissociation dynamics and atmospheric chemistry

    NASA Astrophysics Data System (ADS)

    Wayne, R. P.

    1993-07-01

    The paper uses data from the literature to explore photodissociation dynamics of molecules possessing three, four, and five atoms, as represented by O3 and CO2, NH3 and C2H2, and CH4, respectively. The results yield many details, even in regard to the disposal of energy into rotation, which have applications to atmospheric problems. For instance, experiments probing the translational energies of the O and the vibrational and rotational distributions in the CO suggest that a spin-forbidden channel operates as it does in ozone photolysis. The data for both O3 and CO2 suggest a relationship between the structure of the parent molecule and the dynamics of dissociation.

  14. Carbon Chemistry in Photodissociation Regions

    NASA Astrophysics Data System (ADS)

    Gerin, M.; Roueff, E.; Le Bourlot, J.; Pety, J.; Goicoechea, J. R.; Teyssier, D.; Joblin, C.; Abergel, A.; Fossé, D.

    2005-08-01

    We present recent results on the carbon chemistry in photodissociation regions. We show that carbon chains and rings (CCH, c-C_3H_2 and C_4H) are tightly spatially correlated with each other, and with the mid-infrared emission due to PAHs (7 and 15 μm), mapped by ISOCAM. Neither the spatial distribution, nor the abundances of these species can be fit by state-of-the-art PDR models, which calls for another production mechanism. We discuss model predictions for carbon clusters and simple hydrocarbons. We show how selected abundance ratios can be used as a diagnostic of the physical conditions. We stress the need for more theoretical and laboratory work on fundamental processes relevant for the interstellar medium, which should be taken into account in the astrochemical models, but whose rates are not known accurately enough.

  15. Laser induced fluorescence studies of iodine oxide chemistry. Part II. The reactions of IO with CH3O2, CF3O2 and O3.

    PubMed

    Dillon, Terry J; Tucceri, María E; Crowley, John N

    2006-11-28

    The technique of pulsed laser photolysis was coupled to laser induced fluorescence detection of iodine oxide (IO) to measure rate coefficients, k for the reactions IO + CH(3)O(2)--> products (R1, 30-318 Torr N(2)), IO + CF(3)O(2)--> products (R2, 70-80 Torr N(2)), and IO + O(3)--> OIO + O(2) (R3a). Values of k(1) = (2 +/- 1) x 10(-12) cm(3) molecule(-1) s(-1), k(2) = (3.6 +/- 0.8) x 10(-11) cm(3) molecule(-1) s(-1), and k(3a) <5 x 10(-16) cm(3) molecule(-1) s(-1) were obtained at T = 298 K. In the course of this work, the product yield of IO from the reaction of CH(3)O(2) with I was determined to be close to zero, whereas CH(3)OOI was formed efficiently at 70 Torr N(2). Similarly, no evidence was found for IO formation in the CF(3)O(2) + I reaction. An estimate of the rate coefficients k(CH(3)O(2) + I) = 2 x 10(-11) cm(3) molecule(-1) s(-1) and k(CH(3)OOI + I) = 1.5 x 10(-10) cm(3) molecule(-1) s(-1) was also obtained. The results on k(1)-k(3) are compared to the limited number of previous investigations and the implications for the chemistry of the marine boundary layer are briefly discussed.

  16. Protein relaxation in the photodissociation of myoglobin-CO complexes.

    PubMed

    Angeloni, Leonardo; Feis, Alessandro

    2003-07-01

    Laser-induced optoacoustic spectroscopy has been applied to the study of the photodissociation of myoglobin-CO complexes. Time-resolved optoacoustic signals have been measured from aqueous solutions of horse myoglobin-CO complex (hMbCO) at pH 3.5 and 8, and of sperm whale myoglobin-CO complex (swMbCO) at pH 8, in the temperature range 273-300 K. The signal of hMbCO at pH 8 exhibits three components. The first, which is faster than 20 ns and is associated with a reaction enthalpy of 61 kJ mol(-1), corresponds to Fe-CO bond breakage. The second component has a decay time of 80 ns at 293 K and is associated with an exothermic protein relaxation (-13 kJ mol(-1)) and a volume change of -3 ml mol(-1). The relaxation, which involves a state where the photo-dissociated CO is still in a protein docking site, is thermally activated, with an activation enthalpy of 51 kJ mol(-1). The third component has a decay time of 800 ns at 293 K and an activation enthalpy of 39 kJ mol(-1), and is associated with an endothermic process (26 kJ mol(-1)) and an expansion of 19 ml mol(-1). This process is ascribed to the migration of the photodissociated CO to the bulk solvent. At acidic pH, the latter process becomes faster (230 ns) and the volume change decreases. These features are correlated with the presence of an open form of the protein. swMbCO exhibits two components only, due to the overlap of the two fastest processes. The first involves a reaction enthalpy of 49 kJ mol(-1) and a volume contraction of -4.9 ml mol(-1). The second component (900 ns at 293 K, activation enthalpy 45 kJ mol(-1)) is associated with a reaction enthalpy of 38 kJ mol(-1) and a volume expansion of 15.3 ml mol(-1). These experimental findings have been interpreted by means of a new model, which also takes into account both laser flash photolysis results and structural information. The model is based on a two-dimensional scheme which describes both protein relaxation and the CO pathway following

  17. Hair Iodine for Human Iodine Status Assessment

    PubMed Central

    Prejac, Juraj; Višnjević, Vjeran; Skalnaya, Margarita G.; Mimica, Ninoslav; Drmić, Stipe; Skalny, Anatoly V.

    2014-01-01

    Background: Today, human iodine deficiency is, after iron, the most common nutritional deficiency in developed European and underdeveloped third world countries. A current biological indicator of iodine status is urinary iodine, which reflects very recent iodine exposure; a long-term indicator of iodine status remains to be identified. Methods: We analyzed hair iodine in a prospective, observational, cross-sectional, and exploratory study involving 870 apparently healthy Croatians (270 men and 600 women). Hair iodine was analyzed with inductively coupled plasma mass spectrometry. Results: The hair iodine median was 0.499 μg/g, and was 0.482 and 0.508 μg/g for men and women respectively, suggesting no sex-related difference. We studied hair iodine uptake by analyzing the logistic sigmoid saturation curve of the median derivatives to assess iodine deficiency, adequacy, and excess. We estimated overt iodine deficiency to occur when hair iodine concentration was below 0.1–0.15 μg/g. Then there was a saturation range interval of about 0.1–2.0 μg/g where the deposition of iodine in the hair was linearly increasing (R2=0.994). Eventually, the sigmoid curve became saturated at about 2.0 μg/g and upward, suggesting excessive iodine exposure. Conclusion: Hair appears to be a valuable and robust biological indicator tissue for assessing long-term iodine status. We propose that an adequate iodine status corresponds with hair iodine uptake saturation of 0.565–0.739 μg/g (55–65%). PMID:24446669

  18. Application of an InGaAsP diode laser to probe photodissociation dynamics - I(asterisk) quantum yields from n- and i-C3F7I and CH3I by laser gain vs absorption spectroscopy

    NASA Technical Reports Server (NTRS)

    Hess, W. P.; Kohler, S. J.; Haugen, H. K.; Leone, S. R.

    1986-01-01

    Initial measurements on I-asterisk yields of alkyl iodides at 266 nm are reported using gain vs. absorption spectroscopy with an InGaAsP diode probe laser. The results are 102 percent + or - 4 percent, 102 percent + or - 7 percent, and 73 percent + or - 4 percent for n-C3F7I, i-C3F7I, and CH3I respectively. Future prospects for the development of diode laser systems and for their use in dynamical studies are discussed.

  19. Application of an InGaAsP diode laser to probe photodissociation dynamics - I(asterisk) quantum yields from n- and i-C3F7I and CH3I by laser gain vs absorption spectroscopy

    NASA Technical Reports Server (NTRS)

    Hess, W. P.; Kohler, S. J.; Haugen, H. K.; Leone, S. R.

    1986-01-01

    Initial measurements on I-asterisk yields of alkyl iodides at 266 nm are reported using gain vs. absorption spectroscopy with an InGaAsP diode probe laser. The results are 102 percent + or - 4 percent, 102 percent + or - 7 percent, and 73 percent + or - 4 percent for n-C3F7I, i-C3F7I, and CH3I respectively. Future prospects for the development of diode laser systems and for their use in dynamical studies are discussed.

  20. High steady-state column density of I(2P3/2) atoms from I2 photodissociation at 532 nm: Towards parity non-conservation measurements

    PubMed Central

    Katsoprinakis, G. E.; Chatzidrosos, G.; Kypriotakis, J. A.; Stratakis, E.; Rakitzis, T. P.

    2016-01-01

    Steady-state column densities of 1017 cm−2 of I(2P3/2) atoms are produced from photodissociation of I2 vapour at 290.5 K using 5 W of 532 nm laser light. Recombination of the I(2P3/2) atoms at the cell walls is minimized by coating the cell surface with a hydrophobic silane (dimethyldichlorosilane/DMDCS). Operation at room temperature, and at an I2 vapour pressure of ~0.2 mbar, without using a buffer gas, allows relatively low Lorentz and Doppler widths of ~2π × 1.5 (FWHM) and ~2π × 150 (HW at 1/e2) Mrad/s, respectively, at the M1 transition of atomic iodine at 1315 nm. These high column densities and low linewidths are favorable for parity nonconservation optical rotation measurements near this M1 transition. Furthermore, as the cell is completely sealed, this method of production of high-density 127I(2P3/2) atoms is also compatible with using iodine radioisotopes, such as for the production of high-density 129I(2P3/2). PMID:27629914

  1. High steady-state column density of I(2P3/2) atoms from I2 photodissociation at 532 nm: Towards parity non-conservation measurements

    NASA Astrophysics Data System (ADS)

    Katsoprinakis, G. E.; Chatzidrosos, G.; Kypriotakis, J. A.; Stratakis, E.; Rakitzis, T. P.

    2016-09-01

    Steady-state column densities of 1017 cm‑2 of I(2P3/2) atoms are produced from photodissociation of I2 vapour at 290.5 K using 5 W of 532 nm laser light. Recombination of the I(2P3/2) atoms at the cell walls is minimized by coating the cell surface with a hydrophobic silane (dimethyldichlorosilane/DMDCS). Operation at room temperature, and at an I2 vapour pressure of ~0.2 mbar, without using a buffer gas, allows relatively low Lorentz and Doppler widths of ~2π × 1.5 (FWHM) and ~2π × 150 (HW at 1/e2) Mrad/s, respectively, at the M1 transition of atomic iodine at 1315 nm. These high column densities and low linewidths are favorable for parity nonconservation optical rotation measurements near this M1 transition. Furthermore, as the cell is completely sealed, this method of production of high-density 127I(2P3/2) atoms is also compatible with using iodine radioisotopes, such as for the production of high-density 129I(2P3/2).

  2. High steady-state column density of I((2)P3/2) atoms from I2 photodissociation at 532 nm: Towards parity non-conservation measurements.

    PubMed

    Katsoprinakis, G E; Chatzidrosos, G; Kypriotakis, J A; Stratakis, E; Rakitzis, T P

    2016-09-15

    Steady-state column densities of 10(17) cm(-2) of I((2)P3/2) atoms are produced from photodissociation of I2 vapour at 290.5 K using 5 W of 532 nm laser light. Recombination of the I((2)P3/2) atoms at the cell walls is minimized by coating the cell surface with a hydrophobic silane (dimethyldichlorosilane/DMDCS). Operation at room temperature, and at an I2 vapour pressure of ~0.2 mbar, without using a buffer gas, allows relatively low Lorentz and Doppler widths of ~2π × 1.5 (FWHM) and ~2π × 150 (HW at 1/e(2)) Mrad/s, respectively, at the M1 transition of atomic iodine at 1315 nm. These high column densities and low linewidths are favorable for parity nonconservation optical rotation measurements near this M1 transition. Furthermore, as the cell is completely sealed, this method of production of high-density (127)I((2)P3/2) atoms is also compatible with using iodine radioisotopes, such as for the production of high-density (129)I((2)P3/2).

  3. Infrared photodissociation of size-selected methanol clusters

    NASA Astrophysics Data System (ADS)

    Buck, U.; Gu, X. J.; Lauenstein, Ch.; Rudolph, A.

    1990-05-01

    Size-selective IR photodissociation spectra of (CH3OH)n clusters from n = 2 to n = 9 near the absorption band of the C-O stretching mode of the monomer at 1033.5/cm were measured using an experimental apparatus with a CW CO2 laser collinear to the size-selected cluster beam. The observed spectral features vary from dimer to octamer, with a special transition from the pentamer to the hexamer. An intermolecular model potential is used to derive a correlation between the observed spectra and the cluster configuration of minimum energy. The results show that only internally excited dimers and trimers can be dissociated with one or two CO2 laser photons, respectively.

  4. Photodissociation dynamics of the ortho- and para-xylyl radicals

    NASA Astrophysics Data System (ADS)

    Pachner, Kai; Steglich, Mathias; Hemberger, Patrick; Fischer, Ingo

    2017-08-01

    The photodissociation dynamics of the C8H9 isomers ortho- and para-xylyl are investigated in a free jet. The xylyl radicals are generated by flash pyrolysis from 2-(2-methylphenyl)- and 2-(4-methylphenyl) ethyl nitrite and are excited into the D3 state. REMPI- spectra show vibronic structure and the origin of the transition is identified at 32 291 cm-1 for the para- and at 32 132 cm-1 for the ortho-isomer. Photofragment H-atom action spectra show bands at the same energy and thus confirm H-atom loss from xylyl radicals. To gain further insight into the photodissociation dynamics, velocity map images of the hydrogen atom photofragments are recorded. Their angular distribution is isotropic and the translational energy release is in agreement with a dissociation to products in their electronic ground state. Photodissociation of para-xylyl leads to the formation of para-xylylene (C8H8), while the data for ortho-xylyl agree much better with the isomer benzocyclobutene as the dominant molecular fragment rather than ortho-xylylene. In computations we identified a new pathway for the reaction ortho-xylyl → benzocyclobutene + H with a barrier of 3.39 eV (27 340 cm-1), which becomes accessible at the employed excitation energy. It proceeds via a combination of scissoring and rotational motion of the -CH2 and -CH3 groups. However, the observed rate constants measured by delaying the excitation and ionization laser with respect to each other are significantly faster than computed ones, indicating intrinsic non-RRKM behaviour. A comparably high value of around 30% of the excess energy is released as translation of the H-atom photofragment.

  5. C60 in Photodissociation Regions

    NASA Astrophysics Data System (ADS)

    Castellanos, Pablo; Berné, Olivier; Sheffer, Yaron; Wolfire, Mark G.; Tielens, Alexander G. G. M.

    2014-10-01

    Recent studies have confirmed the presence of buckminsterfullerene (C60) in different interstellar and circumstellar environments. However, several aspects regarding C60 in space are not yet well understood, such as the formation and excitation processes, and the connection between C60 and other carbonaceous compounds in the interstellar medium, in particular polycyclic aromatic hydrocarbons (PAHs). In this paper, we study several photodissociation regions (PDRs) where C60 and PAHs are detected and the local physical conditions are reasonably well constrained to provide observational insights into these questions. C60 is found to emit in PDRs where the dust is cool (Td = 20-40 K) and even in PDRs with cool stars. These results exclude the possibility for C60 to be locked in grains at thermal equilibrium in these environments. We observe that PAH and C60 emission are spatially uncorrelated and that C60 is present in PDRs where the physical conditions (in terms of radiation field and hydrogen density) allow for full dehydrogenation of PAHs, with the exception of Ced 201. We also find trends indicative of an increase in C60 abundance within individual PDRs, but these trends are not universal. These results support models where the dehydrogenation of carbonaceous species is the first step toward C60 formation. However, this is not the only parameter involved and C60 formation is likely affected by shocks and PDR age.

  6. Photodissociation dynamics of hydroxybenzoic acids

    SciTech Connect

    Yang Yilin; Dyakov, Yuri; Lee, Y. T.; Ni, Chi-Kung; Sun Yilun; Hu Weiping

    2011-01-21

    Aromatic amino acids have large UV absorption cross-sections and low fluorescence quantum yields. Ultrafast internal conversion, which transforms electronic excitation energy to vibrational energy, was assumed to account for the photostability of amino acids. Recent theoretical and experimental investigations suggested that low fluorescence quantum yields of phenol (chromophore of tyrosine) are due to the dissociation from a repulsive excited state. Radicals generated from dissociation may undergo undesired reactions. It contradicts the observed photostability of amino acids. In this work, we explored the photodissociation dynamics of the tyrosine chromophores, 2-, 3- and 4-hydroxybenzoic acid in a molecular beam at 193 nm using multimass ion imaging techniques. We demonstrated that dissociation from the excited state is effectively quenched for the conformers of hydroxybenzoic acids with intramolecular hydrogen bonding. Ab initio calculations show that the excited state and the ground state potential energy surfaces change significantly for the conformers with intramolecular hydrogen bonding. It shows the importance of intramolecular hydrogen bond in the excited state dynamics and provides an alternative molecular mechanism for the photostability of aromatic amino acids upon irradiation of ultraviolet photons.

  7. The photodissociation dynamics of tetrachloroethylene

    SciTech Connect

    Herath, Nuradhika; Hause, Michael L.; Suits, Arthur G.

    2011-04-28

    We present a direct current slice imaging study of tetrachloroethylene (C{sub 2}Cl{sub 4}) photodissociation, probing the resulting ground state Cl ({sup 2}P{sub 3/2}) and spin-orbit excited state Cl* ({sup 2}P{sub 1/2}) products. We report photofragment images, total translational energy distributions and the product branching ratio of Cl*/Cl following dissociation at 235 and 202 nm, obtained using a two-color reduced-Doppler dissociation/probe. Near 235 nm, the Cl translational energy distribution shows a peak at the limit of the available energy, indicating a direct dissociation through a {sigma}*(C-Cl) (leftarrow){pi} (C=C) transition, which is superimposed on a broader underlying distribution. The ground state Cl image and associated translational energy distribution at 202 nm is broad and peaked at lower energy, suggesting either internal conversion to the ground state or a lower excited state prior to dissociation. The Cl* images are similarly broad at both wavelengths. The branching ratio is presented as a function of recoil energy, but after integration shows a near-statistical average of Cl:Cl* as 70:30 at both wavelengths. All the images are largely isotropic, with anisotropy parameters ({beta}) of 0.05 {+-} 0.03.

  8. Reactions of excited I*(/sup 2/P /SUB 1/2/ ) and unexcited I(/sup 2/P /SUB 3/2/ ) iodine atoms in perfluoroalkyl radicals

    SciTech Connect

    Andreeva, T.L.; Kuznetsova, S.V.; Maslov, A.I.; Sobel'man, I.I.

    1983-01-01

    A method of investigating reactions of excited and unexcited atoms is discussed. It is based on pulsed photolysis of molecules with simultaneous passage of laser radiation through the working medium. The method proposed is used to investigate the reactions that accompany the photolysis of the molecules RI(CF/sub 3/I, n-C/sub 3/F/sub 7/I, i-C/sub 3/F/sub 7/I). The rate constants of the recombination of iodine atoms into I/sub 2/ in the presence of RI molecules are calculated for the atoms I(/sup 2/P /SUB 3/2/ ) and I*(/sup 2/P /SUB 1/2/ ), as are the recombination constants of the radicals R into R/sub 2/ and with the atoms I*(/sup 2/P /SUB 1/2/ ) and I(/sup 2/P /SUB 3/2/ ) into the RI molecule. It is shown that the I(/sup 2/P /SUB 3/2/ ) atoms are much more active in the recombination into I/sub 2/ and RI than the I*(/sup 2/P /SUB 1/2/ ) atoms. The role of the investigated reactions in the kinetics of a photodissociation iodine laser (PDIL) is discussed. The results are compared with the published data.

  9. Experimental verification of the Einstein A-coefficient used for evaluation of O2(1Δg) concentration in the chemical oxygen-iodine laser

    NASA Astrophysics Data System (ADS)

    Spalek, O.; Kodymová, J.; Stopka, P.; Micek, I.

    1999-04-01

    This paper is a contribution to the current discussion on the Einstein coefficient for spontaneous emission (A-coefficient) of singlet delta oxygen, O2(1Δg), that is often used for an evaluation of O2(1Δg) concentration in a chemical oxygen-iodine laser (COIL). The published values of the A-coefficient vary in a wide range, corresponding to a radiative lifetime of O2(1Δg), τ_Δ^rad, from ~53 to ~151 min. This could make an evaluation of COIL operation questionable. In this paper, the Einstein A-coefficient is estimated, based on the comparison of O2(1Δg) concentrations determined by two independent methods: electron paramagnetic resonance and emission spectroscopy. Within the accuracy of the experimental techniques used, the value of the A-coefficient resulting from our investigation is (2.24±0.40) × 10-4 s-1, corresponding to τ_Δ^rad of ~74 min. This result is more consistent with the value of 2.58 × 10-4 s-1 of Badger et al [1] than with the value of 1.47 × 10-4 s-1 reported recently by Mlynczak and Nesbitt [2], who raised doubt about the Badger et al value.

  10. Dependence of the molecular iodine B-state predissociation induced by a femtosecond laser pulse on pulse phase modulation

    SciTech Connect

    Kostyukevich, Yu I; Umanskii, Stanislav Ya

    2011-12-31

    The processes of pumping and laser-induced predissociation of B-states of the I{sub 2} molecule under the action of femtosecond laser pulses are considered theoretically. An analytical formula is derived, which describes the dependence of the predissociation on such parameters of femtosecond pulses as spectral chirp, spectral width and delay time between pulses. The formula is used to calculate numerically the dependence of the predissociation yield on the parameters of the phase modulation of the pump pulse and coupling pulse.

  11. Photodissociation dynamics of polyatomic molecules

    SciTech Connect

    Zhao, Hequan

    1998-02-23

    This report consists of five studies as follows: A laser photofragmentation time-of-flight mass spectrometric study of acetophenone at 193 and 248 nm; A 193 nm laser photofragmentation time-of-flight mass spectrometric study of dimethylsulfoxide; 193 nm laser photofragmentation time-of-flight mass spectrometric study of HSCH2CH2SH; Thiophene biradical decay of the primary laser photofragmentation product at 193 nm; and Scattering cross sections for O(3P)[SO(X,3Σ-)] + He[Ne, Ar, Kr]. Chapters are included for the introduction and general conclusions.

  12. Photodissociation pathways and lifetimes of protonated peptides and their dimers

    SciTech Connect

    Aravind, G.; Klaerke, B.; Rajput, J.; Toker, Y.; Andersen, L. H.; Bochenkova, A. V.; Antoine, R.; Racaud, A.; Dugourd, P.; Lemoine, J.

    2012-01-07

    Photodissociation lifetimes and fragment channels of gas-phase, protonated YA{sub n} (n = 1,2) peptides and their dimers were measured with 266 nm photons. The protonated monomers were found to have a fast dissociation channel with an exponential lifetime of {approx}200 ns while the protonated dimers show an additional slow dissociation component with a lifetime of {approx}2 {mu}s. Laser power dependence measurements enabled us to ascribe the fast channel in the monomer and the slow channel in the dimer to a one-photon process, whereas the fast dimer channel is from a two-photon process. The slow (1 photon) dissociation channel in the dimer was found to result in cleavage of the H-bonds after energy transfer through these H-bonds. In general, the dissociation of these protonated peptides is non-prompt and the decay time was found to increase with the size of the peptides. Quantum RRKM calculations of the microcanonical rate constants also confirmed a statistical nature of the photodissociation processes in the dipeptide monomers and dimers. The classical RRKM expression gives a rate constant as an analytical function of the number of active vibrational modes in the system, estimated separately on the basis of the equipartition theorem. It demonstrates encouraging results in predicting fragmentation lifetimes of protonated peptides. Finally, we present the first experimental evidence for a photo-induced conversion of tyrosine-containing peptides into monocyclic aromatic hydrocarbon along with a formamide molecule both found in space.

  13. Molecular dynamics simulation of photodissociation of carbon monoxide from hemoglobin

    SciTech Connect

    Henry, E.R.; Levitt, M.; Eaton, W.A.

    1985-04-01

    A molecular dynamics simulation of the photodissociation of carbon monoxide from the alpha subunit of hemoglobin is described. To initiate photodissociation, trajectories of the liganded molecule were interrupted, the iron-carbon monoxide bond was broken, and the parameters of the iron-nitrogen bonds were simultaneously altered to produce a deoxyheme conformation. Heme potential functions were used that reproduce the energies and forces for the iron out-of-plane motion obtained from quantum mechanical calculations. The effect of the protein on the rate and extent of the displacement of the iron from the porphyrin plane was assessed by comparing the results with those obtained for an isolated complex of heme with imidazole and carbon monoxide. The half-time for the displacement of the iron from the porphyrin plane was found to be 50-150 fs for both the protein and the isolated complex. These results support the interpretation of optical absorption studies using 250-fs laser pulses that the iron is displaced from the porphyrin plane within 350 fs in both hemoglobin and a free heme complex in solution.

  14. Epidemiology of iodine deficiency.

    PubMed

    Vanderpump, Mark P

    2017-04-01

    Iodine is an essential component of the thyroid hormones thyroxine (T4) and triiodothyronine (T3) produced by the thyroid gland. Iodine deficiency impairs thyroid hormone production and has adverse effects throughout life, particularly early in life as it impairs cognition and growth. Iodine deficiency remains a significant problem despite major national and international efforts to increase iodine intake, primarily through the voluntary or mandatory iodization of salt. Recent epidemiological data suggest that iodine deficiency is an emerging issue in industrialized countries, previously thought of as iodine-sufficient. International efforts to control iodine deficiency are slowing, and reaching the third of the worldwide population that remains deficient poses major challenges.

  15. Iodine volatility. [PWR; BWR

    SciTech Connect

    Beahm, E.C.; Shockley, W.E.

    1984-01-01

    The ultimate aim of this program is to couple experimental aqueous iodine volatilities to a fission product release model. Iodine partition coefficients, for inorganic iodine, have been measured during hydrolysis and radiolysis. The hydrolysis experiments have illustrated the importance of reaction time on iodine volatility. However, radiolysis effects can override hydrolysis in determining iodine volatility. In addition, silver metal in radiolysis samples can react to form silver iodide accompanied by a decrease in iodine volatility. Experimental data are now being coupled to an iodine transport and release model that was developed in the Federal Republic of Germany.

  16. Iodine deficiency: Clinical implications.

    PubMed

    Niwattisaiwong, Soamsiri; Burman, Kenneth D; Li-Ng, Melissa

    2017-03-01

    Iodine is crucial for thyroid hormone synthesis and fetal neurodevelopment. Major dietary sources of iodine in the United States are dairy products and iodized salt. Potential consequences of iodine deficiency are goiter, hypothyroidism, cretinism, and impaired cognitive development. Although iodine status in the United States is considered sufficient at the population level, intake varies widely across the population, and the percentage of women of childbearing age with iodine deficiency is increasing. Physicians should be aware of the risks of iodine deficiency and the indications for iodine supplementation, especially in women who are pregnant or lactating.

  17. Surface chemistry in photodissociation regions

    NASA Astrophysics Data System (ADS)

    Esplugues, G. B.; Cazaux, S.; Meijerink, R.; Spaans, M.; Caselli, P.

    2016-06-01

    Context. The presence of dust can strongly affect the chemical composition of the interstellar medium. We model the chemistry in photodissociation regions (PDRs) using both gas-phase and dust-phase chemical reactions. Aims: Our aim is to determine the chemical compositions of the interstellar medium (gas/dust/ice) in regions with distinct (molecular) gas densities that are exposed to radiation fields with different intensities. Methods: We have significantly improved the Meijerink PDR code by including 3050 new gas-phase chemical reactions and also by implementing surface chemistry. In particular, we have included 117 chemical reactions occurring on grain surfaces covering different processes, such as adsorption, thermal desorption, chemical desorption, two-body reactions, photo processes, and cosmic-ray processes on dust grains. Results: We obtain abundances for different gas and solid species as a function of visual extinction, depending on the density and radiation field. We also analyse the rates of the formation of CO2 and H2O ices in different environments. In addition, we study how chemistry is affected by the presence/absence of ice mantles (bare dust or icy dust) and the impact of considering different desorption probabilities. Conclusions: The type of substrate (bare dust or icy dust) and the probability of desorption can significantly alter the chemistry occurring on grain surfaces, leading to differences of several orders of magnitude in the abundances of gas-phase species, such as CO, H2CO, and CH3OH. The type of substrate, together with the density and intensity of the radiation field, also determine the threshold extinction to form ices of CO2 and H2O. We also conclude that H2CO and CH3OH are mainly released into the gas phase of low, far-ultraviolet illuminated PDRs through chemical desorption upon two-body surface reactions, rather than through photodesorption.

  18. The photodissociation of CO in circumstellar envelopes

    NASA Technical Reports Server (NTRS)

    Mamon, G. A.; Glassgold, A. E.; Huggins, P. J.

    1988-01-01

    The CO photodissociation rate for the unshielded ISM is calculated using recent laboratory results which confirm that photodissociation occurs by way of line absorption. A value of 2.0 x 10 to the -10th/s, an order of magnitude higher than the rate used in the past, is obtained. The new rate and a treatment of the radiative transfer and shielding are used to develop a theory for the CO abundance in the circumstellar envelopes of cool, evolved stars, and results are presented on the spatial variation of CO, C, and C(+). It is shown that these distributions play important roles in determining the observational properties of circumstellar envelopes.

  19. Photodissociation of Mg +(NH 3) ion

    NASA Astrophysics Data System (ADS)

    Yoshida, Shinji; Okai, Nobuhiro; Fuke, Kiyokazu

    2001-10-01

    Electronically excited states of Mg +(NH 3) are studied by photodissociation after mass selection. The dissociation spectrum shows relatively sharp vibronic transitions centered at about 28 000 and 36 000 cm-1. These absorption bands are assigned to the 2P- 2S type transitions localized on the Mg + ion. In photodissociation, a photoinduced charge-transfer process to produce NH 3+ is observed in addition to evaporation and intracluster reaction processes to produce Mg + and MgNH 2+ ions, respectively. The mechanism for the production of these ions is discussed in terms of the predissociative and non-adiabatic interactions between the low-lying states.

  20. Quantum yield for carbon monoxide production in the 248 nm photodissociation of carbonyl sulfide (OCS)

    NASA Astrophysics Data System (ADS)

    Zhao, Z.; Stickel, R. E.; Wine, P. H.

    1995-03-01

    Tunable diode laser absorption spectroscopy has been coupled with excimer laser flash photolysis to measure the quantum yield for CO production from 248 nm photo-dissociation of carbonyl sulfide (OCS) relative to the well-known quantum yield for CO production from 248 nm photolysis of phosgene (Cl2CO). The temporal resolution of the experiments was sufficient to distinguish CO formed directly by photodissociation from that formed by subsequent S(³PJ) reaction with OCS. Under the experimental conditions employed, CO formation via the fast S(¹D2) + OCS reaction was minimal. Measurements at 297K and total pressures from 4 to 100 Torr N2 + N2O show the CO yield to be greater than 0.95 and most likely unity. This result suggests that the contribution of OCS as a precursor to the lower stratospheric sulfate aerosol layer is somewhat larger than previously thought.

  1. Quantum yield for carbon monoxide production in the 248 nm photodissociation of carbonyl sulfide (OCS)

    NASA Technical Reports Server (NTRS)

    Zhao, Z.; Stickel, R. E.; Wine, P. H.

    1995-01-01

    Tunable diode laser absorption spectroscopy has been coupled with excimer laser flash photolysis to measure the quantum yield for CO production from 248 nm photodissociation of carbonyl sulfide (OCS) relative to the well-known quantum yield for CO production from 248 nm photolysis of phosgene (Cl2CO2). The temporal resolution of the experiments was sufficient to distinguish CO formed directly by photodissociation from that formed by subsequent S((sup 3)P(sub J)) reaction with OCS. Under the experimental conditions employed, CO formation via the fast S((sup 1)D(sub 2)) + OCS reaction was minimal. Measurements at 297K and total pressures from 4 to 100 Torr N2 + N2O show the CO yield to be greater than 0.95 and most likely unity. This result suggests that the contribution of OCS as a precursor to the lower stratospheric sulfate aerosol layer is somewhat larger than previously thought.

  2. The photodissociation and reaction dynamics of vibrationally excited molecules. Technical progress report, 1993--1994

    SciTech Connect

    Not Available

    1994-04-01

    Combined vibrational overtone excitation and laser induced fluorescence detection was used to study dissociation dynamics of hydroxylamine (NH{sub 2}OH), laser induced grating experiments on water were analyzed, discovering the important role that electrostriction and thermal relaxation play, and a new apparatus for preparing vibrationally excited molecules with simulated Raman excitation was completed and the first measurements made. Role of vibrational excitation in photodissociation dynamics was studied using a vibrational state preparation technique, such as vibrational overtone excitation or stimulated Raman excitation, to create molecules with particular nuclear motions and then excite that molecule to a dissociative electronic state. Because the vibrational excitation alters the dissociation dynamics in the excited state, both by providing access to different portions of the excited state surface and by altering the motion of the system on the surface, it is usually refered to as vibrationally mediated photodissociation.

  3. Photodissociation Dynamics of 2-BROMOETHYLNITRITE at 351 NM and C-C Bond Fission in the β - Radical Product

    NASA Astrophysics Data System (ADS)

    Wang, Lei; Chhantyal-Pun, Rabi; Brynteson, Matt D.; Miller, Terry A.; Butler, Laurie J.

    2013-06-01

    We used a crossed laser-molecular beam scattering experiment to investigate the primary photodissociation channels of bromoethylnitrite at 351 nm. Only the O-NO bond fission channel forming the β -bromoethoxy radical and NO, no HBr photoelimination, was detected upon 351 nm photoexcitation,. The subsequent decomposition of the highly vibrational excited β -bromoethoxy radical to formaldehyde + CH{_2}Br was also investigated.

  4. Iodine Absorption Cells Purity Testing

    PubMed Central

    Hrabina, Jan; Zucco, Massimo; Philippe, Charles; Pham, Tuan Minh; Holá, Miroslava; Acef, Ouali; Lazar, Josef; Číp, Ondřej

    2017-01-01

    This article deals with the evaluation of the chemical purity of iodine-filled absorption cells and the optical frequency references used for the frequency locking of laser standards. We summarize the recent trends and progress in absorption cell technology and we focus on methods for iodine cell purity testing. We compare two independent experimental systems based on the laser-induced fluorescence method, showing an improvement of measurement uncertainty by introducing a compensation system reducing unwanted influences. We show the advantages of this technique, which is relatively simple and does not require extensive hardware equipment. As an alternative to the traditionally used methods we propose an approach of hyperfine transitions’ spectral linewidth measurement. The key characteristic of this method is demonstrated on a set of testing iodine cells. The relationship between laser-induced fluorescence and transition linewidth methods will be presented as well as a summary of the advantages and disadvantages of the proposed technique (in comparison with traditional measurement approaches). PMID:28067834

  5. Lone-pair interactions and photodissociation of compressed nitrogen trifluoride.

    PubMed

    Kurzydłowski, D; Wang, H B; Troyan, I A; Eremets, M I

    2014-08-14

    High-pressure behavior of nitrogen trifluoride (NF3) was investigated by Raman and IR spectroscopy at pressures up to 55 GPa and room temperature, as well as by periodic calculations up to 100 GPa. Experimentally, we find three solid-solid phase transitions at 9, 18, and 39.5 GPa. Vibrational spectroscopy indicates that in all observed phases NF3 remains in the molecular form, in contrast to the behavior of compressed ammonia. This finding is confirmed by density functional theory calculations, which also indicate that the phase transitions of compressed NF3 are governed by the interplay between lone‑pair interactions and efficient molecule packing. Although nitrogen trifluoride is molecular in the whole pressure range studied, we show that it can be photodissociated by mid-IR laser radiation. This finding paves the way for the use of NF3 as an oxidizing and fluorinating agent in high-pressure reactions.

  6. Lone-pair interactions and photodissociation of compressed nitrogen trifluoride

    NASA Astrophysics Data System (ADS)

    Kurzydłowski, D.; Wang, H. B.; Troyan, I. A.; Eremets, M. I.

    2014-08-01

    High-pressure behavior of nitrogen trifluoride (NF3) was investigated by Raman and IR spectroscopy at pressures up to 55 GPa and room temperature, as well as by periodic calculations up to 100 GPa. Experimentally, we find three solid-solid phase transitions at 9, 18, and 39.5 GPa. Vibrational spectroscopy indicates that in all observed phases NF3 remains in the molecular form, in contrast to the behavior of compressed ammonia. This finding is confirmed by density functional theory calculations, which also indicate that the phase transitions of compressed NF3 are governed by the interplay between lone-pair interactions and efficient molecule packing. Although nitrogen trifluoride is molecular in the whole pressure range studied, we show that it can be photodissociated by mid-IR laser radiation. This finding paves the way for the use of NF3 as an oxidizing and fluorinating agent in high-pressure reactions.

  7. Photodissociation of methyl formate: Conical intersections, roaming and triple fragmentation

    SciTech Connect

    Lin, King-Chuen; Tsai, Po-Yu; Chao, Meng-Hsuan; Kasai, Toshio; Lombardi, Andrea; Palazzetti, Federico; Aquilanti, Vincenzo

    2015-12-31

    The photodissociation channels of methyl formate have been extensively investigated by two different advanced experimental techniques, ion imaging and Fourier-Transform-Infrared emission spectroscopy, combined with quantum chemical calculations and molecular dynamics simulations. Our aim is to characterize the role of alternative routes to the conventional transition-state mediated pathway: the roaming and the triple fragmentation processes. The photolysis experiments, carried out at a range of laser wavelengths in the vicinity of the triple fragmentation threshold, beside the simulation of large bunches of classical trajectories with different initial conditions, have shown that both mechanisms share a common path that involves a conical intersection during the relaxation process from the electronic excited state S{sub 1} to the ground state S{sub 0}.

  8. Near infrared photodissociation spectra of the aniline +-argon ionic complexes

    NASA Astrophysics Data System (ADS)

    Pino, T.; Douin, S.; Boudin, N.; Bréchignac, Ph.

    2006-02-01

    The near infrared spectra of the ionic complexes aniline(NH 2) +-argon and aniline(ND 2) +-argon have been measured by laser photodissociation spectroscopy. The bands observed from 10 500 to 13 500 cm -1 have been assigned to the D1(A˜2A2)←D0(X˜2B1) electronic transition within the solvated chromophore. They are characterized by a long vibrational progression involving the 6a mode. On the basis of CASSCF calculations, a large change of geometry along this coordinate is found while the amino group remains in the ring plane. Therefore, a change of the conjugation of the ring rather than a charge transfer is inferred. This is thought to be the origin of the extent of the progression.

  9. Lone-pair interactions and photodissociation of compressed nitrogen trifluoride

    SciTech Connect

    Kurzydłowski, D.; Wang, H. B.; Eremets, M. I.; Troyan, I. A.

    2014-08-14

    High-pressure behavior of nitrogen trifluoride (NF{sub 3}) was investigated by Raman and IR spectroscopy at pressures up to 55 GPa and room temperature, as well as by periodic calculations up to 100 GPa. Experimentally, we find three solid-solid phase transitions at 9, 18, and 39.5 GPa. Vibrational spectroscopy indicates that in all observed phases NF{sub 3} remains in the molecular form, in contrast to the behavior of compressed ammonia. This finding is confirmed by density functional theory calculations, which also indicate that the phase transitions of compressed NF{sub 3} are governed by the interplay between lone‑pair interactions and efficient molecule packing. Although nitrogen trifluoride is molecular in the whole pressure range studied, we show that it can be photodissociated by mid-IR laser radiation. This finding paves the way for the use of NF{sub 3} as an oxidizing and fluorinating agent in high-pressure reactions.

  10. Photodissociation and spectroscopy of gas phase bimetallic clusters

    SciTech Connect

    Duncan, M.A.

    1992-05-01

    Focus of the research program is the study of gas phase metal clusters for modeling fundamental interactions on metal surfaces. We characterize the chemical bonding between component atoms in clusters as well as the bonding in adsorption on cluster surfaces. Electronic spectra, vibrational frequencies and bond dissociation energies are measured for both neutral and ionized clusters with laser/mass spectrometry techniques. Small bimetallic cluster cations containing Bi/Cr, Bi/Fe, Sn/Bi, and Pb/Sb were photodissociated at various uv wavelengths. Silver dimer van der Waals complexes were produced with a series of rare gas atoms (Ar, Kr, Xe), and their vibrational frequencies and dissociation energies were obtained. (DLC)

  11. Isotope separation by selective photodissociation of glyoxal

    DOEpatents

    Marling, John B.

    1976-01-01

    Dissociation products, mainly formaldehyde and carbon monoxide, enriched in a desired isotope of carbon, oxygen, or hydrogen are obtained by the selective photodissociation of glyoxal wherein glyoxal is subjected to electromagnetic radiation of a predetermined wavelength such that photon absorption excites and induces dissociation of only those molecules of glyoxal containing the desired isotope.

  12. Iodine absorption cells quality evaluation methods

    NASA Astrophysics Data System (ADS)

    Hrabina, Jan; Zucco, Massimo; Holá, Miroslava; Šarbort, Martin; Acef, Ouali; Du-Burck, Frédéric; Lazar, Josef; Číp, Ondřej

    2016-12-01

    The absorption cells represent an unique tool for the laser frequency stabilization. They serve as irreplaceable optical frequency references in realization of high-stable laser standards and laser sources for different brands of optical measurements, including the most precise frequency and dimensional measurement systems. One of the most often used absorption media covering visible and near IR spectral range is molecular iodine. It offers rich atlas of very strong and narrow spectral transitions which allow realization of laser systems with ultimate frequency stabilities in or below 10-14 order level. One of the most often disccussed disadvantage of the iodine cells is iodine's corrosivity and sensitivity to presence of foreign substances. The impurities react with absorption media and cause spectral shifts of absorption spectra, spectral broadening of the transitions and decrease achievable signal-to-noise ratio of the detected spectra. All of these unwanted effects directly influence frequency stability of the realized laser standard and due to this fact, the quality of iodine cells must be precisely controlled. We present a comparison of traditionally used method of laser induced fluorescence (LIF) with novel technique based on hyperfine transitions linewidths measurement. The results summarize advantages and drawbacks of these techniques and give a recommendation for their practical usage.

  13. Photodissociation of protonated leucine-enkephalin in the VUV range of 8-40 eV

    SciTech Connect

    Bari, S.; Gonzalez-Magana, O.; Reitsma, G.; Hoekstra, R.; Schlathoelter, T.; Werner, J.; Schippers, S.

    2011-01-14

    Until now, photodissociation studies on free complex protonated peptides were limited to the UV wavelength range accessible by intense lasers. We have studied photodissociation of gas-phase protonated leucine-enkephalin cations for vacuum ultraviolet (VUV) photons energies ranging from 8 to 40 eV. We report time-of-flight mass spectra of the photofragments and various photofragment-yields as a function of photon energy. For sub-ionization energies our results are in line with existing studies on UV photodissociation of leucine-enkephalin. For photon energies exceeding 10 eV we could identify a new dissociation scheme in which photoabsorption leads to a fast loss of the tyrosine side chain. This loss process leads to the formation of a residual peptide that is remarkably cold internally.

  14. Consequences of excess iodine

    PubMed Central

    Leung, Angela M.; Braverman, Lewis E.

    2014-01-01

    Iodine is a micronutrient that is essential for the production of thyroid hormones. The primary source of iodine is the diet via consumption of foods that have been fortified with iodine, including salt, dairy products and bread, or that are naturally abundant in the micronutrient, such as seafood. Recommended daily iodine intake is 150 μg in adults who are not pregnant or lactating. Ingestion of iodine or exposure above this threshold is generally well-tolerated. However, in certain susceptible individuals, including those with pre-existing thyroid disease, the elderly, fetuses and neonates, or patients with other risk factors, the risk of developing iodine-induced thyroid dysfunction might be increased. Hypothyroidism or hyperthyroidism as a result of supraphysiologic iodine exposure might be either subclinical or overt, and the source of the excess iodine might not be readily apparent. PMID:24342882

  15. Laser power transmission

    NASA Technical Reports Server (NTRS)

    Conway, Edmund J.

    1992-01-01

    An overview of previous studies related to laser power transmission is presented. Particular attention is given to the use of solar pumped lasers for space power applications. Three general laser mechanisms are addressed: photodissociation lasing driven by sunlight, photoexcitation lasing driven directly by sunlight, and photoexcitation lasing driven by thermal radiation.

  16. Solar pumped laser

    NASA Technical Reports Server (NTRS)

    Lee, J. H.; Hohl, F.; Weaver, W. R. (Inventor)

    1984-01-01

    A solar pumped laser is described in which the lasant is a gas that will photodissociate and lase when subjected to sunrays. Sunrays are collected and directed onto the gas lasant to cause it to lase. Applications to laser propulsion and laser power transmission are discussed.

  17. Iodinated humic acids

    NASA Astrophysics Data System (ADS)

    Christiansen, Jesper V.; Carlsen, Lars

    Humic acids are iodinated by elemental iodine and, if the iodine is present as iodide, by peroxidase-mediated reactions. It is demonstrated that iodination of humic acids leads to a product with a uniform distribution of iodine. It could not be unambiguously verified whether the enzymatically mediated iodination is a direct reaction between a peroxidase-iodine complex and the humic acid molecule or a two-step reaction in which the enzyme creates elemental iodine, which consecutively reacts with the humic acid. Based on a simple model of a reaction between sites in the humic acids available for iodination and the electrophilic iodinating species, it was concluded that the reaction should be described as an equilibrium with a logarithmic equilibrium constant of approximately 4. The number of sites available for iodination was, in the humic acids studied, determined to be approximately 4×10-4 per gram humic acid. The different parameters influencing the enzymatically controlled iodination of humic acids are discussed.

  18. The {sup 2}P{sub 1/2} {yields} {sup 2}P{sub 3/2} laser transition in atomic iodine and the problem of search for signals from extraterrestrial intelligence

    SciTech Connect

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

    2007-07-31

    It is proposed to search for signals from extraterrestrial intelligence (ETI) at a wavelength of 1.315 {mu}m of the laser {sup 2}P{sub 1/2} {yields} {sup 2}P{sub 3/2} transition in the atomic iodine, which can be used for this purpose as the natural frequency reference. The search at this wavelength is promising because active quantum filters (AQFs) with the quantum sensitivity limit have been developed for this wavelength, which are capable of receiving laser signals, consisting of only a few photons, against the background of emission from a star under study. In addition, high-power iodine lasers emitting diffraction-limited radiation at 1.315 {mu}m have been created, which highly developed ETI also can have. If a ETI sends in our direction a diffraction-limited 10-ns, 1-kJ laser pulse with the beam diameter of 10 m, a receiver with an AQF mounted on a ten-meter extra-atmospheric optical telescope can detect this signal at a distance of up to 300 light years, irrespective of the ETI position on the celestial sphere. The realisation of the projects for manufacturing optical telescopes of diameter 30 m will increase the research range up to 2700 light years. A weak absorption of the 1.315-{mu}m radiation in the Earth atmosphere (the signal is attenuated by less than 20%) allows the search for ETI signals by using ground telescopes equipped with adaptive optical systems. (laser applications and other topics in quantum electronics)

  19. Spectroscopy, reaction, and photodissociation in highly vibrationally excited molecules. Technical progress report

    SciTech Connect

    Not Available

    1991-12-31

    Highly vibrationally excited molecules often control the course of chemical reactions in the atmosphere, combustion, plasmas, and many other environments. The research described in this Progress Report uses laser excitation and interrogation techniques to study and control the dynamics of highly vibrationally excited molecules. In particular, they show that it is possible to unravel the details and influence the course of photodissociation and bimolecular reaction. The experiments use laser excitation of overtone vibrations to prepare highly vibrationally excited molecules, frequently with single quantum state resolution, and laser spectroscopy to monitor the subsequent behavior of the excited molecule. We have studied the vibrationally mediated photodissociation and the bond- and state-selected bimolecular reaction of highly vibrationally excited molecules. In the first process, one photon creates a highly excited molecule, a second photon from another laser dissociates it, and light from a third laser detects the population of individual product quantum states. This approach allows us to explore otherwise inaccessible regions of the ground and excited state potential energy surface and, by exciting to the proper regions of the surface, to control the breaking of a selected chemical bond. In the second process, the highly vibrationally excited molecule reacts with an atom formed either in a microwave discharge or by photolysis and another laser interrogates the products. We have used this approach to demonstrate mode- and bond-selected bimolecular reactions in which the initial excitation controls the subsequent chemistry. 30 refs., 8 figs.

  20. Photodissociation dynamics of ethyl ethynyl ether: A ketenyl radical precursor

    NASA Astrophysics Data System (ADS)

    Krisch, Maria; Miller, Johanna; Butler, Laurie; Su, Hongmei; Bersohn, Richard; Shu, Jinian

    2006-03-01

    We investigate the photodissociation dynamics of ethyl ethynyl ether at 193.3 nm with crossed laser-molecular beam photofragment translational spectroscopy and laser-induced fluorescence. We establish ethyl ethynyl ether as the first clean precursor to the ketenyl radical, a key species in combustion reactions. One major bond fission channel was observed for the system, cleavage along the HCCO-C2H5 bond, leading to ground state C2H5 (ethyl) radicals and HCCO (ketenyl) radical products in two distinct electronic states. We observed neither cleavage of the other C-O bond nor molecular elimination to form C2H4 + CH2CO (ketene). Ketenyl radicals formed in the higher recoil kinetic energy channel could be either X(^2A") or Ã(^2A') state ketenyl radical. We assign the lower recoil kinetic energy channel to the spin forbidden ã(^4A") state of the ketenyl radical, reached through intersystem crossing. Laser-induced fluorescence from the ketenyl radical peaks after a 20 μs delay, indicating that it is formed with a significant amount of internal energy and subsequently relaxes to the lowest vibrational level of the ground electronic state, a result consistent with the product assignment.

  1. Ultravioret and Infrared Photodissociation Spectroscopy of Hydrated Anilinium Ion

    NASA Astrophysics Data System (ADS)

    Kurusu, Itaru; Yagi, Reona; Kasahara, Yasutoshi; Ishikawa, Haruki

    2015-06-01

    To understand the temperature effect on the microscopic hydration, we have been carrying out the laser spectroscopy of temperature-controlled hydrated phenol cation clusters using our temperature-variable ion trap apparatus. In the present study, we have chosen an anilinium ion (AnH^+) as a solute. Since the phenol cation has (π)-1 configuration, the phenyl ring does not play as a proton-acceptor. On the contrary, the π-orbitals in the AnH^+ are fulfilled and both the NH_3^+ and phenyl groups can behave as hydrogen-bonding sites. Thus, hydration structures around the AnH^+ are expected to be different from those of the phenol cation. Since there is no spectroscopic report on the hydrated AnH^+ clusters, we have carried out the UV and IR photodissociation spectroscopy of AnH^+(H_2O) clusters. In the present study, the AnH^+(H_2O) is produced by an electrospray ionization method. As the first step, spectroscopic measurements are carried out without temperature control. In the UV photodissociation spectrum, the 0-0 band appears at 36351 cm-1 which is red-shifted by 1863 cm-1 from that of the AnH^+ monomer. The band pattern is similar to that of the AnH^+ monomer. This indicates that the structure of the AnH^+ is not so affected by the single hydration. In the IR photodissociation spectrum, OH stretching band of the H_2O moiety and free NH stretching band of AnH^+ moiety are observed. Comparison with the results of the DFT calculation at M05-2X/6-31++G(d,p) level, we determined the structure of the AnH^+(H_2O) cluster. R.~Yagi, Y.~Kasahara, H.~Ishikawa, the 70th International Symposium on Molecular Spectroscopy (2015). H.~Ishikawa, T.~Nakano, T.~Eguchi, T.~Shibukawa, K.~Fuke Chem. Phys. Lett. 514, 234 (2011). G.~Féraud, et al. Phys. Chem. Chem. Phys. 16, 5250 (2014).

  2. The photodissociation and reaction dynamics of vibrationally excited molecules. Technical progress report, 1992--1993

    SciTech Connect

    Not Available

    1993-04-01

    We have used combined vibrational overtone excitation and laser induced fluorescence detection to study dissociation dynamics of hydroxylamine (NH{sub 2}OH), have performed our first laser induced grating experiments on water, and have begun assembling a new apparatus for preparing vibrationally excited molecules with simulated Raman excitation. We study role of vibrational excitation in photodissociation dynamics by using a vibrational state preparation technique, such as vibrational overtone excitation or stimulated Raman excitation, to create molecules with particular nuclear motions and then to excite that molecule to a dissociative electronic state.

  3. An ion mobility mass spectrometer for investigating photoisomerization and photodissociation of molecular ions

    NASA Astrophysics Data System (ADS)

    Adamson, B. D.; Coughlan, N. J. A.; Markworth, P. B.; Continetti, R. E.; Bieske, E. J.

    2014-12-01

    An ion mobility mass spectrometry apparatus for investigating the photoisomerization and photodissociation of electrosprayed molecular ions in the gas phase is described. The device consists of a drift tube mobility spectrometer, with access for a laser beam that intercepts the drifting ion packet either coaxially or transversely, followed by a quadrupole mass filter. An ion gate halfway along the drift region allows the instrument to be used as a tandem ion mobility spectrometer, enabling mobility selection of ions prior to irradiation, with the photoisomer ions being separated over the second half of the drift tube. The utility of the device is illustrated with photoisomerization and photodissociation action spectra of carbocyanine molecular cations. The mobility resolution of the device for singly charged ions is typically 80 and it has a mass range of 100-440 Da, with the lower limit determined by the drive frequency for the ion funnels, and the upper limit by the quadrupole mass filter.

  4. An ion mobility mass spectrometer for investigating photoisomerization and photodissociation of molecular ions.

    PubMed

    Adamson, B D; Coughlan, N J A; Markworth, P B; Continetti, R E; Bieske, E J

    2014-12-01

    An ion mobility mass spectrometry apparatus for investigating the photoisomerization and photodissociation of electrosprayed molecular ions in the gas phase is described. The device consists of a drift tube mobility spectrometer, with access for a laser beam that intercepts the drifting ion packet either coaxially or transversely, followed by a quadrupole mass filter. An ion gate halfway along the drift region allows the instrument to be used as a tandem ion mobility spectrometer, enabling mobility selection of ions prior to irradiation, with the photoisomer ions being separated over the second half of the drift tube. The utility of the device is illustrated with photoisomerization and photodissociation action spectra of carbocyanine molecular cations. The mobility resolution of the device for singly charged ions is typically 80 and it has a mass range of 100-440 Da, with the lower limit determined by the drive frequency for the ion funnels, and the upper limit by the quadrupole mass filter.

  5. An ion mobility mass spectrometer for investigating photoisomerization and photodissociation of molecular ions

    SciTech Connect

    Adamson, B. D.; Coughlan, N. J. A.; Markworth, P. B.; Bieske, E. J.; Continetti, R. E.

    2014-12-15

    An ion mobility mass spectrometry apparatus for investigating the photoisomerization and photodissociation of electrosprayed molecular ions in the gas phase is described. The device consists of a drift tube mobility spectrometer, with access for a laser beam that intercepts the drifting ion packet either coaxially or transversely, followed by a quadrupole mass filter. An ion gate halfway along the drift region allows the instrument to be used as a tandem ion mobility spectrometer, enabling mobility selection of ions prior to irradiation, with the photoisomer ions being separated over the second half of the drift tube. The utility of the device is illustrated with photoisomerization and photodissociation action spectra of carbocyanine molecular cations. The mobility resolution of the device for singly charged ions is typically 80 and it has a mass range of 100-440 Da, with the lower limit determined by the drive frequency for the ion funnels, and the upper limit by the quadrupole mass filter.

  6. Photodissociation of an Internally Cold Beam of CH+ Ions in a Cryogenic Storage Ring

    NASA Astrophysics Data System (ADS)

    O'Connor, A. P.; Becker, A.; Blaum, K.; Breitenfeldt, C.; George, S.; Göck, J.; Grieser, M.; Grussie, F.; Guerin, E. A.; von Hahn, R.; Hechtfischer, U.; Herwig, P.; Karthein, J.; Krantz, C.; Kreckel, H.; Lohmann, S.; Meyer, C.; Mishra, P. M.; Novotný, O.; Repnow, R.; Saurabh, S.; Schwalm, D.; Spruck, K.; Sunil Kumar, S.; Vogel, S.; Wolf, A.

    2016-03-01

    We have studied the photodissociation of CH+ in the Cryogenic Storage Ring at ambient temperatures below 10 K. Owing to the extremely high vacuum of the cryogenic environment, we were able to store CH+ beams with a kinetic energy of ˜60 keV for several minutes. Using a pulsed laser, we observed Feshbach-type near-threshold photodissociation resonances for the rotational levels J =0 - 2 of CH+, exclusively. In comparison to updated, state-of-the-art calculations, we find excellent agreement in the relative intensities of the resonances for a given J , and we can extract time-dependent level populations. Thus, we can monitor the spontaneous relaxation of CH+ to its lowest rotational states and demonstrate the preparation of an internally cold beam of molecular ions.

  7. Photodissociation of an Internally Cold Beam of CH^{+} Ions in a Cryogenic Storage Ring.

    PubMed

    O'Connor, A P; Becker, A; Blaum, K; Breitenfeldt, C; George, S; Göck, J; Grieser, M; Grussie, F; Guerin, E A; von Hahn, R; Hechtfischer, U; Herwig, P; Karthein, J; Krantz, C; Kreckel, H; Lohmann, S; Meyer, C; Mishra, P M; Novotný, O; Repnow, R; Saurabh, S; Schwalm, D; Spruck, K; Sunil Kumar, S; Vogel, S; Wolf, A

    2016-03-18

    We have studied the photodissociation of CH^{+} in the Cryogenic Storage Ring at ambient temperatures below 10 K. Owing to the extremely high vacuum of the cryogenic environment, we were able to store CH^{+} beams with a kinetic energy of ∼60  keV for several minutes. Using a pulsed laser, we observed Feshbach-type near-threshold photodissociation resonances for the rotational levels J=0-2 of CH^{+}, exclusively. In comparison to updated, state-of-the-art calculations, we find excellent agreement in the relative intensities of the resonances for a given J, and we can extract time-dependent level populations. Thus, we can monitor the spontaneous relaxation of CH^{+} to its lowest rotational states and demonstrate the preparation of an internally cold beam of molecular ions.

  8. Extreme ultraviolet photodissociative excitation of molecular oxygen

    NASA Technical Reports Server (NTRS)

    Carlson, R. W.

    1974-01-01

    Photodissociation processes in molecular oxygen occurring in the wavelength range from 500 to 900 A, investigated through observations of the resulting atomic fluorescence radiation, are reported. The dispersed radiation from a continuous light source was used to excite the gas, and the resulting fluorescence radiation was observed in the ultraviolet and infrared. The results obtained are compared with the dissociation cross sections derived by Matsunaga and Watanabe (1967).

  9. Initial cross section for photodissociation of phosgene on Ag(111)

    NASA Astrophysics Data System (ADS)

    Zhou, X.-L.; White, J. M.

    1990-01-01

    The initial cross section for UV photodissociation of phosgene (Cl2CO) on Ag(111) at 100 K has been measured. With photon energies greater than 2.6 eV, submonolayer Cl2CO is readily photodissociated to surface Cl(a) and gas phase CO(g). The evolution of CO during photodissociation is readily monitored and used to calculate the initial photodissociation rate and cross section. The cross section is higher than the gas phase absorption cross section and is in the range of 10-18-10-19 cm2. It depends on the wavelength and the Cl2CO coverage.

  10. Investigation of Singly Ionized Iodine Spectroscopy in Support of Electrostatic Propulsion Diagnostics Development

    DTIC Science & Technology

    2012-07-02

    lab.32,16 However, commercially available single mode diode lasers have also been successfully used in the past.33,25 Such lasers provide a...significantly less expensive laser source capable of scanning across 20 GHz, or more. It should be noted that the line widths of commercial laser diodes are 15–30...transitions for laser -induced fluorescence of an accelerated atomic iodine singly charged ion (I+). While the second spectrum of iodine has been analyzed

  11. Resonant photodissociation in substituted benzenes

    NASA Astrophysics Data System (ADS)

    Scarborough, Tim; McAcy, Collin; Foote, David; Uiterwaal, Cornelis

    2011-05-01

    Cyclic aromatic molecules are abundant in organic chemistry, with a wide variety of applications, including pharmacology, pollution studies and genetic research. Among the simplest of these molecules is benzene (C6H6) , with many relevant molecules being benzene-like with a single atomic substitution. In such a substitution, the substituent determines a characteristic perturbation of the electronic structure of the molecule. We discuss the substitution of halogens into the ring (C6H5X), and its effects on the dynamics of ionization and dissociation of the molecule without the focal volume effect. In particular, using 800-nm, 50-fs laser pulses, we present results in the dissociation of fluorobenzene, chlorobenzene, bromobenzene and iodobenzene into the phenyl ring (C6H5) and the atomic halogen, and the subsequent ionization of these fragments. The impact of the ``heavy atom effect'' on a 1 (π , π*) -->3 (n , σ*) singlet-triplet intersystem crossing will be emphasized. Currently under investigation is whether such a dissociation can be treated as an effective source of the neutral substituent. This material is based upon work supported by the National Science Foundation under Grant No. PHY-0355235.

  12. Characterization of Iodine Quenching and Energy Transfer Rate Constants for Supersonic Flow Visualization Applications

    DTIC Science & Technology

    2007-09-28

    SUBTITLE Sm. CONTRACTNUBER Characterization of iodine quenching and energy transfer rate FA9550-41-- o3G Sb. GRANT NUMBER constants for supersonic flow...in the nozzle from a chemical oxygen iodine laser (COIL). PLIF images are recorded using laser excitation of the I= B-X transition. Data for the...Preacolbed byANSI Sad Z30.16 20071015188 Final report for the project, "Characterization of iodine quenching and energy transfer rate constants for

  13. Linkage and Anomeric Differentiation in Trisaccharides by Sequential Fragmentation and Variable-Wavelength Infrared Photodissociation

    NASA Astrophysics Data System (ADS)

    Tan, Yanglan; Polfer, Nicolas C.

    2015-02-01

    Carbohydrates and their derivatives play important roles in biological systems, but their isomeric heterogeneity also presents a considerable challenge for analytical techniques. Here, a stepwise approach using infrared multiple-photon dissociation (IRMPD) via a tunable CO2 laser (9.2-10.7 μm) was employed to characterize isomeric variants of glucose-based trisaccharides. After the deprotonated trisaccharides were trapped and fragmented to disaccharide C2 fragments in a Fourier transform ion cyclotron resonance (FTICR) cell, a further variable-wavelength infrared irradiation of the C2 ion produced wavelength-dependent dissociation patterns that are represented as heat maps. The photodissociation patterns of these C2 fragments are shown to be strikingly similar to the photodissociation patterns of disaccharides with identical glycosidic bonds. Conversely, the photodissociation patterns of different glycosidic linkages exhibit considerable differences. On the basis of these results, the linkage position and anomericity of glycosidic bonds of disaccharide units in trisaccharides can be systematically differentiated and identified, providing a promising approach to characterize the structures of isomeric oligosaccharides.

  14. Ultracold photodissociation and progress towards a molecular lattice clock with 88 Sr

    NASA Astrophysics Data System (ADS)

    Lee, Chih-Hsi; McGuyer, Bart; McDonald, Mickey; Apfelback, Florian; Grier, Andrew; Zelevinsky, Tanya

    2016-05-01

    Techniques originally developed for the construction of atomic clocks can be adapted to the study of ultracold molecules, with applications ranging from studies of ultracold chemistry to searches for new physics. We present recent experimental results involving studies of fully quantum state-resolved photodissociation of 88 Sr2 molecules, as well as progress toward building a molecular clock. First, our system has allowed for precise, quantum state-resolved photodissociation studies, revealing not only excellent control over quantum states but also a more accurate way to describe the photodissociation of diatomic molecules and access ultracold chemistry. Second, the molecular clock will allow us to search for a possible time variation of the proton-electron mass ratio. The ``oscillator'' of such a molecular clock would consist of the frequency difference between two lasers driving a two-photon Raman transition between deeply and intermediately-bound rovibrational levels in the electronic ground state. Accomplishing this task requires exploring several research directions, including the precision spectroscopy of bound states and developing tools for the control and minimization of differential lattice light shifts.

  15. Imaging of rotational wave-function in photodissociation of rovibrationally excited HCl molecules

    NASA Astrophysics Data System (ADS)

    Grygoryeva, K.; Rakovský, J.; Votava, O.; Fárník, M.

    2017-07-01

    We demonstrate a visualization of quantum mechanical phenomena with the velocity map imaging (VMI) technique, combining vibrationally mediated photodissociation (VMP) of a simple diatomic HCl with the VMI of its H-photofragments. Free HCl molecules were excited by a pump infrared (IR) laser pulse to particular rotational J levels of the v = 2 vibrational state, and subsequently a probe ultraviolet laser photodissociated the molecule at a fixed wavelength of 243.07 nm where also the H-fragments were ionized. The molecule was aligned by the IR excitation with respect to the IR laser polarization, and this alignment was reflected in the angular distribution of the H-photofragments. In particular, the highest degree of molecular alignment was achieved for the J =1 ←0 transition, which exclusively led to the population of a single rotational state with M = 0. The obtained images were analyzed for further details of the VMP dynamics, and different J states were studied as well. Additionally, we investigated the dynamic evolution of the excited states by changing the pump-probe laser pulse delay; the corresponding images reflected dephasing due to a coupling between the molecular angular momentum and nuclear spin. Our measurements confirmed previous observation using the time-of-flight technique by Sofikitis et al. [J. Chem. Phys. 127, 144307 (2007)]. We observed a partial recovery of the originally excited state after 60 ns in agreement with the previous observation.

  16. Iodine deficiency in children.

    PubMed

    Pearce, Elizabeth N

    2014-01-01

    Iodine is an essential trace mineral, required for the production of thyroid hormone. Iodine deficiency may result in goiter, hypothyroidism, miscarriage, stillbirth, congenital anomalies, infant and neonatal mortality, and impaired growth. Adequate thyroid hormone is critically important for normal growth and neurodevelopment in fetal life, infancy and childhood. The population iodine status is most commonly assessed using median urinary iodine concentration values, but goiter prevalence (determined by palpation or by ultrasound), serum thyroglobulin levels, and neonatal thyroid-stimulating hormone values can also be used. Universal salt iodization programs have been the mainstay of public health efforts to eliminate iodine deficiency worldwide. However, in some regions targeted fortification of foods such as bread has been used to combat iodine deficiency. Iodine supplementation may be required in areas where dietary fortification is not feasible or where it is not sufficient for vulnerable groups such as pregnant women. Although international public health efforts over the past several decades have been highly effective, nearly one third of children worldwide remain at risk for iodine deficiency, and iodine deficiency is considered the leading preventable cause of preventable intellectual deficits.

  17. Low Sulfur Depletion in Photodissociation Regions

    NASA Astrophysics Data System (ADS)

    Goicoechea, J. R.; Pety, J.; Gerin, M.; Teyssier, D.; Roueff, E.; Hily-Blant, P.

    2006-06-01

    Sulfur is an abundant element which remains undepleted in diffuse interstellar gas but it is historically assumed to deplete (by factors of ˜1000) on grains at higher densities. Photodissociation regions (PDRs) are an interesting intermediate medium between translucent and dark clouds where the energetics and dynamics are dominated by an illuminating FUV radiation field, and thus they can provide some new insights about the sulfur depletion problem. In this work we present our latest studies on CS and HCS^+ photochemistry, excitation and radiative transfer in the Horsehead PDR, allowing us to infer the sulfur abundance.

  18. Characterization of low-molecular weight iodine-terminated polyethylenes by gas chromatography/mass spectrometry and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry with the use of derivatization.

    PubMed

    Zaikin, Vladimir G; Borisov, Roman S; Polovkov, Nikolai Yu; Zhilyaev, Dmitry I; Vinogradov, Aleksei A; Ivanyuk, Aleksei V

    2013-01-01

    Gas chromatography/mass spectrometry (GC/MS) and matrix-assisted laser desorption/ionization time-of-flight (MALDI-ToF) mass spectrometry, in conjunction with various derivatization approaches, have been applied to structure determination of individual oligomers and molecular-mass distributions (MMD) in low-molecular mass polyethylene having an iodine terminus. Direct GC/MS analysis has shown that the samples under investigation composed of polyethyelene-iodides (major components) and n-alkanes. Exchange reaction with methanol in the presence of NaOH gave rise to methoxy-derivatives and n-alkenes. Electron ionization mass spectra have shown that the former contained terminal methoxy groups indicating the terminal position of the iodine atom in the initial oligomers. MMD parameters have been determined with the aid of MALDI mass spectrometry followed by preliminary derivatization-formation of covalently bonded charge through the reaction of iodides with triphenylphosphine, trialkylamines, pyridine or quinoline. The mass spectra revealed well-resolved peaks for cationic parts of derivatized oligomers allowing the determination of MMD. The latter values have been compared with those calculated from GC/MS data.

  19. Sequence- and site-specific photodissociation at 266 nm of protonated synthetic polypeptides containing a tryptophanyl residue.

    PubMed

    Oh, Joo Yeon; Moon, Jeong Hee; Kim, Myung Soo

    2004-01-01

    Photodissociation at 266 nm of protonated synthetic polypeptides containing a tryptophanyl residue was investigated using a homebuilt tandem time-of-flight mass spectrometer equipped with a matrix-assisted laser desorption/ionization source. Efficient photodissociation of the protonated peptides was demonstrated. Most of the intense peaks in the laser-induced tandem mass spectra were sequence ions. Furthermore, sequence ions due to cleavages at all the peptide bonds were observed; this is a feature of the technique that is particularly useful for peptide sequencing. Fragmentations at both ends of the tryptophanyl residue were especially prevalent, which can be useful for location of the tryptophanyl chromophore in a peptide. Copyright (c) 2004 John Wiley & Sons, Ltd.

  20. Imaging the photodissociation dynamics of the methyl radical from the 3s and 3pz Rydberg states

    PubMed Central

    Marggi Poullain, Sonia; Chicharro, David V.; Zanchet, Alexandre; González, Marta G.; Rubio-Lago, Luis; Senent, María L.; García-Vela, Alberto; Bañares, Luis

    2016-01-01

    The photodissociation dynamics of the methyl radical from the 3s and 3pz Rydberg states have been studied using velocity map and slice ion imaging in combination with pump-probe nanosecond laser pulses. The reported translational energy and angular distributions of the H(2S) photofragment detected by (2+1) REMPI highlight different dissociation mechanisms for the 3s and 3pz Rydberg states. A narrow peak in the translational energy distribution and an anisotropic angular distribution characterizes the fast 3s photodissociation, while for the 3pz state Boltzmann-type translational energy and isotropic angular distributions are found. High level ab initio calculations have been performed in order to elucidate the photodissociation mechanisms from the two Rydberg states and to rationalize the experimental results. The calculated potential energy curves highlight a typical predissociation mechanism for the 3s state, characterized by the coupling between the 3s Rydberg state and a valence repulsive state. On the other hand, the photodissociation on the 3pz state is initiated by a predissociation process due to the coupling between the 3pz Rydberg state and a valence repulsive state and constrained, later on, by two conical intersections that allow the system to relax to lower electronic states. Such mechanism opens different reaction pathways leading to CH2 photofragments in different electronic states and inducing a transfer of energy between translational and internal modes. PMID:27296907

  1. Imaging the photodissociation dynamics of the methyl radical from the 3s and 3pz Rydberg states.

    PubMed

    Marggi Poullain, Sonia; Chicharro, David V; Zanchet, Alexandre; González, Marta G; Rubio-Lago, Luis; Senent, María L; García-Vela, Alberto; Bañares, Luis

    2016-06-22

    The photodissociation dynamics of the methyl radical from the 3s and 3pz Rydberg states have been studied using the velocity map and slice ion imaging in combination with pump-probe nanosecond laser pulses. The reported translational energy and angular distributions of the H((2)S) photofragment detected by (2+1) REMPI highlight different dissociation mechanisms for the 3s and 3pz Rydberg states. A narrow peak in the translational energy distribution and an anisotropic angular distribution characterize the fast 3s photodissociation, while for the 3pz state Boltzmann-type translational energy and isotropic angular distributions are found. High level ab initio calculations have been performed in order to elucidate the photodissociation mechanisms from the two Rydberg states and to rationalize the experimental results. The calculated potential energy curves highlight a typical predissociation mechanism for the 3s state, characterized by the coupling between the 3s Rydberg state and a valence repulsive state. On the other hand, the photodissociation on the 3pz state is initiated by a predissociation process due to the coupling between the 3pz Rydberg state and a valence repulsive state and constrained, later on, by two conical intersections that allow the system to relax to lower electronic states. Such a mechanism opens up different reaction pathways leading to CH2 photofragments in different electronic states and inducing a transfer of energy between translational and internal modes.

  2. THE PHOTODISSOCIATION OF FORMALDEHYDE IN COMETS

    SciTech Connect

    Feldman, Paul D.

    2015-10-20

    Observations of comets in the 905–1180 Å spectral band made with the Far Ultraviolet Spectroscopic Explorer in 2001 and 2004 show unusual features in the fluorescent emissions of CO and H{sub 2}. These include emission from a non-thermal high-J rotational population of CO and solar Lyα induced fluorescence from excited vibrational levels of H{sub 2}, both of which are attributed to the photodissociation of formaldehyde. In this paper we model the large number of observed H{sub 2} lines and demonstrate the dependence of the pumping on the heliocentric velocity of the comet and the solar line profiles. We also derive the rotational and vibrational populations of H{sub 2} and show that they are consistent with the results of laboratory studies of the photodissociation of H{sub 2}CO. In addition to the principal series of H i and O i, the residual spectrum is found to consist mainly of the Rydberg series of C i multiplets from which we derive the mean carbon column abundance in the coma. Fluorescent emissions from N i and N{sub 2} are also searched for.

  3. High-Resolution Photoionization, Photoelectron and Photodissociation Studies. Determination of Accurate Energetic and Spectroscopic Database for Combustion Radicals and Molecules

    SciTech Connect

    Ng, Cheuk-Yiu

    2016-04-25

    The main goal of this research program was to obtain accurate thermochemical and spectroscopic data, such as ionization energies (IEs), 0 K bond dissociation energies, 0 K heats of formation, and spectroscopic constants for radicals and molecules and their ions of relevance to combustion chemistry. Two unique, generally applicable vacuum ultraviolet (VUV) laser photoion-photoelectron apparatuses have been developed in our group, which have used for high-resolution photoionization, photoelectron, and photodissociation studies for many small molecules of combustion relevance.

  4. Photodissociation and photoionization of organosulfur radicals

    SciTech Connect

    Hsu, Chia-Wei

    1994-05-27

    The dynamics of S(3P2,1,0, 1D2) production from the 193 nm photodissociation of CH3SCH3, H2S and CH3SH have been studied using 2 + 1 resonance-enhanced multiphoton ionization (REMPI) techniques. The 193 nm photodissociation cross sections for the formation of S from CH3S and HS initially prepared in the photodissociation of CH3SCH3 and H2S are estimated to be 1 x 10-18 and 1.1 x 10-18 cm2, respectively. The dominant product from CH3S is S(1D), while that from SH is S(3P). Possible potential energy surfaces involved in the 193 nm photodissociation of CH3S($\\tilde{X}$) and SH(X) have been also examined. Threshold photoelectron (PE) spectra for SH and CH3S formed in the ultraviolet photodissociation of H2S and CH3SH, respectively, have been measured using the nonresonant two-photon pulsed field ionization (N2P-PFI) technique. The rotationally resolved N2P-PFI-PE spectrum obtained for SH indicates that photoionization dynamics favors the rotational angular momentum change ΔN < 0 with the ΔN value up to -3, an observation similar to that found in the PFI-PE spectra of OH (OD) and NO. The ionization energies for SH(X2Π3,2) and CH3S($\\tilde{X}$2E3/2) are determined to be 84,057.5 ± 3 cm-1 and 74,726 ± 8 cm-1 respectively. The spin-orbit splittings for SH(X2Π3/2, 1/2) and CH3S($\\tilde{X}$2E3/2, 1/2) are found to be 377 ± 2 and 257 ± 5 cm-1, respectively, in agreement with previous measurements. The C-S stretching frequency for CH3S+($\\tilde{X}$3A2) is 733 ± 5 cm-1. This study illustrates that the PFI-PE detection method can be a

  5. Picosecond absorption studies on the photodissociation of alpha- and beta-nitrosyl hemoglobin monomers

    SciTech Connect

    Guest, C.R.; Noe, L.J.

    1988-10-01

    Transient absorption studies of the pump-probe type were performed on the NO forms of the alpha- and beta-monomers of hemoglobin using a Nd3+ phosphate-glass laser. A second harmonic 531-nm, 8-ps fwhm pulse pumped the Q-band while a delayed continuum generated pulse was used to monitor pi pi* Soret absorption changes in the 410-453-nm region. Photodissociation of nitrosyl alpha- and beta-monomers was found to differ markedly from the tetramer in what we believe to be the formation of a five-coordinate HbNO (with proximal imidazole detached) photoproduct within the first 50 ps after photon absorption.

  6. Iodine generator for reclaimed water purification

    NASA Technical Reports Server (NTRS)

    Wynveen, R. A.; Powell, J. D.; Schubert, F. H. (Inventor)

    1977-01-01

    The system disclosed is for controlling the iodine level in a water supply in a spacecraft. It includes an iodine accumulator which stores crystalline iodine, an electrochemical valve to control the input of iodine to the drinking water and an iodine dispenser. A pump dispenses fluid through the iodine dispenser and an iodine sensor to a potable water tank storage. The iodine sensor electronically detects the iodine level in the water, and through electronic means, produces a correction current control. The correction current control operates the electro-chemical iodine valve to release iodine from the iodine accumulator into the iodine dispenser.

  7. Ab initio study of the KrH+ photodissociation.

    PubMed

    Alekseyev, Aleksey B; Buenker, Robert J; Liebermann, Heinz-Peter

    2008-06-21

    The multireference spin-orbit configuration interaction method is employed to calculate potential energy curves for the ground and low-lying excited states of the KrH(+) cation. For the first time, the spin-orbit interaction is taken into account and electric dipole moments are computed for transitions to the states responsible for the first absorption continuum (A band) of KrH(+). On this basis, the partial and total absorption spectra in this energy range are obtained. It is shown that the A-band absorption is dominated by the parallel A (1)Sigma(+)<--X (1)Sigma(+) transition. In the low-energy part of the band (<83x10(3) cm(-1)) the absorption is mainly caused by the spin-forbidden b (3)Pi(0(+) )<--X (1)Sigma(+) excitation, while perpendicular transitions to the B (1)Pi and b (3)Pi(1) states are significantly weaker. The branching ratio Gamma for the photodissociation products is calculated and it is shown to increase smoothly from 0 in the red tail of the band to 1 at E>or=90x10(3) cm(-1). The latter value corresponds to the exclusive formation of the spin-excited Kr(+)((2)P(12)) ions, which may be used to obtain laser generation on the Kr(+)((2)P(12)-(2)P(32)) transition.

  8. Photodissociation of Acetaldehyde and the Photoionization Cross Section of HCO

    NASA Astrophysics Data System (ADS)

    Shubert, V. Alvin; Pratt, Stephen T.

    2010-06-01

    Acetaldehyde was photodissociated with near UV laser light, and the methyl (CH_3) and formyl (HCO) radical fragments were photoionized with vacuum ultraviolet (VUV) light. The fragments were detected by using both time of flight mass spectrometry and velocity ion map imaging. With the former technique, simultaneous detection of both fragments provided the intensity of HCO+ relative to CH_3+ with I(HCO+)/I(CH_3+) ≈ 0.8. Because the absolute photoionization cross section of the CH_3 radical has been characterized (≈ 5 Mb) at the VUV energies of interest, the absolute photoionization cross section of HCO could be determined from the intensity ratio, yielding an HCO cross section of ≈ 4 Mb at 10.3 eV. However, because some of the HCO fragments could be formed with enough internal energy to undergo secondary dissociation, velocity ion map imaging was employed to determine the extent of any secondary dissociation that occurred. The translational energy distributions obtained for both the CH_3 and HCO fragments are nearly identical, indicating that no HCO fragments underwent secondary dissociation. A surprising result was the smaller photoionization cross section of HCO relative to CH_3. Comparison to the isoelectronic species of NO will be discussed and a potential explanation will be offered for this observation. This work was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences under contract No. DE-AC02-06CH11357.

  9. Photodissociation studies of CBr(4) (+) and CBr(3) (+) at 267 nm using ion velocity imaging.

    PubMed

    Greene, Jamila R; Francisco, Joseph S; Huang, Jianhua; Xu, Dadong; Jackson, William M

    2004-09-22

    Time-of-flight (TOF) mass spectroscopy and ion velocity imaging were employed to study the formation and photodissociation of CBr(4) (+) and CBr(3) (+) ions that were observed in the TOF spectrum when a CBr(4) beam was irradiated with 118 nm and 355 nm lasers. Energy dependence measurements show that both CBr(4) (+) and CBr(3) (+) ions depend on the fourth power of the 355 nm laser energy, which indicates that direct ionization and dissociative ionization of CBr(4) have low probabilities from the state initially excited at 118 nm. This is likely due to the large geometry change in the CBr(4) (+) ion. Two ionic fragments Br(+) and CBr(2) (+) were observed from the dissociation of CBr(4) (+) and CBr(3) (+) ions when another laser at 267 nm was introduced to the interaction region at a delayed time. The possible dissociation pathways and the angular and translational distributions are discussed in the paper.

  10. Development of a linear ion trap/orthogonal-time-of-flight mass spectrometer for time-dependent observation of product ions by ultraviolet photodissociation of peptide ions.

    PubMed

    Kim, Tae-Young; Schwartz, Jae C; Reilly, James P

    2009-11-01

    A hybrid linear ion trap/orthogonal time-of-flight (TOF) mass spectrometer has been developed to observe time-dependent vacuum ultraviolet photodissociation product ions. In this apparatus, a reflectron TOF mass analyzer is orthogonally interfaced to an LTQ using rf-only octopole and dc quadrupole ion guides. Precursor ions are generated by electrospray ionization and isolated in the ion trap. Subsequently they are directed to the TOF source where photodissociation occurs and product ions are extracted for mass analysis. To detect photodissociation product ions having axially divergent trajectories, a large rectangular detector is utilized. With variation of the time between photodissociation and orthogonal extraction in the TOF source, product ions formed over a range of times after photoexcitation can be sampled. Time-dependent observation of product ions following 157 nm photodissociation of a singly charged tryptic peptide ion (NWDAGFGR) showed that prompt photofragment ions (x- and v-type ions) dominate the tandem mass spectrum up to 1 micros after the laser shot, but the intensities of low energy thermal fragment ions (y-type ions) become comparable several microseconds later. Different proton mobilization time scales were observed for arginine- and lysine-terminated tryptic peptides.

  11. Photodissociation of vanadium, niobium, and tantalum oxide cluster cations.

    PubMed

    Molek, K S; Jaeger, T D; Duncan, M A

    2005-10-08

    Transition-metal oxide clusters of the form M(n)O(m) (+)(M=V,Nb,Ta) are produced by laser vaporization in a pulsed nozzle cluster source and detected with time-of-flight mass spectrometry. Consistent with earlier work, cluster oxides for each value of n produce only a limited number of stoichiometries, where m>n. The cluster cations are mass selected and photodissociated using the second (532 nm) or third (355 nm) harmonic of a Nd:YAG (yttrium aluminum garnet) laser. All of these clusters require multiphoton conditions for dissociation, consistent with their expected strong bonding. Dissociation occurs by either elimination of oxygen or by fission, repeatedly producing clusters having the same specific stoichiometries. In oxygen elimination, vanadium species tend to lose units of O(2), whereas niobium and tantalum lose O atoms. For each metal increment n, oxygen elimination proceeds until a terminal stoichiometry is reached. Clusters having this stoichiometry do not eliminate more oxygen, but rather undergo fission, producing smaller M(n)O(m) (+) species. The smaller clusters produced as fission products represent the corresponding terminal stoichiometries for those smaller n values. The terminal stoichiometries identified are the same for V, Nb, and Ta oxide cluster cations. This behavior suggests that these clusters have stable bonding networks at their core, but additional excess oxygen at their periphery. These combined results determine that M(2)O(4) (+), M(3)O(7) (+), M(4)O(9) (+), M(5)O(12) (+), M(6)O(14) (+), and M(7)O(17) (+) have the greatest stability for V, Nb, and Ta oxide clusters.

  12. Ultraviolet Photodissociation Action Spectroscopy of Protonated Azabenzenes

    NASA Astrophysics Data System (ADS)

    Hansen, Christopher S.; Blanksby, Stephen J.; Bieske, Evan; Reimers, Jeffrey R.; Trevitt, Adam J.

    2014-06-01

    Azabenzenes are derivatives of benzene containing between one and six nitrogen atoms. Protonated azabenzenes are the fundamental building blocks of many biomolecules, charge-transfer dyes, ionic liquids and fluorescent tags. However, despite their ubiquity, there exists limited spectroscopic data that reveals the structure, behaviour and stability of these systems in their excited states. For the case of pyridinium (C_5H_5N-H^+), the simplest azabenzene, the electronic spectroscopy is complicated by short excited state lifetimes, efficient non-radiative deactivation methods and limited fluorescence. Ultraviolet (UV) photodissociation (PD) action spectroscopy provides new insight into the spectroscopic details, excited state behaviour and photodissociation processes of a series of protonated azabenzenes including pyridinium, diazeniums and their substituted derivatives. The room-temperature UV PD action spectra, often exhibiting vibronic detail,^b will be presented alongside PD mass spectra and the kinetic data from structurally-diagnostic ion-molecule reaction kinetics. Analysis of the spectra, with the aid of quantum chemical calculations, reveal that many azabenzenes prefer a non-planar excited state geometry reminiscent of the structures encountered in 'channel 3'-like deactivation of aromatics. The normal modes active in this isomerization contribute largely to the spectroscopy of the N-pyridinium ion as they build upon totally-symmetric vibronic transitions leading to repeating sets of closely-spaced spectral features. Hansen, C.S. et al.; J. Am. Soc. Mass Spectrom. 24:932-940 (2013) Hansen, C.S. et al.; J. Phys. Chem. A 117:10839-10846 (2013)

  13. Photodissociation of CO in turbulent molecular clouds

    NASA Astrophysics Data System (ADS)

    Röllig, M.; Hegmann, M.; Kegel, W. H.

    2002-09-01

    We study the formation of CO molecules at the edge of dense molecular clouds. As shown by van Dishoeck & Black \\cite{dishoeck88} the CO photodissociation process is dominated by line rather than continuous absorption. Hence, a turbulent velocity field, modifying the line shape, strongly affects the CO density distribution. We investigate these effects in detail. To describe the turbulent velocity field we use the statistical approach by G. Traving and collaborators (cf. Gail et al. \\cite{GaH74}) which accounts for a finite correlation length for the velocity field. We solve the radiative transfer equation selfconsistently with the rate equations describing the chemical reactions. One main goal of the investigation is an improvement of molecular cloud models used to analyze observational data. To bring the observational data into agreement with the model of an isothermal spherical cloud being stabilized by turbulent and thermal pressure it turned out to be neccessary to implement a cut off radius for the CO density distribution in order to define a cloud edge (Piehler & Kegel \\cite{Pie95}). This radius depends heavily on the intensity and density distribution in the outer parts of the cloud. Our calculations show that turbulence has substantial influence on the penetration of UV radiation into a molecular cloud. Even turbulent velocities in the order of a few thermal velocities are sufficient to allow the radiation to penetrate significantly deeper into the cloud than in a nonturbulent medium. On the other hand correlation length effects may lead to a decrease in photodissociation efficiency. By accounting for a finite correlation length of the stochastic velocity field the self-shielding of CO absorption bands is considerably enhanced and CO molecules can effectively form in depths that have a much stronger UV intensity in standard radiative transfer models.

  14. Photodissociation mass spectrometry: New tools for characterization of biological molecules

    PubMed Central

    Brodbelt, Jennifer S.

    2014-01-01

    Photodissociation mass spectrometry combines the ability to activate and fragment ions using photons with the sensitive detection of the resulting product ions by mass spectrometry. The resulting combination affords a versatile tool for characterization of biological molecules. The scope and breadth of photodissociation mass spectrometry have increased substantially over the past decade as new research groups have entered the field and developed a number of innovative applications that illustrate the ability of photodissociation to produce rich fragmentation patterns, to cleave bonds selectively, and to target specific molecules based on incorporation of chromophores. This review focuses on many of the key developments in photodissociation mass spectrometry over the past decade with a particular emphasis on its applications to biological molecules. PMID:24481009

  15. Combining UV photodissociation with electron transfer for peptide structure analysis.

    PubMed

    Shaffer, Christopher J; Marek, Ales; Pepin, Robert; Slovakova, Kristina; Turecek, Frantisek

    2015-03-01

    The combination of near-UV photodissociation with electron transfer and collisional activation provides a new tool for structure investigation of isolated peptide ions and reactive intermediates. Two new types of pulse experiments are reported. In the first one called UV/Vis photodissociation-electron transfer dissociation (UVPD-ETD), diazirine-labeled peptide ions are shown to undergo photodissociation in the gas phase to form new covalent bonds, guided by the ion conformation, and the products are analyzed by electron transfer dissociation. In the second experiment, called ETD-UVPD wherein synthetic labels are not necessary, electron transfer forms new cation-peptide radical chromophores that absorb at 355 nm and undergo specific backbone photodissociation reactions. The new method is applied to distinguish isomeric ions produced by ETD of arginine containing peptides. Copyright © 2015 John Wiley & Sons, Ltd.

  16. Atomic polarization in the photodissociation of diatomic molecules.

    PubMed

    Clark, A P; Brouard, M; Quadrini, F; Vallance, C

    2006-12-28

    The angular momentum polarization of atomic photofragments provides a detailed insight into the dynamics of the photodissociation process. In this article, the origins of electronic angular momentum polarization are introduced and experimental and theoretical methods for the measurement or calculation of atomic orientation and alignment parameters described. Many diatomic photodissociation systems are surveyed, in order to provide an overview both of the historical development of the field and of the most state-of-the-art contemporary studies.

  17. Radioactive iodine uptake

    MedlinePlus

    ... too much thyroid hormone medicine or supplements) Iodine overload Subacute thyroiditis (swelling or inflammation of the thyroid ... to achieve this important distinction for online health information and services. Learn more about A.D.A. ...

  18. Iodine Clock Reaction.

    ERIC Educational Resources Information Center

    Mitchell, Richard S.

    1996-01-01

    Describes a combination of solutions that can be used in the study of kinetics using the iodine clock reaction. The combination slows down degradation of the prepared solutions and can be used successfully for several weeks. (JRH)

  19. Iodine Clock Reaction.

    ERIC Educational Resources Information Center

    Mitchell, Richard S.

    1996-01-01

    Describes a combination of solutions that can be used in the study of kinetics using the iodine clock reaction. The combination slows down degradation of the prepared solutions and can be used successfully for several weeks. (JRH)

  20. Laboratory Submillimeter Spectroscopy as a Probe of Methanol Photodissociation

    NASA Astrophysics Data System (ADS)

    Laas, Jacob C.; Weaver, Susanna L. Widicus

    2011-06-01

    Radical-radical addition reactions on the ice surfaces of interstellar grains lead to the formation of many complex organic molecules in the interstellar medium. Methanol photodissociation is the dominant source of the three organic radicals CH_3O, CH_2OH, and CH_3. Recent chemical models show that changes to the methanol photodissociation branching ratios directly impact the relative abundances of many complex organics, most notably methyl formate and its structural isomers glycolaldehyde and acetic acid. Neither the condensed-phase nor the gas-phase methanol photodissociation branching ratios required for these models have been quantified in the laboratory. Interpretation of the results from condensed-phase measurements rely upon the use of complicated chemical networks that offer only a limited view of the chemistry and often lead to difficulty in obtaining more than semi-quantitative results. However, gas-phase measurements enable independent, quantitative monitoring of each dissociation channel. We are therefore studying the methanol photodissociation mechanism using submillimeter spectroscopy to directly detect the gas-phase photodissociation products. Here we will present our progress toward the quantification of the gas-phase methanol photodissociation branching ratios, and will discuss these results in the context of interstellar organic chemistry.

  1. Iodine Hall Thruster

    NASA Technical Reports Server (NTRS)

    Szabo, James

    2015-01-01

    Iodine enables dramatic mass and cost savings for lunar and Mars cargo missions, including Earth escape and near-Earth space maneuvers. The demonstrated throttling ability of iodine is important for a singular thruster that might be called upon to propel a spacecraft from Earth to Mars or Venus. The ability to throttle efficiently is even more important for missions beyond Mars. In the Phase I project, Busek Company, Inc., tested an existing Hall thruster, the BHT-8000, on iodine propellant. The thruster was fed by a high-flow iodine feed system and supported by an existing Busek hollow cathode flowing xenon gas. The Phase I propellant feed system was evolved from a previously demonstrated laboratory feed system. Throttling of the thruster between 2 and 11 kW at 200 to 600 V was demonstrated. Testing showed that the efficiency of iodine fueled BHT-8000 is the same as with xenon, with iodine delivering a slightly higher thrust-to-power (T/P) ratio. In Phase II, a complete iodine-fueled system was developed, including the thruster, hollow cathode, and iodine propellant feed system. The nominal power of the Phase II system is 8 kW; however, it can be deeply throttled as well as clustered to much higher power levels. The technology also can be scaled to greater than 100 kW per thruster to support megawatt-class missions. The target thruster efficiency for the full-scale system is 65 percent at high specific impulse (Isp) (approximately 3,000 s) and 60 percent at high thrust (Isp approximately 2,000 s).

  2. Prediction of I2P 1/2-->2P 3/2 transition lineshapes from 3-D, time dependent simulations of chemical oxygen-iodine laser (COIL) flowfields

    NASA Astrophysics Data System (ADS)

    Madden, Timothy J.

    2008-02-01

    The lineshape of the I2P 1/2-->2P 3/2 transition provides a means to ascertain a variety of useful information regarding the performance of the chemical oxygen-iodine laser (COIL). The value at the center of the lineshape, commonly referred to as the 'line center,' is proportional to the laser amplification on the I2P 1/2-->2P 3/2 transition. The infinite integral of the lineshape is proportional to the number density of the ground and excited states of atomic iodine in the gas, indicating the degree of I II dissociation. And the width of the lineshape indicates the amount of broadening of the transition, both due to collisional and Doppler shift effects. As the Doppler shift is proportional to velocity, the width of the transition can be used to estimate the degree of random molecular motion in the gas, expressed in macroscopic terms as temperature. A Doppler shift to the frequencies in the transition can also occur through the straight-line, bulk motion of the gas, and this can be used to examine the velocity field of the gas. However, the flow may experience rotation through the presence of eddies carried within the gas, and these too may contribute to the Doppler shift of the lineshape frequencies. Given that eddies by virtue of their positive and negative velocity components can induce positive and negative Doppler shift, the widening of the lineshape is similar to thermal motion which also includes positive and negative velocities. Thus, when interpreting transition lineshapes, if some account is not made for both thermal and rotational motion, the effect of either physical process will be over-estimated. The work discussed here is oriented toward examining the interplay between the gas dynamics and the lineshape of the I2P 1/2-->2P 3/2 transition, and in turn determine the ramifications for the use of spectroscopic lineshape based diagnostics and interpretation of their data. These efforts in turn are directly linked to efforts improve the understanding of

  3. Photodissociation of TEMPO-modified peptides: new approaches to radical-directed dissociation of biomolecules.

    PubMed

    Marshall, David L; Hansen, Christopher S; Trevitt, Adam J; Oh, Han Bin; Blanksby, Stephen J

    2014-03-14

    Radical-directed dissociation of gas phase ions is emerging as a powerful and complementary alternative to traditional tandem mass spectrometric techniques for biomolecular structural analysis. Previous studies have identified that coupling of 2-[(2,2,6,6-tetramethylpiperidin-1-oxyl)methyl]benzoic acid (TEMPO-Bz) to the N-terminus of a peptide introduces a labile oxygen-carbon bond that can be selectively activated upon collisional activation to produce a radical ion. Here we demonstrate that structurally-defined peptide radical ions can also be generated upon UV laser photodissociation of the same TEMPO-Bz derivatives in a linear ion-trap mass spectrometer. When subjected to further mass spectrometric analyses, the radical ions formed by a single laser pulse undergo identical dissociations as those formed by collisional activation of the same precursor ion, and can thus be used to derive molecular structure. Mapping the initial radical formation process as a function of photon energy by photodissociation action spectroscopy reveals that photoproduct formation is selective but occurs only in modest yield across the wavelength range (300-220 nm), with the photoproduct yield maximised between 235 and 225 nm. Based on the analysis of a set of model compounds, structural modifications to the TEMPO-Bz derivative are suggested to optimise radical photoproduct yield. Future development of such probes offers the advantage of increased sensitivity and selectivity for radical-directed dissociation.

  4. Quantum yield for carbon monoxide production in the 248 nm photodissociation of carbonyl sulfide (OCS)

    SciTech Connect

    Zhao, Z.; Stickel, R.E.; Wine, P.H.

    1995-03-01

    Tunable diode laser absorption spectroscopy has been coupled with excimer laser flash photolysis to measure the quantum yield for CO production from 248 nm photodissociation of carbonyl sulfide (OCS) relative to the well known quantum yield for CO production from 248 nm photolysis of phosgene (Cl{sub 2}CO). The temporal resolution of the experiments was sufficient to distinguish CO formed directly by photodissociation from that formed by subsequent S({sup 3}P{sub j}) reaction with OCS. Under the experimental conditions employed, CO formation via the fast S({sup 1}D{sub 2})+OCS reaction was minimal. Measurements at 297K and total pressures from 4 to 100 Torr N{sub 2}+N{sub 2}O show the CO yield to be greater than 0.95 and most likely unity. This result suggests that the contribution of OCS as a precursor to the lower stratospheric sulfate aerosol layer is somewhat larger than previously thought. 25 refs., 1 fig., 2 tabs.

  5. Photodissociation of the carbon monoxide dication in the (3)Σ(-) manifold: Quantum control simulation towards the C(2+) + O channel.

    PubMed

    Vranckx, S; Loreau, J; Vaeck, N; Meier, C; Desouter-Lecomte, M

    2015-10-28

    The photodissociation and laser assisted dissociation of the carbon monoxide dication X(3)Π CO(2+) into the (3)Σ(-) states are investigated. Ab initio electronic structure calculations of the adiabatic potential energy curves, radial nonadiabatic couplings, and dipole moments for the X (3)Π state are performed for 13 excited (3)Σ(-) states of CO(2+). The photodissociation cross section, calculated by time-dependent methods, shows that the C(+) + O(+) channels dominate the process in the studied energy range. The carbon monoxide dication CO(2+) is an interesting candidate for control because it can be produced in a single, long lived, v = 0 vibrational state due to the instability of all the other excited vibrational states of the ground (3)Π electronic state. In a spectral range of about 25 eV, perpendicular transition dipoles couple this (3)Π state to a manifold of (3)Σ(-) excited states leading to numerous C(+) + O(+) channels and a single C(2+) + O channel. This unique channel is used as target for control calculations using local control theory. We illustrate the efficiency of this method in order to find a tailored electric field driving the photodissociation in a manifold of strongly interacting electronic states. The selected local pulses are then concatenated in a sequence inspired by the "laser distillation" strategy. Finally, the local pulse is compared with optimal control theory.

  6. Photodissociation of the carbon monoxide dication in the 3Σ- manifold: Quantum control simulation towards the C2+ + O channel

    NASA Astrophysics Data System (ADS)

    Vranckx, S.; Loreau, J.; Vaeck, N.; Meier, C.; Desouter-Lecomte, M.

    2015-10-01

    The photodissociation and laser assisted dissociation of the carbon monoxide dication X3Π CO2+ into the 3Σ- states are investigated. Ab initio electronic structure calculations of the adiabatic potential energy curves, radial nonadiabatic couplings, and dipole moments for the X 3Π state are performed for 13 excited 3Σ- states of CO2+. The photodissociation cross section, calculated by time-dependent methods, shows that the C+ + O+ channels dominate the process in the studied energy range. The carbon monoxide dication CO2+ is an interesting candidate for control because it can be produced in a single, long lived, v = 0 vibrational state due to the instability of all the other excited vibrational states of the ground 3Π electronic state. In a spectral range of about 25 eV, perpendicular transition dipoles couple this 3Π state to a manifold of 3Σ- excited states leading to numerous C+ + O+ channels and a single C2+ + O channel. This unique channel is used as target for control calculations using local control theory. We illustrate the efficiency of this method in order to find a tailored electric field driving the photodissociation in a manifold of strongly interacting electronic states. The selected local pulses are then concatenated in a sequence inspired by the "laser distillation" strategy. Finally, the local pulse is compared with optimal control theory.

  7. Iodine deficiency and thyroid disorders.

    PubMed

    Zimmermann, Michael B; Boelaert, Kristien

    2015-04-01

    Iodine deficiency early in life impairs cognition and growth, but iodine status is also a key determinant of thyroid disorders in adults. Severe iodine deficiency causes goitre and hypothyroidism because, despite an increase in thyroid activity to maximise iodine uptake and recycling in this setting, iodine concentrations are still too low to enable production of thyroid hormone. In mild-to-moderate iodine deficiency, increased thyroid activity can compensate for low iodine intake and maintain euthyroidism in most individuals, but at a price: chronic thyroid stimulation results in an increase in the prevalence of toxic nodular goitre and hyperthyroidism in populations. This high prevalence of nodular autonomy usually results in a further increase in the prevalence of hyperthyroidism if iodine intake is subsequently increased by salt iodisation. However, this increase is transient because iodine sufficiency normalises thyroid activity which, in the long term, reduces nodular autonomy. Increased iodine intake in an iodine-deficient population is associated with a small increase in the prevalence of subclinical hypothyroidism and thyroid autoimmunity; whether these increases are also transient is unclear. Variations in population iodine intake do not affect risk for Graves' disease or thyroid cancer, but correction of iodine deficiency might shift thyroid cancer subtypes toward less malignant forms. Thus, optimisation of population iodine intake is an important component of preventive health care to reduce the prevalence of thyroid disorders. Copyright © 2015 Elsevier Ltd. All rights reserved.

  8. Estimation of the quantum efficiency of the photodissociation of HbO2 and HbCO

    NASA Astrophysics Data System (ADS)

    Gisbrecht, A. I.; Mamilov, S. A.; Esman, S. S.; Asimov, M. M.

    2016-01-01

    The paper presents our results on the study of the efficiency of inter-fractional changes in hemoglobin molecules depending on the laser radiation parameters. The evaluation of the quantum efficiency of light interaction in vivo with oxyhemoglobin (HbO2) and carboxyhemoglobin (HbCO) in the blood at wavelengths for 525 and 605 nm is presented. The photodissociation yield of 11% for HbO2 and 79% for HbCO are measured at the wavelength of 525 nm and 10 % for HbO2 and 76 % for HbCO at a wavelength of 605 nm. Thus, the quantum yield of photodissociation of the HbCO is considerably higher, which ensures high efficiency of photodecomposition of the HbCO in the blood. The obtained results can be used in the clinical phototherapy practice for effective treatment of CO poisoning.

  9. Ion Imaging Studies of CH_2I_2 Photodissociation at 248 NM

    NASA Astrophysics Data System (ADS)

    Lehman, Julia H.; Li, Hongwei; Lester, Marsha I.

    2013-06-01

    CH_2I_2 plays an important role in atmospheric chemistry as a significant natural source of organohalide compounds. The photodissociation dynamics of CH_2I_2 in the ultraviolet range of 277-305 nm via the two lowest B_1 excited states has been well studied using one-color velocity map ion imaging (VMI) and photofragment translational spectroscopy. In this two-color experimental study, CH_2I_2 is photodissociated by 248 nm via the B_2 or A_1 excited states to give rise to CH_2I and I (^2P_3_/_2) or I^* (^2P_1_/_2). The iodine atoms are then state selectively ionized using a (2+1) resonance-enhanced multiphoton ionization process near 310 nm and detected by VMI. Preliminary results show about 85% of the available energy is being funneled into the internal energy of the CH_2I fragment, consistent with prior infrared emission results of Baughcum and Leone. The anisotropy parameter derived from the image indicates this is a fast dissociation process and reflects the character of the electronic transition. The internal energy distribution of the CH_2I fragment is of particular interest because of its subsequent reaction with O_2 in a near thermo-neutral reaction to produce the smallest Criegee intermediate, CH_2OO. We anticipate that the internal energy contained in CH_2I will likely be carried into CH_2OO. S. L. Baughcum and S. R. Leone, J. Chem. Phys. 72, 6531 (1980).

  10. Iodine Supplementation in the Newborn

    PubMed Central

    Ghirri, Paolo; Lunardi, Sara; Boldrini, Antonio

    2014-01-01

    Iodine deficiency can be defined as the world’s greatest single cause of preventable brain damage. Fetal and neonatal hypothyroidism, caused by iodine deficiency can be prevented prior to conception and then during pregnancy and lactation when an adequate iodine supplementation is ensured. Extremely low birth weight preterm babies risk having a negative iodine balance status in the first weeks of life, exacerbating the hypothyroxinaemia of the prematurity. It is important to ensure that these babies are provided with an adequate iodine intake from the first days of life. Mothers and newborns should avoid environmental iodine excess during pregnancy or lactation. PMID:24448111

  11. Iodine nutrition in pregnancy and lactation.

    PubMed

    Leung, Angela M; Pearce, Elizabeth N; Braverman, Lewis E

    2011-12-01

    Adequate iodine intake is required for the synthesis of thyroid hormones that are important for normal fetal and infant neurodevelopment. In this review, we discuss iodine physiology during pregnancy and lactation, methods to assess iodine sufficiency, the importance of adequate iodine nutrition, studies of iodine supplementation during pregnancy and lactation, the consequences of hypothyroidism during pregnancy, the current status of iodine nutrition in the United States, the global efforts toward achieving universal iodine sufficiency, and substances that may interfere with iodine use.

  12. Iodine deficiency in Europe.

    PubMed

    Delange, F

    1995-01-18

    Iodine is a trace element present in the human body in minute amounts (15-20 mg in adults, i.e. 0.0285 x 10(-3)% of body weight). The only confirmed function of iodine is to constitute an essential substrate for the synthesis of thyroid hormones, tetraiodothyronine, thyroxine or T4 and triiodothyronine, T3 (1). In thyroxine, iodine is 60% by weight. Thyroid hormones, in turn, play a decisive role in the metabolism of all cells of the organism (2) and in the process of early growth and development of most organs, especially of the brain (3). Brain development in humans occurs from fetal life up to the third postnatal year (4). Consequently, a deficit in iodine and/or in thyroid hormones occurring during this critical period of life will result not only in the slowing down of the metabolic activities of all the cells of the organism but also in irreversible alterations in the development of the brain. The clinical consequence will be mental retardation (5). When the physiological requirements of iodine are not met in a given population, a series of functional and developmental abnormalities occur (Table 1), including thyroid function abnormalities and, when iodine deficiency is severe, endemic goiter and cretinism, endemic mental retardation, decreased fertility rate, increased perinatal death, and infant mortality. These complications, which constitute an hindrance to the development of the affected population, are grouped under the general heading of Iodine Deficiency Disorders, IDD (6). Broad geographic areas exist in which the population is affected by IDD.(ABSTRACT TRUNCATED AT 250 WORDS)

  13. Quantum State Resolved Photodissociation Dynamics of the Formyl Radical.

    NASA Astrophysics Data System (ADS)

    Neyer, David William

    The photodissociation dynamics of the formyl (HCO) radical have been investigated both experimentally and theoretically. HCO molecules, produced in a molecular beam by the laser photolysis of acetaldehyde, were excited to metastable levels with quantum state resolution. The rotational and vibrational states of the CO products from the dissociation of these levels were probed by laser-induced fluorescence using a tunable vacuum ultraviolet laser. Measurement of detailed state-to-state dissociation cross sections and theoretical modeling of these dynamics have provided valuable information about the potential energy surface of the ground electronic state (X) of the HCO system. HCO was excited to predissociative levels of the first electronic state (A) characterized by their vibrational and K-rotational quantum numbers, and the rotational and vibrational populations of the CO products were measured. While the K-state excited in the HCO has little effect on the CO products, the vibrational character of the parent causes specific changes in the product state distributions. Addition of bending or C-H stretching quanta to the HCO parent leads to increased rotational excitation in the CO(nu =O) products. Adding C-O stretch to the parent state produces increased vibrational excitation in the CO products, The dynamics of this dissociation process, which involves Renner-Teller coupling between the X and A states, was modeled using classical trajectories calculated on a global X-state potential energy surface. Stimulated emission pumping (SEP) was used to prepare HCO in metastable resonances on the X state of HCO with vibrational and rotational resolution. The energies and linewidths of these resonances were measured, and the rotational and vibrational distributions of the CO products were determined. The linewidths and product state distributions show highly non-statistical behavior which depends on the vibrational character of the HCO resonance. The rotational distributions

  14. Preliminary conceptual design and weight of a one-megawatt space-based laser power station utilizing a solar-pumped iodine lasant

    NASA Technical Reports Server (NTRS)

    De Young, R. J.; Walker, G. H.; Williams, M. D.; Schuster, G. L.; Conway, E. J.

    1987-01-01

    A preliminary conceptual design of a space-based solar-pumped iodide laser emitting 1 MW of laser power for space-to-space power transmission is described. A near-parabolic solar collector focuses sunlight onto the t-C4F9I lasant within a transverse-flow optical cavity. Using waste heat, a thermal system supplies compressor and auxiliary power. The major system components are designed with weight estimates assigned. In particular, it is found that laser efficiency is not a dominant weight factor, the dominant factor being the laser transmission optics. The station mass is 92,000 kg, requiring approximately eight Shuttle flights to LEO, where an orbital transfer vehicle can transport it to the final altitude of 6378 km.

  15. Preliminary conceptual design and weight of a one-megawatt space-based laser power station utilizing a solar-pumped iodine lasant

    NASA Technical Reports Server (NTRS)

    De Young, R. J.; Walker, G. H.; Williams, M. D.; Schuster, G. L.; Conway, E. J.

    1987-01-01

    A preliminary conceptual design of a space-based solar-pumped iodide laser emitting 1 MW of laser power for space-to-space power transmission is described. A near-parabolic solar collector focuses sunlight onto the t-C4F9I lasant within a transverse-flow optical cavity. Using waste heat, a thermal system supplies compressor and auxiliary power. The major system components are designed with weight estimates assigned. In particular, it is found that laser efficiency is not a dominant weight factor, the dominant factor being the laser transmission optics. The station mass is 92,000 kg, requiring approximately eight Shuttle flights to LEO, where an orbital transfer vehicle can transport it to the final altitude of 6378 km.

  16. [Iodinated contrast media and iodine allergy: myth or reality?].

    PubMed

    Meunier, B; Joskin, J; Damas, F; Meunier, P

    2013-09-01

    The term "iodine allergy" is an old phrase that refers to a reaction to iodinated contrast media. After a brief review of definitions, pathophysiological mechanisms and risk factors of this clinical entity, management is urged immediate and delayed according to the most recent recommendations from the literature. We underline that iodine allergy, as such, does not really exist.

  17. The photodissociation dynamics of alkyl radicals

    SciTech Connect

    Giegerich, Jens; Fischer, Ingo

    2015-01-28

    The photodisscociation dynamics of the alkyl radicals i-propyl (CH(CH{sub 3}){sub 2}) and t-butyl (C(CH{sub 3}){sub 3}) are investigated by H-atom photofragment imaging. While i-propyl is excited at 250 nm, the photodynamics of t-butyl are explored over a large energy range using excitation wavelengths between 347 nm and 233 nm. The results are compared to those obtained previously for ethyl, CH{sub 3}CH{sub 2}, and to those reported for t-butyl using 248 nm excitation. The translational energy (E{sub T}) distribution of the H-atom photofragments is bimodal and appears rather similar for all three radicals. The low E{sub T} part of the distribution shows an isotropic photofragment angular distribution, while the high E{sub T} part is associated with a considerable anisotropy. Thus, for t-butyl, two H-atom loss channels of roughly equal importance have been identified in addition to the CH{sub 3}-loss channel reported previously. A mechanism for the photodissociation of alkyl radicals is suggested that is based on interactions between Rydberg- and valence states.

  18. Fast beam studies of free radical photodissociation

    SciTech Connect

    Cyr, Douglas Robert

    1993-11-01

    The photodissociation of free radicals is studied in order to characterize the spectroscopy and dissociation dynamics of the dissociative electronic states in these species. To accomplish this, a novel method of radical production, based on the photodetachment of the corresponding negative ion, has been combined with a highly complementary form of photofragment translational spectroscopy. The optical spectroscopy of transitions to dissociative states is determined by monitoring the total photofragment yield as a function of dissociation photon energy. Branching ratios to various product channels, internal energy distributions of the fragments, bond dissociation energies, and the translational energy-dependent photofragment recoil angular distributions are then determined at selected excitation energies. A detailed picture of the dissociation dynamics can then be formulated, allowing insight concerning the interactions of potential energy surfaces involved in the dissociation. After an introduction to the concepts and techniques mentioned above, the experimental apparatus used in these experiments is described in detail. The basis and methods used in the treatment of data, especially in the dissociation dynamics experiments, are then put forward.

  19. Lasers.

    ERIC Educational Resources Information Center

    Schewe, Phillip F.

    1981-01-01

    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)

  20. Lasers.

    ERIC Educational Resources Information Center

    Schewe, Phillip F.

    1981-01-01

    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)

  1. Photodissociation of Small Molecules and Photoionization of Free Radicals Using the VUV Velocity-Map Imaging Photoion and Photoelectron Method

    NASA Astrophysics Data System (ADS)

    Gao, Hong

    The tunable vacuum ultraviolet (VUV) laser generated through the two-photon resonance-enhanced four-wave mixing scheme is combined with the newly developed time-slice velocity map imaging photoion method to study the photodissociation of small molecules in the VUV region, and with the velocity map imaging photoelectron method to study the photoionization of free radicals. The photodissociation dynamics of NO in the energy region around 13.5 eV has been investigated. Branching ratios of the three lowest dissociation channels of 12C 16O that produce C(3P) + O(3P), C( 1D) + O(3P) and C(3P) + O(1D) are measured for the first time in the VUV region from 102,500 cm-1 to 110,500 cm-1, valuable information of the dissociation dynamics for this prototype system has been deduced. We demonstrated an experiment that has two independently tunable VUV lasers and a time-slice velocity map imaging setup, this provides us a global way to perform systematic state-selected photodissociation of small molecules via state-selected detection of the atomic products in the VUV region. The velocity map imaging photoelectron method was successfully used to obtain the photoelectron spectrum of the propargyl radical (C3H3) via a single VUV photoionization process. The propargyl radical is generated by the 193 nm laser photodissociation of the precursor C3H3Cl. This is the first time that the velocity map imaging photoelectron method is used to get the photoelectron spectra of free radicals, indicating that it is a powerful technique for studying the photoionization of free radicals which are always hard to be produced with high enough number densities for spectroscopic studies. This dissertation is mainly based on the following peer-reviewed journal articles: 1. Hong Gao, Yang Pan, Lei Yang, Jingang Zhou, C. Y. Ng and William M. Jackson. "Time-slice velocity-map ion imaging studies of the Photodissociation of NO in the vacuum ultraviolet region", the Journal of Chemical Physics, 136, 134302

  2. Volatilization of iodine from vegetation

    NASA Astrophysics Data System (ADS)

    Amiro, B. D.; Johnston, F. L.

    Gaseous emissions of iodine were measured from bean plant foliage. A gamma-emitting iodine tracer, Na 125I, was taken up by the plants from a hydroponic growth medium and released to a cuvette atmosphere. The dynamics of the flux were studied using a flow-through gamma detector. The relationship between leaf radioactive tracer activity and growth-medium activity was linear, as was the relationship between the iodine flux and both leaf and growth-medium activity. Iodine flux and leaf conductance to water responded similarly to changes in light levels, suggesting that the stomata may partially control the flux. The flux was inhibited by aeration of the hydroponic growth medium, and we postulate that methylation causes the iodine flux. Iodine emissions from living vegetation probably contribute <0.1 % to the stable iodine concentration in the atmosphere above terrestrial areas. However, this pathway may be a direct route for radioactive iodine transport from contaminated soils to the atmosphere.

  3. [Is iodine deficiency still relevant?].

    PubMed

    Gärtner, R

    2007-02-22

    In Germany, iodine deficiency and its consequences is still a problem, although it is of less importance than it was twenty years ago. In accordance with the WHO definition, Germany still belongs among those countries with mild iodine deficiency and too low an intake of iodine. As a result groups at particular risk, such as pregnant and nursing women, must still receive iodine supplementation, since, in the absence of supplemental iodine,the amount of iodine in the mother's milk continues to be below average throughout Germany. Both in private households and in the food industry, the aim is to increase the use of iodized salt to more than go%. This entails no risk of an iodine overdose. The current average daily uptake of iodine of approximately 120 micrograms is responsible neither for the development or progression of an autoimmune disease nor a functional disorder of the thyroid gland.

  4. Iodine deficiency disorders in Europe.

    PubMed Central

    Delange, F.; Bürgi, H.

    1989-01-01

    Recent data on iodine excretion in the urine of adults, adolescents and newborns and on the iodine content of breast milk indicate a high prevalence of iodine deficiency (moderate in many cases and severe in a few) in many European countries. These cases may manifest as subclinical hypothyroidism in neonates and as goitre in adolescents and adults. Lack of iodine causes not only goitre, but also mental deficiency, hearing loss and other neurological impairments, and short stature due to thyroid insufficiency during fetal development and childhood. Although iodinated salt is available theoretically in most countries where it is needed, its quality and share of the market are often unsatisfactory. In many countries where only household salt is iodinated the iodine content has been set too low owing to an overestimation of household salt consumption. Governments are therefore urged to pass legislation and provide means for efficient iodination of salt wherever this is necessary. PMID:2670299

  5. Aqueous chemistry of iodine

    SciTech Connect

    Toth, L.M.; Pannell, K.D.; Kirkland, O.L.

    1984-01-01

    The chemistry of iodine has been examined in aqueous solutions of pH 6 to 10 containing 2500 ppM boron as H/sub 3/BO/sub 3/ at temperatures up to 150/sup 0/C using absorption spectrophotometry to identify and monitor the iodine species present. Kinetic rate constants for the disproportionation of the HOI intermediate, 3HOI= IO/sub 3//sup -/ + 2I/sup -/ + 3H/sup +/, have been measured as a function of pH even though no direct spectral evidence for HOI itself has been observed. An HOI partition coefficient >10/sup 4/ has been estimated; results of ionic strength tests are consistent with HOI being present as an uncharged triatomic species in solution. Redox and radiation effects on the aqueous iodine chemistry have also been described. 11 refs., 2 figs., 3 tabs.

  6. Effect of dietary iodine on production of iodine enriched eggs

    PubMed Central

    Sumaiya, Shaikh; Nayak, Sunil; Baghel, R. P. S.; Nayak, Anju; Malapure, C. D.; Kumar, Rajesh

    2016-01-01

    Aim: Objective of this study was to investigate the effect of different levels of iodine supplementation on iodine content of eggs in laying hens. Materials and Methods: In the experiment, 135 laying hens (White Leghorn) of 55 weeks age were randomly distributed to 5 dietary treatments; each group contained 27 laying hens distributed in three replicates of 9 birds each. Diet T1 was control basal layer diet without iodine enrichment in which iodine content (I2) was as per NRC recommendation. Basal diets were supplemented with calcium iodate (Ca (IO3)2) at 5, 10, 15 and 20 mg/kg in T2, T3, T4 and T5 groups, respectively. The iodine content in the calcium iodate is 65.21%, therefore, the diets T2, T3, T4 and T5 contained 3.25, 6.50, 9.75 and 13.0 ppm iodine, respectively. The laying hens were fed the respective experimental diets ad libitum during the experimental period of 10-week. The iodine content of egg yolk and albumen was analyzed at the end of 5th and 10th week of the experiment. Economics of feeding for the production of iodine enriched egg was calculated at the end of the experiment. Results: Increasing iodine levels in diet of hens from 0.45 to 13.0 ppm significantly increased egg iodine concentration, the highest concentration of egg iodine was observed in the group fed diet supplemented with 13.0 ppm iodine followed by those fed 9.75, 6.50, 3.25 and 0.45 ppm iodine in diet. There was no significant difference in the iodine levels of unboiled versus boiled eggs. Therefore, the consumers are ensured to receive the optimal levels of iodine from boiled iodine-enriched eggs. Among different diets, minimum and significantly lower feeding cost (Rs. per dozen or per kg eggs) was noticed in hens allotted T3 diet (6.50 ppm I2). However, feeding cost of hens receiving 3.25 and 9.25 ppm I2 was statistically (p<0.05) similar to control group (T1). Further, it was noticed that feeding cost (Rs. per dozen or per kg eggs) was significantly increased due to the inclusion

  7. Laser induced photoluminescence spectroscopy of cometary radicals

    NASA Technical Reports Server (NTRS)

    Jackson, W. M.; Cody, R. J.; Sabety-Dzvonik, M.

    1976-01-01

    Flash photolysis together with laser excitation of the product fragments was used in laboratory studies of cometary radicals. The LIPS method has been applied to the CN radical to determine: (1) Radiative lifetimes of individual rotational levels in the zeroth vibrational level of the B state; (2) energy partitioning during photodissociation of C2N2; and (3) vibrational and rotational excitation during formation of CN radicals in the photodissociation of dicyanoacetylene.

  8. Rovibrational analysis of the XUV photodissociation of HeH{sup +} ions

    SciTech Connect

    Loreau, J.; Lecointre, J.; Urbain, X.; Vaeck, N.

    2011-11-15

    We investigate the dynamics of the photodissociation of the helium hydride ion HeH{sup +} by XUV radiation with the aim to establish a detailed comparison with a recent experimental work carried out at the FLASH free electron laser using both vibrationally hot and cold ions. We determine the corresponding rovibrational distributions using a dissociative charge transfer setup and the same source conditions as in the FLASH experiment. Using a nonadiabatic time-dependent wave-packet method, we calculate the partial photodissociation cross sections for the n=1-3 coupled electronic states of HeH{sup +}. We find good agreement with the experiment for the cross section into the He + H{sup +} dissociative channel. On the other hand, we show that the experimental observation of the importance of the electronic states with n>3 cannot be well explained theoretically, especially for cold (v=0) ions. We find a good agreement with the experiment on the relative contribution of the {Sigma} and {Pi} states to the cross section for the He{sup +} + H channel, but only a qualitative one for the He + H{sup +} channel. We discuss the factors that could explain the remaining discrepancies between theory and experiment.

  9. Intense-Field Multiple-Detachment of F2¯: Competition with Photodissociation.

    PubMed

    Shahi, Abhishek; Albeck, Yishai; Strasser, Daniel

    2017-04-07

    The competition of intense-field multiple-detachment with efficient photodissociation of F2¯ is studied as a function of laser peak intensity. The main product channels are disentangled and characterized by 3D coincidence fragment imaging. The presented kinetic energy release spectra, angular distributions as well as two color pump-probe measurements allow identification of competing sequential and non-sequential mechanisms. Dissociative detachment, producing two neutral atoms (F + F) is found to be dominated by a sequential mechanism of photodissociation (F¯ + F) followed by detachment of the atomic anion fragment. In contrast, dissociative ionization (F + F(+)) shows competing contributions of both a sequential two-step mechanism as well as a non-sequential double-detachment of the molecular anion, which are distinguished by the kinetic energy released in the dissociation. Triple-detachment is found to be non-sequential in nature and results in Coulomb explosion (F(+)+F(+)). Furthermore, the measured kinetic energy release for dissociation on the (2)Σg(+) state provides a direct measurement of the F2¯ dissociation energy, D0 = 1.26±0.03 eV.

  10. Theoretical studies of photodissociation of small molecules of astrophysical importance

    NASA Technical Reports Server (NTRS)

    Saxon, R. P.

    1983-01-01

    The radicals and ions observed in comets result from photodissociation and photoionization of molecules. According to current models, a comet is composed chiefly of a large, solid nucelus of frozen gases (parent molecules) such as H2O, HCN, and NH3. It is believed comets were formed at the same time and in the same region of space as the major planets and that their chemical composition is the same as that of the early solar system. As the comet nears the Sun, the surface heats up, liberating the frozen gases as well as dust particles. Solar radiation photodissociates the parent molecules into fragments that are observed by resonance fluorescence. Both polyatomic molecules, present in the interstellar medium, and cometary radicals were observed. Using laboratory photo-dissociation data and computer models, astronomers are attempting to identify the parent molecules that account for all observed radicals and ions.

  11. Photodissociation dynamics and spectroscopy of free radical combustion intermediates

    SciTech Connect

    Osborn, David Lewis

    1996-12-01

    The photodissociation spectroscopy and dynamics of free radicals is studied by the technique of fast beam photofragment translational spectroscopy. Photodetachment of internally cold, mass-selected negative ions produces a clean source of radicals, which are subsequently dissociated and detected. The photofragment yield as a function of photon energy is obtained, mapping out the dissociative and predissociative electronic states of the radical. In addition, the photodissociation dynamics, product branching ratios, and bond energies are probed at fixed photon energies by measuring the translational energy, P(ET), and angular distribution of the recoiling fragments using a time- and position-sensitive detector. Ab initio calculations are combined with dynamical and statistical models to interpret the observed data. The photodissociation of three prototypical hydrocarbon combustion intermediates forms the core of this work.

  12. Ar sup + sub 3 photodissociation and its mechanisms

    SciTech Connect

    Chen, Z.Y.; Albertoni, C.R.; Hasegawa, M.; Kuhn, R.; Castleman, A.W. Jr. )

    1989-10-01

    The photodissociation spectrum of Ar{sup +}{sub 3} between 520 and 620 nm is reported. A broadband peaking near 520 nm is observed with a cross section of {similar to}1.8{times}10{sup {minus}16} cm{sup 2} at the peak, in agreement with the findings of Levinger {ital et} {ital al}. (J. Chem. Phys. {bold 89}, 71 (1988)). However, in the present work, a shoulder whose prominence is highly temperature dependent is observed between 545 and 555 nm. The new results are discussed in terms of various electronic transitions and pathways to dissociation. The photodissociation mechanisms are studied by translational energy analysis of photofragmentation. Three photodissociation mechanisms that involve two electronic energy surfaces are proposed which account for the experimental findings.

  13. Photoevaporation of Clumps in Photodissociation Regions

    NASA Technical Reports Server (NTRS)

    Gorti, Uma; Hollenbach, David; DeVincenzi, D. (Technical Monitor)

    2002-01-01

    We present the results of an investigation of the effects of Far Ultraviolet (FUV) radiation (6.0eV < hv < 13.6eV) from hot early type OB stars on clumps in star-forming molecular clouds. Clumps in FUV-illuminated regions (or photodissociation regions or PDRs) undergo external heating and photodissociation as they are exposed to the FUV field, resulting in a loss of cold, molecular lump mass as it is converted to warm atomic gas. The heating, if rapid, creates strong photoevaporative mass flows off the clump surfaces, and drives shocks into the clumps, compressing them to high densities. The clumps lose mass on relatively short timescales. The evolution of an individual clump is found to be sensitive to three dimensionless parameters: Nc0, the ratio of the initial column density of the clump to the column N(0) approx. 10(exp 21) cm(exp -2) of a warm FUV-heated surface region; upsilon, the ratio of the sound speed in the heated surface to that in the cold clump material: and t(FUV)t(c), the ratio of the "turn-on time" t(FUV) of the heating flux on a clump to its initial sound crossing-time t(c). The evolution also depends on whether a confining interclump medium exists, or whether the interclump region has negligible pressure, as is the case for turbulence-generated clumps. In this paper, we use spherical 1-D numerical hydrodynamic models as well as approximate analytical models to study the dependence of clump photoevaporation on the physical parameters of the clump, and to derive the dynamical evolution, mass loss rates and photoevaporative timescales of a clump for a variety of astrophysical situations. Turbulent clumps evolve so that their column densities are equal to a critical value determined by the local FUV field, and typically have short photo evaporation timescales, approx. 10(exp 4-5) years for a 1 M(solar mass) clump in a typical star-forming region (Nc0 = 10, upsilon = 10). Clumps with insufficient magnetic pressure support, and in strong FUV fields

  14. Ultraviolet photodissociation dynamics of the phenyl radical

    SciTech Connect

    Song Yu; Lucas, Michael; Alcaraz, Maria; Zhang Jingsong; Brazier, Christopher

    2012-01-28

    Ultraviolet (UV) photodissociation dynamics of jet-cooled phenyl radicals (C{sub 6}H{sub 5} and C{sub 6}D{sub 5}) are studied in the photolysis wavelength region of 215-268 nm using high-n Rydberg atom time-of-flight and resonance enhanced multiphoton ionization techniques. The phenyl radicals are produced from 193-nm photolysis of chlorobenzene and bromobenzene precursors. The H-atom photofragment yield spectra have a broad peak centered around 235 nm and are in good agreement with the UV absorption spectra of phenyl. The H + C{sub 6}H{sub 4} product translational energy distributions, P(E{sub T})'s, peak near {approx}7 kcal/mol, and the fraction of average translational energy in the total excess energy, , is in the range of 0.20-0.35 from 215 to 268 nm. The H-atom product angular distribution is isotropic. The dissociation rates are in the range of 10{sup 7}-10{sup 8} s{sup -1} with internal energy from 30 to 46 kcal/mol above the threshold of the lowest energy channel H +o-C{sub 6}H{sub 4} (ortho-benzyne), comparable with the rates from the Rice-Ramsperger-Kassel-Marcus theory. The results from the fully deuterated phenyl radical are identical. The dissociation mechanism is consistent with production of H +o-C{sub 6}H{sub 4}, as the main channel from unimolecular decomposition of the ground electronic state phenyl radical following internal conversion of the electronically excited state.

  15. C{sub 60} in photodissociation regions

    SciTech Connect

    Castellanos, Pablo; Tielens, Alexander G.G.M.; Berné, Olivier; Sheffer, Yaron; Wolfire, Mark G.

    2014-10-10

    Recent studies have confirmed the presence of buckminsterfullerene (C{sub 60}) in different interstellar and circumstellar environments. However, several aspects regarding C{sub 60} in space are not yet well understood, such as the formation and excitation processes, and the connection between C{sub 60} and other carbonaceous compounds in the interstellar medium, in particular polycyclic aromatic hydrocarbons (PAHs). In this paper, we study several photodissociation regions (PDRs) where C{sub 60} and PAHs are detected and the local physical conditions are reasonably well constrained to provide observational insights into these questions. C{sub 60} is found to emit in PDRs where the dust is cool (T{sub d} = 20-40 K) and even in PDRs with cool stars. These results exclude the possibility for C{sub 60} to be locked in grains at thermal equilibrium in these environments. We observe that PAH and C{sub 60} emission are spatially uncorrelated and that C{sub 60} is present in PDRs where the physical conditions (in terms of radiation field and hydrogen density) allow for full dehydrogenation of PAHs, with the exception of Ced 201. We also find trends indicative of an increase in C{sub 60} abundance within individual PDRs, but these trends are not universal. These results support models where the dehydrogenation of carbonaceous species is the first step toward C{sub 60} formation. However, this is not the only parameter involved and C{sub 60} formation is likely affected by shocks and PDR age.

  16. Airborne Laser (ABL): Issues for Congress

    DTIC Science & Technology

    2007-07-09

    bulbous turret on the front of the aircraft, but the COIL (Chemical Oxygen Iodine laser) is located in the aft section of the aircraft. System Overview...Chemical Oxygen Iodine Laser). COIL generates its energy through an onboard chemical reaction of oxygen and iodine molecules. Because this laser...The Air Force, and other Services, frequently complain about the onerous and disproportionate O&S (Operations and Support) costs of “high demand, low

  17. Femtosecond photodissociation of molecules facilitated by noise

    SciTech Connect

    Singh, Kamal P.; Kenfack, Anatole; Rost, Jan M.

    2008-02-15

    We investigate the dynamics of diatomic molecules subjected to both a femtosecond midinfrared laser pulse and Gaussian white noise. The stochastic Schroedinger equation with a Morse potential is used to describe the molecular vibrations under noise and the laser pulse. For weak laser intensity, well below the dissociation threshold, it is shown that one can find an optimum amount of noise that leads to a dramatic enhancement of the dissociation probability. The enhancement landscape, which is shown as a function of both the noise and the laser strength, exhibits a global maximum. A frequency-resolved gain profile is recorded with a pump-probe setup which is experimentally realizable. With this profile we identify the linear and nonlinear multiphoton processes created by the interplay between laser and noise and assess their relative contribution to the dissociation enhancement.

  18. Photodissociation near a rough metal surface: Effect of reaction fields

    NASA Astrophysics Data System (ADS)

    Das, Purna C.; Puri, Ashok; George, Thomas F.

    1990-12-01

    The modification of the photochemical dissociation rate of molecules in the presence of a rough metal surface is explored. Classical electromagnetic calculations are presented for the photodissociation rate of a point dipole near a rough surface modeled as a hemispheroidal bump on a semi-infinite flat plane. A correction is introduced by accounting for the reaction fields due to the dipole-substrate system radiating photons and coupling to delocalized surface plasmons. The effects of the shape and size of the bump, and the separation of the molecule from the bump on the rate of photodissociation of the molecule, are studied numerically.

  19. Photodissociation of methyl chloride and methyl bromide in the atmosphere

    NASA Technical Reports Server (NTRS)

    Robbins, D. E.

    1976-01-01

    Methyl chloride (CH3Cl) and methyl bromide (CH3Br) have been suggested to be significant sources of the stratospheric halogens. The breakup of these compounds in the stratosphere by photodissociation or reaction with OH releases halogen atoms which catalytically destroy ozone. Experimental results are presented for ultraviolet photoabsorption cross sections of CH3Cl and CH3Br. Calculations are presented of loss rates for the methyl halides due to photodissociation and reaction with OH and of mixing ratios of these species in the stratosphere.

  20. Photoabsorption and photodissociation of molecules important in the interstellar medium

    NASA Technical Reports Server (NTRS)

    Lee, L. C.

    1986-01-01

    In the period from May 15, 1985 to May 14, 1986, the photoabsorption and photodissociation cross sections of the interstellar radical of SO and the interstellar molecules of HCl, H2CO, and CH3CN were measured and the results were reported in scientific papers. In the meantime, a windowless apparatus is used to measure the photoabsorption and photodissociation cross sections of CO in the 90-105 nm region. The optical data obtained in this research program are needed for the determination of the formation and destruction rates of molecules and radicals in the interstellar medium. Accomplishments in this research period are summarized below.

  1. Ab initio computations of photodissociation products of CFC alternatives

    SciTech Connect

    Tai, S.; Illinger, K.H.; Kenny, J.E.

    1995-12-31

    Ab initio computations, have already been used to examine the energetics of the photodissociation of stratospheric chlorofluorocarbons. Our awn research has investigated the ab initio computation of vibrational frequencies and infrared intensities of CF{sub 3}CH{sub 2}F, CF{sub 3}CF{sub 2}H, and CF{sub 3}CH{sub 3}; continuing research will attempt to expand these computations to the energetics of the photodissociation of these molecules, since sane of the most common types of chlorofluorocarbon substitutes are hydrofluoroethanes.

  2. Iodine: deficiency and therapeutic considerations.

    PubMed

    Patrick, Lyn

    2008-06-01

    Iodine deficiency is generally recognized as the most commonly preventable cause of mental retardation and the most common cause of endocrinopathy (goiter and primary hypothyroidism). Iodine deficiency becomes particularly critical in pregnancy due to the consequences for neurological damage during fetal development as well as during lactation. The safety of therapeutic doses of iodine above the established safe upper limit of 1 mg is evident in the lack of toxicity in the Japanese population that consumes 25 times the median intake of iodine consumption in the United States. Japan's population suffers no demonstrable increased incidence of autoimmune thyroiditis or hypothyroidism. Studies using 3.0- to 6.0-mg doses to effectively treat fibrocystic breast disease may reveal an important role for iodine in maintaining normal breast tissue architecture and function. Iodine may also have important antioxidant functions in breast tissue and other tissues that concentrate iodine via the sodium iodide symporter.

  3. Adsorption of iodine from COIL waste gas on soaked coal-based activated carbon

    NASA Astrophysics Data System (ADS)

    Zhou, Junbo; Hao, Shan; Gao, Liping

    2014-04-01

    The chemical oxygen-iodine laser (COIL) has wide application prospects in military, industrial and medical treatment fields as a second generation gas chemical laser to follow the first HF/DF chemical laser. However, a COIL releases large amounts of gas, such as helium, oxygen, chlorine and iodine. Chlorides have a serious corrosive effect on the system, especially iodine vapor crystallization, which seriously endangers the normal use of vacuum systems, and radioactive methyl iodide, which is hazardous to operators and pollutes the environment. The use of soaked coal-based activated carbon as an adsorbent for removing methyl iodine is proposed, while it is proposed that coal-based activated carbon is an effective adsorbent for removing stable iodine. The research conducted in this work shows that iodine residues are less than 0.5 μg ml-1 after the adsorption treatment and the decontamination factor of the coal-based activated carbon for removing stable iodine is more than 1000. Using this method can achieve the purpose of removing harmful iodine, satisfy the requirements for engineering applications, and also be applied to other nuclear power plant flue gas treatments.

  4. The stability of allyl radicals following the photodissociation of allyl iodide at 193 nm.

    SciTech Connect

    Fan, H.; Pratt, S. T.; Chemistry

    2006-01-01

    The photodissociation of allyl iodide (C{sub 3}H{sub 5}I) at 193 nm was investigated by using a combination of vacuum-ultraviolet photoionization of the allyl radical, resonant multiphoton ionization of the iodine atoms, and velocity map imaging. The data provide insight into the primary C-I bond fission process and into the dissociative ionization of the allyl radical to produce C{sub 3}H{sup 3+}. The experimental results are consistent with the earlier results of Szpunar et al. [J. Chem. Phys. 119, 5078 (2003)], in that some allyl radicals with internal energies higher than the secondary dissociation barrier are found to be stable. This stability results from the partitioning of available energy between the rotational and vibrational degrees of freedom of the radical, the effects of a centrifugal barrier along the reaction coordinate, and the effects of the kinetic shift in the secondary dissociation of the allyl radical. The present results suggest that the primary dissociation of allyl iodide to allyl radicals plus I*({sup 2}P{sub 1/2}) is more important than previously suspected.

  5. Epidemiology of iodine deficiency: Salt iodisation and iodine status.

    PubMed

    Andersson, Maria; de Benoist, Bruno; Rogers, Lisa

    2010-02-01

    Universal salt iodisation (USI) and iodine supplementation are highly effective strategies for preventing and controlling iodine deficiency. USI is now implemented in nearly all countries worldwide, and two-thirds of the world's population is covered by iodised salt. The number of countries with iodine deficiency as a national public health problem has decreased from 110 in 1993 to 47 in 2007. Still one-third of households lack access to adequately iodised salt. Iodine deficiency remains a major threat to the health and development of populations around the world, particularly in children and pregnant women in low-income countries. Data on iodine status are available from 130 countries and approximately one-third of the global population is estimated to have a low iodine intake based on urinary iodine (UI) concentrations. Insufficient control of iodine fortification levels has led to excessive iodine intakes in 34 countries. The challenges ahead lie in ensuring higher coverage of adequately iodised salt, strengthening regular monitoring of salt iodisation and iodine status in the population, together with targeted interventions for vulnerable population groups. Copyright 2009 Elsevier Ltd. All rights reserved.

  6. Iodine supplementation improves cognition in mildly iodine-deficient children.

    PubMed

    Gordon, Rosie C; Rose, Meredith C; Skeaff, Sheila A; Gray, Andrew R; Morgan, Kirstie M D; Ruffman, Ted

    2009-11-01

    The effects of severe iodine deficiency during critical periods of brain development are well documented. There is little known about the consequences of milder forms of iodine deficiency on neurodevelopment. The objective was to determine whether supplementing mildly iodine-deficient children with iodine improves cognition. A randomized, placebo-controlled, double-blind trial was conducted in 184 children aged 10-13 y in Dunedin, New Zealand. Children were randomly assigned to receive a daily tablet containing either 150 microg I or placebo for 28 wk. Biochemical, anthropometric, and dietary data were collected from each child at baseline and after 28 wk. Cognitive performance was assessed through 4 subtests from the Wechsler Intelligence Scale for Children. At baseline, children were mildly iodine deficient [median urinary iodine concentration (UIC): 63 microg/L; thyroglobulin concentration: 16.4 microg/L]. After 28 wk, iodine status improved in the supplemented group (UIC: 145 microg/L; thyroglobulin: 8.5 microg/L), whereas the placebo group remained iodine deficient (UIC: 81 microg/L; thyroglobulin: 11.6 microg/L). Iodine supplementation significantly improved scores for 2 of the 4 cognitive subtests [picture concepts (P = 0.023) and matrix reasoning (P = 0.040)] but not for letter-number sequencing (P = 0.480) or symbol search (P = 0.608). The overall cognitive score of the iodine-supplemented group was 0.19 SDs higher than that of the placebo group (P = 0.011). Iodine supplementation improved perceptual reasoning in mildly iodine-deficient children and suggests that mild iodine deficiency could prevent children from attaining their full intellectual potential. The trial was registered with the Australia New Zealand Clinical Trials Register as ACTRN12608000222347.

  7. Photodissociation Studies of Polyatomic Free Radicals

    DTIC Science & Technology

    1993-08-01

    Box 23346 UPR Station AMOR R ~ Rio Piedras, PR 00931 9. SPONSORING/ MONITORING AGENCY NAME(S) AND ADDRESSIES) 10. SPONSORING/ MONITORING AGENCY REPORT...Latinoamericano de Quimica , Buefios Aires, Argentina, November 1990. "Probing Chemical Reactions with Lasers." (invited) Brad R. Weiner Department of...de Quimica , Buefios Aires, Argentina, November 1990. "Probing Chemical Reactions with Lasers." (invited) Brad R. Weiner Department of Chemistry

  8. The Photodissociation of Nitromethane at 193 nm.

    DTIC Science & Technology

    1983-02-28

    gas fill; the focus and alignment were kept constant. The dissociation products were detected in the plane of the laser and molecular beams by a...This background is presumably due to scattereo light from the intense laser dissociating or desorbing diffusion pump oil from the wall behind the...When dissociated , other nitroalkanes exhibit the same emission spectrum as CH3NO2, suggesting little transfer of energy from the excited NO2 group to

  9. An iodine hypersonic wind tunnel for the study of nonequilibrium reacting flows

    NASA Technical Reports Server (NTRS)

    Pham-Van-diep, G. C.; Muntz, E. P.; Weaver, D. P.; Dewitt, T. G.; Bradley, M. K.; Erwin, D. A.; Kunc, J. A.

    1992-01-01

    A pilot scale hypersonic wind tunnel operating on pure iodine vapor has been designed and tested. The wind tunnel operates intermittently with a run phase lasting approximately 20 minutes. Successful recirculation of the iodine used during the run phase has been achieved but can be improved. Relevant issues regarding the full scale facility's design and operation, and the use of iodine as a working gas are discussed. Continuous wave laser induced fluorescence was used to monitor number densities within the plume flowfield, while pulsed laser induced fluorescence was used in an initial attempt to measure vibrational energy state population distributions. Preliminary nozzle flow calculations based on finite rate chemistry are presented.

  10. An iodine hypersonic wind tunnel for the study of nonequilibrium reacting flows

    NASA Technical Reports Server (NTRS)

    Pham-Van-diep, G. C.; Muntz, E. P.; Weaver, D. P.; Dewitt, T. G.; Bradley, M. K.; Erwin, D. A.; Kunc, J. A.

    1992-01-01

    A pilot scale hypersonic wind tunnel operating on pure iodine vapor has been designed and tested. The wind tunnel operates intermittently with a run phase lasting approximately 20 minutes. Successful recirculation of the iodine used during the run phase has been achieved but can be improved. Relevant issues regarding the full scale facility's design and operation, and the use of iodine as a working gas are discussed. Continuous wave laser induced fluorescence was used to monitor number densities within the plume flowfield, while pulsed laser induced fluorescence was used in an initial attempt to measure vibrational energy state population distributions. Preliminary nozzle flow calculations based on finite rate chemistry are presented.

  11. NO sub 3 , the study of molecular properties and photodissociation by ab initio method, spectroscopy, and translational spectroscopy

    SciTech Connect

    Kim, B.

    1990-10-01

    This report discusses the following topics: molecular structure of NO{sub 3} radical studied by laser induced fluorescence; photodissociation and fluorescence spectroscopy of NO{sub 3} in molecular beam; vertical electronic spectrum of NO{sub 3}:{sup 2}A{prime}{sub 2}, {sup 2}E{double prime}({sup 2}A{sub 2}{sup 2}B{sub 1}), and {sup 2}E{prime} states; and Ab initio study of the vibrational spectra of NO{sub 3}.

  12. Update on iodine status worldwide.

    PubMed

    Zimmermann, Michael B; Andersson, Maria

    2012-10-01

    Salt iodization has been introduced in many countries to control iodine deficiency. The two most commonly used approaches to assessing iodine nutrition on the population level are estimation of the household penetration of adequately iodized salt (HHIS) and measurement of urinary iodine concentrations (UICs). The aim of this review is to assess global and regional iodine status in 2012 by using each of these indicators. The most recent national data on HHIS were obtained from UNICEF. The most recent data on UICs, primarily national data in school-age children, were obtained from a systematic literature search, the International Council for the Control of Iodine Deficiency Disorders and the WHO Micronutrients Database. The median UIC was used to classify national iodine status and the UIC distribution to estimate the number of individuals with low iodine intakes. Thirty-two countries are iodine deficient based on the national median UIC. Globally, 29.8% of school-age children (246 million) are estimated to have insufficient iodine intake. Out of 128 countries with HHIS data, 37 countries have salt iodization coverage that meets the international goal of at least 90% of households consuming adequately iodized salt and 39 countries have coverage rates of less than 50%. Overall, ≈70% of households worldwide have access to iodized salt. Iodized salt programs need to be strengthened and extended to reach nearly one-third of the global population that still has inadequate iodine intakes.

  13. Photodissociation spectroscopy of the Mg + -CO2 complex and its isotopic analogs

    NASA Astrophysics Data System (ADS)

    Yeh, C. S.; Willey, K. F.; Robbins, D. L.; Pilgrim, J. S.; Duncan, M. A.

    1993-02-01

    Mg+-CO2 ion-molecule cluster complexes are produced by laser vaporization in a pulsed nozzle cluster source. The vibronic spectroscopy in these complexes is studied with mass-selected photodissociation spectroscopy in a reflectron time-of-flight mass spectrometer. Two excited electronic states are observed (2) 2Σ+ and 2Π. The 2Π state has a vibrational progression in the metal-CO2 stretching mode (ωe'=381.8 cm-1). The complexes are linear (Mg+-OCO) and are bound by the charge-quadrupole interaction. The dissociation energy (D0`) is 14.7 kcal/mol. Corresponding spectra are measured for each of the 24, 25, and 26 isotopes of magnesium. These results are compared to theoretical predictions made by Bauschlicher and co-workers.

  14. Coherent phase control of the product branching ratio in the photodissociation of dimethylsulfide

    SciTech Connect

    Nagai, Hidekazu; Ohmura, Hideki; Ito, Fumiyuki; Nakanaga, Taisuke; Tachiya, Masanori

    2006-01-21

    Coherent phase control of the photodissociation reaction of the dimethylsulfide has been achieved by means of quantum-mechanical interference between one- and three-photon transitions. Dimethylsulfide was irradiated by fundamental and frequency-tripled outputs of a visible laser (600.5-602.5 nm), simultaneously to yield CH{sub 3}S{sup +} and CH{sub 3}SCH{sub 2}{sup +} fragment ions. The branching ratio of the two product channels could be modulated with variation of the phase difference between the light fields. This accounted for the difference between the molecular phases of the two product channels. The phase lag was observed to have a maximum value of 8 deg. at 601.5 nm. This is the first result of a selective bond breaking in a polyatomic molecule by the coherent phase control.

  15. SITS Derivatization of Peptides to Enhance 266 nm Ultraviolet Photodissociation (UVPD)

    NASA Astrophysics Data System (ADS)

    Quick, M. Montana; Mehaffey, M. Rachel; Johns, Robert W.; Parker, W. Ryan; Brodbelt, Jennifer S.

    2017-07-01

    N-terminal derivatization of peptides with the chromogenic reagent 4-acetamido-4-isothiocyanatostilbene-2,2-disulfonic acid (SITS) is demonstrated to enhance the efficiency of 266 nm ultraviolet photodissociation (UVPD). Attachment of the chromophore results in a mass shift of 454 Da and provides significant gains in the number and abundances of diagnostic fragment ions upon UVPD. Activation of SITS-tagged peptides with 266 nm UVPD leads to many fragment ions akin to the a/b/y ions commonly produced by CID, along with other sequence ions ( c, x, and z) typically accessed through higher energy pathways. Extreme bias towards C-terminal fragment ions is observed upon activation of SITS-tagged peptides using multiple 266 nm laser pulses. Due to the high reaction efficiency of the isothiocyanate coupling to the N-terminus of peptides, we demonstrate the ability to adapt this strategy to a high-throughput LC-MS/MS workflow with 266 nm UVPD.

  16. SITS Derivatization of Peptides to Enhance 266 nm Ultraviolet Photodissociation (UVPD)

    NASA Astrophysics Data System (ADS)

    Quick, M. Montana; Mehaffey, M. Rachel; Johns, Robert W.; Parker, W. Ryan; Brodbelt, Jennifer S.

    2017-03-01

    N-terminal derivatization of peptides with the chromogenic reagent 4-acetamido-4-isothiocyanatostilbene-2,2-disulfonic acid (SITS) is demonstrated to enhance the efficiency of 266 nm ultraviolet photodissociation (UVPD). Attachment of the chromophore results in a mass shift of 454 Da and provides significant gains in the number and abundances of diagnostic fragment ions upon UVPD. Activation of SITS-tagged peptides with 266 nm UVPD leads to many fragment ions akin to the a/b/y ions commonly produced by CID, along with other sequence ions (c, x, and z) typically accessed through higher energy pathways. Extreme bias towards C-terminal fragment ions is observed upon activation of SITS-tagged peptides using multiple 266 nm laser pulses. Due to the high reaction efficiency of the isothiocyanate coupling to the N-terminus of peptides, we demonstrate the ability to adapt this strategy to a high-throughput LC-MS/MS workflow with 266 nm UVPD.

  17. Oxalate Formation in Titanium-Carbon Dioxide Anionic Clusters Studied by Infrared Photodissociation Spectroscopy

    NASA Astrophysics Data System (ADS)

    Dodson, Leah G.; Thompson, Michael C.; Weber, J. Mathias

    2017-06-01

    Carbon-carbon bond formation during carbon dioxide fixation would enable bulk synthesis of hydrocarbon chains, generally through formation of an oxalate intermediate. In this talk, we demonstrate the formation of [Ti(CO_{2})_{y}]^{-} (y = 4-6) gas phase clusters with an oxalate ligand bearing significant (> 1 e^{-}) negative charge. Gas phase anionic clusters were generated using laser ablation of a titanium metal target in the presence of a CO_{2} expansion, and the infrared photodissociation spectra were measured from 950-2400 cm^{-1}, revealing vibrations characteristic of the oxalate anion. The molecular structure of these clusters was identified by comparing the experimental vibrational spectra with density functional theory calculations.

  18. Photodissociation and spectroscopy of gas phase bimetallic clusters. Annual progress report

    SciTech Connect

    Duncan, M.A.

    1992-05-01

    Focus of the research program is the study of gas phase metal clusters for modeling fundamental interactions on metal surfaces. We characterize the chemical bonding between component atoms in clusters as well as the bonding in adsorption on cluster surfaces. Electronic spectra, vibrational frequencies and bond dissociation energies are measured for both neutral and ionized clusters with laser/mass spectrometry techniques. Small bimetallic cluster cations containing Bi/Cr, Bi/Fe, Sn/Bi, and Pb/Sb were photodissociated at various uv wavelengths. Silver dimer van der Waals complexes were produced with a series of rare gas atoms (Ar, Kr, Xe), and their vibrational frequencies and dissociation energies were obtained. (DLC)

  19. Orbital alignment in photodissociation probed using strong field ionization

    SciTech Connect

    Lin Yunfei; Yan Lu; Lee, Suk Kyoung; Herath, Thushani; Li Wen

    2011-12-21

    The photodissociation of molecules often produces atomic fragments with polarized electronic angular momentum, and the atomic alignment, for example, can provide valuable information on the dynamical pathways of chemical reactions unavailable by other means. In this work, we demonstrate for the first time that orbital polarization in chemical reactions can be measured with great sensitivity using strong field ionization by exploiting its extreme nonlinearity.

  20. Iodine deficiency disorders in the iodine-replete environment.

    PubMed

    Nyenwe, Ebenezer A; Dagogo-Jack, Samuel

    2009-01-01

    Iodine deficiency disorders (IDD) constitute significant public health problems in parts of the world with poor iodine nutrition, but have been eradicated in North America and other regions. We herein report 3 cases of IDD, which occurred in women living in iodine-replete environments. The clinical presentation, biochemical findings, and radiological features of the patients were analyzed and presented in 3 case reports. The radiological features are illustrated in sonographic and scintigraphic images. A literature review and discussion, which highlight the risk factors, pathogenesis, ancillary investigations, and rational treatment of iodine deficiency goiter and hypothyroidism are provided. All 3 patients were young women, aged 24 to 38 years, who had goiter. Two of them presented with goitrous hypothyroidism. Radioactive iodine scintigraphy showed a characteristic finding of diffusely increased uptake (in the absence of clinical and biochemical evidence of hyperthyroidism). This scintigraphic pattern was found to be pathognomonic. Dietary iodine supplementation alone resulted in complete remission of IDD in the subjects, including the 2 patients with hypothyroidism. IDD can occur in iodine-replete environments. A high index of suspicion is needed to recognize these cases. It is pertinent that the correct diagnosis be made to avoid unwarranted life-long thyroxine therapy in patients presenting with goiter and hypothyroidism, which is easily treatable with iodized salt. These cases underscore the need for considering iodine deficiency in the etiologic diagnosis of goiter and hypothyroidism, even in iodine-sufficient regions.

  1. Iodine addition using triiodide solutions

    NASA Technical Reports Server (NTRS)

    Rutz, Jeffrey A.; Muckle, Susan V.; Sauer, Richard L.

    1992-01-01

    The study develops: a triiodide solution for use in preparing ground service equipment (GSE) water for Shuttle support, an iodine dissolution method that is reliable and requires minimal time and effort to prepare, and an iodine dissolution agent with a minimal concentration of sodium salt. Sodium iodide and hydriodic acid were both found to dissolve iodine to attain the desired GSE iodine concentrations of 7.5 +/- 2.5 mg/L and 25 +/- 5 mg/L. The 1.75:1 and 2:1 sodium iodide solutions produced higher iodine recoveries than the 1.2:1 hydriodic acid solution. A two-hour preparation time is required for the three sodium iodide solutions. The 1.2:1 hydriodic acid solution can be prepared in less than 5 min. Two sodium iodide stock solutions (2.5:1 and 2:1) were found to dissolve iodine without undergoing precipitation.

  2. Iodine addition using triiodide solutions

    NASA Technical Reports Server (NTRS)

    Rutz, Jeffrey A.; Muckle, Susan V.; Sauer, Richard L.

    1992-01-01

    The study develops: a triiodide solution for use in preparing ground service equipment (GSE) water for Shuttle support, an iodine dissolution method that is reliable and requires minimal time and effort to prepare, and an iodine dissolution agent with a minimal concentration of sodium salt. Sodium iodide and hydriodic acid were both found to dissolve iodine to attain the desired GSE iodine concentrations of 7.5 +/- 2.5 mg/L and 25 +/- 5 mg/L. The 1.75:1 and 2:1 sodium iodide solutions produced higher iodine recoveries than the 1.2:1 hydriodic acid solution. A two-hour preparation time is required for the three sodium iodide solutions. The 1.2:1 hydriodic acid solution can be prepared in less than 5 min. Two sodium iodide stock solutions (2.5:1 and 2:1) were found to dissolve iodine without undergoing precipitation.

  3. Improving COIL Efficiency By Iodine Pre-Dissociation Via Corona Discharge In The Transonic Section Of The Secondary Flow

    DTIC Science & Technology

    2006-08-01

    chemical laser operating to date. Iodine atoms are pumped by a near resonant energy transfer from oxygen molecules in the excited singlet-delta state, O2...dissociation of molecular iodine to atomic iodine which is subsequently excited via reaction (1). O I2 2(1Δ) is the energy carrier for the COIL...expanding flows, near the critical cross section, for spectroscopy of jet-cooled ions and radicals3. Using this corona excited supersonic expansion ( CESE

  4. Radioactive Iodine (I-131) Therapy for Hyperthyroidism

    MedlinePlus

    ... Physician Resources Professions Site Index A-Z Radioactive Iodine (I-131) Therapy Radioiodine therapy is a nuclear ... thyroid cancer. When a small dose of radioactive iodine I-131 (an isotope of iodine that emits ...

  5. Iodine dynamics in soils

    NASA Astrophysics Data System (ADS)

    Shetaya, W. H.; Young, S. D.; Watts, M. J.; Ander, E. L.; Bailey, E. H.

    2012-01-01

    We investigated changes in iodine (129I) solubility and speciation in nine soils with contrasting properties (pH, Fe/Mn oxides, organic carbon and iodine contents), incubated for nine months at 10 and 20 °C. The rate of 129I sorption was greater in soils with large organic carbon contents (%SOC), low pH and at higher temperatures. Loss of iodide (I-) from solution was extremely rapid, apparently reaching completion over minutes-hours; iodate (IO3-) loss from solution was slower, typically occurring over hours-days. In all soils an apparently instantaneous sorption reaction was followed by a slower sorption process for IO3-. For iodide a faster overall reaction meant that discrimination between the two processes was less clear. Instantaneous sorption of IO3- was greater in soils with high Fe/Mn oxide content, low pH and low SOC content, whereas the rate of time-dependent sorption was greatest in soils with higher SOC contents. Phosphate extraction (0.15 M KH2PO4) of soils, ∼100 h after 129I spike addition, indicated that concentrations of sorbed inorganic iodine (129I) were very low in all soils suggesting that inorganic iodine adsorption onto oxide phases has little impact on the rate of iodine assimilation into humus. Transformation of dissolved inorganic 129IO3- and 129I- to sorbed organic forms was modelled using a range of reaction- and diffusion-based approaches. Irreversible and reversible first order kinetic models, and a spherical diffusion model, adequately described the kinetics of both IO3- and I- loss from the soil solution but required inclusion of a distribution coefficient (kd) to allow for instantaneous adsorption. A spherical diffusion model was also collectively parameterised for all the soils studied by using pH, soil organic carbon concentration and combined Fe + Mn oxide content as determinants of the model parameters (kd and D/r2). The kinetic model parameters were not directly related to a single soil parameter; inclusion of pH, SOC, oxide

  6. Iodine neutron capture therapy

    NASA Astrophysics Data System (ADS)

    Ahmed, Kazi Fariduddin

    A new technique, Iodine Neutron Capture Therapy (INCT) is proposed to treat hyperthyroidism in people. Present thyroid therapies, surgical removal and 131I treatment, result in hypothyroidism and, for 131I, involve protracted treatment times and excessive whole-body radiation doses. The new technique involves using a low energy neutron beam to convert a fraction of the natural iodine stored in the thyroid to radioactive 128I, which has a 24-minute half-life and decays by emitting 2.12-MeV beta particles. The beta particles are absorbed in and damage some thyroid tissue cells and consequently reduce the production and release of thyroid hormones to the blood stream. Treatment times and whole-body radiation doses are thus reduced substantially. This dissertation addresses the first of the several steps needed to obtain medical profession acceptance and regulatory approval to implement this therapy. As with other such programs, initial feasibility is established by performing experiments on suitable small mammals. Laboratory rats were used and their thyroids were exposed to the beta particles coming from small encapsulated amounts of 128I. Masses of 89.0 mg reagent-grade elemental iodine crystals have been activated in the ISU AGN-201 reactor to provide 0.033 mBq of 128I. This activity delivers 0.2 Gy to the thyroid gland of 300-g male rats having fresh thyroid tissue masses of ˜20 mg. Larger iodine masses are used to provide greater doses. The activated iodine is encapsulated to form a thin (0.16 cm 2/mg) patch that is then applied directly to the surgically exposed thyroid of an anesthetized rat. Direct neutron irradiation of a rat's thyroid was not possible due to its small size. Direct in-vivo exposure of the thyroid of the rat to the emitted radiation from 128I is allowed to continue for 2.5 hours (6 half-lives). Pre- and post-exposure blood samples are taken to quantify thyroid hormone levels. The serum T4 concentration is measured by radioimmunoassay at

  7. Picosecond real time study of the bimolecular reaction O(3P)+C2H4 and the unimolecular photodissociation of CH3CHO and H2CO

    NASA Astrophysics Data System (ADS)

    Abou-Zied, Osama K.; McDonald, J. Douglas

    1998-07-01

    The bimolecular reaction of O(3P) with ethylene and the unimolecular photodissociation of acetaldehyde and formaldehyde have been studied using a picosecond pump/probe technique. The bimolecular reaction was initiated in a van der Waals dimer precursor, C2H4ṡNO2, and the evolution of the vinoxy radical product monitored by laser-induced fluorescence. The NO2 constituent of the complex was photodissociated at 266 nm. The triplet oxygen atom then attacks a carbon atom of C2H4 to form a triplet diradical (CH2CH2O) which subsequently dissociates to vinoxy (CH2CHO) and H. The rise time of vinoxy radical production was measured to be 217 (+75-25) ps. RRKM theory was applied and a late high exit barrier was invoked in order to fit the measured rise time. The structure and binding energy of the van der Waals complex have been modeled using Lennard-Jones type potentials and the results were compared with other systems. The unimolecular side of the potential energy surfaces of this reaction has been investigated by photodissociating acetaldehyde at the same pump energy of 266 nm. The resulting photoproducts, acetyl radical (CH3CO) and formyl radical (HCO), have been monitored by resonance enhanced multiphoton ionization (REMPI) combined with a time-of-flight mass spectrometer. The similarity in the measured evolution times of both radicals indicates the same photodissociation pathway of the parent molecule. The photodissociation rate of acetaldehyde is estimated from RRKM theory to be very fast (3×1012s-1). The T1←S1 intersystem crossing (ISC) rate is found to be the rate determining step to photodissociation and increases with energy. The REMPI mechanism for the production of CH3CO+ is proposed to be the same as that of HCO+(2+1). The HCO product from the photodissociation of formaldehyde at 266 nm reveals a faster T1←S1 ISC rate than in acetaldehyde.

  8. Determination of the rapid energy redistribution in a transition state by using molecular rotation as a clock and translational energy release as an energy monitor: The photodissociation of iodobenzene

    NASA Astrophysics Data System (ADS)

    Hwang, Hyun Jin; El-Sayed, Mostafa A.

    1992-01-01

    State-selective photofragment translational spectroscopy is used to determine the spatial and velocity distributions of the ground state iodine atoms produced from the photodissociation of iodobenzene at 304.67 nm. In addition to an alkyl iodide type fast dissociation, a slow dissociation was observed. From the observed velocity dependence of the spatial anisotropy of the latter dissociation and the theoretical dissociation time dependence of the spatial anisotropy obtained from the rotational correlation function, we were able to determine the rate of energy redistribution to the phenyl ring modes during the dissociation process.

  9. Photodissociation of HBr. 1. Electronic structure, photodissociation dynamics, and vector correlation coefficients.

    PubMed

    Smolin, Andrey G; Vasyutinskii, Oleg S; Balint-Kurti, Gabriel G; Brown, Alex

    2006-04-27

    Ab initio potential energy curves, transition dipole moments, and spin-orbit coupling matrix elements are computed for HBr. These are then used, within the framework of time-dependent quantum-mechanical wave-packet calculations, to study the photodissociation dynamics of the molecule. Total and partial integral cross sections, the branching fraction for the formation of excited-state bromine atoms Br(2P(1/2)), and the lowest order anisotropy parameters, beta, for both ground and excited-state bromine are calculated as a function of photolysis energy and compared to experimental and theoretical data determined previously. Higher order anisotropy parameters are computed for the first time for HBr and compared to recent experimental measurements. A new expression for the Re[a1(3) (parallel, perpendicular)] parameter describing coherent parallel and perpendicular production of ground-state bromine in terms of the dynamical functions is given. Although good agreement is obtained between the theoretical predictions and the experimental measurements, the discrepancies are analyzed to establish how improvements might be achieved. Insight is obtained into the nonadiabatic dynamics by comparing the results of diabatic and fully adiabatic calculations.

  10. Helium Tagging Infrared Photodissociation Spectroscopy of Reactive Ions.

    PubMed

    Roithová, Jana; Gray, Andrew; Andris, Erik; Jašík, Juraj; Gerlich, Dieter

    2016-02-16

    The interrogation of reaction intermediates is key for understanding chemical reactions; however their direct observation and study remains a considerable challenge. Mass spectrometry is one of the most sensitive analytical techniques, and its use to study reaction mixtures is now an established practice. However, the information that can be obtained is limited to elemental analysis and possibly to fragmentation behavior, which is often challenging to analyze. In order to extend the available experimental information, different types of spectroscopy in the infrared and visible region have been combined with mass spectrometry. Spectroscopy of mass selected ions usually utilizes the powerful sensitivity of mass spectrometers, and the absorption of photons is not detected as such but rather translated to mass changes. One approach to accomplish such spectroscopy involves loosely binding a tag to an ion that will be removed by absorption of one photon. We have constructed an ion trapping instrument capable of reaching temperatures that are sufficiently low to enable tagging by helium atoms in situ, thus permitting infrared photodissociation spectroscopy (IRPD) to be carried out. While tagging by larger rare gas atoms, such as neon or argon is also possible, these may cause significant structural changes to small and reactive species, making the use of helium highly beneficial. We discuss the "innocence" of helium as a tag in ion spectroscopy using several case studies. It is shown that helium tagging is effectively innocent when used with benzene dications, not interfering with their structure or IRPD spectrum. We have also provided a case study where we can see that despite its minimal size there are systems where He has a huge effect. A strong influence of the He tagging was shown in the IRPD spectra of HCCl(2+) where large spectral shifts were observed. While the presented systems are rather small, they involve the formation of mixtures of isomers. We have therefore

  11. A velocity-map imaging study of methyl non-resonant multiphoton ionization from the photodissociation of CH3I in the A-band.

    PubMed

    Poullain, Sonia Marggi; Chicharro, David V; Rubio-Lago, Luis; García-Vela, Alberto; Bañares, Luis

    2017-04-28

    Chemical reaction dynamics and, particularly, photodissociation in the gas phase are generally studied using pump-probe schemes where a first laser pulse induces the process under study and a second one detects the produced fragments. Providing an efficient detection of ro-vibrationally state-selected photofragments, the resonance enhanced multiphoton ionization (REMPI) technique is, without question, the most popular approach used for the probe step, while non-resonant multiphoton ionization (NRMPI) detection of the products is scarce. The main goal of this work is to test the sensitivity of the NRMPI technique to fragment vibrational distributions arising from molecular photodissociation processes. We revisit the well-known process of methyl iodide photodissociation in the A-band at around 280 nm, using the velocity-map imaging technique in conjunction with NRMPI of the methyl fragment. The detection wavelength, carefully selected to avoid any REMPI transition, was scanned between 325 and 335 nm seeking correlations between the different observables-the product vibrational, translational and angular distributions-and the excitation wavelength of the probe laser pulse. The experimental results have been discussed on the base of quantum dynamics calculations of photofragment vibrational populations carried out on available ab initio potential-energy surfaces using a four-dimensional model.This article is part of the themed issue 'Theoretical and computational studies of non-equilibrium and non-statistical dynamics in the gas phase, in the condensed phase and at interfaces'. © 2017 The Author(s).

  12. Iodine-Catalyzed Polysaccharide Esterification

    USDA-ARS?s Scientific Manuscript database

    A review is provided of the recent reports to use iodine-catalyzed esterification reaction to produce esters from polysaccharides. The process entails reaction of the polysaccharide with an acid anhydride in the presence of a catalytic level of iodine, and in the absence of additional solvents. T...

  13. Hypothyroidism following iodine-131 therapy

    SciTech Connect

    Hays, M.T.

    1982-02-01

    A teaching editorial dealing with the hypothyroidism side effect of Iodine-131 radiotherapy is presented. The author reviews two articles in this issue of the Journal of Nuclear Medicine on the subject, discusses Graves' disease, Iodine 125 radiotherapy, and the patient-physician relationship when dealing with the problem. (JMT)

  14. Imide photodissociation investigated by X-ray absorption spectroscopy.

    PubMed

    Johnson, Phillip S; Cook, Peter L; Liu, Xiaosong; Yang, Wanli; Bai, Yiqun; Abbott, Nicholas L; Himpsel, F J

    2012-06-21

    X-ray absorption spectroscopy is used to investigate the photodissociation of the imides PMDI (pyromellitic diimide) and SSMCC (sulfosuccinimidyl 4-(N-maleimidomethyl) cyclohexane-1-carboxylate). PMDI contains only one type of imide, and its photodissociation can be explained by a simple conversion from imide to a mix of imine and nitrile after desorption of the oxygens from the imide. SSMCC contains two different imides. One reacts like PMDI, the other in a more complex multistep process. Eventually, N(2) is formed in the bulk of the sample at high radiation density. The sequence of reactions is inferred from the π* peaks in total electron yield and fluorescence yield absorption spectra at the N 1s and O 1s edges. First-order rate equations are used to model the evolution of the peak areas versus radiation dose.

  15. Anatomy of the Photodissociation Region in the Orion Bar

    NASA Technical Reports Server (NTRS)

    Tielens, A. G. G. M.; Meixner, M. M.; vanderWerf, P. P.; Bregman, J.; Tauber, J. A.; Stutzki, J.; Rank, D.

    1993-01-01

    Much of the interstellar gas resides in photodissociation regions whose chemistry and energy balance is controlled by the flux of far-ultraviolet radiation upon them. These photons can ionize and dissociate molecules and heat the gas through the photoelectric effect working on dust grains. These regions have been extensively modeled theoretically, but detailed observational studies are few. Mapping of the prominent Orion Bar photo-dissociation region at wavelengths corresponding to the carbon-hydrogen stretching mode of polycyclic aromatic hydrocarbons, the 1-0 S(l) line of molecular hydrogen, and the J = 1-0 rotational line of carbon monoxide allows the penetration of the far-ultraviolet radiation into the cloud to be traced. The results strongly support the theoretical models and show conclusively that the incident far-ultraviolet radiation field, not shocks as has sometimes been proposed, is responsible for the emission in the Orion Bar.

  16. Photodissociation spectroscopy and dynamics of free radicals, clusters, and ions

    SciTech Connect

    Choi, Hyeon

    1999-12-01

    The photodissociation spectroscopy and dynamics of free radicals and ions is studied to characterize the dissociative electronic states in these species. To accomplish this, a special method of radical production, based on the photodetachment of the corresponding negative ion, has been combined with the technique of fast beam photofragment translational spectroscopy. The photofragment yield as a function of photon energy is obtained, mapping out the dissociative and predissociative electronic states. Branching ratios to various product channels, the translational energy distributions of the fragments, and bond dissociation energies are then determined at selected photon energies. The detailed picture of photodissociation dynamics is provided with the aid of ab initio calculations and a statistical model to interpret the observed data. Important reaction intermediates in combustion reactions have been studied: CCO, C2H5O, and linear Cn (n = 4--6).

  17. Investigation of VUV Photodissociation Propensities Using Peptide Libraries

    PubMed Central

    Liu, Xiaohui; Li, Yong Fuji; Bohrer, Brian C.; Arnold, Randy J.; Radivojac, Predrag; Tang, Haixu; Reilly, James P.

    2011-01-01

    PSD does not usually generate a complete series of y-type ions, particularly at high mass, and this is a limitation for de novo sequencing algorithms. It is demonstrated that b2 and b3 ions can be used to help assign high mass xN-2 and xN-3 fragments that are found in vacuum ultraviolet (VUV) photofragmentation experiments. In addition, vN-type ion fragments with side chain loss from the N-terminal residue often enable confirmation of N-terminal amino acids. Libraries containing several thousand peptides were examined using photodissociation in a MALDI-TOF/TOF instrument. 1345 photodissociation spectra with a high S/N ratio were interpreted. PMID:22125417

  18. Photodissociable dimer reduction products of 2-thiopyrimidine derivatives.

    PubMed

    Wrona, M; Giziewicz, J; Shugar, D

    1975-12-01

    Both 4,6-dimethyl-2-thipyrimidine and its 1-methyl derivative undergo polarographic reduction in aqueous medium, via a 1e/1H+ reduction to a free radical which rapidly dimerizes to products isolates and identified as 4,4'-bis-(4,6-dimethyl-3,4-dihydropyrimidin-2-thione) and the corresponding 1-methyl dimer. The dimers may be oxidized electrolytically to regenerate the parent monomers. Both dimers also undergo photodissociation to quantitatively regenerate the parent monomers, in high quantum yield, 0.23 and 0.35 M/Einstein. The correlation between electrochemical and photochemical reductions of 2-thiopyrimidines are discussed, as well as the significance of the dimer photodissociation reactions in relation to nucleic acid photochemistry.

  19. Anatomy of the Photodissociation Region in the Orion Bar

    NASA Technical Reports Server (NTRS)

    Tielens, A. G. G. M.; Meixner, M. M.; vanderWerf, P. P.; Bregman, J.; Tauber, J. A.; Stutzki, J.; Rank, D.

    1993-01-01

    Much of the interstellar gas resides in photodissociation regions whose chemistry and energy balance is controlled by the flux of far-ultraviolet radiation upon them. These photons can ionize and dissociate molecules and heat the gas through the photoelectric effect working on dust grains. These regions have been extensively modeled theoretically, but detailed observational studies are few. Mapping of the prominent Orion Bar photo-dissociation region at wavelengths corresponding to the carbon-hydrogen stretching mode of polycyclic aromatic hydrocarbons, the 1-0 S(l) line of molecular hydrogen, and the J = 1-0 rotational line of carbon monoxide allows the penetration of the far-ultraviolet radiation into the cloud to be traced. The results strongly support the theoretical models and show conclusively that the incident far-ultraviolet radiation field, not shocks as has sometimes been proposed, is responsible for the emission in the Orion Bar.

  20. Photodissociation of CO2 and quenching of metastables

    NASA Technical Reports Server (NTRS)

    Slanger, T. G.

    1978-01-01

    Investigations in four different areas were carried out to further our understanding of the chemistry of the atmospheres of Mars and Venus. CO2 photodissociation quantum yields were determined in the 1300-1500 A spectral region by measuring both CO and oxygen atoms. The O(1S) quantum yield was determined for CO2 photodissociation in the 1060-1175 A spectral region. The measurement resolves the differences between two earlier experiments, and demonstrates that the O(1S) yield is unity throughout most of the measured region. The pathways for the quenching of O(1S) by N2O, CO2, H2O and NO were investigated and the source of the Venus nightglow, detected by Venera 9 and 10, was investigated. What appears to be a new O2 band system, was detected although the identity of the transition is not yet evident.

  1. Photodissociation yield spectroscopy of vinyl bromide cation generated by mass-analyzed threshold ionization: Vibrational spectroscopy and decay dynamics in the B ˜ state

    NASA Astrophysics Data System (ADS)

    Lee, Mina; Kim, Myung Soo

    2007-04-01

    A new technique [mass-analyzed threshold ionization (MATI)-photodissociation yield spectroscopy] to probe bound excited states of a cation was developed, which measures photodissociation yield of the cation generated by mass-analyzed threshold ionization. A vibrational spectrum of vinyl bromide cation in the B ˜ state was obtained using this technique. Optical resolution in the low vibrational energy range of the spectrum was far better than in conventional MATI spectra. The origin of the B ˜ state was found at 2.2578±0.0003eV above the first ionization onset. Almost complete vibrational assignment was possible for peaks appearing in the spectrum. Analysis of time-of-flight profiles of C2H3+ product ion obtained with different laser polarization angles suggested that photoexcited vinyl bromide cation remained in the B ˜ state for several hundred picoseconds prior to internal conversion to the ground state and dissociation therein.

  2. Photodissociation of Cl2O2 in the spring Antarctic lower stratosphere

    NASA Technical Reports Server (NTRS)

    Eberstein, Igor J.

    1990-01-01

    The likely photodissociation pathways of chlorine peroxide are examined. Reasoning by analogy between hydrogen peroxide and chlorine peroxide, it is shown that photodissociation of chlorine peroxide at wavelengths longer than 250 nm is not likely to give chlorine atoms as a primary product. Reasoning by analogy with molecules whose visible spectra are known, it is concluded that chlorine peroxide is also likely to photodissociate in the visible to give ClO radicals as primary products.

  3. Photodissociation of carbon dioxide in the Mars upper atmosphere

    NASA Technical Reports Server (NTRS)

    Barth, C. A.

    1974-01-01

    Calculation of the intensity of two of the emissions produced during the dissociative excitation of carbon dioxide in the upper atmosphere of Mars by solar ultraviolet radiation. The calculation tangential column emission rates of the atomic oxygen 2972-A line and the carbon monoxide Cameron bands produced by the photodissociative mechanism are found to be factors of 3 and 10, respectively, smaller than the emission rates observed by Mariner ultraviolet spectrometers.

  4. Breast Milk Iodine Concentration Is a More Accurate Biomarker of Iodine Status Than Urinary Iodine Concentration in Exclusively Breastfeeding Women.

    PubMed

    Dold, Susanne; Zimmermann, Michael B; Aboussad, Abdelmounaim; Cherkaoui, Mohamed; Jia, Qingzhen; Jukic, Tomislav; Kusic, Zvonko; Quirino, Antonio; Sang, Zhongna; San Luis, Teofilo Ol; Vandea, Elena; Andersson, Maria

    2017-04-01

    Background: Iodine status in populations is usually assessed by the median urinary iodine concentration (UIC). However, iodine is also excreted in breast milk during lactation; thus, breast milk iodine concentration (BMIC) may be a promising biomarker of iodine nutrition in lactating women. Whether the mammary gland can vary fractional uptake of circulating iodine in response to changes in dietary intake is unclear.Objective: We evaluated UIC and BMIC as biomarkers for iodine status in lactating women with a wide range of iodine intakes.Methods: We recruited 866 pairs of lactating mothers and exclusively breastfed infants from 3 iodine-sufficient study sites: Linfen, China (n = 386); Tuguegarao, Philippines (n = 371); and Zagreb, Croatia (n = 109). We also recruited iodine-deficient lactating women from Amizmiz, Morocco (n = 117). We collected urine and breast milk samples and measured UIC and BMIC.Results: In the 3 iodine-sufficient sites, a pooled regression analysis of the estimated iodine excretion revealed higher fractional iodine excretion in breast milk than in urine at borderline low iodine intakes. In contrast, in the iodine-deficient site in Morocco, a constant proportion (∼33%) of total iodine was excreted into breast milk.Conclusions: In iodine-sufficient populations, when iodine intake in lactating women is low, there is increased partitioning of iodine into breast milk. For this reason, maternal UIC alone may not reflect iodine status, and BMIC should also be measured to assess iodine status in lactating women. Our data suggest a BMIC reference range (2.5th and 97.5th percentiles) of 60-465 μg/kg in exclusively breastfeeding women. This trial was registered at clinicaltrials.gov as NCT02196337. © 2017 American Society for Nutrition.

  5. Investigations of Ferric Heme Cyanide Photodissociation in Myoglobin and Horseradish Peroxidase

    PubMed Central

    Zeng, Weiqiao; Sun, Yuhan; Benabbas, Abdelkrim; Champion, Paul M.

    2013-01-01

    The photodissociation of cyanide from ferric myoglobin (MbCN) and horseradish peroxidase (HRPCN) has been definitively observed. This has implications for the interpretation of ultrafast IR (Helbing et al. Biophys. J. 2004, 87, 1881–1891) and optical (Gruia et al. Biophys. J. 2008, 94, 2252–2268) studies that had previously suggested the Fe-CN bond was photostable in MbCN. The photolysis of ferric MbCN takes place with a quantum yield of ~75% and the resonance Raman spectrum of the photoproduct observed in steady-state experiments as a function of laser power and sample spinning rate is identical to that of ferric Mb (metMb). The data are quantitatively analyzed using a simple model where cyanide is photodissociated and, although geminate rebinding with a rate kBA ≈ (3.6 ps)−1 is the dominant process, some CN− exits from the distal heme pocket and is replaced by water. Using independently determined values for the CN− association rate, we find that the CN− escape rate from the ferric myoglobin pocket to the solution at 293 K is kout ≈ 1–2 × 107 s−1. This value is very similar to, but slightly larger than, the histidine gated escape rate of CO from Mb (1.1×107 s−1) under the same conditions. The analysis leads to an escape probability kout/(kout+kBA) ~ 10−4, which is unobservable in most time domain kinetic measurements. However, the photolysis is surprisingly easy to detect in Mb using cw resonance Raman measurements. This is due to the anomalously slow CN− bimolecular association rate (170 M−1s−1), which arises from the need for water to exchange at the ferric heme binding site of Mb. In contrast, ferric HRP does not have a heme bound water molecule and its CN− bimolecular association rate is larger by ~103 making the CN− photolysis more difficult to observe. PMID:23472676

  6. Photodissociation of semiconductor positive cluster ions

    SciTech Connect

    Zhang, Q.; Liu, Y.; Curl, R.F.; Tittel, F.K.; Smalley, R.E.

    1988-02-01

    Laser photofragmentation of Si, Ge, and GaAs positive cluster ions prepared by laser vaporization and supersonic beam expansion has been investigated using tandem time-of-flight mass spectrometry. Si clusters up to size 80, Ge clusters to size 40, and GaAs clusters up to a total of 31 atoms were studied. Si/sup +//sub n/ and Ge/sup +//sub n/ for n = 12--26 give daughter ions of about half their original size. For both Si and Ge, this apparent positive ion fissioning appears to go over with increasing n to neutral loss of seven and ten, but for Si/sup +//sub n/ the range of n values where this is observed is rather small. At low fluences, the larger Ge/sup +//sub n/ clusters up to the maximum size observed (50) sequentially lose Ge/sub 10/ (and in some cases with lower intensity Ge/sub 7/). Larger Si/sup +//sub n/ clusters (n>30) always fragment primarily to produce positive ion clusters in the 6--11 size range with a subsidiary channel of loss of a single Si atom. At high laser fluences, Ge/sup +//sub n/ also fragments to produce primarily positive ion clusters in the 6--11 size range with an intensity pattern essentially identical to Si/sup +//sub n/ at similar fluences. Ga/sub x/As/sup +//sub y/ clusters lose one or more atoms in what is probably a sequential process with positive ion clusters in which the total number of atoms, x+y, is odd being more prominent.

  7. Photodissociation of ultracold diatomic strontium molecules with quantum state control

    NASA Astrophysics Data System (ADS)

    McDonald, M.; McGuyer, B. H.; Apfelbeck, F.; Lee, C.-H.; Majewska, I.; Moszynski, R.; Zelevinsky, T.

    2016-07-01

    Chemical reactions at ultracold temperatures are expected to be dominated by quantum mechanical effects. Although progress towards ultracold chemistry has been made through atomic photoassociation, Feshbach resonances and bimolecular collisions, these approaches have been limited by imperfect quantum state selectivity. In particular, attaining complete control of the ground or excited continuum quantum states has remained a challenge. Here we achieve this control using photodissociation, an approach that encodes a wealth of information in the angular distribution of outgoing fragments. By photodissociating ultracold 88Sr2 molecules with full control of the low-energy continuum, we access the quantum regime of ultracold chemistry, observing resonant and nonresonant barrier tunnelling, matter-wave interference of reaction products and forbidden reaction pathways. Our results illustrate the failure of the traditional quasiclassical model of photodissociation and instead are accurately described by a quantum mechanical model. The experimental ability to produce well-defined quantum continuum states at low energies will enable high-precision studies of long-range molecular potentials for which accurate quantum chemistry models are unavailable, and may serve as a source of entangled states and coherent matter waves for a wide range of experiments in quantum optics.

  8. ROVIBRATIONALLY RESOLVED PHOTODISSOCIATION OF HeH{sup +}

    SciTech Connect

    Miyake, S.; Gay, C. D.; Stancil, P. C. E-mail: stancil@physast.uga.edu

    2011-07-01

    Accurate photodissociation cross sections have been obtained for the A{sup 1}{Sigma}{sup +} <- X{sup 1}{Sigma}{sup +} electronic transition of HeH{sup +} using ab initio potential curves and dipole transition moments. Partial cross sections have been evaluated for all rotational transitions from the vibrational levels v'' = 0-11 and over the entire accessible wavelength range {lambda}{lambda}100-1129. Assuming a Boltzmann distribution of the rovibrational levels of the X{sup 1}{Sigma}{sup +} state, photodissociation cross sections are presented for temperatures between 500 and 12,000 K. A similar set of calculations was performed for the pure rovibrational photodissociation in the X{sup 1}{Sigma}{sup +} electronic ground state, but covering photon wavelengths into the far-infrared. Applications of the cross sections to the destruction of HeH{sup +} in the early universe and in UV-irradiated environments such as primordial halos and protoplanetary disks are briefly discussed.

  9. Photodissociation of ultracold diatomic strontium molecules with quantum state control.

    PubMed

    McDonald, M; McGuyer, B H; Apfelbeck, F; Lee, C-H; Majewska, I; Moszynski, R; Zelevinsky, T

    2016-07-07

    Chemical reactions at ultracold temperatures are expected to be dominated by quantum mechanical effects. Although progress towards ultracold chemistry has been made through atomic photoassociation, Feshbach resonances and bimolecular collisions, these approaches have been limited by imperfect quantum state selectivity. In particular, attaining complete control of the ground or excited continuum quantum states has remained a challenge. Here we achieve this control using photodissociation, an approach that encodes a wealth of information in the angular distribution of outgoing fragments. By photodissociating ultracold (88)Sr2 molecules with full control of the low-energy continuum, we access the quantum regime of ultracold chemistry, observing resonant and nonresonant barrier tunnelling, matter-wave interference of reaction products and forbidden reaction pathways. Our results illustrate the failure of the traditional quasiclassical model of photodissociation and instead are accurately described by a quantum mechanical model. The experimental ability to produce well-defined quantum continuum states at low energies will enable high-precision studies of long-range molecular potentials for which accurate quantum chemistry models are unavailable, and may serve as a source of entangled states and coherent matter waves for a wide range of experiments in quantum optics.

  10. Iodine-123 generator/iodination kit: a preliminary report

    SciTech Connect

    Richards, P; Prach, T; Srivastava, S C; Meinken, G E

    1980-01-01

    Preliminary results are described of a xenon-123 filled device to serve as a combination iodine-123 generator/iodination kit. Xenon-123 is produced in the Brookhaven Linac Isotope Producer (BLIP) by the reaction /sup 127/I(p, 5n)/sup 123/Xe. The device consists of a small glass ampoule containing an internal glass breakseal and a flanged neck on which is crimped a multi-injection type septum. The ampoule contains a hydrogen sulfide atmosphere to assure that the iodine generated from the decay of the xenon is in the form of iodide. Following an adequate period for xenon-123 to decay (this period can be used for shipment), a needle is forced through the septum breaking the seal and residual gases are pumped off. The iodine-123 in the form of iodide can then be rinsed from the ampoule with any desired solvent or reagent added directly to the device to carry out an iodination in an enclosed environment. Preliminary results of both iodine recovery and iodinations have been promising.

  11. Iodine content of infant formulas and iodine intake of premature babies: high risk of iodine deficiency.

    PubMed

    Ares, S; Quero, J; Durán, S; Presas, M J; Herruzo, R; Morreale de Escobar, G

    1994-11-01

    As part of a study of thyroid function in premature babies, the iodine content of their mothers' breast milk, that of 32 formulas from different brands used in Spain, and that of 127 formulas used in other countries was determined. Breast milk contained more iodine--mean (SEM) 10 (1) microgram/dl--than most of the formulas, especially those for premature babies. Iodine intakes were therefore below the recommended daily amount (RDA) for newborns: babies of 27-30 weeks' gestational age took 3.1 (1.1) micrograms/day at 5 days of age and 29.8 (2.7) micrograms by 2 months of age. This problem is not exclusive to Spanish premature babies as the iodine content of many of the formulas on sale in other countries was also inadequate. It is concluded that preterm infants who are formula fed are at high risk of iodine deficiency.

  12. Iodine content of infant formulas and iodine intake of premature babies: high risk of iodine deficiency.

    PubMed Central

    Ares, S; Quero, J; Durán, S; Presas, M J; Herruzo, R; Morreale de Escobar, G

    1994-01-01

    As part of a study of thyroid function in premature babies, the iodine content of their mothers' breast milk, that of 32 formulas from different brands used in Spain, and that of 127 formulas used in other countries was determined. Breast milk contained more iodine--mean (SEM) 10 (1) microgram/dl--than most of the formulas, especially those for premature babies. Iodine intakes were therefore below the recommended daily amount (RDA) for newborns: babies of 27-30 weeks' gestational age took 3.1 (1.1) micrograms/day at 5 days of age and 29.8 (2.7) micrograms by 2 months of age. This problem is not exclusive to Spanish premature babies as the iodine content of many of the formulas on sale in other countries was also inadequate. It is concluded that preterm infants who are formula fed are at high risk of iodine deficiency. PMID:7820714

  13. Iodine deficiency and nutrition in Scandinavia.

    PubMed

    Manousou, Sofia; Dahl, Lisbeth; Heinsbaek Thuesen, Betina; Hulthén, Lena; Nyström Filipsson, Helena

    2017-04-01

    Iodine nutrition is a result of geological conditions, iodine fortification and monitoring strategies within a country together with the dietary habits of the population. This review summarizes the basis for the current iodine situation in the Scandinavian countries in order to identify gaps in knowledge, determine necessary future steps, highlight landmarks in Scandinavian iodine research and consider ongoing studies in Scandinavian countries with high international impact. Historically, iodine deficiency disorders such as goiter were common in Norway and Sweden, but not in Denmark. Different strategies have been used in Scandinavia to improve iodine nutrition. The major source of iodine is iodized salt in Sweden and from milk and dairy products in Norway. In Denmark, drinking water, milk, dairy products and iodized salt used in commercial production of bread are the important sources of iodine. The current iodine status in Scandinavia is not optimal and action is ongoing to increase iodination in Denmark, where there is mild iodine deficiency in the general population. Data from all three countries indicate insufficient iodine nutrition during pregnancy and there is a need for data from children, adolescents and young women. Monitoring a population's iodine status and dietary iodine sources is necessary to secure iodine nutrition in Scandinavia. Ongoing studies in Scandinavia will contribute significantly to the knowledge about the effects of mild to moderate iodine deficiency.

  14. Iodine Tagging Velocimetry in a Mach 10 Wake

    NASA Technical Reports Server (NTRS)

    Balla, Robert Jeffrey

    2013-01-01

    A variation on molecular tagging velocimetry (MTV) [1] designated iodine tagging velocimetry (ITV) is demonstrated. Molecular iodine is tagged by two-photon absorption using an Argon Fluoride (ArF) excimer laser. A single camera measures fluid displacement using atomic iodine emission at 206 nm. Two examples ofMTVfor cold-flowmeasurements areN2OMTV [2] and Femtosecond Laser Electronic Excitation Tagging [3]. These, like most MTV methods, are designed for atmospheric pressure applications. Neither can be implemented at the low pressures (0.1- 1 Torr) in typical hypersonic wakes. Of all the single-laser/singlecamera MTV approaches, only Nitric-Oxide Planar Laser Induced Fluorescence-based MTV [4] has been successfully demonstrated in a Mach 10 wake. Oxygen quenching limits transit times to 500 ns and accuracy to typically 30%. The present note describes the photophysics of the ITV method. Off-body velocimetry along a line is demonstrated in the aerothermodynamically important and experimentally challenging region of a hypersonic low-pressure near-wake in a Mach 10 air wind tunnel. Transit times up to 10 µs are demonstrated with conservative errors of 10%.

  15. Excited state property of hardly photodissociable heme-CO adduct studied by time-dependent density functional theory.

    PubMed

    Ohta, Takehiro; Pal, Biswajit; Kitagawa, Teizo

    2005-11-10

    While most of CO-bound hemes are easily photodissociated with a quantum yield of nearly unity, we occasionally encounter a CO-heme which appears hardly photodissociable under the ordinary measurement conditions of resonance Raman spectra using CW laser excitation and a spinning cell. This study aims to understand such hemes theoretically, that is, the excited-state properties of the five-coordinate heme-CO adduct (5cH) as well as the 6c heme-CO adduct (6cH) with a weak axial ligand. Using a hybrid density functional theory, we scrutinized the properties of the ground and excited spin states of the computational models of a 5cH and a water-ligated 6cH (6cH-H(2)O) and compared these properties with those of a photodissociable imidazole-ligated 6cH (6cH-Im). Jahn-Teller softening for the Fe-C-O bending potential in the a(1)-e excited state was suggested. The excited-state properties of 6cH-Im and 5cH were further studied with time-dependent DFT theory. The reaction products of 6cH-Im and 5cH were assumed to be quintet and triplet states, respectively. According to the time-dependent DFT calculations, the Q excited state of 6cH-Im, which is initially a pure pi-pi state, crosses the Fe-CO dissociative state (2A') without large elongation of the Fe-CO bond. In contrast, the Q state of the 5cH does not cross the Fe-CO dissociative state but results in the formation of the excited spin state with a bent Fe-C-O. Consequently, photoisomerization from linear to bent Fe-C-O in the 5cH is a likely mechanism for apparent nonphotodissociation.

  16. Photodissociation dynamics of ethyl ethynyl ether: A new ketenyl radical precursor

    NASA Astrophysics Data System (ADS)

    Krisch, M. J.; Miller, J. L.; Butler, L. J.; Su, H.; Bersohn, R.; Shu, J.

    2003-07-01

    The work presented here investigates the dynamics of the photodissociation of ethyl ethynyl ether at 193.3 nm with photofragment translational spectroscopy and laser-induced fluorescence. The data from two crossed laser-molecular beam apparatuses, one with vacuum ultraviolet photoionization detection and one with electron bombardment detection, showed that only cleavage of the C-O bond to form a C2HO radical and a C2H5 (ethyl) radical occurs. We observed neither cleavage of the other C-O bond nor molecular elimination to form C2H4+CH2CO (ketene). The C2HO radical is formed in two distinct product channels, with 37% of the radicals formed from a channel with recoil kinetic energies extending from about 10 to 70 kcal/mole and the other 63% formed from a channel with lower average recoil energies ranging from 0 to 40 kcal/mole. The measurements using photoionization detection reveal that the C2HO radical formed in the higher recoil kinetic-energy channel has a larger ionization cross section for photon energies between 10.3 and 11.3 eV than the radical formed in the lower recoil kinetic-energy channel, and that the transition to the ion is more vertical. The radicals formed in the higher recoil kinetic-energy channel could be either X˜(2A″) or Ã(2A') state ketenyl (HCCO) product and the shape of the recoil kinetic-energy distribution fitting this data does not vary with ionization energy between 10.3 and 11.3 eV. The C2HO formed in the channel with the lower kinetic-energy release is likely the spin forbidden ã(4A″) state of the ketenyl radical, reached through intersystem crossing. The B˜ state of ketenyl is energetically inaccessible. We also consider the possibility that the lower kinetic-energy channel forms two other C2HO isomers, the CCOH (hydroxyethynyl) radical or the cyclic oxiryl radical. Signal from laser-induced fluorescence of the HCCO photofragment was detected at the electronic origin and the 510 band. The fluorescence signal peaks after a 20

  17. Spectral properties of molecular iodine in absorption cells filled to specified saturation pressure.

    PubMed

    Hrabina, Jan; Šarbort, Martin; Acef, Ouali; Burck, Frédéric Du; Chiodo, Nicola; Holá, Miroslava; Číp, Ondřej; Lazar, Josef

    2014-11-01

    We present the results of measurement and evaluation of spectral properties of iodine absorption cells filled at certain saturation pressure. A set of cells made of borosilicate glass instead of common fused silica was tested for their spectral properties in greater detail with special care for the long-term development of the absorption media purity. The results were compared with standard fused silica cells and the high quality of iodine was verified. A measurement method based on an approach relying on measurement of linewidth of the hyperfine transitions is proposed as a novel technique for iodine cell absorption media purity evaluation. A potential application in laser metrology of length is also discussed.

  18. Photodissociation dynamics of CBr{sub 4} at 267 nm by means of ion velocity imaging

    SciTech Connect

    Greene, Jamila R.; Francisco, Joseph S.; Xu Dadong; Huang Jianhua; Jackson, William M.

    2006-10-07

    The photodissociation dynamics of CBr{sub 4} at 267 nm has been studied using time of flight (TOF) mass spectrometry and ion velocity imaging techniques. The photochemical products are detected with resonance enhanced multiphoton ionization (REMPI) as well as single-photon vacuum ultraviolet ionization at 118 nm. REMPI at 266.65 and 266.71 nm was used to detect the ground Br({sup 2}P{sub 3/2}) and spin-orbit excited Br({sup 2}P{sub 1/2}) atoms, respectively. The translational energy and angular distributions are consistent with direct dissociation from an excited triplet state and indirect dissociation from high vibrational levels on the singlet ground state surface. Br{sub 2}{sup +} ions are also observed in the TOF spectra with a focused 267 nm laser. The counter fragment, CBr{sub 2}{sup +}, is observed when this photolysis laser is unfocused, and photons at 118 nm are used to ionize the radical products. The translational energy distributions of the CBr{sub 2}{sup +} and Br{sub 2}{sup +} products can be momentum matched, which indicates that molecular Br{sub 2} elimination is one of the primary dissociation channels.

  19. Ultrafast Molecular Photodissociation Dynamics Studied by Femtosecond Photoelectron-Photoion Coincidence Spectroscopy

    NASA Astrophysics Data System (ADS)

    Thaler, Bernhard; Heim, Pascal; Ernst, Wolfgang E.; Koch, Markus

    2017-06-01

    To completely characterize photodissociation mechanisms with time-resolved spectroscopy, it is essential to obtain unequivocal experimental information about the fragmentation dynamics induced by the laser pulse. We apply time-resolved photoelectron-photoion coincidence (PEPICO) detection in combination with different excitation schemes to obtain a mechanistic picture of the fragmentation process. For gas phase acetone molecules excited to high lying Rydberg states we are able to disentangle different ionization channels and investigate the fragmentation behavior of each channel separately. In particular, the high differentiability of PEPICO allows to distinguish channels where fragmentation proceeds after ionization from channels with fragmentation in the neutral. We show that excited Rydberg state population undergoes internal conversion due to coupling to valence states, which takes place within (150 ± 30) fs. The corresponding non-adiabatic, ultrafast relaxation dynamics to lower lying states causes conversion of electronic to vibrational energy and is found to play a crucial role in the fragmentation process (see figure 1). By studying the influence of photon energy, pulse duration, chirp and intensity of the laser pulses, we are able to determine the energy-threshold that is required for fragmentation, as well as corresponding fragmentation ratios. Surprisingly, for excitation with pulses possessing a strong negative chirp we observe significantly reduced fragmentation, indicating different internal conversion pathways and the associated intramolecular vibrational redistribution.

  20. Research needs for assessing iodine intake, iodine status, and the effects of maternal iodine supplementation.

    PubMed

    Ershow, Abby G; Goodman, Gay; Coates, Paul M; Swanson, Christine A

    2016-09-01

    The Office of Dietary Supplements of the NIH convened 3 workshops on iodine nutrition in Rockville, Maryland, in 2014. The purpose of the current article is to summarize and briefly discuss a list of research and resource needs developed with the input of workshop participants. This list is composed of the basic, clinical, translational, and population studies required for characterizing the benefits and risks of iodine supplementation, along with related data, analyses, evaluations, methods development, and supporting activities. Ancillary studies designed to use the participant, biological sample, and data resources of ongoing and completed studies (including those not originally concerned with iodine) may provide an efficient, cost-effective means to address some of these research and resource needs. In the United States, the foremost question is whether neurobehavioral development in the offspring of mildly to moderately iodine-deficient women is improved by maternal iodine supplementation during pregnancy. It is important to identify the benefits and risks of iodine supplementation in all population subgroups so that supplementation can be targeted, if necessary, to avoid increasing the risk of thyroid dysfunction and related adverse health effects in those with high iodine intakes. Ultimately, there will be a need for well-designed trials and other studies to assess the impact of maternal supplementation on neurodevelopmental outcomes in the offspring. However, 2 basic information gaps loom ahead of such a study: the development of robust, valid, and convenient biomarkers of individual iodine status and the identification of infant and toddler neurobehavioral development endpoints that are sensitive to mild maternal iodine deficiency during pregnancy and its reversal by supplementation. © 2016 American Society for Nutrition.

  1. Immobilization of iodine in concrete

    DOEpatents

    Clark, Walter E.; Thompson, Clarence T.

    1977-04-12

    A method for immobilizing fission product radioactive iodine recovered from irradiated nuclear fuel comprises combining material comprising water, Portland cement and about 3-20 wt. % iodine as Ba(IO.sub.3).sub.2 to provide a fluid mixture and allowing the fluid mixture to harden, said Ba(IO.sub.3).sub.2 comprising said radioactive iodine. An article for solid waste disposal comprises concrete prepared by this method. BACKGROUND OF THE INVENTION This invention was made in the course of, or under a contract with the Energy Research and Development Administration. It relates in general to reactor waste solidification and more specifically to the immobilization of fission product radioactive iodine recovered from irradiated nuclear fuel for underground storage.

  2. Thyroidectomy: is Lugol's iodine necessary?

    PubMed Central

    Coyle, P J; Mitchell, J E

    1982-01-01

    In a randomised controlled clinical trial of Lugol's iodine against placebo in 44 patients undergoing thyroidectomy we have failed to show any benefit in terms of reduced bleeding or operative facility after using iodide solution. PMID:7051944

  3. Facilities for radio-iodination.

    PubMed

    Ramsey, N W; Bhattacharyya, A K; Dunn, M J

    1980-02-01

    A fume cabinet with a sloping front, fitted with a chemical absorbing filter and extractor fan, but without exhaust ducting, appears to possess considerable advantages for radio-iodination work compared with standard fume cupboards.

  4. Thyroidectomy: is Lugol's iodine necessary?

    PubMed

    Coyle, P J; Mitchell, J E

    1982-09-01

    In a randomised controlled clinical trial of Lugol's iodine against placebo in 44 patients undergoing thyroidectomy we have failed to show any benefit in terms of reduced bleeding or operative facility after using iodide solution.

  5. Lithium-iodine pacemaker cell

    SciTech Connect

    Schneider, A.A.; Snyder, S.E.; DeVan, T.; Harney, M.J.; Harney, D.E.

    1980-01-01

    The lithium-iodine pacemaker cell is described as supplied by several manufacturers. The features of each design are discussed along with their effect on energy density, self-discharge and shape of the discharge curve. Differences in performance characteristics are related to morphology of the lithium iodine electrolyte and to the form of the cathode. A new, high-drain cell is mentioned which can supply 60 /mu/a/cm/sup 2/. 10 refs.

  6. Elucidating the decomposition mechanism of energetic materials with geminal dinitro groups using 2-bromo-2-nitropropane photodissociation.

    PubMed

    Booth, Ryan S; Lam, Chow-Shing; Brynteson, Matthew D; Wang, Lei; Butler, Laurie J

    2013-10-03

    These experiments photolytically generate two key intermediates in the decomposition mechanisms of energetic materials with nitro substituents, 2-nitropropene, and 2-nitro-2-propyl radicals. These intermediates are produced at high internal energies and access a number of competing unimolecular dissociation channels investigated herein. We use a combination of crossed laser-molecular beam scattering and velocity map imaging to study the photodissociation of 2-bromo-2-nitropropane at 193 nm and the subsequent unimolecular dissociation of the intermediates above. Our results demonstrate that 2-bromo-2-nitropropane has four primary photodissociation pathways: C-Br bond fission yielding the 2-nitro-2-propyl radical, HBr elimination yielding 2-nitropropene, C-N bond fission yielding the 2-bromo-2-propyl radical, and HONO elimination yielding 2-bromopropene. The photofragments are formed with significant internal energy and undergo many secondary dissociation events, including the exothermic dissociation of 2-nitro-2-propyl radicals to NO + acetone. Calculations at the G4//B3LYP/6-311++g(3df,2p) level show that the presence of a radical at a nitroalkyl center changes the mechanism for and substantially lowers the barrier to NO loss. This mechanism involves an intermediate with a three-center ring rather than the intermediate formed during the traditional nitro-nitrite isomerization. The observed dissociation pathways of the 2-nitro-2-propyl radical and 2-nitropropene help elucidate the decomposition mechanism of larger energetic materials with geminal dinitro groups.

  7. The photodissociation dynamics of O2 at 193 nm: an O3PJ angular momentum polarization study.

    PubMed

    Brouard, M; Cireasa, R; Clark, A P; Quadrini, F; Vallance, C

    2006-12-21

    In the following paper we present translational anisotropy and angular momentum polarization data for O((3)P(1)) and O((3)P(2)) products of the photodissociation of molecular oxygen at 193 nm. The data were obtained using polarized laser photodissociation coupled with resonantly enhanced multiphoton ionization and velocity-map ion imaging. Under the jet-cooled conditions employed, absorption is believed to be dominated by excitation into the Herzberg continuum. The experimental data are compared with previous experiments and theoretical calculations at this and other wavelengths. Semi-classical calculations performed by Groenenboom and van Vroonhoven [J. Chem. Phys, 2002, 116, 1965] are used to estimate the alignment parameters arising from incoherent excitation and dissociation and these are shown to agree qualitatively well with the available experimental data. Following the work of Alexander et al. [J. Chem. Phys, 2003, 118, 10566], orientation and alignment parameters arising from coherent excitation and dissociation are modelled more approximately by estimating phase differences generated subsequent to dissociation via competing adiabatic pathways leading to the same asymptotic products. These calculations lend support to the view that large values of the coherent alignment moments, but small values of the corresponding orientation moments, could arise from coherent excitation of (and subsequent dissociation via) parallel and perpendicular components of the Herzberg I, II and III transitions.

  8. Fluorescence emission of Ca-atom from photodissociated Ca2 in Ar-doped helium droplets. I. Experimental.

    PubMed

    Masson, A; Briant, M; Hernando, A; Halberstadt, N; Mestdagh, J-M; Gaveau, M-A

    2012-11-14

    The Ca(2) → Ca(4s4p(1)P) + Ca(4s(2)(1)S) photodissociation was investigated in a He droplet isolation experiment where the droplets are doped by Ar atoms. Fluorescence spectra associated with the Ca(4s4p(1)P → 4s(2)(1)S) emission were recorded as a function of the average number of Ar atoms per droplet. Three contributions were observed depending on whether the emitting Ca atoms are free, bound to helium atoms or bound to argon atoms. Moreover, the full Ca(4s4p(1)P → 4s(2)(1)S) fluorescence emission was recorded as a function of the wavelength of the photodissociation laser, hence providing the action spectrum of the Ca(2) → Ca(4s4p(1)P) + Ca(4s(2)(1)S) process. The latter spectrum suggests that in He droplets doped by argon, Ca atoms are attracted inside the droplet where they associate as Ca(2). Full analysis of the spectra indicate that the emission of Ca bound to a single Ar atom is redshifted by 94 cm(-1) with respect to the emission of free Ca.

  9. Photodissociation dynamics of C{sub 3}H{sub 5}I in the near-ultraviolet region

    SciTech Connect

    Sumida, Masataka; Hanada, Takuya; Yamasaki, Katsuyoshi; Kohguchi, Hiroshi

    2014-09-14

    The ultraviolet photodissociation dynamics of allyl iodide (C{sub 3}H{sub 5}I) have been studied by ion-imaging at 266 nm and 213 nm. These photolysis wavelengths are located in the two lowest absorption bands in the near-ultraviolet region. The atomic iodine products were detected by [2+1] resonantly enhanced multiphoton ionization spectroscopy. The spectra showed that the branching fraction for the spin-orbit excited ({sup 2}P{sub 1/2}) state was larger than that for the ground ({sup 2}P{sub 3/2}) state at both photolysis wavelengths. The state-resolved scattering images of iodine showed two maxima in the velocity distributions in the {sup 2}P{sub 3/2} state and a single peak in the {sup 2}P{sub 1/2} state. The spin-orbit specificity indicates that the C−I bond cleavage at both absorption bands is governed by the dissociative n{sub I}σ{sup *}{sub C−I} potential energy surfaces. The nascent internal energy distribution of the allyl radical (C{sub 3}H{sub 5}) counter product, which was obtained by the analysis of the state-resolved scattering distributions, showed a marked difference between the photolysis at 266 nm and 213 nm. The generation of the colder C{sub 3}H{sub 5} with the higher translational energy at 266 nm implied the direct photoexcitation to the n{sub I}σ{sup *}{sub C−I} repulsive surfaces, whereas the internally hot C{sub 3}H{sub 5} at 213 nm was ascribed to the local π{sub CC}π{sup *}{sub CC} photoinitiation in the allyl framework followed by predissociation to the n{sub I}σ{sup *}{sub C−I} states.

  10. Iodoperfluorohexane as a Lasant for Iodine Lasers

    DTIC Science & Technology

    1990-07-01

    0 Justification D iStrb ut on I Dr. Iagher M. Tabibi Availability Codes Avail aridlor Dist Special Dr. Demetrius D. Venable STAtMNT "A" per Major J...Whisker Total Army Personnel ConWmand/TAPC-PB-D 200 Stovall Alexandria, VA 22332-0411 TELECON 9/6/90 VG ir. .Lee Dr. Demetrius D. Venable Dean of the...like to express my appreciation to Dr. Bagher M. Tabibi and to Dr. Demetrius D. Venable for the patience and support provided during this graduate

  11. Micro Chemical Oxygen-Iodine Laser (COIL)

    DTIC Science & Technology

    2007-10-01

    required to form a good o-ring seal. Steam generator design A pumping system based on steam ejectors was designed during the course of the previous HEL-JTO...options for the steam generator design . The first is to catalyze the decomposition of hydrogen peroxide through the use of a standard solid

  12. CO product distributions from the visible photodissociation of HCO

    NASA Astrophysics Data System (ADS)

    Neyer, D. W.; Kable, S. H.; Loison, J.-C.; Houston, P. L.; Burak, I.; Goldfield, E. M.

    1992-12-01

    The CO product distributions following photodissociation of selected quantum levels of the A(tilde) state of HCO are investigated. The effects of differential initial vibrational states on the CO products are presented. Pure bending levels with six to 16 quanta have been investigated in addition to levels involving combinations of either the CH stretch and the HCO bend or the CO stretch and the HCO bend. Classical trajectories using the BBH potential energy surface are attempted in order to understand the underlying dynamics of this dissociation.

  13. Photodissociation and photoionisation of atoms and molecules of astrophysical interest

    NASA Astrophysics Data System (ADS)

    Heays, A. N.; Bosman, A. D.; van Dishoeck, E. F.

    2017-06-01

    A new collection of photodissociation and photoionisation cross sections for 102 atoms and molecules of astrochemical interest has been assembled, along with a brief review of the basic physical processes involved. These have been used to calculate dissociation and ionisation rates, with uncertainties, in a standard ultraviolet interstellar radiation field (ISRF) and for other wavelength-dependent radiation fields, including cool stellar and solar radiation, Lyman-α dominated radiation, and a cosmic-ray induced ultraviolet flux. The new ISRF rates generally agree within 30% with our previous compilations, with a few notable exceptions. Comparison with other databases such as PHIDRATES is made. The reduction of rates in shielded regions was calculated as a function of dust, molecular and atomic hydrogen, atomic C, and self-shielding column densities. The relative importance of these shielding types depends on the atom or molecule in question and the assumed dust optical properties. All of the new data are publicly available from the Leiden photodissociation and ionisation database. Sensitivity of the calculated rates to variation of temperature and isotope, and uncertainties in measured or calculated cross sections, are tested and discussed. Tests were conducted on the new rates with an interstellar-cloud chemical model, and find general agreement (within a factor of two) in abundances obtained with the previous iteration of the Leiden database assuming an ISRF, and order-of-magnitude variations assuming various kinds of stellar radiation. The newly parameterised dust-shielding factors makes a factor-of-two difference to many atomic and molecular abundances relative to parameters currently in the UDfA and KIDA astrochemical reaction databases. The newly-calculated cosmic-ray induced photodissociation and ionisation rates differ from current standard values up to a factor of 5. Under high temperature and cosmic-ray-flux conditions the new rates alter the equilibrium

  14. Photodissociation dynamics of dimethylnitrosamine studied by resonance Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Lenderink, Egbert; Wiersma, Douwe A.

    1994-02-01

    The initial molecular dynamics in the dissociative S 1 (n, π *) state of dimethylnitrosamine (DMN) is investigated using resonance Raman spectroscopy. We find that photochemical N-N bond cleavage in DMN proceeds via a bent conformation around the amine N atom, which supports the outcome of ab initio and classical trajectory calculations [M. Persico, I. Cacelli and A. Ferretti, J. Chem. Phys. 94 (1991) 5508]. Additional information is obtained about the other motions that accompany the photodissociation: a stretch of the N-N bond and a change of the NNO angle.

  15. Photoabsorption and photodissociation of molecules important in the interstellar medium

    NASA Technical Reports Server (NTRS)

    Lee, Long C.; Suto, Masako

    1991-01-01

    The photoabsorption, photodissociation, and fluorescence cross sections of interstellar molecules are measured at 90 to 250 nm. These quantitative optical data are needed for the understanding of the formation and destruction processes of molecules under the intense interstellar UV radiation field. Research covering the following topics is presented: (1) fluorescences from photoexcitation of CH4, CH3OH, and CH3SH; (2) NO gamma emission from photoexcitation of NO; (3) photoexcitation cross sections of aromatic molecules; (4) IR emission from UV excitation of HONO2; (5) IR emission from UV excitation of benzene and methyl-derivitives; and (6) IR emission from UV excitation of polycyclic aromatic hydrocarbon molecules.

  16. Iodine deficiency in Danish pregnant women.

    PubMed

    Andersen, Stine Linding; Sørensen, Louise Kolding; Krejbjerg, Anne; Møller, Margrethe; Laurberg, Peter

    2013-07-01

    Maternal iodine requirements increase during pregnancy. Studies performed before the introduction of mandatory iodine fortification of salt in Denmark in 2000 showed that pregnant women with no intake of iodine-containing supplements were moderately iodine-deficient and showed signs of thyroidal stress. We investigated the intake of iodine-containing supplements and urinary iodine excretion in Danish pregnant women after the introduction of iodine fortification of salt. We conducted a cross-sectional study between June and August 2012 in an area of Denmark where iodine deficiency had previously been moderate. Pregnant women coming to Aalborg University Hospital for obstetric ultrasound were recruited consecutively. Participants filled in a questionnaire and handed in a spot urine sample for measurement of iodine and creatinine. Among the pregnant women included (n = 245) 84.1% reported an intake of iodine-containing supplements, and compared with those not taking iodine supplements the median urinary iodine concentration was significantly higher in this group: 109 g/l (25th-75th percentile: 66-191 µg/l). On the other hand, the median urinary iodine concentration was considerably below the recommended level, even for the non-pregnant state in pregnant women with no iodine supplement intake: 68 µg/l (35-93 µg/l), p < 0.001. The majority of pregnant women took iodine-containing supplements, but the subgroup of non-users was still iodine-deficient after the introduction of iodine fortification of salt. Iodine supplement intake during pregnancy in Denmark should be officially recommended. The study was supported by a grant from Musikforlæggerne Agnes og Knut Mørks Fond and from Speciallæge Heinrich Kopps Legat. not relevant.

  17. Development of an online method for quantification of maritime molecular iodine and other gaseous iodine containing inorganic compounds

    NASA Astrophysics Data System (ADS)

    Götz, Sven; Hoffmann, Thorsten

    2014-05-01

    The atmospheric chemistry of iodine is important in multiple ways. The focus lies on the ability to influence the oxidizing capacity of the atmosphere, i.e. by destruction of ozone, and the formation of iodine oxide particles (IOP), i.e. the influence on condensation nuclei (CCN). Using a variation of techniques, like differential optical absorption spectroscopy (DOAS), laser-induced fluorescence (LIF), inductively coupled plasma mass spectrometry (ICP-MS) and atmospheric pressure chemical ionization with tandem mass spectrometry (APCI-MS/MS), the reactive iodine species of atomic iodine (I), molecular iodine (I2), iodine monoxide (IO) and iodine dioxide (OIO) have all been detected in the atmosphere from Antarctica to the equatorial marine boundary layer (MBL). In the past few years there have been active research on IO, especially after revealing significant levels in open ocean measurements, OIO and higher iodine oxides. In addition to atmospheric measurements, significant developments in laboratory kinetics, photochemistry and heterogeneous chemistry of iodine species have been accomplished. [1] Here we introduce an online-method for detecting gaseous molecular iodine and other gaseous iodine-containing inorganic compounds such as HOI, which is a further development of the technique used by Carpenter et al. [2]. The method is based on selective photolytic dissociation of the analytes, followed by oxidization and particle formation of the iodine compounds. The particles are than size-segregated and detected by a scanning mobility particle sizer (SMPS) system. Initial IOP forming is performed in a reaction chamber providing specific wavelengths according to corresponding bond dissociation thresholds. Atmospheric samples can also be pre concentrated by diffusion denuder (with α Cyclodextrin modified and immobilised silica coating) [3-5] and afterwards released by thermodesorption. First attempts of quantification are carried out by external calibration using an

  18. High-Performance Water-Iodinating Cartridge

    NASA Technical Reports Server (NTRS)

    Sauer, Richard; Gibbons, Randall E.; Flanagan, David T.

    1993-01-01

    High-performance cartridge contains bed of crystalline iodine iodinates water to near saturation in single pass. Cartridge includes stainless-steel housing equipped with inlet and outlet for water. Bed of iodine crystals divided into layers by polytetrafluoroethylene baffles. Holes made in baffles and positioned to maximize length of flow path through layers of iodine crystals. Resulting concentration of iodine biocidal; suppresses growth of microbes in stored water or disinfects contaminated equipment. Cartridge resists corrosion and can be stored wet. Reused several times before necessary to refill with fresh iodine crystals.

  19. High-Performance Water-Iodinating Cartridge

    NASA Technical Reports Server (NTRS)

    Sauer, Richard; Gibbons, Randall E.; Flanagan, David T.

    1993-01-01

    High-performance cartridge contains bed of crystalline iodine iodinates water to near saturation in single pass. Cartridge includes stainless-steel housing equipped with inlet and outlet for water. Bed of iodine crystals divided into layers by polytetrafluoroethylene baffles. Holes made in baffles and positioned to maximize length of flow path through layers of iodine crystals. Resulting concentration of iodine biocidal; suppresses growth of microbes in stored water or disinfects contaminated equipment. Cartridge resists corrosion and can be stored wet. Reused several times before necessary to refill with fresh iodine crystals.

  20. PRODUCTION OF RADIOACTIVE IODINE.

    SciTech Connect

    SCHLYER,D.J.

    2001-08-08

    Probably the most widely used cyclotron produced radiohalogen is I-123. It has gradually replaced I-131 as the isotope of choice for diagnostic radiopharmaceuticals containing radioiodine. It gives a much lower radiation dose to the patient and the gamma ray energy of 159 keV is ideally suited for use in a gamma camera. The gamma ray will penetrate tissue very effectively without excessive radiation dose. For this reason, it has in many instances replaced the reactor produced iodine-131 (Lambrecht and Wolf 1973). A great number of radiopharmaceuticals have been labeled using I-123 and the number is increasing. One of the most promising uses of I-123 is in the imaging of monoclonal antibodies to localize and visualize tumors. However, preclinical and clinical experiences with radiolabeled antibodies have not realized the expectations regarding specificity and sensitivity of tumor localization with these agents. It appears that much of the administered activity is not associated with the tumor site and only a small fraction actually accumulates there. Work continues in this area and tumor-associated antigens can be targets for specific antibody reagents.

  1. The changing epidemiology of iodine deficiency.

    PubMed

    Li, Mu; Eastman, Creswell J

    2012-04-03

    Globally, about 2 thousand million people are affected by iodine deficiency. Although endemic goitre is the most visible sign of iodine deficiency, its most devastating consequence is brain damage causing mental retardation in children. The relationship between iodine deficiency and brain damage was not clearly established until the 1980s when the term iodine deficiency disorders (IDDs), which encompass a spectrum of conditions caused by iodine deficiency, was introduced. This paradigm shift in the understanding of the clinical consequences of iodine deficiency led to a change in iodine deficiency assessment. The median urinary iodine excretion level has been recommended as the preferred indicator for monitoring population iodine deficiency status since 2001. The 2007 WHO urinary iodine data in schoolchildren from 130 countries revealed that iodine intake is still insufficient in 47 countries. Furthermore, about one-third of countries lack national estimates of the prevalence of iodine deficiency. The picture that has emerged from available data worldwide over the past two decades is that IDDs are not confined to remote, mountainous areas in developing countries, but are a global public health problem that affects most countries, including developed countries and island nations. The recognition of the universality of iodine deficiency highlights the need to develop and apply new strategies to establish and maintain sustainable IDD elimination and strengthen regular monitoring programmes.

  2. Formaldehyde photodissociation: molecular beam, product appearance rate, and carbon-14 isotopic-enrichment studies

    SciTech Connect

    Ho, P.

    1981-12-01

    Several aspects of the formaldehyde photopredissociation mechanism were studied. The technique of crossed laser and molecular beams was used to study the system under collisionless conditions. Detection of the molecular product CO after excitation of H/sub 2/CO near the S/sub 1/ origin gives strong support to the sequential decay model for fast nonradiative decay of S/sub 1/ states. For H/sub 2/CO excitation at 283.9 nm, formation of the radical product HCO dominates dissociation to molecular products by an order of magnitude. CO appearance rates for H/sub 2/CO excitation at 354.7, 317.0, 298.5 and 283.9 nm were measured by time-resolved absorption of a CO laser, and were the same within approx. 20%. These measurements could be complicated by rotational relaxation; an impulse approximation calculation using the CO translational energy distribution from the molecular beam experiment suggests that CO should be formed in high J states. The evidence for an intermediate in H/sub 2/CO photodissociation may thus be compromised. Simultaneous high resolution spectra of H/sub 2//sup 14/CO and H/sub 2//sup 12/CO between 290 and 345 nm were measured. About 30 lines with spectra selectivities C greater than or equal to 50 were found. Photolysis on one such line at 326.9 nm of a dilute mixture of H/sub 2//sup 14/CO in natural H/sub 2/CO gave one-step enrichment factors of up to 150. Since a factor of 150 in /sup 14/C concentration corresponds to approx. 7.2 half-lives, or 41,000 years, laser enrichment of archaeological samples could greatly improve the range of radiocarbon dating.

  3. Uv Photodissociation Spectroscopy of Temperature Controlled Hydrated Phenol Cluster Cation

    NASA Astrophysics Data System (ADS)

    Kurusu, Itaru; Yagi, Reona; Kasahara, Yasutoshi; Ishikawa, Haruki

    2016-06-01

    Owing to various developments of spectroscopic techniques, microscopic hydration structures of various clusters in the gas phase have been determined so far. The next step for further understanding of the microscopic hydration is to reveal the temperature effect, such as a fluctuation of the hydration structure. Thus, we have been carrying out photodissociation spectroscopy on the hydrated phenol cation clusters, [PhOH(H_2O)_n]^+, trapped in our temperature-variable ion trap. After the last symposium, we succeeded in improving our experimental condition and recorded the UV photodissociation spectra of [PhOH(H_2O)_5]^+ at the trap temperatures of 20, 50, and 100 K. We identified three groups of bands by their temperature dependence in the spectra. Based on the results of the DFT calculations, we estimated the temperature dependence of the relative populations among the isomers. As a results, the isomers were grouped into three groups having different motifs of the hydrogen-bond structures. Comparing the experimental with the theoretical results, we assigned the relation between the band carriers and the hydrogen-bond structure motifs. Details of the discussion will be presented in the paper. H. Ishikawa, T. Nakano, T. Eguchi, T. Shibukawa, K. Fuke, Chem. Phys. Lett. 514, 234 (2011) R. Yagi, Y. Kasahara, H. Ishikawa, WH12, the 70th International Symposium on Molecular Spectroscopy (2015)

  4. Photo-dissociation of dimethylamine by KrBr* excilamp.

    PubMed

    Han, Qiuyi; Ye, Zhaolian; Zhao, Jie; Lister, Graeme; Zhang, Shanduan

    2013-10-01

    A study of dimethylamine photo-dissociation in the gas phase has been conducted using UV radiation delivered from a KrBr(*) excilamp, driven by a sinusoidal electronic control gear with maximum emission at wavelength of 207 nm. The electrical input power and radiant power of the lamp were measured to determine their effects on the degradation. The influence of flow velocity and initial concentration of dimethylamine were also examined. In order to evaluate the photo-dissociation process comprehensively, several parameters were investigated, including removal efficiency, energy yield, carbon balance and CO₂ selectivity. It is shown that the removal efficiency increases with enhanced input power and decreased gas flow rate. A high removal efficiency of 68% is achieved for lamp power 102W and flow velocity 15 m(3) h(-1). The optimum dimethylamine initial concentration is around 3520 mg m(-3), for which the energy yield reaches up to 442 gk Wh(-1) when the input power is 65W. In addition, two chain compounds (1,3-bis-dimethylamino-2-propanol; 3-penten-2-one, 4-amino) and three ring organic matters (1-azetidinecarboxaldehyde, 2,2,4,4-tetramethyl; N-m-tolyl-succinamic acid; p-acetoacetanisidide), were identified by GC-MS as secondary products, in order to demonstrate the pathways of the dimethylamine degradation. Copyright © 2013 Elsevier Ltd. All rights reserved.

  5. Photodissociation of metallo-carbohedrene (met-cars) cluster cations

    SciTech Connect

    Pilgrim, J.S.; Duncan, M.A. )

    1993-05-19

    Castleman and co-workers have recently reported the formation of especially stable metal-carbon clusters designated [open quotes]metallo-carbohedrenes[close quotes], or [open quotes]met-cars[close quotes]. In their work, metal-carbon mixed clusters having the formula M[sub 8]C[sub 12] form preferentially from plasmas containing a carbon precursor and transition metals (e.g., Ti[sub 8]C[sub 12]). We report here the first mass-selected photo-dissociation experiments on met-cars clusters. These experiments reveal the decomposition mechanism of these species and provide new insight into their bonding and stabilities. These photodissociation experiments indicate that there are at least two general mechanisms important in met-cars cluster decomposition, metal atom elimination and M-C[sub 2] elimination. Chromium and iron met-cars clusters are suggested to be less stable overall than titanium and vanadium systems, while the M-C[sub 2] interactions are suggested to be especially strong for zirconium met-cars cluster. 10 refs., 1 fig.

  6. Photodissociation spectroscopy of the dysprosium monochloride molecular ion

    SciTech Connect

    Dunning, Alexander Schowalter, Steven J.; Puri, Prateek; Hudson, Eric R.; Petrov, Alexander; Kotochigova, Svetlana

    2015-09-28

    We have performed a combined experimental and theoretical study of the photodissociation cross section of the molecular ion DyCl{sup +}. The photodissociation cross section for the photon energy range 35 500 cm{sup −1} to 47 500 cm{sup −1} is measured using an integrated ion trap and time-of-flight mass spectrometer; we observe a broad, asymmetric profile that is peaked near 43 000 cm{sup −1}. The theoretical cross section is determined from electronic potentials and transition dipole moments calculated using the relativistic configuration-interaction valence-bond and coupled-cluster methods. The electronic structure of DyCl{sup +} is extremely complex due to the presence of multiple open electronic shells, including the 4f{sup 10} configuration. The molecule has nine attractive potentials with ionically bonded electrons and 99 repulsive potentials dissociating to a ground state Dy{sup +} ion and Cl atom. We explain the lack of symmetry in the cross section as due to multiple contributions from one-electron-dominated transitions between the vibrational ground state and several resolved repulsive excited states.

  7. Photodissociation of HI and DI: Polarization of atomic photofragments

    NASA Astrophysics Data System (ADS)

    Brown, Alex

    2005-02-01

    The complete angular momentum distributions and vector correlation coefficients (orientation and alignment) of ground state I(P3/22) and excited state I(P1/22) atoms resulting from the photodissociation of HI have been computed as a function of photolysis energy. The orientation and alignment parameters aQ(K)(p) that describe the coherent and incoherent contributions to the angular momentum distributions from the multiple electronic states accessed by parallel and perpendicular transitions are determined using a time-dependent wave packet treatment of the dissociation dynamics. The dynamics are based on potential energy curves and transition dipole moments that have been reported previously [R. J. LeRoy, G. T. Kraemer, and S. Manzhos, J. Chem. Phys. 117, 9353 (2002)] and used to successfully model the scalar (total cross section and branching fraction) and lowest order vector (anisotropy parameter β) properties of the photodissociation. Predictions of the aQ(K)(p), parameters for the isotopically substituted species DI are reported and contrasted to the analogous HI results. The resulting polarization for the corresponding H/D partners are also determined and demonstrate that both H and D atoms produced can be highly spin polarized. Comparison of these predictions for HI and DI with experimental measurement will provide the most stringent test of the current model for the electronic structure and the interpretation of the dissociation based on noncoupled excited state dynamics.

  8. Photodissociation dynamics of HI and DI at 157 nm

    NASA Astrophysics Data System (ADS)

    Wang, Fengyan; Lu, I.-Chung; Yuan, Kaijun; Cheng, Yuan; Wu, Malcom; Parker, David H.; Yang, Xueming

    2007-11-01

    Photodissociation dynamics of HI and DI have been studied at 157 nm using the H atom Rydberg tagging time-of-flight technique. The photofragment translational energy distribution spectra and angular distributions of H/D atom products have been measured. Both the I( 2P 3/2) and I( 2P 1/2) products come almost exclusively from a perpendicular transition at 157 nm dissociation process, in agreement with the prediction of LeRoy's model [R.J. LeRoy, G.T. Kraemer, S. Manzhos, J. Chem. Phys. 117 (2002) 9353]. However, the branching ratios of I ∗/I measured in the experiment suggests that weak coupling may take place between the potential energy curves, which is noticeably different from the photodissociation of HI in the UV region. The experimental result in this work also suggests that the repulsive state, which has little contribution to the A-band absorption (33 000-53 000 cm -1), plays a greater role in the dissociation of HI and DI at 157 nm.

  9. Photodissociation and photoisomerization dynamics of CH2=CHCHO in solution

    NASA Astrophysics Data System (ADS)

    Wu, Weiqiang; Yang, Chunfan; Zhao, Hongmei; Liu, Kunhui; Su, Hongmei

    2010-03-01

    By means of time-resolved Fourier transform infrared absorption spectroscopy, we have investigated the 193 nm photodissociation and photoisomerization dynamics of the prototype molecule of α,β-enones, acrolein (CH2CHCHO) in CH3CN solution. The primary photolysis channels and absolute branching ratios are determined. The most probable reaction mechanisms are clarified by control experiments monitoring the product yields varied with the triplet quencher addition. The predominant channel is the 1,3-H migration yielding the rearrangement product CH3CHCO with a branching ratio of 0.78 and the less important channel is the α cleavage of CH bond yielding radical fragments CH2CHCO+H with a branching ratio of only 0.12. The 1,3-H migration is strongly suggested to correlate with the triplet (ππ ∗)3 state rather than the ground S0 state and the α cleavage of CH bond is more likely to proceed in the singlet S1 (nπ∗)1 state. From the solution experiments we have not only acquired clues clarifying the previous controversial mechanisms, but also explored different photochemistry in solution. Compared to the gas phase photolysis which is dominated by photodissociation channels, the most important channel in solution is the photoisomerization of 1,3-H migration. The reason leading to the different photochemistry in solution is further ascribed to the solvent cage effect.

  10. Photodissociation dynamics of phenol: multistate trajectory simulations including tunneling.

    PubMed

    Xu, Xuefei; Zheng, Jingjing; Yang, Ke R; Truhlar, Donald G

    2014-11-19

    We report multistate trajectory simulations, including coherence, decoherence, and multidimensional tunneling, of phenol photodissociation dynamics. The calculations are based on full-dimensional anchor-points reactive potential surfaces and state couplings fit to electronic structure calculations including dynamical correlation with an augmented correlation-consistent polarized valence double-ζ basis set. The calculations successfully reproduce the experimentally observed bimodal character of the total kinetic energy release spectra and confirm the interpretation of the most recent experiments that the photodissociation process is dominated by tunneling. Analysis of the trajectories uncovers an unexpected dissociation pathway for one quantum excitation of the O-H stretching mode of the S1 state, namely, tunneling in a coherent mixture of states starting in a smaller ROH (∼0.9-1.0 Å) region than has previously been invoked. The simulations also show that most trajectories do not pass close to the S1-S2 conical intersection (they have a minimum gap greater than 0.6 eV), they provide statistics on the out-of-plane angles at the locations of the minimum energy adiabatic gap, and they reveal information about which vibrational modes are most highly activated in the products.

  11. Photodissociation of HI and DI: polarization of atomic photofragments.

    PubMed

    Brown, Alex

    2005-02-22

    The complete angular momentum distributions and vector correlation coefficients (orientation and alignment) of ground state I((2)P(32)) and excited state I((2)P(12)) atoms resulting from the photodissociation of HI have been computed as a function of photolysis energy. The orientation and alignment parameters a(Q) ((K))(p) that describe the coherent and incoherent contributions to the angular momentum distributions from the multiple electronic states accessed by parallel and perpendicular transitions are determined using a time-dependent wave packet treatment of the dissociation dynamics. The dynamics are based on potential energy curves and transition dipole moments that have been reported previously [R. J. LeRoy, G. T. Kraemer, and S. Manzhos, J. Chem. Phys. 117, 9353 (2002)] and used to successfully model the scalar (total cross section and branching fraction) and lowest order vector (anisotropy parameter beta) properties of the photodissociation. Predictions of the a(Q) ((K))(p), parameters for the isotopically substituted species DI are reported and contrasted to the analogous HI results. The resulting polarization for the corresponding H/D partners are also determined and demonstrate that both H and D atoms produced can be highly spin polarized. Comparison of these predictions for HI and DI with experimental measurement will provide the most stringent test of the current model for the electronic structure and the interpretation of the dissociation based on noncoupled excited state dynamics.

  12. Analytic H i-to-H2 Photodissociation Transition Profiles

    NASA Astrophysics Data System (ADS)

    Bialy, Shmuel; Sternberg, Amiel

    2016-05-01

    We present a simple analytic procedure for generating atomic (H i) to molecular ({{{H}}}2) density profiles for optically thick hydrogen gas clouds illuminated by far-ultraviolet radiation fields. Our procedure is based on the analytic theory for the structure of one-dimensional H i/{{{H}}}2 photon-dominated regions, presented by Sternberg et al. Depth-dependent atomic and molecular density fractions may be computed for arbitrary gas density, far-ultraviolet field intensity, and the metallicity-dependent H2 formation rate coefficient, and dust absorption cross section in the Lyman-Werner photodissociation band. We use our procedure to generate a set of {{H}} {{I}}{-}{to}{-}{{{H}}}2 transition profiles for a wide range of conditions, from the weak- to strong-field limits, and from super-solar down to low metallicities. We show that if presented as functions of dust optical depth, the {{H}} {{I}} and {{{H}}}2 density profiles depend primarily on the Sternberg “α G parameter” (dimensionless) that determines the dust optical depth associated with the total photodissociated {{H}} {{I}} column. We derive a universal analytic formula for the {{H}} {{I}}{-}{to}{-}{{{H}}}2 transition points as a function of just α G. Our formula will be useful for interpreting emission-line observations of H i/{{{H}}}2 interfaces, for estimating star formation thresholds, and for sub-grid components in hydrodynamics simulations.

  13. Comparison of the magnetic properties of deoxy- and photodissociated myoglobin.

    PubMed Central

    Roder, H; Berendzen, J; Bowne, S F; Frauenfelder, H; Sauke, T B; Shyamsunder, E; Weissman, M B

    1984-01-01

    The magnetic susceptibility of photodissociated carbon monoxy myoglobin has been measured over the temperature range from 1.7 to 25 K at 10 and 50 kG with a superconducting susceptometer. The spin and the crystal field parameters of the iron ion were extracted by a spin Hamiltonian approach. Under equivalent conditions the magnetic susceptibility of deoxy myoglobin was measured. In both experiments the CO-bound protein was used as a diamagnetic reference. Above about 5 K the metastable photolysed state and the equilibrium deoxy form of myoglobin are magnetically indistinguishable and can be fitted with S = 2 and g = 2. The transition from spin 0 to spin 2 and the conformational changes known to accompany the electronic change thus also occur after photolysis at low temperature. At temperatures below 5 K, differences become apparent, indicating a somewhat smaller zero-field splitting in the photoproduct as compared to the ligand-free state at equilibrium. In qualitative agreement with observations made by other techniques, the data imply that even at 1.7 K substantial structural relaxation occurs in the heme region of myoglobin after photodissociation. The results are important for the interpretation of the ligand binding kinetics after flash photolysis at low temperature and contribute to the understanding of the relationship between electronic structure and function in heme proteins. PMID:6585802

  14. Ultraviolet Photodissociation Dynamics of the 3-CYCLOHEXENYL Radical

    NASA Astrophysics Data System (ADS)

    Lucas, Michael; Liu, Yanlin; Bryant, Raquel; Minor, Jasmine; Zhang, Jingsong

    2014-06-01

    The ultraviolet (UV) photodissociation dynamics of the cyclohexenyl radical (c-C_6H_9) was studied for the first time in the photolysis region of 232-262 nm using the high-n Rydberg atom time-of-flight (HRTOF) technique. The cyclohexenyl radical was produced by the 193 nm photodissociation of 3-chlorocyclohexene and 3-bromocyclohexene. The H-atom photofragment yield (PFY) spectrum contains a broad peak centering around 250 nm, in good agreement with the UV absorption spectra of the 2B1 ← 2A2 transition in cyclohexenyl. The translational energy distributions of the H-atom loss product channel, P(ET)'s, for cyclohexenyl show a modest translational energy release peak at ˜ 10 kcal/mol. The fraction of average translational energy in the total excess energy, , is ˜ 0.16 from 232-262 nm. The H-atom product angular distribution is isotropic with a β parameter ˜ 0. The dissociation mechanism is a statistical unimolecular dissociation of a hot radical following internal conversion from the excited electronic state to produce the lowest energy product, H + cyclohexadiene. The dissociation mechanisms of the cyclohexenyl radical and cyclohexyl radical will be compared.

  15. CO2 photodissociation and vibrational excitation in the planetary atmospheres

    NASA Technical Reports Server (NTRS)

    Slanger, T. G.

    1974-01-01

    The principal subjects of investigation were the determination of the CO2 photodissociation quantum yields at the wavelengths from 1200 A to 1500 A, and the efficiency of electronic-to-vibrational energy transfer in the systems 0(1D) + CO, N2, CO2 yields 0(3P) + CO N2, CO2 vibrational energies. Measurements on the photodissociation quantum yield of CO2 in the 1200-1500 A region show that it is wavelength dependent, and for the six atomic line sources used, the quantum yield varied from 0.2 to 0.8. The data appear to fit the interpretation of stable CO2 bound states mixed with repulsive or predissociating states, since the low quantum yields coincide with the maximum structure in the CO2 absorption spectrum. The first reliable measurements were made on the efficiency of electronic-to-vibrational energy transfer in the systems 0(1D)-CO and 0(1D)-N2, using a uv resonance fluorescence technique. The 0(1D)-CO2 interaction was investigated by infrared techniques.

  16. Photodissociation spectroscopy of the Mg{sup +}-acetic acid complex

    SciTech Connect

    Abate, Yohannes; Kleiber, P. D.

    2006-11-14

    We have studied the structure and photodissociation of Mg{sup +}-acetic acid clusters. Ab initio calculations suggest four relatively strongly bound ground state isomers for the [MgC{sub 2}H{sub 4}O{sub 2}]{sup +} complex. These isomers include the cis and trans forms of the Mg{sup +}-acetic acid association complex with Mg{sup +} bonded to the carbonyl O atom of acetic acid, the Mg{sup +}-acetic acid association complex with Mg{sup +} bonded to the hydroxyl O atom of acetic acid, or to a Mg{sup +}-ethenediol association complex. Photodissociation through the Mg{sup +}-based 3p<-3s absorption bands in the near UV leads to direct (nonreactive) and reactive dissociation products: Mg{sup +}, MgOH{sup +}, Mg(H{sub 2}O){sup +}, CH{sub 3}CO{sup +}, and MgCH{sub 3}{sup +}. At low energies the dominant reactive quenching pathway is through dehydration to Mg(H{sub 2}O){sup +}, but additional reaction channels involving C-H and C-C bond activation are also open at higher energies.

  17. Slice imaging of photodissociation of spatially oriented molecules

    SciTech Connect

    Lipciuc, M. Laura; Brom, Alrik J. van den; Dinu, Laura; Janssen, Maurice H.M.

    2005-12-15

    An electrostatic ion lens to spatially orient parent molecules and to image the angular distribution of photofragments is presented. Photodissociation of laboratory-oriented molecules makes it possible to study the dynamics of the dissociation process in more detail compared to photodissociation of nonoriented molecules. Using the velocity map imaging technique in combination with the slice imaging technique, the spatial recoil distribution of the photofragments can be measured with high resolution and without symmetry restrictions. Insertion of orientation electrodes between the repeller and the extractor of a velocity mapping electrostatic lens severely distorts the ion trajectories. The position where the ions are focused by the lens, the focal length, can be very different in the directions parallel and perpendicular to the inserted orientation electrodes. The focal length depends on the exact dimensions and positions of the electrodes of the ion lens. As this dependence is different in both directions, this dependence can be used to correct for the distorted ion trajectories. We discuss the design of an electrostatic ion lens, which is able to orient parent molecules and map the velocity of the photofragments. We report sliced images of photofragments from photolysis of spatially oriented CD{sub 3}I molecules to demonstrate the experimental combination of molecular orientation and velocity map slice imaging with good resolution.

  18. Radioactive Iodine (I-131) Therapy for Hyperthyroidism

    MedlinePlus

    ... of your treatment team. top of page What equipment is used? There is no equipment used during ... iodine therapy. top of page Who operates the equipment? There is no equipment used during radioactive iodine ...

  19. Iodine deficiency in vegetarians and vegans.

    PubMed

    Krajcovicová-Kudlácková, M; Bucková, K; Klimes, I; Seboková, E

    2003-01-01

    Iodine content in food of plant origin is lower in comparison with that of animal origin due to a low iodine concentration in soil. Urinary iodine excretion was assessed in 15 vegans, 31 lacto- and lacto-ovovegetarians and 35 adults on a mixed diet. Iodine excretion was significantly lower in alternative nutrition groups - 172 microg/l in vegetarians and 78 microg/l in vegans compared to 216 microg/l in subjects on a mixed diet. One fourth of the vegetarians and 80% of the vegans suffer from iodine deficiency (iodine excretion value below 100 microg/l) compared to 9% in the persons on a mixed nutrition. The results show that under conditions of alternative nutrition, there is a higher prevalence of iodine deficiency, which might be a consequence of exclusive or prevailing consumption of food of plant origin, no intake of fish and other sea products, as well as reduced iodine intake in the form of sea salt.

  20. The Absorption Spectrum of Iodine Vapour

    ERIC Educational Resources Information Center

    Tetlow, K. S.

    1972-01-01

    A laboratory experiment is described which presents some molecular parameters of iodine molecule by studying iodine spectrum. Points out this experiment can be conducted by sixth form students in high school laboratories. (PS)