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Thick and thin films of Al targets were irradiated in vacuum with iodine laser at 1315 nm wavelength, 300 ps pulse duration at a maximum intensity of about 1016W/cm² by varying the pulse energy and focal position. The laser-generated plasma was monitored in forward and backward directions by using ion collectors, SiC detectors, Thomson parabola spectrometer, and X-ray streak camera. Ion emission shows maximum proton energy of about 4MeV in self-focusing conditions and a maximum Al ion energy of about 50MeV. An evaluation of the electric field driving ions in conditions of target normal sheath acceleration is given. [ABSTRACT FROM AUTHOR]

A parametric study of the output power of supersonic chemical oxygen-iodine lasers (COILs) is carried out, applying a kinetic-fluid dynamics model calculations as well as an analytical model and comparing the results to experimental studies. The I2 dissociation mechanism recently suggested by Azyazov et al. [J. Chem. Phys. 130, 104306 (2009)], which was previously used for comparison of model calculations to measurements of the small signal gain [K. Waichman et al., J. Appl. Phys. 106, 063108 (2009)], is applied here for a similar, but more sensitive, comparison of the laser output power. The dependence of the power on iodine flow rate and on mirror transmission is studied for low and high pressure COILs, respectively. Good agreement between the calculated and measured power is obtained for both low and high pressure COILs only when the processes suggested by Azyazov et al. are included in the calculations. This is different from the situation for the gain where for high pressure COILs, the calculated values were insensitive to the assumed dissociation mechanism, although for low pressure the measurements were reproduced only by applying the Azyazov et al. mechanism. We believe that the results of the present work strongly support the application of this mechanism for modeling the COIL operation. [ABSTRACT FROM AUTHOR]

We have studied the dynamics of strong radiative shocks generated with the high-energy subnanosecond iodine laser at Prague Asterix Laser System facility (Prague) over long time scales, up to 100 ns. These shock waves are characterized by a developed radiative precursor, a radiation driven ionization wave in front of the density jump of the shock. Electronic density profiles are measured at different times after the laser pulse and at different distances from the axis of the shock tube. A new feature, described as a split precursor, has been observed. Comparisons with two-dimensional computations are shown. [ABSTRACT FROM AUTHOR]

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 1Σg+,10≤v<25), I2(X 1Σg+,25≤v≤47), I2(A′ 3Π2u), I2(A 3Π1u), O2(X 3Σg-,v), O2(a 1Δg,v), O2(b 1Σg+,v), and I(2P1/2) 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. [ABSTRACT FROM AUTHOR]

The rate constant for quenching of I(2P1/2) by O(3P) has been measured for the temperature range 295–360 K. Pulsed laser photolysis of mixtures N2O and I2 was used to examine the kinetics. O(3P) atoms were produced by the photoinitiated reaction sequences N2O+hν→O(1D)+N2 and O(1D)+M→O(3P)+M, while singlet oxygen was generated by the secondary reaction O(1D)+N2O→O2(a 1Δ)+N2. Iodine atoms were produced by I2 photodissociation and from the secondary reactions of I2 with O(3P) atoms. Subsequent excitation of I by O2(a 1Δ) led to I(2P1/2) formation, with I(2P1/2) concentrations monitored using time-resolved 1315 nm emission. The rate constant of the quenching process was determined by fitting a kinetic model to the observed emission traces. Special attention was given to the gas flow conditions. A modest temperature dependence of the quenching rate constant was found, and this was well represented by the equation k=(6.5±1)×10-12(T/300)1.76 cm3 s-1. The room temperature rate constant differs from previous experimental determinations but agrees well with the value determined by modeling of the data from discharge driven oxygen-iodine lasers. [ABSTRACT FROM AUTHOR]

Experiments were carried out in a flow cell apparatus under conditions corresponding to those of a typical oxygen-iodine laser. The cell was equipped with a chemical jet type singlet oxygen generator and an electric discharge for the production of iodine atoms. The properties of the discharge generator and the active medium were studied using laser-induced fluorescence and emission spectroscopy. I2 or CH3I entrained in a carrier flow of Ar were used as atomic iodine precursors. About 50% of the iodine contained in CH3I molecules was extracted in the generator. 2.6% of the electric power loaded into the discharge was used in CH3I dissociation. Right after the discharge 80%–90% of the iodine flow consisted of atoms. However, due to recombination during transport, only 20%–50% of atoms remained at the point of injection into the oxygen flow. A straightforward comparison of two methods of oxygen-iodine medium production—conventional, by means of I2 dissociation in the singlet oxygen flow and with iodine atoms produced externally in the electric discharge—was performed. It was found that the lifetime for the energy stored in singlet oxygen was about 30% longer, when atomic iodine was produced from CH3I in the discharge, as compared to the conventional chemical dissociation of I2 in the singlet oxygen flow. [ABSTRACT FROM AUTHOR]

The mechanism by which I2(B3Π0) is excited in the chemical oxygen-iodine laser was studied by means of emission spectroscopy. Using the intensity of the O2(b1Σ,υ′=0)→O2(X3Σ,υ″=0) band as a reference, I2(B3Π0) relative number densities were assessed by measuring the I2(B3Π0,υ′)→I2(X1Σ,υ″) emission intensities. Vibrationally excited singlet oxygen molecules O2(a1Δ,υ′=1) were detected using infrared emission spectroscopy. The measured relative density of O2(a1Δ,υ′=1) for the conditions of a typical oxygen-iodine laser medium amounted to ∼15% of the total O2(a1Δ) content. Mechanisms for I2(B3Π0) formation were proposed for both the I2 dissociation zone and the region downstream of the dissociation zone. Both pumping mechanisms involved electronically excited molecular iodine I2(A′3Π2u, A3Π1u) as an intermediate. It is proposed that in the dissociation zone the molecular iodine A′3Π2u and A3Π1u states are populated in collisions with vibrationally excited singlet oxygen molecules O2(a1Δ,υ′), whereas in the downstream region of the dissociation zone those intermediate states are populated by the atomic iodine recombination process. I2(B3Π0) is subsequently formed in collisions of I2(A′3Π2u, A3Π1u) with singlet oxygen. We also demonstrated that I2(B3Π0) does not participate measurably in the I2 dissociation process, and that energy transfer from O2(b1Σ) does not excite I2(B3Π0) to a significant degree. [ABSTRACT FROM AUTHOR]

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(a 1Δg) 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′ 3Π2u), I2(A 3Π1u), and O2(a 1Δg,v) are significant dissociation intermediates, with the “standard” chain branching mechanism of Heidner III et al. [J. Phys. Chem. 87, 2348 (1983)], involving I(2P1/2) and I2(X 1Σg+,v). [ABSTRACT FROM AUTHOR]

In chemical oxygen iodine lasers (COILs), oscillation at 1.315 μm in atomic iodine (2P1/2→2P3/2) is produced by collisional excitation transfer of O2(1Δ) to I2 and I. Plasma production of O2(1Δ) in electrical COILs (eCOILs) eliminates liquid phase generators. For the flowing plasmas used for eCOILs (He/O2, a few to tens of torr), self-sustaining electron temperatures, Te, are 2–3 eV whereas excitation of O2(1Δ) optimizes with Te=1–1.5 eV. One method to increase O2(1Δ) production is by lowering the average value of Te using spiker-sustainer (SS) excitation where a high power pulse (spiker) is followed by a lower power period (sustainer). Excess ionization produced by the spiker enables the sustainer to operate with a lower Te. Previous investigations suggested that SS techniques can significantly raise yields of O2(1Δ). In this paper, we report on the results from a two-dimensional computational investigation of radio frequency (rf) excited flowing He/O2 plasmas with emphasis on SS excitation. We found that the efficiency of SS methods generally increase with increasing frequency by producing a higher electron density, lower Te, and, as a consequence, a more efficient production of O2(1Δ). [ABSTRACT FROM AUTHOR]

Chemical oxygen-iodine lasers (COILs) have promising applications due to their high efficiency and ease of scaling to multikilowatt powers. Recent research has focused on pumping the iodine with O2(1Δ) produced by electric discharges. In a previous work, a global model was used to develop reaction mechanisms and determine the specific energy deposition (eV/O2) required to obtain high O2(1Δ) yields for electric discharge COILs. Experiments have recently achieved positive laser gain and oscillation with these energy depositions and have highlighted the importance of axial expansion of the plasma in optimizing excitation of the O2(1Δ). In this work, the consequences of axial transport on O2(1Δ) yields have been computationally investigated in flowing He/O2 plasmas at a few Torrs using a one-dimensional plasma hydrodynamics and kinetics model. We show that the experimentally observed extension of the plasma glow upstream and downstream of the electrodes is due to electron diffusion and capacitive coupling of the radio-frequency power source. We also show that ≈50% higher O2(1Δ) yields can be achieved with a pulsed discharge combined with continuous-wave discharge. [ABSTRACT FROM AUTHOR]

We report on a detailed parametric study of the extremely efficient supersonic chemical oxygen-iodine laser recently developed in our laboratory [V. Rybalkin, A. Katz, B. D. Barmashenko, and S. Rosenwaks, Appl. Phys. Lett. 85, 5851 (2004)]. At the early stage of operation, 40.0% efficiency was measured for 1 s followed by a sustained 35.5% chemical efficiency for 20 s. The power and spatial distributions of the gain and temperature across the flow were measured for different supersonic nozzles with both staggered and nonstaggered iodine injection holes, different injection locations along the flow and nozzle throat heights. The effects of the partial pressure of O2 and the residence time of the flow in the generator, as well as the heating of the nozzle, are discussed and shown to be crucial in attaining this high efficiency. By carefully studying and optimizing the operation of the chemical generator, 0.73 yield of singlet oxygen was obtained for conditions corresponding to the highest efficiency. [ABSTRACT FROM AUTHOR]

We demonstrate molecular orientation by using phase-controlled two-color ω+2ω laser pulses with an intensity of 1.0×10[sup 12] W/cm[sup 2] and a pulse duration of 130 fs. The orientation of three iodine-containing molecules (IBr, CH[sub 3]I, and C[sub 3]H[sub 5]I) was monitored by the directional asymmetries of the photofragment angular distribution in dissociative ionization. In all three molecules, the directional asymmetry showed an oscillating behavior dependent on the relative phase difference between ω and 2ω pulses. The phase dependence of the directional asymmetry observed in iodine ions and counterpart ions were out of phase with each other. This result shows that a phase-controlled ω+2ω optical field discriminates between parallel and antiparallel configurations of aligned molecules that have a permanent dipole. This method performed well because (1) molecular orientation can be achieved by all-optical fields; (2) the direction of orientation is easily switched by changing the sign of the quantum interference; and (3) this method is free from any resonance constraint and thus can be applied to any molecule. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Presents a study which examined the efficiency of chemical oxygen-iodine laser oscillators. Evaluation of chemical oxygen-iodine laser performance; Types of efficiencies introduced in the examination; Results and discussion.

Presents a study that described the design and operation of an oxygen-iodine chemical laser. Features of the laser; Analysis of the variation of laser power with run time; Calculation of the power extraction efficiency of the laser.

Deals with a study which evaluated the measurement of parameters relevant to the operation of an electron-beam initiated atomic iodine laser by pulse radiolysis. Process of obtaining kinetic data for the parent compound quenching; Focus of investigations of alkyl iodide photolysis; Use of the kinetic spectrophotographic technique.

The pulse characteristics of a photolytic, gain-switched iodine laser are a sensitive measure for relaxation processes that occur in the active medium. On a time scale shorter than a few microseconds this concerns the relaxation of the speed and the angular parts of the anisotropic velocity distribution which is produced by the photodissociation of the parent molecule CF3I. A comprehensive rate equation model of the laser dynamics is fit to experimental data, to obtain time constants for these collision-controlled relaxation processes for various buffer gases and pressures. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Presents a study which generated metastable oxygen in bubble column reactor for chemically pumped iodine lasers. Details of experimental techniques used; Information on the technical application of bubble column reactor; Calculation of the rate of absorption of chlorine and metastable oxygen.

Presents a study which developed a high-power chemical oxygen iodine laser system for industrial applications. Description of the laser system; Comparison of laser power to the effective oxygen power and the volume flow rate measured in the laser head; Correlation between saturation effect on laser power and effective oxygen power and the volume flow rate.

Discusses a study which developed a model for continuous-wave (CW) iodine laser and compared it with the experimental results obtained from a solar-simulator-pumped CW iodine laser. Iodine laser kinetics; Rate equations for continuously pumped iodine laser; Calculation of output power.

Presents a study which intended to improve the performance of a discharge-pumped iodine monofluoride laser. Experimental details; Results and discussion; Conclusion.

Discusses the development of a chemical oxygen-iodine laser for industrial application. Features of the chemical oxygen-iodine laser; Information on experiment and study on high-laser emission; Details on the system design of high-power chemical oxygen-iodine laser for industrial use.

Discusses the potential use of TII/Xe system as a continuous wave (cw), completely cyclic, self-contained atomic iodine laser. Pumping processes for the excited atomic iodine; Shortcomings of cw photolytically excited atomic iodine lasers; Factors that excited the TII dissociative levels in the rf discharge.

Presents a study that described the effect of water vapor on the operation of a chemical oxygen-iodine laser without a water vapor trap. Features of a chemical oxygen-iodine laser; Analysis of the water vapor in the flowing gas; Evaluation of the performance characteristics of the laser.

Focuses on a study which presented a transverse flow carrier wave atomic iodine laser excited by the photolytic pumping of carbon[sub3] fluorine[sub7] iodine. Materials and methodology; Effect of the use of transverse flow; Implications for the use of the atomic iodine.

In this paper, we developed a simple, rapid, selective and colorimetric method to detect iodide (I − ) by etching silver-coated gold nanobipyramids (Au NBs@Ag nanostructure) in the presence of Cu 2+ . The detection is based on the reaction that Cu 2+ could oxidize I − into I 2 , which sequentially etches the Ag shell of Au NBs@Ag nanostructure. When the Ag coating is thick and the Au NBs are buried in Ag nanorods, the decrease of the Ag shell thickness and aspect ratio results in the blue-shift and intensity decrease of the longitudinal localized surface plasmon resonances (LSPR) peak. The blue-shift and intensity decrease of the longitudinal LSPR peak have been employed to quantificationally detect the concentration of I − . The linear range of the detection could be improved by increasing the concentration of Cu 2+ and reaction time. Under the optimized conditions, both the blue-shift and intensity decrease of the longitudinal LSPR have linear correlation with the concentration of I − in the range of 1.0–15 μM. When the Ag coating is very thin, the etching of the Ag shell results in the red shift of the LSPR in the visible range, which further leads to the color of the colloid change from blue to pink. The etching-induced color change of the colloid also depends on the concentration of I − , which enables the visual detection of I − . Compared with other techniques, this method could facilitate multi-model quantitative detection of I − without any sophisticated instrument. Interference studies and real samples test show that I − could be specifically detected in dried kelp using this bimetallic optical nanoprobe. [ABSTRACT FROM AUTHOR]

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 threeframe 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. [ABSTRACT FROM AUTHOR]

Cw oscillation of molecular iodine on many lines in the range of 557-802 nm pumped with a low power common diode pumped and frequency doubled solid state laser DPSSL is reported. The DPSSL is temperature stabilized, operates in single frequency and can be tuned by about 2 nm at 532 nm. Operation conditions of this simple and low cost iodine ring laser will be described and possible applications will be discussed. [ABSTRACT FROM AUTHOR]

The existing kinetic model describing self-sustained and electroionization discharges in mixtures enriched with singlet oxygen has been modified to calculate the characteristics of a flow RF discharge in molecular oxygen and its mixtures with helium. The simulations were performed in the gas plug-flow approximation, i.e., the evolution of the plasma components during their motion along the channel was represented as their evolution in time. The calculations were carried out for the O: He = 1: 0, 1: 1, 1: 2, and 1: 3 mixtures at an oxygen partial pressure of 7.5 Torr. It is shown that, under these conditions, volumetric gas heating in a discharge in pure molecular oxygen prevails over gas cooling via heat conduction even at an electrode temperature as low as ~100 K. When molecular oxygen is diluted with helium, the behavior of the gas temperature changes substantially: heat removal begins to prevail over volumetric gas heating, and the gas temperature at the outlet of the discharge zone drops to ~220-230 K at room gas temperature at the inlet, which is very important in the context of achieving the generation threshold in an electric-discharge oxygen−iodine laser based on a slab cryogenic RF discharge. [ABSTRACT FROM AUTHOR]

A compact and inexpensive iodine-stabilized diode laser system with an output at 531 nm has been applied to long gauge block measurements. Although the optical frequency of the output beam was widely modulated (modulation width of ∼22 MHz), the coherence length and interference phase stability are sufficiently long and high, respectively, for the interferometric measurement of long gauge blocks of up to 1000 mm in length. The effective uncertainty of laser frequency in the interferometric measurement was theoretically and experimentally confirmed to be less than 10 −9 . [ABSTRACT FROM AUTHOR]

Presents information on a study which described the dependence of laser output power on the flow velocity at a cavity for a compact chemical oxygen-iodine laser. Description of chemical oxygen-iodine laser; Experimental apparatus; Results and discussion; Conclusions.

Presents a study that developed a highly efficient chemical oxygen iodine laser (COIL) with industrial uses. Oscillation of the COIL; Design concept of the system; Efficiencies that characterize the COIL.

A theoretical model is proposed for computing simulations of laser radiation interaction with inhomogeneous foam materials doped with heavy elements and undoped materials. The model satisfactorily describes many experiments on the interaction of the first and third harmonics of a 200 J pulsed PALS iodine laser with low-density porous cellulose triacetate targets. The model can be used to analyze experimental data and estimate the reality of experimental results. [ABSTRACT FROM AUTHOR]

The kinetics of oxygen species in the gaseous medium of a discharge singlet oxygen generator has been revisited. Vibrationally excited ozone O 3 ( υ ) formed in O + O 2 recombination is thought to be a significant agent in the deactivation of singlet oxygen O 2 ( a 1 Δ), oxygen atom removal and ozone formation. It is shown that the process O 3 ( υ ⩾ 2) + O 2 ( a 1 Δ) → 2O 2 + O is the main O 2 ( a 1 Δ) deactivation channel in the post-discharge zone. If no measures are taken to decrease the oxygen atom concentration, the contribution of this process to the overall O 2 ( a 1 Δ) removal is significant, even in the discharge zone. A simplified model for the kinetics of vibrationally excited ozone is proposed. Calculations based on this model yield results that are in good agreement with the experimental data. [ABSTRACT FROM AUTHOR]

The Prague Asterix Laser System (PALS) Research Infrastructure (RI) in Prague, one of only four kJ-class laser facilities in EU, has been offering its beam time to European researchers for already 14 years, since 2004 in the framework of the LASERLAB-Europe consortium. Till June 2014, the PALS RI has provided 4313 experimental days for a total of 41 projects with 303 international users from 42 different research institutions. Its principal experimental facility is a terawatt sub-ns iodine laser (1315 nm) with an optional plasma-based zinc XUV laser (21.2 nm), and an auxiliary Ti:Sapphire fs laser (1 J, 70 fs) exploited for femtosecond plasma probing and experiments with synchronised femtosecond and sub-nanosecond laser pulses at mean laser intensities of up to 30 PW/cm2. The lasers are equipped with several target facilities and rich sets of instruments for both active and passive plasma diagnostics. The PALS main research areas include development and applications of secondary laser sources of high-energy ions and both coherent and non-coherent high-intensity XUV radiation, laboratory astrophysical and inertial fusion-relevant studies. In this paper, the main results having been achieved at PALS in the framework of LASERLAB-EUROPE international access activities during the last four years are highlighted. [ABSTRACT FROM PUBLISHER]

This review article describes apparatus for ion and X-ray diagnostics, which were used in experimental studies of laser-produced plasmas performed by the IPPLM's team in collaboration with other researchers at IPPLM and PALS Research Centre in Prague (the Czech Republic). The investigations of expanding laser-produced plasma properties in dependence on laser beam parameters were done by means of ion diagnostics devices: ion collectors (ICs), cylindrical ion energy analyzer (IEA) and the mass spectrograph of the Thomson type. At IPPLM, different types of detectors have been developed for measurement of X-ray emission. Properties of laser-produced beams of ions and X-ray radiation were analysed in the cooperative experiments performed with the use of a high-energy iodine laser PALS at the PALS Research Centre ASCR in the Czech Republic and the low-energy repetitive laser at IPPLM. [ABSTRACT FROM PUBLISHER]