Optimisation of the pulse duration of a discharge-pumped XeF(B→X) excimer laser

In an x-ray preionised XeF(BX) discharge-excited laser driven by a magnetic-spiker sustainer circuit with a magnetic pulse compressor the influence of the various parameters on the optical pulse duration was experimentally investigated. Laser pulses at = 351 nm with a duration of 212 ns (FWHM) have been achieved in a NF₃/Xe/Ne mixture by using very low (0.25 mbar) NF₃ partial pressures in a total gas pressure of 2.5 bar and with a high-reflecting output coupling mirror.     

Gas-discharge XeF* (B→X) laser with high specific output energy

The discharge characteristics of the XeF* (BX) laser are investigated. The NF₃ and Xe partial pressure of the laser gas mixture and the total gas pressure have been varied. A highest specific output energy of 4.7 J/l with an efficiency of 0.5% was obtained from a X-ray preionized Ne/Xe/NF₃ gas mixture at 6 bar with single-pulse excitation through a multichannel spark gap.     

N2 production in e-beam pumped XeF lasers containing NF3

The rate of build-up of N₂ was measured in electron-beam-irradiated Ne/Xe/NF₃ mixtures using mass spectroscopy. the amount of N₂ produced indicated that N₂ is the primary nitrogen bearing stable species created in these mixtures. The rate constant for dissociative electron attachment to the NF₂ fragments produced in electron attachment to NF₃ is estimated to be 5×10^–8 cm³/s in order to explain the amount of N₂ produced.This work was supported by DARPA under Contract No. DAA01-82-C-A125 and monitored by MICOM     

Long pulse ultraviolet laser emissions in an aerodynamically cooled electron-beam excited Ne-NF3 mixture

Long pulse laser action has been achieved at 3378.28 and 3481.96 Å in an electron beam excited supersonic flow. These laser emissions, attributed to NeII transitions, have been obtained when a mixture of Ne and NF₃ at a pressure of 0.2 atm. and aerodynamically cooled to 80 K was excited by a medium intensity electron beam. Laser pulse duration, about 350 ns fwhm for both lines, was only limited by the electron beam pulse length. The second of these laser lines had not been previously reported.     

Simulation of the discharge process in a barrier discharge cell based on a three-parameter model

Electric parameters of a barrier discharge cell with flat tips are studied experimentally and numerically for Xe/NF₃ (50 : 1) and Xe/SF₆ (50 : 1) gas mixtures. The discharge process is simulated using a three-parameter model. The dependences of the computational model parameters on the pressure of the Xe/SF₆ (50 : 1) gas mixture and on the electrode spacing are presented. Comparison of experimental and theoretical results shows that the error of simulation of the main discharge parameters (current, voltage drop, and transferred charge) does not exceed 10%.     

Influence of Ar, Ne, Xe, and CCl4 impurities on luminescence kinetics of Cd II ions (5s22D5/2-5p2P3/2 transition, λ = 441.6 nm) in He-Cd mixture

The luminescence kinetics of the Cd II ion at a wavelength of 441.6 nm has been studied experi-mentally in a high-pressure He-Cd mixture in the presence of Ar, Ne, Xe, and CCl₄ impurities. Cadmium ions were excited through the bombardment of a cadmium foil heated up to 240°C by a pulsed electron beam with an electron energy of 150 keV, a pulse duration of 3 ns, and a current of 500 A. The constants of collisional quenching of the Cd II 5s ^{2 2} D _5/2 level by Ar, Ne, and Xe atoms and CCl₄ molecules and the integral luminescence quenching constants of this level in the helium medium by these impurity gases have been determined. The constants of collisional quenching appeared to be 8.1 × 10⁻¹² (Ar), 1.2 × 10⁻¹² (Xe), 1.5 × 10⁻¹³ (Ne), and 1.8 × 10⁻¹⁰ cm³/s (CCl₄, for λ = 325 nm), while the integral constants were found to be, respectively, 4.1 × 10⁻¹¹, 3.4 × 10⁻¹¹, 9.5 × 10⁻¹², 1.4 × 10⁻⁹ cm³/s for Ar, Ne, Xe, and CCl₄ at a buffer gas pressure of 1 atm. Original Russian Text ? A.I. Miskevich, Liu Tao, 2009, published in Optika i Spektroskopiya, 2009, Vol. 107, No. 1, pp. 45–49.     

Wideband tuning of the blue-green XeF (C→A) laser

Efficient wavelength tuning from 446 to 524 nm with a minimum spectral linewidth of 1 nm was demonstrated for an electron beam pumped XeF(CA) laser. Energy densities of 0.1 J/l were obtained for an optimized Ar/Kr/Xe/F₂/NF₃ mixture.     

Experimental verification of a zero-dimensional model of the kinetics of XeCl* discharges by XeCl*(B)-, XeCl*(C)-, and Xe2Cl*-density measurements

Absolutely calibrated emission spectroscopy has been used to determine the particle number densities of XeCl^*(B), XeCl^*(C), and Xe₂Cl^* in a small scale Ne/Xe/HCl discharge with well-defined current and voltage pulses for a wide range of parameters. The measured particle number densities could be reproduced quite well by numerical model calculations using the rate-coefficient values of Quiñones et al. [1] for the quenching of XeCl^*(B,C) by Ne, Xe, and 2Xe, but 3.0 × 10^–31 cm⁶/s for the formation of Xe₂Cl^* by (Ne + Xe)-quenching. For the electron quenching, we recommend a rate coefficient value of 3.2 × 10^–8 cm³/s. From the equilibrium ratio of the particle number densities of XeCl^*(C) and XeCl^*(B), the energy separation between these states has been estimated to be 72 ± 33 cm^–1 with the B state placed above the C state.     

Kinetic processes of muonic atom and ion formation in rare gases (spur model)

The possibility of_µF^– formation due to electron attachment to a Xe_µF molecule in_µSR-experiments with a gaseous Ne/Xe mixture is considered. This model explains the results of experiments in Ar and Ne with and without an external electric field.     

Collisional effects in IR multiphoton absorption of CDF3

Energy absorption by CDF₃ for different energy fluences from an intense TEA CO₂ laser is reported as function of the pressure of CDF₃ and various bath gases (He, Ne, Ar, Xe, and CHF₃). Collisional behavior at different conditions is discussed.     

Temporal extension of stable glow discharges in fluorine-based excimer laser gas mixtures by the addition of xenon

The effect of addition of xenon on the long term homogeneity of discharges in F₂and ArF excimer laser gas mixtures was investigated in a small-volume discharge chamber. The gas mixture in the discharge chamber was preionized by X-rays. A special electrical excitation circuit containing a pulse forming line provided a long, square-shaped current pumping pulse of a predetermined duration to the discharge electrodes. The initiation and the development of the discharge was monitored via its fluorescence signal with an intensified CCD camera. We found that adding Xe up to partial pressures of 0.53 mbar extended the homogeneous phase of the discharge from 80 ns to approximately 200 ns in He/F₂as well as in He/Ar/F₂and Ne/Ar/F₂excimer laser gas mixtures. Monitoring of the ArF and XeF spontaneous emission signals showed that the formation of ArF excimers remained unaffected by the addition of xenon (up to 1.3 mbar) to the laser gas mixture.     

On the spin-orbit splitting of the rare gas-monohalide molecular ground state

The spin orbit splitting of the molecular ground state of two atomsA(² P _{1/2, 3/2}) andB(¹ S ₀) is discussed. If the spin orbit matrix elements do not depend on the internuclear distance, it is sufficient to know any two of the three potentials of the ground state manifold. The third can then be calculated analytically. Data are presented for theA II 1/2 state of F+Ne; (F, Br)+(Ar, Kr, Xe); and Cl+Xe, as well as for theA I 3/2 state of HeNe⁺.     

An experimental investigation of the pressure and concentration dependence of muonic Coulomb capture and cascade in gases

Muonic Coulomb capture ratios and x-ray intensity patterns in four binary mixtures of the gases N₂, Ne, Ar, Kr, and Xe have been measured at three atomic ratios. An influence of the concentration has been established. The Lyman series intensity patterns of pure N₂, Ne, Ar, Kr, and Xe were measured at pressures between 0.4 and 51 bar and found to depend on the pressure. Possible explanations are discussed.     

On Various Kinds of Dielectric Barrier Discharges

Dielectric barrier discharges in Xe and Ne/Xe, He/Xe mixtures are investigated with regard to the ranges of existence of various discharge types over a wide range of parameters (total gas pressure p, electrode distance d, frequency f and mixture ratio X). The discharges were explained in more detail because of the bistable behaviour and the transfered charges, partly of the peak current and the maximum of the visible radiation pulse. The time behaviour of the discharge was observed, too. In this paper a distinction of various discharge types could be achieved by the similarity parameters f/p and pd. The charge carriers remaining in the volume and long-living plasma species could be identified as essential mechanisms for the development of various types of discharges. The influence of space charges on the bistable behaviour could be shown indirectly.     

Special features of electron beam-excited XeCl-laser generation

The results of experimental investigations on generation in Ar(Ne): Xe: CCl₄(HCl) mixtures at excitation by an electron beam are given. It is shown that the use of CCl₄ and HCl with an Ar buffer gas gives equal radiative energies and efficiencies and ā change of Ne for Ar causes a change in generation spectrum. The special features of XeCl-laser generation are discussed.     

A Miniaturized XeCl Dielectric Barrier Discharge as a Source of Short Lived,Fast Decaying UV Radiation

A dielectric barrier discharge (DBD) of coaxial geometry has been examined as source of intensive, short‐lived UV radiation. A binary gas mixture consisting of 98% Xe + 2% Cl₂ and a ternary composition of 96% Ne + 6% Xe + 0.2% HCl were investigated in the pressure range between 10 and 750 mbar. The discharge was excited by unipolar high voltage square pulses with amplitudes of 3 to 7 kV at a repetition rate of 100 Hz. UV radiation intensity is increased by combining 5 square pulses with a period of 1 μs each in one train (burst). Radiation decay on three orders of magnitude within 10 μs was obtained for both gas mixtures in burst mode. Maximum energy of the light pulse was the same for both gas mixtures and estimated as 40 nJ. It is shown that the optimum gas pressure for highest radiation intensity depends not only on gas composition but also on applied voltage and number of pulses in the train. A variation of the spectral band shape of XeCl emission during the pulse is detected (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The double M-effect induced by noble gases activated with negative ions

The M-effect (monochromatization-effect) is a powerful tool which can give high intensity monochromatic spectra with a certain wavelength depending on the type of used gas mixtures to generate plasma state. The effect consists in the emission of a single spectral line of plasmas ignited in certain gas mixtures. The main condition to obtain the M effect is the presence of an electropositive and an electronegative gas mixture. For example, in the case of Ne+H₂ monochrome radiation was obtained, the wavelength of Ne being 585.3 nm (1s²–2p⁵). In this paper we prove the general character of this effect, i.e. if the optical emission spectra reduced to nearly one line can be observed also in other gas mixture discharges, for example in the case of one electronegative gas and two electropositive gases. Different other mixtures, as Xe+Ne+H₂ and Xe+Ar+H₂ have been studied. In all these cases, the M-effect appeared without doubt.     

Muons and muonium in cryocrystals

We present a collection of measurements of the muon and muonium asymmetries and relaxation parameters in cryocrystals of N₂, CO, Xe,¹³⁶Xe and Ne as functions of temperature. Generally, the fractions of the two species can be attributed to a competition between the formation of muonium or a diamagnetic species, where processes involving transport of spur electrons are important.     

Electronic and geometric structure of doped rare-gas clusters: surface, site and size effects studied with luminescence spectroscopy

The electronic and geometric structure of rare gas clusters doped with rare-gas atoms Rg = Xe, Kr or Ar is investigated with fluorescence excitation spectroscopy in the VUV spectral range. Several absorption bands are observed in the region of the first electronic excitations of the impurity atoms, which are related to the lowest spin-orbit split atomic ³P₁ and ¹P₁ states. Due to influence of surrounding atoms of the cluster, the atomic lines are shifted to the blue and broadened (“electronical cage effect”). From the known interaction potentials and the measured spectral shifts the coordination of the impurity atom in Ar_N, Kr_N, Ne_N and He_N could be studied in great detail. In the interior of Kr_N and Ar_N the Xe atoms are located in substitutional sites with 12 nearest neighbours and internuclear distances comparable to that of the host matrix. In Ne_N and He_N the cluster atoms (18 and 22, respectively) arrange themselves around the Xe impurity with a bondlength comparable to that of the heteronuclear dimer. The results confirm that He clusters are liquid while Ne clusters are solid for N≥ 300. Smaller Ne clusters exhibit a liquid like behaviour. When doping is strong, small Rg_m-clusters (Rg = Xe, Kr, Ar, m≤10 ²) are formed in the interior sites of the host cluster made of Ne or He. Specific electronically excited states, assigned to interface excitons are observed. Their absorption bands appear and shift towards lower energy when the cluster size m increases, according to the Frenkel exciton model. The characteristic bulk excitons appear in the spectra, only when the cluster radius exceeds the penetration depth of the interface exciton, which can be considerably larger than that in free Rg_m clusters. This effect is sensitive to electron affinities of the guest and the host cluster.     

A KrF fast discharge laser in mixtures containing NF3, N2F4 or SF6

A fast discharge KrF laser system (λ = 248.5 nm) has been operated at 25 mJ/pulse, 3.0 MW peak power in high pressure He: Kr: fluoride mixtures containing low concentrations of both krypton and the fluorine donors N₂F₄, NF₃ and SF₆. Lasing action is reported for the first time in N₂F₄ and SF₆ with optimum energy output at 750 and 160 mJ/l respectively.