Source Of Vacuum Ultraviolet Radiation Research Articles

Discharge in a Nonhomogeneous Gas Flow Sustained by Powerful Novosibirsk Free Electron Laser Emission as a Point-Like Source of Vacuum Ultraviolet Radiation

Discharge in a Nonhomogeneous Gas Flow Sustained by Powerful Novosibirsk Free Electron Laser Emission as a Point-Like Source of Vacuum Ultraviolet Radiation

Interaction Study of Energetic Protons and Electrons with the Vacuum Ultra Violet Source used in the Complex Irradiation Facility

Context: One important factor to be considered for space missions is the radiation environment. It is composed of energetic particles, such as protons, electrons and ions, and electromagnetic radiation, photons ranging from Vacuum Ultra Violet (VUV) to Far Infrared (FIR). Each of these radiation sources have an unique energy spectrum that further depends on the location inside the solar system, e. g. Earth orbits or interplanetary space.For material qualification and material engineering, individual irradiation is considered and their effects are superimposed. However, effects occurring when two and more radiation types simultaneously are present have barely been investigated yet. Further complexity is added, when additional interactions take place due to laboratory hardware. Aims: This publication reports on the efforts made to analyse and measure the interaction of a VUV and corpuscular radiation sources. The aim is to quantify the deviations due to interactions and conclude consequences for the simultaneous operation of these radiation sources. Methods: In order to quantify the effects, the Complex Irradiation Facility (CIF), located at the DLR Bremen has been used. It connects proton and electron accelerators together with VUV and UV light sources to an ultra high vacuum chamber. The corpuscular and VUV radiation sources have been operated simultaneously. The reaction of the operation parameters, such as current measured with Faraday Cups (FC) has been tracked and post-processed. Results: It has been discovered, that protons considerably interact with the gas mixture used to operate the VUV source. This interaction decreases for higher beam intensities of the corpuscular irradiation. It was found, that this is likely due to protons ionizing gas atoms which are then measured by the FC as current. For electrons, this phenomena was not observed due to their smaller stopping power. The discovery restricts the acceleration factor of the CIF for proton together with VUV irradiation, but does not necessarily limit the range of application of the CIF depending on the requirements of the material and/or qualification test. Energy range of electrons stays unrestricted.

Barrier Discharge Excilamps with a Small-Diameter Exit Window and Their Application

The principle of operation and technical parameters of excilamps with a small-diameter output window from a series of portable narrow-band ultraviolet and vacuum ultraviolet radiation sources are described. An example of using a KrCl excilamp to excite photoluminescence of crystalline materials is given.

Applications of the gas discharge sustained by the powerful radiation of THz gyrotrons

The terahertz frequency range currently remains the least studied from the point of view of gas-discharge physics. Recent progress in its mastering is associated, first of all, with the creation of powerful sources of terahertz radiation - gyrotrons. Nevertheless, the discharge sustained by the powerful radiation of the terahertz frequency range is of interest not only from the fundamental point of view (because of its lack of knowledge), but also from the applied one. This paper presents results of investigations aimed at studying the point-like THz discharge as a source of vacuum ultraviolet radiation and at research of CW THz plasma torch existing at atmospheric pressure and therefore having promising applications in various fields: plasma medicine, plasma chemistry, material processing etc. It is shown that it is possible to create a point-like plasma in an inhomogeneous gas flow with the density above the cut-off one (4·1015 cm−3 for 0.67 THz). It has been demonstrated that such plasma is an effective source of VUV and EUV radiation. Investigations of the atmospheric plasma torch, sustained by CW sub-terahertz radiation (1 kW @ 0.26 THz), demonstrated the possibility of the creation dense non-equilibrium plasma (2·1015 cm−3) with electron temperature in the range from 1 to 2 eV.

Brunel harmonics generated from ionizing clusters by few-cycle laser pulses.

We study theoretically harmonic generation from ionizing nano-clusters irradiated by intense few-cycle laser pulses and identify a Brunel-type harmonic generation mechanism that originates from subcycle ionization dynamics in clusters. Compared to Brunel harmonics in gases, the spectra are shifted toward odd-order harmonics of Mie frequency ωM due to efficient excitation of Mie oscillations. Considering the appreciable single-cluster harmonic yield and the relaxed phase-matching condition in overdense clustered plasmas, clusters driven by few-cycle laser pulses can be a promising source of vacuum-ultraviolet radiation.

Transition radiation of fast electrons as a broadband vacuum-ultraviolet radiation source

The characteristics of a possible radiation source in the vacuum-ultraviolet and soft X-ray range based on the transition radiation of electrons with an energy of about 100 keV are calculated. The possibilities of enhancing the radiation yield in the geometry of the glancing interaction of electrons with a target are analyzed. The possibility of creating a source with a yield on the order of 10−5 photon/(eV sr) per electron is demonstrated.

Measurements of the intensities of vacuum ultraviolet radiation sources using the flow ionization chamber

A method for measuring the intensities of vacuum ultraviolet lamps in wavelength ranges of 105–147 nm and photon fluxes of 105–1015 photons/s is described. A flow ionization complete-absorption chamber operating under the atmospheric pressure is applied. As a working medium, a mixture of ionized volatile organic-substance vapors, methane or oxygen, and also nitrogen with a known component concentration is used. The flux value is determined from the measured ionization current, quantum ionization yield, and portion of radiation absorbed by the ionized substance.

Differentiation of microbial species and strains in coculture biofilms by multivariate analysis of laser desorption postionization mass spectra

7.87 to 10.5 eV vacuum ultraviolet (VUV) photon energies were used in laser desorption postionization mass spectrometry (LDPI-MS) to analyze biofilms comprised of binary cultures of interacting microorganisms. The effect of photon energy was examined using both tunable synchrotron and laser sources of VUV radiation. Principal components analysis (PCA) was applied to the MS data to differentiate species in Escherichia coli-Saccharomyces cerevisiae coculture biofilms. PCA of LDPI-MS also differentiated individual E. coli strains in a biofilm comprised of two interacting gene deletion strains, even though these strains differed from the wild type K-12 strain by no more than four gene deletions each out of approximately 2000 genes. PCA treatment of 7.87 eV LDPI-MS data separated the E. coli strains into three distinct groups, two "pure" groups, and a mixed region. Furthermore, the "pure" regions of the E. coli cocultures showed greater variance by PCA at 7.87 eV photon energies compared to 10.5 eV radiation. This is consistent with the expectation that the 7.87 eV photoionization selects a subset of low ionization energy analytes while 10.5 eV is more inclusive, detecting a wider range of analytes. These two VUV photon energies therefore give different spreads via PCA and their respective use in LDPI-MS constitute an additional experimental parameter to differentiate strains and species.

Flow-through ionization chamber for measuring the radiation intensity of VUV sources

This paper describes a device for measuring the radiation intensity of sources of vacuum ultraviolet radiation, consisting of a flow-through ionization chamber that operates in the total-radiation-absorption regime at atmospheric pressure. Examples of the use of this chamber to measure the radiation intensity of sealed photoionization lamps are described. The main advantage of the device is that it does not require periodic calibration or complex metrological assurance.

Capacitive-discharge VUV lamp based on a water-vapor–argon mixture

This paper presents the results of a study of the spectral characteristics of the plasma radiation (175–200 nm) of a pulse-periodic capacitive-discharge lamp that operates with a mixture of water vapor and argon. It is shown that capacitive discharge at low argon pressure is a broad-band source of vacuum ultraviolet radiation. The intensity of the emission bands of the capacitive-discharge plasma is optimized as a function of the partial pressures of argon and water vapor. The electron kinetic coefficients are calculated for a discharge in a mixture of argon and water vapor.

Coherent control of the ultrafast dissociative ionization dynamics of bromochloroalkanes

We report on the coherent control of the ultrafast ionization and fragmentation dynamics of the bromochloroalkanes C(2)H(4)BrCl and C(3)H(6)BrCl using shaped femtosecond laser pulses. In closed-loop control experiments on bromochloropropane (C(3)H(6)BrCl) the fragment ion yields of CH(2)Cl(+), CH(2)Br(+), and C(3)H(3)(+) are optimized with respect to that of the parent cation C(3)H(6)BrCl(+). The fragment ion yields are recorded in additional experiments in order to reveal the energetics of cation fragmentation, where laser-produced plasma radiation is used as a tunable pulsed nanosecond vacuum ultraviolet radiation source along with photoionization mass spectrometry. The time structure of the optimized femtosecond laser pulses leads to a depletion of the parent ion and an enhancement of the fragment ions, where a characteristic sequence of pulses is required. Specifically, an intense pump pulse is followed by a less intense probe pulse where the delay is 0.5 ps. Similarly optimized pulse shapes are obtained from closed-loop control experiments on bromochloroethane (C(2)H(4)BrCl), where the fragment ion yield of CH(2)Br(+) is optimized with respect to that of C(2)H(4)BrCl(+) as well as the fragment ion ratios C(2)H(2)(+)/CH(2)Br(+) and C(2)H(3)(+)/C(2)H(4)Cl(+). The assignment of the underlying control mechanism is derived from one-color 804 nm pump-probe experiments, where the yields of the parent cation and several fragments show broad dynamic resonances with a maximum at Δt = 0.5 ps. The experimental findings are rationalized in terms of dynamic ionic resonances leading to an enhanced dissociation of the parent cation and some primary fragment ions.

Photoionisation and structures of jet-formed toluene clusters

Here we report an experimental and computational study of toluene clusters that were formed in a He supersonic jet. A tunable vacuum ultraviolet radiation source was used to measure the ionisation potentials of dimers, trimers and tetramers from the onset of their photoionisation efficiency curves. DFT calculations were performed for different structures of stacked and non-stacked dimers and trimers as well as for a fully-stacked tetramer. Through comparison of the measured and calculated ionisation potentials, we show that under our experimental conditions, toluene nucleation starts from stacked dimers and proceeds through non-stacked trimers and tetramers.

Capillary Plasma Electrode Discharge as an Intense and Efficient Source of Vacuum Ultraviolet Radiation for Plasma Display

The characteristic properties of microscale capillary plasma electrode structures were experimentally investigated and compared to the dielectric barrier discharge (DBD) structure. The vacuum ultraviolet (VUV) emission from the capillary plasma electrode discharges (CPEDs) was more intense and more efficient than the one from the DBD. Based on VUV emission characteristics, it is confirmed that the CPED-based plasma display could be a possible candidate to find the breakthrough in the luminance and luminous efficiency of plasma display.

Development of vacuum ultraviolet radiation sources and their advanced applications

Development of vacuum ultraviolet radiation sources and their advanced applications

Mass-Analyzed Threshold Ionization Study of Vinyl Chloride Cation in the First Excited Electronic State Using Vacuum Ultraviolet Radiation in the 107−102.8 nm Range

Vibrational spectrum of vinyl chloride cation in the first excited electronic state, A2 A', was obtained by one-photon mass-analyzed threshold ionization (MATI) spectroscopy. Use of an improved vacuum ultraviolet radiation source based on four-wave sum frequency mixing in Hg resulted in excellent sensitivity for the MATI signals. From the MATI spectrum, the ionization energy to the A2 A' state of the cation was determined to be 11.6667 +/- 0.0006 eV. Nearly complete vibrational assignment for the MATI peaks was possible by utilizing the vibrational frequencies and Franck-Condon factors calculated at the DFT and TDDFT/B3LYP levels with the 6-311++G(3df,3pd) basis set. Geometry of the cation in the A2 A' state was determined by Franck-Condon fitting of the MATI spectrum.

Durable ultraviolet sensors using highly oriented diamond films

We fabricated vacuum ultraviolet (VUV) sensors using highly oriented diamond (HOD) films and studied their long-term stability to evaluate the feasibility of the sensors for practical use. The sensors are composed of a pair of interdigitated Pt electrodes on the HOD film surfaces, and sealed in the industrially standard can packages. Xenon (Xe) excimer lamps ( λ = 172 nm) and low-pressure mercury (Hg) lamps ( λ = 185 nm) were used as the radiation sources. It was demonstrated that the output signal of the sensors is reproducible and stable over 700 h under the intense VUV irradiation from Xe excimer lamps. The results of low-pressure Hg lamp measurements showed that the sensors were sensitive only to the 185-nm radiation irrespective of the presence of the 254-nm radiation that is five to ten times more intense than the 185-nm radiation. It is thus concluded that the present HOD film sensors make possible a continuous monitoring of the intense VUV radiation sources, and can be applicable to dry cleaning of silicon wafers or glass substrates in semiconductor industry and flat panel display manufacturing processes, respectively.

Mass-analyzed threshold ionization study of vinyl bromide cation in the first excited electronic state using vacuum-ultraviolet radiation generated by four-wave mixing in Hg

The vibrational spectrum of the vinyl bromide cation in the first excited electronic state A 2A' was obtained by one-photon mass-analyzed threshold ionization (MATI) spectroscopy. The use of an improved vacuum-ultraviolet radiation source based on four-wave sum frequency mixing in Hg resulted in excellent sensitivity for MATI signals. From the MATI spectrum, the ionization energy to the A 2A' state of the cation was determined to be 10.9150+/-0.0006 eV. Nearly complete vibrational assignments for the MATI peaks were possible by utilizing the vibrational frequencies and Franck-Condon factors calculated at the density-functional theory (DFT) and time-dependent DFT/B3LYP levels with the 6-311+G(df,p) basis set.

Dissociation of energy-selected c-C2H4S+ in a region 10.6–11.8 eV: Threshold photoelectron—photoion coincidence experiments and quantum-chemical calculations

Dissociation of energy-selected c-C2H4S+ was investigated in a region of 10.6-11.8 eV with a threshold photoelectron-photoion coincidence technique and a synchrotron as a source of vacuum ultraviolet radiation. Branching ratios and average releases of kinetic energy in channels of formation of c-C2H4S+, CH3CS+, and HCS+ were obtained from well-resolved time-of-flight peaks in coincidence mass spectra. Measured average releases of kinetic energy for channel CH3CS+ + H of least energy are substantial and much greater than calculated with quasiequilibrium theory; in contrast, small releases of kinetic energy near the appearance onset for channel HCS+ + CH3 agree satisfactorily with statistical calculations. Calculations of molecular electronic structures and energetics of c-C2H4S+ and C2H3S+ isomers and various fragments and transition states were also performed with Gaussian 3 method to establish dissociation mechanisms. A predicted dissociation energy of 11.05 eV for c-C2H4S --> HCS+ + CH3 agrees with a linearly extrapolated threshold at 10.99+/-0.04 eV and a predicted dissociation mechanism that c-C2H4S+ isomerizes to CH3CHS+ before dissociating to HCS+ + CH3 supports the experimental results. The large releases of kinetic energy for channel CH3CS+ + H might result from a dissociation mechanism according to which c-C2H4S+ isomerizes to a local minimum CH3CSH+ and then dissociates through a transition state to form CH3CS+ + H.

Stability of vacuum-ultraviolet radiometric transfer standards: Electron cyclotron resonance versus hollow cathode source

Established transfer standards such as Penning and hollow cathode discharge sources suffer from limited spectral range and, in particular, a limited lifetime and stability due to electrode erosion. The development of a vacuum-ultraviolet radiation source based on an electron cyclotron resonance (ECR)-created plasma might overcome these limitations. To test such a source with regard to its usefulness as radiometric transfer standard, the emission intensity of a Ne plasma was monitored over an operation period of 180 days, with regard to stability and reproducibility in the 50–75 nm wavelength range. For comparison and calibration, a hollow cathode was used as transfer standard traceable to the electron storage ring BESSY II as primary standard. It was found that the ECR source exceeded the lifetime of the hollow cathode source by far, offering a more balanced spectral emission line variety with similar stability.

Accurate Laboratory Wavelengths of the Vacuum Ultraviolet A ([FORMULA][F]v[SUP][/SUP][/F][/FORMULA]=3)- X ([FORMULA][F]v[SUP][/SUP][/F][/FORMULA]=0) Band of 12 C 17 O and 12 C 18 O

Six individual rotational lines (J'' ≤ 3) of 12C17O, as well as four of 12C18O, were detected in the A 1Π(v' = 3)-X 1Σ+(v'' = 0) vibronic band, and their wavelengths determined using neighboring 12C16O and 13C16O lines as reference. The measurements (fluorescence excitation spectra) were performed in a pulsed supersonic jet (Ar or Ne as carrier gas) employing a tunable pulsed vacuum ultraviolet radiation source with a narrow bandwidth (~5 GHz). The new spectral data on 12C17O and 12C18O are applied to the interpretation of recent vacuum ultraviolet observations of 12C17O and 12C18O in the interstellar medium.