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The spatial distributions of the intensity of fluorescent light emitted from neon and nitrogen excited with 12 keV electron beams at gas pressures from 250 to 1400 hPa are measured. The CASINO program, which performs Monte Carlo simulations of electron scattering, has offered a simple and relatively precise method to predict the spatial distribution of the light emitting species created by low energy electron beams in dense gas.

Single-photon ionization (SPI) using vacuum ultraviolet (VIN) light produced by an electron beam pumped rare gas excimer source has been coupled to a compact and mobile time-of-flight mass spectrometer (TOFMS). The novel device enables real-time on-line monitoring of organic trace substances in complex gaseous matrixes down to the ppb range. The pulsed VUV radiation of the light source is employed for SPI in the ion source of the TOFMS. Ion extraction is also carded out in a pulsed mode with a short time delay with respect to ionization. The experimental setup of the interface VUV light source/ time-of-flight mass spectrometer is described, and the novel SPI-TOFMS system is characterized by means of standard calibration gases. Limits of detection down to 50 ppb for aliphatic and aromatic hydrocarbons were achieved. First on-line applications comprised real-time measurements of aromatic and aliphatic trace compounds in mainstream cigarette smoke, which represents a highly dynamic fluctuating gaseous matrix. Time resolution was sufficient to monitor the smoking process on a puff-by-puff resolved basis. Furthermore, human breath analysis has been carded out to detect differences in the breath of a smoker and a nonsmoker, respectively. Several well-known biomarkers for smoke could be identified in the smoker's breath. The possibility for even shorter measurement times while maintaining the achieved sensitivity makes this new device a promising tool for on-line analysis of organic trace compounds in process gases or biological systems.

The application of soft ionization methods for mass spectrometry (MS), such as single-photon ionization (SPI) using vacuum ultraviolet (VUV) light, provides powerful analytical instrumentation for real-time on-line monitoring of organic substances in gaseous matrixes. A compact and mobile quadrupole mass spectrometer (QMS) system using a novel electron beam pumped rare gas VUV lamp for SPI has been developed for on-line analysis of organic trace compounds (ppb concentrations). The VUV radiation of the light source is employed for SPI in the ion source of the QMS. The concept of the interfacing of the VUV light source with the QMS is described and the SPI-QMS is characterized. On-line detection limits down to 50 ppb for benzene, toluene, and m-xylene were achieved. The instrument is well suited for continuous measurements of aromatic and aliphatic trace compounds and can therefore be used for on-line monitoring of trace compounds in dynamically fluctuating process gases. First measurements of gas standards, petrochemical samples, and on-line monitoring of automotive exhaust are presented.

Intense ([10.sup.11] particles/1[micro]s ~300 MeV/u) heavy ion beams are generated in the heavy-ion synchrotron (SIS) of the GSI-Darmstadt facility. Large volumes of strongly coupled plasmas are produced by heavy ion beam interaction with solid targets, with plasma densities close to the solid state, pressures of about 100 kbar, and temperatures of up to 1 eV, with relevance for equation of state (EOS) of matter, astrophysics, and low-entropy shock compression of solids. The plasmas created by ion beam interaction with metallic converters and cryogenic crystals were studied by backlighting shadowgraphy and by time-resolved spectroscopy in the visible and vacuum ultraviolet ranges. Low entropy weak shockwaves waves induced by the ion beams in the metal-plexiglass multilayered targets were visualized by time resolved schlieren measurements, revealing induced multiple shockwaves with pressures higher than 15 kbar in a plexiglass window and propagation velocities up to 35% higher than the speed of sound in plexiglass at room temperature. To get an insight into the plasma dynamics, both types of experiments are simulated by the BIG-2 two-dimensional hydrodynamic code. Index Terms--Heavy ions, shock compression, strongly coupled plasma.

Fast on-line detection of organic compounds from complex mixtures, such as industrial process gas streams, require selective and sensitive analytical methods. One feasible approach for this purpose is the use of mass spectrometry (MS) with a selective and soft (fragment-free) ionization technique, such as chemical ionization (CI) or photo ionization (PI). Single photon ionization (SPI) with vacuum ultraviolet (VUV) light is a particularly soft ionization technique, well-suited for detection of both aromatic and aliphatic species. Problematic, however, is the generation of the VUV light. In general, the vacuum ultraviolet (VUV) light sources for SPI-MS are based either on lasers (e.g., 118-nm radiation generated by frequency-tripling of the third harmonic of a Nd:YAG laser) or on conventional VUV lamps, such as deuterium lamps. Although the laser-based techniques are very sophisticated and expensive, the conventional lamps have serious drawbacks regarding their optical parameters, such as low-output power, low spectral power density, and broad emission bands. In this work, a novel excimer VUV light source, in which an electron beam is used to form rare gas excimer species, is used. The excimer VUV light source produces brilliant and intense VUV light. The novel VUV light source was coupled to a compact and mobile time-of-flight mass spectrometer (TOFMS). A special interface design, including optical (VUV optics) as well as electronic measures (e.g., pulsed ion extraction) was realized. The use of the excimer VUV lamp for SPI will allow the realization of very compact, rugged, and sensitive SPI-TOFMS devices, which preferably will be adapted for process analytical application or monitoring issues (e.g., chemical warfare detection). The excimer VUV-lamp technology delivers VUV light with a good beam quality and highoutput power at low costs. Furthermore, it allows changing the emitted wavelength as well as the bandwidth of the excimer VUV lamp in the 100-200-nm region by changing the gas filling. Consequently, SPI-TOFMS with an excimer light source is a fast detection technique that can be used for online monitoring, for example, in environmental studies or industrial manufacturing processes. In this paper, technology and characteristics of the new excimer light source, as well as the combination with the TOFMS, are presented. Furthermore, a first characterization of the SPI-TOFMS instrument, regarding analytical parameters such as detection limits and selectivity, is given. This includes a discussion of potential improvements that probably will be achievable within a future prototype generation. Finally, first applications of the system for on-line measurement of organic trace species in a complex gas mixture (here, motorcycle exhaust gas) are presented.

A new study uses a continuous wave electron beam to investigate energy flow, radiative decay and reaction rates in continuous wave rare gas-halogen systems.

A 1.73 micrometer xenon-iodide infrared laser is used to demonstrate the idea of using low-energy electron beams for pumping laser systems in dense gases to achieve high specific power deposition. SiNx ceramic foils of 300 nm-width were used as entrance window in a traverse geometry resulting in a configuration that permits several atmospheres in pressure differentials with only a minimum of energy being lost during the transmission.

Evaporations of dense gas obtained by heavy ion pumping from a surface of solid xenon yields spontaneous emission on the excimer continuum of the second xenon at a wavelength of 172 nanometers. The experiment involves a 3.78 MeV Kr+ pulsed beam obtained from a quadrupole accelerator with a radio-frequency. An ultraviolet spectral zone with a vacuum employs excimer emissions as a good source of light.

Continuous 8–15 keV electron beams were used to excite Ne, Ar, Kr, and Xe at pressures ranging from 75 to 1400 hPa. Conversion efficiencies of the energy deposited by the electron beam in the gas to vacuum ultraviolet light emitted from excimers are obtained. At pressures above 500 hPa, the efficiencies show constant values of 0.31±0.06 for Ne, 0.33±0.04 for Ar, 0.42±0.05 for Kr, and 0.42±0.05 for Xe. Apparent energy conversion efficiencies for practical devices utilizing this excitation technique are also reported. [ABSTRACT FROM AUTHOR]

Energy- and charge-transfer processes in neon-hydrogen mixtures (500–1400 hPa neon and 0.001–3 hPa hydrogen partial pressures) excited by a pulsed low-energy (∼10 keV) electron beam were investigated using time-resolved spectroscopy. Time spectra of the hydrogen Lyman-α line, neon excimer emission (second continuum), and neon atomic lines (3p–3s transitions) were recorded. The time-integrated intensity of the Lyman-α emission was measured for the same range of gas mixtures. It is shown that direct energy transfer from Ne2* excimers and neon atoms in the four lowest excited states as well as recombination of H3+ ions are the main channels populating atomic hydrogen in the n=2 state. A rate constant of (4.2±1.4)×10-11 cm3 s-1 was obtained for the charge transfer from Ne2+ ions to molecular hydrogen. A lower limit for the depopulation rate constant of Ne2* excimers by molecular hydrogen (combination of energy transfer and ionization) was found to be 1.0×10-10 cm3 s-1. [ABSTRACT FROM AUTHOR]

The ratio of the scintillation intensity in the near-infrared (NIR) and in the vacuum-ultraviolet (VUV) from liquid argon with a volumetric fraction of of xenon (10 ppm) was studied with ion-beam excitation. Hydrogen, lithium, carbon, sulfur, and iodine ions from the Munich Tandem accelerator were used for excitation. Average linear energy transfer (LET) values from 4.4 to 3500 MeV /mm were tested by the experiments. A variation of the NIR to VUV intensity ratios by a factor of 20 was observed. This is a promising result for the development of liquid argon-xenon detectors with sole optical particle identification and background reduction in rare-event physics. The results are interpreted on the basis of energy deposition around the particle tracks. [ABSTRACT FROM AUTHOR]