Facility monitoring of chemical warfare agent simulants in air using an automated, field-deployable, miniature mass spectrometer

Vapors of four chemical warfare agent (CWA) stimulants, 2-chloroethyl ethyl sulfide (CEES), diethyl malonate (DEM), dimethyl methylphosphonate (DMMP), and methyl salicylate (MeS), were detected, identified, and quantitated using a fully automated, field-deployable, miniature mass spectrometer. Samples were ionized using a glow discharge electron ionization (GDEI) source, and ions were mass analyzed with a cylindrical ion trap (CIT) mass analyzer. A dual-tube thermal desorption system was used to trap compounds on 50:50 Tenax TA/Carboxen 569 sorbent before their thermal release. The sample concentrations ranged from low parts per billion [ppb] to two parts per million [ppm]. Limits of detection (LODs) ranged from 0.26 to 5.0 ppb. Receiver operating characteristic (ROC) curves are presented for each analyte. A sample of CEES at low ppb concentration was combined separately with two interferents, bleach (saturated vapor) and diesel fuel exhaust (1%), as a way to explore the capability of detecting the simulant in an environmental matrix. Also investigated was a mixture of the four CWA simulants (at concentrations in air ranging from 270 to 380 ppb). Tandem mass (MS/MS) spectral data were used to identify and quantify the individual components.     

Subnanosecond collapse and pinch dynamics at the plasma focus

Compression and pinch phase at the plasma focus were investigated by streak camera observations of the visible emission. The duration of maximum local compression provides no evidence for magnetic confinement of the focus plasma. With increasing hard X-ray intensity a decreasing of the temporal evoution of the pinch phase is observed, indicating enhanced diffusion of magnetic field energy into the locally compressed plasma.     

Beiträge zur Grenzflächenchemie der Polyorganosiloxane

Ohne ZusammenfassungWir danken den Herren Dr.Gölitz und Dr.de Montigny für ihre Hilfe bei der Präparierung der organofunktionellen Siloxane. Bei der Herstellung der übrigen Präparate und der Auswertung der Messungen unterstützte uns Frl.Edith Geselle.     

Photoluminescence in hydrogenated amorphous germanium (a-Ge:H)

The photoluminescence of glow discharge deposited a-Ge:H is studied. The spectra exhibit a two-band structure with an intrinsic band centered at 0.65 eV and a defect induced band near 0.5 eV, which is enhanced by using less favorable deposition conditions (low substrate temperature) and by hydrogen effusion. Even in films of good quality the quantum efficiency is only about 1 % of that of good a-Si:H-films. It is suggested that the non-radiative recombination centers are Ge- dangling bonds and that the low efficiency as compared to a-Si:H-films of similar defect density is due to the larger localization length of the db-states which enhances radiationless tunneling processes.