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The scintillation light of liquid argon has been recorded wavelength and time resolved with very good statistics in a wavelength interval ranging from 118 nm through 970 nm. Three different ion beams, protons, sulfur ions and gold ions, were used to excite liquid argon. Only minor differences were observed in the wavelength-spectra obtained with the different incident particles. Light emission in the wavelength range of the third excimer continuum was found to be strongly suppressed in the liquid phase. In time-resolved measurements, the time structure of the scintillation light can be directly attributed to wavelength in our studies, as no wavelength shifter has been used. These measurements confirm that the singlet-to-triplet intensity ratio in the second excimer continuum range is a useful parameter for particle discrimination, which can also be employed in wavelength-integrated measurements as long as the sensitivity of the detector system does not rise steeply for wavelengths longer than 190 nm. Using our values for the singlet-to-triplet ratio down to low energies deposited a discrimination threshold between incident protons and sulfur ions as low as ∼2.5 keV seems possible, which represents the principle limit for the discrimination of these two species in liquid argon. [ABSTRACT FROM AUTHOR]

The transmission of liquid argon has been measured, wavelength resolved, for a wavelength interval from 118 to 250 nm. The wavelength dependent attenuation length is presented for pure argon. It is shown that no universal wavelength independent attenuation length can be assigned to liquid argon for its own fluorescence light due to the interplay between the wavelength dependent emission and absorption. A decreasing transmission is observed below 130 nm in both chemically cleaned and distilled liquid argon and assigned to absorption by the analogue of the first argon excimer continuum. For not perfectly cleaned argon a strong influence of impurities on the transmission is observed. Two strong absorption bands at 126.5 and 141.0 nm with approximately 2 and 4 nm width, respectively, are assigned to traces of xenon in argon. A broad absorption region below 180 nm is found for unpurified argon and tentatively attributed to the presence of water in the argon sample. [ABSTRACT FROM AUTHOR]

table-top setup for characterizing gaseous and liquid scintillating material is described. The key part of the instrumentation is a 300 nm thin ceramic membrane made from silicon nitride and silicon oxide. Low energy electrons with 12 keV particle energy are sent through this membrane into the material to be tested. Both fully continuous and pulsed beams can be used. Time resolved optical spectroscopy is used as the diagnostic method. The fluorescence of nitrogen and solutions of liquid scintillation material are described as examples for applying the technique. [ABSTRACT FROM AUTHOR]

The temperature dependences of the quenching rate constants of the states N2 ( ${\rm C} \ {^{3}{ \rm \Pi }_{u}}$ v′=0,1) by N2 (X) and of the state N2 ( ${\rm C} \ {^{3}{ \rm \Pi }_{u}} \ v^{\prime}=0$) by O2 (X) are studied. Time-resolved light emission from the gas was analyzed in the temperature range from 300 K to 210 K keeping the gas at constant density. In case of quenching by N2 (X), the quenching rate constant for the vibrational level v′= 0 increases by (13 ±3)% with gas cooling whereas the quenching rate constant for v′= 1 decreases by (5.0 ±2.5)% in this temperature range. For quenching by O2 (X), the quenching rate constant decreases by (3 ±2)% with gas cooling. The temperature variation of the N2 (C 3Πu v′=0) emission intensity for pure nitrogen and dry air are calculated using the obtained quenching rate constants and is compared with the experimental data available in the literature. [ABSTRACT FROM AUTHOR]

The 1.73 μm XeI laser has been operated in a fully continuous mode using a table-top electron beam pumped laser setup. A 12 keV electron beam sent through a 300 nm thick silicon nitride membrane into a laser gas mixture of typically 600 mbar gas pressure was used for pumping. A low loss cavity was installed, resulting in a very low pumping power of 37 mW to reach laser threshold. The geometrical conditions for the laser setup such as the shape of the beam pumped volume and its overlap with the optical mode volume are discussed. The laser scheme has been clearly identified as a recombination laser scheme by operating the laser in pulsed mode and observing the time structure of the laser pulse. [ABSTRACT FROM AUTHOR]

Electron beams with particle energy of ~10 keV were sent through 300 nm thick ceramic (Si3N4 + SiO2) foils and the resulting electron energy distribution functions were recorded using a retarding grid technique. The results are compared with Monte Carlo simulations performed with two publicly available packages, Geant4 and Casino v2.42. It is demonstrated that Geant4, unlike Casino, provides electron energy distribution functions very similar to the experimental distributions. Both simulation packages provide a quite precise average energy of transmitted electrons: we demonstrate that the maximum uncertainty of the calculated values of the average energy is 6% for Geant4 and 8% for Casino, taking into account all systematic uncertainties and the discrepancies in the experimental and simulated data. [ABSTRACT FROM AUTHOR]

Continuous and pulsed 12 keV electron beams were used to excite nitrogen within a gas cell at pressures ranging from 10 to 1400 hPa. The pressure dependence of the ratio of photon fluxes for emission from vibrational levels v'=0 and 1 of the C 3Π u state has been studied. The results confirm the presence of a collisional excitation mechanism populating v'=0, 1 in addition to electron impact excitation. Rate constants of (1.27 ±0.04)×10-11 cm3s-1 [ v'=0] and (2.68 ±0.08)×10-11 cm3s-1 [ v'=1] were measured for C 3Π u quenching by ground state nitrogen. For electron beam conditions relative excitation efficiencies of 1:0.59:0.22 for vibrational levels 0, 1 and 2 were calculated. The recorded flux ratios are compared with the predictions given by a vibrational relaxation model. [ABSTRACT FROM AUTHOR]

A table-top set-up for studying gas kinetic processes in dense gases via time resolved optical spectroscopy is presented. The set-up uses low energy electron beams for gas excitation. A thin silicon nitride membrane separating the electron source and the gas cell allows to use electron energies as low as 10–15 keV. The electron source is operated in a fast pulsing mode with a pulse width of 5 ns and repetition rates up to 30 kHz. Light emission from the target gas sample is studied and time resolved photon counting is used to measure decay times and collisional rate constants for specific excited states. The experimental concept is applied to measure the rate constants for quenching of molecular nitrogen in the C 3Πu state (vibrational levels 0 and 1) by water vapour. Quenching rate constants of (7.1 ±0.7) × 10-10 s-1 cm3 and (6.7 ±0.7) × 10-10 s-1 cm3 were obtained for the C 3Πu (v = 0) and C 3Πu (v = 1) vibrational levels, respectively. [ABSTRACT FROM AUTHOR]

Optical gain on the 476.5 nm Ar II 4 p−4 s ion laser transition has been observed in argon-gas excited by 2.5 ns pulses of 90 MeVS ions with a repetition rate of 4883 Hz. The energy per pulse was 23 μJ. The projectiles were stopped in the target at pressures between 5 and 20 kPa. Gain was determined from a measured transient increase of the intensity of a 476.5 nm probe laser beam sent along the ion beam axis and back reflected by an aluminum foil. The maximum gain observed was (0.4±0.1)×10 at a target-gas pressure of 5 kPa. Control experiments using krypton as target-gas were performed and yielded a null result. The optical gain observed in argon is consistent with the result from an analysis of spectroscopic studies of rare-gas targets excited by heavy ion beams. [ABSTRACT FROM AUTHOR]

The peanut lectin (PNL) receptor density of the cell membrane and several metabolic parameters of cultured fibroblasts of normal human individuals and of patients with muscular dystrophy were measured by simultaneous two and three parameter flow cytometry. The PNL-receptor density was significantly decreased on muscular dystrophy fibroblasts (between 20.7 and 33.6%) as compared to normal fibroblasts. The cell volume, the esterase activity, the intracellular pH, and the percentage of proliferating cells of both types of fibroblasts were not significantly altered. The mean cell volume of different fibroblast cultures varied between 2500 and 6000μm. The concentration of the intracellular esterase activity of fibroblasts was low (0.169 relative units) as compared to lymphocytes and granulocytes of the peripheral blood (1.56 and 2.17 relative units). The fibroblasts had an acidic intracellular pH of 6.52 while lymphocytes and granulocytes had basic pH values of 7.30 and 7.17. Some of the fibroblasts were in the S+G2/M phase of the cell cycle (20%). The study shows that the measurement of biochemical parameters of vital and fixed single fibroblasts by flow-cytometry is of great interest for the recognition of differences between normal individuals and muscular dystrophy patients. [ABSTRACT FROM AUTHOR]

The emission of light from rare gas targets at pressures of more than 100 Pa excited by a pulsed heavy ion beam has been studied. The absolute intensity of several spectral lines has been measured as a function of time at different target gas pressures. Population densities, excitation cross sections, and rate constants for collisional quenching were determined from the line intensities and the lifetimes of the excited states. [ABSTRACT FROM AUTHOR]