Volume 80, Issue 3, March 2009
Index of content:
80(2009); http://dx.doi.org/10.1063/1.3082016View Description Hide Description
An imaging photoelectron photoion coincidence spectrometer at the vacuum ultraviolet (VUV) beamline of the Swiss Light Source is presented and a few initial measurements are reported. Monochromatic synchrotron VUV radiation ionizes the cooled or thermal gas-phase sample. Photoelectrons are velocity focused, with better than 1 meV resolution for threshold electrons, and also act as start signal for the ion time-of-flight analysis. The ions are accelerated in a relatively low, field, which enables the direct measurement of rate constants in the range. All electron and ion events are recorded in a triggerless multiple-start/multiple-stop setup, which makes it possible to carry out coincidence experiments at event frequencies. As examples, the threshold photoelectron spectrum of the argon dimer and the breakdown diagrams for hydrogen atom loss in room temperature methane and the chlorine atom loss in cold chlorobenzene are shown and discussed.
A system to investigate the remediation of organic vapors using microwave-induced plasma with fluidized carbon granules80(2009); http://dx.doi.org/10.1063/1.3089823View Description Hide Description
This article describes a system to investigate the parameters for the remediation of organic vapors using microwave-induced plasma on fluidized carbon granules. The system is based on a single mode microwave apparatus with a variable power (2.45 GHz) generator. Carbon granules are fluidized in a silica tube situated in the sample section of a waveguide incorporating two additional ports to allow plasma intensity monitoring using a light sensor and imaging with a digital camera. A fluoroptic probe is used for in situmeasurement of the carbon granule temperature, while the effluent gas temperature is measured with a thermocouple situated in the silica tube outside the cavity. Data acquisition and control software allow experiments using a variety of microwave power regimes while simultaneously recording the light intensity of any plasma generated within the carbon bed, together with its temperature. Evaluation using two different granular activated carbons and ethyl acetate, introduced as a vapor into the fluidizing air stream at a concentration of 1 ppm, yielded results which indicated that significant destruction of ethyl acetate, as monitored using a mass spectrometer, was achieved only with the carbon granules showing high plasma activity under pulsed microwave conditions. The system is therefore suitable for comparison of the relative microwave activities of various activated carbon granules and their performance in microwave remediation and regeneration.
80(2009); http://dx.doi.org/10.1063/1.3096296View Description Hide Description
A novel fiber sensor for measuringsolidsolubilities of salt-water systems in situ is described. The sensor consists of a diode laser as light source, three couplers, two sensing fiber ends with protective cladding, and two photodetectors. The measurement principle is based on relative Fresnel reﬂective intensity. This method enabled us to observe in situ transitional process of the equilibration of a solid-liquid system with a small quantity of specimens. By the relatively simple technique, fast determination of the solidsolubility is possible. We applied this method to measure a temperature dependence of the solubility of potassium chloride in water in situ and compared with the previous data obtained by other techniques. The measured result has the long-term standard deviation of the concentration of 0.1%, and agrees with the data obtained by the classical method within the error of ±1%. This method is precise and sample saving and is suitable to measure the solubilities of rare and expensive materials.
A new instrument for thermal electron attachment at high temperature: and attachment rate constants up to 1100 K80(2009); http://dx.doi.org/10.1063/1.3097185View Description Hide Description
A new high temperature flowing afterglow Langmuir probe (HT-FALP) apparatus is described. A movable Langmuir probe and a four-needle reactant gas inlet were fitted to an existing high temperature flowing afterglow apparatus. The instrument is suitable for study of electron attachment from 300–1200 K, the upper limit set to avoid softening of the quartzflow tube. We present results for two reactions over extended ranges: (300–900 K) and (600–1100 K). Electron attachment rate constants for had been measured earlier using our conventional FALP apparatus. Those measurements were repeated with the FALP and then extended to 900 K with the HT-FALP. attaches electrons too weakly to study with the low temperature FALP but reaches a value of at 1100 K. is produced in attachment at all temperatures and in attachment, as determined by a quadrupole mass spectrometer at the end of the flow tube. Future modifications to increase the plasma density should allow study of electron-ion recombination at high temperatures.