Search

Abstract: Photoionization detector (PID) was developed for a sensitive on-site detection of trace amounts of volatile organic compounds (VOCs) based on an annular type ion collection electrode assembly. An ion collector with an annular geometry could detect more stable ion signals in the PID system when compared to the other types of ion collectors when an UV lamp of 10.6eV was used as an ionization source. In order to enhance the detection sensitivity, a pre-concentration system, which was developed by adopting a ceramic heater packed with rod shaped molecular sieves, was adopted for a detection of VOCs. The adopted ceramic heaters had a resistance of 10–20Ohm, and the temperature of the heater was optimized by controlling the heating time of the resistor. The enhancement of the detection sensitivity was found to be 8–10 times with the PID system when compared to the signals measured without a pre-concentrator. The overall detection sensitivity of the developed PID system was estimated as 10ppb or better. [Copyright &y& Elsevier]

Abstract: Isotope analysis of metal microparticles was performed by adopting a laser ionization mass spectrometry with slightly defocused ablation laser beam. The analyzed sample particles were Pb, Zn, Ni and Gd2O3. The sizes of particle size were 75, 50, 10, and <10μm, for Pb, Zn, Ni and Gd2O3, respectively. Sample particles were loaded onto a tantalum or zirconium sheet by using a Collodion. For large-sized particles such as Pb and Zn, a single particle was loaded on the metal sheet for a laser ablation, while several particles were loaded for particles with less than 10μm in size due to a limitation in the particle handling technique. An isotope analysis was performed by a direct laser ionization followed by a mass analysis of the loaded samples with the Collodion using a 532nm laser. A slight defocusing of the adopted laser provided a longer time for the experiment with a single microparticle. The isotope abundances of the adopted elements were measured and the deviation from the natural abundance was calculated as less than 5–10% depending on samples used except for the minor isotopes. [Copyright &y& Elsevier]

Focuses on the direct observation of the 2'A[subg] state in unsubstituted hexatriene. Experimental details; Low energy portion of the excitation profile for resonantly enhanced 1+1 multiphoton ionization of cis-hexatriene.

We report vibrationally resolved S0→S1 excitation spectra and vibronic level decay times for the phenyl-substituted polyenes 1-phenylbutadiene and 1-phenylhexatriene seeded in supersonic He expansions. This information was obtained using one- and two-color resonance-enhanced multiphoton ionization techniques. The shift in the excitation energy of the lowest excited singlet state upon deuteration of the phenyl ring demonstrates that in 1-phenylbutadiene S1 is mainly an excitation of the benzene ring while in 1-phenylhexatriene S1 is mainly the 2 1Ag state of hexatriene. Analysis of the excitation spectrum of 1-phenylhexatriene shows that the spectrum contains contributions from two species, the trans,trans and the trans,cis isomers, whose 2 1Ag state excitation energies differ by about 155 cm-1. The lifetimes of 2 1Ag zero-point levels and, in particular, the activity of the C–C and C=C stretch vibrations are markedly different for the two isomers. From these results we obtain a picture of the influence that the phenyl group has on such aspects of the electronic structure of the 2 1Ag state of hexatriene as the effective conjugation length, the symmetry properties, and the fluorescence quantum yield. [ABSTRACT FROM AUTHOR]

An analytical procedure for the bulk analysis of environmental samples, consisting of decomposition of samples, acid digestion of the recovered materials, chemical separation of uranium and plutonium, and isotopic measurements by thermal ionization mass spectrometry and isotope dilution mass spectrometry. The determination of the total amount of uranium contained in four process blanks was performed to verify the reproducibility of the bulk analysis procedure. The analytical results of a simulated environmental sample prepared from certified reference materials met the qualification requirements of the network of analytical laboratories for bulk analysis. [ABSTRACT FROM AUTHOR]