ISBN: 9783896853738

[ED: Softcover], [PU: Wissenschaft & Technik Verlag, Inhaber Dr. Jrgen Groá / Wissenschaft + Technik Ve], This thesis discusses new developments and applications of a mobile laserphotoaco… Más…

[ED: Softcover], [PU: Wissenschaft & Technik Verlag, Inhaber Dr. Jrgen Groá / Wissenschaft + Technik Ve], This thesis discusses new developments and applications of a mobile laserphotoacoustic spectrometer for in-situ multicomponent of trace gases in different environments. The implementation of a novel highly sensitive, acoustically resonant multipass photoacoustic (PA) cell which is designed for flow mode operation in order to reduce absorption effects enables the detection of trace-gas concentrations down to the sub-ppbV (10-9 per volume or rather nmole/mole) level. The high sensitivity is demonstrated with measurements on 20 trace gases. For example, detection limits of 70 pptV (70*10-12 per volume) for ethene and for ammonia have been achieved with a line-tunable CO2 laser as pump source. This corresponds to a minimum measurable absorption coefficient amin(CO2) =2*10-9cm-1 for a signal-to-noise ratio (SNR) of 3. This limit compares favourably with other highly sensitive methods, notably intracativity photoacoustics, yet while retaining the large dynamic range as advantageous feature. The multicomponent capability of the system which mainly depends on the accessible spectral range for the detection of the infared absorption structures of the different compounds was considerably improved in comparision to a previous version of the set-up by the implementation of a second CO2 laser operated with the 13C16O2 isotope. Thus, the spectral range from 868 to 1088 cm-1 can now be covered with 132 different laser transitions (67 of the 12C16O2 laser and 65 of the 13C16O2 laser). The multicomponent capability is demonstrated with measurements on an air sample of unknown composition. The sample was taken during surgery on human tissue with a high-frequency (HF) electro knife in a hospital. The generated fume was analyzed with respect to toxic compounds. A total of 15 species could be identified. The mobility of our fully automated system is illustrated by in-situ studies performed on a steady flow of air from a fruit storage chamber. Continuous sequential measurements over serveral days on traces of ethene, methanol vapor, and ethanol vapor at ppmV concentrations in the presence of some percent of CO2 and H2O vapor yield valuable information on fermentation processes and fruit-storage conditions with the goal of storage in a dynamically controlled atmosphere. Furthermore, the implementation of the novel PA cell enables the use of other laser types with output powers in the mW range, e.g. recently developed quantum-cascade lasers (QCLs). These lasers are becoming available with emission wavelelengths between 3,5 and 19m. Their pulsed opertion near room temperature results in a average output power of typically a few mW, in a tuning range of a few wavenumbers and in a linewidth of 0,2 cm-1.QCLs with cryogenic cooling offer higher power, but are not well suited for a mobile system. We have used single-mode distributed feedback QCLs with emission wavelengths around 965 cm-1 and 980 cm-1 and tuning range of approximately 3 cm-1 for first measurements on CO2,methanol vapor and ammonia to demonstrate the system performance. The implementation of compact QCLs as pump sources resulted in a minimum measurable absorption coefficient amin(QCL)= 2.2+10-5cm-1 (SNR = 3), corresponding, e.g., to a detection limit of 0.3 ppmV for ammonia. Finally, the key features of the CO2 laser- and the QCL-operated PA spectrometers are compared, and the potential for QCL-based gas sensors is evaluated. 45 Abbildungen Sofort lieferbar, DE, [SC: 0.00], Neuware, gewerbliches Angebot, Offene Rechnung (Vorkasse vorbehalten)<

2001, ISBN: 9783896853738

[ED: Taschenbuch], [PU: Wissenschaft + Technik Ve], Neuware -, DE, [SC: 0.00], Neuware, gewerbliches Angebot, FixedPrice, 100, [GW: 226g], Offene Rechnung (Vorkasse vorbehalten), Sofortüb… Más…

[ED: Taschenbuch], [PU: Wissenschaft + Technik Ve], Neuware -, DE, [SC: 0.00], Neuware, gewerbliches Angebot, FixedPrice, 100, [GW: 226g], Offene Rechnung (Vorkasse vorbehalten), Sofortüberweisung, PayPal, Banküberweisung, Internationaler Versand<

ISBN: 9783896853738

[ED: Taschenbuch], [PU: Wissenschaft + Technik Ve], Neuware -, DE, [SC: 7.00], Neuware, gewerbliches Angebot, 205x147x12 mm, 100, [GW: 226g], PayPal, Offene Rechnung, Banküberweisung, Int… Más…

[ED: Taschenbuch], [PU: Wissenschaft + Technik Ve], Neuware -, DE, [SC: 7.00], Neuware, gewerbliches Angebot, 205x147x12 mm, 100, [GW: 226g], PayPal, Offene Rechnung, Banküberweisung, Internationaler Versand<

2001, ISBN: 9783896853738

[ED: Taschenbuch], [PU: Wissenschaft + Technik Ve], DE, [SC: 0.00], Neuware, gewerbliches Angebot, 100, [GW: 226g], Sofortüberweisung, PayPal, Banküberweisung

2001, ISBN: 9783896853738

[ED: Taschenbuch], [PU: Wissenschaft + Technik Ve], DE, Neuware, gewerbliches Angebot, 100, [GW: 226g], Sofortüberweisung, PayPal, Banküberweisung