Laser Applications to Chemical Analysis最新文献

{"title":"Time-resolved Thermometry in a Condensing Laser-ablated Copper Plasma Plume by Doppler-resolved Laser Induced Fluorescence","authors":"D. Zerkle, A. Sappey","doi":"10.2514/6.1994-2442","DOIUrl":"https://doi.org/10.2514/6.1994-2442","url":null,"abstract":"Doppler-resolved laser-induced fluorescence (LIF) excitation scans of the Cu atom ground state are used for thermometry in laser-ablated plasma plumes. The resulting LIF line shape is analyzed by fitting Voigt profiles to determine the Doppler width of the transition which then yields directly, translational temperature. Temperature is an extremely important parameter in determining the rate and extent of condensation occurring in metal vapor plumes such as the copper plumes which we have been studying. The other seminal controlling parameter, density, has been determined using a combination of hook spectroscopy and planar laser-induced fluorescence (PLIF) as described in several preceding papers1,2 and a newer, more extensive study which is to be published3. In this work, the plume is produced by excimer laser bombardment of an OFC copper target rotating in a vacuum chamber (308 nm, > 20 J/cm2, 1-5 GW/cm2). The copper plasma plume expands rapidly into a helium or argon background gas at pressures of 1 and 10 torr. Scans with 25 torr of background gas yield no useful data as a result of various broadening mechanisms which make fitting unique Voigt profiles difficult. We find that plumes expanding into argon are kinetically hotter and cool more slowly than those in helium. For example, temperatures in 1 torr of helium and delay times between the ablation and probe pulses of 0.5, 1.0 and 3.0 msec are 1800 ± 250 K, 1600 ± 200 K, and 1300 ± 150 K , while temperatures in 1.0 torr of argon for identical delays are 3900 ± 700 K, 3000 ±350 K, and 2600 ± 250 K. In 10 torr of helium, the temperatures are 300 ± 150 K, 300 ± 300 K, and 300 ± 300 K for delays of 0.2, 0.5, and 1.0 msec; whereas temperatures for the identical delay times in argon background gas at 10 torr are 2000 ± 350 K, 1600 ± 200 K, and 1000 ± 100 K. This result helps to explain our earlier observation that the rate of disappearance of Cu atom due to condensation reactions in these plumes is faster in helium than in argon as well as the more general observation that forming clusters and particulate in argon is not as easy as in helium3,4. Physically, this likely results from the higher thermal conductivity of helium relative to argon making helium better suited at removing the excess heat from the plume.","PeriodicalId":252738,"journal":{"name":"Laser Applications to Chemical Analysis","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134261795","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Suppression of scattering resonances in inhomogeneous microdroplets","authors":"D. Ngo, R. Pinnick","doi":"10.1364/JOSAA.11.001352","DOIUrl":"https://doi.org/10.1364/JOSAA.11.001352","url":null,"abstract":"Resonance structure in elastic scattering from microdroplets was first observed more than 15 years ago by Ashkin and Dziedzic1, who measured the time evolution of scattering from slowly evaporating optically levitated silicon oil droplets. On the heels of this discovery, Chylek et al2 identified the observed peaks in Ashkin’s data with predicted resonances in the Mie partial wave scattering amplitudes. Resonances were characterized as either transverse electric (TE1n) or transverse magnetic (TM1n) , having a mode number n and mode order 1 corresponding to the 1th resonance in the nth partial wave scattering amplitude. Since these early advances, the importance of these resonances (commonly called morphology dependent resonances or MDR’s) has been recognized not only in elastic scattering, but also in inelastic scattering processes3.","PeriodicalId":252738,"journal":{"name":"Laser Applications to Chemical Analysis","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131493182","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Zeeman Laser Interferometry for Detection and Chemical Analysis","authors":"R. Johnston","doi":"10.1364/laca.1994.thb.5","DOIUrl":"https://doi.org/10.1364/laca.1994.thb.5","url":null,"abstract":"Zeeman Laser Interferometry Zeeman laser interferometry [1-3] relies on use of a two-frequency, Zeeman effect laser. This helium-neon laser uses a carefully controlled magnetic field to cause a Zeeman energy level splitting inside the laser plasma tube. As a result, the laser emits two collinear laser lines with orthogonal linear polarizations. The two laser lines have a wavelength near λ = 632.8 nm, and differ by only 250 kHz in frequency.","PeriodicalId":252738,"journal":{"name":"Laser Applications to Chemical Analysis","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122909189","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Trace Organic Chemical Detection Using an Ultraviolet Excitation Molecular Beam Fluorometer","authors":"B. Preppernau, P. Hargis","doi":"10.1364/laca.1994.tub.5","DOIUrl":"https://doi.org/10.1364/laca.1994.tub.5","url":null,"abstract":"Detection of air-borne environmental contaminants, such as organic solvents, requires unambiguous compound identification and sensitivity to concentrations below those permitted by regulating agencies. One promising detection approach uses a pulsed supersonic molecular beam vacuum expansion in combination with fluorescence signal spectral analysis to identify species in a chemical mixture. Expanding a contaminated atmospheric sample through a supersonic molecular beam expansion acts to cool the sample and greatly reduce the spectral density in a fluorescence or photoionization spectrum. Most organic contaminants of interest have electronic transitions in the ultraviolet with near-featureless broad band fluorescence spectra when recorded at atmospheric pressure and room temperature. By using a supersonic vacuum expansion, cooling to within a few degrees of absolute zero can reduce the effective rotational and translational temperatures of the sample molecules and provide a sharply defined spectra which can be used to unambiguously identify specific molecules and their concentrations.","PeriodicalId":252738,"journal":{"name":"Laser Applications to Chemical Analysis","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122316532","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Molecular Oxygen Detection Using Frequency Modulation Diode Laser Spectroscopy","authors":"Liang-guo Wang, G. Sachse","doi":"10.1364/laca.1990.wa8","DOIUrl":"https://doi.org/10.1364/laca.1990.wa8","url":null,"abstract":"There are a variety of industrial and research applications for molecular oxygen (O2) sensors. Most existing oxygen sensors, however, are either intrusive and have slow response (e.g. electrochemical methods and mass spectrometry) or are expensive (e.g. UV laser-induced fluorescence). An attractive method for detecting O2 that is both non-intrusive and relatively inexpensive was first demonstrated by Kroll et al1 and involves the use of wavelength modulation (at 5 KHz) spectroscopy techniques with a GaAlAs diode laser. In this paper we extend this earlier work by making spectroscopic measurements of O2 using high frequency (≈1 GHz) modulation of GaAlAs lasers. This so-called frequency modulation spectroscopy (FMS) technique has the potential for achieving near quantum noise limited sensitivity and time response on the order of microseconds.","PeriodicalId":252738,"journal":{"name":"Laser Applications to Chemical Analysis","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1990-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125313088","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Two-Photon-Excited Stimulated Emission from Atomic Hydrogen in Flames","authors":"J. Goldsmith","doi":"10.1364/JOSAB.6.001979","DOIUrl":"https://doi.org/10.1364/JOSAB.6.001979","url":null,"abstract":"Two-photon-excited stimulated emission (SE) has been studied in a variety of atomic and molecular systems for over a decade. However, the effect that SE may have on diagnostic applications of multiphoton-excited fluorescence (FL) detection, and the potential use of SE detection as a useful technique in its own right, have received little attention until a recent report describing SE from atomic oxygen in flames.1 In this summary, we describe two-photon-excited SE and FL measurements of atomic hydrogen in flames.","PeriodicalId":252738,"journal":{"name":"Laser Applications to Chemical Analysis","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1989-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129100036","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Robust Fitting of CARS Spectra for Temperature Measurement in Hostile Combustion Environments","authors":"D. Dunn-Rankin","doi":"10.1364/laca.1990.tuc3","DOIUrl":"https://doi.org/10.1364/laca.1990.tuc3","url":null,"abstract":"As Coherent Anti-Stokes Raman Scattering (CARS) becomes actively applied in complex, hostile, and practical combustion systems, the trade-off between reliability and accuracy of CARS temperature measurement becomes important. Noise in the CARS signal can undermine detailed spectral fitting techniques, leaving calculated temperatures somewhat uncertain. This paper uses the CARS fitting code developed at Sandia National Laboratories (Palmer, 1989) to explore the robustness of “quick” fit, or integral fitting methods, as a technique for avoiding the difficulties in fine detail fitting of noisy CARS data. The theoretical temperature resolution from such integral fitting is much lower than for detailed calculations, but the reliability of the temperature can be significantly improved.","PeriodicalId":252738,"journal":{"name":"Laser Applications to Chemical Analysis","volume":"60 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115681851","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Laser-Based Imaging Diagnostics For Combustion","authors":"R. Hanson, P. Paul, J. Seitzman, M. Lee, B. Mcmillin","doi":"10.1364/laca.1990.wa2","DOIUrl":"https://doi.org/10.1364/laca.1990.wa2","url":null,"abstract":"Laser-based combustion diagnostics which yield multi-dimensional data\u0000 sets (e.g., 2-D, 3-D or 2-D plus time) are currently under\u0000 .investigation in several laboratories. Work thus far has emphasized\u0000 Planar Laser-Induced Fluorescence (PLIF), owing particularly to its\u0000 signal strength and species sensitivity, but alternative sensing\u0000 strategies based on Rayleigh, Raman and degenerative four-wave mixing\u0000 (DFWM) concepts are also of interest. In all cases, significant\u0000 progress is being made owing to advances in laser systems, solid-state\u0000 camera technology and improved understanding of laser-gas\u0000 interactions, especially at high spectral intensities.","PeriodicalId":252738,"journal":{"name":"Laser Applications to Chemical Analysis","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126023436","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Application of UV Laser-Produced Microplasmas as a Novel Detector for Gas Chromatography","authors":"A. Miziolek, Jeffrey B. Morris, B. Forch","doi":"10.1364/laca.1990.tua2","DOIUrl":"https://doi.org/10.1364/laca.1990.tua2","url":null,"abstract":"Earlier work in our laboratory has demonstrated the unusual ability of UV lasers to produce microplasmas in gaseous flows using very low pulse energies (< 1 mJ). One of the reasons that this pulse energy requirement is so low is that there are strong resonance effects in the production of the seed electrons necessary for microplasma growth. One application of this phenomenon is to use microplasma formation in the effluent gases of a gas chromatograph (GC) as the basis for a new GC detector.","PeriodicalId":252738,"journal":{"name":"Laser Applications to Chemical Analysis","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122188955","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Laser-Induced Sorption at Silicon Surface in Liquid","authors":"V. Beklemyshev, Y. Petrov, A. Prokhorov, V. Pustovoy","doi":"10.1364/laca.1990.tuc6","DOIUrl":"https://doi.org/10.1364/laca.1990.tuc6","url":null,"abstract":"The laser radiation action upon the surface of a solid gives rise to\u0000 different changes of both the system itself and the reactions running\u0000 with the surface participation. Among the most studied processes are\u0000 laser-induced catalytic reactions, alloying, etching, etc. To a less\u0000 extent is studied the influence of laser radiation upon the surface of\u0000 a semiconductor immersed into water.","PeriodicalId":252738,"journal":{"name":"Laser Applications to Chemical Analysis","volume":"55 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129780208","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}