Laser LIBS

To increase the radiation absorption and ionization efficiency of IR YAG-Nd laser (wave length - 1064 nm) used in for analysis of synthetic oxide single crystals Bi Ge O, Li MoO, LiB O, the samples were grounded and pills of 010 mm were pressed and analyzed by LIMS EMAL-2 (Uki aine) ... 

Different analytical techniques are used for detection of the elemental composition of the solid samples. The simplest is direct detection of emission from the plasma of the ablated material formed above a sample surface. This technique is generally referred to as LIBS or LIPS (laser induced breakdown/plasma spectroscopy). Strong continuous background radiation from the hot plasma plume does not enable detection of atomic and ionic lines of specific elements during the first few hundred nanoseconds of plasma evolution. One can achieve a reasonable signal-to-noise ra-... 

The intrinsic drawback of LIBS is a short duration (less than a few hundreds microseconds) and strongly non-stationary conditions of a laser plume. Much higher sensitivity has been realized by transport of the ablated material into secondary atomic reservoirs such as a microwave-induced plasma (MIP) or an inductively coupled plasma (ICP). Owing to the much longer residence time of ablated atoms and ions in a stationary MIP (typically several ms compared with at most a hundred microseconds in a laser plume) and because of additional excitation of the radiating upper levels in the low pressure plasma, the line intensities of atoms and ions are greatly enhanced. Because of these factors the DLs of LA-MIP have been improved by one to two orders of magnitude compared with LIBS. 

The potential of LA-based techniques for depth profiling of coated and multilayer samples have been exemplified in recent publications. The depth profiling of the zinc-coated steels by LIBS has been demonstrated [4.242]. An XeCl excimer laser with 28 ns pulse duration and variable pulse energy was used for ablation. The emission of the laser plume was monitored by use of a Czerny-Turner grating spectrometer with a CCD two-dimensional detector. The dependence of the intensities of the Zn and Fe lines on the number of laser shots applied to the same spot was measured and the depth profile of Zn coating was constructed by using the estimated ablation rate per laser shot. To obtain the true Zn-Fe profile the measured intensities of both analytes were normalized to the sum of the line intensities. The LIBS profile thus obtained correlated very well with the GD-OES profile of the same sample. Both profiles are shown in Fig. 4.40. The ablation rate of approximately 8 nm shot ... 

The depth profiling of the Cu-Ag-Si samples was performed with the laser beam focused on to the sample surface to the spot of approximately 30-40 pm. To obtain the best depth resolution the laser fluence was maintained near the 1 J cm level, close to the threshold of the LIBS detection scheme. The intensity profiles of Cu and Ag emission lines are shown in Fig. 4.43. The individual layers of Cu and Ag were defi-... 

The "soft" ablation of the TiN-TiAlN samples by the low fluence laser beam was performed by use of LA-TOF-MS. Because of the greater sensitivity of this technique compared with direct LIBS the lower laser fluence of approximately 0.3-0.4 J cm was used. One of the depth profiles, obtained by use of femtosecond LA-TOF-MS, is shown in Fig. 4.44. Each 280-nm-thick layer was ablated by approximately 20-25 pulses, which result in an average ablation rate of 11-14 nm pulse . The ablation rate was low enough for resolution of all layers. 

This chapter deals mainly with (multi)hyphenated techniques comprising wet sample preparation steps (e.g. SFE, SPE) and/or separation techniques (GC, SFC, HPLC, SEC, TLC, CE). Other hyphenated techniques involve thermal-spectroscopic and gas or heat extraction methods (TG, TD, HS, Py, LD, etc.). Also, spectroscopic couplings (e.g. LIBS-LIF) are of interest. Hyphenation of UV spectroscopy and mass spectrometry forms the family of laser mass-spectrometric (LAMS) methods, such as REMPI-ToFMS and MALDI-ToFMS. In REMPI-ToFMS the connecting element between UV spectroscopy and mass spectrometry is laser-induced REMPI ionisation. An intermediate state of the molecule of interest is selectively excited by absorption of a laser photon (the wavelength of a tuneable laser is set in resonance with the transition). The excited molecules are subsequently ionised by absorption of an additional laser photon. Therefore the ionisation selectivity is introduced by the resonance absorption of the first photon, i.e. by UV spectroscopy. However, conventional UV spectra of polyatomic molecules exhibit relatively broad and continuous spectral features, allowing only a medium selectivity. Supersonic jet cooling of the sample molecules (to 5-50 K) reduces the line width of their... 

ISFET Ion-selective field effect transistor LIBS Laser-induced breakdown... 

LIBS Acronym for laser-induced breakdown spectroscopy. 

Anglos, D. (2001), Laser-induced breakdown spectroscopy (LIBS) in art and archaeology, Appl. Spectrosc. 55(6), 186A-205A. 

Burgio, L., R. J. H. Clark, T. Stratoudaki, M. Doulgeridis, and D. Anglos (2000), Pigment identification in painted artworks A dual analytical approach employing LIBS (laser-induced breakdown spectroscopy) and Raman microscopy, Appl. Spectrosc. 54(4), 463-469. 

Melessanaki, K., S. Kotoulas, A. Petrakis, A. Hatziapostolou, D. Anglos, S. Ferrence, and P. P. Betancourt (2002), LIBS (laser induced breakdown spectroscopy) A new tool in archaeometry , Trends Opt. Photon. 81, 57-59. 

In recent years, several groups have proposed the use of Laser Induced Breakdown Spectroscopy as a technique capable of giving information on the pigment compositions with minimal damage of the artwork. However, until the development of quantitative methods for accurate elemental analysis, the LIBS technique was hardly competitive with other methods for quantitative analysis of the samples. 

The laser source is a Nd YAG pulsed laser, operating at 1064 nm, which delivers about 10 mJ on the sample surface, in 8 ns. The spatial lateral resolution of the LIBS measurements corresponds to the dimensions of the micro-crater left by the laser on the sample surface. The same dimensions are also a measurement of the damage induced on the pigment. A computer-enhanced enlargement of a typical laser crater is shown in Figure 2 its diameter does not exceed 10 pm, which is practically invisible at naked eye. The reduced size of the crater also allows for a high spatial resolution of the LIBS analysis. 

The LIBS spectral signal is detected using an Echelle spectrometer + iCCD camera, which provides the whole time-resolved NUV-NIR spectrum in a single laser shot. 

Vukjovic et al.199 recently proposed a simple, fast, sensitive, and low-cost procedure based on solid phase spectrophotometric (SPS) and multicomponent analysis by multiple linear regression (MA) to determine traces of heavy metals in pharmaceuticals. Other spectroscopic techniques employed for high-throughput pharmaceutical analysis include laser-induced breakdown spectroscopy (LIBS),200 201 fluorescence spectroscopy,202 204 diffusive reflectance spectroscopy,205 laser-based nephelometry,206 automated polarized light microscopy,207 and laser diffraction and image analysis.208... 

KEYWORDS Laser-induced breakdown spectroscopy, garnet, LIBS, multivariate principal components... 

The emerging analytical technique of laser-induced breakdown spectroscopy (LIBS) is a simple atomic emission spectroscopy technique that has the potential for real-time man-portable chemical analysis in the field. Because LIBS is simultaneously sensitive to all elements, a single laser shot can be used to record the broadband emission spectra, which provides a chemical fingerprint of a material. 

In LIBS analysis, a pulsed laser is focused on the gem surface. The laser energy ablates a small amount of gem material which burns in a short-lived plasma. As the plasma cools, excited electrons decay into lower-energy orbitals, releasing energy in the form of photons in the ultraviolet-visible-infrared range. This light is collected by optic fiber, diffracted, and recorded as a spectrum, generally between 200 and 1000 nm. 

This paper explores the trade-offs of gem damage during LIBS analysis and data quality under a variety of analytical conditions. Two lasers, a Big Sky Laser Technology (now Quantel USA) Nd-YAG nano-second laser operated at its fundamental wavelength of 1064 nm, and a Raydiance, Inc., pico-second laser operated at its fundamental wavelength of 1552 nm as well as harmonics at 776, 517.2, and 388 nm, are used in separate LIBS systems. Furthermore, the use of inert gas environment (He or Ar) is explored to increase peak intensities at lower laser power and sample damage. 

The pico-second laser causes significantly less damage to the stone than the nanosecond laser however, fewer trace element peaks may be observed in the pico-second LIBS spectra (Fig. 1). The sensitivity of the pico-second LIBS system to trace elements may be enhanced in Ar or He, with a better lens system than currently employed, or by using the harmonic wavelengths. These parameters are under investigation. 

Since the 1990s, orange sapphires that have been diffused with Be have been found on the gem market (Emmett et al. 2003). Similar to leaded rubies, Be-diffused sapphires are easy to detect with LIBS because natural sapphires have low concentrations of Be (Emmett et al. 2003). Figure 3 shows LIBS spectra of six sapphires, three of which show the presence of Be at the dominant 313.1 nm peak. Further analyses are underway, in order to compare the pico-second LIBS spectra to their nano-second counterparts, to test different harmonic wavelengths of the pico-second laser, and to explore the use of Ar or He environment to reduce damage and increase peak intensity. 

Laser ablation chemical analysis LIBS and LA-ICP-MS for geochemical... 

KEYWORDS laser ablation, LIBS, ICP-MS, real-time analysis, instrumentation... 

This presentation will summarize developments in laser ablation with emphasis on LIBS (laser induced breakdown spectroscopy) and inductively coupled plasma mass spectrometry (ICPMS) as analytical tools for real time chemical analysis (Fig. 1) (Russo et al. 

Gonzalez et al. 2008). Laser ablation is a direct sampling technique by which a high energy laser is focused on the surface of a material and atoms, ions, and particles are ejected. The particles, which are chemically representative of the bulk sample, are then transported into an ICPMS for analysis. In LIBS, a luminous, short-lived plasma is created on the sample surface by the focused laser beam and its emission spectra are analyzed to provide both qualitative and quantitative chemical compositional analysis (Cremers... 

This paper presents an overview of the current research issues and commercialization efforts related to laser ablation for chemical analysis, discusses several fundamental studies of laser ablation using time-resolved shadowgraph and spectroscopic imaging, and describes recent data using nanosecond laser pulsed ablation sampling for ICP-MS and LIBS. Efforts towards commercialization of field based LIBS systems also will be described. 

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