Source optics

Spectroscopic methods for the deterrnination of impurities in niobium include the older arc and spark emission procedures (53) along with newer inductively coupled plasma source optical emission methods (54). Some work has been done using inductively coupled mass spectroscopy to determine impurities in niobium (55,56). X-ray fluorescence analysis, a widely used method for niobium analysis, is used for routine work by niobium concentrates producers (57,58). Paying careful attention to matrix effects, precision and accuracy of x-ray fluorescence analyses are at least equal to those of the gravimetric and ion-exchange methods. 

When the spectral characteristics of the source itself are of primary interest, dispersive or ftir spectrometers are readily adapted to emission spectroscopy. Commercial instmments usually have a port that can accept an input beam without disturbing the usual source optics. Infrared emission spectroscopy at ambient or only moderately elevated temperatures has the advantage that no sample preparation is necessary. It is particularly appHcable to opaque and highly scattering samples, anodized and painted surfaces, polymer films, and atmospheric species (135). The interferometric... 

Radiation sources (optical), 664 Raies ultimes 759 Reagents 104... 

The main features of f.a.b.-m.s. are shown schematically in Fig. 1. The hardware consists of (i) an atom gun (or ion gun, see later) which is either mounted on the source housing of the mass spectrometer or, if small enough, inside the housing on the source itself, (it) a sample probe to the end of which is attached a small metal target onto which the sample is loaded, and (Hi) suitable source-optics for the efficient extraction of ions into the analyzer of the mass spectrometer. 

A modern spectrophotometer (UV/VIS, NIR, mid-IR) consists of a number of essential components source optical bench (mirror, filter, grating, Fourier transform, diode array, IRED, AOTF) sample holder detector (PDA, CCD) amplifier computer control. Important experimental parameters are the optical resolution (the minimum difference in wavelength that can be separated by the spectrometer) and the width of the light beam entering the spectrometer (the fixed entrance slit or fibre core). Modern echelle spectral analysers record simultaneously from UV to NIR. 

Plasma sources were developed for emission spectrometric analysis in the late-1960s. Commercial inductively coupled and d.c. plasma spectrometers were introduced in the mid-1970s. By comparison with AAS, atomic plasma emission spectroscopy (APES) can achieve simultaneous multi-element measurement, while maintaining a wide dynamic measurement range and high sensitivities and selectivities over background elements. As a result of the wide variety of radiation sources, optical atomic emission spectrometry is very suitable for multi-element trace determinations. With several techniques, absolute detection limits are below the ng level. 

In recent years, the evolution of the technological components required for IR sensor systems has been denoted by a significant miniaturisation of light sources, optics and detectors. Essentially, an IR sensor consists of (i) a polychromatic or monochromatic radiation source, (ii) a sensor head and (iii) a spectral analyser with a detector. As sensors where all optical elements can be included in the sensor head are the exception rather than the rule, also various optics, waveguides and filters may form essential parts of IR-optical chemical sensors. Another important building block, in particular when aiming at sensors capable of detecting trace levels, are modifications of the sensor element itself. 

One promising application for C60 is as an optical limiter. Optical limiters are used to protect people and materials from damage by high light intensities usually associated with intense pulsed sources. Optical limiting is accom-... 

The EXAFS oscillations arc suj rimposed on a smooth but much larger background absorption resulting from the electronic excitation of the metal atom. Thus, high quality EXAFS data cannot be obtained imless most stringent experimental conditions are met in terms of x-ray source, optics and detectors. In this section, some of these aspects are discussed. 

Studies of atmospheric properties using IR spectroscopy techniques have been reported in the literature for nearly 100 years. This paper presents a brief historical review of the development of this area of science and discusses the common features of spectrographic instruments. Two state of the art instruments on opposite ends of the measurement spectrum are described. The first is a fast response iri situ sensor for the measurement of the exchange of CO2 between the atmosphere and the earth s surface. The second is a rocketborne field-widened spectrometer for upper atmosphere composition studies. The thesis is presented that most improvements in current measurement systems are due to painstakingly small performance enhancements of well understood system components. The source, optical and thermal control components that allow these sensors to expand the state of the art are detailed. Examples of their application to remote canopy photosynthesis measurement and upper atmosphere emission studies are presented. 

In the time-correlated single-photon counting (TCSPC) technique, the sample is excited with a pulsed light source. The light source, optics, and detector are adjusted so that, for a given sample, no more than one photon is detected. When the source is pulsed, a timer is started. When a photon reaches the detector, the time is measured. Over the course of the... 

Background correction and sample measurements are performed consecutively and, unless the original state of the sample is used for background correction, the specimen that is analyzed needs to be exchanged. Hence it is important that filling of material into any sample holder or reactor be reproducible. Specimen manipulation should not affect the relative positions of source, optics, sample holder and detector—these parts must remain in position, or their placement must be well defined. In general, instruments with integrating spheres are less sensitive than... 

Reactant medium Chiral source Optical differentiation... 

A typical IR spectrometer consists of the following components radiation source, sampling area, monochromator (in a dispersive instrument), an interference filter or interferometer (in a non-dispersive instrument), a detector, and a recorder or data-handling system. The instrumentation requirements for the mid-infrared, the far-infrared, and the near-infrared regions are different. Most commercial dispersive infrared spectrometers are designed to operate in the mid-infrared region (4000-400 cm ). An FTIR spectrometer with proper radiation sources and detectors can cover the entire IR region. In this section, the types of radiation sources, optical systems, and detectors used in the IR spectrometer are discussed. 

Recent developments of pulsed light sources, optical components, fast and sensitive detectors and electronic equipment for data collection and analysis have permitted the construction of numerous instruments, often commercially available, for the collection of luminescence data with excellent resolution in time, spectral distribution and space. The sensitivity has reached the ultimate level that allows the characterization of such properties for single molecules (see Section 3.13). Only an overview of some of these techniques is given here. 

Instrumentation consists of a light source, optical filters, the fiber-optic cable, a sensing zone (the fluorophore and ancillary membranes or reagents), and a detector. Lasers, xenon lamps, hydrogen, deuterium, mercury, and halogen... 

D. Basting (Ed.), Excimer Laser Technology Laser Sources, Optics, Systems and Applications, Lambda Physics, Gottingen, 2001. 

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