Laser instrumentation

Resonance ionization methods (RIMS) have also been explored for improving Th ionization efficiency for mass spectrometric measurement (Johnson and Fearey 1993). As shown in Figure 3, two lasers are required, a continuous resonant dye laser for resonance of thorium atoms, and a continuous UV argon laser for transition from resonance to ionization. Consequently, sophisticated laser instrumentation is required for these methods. 

The number of cellular parameters that can be evaluated simultaneously depends on the optical and electronic configuration of a given instrument. A flow cytometer may be a single-laser analyzer that can measure three fluorescence colors and two hght scatter parameters (five parameters), or a complex instrument with multiple lasers and detectors capable of recording signals for as many as 13 fluorescence colors (15 parameters) in individual cells. For example, two widely used single-laser instruments, the BD... 

The latter is particularly the case for laser instruments where attention to optical interfacing is essential, and often features specialized optical hber based optical coupling. 

In recent years, Raman spectroscopy has undergone a major transformation from a specialist laboratory technique to a practical analytical tool. This change was driven on several parallel fronts by dramatic advances in laser instrumentation, detectors, spectrometers, and optical filter technology. This resulted in the advent of a new generation of compact and robust Raman instruments with improved sensitivity and flexibility. These devices could be operated for the first time by non-specialists outside the laboratory environment. Indeed, Raman spectroscopy is now found in the chemical and pharmaceutical industries for process control and has very recently been introduced into hospitals. Handheld instruments are used in forensic and other security applications and battery-operated versions for field use are found in environmental and geological studies. 

Note that the examples above are over-simplifications to some extent, and other critical elements, such as optics, the associated electronics and the sampling interfaces are also important for a final implementation. The latter is particularly the case for laser instruments, where attention to optical interfacing is essential and often features specialized optical fiber-based optical coupling. 

NIR tunable diode laser instrument layouts. (Courtesy of Analytical Specialties for Norsk Elek-tro Optikk AS.)... 

Buker JF, Sample JD (1976) Tunable Diode Laser Instruments, ISA Reprint. Pittsburg, pp 76-613 Bulkin BJ (1976) Vibrational spectroscopy of liquid crystals. In Brown GH (ed) Advances in liquid crystals, vol 2. Academic, New York, p 199 Bulkin BJ (1981) Vibrational spectra of liquid crystals. In Clark RJH, Hester RE (eds) Advances in infrared and Raman spectroscopy, vol 8. Heyden, London, p 151 Bunker PR (1979) Molecular Symmetry and Spectroscopy. Academic Press, New York Bunow MR, Levin IW (1977a) Biochim Biophys Acta 464 202 Burch DE, Gryvnak DA (1967) J Chem Phys 47 4930... 

Ultrasonic-laser instruments can use short-pulse lasers (a few nanoseconds long) to generate ultrasound and long-pulse (tens of microseconds long) or continuous lasers, coupled to an optical interferometer for the detection of US (I.e. the corresponding mechanical displacements) [22]. 

Acoustic microscopy. Although this technique is mainly used in the medical field, various interesting analytical applications have been developed and analytical chemists are encouraged to contribute new ones by exploiting advances in instrumentation in this field. An aooustic microscope, which also constitutes an example of a half-laser instrument, is desoribed below. 

Laser Monitoring Devices. A wide variety of laser radiation detectors are commercially available to fulfill the diversified needs resnlting from different wavelengths, pulse durations, and power and energy densities of various laser instruments. Laser radiation detectors are generally based on either of two basic principles—photon or thermal detection. 

The National Physical Laboratory in the United Kingdom made measurements on a similar device, the Laser Instrumentation 17S radiometer. They assumed... 

Laser Instrumentation Ltd., Unit 4 Bear Court, Basingstoke Hamps. RG24 OQT, England... 

F1g.7.5. Schematic diagram of a tunable diode laser instrument for high-resolution spectrometry (Courtesy Spectra Physics)... 

The properties of the laser and the laser instrumentation which make the system suitable for the ablation process required for sample introduction for elemental analysis are the laser wavelength, power density, pulse-to-pulse stability, pulse frequency, pulse duration, laser beam profile and ablation spot size. 

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