Lamp sources

In these instruments the monochromated beam of radiation, from tungsten and deuterium lamp sources, is divided into two identical beams, one of which passes through the reference cell and the other through the sample cell. The signal for the absorption of the contents of the reference cell is automatically subtracted from that from the sample cell giving a net signal corresponding to the absorption for the components in the sample solution. 

The first successful application of the continuous wave (CW) He-Ne gas laser as a Raman excitation source by Kogelnik and Porto (14) was reported in 1963. Since that time, significant improvements in instrumentation have been continually achieved which have circumvented a great number of problems encountered with mercury lamp sources. The renaissance of Raman spectroscopy has also been due to improvements in the design of monochromators and photoelectric recording systems. 

Since color matching is meant for humans, it is natural to define color in terms of an average, or "Standard Observer". Our first step is to build an instrument which contains three colored lamp sources, a place for the individual observer, intensity detectors, and a monochromator, as shown in 7.8.19. on the next page. 

The difficulty in setting up the initial system for color comparisons cannot be underestimated. The problem was enormous. Questions as to the suitability of various lamp sources, the nature of the filters to be used, and the exact nature of the primary colors to be defined occupied many years before the first attempts to specify color in terms of the standard observer were started. As we said previously, the Sun is a black-body radiator having a spectral temperature of about 10,000 °K (as viewed directly from space). Scattering and reflection... 

Later investigations have fully confirmed the conclusion that the crosslinking of the higher alkyl methacrylate polymers will take place on a gallery wall. We have been able to demonstrate that an induction time of about 11 years occurs before insoluble matter begins to form in commercial normal and isobutyl polymers on a well-illuminated museum wall (1,11). Protection against such loss of solubility is one of a number of reasons for recommending the use of ultraviolet filters over windows and over fluorescent-lamp sources in museums (12). 

Historically, this has been the most constrained parameter, particularly for confocal laser scanning microscopes that require spatially coherent sources and so have been typically limited to a few discrete excitation wavelengths, traditionally obtained from gas lasers. Convenient tunable continuous wave (c.w.) excitation for wide-held microscopy was widely available from filtered lamp sources but, for time domain FLIM, the only ultrafast light sources covering the visible spectrum were c.w. mode-locked dye lasers before the advent of ultrafast Ti Sapphire lasers. 

In view of the surprising results obtained for the monofunctional maleimide HM/IPDBDVE system in Figure 3 for polymerization in air, an equimolar mixture of CHVE and MPBM [bismaleimide made from maleic anhydride and 2-methyl-l,5-pentanediamine] was polymerized via a mercury lamp source in the absence and presence of air (Figure 7). As might be expected from the earlier results in Figure 3, the difunctional maleimide/divinyl ether system exhibits a remarkably high polymerization rate in the presence of oxygen (air). 

Both instruments are equipped with a xenon discharge lamp source and have an excitation wavelength range of 230-720nm and an emission wavelength range of 250-800nm. 

Table II. Measured and Fitted Parameters Obtained in Studies of the Photodissolution of f-FeOOH Suspended in pH 4, 0.01M NaCl Containing Various Organic Acids. Illumination provided by a Hg arc lamp source and 365 nm band-pass filter (total radiation output 85 pE cm-2 min- ).

The light hollow-cathode-lamp source (A) passes through the slit S, and strikes at mirrors M, and M2. The Mirrors M3 splits chopped beam from the source into two parts one passes through the mirror M4-slit... 

Where vapour discharge lamp sources exist (for volatile elements such as Hg, Na, Cd, Ga, In, T1 and Zn) they can be used. Hollow-cathode lamps are insufficiently intense, unless operated in a pulsed mode. Microwave-excited electrodeless discharge lamps are very intense (typically 200-2000 times more intense than hollow-cathode lamps) and have been widely used. They are inexpensive and simple to make and operate. Stability has always been a problem with this type of source, although improvements can be made by operating the lamps in microwave cavities thermostated by warm air currents. A typical electrodeless discharge lamp is shown in Fig. 6.3. 

There are three instrument designs in use with fiber-optic probes. One system makes simultaneous measurements on up to eight dissolution bath probes using a CCD-based spectrophotometer with xenon flash lamp source. The signals from all eight probes are simultaneously imaged onto a single CCD detector and concentrations determined in real... 

Figure 4. Experimental arrangement for multichannel-detected CD. So, 30 W deuterium lamp source P, beam steering prism Lj, L2, beam focusing, collimating lenses M,...

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