Source laser line

A list of the principal laser lines useful as Raman excitation source is... 

Fig. 3 a UV-Vis DRS spectra of dehydrated TS-1 catalyst reporting the typical 208 nm (48000cm i) LMCT hand, see Fig. 2h also reported are the four excitation laser lines used in this Raman study near-lR (dotted), visible (full), near-UV (dashed) and far-UV (dot-dashed), b Raman spectra of dehydrated TS-1 obtained with four different lasers emitting at 7 = 1064,422,325, and 244 nm (dotted, full, dashed, and dot-dashed lines, respectively). Raman spectra have been vertically shifted for clarity. Although the intensity of each spectrum depends upon different factors, the evolution of the 7(1125)//(960) ratio by changing the laser source is remarkable. The inset reports the Raman spectrum collected with the 244 nm laser in its full scale, in order to appreciate the intensity of the 1125 cm enhanced mode. Adapted from [48] with permission. Copyright (2003) by The Owner Societies 2003... 

Thus, the region 2100-1830 cm 1 can be covered. This allows us to monitor CO(v,J) by resonance absorption and various M(CO)n [n = 3-6] as a result of near coincidences between the CO laser lines and the carbonyl stretching vibrations of these species. The temporal response of the detection system is ca. 100 ns and is limited by the risetime of the InSb detector. Detection limits are approximately 10 5 torr for CO and M(CO)n. The principal limitation of our instrumentation is associated with the use of a molecular, gas discharge laser as an infrared source. The CO laser is line tuneable laser lines have widths of ca. lO cm 1 and are spaced 3-4 cm 1 apart. Thus, spectra can only be recorded point-by-point, with an effective resolution of ca. 4 cm 1. As a result, band maxima (e.g. in the carbonyl stretching... 

Because on CCD setups excitation for D, S, and A images is usually filter-selected from a single white light source the relative intensity of excitation is approximately fixed. Confocal microscopes use separate laser lines, often from distinct lasers, that can (and for optimal imaging should) be independently adjusted. Thus, on CCD setups y (Eq. (7.6)) is constant for a given set of filters whereas on the confocal, it varies from image to image (also, see Sect. 7.4.2). 

When compared to fluorescence detectors for HPLC, the design of a fluorescence detector for CE presents some technical problems. In order to obtain acceptable sensitivity, it is necessary to focus sufficient excitation light on the capillary lumen. This is difficult to achieve with a conventional light source but is easily accomplished using a laser. The most popular source for laser-induced fluorescence (LIF) detection is the argon ion laser, which is stable and relatively inexpensive. The 488-nm argon ion laser line is close to the desired excitation wavelength for several common fluorophores. The CLOD for a laser-based fluorescence detector can be as low as 10 12 M. 

The last two chapters discussed spectroscopic studies which used coincidences between laser lines and transitions in other atoms or molecules. These investigations have been performed either with lasers as external light sources, or inside the laser cavity. In the latter case coupling phenomena occur between the absorbing species and the laser emission, one example of which is the saturation effect employed in Lamb dip spectroscopy and laser frequency stabilization. This chapter will deal with spectroscopic investigations of the laser medium itself and some perceptions one may obtain from it. 

In experimental measurements, such sharp 8-function peaks are, of course, not observed. Even when very narrow band width laser light sources are used (i.e., for which g(co) is an extremely narrowly peaked function), spectral lines are found to possess finite widths. Let us now discuss several sources of line broadening, some of which will relate to deviations from the "unhindered" rotational motion model introduced above. 

Owing to aberrations, grating defects, and so on, it may not be adequate to approximate the response function by formulas based on idealized models. If a line source could be found having the spectrum that approximates a 8 function, then perhaps the measurement of such a line would adequately determine the response function. We have learned, however, that the spatial coherence of the source plays an important part in the shape of the response function. This precludes the use of a laser line source to measure the response function applicable to absorption spectroscopy. Furthermore, we... 

The use of CW tunable semiconductor lasers as a source in IR spectroscopy research makes possible a very great increase in resolving power over traditional IR grating spectrometers. IR studies with laser sources have been done on several gases (e.g., H20,NH3,SF6,N0). The laser line width is typically 1/100th the width of the Doppler-broadened absorption lines of the gases, so the fine details of the IR line shapes are... 

This process has the advantage of low-temperature deposition, which may be needed for the growth of thin films on temperature-sensitive substrates such as compound semiconductors and polymers. If a laser is used as the light source, fine lines of materials can be written directly, and possibly, lithographic steps can be avoided and damaged lines can be repaired. 

We summarize hoe some considerations affecting the potential accuracy of a spectroscopic measurement of the IS ->2S transition. We shall not dwell on the challenging problems of laser stabilization and optical frequency metrology, but only on the atomic considerations. In particular, we shall consider the major sources of line broadening and possible systematic shifts. We discuss below some of the factors which govern the accuracy of IS —>2S spectroscopy in the hydrogen trap. 

Fig. 1. Some useful laser sources in the visible and ultraviolet spectrum. For infrared lasers and also a more complete listing of laser lines see, for example, ref. 1. YAG (II) and YAG (III) signify the second and third harmonics, respectively, of the neodymium YAG laser. KDP, potasium dihydrogen phosphate, and KPB, potassium pentaborate, are frequency doubling crystals.

As we mentioned in the introduction to this section, it was known forty years ago from optical spectroscopy that CH is a component of interstellar gas clouds and the search was on for a spectroscopic detection of the radical at higher resolution so that the /l-doubling in the lowest rotational level (J = 1/2) could be measured or predicted accurately. This would enable the detection of CH by radio-astronomers and so allow the distribution of CH in these remote sources to be mapped out. The race was won by Evenson, Radford and Moran [48] using the then new technique of far-infrared LMR in the Boulder laboratories of the NBS (now known as NIST). They realised that there was a good near-coincidence between the water discharge laser line at 118.6 qm (84.249 cm ) and the N = 3 <- 2, J = 7/2 5/2 transition of CH in the / ) spin... 

Because of the wide transmission range and low phonon energies of fluoride glasses, the observation of numerous rare-earth laser lines is possible at wavelengths beyond 2 fim, where the transmission of silica fibers is extremely poor. Laser sources around 2 /jm are of special interest because they belong, not only to the eye-safe spectral domain, but also to an optical transparency window of the atmosphere. Two fluoride glass fiber lasers have been demonstrated in that region. First, a Ho3+ laser with the 5I7 -> 5I8 transition at 2.024 /on which delivers 250 mW with 60%... 

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