Helium-cadmium laser

Fig. 10.8. Isocratic electrochromatography of the oligosaccharide ladder in a capillary filled with a macroporous polyacrylamide/poly(ethylene glycol) matrix, derivatized with a C4 ligand (15%) and containing vinylsulfonic acid (10%). Conditions capillary, 500 mm (400 mm effective length) x 100 pm i.d. mobile phase, acetic acid 1 1000 containing 5% (v/v) acetonitrile field strength, 600 V/cm injection 5 s (100 V/cm) detection, LIF (helium-cadmium laser, excitation at 325 nm, emission at > 495 nm). Reproduced with permission from Palm and Novotny [36]. Copyright 1997 American Chemical Society.

Cadmium-helium laser See Helium-Cadmium laser. 

Helium-cadmium laser A CW laser emitting mainly at 325.0 and 441.6 nm from singly ionized cadmium. 

See argon ion, helium-cadmium, chemical, CO2 copper vapor, diode, dye, excimer, free electron, free-running, gas, helium-neon, krypton ion, mode-locked, neodymium, nitrogen, Q-switched, solid state, and ruby laser. 

Photon Correlation Spectroscopy. Measurements were made with a commercial 96-channel photon correlator (Malvern K7023) using a helium-cadmium laser and with a 256-channel correlator (Malvern K7032) using a helium-neon laser with a standard spectrometer system (Malvern 4700), adopting procedures as described previously (12). 

Laser Fluorescence Detector. A helium-cadmium laser (Model 4240B, Llconlx, Sunnyvale, CA) was (diosen as the excitation source because of Its stability and convenient wavelengths (325 and 442 nm). The UV laser radiation (325 nm, 5-10 mH cw) was Isolated with a dielectric mirror and was focused on the miniaturized flowcell with a quartz lens. Sample fluorescence, collected perpendicular to and coplanar with the excitation beam, was spectrally Isolated by appropriate Interference filters and then focused on a photomultiplier tube (Centronlc Model Q 4249 B, Bailey Instruments Co., Inc., Saddle Brook, NJ). The resulting photocurrent was amplified with a plcoammeter (Model 480, Kelthley Instruments,... 

The helium-cadmium ion gas laser furnishes an excellent example of one mechanism of laser excitation and emission. Figure 2-12 presents the... 

FIGURE 2-12. Energy level diagram of a helium-cadmium ion laser system. 

Solid substances also are used to produce laser action. The most common of these is the ruby laser, AI2O3 containing about 0.05 % Cr203. The electronic levels of the Cr ion are used to produce laser action in a manner similar to that described for the helium-cadmium ion system. In the ruby laser, energy is produced at a wavelength of 6943 A. 

In addition to UV detection, two other more sensitive and selective detection systems have attracted attention for the analysis of drugs and metabolites in biological samples laser-induced fluorescence (LIF) and mass spectrometry (MS). A powerful detection system is that which is based on LIF. The LIF detection provides extremely high mass sensitivity, but it is only applicable to some analytes that absorb in the 325 nm (helium-cadmium) or 488 nm (argon) region, as lasers are only commercially available for these wavelengths. Derivatization with fluorescent tags is an alternative for non-fluorescent species. "- ... 

Laboratories and in 1966 the blue helium-cadmium metal vapor ion laser discovered by W. T. Silfvast, G. R. Fowles, and B. D. Hopkins at the University of Utah. The first liquid laser in the form of a fluorescent dye was discovered that same year by R P. Sorokin and J. R. Lankard of the IBM Research Laboratories, leading to the development of broadly tunable lasers. The first of the rare-gas-halide excimer lasers was first observed in xenon fluoride by J. J. Ewing and C. Brau of the Avco-Everett Research Laboratory in 1975. In 1976, J. M. J. Madey and co-workers at Stanford University developed the first fi ee-electron laser amplifier operating at the infi ared carbon dioxide laser wavelength. In 1985 the first soft X-ray laser was successfully demonstrated in a highly ionized selenium plasma by D. Matthews and a large number of co-workers at the Lawrence Livermore National Laboratory. 

The helium-cadmium laser operates primarily at three wavelengths, in the blue at 441.6 rim and in the ultraviolet... 

Two-wave laser interference (Fig. 20(a)) may be used to record periodic elements with subwavelength features (A 100 nm). The UV laser (for example helium cadmium, argon-ion, or excimer laser) beam is focused down with an objective lens and passed through a matching pinhole to spatially filter the beam. The central part of the emerging spherical wave, which has nearly planar phase fronts, illuminates the sample directly. A part of the wave is reflected towards the sample as shown. These two waves interfere to produce a standing, periodic intensity pattern with period... 

We have performed an independent experiment to observe the phase-transition temperature shift following illumination of an NLC by a helium-cadmium laser. The change of the temperature was recorded in terms of the charge of the birefringence of the liquid crystal by the action of this radiation. 

The measurements were made with a nonlinear polarization interferometer (see Fig. 3). A thermostat with the liquid crystal was placed between two crossed polarizers pi and/ 2- The beam from a helium-neon laser A = 0.638 pm), whose 2 is vanishingly small, was broadened by a telescope T and passed through polarizers into a cell with the NLC. Polarized and intensity-modulated emission from a helium-cadmium laser was also guided into the cell with the crystal whose birefringence it altered on account of conformation... 

The diameter of the helium-cadmium laser beam was substantially less than the diameter of the helium-neon laser beam. The interferometer output was the interference pattern of the polarized beams of the helium-neon laser, against the background of which was observed a periodically time-varying intensity region corresponding to the action of the helium-cadmium laser. 

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