Lasers helium neon, HeNe

Neon (Ne), 17 344. See also Helium-neon (HeNe) lasers commercial, 17 368t thermophysical properties, 8 Alt Neon atoms, 14 659-660 Neon column, 17 361... 

The helium-neon (HeNe) laser immediately comes to mind, having a very useful spectral line at 633 nm for steady-state red/near-IR fluorescence studies. Kessler and Wolfbeis have demonstrated the fluorescence assay of the protein human serum albumin using the probe albumin blue excited with a red HeNe laser.(71) Another useful wavelength available from the green HeNe laser is at 543.5 nm and this has been used with phase-modulation fluorometry by Lakowicz etal. to study probes such as carboxy seminaphtorhodafluor-6 (SNARF-6) as a means of measuring pH.(72)... 

FIAs can be based on steady-state intensity measurements without probe amplification, owing to the sensitivity of detection that is possible with fluorescence instrumentation, which exceeds that of spectrophotometers by two or three orders of magnitude. A sensitive fluorometer has been described for an estradiol assay(36) in which the limit of estradiol detection is 3 x KT11 M. Estradiol antibody labeled with rhodamine B is reacted with estradiol samples. Unreacted labeled antibody is removed with Sepharose-estradiol-casein beads, and the remaining fluorescence is directly proportional to the analyte concentration. The detection limit of rhodamine B on the same fluorometer is 5 x 1(T12 M. This instrument uses a 0.75 mW green helium-neon (HeNe) laser to irradiate the sample from above, at the air-liquid interface, to increase the light path and to decrease surface reflections. The sample compartment has a top-mounted photon trap, and a mirror mounted on the side of the sample compartment opposite the PMT to enhance detection. 

Another common laser class is that of gas lasers, which includes helium neon (HeNe) lasers, carbon dioxide (CO2) lasers, nitrogen lasers, and so on. The helium neon laser, widely used until the advent of the diode laser, was one of the first types developed and commercialized. As described above, it is a discharge-pumped gas laser, which generally produces an output measuring a few mW in power. 

When a helium-neon (HeNe) laser with X = 632.8 nm is used as the input beams and the two equal beams are separated and refocused to give an intersection angle a = 10.72° for each beam, the relative velocity of the scattering particles relates to the observed difference frequency as... 

The 632.8 nm helium-neon (HeNe) laser is also very popular for Raman spectroscopy because it is small, portable, mature, and very inexpensive. The resulting Raman wavelengths are well matched to the optimum sensitivity of charge-coupled device (CCD) detectors. HeNe lasers used for Raman spectroscopy typically deliver 5-30 mW of optical power. Sometimes they also sporadically deliver a weaker laser-like beam at 650 nm that can cause a huge line in the Raman spectrum at 418cm. The 650nm radiation is due to an intracavity pumped laser Raman transition. 

Thered(/l = 634.8 nm),highly collimated lightbeam from the helium-neon (HeNe) gas laser is a familiar sight in scientific and teaching laboratories. Because of their relative small size and normally good TEMoo beam quality, HeNe lasers are commonly used as an alignment tool. 

Figure 7. Thermal lensing experiment. Kr, krypton ion laser Dye, dye laser M, monochromator Gj, G, G3, glass plate A, attenuator S, shutter, L, lens (/ = 200 mm) I, iris diaphragm C, dye cell (path 1 cm) F, interference filter (A = 633 nm) Fj, neutral density filter P, pinhole (diameter d = 1 mm) D Dj, detector HeNe, helium-neon laser.

FT-NIR spectrophotometer uses a monochromatic source (typically a HeNe (helium neon) laser) to control the movement of the mirror, ensure alignment of the interferometer, and provide wavelength precision. The detector signal intensity is a cosine function I(t) = F cos(4 rvat) where a is the... 

The optical gain medium comprises a mixture of helium and neon at low pressure in a capillary glass tube, typically at a ratio of around 7 1 to 10 1, and total pressure of 3-7 mbar. Electrodes sealed into the tube allow for the passage of high-voltage DC to excite the discharge. Most commonly, HeNe laser tubes are 125-350 mm in overall length, and about 20—40 mm in diameter. 

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