Laser isotope

B2.5.5.4 LASER ISOTOPE SEPARATION AND MODE-SELECTIVE REACTIONS... 

Although this limit is not always reaehed. The same is true for the eoherenee of the radiation. Eaeh of these properties ean be exploited for partieular ehemieal applieations. The monoeliromatieity ean be used to initiate a ehemieal reaetion of partieular moleeules in a mixture. The laser isotope separation of and in nafriral abimdanee exploits the isotope shift of moleeular vibrational frequeneies. At 10-50 em, the eorresponding shift of IR absorption wavenumbers is large eompared to the speetral width of the CO2 laser... 

Early laser Isotope separation after IR multiphoton excitation high selectivity at room temperature... 

Atomic vapor laser isotope separation (AVLIS)... 

Laser isotope separation techniques have been demonstrated for many elements, including hydrogen, boron, carbon, nitrogen, oxygen, sHicon, sulfur, chlorine, titanium, selenium, bromine, molybdenum, barium, osmium, mercury, and some of the rare-earth elements. The most significant separation involves uranium, separating uranium-235 [15117-96-1], from uranium-238 [7440-61-1], (see Uranium and uranium compounds). The... 

Atomic- Vapor Laser Isotope-Separation. Although the technology has been around since the 1970s, laser isotope separation has only recently matured to the point of industrialization. In particular, laser isotope separation for the production of fuel and moderators for nuclear power generation is on the threshold of pilot-plant demonstrations in several countries. In the atomic vapor laser isotope-separation (AVLIS) process, vibrationaHy cooled U metal atoms are selectively ionized by means of a high power (1—2 kW) tunable copper vapor or dye laser operated at high (kHz) repetition rates (51,59,60). 

A promising alternative is provided by Laser isotope separation . Because the ionization energies of and differ slightly, it is possible to ionize the former selectively by irradiating U vapour with laser beams precisely tuned to the appropriate wavelength. The ions can then be collected at a negative electrode. 

LLNL AVLIS Laser. The first WFS measurements using a Na LGS were performed at LLNL (Max et al., 1994 Avicola et al., 1994). These experiments utilized an 1100 W dye laser, developed for atomic vapor laser isotope separation (AVLIS). The wavefront was better than 0.03 wave rms. The dye laser was pumped by 1500 W copper vapor lasers. They are not well suited as a pump for LGSs because of their 26 kHz pulse rate and 32 ns pulse length. The peak intensity at the Na layer, with an atmospheric transmission of 0.6 and a spot diameter of 2.0 m, is 25 W/cm, 4x the saturation. The laser linewidth and shape were tailored to match the D2 line. The power was varied from 7 to 1100 W on Na layer to study saturation. The spot size was measured to be 7 arcsec FWHM at 1100 W. It reduced to 4.6 arcsec after accounting for satura-... 

Atomic systems, in lasers, 74 666-669 Atomic Vapor Laser Isotope Separation (AVLIS) process, 25 416 Atomic weight, 75 748 Atomization, 77 774-775 in spray coating, 7 69-74 technology of, 23 175 Atomizer operation, concerns related to, 23 195... 

Laser-induced plasma spectroscopy (LIPS), archaeological materials, 5 743 Laser isotope separation, 25 416 417 Laser light, 14 655-656 Laser light sources, in photochemical technology, 19 107-108... 

Molecular hydrogen, 23 759 Molecular imprinting, 6 397 Molecular interactions, 25 103 Molecular interaction theories, 24 38 Molecular Laser Isotope Separation (MLIS) process, 25 416 417 Molecular level machine, 2 7 58 Molecularly imprinted plastics (MIPs) smart, 22 717)... 

Uranium enrichment using LIS has been exhaustively studied and the conceptual outlines of two different methods can be found in the open literature. These methods are multi-photon dissociation of UF6 (SILEX, or Separation of Isotopes by Laser Excitation) and laser excitation of monatomic uranium vapor (Atomic Vapor Laser Isotope Separation, or AVLIS). Following an enormous investment, AVLIS was used by the United States DOE in the 1980s and early 1990s, but due to the present oversupply of separated uranium, the plant has been shut down. 

The dramatic growth occurring over the past few years in laser chemistry and laser isotope separation has refocused interests upon dissociative processes in molecules. Collectively, these interests are traceable to the pragmatic goals of producing appreciable populations of selected atomic or molecular states having useful reactive properties or isotopic content. From this perspective, it is natural that photodissociation of some parent molecule would appear to be the ideal means for obtaining a desired product. 

Laser isotope separation (LIS) utilizes small differences in the spectroscopic properties of isotopic substances. Each isotope-bearing substance absorbs a radiation of a particular wavelength. Separation of the excited species can be achieved by multiple-photon absorption or photopredissociation of molecules or chemical scavenging. 

A basic flow sheet containing common features of an LIS plant is schematically shown in Fig. 5. The two major components in a deuterium LIS plant are the laser isotopic separator and chemical exchange reactor. 

---