Temperature laser cooling

Number, Temperature, Laser Cooling Rate, Heating Rate, Sympathetic Rate,... 

Laser Cooling The 1997 Nobel Prize in physics was shared by Steven Chu of Stanford University, William D. Phillips of the National Institute of Science and Technology, and Claude N. Cohen-Tannoudje of the College de France for their development and theoretical explanation of laser cooling, a process that can lower the temperature of a gas to a very low value. 

The possibility of producing a system of positronium atoms at a sufficiently high density and low temperature to produce Bose-Einstein (BE) condensation has been raised by Liang and Dermer (1988) and Platzman and Mills (1994). The former authors outlined a scheme in which positronium atoms are laser-cooled in vacuum, which seems feasible despite their short lifetimes because of their low mass. The required temperature of the positronium is around 0.1 K and the density is 1015 cm-3. Liang and Dermer (1988) argued that the overall scheme appears possible, but hitherto neither the temperature nor the density condition has been approached and laser cooling of positronium has not yet been attempted. 

Experiments with trapped a cryogenic plasma of electrons at temperatures as low as 50K and densities as high as 1010/cm3 have begun to probe plasma behavior below the classical plasma region in Fig. 2. Experiments with laser-cooled trapped ions have been underway to probe the liquid region.33 Very recently crystalization was observed with only a few ions34 35 and with more than 100 ions.36 A very nice feature of the measurements is that one can learn the positions of shells of ions and even individual ions by imaging the fluorescence from the ions. A numerical simulation produced crystalization very similar to what was observed.37... 

The Bose condensation has been observed on Earth in laser-cooled (Chu,10 Cohen-Tannouji,11 and Phillips12) collections of alkali atoms in ultra-high vacuum at very low temperatures in 1995 (Cornell13 and... 

The photoluminescent behavior of a complex of the type Zn(diimine)(dtsq), where diimine = 2,2 -biquinoline, phen (44), or 4,7-diphenyl-2,9-dimethyl-phen (batho) and dtsq = dithiosquarate, have been reported by Gronlund et al (135). The phen and batho complexes display broad, featureless luminescence spectra in the solid state at room temperature. Upon cooling to 77 K, the emission spectrum of Zn(batho)(dtsq) resolves into three sharp peaks overlapping the broad emission feature these sharp peaks are assigned to a diimine localized ji-ji emission. The Zn(diimine)(dithiolate) solids degrade upon UV laser excitation, which has inhibited accurate lifetime measurements. 

Over two hundred years ago the work of Charles and Gay-Lussac led to the suspicion that an absolute low temperature exists for matter. In recent years scientists have come very close to cooling matter to 0 K. The latest low-temperature record was achieved at the University of Colorado in Boulder when a team of scientists led by Carl Wieman reported that they had cooled a sample containing 2 X 107 cesium atoms to 1.1 X 10-6 K, about one-millionth of a degree above absolute zero. This record-low temperature was achieved by a technique known as laser cooling, in which a laser beam is directed against a beam of individual atoms, dramatically slowing the movement of the... 

SUB-DOPPUIR COOLING In 1988 the NIST-Gaithersburg group made careful measurements of the temperature of atoms laser cooled in optical molasses, cind found temperatures significantly below the Doppler cooling limit 113). The initial measurements on laser cooled sodium atoms gave temperatures of about 40 pK, about six times lower tham the predicted lower limit of 240 pK. 

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