Trapped atoms

Early experiments witli MOT-trapped atoms were carried out by initially slowing an atomic beam to load tire trap [20, 21]. Later, a continuous uncooled source was used for tliat purjDose, suggesting tliat tire trap could be loaded witli tire slow atoms of a room-temperature vapour [22]. The next advance in tire development of magneto-optical trapping was tire introduction of tire vapour-cell magneto-optical trap (VCMOT). This variation captures cold atoms directly from the low-velocity edge of tire Maxwell-Boltzmann distribution always present in a cell... 

Depending on tire sign of U and F, atoms in states whose energy increases or decreases witli magnetic field are called weak-field seekers or strong-field seekers , respectively. One could, in principle, trap atoms in any of tliese states. 

Monroe C, Swann W, Robinson H and Wieman C 1990 Very oold trapped atoms in a vapor oell Phys.Rev.Lett. 65 1571-4... 

The possibility that an even larger impact caused the P T extinction received support when Becker and Poreda found that helium and argon atoms were present in the inner cores of some of the fullerenes from the P T boundary sediments (The cover of this book shows a helium atom inside a mol ecule of Ceo) What is special about the fullerene trapped atoms is that the mixtures of both helium and argon isotopes resemble extraterrestrial isotopic mixtures more than earthly ones The He/ He ratio in the P T boundary fullerenes for example is 50 times larger than the natural abundance ratio... 

With time-dependent computer simulation and visualization we can give the novices to QM a direct mind s eye view of many elementary processes. The simulations can include interactive modes where the students can apply forces and radiation to control and manipulate atoms and molecules. They can be posed challenges like trapping atoms in laser beams. These simulations are the inside story of real experiments that have been done, but without the complexity of macroscopic devices. The simulations should preferably be based on rigorous solutions of the time dependent Schrddinger equation, but they could also use proven approximate methods to broaden the range of phenomena to be made accessible to the students. Stationary states and the dynamical transitions between them can be presented as special cases of the full dynamics. All these experiences will create a sense of familiarity with the QM realm. The experiences will nurture accurate intuition that can then be made systematic by the formal axioms and concepts of QM. 

The main hardware types offered by physics are mentioned, namely trapped ions (or trapped atoms), quantum dots, quantum optical cavities, rf superconducting quantum interference devices (SQUIDs) and nitrogen-vacancy (NV) defects on diamond. Some are important simply as a benchmark to evaluate the quality of the implementations offered by chemistry, whereas others might be combined with lanthanide complexes to produce heterogeneous quantum information processors which combine the advantages of different hardware types. 

The use of trapped ions, or trapped atoms, as qubits [46, 47] is one of the most mature techniques. They have been used to achieve remarkable feats, mainly in the field of quantum simulation [48]. However, there is no clear link between this technology and molecular systems. 

The presence of lattice defects and/or intentionally placed impurities in the alkali halide crystal will cause the formation of local energy levels in the forbidden gap, called traps or activator centers. Figure 18.19 shows the energy levels of an alkali halide crystal, including the activator centers and traps. (Atomic thallium is a common activator for alkali halide crystals.)... 

Recent advances in the production and storage of positrons and antiprotons have made it possible to think about the synthesis of atomic antimatter in the laboratory. Parallely, contemporary advances in cooling and trapping atoms have led to an unprecedented accuracy of spectroscopic measurments. The important difference between the spectroscopy of atoms and antiatoms is that in the latter case, because of annihilation, the sample must be isolated from the surrounding environment. 

Rather than attempting to cool warm molecules one can try to synthesize cold molecules by associating cold atoms. The molecules thus formed are expected to maintain the translational temperature of the recombining atoms because the center-of-mass motion remains unchanged in the association process (save for the little. momentum imparted by the photon). This idea was first proposed by Julienne and j co-workers [343, 344] who envisioned a multistep association, first involving the continuum-to-bound excitation of translational continuum states of cold trapped. atoms to an excited vibrational level in an excited electronic molecular state. This step was followed by bound-bound spontaneous emission to the ground electronic state. (I... 

The density and the number of trapped atoms can be inferred from the decay of the sample. Atoms are dumped from the trap by lowering one of the axial confining fields. The emerging atoms recombine rapidly on the walls of the cell, releasing an energy of 4.6 eV per recombination. A fraction of this energy is collected on a small quartz bolometer [24]. The total integrated power is proportional to the total number of atoms in the trap. 

The rapid development of techniques for cooling and trapping atoms using laser light has created a new subfield of atomic physics. Research opportunities include the study of matter at ultra low temperature, ultra precise atomic spectroscopy and the study of light-matter interaction in a new quantum regime. 

F. Li, E. Rossipal, K. J. Irgolic, Determination of selenium in human milk by hydride cold-trapping atomic absorption spectrometry and calculation of daily selenium intake, J. Agric. Food Chem., 47 (1999), 3265-3268. 

The individual specific rate and adsorption equilibrium constants are defined in Table 1. In Equations (4) and (5) [Sitesjrefer to the available concentration of sites for adsorption on the Ti02 film, [O2] to the liquid phase oxygen concentration, [M] to the concentration of water, atomic or free radical species, reactor walls or other surfaces trapping atomic chlorine, and Rg to the superficial rate of electrons and holes generation. 

Trapping atoms at these extremely low temperatures for several seconds should allow the study of low-energy collisions, the ways that atoms attract each other to form aggregates, and of other properties that would provide tests of the fundamental theories of matter. ... 

The sample decay curve, N t), is obtained by measuring the number of trapped atoms after various holding times. The local decay n decreases due to dipolar decay according to n = —gn , were g = 1.1 x 10 cm /s is the dipolar decay constant, which is known from measurements [25,26] and theory [27,28]. Integration over the trap volume yields N = —KgN, where k ps 0.2 results from the distribution of densities. The result is N t)/N 0) = l/ l + ngnot), thus determining the peak density no (Fig. 3). Typically, at a density of 10 cm ... 

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