Magnetic atomic-beam

In the experiment, target 1 (semiconductor ZnO film) was exposed to a beam of metal particles for a specified time interval by activating a shutter 3 (controlled by a magnetic device) installed in front of a diaphragm 4, with magnetic field on and magnetic field off. The rate of variation of an electric conductivity was measured. At small surface coverages, this rate is strictly directly proportional to the number of metal atoms incident on the film surface, i.e., (da/dt) /, where is the atomic beam intensity. The shorter was the time of exposition and... 

The transeinsteinium actinides, fermium (Fm), mendelevium (Md), nobelium (No), and lawrencium (Lr), are not available in weighable (> ng) quantities, so these elements are unknown in the condensed bulk phase and only a few studies of their physicochemical behavior have been reported. Neutral atoms of Fm have been studied by atomic beam magnetic resonance 47). Thermochromatography on titanium and molybdenum columns has been employed to characterize some metallic state properties of Fm and Md 61). This article will not deal with the preparation of these transeinsteinium metals. 

The discovery of fermium (also einsteinium) was not the result of very carefully planned experiments, as in the cases of the other trans uranium elements, bill fermiuni and einsteinium were found in Ihe debris of an atomic weapon lest in the Pacific in November 1952. Researchers, using the Oak Ridge High Flux Isotope Reactor (HFIR) which produced 3.2-hour " Fm. determined ihe magnetic moment of the atomic ground state of the neutral fermium atom with a modified atomic beam magnetic resonance... 

Fig. 14.13 Experimental arrangement for velocity selecting and focusing the atomic beam. The rotating slotted disc and the pulsed laser beam select atoms in a velocity group, and the hexapole magnet focuses them where they cross the laser beam (from ref. 18).

Hyperfine structure measurements using on-line atomic-beam techniques are of great importance in the systematic study of spins and moments of nuclei far from beta-stability. We will discuss the atomic-beam magnetic resonance (ABMR) method, and laser spectroscopy methods based on crossed-beam geometry with a collimated thermal atomic-beam and collinear geometry with a fast atomic-beam. Selected results from the extensive measurements at the ISOLDE facility at CERN will be presented. 

To carry out this scheme, a fast atomic beam (v/c = 0.01) is used to translate the required nanosecond time intervals into convenient laboratory distances. To avoid complications due to motional electric fields, the entire experiment is performed in zero magnetic field and the resonance is tuned through directly by changing the frequency of the applied rf field. Other rf fields are used to select one hyperfine state so as to simplify the line shape. 

Fig. 4. Hydrogen atomic beam apparatus and scheme for laser cooling and magnetic trapping of hydrogen atoms.

The ideal conditions for studying an atom is to have it at rest in free space, or in free fall as in a "fountain" experiment. Any process which confines an atom perturbs it However, as has been shown, at ultra low temperatures the perturbations of hydrogen due to a magnetic trap are small. Furthermore, the trap provides an enormous advantage in density compared to atomic beams or fountains density of 10u - 1012cm-3 is readily available. Thus, the trap is particularly attractive from the point of view of signal to noise ratio. 

Fig. 34. One-dimensional antiferromagnetic arrays. The solid and open circles denote magnetic and non-magnetic atoms respectively. The arrows give the spin directions. Cases (a) and (b) will scatter neutrons of opposite polarization differently, Case (c) is intensitive to the polarization of the incident beam [after Ref. (57)]...

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