Atomic systems interference pattern

When an electron scatters from an atom, its phase is changed so that the reflected wave is not in phase with the incoming wave. This changes the interference pattern and hence the apparent distance between the two atoms. Knowledge of this phase shift is the key to getting precise bond lengths from SEXAFS. Phase shifts depend mainly on which atoms are involved, not on their detailed chemical environment, and should therefore be transferable from a known system to unknown systems. The phase shifts may be obtained ftom theoretical calculations, and there are published tabulations, but practically it is desirable to check the phase shifts using... 

If the quenching field Eq is put off, that is the 25-atoms pass through the slit system, distinct intensity oscillations of the 2P-atom Hux are observed, that is the interference of this state (curve run 1 in Fig. 3. On contrary, when 25-atoms are removed from the beam (quenching field is put on), 2P intensity oscillations disappear completely-curve run 2. This curve is the sum of exponential decay curves of excited H-atoms with n = 2,3,... arising due to collisions of the Hi, -beam with the collimator walls. Subtracting the background curve run 2 from the curve run 1, we get the pure interference pattern (Fig. 4). 

Nevertheless, his hypothesis, even in its present form, allows for some quantitative comparisons between experimental results and theoretical predictions. First of all, experiments were implemented to determine the strength and direction of the effective field Eef / with respect to the direction of the atom velocity. For this purpose the system with longitudinal (that is. parallel or antiparallel to the atom velocity vector) electric field was installed. If the electrodes, creating the field are shortened and grounded, then, with change of distance L, distinct 2P-interference pattern is observed, produced by the field Pe// With presence of an external electric field coinciding with the velocity direction, the amplitude of beets is increased, and the character of the interference curve testifies coincidence of the phases of beets caused by the external field and the field Pe// ... 

An alternative way to detect an internal state of the two atom system is to observe an interference pattern of the fluorescence field emitted in the direction R, not necessary perpendicular to the interatomic axis. The usual measure of the depth of modulation of the interference fringes is a visibility defined as... 

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