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The crystal scattering of two coherent neutron beams is discussed. It is found that the conventional pair correlation function used in single-beam scattering is insufficient to describe the scattering of two coherent neutron beams. A generalized pair correlation function with unequal momentum transfer is introduced. It is found that the energy exchange between vibrational quanta of the crystal and incident neutrons leads to a modification of the scattering amplitude. Through the scattering of two coherent neutron beams one is able to measure directly the phase of the scattering amplitude.

The crystal scattering of two coherent neutron beams is discussed. It is found that the conventional pair correlation function used in single-beam scattering is insufficient to describe the scattering of two coherent neutron beams. A generalized pair correlation function with unequal momentum transfer is introduced. It is found that the energy exchange between vibrational quanta of the crystal and incident neutrons leads to a modification of the scattering amplitude. Through the scattering of two coherent neutron beams one is able to measure directly the phase of the scattering amplitude.

Proposed and performed experiments on the Doppler-free two-photon absorption of two coherent laser beams are discussed. The coherent phenomenon in experiments follows directly from basic quantum mechanics. It is shown that, to excite the coherent absorption, the laser beams need not be spatially or temporally separated.

This is a continuation in the theoretical study of scattering initiated by two coherent beams. Here the scattering by multiple independent centers is discussed. The presence of these centers involves some problems, which are not present in scattering with a single beam. I show how these problems may be overcome, thus allowing the phase of the scattering amplitude to be determined experimentally.

Separated-beam experiments for both the Doppler-free two-photon and saturated absorptions are under consideration. In the Doppler-free two-photon absorption, the experimental arrangement is important. Such important has not been recognized before. Three different arrangements are discussed here. In the first one, the separated-beam experiment is not coherent and the Ramsey fringe variation cannot be observed. In the second, the transit-time broadening is present and the Ramsey fringe variation depends on the atom's time of flight as well as the transit time. Finally, in the third arrangement, the transit-time broadening is eliminated and the Ramsey fringe variation depends on the atom's time of flight alone. These examples have shown that in the Doppler-free two-photon absorption, the elimination of the transit-time broadening is through a mechanism other than the beam separation. In the saturated absorption the situation is quite different. Even in the presence of transit-time broadening, the Ramsey fringe spacing depends only on the atom's time of flight.

It was shown theoretically that through the diffraction of two coherent beams, one is able to measure both the magnitude and phase of the structure factor directly. Here some experimental comments concerning the performance of the proposed experiment are presented.

The two-photon absorption initiated by two coherent beams is considered. It is shown that the resonance fringe variation, which appeared in the Doppler-free two-photon absorption of pulsed laser beams, can also be observed in absorption with a Doppler shift.

A new-type Bohm-Aharonov experiment is proposed. The experiment can be carried out in a large scale without the help of an electron microscope.

It is shown that the generalized optical theorem in quantum mechanics is a useful theorem in the scattering of two coherent beams.

A theory, which exhibits the characteristic features of scatterings initiated by two coherent beams, is discussed in the present paper. We show that the imaginary part of the scattering amplitude is an experimentally measurable quantity. To know the imaginary part of the amplitude is quite important for certain aspects of quantum mechanics, for example, the dispersion relation for a fixed momentum transfer. This relation has not yet been experimentally verified.