Vladimir K. Ignatovich

Neutron reflection from condensed matter, the Goos–Hänchen effect and coherence

Abstract The Goos–Hanchen (GH) effect for neutron reflection from condensed matter is considered. An experiment to quantify the effect is proposed. The relation of GH shift to the neutron coherence length is considered.

Generalized matrix method for the transmission of neutrons through multilayer magnetic systems with noncollinear magnetization

Abstract A generalized matrix method for the reflection and transmission of polarized and nonpolarized neutrons for multilayer systems with noncollinear magnetization of the neighboring layers is developed. The transmission and reflection of a particular system are calculated. Computation of the transmission, reflection and wave functions inside some layers shows that the generalized matrix method is less time consuming than the recurrence method.

Theoretical description of neutron resonances in multilayer systems

The recurrence method (RM) in multilayer systems (MS) is discussed. It is shown that this method is the most powerful one for analytical calculations. The precise analytical calculations of positions and widths of neutron resonances in nonmagnetic MS, and also of reflection, transmission amplitudes and enhancement factor of the neutron wave function in resonant layers are given. A practical multilayer resonator is used to illustrate the properties of the neutron resonances in the spacer layer.

Experimental determination of the neutron channeling length in a planar waveguide

In neutron waveguides, the neutron wave is confined inside the guiding layer of the structure and can escape from the layer edge as a microbeam. The channeling within the guiding layer is accompanied by an exponential decay of the neutron wave function density inside the waveguide. Here, we report direct determination of the corresponding decay constant, termed the neutron channeling length. For this, we measured the microbeam intensity as a function of the length of a neutron absorbing layer of variable length placed onto the surface of a waveguide structure. Such planar neutron waveguides transform a conventional neutron beam into an extremely narrow but slightly divergent microbeam, which can be used for the investigation of nanostructures with submicron spatial resolution.

The Kruger problem and neutron spin games

We present a compact solution to the one-dimensional problem of neutron scattering from two mutually perpendicular magnetic fields: permanent and rotating ones. Both fields are confined inside a layer of matter or a layer of a free space. The applications of this solution to the interpretation of some experiments with polarized neutrons are considered.

Neutron standing waves in layered systems

A theory of propagation of neutron waves in multilayer magnetic and nonmagnetic systems is presented. It is shown how a system forms the wave function of a neutron, how the wave function formed can be controlled, and how this function can be used to investigate materials. The results of experimental investigations of the neutron reflection from multilayer systems with simultaneous measurement of different types of secondary radiation are reported.

Neutron Time Interferometry

We compare a “Mach-Zehnder interferometer in time” for cold neutrons with its well-known spatial counterpart and demonstrate the intimate connection between space and time for both setups. Further, we outline a combined space-time interferometer, which coherently splits a wavepacket in longitudinal and lateral direction. On the way towards time interferometry “neutron computer holography” seems to be an attractive application. It allows the three-dimensional reconstruction of an object from the scattered intensity, but in contrast to holography with light, there is no need for a reference wave. On the other hand, the possible resolution is worse than in the light case.

Those wonderful elastic waves

We consider elastic waves in isotropic and anisotropic media and discuss their polarization, speeds, reflection from interfaces with mode conversion, and surface waves. The waves are represented by a wave function. For isotropic media this representation greatly simplifies the theory. The reflection of quasitransverse waves in anisotropic media from a free surface is shown to be characterized by three critical angles.

An algebraic approach to the propagation of waves and particles in layered media

Abstract For the solution of a variety of physical problems in application to any medium it is very fruitful to split the medium in parts by introducing infinitesimal gaps. If a problem can be solved for one part, then after application of recurrent relations we obtain the solution for the whole medium. This approach is applied to the wave propagation in any periodic potential, to the diffraction of scalar radiation (neutrons, for example) from an ideal crystal and to the albedo of particles from a homogeneous medium filled with randomly distributed scatterers.

Nonspreading wave packets in quantum mechanics

In this paper a nonspreading, unnormalizable wave packet satisfying the Schrödinger equation is constructed. A modification of the Schrödinger equation is considered which allows the normalization of the wave packet. The case is generalized for relativistic mechanics.