Synchrotron-type radiation processes in crystals and polarization phenomena accompanying them

Abstract

In the present investigation. photon correlation spectroscopy in an extended form has been used for studying both the Rayleigh and Brillouin components of a dense fluid including their intensity ratio (Landau-Placzek ratio).As for the Brillouin component this amounts to spectroscopy in the ultrasonic region. Results for both phases of saturated n-butane in a broad temperature range are reported. They are compared with data from various sources. Although the approach to the critical temperature was limited (1.5 K for the liquid, 0.95 K for the vapour) the transition from normal lo critical behaviour is distinctly marked.

Quantum features of high energy particle incoherent scattering in crystals

“…(8) convolution with the scattering nuclei distribution (2), which nullifies the linear in α contribution, leaving only the quadratic ones in Eq. (8). Owing to the Fourier integral presence in Eq.…”

“…High energy particle interaction with oriented crystals makes it possible to both observe many remarkable phenomena and apply them to develop diverse sources of x and gamma radiation [1][2][3], to efficiently deflect high energy particle beams [4][5][6], to measure and even to modify elementary particle properties, such as magnetic momenta [1], and to reduce the thickness of particle detectors as well as to make the latter sensitive to both the direction and polarization [7][8][9][10]. All the pronounced effects, induced by the coherent particle interaction with an oriented crystal lattice, are described by the averaged (continuum) potential of atomic strings or planes [11,12] introduced by Lindhard, who also proved that the particle motion in the averaged potential can be treated classically at a high enough energy.…”

“…This problem is readily solved by the quantum treatment of transverse particle motion [25,26], being, however, both really necessary and practically feasible only at the electron and positron energies of a few dozen MeV and less. However, most of the current investigations are conducted at GeV [13,14,27] and higher [1][2][3][4][5][6][7][8][9][10][15][16][17][28][29][30][31][32][33][34] energies, at which the quantum description of particle motion in the averaged crystal field becomes both redundant and cumbersome, revealing the necessity for the introduction of classical particle motion features into the treatment of their incoherent scattering by the inhomogeneously distributed nuclei. Till now, a redefinition of the scattering impact parameter upper limit R → u 1 [28][29][30][31]35] has been used, which did not take into consideration any incoherent scattering dependence on the transverse particle coordinate, giving, thus, a qualitative estimate only.…”

Numerical approach to the semiclassical method of radiation emission for arbitrary electron spin and photon polarization

“…Thus, we will only apply the approach in the case of a single particle starting with and angle of 0 and a distance of u 0 = 0.083 Å from the plane (this value corresponds to the thermal vibrational amplitude of the nuclei in the crystal lattice). The maximum polarization that can be asymptotically obtained, A, is given by [23,40]…”

Strong Reduction of the Effective Radiation Length in an Axially Oriented Scintillator Crystal

“…the channeling phenomenon, leading to a specific e.m. radiation emission, thereby called channeling radiation. Indeed, for small angle between charged particle trajectory and crystal axes/planes direction, successive collisions of the particles with the atoms in the same plane/row are correlated and it is possible to replace the screened Coulomb potential of each atom with an average continuous potential of the whole plane/string [6], corresponding to a strong electric field E ∼ 10 10 − 10 12 V/cm [7,8]. Channeling may occur if the incidence angle of the charged particle with respect to the crystal planes/axes, ψ, is lower than the critical value introduced by Lindhard θ c = 2V 0 /ε, where ε is the particle energy and V 0 the average potential energy amplitude.…”