A.S. Ilyushin

The hypertine structure of the Mossbauer spectrum of FeMn$_2$Al has been calculated, and it is shown that the ion atoms in this structure of β—Mn type are in different electronic states. The ordering of the iron atoms in the β—Mn structure has been determined by experiment.

G.B. Demidovich and A.A. Skiyankin

Direct measurements have been made of the differential heats of adsorption of oxygen on atomically clean surfaces of germanium, silicon, and lead sulfide; which have been produced by crushing the initial single crystals under ultrahigh vacuum. The high heats of adsorption for Ge and Si (115 ± 10 and 210 ± 30 kcal/mol, respectively) are associated with the formation of double bonds. The interaction of an atomically clean surface of Ge with oxygen is dependent on the presence of minute traces of water. No such relationship is observed for silicon.

M.F. Vlasenko, I.V. Mityusheva and A.N. Penin

Results are presented on a gadolinium molybdate crystal examined in spontaneous parametric scattering at polaritons; the frequency-angle spectra indicate the dispersion of the ordinary refractive index In the range 350-5000 cm$^{-1}$. The frequencies of the type B$_1$ lattice modes have been determined. Two-particle state bands are observed, which determine the absorption of the crystal in the region around ~1800 cm$^{-1}$.

U.Kh. Kopvillem and R.N. Kuz'min

Приведены оценки потока рентгеновских и гамма-гравитонов на поверхности детектора (приемной антенны). Предлагается один из возможных путей регистрации высокочастотных гравитонов с использованием избирательного (резонансного) детектирования на мёссбауэровских Ƴ-переходах. Электромагнитное излучение, происходящее от взрыва сверхновых звезд, содержит линии спектра ионов железа, поэтому эксперименты по поиску гамма-гравитонов наиболее перспективны для распространенного мёссбауэровского изотопа железа $^{57}$Fe. Приведена оценка скорости счета, которая равна 10$^{-3}_{\text{квант}}* c^{-1}$ см$^{-2}$.

M.V. Piskareva and F.V. Shugaev

В.А.Касильников

Yu.G. Раvlеnkо

An expression is obtained for the spectrum of photons equivalent to a particle moving in an external field; this is a generalization of the well-known result of Weizsacker and Williams.

L.S. Кuz'mеnkоv, Р.А. Роlуаkоv

We investigate the influence of relativistic effects and radiative damping on beam instability. Expressions are obtained for the increment, the effective excitation width of the waves, and the criteria for the occurrence of instability, enabling one to draw a number of new physical conclusions. In particular, in a dense enough plasma the beam instability can be suppressed by radiative damping. We make numerical estimates. For large values of the plasma density and beam energy the effective excitation width of the waves can be so small that excitation of plasma waves becomes practically impossible.

V.Ch. Zhukоvskii, Shаrif АЬdаllа Наmid

We examine the production of $e^{+}$ $e^{-}$ pairs by a massive photon and the annihilation of $e^{+}$ $e^{-}$ pairs with the formation of a massive photon in13 an ultrastrong magnetic field $H≥ B_{0}= 4.41∙10^{13}G$. We obtain the conditions under which the external magnetic field begins to exert a substantial effect on these processes.

V.В. Gоstеv, А.R. Frеnkin

We propose a method of solving (without investigating the questions of convergence and the possibility of readjusting the limits of integration) Fredholm (Volterra) integral equations of the first kind, which, if only formally, admit exact inversion. We describe a class of kernels to which one can apply the method of double integral transforms. Examples of exactly solved integral equations are given.