A temperature behavior of the frustrated translational mode of adsorbate and the nature of the "adsorbate-substrate" interaction

A temperature behavior of the frustrated translational mode (T-mode) of a light particle, coupled by different regimes of ohmicity to the surface, is studied within a formalism of the generalized diffusion coefficients. The memory effects of the adsorbate motion are considered to be the main reason of the T-mode origin. Numerical calculations yield a thermally induced shift and broadening of the T-mode, which is found to be linear in temperature for Ohmic and super-Ohmic systems and nonlinear for strongly sub-Ohmic ones. We obtain analytical expressions for the T-mode shift and width at weak coupling for the systems with integer "ohmicity" indexes n = 0÷2 in zero temperature and high temperature limits. We provide an explanation of the experimentally observed blue- or redshifts of the T-mode on the basis of a comparative analysis of two typical times of the system evolution: a time of decay of the "velocity-velocity" autocorrelation function, and a correlation time of the thermal bath random forces. A relation of the T-mode to the multiple jumps of the adsorbate is discussed, and generalization of conditions of the multiple hopping to the case of quantum surface diffusion is performed.     

Upgrade of recommended nuclear cross section data base for production of therapeutic radionuclides

Journal of Radioanalytical and Nuclear Chemistry - The IAEA Nuclear Data Section has coordinated several actions to setup and improve a database for recommended cross sections and nuclear decay...     

Structural study of copper and chromium poly[3,3′-dithiobis(2,4-pentanedionates)]

The structures of copper poly[3,3′-dithiobis(2,4-pentanedionate)], obtained from 3,3′-dithiobis(2,4-pentanedione) and copper chloride, and chromium oligo-3,3′-dithiobis(2,4-pentanedionate), obtained by treating chromium tris(3-chlorosulfenyl-2,4-pentanedionate) with butyl magnesium bromide, are studied by comparing the calculated and experimental X-ray scattering functions. Optimal models for the copper and chromium polychelate structures are suggested. The structure of the macromolecular chain depends on the mutual arrangement of metallochelate nuclei, which is similar to that in a crystal matrix of a monomer, rather than on the stereochemistry of the disulfide bond. Far-East State University, Vladivostok. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 1, pp. 152–156, January–February, 1995. Translated by I. Izvekova     

Measurement and simulation of the cross sections for the production of 148Gd in thin natW and 181Ta targets irradiated with 0.4- to 2.6-GeV protons

The cross sections for the production of ¹⁴⁸Gd in ^natW and ¹⁸¹Ta targets irradiated by 0.4-, 0.6-, 0.8-, 1.2-, 1.6-, and 2.6-GeV protons at the ITEP accelerator complex have been measured by direct α spectrometry without chemical separation. The experimental data have been compared with the data obtained at other laboratories and with the theoretical simulations of the yields on the basis of the BERTINI, ISABEL, CEM03.02, INCL4.2, INCL4.5, CASCADE07, and PHITS codes.     

Measurement and simulation of the cross sections for nuclide production in 93Nb and natNi targets irradiated with 0.04- to 2.6-GeV protons

The cross sections for nuclide production in thin ⁹³Nb and ^natNi targets irradiated by 0.04- to 2.6-GeV protons have been measured by direct γ spectrometry using two γ spectrometers with the resolutions of 1.8 and 1.7 keV in the ⁶⁰Co 1332-keV γ line. As a result, 1112 yields of radioactive residual nuclei have been obtained. The ²⁷Al(p, x)²²Na reaction has been used as a monitor reaction. The experimental data have been compared with the MCNPX (BERTINI, ISABEL), CEM03.02, INCL4.2, INCL4.5, PHITS, and CASCADE07 calculations.     

Structural effects in nuclide distributions from fission and fragmentation

A survey is given on structural effects in the nuclide production from fission and fragmentation reactions, including recent results from GSI. The prominent structural features found in low-energy fission are related to pairing correlations and shell effects as described by standard models. A complex fine structure observed in the end products after the deexcitation of highly excited nuclei is deduced from the production yields of the system ²³⁸U+Ti at 1 A GeV. Possible reasons for this structure are discussed, which go beyond the features found in low-energy fission.