Search

Poster: "ECR 2017 / C-2942 / Morphological description of uterine scar one year after cesarean section by T2 3D SPACE 3.0T MR" by: "N. Ding, Y. Qi, Y. He, H. D. Xue, Z. Jin; Beijing/CN"

ERDA [J. L'Ecuyer et al., J. Appl. Phys. 47 (1976) 381] is a technique of great interest for quantitative depth profiling of light elements in matter. The use of crossed electric and magnetic fields (E × B filter) [G.G. Ross et al. J. Nucl. Mater. 128/129 (1992) 484; G.G. Ross and L. Leblanc, Nucl. Instr. and Meth. B 62 (1992) 484] in place of the traditional absorber, enhances the resolution by eliminating the straggling induced normally by the absorber and removes the uncertainty on the absorber thickness. The E × B filter allows the simultaneous detection of different particles such as H, D and He. This work presents the first ERD E × B depth profiling by means of a heavy ion beam. Compared with the usual ERD E × B with 350 keV He, the 2.54 MeV 15N beam enhances scattering cross section by a factor of 3, has equivalent depth resolution (1–3 nm at surface) and gives a depth probe twice deeper. However, 15N ions sometimes induce high desorption compared to He. H, D and He were implanted in Be and Si at energies from 800 eV to 10 keV. The experimental depth distributions are compared with those obtained by TRIM95 [J.F. Ziegler and J.P. Biersack, The Stopping and Range of Ions in Solids (Pergamon, New York, 1995)] and by other experimental techniques. Reproducibility is very good between the different results obtained experimentally. Profile modification induced by the ion beam is also shown.

A recent adaptation of the collisional cooling technique which permits gas‐phase spectroscopy from 5 K to ≥20 K is described. The new apparatus was used to measure pressure broadening parameters and cross sections for the the J=0–1, K=0 rotational transition of CH3F broadened by helium from 5 to 21 K. The cross sections show a general upward trend with decreasing temperature ranging from 55.9 A2 at 20 K, to 114.0 A2, at 5 K. This compares with a 295 K cross section of 48.8 A2. While an accurate CH3F–He potential surface is not presently available for calculating theoretical cross sections, the rise in cross section at low temperature can be attributed to the dominance of resonant collisional processes at very low energy. Although resonant structure in many systems (e.g., CO–He, H(D)Cl–He) appears to be smoothed out by Boltzmann averaging, there is experimental evidence that at least one resonance may survive the thermal average in the CH3F–He system.

Accurate lower and upper bonds for the nonrelativistic ground state energies E o of the real systems 4 He, H − , D − , and T − were calculated by the method of variance minimization using wave functions which include logarithmic terms. In addition, an analogous treatment with an infinite mass approximation for H − , He, and the isoelectronic series up to Z=10 was carried out. Especially for H − and He the results (a.u.) are given by −0.52775101712297 4

We have measured the absolute angular differential cross section and the energy distribution of the negative monatomic ions produced by the collisions of H3 +, D3 + and HD2 + on He. The relevance of the negative ion production of the mentioned reaction has been widely discussed, not only for its relation with thermonuclear research but also because recently the process H3 (D3 + or HD2 +) + He – – –> H– (D–) + 2 H+ (or D+) was considered as a heavy particle analog to the threshold ionization process e– + He —> (He–)* —> He+ + 2e. In the heavy particle alternative, at keV energies, the charge transfer is unlikely and the negative atomic ions are assumed to be formed as a result from three body coulomb break up. It is supposed that the triatomic molecules are excited through a collision with He.