Analytical treatment of spin diffusion in a three-spin (AMX and ABX) system in the long-correlation-time (ω0gtc, ⪢ 1) limit, for estimation of internuclear distances in macromolecules

1990 ◽  
Vol 88 (2) ◽  
pp. 284-304 ◽  
Author(s):  
A Majumdar ◽  
R.V Hosur
Keyword(s):  
Correlation Time ◽  
Spin Diffusion ◽  
Analytical Treatment ◽  
Internuclear Distances

Atomic Imaging of Crystals using Large-Angle Electron Scattering in STEM

1990 ◽  
Vol 48 (1) ◽  
pp. 74-75
Author(s):  
D.E. Jesson ◽  
S. J. Pennycook
Keyword(s):  
Wave Function ◽  
Electron Scattering ◽  
Numerical Solutions ◽  
Large Angle ◽  
Real Space ◽  
High Angle ◽  
Analytical Treatment ◽  
Order Zero ◽  
Experimental Conditions ◽  
Ewald Sphere

It is well known that conventional atomic resolution electron microscopy is a coherent imaging process best interpreted in reciprocal space using contrast transfer function theory. This is because the equivalent real space interpretation involving a convolution between the exit face wave function and the instrumental response is difficult to visualize. Furthermore, the crystal wave function is not simply related to the projected crystal potential, except under a very restrictive set of experimental conditions, making image simulation an essential part of image interpretation. In this paper we present a different conceptual approach to the atomic imaging of crystals based on incoherent imaging theory. Using a real-space analysis of electron scattering to a high-angle annular detector, it is shown how the STEM imaging process can be partitioned into components parallel and perpendicular to the relevant low index zone-axis.It has become customary to describe STEM imaging using the analytical treatment developed by Cowley. However, the convenient assumption of a phase object (which neglects the curvature of the Ewald sphere) fails rapidly for large scattering angles, even in very thin crystals. Thus, to avoid unpredictive numerical solutions, it would seem more appropriate to apply pseudo-kinematic theory to the treatment of the weak high angle signal. Diffraction to medium order zero-layer reflections is most important compared with thermal diffuse scattering in very thin crystals (<5nm). The electron wave function ψ(R,z) at a depth z and transverse coordinate R due to a phase aberrated surface probe function P(R-RO) located at RO is then well described by the channeling approximation;

Nuclear spin diffusion in a rare spin species

1982 ◽  
Vol 43 (7) ◽  
pp. 1049-1058 ◽  
Author(s):  
M. Goldman ◽  
J.F. Jacquinot
Keyword(s):  
Nuclear Spin ◽  
Spin Diffusion ◽  
Spin Species

Longitudinal electronic and nuclear spin diffusion in atomic hydrogen

1985 ◽  
Vol 46 (8) ◽  
pp. 1335-1344 ◽  
Author(s):  
J.P. Bouchaud ◽  
C. Lhuillier
Keyword(s):  
Nuclear Spin ◽  
Atomic Hydrogen ◽  
Spin Diffusion

Study of polymer chain dynamics in solution by time-resolved spectrofluorometry

1989 ◽  
Vol 54 (11) ◽  
pp. 3011-3024 ◽  
Author(s):  
Vlastimil Fidler ◽  
Stefan Vajda ◽  
Zuzana Limpouchová ◽  
Jiří Dvořák ◽  
Karel Procházka ◽  
...  
Keyword(s):  
Aqueous Solutions ◽  
Conformational Changes ◽  
Methacrylic Acid ◽  
Correlation Time ◽  
General Level ◽  
Polymeric Chain ◽  
Relative Molecular Mass ◽  
Chain Dynamics ◽  
Time Resolved ◽  
Covalently Bonded

The methodology of polarization time-resolved fluorometry and interpretation of its results are outlined at a general level, and the measurement on and use of facilities of the Edinburgh Instruments Model 299T apparatus are discussed in detail. The dynamics of conformational changes in chains of poly(methacrylic acid) containing covalently bonded dansyl labels are studied in aqueous solutions at various pH. It is shown that at pH > 6, the shorter effective rational correlation time τr < 2 ns corresponds to the rotation of the free dansyl label about bonds by which it is attached to the polymeric chain; at pH < 4 the longer effective rational correlation time τr = 20-26 ns corresponds to the rotation of the compact spherical formation constituted by a part of the collapsed polymeric chain in which the label is fixed and whose relative molecular mass is approx. 15 000-20 000.

Incoherent spin current

2017 ◽  
Author(s):  
K. Ando ◽  
E. Saitoh
Keyword(s):  
Diffusion Equation ◽  
Spin Density ◽  
Spin Diffusion ◽  
Spin Injection ◽  
Spin Current ◽  
Ferromagnetic Semiconductor ◽  
Electrochemical Potential ◽  
Semiconductor Interface ◽  
Interface Resistance ◽  
Inhomogeneous Spin

This chapter introduces the concept of incoherent spin current. A diffusive spin current can be driven by spatial inhomogeneous spin density. Such spin flow is formulated using the spin diffusion equation with spin-dependent electrochemical potential. The chapter also proposes a solution to the problem known as the conductivity mismatch problem of spin injection into a semiconductor. A way to overcome the problem is by using a ferromagnetic semiconductor as a spin source; another is to insert a spin-dependent interface resistance at a metal–semiconductor interface.

Sign in / Sign up

Export Citation Format

Share Document