Intermediate scattering function for macromolecules in solutions probed by neutron spin echo

AbstractThe Fixman-Kovac formulation of chain dynamics with constraints is used to calculate the first cumulant Q(q) of the dynamic scattering function. This general formalism is applied to the case of freely jointed chains. It is shown that the large q limit (q being the scattering wavenumber) of Q(q) for a chain of N bonds in the absence of hydrodynamic interaction is proportional to the ratio (2N+3)/3(N+l) representing the fraction of unconstrained degrees of freedom of the chain. The inclusion of hydrodynamic interaction seems to enhance the apparent segmental diffusion. The use of constrained chain dynamics has no appreciable effects, however, on the behavior of Q(q) in the small and intermediate q regions for long enough chains. This formalism can be used to interpret neutron (spin echo) scattering experiments from semiflexible polymers in solution.

Download Full-text

Data Analysis and Background Subtraction in Neutron Spin Echo Spectroscopy

Frontiers in Physics ◽

10.3389/fphy.2020.620082 ◽

2021 ◽

Vol 8 ◽

Author(s):

Ingo Hoffmann

Keyword(s):

Data Analysis ◽

Dynamic Range ◽

Time Window ◽

Spin Echo ◽

Neutron Spin ◽

Large Dynamic Range ◽

Single Measurement ◽

Complex Samples ◽

Neutron Spin Echo ◽

Intermediate Scattering Function

With the constantly improving performance of neutron spin echo (NSE) spectrometers it becomes possible to perform measurements on increasingly complex samples and to study more and more delicate effects. To properly study such effects, proper background correction becomes increasingly important. In this paper, we will review different methods to subtract the buffer from NSE measurements and study the effect of small errors in the subtraction of the background. In the large dynamic range of modern neutron spin-echo spectrometers multiple effects become visible in a single measurement. Specifically, for vesicles both membrane undulations and translational diffusion have an effect on the intermediate scattering function in the NSE time window and here, we will investigate how taking this into account differently affects the results obtained from data analysis.

Download Full-text

Study on the temperature-dependent coupling among viscosity, conductivity and structural relaxation of ionic liquids

Physical Chemistry Chemical Physics ◽

10.1039/c5cp02335a ◽

2015 ◽

Vol 17 (29) ◽

pp. 19126-19133 ◽

Cited By ~ 13

Author(s):

Tsuyoshi Yamaguchi ◽

Takuya Yonezawa ◽

Shinobu Koda

Keyword(s):

Ionic Liquids ◽

Structural Relaxation ◽

Spin Echo ◽

Neutron Spin ◽

Temperature Dependent ◽

Frequency Dependent ◽

Neutron Spin Echo ◽

Dependent Viscosity

The frequency-dependent viscosity and conductivity of three imidazolium-based ionic liquids were measured at several temperatures in the MHz region, and the results are compared with the intermediate scattering functions determined by neutron spin echo spectroscopy.

Download Full-text