PHONON CONFINEMENT IN ULTRATHIN METALLIC FILMS: INTERPRETATION OF RECENT FEMTOSECOND PUMP-PROBE EXPERIMENTAL DATA

Author(s):  
A. MELIKYAN ◽  
H. MINASSIAN
2020 ◽  
Vol 221 ◽  
pp. 110-132 ◽  
Author(s):  
Max Marcus ◽  
George C. Knee ◽  
Animesh Datta

We propose a witness for quantum coherence in EET that can be extracted directly from two-pulse pump–probe spectroscopy experimental data.


1995 ◽  
Vol 04 (01) ◽  
pp. 245-260 ◽  
Author(s):  
K. J. McEWAN ◽  
R. C. HOLLINS

The contributions to the nonlinear absorption of liquid crystal media in their isotropic phase are measured using a picosecond pump/probe technique at 587 nm. Good agreement between the experimental data and theory is obtained by assuming that two-photon absorption and excited state absorption dominate the nonlinear optical response. The important parameters are extracted from the experimental data and it is shown that the nonlinear absorption depends strongly on the molecular structure. The lifetime of the excited state is measured and found to compare well with the fluorescence lifetime.


1998 ◽  
Vol 528 ◽  
Author(s):  
H. Dreysse ◽  
M. Freyss ◽  
D. Stoeffler

AbstractGrowth phenomena and magnetism of metallic films are not easy to describe at the same level of precision. A small variation of distances can drastically modify the magnetic properties of thin metallic films. In this contribution different aspects encountered in the growth of thin magnetic metallic films are addressed. Within an itinerant magnetism scheme, the main difficulty arises from the number of possible magnetic arrangements induced by the competition between nearest-neighbors Ferromagnetic and Antiferromagnetic couplings. However we show that the description of the electronic and magnetic structure at T = 0 K by well-established band structure frameworks provides useful and precise information on the growth of a transition metal on another. Due to the large amount of experimental data available, the Fe/Cr system is taken as an example. The influence of steps at the interface is discussed and the possibility of magnetic domains is shown. A simple model of growth taking into account variable interdiffusion rate and layer-by-layer quality is given. These simulations are used to explain experimental results where interdiffusion at the interface is very common.


1994 ◽  
Vol 116 (1) ◽  
pp. 28-34 ◽  
Author(s):  
Sunil Kumar ◽  
George C. Vradis

This study examines the effect of transverse thickness on the in-plane thermal conductivity of single crystal, defect-free, thin metallic films. The imposed temperature gradient is along the film and the transport of thermal energy is predominantly due to free electron motion. The small size necessitates an evaluation of the Boltzmann equation of electron transport along with appropriate electron scattering boundary conditions. Simple expressions for the reduction of conductivity due to increased dominance of boundary scattering are presented and the results are compared with other simplified approaches and experimental data from the literature. Grain boundary scattering is also considered via simple arguments.


Author(s):  
A. Gómez ◽  
P. Schabes-Retchkiman ◽  
M. José-Yacamán ◽  
T. Ocaña

The splitting effect that is observed in microdiffraction pat-terns of small metallic particles in the size range 50-500 Å can be understood using the dynamical theory of electron diffraction for the case of a crystal containing a finite wedge. For the experimental data we refer to part I of this work in these proceedings.


Author(s):  
J. Silcox ◽  
R. H. Wade

Recent work has drawn attention to the possibilities that small angle electron scattering offers as a source of information about the micro-structure of vacuum condensed films. In particular, this serves as a good detector of discontinuities within the films. A review of a kinematical theory describing the small angle scattering from a thin film composed of discrete particles packed close together will be presented. Such a model could be represented by a set of cylinders packed side by side in a two dimensional fluid-like array, the axis of the cylinders being normal to the film and the length of the cylinders becoming the thickness of the film. The Fourier transform of such an array can be regarded as a ring structure around the central beam in the plane of the film with the usual thickness transform in a direction normal to the film. The intensity profile across the ring structure is related to the radial distribution function of the spacing between cylinders.


Author(s):  
K.B. Reuter ◽  
D.B. Williams ◽  
J.I. Goldstein

In the Fe-Ni system, although ordered FeNi and ordered Ni3Fe are experimentally well established, direct evidence for ordered Fe3Ni is unconvincing. Little experimental data for Fe3Ni exists because diffusion is sluggish at temperatures below 400°C and because alloys containing less than 29 wt% Ni undergo a martensitic transformation at room temperature. Fe-Ni phases in iron meteorites were examined in this study because iron meteorites have cooled at slow rates of about 10°C/106 years, allowing phase transformations below 400°C to occur. One low temperature transformation product, called clear taenite 2 (CT2), was of particular interest because it contains less than 30 wtZ Ni and is not martensitic. Because CT2 is only a few microns in size, the structure and Ni content were determined through electron diffraction and x-ray microanalysis. A Philips EM400T operated at 120 kV, equipped with a Tracor Northern 2000 multichannel analyzer, was used.


Author(s):  
C. C. Ahn ◽  
D. H. Pearson ◽  
P. Rez ◽  
B. Fultz

Previous experimental measurements of the total white line intensities from L2,3 energy loss spectra of 3d transition metals reported a linear dependence of the white line intensity on 3d occupancy. These results are inconsistent, however, with behavior inferred from relativistic one electron Dirac-Fock calculations, which show an initial increase followed by a decrease of total white line intensity across the 3d series. This inconsistency with experimental data is especially puzzling in light of work by Thole, et al., which successfully calculates x-ray absorption spectra of the lanthanide M4,5 white lines by employing a less rigorous Hartree-Fock calculation with relativistic corrections based on the work of Cowan. When restricted to transitions allowed by dipole selection rules, the calculated spectra of the lanthanide M4,5 white lines show a decreasing intensity as a function of Z that was consistent with the available experimental data.Here we report the results of Dirac-Fock calculations of the L2,3 white lines of the 3d and 4d elements, and compare the results to the experimental work of Pearson et al. In a previous study, similar calculations helped to account for the non-statistical behavior of L3/L2 ratios of the 3d metals. We assumed that all metals had a single 4s electron. Because these calculations provide absolute transition probabilities, to compare the calculated white line intensities to the experimental data, we normalized the calculated intensities to the intensity of the continuum above the L3 edges. The continuum intensity was obtained by Hartree-Slater calculations, and the normalization factor for the white line intensities was the integrated intensity in an energy window of fixed width and position above the L3 edge of each element.


1991 ◽  
Vol 16 (6) ◽  
pp. 623-638 ◽  
Author(s):  
P.A. Badoz ◽  
F. Arnaud d'Avitaya ◽  
E. Rosencher

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