scholarly journals Experimental evidence of strong phonon scattering in isotopical disordered systems: The case ofLiHxD1−x

1995 ◽  
Vol 51 (14) ◽  
pp. 8874-8877 ◽  
Author(s):  
V. G. Plekhanov
Keyword(s):  
Experimental Evidence ◽  
Disordered Systems ◽  
Phonon Scattering

Experimental evidence for trapped exciton states in liquid rare gases

1970 ◽  
Vol 317 (1528) ◽  
pp. 113-131 ◽  
Keyword(s):  
Experimental Evidence ◽  
Absorption Spectra ◽  
Disordered Systems ◽  
Vacuum Ultraviolet ◽  
Solid Phase ◽  
Liquid System ◽  
Rare Gases ◽  
Line Broadening ◽  
Absorption Bands ◽  
Additional Line

In connexion with studies of the electronic structure of disordered systems, we enquire whether there exist exciton states in simple liquids. We report the results of a vacuum ultraviolet spectroscopic study of liquid argon and of liquid krypton doped with xenon. Experimental evidence was obtained for Wannier-Mott type impurity states in liquids which have no parentage in the excited states of the isolated atoms constituting the dense fluid. The absorption spectra of the doped liquid rare gases were monitored in the region 160 to 120 nm. The following experimental results are reported: (a) In the Xe/Ar liquid two absorption bands corresponding to the 1 S 0 → 3 P 1 and to the 1 S 0 → 1 P 1 transitions (or alternatively to the n = 1 Wannier states) were identified at 141 nm (8.80eV)† and at 123nm (10.1 eV). An additional line was observed at 127 nm (9.76eV). (b) In the Xe/Kr liquid three absorption bands were observed at 144.5 nm (8.59 eV), 125.5 nm (9.89 eV) and 129 nm (9.6 eV). (c) The absorption spectra of the doped liquids were compared with the spectra of 1 cm thick doped solid rare-gas crystals. From these results we conclude that: (a) The 127 nm (9.76 eV) band in the Xe/Ar liquid system and the 129 nm (9.61 eV) band in the Xe/Kr liquid system cannot be attributed to a perturbed ‘atomic’ state and are assigned to the n = 2 Wannier state in the liquid. (b) Line broadening of exciton states in the liquid can be accounted for by a simple scattering model. (c) Preliminary information on band gaps in liquid rare gases were obtained from the spectroscopic data. (d) The effect of liquid-solid phase transition on the line broadening of exciton states is consistent with electron mobility data in these systems.

scholarly journals Experimental evidence of disorder enhanced electron-phonon scattering in graphene devices

Carbon ◽  
2020 ◽  
Author(s):  
Charalambos Evangeli ◽  
Edward McCann ◽  
Jacob L. Swett ◽  
Sumit Tewari ◽  
Xinya Bian ◽  
...  
Keyword(s):  
Experimental Evidence ◽  
Phonon Scattering ◽  
Graphene Devices ◽  
Electron Phonon Scattering

scholarly journals A universal Urbach rule for disordered organic semiconductors

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Christina Kaiser ◽  
Oskar J. Sandberg ◽  
Nasim Zarrabi ◽  
Wei Li ◽  
Paul Meredith ◽  
...  
Keyword(s):  
Organic Semiconductors ◽  
Organic Solar Cells ◽  
Disordered Systems ◽  
Urbach Energy ◽  
Phonon Scattering ◽  
Exponential Tail ◽  
Temperature Dependent ◽  
Static Disorder ◽  
Line Shapes ◽  
Gaussian Density

AbstractIn crystalline semiconductors, absorption onset sharpness is characterized by temperature-dependent Urbach energies. These energies quantify the static, structural disorder causing localized exponential-tail states, and dynamic disorder from electron-phonon scattering. Applicability of this exponential-tail model to disordered solids has been long debated. Nonetheless, exponential fittings are routinely applied to sub-gap absorption analysis of organic semiconductors. Herein, we elucidate the sub-gap spectral line-shapes of organic semiconductors and their blends by temperature-dependent quantum efficiency measurements. We find that sub-gap absorption due to singlet excitons is universally dominated by thermal broadening at low photon energies and the associated Urbach energy equals the thermal energy, regardless of static disorder. This is consistent with absorptions obtained from a convolution of Gaussian density of excitonic states weighted by Boltzmann-like thermally activated optical transitions. A simple model is presented that explains absorption line-shapes of disordered systems, and we also provide a strategy to determine the excitonic disorder energy. Our findings elaborate the meaning of the Urbach energy in molecular solids and relate the photo-physics to static disorder, crucial for optimizing organic solar cells for which we present a revisited radiative open-circuit voltage limit.

Enhancement of interaction constants in disordered systems: Experimental evidence

1986 ◽  
Vol 33 (10) ◽  
pp. 7277-7280 ◽  
Author(s):  
C. Castellani ◽  
C. DiCastro ◽  
H. Fukuyama ◽  
P. A. Lee ◽  
M. Ma
Keyword(s):  
Experimental Evidence ◽  
Disordered Systems

scholarly journals Experimental evidence of enhanced broadband transmission in disordered systems with mirror symmetry

2021 ◽  
Vol 119 (14) ◽  
pp. 141104
Author(s):  
Matthieu Davy ◽  
Clément Ferise ◽  
Élie Chéron ◽  
Simon Félix ◽  
Vincent Pagneux
Keyword(s):  
Experimental Evidence ◽  
Mirror Symmetry ◽  
Disordered Systems

scholarly journals Phonon Lifetimes and Thermal Conductivity of the Molecular Crystal α-RDX

MRS Advances ◽  
2019 ◽  
Vol 4 (40) ◽  
pp. 2191-2199 ◽  
Author(s):  
Gaurav Kumar ◽  
Francis G. VanGessel ◽  
Daniel C. Elton ◽  
Peter W. Chung
Keyword(s):  
Thermal Conductivity ◽  
Thermal Transport ◽  
Disordered Systems ◽  
Molecular Crystal ◽  
Amorphous Materials ◽  
Phonon Scattering ◽  
Large Degree ◽  
Crystalline Materials ◽  
Boltzmann Model ◽  
Transfer Properties

ABSTRACTThe heat transfer properties of the organic molecular crystal α-RDX were studied using three phonon scattering based thermal conductivity models. It was found that the widely used Peierls-Boltzmann model for thermal transport in crystalline materials breaks down for α-RDX. We show this breakdown is due to a large degree of anharmonicity that leads to a dominance of diffusive-like carriers. Despite being developed for disordered systems, the Allen-Feldman theory for thermal conductivity actually gives the best description of thermal transport. This is likely because diffusive carriers contribute to over 95% of the thermal conductivity in α-RDX. The dominance of diffusive carriers is larger than previously observed in other fully ordered crystalline systems. These results indicate that van der Waals bonded organic crystalline solids conduct heat in a manner more akin to amorphous materials than simple atomic crystals.

How do memory modules differentially contribute to familiarity and recollection?

2019 ◽  
Vol 42 ◽  
Author(s):  
Olya Hakobyan ◽  
Sen Cheng
Keyword(s):  
Recognition Memory ◽  
Experimental Evidence ◽  
Subjective Experience ◽  
Target Article ◽  
Memory Modules ◽  
Familiarity And Recollection ◽  
Memory Contents

Abstract We fully support dissociating the subjective experience from the memory contents in recognition memory, as Bastin et al. posit in the target article. However, having two generic memory modules with qualitatively different functions is not mandatory and is in fact inconsistent with experimental evidence. We propose that quantitative differences in the properties of the memory modules can account for the apparent dissociation of recollection and familiarity along anatomical lines.

Redox Reactions in Lipid Membranes as a Model for Primordial Energy-Conserving Systems

1997 ◽  
Vol 161 ◽  
pp. 437-442
Author(s):  
Salvatore Di Bernardo ◽  
Romana Fato ◽  
Giorgio Lenaz
Keyword(s):  
Experimental Evidence ◽  
Lipid Membranes ◽  
Energy Supply ◽  
Redox Reactions ◽  
Living Systems ◽  
Asymmetric Distribution ◽  
Conservation Of Energy ◽  
Asymmetrical Distribution ◽  
Energy Conserving ◽  
Living Organisms

AbstractOne of the peculiar aspects of living systems is the production and conservation of energy. This aspect is provided by specialized organelles, such as the mitochondria and chloroplasts, in developed living organisms. In primordial systems lacking specialized enzymatic complexes the energy supply was probably bound to the generation and maintenance of an asymmetric distribution of charged molecules in compartmentalized systems. On the basis of experimental evidence, we suggest that lipophilic quinones were involved in the generation of this asymmetrical distribution of charges through vectorial redox reactions across lipid membranes.

A Method for Setting the Clearance Angle

1972 ◽  
Vol 30 ◽  
pp. 388-389
Author(s):  
Michael T. Bucek ◽  
Howard J. Arnott
Keyword(s):  
Experimental Evidence ◽  
Light Source ◽  
Black Spot ◽  
Critical Factor ◽  
Clearance Angle ◽  
Crude Approximation ◽  
Ultrathin Sections

It is believed by the authors, with supporting experimental evidence, that as little as 0.5°, or less, knife clearance angle may be a critical factor in obtaining optimum quality ultrathin sections. The degree increments located on the knife holder provides the investigator with only a crude approximation of the angle at which the holder is set. With the increments displayed on the holder one cannot set the clearance angle precisely and reproducibly. The ability to routinely set this angle precisely and without difficulty would obviously be of great assistance to the operator. A device has been contrived to aid the investigator in precisely setting the clearance angle. This device is relatively simple and is easily constructed. It consists of a light source and an optically flat, front surfaced mirror with a minute black spot in the center. The mirror is affixed to the knife by placing it permanently on top of the knife holder.

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