DIFFUSION OF LIGHT ADATOMS ON SOLID SURFACES

1995 ◽  
Vol 09 (06) ◽  
pp. 307-318
Author(s):  
L. Y. CHEN ◽  
S. C. YING
Keyword(s):  
Experimental Data ◽  
Low Temperature ◽  
Theoretical Approach ◽  
Temperature Regime ◽  
Quantum Tunneling ◽  
Entire Range ◽  
Solid Surfaces ◽  
Recent Experimental Data ◽  
Thermally Activated ◽  
Theoretical Results

We present a brief review of a theoretical approach to the diffusion of light adatoms that covers the entire range from the classical regime of thermally activated hopping to the low temperature regime of quantum tunneling between adjacent sites. We compare our theoretical results with recent experimental data for the system H/Ni(100). We also contrast our results with those obtained from the quantum transition state approach.

TWO-LEVEL TUNNELLING MODEL DESCRIPTION OF THERMAL CONDUCTIVITY FOR CuxSn1-x METALLIC GLASSES AT LOW TEMPERATURE

2003 ◽  
Vol 17 (11) ◽  
pp. 2259-2271
Author(s):  
G. M. BHUIYAN ◽  
MD. SHAHJAHAN ◽  
ISSAM ALI ◽  
S. M. MUJIBUR RAHMAN
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Low Temperature ◽  
Metallic Glasses ◽  
Model Description ◽  
Recent Experimental Data ◽  
Model Parameters ◽  
Scattering Mechanism ◽  
Fitting Procedure ◽  
Theoretical Results

The two level tunnelling model is applied to analyze recent experimental data on low temperature thermal conductivity of Cu x Sn 1-x metallic glasses. An extra scattering mechanism due to Rayleigh is introduced to describe three characteristic regions of conductivity. Model parameters are determined using least-squares fitting procedure. Results derived from the parameters allow one to predict several interesting low temperature properties of metallic glasses in particular the characteristic plateau of conductivity. Theoretical results are also compared and contrasted with those of other metallic and non-metallic systems, and both common and uncommon features that exist between them are discussed.

scholarly journals Mobility Enhancement in Square Quantum Wells: Symmetric Modulation of the Envelop Wave Function

2010 ◽  
Vol 20 (3) ◽  
pp. 193
Author(s):  
Doan Nhat Quang ◽  
Nguyen Huyen Tung ◽  
Nguyen Trung Hong ◽  
Tran Thi Hai
Keyword(s):  
Experimental Data ◽  
Wave Function ◽  
Low Temperature ◽  
Quantum Wells ◽  
Quantum Transport ◽  
Variational Approach ◽  
Theoretical Study ◽  
Recent Experimental Data ◽  
Carrier Distribution ◽  
Analytic Expressions

We present a theoretical study of the effects from symmetric modulation of the envelop wave function on quantum transport in square quantum wells (QWs). Within the variational approach we obtain analytic expressions for the carrier distribution and their scattering in symmetric two-side doped square QWs. Roughness-induced scattering are found significantly weaker than those in the asymmetric one-side doped counterpart. Thus, we propose symmetric modulation of the wave function as an efficient method for enhancement of the roughness-limited QW mobility. Our theory is able to well reproduce the recent experimental data about low-temperature transport of electrons and holes in two-side doped square QWs, e.g., the mobility dependence on the channel width, which have not been explained so far.

scholarly journals Effect of Solar Modulation on the Low Energy Sea Level Muon Spectrum Near the Geomagnetic Equator

1978 ◽  
Vol 31 (5) ◽  
pp. 451 ◽  
Author(s):  
DP Bhattacharyya
Keyword(s):  
Experimental Data ◽  
Sea Level ◽  
Low Energy ◽  
Solar Modulation ◽  
Recent Experimental Data ◽  
Geomagnetic Equator ◽  
Muon Spectrum ◽  
Muon Intensity ◽  
Theoretical Results

A study is made of the influence of long-term solar modulation on the low energy sea level muon spectrum near the geomagnetic equator. Recent experimental data are compared with theoretical results calculated from the phenomenological model of Allkofer and Dau. It is suggested that the observed enhancement in the muon intensity is mainly due to a shift in the solar potential.

scholarly journals The quasi-low temperature behaviour of specific heat

2019 ◽  
Vol 6 (1) ◽  
pp. 171285 ◽  
Author(s):  
Yuri Vladimirovich Gusev
Keyword(s):  
Field Theory ◽  
Experimental Data ◽  
Low Temperature ◽  
Specific Heat ◽  
Temperature Regime ◽  
Silver Chloride ◽  
Condensed Matter ◽  
Fourth Power ◽  
Temperature Behaviour ◽  
Lattice Materials

A new mathematical approach to condensed matter physics, based on the finite temperature field theory, was recently proposed. The field theory is a scale-free formalism; thus, it denies absolute values of thermodynamic temperature and uses dimensionless thermal variables, which are obtained with the group velocities of sound and the interatomic distance. This formalism was previously applied to the specific heat of condensed matter and predicted its fourth power of temperature behaviour at sufficiently low temperatures, which was tested by experimental data for diamond lattice materials. The range of temperatures with the quartic law varies for different materials; therefore, it is called the quasi-low temperature regime. The quasi-low temperature behaviour of specific heat is verified here with experimental data for the fcc lattice materials, silver chloride and lithium iodide. The conjecture that the fourth order behaviour is universal for all condensed matter systems has also supported the data for glassy matter: vitreous silica. This law is long known to hold for the bcc solid helium-4. The characteristic temperatures of the threshold of the quasi-low temperature regime are found for the studied materials. The scaling in the specific heat of condensed matter is expressed by the dimensionless parameter, which is explored with the data for several glasses. The explanation of the correlation of the ‘boson peak’ temperature with the shear velocity is proposed. The critique of the Debye theory of specific heat and the Born–von Karman model of the lattice dynamics is given.

Many Band Effects in Cuprate Superconductors

1997 ◽  
Vol 11 (13) ◽  
pp. 585-592
Author(s):  
S. P. Kruchinin ◽  
A. M. Yaremko ◽  
E. V. Mozdor
Keyword(s):  
Experimental Data ◽  
Fermi Level ◽  
Temperature Dependence ◽  
Theoretical Approach ◽  
Cuprate Superconductors ◽  
Electron Pair ◽  
Recent Experimental Data ◽  
Natural Manner ◽  
System A ◽  
Interacting Electrons

The new theoretical approach is proposed for study the states responsible for superconductivity of crystals. Within the frameworks of worked out approach it is shown that in electron–phonon system a class of new so-called coupled states arises. Postulated in BCS method electron-pair states k1 + k2 = 0, s + s′ = 0 are in natural manner included in this class. The model numerical calculations have shown that SC gap depends on number of bands crossing the Fermi level on the momenta k1+k2 = K≠ 0 of interacting electrons and that the temperature dependence of SC gap for HTSC is more complicated (in agreement with the recent experimental data) then predicted in BCS approach.

Tsallis-Statistical Approach to the Specific Heat of LIQUID 4HE: Comparison with Other Results

1997 ◽  
Vol 11 (19) ◽  
pp. 2303-2310 ◽  
Author(s):  
Sergio Curilef ◽  
Andrés R. R. Papa
Keyword(s):  
Experimental Data ◽  
Comparative Analysis ◽  
Quantum Group ◽  
Specific Heat ◽  
High Precision ◽  
Theoretical Approach ◽  
Statistical Approach ◽  
Precision Measurements ◽  
Best Fitting ◽  
Theoretical Results

A theoretical approach within a quantum-group formalism has recently been proposed and successfully compared to Greywall's high precision measurements of the liquid 4 He specific heat. We calculate here the specific heat for 4 He using Tsallis' non-extensive thermostatistics. A comparative analysis reveals that there is a temperature range where our theoretical results yield the best fitting to experimental data.

Study of Electrical Conductivity in WO3-doped Nonstoichiometric LiTaO3

2012 ◽  
Vol 57 (8) ◽  
pp. 834
Author(s):  
M. Tahiri ◽  
N. Masaif ◽  
A. Jennane ◽  
E.M. Lotfi
Keyword(s):  
Experimental Data ◽  
Electrical Conductivity ◽  
Ternary System ◽  
Curie Temperature ◽  
Solid Solutions ◽  
Theoretical Approach ◽  
Defect Structure ◽  
Experimental Conductivity ◽  
Theoretical Results ◽  
Good Agreement

The results of experimental and analytical studies of the electrical conductivity for different solid solutions synthesized in a vicinity of LiTaO3 in the ternary system Li2O–Ta2O5–(WO3)2 are presented. It is shown that the electrical conductivity increases linearly with the Curie temperature. The experimental conductivity between 200 and 700 ºC was measured using an LCR bridge HP4192A on ceramics sintered at 1250 ºC. Within the theoretical approach to the defect structure analysis combined with our proposed vacancy models, the theoretical results are in a good agreement with the experimental data.

Two temperature regimes of triplet transfer in the dissociation of the correlated triplet pair after singlet fission

2019 ◽  
Vol 97 (6) ◽  
pp. 465-473 ◽  
Author(s):  
Tia S. Lee ◽  
YunHui L. Lin ◽  
Hwon Kim ◽  
Barry P. Rand ◽  
Gregory D. Scholes
Keyword(s):  
Low Temperature ◽  
Temperature Dependence ◽  
Temperature Regime ◽  
Transient Absorption Spectroscopy ◽  
Type Model ◽  
Singlet Fission ◽  
Temperature Dependent ◽  
Thermally Activated ◽  
Pair Separation ◽  
Triplet Pair

The ability to undergo spin-allowed exciton multiplication makes singlet fission materials promising for photovoltaic applications. Here, we examine the separation of correlated triplet pairs, 1(T…T), in polycrystalline pentacene films via temperature-dependent transient absorption spectroscopy. Single wavelength analysis reveals a profound delay in 1(T…T) dynamics. Moreover, the dynamics of 1(T…T) exhibit temperature dependence, whereas other features show no discernable temperature dependence. Previous literatures have suggested that correlated triplet separation is mediated by a thermally activated hopping process. Surprisingly, we found that the time constants governing triplet pair separation display two distinct temperature-dependent regimes of triplet transport. The high temperature regime follows a thermally activated hopping mechanism. The experimentally derived reorganization energy and electronic coupling is verified by density matrix renormalization group quantum chemical calculations. In addition, we evaluated the low temperature regime and show that the trend can be modelled by a Miller–Abrahams-type model that incorporates the effects of energetic disorder. We conclude that the correlated triplet pair separation is mediated by thermally activated hopping or a disorder driven Miller–Abrahams-type mechanism at high and low temperature, respectively. We observe that crossover between two regimes occurs ∼226 K. We find the time constant for triplet–triplet energy transfer to be 1.8 ps at ambient temperature and 21 ps at 77 K.

Fusion and Breakup Reactions of 17S + 208Pb and 15C + 232ThHalo Nuclei Systems

2015 ◽  
Vol 11 (2) ◽  
pp. 2972-2978
Author(s):  
Fouad A. Majeed ◽  
Yousif A. Abdul-Hussien
Keyword(s):  
Experimental Data ◽  
Cross Section ◽  
Fusion Reaction ◽  
Fusion Cross Section ◽  
Reaction Cross ◽  
Recent Experimental Data ◽  
Barrier Distribution ◽  
Coupled Channel ◽  
Total Fusion ◽  
Full Quantum

In this study the calculations of the total fusion reaction cross section have been performed for fusion reaction systems 17F + 208Pb and 15C + 232Th which involving halo nuclei by using a semiclassical approach.The semiclassical treatment is comprising the WKB approximation to describe the relative motion between target and projectile nuclei, and Continuum Discretized Coupled Channel (CDCC) method to describe the intrinsic motion for both target and projectile nuclei. For the same of comparsion a full quantum mechanical clacualtions have been preforemd using the (CCFULL) code. Our theorticalrestuls are compared with the full quantum mechaincialcalcuations and with the recent experimental data for the total fusion reaction  checking the stability of the distancesThe coupled channel calculations of the total fusion cross section σfus, and the fusion barrier distribution Dfus. The comparsion with experiment proves that the semiclassiacl approach adopted in the present work reproduce the experimental data better that the full quantal mechanical calcautions. 

Seeking the Good Fitting Procedure of PALS Polymer Spectra

2008 ◽  
Vol 607 ◽  
pp. 64-66
Author(s):  
Nicolas Laforest ◽  
Jérémie De Baerdemaeker ◽  
Corine Bas ◽  
Charles Dauwe
Keyword(s):  
Experimental Data ◽  
Low Temperature ◽  
Positron Annihilation ◽  
Physical Meaning ◽  
Lifetime Measurements ◽  
Positron Annihilation Lifetime ◽  
Fitting Procedure ◽  
Fitting Procedures ◽  
Blob Model

Positron annihilation lifetime measurements on polymethylmethacrylate (PMMA) at low temperature were performed. Different discrete fitting procedures have been used to analyze the experimental data. It shows that the extracted parameters depend strongly on the fitting procedure. The physical meaning of the results is discussed. The blob model seems to give the best annihilation parameters.

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