Experimental detection of collective modes In a polar liquid: application to the case of the solvated electron in H2O and NH3

1977 ◽  
Vol 55 (11) ◽  
pp. 1916-1919 ◽  
Author(s):  
Gianni Ascarelli
Keyword(s):  
Ionic Crystal ◽  
Collective Mode ◽  
Continuum Theory ◽  
Longitudinal Optical ◽  
Collective Modes ◽  
Coupling Constant ◽  
Optical Mode ◽  
Solvated Electron ◽  
Low Frequencies ◽  
Longitudinal Optical Mode

We present experimental data that confirm the predicted existence of a collective mode in a liquid corresponding to the longitudinal optical mode in an ionic crystal. The experimental investigation was carried out in nitromethane, and the results bear out all the calculated properties of this collective mode: the dipolar plasmon. The calculated frequency of the dipolar plasmon, as well as the dielectric constant at high and low frequencies, are then used to calculate without adjustable parameters the polaron coupling constant of the solvated electron in NH3 and H2O. A comparison of the calculated and measured properties of the solvated electron indicates that in either case a polaron-like continuum theory can at most account for only a fraction of the energy of the observed optical absorption.

Redshift ofA1(longitudinal optical) mode for GaN crystals under strong electric field

2017 ◽  
Vol 11 (1) ◽  
pp. 011002 ◽  
Author(s):  
Hong Gu ◽  
Kaijie Wu ◽  
Shunan Zheng ◽  
Lin Shi ◽  
Min Zhang ◽  
...  
Keyword(s):  
Electric Field ◽  
Strong Electric Field ◽  
Longitudinal Optical ◽  
Optical Mode ◽  
Longitudinal Optical Mode

Mechanisms of Raman Scattering in doped Indium Nitride

2004 ◽  
Vol 831 ◽  
Author(s):  
Claire Pinquier ◽  
François Demangeot ◽  
Jean Frandon ◽  
Miguel Gaio ◽  
Olivier Briot ◽  
...  
Keyword(s):  
Light Scattering ◽  
Raman Scattering ◽  
Charge Density ◽  
Dielectric Function ◽  
Density Fluctuation ◽  
Indium Nitride ◽  
Longitudinal Optical ◽  
Optical Mode ◽  
Longitudinal Optical Mode ◽  
Strong Mode

ABSTRACTHighly n-doped InN layers are investigated by means of Raman scattering: a strong mode is evidenced near the frequency of the A1(LO) phonon, despite the high conductivity of the films. This observation is interpreted assuming the breakdown of the wave-vector conservation leading to the decoupling of the plasmon from the phonon. The lineshape of the longitudinal optical mode is simulated using the Lindhard-Mermin dielectric function for various light scattering processes: we found that the charge density fluctuation mechanism is dominant, at least in the visible excitation range.

The Effects of Substrate Bias and Si Doping on the Properties of Rf Sputtered Bn Films

1992 ◽  
Vol 242 ◽  
Author(s):  
P.K. Banerjee ◽  
J.S. Kim ◽  
B. Chatterjee ◽  
M. Platek ◽  
S.S. Mitra
Keyword(s):  
Boron Nitride ◽  
Longitudinal Optical ◽  
Substrate Bias ◽  
Optical Mode ◽  
Linear Change ◽  
Temperature Range ◽  
Ir Transmission ◽  
Si Doped ◽  
Reflectivity Data ◽  
Boron Nitride Films

ABSTRACTThe effect of substrate bias on the properties of rf sputtered boron nitride films on Si and GaAs substrate were investigated. IR transmission and reflectivity of films with different substrate bias were measured with Perkin Elmer 983 IR spectroscopy. From the IR reflectivity data, transverse optical mode(TO) and longitudinal optical mode(LO) frequencies were derived by fitting Kramer-Kronig model. Absorption coefficient was determined from IR transmission data. The resultant TO and LO modes showed that substrate bias caused broadening of reststrahlen band of rf sputtered boron nitride. We also tried to dope boron nitride films with silicon by alternate sputtering of BN and Si targets controlling sputtering time of each target followed by annealing. Electrical resistivity was measured over the temperature range between 175 K to 370 K for both intrinsic and Si-doped boron nitride films. Intrinsic rf sputtered boron nitride showed Little change in resistivity (109 Ω cm - 1011 Ω cm ) over the temperature range studied. While Si doped BN showed linear change in resistivity with increasing temperature and its activation energy was about 0.22 eV. The effect of substrate bias was also investigated by monitoring the XPS core level spectra of both Bis and N Is peaks, respectively. Substrate bias caused the shift of both B ls and N ls peak to higher binding energy. The effect of substrate bias on refractive index was also studied.

On the thermodynamics of phase transitions in metal hydrides

Open Physics ◽  
2012 ◽  
Vol 10 (1) ◽  
Author(s):  
Andrea Vita
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Collective Mode ◽  
Metal Hydrides ◽  
Correlation Radius ◽  
Statistical Weight ◽  
Collective Modes ◽  
Boltzmann Factor ◽  
System Approaches ◽  
Second Order Phase Transition

AbstractMetal hydrides are solutions of hydrogen in a metal, where phase transitions may occur depending on temperature, pressure etc. We apply Le Chatelier’s principle of thermodynamics to a particular phase transition in TiHx, which can approximately be described as a second-order phase transition. We show that the fluctuations of the order parameter correspond to fluctuations both of the density of H+ ions and of the distance between adjacent H+ ions. Moreover, as the system approaches the transition and the correlation radius increases, we show -with the help of statistical mechanics-that the statistical weight of modes involving a large number of H+ ions (‘collective modes’) increases sharply, in spite of the fact that the Boltzmann factor of each collective mode is exponentially small. As a result, the interaction of the H+ ions with collective modes makes a tiny suprathermal fraction of the H+ population appear. Our results hold for similar transitions in metal deuterides, too. A violation of an -insofar undisputed-upper bound on hydrogen loading follows.

scholarly journals Single-particle states vs. collective modes: friends or enemies ?

2018 ◽  
Vol 178 ◽  
pp. 02003 ◽  
Author(s):  
T. Otsuka ◽  
Y. Tsunoda ◽  
T. Togashi ◽  
N. Shimizu ◽  
T. Abe
Keyword(s):  
Single Particle ◽  
Collective Motion ◽  
Collective Mode ◽  
Self Organization ◽  
Collective Modes ◽  
Particle State ◽  
Nuclear Forces ◽  
Atomic Nuclei ◽  
Many Body Systems ◽  
Underlying Mechanisms

The quantum self-organization is introduced as one of the major underlying mechanisms of the quantum many-body systems. In the case of atomic nuclei as an example, two types of the motion of nucleons, single-particle states and collective modes, dominate the structure of the nucleus. The collective mode arises as the balance between the effect of the mode-driving force (e.g., quadrupole force for the ellipsoidal deformation) and the resistance power against it. The single-particle energies are one of the sources to produce such resistance power: a coherent collective motion is more hindered by larger spacings between relevant single particle states. Thus, the single-particle state and the collective mode are “enemies” against each other. However, the nuclear forces are rich enough so as to enhance relevant collective mode by reducing the resistance power by changing single-particle energies for each eigenstate through monopole interactions. This will be verified with the concrete example taken from Zr isotopes. Thus, the quantum self-organization occurs: single-particle energies can be self-organized by (i) two quantum liquids, e.g., protons and neutrons, (ii) monopole interaction (to control resistance). In other words, atomic nuclei are not necessarily like simple rigid vases containing almost free nucleons, in contrast to the naïve Fermi liquid picture. Type II shell evolution is considered to be a simple visible case involving excitations across a (sub)magic gap. The quantum self-organization becomes more important in heavier nuclei where the number of active orbits and the number of active nucleons are larger.

KINETIC PHASE TRANSITION IN HONEYBEE FORAGING DYNAMICS: SYNERGY OF INDIVIDUAL AND COLLECTIVE

2020 ◽  
Vol 23 (06) ◽  
pp. 2050019
Author(s):  
VALERY TERESHKO
Keyword(s):  
Dynamical System ◽  
Collective Mode ◽  
Individual Behavior ◽  
Collective Modes ◽  
Complex Phase ◽  
Nectar Sources ◽  
Honeybee Colony ◽  
Collective Foraging ◽  
The Individual ◽  
Kinetic Phase Transition

We consider a honeybee colony as a dynamical system gathering information from an environment and accordingly adjusting its behavior. Collective foraging behavior is shown to be triggered by the change of either colony size or profitability of exploited nectar sources. The collective mode provides greater productivity compared to the individual one. The latter does not diminish the importance of individual behavior that ensures the adaptivity of the system. Thus, the transition from the phase of individual behavior to a more complex phase, combining both individual and collective modes, provides the most effective scenario of honeybee colony foraging.

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