oalib
Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Photo- excitation of Cd atom by optogalvanic technique monitoring  [cached]
M. H. Mahdieh,H. Ghasem,N. Mohammadzadeh
Iranian Journal of Physics Research , 2004,
Abstract: Optogalavanic technique has been used widely in laser spectroscopy. In this paper we have presented the results of an experimental three- step photo- excitation of Gd atom, using optogalvanic technique. Three tunable dye laser pulses were applied to excite the Gd atom in a three-step photo – excitation process. The optogalvanic signal was used to monitor the laser wavelength and efficiency of the excitation process. The results show that the optogalvanic signal is very sensitive to the first photo- excitation step in comparison with those of the second and the third step.
Fluctuation-Dissipation Relations of a Tunnel Junction Driven by a Quantum Circuit  [PDF]
O. Parlavecchio,C. Altimiras,J. -R. Souquet,P. Simon,I. Safi,P. Joyez,D. Vion,P. Roche,D. Esteve,F. Portier
Physics , 2014, DOI: 10.1103/PhysRevLett.114.126801
Abstract: We derive fluctuation-dissipation relations for a tunnel junction driven by a high impedance microwave resonator, displaying strong quantum fluctuations. We find that the fluctuation-dissipation relations derived for classical forces hold, provided the effect of the circuit's quantum fluctuations is incorporated into a modified non-linear $I(V)$ curve. We also demonstrate that all quantities measured under a coherent time dependent bias can be reconstructed from their dc counterpart with a photo-assisted tunneling relation. We confirm these predictions by implementing the circuit and measuring the dc current through the junction, its high frequency admittance and its current noise at the frequency of the resonator.
Investigation of dissipation in a quantum LC circuit  [cached]
D Nasr Esfahani,F Kheirandish
Iranian Journal of Physics Research , 2010,
Abstract: In this article we consider the resistance of a quantum LC circuit as a heat bath. The heat bath can be modeled by a collection of quantum harmonic oscillators with a continuum of frequencies. By using the minimal coupling method between the circuit and the field describing the environment, the process of energy dissipation and probability transitions between the energy levels of the quantum circuit, are obtained.
Correlation between Trion and Hole in Fermi Distribution in Process of Trion Photo-excitation in Doped QWs  [PDF]
R. A. Suris
Physics , 2013,
Abstract: The problem of correlation between a trion and a hole in the electron Fermi distribution created in the process of trion photo-excitation in doped quantum wells is under consideration. The hole in the Fermi distribution appears in the trion creation process consisting of picking of the Fermi Sea electron up by the exciton created in virtual state due to photon absorption. It is demonstrated that the interaction results in formation of a correlated state of the trion and the hole in the Fermi Sea. The state has excitation energy which is less then trion energy minus Fermi energy that can be obtained as a lower edge of trion excitation band using the simple energy conservation low in the picture of independent trion and electrons. The wave function of the correlated state is real and decreases with increase of distance between the trion and the Fermi Sea hole, r, as 1/r^3/2. The wave function can be normalized to unity and it corresponds to correlated state of the trion and Fermi Sea hole. In contrast to this state, the states with excitation energies in the absorption band between the trion energy and the trion energy minus Fermi energy have complex wave functions that decrease as 1/r^1/2. These states correspond to the trion and the Fermi Sea hole that is running away from the trion. The correlated state described above is supposed to be responsible for the narrow trion absorption line that was observed experimentally.
Photo-excited Carrier Dynamics and Impact Excitation Cascade in Graphene  [PDF]
Justin C. W. Song,Klaas J. Tielrooij,Frank H. L. Koppens,Leonid S. Levitov
Physics , 2012, DOI: 10.1103/PhysRevB.87.155429
Abstract: Photo-excitation in solids can trigger a cascade in which multiple particle-hole excitations are generated. We analyze the carrier multiplication cascade of impact excitation processes in graphene and show that the number of pair excitations has a strong dependence on doping, which makes carrier multiplication gate-tunable. We also predict that the number of excited pairs as well as the characteristic time of the cascade scale linearly with photo-excitation energy. These dependences, as well as sharply peaked angular distribution of pair excitations, provide clear experimental signatures of carrier multiplication.
Equivalent circuit with complex physical constants and equivalent-parameters-expressed dissipation factors of piezoelectric materials
Chen Yu,Wen Yu-Mei,Li Ping,
陈 雨
,文玉梅,李 平

中国物理 B , 2006,
Abstract: The equivalent circuit with complex physical constants for a piezoelectric ceramic in thickness mode is established. In the equivalent circuit, electric components (equivalent circuit parameters) are connected to real and imaginary parts of complex physical coefficients of piezoelectric materials. Based on definitions of dissipation factors, three of them (dielectric, elastic and piezoelectric dissipation factors) are represented by equivalent circuit parameters. Since the equivalent circuit parameters are detectable, the dissipation factors can be easily obtained. In the experiments, the temperature and the stress responses of the three dissipation factors are measured.
Photon condensation in circuit QED by engineered dissipation  [PDF]
D. Marcos,A. Tomadin,S. Diehl,P. Rabl
Physics , 2012, DOI: 10.1088/1367-2630/14/5/055005
Abstract: We study photon condensation phenomena in a driven and dissipative array of superconducting microwave resonators. Specifically, we show that by using an appropriately designed coupling of microwave photons to superconducting qubits, an effective dissipative mechanism can be engineered, which scatters photons towards low-momentum states while conserving their number. This mimics a tunable coupling of bosons to a low temperature bath, and leads to the formation of a stationary photon condensate in the presence of losses and under continuous-driving conditions. Here we propose a realistic experimental setup to observe this effect in two or multiple coupled cavities, and study the characteristics of such an out-of-equilibrium condensate, which arise from the competition between pumping and dissipation processes.
Model of Excitation of Chaotic Fluctuations in Oscillatory system with dissipation
American Journal of Signal Processing , 2012, DOI: 10.5923/j.ajsp.20120205.09
Abstract: The mathematical model of excitement of oscillator with dissipation of energy of general form is considered. The received analytical expression in an explicit form describes changes of amplitude and the phases of a signal brought by an exciting signal. The signal of excitement of oscillator is modulated by periodic sequence of rectangular impulses and restriction of square-law integratability is imposed on it. Finite-difference approximation of the offered model by a method of state variables is constructed and the method of generation of chaotic sequences with fractal properties created on its basis. Results of numerical modelling of chaotic sequences with fractional value of the fractal dimensionality calculated by a method of correlative integral are given. The type of the attractors constructed on the basis of finite-difference approximation of received model is given, and it is shown that by change of parameters of model there is possible to receive chaotic sequences with fractal properties.
Detection of finite frequency photo-assisted shot noise with a resonant circuit  [PDF]
Denis Chevallier,Thibaut Jonckheere,Elisabetta Paladino,Giuseppe Falci,Thierry Martin
Physics , 2010, DOI: 10.1103/PhysRevB.81.205411
Abstract: Photo-assisted transport through a mesoscopic conductor occurs when an oscillatory (AC) voltage is superposed to the constant (DC) bias which is imposed on this conductor. Of particular interest is the photo assisted shot noise, which has been investigated theoretically and experimentally for several types of samples. For DC biased conductors, a detection scheme for finite frequency noise using a dissipative resonant circuit, which is inductively coupled to the mesoscopic device, was developped recently. We argue that the detection of the finite frequency photo-assisted shot noise can be achieved with the same setup, despite the fact that time translational invariance is absent here. We show that a measure of the photo-assisted shot noise can be obtained through the charge correlator associated with the resonant circuit, where the latter is averaged over the AC drive frequency. We test our predictions for a point contact placed in the fractional quantum Hall effect regime, for the case of weak backscattering. The Keldysh elements of the photo-assisted noise correlator are computed. For simple Laughlin fractions, the measured photo-assisted shot noise displays peaks at the frequency corresponding to the DC bias voltage, as well as satellite peaks separated by the AC drive frequency.
Trinucleon Photo Reactions with $Δ$-Isobar Excitation: Radiative Nucleon-Deuteron Capture and Two-Body Photo Disintegration of the Three-Nucleon Bound State  [PDF]
L. P. Yuan,K. Chmielewski,M. Oelsner,P. U. Sauer,A. C. Fonseca,J. Adam Jr
Physics , 2002, DOI: 10.1007/s00601-002-0109-1
Abstract: Radiative nucleon-deuteron capture and photo disintegration of the three-nucleo n bound state with two-body final states are described. The description uses nucleon degrees of freedom extended to include the excitation of a single nucleon to a \diso. The baryonic interaction and the electromagnetic cu rrent couple nucleonic states and states with a \diso. Exact solutions of three-p article scattering equations are employed for the initial or final states of the reactions. The current has one-baryon and two-baryon contributions. The role of t he \diso in the description of the considered photo reactions is discussed and fo und to be moderate. The spin observables $A_{yy}$ and $T_{20}$ at $90^{\circ}$ la b scattering angle can be calculated model-independently from the $E1$ Siegert te rm in the long-wavelength limit.
Page 1 /100
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.