Adiabatic Approximation
Mostrando 1-12 de 13 artigos, teses e dissertações.
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1. Triatomic molecules in two-dimensional layers
We found universal laws for the spectrum of two-dimensional three-body systems, composed by two identical particles and a distinct one (AAB). These universal laws appear when the potential range (r_0) is much smaller than the size of the system. In two dimensions this condition is formulated as (E2 is the two-body energy and ? is the reduced mass). The zero
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 14/06/2012
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2. Berry's phase in the two-level model
We study the adiabatic evolution of a two-level model in the presence of an external classical electric field. The coupling between the quantum model and the classical field is taken in the electric dipole approximation. In this regime, we show the absence of geometric phases in the interacting two-level model in the presence of any periodic real time-depend
Brazilian Journal of Physics. Publicado em: 2009-06
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3. Fases geométricas e invariantes dinâmicos em mecânica quântica
The increasing interest to understand the geometric phases (mainly due to the possi- bility to achieve geometric quantum computation robust against some kind of errors) and the search for new techniques to solve time-dependent problems in Quantum Mechanics, are the topics approached in this thesis. i) Within nowadays technology, it is presented a scheme to c
Publicado em: 2007
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4. D0 energy spectrum in In(Al)As/Ga(Al)As quasi-one-dimensional nanorings
We analyze the spectrum of a neutral donor located inside or outside of a finite-barrier toroidal-shaped nanoring whose radius is much larger than the height. We derive a one-dimensional wave equation which describes the low-lying donor levels corresponding to the slow electron motion along the ring, by using the adiabatic approximation. Numerical solution o
Brazilian Journal of Physics. Publicado em: 2006-09
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5. Negatively charged donors in flat quantum dots
The ground state energies of off-axis negatively charged donors in axially symmetrical quantum dots, with different shapes but in all cases with a small height-to-base radius aspect ratio are calculated in adiabatic approximation by using the Hylleraas-type trial function. The dependencies of the neutral and negative donor binding energies and their ratios o
Brazilian Journal of Physics. Publicado em: 2006-09
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6. Theoretical calculus of magnetocaloric effects of La(FexSi1-x)13. / Cálculo teórico do efeito magnetocalórico do composto La(FexSi1-x)13.
The study of the magnetocaloric effect of the compound La(FexSi1-x)13 became very important, once recent experiments revealed that this compound exhibits great values of the isothermal entropy change (Δ S) and the adiabatic temperature change(ΔTad), which are the quantities used to characterize the power of refrigeration of any compound. We studied
Publicado em: 2006
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7. Elastic and rotational excitation cross sections for electron scattering by polyatomic molecules
In this work we present a theoretical study on electron scattering by both polar and nonpolar polyatomic molecules in the low-energy range. More specifically, we report calculated elastic and rotationally inelastic differential cross sections for electron scattering by CH4, H2O, and H2S in the (2.14-30)-eV range. Exact static-exchange plus model correlation-
Brazilian Journal of Physics. Publicado em: 2002-09
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8. Applications of the Schwinger Multichannel method with pseudopotentials to electron scattering from polyatomic molecules II: rotational excitation cross sections
This paper reports results for rotational excitation of H2O and H2S molecules by electron impact. It is also a databasis including tables of previously published rotationally resolved cross sections for CH4, SiH4, GeH4, SnH4, PbH4, NH3, PH3, AsH3, SbH3, CF4, CCl4, SiCl4 SiBr4, and SiI4. Our scattering amplitudes were calculated using the Schwinger multichann
Brazilian Journal of Physics. Publicado em: 2001-03
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9. Analise da convecção natural em superficies com fontes de calor protuberantes
In this work a numerical study of natural convection in fluid flow and heat transfer on an adiabatic surface (like plate, channel and cavity) with protruding heat sources is carried out. The flow is considered steady, laminar and two-dimensional. The physical properties are considered constant and the Boussinesq approximation is used. The finite control volu
Publicado em: 1998
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10. Excitações rotacionais de moleculas poliatomicas pelo impacto de eletrons de baixa energia
In the present work, the Schwinger Multichannel Method with Pseudopotentials (SMCPP) was applied, along with the Adiabatic Nuclei Rotation (ANR) approximation, to study rotational excitations of XH4 (X: C, Si, Ge, Sn, Pb), XH3 (X: N, P, As, Sb), CX4 (X: F, Cl), SiX4 (X: Cl, Br, I), CClF3 and CCl3F by electron impact (7.5 to 30 eV). For CH4, SiH4 and NH3, our
Publicado em: 1997
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11. Computation of the sticking probability of a incident atom on metallic surface. / Cálculo da probabilidade de adesão de átomo incidente em superfície metálica.
A new procedure that calculates sticking coefficients for atomic beams incident upon metallic surfaces is discussed. A model Hamiltonian describing the normal incidence of an ad-atom and its interaction with the conduction electrons of the adsorbate is introduced. The Hamiltonian accounts for two couplings: (1) the overlap between the atomic orbital and the
Publicado em: 1986
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12. Rate constant of vibrational redistribution in molecules using adiabatic approximation model
By means of the proposed adiabatic approximation model for vibrational redistribution [Lin, S. H. (1980) Chem. Phys. Lett. 70, 492-499], the calculations of various rate constants caused by different couplings have been given in detail. By two methods it has been demonstrated that the rate constant caused by the Born-Oppenheimer mechanism, corrected by the n