... ion impact: the CDW-EIS-SVIM model RF Nascimento1, LE Machado2, CE Bielschowsky3 andGinette Jalbert1 ... Opt. Phys. 41 045203 [16] Michelin SE, Arretche F, Mazon KT, Piacentini JJ, Marin A, Oliveira HL, Travessini D, Lee MT, Iga I and... more
... ion impact: the CDW-EIS-SVIM model RF Nascimento1, LE Machado2, CE Bielschowsky3 andGinette Jalbert1 ... Opt. Phys. 41 045203 [16] Michelin SE, Arretche F, Mazon KT, Piacentini JJ, Marin A, Oliveira HL, Travessini D, Lee MT, Iga I and Fujimoto MM 2007 J. Phys. B: At. ...
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ABSTRACT In this work we present our results for calculations of doubly excited states of potential curves of H2 and the corresponding double excitation cross sections by electron impact using the First Born Approximation. The wave... more
ABSTRACT In this work we present our results for calculations of doubly excited states of potential curves of H2 and the corresponding double excitation cross sections by electron impact using the First Born Approximation. The wave functions and potential energy curves were calculated using the Configuration Interaction method.
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... b," and with quasi-momentum k in a crystal potential V(r). By expanding the Bloch states into momentum eigenstates Ib,k>= Y-bGIG,k> , G where G is a reciprocal lattice vector, P(k) can be written as P(k) = 2: SI, z Sr , ,... more
... b," and with quasi-momentum k in a crystal potential V(r). By expanding the Bloch states into momentum eigenstates Ib,k>= Y-bGIG,k> , G where G is a reciprocal lattice vector, P(k) can be written as P(k) = 2: SI, z Sr , , with SN = ~ ~: b*GbG <G', n' IAo > nn' i ... [8] JH Shirley, Phys. ...
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We studied the H- production from the dissociation of fast HeH+ projectiles, which occurs only through the He2++H- dissociative channel as electron capture is negligible at large velocities. We measured the lateral profiles of the H- ions... more
We studied the H- production from the dissociation of fast HeH+ projectiles, which occurs only through the He2++H- dissociative channel as electron capture is negligible at large velocities. We measured the lateral profiles of the H- ions produced in collisions of HeH+ with He and Ar atoms at velocities of 2.8, 4.0, and 4.9 a.u. and extracted from them an
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... (2.27) The properties of the eigenvalues and eigenvectors of this equation are extensively discussed in the literature (Shirley 1965) in the context of the Floquet Hamiltonian. ... therefore, using (2.28) and redefining the indices,... more
... (2.27) The properties of the eigenvalues and eigenvectors of this equation are extensively discussed in the literature (Shirley 1965) in the context of the Floquet Hamiltonian. ... therefore, using (2.28) and redefining the indices, we may rewrite (3.8) as: 2 x (G'rl IAo>(A, I IC]) 1 * ...
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We propose to use a double longitudinal Stern-Gerlach atom interferometer in order to investigate quantitatively the angular momentum coherence of molecular fragments. Assuming that the dissociated molecule has a null total angular... more
We propose to use a double longitudinal Stern-Gerlach atom interferometer in order to investigate quantitatively the angular momentum coherence of molecular fragments. Assuming that the dissociated molecule has a null total angular momentum, we investigate the propagation of the corresponding atomic fragments in the apparatus. We show that the envisioned interferometer enables one to distinguish unambiguously a spin-coherent from a spin-incoherent dissociation, as well as to estimate the purity of the angular momentum density matrix associated with the fragments. This setup, which may be seen as an atomic analogue of a twin-photon interferometer, can be used to investigate the suitability of molecule dissociation processes -- such as the metastable hydrogen atoms H($2^2 S$)-H($2^2 S$) dissociation - for coherent twin-atom optics.
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The multiphoton absorption rate of circularly polarized light, by direct‐gap crystals, is investigated following a non‐perturbative scheme proposed by Jones and Reiss. It is possible to derive closed analytical solutions, for the N‐photon... more
The multiphoton absorption rate of circularly polarized light, by direct‐gap crystals, is investigated following a non‐perturbative scheme proposed by Jones and Reiss. It is possible to derive closed analytical solutions, for the N‐photon transition rate, valid for all field strengths of practical interest. The accuracy of the approximations introduced in deriving these results is determined comparing the numerical computations of the multiphoton transition rate (“exact”) with the analytical solutions. Specific calculations are done for ZnS and GaAs in the presence of a Nd laser. It is shown that this formalism leads to a total transition rate which has not the tunneling behavior previously discussed by several authors within similar contexts.
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Abstract We calculate the single step cross sections for excitation of Q2 states of H2 and its subsequent dissociation. The cross section calculations were performed within the first Born approximation and the electronic wave functions... more
Abstract We calculate the single step cross sections for excitation of Q2 states of H2 and its subsequent dissociation. The cross section calculations were performed within the first Born approximation and the electronic wave functions were obtained via State-Averaged Multiconfigurational Self-Consistent Field followed by Configuration Interaction. We have assumed autoionization is the only important process competing with dissociation into neutral atoms. We have estimated its probability through a semi classical approach and compared with results of literature. Special attention was given to the Q21Σg+(1) state which, as has been shown in a previous work, may dissociate into H(2sσ) + H(2sσ) fragments (some figures in this article are in colour only in the electronic version). Graphical abstract
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ABSTRACT The electron-detachment cross section was measured for the molecular negative ions ${\mathrm{CN}}^{$-${}}$ and ${\mathrm{O}}_{2}^{$-${}}$ incident on N${}_{2}$, in the 0.08\char21{}1.2 a.u. velocity region. Our setup uses the gas... more
ABSTRACT The electron-detachment cross section was measured for the molecular negative ions ${\mathrm{CN}}^{$-${}}$ and ${\mathrm{O}}_{2}^{$-${}}$ incident on N${}_{2}$, in the 0.08\char21{}1.2 a.u. velocity region. Our setup uses the gas stripper of a tandem accelerator as a gas chamber. All cross sections present a maximum near 0.4 a.u., a velocity corresponding to the well-known shape-resonance that appears in the electron-N${}_{2}$ collisions. A semiclassical model is employed to analyze the data. The role of this shape resonance is discussed in this article.
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A closed analytical expression for multiphoton transition rate, in direct gap crystals, is obtained from a non‐perturbative approach in theweak‐field limit. This scheme is related to an approximate high order perturbation theory and... more
A closed analytical expression for multiphoton transition rate, in direct gap crystals, is obtained from a non‐perturbative approach in theweak‐field limit. This scheme is related to an approximate high order perturbation theory and compared with tunneling‐like theories as proposed by Keldysh. The accuracy and the limitations of the use of the saddle‐point in this type of methods are discussed.
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We study the effects of a laser on the splitting of the lowest electronic states of a pair of two-dimensional (2D) GaAs-(Ga,Al)As coupled quantum dots, in the presence of a homogeneous external magnetic field. The interaction of light... more
We study the effects of a laser on the splitting of the lowest electronic states of a pair of two-dimensional (2D) GaAs-(Ga,Al)As coupled quantum dots, in the presence of a homogeneous external magnetic field. The interaction of light with the 2D quantum dots is treated within a dressed-band approach in which a two-band scheme is used to model the GaAs bulk semiconductor whereas the interaction with the laser field is treated through the renormalization of the semiconductor energy gap and conduction/valence effective masses. This approach is valid far from resonances and has been successfully used to treat other confined semiconductor heterostructures. We focus our attention on the splitting of the lowest singlet and triplet states and on their double occupation probability. We analyze the exchange coupling (J) in the effective Heisenberg model as a function of the laser field and its detuning, as well as of the magnetic field (B) within the Heitler-London approximation of molecular physics. We find that due to the electronic confinement the laser may play a role similar to the external magnetic field in the qualitative behavior of the exchange parameter J. Furthermore, the presence of the laser may assure both the sizable exchange coupling and the vanishingly small double occupation probability required for efficient quantum computer operations, even in the absence of an external magnetic field. Besides being of fundamental interest, these features may be used as an efficient two-qubit gate control.
Research Interests: Engineering, Physics, Condensed Matter Physics, Applied Physics, Magnetic field, and 12 moreMathematical Sciences, Solid State electronic devices, Physical sciences, Renormalization, Quantum Computer, Exchange coupling, Quantum Dot, Effective mass, Impulse Response Function, Fermi Surface, HEISENBERG-MODEL, and Quantum-Dot Laser
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Research Interests: Physics and Carbon Fibers
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Two electron inner shells vacancies may me produced with considerable probability in heavy ion atom collision. As an alternative process, these double inner shell vacancies may decay by the simultaneous filling of the two vacancies... more
Two electron inner shells vacancies may me produced with considerable probability in heavy ion atom collision. As an alternative process, these double inner shell vacancies may decay by the simultaneous filling of the two vacancies followed by the emission of a single x-ray photon. The evidence for these cooperative two electron transitions was reported by Wolfli et al (1975).
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A method to calculate the autoionization width from a discretized pseudo-spectrum is proposed. This method relies on an analytic continuation of Green’s function within the Fano–Feshbach formalism. The pseudo-spectrum is obtained at the... more
A method to calculate the autoionization width from a discretized pseudo-spectrum is proposed. This method relies on an analytic continuation of Green’s function within the Fano–Feshbach formalism. The pseudo-spectrum is obtained at the multireference configuration interaction level in a square-integrable basis set, commonly found in quantum chemistry software. Few states around the desired resonance are needed to perform the analytic continuation. This method was applied to atomic (He and Ne) and molecular (HF and benzene) systems, and the results for the autoionization width show good agreement with the available theoretical and experimental values.
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Abstract We calculate the single step cross sections for excitation of Q2 states of H2 and its subsequent dissociation. The cross section calculations were performed within the first Born approximation and the electronic wave functions... more
Abstract We calculate the single step cross sections for excitation of Q2 states of H2 and its subsequent dissociation. The cross section calculations were performed within the first Born approximation and the electronic wave functions were obtained via State-Averaged Multiconfigurational Self-Consistent Field followed by Configuration Interaction. We have assumed autoionization is the only important process competing with dissociation into neutral atoms. We have estimated its probability through a semi classical approach and compared with results of literature. Special attention was given to the Q21Σg+(1) state which, as has been shown in a previous work, may dissociate into H(2sσ) + H(2sσ) fragments (some figures in this article are in colour only in the electronic version). Graphical abstract
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Abtract Mul tiphoton transi tions in direct - gap crystals are stud i ed considering a "non-perturbatlv e" approach, similar to Keldysh approximation. We consider a slmple two parabolic band model in the effective mass... more
Abtract Mul tiphoton transi tions in direct - gap crystals are stud i ed considering a "non-perturbatlv e" approach, similar to Keldysh approximation. We consider a slmple two parabolic band model in the effective mass approximation, so that exact solutions associated to the ful I, crystal plus f ield, Hamil tonlan may be approximated by Vol k ov wavefunctio~is. In this manner we construct an S-matrix which incorporates t he electromagnetic field t o a11 orders in an approxirnated way, leadlng to analytical solutions for the multiphoton transition rates. We discuss the use of the s addle - polnt method and its limitations as well as the connectlon between multiphoton a bsorption and tunnelinq.We show that fcir near threshold excitations the Keldysh approach isfairly accurate as long as terms arising from the saddle - point integration are consistently accounted.
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Absolute total destruction cross sections of B n - (n=1,2) and Al n - (n=1–4) clusters colliding with N 2 were measured for relative velocities in the interval 0.2–1.0 au All cross-section curves may be described as a single curve,... more
Absolute total destruction cross sections of B n - (n=1,2) and Al n - (n=1–4) clusters colliding with N 2 were measured for relative velocities in the interval 0.2–1.0 au All cross-section curves may be described as a single curve, presenting a maximum around the velocity of 0.3 au, ...
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... (2.27) The properties of the eigenvalues and eigenvectors of this equation are extensively discussed in the literature (Shirley 1965) in the context of the Floquet Hamiltonian. ... therefore, using (2.28) and redefining the indices,... more
... (2.27) The properties of the eigenvalues and eigenvectors of this equation are extensively discussed in the literature (Shirley 1965) in the context of the Floquet Hamiltonian. ... therefore, using (2.28) and redefining the indices, we may rewrite (3.8) as: 2 x (G'rl IAo>(A, I IC]) 1 * ...
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ABSTRACT
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ABSTRACT