Reliable measurements are essential to guarantee all aspects required for the sustainable development of nations. There is an increasing awareness of the need to discuss, compare and improve infrastructures in the context of global... more
Reliable measurements are essential to guarantee all aspects required for the sustainable development of nations. There is an increasing awareness of the need to discuss, compare and improve infrastructures in the context of global economic efficiency, and market access for goods and services for both developed and developing countries. This is where metrology, standardization and conformity assessment come in. In
Publication Date: 2009
Publication Name: Accreditation and Quality Assurance
We study the scattering of charged particles in the presence of a homogeneous magnetic field. Using the Green's function formalism, an appropriate transition amplitude for the scattering process is defined, and application is made on... more
We study the scattering of charged particles in the presence of a homogeneous magnetic field. Using the Green's function formalism, an appropriate transition amplitude for the scattering process is defined, and application is made on scattering by a Coulomb potential in the high-energy approximation. For this case, the transition amplitude is obtained in a closed form; its behavior with the magnetic field intensity and initial translational energy is qualitatively discussed for transitions from the first Landau level. In the ultrastrong-field limit, the total transition probability presents periodic threshold structures with increasing values of the initial translational energy.
The bound-bound transition of hydrogen atoms in strong magnetic fields are studied with the aid of wave functions obtained by Brandi (1975), and the results are compared with those of Smith et al. (1973), who used a variational scheme for... more
The bound-bound transition of hydrogen atoms in strong magnetic fields are studied with the aid of wave functions obtained by Brandi (1975), and the results are compared with those of Smith et al. (1973), who used a variational scheme for wave functions. The transition probabilities and oscillator strengths for the v to v prime transitions are calculated for magnetic fields
ABSTRACT We treat the interaction of light with a spherical GaAs-(Ga,Al)As quantum dot within a dressed-band approach. The Kane band-structure scheme is used to model the GaAs bulk semiconductor and the interaction with the laser field is... more
ABSTRACT We treat the interaction of light with a spherical GaAs-(Ga,Al)As quantum dot within a dressed-band approach. The Kane band-structure scheme is used to model the GaAs bulk semiconductor and the interaction with the laser field is treated through the renormalization of the semiconductor energy gap and conduction/valence effective masses. This approach, valid far from resonances, is used to investigate the light shifts induced in the electronic and shallow on-center donor states in semiconductor quantum dots, which are shown to be quite considerable. This model calculation may be extended to include magnetic-field effects, and it is suggested that the strong localization of the electronic and impurity states due to the quantum dot and enhanced by laser confinement may prove useful for manipulation of electronic and donor states in some proposed solid-state-based quantum computers.
We have extended the transfer matrix technique to determine the Green's function for 1-dimensional systems with long range interactions. The formalism is applied to study the density of states and impurity modes of linear chains;... more
We have extended the transfer matrix technique to determine the Green's function for 1-dimensional systems with long range interactions. The formalism is applied to study the density of states and impurity modes of linear chains; calculations are presented for nearest and next nearest neighbors interactions.
... C 6, 229 (1973) [INSPEC][ADS][CAS]. DF Daly and RL Mieher, Phys. Rev. 183, 368 (1969) [INSPEC];[CAS]. S. Costa Ribeiro, OR Nascimento, and HS Brandi, Phys. ... F. Daly and RL Mieher, Phys. Rev. 183, 368 (1969). "S. Costa Ribeiro,... more
... C 6, 229 (1973) [INSPEC][ADS][CAS]. DF Daly and RL Mieher, Phys. Rev. 183, 368 (1969) [INSPEC];[CAS]. S. Costa Ribeiro, OR Nascimento, and HS Brandi, Phys. ... F. Daly and RL Mieher, Phys. Rev. 183, 368 (1969). "S. Costa Ribeiro, 0. R. Nascimento, and HS Brandi, Phys. ...
We study the electronic band structure for a model one-dimensional periodic potential in the presence of a spacially homogeneous laser field. The statistical properties of the energy bands depend on the coupling between the crystal and... more
We study the electronic band structure for a model one-dimensional periodic potential in the presence of a spacially homogeneous laser field. The statistical properties of the energy bands depend on the coupling between the crystal and the laser field, going from Poisson to Wigner-Dyson (GOE) and back to Poisson as the coupling increases. We argue that the classical dynamics of this system resembles that of a periodically driven pendulum. We find that the chaotic regime is not restricted solely to high-lying bands and should thus be of easier access to optical experiments.
We investigate the effect of an electromagnetic field in the vibrational excitations of diatomic molecules, considering its collisions with noble gas atoms. Considering colinear collisions we obtain an expression for the vibrational... more
We investigate the effect of an electromagnetic field in the vibrational excitations of diatomic molecules, considering its collisions with noble gas atoms. Considering colinear collisions we obtain an expression for the vibrational transition amplitudes, and we apply the formalism to the specific collision He+H/sup +/â in COâ laser field, in the high energy approximation. The general behavior of the multiphoton
Expressions for the scattering amplitude of multiphoton processes occurring during the collision of electrons with a hydrogen atom in the presence of an electromagnetic field have been obtained in several approximations: the momentum... more
Expressions for the scattering amplitude of multiphoton processes occurring during the collision of electrons with a hydrogen atom in the presence of an electromagnetic field have been obtained in several approximations: the momentum translation, the space translation, and the Keldysh approximation for the bound-electron wave function. We also propose a perturbation approach based on the space-translation approximation to treat the hydrogen-atom bound states. Our results show that it is of fundamental importance ot consider the modifications of bound states due to the presence of the field.
