22,911 research outputs found
Energy Dependence of the NN t-matrix in the Optical Potential for Elastic Nucleon-Nucleus Scattering
The influence of the energy dependence of the free NN t-matrix on the optical
potential of nucleon-nucleus elastic scattering is investigated within the
context of a full-folding model based on the impulse approximation. The
treatment of the pole structure of the NN t-matrix, which has to be taken into
account when integrating to negative energies is described in detail. We
calculate proton-nucleus elastic scattering observables for O,
Ca, and Pb between 65 and 200 MeV laboratory energy and study
the effect of the energy dependence of the NN t-matrix. We compare this result
with experiment and with calculations where the center-of-mass energy of the NN
t-matrix is fixed at half the projectile energy. It is found that around 200
MeV the fixed energy approximation is a very good representation of the full
calculation, however deviations occur when going to lower energies (65 MeV).Comment: 11 pages (revtex), 6 postscript figure
Variational solution of the T-matrix integral equation
We present a variational solution of the T-matrix integral equation within a
local approximation. This solution provides a simple form for the T matrix
similar to Hubbard models but with the local interaction depending on momentum
and frequency. By examining the ladder diagrams for irreducible polarizability,
a connection between this interaction and the local-field factor is
established. Based on the obtained solution, a form for the T-matrix
contribution to the electron self-energy in addition to the GW term is
proposed. In the case of the electron-hole multiple scattering, this form
allows one to avoid double counting.Comment: 7 pages, 7 figure
VCSEL intrinsic response extraction using T-Matrix formalism
We present a new method to remove the parasitics contribution to the VCSEL chip response, in order to obtain the intrinsic S21 behavior. The on-chip VCSEL is defined as two cascaded two-port subsystems representing the electrical access and the VCSEL optical cavity respectively. S11 and S21 parameters measurements are carried-out using a probe station to characterize the chip response. An electrical equivalent circuit defining the behavior of the electrical access is combined with T-Matrix formalism to remove the parasitics contribution from the measured S21 response. Results allow us to determine the intrinsic 3-dB bandwidth of the VCSEL
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