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Physics Faculty Publications and Presentations

2006

University of Portland

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Articles 1 - 3 of 3

Full-Text Articles in Physics

Two-Photon Spectroscopy Of Rubidium Using A Grating-Feedback Diode Laser, Abraham J. Olson, Evan J. Carlson, Shannon K. Mayer Mar 2006

Two-Photon Spectroscopy Of Rubidium Using A Grating-Feedback Diode Laser, Abraham J. Olson, Evan J. Carlson, Shannon K. Mayer

Physics Faculty Publications and Presentations

We describe an experiment for investigating the 5S1/2→5D5/2 two-photon transition in rubidium using a single grating-feedback diode laser operating at 778.1nm (385 THz). Continuous tuning of the laser frequency over 4GHz allows for the clear resolution of the Doppler-free spectral features and allows accurate measurement of the hyperfine ground-state splitting. A direct comparison between Doppler-broadened and Doppler-free spectral features is possible because both are distinctly evident in the two-photon spectra. By independently modifying the polarization state of the two laser fields, the impact of electric dipole selection rules on the two-photon transition spectra is ...


Quantum Phase Transitions In The Transverse One-Dimensional Ising Model With Four-Spin Interactions, O. F. De Alcantara Bonfim, J. Florencio Jan 2006

Quantum Phase Transitions In The Transverse One-Dimensional Ising Model With Four-Spin Interactions, O. F. De Alcantara Bonfim, J. Florencio

Physics Faculty Publications and Presentations

In this work we investigate the quantum phase transitions at zero temperature of the one-dimensional transverse Ising model with an extra term containing four-spin interactions. The competition between the energy couplings of the model leads to an interesting zero-temperature phase diagram. We use a modified Lanczos method to determine the ground state and the first excited state energies of the system, with sizes of up to 20 spins. We apply finite size scaling to the energy gap to obtain the boundary region where ferromagnetic to paramagnetic transition takes place. We also find the critical exponent associated with the correlation length ...


Exact And Approximate Energy Spectrum For The Finite Square Well And Related Potentials, O. F. De Alcantara Bonfim, David J. Griffiths Jan 2006

Exact And Approximate Energy Spectrum For The Finite Square Well And Related Potentials, O. F. De Alcantara Bonfim, David J. Griffiths

Physics Faculty Publications and Presentations

We investigate the problem of a quantum particle in a one-dimensional finite square well. In the standard approach the allowed energies are determined implicitly as the solutions to a transcendental equation. We obtain the spectrum analytically as the solution to a pair of parametric equations and algebraically using a remarkably accurate approximation to the cosine function. The approach is also applied to a variety of other quantum wells.