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National Repository of Grey Literature 12 records found  previous11 - 12  jump to record: Search took 0.00 seconds. 
Model průchodu dvojitou bariérou s anharmonickými vibracemi
 Gráf, Lukáš ; Čížek, Martin (advisor) ; Houfek, Karel (referee)
In the presented thesis we study the electron scattering off a molecular junction with anharmonic vibrations. This junction we simulate by a double barrier in- cluding the cosine dependence on the vibrational coordinate. The electron trans- mission through the barrier can be viewed as movement of the electron on the surface of infinitely long cylinder with zero potential energy everywhere except for a finite region where it is described by delta function terms. We solve this 2D problem employing the transfer matrix method and we present also the scat- tering theory approach to the problem. Using our own program we compute the numerically exact transmission probability and we investigate its dependence on parameters characterizing the model. We compare particular parametric regimes with various approximations which can be used for given settings. The elastic scattering is approximated by one-dimensional and Chase approximations where- as in case of vibrational excitation we employ the LCP approximation. Resulting graphs affirm that these approximation methods often used in molecular physics work very well.
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Study of resonance and threshold effects on simple two-channel model
 Kocák, Jakub ; Čížek, Martin (advisor) ; Kolorenč, Přemysl (referee)
In this thesis we study simple one-dimensional two-channel scattering model where pointlike coupling between channels is provided by the delta potential. The scattering task can be completely solved analytically. The solution of the Lippmann-Schwinger equation leads to improper scattering eigenvectors, consequently to scattering S matrix elements and eigenphases. We study how the setting of parameters affects threshold and resonant behaviour (presence, position, width) and the mutual relationship between resonances and poles of the S matrix in complex k-plane. Then we apply projection- operator formalism to model with resonance and the on-shell T matrix is separated into the orthogonal, direct and resonant term. We discuss how choice of subspace of quasi-bound states effects the separation. Powered by TCPDF (www.tcpdf.org)
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National Repository of Grey Literature : 12 records found   previous11 - 12  jump to record:
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