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Dissertation
Bestimmung der magnetischen Streufeldstärke von künstlichen magnetischen Domänen austauschverschobener Dünnschichtsysteme und deren Einfluss auf die Selbstassemblierung organischer Moleküle
(2015-11-16)
Die lokale Anlagerung molekularer Substanzen auf Oberflächen ist technologisch von großem Interesse. Die Beeinflussung selbstassemblierender Materialien bietet dabei große Vorteile, da sie kostengünstig und großflächig angewendet werden kann. Untersuchungen einer solchen Beeinflussung mithilfe von magnetischen Feldern wurden bisher jedoch noch nicht durchgeführt. Ursache hierfür ist das, insbesondere bei der Verwendung von diamagnetischen Substanzen, geringe induzierte magnetische Moment und die daraus resultierenden ...
Aufsatz
Femtosecond real-time probing of reactions. 12. Vectorial dynamics of transition states
(1993)
Femtosecond time-resolved techniques with KETOF (kinetic energy time-of-flight) detection in a molecular beam are developed for studies of the vectorial dynamics of transition states. Application to the dissociation reaction of IHgI is presented. For this system, the complex [I---Hg---I](++)* is unstable and, through the symmetric and asymmetric stretch motions, yields different product fragments: [I---Hg---I](++)* -> HgI(X^2/sigma^+) + I(^2P_3/2) [or I*(^2P_l/2)] (1a); [I---Hg---I](++)* -> Hg(^1S_0) + I(^2P_3/2) + ...
Aufsatz
Femtosecond real-time probing of reactions
(1993)
Femtosecond reaction dynamics of OClO in a supersonic molecular beam are reported. The system is excited to the A^2A_2 state with a femtosecond pulse, covering a range of excitation in the symmetric stretch between v_1 = 17 to v_1 = 11 (308-352 nm). A time-delayed femtosecond probe pulse ionizes the OClO, and OClO^+ is detected. This ion has not been observed in previous experiments because of its ultrafast fragmentation. Transients are reported for the mass of the parent OClO as well as the mass of the ClO. Apparent ...
Aufsatz
Femtosecond time-resolved molecular multiphoton ionization and fragmentation of Na_2
(1993)
We present a comparison between experimental and theoretical results for pump/probe multiphoton ionizing transitions of the sodium dimer, initiated by femtosecond laser pulses. It is shown that the motion of vibrational wavepackets in two electronic states is probed simultaneously and their dynamics is reflected in the total Na^+_2 ion signal which is recorded as a function of the time delay between pump and probe pulse. The time dependent quantum calculations demonstrate that two ionization pathways leading to the ...
Aufsatz
Fundamental interactions of molecules (Na_2, Na_3) with intense femtosecond laser pulses
(1994)
The real-time dynamics of multiphoton ionization and fragmentation of molecules Na_2 and Na_3 has been studied in molecular beam experiments employing ion and electron spectroscopy together with femtosecond pump-probe techniques. Experiments with Na_2 and Na_3 reveal unexpected features of the dynamics of the absorption of several photons as seen in the one- and three-dimensional vibrational wave packet motion in different potential surfaces and in high laser fields: In Na_2 a second major resonance-enhanced multiphoton ...
Aufsatz
Femtosecond time-resolved wave packet motion in molecular multiphoton ionization and fragmentation
(1991)
The dynamics of molecular multiphoton ionization and fragmentation of a diatomic molecule (Na_2) have been studied in molecular beam experiments. Femtosecond laser pulses from an amplified colliding-pulse mode-locked (CPM) ring dye laser are employed to induce and probe the molecular transitions. The final continuum states are analyzed by photoelectron spectroscopy, by ion mass spectrometry and by measuring the kinetic energy of the formed ionic fragments. Pump-probe spectra employing 70-fs laser pulses have been ...
Aufsatz
Femtosecond dynamics of molecules and clusters
(Ed. by Douwe A. Wiersma, 1994)
The real-time dynamics of multiphoton ionization and fragmentation of molecules - Na_2 , Na_3 - and clusters - Na_n, Hg_n - has been studied in molecular beam experiments employing ion and electron spectroscopy together with femtosecond pump-probe techniques. Experiments with Na_2 and Na_3 reveal unexpected features of the dynamics of the absorption of several photons as seen in the one- and three dimensional vibrational wave packet motion in different potential surfaces and in high laser fields. Cluster size dependent ...
Aufsatz
Femtosecond real-time probing of reactions. 13. Multiphoton dynamics of IHgI
(1993)
Real-time studies of the dynamics were performed on the reaction of HgI_2 in a molecular beam. Excitation was by either one or multi pump photons (311 nm), leading to two separate sets of dynamics, each of which could be investigated by a time-delayed probe laser (622 nm) that ionized the parent molecule and the fragments by REMPI processes. These dynamics were distinguished by combining the information from transients taken at each mass (HgI_2, HgI, I_2, Hg, and I) with the results of pump (and probe) power dependence ...
Aufsatz
Femtosecond two-photon ionization spectroscopy of the B state of Na_3 clusters
(1993)
We report time-resolved experiments studying the dynamics of the Na_3 B-X system. Femtosecond pump-probe techniques combined with ion time-of-flight (TOF) and zero kinetic energy (ZEKE) photoelectron spectroscopy allow us to observe the three-dimensional wavepacket motion in the excited Na_3 B state and in the Na_3 X state. The ground state wavepacket is induced by stimulated emission pumping during the pump pulse. The X-state dynamics is dominated by the three vibrational modes of the Na_3. Furthermore we observed ...
Dissertation
Optimizing Robust Quantum Gates in Open Quantum Systems
(2015-05-27)
We are currently at the cusp of a revolution in quantum technology that relies not just on the passive use of quantum effects, but on their active control. At the forefront of this revolution is the implementation of a quantum computer. Encoding information in quantum states as “qubits” allows to use entanglement and quantum superposition to perform calculations that are infeasible on classical computers. The fundamental challenge in the realization of quantum computers is to avoid decoherence – the loss of quantum ...