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1.
Advantages and disadvantages of experiments with ultrashort two-color pulses
Matija Stupar, doktorska disertacija

Opis: Advances in the development of lasers have led to a new class of radiation sources generating coherent, tunable, ultrashort light pulses in the spectral region ranging from infrared to soft X-rays. This includes high-order harmonics generation in gas (HHG), on which relies the CITIUS facility at University of Nova Gorica (Slovenia), and free-electron lasers (FELs), such as the facility FERMI at Elettra-Sincrotrone Trieste (Italy). The distinctive structure of HHG and FEL radiation paved the way to time-resolved experiments, which are performed to investigate events occurring on a short, or very short, temporal scale, from picoseconds to femtoseconds. This work focuses on the advantages and disadvantages of some experimental techniques based on using these novel light sources to investigate the microscopic and/or ultrafast dynamics of matter samples, which have been previously driven out of equilibrium. Advantages rely on the implementation of various applications based on two-color schemes and, more specifically, include the possibility of acquiring two-dimensional frequency maps, measuring electrons’ effective masses, or investigating electronic properties decoupled from the influence of the lattice. Particular focus will be put on experimental methods relying on photoelectric effect and photoelectron spectroscopy. In all experiments, we took advantage of one or more specific properties of HHG and FEL sources, such as controllable chirp, to study laser dressed states in helium, variable polarization, to study electronic properties of iron-based pnictides and ultrashort pulses (< 10 fs) to study the purely electronic dynamics in transition metal dichalcogenides. On the other hand, the study of the interface between a molecule and a topological insulator revealed some intrinsic limitations and physical drawbacks of the technique, such as spurious effects originating from the high power pulses, like multiphoton absorption and the space charge effect, or the reduction of experimental resolution when pushing for shorter and shorter pulse durations. Some disadvantages are also connected to the current state-of-the-art in the field of ultrashort laser systems, where a trade-off needs to be found between repetition rate and laser power. Finally, state-of-the-art experiments based on the ability to generate ultrashort pulses carrying orbital angular momentum in visible, near-infrared as well as extreme UV range will be presented. The use of these pulses opens the door to the investigation of new physical phenomena, such as probing magnetic vortices using extreme ultraviolet light from a free-electron laser or imprinting the spatial distribution of an ultrashort infrared pulse carrying orbital angular momentum onto a photoelectron wave packet.
Najdeno v: ključnih besedah
Povzetek najdenega: ...possibility of acquiring two-dimensional frequency maps, measuring electrons effective masses, or investigating electronic properties decoupled...
Ključne besede: ultrafast lasers, two-color experiments, photoemission, high-order harmonic generation, free-electron lasers, hot-electrons dynamics, surface science, pump-probe photoemission, ultraviolet photoemission, orbital angular momentum
Objavljeno: 02.12.2020; Ogledov: 128; Prenosov: 0
.pdf Polno besedilo (19,78 MB)

2.
The H.E.S.S. measurement of the cosmic-ray electron spectrum
Serguei Vorobiov, Kathrin Egberts, 2010, objavljeni povzetek znanstvenega prispevka na konferenci

Najdeno v: ključnih besedah
Povzetek najdenega: ...system, Cherenkov telescopes, very high energy, cosmic-ray electrons, energy spectrum, ...
Ključne besede: ground based y-ray telescopes, H.E.S.S. system, Cherenkov telescopes, very high energy, cosmic-ray electrons, energy spectrum
Objavljeno: 25.04.2014; Ogledov: 2196; Prenosov: 15
URL Polno besedilo (0,00 KB)

3.
Ultra-visokovakuumski sistem za naparevanje organskih polprevodnikov
Robert Hudej, Gvido Bratina, 2001, izvirni znanstveni članek

Opis: A new molecular-beam-epitaxy system for the growth of organic semiconductor layers was recently installed in the Laboratory for epitaxy and nanostructures of the Nova Gorica Polytechnic. The system is built around an ultra-high-vacuum chamber. The organic semiconductor material is evaporated from a low-temperature Knudsen cell. The system is equipped with a refraction high-energy electron-difraction system, a quadrupole mass spectrometer and a spectroscopic ellipsometer.
Najdeno v: ključnih besedah
Povzetek najdenega: ...The system is equipped with a refraction high-energy electron-difraction system, a quadrupole mass spectrometer and... ...cell, mass quadrupole spectrometer, spectroscopic ellipsometer, high-energy electrons, ...
Ključne besede: ultra-high vacuum, molecular-beam epitaxy, Knudsen cell, mass quadrupole spectrometer, spectroscopic ellipsometer, high-energy electrons
Objavljeno: 10.07.2015; Ogledov: 2820; Prenosov: 13
URL Polno besedilo (0,00 KB)

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