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1.
Chemical and structural investigation of the cobalt phthalocyanine
Matija Stupar, 2015, magistrsko delo

Opis: In the last two decades, studies on organic molecules mimicking substances of fundamental importance in nature, like chlorophyll or hemoglobin, have attracted researchers’ attention. These molecules are building blocks for a family of materials also referred to as “organic semiconductors”. Such compounds can be implemented in numerous applications, ranging from data-storage to light harvesting. Some of their fundamental advantages include low cost, light weight, relatively easy engineering and mechanical flexibility, compatible with bending plastic substrates. In this thesis work we investigated the chemical, structural and electronic properties of cobalt phthalocyanines (CoPc). These molecules have promising applications in the field of magnetic data storage and spintronics in general, due to the ferromagnetic properties of the cobalt atom. Several techniques like photoemission core-level spectroscopy and valence band spectroscopy, together with X-ray absorption, have been used in order to determine the CoPc properties in gaseous phase, i.e. in the absence of interaction with the surrounding environment. Another set of experiments was devoted to the commissioning of the CITIUS time-resolved photoemission setup, that will be used in future studies of CoPc molecules on surfaces.
Najdeno v: ključnih besedah
Povzetek najdenega: ...X-ray absorption spectroscopy (XAS), synchrotron radiation, laser, high order harmonic generation (HHG), time resolved spectroscopy...
Ključne besede: Cobalt phthalocyanine (CoPc), photoemission spectroscopy (PES), X-ray absorption spectroscopy (XAS), synchrotron radiation, laser, high order harmonic generation (HHG), time resolved spectroscopy
Objavljeno: 29.09.2015; Ogledov: 3964; Prenosov: 188
.pdf Polno besedilo (2,96 MB)

2.
Observation of short-lived laser-dressed quantum states in the frequency plane
Matjaz Zitnik, Giovanni De Ninno, 2019, izvirni znanstveni članek

Najdeno v: ključnih besedah
Povzetek najdenega: ...Laser-dressed quantum states, high-harmonic generation...
Ključne besede: Laser-dressed quantum states, high-harmonic generation
Objavljeno: 27.10.2020; Ogledov: 66; Prenosov: 0
.pdf Polno besedilo (1,73 MB)

3.
Control of ellipticity in high-order harmonic generation driven by two linearly polarized fields
Benoit Mahieu, Giovanni De Ninno, 2018, izvirni znanstveni članek

Najdeno v: ključnih besedah
Ključne besede: High-harmonic generation, polarization
Objavljeno: 27.10.2020; Ogledov: 51; Prenosov: 0
.pdf Polno besedilo (575,74 KB)

4.
Self-amplified photo-induced gap quenching in a correlated electron material
Jurij Urbančič, Eich Steffen, Mathias Stefan, 2016, izvirni znanstveni članek

Opis: Capturing the dynamic electronic band structure of a correlated material presents a powerful capability for uncovering the complex couplings between the electronic and structural degrees of freedom. When combined with ultrafast laser excitation, new phases of matter can result, since far-from-equilibrium excited states are instantaneously populated. Here, we elucidate a general relation between ultrafast non-equilibrium electron dynamics and the size of the characteristic energy gap in a correlated electron material. We show that carrier multiplication via impact ionization can be one of the most important processes in a gapped material, and that the speed of carrier multiplication critically depends on the size of the energy gap. In the case of the charge-density wave material 1T-TiSe 2 , our data indicate that carrier multiplication and gap dynamics mutually amplify each other, which explains—on a microscopic level—the extremely fast response of this material to ultrafast optical excitation. Self-amplified photo-induced gap quenching in a correlated electron material. Available from: https://www.researchgate.net/publication/308804379_Self-amplified_photo-induced_gap_quenching_in_a_correlated_electron_material [accessed Apr 20, 2017].
Najdeno v: ključnih besedah
Povzetek najdenega: ... high harmonic generation, charge-density wave material, 1T-TiSe2, non-equilibrium...
Ključne besede: high harmonic generation, charge-density wave material, 1T-TiSe2, non-equilibrium electron dynamics, ultrafast surface science
Objavljeno: 20.04.2017; Ogledov: 2261; Prenosov: 0
.pdf Polno besedilo (1,10 MB)

5.
Time- and angle-resolved photoemission spectroscopy with optimized high-harmonic pulses using frequency-doubled Ti:Sapphire lasers
Steffen Eich, Jurij Urbančič, 2014, izvirni znanstveni članek

Opis: Time- and angle-resolved photoemission spectroscopy (trARPES) using femtosecond extreme ultraviolet high harmonics has recently emerged as a powerful tool for investigating ultrafast quasiparticle dynamics in correlated-electron materials. However, the full potential of this approach has not yet been achieved because, to date, high harmonics generated by 800 nm wavelength Ti:Sapphire lasers required a trade-off between photon flux, energy and time resolution. Photoemission spectroscopy requires a quasi-monochromatic output, but dispersive optical elements that select a single harmonic can significantly reduce the photon flux and time resolution. Here we show that 400 nm driven high harmonic extreme-ultraviolet trARPES is superior to using 800 nm laser drivers since it eliminates the need for any spectral selection, thereby increasing photon flux and energy resolution to <150 meV while preserving excellent time resolution of about 30 fs.
Najdeno v: ključnih besedah
Povzetek najdenega: ...angle-resolved photoemission spectroscopy, ARPES, high harmonic generation, ultrafast surface science...
Ključne besede: angle-resolved photoemission spectroscopy, ARPES, high harmonic generation, ultrafast surface science
Objavljeno: 20.04.2017; Ogledov: 2176; Prenosov: 0
.pdf Polno besedilo (1,80 MB)

6.
7.
Echo-enabled harmonic generation studies for the FERMI free-electron laser
Primož Rebernik Ribič, Eléonore Roussel, Gregory Penn, Giovanni De Ninno, Luca Giannessi, G. Penco, E. Allaria, 2017, izvirni znanstveni članek

Najdeno v: ključnih besedah
Povzetek najdenega: ...free electron laser, harmonic up-conversion, high-harmonic generation, seeding, x-ray, pump-probe, microbunching instability...
Ključne besede: free electron laser, harmonic up-conversion, high-harmonic generation, seeding, x-ray, pump-probe, microbunching instability
Objavljeno: 13.01.2020; Ogledov: 443; Prenosov: 2
Gradivo ima več datotek! Več...

8.
Generation and applications of extreme-ultraviolet vortices
Carlos Hernández-García, Jorge Vieira, Jose T. Mendonça, Laura Rego, Julio San Román, Luis Plaja, Primož Rebernik Ribič, David Gauthier, Antonio Picón, 2017, izvirni znanstveni članek

Najdeno v: ključnih besedah
Povzetek najdenega: ...XUV/X-ray vortices, orbital angular momentum of photons, high-harmonic generation, free-electron lasers, plasma physics...
Ključne besede: XUV/X-ray vortices, orbital angular momentum of photons, high-harmonic generation, free-electron lasers, plasma physics
Objavljeno: 13.01.2020; Ogledov: 460; Prenosov: 1
Gradivo ima več datotek! Več...

9.
Ultrafast Element-Specific Demagnetization in Alloys
Jurij Urbančič, doktorska disertacija

Opis: The study of magnetism has long been an active area of interest for the scientific research, while also providing vast technological applications such as information storage. It was first observed in the middle of the 90s that irradiating a ferromagnetic material with an intense femtosecond laser pulse can result in a loss of magnetization occurring below one picosecond. Since then, the study of magnetism on these femtosecond timescales has been a field of growing interest, addressing the question of how fast can the magnetization modification occurs and what presents the fundamental limit of this speed. For the understanding of these experimental observations, a number of different models were proposed, although the responsible microscopic mechanisms are still under discussion. According to one group of models, the change in magnetic moment is due to the spin-flip mechanism occurring during scattering events between electrons and (quasi-)particles. An example of this is the so-called Microscopic Three-Temperature Model (M3TM). A different approach is employed by the Superdiffusive Spin Current Model, where the loss of magnetization is attributed to a flow of chargeless spin particles taking place after the laser excitation. With the purpose to explore the magnetic characteristic of materials, a range of investigation methods has been developed. One of them relies on the exploitation of the Magneto-Optical Kerr Effect (MOKE) and an incorporation of femtosecond laser pulses in pump-probe configuration. In this way, part of the beam from the same laser system is used to optically excite the system (the pump), while another part takes a snapshot of it (the probe), thus allowing us to investigate the magnetization dynamics with a femtosecond temporal resolution. In the experimental part of the thesis, we apply this MOKE technique to explore the demagnetization dynamics of a ferromagnetic alloy consisting of iron and nickel, also called Permalloy. It is observed that the magnetization is suppressed (quenched) in the first few hundred femtoseconds. Part of the experiments were performed using visible light with different fluences of the pump. The most notable observation is that this alloy exhibits different demagnetization dynamics at lower and higher fluence. What we see is a transition from one-step (demagnetization followed by a recovery on a much longer timescale) to a two-step (demagnetization followed by another slower demagnetization step) magnetization process occurring with the increment of pump fluence. This behavior is predicted and reproduced by the M3TM, which is applied for a comparison between experiments and theory.
Najdeno v: ključnih besedah
Povzetek najdenega: ... High Harmonic Generation, Magnetism, Ultrafast, Materials...
Ključne besede: High Harmonic Generation, Magnetism, Ultrafast, Materials
Objavljeno: 08.05.2020; Ogledov: 431; Prenosov: 0
.pdf Polno besedilo (12,06 MB)

10.
Towards ultrafast X-ray condensed matter physics with MHz repetition rate HHG sources
Jurij Urbančič, 2015, objavljeni povzetek znanstvenega prispevka na konferenci

Opis: In recent years, an increasing number of ultrafast material science experiments are based on the use of table-top high-harmonic generation (HHG) lightsources [1,2]. Despite the huge success of these first experiments, a major drawback has been the limited repetition rate of these lightsources, in particular with respect to all types of photoemission experiments. Here, we combine newly developed high-repetition rate HHG sources [3,4] with state-of-the-art element-specific magneto-optical Kerr experiments. The chances and prospects for future ultrafast materials science experiments with these lightsources will be discussed.
Najdeno v: ključnih besedah
Povzetek najdenega: ...are based on the use of table-top high-harmonic generation (HHG) lightsources [1,2]. Despite the huge...
Ključne besede: High Harmonic Generation, X-Rays, Condensed Matter
Objavljeno: 22.05.2020; Ogledov: 276; Prenosov: 0

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