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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: ...harmonic generation, free-electron lasers, hot-electrons dynamics, surface science, pump-probe photoemission, ultraviolet photoemission, orbital angular momentum...
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: 8; Prenosov: 0
.pdf Polno besedilo (19,78 MB)

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: [accessed Apr 20, 2017].
Najdeno v: ključnih besedah
Ključne besede: high harmonic generation, charge-density wave material, 1T-TiSe2, non-equilibrium electron dynamics, ultrafast surface science
Objavljeno: 20.04.2017; Ogledov: 2280; Prenosov: 0
.pdf Polno besedilo (1,10 MB)

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
Ključne besede: angle-resolved photoemission spectroscopy, ARPES, high harmonic generation, ultrafast surface science
Objavljeno: 20.04.2017; Ogledov: 2196; Prenosov: 0
.pdf Polno besedilo (1,80 MB)

Social and Cultural Aspects of Socializing of Slovenian Students in the Habsburg Monarchy in the 19th and the 20th Centuries
Željko Oset, prispevek na konferenci brez natisa

Najdeno v: ključnih besedah
Povzetek najdenega: ...Slovene Students, Science, History, University of Vienna, University of Graz...
Ključne besede: Slovene Students, Science, History, University of Vienna, University of Graz
Objavljeno: 12.12.2017; Ogledov: 1230; Prenosov: 0
.pdf Polno besedilo (840,41 KB)

Art or Science? Images of scientific research
Tanja Petrushevska, 2017, umetniško delo

Opis: Looking at the pinking of a sky at sunset we see a delicate impressionist watercolor or rather the spectacular effect of the refraction of the sun on the particles of the atmosphere? Can the extraordinary geometries of the cubic lattices of a salt crystal be considered a perfect composition deserving of admiration like a cubist painting? All the "infinite forms, ever more beautiful and wonderful" of life, as defined by the famous naturalist Charles Darwin, are art or science? The Art or Science photo contest? was born to emphasize the contamination between these two fields, only apparently distant, of human knowledge, exalting the beauty of scientific research and rewarding the photographic talent of those who work in science. The 2017 edition of the competition, conceived and promoted by the University of Trieste and Immaginario Scientifico, has collected 116 images of students and scientists from universities and research institutions. Among these were selected 30 photos, exhibited from 18 to 23 September 2017 in Trieste, at Palazzo Costanzi, as part of the Trieste Next-Festival of Scientific Research.
Najdeno v: ključnih besedah
Ključne besede: art and science
Objavljeno: 23.01.2018; Ogledov: 1081; Prenosov: 0
.pdf Polno besedilo (501,25 KB)

Inner and Outer Space - our Universe expands
R. Amanullah, Chad Finley, Emily Freeland, Lucia Guaita, Fabio Iocco, Martin Sahlen, Bo Sundborg, Tanja Petrushevska, 2013, katalog razstave

Najdeno v: ključnih besedah
Ključne besede: art and science
Objavljeno: 25.01.2018; Ogledov: 934; Prenosov: 0
.pdf Polno besedilo (136,04 KB)

Tanja Petrushevska, S. Papadogiannakis, Emir Karamehmetoglu, 2015, druga izvedena dela

Opis: Fysik i Kungsträdgården is one of the major outreach events in Stockholm where scientists have the chance to show their research. This year the supernova group at the OKC invited the public to look for supernovae with us using the intermediate Palomar (Transient) Factory (iPTF) collaboration telescope in Palomar, California, U.S.A. Due to the time difference between Stockholm and California, we were able to look at live images as they were taken from the telescope, to search for new transient objects such as supernovae. The event was successful, bringing a lot of people from the park in central Stockholm to come and search with us.
Najdeno v: ključnih besedah
Povzetek najdenega: ... science outreach, supernova hunting for the public...
Ključne besede: science outreach, supernova hunting for the public
Objavljeno: 09.02.2018; Ogledov: 1248; Prenosov: 0
.pdf Polno besedilo (572,84 KB)

Жените во науката
Daniel Evrosimoski, Tanja Petrushevska, 2018, intervju

Najdeno v: ključnih besedah
Povzetek najdenega: ...women in science, international day of women in science, interview,...
Ključne besede: women in science, international day of women in science, interview, newspaper
Objavljeno: 12.02.2018; Ogledov: 1199; Prenosov: 0 
(1 glas)
.pdf Polno besedilo (1,57 MB)

The Topic of Mining in Secondary School Literature Textbooks from 1850 to 1950
Zoran Božič, 2018, izvirni znanstveni članek

Opis: During the first century of secondary school literature textbook publishing (from the introduction of Slovenian language as a school subject after the March Revolution in the Austrian Empire to the first Five-Year Plan after World War II) over a hundred texts featuring the topic of mining and related activities were included. The first writings have a clearly affirmative attitude towards mining, perceived and presented as a way of promoting general prosperity. The first mentions of the negative aspects of mining and the deceptive folly of coveting precious mineral resources appear towards the end of the 19th century. Only during the interwar period, however, were there various texts which presented mining as an inhumane and dangerous activity. After World War II the approach was again optimistic: in central literature textbooks mining was depicted as the glorification of socialist progress. Relevant texts were published in eight series of textbooks, the first as early as in the Bleiweis series for lower secondary schools in 1850 and the last in the ethnic Slovenian Beličič series of textbooks in 1947. The discovery of mercury in the Idrija mine was described by Valvazor, Kastelic, Hrovat and Oblak.
Najdeno v: ključnih besedah
Povzetek najdenega: ...natural science, didactics, mineral resources, Idrija mine, mercury...
Ključne besede: natural science, didactics, mineral resources, Idrija mine, mercury
Objavljeno: 30.08.2018; Ogledov: 1414; Prenosov: 75
.pdf Polno besedilo (361,27 KB)

Mateja Golež, 2019, doktorska disertacija

Opis: The doctoral dissertation in question presents in detail the issue of protecting architectural heritage as ruins on the example of the Žiče Charterhouse complex in Slovenia. The author based her work on the history of conservation, internationally applicable charters related to architectural heritage protection and on examples taken from international conservation practice. Although the Slovenian conservation profession, as an independent technical and scientific discipline, received its formal legal status through the emergence of independent Slovenia merely a couple of decades ago, it is possible to claim that Slovenia, with its first academically qualified conservation specialists Avguštin Stegenšek and France Stele, was in contact with active policy on heritage protection as early as before World War I, when the Slovenian territory was part of the Austro-Hungarian Empire, and also after the War, when the territory was annexed to the Kingdom of Yugoslavia. Despite long-standing efforts, Slovenians did not achieve the legal protection of architectural heritage until early 1980s, when an independent act on the protection of natural and cultural heritage was adopted in former Yugoslavia. Because of this, the tasks carried out by conservation specialists until that time primarily focused on documenting heritage and carrying out the most pressing maintenance works. Since all major international charters related to cultural heritage protection were signed when Slovenia was part of former Yugoslavia and after it became independent, it is not possible to claim that the profession did not follow the international legal order in this field. This is why it is sometimes difficult to understand the large gap between international technical criteria and the conservation decisions made by Slovenian conservation experts when performing intervention works on structures or sites of cultural value in Slovenia. To improve this condition, it is therefore vital that buildings be treated comprehensively prior to interventions, including in terms of carrying out natural science and technical research studies that provide an insight into the materials, structural frame and building physics of a building, as shown in the doctoral dissertation on the example of the ruin of the Church of St. John the Baptist at Žiče Charterhouse. Only by carefully analysing historic materials, it is possible to make the right decision on the use of adequate substitute materials for the needs of maintaining a ruin and, only on the basis of preliminary research made into structural frames, it will be possible to monitor the vitality of ruins in future, whereby using state-of-the-art research methods from conservation science. Since the Church of St. John the Baptist has lost its original intended use and also the possibility to get it back, the author of the dissertation proposes that the structure not be reconstructed, since this would imply a major deviation from original architecture, with a shortage of adequate documentation that would provide a basis for credible reconstruction. For this reason, the author of the doctoral dissertation defends the position that the Church be protected as a ruin. The operator of the monastery complex and the entire valley of St. John, where the remains of the lower and upper monastic houses of the Žiče Charterhouse are located, now faces quite a challenging task. It will have to prepare a management plan that will foresee expert bases for sustainable use of natural and cultural values of this site and a suitable development policy, whereby giving the key role to the local community.
Najdeno v: ključnih besedah
Povzetek najdenega: ...including in terms of carrying out natural science and technical research studies that provide an...
Ključne besede: ruins, architectural history, legislation, international charters, revitalization, natural science research, Žiče monastery
Objavljeno: 22.01.2019; Ogledov: 1217; Prenosov: 63
.pdf Polno besedilo (12,67 MB)

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