Repository of University of Nova Gorica

Search the repository
A+ | A- | Help | SLO | ENG

Query: search in
search in
search in
search in
* old and bolonia study programme


41 - 49 / 49
First pagePrevious page12345Next pageLast page
Coherent soft X-ray pulses from an echo-enabled harmonic generation free-electron laser
Giovanni De Ninno, Primož Rebernik Ribič, 2019, original scientific article

Abstract: X-ray free-electron lasers (FELs), which amplify light emitted by a relativistic electron beam, are extending nonlinear optical techniques to shorter wavelengths, adding element specificity by exciting and probing electronic transitions from core levels. These techniques would benefit tremendously from having a stable FEL source, generating spectrally pure and wavelength-tunable pulses. We show that such requirements can be met by operating the FEL in the so-called echo-enabled harmonic generation (EEHG) configuration. Here, two external conventional lasers are used to precisely tailor the longitudinal phase space of the electron beam before emission of X-rays. We demonstrate high-gain EEHG lasing producing stable, intense, nearly fully coherent pulses at wavelengths as short as 5.9 nm (~211 eV) at the FERMI FEL user facility. Low sensitivity to electron-beam imperfections and observation of stable, narrow-band, coherent emission down to 2.6 nm (~474 eV) make the technique a prime candidate for generating laser-like pulses in the X-ray spectral region, opening the door to multidimensional coherent spectroscopies at short wavelengths.
Found in: ključnih besedah
Keywords: free electron laser, coherence, x-rays
Published: 07.05.2019; Views: 1530; Downloads: 0
.pdf Fulltext (6,89 MB)

A detailed investigation of single-photon laser enabled Auger decay in neon
Primož Rebernik Ribič, Giovanni De Ninno, 2019, original scientific article

Abstract: Single-photon laser enabled Auger decay (spLEAD) is an electronic de-excitation process which was recently predicted and observed in Ne. We have investigated it using bichromatic phase-locked free electron laser radiation and extensive angle-resolved photoelectron measurements, supported by a detailed theoretical model. We first used separately the fundamental wavelength resonant with the Ne+ 2s–2p transition, 46.17 nm, and its second harmonic, 23.08 nm, then their phase-locked bichromatic combination. In the latter case the phase difference between the two wavelengths was scanned, and interference effects were observed, confirming that the spLEAD process was occurring. The detailed theoretical model we developed qualitatively predicts all observations: branching ratios between the final Auger states, their amplitudes of oscillation as a function of phase, the phase lag between the oscillations of different final states, and partial cancellation of the oscillations under certain conditions.
Found in: ključnih besedah
Keywords: laser enabled Auger decay, free-electron lasers, neon
Published: 12.01.2020; Views: 1181; Downloads: 0
.pdf Fulltext (996,35 KB)

Element selective probe of the ultra-fast magnetic response to an element selective excitation in Fe-Ni compounds using a two-color FEL source
Eugenio Ferrari, C. Spezzani, Franck Fortuna, Renaud Delaunay, Franck Vidal, Ivaylo Nikolov, Paolo Cinquegrana, B. Diviacco, David Gauthier, G. Penco, Primož Rebernik Ribič, Giovanni De Ninno, 2017, original scientific article

Found in: ključnih besedah
Summary of found: electron laser, two-color source, ultra-fast dynamics...
Keywords: free electron laser, two-color source, ultra-fast dynamics
Published: 13.01.2020; Views: 1333; Downloads: 4
This document has many files! More...

Shaping FEL radiation
Primož Rebernik Ribič, 2016, published scientific conference contribution abstract (invited lecture)

Found in: ključnih besedah
Keywords: radiation, synchrotron, free-electron laser
Published: 16.01.2020; Views: 1216; Downloads: 4
This document has many files! More...

Narrowband high harmonic pulses for trARPES using frequency-upconverted Ti:Sapphire lasers
Jurij Urbančič, published scientific conference contribution abstract

Abstract: trARPES using femtosecond XUV 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 shorter wavelength 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 while preserving excellent time resolution.
Found in: ključnih besedah
Summary of found: ...harmonics generated by 800 nm wavelength Ti:Sapphire lasers required a trade-off between photon flux, energy...
Keywords: HHG, ARPES, Laser
Published: 22.05.2020; Views: 1036; Downloads: 0

Element-resolved study on the influence of a magnetic dopant on the exchange interaction in FePt on ultrashort timescales
Jurij Urbančič, 2017, published scientific conference contribution abstract

Abstract: In this study, we investigate the optically induced ultrafast demagnetization dynamics of a FePt alloy doped with Mn atoms on the characteristic timescale of the exchange interaction of a few femtoseconds. We use high harmonic generation with photon energies in the XUV to gain elemental resolution in a femtosecond magneto-optical Kerr-effect experiment [1] in transversal geometry. Following up on earlier experiments, which showed the importance of the exchange interaction in the demagnetization process in alloys [2,3], we see clear differences in the dynamical responses of the three elements Fe, Pt, and Mn. Our results suggest, that the exchange coupling between the magnetic moments of the FePt alloy and the Mn dopant changes on ultrashort timescales.
Found in: ključnih besedah
Summary of found: ...FePt, High Harmonic Generation, Laser, Magnetic Materials...
Keywords: FePt, High Harmonic Generation, Laser, Magnetic Materials
Published: 22.05.2020; Views: 1227; Downloads: 0

Slow interatomic Coulombic decay of multiply excited neon clusters
Giovanni De Ninno, Denis Iablonskyi, 2016, original scientific article

Abstract: Ne clusters (∼ 5000 atoms) were resonantly excited (2 p→ 3 s) by intense free electron laser (FEL) radiation at FERMI. Such multiply excited clusters can decay nonradiatively via energy exchange between at least two neighboring excited atoms. Benefiting from the precise tunability and narrow bandwidth of seeded FEL radiation, specific sites of the Ne clusters were probed. We found that the relaxation of cluster surface atoms proceeds via a sequence of interatomic or intermolecular Coulombic decay (ICD) processes while ICD of bulk atoms is additionally affected by the surrounding excited medium via inelastic electron scattering. For both cases, cluster excitations relax to atomic states prior to ICD, showing that this kind of ICD is rather slow (picosecond range). Controlling the average number of excitations per cluster via the FEL intensity allows a coarse tuning of the ICD rate.
Found in: ključnih besedah
Summary of found: ...p→ 3 s) by intense free electron laser (FEL) radiation at FERMI. Such multiply excited...
Keywords: Clusters, low-denisty matter, free-electron laser
Published: 27.10.2020; Views: 662; Downloads: 0
.pdf Fulltext (309,21 KB)

Laser ablation-single-particle-inductively coupled plasma mass spectrometry as a multimodality bioimaging tool in nano-based omics
Samo B. Hočevar, Mitja Kolar, Vid Simon Šelih, Iztok Arčon, Katarina Vogel-Mikuš, Martin Šala, Johannes Teun van Elteren, Dino Metarapi, 2021, original scientific article

Abstract: Advanced data processing and visualization techniques were applied to laser ablation-single particleinductively coupled plasma mass spectrometry (LA-sp-ICPMS) data obtained from imaging of roots of sunflower (Helianthus annuus L.) which were exposed to ionic silver (Ag+). Highly multiplexed images with tissue level resolution were generated, showing the uptake and transformation of Ag+ to silver nanoparticles (AgNPs) in whole root cross-sections, and revealing that the size of biosynthesized AgNPs is predisposed by the reducing power of particular root compartments. Various Ag+ and AgNP visualization strategies are shown with special emphasis on spatially resolved information associated with the number and spherical-equivalent size of individual AgNPs in user-selected root cross-sectional regions, including statistical analysis of the AgNP distribution. Normally, this multimodality information can only be obtained by combining the results of techniques from several complementary platforms.
Found in: ključnih besedah
Keywords: Laser ablation, Ag XANES, bioimaging
Published: 03.06.2021; Views: 388; Downloads: 13
URL Fulltext (0,00 KB)
This document has many files! More...

Search done in 0 sec.
Back to top