Photoelectric effect with a twist De Ninno Giovanni; Wätzel Jonas; Rebernik, Ribič Primož ...
Nature photonics,
09/2020, Letnik:
14, Številka:
9
Journal Article
Recenzirano
Odprti dostop
Photons have fixed spin and unbounded orbital angular momentum (OAM). While the former is manifested in the polarization of light, the latter corresponds to the spatial phase distribution of its ...wavefront1. The distinctive way in which the photon spin dictates the electron motion upon light–matter interaction is the basis for numerous well-established spectroscopies. By contrast, imprinting OAM on a matter wave, specifically on a propagating electron, is generally considered very challenging and the anticipated effect undetectable2. In refs. 3,4, the authors provided evidence of OAM-dependent absorption of light by a bound electron. Here, we seek to observe an OAM-dependent dichroic photoelectric effect, using a sample of He atoms. Surprisingly, we find that the OAM of an optical field can be imprinted coherently onto a propagating electron wave. Our results reveal new aspects of light–matter interaction and point to a new kind of single-photon electron spectroscopy.The findings that the spatial distribution of an optical field with vortex phase profile can be imprinted coherently onto a propagating electron wave reveal new aspects of light–matter interactions and will help develop future single-photon electron spectroscopy.
Triggering and switching magnetic moments is of key importance for applications ranging from spintronics to quantum information. A noninvasive ultrafast control at the nanoscale is, however, an open ...challenge. Here, we propose a novel laser-based scheme for generating atomic-scale charge current loops within femtoseconds. The associated orbital magnetic moments remain ferromagnetically aligned after the laser pulses have ceased and are localized within an area that is tunable via laser parameters and can be chosen to be well below the diffraction limit of the driving laser field. The scheme relies on tuning the phase, polarization, and intensities of two copropagating Gaussian and vortex laser pulses, allowing us to control the spatial extent, direction, and strength of the atomic-scale charge current loops induced in the irradiated sample upon photon absorption. In the experiment we used He atoms driven by an ultraviolet and infrared vortex-beam laser pulses to generate current-carrying Rydberg states and test for the generated magnetic moments via dichroic effects in photoemission. Ab initio quantum dynamic simulations and analysis confirm the proposed scenario and provide a quantitative estimate of the generated local moments.
The relative phase of first (
ω
1
) and third harmonics (
ω
3
) extreme ultraviolet light pulses was varied to control the population of the
2
s
2
state in helium through the interference of
ω
1
+
ω
...1
and
ω
3
−
ω
1
two-photon excitation paths. The population was monitored by observing the total electron yield due to the
2
s
2
autoionization decay. Maximum yield occurs when the relative phase of the two harmonics matches the phase difference of complex atomic amplitudes governing the two excitation paths. The calculated trend of atomic phase differences agrees well with the measured data in the spectral region of the resonance, provided that time-reversed
−
ω
1
+
ω
3
path is also taken into account. These results open the way to accessing phase differences of two-photon ionization paths involving energetically distant intermediate states and to perform interferometry in the extreme ultraviolet range by monitoring final state populations.
Digitalizacija na podeželju v Sloveniji Hauptman, Barbara; Ivanc, Taja; Jelovčan, Matej ...
Dela (Univerza v Ljubljani. Oddelek za geografijo),
12/2023
60
Journal Article
Recenzirano
Digitalizacija podeželja temelji na vzpostavitvi digitalne infrastrukture in uporabi digitalnih orodij. V tem procesu obstajajo med podeželskimi območji pomembne razlike glede razvojnih korakov (npr. ...časovni, investicijski, prostorski vidik vzpostavitve digitalne infrastrukture in orodij) in se oblikujejo digitalni razkoraki (razlike v razpoložljivosti in dostopnosti digitalne infrastrukture, uporabi digitalnih orodij), kar smo preučevali na območju lokalne akcijske skupine (LAS) Od Pohorja do Bohorja. Za vpogled v pragmatični vidik neposrednega uporabnika digitalne infrastrukture in digitalnih orodij smo izvedli spletni anketi, v katerih se je izkazalo, da lokalni prebivalci digitalizacijo večinoma dojemajo pozitivno kot orodje pri vsakodnevnih opravilih, da pozitivno digitalizacijo dojemajo tudi osnovnošolci, pri čemer se zavedajo tudi negativnih plati. Prostorska analiza obstoječe digitalne infrastrukture je pokazala, da je le-ta v večini občin LAS Od Pohorja do Bohorja pomanjkljiva, redke investicije v digitalno infrastrukturo so pogosto omejene na središča občin. Ker je digitalizacija postala sestavni in nemalokrat tudi ključni del sodobnega življenja in dela, smo s pomočjo kritične samorefleksije intervjuvancev na preučevanem območju prepoznali, da ima vsak posameznik drugačno dojemanje, razumevanje in stopnjo uporabe digitalne infrastrukture in digitalnih orodij. Empirično-konceptualne ugotovitve fokusne skupine nakazujejo neučinkovitost državnih organov pri investicijah v digitalno opremljenost, premalo informacijskih vsebin v predmetniku osnovne šole ter veliko vlogo digitalne infrastrukture in digitalnih orodij pri delu in prostem času.
Digitalizacija na podeželju v Sloveniji Barbara Hauptman; Taja Ivanc; Matej Jelovčan ...
Dela (Univerza v Ljubljani. Oddelek za geografijo),
12/2023
60
Journal Article
Recenzirano
Odprti dostop
Digitalizacija podeželja temelji na vzpostavitvi digitalne infrastrukture in uporabi digitalnih orodij. V tem procesu obstajajo med podeželskimi območji pomembne razlike glede razvojnih korakov (npr. ...časovni, investicijski, prostorski vidik vzpostavitve digitalne infrastrukture in orodij) in se oblikujejo digitalni razkoraki (razlike v razpoložljivosti in dostopnosti digitalne infrastrukture, uporabi digitalnih orodij), kar smo preučevali na območju lokalne akcijske skupine (LAS) Od Pohorja do Bohorja. Za vpogled v pragmatični vidik neposrednega uporabnika digitalne infrastrukture in digitalnih orodij smo izvedli spletni anketi, v katerih se je izkazalo, da lokalni prebivalci digitalizacijo večinoma dojemajo pozitivno kot orodje pri vsakodnevnih opravilih, da pozitivno digitalizacijo dojemajo tudi osnovnošolci, pri čemer se zavedajo tudi negativnih plati. Prostorska analiza obstoječe digitalne infrastrukture je pokazala, da je le-ta v večini občin LAS Od Pohorja do Bohorja pomanjkljiva, redke investicije v digitalno infrastrukturo so pogosto omejene na središča občin. Ker je digitalizacija postala sestavni in nemalokrat tudi ključni del sodobnega življenja in dela, smo s pomočjo kritične samorefleksije intervjuvancev na preučevanem območju prepoznali, da ima vsak posameznik drugačno dojemanje, razumevanje in stopnjo uporabe digitalne infrastrukture in digitalnih orodij. Empirično-konceptualne ugotovitve fokusne skupine nakazujejo neučinkovitost državnih organov pri investicijah v digitalno opremljenost, premalo informacijskih vsebin v predmetniku osnovne šole ter veliko vlogo digitalne infrastrukture in digitalnih orodij pri delu in prostem času.
An approach to modeling the dynamics of x-ray amplified spontaneous emission and superfluorescence -- the phenomenon of collective x-ray emission initiated by intense pulses of X-ray Free Electron ...Lasers -- is developed based on stochastic partial differential equations. The equations are derived from first principles, and the relevant approximations, derivation steps, and extensions specific to stimulated x-ray emission are presented. The resulting equations take the form of three-dimensional generalized Maxwell-Bloch equations augmented with noise terms for both field and atomic variables. The derived noise terms possess specific correlation properties that enable the correct reconstruction of spontaneous emission. Consequently, the developed theoretical formalism is universally suitable for describing all stages of stimulated x-ray emission: spontaneous emission, amplified spontaneous emission, and superfluorescence. We present numerical examples that illustrate various properties of the emitted field, including spatio-temporal coherence, spectral-angular and polarization characteristics. We anticipate that the proposed theoretical framework will establish a robust foundation for interpreting measurements in stimulated x-ray emission spectroscopy, modeling x-ray laser oscillators, and describing other experiments leveraging x-ray superfluorescence.
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