| 1. |
- Laurell, Hugo, et al.
(författare)
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Measuring the quantum state of photoelectrons
- 2023
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- A photoelectron, emitted due to the absorption of light quanta as described by the photoelectric effect, is often characterized experimentally by a classical quantity, its momentum. However, since the photoelectron is a quantum object, its rigorous characterization requires the reconstruction of the complete quantum state, the photoelectron's density matrix. Here, we use quantum state tomography to fully characterize photoelectrons emitted from helium and argon atoms upon absorption of ultrashort, extreme ultraviolet light pulses. While in helium we measure a pure photoelectronic state, in argon, spin-orbit interaction induces entanglement between the ion and the photoelectron, leading to a reduced purity of the photoelectron state. Our work shows how state tomography gives new insights into the fundamental quantum aspects of light-induced electronic processes in matter, bridging the fields of photoelectron spectroscopy and quantum information, and offering new spectroscopic possibilities for quantum technology.
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| 2. |
- Mølster, Kjell Martin, 1992-, et al.
(författare)
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THz time-domain reflection spectroscopy of KTiOPO4
- 2019
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Konferensbidrag (refereegranskat)abstract
- There is an ongoing development of THz sources for high-field applications, especially with the view of potential for THz-driven particle accelerators. For such sources nonlinear materials with high optical damage threshold and low loss are required. KTiOPO4, (KTP) is a well-established material for nonlinear optical applications in the visible and near-IR region thanks to its large transparency, high nonlinear coefficient and damage threshold. Its reasonably low absorption [1, 2] and strong coupling to phonon-polariton degree of freedom [1]. This shows promise for efficient IR to THz conversionprocess. Indeed,Wu et al.[2] recently demonstrated its superiority to LiNbO3and LiTaO3in a back to back experiment. In view of this, it is important to determinethe spectrum of complex refractive index over larger spectral range and with higher accuracy than has been do so far. KTP is an orthorhombic crystal belonging to mm2 point group with a rather complex vibrational mode structure containing 192 degrees of freedom. Earlier spectroscopic studies of KTP have either lacked the possibility of directly extracting the complex refractive index [3] or been limited by absorption of the transmitted signal due to the strong resonances of KTP, limiting the spectral extenttoabout 2.5 THz [4]. In this work we utilize reflection THz time-domain spectroscopy (TTDS) to determine the spectrum of the refractive index, n, and the absorption coefficient, , between 0.5 THz and up to 7 THz for two eigenpolarizations on the (001) plane.
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| 3. |
- Mølster, Kjell Martin, 1992-, et al.
(författare)
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THz time-domain reflection spectroscopy of KTiOPO4
- 2019
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Ingår i: Optics InfoBase Conference Papers. - : OSA - The Optical Society. - 9781557528209
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Konferensbidrag (refereegranskat)abstract
- Terahertz (THz) radiation has been of increasing interest in the last decades, for security, manufacturing, quality control, medical and security imaging applications. The field requires more efficient and affordable sources and nonlinear upconversion schemes point in this direction. KTiOPO, (KTP) is a well-established material for nonlinear optical applications in the visible and near-IR region thanks to its large transparency, high nonlinear coefficient and damage threshold. Its reasonably low absorption [1, 2] and strong polariton resonances [1] show promise for efficient IR to THz upconversion and Wu et al. [2] recently demonstrated its superiority to LiNbO3 and LiTaO3 in a back to back experiment. However, the complex refractive index needs to be measured before further power scaling is realistic.
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| 4. |
- Mølster, Kjell Martin, 1992-, et al.
(författare)
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Time-domain spectroscopy of KTiOPO4 in the frequency range 0.6–7.0 THz
- 2019
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Ingår i: OSA Continuum. - : Optical Society of America. - 2578-7519. ; 2:12, s. 3521-3538
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Tidskriftsartikel (refereegranskat)abstract
- We report on THz time-domain spectroscopy measurements of flux grown KTiOPO4 in the frequency range 0.6–7.0 THz (20 to 240 cm−1). Our results compare well with earlier Raman and far-infrared measurements. We theorize that the differences between the optical phonon mode resonances reported in the literature are due to what growth parameters and melt compositions are used to grow the crystals. We also report on a new feature at 1.4 THz (47 cm−1).
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| 5. |
- Busto, David, et al.
(författare)
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Probing electronic decoherence with high-resolution attosecond photoelectron interferometry
- 2022
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Ingår i: European Physical Journal D. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 76:7
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Tidskriftsartikel (refereegranskat)abstract
- Abstract: Quantum coherence plays a fundamental role in the study and control of ultrafast dynamics in matter. In the case of photoionization, entanglement of the photoelectron with the ion is a well-known source of decoherence when only one of the particles is measured. Here, we investigate decoherence due to entanglement of the radial and angular degrees of freedom of the photoelectron. We study two-photon ionization via the 2s2p autoionizing state in He using high spectral resolution photoelectron interferometry. Combining experiment and theory, we show that the strong dipole coupling of the 2s2p and 2p2 states results in the entanglement of the angular and radial degrees of freedom. This translates, in angle-integrated measurements, into a dynamic loss of coherence during autoionization. Graphic Abstract: [Figure not available: see fulltext.]. © 2022, The Author(s).
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| 6. |
- Laurell, Hugo
(författare)
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Attosecond photoelectron interferometry: from wavepackets to density matrices
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Through the advent of high-order harmonic generation and attosecond light pulses, photoionization dynamics has been studied on the attosecond time-scale, the intrinsic time-scale of such dynamics. When the electron leaves the atomic potential a phase shift is imprinted on the electron wavefunction. The measurement of this phase, together with amplitude allows us to determine the dynamics that of the photoionization.In this thesis, attosecond (10−18 s) and femtosecond (10−15 s) photoionization dynamics are studied using the photoelectron interferometry technique, Reconstruction of Attosecond Beating By Interference of two-photon Transitions (RABBIT). In RABBIT, the electron wave-packet is interfered with itself, and through this spectral interference, the spectral amplitude and phase can be retrieved.Attosecond time-delay measurements, are performed in argon and xenon where different aspects of electron correlation are investigated. In argon photoionization is studied in the region of the Cooper minumum, where the ionization cross section rapidly decrease. In xenon photoionization is studied across the 4d giant dipole resonance. Resonant dynamics is stud- ied using energy-resolved RABBIT. The studied resonances are the 1s3p, 1s4p, 1s5p (below threshold) and 2s2p (above threshold) in He and 3s−14p (above threshold) in Ar. Most of the measurements in the thesis are angular-integrated.If the photoelectron is prepared as a mixed state, RABBIT is unsuccessful in characterizing the quantum state of the electron, since it cannot be represented as a wavefunction. Therefore a quantum state tomography protocol for photoelectrons (KRAKEN) was developed and tested experimentally in non-resonant ionization of helium, neon and argon. In the case of neon and argon, due to spin-orbit splitting, the entanglement between the photoelectron and ion leads to decoherence induced by incomplete measurements where the state of the ion is not measured.
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| 7. |
- Luo, Sizuo, et al.
(författare)
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Ultra-stable and versatile high-energy resolution setup for attosecond photoelectron spectroscopy
- 2023
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Ingår i: Advances in Physics: X. - 2374-6149. ; 8:1
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Forskningsöversikt (refereegranskat)abstract
- Attosecond photoelectron spectroscopy has opened up for studying light–matter interaction on ultrafast time scales. It is often performed with interferometric experimental setups that require outstanding stability. We demonstrate and characterize in detail an actively stabilized, versatile, high spectral resolution attosecond beamline based on a Mach-Zehnder interferometer. The active stabilization keeps the interferometer ultra-stable for several hours with an RMS stability of 13 as and a total pump-probe delay scanning range of (Formula presented.) fs. A tunable femtosecond laser source to drive high-order harmonic generation allows for precisely addressing atomic and molecular resonances. Furthermore, the interferometer includes a spectral shaper in 4f-geometry in the probe arm as well as a tunable bandpass filter in the pump arm, which offer additional high flexibility in terms of tunability as well as narrowband or polychromatic probe pulses. We demonstrate the capabilities of the beamline via experiments using several variants of the RABBIT (reconstruction of attosecond beating by two photon transitions) technique. In this setup, the temporal-spectral resolution of photoelectron spectroscopy can reach a new level of accuracy and precision.
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| 8. |
- Samuelsson, Oscar, et al.
(författare)
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Pilotförsök med membranbioreaktor för avloppsvattenrening
- 2014
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Det finns ett växande intresse för kommunal avloppsvattenrening med membranteknik i Sverige. Fördelarna med membranteknik är att låga utsläpps- och partikelhalter kan uppnås på en liten anläggningsyta. Den största nackdelen är en ökad energi-förbrukning, på grund av den ökade luftning för rengöring av membranen och stora recirkulationsflöden som innebär ökad pumpenergi. Stockholm Vatten har beslutat att införa membranteknik i befintliga volymer på Henriksdal avloppsreningsverk. Detta för att klara både framtida skärpta utsläppskrav och en ökad belastning (fördubblad till år 2040, jämfört med dagens belastning). Ökningen orsakas av avvecklingen av Bromma reningsverk i kombination med en allmän befolkningstillväxt. Försök med en MembranBioReaktor (MBR) har under ett år genomförts på Hammarby Sjöstadsverk där en skalenlig pilotanläggning med membranteknik, Sjöstadsverkets Linje 1, har jämförts med en konventionell reningsanläggning, Henriksdal. Flödena under försöket motsvarade prognosticerade flöden för Henriksdal år 2040. Fyra olika driftsfall studerades i pilotförsöken där inflödet av avloppsvattnet varierade mellan: konstant medelflöde, dynamiskt medelflöde och maximalt flöde (förväntad maximal veckobelastning år 2040). Följande slutsatser kunde dras: Förväntade utsläppskrav, <0,2 mg/L Tot-P och <6 mg/L Tot-N, var möjliga att uppnå under minst en månad för samtliga driftsfall. Vid maximalt flöde tilläts en högre dos av både järnsulfat och kolkälla. Vid normal dosering av järnsulfat noterades ingen negativ effekt med fouling på membranen. Det fanns inte heller några indikationer på att förbrukningen av järnsulfat, vid normal dosering, skilde sig i MBR-systemet jämfört med Henriksdal. Vid maximala belastningsfallet doserades en högre halt järnsulfat vilket resulterade i låg utgående fosfathalt kring 0,1 mg/L. Det fanns dock en indikation på att förhållandet mellan avskild mängd fosfor per doserad mängd järn försämrades vid den högre dosen. Membranen hade en hög medelpermeabilitet och robust avskiljning av partikulärt material under hela försöksåret. Slammets filtrerbarhet analyserades med två mätmetoder inom ett examensarbete. Filtrerbarheten förbättrades under tiden som försöket pågick, och var god enligt mätmetodernas referensvärden. Membranen rengjordes med kemikalier, oxalsyra och natriumhypoklorit, vid fem tillfällen. Vid ett av dessa tillfällen analyserades halten klororganiska föreningar, AOX, i utgående vatten. AOX ökade under det dygn som rengöringen genomfördes från 0,03 till 0,6 mg/L i utgående vatten. Efterföljande dygn var halterna åter 0,03 mg/L. Det var möjligt att hålla en hög slamhalt i Sjöstadsverket Linje 1, 4000 -10 000 mg/L, genom hela försöket. Även den totala slamåldern var hög jämfört med traditionella system; 15-50 dygn. En jämförelse mellan slammets aktivitet; nitrifikations- och denitrifikationshastighet, visade dock att aktiviteten var lägre i MBR-systemet än i Henriksdal. Nitrifikation noterades i MBR-reaktoren vid belastningstoppar av ammonium. Detta gjorde att nitrifikationen, från systemet i sin helhet, var fullständig under hela försöksåret.
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| 9. |
- Zhong, Shiyang, et al.
(författare)
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Attosecond electron–spin dynamics in Xe 4d photoionization
- 2020
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- The photoionization of xenon atoms in the 70–100 eV range reveals several fascinating physical phenomena such as a giant resonance induced by the dynamic rearrangement of the electron cloud after photon absorption, an anomalous branching ratio between intermediate Xe+ states separated by the spin-orbit interaction and multiple Auger decay processes. These phenomena have been studied in the past, using in particular synchrotron radiation, but without access to real-time dynamics. Here, we study the dynamics of Xe 4d photoionization on its natural time scale combining attosecond interferometry and coincidence spectroscopy. A time-frequency analysis of the involved transitions allows us to identify two interfering ionization mechanisms: the broad giant dipole resonance with a fast decay time less than 50 as, and a narrow resonance at threshold induced by spin-flip transitions, with much longer decay times of several hundred as. Our results provide insight into the complex electron-spin dynamics of photo-induced phenomena.
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