| 1. |
- Alagia, M, et al.
(författare)
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Angular effects in autoionization of 3 P doubly excited states in He
- 2009
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Ingår i: Journal of Physics: Conference Series. ; 194
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Tidskriftsartikel (refereegranskat)abstract
- The first members of dipole allowed 3 P o doubly excited series in helium have been observed in resonant photoexcitation of 1 s 2 s 3 S e metastable atoms. A good agreement measured relative photoionization cross sections is achieved when theory includes the radiation damping and, also important, the effects of spin-orbit multiplet splitting on electron angular distribution.
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| 2. |
- Alagia, M., et al.
(författare)
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Excitation of 1S and 3S Metastable Helium Atoms to Doubly Excited States
- 2009
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 102:15, s. 153001-
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Tidskriftsartikel (refereegranskat)abstract
- We present spectra of triplet and singlet metastable helium atoms resonantly photoexcited to doubly excited states. The first members of three dipole-allowed 1,3Po series have been observed and their relative photoionization cross sections determined, both in the triplet (from 1s2s 3Se) and singlet (from 1s2s 1Se) manifolds. The intensity ratios are drastically different with respect to transitions from the ground state. When radiation damping is included the results for the singlets are in agreement with theory, while for triplets spin-orbit interaction must also be taken into account.
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| 3. |
- Asmussen, J. D., et al.
(författare)
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Time-Resolved Ultrafast Interatomic Coulombic Decay in Superexcited Sodium-Doped Helium Nanodroplets
- 2022
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Ingår i: Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 13:20, s. 4470-4478
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Tidskriftsartikel (refereegranskat)abstract
- The autoionization dynamics of super excited superfluid He nanodropletsdoped with Na atoms is studied by extreme-ultraviolet (XUV) time-resolved electronspectroscopy. Following excitation into the higher-lying droplet absorption band, the dropletrelaxes into the lowest metastable atomic 1s2s1,3Sstates from which interatomic Coulombicdecay (ICD) takes place either between two excited He atoms or between an excited He atomand a Na atom attached to the droplet surface. Four main ICD channels are identified, andtheir decay times are determined by varying the delay between the XUV pulse and a UV pulsethat ionizes the initial excited state and thereby quenches ICD. The decay times for thedifferent channels all fall in the range of similar to 1 ps, indicating that the ICD dynamics are mainlydetermined by the droplet environment. A periodic modulation of the transient ICD signals istentatively attributed to the oscillation of the bubble forming around the localized Heexcitation
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| 4. |
- Asmussen, J. D., et al.
(författare)
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Unravelling the full relaxation dynamics of superexcited helium nanodroplets
- 2021
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 23:28, s. 15138-15149
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Tidskriftsartikel (refereegranskat)abstract
- The relaxation dynamics of superexcited superfluid He nanodroplets is thoroughly investigated by means of extreme-ultraviolet (XUV) femtosecond electron and ion spectroscopy complemented by time-dependent density functional theory (TDDFT). Three main paths leading to the emission of electrons and ions are identified: droplet autoionization, pump-probe photoionization, and autoionization induced by re-excitation of droplets relaxing into levels below the droplet ionization threshold. The most abundant product ions are He-2(+), generated by droplet autoionization and by photoionization of droplet-bound excited He atoms. He+ appear with some pump-probe delay as a result of the ejection He atoms in their lowest excited states from the droplets. The state-resolved time-dependent photoelectron spectra reveal that intermediate excited states of the droplets are populated in the course of the relaxation, terminating in the lowest-lying metastable singlet and triplet He atomic states. The slightly faster relaxation of the triplet state compared to the singlet state is in agreement with the simulation showing faster formation of a bubble around a He atom in the triplet state.
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| 5. |
- Bolognesi, P., et al.
(författare)
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A study of the dynamical energy flow in uracil
- 2015
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 635
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Tidskriftsartikel (refereegranskat)abstract
- The time resolved photoionization of C 1s in uracil following excitation of the neutral molecule by 260 nm pulses has been studied at LCLS.
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| 6. |
- Braam, A. W., et al.
(författare)
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Depression, subthreshold depression and comorbid anxiety symptoms in older Europeans: Results from the EURODEP concerted action
- 2014
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Ingår i: Journal of Affective Disorders. - : Elsevier BV. - 0165-0327. ; 155, s. 266-272
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Tidskriftsartikel (refereegranskat)abstract
- Background: In the epidemiology of late life depression, few insights are available on the co-occurrence of subthreshold depression and comorbicl symptoms of anxiety. The current study aims to describe prevalence patterns of comorbid anxiety symptoms across different levels of depression in old age, and to describe the burden of depressive symptoms and functional disability across patterns of comorbidity. Methods: Respondents were older adults in the community, age 65-104 (N=14,200), from seven European countries, with in total nine study centres, collaborating in the EURODEP concerted action. Depression and anxiety were assessed using the Geriatric Mental State examination (GMS-AGECAT package), providing subthreshold level and case level diagnoses. Presence of anxiety symptoms was defined as at least three distinct symptoms of anxiety. Number of depressive symptoms was assessed with the EURO-D scale. Results: The prevalence of anxiety symptoms amounts to 32% for respondents without depression, 67% for those with subthreshold depression, and 87% for those with case level depression. The number of depressive symptoms is similar for those with subthreshold level depression with cornorbid anxiety, compared to case level depression without symptoms of anxiety. In turn, at case level, comorbid symptoms of anxiety are associated with higher levels of depressive symptoms and more functional disability. Limitations: GMS-AGECAT is insufficiently cciuipped with diagnostic procedures to identify specific types of anxiety disorders. conclusions: Anxiety symptoms in late life depression are highly prevalent, and are likely to contribute to the burden of symptoms of the depression, even at subthreshold level. (C) 2013 Elsevier By. All rights reserved.
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| 7. |
- Coreno, M, et al.
(författare)
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A new system for photon induced fluorescence spectroscopy applied to the study of doubly excited states of helium
- 2005
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048. ; 144-147, s. 39-42
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Tidskriftsartikel (refereegranskat)abstract
- A new system for photon induced fluorescence spectroscopy (PIFS) at the gas phase photoemission beamline (Elettra, Trieste) is described. It consists of a novel non-dispersive detector for VUV photons and a spectrometer for UV/visible light with cooled CCD detector. To illustrate the performance of the apparatus, the fluorescence decay of the doubly excited states of helium below the N = 2 ionization threshold has been studied. Fluorescence emission from both singlet and triplet states has been observed, and in particular weak visible emission resulting from decay of 7(3D) and 8(3D) triplet states confirmed the recently published assignment of these states. This illustrates how PIFS can be used to provide a direct and unambiguous verification of the assignments of states observed in photoabsorption.
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| 8. |
- Fang, L., et al.
(författare)
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Multiple Ionization and Double Core-hole Production in Molecules using the LCLS X-ray FEL
- 2012
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 388:3, s. 032028-
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Tidskriftsartikel (refereegranskat)abstract
- We used the world's first hard x-ray FEL to investigate the response of molecular systems to the ultra-intense, femtosecond x-ray radiation. We report sequential multiphoton ionization, frustrated absorption and double core hole production mechanisms.
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| 9. |
- Finetti, P., et al.
(författare)
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Optical setup for two-colour experiments at the low density matter beamline of FERMI
- 2017
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Ingår i: Journal of optics. - : IOP Publishing. - 0150-536X .- 2040-8978 .- 2040-8986. ; 19:11
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Tidskriftsartikel (refereegranskat)abstract
- The low density matter beamline of the free electron laser facility FERMI is dedicated to the study of atomic, molecular and cluster systems, and here we describe the optical setup available for two-colour experiments. Samples can be exposed to ultrashort pulses from a Ti:Sapphire source (fundamental, or second or third harmonic), and ultrashort light pulses of FERMI in the EUV/soft x-ray region with a well-defined temporal delay, and negligible jitter (<10 fs) compared to the pulse durations (40–100 fs). Detection schemes available include electron, ion and optical spectroscopy. The majority of experiments using this apparatus are pump-and-probe, where either wavelength can be pump or probe, but the system is also useful for other techniques, such as multi-photon spectroscopy, cross-correlation measurements and alignment of molecules in space.
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| 10. |
- Finetti, P., et al.
(författare)
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Pulse duration of seeded free electron lasers
- 2017
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Ingår i: Physical Review X. - 2160-3308. ; 7:2
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Tidskriftsartikel (refereegranskat)abstract
- The pulse duration, and, more generally, the temporal intensity profile of free-electron laser (FEL) pulses, is of utmost importance for exploring the new perspectives offered by FELs; it is a nontrivial experimental parameter that needs to be characterized. We measured the pulse shape of an extreme ultraviolet externally seeded FEL operating in high-gain harmonic generation mode. Two different methods based on the cross-correlation of the FEL pulses with an external optical laser were used. The two methods, one capable of single-shot performance, may both be implemented as online diagnostics in FEL facilities. The measurements were carried out at the seeded FEL facility FERMI. The FEL temporal pulse characteristics were measured and studied in a range of FEL wavelengths and machine settings, and they were compared to the predictions of a theoretical model. The measurements allowed a direct observation of the pulse lengthening and splitting at saturation, in agreement with the proposed theory.
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