| 1. |
- Dahlström, Jan Marcus, et al.
(författare)
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Attosecond transient absorption of a bound wave packet coupled to a smooth continuum
- 2017
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Ingår i: Journal of Optics. - : IOP Publishing. - 2040-8978 .- 2040-8986. ; 19:11
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the possibility of using transient absorption of a coherent bound electron wave packet in hydrogen as an attosecond pulse characterization technique. In a recent work, we have shown that photoionization of such a coherent bound electron wave packet opens up for pulse characterization with unprecedented temporal accuracy-independent of the atomic structure-with maximal photoemission at all kinetic energies given a wave packet with zero relative phase (Pabst and Dahlstrom Phys. Rev. A 94 13411 (2016)). Here, we perform numerical propagation of the time-dependent Schrodinger equation and analytical calculations based on perturbation theory to show that the energy-resolved maximal absorption of photons from the attosecond pulse does not uniquely occur at a zero relative phase of the initial wave packet. Instead, maximal absorption occurs at different relative wave packet phases, distributed as a non-monotonous function with a smooth -pi/2 shift across the central photon energy (given a Fourier-limited Gaussian pulse). Similar results are also found in helium. Our finding is surprising, because it implies that the energy-resolved photoelectrons are not mapped one-to-one with the energy-resolved absorbed photons of the attosecond pulse.
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| 2. |
- Dahlström, Jan Marcus, et al.
(författare)
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Pulse analysis by delayed absorption from a coherently excited atom
- 2019
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Ingår i: Apl Photonics. - : AIP Publishing. - 2378-0967. ; 4:1
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Tidskriftsartikel (refereegranskat)abstract
- In this tutorial, we provide a short review of attosecond pulse characterization techniques and a pedagogical account of a recently proposed method called Pulse Analysis by Delayed Absorption (PANDA) [S. Pabst and J. M. Dahlstrom, Phys. Rev. A 94, 013411 (2016)]. We discuss possible implementations of PANDA in alkali atoms using either principal quantum number wave packets or spin-orbit wave packets. The main merit of the PANDA method is that it can be used as a pulse characterization method that is free from atomic latency effects, such as scattering phase shifts and long-lived atomic resonances. Finally, we propose that combining the PANDA method with angle-resolved photoelectron detection should allow for experimental measurements of attosecond delays in photoionization from bound wave packets on the order of tens of attoseconds.
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| 3. |
- Kaiser, Stefan, 1968, et al.
(författare)
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White Paper: Broadband Multi-Carrier Based Air Interface (version 1.4)
- 2002
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Ingår i: Proceedings 7th Wireless World Research Forum Workshop, Eindhoven, the Netherlands.
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Konferensbidrag (refereegranskat)abstract
- The future success of the mobile communications revolution strongly depends on increasing the data rate and quality of service (QoS) available to the mobile user. This will enable value added services, which are not possible with current state of the art mobile wireless radio systems. While an increase in data rate, and maybe to some extent also QoS, could be achieved by combining techniques in the form of multi mode terminals (e.g. UMTS and wireless LAN), this has the disadvantage that for each new scenario another mode has to be added. The combination may also not be suitable for the mobility requirements of wireless radio systems. This paper proposes using a broadband multi-carrier based air interface. It also includes a discussion of the enabling technologies for multi-carrier mobile systems and the technology trends for future research. The multi-carrier technology offers the desired high data rates for the 4G mobile environments and also has advantages for spectral efficiency and low-cost implementation.
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| 4. |
- Pabst, Stefan, et al.
(författare)
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Characterizing attosecond pulses in the soft x-ray regime
- 2017
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 50:10
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Tidskriftsartikel (refereegranskat)abstract
- Attosecond x-ray pulses offer unprecedented opportunities for probing and triggering new types of ultrafast motion. At the same time, pulse characterization of x-rays presents new challenges that do not exist in the UV regime. Inner-shell ionization is the dominant ionization mechanism for x-rays and it is followed by secondary processes like fluorescence, Auger decay, and shake-up. In general, we find that inner-shell ionization and secondary processes can create additional delay-dependent modulations that will affect pulse reconstruction schemes. Our recently proposed pulse characterization method (Pabst and Dahlstrom 2016 Phys. Rev. A 94 013411), where a bound electron wavepacket is sequentially photoionized by the attosecond pulse, can be adapted to mitigate the impact of these effects, thus opening up an avenue for reliable pulse reconstruction in the x-ray regime.
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| 5. |
- Pabst, Stefan, et al.
(författare)
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Eliminating the dipole phase in attosecond pulse characterization using Rydberg wave packets
- 2016
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Ingår i: Physical Review A. - 2469-9926. ; 94:1
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Tidskriftsartikel (refereegranskat)abstract
- We propose a technique to fully characterize the temporal structure of extreme ultraviolet pulses by ionizing a bound coherent electronic wave packet. The influence of the dipole phase, which is the main obstacle for state-of-the-art pulse characterization schemes, can be eliminated by angle integration of the photoelectron spectrum. We show that in particular, atomic Rydberg wave packets are ideal and that wave packets involving multiple electronic states provide redundant information that can be used to cross-check the consistency of the phase reconstruction.
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