2016, Bruner, Barry D., Mašín, Zdeněk, Negro, Matteo, Morales, Felipe, Brambila, Danilo, Devetta, Michele, Faccialà, Davide, Harvey, Alex G., Ivanov, Misha, Mairesse, Yann, Patchkovskii, Serguei, Serbinenko, Valeria, Soifer, Hadas, Stagira, Salvatore, Vozzi, Caterina, Dudovich, Nirit, Smirnova, Olga

High harmonic generation (HHG) spectroscopy has opened up a new frontier in ultrafast science, where electronic dynamics can be measured on an attosecond time scale. The strong laser field that triggers the high harmonic response also opens multiple quantum pathways for multielectron dynamics in molecules, resulting in a complex process of multielectron rearrangement during ionization. Using combined experimental and theoretical approaches, we show how multi-dimensional HHG spectroscopy can be used to detect and follow electronic dynamics of core rearrangement on sub-laser cycle time scales. We detect the signatures of laser-driven hole dynamics upon ionization and reconstruct the relative phases and amplitudes for relevant ionization channels in a CO2 molecule on a sub-cycle time scale. Reconstruction of channel-resolved complex ionization amplitudes on attosecond time scales has been a long-standing goal of high harmonic spectroscopy. Our study brings us one step closer to fulfilling this initial promise and developing robust schemes for sub-femtosecond imaging of multielectron rearrangement in complex molecular systems.

2019, Chau, J.L., Urco, J.M., Vierinen, J.P., Volz, R.A., Clahsen, M., Pfeffer, N., Trautner, J.

Typical specular meteor radars (SMRs) use one transmitting antenna and at least a five-antenna interferometric configuration on reception to study the mesosphere and lower thermosphere (MLT) region. The interferometric configuration allows the measurement of the angle-of-arrival (AOA) of the detected meteor echoes, which in turn is needed to derive atmospheric parameters (e.g., mean winds, momentum fluxes, temperatures, and neutral densities). Recently, we have shown that coherent MIMO configurations in atmospheric radars, i.e., multiple input (transmitters) and multiple output (receivers), with proper diversity in transmission can be used to enhance interferometric atmospheric and ionospheric observations. In this study we present novel SMR systems using multiple transmitters in interferometric configuration, each of them employing orthogonal pseudorandom coded transmitted sequences. After proper decoding, the angle of departure (AOD) of the detected meteor echoes with respect to the transmitter site are obtained at each receiving antenna. We present successful bistatic implementations of (1) five transmitters and one receiver using coded continuous wave (CW) (MISO-CW), and (2) five transmitters and five receivers using coded CW (MIMO-CW). The latter system allows simultaneous independent observations of the specular meteor trails with respect to the transmitter (AOD) and with respect to the receiver (AOA). The quality of the obtained results is evaluated in terms of the resulting mean winds, the number of detections and the daily diffusion trail vs. altitude behavior. We show that the proposed configurations are good alternatives to explore the MLT region. When combined with multi-static approaches, they can increase the number of meteor detections, thereby improving the quality of atmospheric estimates and allowing the measurement of new atmospheric parameters (e.g., horizontal divergence, vorticity), The use of multiple collocated transmitters for interferometric AOD determination makes building a multi-static radar network easier logistically, as only one receiver per receiving site antenna is sufficient. © 2019. This work is distributed under the Creative Commons Attribution 4.0 License.

2018, Cirelli, Claudio, Marante, Carlos, Heuser, Sebastian, Petersson, C.L.M., Galán, Álvaro Jiménez, Argenti, Luca, Zhong, Shiyang, Busto, David, Isinger, Marcus, Nandi, Saikat, Maclot, Sylvain, Rading, Linnea, Johnsson, Per, Gisselbrecht, Mathieu, Lucchini, Matteo, Gallmann, Lukas, Dahlström, J. Marcus, Lindroth, Eva, L’Huillier, Anne, Martín, Fernando, Keller, Ursula

Electron correlation and multielectron effects are fundamental interactions that govern many physical and chemical processes in atomic, molecular and solid state systems. The process of autoionization, induced by resonant excitation of electrons into discrete states present in the spectral continuum of atomic and molecular targets, is mediated by electron correlation. Here we investigate the attosecond photoemission dynamics in argon in the 20-40 eV spectral range, in the vicinity of the 3s -1 np autoionizing resonances. We present measurements of the differential photoionization cross section and extract energy and angle-dependent atomic time delays with an attosecond interferometric method. With the support of a theoretical model, we are able to attribute a large part of the measured time delay anisotropy to the presence of autoionizing resonances, which not only distort the phase of the emitted photoelectron wave packet but also introduce an angular dependence.

2021, Lachmann, Maike D., Ahlers, Holger, Becker, Dennis, Dinkelaker, Aline N., Grosse, Jens, Hellmig, Ortwin, Müntinga, Hauke, Schkolnik, Vladimir, Seidel, Stephan T., Wendrich, Thijs, Wenzlawski, André, Carrick, Benjamin, Gaaloul, Naceur, Lüdtke, Daniel, Braxmaier, Claus, Ertmer, Wolfgang, Krutzik, Markus, Lämmerzahl, Claus, Peters, Achim, Schleich, Wolfgang P., Sengstock, Klaus, Wicht, Andreas, Windpassinger, Patrick, Rasel, Ernst M.

Bose-Einstein condensates (BECs) in free fall constitute a promising source for space-borne interferometry. Indeed, BECs enjoy a slowly expanding wave function, display a large spatial coherence and can be engineered and probed by optical techniques. Here we explore matter-wave fringes of multiple spinor components of a BEC released in free fall employing light-pulses to drive Bragg processes and induce phase imprinting on a sounding rocket. The prevailing microgravity played a crucial role in the observation of these interferences which not only reveal the spatial coherence of the condensates but also allow us to measure differential forces. Our work marks the beginning of matter-wave interferometry in space with future applications in fundamental physics, navigation and earth observation.