2020, Gazibegović-Busuladžić, A., Busuladžić, M., Čerkić, A., Hasović, E., Becker, W., Milošević, D.B.

We investigate strong-field ionization of linear molecules by a two-color laser field of frequencies rω and sω having coplanar counterrotating or corotating elliptically polarized components (ω is the fundamental laser field frequency and r and s are integers). Using the improved molecular strong-field approximation we analyze direct above-threshold ionization (ATI) and high-order ATI (HATI) spectra. More precisely, reflection and rotational symmetries of these spectra for linear molecules aligned in the laser-field polarization plane are considered. The reflection symmetries for particular molecular orientations, known to be valid for a bicircular field (this is the field with circularly polarized counterrotating components), are valid also for arbitrary component ellipticities. However, specific rotational symmetries that are satisfied for HATI by a bicircular field, are violated for an arbitrary elliptically polarized field with counterrotating components. For the corotating case and the N2 molecule we analyze molecular-orientation-dependent interferences and plateau structures for various ellipticities.

2015, Hasović, Elvedin, Milošević, Dejan B., Gazibegović-Busuladži, Azra, Čerkić, Aner, Busuladžić, Mustafa

We consider high-order above-threshold ionization (HATI) of polyatomic molecules ionized by a strong linearly polarized laser field. Improved molecular strong-field approximation by which the HATI process on polyatomic molecular species can be described is developed. Using this theory we calculate photoelectron angular-energy spectra for different triatomic molecules. Special attention is devoted to the minima that are observed in the calculated high-energy electron spectra of the ozone and carbon dioxide molecules. A key difference between these minima and minima that are observed in the corresponding spectra of diatomic molecules are presented.

2015, Mašín, Zdeněk, Harvey, Alex, Houfek, Karel, Brambila, Danilo S., Morales, Felipe, Gorfinkiel, Jimena D., Tennyson, Jonathan, Smirnova, Olga

We report on recent developments of the UKRmol suite, an implementation of the molecular R- matrix method and present examples of the calculations (e.g. electron scattering, photoionization, high harmonic generation, etc.) it has enabled.

2020, Schmidt, P., Music, V., Hartmann, G., Boll, R., Erk, B., Bari, S., Allum, F., Baumann, T.M., Brenner, G., Brouard, M., Burt, M., Coffee, R., Dörner, S., Galler, A., Grychtol, P., Heathcote, D., Inhester, L., Kazemi, M., Larsson, M., Li, Z., Lutmann, A., Manschwetus, B., Marder, L., Mason, R., Moeller, S., Osipov, T., Otto, H., Passow, C., Rolles, D., Rupprecht, P., Schubert, K., Schwob, L., Thomas, R., Vallance, C., Von Korff Schmising, C., Wagner, R., Walter, P., Wolf, T.J.A., Zhaunerchyk, V., Meyer, M., Ehresmann, A., Knie, A., Demekhin, P.V., Ilchen, M.

(X-ray) free-electron lasers are employed to site specifically interrogate atomic fragments during ultra-fast photolysis of chiral molecules via time-resolved photoelectron circular dichroism. © 2020 Institute of Physics Publishing. All rights reserved.

2016, Pisanty, Emilio, Ivanov, Misha

We propose and discuss a kinematic mechanism underlying the recently discovered 'near-zero energy structure' in the photoionization of atoms in strong mid-infrared laser fields, based on trajectories which revisit the ion at low velocities exactly analogous to the series responsible for low-energy structures. The different scaling of the new series, as $E\sim {I}_{p}^{2}/{U}_{p}$, suggests that the near-zero energy structure can be lifted to higher energies, where it can be better resolved and studied, using harder targets with higher ionization potential.

2015, Barillot, T., Magrakvelidze, M., Loriot, V., Bordas, C., Hervieux, P.-A., Gisselbrecht, M., Johnsson, P., Laksman, J., Mansson, E.P., Sorensen, S., Canton, S.E., Dahlström, J.M., Dixit, G., Madjet, M.E., Lépine, F., Chakraborty, H.S.

We perform time-dependent local density functional calculations of the time delay in C60 HOMO and HOMO-1 photoionization at giant plasmon energies. A semiclassical model is used to develop further insights.

2015, Brambila, Danilo S., Harvey, Alex G., Mašín, Zdeněk, Smirnova, Olga

We present R-matrix calculations of photoionization from NO2, resolved in energy, angle, and both neutral and ionic state, for a range of molecular geometries, including in the vicinity of the 2A1/2B2 conical intersection.

2018, Gross, M., Lishilin, O., Loisch, G., Boonpornprasert, P., Chen, Y., Engel, J., Good, J., Huck, H., Isaev, I., Krasilnikov, M., Li, X., Niemczyk, R., Oppelt, A., Qian, H., Renier, Y., Stephan, F., Zhao, Q., Brinkmann, R., Martinez de la Ossa, A., Osterhoff, J., Grüner, F.J., Mehrling, T., Schroeder, C.B., Will, I.

The self-modulation instability is fundamental for the plasma wakefield acceleration experiment of the AWAKE (Advanced Wakefield Experiment) collaboration at CERN where this effect is used to generate proton bunches for the resonant excitation of high acceleration fields. Utilizing the availability of flexible electron beam shaping together with excellent diagnostics including an RF deflector, a supporting experiment was set up at the electron accelerator PITZ (Photo Injector Test facility at DESY, Zeuthen site), given that the underlying physics is the same. After demonstrating the effect [1] the next goal is to investigate in detail the self-modulation of long (with respect to the plasma wavelength) electron beams. In this contribution we describe parameter studies on self-modulation of a long electron bunch in an argon plasma. The plasma was generated with a discharge cell with densities in the 1013 cm-3 to 1015 cm-3 range. The plasma density was deduced from the plasma wavelength as indicated by the self-modulation period. Parameter scans were conducted with variable plasma density and electron bunch focusing.

2020, Poyyathuruthy Bruno, Binal, Schütze, Robert, Grunwald, Ruediger, Wallrabe, Ulrike

We present the design and fabrication of a miniaturized array of piezoelectrically actuated high speed Fresnel mirrors with individual mirror control. These Fresnel mirrors can be used to generate propagation invariant and self-healing interference patterns. The mirrors are actuated using piezobimorph actuators, and the consequent change of the tilting angle of the mirrors changes the fringe spacing of the interference pattern generated. The array consists of four Fresnel mirrors each having an area of 2 × 2 mm2 arranged in a 2x2 configuration. The device, optimized using FEM simulations, is able to achieve maximum mirror deflections of 15 mrad, and has a resonance frequency of 28 kHz.

2015, Schütte, Bernd, Arbeiter, Mathias, Fennel, Thomas, Jabbari, Ghazal, Gokhberg, Kirill, Kuleff, Alexander I., Vrakking, Marc J. J., Rouzée, Arnaud

We report on the observation of a novel intracluster Coulombic decay process following Rydberg atom formation in clusters ionized by intense near-infrared fields. A new decay channel emerges, in which a Rydberg atom relaxes to the ground state by transferring its excess energy to a weakly bound electron in the environment that is emitted from the cluster. We find evidence for this process in the electron spectra, where a peak close to the corresponding atomic ionization potential is observed. For Ar clusters, a decay time of 87 ps is measured, which is significantly longer than in previous time-resolved studies of interatomic Coulombic decay.