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![Upper part: density plot of momentum of electron 1 versus momentum of electron 2 for the two different laser intensities for double ionization of Ar (see text) projected on the plane perpedicular to laser impact direction. Middle part: density plot of He 2+ recoil momentum for two different laser intensities. Lower part: projection of the recoil momentum distribution on the z-axis. Black line: doubly charged ions, red line: singly charged ions. [37d]](publication/353527546/figure/fig11/AS:1050717171224594@1627521903665/Upper-part-density-plot-of-momentum-of-electron-1-versus-momentum-of-electron-2-for-the.jpg)
Upper part: density plot of momentum of electron 1 versus momentum of electron 2 for the two different laser intensities for double ionization of Ar (see text) projected on the plane perpedicular to laser impact direction. Middle part: density plot of He 2+ recoil momentum for two different laser intensities. Lower part: projection of the recoil momentum distribution on the z-axis. Black line: doubly charged ions, red line: singly charged ions. [37d]
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![Figure 3. C-REMI spectrometer installed in ion storage rings. [1a,c,d,e]](publication/353527546/figure/fig1/AS:1050717167050752@1627521902602/C-REMI-spectrometer-installed-in-ion-storage-rings-1a-c-d-e_Q320.jpg)
![Figure 4. Upper part: scheme of supersonic gas jet formation. [11]...](publication/353527546/figure/fig2/AS:1050717167046668@1627521902877/Upper-part-scheme-of-supersonic-gas-jet-formation-11-Lower-part-comparison-of_Q320.jpg)
The COLTRIMS Reaction Microscope C‐REMI can image the momentum vectors of all emitted charged fragments in an atomic or molecular reactions similar to the bubble chamber in high energy particle physics. C‐REMI can detect fragments with “zero” kinetic energy in an ultrahigh vacuum environment by projecting them with weak electromagnetic fields onto...
Citations
... In the half-scattering process [38,45], the emission of a photoelectron alongside the formation of an ion (a parent molecular ion) from an atom (molecule) fulfills the momentum conservation: ...
Photoionization is one of the most fundamental processes in light–matter interaction. Advanced attosecond photoelectron spectroscopy provides the possibility to characterize the ultrafast photoemission process in an extremely short attosecond time scale. Following scattering symmetry rules, residual ions encode ultrafast photoionization prints at the instant of electron removal forming an alternative electron emission chronoscope. Here, we experimentally illustrate the attosecond ion reconstruction of attosecond beating by interference of two-photon transition (RABBIT)-like interferometry through the development of high-resolution ion momentum detection in atomic photoionization processes. Our ion interferometry presents identical momentum- and time-dependent scattering phase shift, as we observed in photoelectron spectroscopy, and thus demonstrates that ion interferometry can be a possible alternative attosecond approach to resolve the photoionization process, without the electron homogeneity limitation.
... The concept of molecular orbitals plays a key role for understanding electronic and chemical properties of materials [1,2]. This has evoked considerable interest for direct imaging of frontier molecular orbitals, i.e., experimentally revealing their distribution either in real or reciprocal (momentum, k) space [3,4]. Several years ago, the technique of photoemission orbital tomography (POT) was introduced and proved to be a powerful method to identify and even reconstruct orbitals of well-ordered molecular systems [5][6][7][8][9][10][11][12]. ...
... In particular, at 4000 [36] and 4080 keV [37], the measured cross sections differ by an enormous factor of about 20. This situation underscores the need for some new, more precise measurements on Q at higher energies, e.g. by COLTRIMS [24,38,45]. Reduced accuracy of the measured cross sections for DC compared to SC is partially caused by the weakness of the former process. ...
An analysis is presented using six quantum-mechanical four-body distorted wave (DW) theories for double capture (DC) in ion-atom collisions at intermediate and high energies. They all satisfy the correct boundary conditions in the entrance and exit channels. This implies the usage of short-range perturbation potentials in compliance with the exact behaviors of scattering wave functions at infinitely large separations of particles. Specifically, total cross sections Q are analyzed for collisions of alpha particles with helium targets. Regarding the relative quantitative performance of the studied DW theories at different impact energies E, our main focus is on the sensitivity of Q to various collisional mechanisms. The usual mechanism in most DW theories assumes that both electrons undergo the same type of collisions with nuclei. These are either single or double collisions in one or two steps, respectively, per channel, but without their mixture in either channel. The signatures of double collisions in differential cross sections are the Thomas peaks. By definition, these cannot be produced by single collisions. There is another DC pathway, which is actually favored by the existing experimental data. It is a hybrid, two-center mechanism which, in each channel separately, combines a single collision for one electron with a double collision for the other electron. The ensuing DW theory is called the four-body single-double scattering (SDS-4B) method. It appears that this mechanism in the SDS-4B method is more probable than double collisions for each electron in both channels predicted by the four-body continuum distorted wave (CDW-4B) method. This is presently demonstrated for Q at energies E=[200,8000] keV in DC exemplified by alpha particles colliding with helium targets.
... Yttberbium technology, combined with optical parametric amplification, has led to the development of high-repetition rate optical parametric chirped-pulse amplifiers (OPCPA) [8,9] that achieve unprecedented peak power at high average power for tabletop systems. Major efforts have been made to reach the mid-infrared (MIR) spectral range [10][11][12][13], which is of great importance for experimental investigations in strong-field physics that are currently carried out at lower repetition rate, including time-and angle-resolved photoemission spectroscopy (TR-ARPES) [14][15][16][17], cold target recoil-ion momentum spectroscopy (COLTRIMS) [18,19], Coulomb explosion imaging (CEI) [20,21], and high harmonic generation (HHG) [22,23]. Nevertheless, characterizing such systems with ultrashort and broadband pulses at high repetition rate remains a challenging and intricate task. ...
We demonstrate experimentally that frequency resolved optical switching (FROSt) can be used to characterize ultra-broadband pulses at high repetition rates up to 500 kHz. Specifically, we present the complete temporal characterization of an optical parametric amplifier (OPA), from the supercontinuum (SC) to the second stage of amplification. Simultaneous characterization of co-propagating signal and idler pulses enables retrieval of their group delay, as well as their temporal phase and intensity. Our study focuses on an extensive frequency range spanning the infrared region (1.2 to 2.4 µm) and confirms the strength and convenience of FROSt as a single tool for characterizing a wide range of pulses at high repetition rates.
... The beamline is equipped with a Reaction Microscope (ReMi, or called COLd-Target Recoil-Ion Momentum Spectrometer -COLTRIMS), being an indispensable experimental instrumentation tool of today's atomic-, molecularand optical (AMO) physics [8]. The first experiments with this equipment have been carried out already, one of them aiming to probe molecular environment through photoemission delays similarly to the work of S. Biswas and co-workers [9]. ...
... In the last few decades, much detailed investigations of fragmentation of small hydrocarbons (e.g. C 2 H 2 , CH 4 ) [1][2][3][4] have been reported after the advent of multiparticle coincident detection techniques [5]. The acetylene molecule is one of the simplest hydrocarbon which has been widely studied due to its importance as a model system for exploring the phenomenon of hydrogen migration [6][7][8][9] and its role in molecular growth processes [10][11][12]. ...
The three body breakup of [C 2 H 2 ] ³⁺ formed in collision with Xe ⁹⁺ moving at 0.5 atomic units of velocity is studied using recoil ion momentum spectroscopy. Three body breakup channels leading to (H ⁺ , C ⁺ , CH ⁺ ) and (H ⁺ , H ⁺ , C 2 ⁺ ) fragments are observed in the experiment and their kinetic energy release is measured. The breakup into (H ⁺ , C ⁺ , CH ⁺ ) occurs via concerted as well as sequential mode while breakup into (H ⁺ , H ⁺ , C 2 ⁺ ) shows the concerted mode only. By collecting events coming exclusively from the sequential breakup leading to (H ⁺ , C ⁺ , CH ⁺ ), we have determined the kinetic energy release for the unimolecular fragmentation of the molecular intermediate, [C 2 H] ²⁺ . Using ab-initio calculations, the potential energy surface for the lowest electronic state of [C 2 H] ²⁺ is generated which shows the existence of a metastable state with two possible dissociation pathways. A discussion on the agreement between our experimental results and these ab-initio calculations is presented.
... The latter electrostatic OAM sorter 56 boasts high efficiency and was retrofitted as an OAM analyzing element to a transmission electron microscope. Thus, such an element could be conceivably added to a typical reaction microscope (ReMi) 84,85 employed for NSDI-a ReMi measures correlation of the ion and the two electrons, thus, it is already well-suited for studying entanglement 86 . Beyond the measurement of OAM, there will be some difficulty in using alkaline earth metals in experiment over the typical nobel gas targets. ...
Entanglement has a capacity to enhance imaging procedures, but this remains unexplored for attosecond imaging. Here, we elucidate that possibility, addressing orbital angular momentum (OAM) entanglement in ultrafast processes. In the correlated process non-sequential double ionization (NSDI) we demonstrate robust photoelectron entanglement. In contrast to commonly considered continuous variables, the discrete OAM allows for a simpler interpretation, computation, and measurement of entanglement. The logarithmic negativity reveals that the entanglement is robust to incoherence and an entanglement witness minimizes the number of measurements to detect the entanglement, both quantities are related to OAM coherence terms. We quantify the entanglement for a range of targets and field parameters to find the most entangled photoelectron pairs. This methodology provides a general way to use OAM to quantify and measure entanglement, well-suited to attosecond processes, and can be exploited to enhance imaging capabilities through correlated measurements, or for generation of OAM-entangled electrons.
... Most promising is the so-called OAM sorter [81,82], this has been proposed [83,84] and experimentally demonstrated [85] as an OAM analyzing element to an electron microscope. Thus, such an element could be conceivably added to a typical reaction microscope (ReMi) [86][87][88] employed for NSDI-a ReMi measures correlation of the ion and the two electrons, thus, it is already well-suited for studying entanglement [89]. To detect entanglement, the OAM sorter must be tuned to perform incompatible measurements on either electron independently. ...
We demonstrate entanglement between the orbital angular momentum (OAM) of two photoelectrons ionized via the strongly correlated process of non-sequential double ionization (NSDI). Due to the quantization of OAM, this entanglement is easily quantified and has a simple physical interpretation in terms of conservation laws. We explore detection by an entanglement witness, decomposable into local measurements, which strongly reduces the difficulty of experimental implementation. We compute the logarithmic negativity measure, which is directly applicable to mixed states, to demonstrate that the entanglement is robust to incoherent effects such as focal averaging. Using the strong-field approximation, we quantify the entanglement for a large range of targets and field parameters, isolating the best targets for experimentalists. The methodology presented here provides a general way to use OAM to quantify and, in principle, measure entanglement, that is well-suited to attosecond processes, can enhance our understanding and may be exploited in imaging processes or the generation of OAM-entangled electrons.
Studying the direct effects of DNA irradiation is essential for understanding the impact of radiation on biological systems. Gas‐phase interactions are especially well suited to uncover the molecular mechanisms underlying these direct effects. Only relatively recently, isolated DNA oligonucleotides were irradiated by ionizing particles such as VUV or X‐ray photons or ion beams, and ionic products were analyzed by mass spectrometry. This article provides a comprehensive review of primarily experimental investigations in this field over the past decade, emphasizing the description of processes such as ionization, fragmentation, charge and hydrogen transfer triggered by photoabsorption or ion collision, and the recent progress made thanks to specific atomic photoabsorption. Then, we outline ongoing experimental developments notably involving ion‐mobility spectrometry, crossed beams or time‐resolved measurements. The discussion extends to potential research directions for the future.
Coulomb explosion imaging (CEI) with x-ray free electron lasers has recently been shown to be a powerful method for obtaining detailed structural information of gas-phase planar ring molecules [R. Boll et al., X-ray multiphoton-induced Coulomb explosion images complex single molecules, Nat. Phys. 18, 423 (2022).]. In this Letter, we investigate the potential of CEI driven by a tabletop laser and extend this approach to differentiating three-dimensional structures. We study the static CEI patterns of planar and nonplanar organic molecules that resemble the structures of typical products formed in ring-opening reactions. Our results reveal that each molecule exhibits a well-localized and distinctive pattern in three-dimensional fragment-ion momentum space. We find that these patterns yield direct information about the molecular structures and can be qualitatively reproduced using a classical Coulomb explosion simulation. Our findings suggest that laser-induced CEI can serve as a robust method for differentiating molecular structures of organic ring and chain molecules. As such, it holds great promise as a method for following ultrafast structural changes, e.g., during ring-opening reactions, by tracking the motion of individual atoms in pump-probe experiments.
