We have measured fully differential cross sections (FDCSs) for ionization of helium by 75 keV proton impact. Data were analyzed for electrons ejected into the scattering plane at projectile energy losses well below and above the matching velocity and for scattering angles ranging between 0.1 and 0.5 mrad. Earlier, we observed clear signatures of the postcollision interaction (PCI) at the matching velocity; however, in the current data these signatures are completely absent at small energy losses and residues remain at large energy losses. At small energy losses the FDCSs are dominated by non-PCI higher-order effects.

We have measured and calculated fully differential cross sections (FDCS) for dissociative capture in 75-keV p + H2 collisions. FDCS were analyzed in the kinetic energy release (KER) ranges 0 to 2.1 eV and 4 to 7 eV for two different molecular orientations. In the latter range, dissociation is dominated by electronic excitation to the 2p pi u state. Here, we observed two-center interference for an orientation in the plane perpendicular to the initial beam axis and parallel to the transverse momentum transfer. The interference pattern is afflicted with a constant phase shift of pi. In the range KER = 0 to 2.1 eV, dissociation is dominated by vibrational excitation. Here, we observed structures in the KER dependence, which we interpret as interference between two different paths of the molecular fragments during the dissociation.

Is there a saddle-point mechanism for ionization in intermediate-energy ion-atom collisions? Since Olson [Phys. Rev. A 33, 4397 (1986)] proposed the idea that the electrons stranded in the potential saddle between the two Coulomb centers dominate the ejected-electron spectra, multiple experimental and theoretical attempts have been made to answer this question. However, the topic has remained controversial. Here we provide a theoretical analysis of this question which can contribute significantly to a definitive answer, at least for intermediate and large projectile energies. To this end we calculate the energy and angular distribution of electrons emitted in proton-helium collisions. We use the two-center four-body wave-packet convergent close-coupling method based on the correlated two-electron structure for the helium target. The doubly differential cross sections obtained at 52 and 103 keV show no sign of a hump near one-half the relative velocity of the collision, which is expected according to the saddle-point ionization theory. At the same time, the results are in excellent agreement with measurements by Meckbach et al. [J. Phys. B 24, 3763 (1991)]. Two mechanisms for the production of electrons are clearly identified: direct ionization (direct knockout) and electron capture to the continuum (ECC) of the projectile. The electron speed (equivalently, energy) where direct ionization peaks is found to be practically independent of the ejection angle. However, the ECC peak is shown to shift towards one-half the relative velocity with increasing electron angle. It is concluded that the signatures of the suggested saddle-point mechanism may actually be due to a shift of the well-known ECC peak when electrons are emitted into angles away from the forward direction. Thus, the answer to the question is in the negative.

We have measured multiple differential cross sections for dissociative capture in collisions of 75-keV protons with D-2. Data were analyzed for kinetic energy releases (KERs) ranging from 0 to 2 eV, where the dissociation is primarily caused by excitation of the nuclear motion to a vibrational continuum state. Pronounced signatures of two-center interference effects were observed. The data were compared to previously published cross sections for dissociative capture in p + H-2 collisions, for which we reported a scattering angle dependent phase shift in the interference term. The D-2 data reveal qualitative differences in the interference structure to the H-2 case. Some aspects of the present results appear to support a hypothetical explanation which we offered earlier for the H-2 data, but other aspects are not fully understood yet.

We use the two-center wave-packet convergent close-coupling approach to ion-atom collisions to calculate the energy and angular distribution of electrons emitted in proton collisions with atomic hydrogen. Results are provided across a wide range of intermediate energies where many competing reaction channels make calculations challenging. The present data consistently agree with the available experimental measurements and improve upon previously available results based on perturbative and classical methods. Furthermore, we extend the range of electron angles and energies over which theoretical data are available for the doubly differential cross section for ionization. This provides strong evidence that at the level of doubly differential cross sections nonperturbative high-order methods are required to accurately model the ionization process.

Our presentation explores design strategies for high-flux High-Harmonic Generation (HHG) sources, using advanced nonlinear technologies like optical-parametric chirped-pulse amplifiers and multi-pass cells with Yb-doped lasers. Demonstrating immense power scalability and optimal HHG driver parameters, we present systems efficient at various wavelengths, promising significant applications in fields like material science and semiconductor metrology.

We present an experimental study of the dissociative excitation in the collision of helium ions with nitrogen and oxygen molecules for collision energy of 0.7−10.0 keV. Absolute emission cross sections are measured and reported for the most pronounced nitrogen and oxygen atomic and ionic lines in vacuum ultraviolet (80−130nm) and visible (380−670nm) spectral regions. Remarkable similarities of the processes realized in He++N2 and He++O2 collision systems are observed. We present polarization measurements for He++N2 collision system.The emission of excited dissociative products was detected using an improved high-resolution optical spectroscopy method. This method incorporates the retarding potential method and a high resolution electrostatic energy analyzer to precisely measure the energy of incident particles and the energy of dispersion. The improvement in the optical sensitivity allows us to measure the cross section on the order of 10−19 cm2 or lower.

The wave-packet convergent close-coupling (WP-CCC) approach is applied to calculate the energy spectrum of electrons ejected in p + H2 collisions as a function of the scattering angle of the projectile. The calculations are performed for projectile energies of 75, 100, and 200 keV. At these incident energies there are many competing reaction channels that play an essential role in the collision dynamics. The target is modeled as an orientationally averaged effective one-electron system. The results are compared with available perturbative calculations and experimental data. Good agreement between the WP-CCC results and experimental data is found for small emission energies, especially when the projectile is scattered at small angles. However, when the electron is emitted with a speed comparable to or greater than the projectile speed we find that our method predicts smaller cross sections near zero scattering angles and a slower fall off than the experimental data. This is in agreement with other calculations. Furthermore, the structure observed in the experimental data at large scattering angles is not supported by our results. Interestingly, we find very good agreement with the continuum-distorted-wave eikonal-initial-state molecular-orbital calculations that use a two-effective center approximation, though our method describes the target as an effective one-electron spherically symmetric system. This suggests that in these models two-center interference effects may have a small effect on this particular cross section. Furthermore, we find that the experimentally observed decrease in average scattering angle in proton collisions with H2 near the electron-projectile matching speed is not reproduced by our results. We also present the doubly differential cross section for ionization as a function of the scattering angle of the projectile at select emission angles.

We have measured and calculated fully differential cross sections for vibrational dissociation following capture in 75-keV p + H-2 collisions. For a molecular orientation perpendicular to the projectile beam axis and parallel to the transverse momentum transfer we observe a pronounced interference structure. The positions of the interference extrema suggest that the interference term is afflicted with a phase shift which depends on the projectile scattering angle. However, no significant dependence on the kinetic-energy release was observed. Considerable discrepancies between our calculations and experimental data were found.

We report the design for a high-power optical parametric chirped-pulse amplifier (OPCPA) at 3200 nm central wavelength for the MIR-HE laser at ELI-ALPS, aiming to provide 20 mJ pulse energy and sub-2.5 cycles pulse length.

We study the electron-impact induced ionization of O$_{2}$ from threshold to 120 eV using the electron spectroscopy method. Our approach is simple in concept and embodies the ion source with a collision chamber and a mass spectrometer with a quadruple filter as a selector for the product ions. The combination of these two devices makes it possible to unequivocally collect all energetic fragment ions formed in ionization and dissociative processes and to detect them with known efficiency. The ion source allows to vary and tune the electron-impact ionization energy and the target-gas pressure. We demonstrate that for obtaining reliable results of cross sections for inelastic processes and determining mechanisms for the formation of O$^{+}$($^{4}S,^2{D},^2{P}$) ions, it is crucial to control the electron-impact energy for production of ion and the pressure in the ion source. A comparison of our results with other experimental and theoretical data shows good agreement and proves the validity of our approach.

Recent studies of projectile coherence effects in ion-atom collisions are presented. For intermediate-energy proton collisions an extensive literature provides strong support for the importance of such effects. In this regime coherence effects are now used as a tool to study the few-body dynamics very sensitively. In contrast, for high-energy ion impact the literature is much sparser and here an important role of coherence effects cannot be regarded as being established. In this context, a recent claim that in COLTRIMS experiments the coherence properties are determined only by the target beam is rebutted.

Fully differential cross sections (FDCS) for ionization in p + H-2 collisions in the region of the electron-projectile velocity matching were measured and calculated. The FDCS were found to be very sensitive to the details of the few-body dynamics underlying the reaction.

A review of current high power (100 W-level), femtosecond, optical parametric chirped-pulse amplifiers (OPCPA) at near IR (NIR) and short-wave IR (SWIR) wavelengths pumped by Yb-based solid-state lasers is presented. OPCPA technology together with white-light-generation (WLG) makes it possible to provide CEP-stable femtosecond broadband or tunable pulses (from 700nm to 2.1 μm), which are potentially scalable to much high power levels. An important feature of these new OPCPAs is their reliability and compact design, requiring no complex cooling systems.

We have measured fully momentum-analyzed recoiling target ions and scattered projectiles, produced in ionization of He and H-2 by 75 keV proton impact, in coincidence. The momentum of the ejected electrons was deduced from momentum conservation. From the data we extracted fully differential ionization cross sections as a function of the polar electron emission angle (for fixed electron energies) and as a function of the electron energy (for fixed electron emission angles). Comparison between experiment and various distorted wave calculations confirms that under kinematic conditions where the post-collision interaction plays an important role, the few-body dynamics underlying the ionization process are still poorly understood.

We have measured characteristic K x rays in coincidence with the scattered particles from collisions of hydrogenlike Ge ions with Kr atoms. The ions were first accelerated to 8.6 MeV/amu, post-stripped to H-like charge state, and decelerated to around 2.5 MeV/amu. From the measurements the probabilities for K-shell to K-shell charge transfer as a function of collision impact parameters were obtained. The probabilities show an onset of oscillations which are interpreted as quantum interference between the K-shell to K-shell electron transfer amplitudes in two spatially separated coupling regions in the incoming and outgoing parts of the collision. The probabilities of K-shell vacancy distribution created by the collision are calculated within a relativistic independent electron model using the coupled-channel approach with atomlike Dirac-Fock-Sturm orbitals. A reasonable agreement between the theoretical results and the experimental data is found.

Double differential cross sections (DDCS) for ionization in p + Ne, Ar collisions were measured and calculated for a broad range of projectile energy losses as a function of scattering angle. PCI effects in the DDCS were found to be become increasingly prominent with increasing ionization potential I probably due to a greater importance of the nucleus-nucleus interaction when I becomes larger.

Fully differential cross sections (FDCS) for ionization in p + He collisions were measured and calculated for several projectile energy losses. The electron angular dependence of the FDCS reveals structures not seen in previous studies.

High power and high repetition rate femtosecond lasers are crucial tools furthering the scientific development across many fields. So far, these systems have been realized by Ti:Sapphire lasers at 800 nm, being limited in power scaling. A novel optical parametric chirped-pulse amplifier (OPCPA), pumped by high-power Yb-doped solid state lasers, and combined with bulk crystal white-light-generation seeding (WLG) allows to circumvent the limitation in average power. The presented laser system features carrier-envelope phase (CEP) stable sub 20 fs pulses centered at 800 nm with millijoule pulse energies and average power of 20 W while remaining on a compact footprint. Such systems have recently become commercially available from Class 5 Photonics and allow for scalability beyond millijoule pulse energies at up to 100 W average power.

Measurements of emission cross sections for the [Formula: see text] collision system with the incident beam of 1–10 keV [Formula: see text] in the ground [Formula: see text]) and metastable [Formula: see text] and [Formula: see text] states are reported. The emission cross section induced by incident ions in the metastable state [Formula: see text] is much larger than that for the ground [Formula: see text] state. The emission cross section of [Formula: see text] ion for [Formula: see text], [Formula: see text], and [Formula: see text] bands system is measured and the ratio of intensities for these bands is established as [Formula: see text] It is shown that the cross sections for the [Formula: see text] ions emissions in the dissociative charge exchange processes increase with the increase of the incident ion energy. The energy dependence of the emission cross section of the band [Formula: see text] [Formula: see text] nm of the first-negative band system of the [Formula: see text] and degree of linear polarization of emission in [Formula: see text] collision are measured for the first time. An influence of an admixture of the ion metastable state on a degree of linear polarization is revealed. The mechanism of the processes realized during collisions of ground and metastable oxygen ions on molecular nitrogen have been established. It is demonstrated that for [Formula: see text] collision system the degree of linear polarization by metastable [Formula: see text] ions is less compared to those that are in the ground [Formula: see text] state and the sign of emission of degree of linear polarization of excited molecular ions does not change.