The Low Density Matter (LDM) beamline at FERMI: Optical layout and first commissioning

The Low Density Matter (LDM) beamline has been built as part of the FERMI free-electron laser (FEL) facility to serve the atomic, molecular and cluster physics community. After the commissioning phase, it received the first external users at the end of 2012. The design and characterization of the LDM photon transport system is described, detailing the optical components of the beamline

The Impact of Crystal Light Yield Non-Proportionality on a Typical Calorimetric Space Experiment: Beam Test Measurements and Monte Carlo Simulations

Calorimetric space experiments were employed for the direct measurements of cosmic-ray spectra above the TeV region. According to several theoretical models and recent measurements, relevant features in both electron and nucleus fluxes are expected. Unfortunately, sizable disagreements among the current results of different space calorimeters exist. In order to improve the accuracy of future experiments, it is fundamental to understand the reasons of these discrepancies, especially since they are not compatible with the quoted experimental errors. A few articles of different collaborations suggest that a systematic error of a few percentage points related to the energy-scale calibration could explain these differences. In this work, we analyze the impact of the nonproportionality of the light yield of scintillating crystals on the energy scale of typical calorimeters. Space calorimeters are usually calibrated by employing minimal ionizing particles (MIPs), e.g., nonshowering proton or helium nuclei, which feature different ionization density distributions with respect to particles included in showers. By using the experimental data obtained by the CaloCube collaboration and a minimalist model of the light yield as a function of the ionization density, several scintillating crystals (BGO, CsI(Tl), LYSO, YAP, YAG and BaF2) are characterized. Then, the response of a few crystals is implemented inside the Monte Carlo simulation of a space calorimeter to check the energy deposited by electromagnetic and hadronic showers. The results of this work show that the energy scale obtained by MIP calibration could be affected by sizable systematic errors if the nonproportionality of scintillation light is not properly taken into account

Attosecond pulse shaping using a seeded free-electron laser

Attosecond pulses are central to the investigation of valence- and core-electron dynamics on their natural timescales1–3. The reproducible generation and characterization of attosecond waveforms has been demonstrated so far only through the process of high-order harmonic generation4–7. Several methods for shaping attosecond waveforms have been proposed, including the use of metallic filters8,9, multilayer mirrors10 and manipulation of the driving field11. However, none of these approaches allows the flexible manipulation of the temporal characteristics of the attosecond waveforms, and they suffer from the low conversion efficiency of the high-order harmonic generation process. Free-electron lasers, by contrast, deliver femtosecond, extreme-ultraviolet and X-ray pulses with energies ranging from tens of microjoules to a few millijoules12,13. Recent experiments have shown that they can generate subfemtosecond spikes, but with temporal characteristics that change shot-to-shot14–16. Here we report reproducible generation of high-energy (microjoule level) attosecond waveforms using a seeded free-electron laser17. We demonstrate amplitude and phase manipulation of the harmonic components of an attosecond pulse train in combination with an approach for its temporal reconstruction. The results presented here open the way to performing attosecond time-resolved experiments with free-electron lasers

Comparative Experimental and Theoretical Study of the C and O K-Edge X-ray Absorption Spectroscopy in Three Highly Popular, Low Spin Organoiron Complexes: [Fe(CO)5], [(\u3b75-C5H5)Fe(CO)(\u3bc-CO)]2, and [(\u3b75-C5H5)2Fe]

The unoccupied electronic structures of three closed-shell, highly popular organoiron complexes ([Fe(CO)5], [(\u3b75-C5H5)Fe(CO)(\u3bc-CO)]2, and [(\u3b75-C5H5)2Fe]; 0, I, and II, respectively) have been investigated both experimentally and theoretically by combining original gas-phase X-ray absorption spectroscopy (XAS) outcomes recorded at the C and O K-edge with results of scalar relativistic time-dependent density functional calculations carried out within the zeroth order regular approximation. Experimental evidence herein discussed complement the Fe L2,3-edges XAS ones we recently recorded, modeled, and assigned for the same complexes (Carlotto et al. Inorg. Chem. 2019, 58, 5844). The first-principle simulation of the C and O K-edge features allowed us to univocally identify the electronic states associated to the ligand-to-metal charge transfer (LMCT) transitions both in I and in II. At variance to that, LMCT transitions with sizable oscillator strengths do not play any role in determining neither the C nor the O K-edge spectral pattern of 0. The higher \u3c0-acceptor capability of the CO ligand, regardless of its terminal or bridging coordination, with respect to [(\u3b75-C5H5)]- is herein ultimately confirmed

Comparative Experimental and Theoretical Study of the Fe L 2,3 -Edges X-ray Absorption Spectroscopy in Three Highly Popular, Low-Spin Organoiron Complexes: [Fe(CO) 5 ], [(\u3b7 5 -C 5 H 5 )Fe(CO)(\u3bc-CO)] 2 , and [(\u3b7 5 -C 5 H 5 ) 2 Fe]

The occupied and unoccupied electronic structures of three highly popular, closed shell organoiron complexes ([Fe(CO)5], [(\u3b75-C5H5)Fe(CO)(\u3bc-CO)]2, and [(\u3b75-C5H5)2Fe]) have been theoretically investigated by taking advantage of density functional theory (DFT) calculations coupled to the isolobal analogy (Elian et al. Inorg. Chem. 1976, 15, 1148). The adopted approach allowed us to look into the relative role played by the ligand \u2192 Fe donation and the Fe \u2192 ligand back-donation in title molecules, as well as to investigate how CO- (terminal or bridging) and [(\u3b75-C5H5)] 12-based \u3c0* orbitals compete when these two ligands are simultaneously present as in [(\u3b75-C5H5)Fe(CO)(\u3bc-CO)]2. Insights into the nature and the strength of the bonding between Fe and the C donor atoms have been gained by exploiting the Nalewajski 12Mrozek bond multiplicity index (Nalewajski et al. Int. J. Quantum Chem. 1994, 51, 187), which have been found especially sensitive even to tiny bond distance variations. The bonding picture emerging from ground state DFT results proved fruitful to guide the assignment of original, high-resolution, gas-phase L2,3-edges X-ray absorption spectra of the title molecules, which have been modeled by the two-component relativistic time-dependent DFT including spin orbit coupling and correlation effects and taking advantage of the full use of symmetry. Assignments alternative to those reported in the literature for both [Fe(CO)5] and [(\u3b75-C5H5)2Fe] are herein proposed. Despite the high popularity of the investigated molecules, the complementary use of symmetry, orbital, and spectroscopy allowed us to further look into the metal 12ligand symmetry-restricted-covalency and the differential-orbital covalency, which characterize them

Prenatal exposure to the cannabinoid receptor agonist WIN 55,212-2 and carbon monoxide reduces extracellular glutamate levels in primary rat cerebral cortex cell cultures

none11The effects of prenatal exposure to the cannabinoid receptor agonist WIN 55,212-2 (0.5 mg/kg s.c.), alone or in combination with carbon monoxide, on extracellular glutamate levels in primary rat cerebral cortical neuronal cultures, were investigated. Dam weight gain, pregnancy length and litter size at birth were not affected by prenatal treatment with WIN 55,212-2 and carbon monoxide alone or in combination. Basal and K(+)-evoked extracellular glutamate levels were reduced in cortical cultures from pups born to mothers exposed to WIN 55,212-2 and carbon monoxide alone or in combination compared to cultures from rats born to vehicle-treated mothers. In cultures obtained from rats exposed to vehicle or carbon monoxide alone during gestation, WIN 55,212-2 (0.01-100 nM) increased extracellular glutamate levels, displaying a bell-shaped concentration-response curve. In cultures from rats born to mothers exposed to WIN 55,212-2 alone or in combination with carbon monoxide the WIN 55,212-2 ( 1 nM)-induced increase in extracellular glutamate levels was lower than that observed in cultures from rats born to vehicle-treated mothers and similar at those observed at 10 and 100 nM concentrations. The selective CB1 receptor antagonist SR141716A (10 nM) counteracted the WIN 55,212-2-induced increase in extracellular glutamate levels in cultures exposed to vehicle or carbon monoxide during gestation, but failed to antagonise it in cultures from rats born to mothers exposed to WIN 55,212-2 alone or in combination with carbon monoxide. These findings provide evidence that prenatal exposure to the cannabinoid receptor agonist WIN 55,212-2 and carbon monoxide, alone or in combination, is associated with an impairment in cortical glutamatergic transmission. It could be speculated that such detrimental effects might be involved in the reported deficit in learning and memory associated with prenatal marijuana exposure.mixedANTONELLI T; TOMASINI MC; TATTOLI M; CASSANO T; FINETTI S; MAZZONI E; TRABACE L; CARRATU MR; CUOMO V; TANGANELLI S; L. FERRAROAntonelli, Tiziana; Tomasini, Maria Cristina; Tattoli, M; Cassano, T; Finetti, Simone; Mazzoni, Elisa; Trabace, L; Carratu, Mr; Cuomo, V; Tanganelli, Sergio; Ferraro, Luca Nicol