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Conferencia invitada. -- 7th Conference on Elementary Processes in Atomic Systems,Průhonice, Prague, September 3-6, 2017.-- https://www.jh-inst.cas.cz/tchem/cepas2017/about-cepas-2017/, MM and FFS acknowledge the Portuguese National Funding Agency FCT-MCTES through PD/BD/106038/2015 and researcher position IF-FCT IF/00380/2014, respectively, and together with PLV the research grant UID/FIS/00068/2013. This work was also supported by Radiation Biology and Biophysics Doctoral Training Programme (RaBBiT, PD/00193/2010); UID/Multi/ 04378/2013 (UCIBIO). GG acknowledges partial financial support from the Spanish Ministerio de Economia, Industria y Competitividad (Project No. FIS2016-80440).

GEC 2016 ; 69th Annual Gaseous Electronics Conference ; Bochum, Germany, Monday–Friday, October 10–14, Recent theoretical and experimental studies have provided a complete set of differential and integral electron scattering cross section data from furfural over a broad energy range1, 2. The energy loss distribution functions have been determined in this study by averaging electron energy loss spectra for different incident energies and scattering angles. All these data have been used as input parameters for an event by event Monte Carlo simulation procedure to obtain the electron energy deposition patterns and electron ranges in liquid furfural. The dependence of these results on the input cross sections is then analysed to determine the uncertainty of the simulated values.

2nd Meeting of the DEA Club, Mumbai, India, 18-20 Nov. 2015; https://indico.tifr.res.in/indico/conferenceDisplay.py?confId=4541, We present a novel experimental setup for studying collision induced products resulting from the interaction of anionic beams with a neutral gas-phase molecular target [1]. The precursor projectile was admitted into vacuum through a commercial pulsed valve, with the anionic beam produced in a hollow cathode discharge-induced plasma, and guided to the interaction region by a set of deflecting plates where it was made to interact with the target beam. Depending on the collision energy regime, negative and positive species can be formed in the collision region and ions were time-of-flight (TOF) mass-analysed. Here, we present data on O2 precursor projectile, where we show clear evidence of O¿ and O2¿ formation from the hollow cathode source as well as preliminary results on the interaction of these anions with nitromethane, CH3NO2. The negative ions formed in such collisions were analysed using time-of-flight mass spectrometry. The five most dominant product anions were assigned to H¿, O¿, NO¿, CNO¿ and CH3NO2¿. The fragmentation pattern is significantly different from that obtained both in dissociative electron attachment and in alkali atom¿molecule collision experiments [2, 3]

We report on the measurements of the electron impact electronic excitation cross sections for XF4 (X = C, Si and Ge) molecules at 100 eV, 5° scattering angle and 30 eV, 30° in the electron energy loss range 8.0 - 18 eV. For a target of GeF4 molecule, the optically-forbidden behavior has been observed in the lower electron energy loss range. publishersversion published

POSMOL 2015, 17-20 July 2015, Lisboa, Portugal; http://eventos.fct.unl.pt/posmol2015/, Pyrimidine is a prototype molecule for numerous biological molecules, such as cytosine, thymine, uracil thiamine, and alloxan. For this reason, it is one of the most interesting molecular targets to perform electron interaction studies. Pyrimidine is stable to moderate heating with a melting point close to room temperature, which makes it easily accessible for scattering experiments in the gaseous phase [1]. Here, we present novel experimental results on electron energy loss distributions from gaseous pyrimidine at 20eV obtained in a magnetically confined electron scattering system (see Fig. 1). This system is based on a strong axial magnetic confinement of the beam (0.1T) inside a collision chamber [2]. The results obtained show that energy resolution of the beam in the given configuration is around of 1.5 eV. In order to improve the energy resolution, some modifications in the system will be implemented. Namely, a nitrogen trap will be introduced in the system to reduce the electron energy spread. The electrons produced by a filament will pass through the chamber filled with nitrogen and will be cooled down to about 50 meV via vibrational excitations of the molecular nitrogen. These electrons will be extracted and accelerated to the energy of the interest while keeping their relative energy spread. The observed energy loss distribution will be compared with that simulated in our Low Energy Particle Track Simulation code [3] in order to check the reliability of the input parameters used in this model. In a future work, the improved system will be used to determine total electron scattering cross sections for different molecules in the energy range (1-1000 eV).

POSMOL 2015, 17-20 July 2015, Lisboa, Portugal; http://eventos.fct.unl.pt/posmol2015/, Radiotherapy for cancer tumour treatment is reliant on the interactions of secondary species (electrons, positrons, radicals, molecular fragments) with important biomolecules within cells to cause (ideally) apoptosis of cancer cells[1]. In order to control the effects of radiotherapy, both to minimise damage to healthy tissue and increase site specific damage to tumours, a detailed understanding of the physicochemical processes occurring between the biological system and the primary and secondary particles is necessary[3]. Charged particle track simulations for the interaction of secondary electrons with biomolecules are usually performed using water as the medium. This is an oversimplification of the living cell, which is composed of approx. 70% water, 24% macromolecules (proteins, nucleic acids, polysaccharides) and 4% inorganic ions, sugars, amino acids, nucleotides, fatty acids and other small molecules[2]. This work compares the track simulations of a 10keV primary ionizing particle in the water medium with the same in pyrimidine (C4H4N2), the commonly used prototypical structure for RNA/DNA bases. As expected, the results for the two mediums differ, including in the secondary electron penetration depth, indicating that a shift towards mixed media modeling is appropriate to truly determine the physicochemical effects and biological implications of radiation treatment. The simulations used the Low-Energy particle Track Simulations code LEPTS[4], a Monte Carlo code for event by event simulation to describe the underlying mechanisms of electron and positron interactions with the relevant target molecules. This includes not only the energy deposition and the stopping power, but also the number and types of interactions taking place along the particle track. Also presented is a database for the scattering cross sections and stopping power of electrons with Pyrimidine, with recommended values chosen from experiment and calculation to cover the incident electron energy range from 1 - 10000 eV. The data for water has been previously compiled.

POSMOL 2015, 17-20 July 2015, Lisboa, Portugal; conferencia invitada; http://eventos.fct.unl.pt/posmol2015/, Seminal studies of Sanche and co-workers revealed the capability of secondary electrons, with energies ¿ 20 eV, to induce single and double strand breaks to DNA [1]. Given the resonant-like behavior of the quantum yield profiles for induction of Double Strand Breaks (DSBs), Single Strand Breaks (SSBs) and loss of the supercoiled DNA form, several theoretical and experimental studies concerning dissociative electron attachment (DEA) to biological relevant molecules in the gas-phase have been performed. In the last few years, special attention has also been given to electron transfer processes in potassium-(bio)molecule collisions [2]. This dissociation mechanism represents an alternative approach to mimic electron driven dissociation reactions within the physiological medium. The scientific community has become more aware of the importance of studies on electron driven reactions in sulphur containing biomolecules, in order to further investigate the role of sulphur in redox reactions. Recent studies on DEA to sulphur containing analogues of thymine and uracil show that the main fragmentation is assigned to sulphur containing anions [3,4]. Here we give the first set of comprehensive experimental and theoretical analysis on the electron interactions with aminomethane sulphonic acid and taurine, two sulphur containing compounds. Taurine is an amino acid comprising several physiological functions. Aminomethane sulfonic acid represents the taurine molecule with one less CH2 group in the carbon chain. The experimental results have been obtained through DEA and electron transfer, from the Siedlce and Lisbon laboratories with negative ions detected by quadrupole and time-of-flight mass spectrometry. From the ionic yields we note a rich fragmentation pattern where the parent anion was not observed. The anionic yields show evidence of resonance-like features with main contributions centered at ~4.7 eV. These resonances are consistent with theoretical predictions obtained through Schwinger multichannel implemented with pseudopotentials, where the data from the Brazilian group indicates a ¿* a shape resonance around 4.75 eV and suggests a ¿* shape resonance around the same energy. Results of electron transfer to taurine reveal that this mechanism may promote further dissociation of the molecule when compared to free electron attachment.

POSMOL 2015, 17-20 July 2015, Lisboa, Portugal; http://eventos.fct.unl.pt/posmol2015/, Acetone (C3H6O) is the simplest carbonyl and aliphatic compound largely used as an industrial solvent for the plastic and fiber industries, and is closely related to human health as a biomarker in the breath of untreated patients with diabetes [1]. Acetone, can also be used in radiobiology, as a radiosensitizer since the presence of ketones may modify the structures of DNA bases, which are sensitive to lowenergy interactions along ionisation tracks [2]. Electron interactions with organic compounds, such as acetone, are a powerful tool to determine elastic and inelastic differential cross sections, which can be used as input data in radiotherapy dose planning [3]. As such, in this joint theoretical and experimental study, we present comprehensive elastic differential cross sections for electron scattering from acetone in the 7 to 50 eV energy electron in the angular range 15 to 90°. The experimental measurements have been obtained in an highresolution electron-energy-loss spectroscopy (HREELS) setup [7], while the theoretical calculations have been performed by the Independent Atom Model-Screening Corrected Additivity Rule (IAMSCAR) [4] and Schwinger Multichannel Methods [5,6]. The level of agreement between these calculations and our measurements is found to be quite remarkable

POSMOL 2015, 17-20 July 2015, Lisboa, Portugal; http://eventos.fct.unl.pt/posmol2015/, It has long been recognized that lignocellulosic biomass is a potential sustainable source of mixed sugars for fermentation to biofuels. During the last decades many technologies have been developed that allow this conversion process to occur and, nowadays, the clear objective is to make the use of such technologies cost-effective. Recently, it has been found that free-electrons and radical species formed within atmospheric plasmas have the ability to overcome the natural resistance of plant cell walls thus allowing for an enhancement of microbial and enzymatic deconstruction [1]. In this context, low-energy electrons which are produced within the plasma environment have the potential to induce breakage of chemical bonds through dissociative electron attachment, electron-impact excitation and other fragmentation processes. In this work we report a joint experimental and theoretical effort in order to determine reliable elastic and electronically inelastic cross sections for low-energy electron collisions with phenol [2], a key structural subunit of lignin.

Sem PDF. This research was supported by the Australian Research Council (ARC) through its Centres of Excellence Program. D.B.J. thanks the ARC for provision of a Discovery Early Career Researcher Award. We also acknowledge the support of the Spanish Ministerio de Economia y Competitivad under Project No. FIS 2012-31230 and the European Union COST Actions (MP1002 and CM1301). P.L.V. acknowledges the Portuguese Foundation for Science and Technology (FCT-MEC) through research grants PTDC/FIS-ATO/1832/2012, UID/FIS/00068/2013, and SFRH/BSAB/105792/2014. P.L.V. also acknowledges his Visiting Professor position at Flinders University, Adelaide, South Australia. Water is often used as the medium for characterizing the effects of radiation on living tissue. However, in this study, charged-particle track simulations are employed to quantify the induced physicochemical and potential biological implications when a primary ionising particle with energy 10 keV strikes a medium made up entirely of water or pyrimidine. Note that pyrimidine was chosen as the DNA/RNA bases cytosine, thymine, and uracil can be considered pyrimidine derivatives. This study aims to assess the influence of the choice of medium on the charged-particle transport, and identify how appropriate it is to use water as the default medium to describe the effects of ionising radiation on living tissue. Based on the respective electron interaction cross sections, we provide a model, which allows the study of radiation effects not only in terms of energy deposition (absorbed dose and stopping power) but also in terms of the number of induced molecular processes. Results of these parameters for water and pyrimidine are presented and compared. publishersversion published

Delhi, India, March 11th-14th, 2015 ; http://www.cdamop.com/index.asp, The Low Energy Particle Track Simulation (LEPTS) procedure [1] is a powerful complementary tool to include the effect of low energy electrons and positrons in medical applications of radiation. In particular, for ion-beam cancer treatments provides a detailed description of the role of the secondary electrons abundantly generated around the Bragg peak as well as the possibility of using transmuted positron emitters (C11, O15) as a complement for ion-beam dosimetry. In this study we present interaction probability data derived from experimental and theoretical studies. We will also update our IAM-SCAR [3, 4] calculated corrective factors for solid and liquid environments. Using these data, single electron and positron tracks in liquid water and pyrimidine have been simulated to provide information about energy deposition as well as the number and type of interactions taking place in any selected ¿nanovolume¿ of the irradiated area.

ICPEAC 2015, Toledo, Spain on 22 –28 July 2015; http://www.icpeac2015.com/, We present interaction probability data of low-energy secondary electrons and positrons produced due to the proton impact. The probability distribution functions serve as input data for the Low Energy Particle Track Simulation (LEPTS) approach which allows one to include the effect of low-energy species in medical applications of radiation and in ion-beam cancer therapy, in particular., his work has been supported by the Spanish Ministry of Economía y Productividad (Project FIS2012-31320). We also acknowledge partial funding from the Portuguese Foundation for Science and Technology (FCT-MCTES), research grant PEstOE/FIS/UI0068/2011,the EU/ESF COST Actions Nano-IBCT - MP1002 and CELINA CM- 1301, and from the FP7 Multi-ITN Project ”Advanced Radiotherapy, Generated by Exploiting Nanoprocesses and Technologies” (ARGENT) (Grant Agreement n◦608163).

POSMOL 2015, 17-20 July 2015, Lisboa, Portugal; http://eventos.fct.unl.pt/posmol2015/, The most abundant secondary species produced by the primary ionizing radiation within the biological environment are low-energy electrons (~ 4×104 by a 1MeV particle) with energies typically below 30 eV [1]. Their interactions with DNA/RNA subunits lead to the formation of short lived anions yielding molecular dissociation and hence single and double strand breaks [2, 3]. However, due to the lack of free electrons in the physiological environment, electron-transfer processes may be prevalent and appear to be a key process in the decomposition of such units [4]. Collision induced dissociation in pyrimidines results in site- and bond-selective excision of N1-H against N3-H by just tuning the proper collision energy [4]. Dissociative electron attachment (DEA) experiments to purine molecules and their derivatives (9- methyl-adenine) have been performed by Denifl et al. [4], where resonances below 1.4eV yield H abstraction from the N9 position in pristine adenine. However, methylation at the N9 site supresses such resonance, where site selectivity yielding the dehydrogenated parent anion was shown to be a relevant process. We have been exploring negative ion formation in collisions of neutral potassium atoms with adenine and 9-methyl-adenine by time-of-flight (TOF) mass spectrometry. Such anionic yields have been obtained as a function of the collision energy and significant differences are noted from DEA experiments. Preliminary ab initio calculations have been performed in order to help interpreting the experimental data. Such details will be presented at the meeting.

ICPEAC 2015, Toledo, Spain on 22 –28 July 2015; http://www.icpeac2015.com/, Analysis of dissociation induced by electron tranfer of electrons from potassium to selected biomolecules

POSMOL 2015, 17-20 July 2015, Lisboa, Portugal; http://eventos.fct.unl.pt/posmol2015/, It is known that ionizing radiation bring adverse effects to living cells. In the femtosecond regime, multiple ionizations may occur in the human body leading ultimately to the formation of radical and/or ionic species. In fact, for every MeV of radiation energy deposited in matter, about 5x10! secondary electrons (-10!!>s time window, these entities may propagate through nanometer distances in the biological medium, leading to several inelastic events [3]. Low energy electrons, with energy below 20 eV can be resonantly captured in unoccupied molecular orbitals (virtual orbitals) [4, 5]. This process results in an unstable excited transient negative ion, which can further decay via auto detachment, dissociation or, in a comparatively long time scale, via photon emission. In the present communication electron transfer studies upon potassium collisions with tryptophan, are presented as well as theoretical DFT analysis. Experimental results have been obtained by means a crossed molecular beam apparatus coupled with Time-of-Flight mass spectrometer. It is clear that for energy collision below 75 eV in the lab frame, the main fragment corresponds to the scission of Cß indole bond, with hydrogen transfer. This has been also described by means to DFT calculations, CAM-B3LYP and BHandHLYP codes