Condensed Matter Systems Exposed to Radiation: Multiscale Theory, Simulations, and Experiment.

This roadmap reviews the new, highly interdisciplinary research field studying the behavior of condensed matter systems exposed to radiation. The Review highlights several recent advances in the field and provides a roadmap for the development of the field over the next decade. Condensed matter systems exposed to radiation can be inorganic, organic, or biological, finite or infinite, composed of different molecular species or materials, exist in different phases, and operate under different thermodynamic conditions.

Infrared Spectral Signatures of Nucleobases in Interstellar Ices I: Purines.

The purine nucleobases adenine and guanine are complex organic molecules that are essential for life. Despite their ubiquitous presence on Earth, purines have yet to be detected in observations of astronomical environments. This work therefore proposes to study the infrared spectra of purines linked to terrestrial biochemical processes under conditions analogous to those found in the interstellar medium.

Current stage and future development of Belgrade collisional and radiative databases/datasets of importance for molecular dynamics.

Atomic and molecular (A&M) databases that contain information about species, their identities and radiative/collisional processes are essential and helpful tools that are utilized in many fields of physics, chemistry, and chem/phys-informatics. Errors or inconsistencies in the datasets are a serious issue since they can lead to inaccurate predictions and generate problems with the modeling. This demonstrates that data curation efforts around A&M databases are still indispensable and that in the curation process studious attention is required.

A systematic mid-infrared spectroscopic study of thermally processed SO ices.

The use of mid-infrared spectroscopy to characterise the chemistry of icy interstellar and Solar System environments will be exploited in the near future to better understand the chemical processes and molecular inventories in various astronomical environments. This is, in part, due to observational work made possible by the recently launched as well as forthcoming missions to the outer Solar System that will observe in the mid-infrared spectroscopic region (, the and the missions). However, such spectroscopic characterisations are crucially reliant upon the generation of laboratory data for comparative purposes.

Structural Analysis of Si(OEt) Deposits on Au(111)/SiO Substrates at the Nanometer Scale Using Focused Electron Beam-Induced Deposition.

The focused electron beam-induced deposition (FEBID) process was used by employing a GeminiSEM with a beam characteristic of 1 keV and 24 pA to deposit pillars and line-shaped nanostructures with heights between 9 nm and 1 μm and widths from 5 nm to 0.5 μm. All structures have been analyzed to their composition looking at a desired Si/O/C content measuring a 1:2:0 ratio.

Energetic electron irradiations of amorphous and crystalline sulphur-bearing astrochemical ices.

Laboratory experiments have confirmed that the radiolytic decay rate of astrochemical ice analogues is dependent upon the solid phase of the target ice, with some crystalline molecular ices being more radio-resistant than their amorphous counterparts. The degree of radio-resistance exhibited by crystalline ice phases is dependent upon the nature, strength, and extent of the intermolecular interactions that characterise their solid structure. For example, it has been shown that crystalline CHOH decays at a significantly slower rate when irradiated by 2 keV electrons at 20 K than does the amorphous phase due to the stabilising effect imparted by the presence of an extensive array of strong hydrogen bonds.

Ozone production in electron irradiated CO:O ices.

The detection of ozone (O) in the surface ices of Ganymede, Jupiter's largest moon, and of the Saturnian moons Rhea and Dione, has motivated several studies on the route of formation of this species. Previous studies have successfully quantified trends in the production of O as a result of the irradiation of pure molecular ices using ultraviolet photons and charged particles (, ions and electrons), such as the abundances of O formed after irradiation at different temperatures or using different charged particles. In this study, we extend such results by quantifying the abundance of O as a result of the 1 keV electron irradiation of a series of 14 stoichiometrically distinct CO:O astrophysical ice analogues at 20 K.

Systematic investigation of CO : NH ice mixtures using mid-IR and VUV spectroscopy - part 2: electron irradiation and thermal processing.

Many experimental parameters determine the chemical and physical properties of interstellar ice analogues, each of which may influence the molecular synthesis that occurs in such ices. In part 1, James , , 2020, , 37517, we demonstrated the effects that the stoichiometric mixing ratio had on the chemical and physical properties of CO : NH mixtures and the impact on molecular synthesis induced by thermal processing. Here, in part 2, we extend this to include 1 keV electron irradiation at 20 K of several stoichiometric mixing ratios of CO : NH ices followed by thermal processing.

Comparative electron irradiations of amorphous and crystalline astrophysical ice analogues.

Laboratory studies of the radiation chemistry occurring in astrophysical ices have demonstrated the dependence of this chemistry on a number of experimental parameters. One experimental parameter which has received significantly less attention is that of the phase of the solid ice under investigation. In this present study, we have performed systematic 2 keV electron irradiations of the amorphous and crystalline phases of pure CHOH and NO astrophysical ice analogues.

Molecular Dynamics Characterization of Radiosensitizing Coated Gold Nanoparticles in Aqueous Environment.

Functionalized metal nanoparticles (NPs) have been proposed as promising radiosensitizing agents for more efficient radiotherapy treatment using photons and ion beams. Radiosensitizing properties of NPs may depend on many different parameters (such as size, composition, and density) of the metal core, the organic coatings, and the molecular environment. A systematic exploration of each of these parameters on the atomistic level remains a formidable and costly experimental task, but it can be addressed by means of advanced computational modeling.

The Ice Chamber for Astrophysics-Astrochemistry (ICA): A new experimental facility for ion impact studies of astrophysical ice analogs.

The Ice Chamber for Astrophysics-Astrochemistry (ICA) is a new laboratory end station located at the Institute for Nuclear Research (Atomki) in Debrecen, Hungary. The ICA has been specifically designed for the study of the physico-chemical properties of astrophysical ice analogs and their chemical evolution when subjected to ionizing radiation and thermal processing. The ICA is an ultra-high-vacuum compatible chamber containing a series of IR-transparent substrates mounted on a copper holder connected to a closed-cycle cryostat capable of being cooled down to 20 K, itself mounted on a 360° rotation stage and a z-linear manipulator.

Possible detection of hydrazine on Saturn's moon Rhea.

We present the first analysis of far-ultraviolet reflectance spectra of regions on Rhea's leading and trailing hemispheres collected by the Cassini Ultraviolet Imaging Spectrograph during targeted flybys. In particular, we aim to explain the unidentified broad absorption feature centred near 184 nm. We have used laboratory measurements of the UV spectroscopy of a set of candidate molecules and found a good fit to Rhea's spectra with both hydrazine monohydrate and several chlorine-containing molecules.

Shock Processing of Amino Acids Leading to Complex Structures-Implications to the Origin of Life.

The building blocks of life, amino acids, are believed to have been synthesized in the extreme conditions that prevail in space, starting from simple molecules containing hydrogen, carbon, oxygen and nitrogen. However, the fate and role of amino acids when they are subjected to similar processes largely remain unexplored. Here we report, for the first time, that shock processed amino acids tend to form complex agglomerate structures.

Systematic investigation of CO : NH ice mixtures using mid-IR and VUV spectroscopy - part 1: thermal processing.

The adjustment of experimental parameters in interstellar ice analogues can have profound effects on molecular synthesis within an ice system. We demonstrated this by systematically investigating the stoichiometric mixing ratios of CO : NH ices as a function of thermal processing using mid-IR and VUV spectroscopy. We observed that the type of CO bonding environment was dependent on the different stoichiometric mixing ratios and that this pre-determined the NH crystallite structure after phase change.

Probing the interaction between solid benzene and water using vacuum ultraviolet and infrared spectroscopy.

We present results of a combined vacuum ultraviolet (VUV) and infrared (IR) photoabsorption study of amorphous benzene : water mixtures and layers to investigate the benzene-water interaction in the solid phase. VUV spectra of 1 : 1, 1 : 10 and 1 : 100 benzene : water mixtures at 24 K reveal a concentration dependent shift in the energies of the 1B2u, 1B1u and 1E1u electronic states of benzene. All the electronic bands blueshift from pure amorphous benzene towards gas phase energies with increasing water concentration.

Vacuum ultraviolet photoabsorption spectroscopy of crystalline and amorphous benzene.

We present the first high resolution vacuum ultraviolet photoabsorption study of amorphous benzene with comparisons to annealed crystalline benzene and the gas phase. Vapour deposited benzene layers were grown at 25 K and annealed to 90 K under conditions pertinent to interstellar icy dust grains and icy planetary bodies in our solar system. Three singlet-singlet electronic transitions in solid benzene correspond to the B, B and E states, redshifted by 0.

Cancer-selective, single agent chemoradiosensitising gold nanoparticles.

Two nanometre gold nanoparticles (AuNPs), bearing sugar moieties and/or thiol-polyethylene glycol-amine (PEG-amine), were synthesised and evaluated for their in vitro toxicity and ability to radiosensitise cells with 220 kV and 6 MV X-rays, using four cell lines representing normal and cancerous skin and breast tissues. Acute 3 h exposure of cells to AuNPs, bearing PEG-amine only or a 50:50 ratio of alpha-galactose derivative and PEG-amine resulted in selective uptake and toxicity towards cancer cells at unprecedentedly low nanomolar concentrations. Chemotoxicity was prevented by co-administration of N-acetyl cysteine antioxidant, or partially prevented by the caspase inhibitor Z-VAD-FMK.

Gold nanoparticles for cancer radiotherapy: a review.

Radiotherapy is currently used in around 50% of cancer treatments and relies on the deposition of energy directly into tumour tissue. Although it is generally effective, some of the deposited energy can adversely affect healthy tissue outside the tumour volume, especially in the case of photon radiation (gamma and X-rays). Improved radiotherapy outcomes can be achieved by employing ion beams due to the characteristic energy deposition curve which culminates in a localised, high radiation dose (in form of a Bragg peak).

Using the C-O stretch to unravel the nature of hydrogen bonding in low-temperature solid methanol-water condensates.

Transmission infrared spectroscopy has been used in a systematic laboratory study to investigate hydrogen bonding in binary mixtures of CH3OH and H2O, vapour deposited at 30 K, as a function of CH3OH/H2O mixing ratio, R. Strong intermolecular interactions are evident between CH3OH and H2O with infrared band profiles of the binary ices differing from that of the pure components and changing significantly with R. Consistent evidence from the O-H and C-H band profiles and detailed analysis of the C-O stretch band reveal two different hydrogen bonding structural regimes below and above R = 0.

Communication: vacuum ultraviolet photoabsorption of interstellar icy thiols.

Following the recent identification of ethanethiol in the interstellar medium (ISM) we have carried out Vacuum UltraViolet (VUV) spectroscopy studies of ethanethiol (CH3CH2SH) from 10 K until sublimation in an ultrahigh vacuum chamber simulating astrochemical conditions. These results are compared with those of methanethiol (CH3SH), the lower order thiol also reported to be present in the ISM. VUV spectra recorded at higher temperature reveal conformational changes in the ice and phase transitions whilst evidence for dimer production is also presented.

Electron induced chemistry: a new frontier in astrochemistry.

The commissioning of the ALMA array and the next generation of space telescopes heralds the dawn of a new age of Astronomy, in which the role of chemistry in the interstellar medium and in star and planet formation may be quantified. A vital part of these studies will be to determine the molecular complexity in these seemingly hostile regions and explore how molecules are synthesised and survive. The current hypothesis is that many of these species are formed within the ice mantles on interstellar dust grains with irradiation by UV light or cosmic rays stimulating chemical reactions.

State selectivity and dynamics in dissociative electron attachment to CF₃I revealed through velocity slice imaging.

In light of its substantially more environmentally friendly nature, CF3I is currently being considered as a replacement for the highly potent global-warming gas CF4, which is used extensively in plasma processing. In this context, we have studied the electron-driven dissociation of CF3I to form CF3(-) and I, and we compare this process to the corresponding photolysis channel. By using the velocity slice imaging (VSI) technique we can visualize the complete dynamics of this process and show that electron-driven dissociation proceeds from the same initial parent state as the corresponding photolysis process.